Risk Factors Associated with Intraoperative Iatrogenic Fracture in Patients Undergoing Intramedullary Nailing for Diaphyseal Atypical Femoral Fractures

Abstract

Introduction: Iatrogenic fractures remain a complication during intramedullary (IM) nailing for atypical femoral fractures (AFFs). The risk factors for iatrogenic fractures remain unclear, although excessive femoral bowing and osteoporosis are hypothesized to be contributing factors. The present study aimed to determine risk factors for iatrogenic fracture occurrence during IM nailing in patients with diaphyseal AFFs.Patients and methods: This retrospective cross-sectional study investigated 95 diaphyseal AFF patients (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 collected from medical records and radiographic measurements were taken. Univariate and multivariate logistic regression analyses were performed to identify risk factors for intraoperative iatrogenic fracture occurrence. A receiver operating curve (ROC) analysis was carried out to determine a cutoff value for prediction of iatrogenic fracture occurrence.Results: Iatrogenic fractures occurred in 20 patients (21.1%). The two groups did not differ significantly in age and other background characteristics. Group I had 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 diaphyseal AFF location, nonunion, and IM nail diameter, length, or nail entry point between the two groups. In the univariate analyses, 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 cutoff value of 9.3° in lateral bowing of the femur for prediction of iatrogenic fracture occurrence during IM nailing for diaphyseal AFF treatment.Conclusions: Lateral bowing angle of the femur is an important predictive factor for intraoperative iatrogenic fracture occurrence in patients undergoing IM nailing for diaphyseal AFF treatment. Level of evidence: III, retrospective comparative study.

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

“…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), [ 24–26 ] 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.…”

“…If possible, obtain DNA from such regions for assessment of epigenetic alterations (compared to DNA in Point 5). For patients engaged in Points 1, & 2, if abnormal imaging is suggestive of altered ECM structure around nutrient canals while on BP, re‐assess after being on a “drug holiday” for a period of time to determine whether the abnormalities detected while on BP are reversed. Based on the above research approaches, obtain blood DNA samples from the patients engaged in the above studies to assess for the presence of known genetic risk factors [discussed in Refs. [3, 44–48]], as well as others, particularly those associated with endothelial cells. 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), [ 24–26 ] 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.…”

“…[3]]. Thus, patients of some Asian populations, [ 22,23 ] and those with bowed femurs [ 24–26 ] 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, [ 44–48 ] the enhanced risks associated with a bowed femur, [ 24–26 ] 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.…”