Kinematic and Mechanical Alignment Yield Similar Outcomes in Total Knee Arthroplasty: A Systematic Review and a Meta-Analysis of Randomized Controlled Trials.

BACKGROUND

Although mechanical alignment (MA) is the current gold standard for total knee arthroplasty (TKA), suboptimal patient satisfaction rates have prompted the exploration of alternative alignment strategies. This review examined whether kinematic alignment (KA) improves outcomes following TKA compared to MA.

METHODS

There were four databases searched through September 23, 2024, to identify randomized controlled trials (RCTs) investigating TKA using KA versus MA. Patient demographics, survivorship, and patient-reported outcome measures (PROMs) were abstracted. Meta-analyses were performed to compare survivorship and PROMs. Risk of bias was assessed using the RoB 2 tool. There were 11 RCTs and 972 patients included (KA: 484, MA: 488). The mean follow-up was 3.9 years (range, one to 13).

RESULTS

There was no statistically significant difference in all-cause reoperation rate between groups (relative risk (RR): 1.34, 95% confidence interval (CI): 0.71 to 2.52, I2 = 0%, P = 0.37). A meta-analysis of two studies with greater than 10-year follow-up found no statistically significant difference in all-cause reoperations (RR: 1.21, 95% CI: 0.6 to 2.47, I2 = 0%, P = 0.59) and component revisions (RR: 1.26, 95% CI: 0.38 to 4.14, I2 = 0%, P = 0.71) between groups. There was no statistically significant difference in PROMs. In two studies including patients who underwent bilateral TKA (KA versus MA), KA was more likely to be the preferred knee (RR: 2.15, 95% CI: 1.36 to 3.40, I2 = 0%, P = 0.00).

CONCLUSIONS

There is no significant difference in objective outcomes or PROMs when comparing KA with MA. However, within-subject comparison from bilateral TKA studies indicates patients are more than twice as likely to prefer their KA knee. Future longer-term studies are warranted to better understand the application of varying alignment strategies in TKA, including which populations may benefit most from KA.

LEVEL OF EVIDENCE: Level I.