Introduction: Thumb duplication is one of the most common congenital malformations of the hand.

The goals of surgery are to ablate the hypoplastic component and to create a stable and well-aligned thumb with a good pinch-function besides a maximum of mobility. Yet this aim is seldom achieved by simple ablative surgery alone which often results in a residual deformity and loss of function.

The objective of this review is a critical analysis of the used surgical techniques in 113 cases of thumb duplication.

Patients and Methods: Within the 11 year period from 1992 to 2003 113 patients (67 male, 46 female) with 120 duplicated thumbs (7 bilateral) underwent surgery at our institution. Details of primary reconstruction, X-ray findings, follow-up details, analysis of secondary deformities and details of secondary surgery were documented and evaluated. The follow-up time ranged from 6 months to 10 years. The patients were evaluated for functional and cosmetic outcomes.

Results: The right thumb was involved in 63 patients, the left in 57 and both sides were affected in 7 cases.11 Patients had associated anomalies.

Using the classification proposed by Wassel to grade the thumb duplication the most frequent types were IV with 53 cases (48%), II with 27 cases (24%). Patient age at the time of initial surgery varied from 5 months to 26 years with a mean age of 20 months.

11 patients underwent previous surgery in another institution and had a second surgery at our hospital.

8 Patients underwent only simple ablation, in 88 cases there was an excision combined with reconstruction of collateral ligaments, in 51 cases combined with a tendon transfer or release and reinsertion. Osteotomy of the metacarpal bone or proximal phalanx was performed in 47 cases. 5 patients received a Bilhaut-Cloquet procedure.

The most common complications were joint deviation (n = 12), joint stiffness (n = 2), joint instability (n = 11), nail deformity (n = 5) and scarring (n = 7). The 10 patients who under-went primary surgery at another institution and had to be reoperated are included in this listing.

The type of secondary reconstruction was in 7 cases scar release, in 6 cases a ligament reconstruction, 4 patients received an arthrodesis and 6 patients needed a corrective osteotomy.

Conclusions: Thumb function is critical to hand function. Despite its seeming simplicity surgery of thumb duplication is a complex procedure. Nowadays it is recognized that simple ablation leeds mostly to poor functional and cosmetic results. Treatment requires a thoroughful preoperative assessment, as well as an appreciation and understanding of the bony, capsuloligamentous and tendinous components involved. Taking this into account in mostly all cases a satisfactory cosmetic and functional result can be achieved.