Postoperative functional outcomes in younger and older patients undergoing 3D-printed guide-assisted total knee arthroplasty: a retrospective analysis

To evaluate whether age influences postoperative clinical outcomes of total knee arthroplasty (TKA) assisted by 3D-printed surgical guides, with particular emphasis on postoperative functional recovery assessed using the Knee Society Score-Function (KSS-F), pain relief, and quality-of-life outcomes in patients aged ≥ 70 and < 70 years. We retrospectively analyzed 80 patients who underwent CT-based customized 3D-printed guide-assisted TKA between May 2016 and June 2022. Patients were stratified into younger (< 70 years, n = 40) and elderly (≥ 70 years, n = 40) groups. The primary outcome was postoperative KSS-F measured at 1, 3, 6, and 12 months; secondary outcomes were visual analog scale (VAS) pain scores and EQ-5D-5L indices. A linear mixed-effects model was used to evaluate the association between age group and postoperative KSS-F across follow-up time points. An exploratory overall comparison of pooled postoperative KSS-F observations was additionally performed using the Wilcoxon rank-sum test because the pooled data were not normally distributed. Baseline characteristics were comparable between groups, except for age. The younger group showed significantly better overall postoperative KSS-F than the elderly group ( P = 0.03). For the overall KSS-F comparison, the Hodges–Lehmann estimate of the between-group difference was 3.00 points (95% CI, 0 to 6.00). No significant differences were observed between groups in VAS scores, EQ-5D-5L, or radiographic measurements ( P > 0.05). Within a standardized 3D-printed guide-assisted TKA workflow, elderly patients showed lower functional recovery compared with younger patients, while both groups achieved comparable improvements in pain relief and quality of life. Further studies with comparative cohorts are needed to establish the relative effectiveness and safety of PSI-assisted TKA across different patient populations.