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The Cam Impinging Femur Has Multiple Morphologic Abnormalities*Philip Noble - Institute of Orthopedic Research and Education - Houston, USAMichael Conditt - MAKO Surgical Corp. - Boerne, USAMatthew Thompson - Institute of Orthopedic Research and Education - Houston, USAMolly Usrey - Institute of Orthopedic Research and Education - Houston, USAGregory Stocks - Fondren Orthopedic Group - Houston, USA*Email: pnoble@bcm.eduIntroduction: Femoro-acetabular impingement (FAI) is a common source of impaired motionof the hip, often attributed to the presence of an aspherical femoral head. However, other typesof femoral deformity, including posterior slip, retroversion, and neck enlargement, can alsolimit hip motion. This study was performed to establish whether the “cam” impinging femur hasa single deformity of the head/neck junction or multiple abnormalities.Materials and Methods: Computer models of 71 femora (28 normal and 43 “cam” impinging)were prepared from CT scans. Morphologic parameters describing the dimensions of the head,neck, and medullary canal were calculated for each specimen. The anteversion angle, alphaangle of Notzli, beta angle of Beaulé, and normalized anterior heads offset were also calculated.Average dimensions were compared between the normal and impinging femora.Results: Compared to the normal controls, the impinging femora had wider necks (AP: 15.2 vs13.3 mm, p2mm), compared to only 14%of normal controls. Average head displacements for the two groups were: FAI: 1.93mm vsNormals: 0.78mm (p