Matthew M Tomaino MD MBA

University of Rochester Medical Center, 601 Elmwood Avenue, Box 665, Rochester, NY 14642, USA

Arthrodesis of the distal interphalangeal (DIP) joint is a common procedure to treat the painful, unstable distal joint in the osteoarthritic and rheumatoid patient. Less common indications include chronic mallet deformity, missed flexor digitorum profundus avulsions, and distal middle phalangeal fracture nonunion. In most cases, successful fusion improves digital function. Morbidity—to the extent that any elective procedure needs to balance the pros and cons—stems from wound healing problems, infection, and painful nonunion. Though Burton and colleagues [1] advocated the use of Kirschner wires (K-wires) alone, reporting a nonunion rate for the small joints of the hand of .6%, wires at the DIP joint, in particular, are frequently a nuisance—they get caught on clothing, get infected, and may back out or fall out altogether. Indeed, Stern and Fulton [2] reported a 20% complication rate, including hardware protrusion or migration, loosening, failure to achieve union, pin track infections, and stiffness. Though nonunion rate did not differ between technical alternatives, buried hardware avoided some of the others.

Based on the expectation that compression across the DIP joint might accelerate fusion, both the Herbert (Zimmer, Warsaw, Indiana) [3-5] and the Mini-Acutrak (Acumed, Beaverton, Oregon) screws have proven successful [6]. The author prefers the Herbert screw over the newer cannulated screws because it is less expensive, is just as easy to insert, and allows manual compression after placement, in the event that the bony surfaces are not entirely coapted after screw placement.

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Surgical technique

Under regional anesthesia, a dorsal bayonet-shaped incision is made, and skin flaps are elevated off the extensor tendon. The tendon is divided transversely, the joint is flexed, and the collateral ligaments are released. Beginning with the head of the middle phalanx, a small rongeur is used to trim dorsal osteophytes. Next the articular surface is removed, leaving the remaining decorticated surface flat relative to the orientation of the shaft. Now, with improved exposure of the base of the distal phalanx, the rongeur is used to decorticate the base of P-3, preserving as much bone stock as possible.

A .045 K-wire is drilled antegrade through the base of P-3 out the finger tip, just deep to the nail bed. This allows the narrower Herbert drill bit, which corresponds to the leading edge of the Herbert screw, to be passed by hand, antegrade, through the same path. When it presses up the skin distally as it exits, a small incision is made. This same narrow drill bit is passed retrograde through the head of P-2 to about midway down the shaft. Next, the larger diameter drill bit, which corresponds to the trailing head of the screw, is passed retrograde through the fingertip incision, into the tip of P-3, until its hub prevents further passage. Starting this bit requires ''catching'' the exit hole at the tip of P-3, which had been made by the antegrade use of the narrower bit.

The screw length is selected by measuring with a ruler the length from mid P-2 to the tip of the fingertip, and then subtracting 4 mm. The screw is inserted from distal to proximal—its leading tip is seen exiting the base of P-3. The screw tip is then placed in the hole previously made in the head of P-2. The assistant compresses the coapted surfaces,

Fig. 1. DIP joint fusion with K-wires (A) Preoperative anteroposterior (AP) radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph. (D) Postoperative lateral radiograph. (E) Fused index DIP joint in flexion facilitates prehension.
Dip Fusion Technique

Fig. 2. DIP joint fusion for P-2 nonunion. (A) Preoperative AP radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph. (D) Postoperative lateral radiograph. (E) Composite flexion after DIP joint fusion. (F) Fused index DIP joint in extension interferes slightly with tip-to-tip prehension.

Fig. 2. DIP joint fusion for P-2 nonunion. (A) Preoperative AP radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph. (D) Postoperative lateral radiograph. (E) Composite flexion after DIP joint fusion. (F) Fused index DIP joint in extension interferes slightly with tip-to-tip prehension.

Herbert Screw Tip

and the screw is inserted until it is buried beneath hyponychial skin. After an additional few turns of the screwdriver, a fluoroscopic image is taken to ensure that the head is nearly buried in P-3. At this point, additional compression is possible across the nonthreaded portion of the Herbert screw, if necessary. The extensor tendon is repaired with absorbable suture if possible, and the skin is closed. A postoperative dressing is removed at 5 to 7 days postoperatively, and motion is started. Sutures are removed between 2 and 3 weeks postoperatively.

Fig. 3. DIP joint fusion for osteoarthritic index and small finger disease with concomitant long finger PIP joint implant arthroplasty. (A) Preoperative AP radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph. (D) Postoperative lateral radiograph.

Fig. 3. DIP joint fusion for osteoarthritic index and small finger disease with concomitant long finger PIP joint implant arthroplasty. (A) Preoperative AP radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph. (D) Postoperative lateral radiograph.

Fig. 3 (continued)
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