Effect of 3D printed patient-specific cutting guide on patellar height and joint line position in total knee arthroplasty

Abstract

Objective To compare the effect of 3D printed patient-specific instrumentation (PSI) and conventional instrumentation (CI) on the patellar height and joint line position in total knee arthroplasty (TKA). Methods A retrospective case-control study was carried out on 58 patients, who underwent primary TKA in our hospital from January 2021 to October 2021. According to the osteotomy tools selected in TKA, the patients were divided into CI-TKA group and PSI-TKA group. The Insall-Salvati index, modified Caton-Deschamps (mCD) index and relative height of joint line before and after TKA were recorded and compared between the 2 groups. Results In terms of the Insall-Salvati index, the absolute difference between preoperative and postoperative score was 0.11 (0.07, 0.15) in the CI-TKA group, and 0.06 (0.03, 0.12) in the PSI-TKA group, and statistical difference was seen in the postoperative index between the 2 groups (P < 0.05). Similarly, the absolute difference between preoperative and postoperative mCD index was 0.16±0.09 in the CI-TKA group and 0.08±0.05 in the PSI-TKA group, and obvious difference was also seen in the postoperative difference between them (P < 0.01). However, the absolute difference between preoperative and postoperative joint line height was 2.53 (1.64, 4.40) mm in the CI-TKA group and 2.27 (1.53, 5.32) mm in the PSI-TKA group. There was no notable difference in postoperative joint line position between the 2 groups, but the position after TKA were significantly higher in both groups than that before TKA (P < 0.05). Conclusion The use of 3D printed PSI can help reduce the impact of TKA on the patella height, but there is no obvious advantage in maintaining the joint line position compared with conventional instrumentation.

Keywords

• total knee arthroplasty
• patient-specific instrumentation
• patellar height
• joint line position