IE83815B1 - Surgical instrumentation - Google Patents

Description

SURGICAL INSTRUMENTATION This invention relates to instrumentation for aligning a surgical tool and primarily although not exclusively relates to instrumentation for use in resecting the distal end of a humerus.

When implanting a total joint prosthesis, it is necessary to resect the ends of the bones which meet at the joint. In the past, resecting has been carried out by eye and relied almost exclusively on the skill of the surgeon. More recently, instrumentation has been produced for resecting the fiemur or tibia for installation of a total knee prosthesis. Such instrumentation comprises a jig to which is fitted a rod. The rod is inserted into a bore drilled into the intramedullary canal and provides alignment of the jig with the longitudinal axis of the bone. One or more openings are provided in the jig for insertion of a drill bit or saw blade. Although this conventional instrumentation provides reasonable alignment with the longitudinal axis of the bone, it does not provide rotational alignment of the jig about the longitudinal axis of the bone, so that the surgeon must have considerable skill and experience before he can carry out an accurate bone resection.

According to the present invention there is provided instrumentation for aligning a surgical tool during the resecting of an end of a bone, the instrumentation comprising a tool guide in which is provided an opening for receiving and guiding a portion of the surgical tool and a pair of clamping members which are adapted to engage opposite sides of the bone, at least one of the clamping members being provided with a bone engaging element which is adapted to engage a particular region of the bone and has a bone engaging surface which has a known orientation relative to the opening in the tool guide, such that when the clamping elements are tightened onto the bone, the opening in the tool guide is at a predetermined rotational orientation with respect to the longitudinal axis of the bone.

Preferably the tool guide is provided with a bone engaging surface which engages the end of the bone during a resecting operation.

Preferably the distance between the bone engaging surface of the bone engaging element and the bone engaging surface of the tool guide is set prior to attachment of the instrumentation to the bone. This distance may be fixed at the time the instrumentation is manufactured or may be adjustable.

In one embodiment of instrumentation in which the said distance is adjustable, the bone engaging element is releasably slidable along an arm connected to the tool guide. Preferably the arm is integrally formed with the tool guide.

The tool guide may be provided with a rod which is inserted into a bore in the intramedullary canal during resection.

The guide opening in the tool guide may comprise a slot for receiving the blade of a saw or may comprise a bore for receiving the shank of a drill. A plurality of guide openings may be provided in the tool guide and may comprise a combination of slots and bores.

The bone engaging element is preferably elongate and when engaging a bone extends substantially transverse to the longitudinal axis of the bone.

Preferably, the instrumentation is used for aligning a surgical tool for the resecting of an end of a bone. In an embodiment adapted for resecting the distal end of a humerus, the bone engaging element engages the posterior cortex of the distal humerus and the distance between the bone engaging surface of the bone engaging element and the bone engaging surface of the tool guide is adjustable between 30 and 40mm.

Preferably, the distance is fixed at 35mm.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a perspective View of instrumentation for aligning a bone saw during resecting of the distal end of a humerus; Figure 2 is a rear View of the instrumentation of Figure 1; Figure 3 is a view on one side of the instrumentation of Figure 1 when fitted to the distal end of a humerus; and Figure 4 is a View from above of the instrumentation of Figure 1 when fitted to the distal end of a humerus.

Referring to the drawings, Figure 1 and 2 are views of instrumentation for aligning a bone saw with the distal end of a humerus. The instrumentation comprises a tool guide 2 integrally formed with an opposing pair of clamping members 4, 6. Slots 8 which are rectangular in cross—section and are adapted to receive the blade of a bone saw extend through the width of the tool guide 2.

Between the slots 8 is provided a bore 10 which slidably receives an intramedullary rod 12. The rod 12 extends from the bone engaging face 11 of the tool guide 2 between the clamping members 4, 6.

The free ends 14, 16 of the clamping members 4, 6 are provided with openings (not shown) which receive the shanks 18, 20 of respective bone engaging elements 22, 24.

The shanks 18, 20 are slidable along a common axis so that the bone engaging elements 20, 24 can be brought closer together or moved further apart, and are fixed in position by means of respective collets operated by finger wheels 26, 28.

The bone engaging elements 22, 24 are of elongate form and taper from a broad base portion to a narrow bone engaging edge 30, 32.

Referring to Figures 3 and 4, in use of the instrumentation a bore 32 is drilled along the intramedullary canal from the distal end 34 of a humerus 36 which is to resected. The finger wheels 26, 28 of the instrumentation are then unscrewed, so that the bone engaging elements can be moved apart sufficiently to accommodate the humerus 36 and the instrumentation is placed onto the humerus with the intramedullary rod 12 removed, such that the face 11 of the tool guide 2 engages the distal end 34 of the humerus 36. The rod 12 is then pushed through the bore in the instrumentation and into the bore 32 in the intramedullary canal of the humerus. The bone engaging elements 22, 24 are then brought together so that the edges 30, 32 of the bone engaging elements 22, 24 are brought into contact with the cortex of the distal humerus 36.

