AU2020201730A1 - Biomechanics specific system for primary total knee replacement (tkr) - Google Patents

Abstract

A main objective of the present invention which is performing three critical bone cuts, distal femur cut 410, posterior femur 410, and tibia cut 430 in such a manner that accepted longitudinal alignment is reproduced and prosthesis will be implanted in conformity with quadriceps (Q-ceps) vector and soft tissues. The invention in one aspect provides fully transparent instruments so surgeon can see in front and behind the instrument. The instruments include component size gauge 230, alignment plate 150, tibia slope gauge 250, sagittal guide 180, restoring assembly 110, Anterior-posterior (AP) cutting block 200, tibia position gauge 205 and gap spacers 260. The elastic rings (210) being disposable and tibia final cut (272) being of optional use are not included. The instruments are made from fully transparent and colourless polycarbonate. In the images, they are given colour tint to improve their contour definition for illustration purposes. 250 2/23 230 252 254 110 ALTER TIVE I STRUME SFR PRIMARY TKR "Andrew Ha lfe" "POLYCAR6ONATEFART ARETRA RfNTANOCOtOURtESS, ECOTOU NTINEISOGVENTOIMPROVECONTOURSDEFINITION2 TIBIA POSITION COMPONENT S12E GUAGE TIBIA SLOPE GUAGE 130 A NMENT PLATE TALGUIDE RESTORING ASSEMBLY AP CUTTING BLOCK GAP SPACERS . . ,... BLY Figure 3 150 180 120 260 200 INSTRUMENTS FUNCTION 208 AP CUTTING BLOCK ASSEMBLY KEY 208 KEY 206 206 PARALLEL BAR PARALLEL BAR 202 STABILISING PLATE 210 ELASTIC RINGS 150 ALIGNMENT PLATE 210 204 ELASTIC RINGS -AP CUTTING JIG Figure 4

Description

250 2/23 230 252 254 110 ALTER TIVE I STRUME SFR PRIMARY TKR "Andrew Ha lfe" "POLYCAR6ONATEFART ARETRA RfNTANOCOtOURtESS, ECOTOU NTINEISOGVENTOIMPROVECONTOURSDEFINITION2

TIBIA POSITION COMPONENT S12E GUAGE TIBIA SLOPE GUAGE

130

A NMENT PLATE TALGUIDE RESTORING ASSEMBLY AP CUTTING BLOCK GAP SPACERS . . ,... BLY

Figure 3

150 180 120 260 200

INSTRUMENTS FUNCTION 208 AP CUTTING BLOCK ASSEMBLY KEY 208 KEY 206 206 PARALLEL BAR PARALLEL BAR

202 STABILISING PLATE 210 ELASTIC RINGS

150 ALIGNMENT PLATE

210 204 ELASTIC RINGS -AP CUTTING JIG

Figure 4

BIOMECHANICS SPECIFIC SYSTEM FOR PRIMARY TOTAL KNEE REPLACEMENT (TKR)

Field of the Invention

[1] The invention relates generally to alternative instruments and surgical technique for primary total knee replacement (TKR) which is specific to longitudinal alignment and soft tissues. The strategy of approach to knee arthroplasty is different from current teaching and methods which focuses on particular longitudinal alignment. In the present invention not alignment but optimal biomechanics of the knee prosthesis is targeted. The invention is an entire novel system which comprises novel techniques (METHOD) and novel instruments (DEVICE).

Background of the Invention

[2] Brief Introduction to Subject of TKR and Basic Terminology: Human knee joint is formed by three bones and surrounding soft tissues.

[3] THE BONES:

1. Distal end of thigh bone (femur) which consists of medial condyle and lateral condyle. The condyles are separated by intercondylar notch.

2. Proximal end of shin bone (tibia) which consists of medial plateau and lateral plateau. The plateaus are separated by elongated bony prominence tibia spine which fits loosely in the intercondylar notch of the femur.

3. Kneecap (patella)

[4] THE SOFT TISSUES:

Consists of PASSIVE ELEMENTS like articular capsule with incorporated ligaments providing for stability and ACTIVE ELEMENTS which are muscles and their tendons providing for movement in the knee joint. The precise interaction between the bones and the soft tissues is a prerequisite for optimal biomechanics of replaced knee joint.

[5] In the process of aging, the wear and tear of articular cartilage occurs - osteoarthritis (OA) leading to deformity and loss of function. Some individuals are more prone to develop OA than others. The OA is not symmetrical and when it affects the inside (medial) side of the knee more, it results in bow knee deformity (varus deformity). When it affects the outside (lateral) side of the knee more, it results in knock knee deformity (valgus deformity).

[6] Principal pathology of OA is degeneration of articular cartilage with loss of structural integrity. This is followed by reactive deformation of the underlying bone and its margins. The structural integrity of the soft tissues is not affected. In TKR, varus or valgus deformities are corrected and longitudinal alignment of the lower extremity is restored to anticipated optimal.

[7] There are many different systems for performing TKR but all of them are designed to conform to "golden standards". The main objective of those standards is that after TKR, the extremity will end up in specific, preconceived as optimal, longitudinal alignment which is 3-5 ° of valgus.

[8] There are 3 schools of thought in the strategy of approach of generally accepted "GOLDEN STANDARDS":

1. MECHANICAL ALIGNMENT

2. ANATOMICAL ALIGNMENT

In both these methods, an attempt is made to achieve alignment of about 3° of valgus (regarded as optimal) so the load is evenly distributed throughout knee joint. Only about 20% of the healthy population have knees aligned in 3° of valgus. The remaining 80% show some degree of varus or valgus deviation which is accepted as constitutional varus or valgus.

3. KINEMATIC ALIGNMENT - in this method an attempt is made to restore alignment to one preconceived as present prior to onset of OA (premorbid).

[9] None of above methods, considered "golden standards", proved to be superior. In all these methods, arguably about 20% of replaced knees show suboptimal functional outcome despite fulfilling "golden standards" surgical objectives (outlays). This lack of consistency indicates the need for a better method and different approach.

[10] The present invention seeks to overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[11] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Invention

[12] The invention provides a method for total knee replacement, the method including the steps of:

extending the intercondylar notch of the femur anteriorly by removing bone in the form of a right angled channel not less than 10 mm deep, the width of the channel being equal to the base of the tibia spine, inserting a smallest 2 mm restoring spacer in the less diseased compartment between one of the facing medial condyle and medial plateau or between the facing lateral condyle and lateral plateau, correcting knee longitudinal alignment to see the degree to which the more diseased compartment opens, inserting the highest stretching restoring spacer for the more diseased compartment for the other of between the facing medial condyle and medial plateau or between the facing lateral condyle and lateral plateau inserting a pin in the functional centre of the patella, flexing the knee to 25° to 30°, contracting the quadriceps muscle by electrical muscle stimulation which causes the patella to self-align with the line of pull of the quadriceps muscle, while the quadriceps muscle is still contracted, driving the pin into the femur leaving a mark for patella tracking.

[13] Preferably, the restoring spacers each comprise a flat lower surface which engage the plateaus and an angled upper surface which engage the condyles.

[14] Preferably, the restoring spacers comprise inward curved extensions which splint opposing sides of the tibial spine and are received into the cut intercondylar notch.

[15] Preferably, the method includes the step of connecting a vertical column to a carrier disposed between the restoring spacers, and aligning the vertical column with the patella tracking mark.

[16] Preferably, the method includes inserting the vertical column into a central aperture of an alignment plate, the alignment plate being made of transparent material and having on both upper and lower surfaces thereof superimposed lines quadriceps vector lines in longitudinal direction and joint lines in transverse direction, the lines serving as optical targeting devices, and wherein the central aperture is elongated along the quadriceps vector line.

[17] Preferably, the method includes the step of positioning of the alignment plate such that the quadriceps vector lines and the joint lines are superimposed over each other, with the quadriceps vector lines aligned with the patella tracking mark in longitudinal direction and the joint lines are aligned with a knee joint line in transverse direction.

[18] Preferably, the method includes the step of securing the alignment plate via pins inserted in the middle of longitudinal pin slots of the alignment plate formed on either side of the central aperture and elongated in the same direction as the central aperture.

[19] Preferably, the method includes the step of attaching a calibrated sagittal guide to the alignment plate, the sagittal guide comprising adjustable pins to engage the femur, wherein the pins are adjusted to the angle required for femoral component inclination.

[20] Preferably, the method includes the step of moving the alignment plate with sagittal guide attached proximally and distally until the joint lines of the alignment plate are aligned with the target knee joint line.

[21] Preferably, a smallest 2 mm restoring spacer is firstly inserted in the less diseased medial or lateral compartment, knee longitudinal alignment is then corrected to see the degree to which the more diseased compartment opens, and the highest restoring spacer is chosen for the other more diseased compartment.

[22] Preferably, the method includes the step of attaching a sagittal guide to an alignment plate, the sagittal guide adjusted to the angle required for femoral component inclination, the alignment plate with the sagittal guide being attached to the restoring assembly by inserting the vertical column into a longitudinal central aperture of the alignment plate, the alignment plate being made of transparent material and having on both upper and lower surfaces thereof superimposed lines in longitudinal and transverse directions which function as quadriceps vector lines and joint lines respectively.

