The case for cam surveillance: the arthroscopic detection of cam femoroacetabular impingement missed on preoperative imaging and its significance.

Classification of femoroacetabular impingement is typically determined by preoperative imaging. Despite measurements such as the alpha angle and anterior offset ratio, cam dysmorphisms may be missed. We present 2 cases of femoroacetabular impingement classified as pincer subtypes where significant cam lesions were not detected until surgery. Arthroscopic cam surveillance includes the intentional visualization of the anterior and lateral proximal head-neck junctional region from the peripheral compartment performed with capsular retraction and/or partial capsulectomy. Static and dynamic cam surveillance of the proximal femur is recommended before the termination of surgery for hip chondrolabral dysfunction and has even greater significance in the arthroscopic management of these patients.