Surgical results of atypical femoral fractures in long-term bisphosphonate and glucocorticoid users - Relationship between fracture reduction and bone union

Does the Nonunion Rate of Atypical Femoral Fractures Differ According to Fracture Site?: A Meta-Analysis

Background

The nonunion rate for atypical femoral fractures (AFF) is known to be higher than that for typical fractures of the femur. We performed a meta-analysis to determine the incidence of nonunion necessitating reoperation following fixation for AFF and compare the rates according to the fracture site (subtrochanter or midshaft).

Methods

A total of 742 AFFs from 29 studies were included. A proportion meta-analysis utilizing a random-effects model was conducted to estimate the prevalence of nonunion. The outcomes were the incidence of reoperations that included osteosynthesis. To determine the association of nonunion with patient mean age or average duration of bisphosphonate use, meta-regression analysis was done.

Results

In proportion meta-analysis, the estimated pooled prevalence of nonunion was 7% (95% confidence interval [CI], 5%-10%) from all studies. There was a significant difference in nonunion rate between the 2 groups (I2 = 34.4%, p = 0.02); the estimated prevalence of nonunion was 15% (95% CI, 10%-20%) in subtrochanteric AFFs and 4% (95% CI, 2%-6%) in midshaft AFFs. From meta-regression analysis, significant correlations were identified between nonunion rate and patient mean age (coefficient: -0.0071, p = 0.010), but not in the average duration of bisphosphonate use (coefficient: -0.0024, p = 0.744).

Conclusions

A notable disparity existed in the nonunion rate among subtrochanteric AFFs and midshaft AFFs group. Therefore, it is critical for orthopedic surgeons to consider the complexity and challenges associated with AFF and to estimate the proper possibility of nonunion according to the fracture site.

Bisphosphonate-Related Atypical Femoral Fractures in Patients with Autoimmune Disease Treated with Glucocorticoids: Surgical Results for 20 Limbs

BACKGROUND

Glucocorticoids induce osteoporosis, while bisphosphonates treat it, yet both can lead to atypical femoral fractures. Patients on both agents may face challenges in healing from such fractures due to their pathophysiology and pharmacological effects.

METHODS

Intramedullary nail surgery was performed on 20 limbs in 19 patients with atypical femoral fractures and autoimmune diseases, who had received bisphosphonates for GC-induced osteoporosis. The average durations of glucocorticoid and bisphosphonate use were 17 and 9 years (standard deviation: 7.59 and 4.35), respectively, and the mean follow-up period was 66 months. Fifteen and five limbs were fractured at the subtrochanter and diaphysis, respectively. The surgical techniques (type of nail) and additional procedures performed in these cases were examined. The post-operative alignment and reduction status on radiographs were examined to determine their relationship with post-operative outcomes.

RESULTS

Cephalomedullary long nails were inserted in nine limbs and antegrade intramedullary nails in 11 limbs. As an additional surgical procedure, open reduction, bone grafting and drilling were carried out on six, two, and five limbs, respectively. Regarding malalignment on radiographs, AP images showed varus in four limbs, and lateral images showed extension in two limbs. Regarding the cortical discontinuity, the distal fragment of the 11th limb shifted posteriorly in the lateral view. Gaps at the fracture sites were observed in 11 limbs. As a result, bone union was confirmed in 13 limbs. Five of the seven nonunion limbs required additional surgery. When comparing union and nonunion, open reduction and drilling were involved in nonunion limbs.

CONCLUSION

The surgical outcomes of atypical femoral fractures in patients with autoimmune disease and on long-term glucocorticoids and bisphosphonates were poor. Although it is not possible to affirm for sure based on these results alone, management with prophylactic surgery before complete fracture is considered to be required to improve outcomes.

Are secondary effects of bisphosphonates on the vascular system of bone contributing to increased risk for atypical femoral fractures in osteoporosis?