[23] Preferably, the method includes the step of aligning the quadriceps vector lines with the patella tracking mark and securing the alignment plate in position via pins inserted in longitudinal slots in the alignment plate parallel to the central aperture thereof to only allow movement of the alignment plate proximally or distally for targeting the joint line.

[24] Preferably, the method includes the step of identifying the joint line which is equidistant to bone cuts to be made.

[25] Preferably, the method includes the step of setting femoral component inclination with the sagittal guide and aligning the joint line in target by moving the alignment plate proximally or distally with sagittal guide as a handle.

[26] Preferably, the method includes the step of pinning the alignment plate to the femur via pins inserted into femur anchoring pin apertures thereof, flexing the knee to an angle required for tibia posterior slope, pinning the alignment plate to the tibia via pins inserted in tibia pin apertures.

[27] Preferably, the method includes the step of inserting marker pins in the tibia and the femur in pin apertures of the alignment plate aligned with the quadriceps vector lines.

[28] Preferably, the method includes the step of performing critical distal femur and tibia cuts using femur saw slots and the tibia saw slots of the alignment plate, the distance between the cuts being 22 mm.

[29] Preferably, the method includes the step of performing an initial condyles cut cuts of both condyles are done through an AP cutting block with the base of the block level with the more protruding condyle and the AP cutting block having saw slots which are 6 mm above the base.

[30] Preferably, the completed initial condyles creates a flat surface parallel with the alignment plate.

[31] Preferably, the method includes the step of placing a stretching gap spacer between the flat surface on condyles and the flat surface on the tibia, wherein the largest possible spacer is chosen so soft tissues and ligaments around the joint are stretched.

[32] Preferably, the method includes the step of placing a final spacer 260 on the flat tibia surface in front of the stretching spacer, wherein the size of the final spacer is chosen by applying the formula: prosthesis condyles height in mm + 6.

[33] Preferably, the method includes the step of moving the AP cutting block down to rest on the final spacer, pinning the AP cutting jig to the femur and performing the final cut through the saw slots in the AP cutting block.

[34] The invention also provides apparatus for total knee replacement, the apparatus comprising: restoring spacers having a generally wedge shaped main portion with a flat lower surface and an upper surface which is angled downwardly relative to the lower surface from an outer edge towards an inside edge thereof.

[35] Preferably, the inside edge has a raised curved extension that extends upwardly.

[36] Preferably, the main portion has a cut therein extending from the outer edge towards the curved extension, the cut allowing the body to flex to adapt to deformity.

[37] Preferably, the apparatus includes two restoring spacers which are mirror images of each other relative, wherein the curved extensions are facing but spaced from each other.

[38] Preferably, the apparatus includes a carrier having a central connector with connector rods respectively received in mount apertures of the respective spacers, the carrier having a vertical column.

[39] The invention also provides apparatus for total knee replacement, the apparatus comprising a transparent alignment plate having transversely extending parallel and aligned joint lines marked along the upper and lower surfaces thereof, and longitudinally extending parallel and aligned quadriceps vector lines marked along the central section of the upper and lower surfaces thereof.

[40] Preferably, the alignment plate comprises a central aperture for receiving the vertical column, the central aperture being formed at the intersection between the joint lines and the quadriceps vector lines, and is elongated along the quadriceps vector lines.

[41] Preferably, the alignment plate includes elongated secure pin slots on opposite sides of the central aperture which are parallel to the central aperture.

[42] Preferably, the alignment plate further comprises alignment pin apertures formed along the quadriceps vector lines.

[43] Preferably, the alignment plate further comprises spaced anchoring pin apertures.

[44] Preferably, the alignment plate further comprises femur saw slots and tibia saw slots, the femur saw slots being formed 10 mm above and parallel to the joint lines, and the tibia saw slots being formed parallel to and below the joint lines, with the tibia saw slot at 12 mm from the joint lines.

[45] Preferably, the alignment plate further comprises two mount apertures for parallel bars of an AP cutting block.

Brief Description of the Drawings

[46] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings in which:

[47] Fig 1. Shows the main objective of the present invention which is performing three critical bone cuts (distal femur, posterior femur, and tibia cuts) in such a manner that accepted longitudinal alignment is reproduced and prosthesis will be implanted in conformity with quadriceps (Q-ceps) vector and soft tissues.

[48] Fig. 2. On the right side shows knee prosthesis - implanted and combined thickness of prosthesis is 20 mm. On the left side is a demonstration that to maintain the joint line level an equal amount of bone from femur and tibia must be removed to accommodate the prosthesis. To end up with 20 mm space for prosthesis with loose fit, the joint is stretched to 22mm.

[49] Fig 3. Shows an overview of the instruments of the present invention. The instruments include component size gauge, alignment plate, tibia slope gauge, sagittal guide, restoring assembly, Anterior-posterior (AP) cutting block, tibia position gauge and gap spacers. The elastic rings (210) being disposable and tibia final cut (272) being of optional use are not included. The instruments are made from fully transparent and colourless polycarbonate. In the images, they are given colour tint to improve their contour definition for illustration purposes.

[50] Fig 4. Shows in detail how the AP cutting block is attached to the alignment plate. In this configuration, the AP block can be moved up and down while remaining securely square with the alignment plate.

[51] Fig. 5. Demonstrates one of three core components of the method (surgical technique) of restoring correct intra-articular relationship between femur and tibia. For this, two anatomical structures: inter-condylar notch and tibia spine are utilized. Image shows that inter condylar notch is extended anteriorly to make room for restoring spacers. The spacers stretch the joint in accepted alignment, they also splint the tibia spine and force it to align with the extended inter-condylar notch. With this, the tibia translation and mal-rotation is simultaneously corrected.

[52] Fig. 5a Shows restoring spacers engaged to a carrier.

[53] Fig.6. Shows how the restoring spacers fit to the distal femur and extended anteriorly inter-condylar notch. The curved inside edges of the restoring spacers engage against the notch preventing the restoring spacers from moving sideways and rotating.

[54] Fig. 6a Shows restoring spacer adaptability to deformity.

[55] Fig.7. Shows how the restoring spacers fit to proximal tibia. The curved internal edges of the restoring spacers splint the tibia spine, and when engaged with the inter-condylar notch, prevent the restoring spacers from moving sideways and rotating.

[56] Fig.8. Shows restoring spacers in place with the resulting stretch of the joint in correct longitudinal alignment with tibia translation and mal-rotation simultaneously corrected.

[57] Fig.9. Shows the restoring spacers in place in oblique view.

[58] Fig.10. Shows a second novel and core component of the method (surgical technique). The vertical pin is introduced to the functional centre of the patella.

[59] Fig 11. Shows precise identification of patella tracking mark. This step is done after the restoring spacers are introduced and the knee is stretched in correct longitudinal alignment with translation and mal-rotation of tibia corrected. Knee is flexed to 25° - 30°. In this position, the quadriceps muscle is made to contract via electric muscle stimulation (EMS). The released patella spontaneously re-aligns with line of quadriceps muscle pull (quadriceps vector). The pin in the patella (introduced previously) is driven into the femur then removed leaving the patella tracking mark. This mark is one of three reference parameters.

[60] Fig.12. Shows patella tracking mark which is also a target for femoral component rotation.

[61] Fig.13. Shows the first step in the process of linking of the restoring spacers with the alignment plate. This link is the vertical column which is attached to the carrier of the restoring spacers.

[62] Fig.14. Shows the vertical column in process to be attached and when in the vertical position, the column can be adjusted sideways via the carrier to be in line with patella tracking mark.

[63] Fig.15. Shows the vertical column aligned with the patella tracking mark and ready for alignment plate to be attached to it.

[64] Fig.16. Shows the alignment plate connected to the vertical column but not fixed to the restoring assembly. The alignment plate is also connected to the sagittal guide.

[65] Fig.17. The image shows the sagittal guide set for neutral positioning of the femoral component.

[66] Fig.18. This image demonstrates the second function of the sagittal guide. 1 mm of lengthening of proximal pin results with 2.7° of femoral component flexion.

[67] Fig.19. This image shows the joint line in yellow. The joint line must be identified while the restoring spacers are in place. The joint line is equidistant to bone cuts to be made. The joint line is equidistant to bones of tibia and femur. The line is not parallel to the carrier, although depending on longitudinal alignment may appear to be so.

[68] Fig.20. The image shows the starting point in optical targeting. The targets are two drawn blue lines. The transverse blue line represents the joint line and longitudinal blue line represents quadriceps vectorwith the patella tracking mark. On each surface (top and bottom) of the transparent alignment plate, there are superimposed lines running in the longitudinal and transverse directions (red and black). The image is showing the alignment plate not aligned so one can see the two longitudinal and two transverse lines on the plate (red and black) and those lines are not superimposed on the blue lines.

[69] Fig.21 Shows the alignment plate aligned with both targets.

[70] Fig. 21a Explains how Q-ceps vector when in target is secured by two pins introduced in longitudinal slots of alignment plate.

