Swan Neck Deformity

Swan Neck Deformity Finger

Figure 71—2. (A) In the swan-neck deformity, terminal tendon rupture may lead to DIP joint flexion and subsequent proximal interphalangeal (PIP) joint hypertension. Decreased volar support of the PIP joint and subsequent hypertension deformity can be due to rupture of the flexor digitorum superficialis tendon. (Continued)

Fusion Dip Joint
Figure 71—2. Continued (B,C) Clinical photos ofa screw neck deformity.

inflammatory arthropathy. In cases where conservative measures fail, arthrodesis becomes a reasonable option. The goal of DIP joint arthrodesis is to obtain a painless, stable, and functional hand.

Surgical Management

As initial conservative management has failed and the patient is having progressive disability secondary to the pain, operative options were discussed. In this situation, a fusion of the distal interphalangeal joint should predictably provide good pain relief and maintenance of sufficient function. The goal of arthrodesis is to provide a painless stable union of the joint in the proper position. As with other hand and finger joints, options include tension band wiring, screw fixation, plate fixation, and the use of external fixation.

Difficulty with gasping and pinching due to pain and instability at the DIP joint is often the indication for surgery. Contraindications include, but are not limited to, inadequate bone quality, infection, dysesthetic finger, or poor function that will not improve with arthrodesis.

The surgical technique involves placing the patient in the supine position. The operative extremity is exsanguinated and a tourniquet is utilized to facilitate a bloodless operative field. The DIP joint is approached through a dorsal curved skin incision. The extensor tendon insertion is dissected sharply off its attachment at the base of the distal phalanx. Once completed, the joint capsule is identified and a transverse incision allows exposure of the collateral ligaments radially and ulnarly. Sectioning of these ligaments permits further exposure of the DIP joint by permitting flexion and delivery of the joint surfaces through the surgical wound. Preparation of the articular surfaces is based on the principle of obtaining a technically appropriate position as well as adequate cancellous bone-to-cancellous bone contact.

Upon delivery of the articular surfaces into the operative field, all articular cartilage is removed. The proximal bone is then shaped into a rounded cone while the distal articular surface is configured into a cup using a small bur (Fig. 71—3). Cancellous bone removed during this step may be saved for later bone graft. A 0.045-inch Kirschner wire (K wire) is drilled distally into the base of the distal phalanx and is allowed to exit just volar to the nail bed from the pulp of the finger. The DIP joint is reduced and the K wire is then drilled retrograde into the medullary canal of the middle phalanx. The image intensifier is used to confirm appropriate placement and to prevent inadvertent violation of the PIP joint. A position of 0 degrees of flexion with 5 degrees of supination and neutral radial and ulnar deviation is recommended for the index finger. The K wire may be left exposed at the finger pulp or cut off below the skin. Bone graft may be added to the fusion site and the capsule is then closed with a 4—0 nonabsorbable interrupted suture, followed by suture reapproximation of the extensor tendon. The skin is closed with a 5—0 nylon interrupted suture.

The rates of fusion for the DIP joint are ~80 to 90%. Consensus regarding position of fusion generally maintains a position of full extension and neutral radial and ulnar deviation. Supination of ~5 to 10 degrees is helpful in the index and long finger to facilitate pinch with the thumb. In general, a "cup and cone" preparation allows precision in positioning and follows the principle of obtaining good cancellous bone-to-bone contact (Fig. 71—3). Currently available are cup and cone reamers to assist with bony preparation. Techniques for subsequent fixation include the use of K wires, intraosseous and tension-band wiring, plates, compression screws, Herbert

Dip Arthrodesis Herbert Screw Technique
cone technique.
Dip Arthrodesis Screw
Figure 71—4. (A,B) Alternative technique of DIP arthrodesis with Herbert screw (AP and lateral (B). x-ray).

screws (Fig. 71—4), Acutrac screws and, potentially, bioabsorbable pins. Biomechan-ical data for these techniques are limited, but information can be extrapolated from a model in which these fixation devices were tested on diaphyseal osteotomies in a metacarpal. These data indicate that bending strength is greatest with a 90—90 intraosseous wire technique, which is comparable to dorsal plating. Despite these data, union rates remain high with each technique, and no study convincingly demonstrates superiority of one type offixation over another. Patient factors, surgical experience, and availability of implants determine which fixation technique one selects.

Postoperative Management

An external aluminum splint is applied postoperatively for 4 to 6 weeks. The K wire may be removed at the end of this time period as suggested by clinical and radiographic examination. This patient went on to union, and at her last follow-up she was noted to have good relief of her pain and return of her pinch strength for activities of daily living and recreational pursuits.

Complications

Complications after DIP joint fusion include hardware irritation, nonunion, deformity, infection, cold intolerance, and acute vascular compromise. As discussed above, nonunion is typically not determined by method of fixation; rather, bone stock appears to be the primary determinant. Meticulous attention to detail to include appropriate bony preparation, positioning, and reapproximation of the extensor tendon helps avoid nonunion, malunion, or postoperative swan-neck deformity. Vascular compromise may occur in cases where chronic fixed flexion contractures are corrected without first resecting adequate bone to relieve soft tissue tension. Intraoperative evaluation of vascular status by deflating the tourniquet can prevent this disastrous complication. Superficial infections should be treated with antibiotics, soaks, and, if indicated, pin or hardware removal. Deeper infections require debridement, acquisition of cultures and sensitivities, and systemic antibiotics.

In summary, complications after DIP joint arthrodesis represent an infrequent though serious occurrence. Prevention through attention to surgical detail and appropriate patient education remain the mainstay of addressing these unwelcome events.

Suggested Readings

Burton RI, Margles SW, Lunseth PA. Small joint arthrodesis in the hand. J Hand Surg [Am] 1986;llA:678-682.

Carroll RE, Hill NA. Small joint arthrodesis in hand reconstruction. J Bone Joint Surg [Am] 1969;51A:1219-1221.

Stern PJ, Fulton DB. Distal interphalangeal joint arthrodesis: an analysis of complications. J Hand Surg [Am] 1992;6:1139-1145.

Vanik RK, Weber RC, Matloub HS, Sanger JR, Gingrass RP. The comparative strengths of internal fixation techniques. J Hand Surg [Am] 1984;9A:216-222.

Wright CS, McMurtry RY. AO arthrodesis in the hand. J Hand Surg [Am] 1983;8: 932-935.

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