Progression of atypical femur stress fracture after discontinuation of bisphosphonate therapy

Incidence and clinical course of femoral localized periosteal thickening and atypical femoral fracture over a 10-year period in patients with autoimmune inflammatory rheumatic disease

Atypical femoral fracture (AFF) is generally a rare complication of long-term use of bisphosphonate (BP); glucocorticoid (GC) use and Asian race are also risk factors. Femoral localized periosteal thickening (LPT, also termed "beaking") of the lateral cortex often precedes AFF. This cohort study investigated the incidence of LPT and AFF and their clinical courses over 10 yr in patients with autoimmune inflammatory rheumatic diseases (AIRDs) treated with BP and GC. The study population consisted of 121 patients with AIRDs taking BP and GC. LPT was screened by X-ray, and the LPT shape was evaluated. Prednisolone (PSL) dose was 10 (8-12) mg/d at enrollment and 9 (6-10) mg/d at the last observation. LPT was evident in 10 patients at enrollment and increased linearly to 31 patients (26%) at the last observation. AFF occurred in 9 femurs of 5 patients with LPT. All patients with AFF had bilateral LPT, and the prevalence of pointed type and LPT height were higher in the AFF-positive group than in the AFF-negative group. AFF occurred before BP discontinuation in 2 patients, 1 yr after BP discontinuation in 1, after BP discontinuation followed by 7 yr of alfacalcidol use in 1, and after switching from alfacalcidol to denosumab in 1. The prevalence rates of AFF and LPT associated with long-term BP use with concomitant use of GC (mostly PSL ≥ 6 mg/d) in Japanese patients with AIRD increased over time. The selection of long-term osteoporosis treatment for LPT-positive patients is difficult in some cases.

Radiological Reversibility of Incomplete Atypical Femoral Fracture with Cessation of Bisphosphonate: Including an Early Stage of Incomplete Fracture

BACKGROUND

We found some important early findings in simple radiographs under the bisphosphonate (BP) treatment through a retrospective study. Here, we report the degree of reversibility of the early findings before overt fracture and analyze the factors affecting the differences through a retrospective case-control study.

METHODS

We retrospectively inspected the clinical charts of patients diagnosed with atypical femoral fracture (AFF) at our institute between March 2006 and September 2018. Among the 209 screened patients, 102 patients were ultimately divided into 3 categories: Category 1 was described as endosteal diffuse flaring (EDF, early IAFF); category 2 was typical IAFF, with a tiny/partial crack that was limited to less than half of the thickness of the cortex; and category 3 was IAFF with a crack through the entire cortex. Demographics, clinical factors, and three categories of incomplete atypical femoral fracture (IAFF) were analyzed to determine whether their radiological condition "improved" or "progressed" after cessation of BP via univariate and multivariate analyses.

RESULTS

Thirty-three, 53, and 16 were classified as categories 1, 2, and 3, respectively. Groups 1 and 2 consisted of 79 patients whose IAFF on the side of interest improved and 23 patients whose IAFF progressed, respectively. The uni/multivariate analyses of the groups demonstrated that the total period of BP (odds ratio [OR] = 1.49) and period of cessation of BP (OR = 0.24) were significant variables. In addition, prophylactic treatment for a contralateral IAFF was a strong factor for progression of the incomplete lesion on the side of interest (OR = 25.99). The rate of progression was significantly higher in patients with a mean treatment period of 43 months or longer, and in those with a mean cessation period shorter than 1.2 months.

CONCLUSION

Early-stage IAFF was found to be a unique finding in simple radiographs before the typical features of AFF. This EDF (category 1) was definitively reversible to normal bone when administration of BP was stopped. In addition, a long period of BP treatment and recent cessation of BP adversely affected IAFF with respect to spontaneous healing.

LEVEL OF EVIDENCE

Level III, a retrospective case-control study.