Purpose: The purpose of this study was to define a safe angle for suture anchor insertion during acetabular labral repair that will facilitate anchor placement within bone and prevent penetration into the hip joint.
Methods: Nine acetabuli were harvested. Anatomic measurements were performed at the anterosuperior quadrant. Electronic calipers were used to measure acetabular bone. "Safe angle" measurements were obtained with suture anchor drills and a protractor. Comparisons between groups were calculated with a 1-way analysis of variance. The Tukey post-hoc analysis was completed for all significant analysis of variance results.
Results: Labral insertion point distances and acetabular bone widths at the labral insertion did not statistically differ. Mean "danger angles" ranged from 17.0 degrees to 23.8 degrees. Safe angle measurements ranged from 20.1 degrees to 27.6 degrees.
Conclusions: The extracapsular labral insertion, located between 2.3 and 2.6 mm from the rim of the anterosuperior acetabulum, is offered as a starting point for insertion of anchors sized less than 3.0 mm. The danger angle and safe angle of anchor insertion serve as guidelines that may improve fixation in bone and lessen intra-articular penetration. A target angle of 10 degrees is recommended.
Clinical relevance: The danger angle and safe angle may be referenced intraoperatively, during imaging and suture anchor insertion, to assure anchor placement within bone and prevent intra-articular penetration. A target angle of 10 degrees is safe and easily remembered.