Association Between Radiographic Haglund Morphology and MRI-Measured Achilles Tendon Rupture Location: A Retrospective Cross-Sectional Study

Background/Objectives: Achilles tendon ruptures usually occur proximal to the calcaneal insertion. Whether posterosuperior calcaneal prominence is associated with rupture location remains uncertain. We examined the association between radiographic Haglund morphology and MRI-measured rupture-to-insertion distance. Methods: In this retrospective cross-sectional study, adults treated for acute Achilles tendon rupture from January 2015 to December 2025 were assessed. Rupture distance was measured on sagittal MRI. Two blinded orthopaedic surgeons measured bump height and the bump–calcaneus ratio on standard lateral ankle radiographs; radiographic Haglund morphology required both thresholds (≥4.0 mm and ≥7.5%, respectively). We compared groups with the Mann–Whitney U test and bootstrap confidence intervals and used median regression adjusted for age, sex, sport-related mechanism, and comorbidity. Results: Of 292 screened patients, 106 were included; 28 (26.4%) met the radiographic criteria. The cohort included 27 women (25.5%) and had a median age of 41.5 years. Interobserver ICC(2,1) values were 0.9976–0.9994, with complete agreement in threshold-derived classification (κ = 1.000). Median rupture distance was 1.60 cm (IQR, 1.49–2.58) with Haglund morphology versus 4.85 cm (IQR, 3.51–5.55) without it. The unadjusted median difference was −3.25 cm (95% CI, −3.40 to −2.68; p < 0.001); the adjusted association was −2.89 cm (95% CI, −3.61 to −2.17; p < 0.001). Conclusions: Radiographic Haglund morphology was associated with more distal Achilles tendon rupture in this selected rupture cohort. The retrospective design and exclusion of 113 patients with incomplete records limit generalizability; the study does not establish causality or whether morphology increases rupture risk.