The effect of flexor tendon adhesions on finger range of motion

Bony and soft tissue hand injuries are common and their ensuing management can result in adhesions between tendons and the surrounding bone, soft tissues or inserted hardware. Knowledge of the patterns of motion restriction imparted by different adhesions has implications for rehabilitation protocols following injury or surgery. The aim of this study was to quantify the degree and pattern of digital motion loss due to adhesions at various levels of the flexor apparatus in a cadaveric model.

Ten cadaveric limbs underwent range of motion assessment of the digits in a standardized fashion. Simulated adhesions were performed by applying suture anchors at the level of the middle phalanx, before subsequently being excised and further adhesions performed at the level of the proximal phalanx. The range of motion of the metacarpophalangeal (MCPJ), proximal (PIPJ) and distal interphalangeal joints (DIPJ) were recorded for each measurement.

Following the placement of a simulated adhesion between the flexor digitorum superficialis and FDP tendons at the level of the proximal phalanx, median total flexion reduced by 32.6°, predominantly occurring at the level of the DIPJ. Extension decreased by 9.2°. When a simulated adhesion was placed between the FDP tendon and middle phalanx, median total flexion reduced by 14.4°, predominantly occurring at the DIPJ. Extension decreased by 8.6°.

Adhesions in the flexor apparatus led to restrictions in both flexion and extension range, with DIPJ flexion being disproportionately affected. Interestingly, adhesions at different locations yielded similar patterns of motion loss, likely secondary to the FDPs substantial role in digital flexion. These findings may inform hypothesis for clinical practice and may assist in the future management of flexor tendon injuries, though must be taken in the context of a cadaveric, FDP dominant model.