GB2101488A

GB2101488A - External fixation frames and fixing pins therefor

Info

Publication number: GB2101488A
Application number: GB08215658A
Authority: GB
Inventors: Shoukry Abdel-Masseih Rizk
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-06-03
Filing date: 1982-05-28
Publication date: 1983-01-19
Also published as: GB2101488B

Abstract

A fixation frame (12) and associated pins (22) for use in fracture surgery, are arranged so that the pins do not transfix the bone. The ends of the pins have a tip which is located in a previously drilled opening in the bone cortex, and a shoulder engages the bone outer wall to prevent penetration of the pin into the central bone tissue. The pins are secured in pin holders 20 which are also used to locate drill guides, the drill guides being used to accurately drill and form the pin openings. <IMAGE>

Description

SPECIFICATION External fixation frames and fixing pins therefor This invention relates to external fixation frames and their associated pins which are used in orthopaedic and fracture surgery.

At present most, if not all, external fixation frames use pins which transfix the bone and are thus invasive to the bone and soft tissues, thereby providing a potential source of infection and injury to muscles, vessels and nerves. Examples of this type of pin are those by Hoffman, Wagner, Anderson,Vidal and ICLH and the following references are relevant:~ 1. Anderson, R.: Surg. Gyne a Obst (1934) 58:639.

2. Charnley, J.: Compression Arthrodesis (1953), Livingstone, Edinburgh.

3. Hoffman, R.: in Congress Francais de Chirurgie (1939).

4. Hoffman, R.: in Acta Chir. Scand. (1954).

5. Mueller, M. E., Allgoewer, M. and Willenegger, H.: Manual of External Fixation (1970). Springer-Verlag, New York.

6. Vidal, J., Rabischang, P., Bonnel, F. and Adrey, J.: Montpeilier Chirurg. 16:52(1970).

7. Wagner, H.: Surgical Lenghtening or Shortening of the Femur and Tibia in "Progress in Orthopaedic Surgery" (1 977). Springer-Verlag, New York, Edited By N. Gschwend et al. Vol. 1.

8. External Fixation - The Current State of the Art. (1979) Edited by A. F. Brooker 8 C. C.

Edwards. Williams 8 Wilkins Co., Baltimore.

The present invention seeks to provide a fixation frame and associated pins in which the pins do not transfix the bone, and in which the drilling sites for the pins can be accurately located using the fixation frame and a variety of drill guides.

Accordingly, the present invention provides an external fixation frame for use in fracture surgery comprising a structure including a number of pin holders, each pin holder having a pin securable therein, each pin having a tip arranged to engage a bone, the tip having a shoulder which prevents the tip penetrating the bone to a depth greater than its length.

The structure can comprise at least two variable width callipers, at least two variable length distraction/compression bars joining the callipers together adjacent to the ends of the bars, each calliper having a pair of oppositely arranged pin holders located adjacent to the ends of the callipers.

The bars can be attached to the callipers by ball and socket joints which can be clamped in position, the ball and socket joints being provided at the connections between the callipers and the bars.

The bars can each comprise a tube and a partly threaded rod which is located inside the tube and held in position by a nut captive on the open end of the tube.

Each calliper can be composed of two arms, each arm having a horizontal and a vertical part.

The horizontal parts of the two arms are held together by two clamps which are releasable to enable the width of the calliper to be varied. The vertical part of each arm ends in a pin holder which lies horizontal.

The pin holder also serves to hold drill guides so that the sites for the pin can be accurately formed.

The pin holders can have one or more clamping screws to hold the pins or drill guides against axial or rotational movement.

In another arrangement for use in fracture surgery of the pelvis, the fixation frame can comprise two fixed length bars, each bar having a number of the pin holders and associated pins, the bars being joined together by a cross bar and a compression device.

The pins can terminate in tips of various shapes, e.g. cylindrical, flat or fork-like. The size and shape of the tips are such as to leave a shoulder with a larger diameter than the tip.

The present invention will now be more particularly described with reference to the accompanying drawings in which: Fig. 1 is a perspective view of one form of fixation frame according to the present invention.

