gms | German Medical Science

Objectives/Interrogation: To analyze the morphologic characteristic of the first web space in thumb duplication in infants (1.5-3 years old) and to assess reliability of three palmar thumb abduction measurement methods about the first web space.

Methods: 130 patients (110 duplication thumbs and 20 tenosynovitis with one side) were involved in between February in 2016 to June in 2018. 18 months to 3 years old, average age was 23.1 ±6.1 months. According to Wassel classification, we classified the 110 thumbs in type I (2), type II (18), type III (7), type IV (48), type V (6), type VI (12), type VII (17). One observer used the special vernier caliper and goniometer to measure the first web space distance in Cambridge-Keeling method, the intermetacarpal distance (IMD) and intermetacarpal angle (DIMA) between the first and second metacarpal in 130 patients to acquire the both sides data. The other one observer measured 50 normal sides (including 20 patients in tenosynovitis and 30 cases in duplication thumbs) independently to determine the intraobserver reliability. Compared the difference between thumb duplication and the normal side using paired t test

Results and Conclusions: There were 38 thumbs in total in Wassel type I, II, III and type IV without the first metacarpal upright ulnar deviation. The first web space distance, IMD and DIMA were 2.59±0.46cm and 2.47±0.39cm,3.47±0.45cm and 3.39±0.37cm,41.84±3.22° and 41.81±3.39° between normal and unnormal sides,without statistically significant difference (the distance t=3.372, p=0.451, IMD:t=1.529, p=0.144, DIMA:t=0.224, p=0.826). There were 72 thumbs in Wassel type IV with the first metacarpal head ulnar deviated and Wassel type V, VI, VII totally. The first web space distance, IMD and DIMA were 2.68±0.33 cm and 2.19±0.47cm, 3.47±0.36 cm and 3.02±0.53 cm,42.32±3.87° and 35.35±6.73° between normal and impaired side, with statistically significant difference (the distance: t=5.257, p=0.000, IMD: t=4.585, p=0.000, DIMA: t=7.730, p=0.000). The mean values of the first web space distance in 130 normal thumbs was 2.62± 0.33 cm.The IMD and DIMA were 3.48 ± 0.31 cm and 43.43 ±3.43°. The intraclass correlation coefficient (ICC) values for intraobserver reliability about the first web space distance, IMD and DIMA were 0.74, 0.80 and 0.71, respectively. The first web space narrowing in thumb duplication was mainly in Wassel type IV with the first metacarpal ulnar deviation and Wassel type V, VI, VII. ICC of the first web space distance, IMD and DIMA indicated substantial reliability to assess the first web space in little children.