[Effect of femoral component rotational alignment in total knee arthroplasty by using 3D-printed patient-specific instruments: a prospective randomized control study].

Objective: To compare the difference between two total knee arthroplasty (TKA) techniques, patient-specific instrumentation (PSI) and conventional instrumentation (CI), regarding the rotational alignment of femoral components. Methods: A prospective, randomized controlled trial in 80 patients with severe knee osteoarthritis who underwent primary unilateral TKA from October 2018 to December 2019 in Peking University Third Hospital was carried out. There were 63 females and 17 males, with an average age of 69 years. The patients were assigned to either PSI-TKA group (n=40) or CI-TKA group (n=40) with bluster random method (block size 4). The femoral component rotation on the transepicondylar axis, the outlier rate of rotational alignment, the rate of anterior knee pain, and the clinical outcomes including HSS and WOMAC score at 1-year follow-up were documented and analyzed. Results: Although no significant difference in femoral component rotational alignment was found between the two groups (CI-TKA: 0.7°, PSI-TKA: 0.6°, P=0.279), the PSI-TKA group achieved less coefficient of variation of rotational alignment (1.50 vs 2.14) and the distributions of the outliers (19.4% vs 7.9%, P=0.185). Six patients (8.1%) experienced anterior knee pain at 1-year follow-up. No significant difference regarding the incidence of anterior knee pain, the HSS, and WOMAC score was found between the two groups one year after the operation (all P>0.05). Conclusions: The satisfied postoperative rotational alignment of femoral components can be attained with the application of PSI in comparison with conventional instrumentation. In addition, PSI offers a potential benefit in the reduction of alignment outliers.