Modular neck total hip arthroplasty – a perfect storm

Purpose: This study was aimed to highlight neck notching as a potential cause of failure in modular neck total hip arthroplasty. It aimed to identify both the combination of modular components that place patients at greatest risk of failure and the potential mechanism for failure. Methods: This study involved a retrospective review of 301 total hip arthroplasties (THA) using Kinectiv modular neck Technology (Zimmer, Warsaw, Indiana). The primary outcome was the presence of neck notching requiring revision. Patient records, operative notes and postoperative radiographs were reviewed. A statistical analysis was performed. Results: A total of 301 THA were performed on 290 patients. There were 7 failures (2.3%). All 7 failures involved a modular combination of an anteverted neck, extended offset and length code -8 (failure rate of 36.8%, p<0.001). Conclusions: We identified femoral neck notching as a potential cause of failure in modular neck THA. The combination of an anteverted neck, extended offset and length code -8 was associated with a high rate of neck notching using the Kinectiv modular neck Technology (Zimmer, Warsaw, Indiana). Based on our experience with this prosthesis we advise caution when using this particular combination of implants.