Fig. 2 is an end elevation of one of the callipers of the frame shown in Fig. 1 in position over the upper end of a tibia.

Fig. 3 a side elevation of one of the callipers of the frame shown in Fig. 1.

Fig. 4 is an exploded view of the ball and socket joint between the distraction/compression bars and the callipers of the frame in Fig. 1.

Fig. 5 shows three different types of drill guides for use with the fixation frame of Fig. 1 for accurate location of drill sites.

Fig. 6 s 7 show a trocar and an osteotome respectively for use with the drill guides shown in Fig. 5.

Fig. 8 (8a to 8e) shows five different types of pins for the frame shown in Fig. 1.

Fig. 9 shows a detail of the construction of the distraction/compression bars of the fixation frame of Fig. 1.

Fig. 10 shows the construction of part of the distraction/compression bar shown in Fig. 9.

Fig. 1 1 shows an alternative form of tube to that shown in Fig. 10.

Fig. 12 shows an alternative form of distraction/compression bar construction to that shown in Fig. 9.

Fig. 13 shows another part of the fixation frame to that shown in Fig. 1 to hold the fracture ends.

Fig. 14 shows one form of small fracture end calliper for use with the frame shown in Fig. 1 instead of the part shown in Fig. 13.

Fig. 1 5 is an alternative form of small fracture end calliper to that shown in Fig. 14.

Fig. 16 shows a compression device for use with the small fracture end callipers shown in Figs.

14 and 15.

Fig. 1 7 shows a compression bar for use with the callipers according to the present invention in knee arthrodesis.

Fig. 18 shows another form of calliper according to the present invention similar to that shown in Fig. 1 but having a ball and socket joint also at the junction between the horizontal and vertical parts of each calliper.

Fig. 19 shows an alternative form of joint between the horizontal and vertical parts of each calliper.

Fig. 20 shows a detail of the joint shown in Fig. 19.

Fig. 21, shows a form of fixation frame according to the present invention for use with the pelvis.

Fig. 22 shows a detail of the frame shown in Fig. 21.

Referring to the figures in Fig. 1 to 4 inclusive a fixation frame 10 comprises a pair of variable width callipers 12 joined together by a pair of variable length distraction/compression bars 14.

Each calliper comprises two portions 16 which are held together by clamps 18, and have at their free ends pin holders 20. The axes of the holders on each calliper are aligned with the holders facing each other. The holders 20 each contain a pin 22 which engage the cortex only of a bone 24 as shown in Fig. 2. Lock screws 26 and 28 are provided to prevent rotation and axial movement of the fixing pins. The distraction/compression bars 14 are joined to the callipers at each end by a ball and socket joint which comprises a socket 30 attached to the holder 20, a ball 32 attached to one end of the distraction/compression bar and a clamping collar 34 which holds the ball in the housing and clamps the joint in a desired position.

Fig. 5 shows three drill guides 58, 60 and 62, the drill guide 58 being used to direct drill bits for the pins shown in Figs. 8a and 8b, the guide 60 being used to direct drill bits for the pin shown in Fig. 8e and the guide 62 being used to direct drill bits for the pins shown in Figs. 8d and 8e.

Figs. 6 and 7 show a trocar 64 and an osteotome 66, the osteotome being used in connection with the drill guide 62 only.

Figs. 8a to Be show a number of fixing pins 22 which can be used with the fixation frame described. The most important feature of the pins is the provision of a tip with a shoulder to prevent the pin penetrating the bone deeper than the length of the tip.

In Figs. 8a and 8b the pin 22 has a cylindrical tip 50 and a shoulder 52, the only difference between the two being the diameter.

In Figs. 8c two cylindrical tips 50 are provided and the shoulder 52 is formed by the base of the pin shank.

The tips 50 are of different lengths to fit the slanting surface of a bone and penetrate the cortex only.

Each pin 22 has a hole 24 near the other end to enable the pin to be removed by the use of a slender rod.

In Fig. 8d the tip 50 is flat and the end of the tip is slanting also to fit the slanting surface of the bone. It thins to a linear edge like an osteotome.

