Popliteal entrapment syndrome—The case for a new classification

Objectives: To assess the ability of the current classification system for popliteal entrapment syndrome to accurately capture all patients, and if not, to design an all-inclusive new classification. Methods: Retrospective review of all interventions performed for popliteal entrapment syndrome between 1994 and 2013 at our institution was performed. Preoperative imaging and intraoperative findings were used to establish the compressive morphology of popliteal entrapment syndrome. Patients were categorized, when possible, into six types of the current classification system (Rich classification, modified by Levien) and into seven types of a new classification. Results: Sixty-seven limbs of 49 patients were operated on for unilateral (31) or bilateral (18) popliteal entrapment syndrome. The current classification system captured the anatomy of only 43 (64%) of 67 limbs with popliteal entrapment syndrome. Compressive morphologies without a defined class included aberrant insertion of the lateral head of gastrocnemius muscle, muscle slip originating from the lateral head of gastrocnemius or hamstrings, hypertrophied hamstring muscle, abnormal fibrous bands, perivascular connective tissue, and prominent lateral femoral condyle. The new classification captured 100% of the limbs with popliteal entrapment syndrome. Conclusions: Current classification of popliteal entrapment syndrome is inadequate as more than one-third of the cases reviewed fell outside of the standard classification system. Consideration of a more inclusive new anatomic classification system is warranted.