gms | German Medical Science

Objectives/Interrogation: The aim of this study was to evaluate the pathological characteristics of congenital clasped thumb, and the results of surgical procedure selection according to these characteristics.

Methods: We reviewed 34 congenital clasped thumbs between 2010 and 2017. The pathological characteristics were ascertained through preoperative examination and intraoperative surgical exploration. The most common pathological change was skin and soft tissue contractures at levels of the first web and thumb palmar in 94.1% cases, while 88.2% cases showed hypoplasia of Extensor Pollicis Brevis (EPB), which are threadlike or absent tendon, with occasional abnormal reinsertion. The contracture of Adductor Pollicis (deep head) and Flexor Pollicis Brevis (transverse head) were seen in 64.7% and 47.1% cases, respectively, often associated with abnormally stronger tendon. The characteristics of Abductor Pollicis Brevis (APB) hypoplasia (58.8%) were similar to EPB hypoplasia. The collateral ligament hypoplasia of MP joint in 38.2% cases was characterized as MP joint instability, ligament laxation, occasionally concurrent with palmar capsule contracture and dorsal capsule laxation, while 14.7% cases were EPL hypoplasia.

Results and Conclusions: Our surgical strategy was as follows: 1. Satisfactory passive motion and no active motion of MP joint was considered to result from extensor and concurrent APB hypoplasia. Tendon transfer was performed (EIP to EPB, one strand of FDS transferred to APB, the other strand transferred to EPL and EPB). 2. MP joint had poor passive and active motion. The first web space and thumb palmar skin was widened using our modified Z-plasty, which was followed by: a. improvement of passive extension and abduction of MP joint (refer to Item 1). b. no improvement of passive motion. Contractures of palmar intrinsic muscle and/or MP joint required attention. We preferred modified tendon lengthening on deep head of Adductor Pollicis and FPB transverse head, and MP joint arthrolysis. 3. Unstable MP joint caused by collateral ligament hypoplasia was provided imbricated ligament in mild cases and chondrodesis in severe cases. MP joint fixation with K-wire was needed. Tendon transfer was performed in the second stage. According to Gilbert assessment, the outcomes of our strategy were excellent/good in 70% cases, fair in 26.5% cases, and poor in 2.9% cases.

Surgical preference based on pathological characteristics of congenital clasped thumb is effective in improving thumb function and cosmetic appearance.