ORTHOPAEDIC DEVICE

Abstract: A bone cutting device for precision elbow surface re­ placement arthroplasty and osteotomy is described. A humeral clamping device is provided with an outrigger to hold the ulna in preselected and rigid relation to the humerus. A bone cut­ ting tool such as a burr is inserted into a selected guide sleeve mounted for oscillatory arcuate movement on the medial side of the clamping device, so as to precisely prepare the hu­ merus. The humeral guide sleeve is removed and replaced with a slightly longer second sleeve which provides the precise spacing required to prepare the ulna in similar manner. A planar radial cutting guide may be mounted on the lateral side of the clamping device, to guide a planar oscillating saw used to prepare the proximal end of the radius.

Description: The invention relates to an orthopaedic bone positioning and tool guide device for attachment on the distal epicondyles of a human humerus, comprising (a) an adjustable clamping means for transverse pivotal mounting on the epocondyles; (b) first and second cutting tool guide means pivotally mountable for accurate movement on the medial side of the clamp, when operatively secured to the humerus, each adapted to receive a cutting tool for accurate bone cutting, wherein the first guide means has a selected radial length arranged so that the cutting tool cuts the humerus and the second guide means has a selected radial length greater than the first guide means so that the cutting tool cuts the ulna adjacent to the humerus. Such an orthopaedic bone positioning and tool guide device is known for example from EP-A-0 132 284 relating to a device for accurate placement of an elbow prosthesis. In this prior art device, a U-shaped frame is provided having respective pins at the opposite arms thereof. While such a device is quite useful for many purposes with its threaded rod allowing an axial adjustment of the respective components, it has been found that a more versatile device is desired in practice in order to deal with the respective individual situations. Background of Invention The complex kinematics, anatomical features and load distribution on an elbow are such that surgical replacement thereof is not simple. Simple constrained and semi-constrained cemented replacements for the elbow joint have proved to be generally unsatisfactory as they do not provide sufficient range of motion and, due to the unnatural stresses placed on the musculature, ligaments and tendons, premature loosening often within a year or two of placement frequently occurs. Loosening is usually accompanied by pain and discomfort and over a period of time distortion of the natural function of the joint may occur. The use of unconstrained resurfacing prostheses, such as those described in US-A-4,242,758 issued 6 January 1981 to Amis et al, appears to offer the potential, by reproduction of normal joint geometry and restoration of ligament balance, to recreate relatively normal kinematics and load bearing and to provide relief of pain. Such prostheses are now generally using the relatively recently developed porous metal coating technique so as to promote bone ingrowth, and this technique precludes the use of cements to secure the prosthesis to the bone or to compensate for cutting inaccuracies. It is now necessary to ensure accurate resection of the bone ends to within a tolerance of mm or better. Such accuracies are not possible using commonly available jigs or with hand held saws or other cutting tools such as router tools. Object Of invention It is therefore an object of the present invention to provide a novel means to hold an elbow joint in a preselected position and to provide guide means to permit extremely accurate resection of the humeral, ulna and radial bones without moving the holding means between cuts. This ensures that the cuts will be precisely positioned to receive a resurfacing prosthesis, of one of five preselected standard sizes. The orthopedic bone positioning and tool guide device is characterized by (c) extensible arm means mounted on the clamping means and extending longitudinally therefrom, including means to lock the arm means at a selected length; (d) transversely mounted adjustable and lockable means at the free end of the arm means, including means to adjustably mount transverse and longitudinal bone securing pins, whereby an ulna may be secured in a preselected orientation relative to the humerus when the clamping means is secured in operative position; and (e) planar cutting tool guide means mountable on the lateral side of the clamping means when operatively secured to the humerus so as to provide a guide for a planar oscillating cutting tool for accurate planar cutting of a radial bone. For further developments of the orthopaedic bone positioning and tool guide device for attachement on the distal epicondyles of a human humerus, reference is made to the respective features as specified in the subclaims. Further features and advantages according to the invention will be apparent from the following description in connection with the accompanying drawings. Brief Description of Drawings Fig. 1 is a plan view of