The pin shown in Fig. Be is similar to that in Fig.

8d except that a square base is provided to enable a spanner to rotate the pin as desired before fixing it.

In the pins of Figs.8c and 8d and Be a shallow slot 56 on both sides is provided so that when the screw 26 is tightened the pin is incapable of movement or rotation.

Fig. 9 shows more clearly the construction of the distraction/compression bar 14. Each distraction/compression bar 14 has an outer tube 36 on which a captive nut 38 is rotatable and the captive nut engages a threaded rod 40 located inside the tube 36. One end of the rod 40 is threaded to screw into the ball of the ball joint whilst the end of the tube remote from the captive nut has a threaded portion to screw into the ball of another ball joint.

Fig. 10 shows the arrangement of the captive nut 38 in which the nut 38 has a slot 42 in which a flange 44 of the tube 36 is located. The rod 40 has two opposed flat surfaces 46 (in Fig. 4) which are engaged by pads 48 to prevent rotation of the rod inside the tube when captive nut 38 is turned, and so that the rod 40 should move outwards or inwards by turning the nut 38.

Fig, 1 The tube 36 in Fig. 9 has a pair of opposed grub screws 49 which in effect replace the pads 48 (of Fig. 10) and engage the flat surfaces on the rod to prevent rotation.

Fig. 12. An alternative form of distraction/compression bar in which rods 14a and 14b have free ends attached each to a ball or a ball and socket joint. The rod 14b is threaded and has a captive nut 1 4c held between two parts of a holder 14d clamped to the rod 14a. The other end of the rod 14b is attached to a slide 14e which can move along the rod 14a when the captive nut 1 4c is rotated.

The distraction/compression bar arrangements in Figs. 9, 10, 11 and 12 enable it to be altered in length so that its lengthening causes distraction of the fracture ends and its shortening causes compression of the fracture ends.

Fig.13 shows another part of the fixation frame of the invention for use when it is necessary to hold the fracture end and to force it into a satisfactory position. Similar components to those already described appear in this part and are given the same reference numbers. A horizontal bar 64 has a number of horizontal slots 66, and fixed to the bar are the limbs 74 of the pin holders 20 by bolt and nut through their slots 66. Each end of the bar 64 is fixed by a nut and bolt to a supporting bar 68 which rests at its lower end on the distraction/compression bar 14 by a clamp 70. A screw 72 tightens the clamps 70 onto the distraction/compression bar 14.

Figs. 14 and 15 show two simpler small forms of fracture end callipers which can be used instead of the arrangement shown in Fig.13.

In Fig. 14 the two limbs 74 of the pin holders 20 are both connected to a small bar 76 and there is no need for supporting bar 68 of Fig. 13.

In Fig.15 the limbs 74 are connected to each other directly without the use of bar 76. In the arrangements of Fig.14 and 15 a compression device (Fig.16) holds and compresses the corresponding limbs 74 on the opposite sides of the fracture.

Fig.16 compression device consists of a threaded rod 78 having a hook 82 at one end shaped to engage either the limb 74 or bar 76 of the callipers and a compression block 84 slidable on the rod 78, also shaped to capture the corresponding limb 74 on bar 76. The wing nut 80 pushes the compression block 84 to achieve compression. Clamping nuts 86 are provided to prevent any displacement of limbs 74 or bars 76 after compression has been applied.

Fig. 17 (in the last sheet of drawings) shows a compression bar for knee arthrodesis, the holding callipers are not shown for clarity, only the pins 22 show in section. A curved tip hook 88 hooks around one pin 22 and a straight threaded part 90 of the compression bar passes through a compression block 92, the lower lip 94 of which hooks around the other pin 22. A compression screw 96 is tightened and approximates the two pins nearer to each other and hence achieves compression.

Fig.18 shows a modified form of calliper 12 (of Fig. 1 and 2) In this arrangement the horizontal and vertical parts of the portions 1 6 are separate and joined together by a ball and socket joint 98.

