3D-printed patient-specific instrumentation significantly improves the accuracy of prosthesis alignment in unicompartmental knee arthroplasty: a retrospective study.

BACKGROUND: Unicompartmental knee arthroplasty (UKA) is an effective treatment for medial compartment knee osteoarthritis, with its outcomes highly dependent on the accuracy of prosthesis positioning. Conventional UKA, performed using traditional instrumentation, often relies heavily on surgical experience and may lead to variability in alignment. The emergence of 3D-printed patient-specific instrumentation (PSI) offers a promising approach to improve prosthesis placement accuracy and operational reproducibility. This study aims to evaluate the postoperative prosthesis position and short-term clinical outcomes of UKA assisted by 3D-printed PSI. METHODS: A retrospective analysis was conducted on 22 patients (25 knees) who underwent PSI-guided UKA between May 2023 and May 2024. These were compared with 25 patients (31 knees) undergoing conventional UKA during the same period. Postoperative radiographic assessments included prosthesis position, limb alignment, and range of motion (ROM) in the sagittal plane. Clinical outcomes were evaluated using functional scores. RESULTS: Both groups showed significant improvement in limb alignment and knee function postoperatively (p < 0.05), with no significant difference in preoperative and postoperative FTA within or between groups. The PSI group demonstrated superior outcomes in AKS-K score (91.7 ± 8.2 vs. 85.5 ± 6.9) and ROM (128.6° ± 9.4° vs. 120.3° ± 7.4°) compared to the control group (p < 0.05). Prosthesis positioning was significantly more accurate in the PSI group regarding coronal and sagittal alignment of both tibial and femoral components (p < 0.05). No significant difference was found in joint line height restoration. CONCLUSION: 3D-printed PSI significantly enhances the accuracy of prosthesis positioning in UKA, reduces operative time, and lowers the learning curve for less-experienced surgeons. Its core value lies in translating complex biomechanical requirements into standardized, executable surgical plans, thereby minimizing outliers in key alignment parameters.