Ankle-foot deformities, such as clubfoot, pose treatment challenges due to complex and patient-specific biomechanics. Accurate assessment of muscle force behavior is essential for tailoring interventions, yet conventional gait analysis is limited in isolating muscle-specific function. Intraoperative force measurements via the muscle’s tendon offer a unique opportunity to directly quantify muscle mechanics. This study aimed to characterize the passive and active force-angle relationship of the tibialis anterior (TA) muscle, intraoperatively. Ten patients (ages 3–62) undergoing corrective foot surgery were enrolled, including five with idiopathic deformities and five with neurogenic conditions (hereditary motor and sensory neuropathy, n = 3; cerebral palsy, n = 2). Isometric TA forces were recorded at multiple ankle angles. Patients with neurogenic deformities exhibited greater ankle range of motion compared to those with idiopathic deformities (by 30.1%, p = 0.006). Passive forces were near 0 N in dorsiflexion and increased toward plantar flexion (PF), with a maximum of 50.3 N at 55° PF; no significant group differences were observed (p = 0.42). Active force-ankle angle profiles showed high inter-individual variability, with peak values ranging from 31.1 N to 431.6 N and no significant differences between groups (p = 0.81). Substantial variability in curve shape remained after normalization, indicating distinct functional profiles across patients. This study demonstrates the feasibility of directly quantifying the patient-specific force-generating capacity of the TA muscle. From a forward-looking perspective, incorporating such patient-specific force data into musculoskeletal models may improve force estimations and support more personalized surgical strategies for ankle–foot deformities.
Keles et al. (Sun,) studied this question.