Patient-Specific Instruments for Total Hip Arthroplasty

摘要

Total hip arthroplasty (THA) is a common surgery, exceeding 330,000 cases per year in the United States alone. The positioning of the implant components is critical to the success of the surgery. Excess or insufficient cup anteversion results in higher risk of anterior or posterior dislocation respectively. Excessive cup inclination correlates to osteolysis from implant edge loading. The stem anteversion must be aligned relative to the cup, to prevent implant impingement and permit a normal range of motion. Both components must be positioned to maintain the center of rotation in order to preserve tissue biomechanics. Discrepancies in leg length and hip offset results in muscle slackness or tightness, distorting normal gait.;Targets for implant orientation have traditionally been defined by `safe zones' of angular position. However it is well known that these zones do not provide safety from dislocation, but only a decreased risk. Recent research has investigated patient-specific targets for implant orientation, based on bone anatomy, hip kinematics, or both. Due to the prevalence of THA, it is expected that research will continue to progress, providing improved patient-specific implant targets. Therefore, it is critical for the surgeon to be effectively equipped to achieve specific targets.;Advanced surgical techniques such as computer navigation and robotic-guided THA have shown high accuracy and precision. However, this equipment is expensive, and may not be economical for low-volume surgeons, despite that low-volume surgeons operate with a lower precision than high-volume surgeons of similar experience. Patient-specific instruments (PSIs) have been introduced in other joints as an alternative solution, but have trailed in progress for THA.;This dissertation investigated the design and testing of PSIs for THA through three specific aims: 1) to establish the design and feasibility of acetabular and femoral PSIs in THA, 2) to investigate if an acetabular PSI can accurately place a surgical pin superior to the acetabular rim and if this pin can accurately guide cup implantation, and 3) to investigate if a femoral resection PSI can accurately control osteotomy and if a secondary femoral PSI can accurately control stem anteversion.;The feasibility of acetabular and femoral PSIs was first established in a pilot cadaver THA procedure. Upon further development of the devices and creation parameters, their accuracy and precision were assessed in a series of 20 cadaveric THA procedures. The acetabular PSI proved to be imprecise in placing the guide pin, with a mean difference (+/-SD) from the target of 7.1° +/- 10.9° in inclination, and 1.6° +/- 10.6° in anteversion. However, the pin proved effective in guiding cup implantation, with a mean difference (+/-SD) from the target of 0.9° +/- 5.3° and 1.7° +/- 3.3° in inclination and anteversion respectively. The femoral resection PSI controlled the resection plane within an average error of 3mm and 7°, while the secondary femoral PSI controlled stem version within an average error of 7°. The overall results highlighted several flaws in the design and process, however also gave promise to future improvement of the devices to enhance THA surgery.