In a pedunculated type of radial polydactyly, ligation at the base as close as possible to its root with 5-0 or 6-0 Nylon with or without local anesthesia can be performed in the outpatient department or nursery (Fig. 1). A ligated hypoplastic thumb will mummify and usually falls off within 2 weeks (Fig. 2). A nubbin or dimple usually remains afterward (Fig. 3). Even in pedunculated type of polydactyly, painful neuroma may develop after the ligation, which is an indication for surgical exploration (Leber and Gosain 2003).

When there is no bony connection between two polydactyly thumbs and a dominant thumb shows good stability, motion, and appearance, simple excision under general anesthesia is indicated (Figs. 4, 5, and 6).

Technique: An elliptical incision is made around the minor thumb. The soft tissue pedicle usually contains neurovascular structures. To avoid bleeding, the vessels should be ligated or cauterized. To prevent painful neuroma, the nerve should be identified, sharply transected, and embedded in the soft tissue.

Most of radial polydactyly can be successfully treated by the “excision and reconstruction” technique (Fig. 7). Main components of this procedure are arthroplasty, corrective osteotomy, and tendon realignment. When one of the two polydactylic thumbs is well developed and the other one less developed, this technique is indicated. However, when both polydactylic thumbs are hypoplastic, this technique results in a small thumb which is sometimes smaller than the index tip. Surgical technique for Wassel types 1 and 2 is similar. Also similar surgical technique can be applied to Wassel types 3, 4, 5, and 6. For the diversity of clinical features, surgical technique for Wassel type 7 should be individualized case by case.

Arthroplasty: Arthroplasty consists of joint stabilization by ligamentoperiosteal flap (Manske 1989) and partial excision of excessive portion of phalangeal or metacarpal head that articulates with the two thumbs.

Two thumbs articulate with a single proximal phalangeal head in Wassel type 1 or 2 radial polydactyly and on a single metacarpal head in type 3 or 4. During dissection of minor thumb, distal insertion of collateral ligament should be preserved with adjacent periosteal tissue for later reconstruction. This ligamentoperiosteal flap is reattached to base of phalangeal bone of the retained main thumb after removal of the minor thumb. The phalangeal or metacarpal head, when minor thumb is removed, is relatively large for the remained dominant thumb. This size mismatching may cause angular deformity and/or bony prominence if it is not corrected. Thus, excessive portion of the head needs to be shaved or removed. Sometimes, a separate facet that articulates with the radial thumb to be deleted is observed. This facet can be used as a guideline to cut excessive portion. Conventional oscillating saw or osteotomes cannot be used for small phalangeal bones of young children. Their phalangeal bones are soft enough that shaving of articular cartilage and partial ostectomy can be performed by a small rongeur or a No. 15 surgical blade. Excessive tension of the reconstructed collateral ligament to correct angular deformity at the joint level is not recommended because the deformity is likely to recur and stiffness of the joint may occur. However, angular deformity of less than 10° at the joint level can be corrected by this arthroplasty procedure. A longitudinal Kirschner wire (K-wire) is inserted to protect the reconstructed collateral ligament.

Corrective Osteotomy: Angulation at interphalangeal joint and reduced nail width are primary issues affecting appearance after the surgery (Goldfarb et al. 2008). More than 20° of angular deformity is not acceptable to most patients and parents. The angulation can be corrected by closed wedge osteotomy. Double-level osteotomy at proximal phalangeal and metacarpal levels can be indicated to align severe divergent-convergent Wassel type 4.

Tendon Realignment: Abnormal insertions of flexor pollicis longus (FPL) and/or extensor pollicis longus (EPL) are not uncommon in radial polydactyly, especially in Wassel type 4. The FPL tendon attaches not only at its customary insertion but also into the extensor by a tendon that passes around the radial aspect of the thumb. This anomalous muscle abducts the thumb instead of flexion and is called as pollex abductus (Tupper 1969; Lister 1991). The abnormal alignment of FPL and/or EPL may cause gradual angular deformity even after successful bony alignment has been achieved by corrective osteotomy. When there are abnormal insertions of FPL and/or EPL tendons, the insertion sites should be realigned to achieve a good flexion-extension arc. The abnormal insertion can be completely detached and reattached into the correct position. The phalangeal bones of young children are soft that the tendon can be sutured into the distal phalanx using 4-0 or 5-0 Nylon. When the phalangeal bone is too hard to be sutured by Nylon suture, a pullout suture technique can be used. When the distal portion of the tendon is bifid and inserted into both polydactylic thumbs, it usually inserts at ulnar side of the radial thumb and radial side of the ulnar thumb. If the radial thumb is to be removed, the tendon is detached from the insertion of radial thumb and reattached into the ulnar side of dominant ulnar thumb like Y shape to balance the vector forces (Figs. 8 and 9).

