Acute Proximal Hamstring Tears Can be Defined Using an Imaged-Based Classification

PURPOSE: To develop a clinically meaningful proximal hamstring tear classification system and to present outcome data for defined subtypes. METHODS: Retrospective review was undertaken of patients diagnosed with proximal hamstring tears at a single institution from 2012 to 2019. Images were reviewed by an orthopedic surgeon and musculoskeletal radiologist. Tears were classified as Type 1: partial with subtypes (1A, 1 cm or mild complete tear; 1B, 1-2 cm or full tear with <2 cm retraction), Type 2: complete single-tendon tears with subtypes (2c conjoint tendon only; 2s semimembranosus tendon only); or Type 3: complete tears with >2 cm retraction. Demographics, patient-reported outcome measures including Hip Outcome Score, Activities of Daily Living Subscore (HOS-ADL) and patient satisfaction were evaluated. A poor outcome was defined as HOS-ADL < 80%, and the patient acceptable symptom state (PASS) was defined as HOS-ADL 89.7%. RESULTS: At a mean follow-up of 38.6 (range: 12-94) months for 114 patients, distributions were as follows: 18.4% Type 1A, 19.2% Type 1B, 7.8% Type 2c, 3.5% Type 2s, and 50.9% Type 3. Intra-observer and inter-observer reliability had a mean Kappa of 0.985 (95% CI: .956, 1.01) and .905 (95% CI: .895 .915). 66 patients underwent surgery, with 68.97% of them being Type 3. The mean HOS-ADL and PASS rate were higher for operatively treated patients (95%, 93.4%) than for nonoperatively treated patients (81.86%, 44.7%). There were significantly more patients satisfied in the surgery group in both Type 1 and Type 3 tears (P = .046 and P = .049). Body mass index was a significant predictor of a poor outcome in Type 3 tears (P = .039). History of corticosteroid or PRP injection, smoking, and diabetes were not significant predictors of a poor outcome. CONCLUSION: We present an MRI-based classification system for proximal hamstring injuries with both excellent intra-observer and inter-observer reliability. Outcome measures were improved in patients who underwent surgery. LEVEL OF EVIDENCE: IV, cohort study: diagnostic case series.