Anatomical studies have established a relationship between the posterior cortex of the distal humerus and the axis of movement of the elbow joint with reference to the coronal plane. Referring to Figure 4, with the distance d1 between the bone engaging face 11 of the tool guide 2 and the bone engaging edge 30 of the upper bone engaging element 22 set at 35mm, the axis of movement of the elbow joint with reference to the coronal plane will be parallel to the posterior cortex of the distal humerus 36 and consequently the bone engaging edge 30 of the upper bone engaging element 22 will itself be parallel to the axis of movement of the elbow joint with reference to the coronal plane. By arranging the slots 8 in the tool guide 2 such that they extend in planes parallel to the bone engaging edge 30 of the upper bone engaging element 22, insertion of a bone saw (not shown) through the slots 8 will result in extremely accurate resection of the distal end of the humerus, so that when a prosthetic implant is attached to the resected bone the axis of the movement of the artificial joint with reference to the coronal plane will coincide exactly or substantially exactly with the axis of movement of the natural joint prior to the operation.

In an alternative embodiment (not illustrated) at least the upper bone engaging element 22 is slidably mounted to the clamping element 4, so that the upper bone engaging element 22 can be slid along a line substantially parallel to the intramedullary rod 12 and the distance dl between the bone engaging edge 30 of the bone engaging element 22 and the bone engaging surface of the tool guide 2 can be adjusted to accommodate variations in the dimensions of the humerus from patient to patient. However it has been found that in most cases if the distance dl in Figure 4 is set at 35mm this is appropriate for most patients.

The adjustability of the position of the upper bone engaging element may be provided by forming a track in the upper clamping member 4 along which the shank 18 of the upper bone engaging element 22 can slide. In such an embodiment, tightening of the finger wheels 26, 28 would not only set the relative separation of the bone engaging elements 22, 24, but would also set the distance between one or more of these elements and the bone engaging face 11 of the tool guide 2.

Instead of a single bore 10 through the tool guide 2, a pair of offset bores (not shown) may be provided such that the instrumentation could be used on either a left or right humerus, simply by inserting the intramedullary rod 12 in the appropriate opening.

The instrumentation is preferably made of stainless steel or titanium, but any appropriate material with sufficient stiffness and strength and which is suitable for autoclaving may also be used.

Claims (13)

1. Instrumentation for aligning a surgical tool during the resecting of an end of a bone, the instrumentation comprising a tool guide in which is provided an opening for receiving and guiding a portion of the surgical tool and a pair of clamping members which are adapted to engage opposite sides of the bone, at least one of the clamping members being provided with a bone engaging element which is adapted to engage a particular region of the bone and has a bone engaging surface which has a known orientation relative to the opening in the tool guide, such that when the clamping elements are tightened onto the bone, the opening in the tool guide is at a predetermined rotational orientation with respect to the longitudinal axis of the bone.

2. Instrumentation as claimed in claim 1, in which the tool guide is provided with a bone engaging surface which engages the end of the bone.

3. Instrumentation as claimed in claim 2, in which the distance between the bone engaging surface of the bone engaging element and the bone engaging surface of the tool guide is adjustable.

4. Instrumentation as claimed in claim 3, in which the tool guide is provided with an arm and the bone engaging element is releasably slidable along the arm to adjust the said distance.

5. Instrumentation as claimed in claim 4, in which the arm is integrally formed with the tool guide.

6. Instrumentation as claimed in any one of the preceding claims, in which the tool guide is provided with an intramedullary rod.

7. Instrumentation as claimed in any one of the preceding claims, in which the guide opening in the tool guide comprises a slot for receiving the blade of a saw.

8. Instrumentation as claimed in any one of the preceding claims, in which a plurality of guide openings are provided.

9. Instrumentation as claimed in any one of the preceding claims, in which the bone engaging element is elongate and when engaging the bone extends substantially transverse to the longitudinal axis of the bone.

10. Instrumentation as claimed in any one of the preceding claims, when appendant to claim 2, for aligning a surgical tool for resecting the distal end of a humerus, in which the distance between the bone engaging surface of the bone engaging element and the bone engaging surface of the tool guide is between 30 and 40mm.

11. Instrumentation as claimed in claim 10, in which the said distance is 35mm.

12. Instrumentation as claimed in claim 10 or 11, in which the bone engaging element engages the posterior cortex of the distal humerus.

13. Instrumentation substantially as described herein with reference to and as shown in the accompanying drawings. MACLACHLAN & DONALDSON Applicants’ Agents 47 Merrion Square DUBLIN 2