Summary

Fracture risk after knee arthroplasty for patients with bilateral osteoarthritis was higher in unilateral TKA group than in bilateral group.

Abstract

The Rotterdam study reported that patients with knee osteoarthritis (OA) had a higher fracture risk than those without osteoarthritis, despite having higher bone density. Although total knee arthroplasty (TKA) is expected to reduce knee pain, the risk of fracture after TKA is still unknown. The purpose of this study was to compare the risk of fracture after TKA in patients with bilateral knee OA between unilateral and bilateral TKA. Subjects and Methods: 497 patients with bilateral OA of grade 3 or higher in Kellgren-Lawrence classification preoperatively and follow-up of at least 3 years after the initial TKA were included in the study. Patients who had revision surgery, rheumatoid arthritis, or surgery at another hospital were excluded. The mean age at the time of the initial surgery was 74.4 ± 6.9 years, 84 were male and 413 were female. The mean postoperative follow-up was 76.3 ± 28.2 months. There were 186 patients in the unilateral TKA group and 311 in the bilateral TKA group, with 65 of the latter group undergoing simultaneous bilateral TKA. There were no significant differences in gender, BMI, or age at fracture between the unilateral and bilateral TKA groups. Fracture history and fracture site were retrospectively investigated based on medical records during annual postoperative follow-up. Results: During follow-up, 105 patients (21.1%) had fractures. The probability of fractures after unilateral TKA was significantly higher (chi-square test, p<0.05). Fracture rates were 26.1% (53/203) and 17.7% (52/294) after unilateral and bilateral TKA. The probability of multiple fractures was significantly higher in the unilateral TKA group. The risk of vertebral fractures did not differ between the two groups (9.4% in unilateral group, 7.5% in bilateral group). However, the risk of nonvertebral fractures was significantly higher in unilateral group with 18.2% in unilateral and 10.2% in bilateral group (chi-square test, p<0.01). Discussion: In the Rotterdam study, both vertebral and nonvertebral fractures were increased in knee OA patients compared to non-OA patients. On the other hand, in the present study, there was no difference in the incidence of vertebral fractures between unilateral and bilateral TKA, but the incidence of nonvertebral fractures was higher in unilateral TKA. We speculate that the reason for this difference may be that fractures in patients with bilateral knee OA are more influenced by fall risk than by bone fragility. Conclusions: In patients with bilateral knee OA, if the risk of fall is high even after unilateral TKA, contralateral surgery may reduce the risk of postoperative fracture.