Comparative Efficacy of Surgical Versus Nonsurgical Management for Acute Achilles Tendon Rupture in a Novel Mouse Model

BACKGROUND: Acute Achilles tendon rupture is a common and serious injury in sports medicine. Clinical studies demonstrate that both surgical and nonsurgical interventions can achieve satisfactory outcomes; however, considerable debate exists regarding the optimal treatment modality for this injury. Currently, most animal experimental studies on acute Achilles tendon rupture lack clinical relevance due to inadequate fixation of the ankle joint. METHODS: This study involved 162 male C57BL/6 mice and 30 Scx-CreER T2 ; Rosa26-tdTomato transgenic mice. The injury+repair groups underwent Achilles tenotomy followed by Kessler suture repair, while the injury+no repair groups underwent tenotomy alone. Ankle joints were immobilized at 160° (plantar flexion) or 90° (neutral alignment). Samples were collected at 2 and 4 weeks post-injury for biomechanical, histological, and quantitative real-time PCR (qPCR) analyses, including tracing of Scx + tendon progenitor stem cells. RESULTS: Biomechanical analysis was performed 2 and 4 weeks post-injury. At 2 weeks, the injury+repair group immobilized at a maximum plantar flexion angle of 160° showed significantly higher failure force and stiffness compared with the injury+no repair+160° group. However, there was no significant difference between the groups at 4 weeks (p > 0.05). The failure force in each 160° group was significantly higher than in the corresponding 90° group (p < 0.0001). Histological analysis indicated better collagen fiber alignment and higher expression of collagen type I alpha 1 (COL1A1) in the injury+repair groups. qPCR revealed generally higher expression of tendon repair-related genes ( Scx, Tnmd, Tgfb1 ) in the injury+repair groups, while inflammatory factors ( Il1b, Il6 ) were higher in the injury+no repair+90° group. Scx + tendon progenitor stem cell tracing showed the greatest percentage in the injury+repair+160° group. CONCLUSIONS: Both surgical and nonsurgical treatments for acute Achilles tendon rupture achieved satisfactory tendon healing results when the ankle joint was maintained in maximum plantar flexion. However, surgical treatment yielded superior histological tendon repair. CLINICAL RELEVANCE: The results suggest that clinical trials may show immobilization in maximum plantar flexion following surgery to be optimal for tendon healing.