[71] Fig. 22. Shows the setup of the invention system when ready to perform two critical bone cuts (distal femur and tibia cuts).

[72] Fig. 23. Shows the stage when critical distal femur and tibia cuts are done. Because of presence of important blood vessels and nerves behind the knee joint, the cuts are done as deep as it is safe. The image also shows three red pins in line with quadriceps vector introduced - one in femur and two in tibia.

[73] Fig 23a Shows a starter chisel engaged in bone in tangential orientation. The chisel fits snugly in the saw slot of the alignment plate and starts the bone cut in the intended direction preventing the saw from veering away from hard bone.

[74] Fig. 24. Shows the stage where distal femur and tibia cuts are completed.

[75] Fig. 25 Shows the stage of preparation for third critical posterior condyle cut. The posterior condyles cut is done in two stages: initial condyles cut and final condyles cut.

[76] Fig. 26. Shows positioning of the AP cutting block for initial condyles cut. The base of the block is level with more protruding condyle and cuts of both condyles are done through the saw slots which are 6 mm above the base. The purpose of initial cut is to create a flat surface parallel with the alignment plate.

[77] Fig. 27 Shows side views of the completed initial condyles cut.

[78] Fig. 28. Show the first step in final condyles cut. The knee is in flexion and needs to be stretched as it was stretched by restoring gap spacers in extension. For this the stretching gap spacer is placed between the flat surface on condyles and the flat surface on tibia. The largest possible gap spacer is chosen so soft tissues and ligaments around the joint are stretched.

[79] Fig. 29. Shows the second step in final condyles cut. The thickness of bone removed from condyles of the femur must be equal to thickness of condyles of prosthesis so appropriate size of the gap spacer for final cut must be chosen. Once final gap spacer is chosen it is put on the flat tibia surface in front of the stretching gap spacer. The AP cutting block is dropped down to rest on the final gap spacer.

[80] Fig. 30. Shows third and last step in final condyles cut. The AP cutting block is pinned to femur with two pins. The stretching and final spacers are removed to prevent jamming of saw blade and final cut is done through saw slots in AP block.

[81] Fig. 31. Show the knee joint after the three critical bone cuts are done. Note that red pins in femur and tibia are retained.

[82] Fig. 32. Shows side view after three critical bone cuts are done. Red pins retained.

[83] Fig. 33. Shows knee in extension after cuts are completed. The 22mm spacer keeps knee stretched and the supporting instrument (tibia position gauge) align all red pins in the same plane maintaining the knee joint in correct alignment.

[84] Fig. 34. Shows that flexion and extension gaps are equal when condyles of prosthesis are of standard 10 mm.

[85] Fig. 35. Shows a formula for choosing femoral component size. The supporting instrument (component size gauge) is slid over red pin and secured with two more pins. The reference for component size is posterior condyles cut.

[86] Fig 35a Shows the AP cutting Block and Stabilising Plate assembly for parallel anterior femur cut. Rotating Stabilising Plate 180° in transverse plane will enable to perform 3° diverging anterior femur cut.

[87] Fig 36. Shows the ALIGNMENT PLATE where (a) perspective view, (b) front view, (c) side view, (d) cross-section view along line A-A and (e) cross-section view along line B-B

[88] Fig 37. Shows the component arrangement of the RESTORING ASSEMBLY where (a) perspective view, (b) front view, (c) side view, (d) top view.

[89] Fig. 38. Shows the SAGITTAL GAUGE where (a) perspective view, (b) front view, (c) top view, (d) end view.

[90] Fig. 39. Shows the AP cutting block where (a) perspective view, (b) front view, (c) top view, (d) end view.

[91] Fig. 40. Shows the STABILISING PLATE where (a) perspective view, (b) front view, (c) top view, (d) end view.

Description of Embodiments

[92] It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

[93] The main objective of the present invention is to ensure optimal biomechanics for knee prosthesis so that the replaced knee will function in conformity with intact soft tissues and in conformity with forces exerted on it when in use.

[94] The present invention method and instruments can be applied in conjunction with most TKR systems on the market by replacing some current instruments with instruments from the present invention.

[95] Fig 1, shows the main objective of the present invention which is performing three critical bone cuts, distal femur cut 410, posteriorfemur 410, and tibia cut 430 in such a manner that accepted longitudinal alignment is reproduced and prosthesis will be implanted in conformity with quadriceps (Q-ceps) vector and soft tissues.

[96] Fig. 2. On the right side shows knee prosthesis 500 - implanted and combined thickness of prosthesis is 20 mm. On the left side is a demonstration that to maintain the joint line level an equal amount of bone from femur and tibia must be removed to accommodate the prosthesis. To end up with 20 mm space for prosthesis with loose fit, the joint is stretched to 22mm.

[97] DEVICE (instruments). The novel element is the introduction of fully transparent instruments so surgeon can see in front and behind the instrument. Transparency provides for superior control in bone cutting. Transparent instruments also function as optical targeting device so bone is cut with accuracy exceeding any technology currently available.

[98] Fig 3. Shows an overview of the instruments of the present invention. The instruments include component size gauge 230, alignment plate 150, tibia slope gauge 250, sagittal guide 180, restoring assembly 110, Anterior-posterior (AP) cutting block 200, tibia position gauge 205 and gap spacers 260. The elastic rings (210) being disposable and tibia final cut (272) being of optional use are not included. The instruments are made from fully transparent and colourless polycarbonate. In the images, they are given colour tint to improve their contour definition for illustration purposes.

[99] There are 18 instruments as listed below

001 Alignment Plate

002 AP Cutting Block

003 Stabilizing Plate

004 Tibia Final Cut Jig

005 Gap Spacer

006 Component Size Gauge

007 Restoring Spacer's assembly

008 Restoring Spacers

009 Restoring Spacer

010 Carrier

011 Vertical Column

012 Parallel Bar

013 Key

014 Vertical column

015 Sagittal Guide

016 Tibia Position Gauge

017 Tibia Slope Gauge

018 Chisel

[100] The instruments 001, 002, 003, 007 and 015 on the above list are core instruments and each of them is an invention in its own right. The instruments enable to identify and to apply three reference parameters which are:

[101] 1. Joint line 2. Patella tracking mark (quadriceps vector) 3. Femoral component position in sagittal plane. (component inclination)

[102] Figures 3 and 37 shows the restoring assembly 110 which comprises two restoring spacers 120, a carrier 130 and a vertical column 140.

[103] Referring to Figure 6a, each restoring spacer 120 comprises a body 121 having a generally wedge shaped main portion 122. The main portion 122 comprises a generally horizontally flat lower surface 123 and an upper surface 124 which is angled downwardly relative to the lower surface 123 from an outer edge 125 towards an inside edge 126 thereof. The inside edge 126 has a raised curved extension 127 that extends upwardly. An upper edge of the body 121 comprises a mount formation 128 with a carrier mount aperture 129 which extends in the lateral direction. The main portion 122 has a cut 131 therein extending from the outer edge 125 adjacent the mount formation 128 and angled at about 45 downwardly towards the curved extension 127. The cut 131 allows the body 121 to flex to adapt to deformity. Fig. 6a shows the restoring spacer's adaptability to deformity.

[104] Referring to Figures 7 and 37, the two restoring spacers 120 are mirror images of each other relative to an axis defined by the column 140. Thus, the extensions 127 are facing but spaced from each other.

[105] Referring to Figure 5a, the carrier 130 comprises a central connector 132 with two connector rods 134 extending outwardly in opposite directions therefrom. In the example, the central connector 134 is cube shaped with the connector rods 134 extending from opposing side faces of the connector 132. The connector 132 comprises apertures 136 at each of the faces thereof extending between the side faces.

[106] The connecting rods 134 are respectively received in the mount apertures 129 of the respective spacers 120. The central connector 134 is thus movable between the mount formations 128 of the spacers 120.

[107] Referring to Figure 37, the vertical column 140 comprises an elongate threaded rod body 142 with a hook connector 144 at a lower end thereof. The hook connector 144 is for insertion mounting into apertures 136 at two opposing faces of the connector 132 which allows the angle of the column 140 relative to the spacers 120 to be varied as further described below.

[108] The restoring spacers 120 will be provided in 9 different thicknesses of the outer edge 125, in 1 mm increments from 2mm to 10 mm .The thickness of the inner edge 26 will remain constant at 2 mm.

[109] Referring to Figures 21 and 36, the alignment plate 150 comprises a 15 mm thick plate shaped body having an upper edge 151, a lower edge 152, and opposing side edges 153. Parallel and aligned joint lines 154 are marked along the upper and lower surfaces of the alignment plate 150, the joint lines 154 extending between the side edges 153. Parallel and aligned quadriceps vector lines 155 are marked along the central section of the upper and lower surfaces of the alignment plate 150, the quadriceps vector lines 155 extending between the upper edge 151 and the lower edge 152. The joint lines 154 are perpendicular to the quadriceps vector lines 155. The joint lines 154 and quadriceps vector lines 155 are shown as coloured for illustration purposes only. In actual instruments, these lines 154 and 155 are grooves formed in the upper and lower surfaces..

