The Center-Center Technique for the Direct Anterior Approach in Total Hip Arthroplasty: Precise Femoral Canal Preparation to Optimize Implant Fit and Fill.

Background: The use of the direct anterior approach has been criticized as a significant risk factor for subsidence, perioperative fracture, and thigh pain. Therefore, the purpose of our study was to evaluate the outcome of using the center-center technique via the direct anterior approach.

Materials And Methods: Consecutive elective primary total hip arthroplasties performed using the center-center technique were retrospectively reviewed from May 2015 to February 2017. All cases were performed by a single surgeon at a high-volume, large academic center. The technique focuses on central alignment of the implant on both anteroposterior and lateral radiographs. Standardized objective radiographic measurements were taken at the first two-week follow-up visit to determine the fit and fill at the proximal and distal anatomic segments. Subsidence was measured by comparing the implant position at final follow up to the initial two-week postoperative visit. Other complications: intra- or postoperative fracture, infection, revision, and patient-reported thigh pain were further assessed. Functional postoperative outcomes were assessed using the Harris Hip Score (HHS).

Results: A total of 138 patients with a mean age of 65 years and average follow up of 2.8 years were assessed. The mean postoperative HHS was 90 points (59-100). Mean implant subsidence was 1mm. A total of 90% (124) of implants had acceptable radiographic fit and fill in both proximal and distal segments. A majority 74% (102) of implants subsided less than 1mm, and 91% (126) subsided less than 2mm. One implant had radiographic subsidence of 9mm, which was treated with a shoe lift. There were no intraoperative fractures. One postoperative lateral cortex fracture three weeks after surgery due to mechanical fall was treated conservatively. No patients required revision arthroplasty for any reason or reported postoperative thigh pain.

Conclusion: The center-center technique can be used to consistently aid in proper femoral stem placement in both coronal and sagittal planes. Optimal fit and fill can be achieved safely using this technique.