300 Section - Posterior ankle soft tissue echo intensity is associated with anterior ankle impingement following ankle fracture surgery: a cross-sectional study

Limited ankle dorsiflexion range of motion (ROM) and anterior ankle pain are common sequelae following ankle fracture surgery. While anterior ankle impingement syndrome (AAIS) is traditionally linked to anterior structural changes, the role of posterior soft tissues such as the flexor hallucis longus (FHL) and Kager’s fat pad (KFP) remains unclear. This study aimed to investigate the association between the echo intensity (EI) of posterior ankle soft tissues and the clinical presentation of AAIS in patients who had undergone ankle fracture surgery.

Design: This cross-sectional study included 40 patients who underwent open reduction and internal fixation for ankle fractures. Anterior ankle pain intensity was assessed using a visual analogue scale during forced dorsiflexion as part of the Molloy–Bendall test in a non–weight-bearing position to capture pain provoked under conditions characteristic of anterior ankle impingement. Ankle dorsiflexion ROM was measured under both weight-bearing and non-weight-bearing conditions. The EI of the FHL and KFP was quantified from grayscale B-mode ultrasound images. Multiple regression analyses were conducted to identify independent predictors of anterior ankle pain and dorsiflexion ROM.

Results:

Increased EI of the FHL (β = 0.698, P < 0.001) and KFP (β = 0.273, P = 0.007) was independently associated with greater anterior ankle pain. Higher FHL EI also predicted reduced dorsiflexion ROM. Participants with a positive FHL stretch test exhibited significantly greater EI values in both the FHL and KFP, higher pain intensity, and more restricted dorsiflexion compared to those with a negative test.

Conclusion:

Increased stiffness of the posterior ankle soft tissues, especially the FHL, is associated with anterior ankle pain and limited dorsiflexion following ankle fracture surgery. These findings highlight the potential value of posterior tissue assessment and targeted rehabilitation to address symptoms of AAIS.