Clinical Presentation, Surgical Treatment, and Outcome in Radial Polydactyly

Abstract

Radial polydactyly or 'thumb duplication' is the most common congenital upper limb anomaly ('CULA') affecting the thumb. The clinical presentation is highly diverse, ranging from an extra thumb floating on a skin bridge to complicated thumb triplications with triphalangeal, deviating, and hypoplastic components. Radial polydactyly can be classified into one of 7 osseous presentations using the Wassel classification, with type IV (45%), type II (20%), and type VII (15%) occurring most frequently. When faced with a radial polydactyly case, hand surgeons specialised in congenital anomalies must weigh the preoperative functional potential and degree of hypoplasia of both thumbs in order to decide whether to resect one thumb and reconstruct the other ('resection and reconstruction'), excise a central part of both thumbs and unite the lateral tissues into one thumb ('the Bilhaut procedure'), transfer the better-developed distal tissues of one thumb onto the better-developed proximal tissues of the other ('on-top plasty'), or discard both severely hypoplastic thumbs and pollicise the index finger. Mere excision of the hypoplastic thumb is rarely indicated since it often requires subsequent revision surgery. Even after being treated by experienced surgeons, about 15% of patients with polydactyly will need additional procedures to correct residual and/or new problems such as deviation from the longitudinal axis and joint instability. Nevertheless, radial polydactyly patients usually achieve unimpaired everyday hand function postoperatively.

The Duplicated Thumb: A Review

“…By combining elements of the Wassel, Buck-Gramcko, and Upton taxonomies, it accounts for joint involvement and associated anomalies in all radial polydactylies, including the triphalangeal thumb and thumb triplication. 17,18 A study by Dijkman et al compared the reliability of the Wassel and Rotterdam classifications. 19 Out of a study population of 520 cases, only 60% could be classified using the Wassel classification, compared with 100% using the Rotterdam classification.…”

“…Joints distal to the duplication may also be hypoplastic, even though the better-developed thumb may exhibit near-normal movement. 17 Children have more difficulty with tip pinch with loss of flexion at the IP joint, but they often compensate well enough to preserve functionality. Stability of the distal thumb is more important than motion, and if the CMC joint is intact, motion should be sacrificed for stability if necessary.…”

“…These tendons may also have eccentric insertions, which can cause distal convergence of the duplicated thumbs. 17 Lastly, the shape of the thumb must be considered, as appearance is of utmost importance to the patient. 6 The duplicated thumbs usually retain smaller nails and pulp compared with the unaffected contralateral side, although the better-developed thumb typically arises from the ulnar side and is the larger of the two in the majority of cases.…”

“…6 The duplicated thumbs usually retain smaller nails and pulp compared with the unaffected contralateral side, although the better-developed thumb typically arises from the ulnar side and is the larger of the two in the majority of cases. Finally, the affected hand should also always be compared with the unaffected side when possible, 17 as bilateral involvement should alert the examiner to a possible syndrome, such as Townes-Brocks syndrome. 20 Radiography is necessary to provide information about the pattern of bone involvement and monitor changes over time.…”

“…4 Although the timing of surgery is somewhat arbitrary, reconstruction is typically performed as pinch function is developing, between 1 and 2 years of age, and before the development of fine motor skills. 17 The main goals of reconstruction are an improved appearance, and the restoration and maintenance of function and pinch activity. 20 When faced with a patient with radial polydactyly, hand surgeons specialized in congenital anomalies must analyze the preoperative functional potential and degree of hypoplasia of both thumbs to decide the best operative technique.…”