The failure to restore mechanical alignment and appropriate rotational axis intraoperatively has been described as one of the most common causes of implant failure in total knee arthroplasty (TKA). Both conventional and computer-assisted TKA have their limitations. Patient-specific jigs (PSJ) offer a possible alternative method for TKA. The aim of this study was to investigate if the use of PSJ offers reproducible and accurate orientation of the components in TKA compared with conventional and computer-assisted surgery.
We conducted a prospective case series looking at 261 consecutive patients undergoing TKA for osteoarthritis using the Signature Patient Specific System (Biomet, North Ryde, NSW, Australia). Each patient underwent a preoperative magnetic resonance imaging for planning. Using a computer software program, specialized femoral and tibial pin placement jigs were generated. Post-operative femoral and tibial component alignment was measured using computed tomography.
Of patients, 96.2% achieved femoral rotational alignment ±3 degrees of the transepicondylar axis. Tibial coronal alignment showed 92.7% of cases were 90 ± 3 degrees to the tibial medullary axis. Implant measurements of the posterior tibial slope demonstrated 76.6% of cases were within our accepted 0 to 7 degrees slope and 81.2% of patients had an overall mechanical axis within ±3 degrees of neutral. We also recorded femoral coronal alignment of the last 98 patients of our group and found that 99% were within 90 ± 3 degrees.
PSJ for TKA shows good accuracy in alignment when compared with conventional TKA. However, improvements in the development of the tibial alignment cutting guides will aid in further increasing its overall accuracy and reproducibility.