In Wassel type 4, 5, 6, or 7 polydactyly of the thumb, some of thenar muscles insert into the radial side thumb. In most cases, the radial thumb is removed and the ulnar thumb is reconstructed. The insertion site of thenar muscles on the radial thumb should be identified and dissected carefully for later reattachment to the main ulnar thumb.

Surgical Technique (Wassel Type 2): A 9-month-old boy showed hypoplastic Wassel type 6 radial polydactyly on right thumb and Wassel type 2 on left (Fig. 10). The nail size, length, and girth of ulnar side thumb of left hand were good enough to perform the “excision of radial thumb and reconstruction” procedure. Although the epiphyses of phalanges and metacarpal are not observed in simple radiograph (Fig. 11), it is easy to decide the surgical plan as “arthroplasty” with or without “tendon realignment.” Corrective osteotomy will not be necessary because angular deformity at the IP joint is minimal. A racquet-shaped incision was designed (Fig. 12). A zigzag incision has an advantage to prevent possible scar contracture, but this technique is not easy to apply to a small-sized thumb less than an inch in length in infant age. The dissection was deepened to expose distal phalangeal bone of the radial thumb, and a ligamentoperiosteal flap was raised using No. 15 blade (Fig. 13). Distal phalanx of the radial thumb was cut to be removed, and articular surface of this radial thumb was seen (Fig. 14). Articular surface for the radial thumb was cut using No. 15 blade (Fig. 15). The consistency of phalangeal bone in infant age is soft enough to be cut by surgical blade. There was no malalignment of tendon found. After the arthroplasty procedure, the articular surface of the proximal phalanx fit that of ulnar thumb (Fig. 16). Before reconstruction of the collateral ligament, a 0.7 mm K-wire was inserted longitudinally to protect it. The ligamentoperiosteal flap for reconstruction of the collateral ligament was attached to the new insertion site by 5-0 absorbable suture (Fig. 17). Direct suture of skin edge to the nail does not achieve normal lateral nail fold. A suture needle was introduced about 3 mm away from the skin flap to be sutured to the nail, and it came out 1 mm away from the skin flap to simulate the lateral nail fold. Then the needle was passed through the nail, and tied (Fig. 18). The reconstructed thumb looked straight and reconstructed lateral nail fold looked adequate (Fig. 19). On a postoperative radiograph, shaved proximal phalangeal head fit distal phalanx so well that IP joint looked natural (Fig. 20).

Surgical Technique (Wassel Type 4): An 11-month-old boy showed a divergent-convergent Wassel type 4 radial polydactyly. The radial thumb of left hand was hypoplastic, but the ulnar thumb showed good size and shape (Fig. 21). There was 40° of angular deformity at the IP joint of ulnar thumb that needed corrective osteotomy at proximal phalangeal neck level (Fig. 22). Medical photos and simple radiographs suggested strong possibility that arthroplasty of MP joint and tendon realignment of EPL, FPL, and thenar muscles were necessary for proper reconstruction. Proximal phalangeal head of the ulnar thumb was underdeveloped, suggesting a potential recurrence of angular deformity postoperatively. A racquet-shaped incision was designed (Fig. 23). The EPL tendon was bifurcated at MP joint level and inserted into both thumbs. The insertion site of radial EPL slip was detached (Fig. 24) and sutured to the ulnar side of dominant thumb to balance the extension force (Fig. 25). The FPL tendon showed the same pattern. The insertion site of radial FPL slip was detached and tagged with suture for later reattachment into the ulnar side of dominant thumb (Fig. 26). The abductor pollicis brevis muscle insertion into the radial thumb was detached from the proximal phalangeal base for later reattachment into the reconstructed thumb. The radial thumb was removed leaving ligamentoperiosteal flap for later reconstruction of the MP joint. The portion of metacarpal head to be resected was lined, and a ligamentoperiosteal flap was raised and preserved (Fig. 27). Excessive portion of articular cartilage and bone was removed by No. 15 blade and small osteotomes (Fig. 28). Then proximal phalanx was dissected subperiosteally for an ulnar-based closed wedge osteotomy to correct angular deformity at the IP joint (Fig. 29). It is convenient to perform ulnar-based closed wedge osteotomy from ulnar side incision. However, simultaneous medial and lateral incision on the same thumb may jeopardize blood circulation. The MP joint was fixed in a reduced position with a K-wire, and also osteotomy site of proximal phalanx was fixed with an additional K-wire (Fig. 30). Finally the FPL tendon detached from the radial thumb was reattached into the ulnar side of reconstructed distal phalanx. The abductor pollicis brevis tendon detached from radial thumb as well as the previously raised ligamentoperiosteal flap for collateral ligament reconstruction was reinserted into the base of proximal phalanx (Fig. 31). Alignment and appearance of the reconstructed thumb (Fig. 32) and the immediate postoperative radiograph (Fig. 33) showed reasonable result.