Paper 12: Mri-based classification of achilles tendon ruptures: reliability and predictors of tear location

"Objectives: The study aimed to evaluate epidemiology of Achilles tendon ruptures to develop an MRI-based classification system for rupture location.
Methods: A comprehensive search was conducted for all patients with acute Achilles tendon injuries between 2003 to 2023. Tear locations were classified by five independent observers as follows (Figure 1): Type I (at the border of the musculotendinous junction), Type IA (2cm zone distal to the musculotendinous junction), Type II (mid-substance), Type III (2cm zone proximal to insertion), Type IIIA (soft-tissue 'peel-off'), Type IIIB (calcaneal bony avulsion). Clinicodemographic data was collected, and tendon thickness, tibiotalar and plantar flexion angle were measured.
Results: A total of 428 patients (mean age 45+-15 years; 17% female) were included. Mean rupture gap size was 30+-16mm in 73+-8° tibiotalar flexion (5+-9° plantar flexion). Mean tear location was 65+-26mm proximal to the calcaneal insertion and 10+-18mm distal from the musculotendinous junction (Table 1). Male sex, age, and tendinopathy were predictive for more distal tear locations (all p<0.01). For each additional year of age, the rupture location was estimated to be 0.4mm (0.3-0.6mm) more distal, while male sex with tendinopathy predicted a proximal tear location. Male sex but not age or tendinopathy were significantly correlated with increased tendon thickness (p < 0.01). Younger age (p < 0.01), distal tear location (p < 0.01), higher tendon thickness (p < 0.01), and higher tibiotalar angle (p < 0.01) were significantly associated with a larger rupture gap. Interobserver (3 observers, n=35) and intraobserver (1 observer, n=35) reliability for tear location measurements were almost perfect (Interobserver, Cohen's Kappa: 0.93; 95% CI (0.74-0.99); Intraobserver, Cohen's Kappa: 0.93; 95% CI (0.86-0.99)).
Conclusions: The MRI-based classification system offers a reliable method for identifying the anatomical location of Achilles tendon ruptures. Higher patient age was a significant predictor of a more distal tear location, whereas male sex with tendinopathy were associated with a proximal tear location. Rupture gap size was influenced by age, tear location, tendon thickness, and tibiotalar angle."