Introduction

The number of complex revision total hip arthroplasties (THA) is predicted to rise. The identification of acetabular bone defects prior to revision THA has important implications on technique and complexity of acetabular reconstruction. Paprosky et al. proposed a classification system including 3 main types with up to 3 subtypes focused on the integrity of the superior rim of the acetabulum and medial wall. However, the classification system is complex and its reliability has been questioned. The purpose of this study was to evaluate the effectiveness of different radiologic imaging modalities (plain radiographs, 2-D CT, 3-D CT reconstructions) in classifying acetabular defects in revision hip arthroplasty cases and their value of at different levels of orthopaedic training.

Hip resurfacing arthroplasty is a technically challenging procedure, and orientation of the femoral component is critical to avoid implant failure. Recently, numerous articles have shown that the use of computer-assisted navigation decreases the learning curve for beginners in hip resurfacing and to improve the surgeon’s ability to produce consistent results. The purpose of this study was to evaluate the learning curve of computer-assisted navigation in the hands of an experienced hip resurfacing surgeon.

This retrospective study was compromised of 100 metal-on-metal total hip resurfacings in 94 patients. The resurfacings were performed by a single fellowship-trained surgeon, with hip resurfacing experience of more than 250 hip resurfacings without navigation. Data collected included gender, age at the time of surgery, BMI, operative time, postoperative complications, and digital planning. Standard nteroposterior (AP) radiographs taken in the preoperative and postoperative period were evaluated to measure neck-shaft and stem-shaft angles, respectively. There were 24 females and 70 males, who had a mean age of 49 years (range, 19 to 68 years). The 100 hips were arranged chronologically by operative date and broken down into four groups of 25. Data also was gathered on 25 non-navigated hip resurfacings to serve as a matching group.

There were no significant differences found between the four groups and matching groups with respect to patient variables, including age, BMI, or gender. There were also no significant differences found among the groups with respect to OR time (p = 0.565). The mean OR time for all 100 navigated hips was 101 minutes, compared to a mean of 104 minutes for the matching group (p = 0.924). Using linear regression analysis, the only variable that was found to influence OR time was BMI (p < 0.001). The mean actual stem-shaft angle (SSA) of the groups became more valgus over time, with group 1 having an SSA of 139; group 2, an SSA of 140; group 3, an SSA of 142; and group 4, an SSA of 144. Compared to the preoperative neck-shaft angle, the postoperative stem-shaft angle for 89% of the femoral components was inserted in a valgus position, with 96% of those in group 4 being inserted in a valgus position. The matching non-navigated group had only 80% of the cases with the stem-shaft angle inserted in valgus.

The data presented here demonstrates that providing an imageless computer-assisted navigation system to an experienced hip resurfacing surgeon offered the benefits of navigated surgery including increased accuracy, with no learning curve effect. Computer-assisted navigation can help the learning curve of a technically demanding procedure in inexperienced surgeons, as described by the literature, while placing real-time feedback and consistent repeatability into the hands of an experienced surgeon.