Osteoporosis: assessing the risk of fragility fracture

Introduction

Osteoporosis is a disease characterised by low bone mass and structural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. Osteoporosis leads to nearly 9 million fractures annually worldwide (Johnell and Kanis, 2006), and over 300,000 patients present with fragility fractures to hospitals in the UK each year (British Geriatrics Society good practice guide on the care of patients with fragility fracture).

Fragility fractures are fractures that result from mechanical forces that would not ordinarily result in fracture, known as low-level (or 'low-energy') trauma (Kanis et al. 2001). The World Health Organization (WHO) has quantified this as forces equivalent to a fall from a standing height or less. Reduced bone density is a major risk factor for fragility fracture. Other factors that may affect the risk of fragility fracture include the use of oral or systemic glucocorticoids, age, sex, previous fractures and family history of osteoporosis. Because of increased bone loss after the menopause in women, and age-related bone loss in both women and men, the prevalence of osteoporosis increases markedly with age, from 2% at 50 years to more than 25% at 80 years in women. As the longevity of the population increases, so will the incidence of osteoporosis and fragility fracture.

Fragility fractures occur most commonly in the spine (vertebrae), hip (proximal femur) and wrist (distal radius). They may also occur in the arm (humerus), pelvis, ribs and other bones. Osteoporotic fractures are defined as fractures associated with low bone mineral density (BMD) and include clinical spine, forearm, hip and shoulder fractures. Osteoporotic fragility fractures can cause substantial pain and severe disability, often leading to a reduced quality of life, and hip and vertebral fractures are associated with decreased life expectancy. Hip fracture nearly always requires hospitalisation, is fatal in 20% of cases and permanently disables 50% of those affected; only 30% of patients fully recover (Sernbo and Johnell, 1993). Projections suggest that, in the UK, hip fracture incidence will rise from 70,000 per year in 2006, to 91,500 in 2015 and 101,000 in 2020 (Department of Health and Social Care Hospital episode statistics 2006).

Direct medical costs from fragility fractures to the UK healthcare economy were estimated at £1.8 billion in 2000, with the potential to increase to £2.2 billion by 2025, and with most of these costs relating to hip fracture care (Burge et al. 2008).

There are a number of therapies and treatments available for the prevention of fragility fractures in people who are thought to be at risk, or to prevent further fractures in those who have already had 1 or more fragility fractures. However, identifying who will benefit from preventative treatment is imprecise. A number of risk assessment tools are available to predict fracture incidence over a period of time, and these may be used to aid decision making. These tools are limited in that they may not include all risk factors, or may lack details of some risk factors. Tools are dependent on the accuracy of the epidemiological data used to derive them and tools validated in other populations may not apply to the UK. Two tools, Fracture Risk Assessment tool (FRAX) and QFracture, are available for use in the UK. It is not clear whether these tools are equally accurate and whether choice of tool should depend on circumstances. This short clinical guideline aims to provide guidance on the selection and use of risk assessment tools in the care of people who may be at risk of fragility fractures in all settings in which NHS care is received.