Bone Volumes and Trajectory Angles for Acetabular Anchor Placement Can Be Optimized.

PURPOSE

The purpose of this study was to determine the optimal anchor placement and trajectory when repairing acetabular labral tears during hip arthroscopy with the primary focus on the 12 to 3 o'clock positions on the acetabular rim.

METHODS

Three-dimensional computational models of the pelvis were generated from 13 cadaveric specimens using 3D slicer medical imaging software. A set of cones, consistent with the dimensions of a commonly used sutured anchor, were virtually embedded into the models at the 12, 1, 2, and 3 o'clock positions around the acetabulum. Mirror images of the cone were extended toward the superficial aspect of the hip. The volume of bone occupied by the virtual anchor, the trajectory angle, and the volume of overlap between adjacent anchor locations were calculated.

RESULTS

Bone volume was significantly greater at the 1 o'clock position (4196.2 [1190.2] mm) compared with all other positions ( < .001). The 3 o'clock position had the smallest volume (629.2 [180.0] mm) and was also significantly less than the 12 ( < .001) and 2 o'clock ( = .014) positions). The trajectory angle of 32.04 [5.05]°) at the 1 o'clock position was significantly greater compared with all other positions ( < .001). The least amount of adjacent position overlap occurred between the 2 and 3 o'clock positions (.12 [.42] mm), and this was statistically smaller than the overlap between cones at the 12 and 1 o'clock positions (214.28 [251.88] mm;  = .029) and the 1 and 2 o'clock positions (139.51 [177.14] mm;  = .044).

CONCLUSIONS

Trajectory angles and the thickness of bone around the acetabulum were the greatest at the 12 to 1 o'clock positions, with the 1 o'clock position identified as that with the largest trajectory angle for safe anchor insertion.

CLINICAL RELEVANCE

The use of a single, workhorse portal, for anchor insertion may not be recommended and careful selection of a portal allowing a direct approach should be used for anterior anchor insertion.