Functional follow-up after endoscopic calcaneoplasty for Haglund's deformity using the biodex isokinetic muscle testing system: A case series

Isokinetic muscle strength test implemented by the Biodex system is a method used for evaluating muscle function that has been applied clinically in the field of sports and rehabilitation medicine. However, information on its application on Haglund's deformity remain insufficient. Therefore, the present study examined the effectiveness of the muscle strength test using the Biodex system in evaluating the recovery of athletic capacity in patients with Haglund's deformity following endoscopic surgery. In total, 34 patients treated by the authors from June 2012 to November 2018 at Peking University Third Hospital (Beijing, China) were included. To compare muscle strength before surgery, then 3 and 6 months after surgery, using the uninjured side as the control, the Biodex system test was conducted in parallel to the collection of the American Orthopaedic Foot and Ankle Score values and visual analog scale scores. The Biodex system test results showed that Haglund's deformity mainly hinders plantar flexion strength. Patients recovered daily living capacity within 3 months and athletic capacity within 6 months following surgery, which matched the AOFAS values, VAS scores and the self-assessments of the patients. These findings suggest that the Biodex system can dynamically reflect the degree of postoperative recovery in Haglund's deformity.