Soft tissue abnormalities in Wassel Type VI radial polydactyly: a detailed anatomical study

Abstract

Wassel VI radial polydactyly is associated with metacarpal adduction and radial deviation of the metacarpophalangeal joint of the ulnar duplicate. The soft tissue abnormalities responsible for these deformities were characterized using preoperative multi-planar three-dimensional ultrasound and intraoperative observation in four patients. In all patients, the abductor pollicis brevis and superficial head of the flexor pollicis brevis inserted into the radial first metacarpal, whereas the adductor pollicis and deep head of the flexor pollicis brevis inserted into the ulnar thumb. Aberrant location of the flexor pollicis longus and absence of the A1 pulley system was associated with severe radial deviation. An additional superficial thenar muscle along the ulnar metacarpal was associated with minimal metacarpal adduction. Uneven forces on the ulnar duplicate could be associated with these characteristic deformities and joint instability. Knowledge of these abnormalities allows better planning of surgery and further insight into this rare radial polydactyly configuration. Level of evidence: II

Triplication and tetraplication of the thumb: a modification of the Rotterdam classification

“…Ongoing challenges remain, for example, a triphalangeal thumb component usually present with different degrees of hypoplasia involving both skeletal and muscle structures (Saito et al, 2018). These variations have led to several recent publications to categorize the deformities more adequately in efforts to facilitate communication (Saito et al, 2021(Saito et al, , 2023.…”

Use of the duplication range concept for understanding morphology and predicting prognosis in thumb polydactyly

“…The syndactylous web between the two thumb duplicates is an area of conglomeration, that is, soft tissues are shared by the two thumbs proximally whereas they are independent distally, albeit hypoplastic. In this area, bifurcating flexor pollicis longus (FPL) tendons pass through wide pulley structures (He and Nan, 2016; Saito et al., 2021; Tien et al., 2007) and the thenar musculature inserts separately into the radial and ulnar thumbs, causing abduction–adduction imbalances (Saito et al., 2021). We proposed the term ‘duplication range’ to refer to the region between the distal margin of the syndactyly and proximal skeletal bifurcation levels.…”