This enables each vertical limb, pin holder and pin to be manipulated independently of those of the opposite side.

Fig.19 and 20 show another alternative of ball joints, the ball joint 104. Each calliper 12 has two vertical portions 100 and a horizontal bar 102, the portions 100 being joined in the bar 102 by ball joints 104 details of which are shown in Fig. 20.

At each joint 104 the bar 102 is located between the two holders of a split ball 106 which is clamped between two plates 108 by a clamp 110. The calliper can be adjusted for width by unlocking the clamps 110 to allow the vertical portions 100 to be moved to the desired position.

Figs. 21 and 22 is an arrangement of the fixation frame to suit a pelvic fracture. It comprises two fixed length side bars 112 alongside the iliac crest. The side bars 112 are joined together by a distraction/compression bar 14 and a bar 114 at their free ends remote from the pelvis. The part of the side bar 112 alongside the iliac crest has holes 11 6 for the passage of the long horizontal pins of the small callipers (Fig. 22) which are like those of Fig. 1 5 except that the horizontal pin 22 is long, the extra length is threaded and passes through one of the holes 11 6 of the side bar 112. Two nuts 118 are engaged on the threaded part of pin 22 one on each side of the side bar 112.

Method of Application of the Frame at Different Sites The fixation frame, its pins and different parts described above can be used for a variety of fractures of the limbs and the pelvis.

When the frame is mounted for fractures of the tibia the main parts used are those of Fig. 1. The fractured leg is kept horizontal and raised on supports on the table. A trocar (Fig. 6) is introduced and held in each pin holder 20 of the callipers 12 and fixed in position by the side set screw 26. The calliper clamps 18 are loosened and the calliper is opened and brought over the leg to bring the trocar tips over the optimum sites of traction for the upper end of the tibia. Two adequate deep incisions are made over these sites down to the bone and the calliper 12 is closed pushing the trocar and the cone shaped end of the holder 20 through the incision to grip the bone.

The clamps 18 are then tightened. On one side the trocar is removed and replaced by a suitable drill guide for the pin to be used. For the pin of Fig. 8e the drill guide 60 is introduced and clamped by screw 26. A suitable diameter drill bit is used to drill the bone cortex through the lower channel of the drill guide. Then the drill bit is replaced by a shorter one to be left temporarily in place and fixed by the screw 28. The pressure of this shorter drill bit fixed and engaging the bone cortex steadies the holder 20 and guide 60 while drilling the cortex through the upper channel of the drill guide 60. When both holes in the cortex have been drilled the drill bits and guide are removed and the pin 8c is introduced, aided by gentle hammering. The pin is secured in position by the screws 26 and 28, the screw 26 engaging one of the slots 56 in the pin.The process is repeated on the opposite side of the leg and calliper. After introducing the second pin on the opposite side of the leg the clamps 18 and the screws 26 and 28 are loosened, the calliper is opened to the desired extent while an assistant holds the pins in place; then the clamps 18 and screws 26 and 28 are tightened again. The process is repeated on the other end of the bone using a flat tip pin as shown in Fig. 8d on the medial side and round tip pin as shown in Fig. 8a on the lateral side. For the pin of Fig. 8d the drill guide 62 is used with the channel facing upwards i.e. anterior in relation to the limb.

The drilling is carried out twice, once in the lower part of the channel and once in the upper part.

When the drill bits are removed a suitable size osteotome (Fig. 7) is introduced into the drill guide to break the bridge of bone between the two drill holes in the cortex and then removed. The path for the pin 8d is now prepared, the drill guide 62 is removed and the pin can be easily introduced through the pin holder 20 and fixed by screws 26 and 28.

