Risk Factors Associated with Intraoperative Iatrogenic Fracture in Patients Undergoing Intramedullary Nailing for Atypical Femoral Fractures with Marked Anterior and Lateral Bowing

Abstract

Background and objectives: Iatrogenic fractures are potential complications during intramedullary (IM) nailing for atypical femoral fractures (AFFs). The risk factors associated with iatrogenic fractures remain unclear, although excessive femoral bowing and osteoporosis are hypothesized to be contributing factors. The present study aimed to determine the risk factors for the occurrence of iatrogenic fractures during IM nailing in patients with AFFs. Materials and Methods: This retrospective cross-sectional study evaluated 95 patients with AFF (all female; age range: 49–87 years) who underwent IM nailing between June 2008 and December 2017. The patients were divided into two groups: Group I (with iatrogenic fracture: n = 20) and Group II (without iatrogenic fracture: n = 75). Background characteristics were retrieved from medical records and radiographic measurements were obtained. Univariate and multivariate logistic regression analyses were performed to identify risk factors for the occurrence of intraoperative iatrogenic fractures. Receiver operating curve (ROC) analysis was conducted to determine a cut-off value for the prediction of iatrogenic fracture occurrence. Results: Iatrogenic fractures occurred in 20 (21.1%) patients. The two groups exhibited no significant differences regarding age and other background characteristics. Group I exhibited significantly lower mean femoral bone mineral density (BMD) and significantly greater mean lateral and anterior femoral bowing angles than Group II (all p < 0.05). There were no significant differences in AFF location, nonunion, and IM nail diameter, length, or nail entry point between the two groups. In the univariate analysis, femoral BMD and lateral bowing of the femur differed significantly between the two groups. On multivariate analysis, only lateral bowing of the femur remained significantly associated with iatrogenic fracture occurrence. The ROC analysis determined a cut-off value of 9.3° in lateral bowing of the femur for prediction of iatrogenic fracture occurrence during IM nailing for AFF treatment. Conclusions: The lateral bowing angle of the femur is an important predictive factor for intraoperative iatrogenic fracture occurrence in patients undergoing IM nailing for AFF treatment.

Towards understanding how bisphosphonate‐dependent alterations to nutrient canal integrity can contribute to risk for atypical femoral fractures: Biomechanical considerations and potential relationship to a real‐world analogy

“…[3]]. Thus, patients of some Asian populations, [22,23] and those with bowed femurs [24][25][26] are reported to be more at risk than some other races or those with different structural features of the femur. In addition, there may be genetic variables at play in enhanced risk also [reviewed in Ref.…”

“…Based on the different aspects of the tree felling analogy, what is happening in this rare subset of patients taking specific BP for an extended period of time may fit a paradigm that explains the enhanced genetic risks for an AFF, [44][45][46][47][48] the enhanced risks associated with a bowed femur, [24][25][26] and the need to be on the drugs for a long period of time. While still somewhat speculative, the model presented does therefore, fit with the existing literature reasonably well and addressing the model could lead to new directions for research at both the biological and biomechanical levels.…”

“…6. While the availability of a relevant preclinical model would definitely offer the potential to accelerate progress, the unique structural features of the femur (bowed femur), [24][25][26] the possible unique genetic and/or differentiated features of the endothelial cells of the nutrient canals [reviewed in Ref. [3]], possible racial features of risk, [22,23] and regulatory aspects associated with being bipedal may diminish the potential to develop a relevant preclinical model, particularly a larger animal model that may have a higher level of potential translation to humans.…”