a trochlear template; Fig. 2 is a plan view of a capitellum template; Fig. 3 is a front view of a humeral clamp according to the invention; Fig. 4 is a side view of a humeral clamp of Fig. 3 with an ulna outrigger installed; Fig. 5 is a bottom view of the device of Fig. 4; Fig. 6 is a diagramatic sketch of the device of Fig. 4, in position on an elbow; Fig. 7 is a side view of a humeral cutting cam; Fig. 8 is a plan view of a radius gauge; Fig. 9 is a side view of a radius centre pin cutter; Fig. 10 is a side view of a radial prosthesis; Fig. 11 is a plan view of the prosthesis of Fig. 10; Fig. 12 is a front view of a humeral prosthesis Fig. 13 is a sketch of an anterior view of a right elbow including the humeral, ulnar and radial prosthesis of the present invention; Fig. 14 is a medial view of an ulna prosthesis; and Fig. 15 is an anterior view of the prosthesis of Fig. 14. Detailed Description of Preferred Embodiments In the copending application filed concurrently herewith a novel humeral resurfacing prosthesis which substantially replicates the distal end of a humerus is described. While it was first thought that the use of external anatomical landmarks, such as the epicondyles, would provide the means to establish the radial centre for the convex semi-circular cut at the distal humerus necessary to receive the prosthesis, this approach was discarded as it was found that the axis (or C-line) of the trochlea and capitellum, which is substantially a straight line, is in fact at an angle of about 2 - 3 o to the transepicondylar line (TEL). Instead use is made of the curved surface of the trochlea and capitellum. An incision is made first on the medial side of the elbow and,after drilling a pilot hole in the centre of the medial epicondyle, the epicondylar crown is removed (for later replacement and securement by a screw inserted into the pilot hole). A series of differently sized semi-circular trochlear templates 10 are placed on the now flattened medial epicondylar plateau to establish, by a "best fit" approach, the geometric centre of the medial aspect of the trochlear, which is then marked and a pilot hole drilled thereat. After making an incision and exposing the lateral side the procedure is repeated with a series of capitellum templates 101, which establishes the geometric centre of the capitellum. A U-shaped width-adjustable humeral clamp 12 with locating pins 13,14 at the ends of the areas thereof, is placed on the humerus and the pins 13,14 located in the respective trochlea (medial) and capitellum (lateral) pilot holes. Once the pins 13,14 are located, the arms 15,16 of the clamp 12 are adjusted towards each other by sliding integral sleeves 151,152 along respective guide rods 153,154 and locked in place by a clamping screw 17 thereby securely locating the clamp 12 and yet still allowing it to be rotated about the C-line axis of the humerus. A humeral cutting cam 18 (Fig. 7) of selected length is axially mounted on shouldered guide pin 42 at the end of the medial arm 15 of the clamp 12 and rotatably secured by means of a locking nut 19 as seen in Fig. 3. The cam 18 comprises a body 20, having a circular hole 21 therethrough adjacent one end, adapted to be mounted on pin 42 which is in turn arranged to receive locking nut 19, and about which the body 20 may be arcuately oscillated, and a hollow guide 22 axially parallel to and spaced a selected distance from the hole 21. A guide 22 is adapted to receive a rotatable burr (not shown) generally 3,17mm (1/8") in diameter. The burr may be rotated by any conventional power or air tool normally found in an operating theatre. The cam 18 with the burr in place, oscillated back and forth to ensure that the correct cutting arc has been established. Once the surgeon is satisfied with the cutting arc, cam 18 may be removed if desired. A 2,38mm (3/32") Steinman pin 24 is then inserted through a hole 23 in the clamp 12 and screwed into the underlying prepared surface of the medial epicondyle. This prevents the clamp 12 from rotating on its axis. A similar Steinman pin may be inserted through a complementary pilot hole 25 on the lateral side to further assist in rigidly mounting the clamp 12. The ulna fixation assembly 26 is next mounted on the humeral clamp 12 by means of a U-clamp 27. The ulna fixation assembly 26 comprises a telescopically expandable arm 28, lockable at any selected length by a U-clamp 29. A crosshead 30 is adjustably and clampingly mounted at the end of the arm 28 by means of a camp 31 intermediate the ends thereof. Coronoid arms 32, 33 extend substantially perpendicularly to the arm 28 and to the crosshead 30 at opposite ends thereof and angularly adjustable relative thereto. Intermediate the ends of the crosshead 30 there is provided an olecranon bracket 34 which may be locked at any desired angle to the arms 32, 33 by means of locking screws 35, 36. The olecranon bracket 34 is adjusted so that the adjustable pin clamp 37 lies adjacent the olecranon, and a threaded Steinman pin 38 may be inserted through clamp 37 and drilled not more than about 1 cm into the olecranon so that pin 38 is substantially parallel to the longitudinal axis