The distraction/compression bars 14 are fitted to the callipers 12 by the ball and socket joints and their length adjusted by the captive nuts 38 to provide distraction until the fracture ends can be manipulated into a good position then the captive nuts 38 are turned to shorten the distraction/compression bar 14 to achieve some compression. During manipulation the ball joints are loose and the callipers can be manipulated to move the fracture end in two planes: the horizontal and coronal planes to correct rhedial or lateral angulation and to correct rotation of the bone.When the pins of Fig. 8c, 8d and 8e are used manipulation of the calliper 12 in three planes is possible, so, manipulation in the sagittal plane can correct also anterior or posterior angulation, as this will bring rotation of the pins which in turn move the fracture ends anteriorly or posteriorly. When a satisfactory position of the fracture is achieved as checked by x-ray the four ball and socket joints are locked by tightening their clamping collars 34. Sometimes when the callipers 12 alone cannot achieve a satisfactory reduction then the small fracture end callipers of Fig. 14 and 15 are used on the arrangement of Fig. 13.

Smaller size pins 22 are used, of type 8b, they are introduced to hold the bone near the fracture at the sites shown in Figs. 13, 14, 1 5. The pins 22 are fixed in their pin holders 20 by screws 28 and their limbs 74 are fixed to the corresponding bars by nuts and bolts through the slots 66, or they are fixed directly to each other (Fig.15). They get a firm hold of the fracture ends and one can move them as desired to force the fracture ends in satisfactory position. Then the horizontal bars 64 are fixed at both ends to the supporting bars 68 which in turn are fixed to the distraction/compression bars 14 by clamps 70.

When using the small callipers of Figs. 14 or 15, after forcing the fracture ends into a satisfactory position each two limbs 74, or small bars 76, on opposite sides of the fracture are held together with the compression device of Fig.16.

The fixation frame of the invention can be used in combination with a cast and the pins are incorporated in the cast, the frame and pins to be removed when the fracture is no more liable to redisplace. In cases of open fractures with much loss of soft tissues or skin when a cast is not applicable the frame can maintain the reduction and immobilise the fracture on its own.

When mounting the frame for fractures of the shaft of femur or the shaft of humerus the parts of the frame of Fig. 1 are used but it is technically more difficult to get access to the optimum sites of traction of these bones than in case of the tibia.

When mounting the frame for fractures of the forearm bone (the radius and ulna) the form of callipers of Fig. 18 or 19 are used, the ball joints 98 (Fig. 18) or the ball joints 104 (Fig.19) make it possible for each vertical limb with its pin holder and pin on one side to manipulate the bone they hold independently of the other bone. The cone can be manipulated in three planes if small flat pins 8d are used.

Because of the great difference between the length of horizontal portions of callipers (Fig.18) at the start of fixation and the length necessary of the horizontal portions at the end of fixation, a longer suitable pair of horizontal portions may be needed. The form of ball joint 104 and horizontal bar 102 of Fig.19 makes this change unnecessary as long as bar 102 is long enough. In the forearm, the frame with or without a cast follows the same principles of the leg frame described previously.

When mounting the frame of the invention for a pelvic fracture (Figs. 21 and 22) the small callipers of Fig. 22 are applied to hold the iliac crest at multiple sites, at least two callipers of Fig. 22 are applied in front of the fracture and only one small calliper of Fig. 22 is applied behind the fracture.

The side bar 1 is made to engage the long horizontal pins 22 of the small callipers of Fig. 22.

Three corresponding small callipers of Fig. 22 are applied on the sound side, and the other side bar 112 is applied to hold them. The distraction/compression bar 14 and the connecting bar 114 are applied to join the two side bars 112. Compression is applied by the bar 14.

To reduce the fracture the compression should only be applied on the pelvic bone in front of the fracture. For this purpose the two long pins 22 in front of the fracture should bear the compression and not the long pin 22 behind the fracture.

To achieve that the inner nuts 114 of the long pins in front of the fracture should lie close to the side bar 98 to receive its compression and transmit it to its pin. Whereas the inner nut 114 of the long pin behind the fracture should be turned away from the bar towards the pin holder to escape compression. After application of adequate compression by the distraction/compression bar 14 and reducing the pelvic fracture (with x-ray check) the small calliper of Fig. 22 behind the fracture is held fixed to the small calliper of Fig. 22 in front of the fracture by two compression devices (Fig.16). When the fracture proves stable most of the frame of Fig. 21 and 22 can be dismantled leaving only two small callipers of Fig.

