E-Poster Presentation 30th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2020

Risk factors for atypical femoral fracture: a retrospective radiographic and demographic study (#92)

Gareth Crouch 1 , Nitesh D Dhanekula 2 , Sue-Lynn Lau 1 3 , Edward Graham 2 , Maria-Liza Nery 4 , Jean Doyle 4 , Lillias Nairn 5 , Karen Byth 1 6 , Andrew Ellis 1 7 , Roderick Clifton-Bligh 1 4 , Christian Girgis 1 3 4
  1. Sydney Medical School, University of Sydney, Sydney, NSW, Australia
  2. Department of Orthopaedic Surgery, Westmead Hospital, Westmead, NSW, Australia
  3. Department of Endocrinology, Westmead Hospital, Westmead, NSW, Australia
  4. Department of Endocrinology, Royal North Shore Hospital, St Leonards, NSW, Australia
  5. Department of Physiotherapy, Royal North Shore Hospital, St Leonards, NSW, Australia
  6. Research and Education Network, Western Sydney Local Health District, Westmead, NSW, Australia
  7. Department of Orthopaedic Surgery, Royal North Shore Hospital, St Leonards, NSW, Australia

Background

Atypical femoral fractures (AFFs) are a serious complication of anti-resorptive therapies, the first line treatment for osteoporosis. It is important to elucidate predictive markers of AFF to clarify the risk:benefit ratio of osteoporosis therapy in patients requiring long-term treatment.

Aims

This study sought to identify demographic risk factors and femoral geometric features associated with AFF development. Additionally, predictors of a subtrochanteric or diaphyseal fracture location were examined.

Methodology

Radiographs of femoral shaft and subtrochanteric fractures treated from January 2008 - May 2017 were retrieved using electronic medical record coding. Subsequently, 413 anteroposterior pelvic radiographs with morphological characteristics of AFFs were reviewed by three expert adjudicators and classified as AFFs/impending AFFs or non-AFFs. Included fractures were further limited to those in females with a low-energy mechanism of injury and no osteo-metabolic or metastatic disease. Geometric, pharmaceutical and demographic data were extracted, and correlated with fracture location and AFF status.

Results

80 AFFs/impending AFFs in 65 individuals and 45 non-AFFs in 45 individuals were included. AFFs occurred in smaller, thinner femurs, with smaller femoral neck widths (35.26vs38.44mm,p<0.001), head diameters (51.45vs54.04mm,p=0.001) and medullary canal widths (16.15vs18.93mm,p<0.001). This may reflect greater bisphosphonate accumulation in smaller femurs and consequent increased microfracture accumulation.  Geometries associated with force transfer also differed; Femoral neck shaft angle (133.3vs129.6degrees,p=0.033) and lateral cortical width at the lesser trochanter (5.19vs4.45mm,p=0.004) were larger and hip axis length (120.36vs125.81mm,p=0.037) smaller in patients with AFFs than controls. AFFs were associated with younger age (76.4vs81.9years,p<0.001), absence of dementia and greater number of medications. No variables studied were associated with fracture location.

Conclusions

This study represents a large Australian cohort of AFFs and suggests femoral geometry and comorbidities are associated with development of these fractures. Further characterisation of these risk factors may lead to the development of a predictive tool for AFF in susceptible patients.