Measures and Application of Lower Leg Length: Fracture Risk Assessment

Abstract

The standardized measurement of lower leg length (knee height) is easy to perform with a high degree of precision. Lower leg length (LLL) is a reliable index of stature in older people because it is virtually unaffected by aged-related high loss. Height has been identified as a risk factor for fracture in middle-aged men and women. In frail older people, vertebral deformities and muscular contraction are common; and these conditions contribute to height loss and lead to increase risk of fracture. The relationship between height and risk of fracture in older people is therefore confounded, and was investigated using LLL rather than using directly measured height. In a prospective cohort of 2,005 institutionalized older men and women, LLL as a risk factor for fracture was examined in different ways in number of studies. The results showed that LLL was a significant risk factor for hip fracture and any fractures after adjusting for the influences of other risk factors. For residents with LLL ≥ 50.5 cm compared to residents with LLL < 50.5 cm, the adjusted relative risk (RR) was 1.45 (95% confidence interval: 1.07–1.99; P = 0.02) for hip fracture and 1.27 (95% confidence interval: 1.00–1.60, P = 0.05) for any fractures. The results also demonstrated that LLL affected the risk of fracture through one or two fracture pathways, namely bone fragility and/or the force of the impact of falling. It is most likely that both the mechanical impact of a fall and the correlation between LLL and hip axis length contribute to the fracture effect of LLL. In conclusion, LLL should be considered as a component for inclusion in future fracture risk assessment tools, especially those tools that to be used among frail older people.