Oral Virtual Presentation (Virtual only) ESA-SRB-ANZBMS 2021

The Sydney AFF Score:  A Simple Tool to Distinguish Females Presenting with Atypical Femur Fractures versus Typical Femur Fractures (#223)

Gareth Crouch 1 , Nitesh Dhanekula 2 , Sue-Lynn Lau 3 , Edward Graham 4 , Maria-Liza Nery 5 , Jean Doyle 5 , Lillias Nairn 5 , Karen Byth 6 , Andrew Ellis 7 , Roderick Clifton Bligh 5 , Christian Girgis 3 5
  1. Royal North Shore Hospital, Sydney, NSW, Australia
  2. Westmead Hospital, Sydney, NSW, Australia
  3. Department of Endocrinology and Diabetes, Westmead Hospital, Sydney, New South Wales, Australia
  4. Department of Orthopaedic Surgery, Westmead Hospital, Sydney, New South Wales, Australia
  5. Department of Endocrinology and Diabetes, Royal North Shore Hospital, Sydney, New South Wales, Australia
  6. WSLHD Research and Education Network , Westmead Hospital, Sydney, New South Wales, Australia
  7. Department of Orthopaedic Surgery , Royal North Shore Hospital, Sydney, New South Wales, Australia

Purpose

Atypical femur fractures (AFF) are a rare but serious complication of long-term bisphosphonate use. Although clearly defined by American Society for Bone and Mineral  Research (ASBMR) criteria, the use of qualitative fracture criteria may lead to uncertainty in AFF diagnosis, with significant therapeutic implications. A score that rapidly and accurately identifies AFFs amongst typical femur fractures using quantitative parameters is needed.

Methodology

Radiographs of femoral shaft and subtrochanteric fractures treated at a tertiary centre in Sydney 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 or non-AFFs. Geometric and demographic data was analysed with multiple logistic regression and decision tree analysis to develop the Sydney AFF risk score. This score was validated on a patient population in an separate ethnically diverse tertiary centre.

Results

This score uses three dichotomised independent variables and adds one point for each: [age £ 80 years] + [femoral neck width <37 mm] + [lateral cortical width at lesser trochanter ³5 mm], (score 0 – 3). In an independent set of 53 female patients at a different centre in Sydney, a score ³2 demonstrated 73.3% sensitivity and 69.6% specificity for AFF (AUC 0.775, SE 0.063) and remained independently associated with AFF after adjustment for bisphosphonate use. Within the AFF population, distinctions in femoral geometry were evident in patients of Asian ethnicity.

Conclusion

The Sydney AFF Score provides a quantitative means of identifying female patients with femur fractures who have sustained an AFF as opposed to a TFF. This score has clear management implications and this score may augment ASBMR diagnostic criteria.