[110] The alignment plate 150 comprises a central aperture 160 for receiving the vertical column 140. The central aperture 160 is formed at the intersection between the joint lines 154 and the quadriceps vector lines 155, and is elongated along the quadriceps vector lines 155 into an oval shape. The alignment plate 150 includes further oval secure pin slots 161 on opposite sides of the central aperture 160 (on each side of Q-ceps vector targeting lines). These allow the alignment plate 150 to be adjustable along the quadriceps vector lines 155 only when placed in the vertical column 140.

[111] The alignment plate 150 further comprises spaced alignment pin apertures 162 formed along the quadriceps vector lines 155. The embodiment shows two pin apertures 162 adjacent the upper edge 151 and three pin apertures 162 adjacent the lower edge 152.

[112] The alignment plate 150 further comprises spaced anchoring pin apertures 164, which includes six apertures 164 adjacent the lower edge 152 at opposite sides of the quadriceps vector lines 155, and eight apertures 164 above the joint lines 154 at opposite sides of the quadriceps vector lines 155. The apertures 164 adjacent the side edges 153 are angled inwardly from the upper surface to the lower surface.

[113] The alignment plate 150 further comprises femur saw slots 166 and tibia saw slots 168a, 168b for a starter chisel. The femur saw slots 166 are formed 10 mm above and parallel to the joint lines 154, and extend from the side edges 153 towards the quadriceps vector lines 155. The femur saw slots 166 stop short of the central aperture 160. The tibia saw slots 168 are formed parallel to and below the joint lines 154, with the slot 168a at 10 mm from the joint lines 154 and the slot 168b at 12 mm from the joint lines 154. The tibia saw slots 168 are formed below the central aperture 160 with ends thereof spaced from the side edges 153.

[114] The alignment plate 150 further comprises two mount apertures 170 for parallel bars 202 of the AP cutting block 200. The mount apertures 170 are disposed slightly above the joint lines 154 and respectively adjacent the side edges 153. Four elastic ring retaining grooves 172 are formed in the side edges 153, two on each side, two above and two below the joint lines 154.

[115] Referring to Figures 16 to 18 and 38, the sagittal guide 180 is shown which comprises a rectangular block body 181 having an insertion pin 182 at a first end thereof, a first locator pin 184 at a mid-portion, and a length adjustable second locator pin 186 at the second end thereof. The pins 182, 184 and 186 extend from the lower surface 183 of the body 181, are parallel to each other, and are aligned along the longitudinal axis of the body 181. The locator pins 184 and 186 have pointed ends.

[116] The insertion pin 182 in the example is 44 mm long from the lower surface 183. The first locator pin 184 is 50 mm long from the lower surface 183 and is 30 mm away from the insertion pin 182. The second locator pin 186 is 20 mm away from the first locator pin 184.

[117] The second locator pin 186 has a threaded upper end 188 which is received in a threaded aperture of the body 181. The second locator pin 186 also has an adjustment knob 190 below the threaded upper end 188. When the adjustment knob 190 abuts against the lower surface 183, the second locator pin 186 is 50 mm long from the lower surface 183. Rotation of the second locator pin 186 relative to the body 181 effectively lengthens the second locator pin 186 and tilts the body 181. Every 1 mm space between the lower surface 183 and the adjustment knob 190 results in 2.73° of femoral component flexion in use.

[118] Referring to Figures 3 and 4, the AP cutting block 200 comprises a stabilising plate 202, AP cutting jig 204, and connector parallel bars 206 with upper end keys 208. Elastic rings 210 are used to enhance contact with the stabilising plate 202 to the alignment plate 150. The parallel bars 206 comprise threaded lower ends.

[119] Referring also to Figure 40, the stabilising plate 202 comprises a rectangular block body with apertures 211 adjacent its respective ends extending from the top to bottom surfaces thereof for the respective parallel bars 206. The apertures 211 are spaced for the parallel bars 206 which are to be inserted into the mount apertures 170 of the alignment plate 150. The stabilising plate 202 also includes apertures 212 which are angled for fastener pins extending from the front to rear surfaces thereof. The apertures 211 in the stabilising plate 202 for the parallel bars 206 are 5mm internal diameter (ID) with no tolerance for the parallel bars 206 which are also 5 mm outer diameter (OD). Forthis reason, the apertures 211 are traversed by slot to create a spring mechanism effect for the parallel bars 206 to be movable with controlled friction resistance and not wobble. The stabilising plate has two angled converging back to front apertures for pins. One of the surfaces is angled 30 relative to main body 202 to enable divergent anterior femur cut.

[120] Referring also to Figure 39, the AP cutting jig 204 comprises a block body with parallel bar insertion apertures 220 extending from a top surface thereof. The AP cutting jig 204 also includes angled apertures 222 extending from the front to rear surfaces thereof for alignment pins. The AP cutting jig 204 further includes saw slots 224 extending from the front to rear surfaces thereof, and extending inwardly from the side surfaces thereof. The saw slots are 6 mm from the base of the AP cutting jig 204. The apertures 220 extend through to the saw slots 224 to allow flush washing. The apertures 220 are threaded short of the saw slots 224 so that parallel bars 206 will not encroach on the saw slots.

[121] As shown in Figure 4, in use, the stabilising plate 202 is placed on top of the alignment plate 150, the AP cutting jig 204 is disposed below the alignment plate 150, with the parallel bars 206 extending though the respective aligned apertures in these components 202, 150 and 204. The lower ends of the parallel bars 206 are threaded into the AP cutting jig 204. The elastic rings 210 are looped around the parallel bars 206 and are received in the elastic ring retaining grooves 172 of the alignment plate 150. The elastic rings 210 maintain close contact of the stabilising plate 202 to the alignment plate 150 to ensure that the AP cutting jig 204 is square. Placed around the parallel bars 206, the rings 210 also provide additional friction when the bars 206 are moving. In this configuration, the AP block 204 can be moved up and down while remaining securely square with the alignment plate 150.

[122] Referring to Figures 3 and 35, the component size gauge 230 comprises a generally rectangular main body 232 with an extended arm 234. The extended arm is shaped to extend over the distal femur features. The main body 232 comprises a pin aperture 236 for an inserted red pin 167a and a fastener pin aperture 238 which is angled to prevent size gauge 230 to slide upwards during measurement There is additional aperture in 234 for fastener pin

240. The apertures 236, 238 and 240 are aligned along the longitudinal axis of the component size gauge 230.

[123] Referring to Figures 3 and 22, the tibia slope gauge 250 comprises a small block body 251 having two mount pins 252 extending from a lower surface thereof, and an angled guide rod 254 extending from a rear surface thereof. The mount pins 252 and guide rod 254 are perpendicular and are aligned along the longitudinal axis of the body 251. The guide rod 254 is angled downwardly at 7° relative to a line perpendicular to the rear surface.

[124] Referring to Figure 3, the systems includes gap spacers 260 which are rectangular blocks which has no apertures in it. The gap spacers 260 have concavities at each end on both surfaces for surgeons fingers to have better control in slippery environment. Gap spacers 260 also has semicircular recess in a back surface to make room for posterior cruciate ligament. The gap spacers 260 are provided in different thicknesses such as 11 mm, 12 mm, 22 mm and 23 mm.

[125] Referring to Figure 24, the tibia cut template 270 is shown which comprises a generally flat plate having two saw slots 272, alignment pin apertures 274 and anchoring pin apertures 276. The saw slots 272 are at a predetermined distance from the alignment pin apertures 274.

[126] METHOD

[127] In the strategy of approach of this invention, the longitudinal alignment is not the prerequisite or target but a product of debridement with removal of deformed parts of bone. Almost in all cases the alignment close to premorbid, or within norms for constitutional deviation, is achieved within soft tissues constrains and without bone cuts. In this invention, the focus of attention is not on achieving any particular alignment, but on reproducing achieved and accepted alignment.

[128] In TKR surgery, some bone needs to be removed to make space for the prosthesis. To reproduce the alignment, the invented instruments of the present invention with optical targeting enable a surgeon to perform appropriate bone cuts with accuracy exceeding current technology and techniques (Fig. 23a).

[129] The present invention identifies the three most important elements in TKR which determine the optimal biomechanics and functional outcome.

1. Joint line.

2. Patella tracking in line with quadriceps vector (femoral component rotation).

3. Preservation of soft tissues

[130] The invention offers novel solutions in the METHOD which is surgical technique and in the DEVICE which is a set of instruments.

[131] THE SURGICAL TECHNIQUE AND INSTRUMENTS OF INVENTION ARE USED AS FOLLOWS:

[132] The patient is in supine position with (Electrical Muscle Stimulation) EMS pads placed on proximal anterior and lateral surface of the femur under the drapes. Bulky drapes are avoided so longitudinal alignment in coronal plane can be visually assessed. Joint is exposed through medial para- patellar (preferably subvastus) approach with anterior metaphysis of the femur accessible. In valgus knee generous lateral release of patella is necessary. In severe valgus extra articular complete release of ilio-tibial band should be done.

