Background: Factors influencing the progression of physical impairment to patient-perceived disability are not well known. We sought to better understand this relationship in the setting of injury.
Methods: We followed a cohort of 302 patients with lower extremity fractures over a 1-year period. Physical impairment was assessed by range of motion, strength, and pain. Range of motion and strength were assessed together as a proportion of normal function of the extremity (impairment score). Pain was assessed using a Visual Analogue Scale (VAS) pain score. Disability was assessed using the Sickness Impact Profile (SIP), a widely used measure of patient-perceived limitations of everyday activities attributable to illness. The SIP was administered during hospitalization to assess preinjury baseline. Impairment assessment and readministration of the SIP were performed at 12 months after injury.
Results: Impairment in leg function (range of motion and strength) was highly correlated (p < 0.001) with overall SIP score at 12 months, but accounted for only 23% of the variance in overall SIP scores. Likewise, VAS pain score was highly correlated (p < 0.001) with overall SIP score at 12 months, but accounted for only 29% of the variance in overall SIP scores. In a multivariate linear regression analysis, variables that were independently associated with overall SIP score included impairment score, VAS pain score, preinjury SIP, poverty status, education status, social support, having hired a lawyer, and involvement with workers' compensation. These variables accounted for 52% of the variance in overall SIP scores at 12 months.
Conclusion: The degree of physical impairment accounts for only a small amount of the variance in disability from lower extremity fracture. Identifiable patient characteristics including age, socioeconomic status, preinjury health, and social support together with impairment account for over half of the variance in long-term disability. Further research is needed to increase understanding of other factors that influence the progression of impairment to disability, especially those factors that may be amenable to intervention.