JOA - 2026-03-18 - Journal Article
Kinematic and Mechanical Alignment Yield Similar Outcomes in Total Knee Arthroplasty: A Systematic Review and A Meta-analysis of Randomized Controlled Trials.
Blackman B, Burow C, Macciacchera M, Hayes E, Garceau S
Topics
Key Takeaway
Across 11 RCTs and 972 patients, KA and MA yield equivalent PROMs and reoperation rates, but patients with bilateral TKA prefer their KA knee over MA knee at a 2.15:1 ratio (RR 2.15, 95% CI 1.36–3.40).
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Summary
This meta-analysis of 11 RCTs compared KA versus MA in primary TKA on survivorship, WOMAC, OKS, FJS, and reoperation rates through September 2024. No statistically significant differences were found in any PROM or all-cause reoperation (RR 1.34, 95% CI 0.71–2.52) including a subgroup of two studies with >10-year follow-up. However, bilateral TKA studies showed patients were 2.15 times more likely to prefer their KA knee (RR 2.15, 95% CI 1.36–3.40, P=0.001).
Key Limitation
The long-term survivorship analysis is limited to two studies, leaving component revision rates beyond 10 years statistically underpowered and clinically inconclusive.
Original Abstract
BACKGROUND
While 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 from inception to September 23, 2024, to identify randomized controlled trials (RCTs) investigating TKA using KA compared to MA. Patient demographics, operative techniques, objective outcomes, and patient-reported outcome measures (PROMs) were abstracted. Meta-analyses were performed to compare survivorship, Western Ontario and McMaster Universities Arthritis Index (WOMAC), Oxford Knee Score (OKS), and Forgotten Joint Score (FJS). Risk of bias was assessed using the RoB 2 tool for RCTs. 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, I 2 = 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, I 2 = 0%, P = 0.59) and component revisions (RR: 1.26, 95% CI: 0.38 to 4.14, I 2 = 0%, P = 0.71) between groups. There was no statistically significant difference in PROMs between groups. In two studies including patients who underwent bilateral TKA (KA versus MA), KA was significantly more likely to be the preferred knee (RR: 2.15, 95% CI: 1.36 to 3.40, I 2 = 0%, P = 0.00).
CONCLUSION
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.