Thumb polydactyly: clinical outcome after reconstruction

Journal of Orthopaedic Surgery, Dec 2006 by Yen, C H, Chan, W L, Leung, H B, Mak, K H

ABSTRACT

Purpose. To evaluate clinical and cosmetic outcomes of reconstruction in thumb polydactyly and prognostic value of the Wassel classification.

Methods. Between 1993 and 2000 inclusive, out of the patients with thumb polydactyly (involving 80 thumbs) operated on, 34 patients (36 thumbs) were available for review and underwent clinical and radiological assessment. Outcomes in terms of the Tada score and complications were recorded.

Results. The mean age of patients at the time of operation was 2.8 (range, 0.6-47) years. The mean follow-up period was 5 (range, 2.4-10) years. According to the Wassel classification, 12 were type- II thumb polydactyly, 3 type-III, 11 type-IV, 6 type-V, one type-VI, and 3 type-VII. There was no perioperative mortality or wound infection. More than 88% of the patients were satisfied or very satisfied with functional and cosmetic outcomes. Postoperative complications such as scar hypertrophy, pulp atrophy, joint deformity, and instability were common but minor. Ridge nail deformity after the Bilhaut Cloquet procedure was amenable to secondary corrective procedures. All types of operated thumb polydactyly achieved similar mean Tada scores (14.7- 16.6 out of 20). The Wassel classification category, age, and surgical procedures were found to have no prognostic value with regard to the Tada score and presence of complications.

Conclusion. Surgery on thumb polydactyly is rewarding. The Wassel classification category can be used as a guide for treatment, although it fails to predict the occurrence of postoperative complications or Tada scores. Our patients' results can serve as guidelines of expected outcomes after reconstructive procedures in different sub-types of thumb polydactyly.

Key words: polydactyly; thumb; treatment outcome

INTRODUCTION

Thumb polydactyly is the most common type of polydactyly in the hand. It is believed to arise from excessive cell proliferation and disturbed cell necrosis of pre-axial ectodermal and mesodermal tissues before the eighth week of embryonic life.1 It occurs sporadically with an incidence of 8 in 100 000 in both black and white populations.2,3 Hereditary influence has not been documented in isolated thumb polydactyly, although Ezaki2 found its association in several syndromes. Autosomal dominance has been reported only in triphalangism and polysyndactyly.

The psychological burden of having an extra finger has been linked with psychosis in adulthood.4 Operation remains the definitive treatment with a goal to improve cosmesis and possibly hand function. 5-7 Since Bilhaut first described an operation for thumb polydactyly in 1890, different surgical procedures based on the type of radiographic abnormality have been reported.8-10 Currently, the Wassel classification is universally accepted to categorise the patho-anatomy of the polydactyly and to guide respective surgical procedures.5 However, its prognostic significance has been speculative as long-term outcomes of surgical treatment are seldom reported.11-13

We aimed at evaluating surgical outcomes and complications according to the Wassel classification category and its prognostic value, particularly to address the effectiveness of secondary surgical procedures to rectify residual deformities, ridge nail deformity, and Z thumb deformity.

MATERIALS AND METHODS

Polydactyly affecting 80 thumbs were operated between 1993 and 2000 in Kwong Wah Hospital. A dedicated surgical team performed all operations according to the guidelines on thumb reconstruction (Table 1). All patients were allowed immediate postoperative free mobilisation of all digits in bulky dressings. 34 of them (entailing 36 polydactyly thumbs) who had complete medical records and preoperative radiography were available for assessment. Intra-operative findings of soft tissue and osseous anomalies and details of the respective surgical procedures were retrieved from the medical record.

Review and measurements were conducted by one of the authors, blinded to the type of polydactyly (to avoid bias). Postoperative functional outcome was evaluated using the Tada score14 comprising of 3 evaluations: cosmetic, functional, and radiological. Patients were assessed clinically with respect to nail width of the operated thumb and cosmetic acceptability. Grip strength, tip and chuck pinch were measured using a Jamar Dynamometer (JA Preston Corp, Jackson [MI], USA) and pinch gauge (B&L Engineering, Pinsco Inc, Santa Fe Springs [CA], USA). Assessment specifically addressed first web contracture and bone growth. Evaluation of growth potential, instability, and deformity were performed clinically and radiologically. X-rays of thumbs were taken in posteroanterior view in full extension, stressed radially and ulnarly (without undue force), with the opposite thumb as self-reference. Full marks on the Tada score was 20.

Definition of growth parameters, first web contracture, stiffness, deformity, and instability were based on the Tada score. Retarded radial growth was defined as the thumb circumference of the distal and/or proximal phalanx being 25% of intermetarcarpal angle between the first and second metacarpal bones, when compared to the normal side. Stiffness was defined as a loss of >25% of the sum of active interphalangeal joint (IPJ) and the metacarpophalangeal joint (MCPJ) range of movement with reference to the normal side. Ulnar deformity was defined as >5° of ulnar angulation at the IPJ or >20° of angulation at the MCPJ in the resting position. Radial instability was defined as >5° of angulation at the IPJ or >20° at the MCPJ when the examiner subjected the thumb to maximal stress from the resting position. In cases of bilateral polydactyly, the digit with the less affected parameter was taken as the normal side for comparison.