Osteoporosis (OP) is a bone disease which affects a number of post-menopausal females and puts many at risk for fractures. A large number of patients are taking bisphosphonates (BPs) to treat their OP and a rare complication is the development of atypical femoral fractures (AFF). No real explanations for the mechanisms underlying the basis for development of where AFF develop while on BPs has emerged. The present hypothesis will discuss the possibility that part of the risk for an AFF is a secondary effect of BPs on a subset of vascular cells in a genetically at-risk population, leading to localized deregulation of the endothelial cell (EC)-bone cell-matrix units in nutrient channels/canals of the femur and increased risk for AFF. This concept of targeting ECs is consistent with location of AFF in the femur, the bilateral risk for occurrence of AFF, and the requirement for long term exposure to the drugs.

Bone Morphogenetic Protein 2 Promotes Bone Formation in Bone Defects in Which Bone Remodeling Is Suppressed by Long-Term and High-Dose Zoledronic Acid

The use of long-term and high-dose bisphosphate is associated with severely suppressed bone turnover and the delayed union of fractures. However, therapeutic methods to overcome the negative effects of bisphosphonate use are lacking. Bone morphogenetic proteins (BMPs) are powerful osteoinductive proteins. The development of the delivery system using BMP has been verified to have an excellent effect on fracture healing and the enhancement of osteointegration. We hypothesized that BMPs had similar effects as autografts in patients with decreased bone healing potential due to long-term bisphosphonate treatment. Forty rats were divided into the following four groups depending upon the materials implanted into the femoral defect after ten weeks of bisphosphonate (zoledronic acid) injections: Group I: absorbable collagen sponge (control); group II: demineralized freeze-dried bone graft; group III: autogenous bone graft; and group IV: rhBMP-2 with an absorbable collagen sponge. Radiographic union, micro-computed tomography (CT) analysis, manual palpation, and histologic analysis were evaluated. The radiographic union rate, manual union rate, and micro-CT bone volume in groups III and IV were significantly higher than those in groups I and II. Groups III and IV showed similar results to each other. Although the amount of immature bone in the BMP-treated group was large, the effect was similar to that of autografts in the bone defect model in which bone turnover was severely reduced by bisphosphonate treatment. BMP might be a good substitute for autografts in patients with decreased bone healing potential due to long-term bisphosphonate treatment.

Subtrochanteric atypical femoral fracture induced solely by glucocorticoid without bisphosphonate treatment: a case report

An AFF is a form of stress fracture induced by excessive physiologic repetitive stress over the bone remodeling capacity. Although glucocorticoid administration is a known risk factor for AFF, no case of AFF with glucocorticoid administration as the only risk factor has been previously reported. In this report, we aimed to highlight the risk of AFF associated with long-term administration of glucocorticoids, and the importance of surveillance and correction of risk factors in patients undergoing long-term glucocorticoid therapy. A 58-year-old male patient was diagnosed with subtrochanteric AFF. He had no medical history of any condition that might disrupt bone metabolism and no known risk factors for AFF, except for long-term administration of glucocorticoid. After fixation of the fracture, the glucocorticoid was replaced with an alternative medication. Although AFF is notorious for delayed union or nonunion, complete union of the fracture was obtained at 14 months postoperatively. This case brought to our attention the possibility that glucocorticoids alone may be responsible for inducing AFF and highlighted the importance of regular assessments in case of necessity of glucocorticoid administration. Additionally, correction of risk factors might expedite the union of AFF.

Technical note on the removal of a "cold-welded" lag screw from a Trigen Meta-Tan nail

Intramedullary or cephalomedullary nail removal often is performed during nonunion reoperations. We have experienced a rare case in which it was difficult to remove the lag screw of the antegrade intramedullary nail, requiring a large amount of force to be applied over a long period. Removal of the lag screw is essential for removal of the nail and subsequent revision surgery. In our case, the lag screw could be removed only by cutting the screw with a carbide drill. For cases in which the nail and lag screw are firmly fixed, surgeons should prepare for the possibility of their separation using a carbide drill. Written informed consent was obtained from the patient for publication of this case report and accompanying images.