[133] After debridement, the alignment is restored. In this, referring to Figure 5, step one of core elements of the METHOD is introduced. The intercondylar notch 310 of the femur 300 is extended anteriorly by removing some bone in the form of a right angled channel 310 not less than 10 mm deep. The width of the channel 310 is equal to the base of the tibia spine 320.

[134] Referring to Figures 6 to 9, after thorough debridement of the joint the smallest 2 mm restoring spacer 120 is inserted in the less diseased compartment - medial or lateral. With it in place, knee longitudinal alignment is corrected to see the degree to which the more diseased compartment opens. At this stage, the highest (stretching) restoring spacer 120 is chosen for the more diseased compartment. Next, both spacers (2mm high and chosen stretching spacer 120 are fitted on the carrier 130 and as a pair they are forced into the extended knee joint making sure they are engaged in squared intercondylar notch.

[135] Figure 6 then shows how the restoring spacers 120 fit to the distal femur 300 and extended anteriorly inter-condylar notch 310. The curved extensions 127 of the restoring spacers 120 engage against the notch 310 preventing the restoring spacers 120 from moving sideways and rotating.

[136] Figure 7 shows how the restoring spacers 120 fit to proximal tibia 315. The curved internal edges of the extensions 127 of the restoring spacers 120 splint the tibia spine 320, and when engaged with the inter-condylar notch 310, prevent the restoring spacers from moving sideways and rotating.

[137] Figure 8 and 9 shows the restoring spacers 120 in place with the resulting stretch of the joint in correct longitudinal alignment with tibia translation and mal-rotation simultaneously corrected.

a. The flat lower surfaces 123 of the restoring spacers 120 engage the plateaus 322 and 324 and the angled upper surfaces 124 engage the condyles 312 and

314. The curved extensions 127 engage/splint opposing sides of the tibial spine 320 and are received into the cut intercondylar notch 310.

[138] This restores and corrects the intra-articular relationship between the femur and tibia via the inter-condylar notch and tibia spine. The spacers 120 stretch the joint in accepted alignment, they also splint the tibia spine and force it to align with the extended inter-condylar notch. With this, the tibia translation and mal-rotation is simultaneously corrected.

[139] The restoring assembly 110 functions as follows: a) Maintaining longitudinal alignment between the femur and tibia, b) Stretching the joint capsule and maintaining ligaments tension in extension, c) Correcting tibia translation relative to the femur, and correcting tibia mal rotation relative to the femur.

[140] In this step, (optional) AP X-ray can be done to confirm and document the longitudinal alignment between the femur and tibia.

[141] Referring to Figure 10. in the next step, a patella tracking mark (femoral component rotation) is required to be identified. For this, a perpendicular pin 330 is inserted in the functional centre of the patella 340.

[142] Referring to Figure 11, after temporary closure of the medial para- patellar exposure with 2 or 3 stitches, the knee in correct alignment and stretched by the restoring assembly 110 which also corrects tibia translation and mal-rotation, is flexed to 25° to 30°. The quadriceps muscle is then contracted by electrical muscle stimulation (EMS), which causes the patella to self-align with the line of pull of the quadriceps muscle (quadriceps vector). While the quadriceps muscle is still contracted, the pin 330 is driven into the femur 300 then removed leaving a mark 350 for patella tracking (see Figure 12). This mark 350 becomes one of three reference parameters and a key for optimal femoral component rotation.

[143] Figure 13 shows the first step in the process of linking of the restoring spacers 120 with the alignment plate 150. This link is the vertical column 140 which is attached to the carrier 130 of the restoring spacers. The hook connector 144 of the vertical column 140 is inserted into the carrier 130, with the threaded rod body 142 extending generally upwardly.

[144] Figure 14 shows the vertical column 140 in process to be attached and when in the vertical position, the column 140 can be adjusted sideways via the carrier 130 to be in line with patella tracking mark 350.

[145] Referring to Figure 15, the threaded rod body 142 is then aligned with the patella tracking mark 350 which moves the carrier 130 between the spacers 120. This positions the vertical column 140 ready for the alignment plate 150 to be attached to it.

[146] Referring to Figures 17 and 18, the length adjustable second locator pin 186 of the sagittal guide 180 is adjusted to the angle required for femoral component inclination, and the sagittal guide 180 is attached to the alignment plate by the insertion pin 182 being inserted into the first alignment pin aperture 162 of the alignment plate 150. The sagittal guide functions are: a) Prevention of placement of femoral component in extension and uncontrolled notching. b) Fine adjustment of femoral component flexion (inclination) from 0° to 100 angle and beyond.

[147] Referring to Figure 16, in the next step the alignment plate 150 (with the sagittal guide 180) is attached (but not fixed) to the restoring assembly 110 by inserting the threaded rod body 142 of the vertical column 140 into the central aperture 160. (Fig 16) The Alignment plate 150 is made of transparent material (Polycarbonate). On both surfaces it has superimposed lines in longitudinal and transverse directions (joint lines 154 and quadriceps vector lines 155). Lines 154 and 155 serve as optical targeting devices. Position of the plate 150 is accurate when lines 154 and 155 are superimposed on each other and on the targets. The targets are the quadriceps vector with patella tracking mark 350 in the longitudinal direction and the joint line (Figure 19) in the transverse direction (Fig 20 and 21).

[148] First -Sagittal Guide 180 calibrated to required reference parameter (femoral component inclination) is attached to Alignment Plate 150 by inserting 182 pin of the Guide 180 into most proximal 162 aperture in the Plate 150.

[149] Second- The Q-ceps vector is made on target by aligning the Q-ceps vector lines 155 with Patella Tracking Mark 350. This position of Alignment Plate 150 is secured with two pins 163 inserted in the middle of longitudinal slots 161. Q-ceps vector and femoral component rotation parameter is identified and secured. (Fig. 20, 21, 21a and 36).

[150] Third- With pins 163 introduced in slots 161 and calibrated Sagittal Guide 180 attached the only movement of Alignment Plate 150 possible is to slide it proximally or distally (as indicated by arrow on Fig. 21a) for targeting third reference parameter joint line 380. This movement is alongside of pins 163 in the slots 161 and alongside Vertical Column 140 in central aperture 160. When in target the third reference parameter, the joint line, is identified and in coordination with femoral component inclination and rotation.

[151] Figure 19 shows the joint line 380 in yellow. The joint line 380 must be identified while the restoring spacers 120 are in place. The joint line 380 is equidistant to bone cuts to be made. The joint line 380 is equidistant to bones of tibia and femur. The joint line 380 is not parallel to the carrier, although depending on longitudinal alignment may appear to be so.

[152] Figure 20 shows the starting point in optical targeting. The targets are two drawn blue lines. The transverse blue line represents the joint line 380 and longitudinal blue line represents quadriceps vector with the patella tracking mark 350.

[153] Figure 21a shows the Alignment Plate 150 with pins 163 in slots 161 to show that the alignment plate 150 is fixed in target to Q-ceps vector (patella tracking mark 350). When sagittal guide is attached, the Alignment Plate 150 can only be moved proximally or distally. This movement is needed for targeting the joint line 380. All three reference parameters can be coordinated attending to only one at the time. First - femoral component inclination. Second-Q-ceps vector (rotation of femoral component) and last to get the joint line in target by moving the Alignment Plate 150 proximally or distally (the only movement possible) with Sagittal Guide 180 as a handle in the last step of targeting process, the alignment plate 150, with sagittal guide 180 attached, is moved proximally and distally until it is in target with the joint line 380. When this is achieved, all three reference parameters:

D Femoral component inclination

D Quadriceps vector (patella tracking mark)

L Joint line

[154] are coordinated and, referring to Figure 22, the alignment plate 150 is pinned first to the femur 300 via pins inserted into the anchoring pin apertures 164 (above the joint lines 154). Next, the tibia slope gauge 250 is attached in distal apertures 162 in the alignment plate 150. After the slope is determined with the knee flexed to an angle required for tibia posterior slope, pins are inserted in the tibia through apertures 164 (below the joint lines 150). The tibia slope gauge 250 is removed to make room in apertures 162 for red pins 167 - two 167b in tibia and one 167a in femur are inserted in line with quadriceps vector through the alignment pin aperture 162.

[155] Figure 23 shows the stage when critical distal femur and tibia cuts are done using the femur saw slots 166 and the tibia saw slots 168. Figure 23a shows a starter chisel engaged in bone in tangential orientation. The chisel fits snugly in the saw slot 166 of the alignment plate 150 and starts the bone cut in the intended direction preventing the saw from veering away from hard bone. The distance between the cuts is 22 mm. Because of presence of important blood vessels and nerves behind the knee joint, the cuts are done as deep as it is safe. The image also shows three red pins in line with quadriceps vector introduced - one in femur and two in tibia.

[156] Figure 24 shows the stage where distal femur and tibia cuts are completed using the final tibial cut jig 270. These cuts are completed with the knee in flexion.

[157] Referring to Figure 25, after critical femur and tibia cuts are done, the pins are removed from tibia and knee flexed. Two (red) pins 167b which are in line with quadriceps vector are re-inserted in the tibia. With knee flexed and with AP cutting block assembly 200 (Fig. 4) attached to the alignment plate 150, the third critical cut of posterior condyles is done in two stages: initial condyles cut and final condyles cut.

