17.1 Introduction

Degenerative changes of the distal interphalangeal (DIP) joints can be painful, disabling, and disfiguring. If nonoperative treatment fails to relieve the pain, arthrodesis is still considered by most surgeons to be the gold standard of operative treatment. Frequently ignored is the failure of fusion of this joint by conventional means, with reported rates of delayed union and nonunion from 0 to 20%, ^{1 , 2} and the need for the expensive extreme of compression screws to avoid this problem. ^{3 , 4} Patients are often unenthusiastic about losing movement of the DIP joints, particularly in the index and middle fingers, realizing that many finer functions of the hand rely on the rapid movement of these joints through a small range of motion. Therefore, they may perceive joint fusion as exchange of one disability for another.

17.2 Characteristic of Silicone Implants for DIP Joint

Since first described in 1968 by Swanson, silicone elastomer spacers have been, and are still, widely used for replacement of proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints destroyed by arthritis. ⁵ These implants maintain the joint space and allow motion whilst retaining stability. However, until 2011, there was little in the literature about silicone arthroplasty of the DIP joints, with the total recorded experience being only 67 distal interphalangeal replacement arthroplasties. ^{6 , 7 , 8 , 9 , 10 , 11} These papers identified this procedure as a good alternative to arthrodesis, achieving excellent pain relief and allowing stable pinch, but with the benefit of retaining 20 to 30 degrees of DIP joint movement. The complication rate leading to implant removal ranged from 1 to 10%, which is comparable to the reported complications following DIP arthrodesis. The standard technique of DIP joint replacement used in these studies involved transection of the extensor tendon, necessitating 6 to 8 weeks of postoperative joint immobilization and risking loss of some of the movement of the joint.

17.3 Own Results in the Literature

In 2011, we reported the results of a study of Swanson replacement of 131 DIP joints for painful osteoarthritis and two younger patients for ongoing joint pain after injury. ¹² A total of 37 arthroplasties (28 patients) were carried out with extensor tendon division and repair, and postoperative immobilization for 8 weeks. The following 94 (60 patients) were then carried out without tendon division, allowing immediate mobilization. This group comprised 60 patients, of which 52 were female and 8 were male. Nineteen patients had two prostheses inserted at a single operation. Five patients had three prostheses at a single operation. Three patients had three prostheses inserted at two operations. One patient had five prostheses inserted at two operations. Forty prostheses were placed in the index finger, 26 in the middle finger, 15 in the ring finger, and 13 in the little finger. At assessment, after a mean period of 57 months, the mean postoperative range of movement was 39 degrees, and the mean extensor lag was 11 degrees, with a statistically significant improvement of both over the preoperative measurements in both operative groups. When compared against each other, there was no statistically significant difference between the postoperative range of movement achieved in the two groups. The severity of pain, as measured subjectively on a visual analog scale (VAS) scale, improved significantly in both groups following surgery. The overall complication rate was 7/131 (5%), with 4/131 (3%) requiring further surgery. Three joints developed cellulitis which settled with antibiotics and one developed osteomyelitis requiring removal of the implant and subsequent joint fusion. Patients were questioned about the stability of the involved joints postoperatively on each occasion on which they attended for surgical follow-up. One DIP joint had subsequent fusion because of persistent lateral instability and one had DIP joint fusion because of persistence of marked preoperative ulnar deviation. One joint had a persistent mallet-type deformity, corrected after 18 months by tendon shortening. Overall patient satisfaction with the appearance of their digit(s) postoperatively was high in both groups and all but one patient were satisfied with the cosmetic result of replacement.

17.4 Own Experience and Preferred Technique for DIP Joint Arthroplasty

Procedures involving a single joint are mostly carried out under digital ring block. Procedures involving multiple joints are carried out under multiple ring blocks, brachial block, or general anesthesia, according to the patient wishes. Initially, a dorsal “H-shaped” incision, creating proximal and distal flaps, was used to approach the DIP joint. More recently, the distal flap has not been raised routinely. The proximal flap is carefully elevated off the underlying extensor tendon and bone and sutured back to give good access. In those cases in which the prosthesis was inserted without extensor tendon division, the collateral ligaments were then divided from the middle phalanx proximally (Fig. 17.1).

The tissues lateral to the extensor tendon were next excised. By laterally flexing the joint and retracting the extensor tendon from one side to another with a tendon hook, one is then able to remove the head of the middle phalanx with a rongeur, without damage to the extensor tendon. The intramedullary canals of the middle and distal phalanges were prepared using reamers or a burr drill. The joint was then sized for either a size 1, 0, or 00 Wright (Swanson type) silastic implants (Wright Medical Technology, Inc., Arlington, TN, USA). Finally, the distal phalangeal surface of the joint was debrided of osteophytes and the appropriate implant was inserted (Fig. 17.2).

Finally, the skin was closed (Fig. 17.3) and the joint placed in a small volar Zimmer splint.