Reconstruction of Chronic Achilles Tendon Ruptures with Hamstring Autografts: Plantar Flexor Strength Is Preserved Despite Shortening of the Moment Arm

Background: Chronic Achilles tendon ruptures present a major surgical challenge due to tendon retraction, degeneration, and large defects. Autologous hamstring tendon grafts have emerged as a reliable reconstructive option, yet their biomechanical consequences remain poorly understood. This study investigated whether Achilles tendon reconstruction with semitendinosus and gracilis autografts alters the plantar flexor moment arm and whether such changes affect muscle strength. Methods: A cohort of 25 patients (mean age: 44.5 years) underwent minimally invasive endoscopic reconstruction using hamstring autografts. This secondary salvage procedure was performed in patients with neglected ruptures or failed primary treatment. Five patients were excluded from the original intervention group due to inadequate radiographic quality. Radiographic measurements of the Achilles tendon moment arm and isometric plantar flexor strength assessments were performed at 12 and 24 months postoperatively. Statistical analyses included paired t-tests, Wilcoxon signed-rank tests, and correlation analyses. Results: Results showed a significant shortening of the Achilles tendon moment arm after reconstruction compared with the preoperative imaging length (mean reduction: 6.6 mm; p < 0.0001). Despite this, plantar flexor strength in the operated limb improved significantly over time at 12 and 24 months (+388.6 N at 24 months; p = 0.0067) and did not correlate with the degree of moment arm shortening (p > 0.3). By 24 months, the operated limb demonstrated comparable or greater strength than the contralateral side, with nearly half of the patients achieving substantial clinically meaningful improvements. Conclusions: In conclusion, Achilles tendon reconstruction with hamstring autografts leads to consistent moment arm shortening, yet this does not impair long-term restoration of plantar flexor strength. A progressive rehabilitation program extending up to two years appears essential to optimize recovery and compensate for biomechanical alterations.