[158] Figure 26 shows positioning of the AP cutting block 204 for initial condyles cut. The base of the block 204 is level with more protruding condyle 314 or 314 and cuts of both condyles 312 and 314 are done through the saw slots 224 which are 6 mm above the base.

[159] Figure 27 shows side views of the completed initial condyles cut. The purpose of initial cut is to create a flat surface 470 parallel with the alignment plate 150.

[160]

[161] Figure 28 shows the first step in the final condyles cut. The knee is in flexion and needs to be stretched as it was stretched by restoring spacers in extension. For this, the stretching spacer (gap spacer 260) is placed between the flat surface 470 on condyles and the flat surface on tibia. The largest possible spacer 260 is chosen so soft tissues and ligaments around the joint are stretched.

[162] The next stage in final condyles cut (Fig. 28, 29, 30 and 31) which is done with reference to the joint line 380 in flexion so amount of bone removed is equivalent to prosthetic condyles thickness so the appropriate size of the final gap spacer 260f for final cut must be chosen. The final spacer height is chosen by applying formula: prosthesis condyles height in mm + 6. Once the final spacer 260f is chosen, the final spacer 260f is put on the flat tibia surface in front of the stretching spacer 260. The AP cutting block 204 is dropped down to rest on the final spacer 260f.

[163] Figure 30 shows third and last step in the final condyles cut. Third, the AP cutting jig is pined to femur with two pins and posterior condyles cuts are made through saw slots in AP cutting jig but before cuts are made the stretching and final spacers are removed to prevent the saw blade jamming under pressure from stretching spacer. (Fig 30)

[164] Figures 31 and 32 show the knee joint after the three critical bone cuts are done. Note that the red pins in femur and tibia are retained.

[165] Figure 33 shows knee in extension after the cuts are completed. The 22mm spacer keeps the knee stretched and the supporting instrument (tibia position gauge 205) align all red pins in the same plane maintaining the knee joint in correct alignment.

[166] Figure 34 shows that flexion and extension gaps are equal when condyles of prosthesis are of standard 10 mm.

[167] Figure 35 shows a formula for choosing femoral component size. The supporting instrument (component size gauge 230) is slid over the red pin in the femur and secured with two more pins. The reference for component size is posterior condyles cut.

[168] Fig 35a Show the AP cutting Block and Stabilising Plate assembly for anterior parallel anterior femur cut. Rotating Stabilising Plate 180° in transverse plane will enable to perform 3° diverging anterior femur cut.

[169] These three: distal and posterior femur and tibia critical bones cuts (Fig31 and 32) conclude the invention's objective and prosthesis seated on those cuts will function in optimal biomechanics being in conformity with longitudinal alignment, quadriceps vector and soft tissues. (Fig 34). The final preparation of cut surfaces for receiving prosthetic components is done with instruments from whatever TKR system is in use. The (red) pins in tibia and femur, which were inserted in line with quadriceps vector, remain in situ and are used as reference for positioning of femoral and tibial components of system in use. All red pins must remain in the same plane. (Fig. 33). Referring to red pins in tibia prevents placing tibial component in translation or mal-rotation. Referring to red pin in femur the medialisation or lateralisation of femoral component is prevented.

[170] The size of femoral component is determined in reference to posterior condyles cut. The instrument "Component Size Gauge" (Fig 3) provides for femoral component size determination. (Fig.35). Should appropriate size not be available, the component of one size smaller (NEVER BIGGER) should be used. In case of difficulty in anterior femur cut with use of instruments from TKR system in use, the AP cutting jig with stabilising plate attached provides for accurate anterior femur cut for both parallel and diverging designs of femoral components. (Fig 35a) The invention provides this option in addition to its main objective.

[171] With regard to METHOD (Surgical Technique) three novel (core) elements are introduced:

[172] 1. UTILIZATION OF INTERCONDYLAR NOTCH AND TIBIA SPINE FOR RESTORATION OF CORRECT RELATIONSHIP BETWEEN FEMUR AND TIBIA

[173] The Alignment plate 150 serves the following functions:

a) It is a rigid external fixator making the knee joint stable during bone cutting process.

b) It identifies joint line level and direction.

c) When aligned with patella tracking mark it determines femoral component rotation by identifying plane for posterior condyles cut.

d) It is a cutting jig for critical distal femur cut (femur saw slots 166).

e) It is a cutting jig for critical tibia cut including required posterior tibia slope (tibia saw slots 168).

f) It coordinates planes for all three reference parameters. (joint line, patella tracking mark and femoral component inclination).

[174] In an arthritic knee, some degree of tibia translation and mal-rotation is always present.

[175] The intercondylar notch is extended anteriorly by removing some bone. This allows insertion of restoring spacers. The spacers stretch joint capsule and ligaments while maintaining achieved alignment. The translation and mal-rotation of tibia is simultaneously corrected by forcing splinted tibia spine to conform to extended intercondylar notch (Fig. 5, 6, 7, 8, and 9). This core element of METHOD is an invention in its own right. 5

[176] 2. ACCURATE, DYNAMIC IDENTIFICATION OF FEMORAL COMPONENT ROTATION CONFORMING TO LONGITUDINAL ALIGNMENT AND IN LINE WITH QUADRICEPS VECTOR UTILISING EMS (Electric Muscle Stimulation)

[177] In current teaching and methods the femoral component rotation is determined in reference to vague landmarks on distal femur (Whiteside lines, posterior reference, epicondylar axis) The femoral component rotation is of critical importance for optimal prosthesis biomechanics but none of these landmarks are suitable for its identification. The destination of quadriceps vector is optimally positioned tibial tuberosity and there is nothing on the distal femur suitable as reference.

[178] In this invention, a perpendicular pin is inserted in functional centre of patella. (Fig 10) The knee in correct alignment and stretched, is flexed to 250-300. (Fig 11). When quadriceps muscle is contracted by EMS, the patella self-align with line of pull of quadriceps muscle (quadriceps vector). While muscle is still contracted the pin is driven in to the femur leaving mark for patella tracking. (Fig 12) This mark becomes one of three reference parameters and a key for correct femoral component rotation. In a valgus knee, to get the mark accurate, a generous lateral release of the patella is necessary. This core element of METHOD is an invention in its own right.

[179] 3. SOFT TISSUES PRESERVATION. The soft tissues may appear abnormal because they were functioning for many years in direct vicinity to, and overlaying deformities. Their structural integrity however remains largely intact. When a conducive biomechanical environment is created, the soft tissues have capacity to restore their pre-morbid qualities. In invention method "soft tissues balancing", routinely performed in "golden standards" and involving invasive release of tissues, has no place.

[180] PROBLEMS WITH CURRENT TKR TECHNIQUES AND SOLUTIONS OFFERED BY DISCLOSED INVENTION

[181] A) Problem:- No regard given to individual's morphology. TKR is done with longitudinal alignment 3-5° of valgus preconceived as optimal, "one fits all" approach.

[182] Solution: In strategy of approach of this invention, no specific alignment is targeted. Restoration of acceptable longitudinal alignment is carried on within soft tissues constrains. In most cases it is possible to achieve the alignment close to premorbid or within constitutional deviations range. In healthy population only about 20% knees are aligned in conformity with "golden standards". The remaining 80% are aligned in a degree of varus or valgus and those are regarded as constitutional deviations. THERE IS NO SCIENTIFIC EVIDENCE THAT KNEES ALIGNED WITH CONSTITUTIONAL DEVIATIONS WILL END UP WITH TKR MORE LIKELY THAN THOSE ALIGNED AS IN "GOLDEN STANDARDS".

[183] B) Problem: Multiplicity of instruments and technologies including robotic, computer navigation and PSI which affects time of surgery, creates probability for compounding errors and makes a steep learning curve for surgeon and staff. Computer glitches are common as no methods are offered to identify critically important data like femoral component rotation or joint line to be fed into computer.

[184] Solution: In invention there is no need and no room for computer navigation or PSI. There is no need for costly and time consuming pre-operative planning. The reference parameters are identified and applied during surgery. Instead of using many instruments, running risk of compounding errors, fewer instruments are used but they perform multiple functions.

[185] Restoring assembly- performs 4 functions a) Maintaining longitudinal alignment b) Stretching the joint capsule and ligaments c) Correcting tibia translation d) Correcting tibia mal-rotation

[186] The sagittal guide - performs 2 functions. a) Prevention of extension of femoral component and uncontrolled notching. b) Fine adjustment of femoral component flexion from to 10 degrees angle and beyond.

[187] The alignment plate - performs 6 functions a) It is a rigid fixator making knee joint stable during bone cutting process. b) It identifies joint line level and direction. c) When aligned with patella tracking mark, it identifies the plane for critical posterior condyle cut which determine femoral component rotation. d) It is a cutting jig for critical distal femur cut. e) It is a cutting jig for critical tibia cut. f) It coordinates planes for all three reference parameters:

[188] The stabilising plate - performs four functions:

[189] a) Provides for square and stable connection of AP Cutting Block Assembly to Alignment Plate

[190] b) Provides for measured resistance in sliding movement of Cutting Block

[191] c) Serves as jig for parallel anterior femur cut.

