Kurzfassung

Background Calcaneal fractures (CF) often result in reduced foot mobility and plantar flexor strength, despite intensive rehabilitation. While treatment mostly focuses on bone restoration, structural and functional adaptation of the ankle plantar flexors during movement is less understood. Research question To investigate medial gastrocnemius fascicle behavior and ankle biomechanics in patients with CF during bipedal heel-rise. Methods Repetitive heel-rise was analyzed in 18 patients with unilateral CF (BMI: 27.3 +/- 3.2 kgm(-2), Age: 50 +/- 13 years) and 18 healthy controls (BMI: 26.3 +/- 3 kgm(-2), Age: 48 +/- 11 years) using motion capture and ultrasound. Patients were measured 3 and 12 months after surgery. Dynamic gastrocnemius fascicle length, pennation angle, thickness, ankle angle, ground reaction force, heel lift, and B & ouml;hler angle were assessed. Results Between 3 and 12 months, pennation angle in patients increased by up to 33 % (p < 0.05), while fascicle length and thickness remained unchanged. Ankle plantarflexion and heel lift showed no improvement, while ground reaction force and symmetry increased by 12 % and 55 %, respectively. Compared to controls, patient's fascicle parameters showed no differences, while a reduced maximum plantarflexion and heel lift by up to 41 % remained. Ground reaction force recovered to control levels at 12 months. The average B & ouml;hler angle was 21.6 degrees (9.8-41.6 degrees). Significance Impaired foot stability and alignment originating from altered calcaneal anatomy after fracture, rather than muscle deficits, primarily contribute to a reduced ankle joint function one year post-surgery.