A new surgical technique for functional implant alignment in varus osteoarthritis using patient-specific instrumentation (PSI)

AIMS AND OBJECTIVES: The use of patient-specific instruments (PSI) in total knee arthroplasty (TKA) has seen growing interest over the past years. A potential disadvantage of PSI is that functional implant alignment is not applicable in this technique. This study therefore aimed to develop a surgical technique for ligament-balanced implant alignment based on PSI, and to present the results obtained using this technique. MATERIALS AND METHODS: 25 patients were included in this prospective study. PSI was used for the resection of the extension gap. Ligament tension was measured after removal of all accessible osteophytes. In the event of asymmetry, the distal femur resection was adjusted up to 2.5° using an adjustable cutting block. The aim was to achieve a symmetrical extension gap without release, not a neutral leg axis. Femoral rotation was aligned on the basis of ligament tension. Patients were followed up 3 months postoperatively. RESULTS: The postoperative whole-leg axis was 2.8°±1.6° varus. Patients achieved a flexion of 118.9°±9°, a Knee Score of 91.5±3.2 and a Function Score of 86.8±8.3 points. CONCLUSION: For the first time, the new surgical technique described here permits a functional, ligament-balanced implant alignment based on PSI. It was shown to be safe, with encouraging clinical and radiological results.