[192] d) Serves as jig for divergent anterior femur cut.

[193] The above four instruments perform sixteen functions. In conventional instrumentation most of functions will require separate instrument.

[194] C) Problem: No method or instruments exist to accurately identify critically important biomechanics specific elements like femoral component rotation and joint line level and direction.

[195] Solution: In invention method the novel solution is introduced for direct and accurate identification of patella tracking in line with quadriceps vector. For this, perpendicular pin is inserted in functional centre of patella. The knee in corrected alignment and stretched, is flexed to 25° - 30°. The patella self-align with line of pull of quadriceps muscle (quadriceps vector) when muscle is stimulated to contract with EMS. The pin is then driven in to femur leaving the mark of patella tracking. This mark becomes one of three reference parameters and a key for correct femoral component rotation. In a valgus knee, to get this mark accurate, generous lateral release of patella is necessary. The joint line level and direction is identified utilising novel optical targeting on alignment plate.

[196] D) Problem: No method or instrument exist to restore correct intraarticular knee relationship in regard to tibia translation and tibia mal-rotation.

[197] Solution: In osteoarthritis of knee joint some degree of tibia translation and mal rotation is always present. Both must be corrected prior identification of quadriceps vector and patella tracking mark. In "golden standard" protocol for femoral component rotation the intraarticular femur-tibia mal-position is disregarded altogether. In disclosed invention the inter-condylar notch and tibia spine are utilised for restoration of correct relationship between femur and tibia in a knee joint. This is one of core elements of the method. The inter-condylar notch is extended anteriorly by removing some bone. This allows insertion of restoring spacers which maintain alignment of stretched joint and simultaneously corrects the translation and mal-rotation of tibia. (Figs. 5, 6, 7, 8 & 9)

[198] E) Problem: No reference parameters offered for alignment specific placement of prosthesis in conformity with soft tissues.

[199] Solution: In "golden standards" protocol no concept of biomechanically sound alignment and soft tissues specific TKR exists. Hence no reference parameters with regards to biomechanics of replaced knee are offered. In disclosed invention there are three, specified below, reference parameters clearly and precisely identified and applied during surgery.

[200] 1. Joint line 2. Patella tracking mark (quadriceps vector) 3. Femoral component position (inclination) in sagittal plane.

[201] F) Problem: TKR done according to "golden standards" require soft tissues balancing which is surgical interference with non-diseased tissues like joint capsule, ligaments and tendons. Collateral damage inflicted in tissues balancing process, irreversibly eliminates potential of affected tissues for restoration of their premorbid qualities.

[202] Solution: The TKR differs from other arthroplasties in that NO INSTANT GRATIFICATION must be expected in some cases. The primary pathology in knee OA is loss of structural integrity and degeneration of articular cartilage. This is followed by reactive deformation of the bones and their margins. This process may take decades before deformity reaches the stage when TKR is needed. The soft tissues overlying deformities have the ability to conform to those deformities and appear as stretched or contracted. There is no evidence however that their structural integrity is irreversibly affected. In fact the soft tissues may be the only not diseased component of the arthritic knee joint and as such have capacity to restore their premorbid qualities. Surgical intrusion eliminates soft tissues capacity to conform to new TKR situation. The "soft tissues balancing" is also a violation of the ethical principle "primum non nocere"(This is in Latin quotation from Hippocrates oath doctors swore at graduation) (FIRST DO NO HARM). In disclosed invention there is no place for "soft tissues balancing. Intact soft tissues contribute significantly to stability in sagittal plane. In some cases no instant functional gratification should be expected. Some degree of transient instability in coronal plane should be accepted even when temporary use of orthosis is indicated. Rarely additional surgery will be necessary but this likely be minor with no need for exposure of replaced joint.

[203] ALTERNATIVES COVERED BY DISCLOSED INVENTION:

[204] The instruments of the device are made of 3 different materials which are:

[205] POLYCARBONATE which is transparent to allow for optical targeting and also enables the surgeon to see behind the instrument. Any transparent material can be used instead, provided it is sterilisable and approved for TKR surgery. Non sterilisable material can also be used when supplied sterile for disposable use.

[206] STAINLESS STEEL - 316 SS is used for metal parts. Instead of SS, any rustproof metal alloy or even plastic composite which meets approval criteria for surgical use, can be utilized. In the disclosed device, the press fit or thread was used when the metal part needed to be attached to polycarbonate. A different solution can be utilized as long as it meets regulatory standards.

[207] ULTRA HIGH DENSITY POLYETHYLENE (UHDP) - in disclosed invention, the restoring spacers are machined from UHDP. However any other approved material and other technology which serves the required purpose can be used. An alternative would be use of adjustable height spacers with or without spreading instrument.

[208] GEOMETRICAL FORM AND DIMENSIONS: The detailed drawings of all core instruments with dimensions are shown in as Fig. 36, 37, 38, 39 and 4. They apply only to the currently disclosed form of invention. The external appearance, thickness of polycarbonate, shape, finish of parts can be changed according to manufacturer preference as long as their functional characteristic is maintained. The same applies to dimensions of parts, pins, pin holes and saw slots as well as their distribution. The invention as disclosed should be appropriate for common sizes of knee joints. For very small or very large knees, some components of instrumentation can be modified accordingly. The invention in its disclosed form and when modified can be used in conjunction with most existing TKR systems. The invention can be modified to fit systems that are different from those currently present.

[209] AUTOMATION: The alternative covered is automated or automation enhanced versions of the invention when methodology of the invention is re-used to determine reference points and cuts guides.

[210] ADVANTAGEOUS EFFECTS OF INVENTION

[211] 1. THE MAIN ADVANTAGE OFFERED BY INVENTION IS FULFILLING THE REQUIREMENTS FOR OPTIMAL BIOMECHANICS OF REPLACED KNEE JOINT. When original joint is replaced with prosthesis of different geometry, some biomechanical conflict is unavoidable. With use of invention it is possible to identify and eliminate the most important and frequent errors, hence biomechanical conflict is minimised. Invention's technique and instruments enable replacing the joint in conformity with alignment, forces exerted on functioning prosthesis and in conformity with soft tissues. This conformity is a prerequisite for optimal functional outcome and longevity of the prosthesis.

[212] 2. PRESERVATION OF SOFT TISSUES RESULTS IN A TRIPLE ADVANTAGE. Healthy articular capsule and ligaments play an important role in knee function. Soft tissues display ability of conforming to deformities resulting from OA. Because their structural integrity is largely preserved, they have the capacity for reversing this process and conform to a new situation of replaced knee joint. Albeit with passage of time. The second advantage is that not interfering surgically with soft tissues shortens the time of surgery, time of healing and eliminates potential for related complications. The third important advantage resulting from preservation of soft tissues is that intact soft tissues contribute significantly to stability of replaced joint in sagittal plane.

[213] 3. ACCURACY. There are at least two elements in TKR surgery that require absolute accuracy. These are identification of patella tracking mark (quadriceps vector) and level and direction of joint line. In conventional techniques no instruments or method exists to satisfy these requirements. This invention offers an accurate, dynamic method to identify projection of quadriceps vector so femoral component rotation can be placed in conformity with it. The joint line level and direction can be determined with the use of optical targeting on alignment plate. The bone cuts are done with accuracy exceeding any technology used for TKR. Each cut is started with special, snugly fitting in the saw slot chisel to ensure correct saw direction. (Fig 23a)

[214] 4. SAFETY AND TIME SAVING are a major advantage. The surgical technique and instruments are easy to understand and apply. Instead of using multiple instruments as in conventional TKR, only few but multifunctional instruments are used. Four multifunctional instrument serve sixteen functions. In conventional TKR instrumentation most of those functions will require separate instrument. This saves time and eliminates potential for compounding errors. The instruments are designed so that it is almost impossible to use them incorrectly. Being transparent and equipped with optical targeting capability minimises the danger of inaccuracy. Prevention of common errors is encompassed in method and instruments of invention. For example, when restoring assembly is applied for correction of alignment and stretching the joint, the tibia translation and mal-rotation is simultaneously corrected.

[215] 5. INEXPENSIVE. The instruments are not disposable, all except of elastic rings are re-usable. There is no need and no room for expensive and time consuming technologies like computer navigation or PSI (patient specific instruments) which function outside of surgeon's control and known for resultant glitches. With use of invention every step is under direct surgeon's control. In conventional TKR, because reference parameters are images based, costly investigations are routinely utilised for pre-operative planning which in PSI need to be done several weeks prior to surgery. In invention strategy of approach, the reference parameters (joint line, patella tracking mark and femoral component inclination) are identified and applied during surgery. Only standard X-ray is required to perform biomechanically sound TKR which can be done by any fully trained orthopaedic surgeon. With no need for sophisticated technologies and costly pre-op planning, the cost of TKR using the invention can be a fraction of the cost currently endured. The invention, being inexpensive, safe and easy to use, can be utilised in places and countries where TKR is not affordable at present.

