Swanson Prosthesis

curette, broach, and microair drill with a smooth leader point bur (Fig. 73-6). In the index finger, the medullary canal of the proximal phalanx requires the rectangular reaming to be performed in an orientation of slight rotation such that the dorsal ulnar corner is more dorsal than the dorsal radial corner, and the radial palmar corner is volar to the ulnar palmar corner of the rectangle when viewed axially. This will favor slight supination to help the index finger function in supination. In the small finger proximal phalanx, the reverse is true and the rectangular reaming should place the dorsal radial corner more dorsal than the dorsal ulnar corner and the ulnar palmar corner is volar to the radial palmar corner. This will favor the slight pronation required for the small digit. Care must be taken to avoid perforation of the cortex. Rough edges are flattened carefully and trial implants are placed for sizing. Evaluation of proper fit should include placing the MP joint into full extension with no demonstrable impingement or instability. Tension may be further modified with soft tissue releases or bony resection. The largest possible implant should be used with good fit of the stem into the canal and appropriate apposition of the midsection with bone (Fig. 73-7). With good bone stock, a grommet may also be used and press-fit into the intramedullary canals with the midsection of the implant resting on the grom-met. Following placement of the implant, residual laxity of the index and occasionally the long finger joint can be addressed by imbricating the radial collateral

Swanson Arthroplasty
Figure 73—7. Implant is placed in the canal with the best fit and appropriate position with bone. (Illustration courtesy of The Indiana Hand Center and Gary Schnitz.)

ligament and capsule over the dorsal aspect of the base of the proximal phalanx at the dorsoradial border through a 1-mm drill hole (Fig. 73-8). Proximal reattachment to the metacarpal may also be necessary. If the radial collateral ligament has become too attenuated for the reconstruction, a proximally based flap using the radial half of the volar plate may be incorporated and similarly sutured to the dorsoradial aspect of the proximal phalanx. The distally released ulnar collateral ligament is then sutured to the ulnar edge of the radial collateral ligament and capsule. The extensor hood is repaired using 4-0 Dexon sutures and inverting the knots. The radial portion of the extensor hood is reefed to centralize the extensor tendon with care to bury the knots. In the index and long fingers, overcorrection of the extensor tendons radially assists in avoiding a pronation force. In some cases, if the extensor tendon does not have adequate longitudinal tension, it requires imbrication. The juncturae tendinum are repaired and the skin is closed with interrupted 5-0 nylon sutures, followed by application of a voluminous hand-conforming dressing.

Juncturae Tendinum

Figure 73—8. Implant in place with imbrication of the radial/collateral ligament added for stability. (Illustration courtesy of The Indiana Hand Center and Gary Schnitz.)

Postoperative Management

Dressings are changed 2 days postoperatively and the patient is fitted for a dynamic extension splint to be worn during the day and a resting splint to be used at night. An occupational therapist is helpful in maintaining proper alignment of the digits during active and active-assisted range of motion. A passive range-of-motion goal of 0 to 70 degrees in the ring and small finger and 0 to 45 degrees in the index and long finger is achievable by approximately 2 weeks. Further aggressive range of motion, articularly in the index and long fingers, is not necessary to promote stability and durability of the implant in these digits. Care must be taken to avoid contracture in other joints, specifically the PIP, elbow, and shoulder. This can be avoided by dorsal extension splints of the PIP to be used during exercise, and concomitant range-of-motion exercises directed at the elbow and shoulder. Therapy is required for a minimum of 3 months.

Complications

Rheumatoid patients with a history of being treated with steroids are at risk for the development of infection, wound healing difficulties, and complications related to poor bone stock such as fractures. Recurrence of deformity with subluxation of the joint or extensor tendons can usually be traced back to insufficient soft tissue balancing and/or inadequate postoperative bracing and therapy. Further complications related to implant wear can result in silicone particles inciting an inflammatory response and subsequent erosive changes. Salvage procedures for complications related to MP joint arthroplasty typically involve revision capsuloligamentous reconstruction in cases ofin-stability, or implant replacement in the event of implant failure or fracture. With more serious complications such as deep infection or bony erosion and loss of bone stock secondary to silicone synovitis, simple resection arthroplasty is a reasonable option.

Acknowledgments

This chapter is dedicated to James W. Strickland who is always willing to share his wisdom through years of experience.

Suggested Readings

Beckenbaugh RD, Dobyns JH, Linscheid RL, Bryan RS. Review and analysis of silicone-rubber metacarpophalangeal implants. J Bone Joint Surg [Am] 1976;58A: 483-487.

Bieber EJ, Weiland AJ, Volenec-Dowling S. Silicone-rubber implant arthroplasty of the metacarpophalangeal joints for rheumatoid arthritis. J Bone Joint Surg [Am] 1986;68A:206-209.

Kirschenbaum D, Schneider LH, Adams DC, Cody RP. Arthroplasty of the metacar-pophalangeal joints with use ofsilicone-rubber implants in patients who have rheumatoid arthritis: long-term results. J Bone Joint Surg [Am] 1993;75A:3-12.

Millender LH, Nalebuff EA. Metacarpophalangeal joint arthroplasty utilizing the silicone rubber prosthesis. Orthop Clin North Am 1973;4:349-371.

Nalebuff EA. Surgical treatment of finger deformities in the rheumatoid hand. Surg Clin North Am 1969;49:833-846.

Swanson AB. Flexible implant arthroplasty for arthritic finger joints. Rationale, technique, and results of treatment. J Bone Joint Surg [Am] 1972;54A:435-455.

Section XII

Congenital Anomalies of the Hand

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