Abstract
Background
Recently, a larger number of elderly individuals with osteoporosis has undergone total knee arthroplasty (TKA). Intuitively, such vulnerable bone condition should deteriorate post-TKA functional recovery compared to a non-osteoporotic condition, but this hypothesis has not been directly examined.
Methods
To address this issue, we analysed prognosis of patients who underwent TKA in Toranomon Hospital in Japan between April 2016 and March 2017 (27 of 40 cases, age 75.0±8.2 years old, BMI 24.5±3.1), and evaluated effects of osteoporosis on the changes in functions of the knees three/six/twelve months after the operation. The knee functions were quantified based on Knee Society Score (KSS), and the severity of the pre-operative osteoporosis was evaluated by T-score. We examined the relationships between these scores using multiple regression analyses with age, BMI, and sex as covariates. We excluded patients with rheumatoid arthritis.
Results
The multiple regression analyses revealed that the severity of osteoporosis (T-score) before TKA did not have sufficient explanatory powers for either type of KSS (for Knee Score, adjusted R2 ≤ 0.16; for Functional Score, adjusted R2 ≤ 0.15). In addition, Pearson correlation coefficients between the pre-operative osteoporosis severity and KSS were weak (for Knee Score, |r| < 0.07, P > 0.78; for Functional Score, |r| < 0.27, P > 0.21; Fig 1). This tendency was qualitatively preserved even when we repeated these analyses for each sex group.
Conclusions
These analyses suggest that counterintuitively, pre-operative osteoporosis does not significantly deteriorate the functional outcome of TKA in the elderly population. Although longer observations of larger samples will be needed, the current findings indicate the possibility that we may not have to hesitate over TKA even for osteoporotic patients.
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