Meta-analysis finds 87% implant survivorship after 10 years in patients under 50 undergoing TKA

This systematic review and meta-analysis synthesized evidence on total knee arthroplasty (TKA) outcomes specifically in patients aged less than 50 years. The analysis included studies published between January 1, 2004, and December 31, 2024, aggregating data from 17,705 patients. The population was defined by age (under 50 years) and the condition requiring TKA, which included osteoarthritis and inflammatory joint conditions. The mean follow-up duration across the included studies was 17 years, providing a long-term perspective on outcomes in this younger demographic. The comparator group was TKA performed in other age groups, though specific data for these groups were not reported in the input, limiting direct age-based comparisons within this analysis.

The intervention was total knee arthroplasty (TKA), with no specific details on surgical techniques, implant types, or perioperative protocols provided in the input. The comparator was TKA in other age groups, but as noted, comparative data were not reported, so the analysis primarily describes outcomes in the under-50 population without statistical contrasts to older patients. Dosing or protocol specifics for TKA were not detailed, which is typical for a meta-analysis of surgical outcomes that aggregates varied approaches from multiple studies.

The primary outcome was implant survivorship, reported as 97% for less than five years, 95% for five to 10 years, and 87% for greater than 10 years. These percentages represent the proportion of implants that did not require revision over these time intervals. No effect sizes, absolute numbers, p-values, or confidence intervals were provided for these survivorship data, indicating descriptive reporting without statistical testing against comparators. The direction of results suggests decreasing survivorship with longer follow-up, which aligns with expected wear and tear in younger, potentially more active patients.

Key secondary outcomes included postoperative range of motion and Knee Society functional score. Postoperative range of motion was 121.5°, with a 95% confidence interval of 107.6 to 135.4, indicating variability across studies but a generally favorable outcome. The postoperative Knee Society functional score was 85.3, with a 95% confidence interval of 79.1 to 91.5, suggesting good functional results on average. No p-values or effect sizes were reported for these secondary outcomes, limiting inferences about statistical significance or clinical importance relative to other groups.

Safety and tolerability findings were limited, with aseptic loosening identified as the leading cause of revision in seven of the included studies. Rates of adverse events, serious adverse events, discontinuations, or specific tolerability issues were not reported, so the safety profile remains incompletely characterized. This gap highlights the need for more detailed reporting on complications in future research to fully assess risks in this population.

Comparing these results to prior landmark studies in TKA, the implant survivorship of 87% after 10 years in patients under 50 appears lower than often reported in older populations, where survivorship can exceed 90% at 10 years. However, direct comparisons are hindered by the lack of comparator data in this analysis. The functional scores and range of motion are comparable to outcomes in broader TKA populations, suggesting that while longevity may be reduced, functional benefits are maintained. This aligns with existing literature indicating that younger age is a risk factor for earlier revision due to higher activity levels and longer life expectancy.

Key methodological limitations include the absence of reported limitations in the input, though meta-analyses generally face issues like heterogeneity across studies, publication bias, and variability in surgical techniques. The lack of comparator data limits causal inferences about age-specific effects, and the descriptive nature of results without p-values or effect sizes reduces statistical robustness. Potential biases may arise from selective reporting in included studies or incomplete follow-up in some cohorts, though these are not specified in the input.

Clinical implications suggest that these findings can aid in patient counseling, expectation setting, and TKA selection for patients under 50. Clinicians can use the survivorship data to discuss long-term prospects, emphasizing the 87% rate at over 10 years and the risk of aseptic loosening. Functional outcomes support TKA as effective for improving knee function in this group, but the reduced survivorship may influence decision-making, particularly for very young or highly active patients where alternative treatments or timing might be considered.

Unanswered questions include the specific factors driving aseptic loosening in this age group, comparative outcomes with non-surgical management or other surgical options, and detailed safety profiles including complication rates. Future research should address these gaps with controlled studies, longer follow-up, and standardized reporting to better guide clinical practice for younger TKA patients.