Abstract
We describe a method of cup and cone arthrodesis using Coughlin concave and convex reamers, which we have used in a series of 22 hand joints in 19 patients. These reamers, originally designed for use in the foot, can be used in the hand to give very accurate preparation of bone surfaces. This results in maximum bone contact and the ability to fuse the joint in any desired position. The procedure is simple, rapid and forgiving. Union was achieved in all 22 cases, usually within 3 months.
INTRODUCTION
Arthrodesis of the small joints of the hand is a commonly performed operation which is often undertaken by junior surgeons during their training. Many techniques of arthrodesis have been described, with fusion rates of between 80 and 100 per cent (Leibovic, 1997). However fusion rate is not the only factor which determines a successful outcome. The position in which the joint is fused is just as critical, especially for the thumb. If the standard technique of flat resection of adjacent bony surfaces is used, the angle of resection must be very precise and this can be technically demanding. If the bone cut is unsatisfactory, the only way of adjusting the angle is by resecting more bone, which can result in excessive shortening and cortical rather than cancellous bone contact.
Preparation of the bony ends using the “cup and cone” method (Carroll and Hill, 1969), allows the surgeon to adjust the position of the joint before fixation without the need for further bone resection. Bone nibblers, osteotomes, curettes and motorized burrs have been used to fashion the bony ends into the required shape (McGlynn et al., 1988). This however can be a painstaking and tedious process and can result in imperfect apposition of the contiguous prepared surfaces. We describe a method of cup and cone arthrodesis using Coughlin reamers (Howmedica Ltd.). The advantages of this method are speed and a high degree of accuracy.
PATIENTS AND METHODS
Between 1996 and 2001, we arthrodesed 22 small joints of the hand in 19 patients using concave and convex reamers. The patients were selected on the basis of a painful arthritic joint irrespective of the aetiology. The age range was 30 to 80 years and 13 patients were women and six were men. The diagnosis was rheumatoid arthritis in 12 patients and osteoarthritis in seven patients. All of the operations were carried out by the senior author (BSG). The digit fused was the thumb in 14 patients (metacarpophalangeal joint in seven patients, interphalangeal joint in six patients and carpometacarpal joint in one patient), the little finger in five patients (proximal interphalangeal joint in four patients and distal interphalangeal joint in one patient), the ring finger (distal interphalangeal joint) in two patients and the index finger (distal interphalangeal joint) in one patient. The indication for fusion was pain, instability or deformity.
Operative technique
Use of a tourniquet is mandatory. A curved dorsal approach is used for the thumb metacarpophalangeal joint, a longitudinal incision for the proximal interphalangeal joints and an H-shaped incision for the distal interphalangeal joints. The joint capsule is incised and reflected, the collateral ligaments released and the joint surfaces exposed. A guide wire is inserted at the desired angle into the centre of the proximal bone surface to be resected and an appropriately sized cannulated “hole saw” (Coughlin, 1990) is selected (Fig 1). This reduces the head and metaphysis of the proximal bone into a cylinder with uniform dimensions. A cannulated concave reamer of equal diameter to the cylinder is then used to fashion the proximal surface into a “cone” (Fig 2) and a cannulated convex reamer is used similarly on the distal surface to make a “cup” (Fig 3). Bone resection is minimal, because the curvature of the reamers approximately corresponds to the natural shape of the articular surfaces (Fig 4). The desired position of fusion is selected according to the individual digit and the joint being fused. Another factor to consider is the mobility of other joints in that digit. The position can be adjusted in all three planes before fixation. The fixation method is a matter of personal choice. We used the Herbert–Whipple screw in 13 cases, the Acutrak screw in three cases, AO cannulated interfragmentary screws in three cases and Kirschner wires in three cases. Postoperative immobilization consists of a thumb spica cast for thumb metacarpophalangeal joint fusions and a malleable aluminium splint for finger interphalangeal joint fusions. The cast or splint is retained for 4 to 6 weeks.
RESULTS
The patients were reviewed in the clinic at 1,2,6, and 12 weeks and 6 months and 1 year. The minimum follow-up was 1 year and radiographs were obtained at the 6- and 12-week follow-up visits. The presence of trabeculae crossing the arthrodesis site was considered as evidence of union (Fig 5) and, using this criterion, all of the joints fused successfully.
We found that 12 out of 22 joints demonstrated radiological union at 6 weeks and another eight by 12 weeks. Two joints in one patient failed to unite by 12 weeks, but union had occurred by the 6-month follow-up.
All the joints fused in the desired position and thus there were no malunions. Minor complications were seen in five patients, four of whom had had a distal interphalangeal joint fusion. These included cold sensitivity, wound maceration, scar tenderness and persistent discomfort on heavy lifting despite radiological and clinical union. All these complications settled by the 6-month follow-up. The patients were questioned regarding pain and function at a minimum of 6-month follow-up and only one was dissatisfied with the outcome. He had had a metacarpophalangeal joint fusion of the thumb, which had united successfully but had resulted in stiffness of the interphalangeal joint and weakness of pinch and power grip.
DISCUSSION
Many methods of arthrodesis of small joints of the hand have been described. Most of these involve cutting the adjacent bones to produce two flat surfaces at the desired angle which is technically demanding.
Coughlin reamers, originally designed for use in the foot, can also be used in the hand, and allow very accurate preparation of bone surfaces. This results in maximum bone contact and the ability to fuse the joint in any desired position. Moberg and Henrickson (1959) stated that “the prime requisites of a good digital arthrodesis are a painless and stable union in proper position and in a reasonable space of time”. Only one of our patients failed to fulfil the above criteria for a good fusion. This compares favourably with the fusion rate of other techniques (Jones and Stern, 1994).
The procedure is simple, rapid and forgiving. It is thus ideal for surgeons of all grades.