of the ulna. With the elbow flexed at about 45 o , and held at that angle by a rigid, telescopically adjustable bracket 83 and wrist 81 and humeral straps the linked, parallel coronoid bracket arms 32, 33 are adjusted to lie adjacent the coronoid areas on their respective side of the ulna. A 3,97mm (5/32"] threaded Steinman pin may now be inserted through medial guide hole 39, drilled through the ulna and into the guide hole 40 on the lateral side. When all the pins are in place and the surgeon is satisfied with the orientation of the ulna and radius relative to the humerus, the adjustment means 26, 27, 31, 35, 36, 37, 41 are locked in place to hold the ulna and humerus in the selected orientation. A selected humeral cutting cam 18 is then remounted, if previously removed, on the pin 42 and secured by the nut 19, preparatory to making the humeral cuts. A selected rotatable burr, preferably provided with a depth control gauge (not shown) inserted into the hole 22 and may then be actuated by any conventional air or electric power source. Once inserted, it is preferable to drill to full depth at each extreme of arc. Subsequently, the cam 18 may be moved in either direction, but generally counterclockwise, to remove the remainder of the bone in the trochleal cutting arc, cutting to a depth of about 1 cm at a time and spraying the burr continuously with a sterile saline solution to prevent overheating of the bone and wash away debris. Once the trochleal surface has been removed, and it is here emphasized that the present protocol is designed to remove a minimum of bone stock, the depth control gauge is adjusted to the depth required to cut the capitellum portion, and the capitellum is cut in similar manner to the trochlea. Without removing the camp 12 from the humerus and ulna, the humeral cutting cam 18 is removed and replaced with an ulna cutting cam which is similar in shape to humeral cutting cam 18, but with a slightly larger, and predetermined selected cutting radius. It will be appreciated that, according to our copending application "Elbow Prosthesis" filed concurrently herewith, it has been possible to generate 5 standard sizes of humeral prostheses to fit 95%, of the population. Complementary ulna and radial prostheses of varying thickness are also available, so that the surgeon may select the most suitably sized humeral prostheses and match it with a similarly standardized ulna or radial prosthesis. Thus the clearance required between the humeral and ulna prepared bone surfaces is readily predetermined, and the exact cutting radius for the ulna cutting cam selected. Once selected, positioned and locked in place by the nut 19, the depth gauge is set and cutting of the ulna proceeds in a similar manner to the humeral cut, it being preferred to rotate the ulna cam in a clockwise manner. The ulna cam is then removed and a flat radius cutting gauge (not shown) is locked in appropriate orientation on the humeral clamp on the lateral side 16 thereof. Using the flat surface thereof as a guide for an orthopaedic oscillating saw (not shown) the head of the radius is resected. Any excess bone or cartilage tissue, which might interfere with prosthesis implantation may be trimmed away, from the medial side, by means of selected profile tools and osteotones. Generally such tools may be guided by means of guides (not shown) mounted on the humeral frame. The frame can then be dismounted from the ulna and humerus. The arm may then be rotated to the lateral side and a radius gauge 51 (Fig. 8) is selected, from a sized set thereof, which most closely corresponds in diameter to that of the radius and placed over the squarely prepared proximal end of the radius. A marker probe is inserted through hole 52 and used to mark the centre of the radius. The gauge 51 is then removed and replaced by radius centre pin cutter 53 (Fig. 9) the centering pin 54 of which is inserted into the marked centre of the radius. The cutter 55 is tapped home by means of a small osteotone which is struck against strike 56. The cutter 53 is then rotated axially about pin 54, in an arc of about 45 o in each direction and then removed, thus removing a cylindrical core of bone from the radius. The radial prosthesis 88 (Figs. 10, 11) is then inserted with the stem 81 projecting into the cored hole formed in the radius. The prosthesis is tapped into position by placing the convexly contoured surface 57 of tool 53 over the concave surface 89 of prosthesis 88 and striking striker 58 with a small osteotone. The arm is again rotated to the medial side and the humeral prosthesis 92 (Fig. 12) is inserted into position, as shown in Fig. 13, tapping if required to achieve the desired position and taking care not to disturb the radial prosthesis. The ulna prosthesis 63 (Fig. 14, 15) is then inserted, also from the medial side, and its position adjusted as necessary. Locating pins, if used, are pressed into the underlying ulna bone. Using a bone screw inserted into the predrilled pilot hole, the medial epicondyle is replaced, oriented and secured in place, and after checking to ensure alignment and free movement, the medial and lateral wounds may be closed.

