Fracture Risk Assessment
Adjusting Hip Fracture Probability in Men and Women Using Hip Axis Length: the Manitoba Bone Density Database

https://doi.org/10.1016/j.jocd.2015.07.004Get rights and content

Abstract

Most studies report that longer hip axis length (HAL) is associated with increased hip fracture risk in women, but comparable data in men are sparse. Using a registry of all dual-energy X-ray absorptiometry (DXA) results for Manitoba, Canada, we identified 4738 men and 50,420 women aged 40 yr and older with baseline hip DXA results, HAL measurements, and Fracture Risk Assessment Tool (FRAX) hip fracture probability computed with femoral neck bone mineral density (BMD). Population-based health service records were assessed for a subsequent hospitalization with a primary diagnosis of hip fracture. During mean 6.2 yr of follow-up, 70 men and 1020 women developed incident hip fractures. Mean HAL was significantly greater in those with vs without incident hip fractures (men 123.0 ± 7.6 vs 121.3 ± 7.4 mm, p = 0.050; women 106.9 ± 6.2 vs 104.6 ± 6.2 mm, p < 0.001). When adjusted for age and femoral neck BMD, each millimeter increase in HAL increased hip fracture risk by 3.6% in men (p = 0.022) and 4.6% in women (p < 0.001); this association was unaffected by sex (p value for interaction = 0.477). When adjusted for log-transformed FRAX hip fracture probability, each millimeter increase in HAL increased hip fracture risk by 3.4% in men (p = 0.031) and 4.8% in women (p < 0.001); this association was again unaffected by sex (p interaction = 0.409). A bilinear adjustment applicable to both men and women was developed: relative increase in hip fracture probability 4.7% for every millimeter that HAL is above the sex-specific average, relative decrease in hip fracture probability 3.8% for every millimeter that HAL is below the sex-specific average. We concluded that greater DXA-derived HAL is associated with increased incident hip fracture risk in both men and women, and this risk is independent of BMD and FRAX probability.

Introduction

Hip fractures are associated with decreased quality of life, excess mortality that exceeds 20% in the initial year, and a large societal economic burden 1, 2, 3, 4. Accurately identifying individuals at greatest risk for hip fracture should optimally lead to targeted intervention to reduce that risk. In addition to nonpharmacological interventions, such as falls prevention, optimization of calcium and vitamin D intake, and exercise programs that promote strength and balance (5), approved pharmacological agents have been shown to reduce hip fractures by about 40% in appropriately selected individuals (6).

Bone mineral density (BMD) measured from dual-energy X-ray absorptiometry (DXA) is widely used to assess hip fracture risk as meta-analyses have shown that each standard deviation (SD) reduction in femoral neck BMD increases hip fracture risk by approximately 2.6-fold 7, 8. Accordingly, BMD of the proximal femur measured by DXA has been designated the reference methodology for the densitometric diagnosis of osteoporosis based on a T-score of −2.5 or lower (9). Notwithstanding the strength of the BMD-fracture relationship, DXA does not capture all aspects of femoral strength or hip fracture risk, and most hip fractures occur in individuals who have a BMD above the osteoporotic threshold 8, 10, 11, 12. The World Health Organization Collaborating Centre Fracture Risk Assessment Tool (FRAX) estimates individual 10-yr probability of hip fracture and major osteoporotic fracture using clinical risk factors derived from meta-analyses and (optionally) femoral neck BMD (13). FRAX has been shown to improve fracture risk assessment over BMD alone in derivation and validation cohorts (14). However, FRAX does not consider non-BMD parameters related to skeletal geometry and strength 15, 16.

Hip axis length (HAL) is conventionally defined as the distance from the base of the greater trochanter to the inner pelvic brim. This measure is associated with hip fracture risk in women; comparable data in men are sparse 17, 18, 19, 21. We have previously shown that longer HAL was an independent risk factor for hip fracture in women after adjustment for BMD and FRAX hip fracture probability (21). The present study was performed to test if HAL had a similar independent effect on hip fracture risk in men and to derive a simple adjustment for FRAX hip fracture probability using HAL to improve clinical risk assessment.