22 one in front and one behind the fracture, to stay till the fracture is united. This is an advantage over other frames where all the big frame has to stay till the fracture is united.

Miniature parts of the frame can be applied around the wrist and ankle and small bones of the hands and feet to reduce their fractures.

Claims

1. An external fixation frame for use in fracture surgery comprising on structure including a number of pin holders, each pin holder having a pin securable therein, each pin having a tip arranged to engage a bone, the tip having a shoulder which prevents the tip penetrating the bone to a depth greater than its length.

2. A fixation frame as claimed in claim 1 in which at least one of the pins has a cylindrical tip and shoulder.

3. A fixation frame as claimed in claim 1 in which at least one of the pins has two cylindrical tips of differing lengths, and a cylindrical shoulder.

4. A fixation frame as claimed in claim 1 in which the tip is flat and has an angled end.

5. A fixation frame as claimed in any one of the preceding claims in which each pin has at least one axial slot which can be engaged by a locking screw on the pin holders to prevent movement of the pin.

6. A fixation frame as claimed in any one of the preceding claims in which the pin holders have clamping means to prevent axial and rotational movement of the pins.

7. A fixation frame as claimed in claim 1 in which the structure comprises at least two variable length distraction/compression bars, at least two variable width callipers joining the bars together, each calliper having a pair of oppositely arranged pin holders located adjacent to the ends of the callipers, each pin holder having a pin securable therein.

8. A fixation frame as claimed in claim 7 in which the bars are attached to the callipers by means of ball and socket joints.

9. A fixation frame as claimed in claim 7 or claim 8 in which the bars comprise a tube having a captive nut at one end, and a threaded bar located inside the tube and engaging the captive nut, the free ends of the rod and tube being attached to respective balls of the ball and socket joints.

10. A fixation frame as claimed in claim 7 in which each calliper has two portions and clamping means to hold the portions together, each portion having a horizontal and a vertical part.

11. A fixation frame as claimed in claim 10 in which the clamping means are attached to the horizontal parts of one or both portions.

12. A fixation frame as claimed in claim 10 in which a pin holder is attached to the lower end of each vertical part of the two calliper portions.

13. A fixation frame as claimed in claim 10 in which the two parts of each portion are separate and joined together by a ball and socket joint.

14. A fixation frame as claimed in claim 1 in which each calliper comprises a horizontal bar and two vertical portions, the portions being joined to the bar by ball and socket joints.

15. A fixation frame as claimed in claim 1 or claim 7 including a pair of fracture end callipers held together by at least one compression device.

16. A fixation frame as claimed in claim 1 5 in which each fracture end calliper comprises two pin holders and associated pins, the pin holders being attached together by mounting means.

17. A fixation frame as claimed in claim 16 in which the mounting means comprises a limb on each pin holder, the limbs being secured together.

1 8. A fixation frame as claimed in claim 1 6 in which the mounting means comprises an arm on each pin holder, and a beam to which the pin holder arms are attached.

19. A fixation drame as claimed in claim 1 5 in which the compression device comprises a hooked rod arranged to engage part of one of the fracture end callipers and a compression block arranged to engage a part of the other one of the fracture end callipers, and means to move the hooked rod relative to the compression block.

20. A fixation frame as claimed in claim 1 particularly for use in fracture surgery of the pelvis in which the structure comprises two bars, attachment means to join the bars together, the attachment means including a compression device, and each bar having a number of the pin holders and associated pins.

21. A fixation frame as claimed in claim 20 in which the bars are of fixed length and the attachment means includes a cross bar connecting together the ends of the bars remote from the fracture site.

22. A fixation frame as claimed in claim 20 in which each pin holder has an auxiliary pin holder and associated pin, each pin holder and its associated pin lying substantially in the same plane, the pin holders being structurally attached together.

23. A fixation frame as claimed in claim 22 in which the pin holder and associated auxiliary pin holder have respective arms which are attached together.

24. A fixation frame and associated pins constructed and arranged for use and operation substantially as herein described, and with reference to the accompanying drawings.