Sex Differences in Patients With CAM Deformities With Femoroacetabular Impingement: 3-Dimensional Computed Tomographic Quantification.

PURPOSE: To determine if significant differences exist between male and female CAM deformities using quantitative 3-dimensional (3D) volume and location analysis.

METHODS: Retrospective analysis of preoperative computed tomographic (CT) scans for 138 femurs (69 from male patients and 69 from female patients) diagnosed with impingement from November 2009 to November 2011 was completed. Those patients who presented with hip complaints and had a history, physical examination (limited range of motion, positive impingement signs), plain radiographs (anteroposterior pelvis, 90° Dunn view, false profile view), and magnetic resonance images consistent with femoroacetabular impingement (FAI) and in whom a minimum of 6 months of conservative therapy (oral anti-inflammatory agents, physical therapy, and activity modification) had failed were indicated for arthroscopic surgery and had a preoperative CT scan. Scans were segmented, converted to point cloud data, and analyzed with a custom-written computer program. Analysis included mean CAM height and volume, head radius, and femoral version. Differences were analyzed using an unpaired t test with significance set at P < .05.

RESULTS: Female patients had greater femoral anteversion compared with male patients (female patients, 15.5° ± 8.3°; male patients, 11.3° ± 9.0°; P = .06). Male femoral head radii were significantly larger than female femoral heads (female patients, 22.0 ± 1.3 mm; male patients, 25.4 ± 1.3 mm; P < .001). Male CAM height was significantly larger than that in female patients (female patients, 0.66 ± 0.61 mm; male patients, 1.51 ± 0.75 mm; P < .001). Male CAM volume was significantly larger as well (male patients, 433 ± 471 mm(3); female patients, 89 ± 124 mm(3); P < .001). These differences persisted after normalizing height (P < .001) and volume (P < .001) to femoral head radius. Average clock face distribution was from the 1:09 o'clock position ± the 2:51 o'clock position to the 3:28 o'clock position ± the 1:59 o'clock position, with an average span from the 3:06 o'clock position ± the 1:29 o'clock position (male patients, the 11:23 o'clock position ± the 0:46 o'clock position to the 3:05 o'clock position ± the 1:20 o'clock position; female patients, the 11:33 o'clock position ± the 0:37 o'clock position to the 2:27 o'clock position ± the 0:45 o'clock position). There were no differences in the posterior (P = .60) or anterior (P = .14) extent of CAM deformities. However, the span on the clock face of the CAM deformities varied when comparing men with women (male patients, the 3:43 o'clock position ± the 1:29 o'clock position; female patients, the 2:54 o'clock position ± the 1:09 o'clock position; P = .02).

CONCLUSIONS: Our data show that female CAM deformities are shallower and of smaller volume than male lesions. Further studies will allow further characterization of the 3D geometry of the proximal femur and provide more precise guidance for femoral osteochondroplasty for the treatment of CAM deformities.

CLINICAL RELEVANCE: Female CAM deformities may not be detectable using current 2D nonquantitative methods. These findings should raise the clinician's index of suspicion when diagnosing a symptomatic CAM lesion in female patients.