Clin Orthop Surg.  2025 Apr;17(2):216-222. 10.4055/cios24103.

Effect of Severe Bowing in BisphosphonateRelated Atypical Femoral Fracture

• Park J
• Lee Y
• Ko YS
• Byun S
• Cho Y
• Koo K

• KMID: 2565822
• DOI: http://doi.org/10.4055/cios24103

Abstract

Background
Long-term use of bisphosphonate is a risk factor for atypical femoral fractures (AFFs). Femoral bowing is known to be associated with AFFs. However, whether femoral bowing quickens the occurrence of AFF is unknown. The purpose of this study was to determine whether AFF occurs earlier in patients with severe femoral bowing than in those without severe bowing.
Methods
One hundred and sixty-four patients (186 AFFs) from January 2006 to December 2022 were included in this study. According to severity of femoral bowing, patients were divided into 2 groups: severe bowing group (26 femurs) and minimal to moderate bowing group (160 femurs). Age, sex, and completeness and location of AFF were compared between the 2 groups. We compared the time of AFF occurrence after bisphosphonate therapy using cumulative percentage between the 2 groups.
Results
Age and sex were similar between the 2 groups, while body mass index (BMI) was lower (22.5 ± 3.0 kg/m 2 vs. 24.5 ± 3.5 kg/m 2 , p = 0.003) in the severe bowing group. The duration of bisphosphonate use was shorter in the severe bowing group than in the minimal to moderate bowing group (3.3 ± 3.8 years vs. 5.0 ± 4.0 years, p = 0.048). In the severe bowing group, 85% of AFFs were diaphyseal in contrast to the 46% in the minimal to moderate bowing group (p < 0.001). Cumulative percentage plot of AFFs in the severe bowing group was left-shifted compared to the minimal to moderate bowing group.
Conclusions
At the time of AFF diagnosis, the severe bowing group exhibited shorter duration of bisphosphonate use, lower BMI, and a higher incidence of diaphyseal location. Shortening the duration of bisphosphonate therapy may be advisable in patients with severe femoral bowing.

Keyword

Osteoporosis; Bisphosphonates; Atypical femoral fracture; Femoral bowing; Risk factor