The simplest method to classify CAM lesions.

CAM lesions are now seen as a significant pathology that could cause osteoarthritis of the hip joint. Currently there is no gold standard for classifying these lesions. We aim to show a simple method for classifying these lesions based on shape and position. Using CT 3D reconstruction, 91 preoperative CT scans from patients who had undergone hip arthroscopy for femoroacetabular impingement, were reconstructed to produce 3D images. Two senior hip surgeons have devised a simple four type classification system from previous experience. The system highlights the position and shape of different CAM lesions present in patients. The two senior surgeons and one junior surgeon reviewed the scans individually to assess whether the system could be used at all levels of surgical experience. The two senior surgeons agreed on which type of CAM lesion was present in all 91 cases. Intra observer reliability scores for the senior surgeons were 0.90 and 0.91. The junior surgeon reviewed the scans and disagreed on eight cases. This gave a Kappa co-efficient score of 0.87, which confirms a reliable system. We believe this classification system is simple and reproducible. It will aid surgeons in pre and intra-operative management of CAM lesions. Surgeons will be able to select the optimal portal placement and resect less capsule depending on the exact CAM lesion identified. This will potentially reduce complications and improve outcomes in junior hip arthroscopy surgeons.