Changes in femoral bone mineral density after total knee arthroplasty: a systematic review and meta-analysis.

BACKGROUND: Bone loss after total knee arthroplasty (TKA) may lead to periprosthetic fractures that are associated with significant costs (morbidity, economic, etc.) and pose a challenge to operative fixation. This meta-analysis quantifies the change in bone mineral density (BMD) of the distal femur after primary TKA.

METHODS: A systematic review of six databases was performed by two independent reviewers. Studies that reported bone density after knee arthroplasty were identified and inclusion/exclusion criteria was applied. Data were extracted and analyzed using the Comprehensive Meta-Analysis Software.

RESULTS: Fourteen studies were included in the analysis. The average decrease in BMD was 0.09 [0.05, 0.13], 0.14 [0.08, 0.20], 0.16 [0.10, 0.23], and 0.16 [0.12, 0.20] g/cm2 at 3, 6, 12, and 24 months, respectively, corresponding to a 9.3%, 13.2%, 15.8%, and 15.4% BMD loss. A high degree of heterogeneity existed between the studies (I2  > 90% at most time points).

CONCLUSION: In summary, there is a rapid and significant 15% decrease in BMD in the first 6 months after TKA that is sustained to 24 months. Better understanding regarding how perioperative optimization of bone health may affect BMD loss and the incidence of periprosthetic fracture is essential.

LEVEL OF EVIDENCE: Therapeutic Level II.