Objective: To evaluate if the complete resection of the femoral bump, in cam-type FAI increases the postoperative flexion and internal rotation.

Material and Method: We reviewed 24 consecutive pre-operative and postoperative hip CT scans in 24 patients with FAI (22 male and 2 female, mean age 36.9 years) who underwent arthroscopic hip surgery for the removal of a bony prominence on the femoral neck-head junction. We measured the alpha angle in two places: in the classical location, in the mid plane of the femoral neck axis and proximally, in the same plane but in first quarter of the femoral neck height. Then we compared these results with the presence of a residual prominence diagnosed in the 3 dimensionally reconstructed images of the postoperative CT scan and the virtual range of motion of the 3D models using impaction detection software.

Results: We found 7 cases with a residual bony prominence at the femoral neck-head junction in the 3D model of the proximal femur after the surgery. In this group the mean mid femoral neck alpha angle was significantly improved from 69.7° before the surgery to 48.3° (p=0.028), however the proximal alpha angle was not significantly improved 71.1° preoperative versus 62.7 (p=0.176) after the surgery. In the 17 patients without a residual bump, both alpha angles were improved, the mid alpha angle from 64.9° before the surgery to 40.76° (p=0.000) after the surgery and the proximal alpha angle from 65.8° to 38.4° (p=0.000). The range of motion of hip in the impaction detection software was also significantly improved in both groups, from flexion of 103° to 116° (p=0.001) in the group without a residual bump and from 102 to 118 (p=0.046) in the group with a residual bony prominence after the surgery. The internal rotation at 90° of flexion was also improved in both groups with a statistically significant difference (p=0.001 versus p=0.028 respectively).

Conclusion: The complete arthroscopic resection of the femoral bump improves significantly the ranges of flex-ion and internal rotation in patients with cam-type FAI.