Section snippets

Study Population

We identified all men and women aged 40 yr and older with health care coverage in the province of Manitoba, Canada, who underwent baseline bone density measurement of the proximal femur with a single fan-beam scanner configuration (Prodigy; GE Healthcare, Madison, WI, USA). For those with more than 1 eligible set of measurements, only the first record was included. In Manitoba, health services are provided to virtually all residents and recorded through a single public health care system. DXA

Results

Baseline characteristics of the cohort, comprising 4738 men and 50,420 women aged 40 yr and older, are summarized in Table 1. Men were slightly older than women (mean age: 66.0 vs 64.3 yr, p < 0.001), femoral neck BMD was higher for men (mean: −1.1 vs −1.4 for women, p < 0.001), whereas hip fracture probability was similar (p = 0.827). Mean HAL was greater in men than women (121.3 vs 104.7 mm, p < 0.001).

During mean follow-up of 6.2 yr, 70 (1.5%) men and 1020 (2.0%) women developed incident hip

Discussion

We have previously shown that longer HAL was a BMD and FRAX-independent risk factor for hip fracture in women (21). The present study provides complementary data in men and confirms that longer HAL is also a risk factor for hip fracture in men. Furthermore, this risk is independent of hip fracture probability estimated with the FRAX algorithm and does not differ according to sex. As a result, a simple bilinear adjustment for FRAX hip fracture probability based on HAL applicable to both men and

Acknowledgments

We are indebted to Manitoba Health for providing data (HIPC File No. 2011/2012-31). The results and conclusions are those of the authors, and no official endorsement by Manitoba Health is intended or should be inferred. This article has been reviewed and approved by the members of the Manitoba Bone Density Program Committee.

Details of contributors and guarantor: Authors substantially contributed to: conception, design, and analysis (William D. Leslie) and interpretation of data (all authors);

References (37)

  • O. Johnell et al.

    Predictive value of BMD for hip and other fractures

    J Bone Miner Res

    (2005)
  • D. Marshall et al.

    Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures

    BMJ

    (1996)
  • A. Cranney et al.

    Low bone mineral density and fracture burden in postmenopausal women

    CMAJ

    (2007)
  • K.L. Stone et al.

    BMD at multiple sites and risk of fracture of multiple types: long-term results from the Study of Osteoporotic Fractures

    J Bone Miner Res

    (2003)
  • A. Oden et al.

    Assessing the impact of osteoporosis on the burden of hip fractures

    Calcif Tissue Int

    (2013)
  • J.A. Kanis

    Assessment of osteoporosis at the primary health-care level. Technical Report

    (2007)
  • J.A. Kanis et al.

    The use of clinical risk factors enhances the performance of BMD in the prediction of hip and osteoporotic fractures in men and women

    Osteoporos Int

    (2007)
  • T.J. Beck et al.

    Predicting femoral neck strength from bone mineral data. A structural approach

    Invest Radiol

    (1990)
  • Cited by (43)

    • Assessment of Skeletal Strength: Bone Density Testing and Beyond

      2021, Endocrinology and Metabolism Clinics of North America
      Citation Excerpt :

      The ISCD has determined that longer HAL is associated with greater hip fracture risk in postmenopausal women, and that other hip geometry parameters (eg, cross-sectional area, cross-sectional moment of inertia, neck shaft angle) should not be used to assess hip fracture risk.58 An analysis of the Manitoba Bone Density Database found a relative increase in hip fracture probability of 4.7% for every millimeter that HAL is above the sex-specific average for both men and women.59 This risk is independent of BMD and FRAX probability.

    • A comparison of fracture risk assessment tools

      2020, Marcus and Feldman’s Osteoporosis
    • Fracture Risk Indices From DXA-Based Finite Element Analysis Predict Incident Fractures Independently From FRAX: The Manitoba BMD Registry

      2019, Journal of Clinical Densitometry
      Citation Excerpt :

      Prolonged glucocorticoid use (≥3 mo in the year prior to BMD test) was captured in the province-wide retail pharmacy database system. We also considered HAL since this is a geometric measurement derived from hip DXA that predicts hip fracture risk independent of BMD and FRAX score (27,28). Continuous variables were reported as means with standard deviations, and counts with percentages.

    View all citing articles on Scopus

    Disclosure: The authors have nothing to disclose related to this work.

    View full text