[216] 6. LESS INVASIVE. Intraoperative and post-operative complications are directly related to surgery time and magnitude of surgical insult. With use of invention the TKR can be done in a shorter time. The surgical insult is significantly smaller because no surgery is done on soft tissues. In most TKR systems opening of medullary canals in femur and tibia are necessary, which is associated with the number of complications and side effects. The invention surgical technique does not require invading internal compartments of femur and tibia. Medullary canals are not opened.

[217] 7. THE INVENTION IS UNIVERSAL. The universality of the invention is that it can be used in conjunction with almost all TKR system on the market. It is achieved by replacing some instruments from the TKR system in use, with instruments from invention. This will ensure that TKR is done in conformity with muscles action and in conformity with soft tissues. The three critical cuts of bones are done with invention's instruments which concludes their role. The procedure is completed utilising instruments from TKR system in use.

[218] 8. ELIMINATE THE FOLLOWING COMMON ERRORS

[219] a) No overcorrection of longitudinal alignment will occur. The alignment will be close to premorbid and always within range of constitutional deviation.

[220] b) No uncontrolled notching of femur will occurs.

[221] c) The replaced knee will never be too tight.

[222] d) The femoral component will never be oversized.

[223] e) Flexion and extension gaps will always be equal, or appropriate.

[224] f) Tibia mal-rotation and translation will be always corrected.

[225] Although a preferred embodiment of the present invention has been described, it will be apparent to skilled persons that modifications can be made to the embodiment shown.

Claims (37)

Claims The claims defining the invention are as follows:

1. A method for total knee replacement, the method including the steps of:

extending the intercondylar notch of the femur anteriorly by removing bone in the form of a right angled channel not less than 10 mm deep, the width of the channel being equal to the base of the tibia spine,

inserting a smallest 2 mm restoring spacer in the less diseased compartment between one of the facing medial condyle and medial plateau or between the facing lateral condyle and lateral plateau,

correcting knee longitudinal alignment to see the degree to which the more diseased compartment opens,

inserting the highest stretching restoring spacer for the more diseased compartment for the other of between the facing medial condyle and medial plateau or between the facing lateral condyle and lateral plateau

inserting a pin in the functional centre of the patella,

flexing the knee to 25° to 30°,

contracting the quadriceps muscle by electrical muscle stimulation which causes the patella to self-align with the line of pull of the quadriceps muscle,

while the quadriceps muscle is still contracted, driving the pin into the femur leaving a mark for patella tracking.

2. The method of claim 1 wherein the restoring spacers each comprise a flat lower surface which engage the plateaus and an angled upper surface which engage the condyles.

3. The method of claim 1 wherein the restoring spacers comprise inward curved extensions which splint opposing sides of the tibial spine and are received into the cut intercondylar notch.

4. The method of claim 1 including the step of connecting a vertical column to a carrier disposed between the restoring spacers, and aligning the vertical column with the patella tracking mark.

5. The method of claim 4 including the inserting the vertical column into a central aperture of an alignment plate, the alignment plate being made of transparent material and having on both upper and lower surfaces thereof superimposed lines quadriceps vector lines in longitudinal direction and joint lines in transverse direction, the lines serving as optical targeting devices, and wherein the central aperture is elongated along the quadriceps vector line.

6. The method of claim 5 including the step of positioning of the alignment plate such that the quadriceps vector lines and the joint lines are superimposed over each other, with the quadriceps vector lines aligned with the patella tracking mark in longitudinal direction and the joint lines are aligned with a knee joint line in transverse direction.

7. The method of claim 6 including the step securing the alignment plate via pins inserted in the middle of longitudinal pin slots of the alignment plate formed on either side of the central aperture and elongated in the same direction as the central aperture.

8. The method of claim 5 including the step of attaching a calibrated sagittal guide to the alignment plate, the sagittal guide comprising adjustable pins to engage the femur, wherein the pins are adjusted to the angle required for femoral component inclination.

9. The method of claim 8 including the step of moving the alignment plate with sagittal guide attached proximally and distally until the joint lines of the alignment plate are aligned with the target knee joint line.

10. The method of claim 6 including the step securing the alignment plate via pins inserted in the middle of longitudinal pin slots of the alignment plate formed on either side of the central aperture and elongated in the same direction as the central aperture.

11. The method of claim 5 including the step of attaching a calibrated sagittal guide to the alignment plate, the sagittal guide comprising adjustable pins to engage the femur, wherein the pins are adjusted to the angle required for femoral component inclination.

12. The method of claim 1 wherein a smallest 2 mm restoring spacer is firstly inserted in the less diseased medial or lateral compartment, knee longitudinal alignment is then corrected to see the degree to which the more diseased compartment opens, and the highest restoring spacer is chosen for the other more diseased compartment.

13. The method of claim 4 including the step of attaching a sagittal guide to an alignment plate, the sagittal guide adjusted to the angle required for femoral component inclination, the alignment plate with the sagittal guide being attached to the restoring assembly by inserting the vertical column into a longitudinal central aperture of the alignment plate, the alignment plate being made of transparent material and having on both upper and lower surfaces thereof superimposed lines in longitudinal and transverse directions which function as quadriceps vector lines and joint lines respectively.

14. The method of claim 14 including the step of aligning the quadriceps vector lines with the patella tracking mark and securing the alignment plate in position via pins inserted in longitudinal slots in the alignment plate parallel to the central aperture thereof to only allow movement of the alignment plate proximally or distally for targeting the joint line.

15. The method of claim 15 including the step of identifying the joint line which is equidistant to bone cuts to be made.

16. The method of claim 16 including the step of setting femoral component inclination with the sagittal guide and aligning the joint line in target by moving the alignment plate proximally or distally with sagittal guide as a handle.

17. The method of claim 17 including the step of pinning the alignment plate to the femur via pins inserted into femur anchoring pin apertures thereof, flexing the knee to an angle required for tibia posterior slope, pinning the alignment plate to the tibia via pins inserted in tibia pin apertures.

18. The method of claim 18 including the step of inserting marker pins in the tibia and the femur in pin apertures of the alignment plate aligned with the quadriceps vector lines.

19. The method of claim 19 including the step of performing critical distal femur and tibia cuts using femur saw slots and the tibia saw slots of the alignment plate, the distance between the cuts being 22 mm.

20. The method of claim 20 including the step of performing an initial condyles cut cuts of both condyles are done through an AP cutting block with the base of the block level with the more protruding condyle and the AP cutting block having saw slots which are 6 mm above the base.

21. The method of claim 21wherein the completed initial condyles creates a flat surface parallel with the alignment plate.

22. The method of claim 22 including the step of placing a stretching spacer between the flat surface on condyles and the flat surface on the tibia, wherein the largest possible spacer is chosen so soft tissues and ligaments around the joint are stretched.

23. The method of claim 23 including the step of placing a final spacer 260 on the flat tibia surface in front of the stretching spacer, wherein the size of the final spacer is chosen by applying the formula: prosthesis condyles height in mm + 6.

24. The method of claim 24 including the step of moving the AP cutting block down to rest on the final spacer, pinning the AP cutting jig to the femur and performing the final cut through the saw slots in the AP cutting block.

25. Apparatus for total knee replacement, the apparatus comprising: restoring spacers having a generally wedge shaped main portion with a flat lower surface and an upper surface which is angled downwardly relative to the lower surface from an outer edge towards an inside edge thereof.

26. The apparatus of claim 26 wherein the inside edge has a raised curved extension that extends upwardly.

27. The apparatus of claim 27 wherein the main portion has a cut therein extending from the outer edge towards the curved extension, the cut allowing the body to flex to adapt to deformity.

28. The apparatus of claim 27 comprising two restoring spacers which are mirror images of each other relative, wherein the curved extensions are facing but spaced from each other.

29. The apparatus of claim 29 further including a carrier having a central connector with connector rods respectively received in mount apertures of the respective spacers, the carrier having a vertical column.

30. Apparatus for total knee replacement, the apparatus comprising a transparent alignment plate having transversely extending parallel and aligned joint lines marked along the upper and lower surfaces thereof, and longitudinally extending parallel and aligned quadriceps vector lines marked along the central section of the upper and lower surfaces thereof.

31. The apparatus of claim 31 wherein the alignment plate comprises a central aperture for receiving the vertical column, the central aperture being formed at the intersection between the joint lines and the quadriceps vector lines, and is elongated along the quadriceps vector lines.

32. The apparatus of claim 32 wherein the alignment plate includes elongated secure pin slots on opposite sides of the central aperture which are parallel to the central aperture.

33. The apparatus of claim 33 wherein the alignment plate further comprises alignment pin apertures formed along the quadriceps vector lines.

34. The apparatus of claim 34 wherein the alignment plate further comprises spaced anchoring pin apertures.

35. The apparatus of claim 35 wherein the alignment plate further comprises femur saw slots and tibia saw slots, the femur saw slots being formed 10 mm above and parallel to the joint lines, and the tibia saw slots being formed parallel to and below the joint lines, with the tibia saw slot at 12 mm from the joint lines.

36. The apparatus of claim 35 wherein the alignment plate further comprises two mount apertures for parallel bars of an AP cutting block.

37. The apparatus of any one of claims 25 to 37, wherein the apparatus is transparent.