Claims: An orthopaedic bone positioning and tool guide device for attachment on the distal epicondyles of a human humerus, comprising (a) an adjustable clamping means (12, 17) for transverse pivotal mounting on the epicondyles, (b) first (18) and second cutting tool guide means pivotally mountable for accurate movement on the medial side of the clamp (12), when operatively secured to the humerus, each adapted to receive a cutting tool for accurate bone cutting, wherein the first guide means (18) has a selected radial length arranged so that the cutting tool cuts the humerus and the second guide means has a selected radial length greater than the first guide means (18) so that the cutting tool cuts the ulna adjacent the humerus, characterized by (c) extensible arm means (28) mounted on the clamping means (12, 17) and extending longitudinally therefrom, including means (29) to lock the arm means (28) at a selected length; (d) transversely mounted adjustable and lockable means (30, 31) at the free end of the arm means (28), including means to adjustably mount transverse (32, 33) and longitudinal (34, 37) bone securing pins, whereby an ulna may be secured in a preselected orientation relative to the humerus when the clamping means (12, 17) is secured in operative position; and (e) planar cutting tool guide means mountable on the lateral side (16) of the clamping means (12, 17) when operatively secured to the humerus so as to provide a guide for a planar oscillating cutting tool for accurate planar cutting of a radial bone. The orthopaedic device according to claim 1, characterized by auxiliary pin locating means (23, 25) on the medial and lateral sides of the clamping means (12, 17) arranged to receive bone pins (24) therethrough to secure the clamping means (12, 17) against rotation on the humerus. The orthopaedic device according to claim 1 or 2, characterized by a plurality of trochlear templates (10) of selected sizes each marked with a centre point whereby the centre of the medial epicondyle may be established for mounting the clamping means (12, 17) thereon. The orthopaedic device according to any of claims 1 to 3, characterized by a plurality of capitellum templates (101) of selected sizes each marked with a centre point whereby the centre of the lateral epicondyle may be established for mounting the clamping means (12, 17) thereon. The orthopaedic device according to any of claims 1 to 4, characterized by a plurality of radial templates (51) of selected sizes each marked with a centre point whereby the centre of a planar resected proximal end of a radius may be determined. The orthopaedic device according to any of claims 1 to 5, characterized by a circular radius centre pin cutting device, the cutting device comprising a rigid member (53) having a circular cutter (55) extending perpendicular therefrom and first strike means (56) on the rigid member (53) spaced from and on an opposite side to the cutter (55). The orthopaedic device according to claim 6, characterized in that the radius pin cutter further includes a radius prosthesis locating means (5) adjacent the end of the rigid member (53) remote from the cutter (55), and second strike means (58) on the rigid member (53) spaced from and on an opposite side to the cutter (55).

Inventors: SAUNDERS, GERALD, SORBIE, CHARLES
Applicants: QUEEN'S UNIVERSITY AT KINGSTON
Application year: 1986
Main classification: A61F2
IPC codes: A61B17