Low Back Pain in Adults With Transfemoral Amputation: A Retrospective Population-Based Study

Background: Low back pain (LBP) is common among individuals with transfemoral amputation (TFA) and has a negative impact on quality of life. Little is known about health care utilization for LBP in this population and whether utilization varies by amputation etiology. Objective: To determine if individuals with TFA have an increased likelihood of seeking care or reporting symptoms of acute or chronic LBP during physician visits after amputation compared with matched individuals without amputation. Design: Retrospective cohort. Setting: Olmsted County, Minnesota (2010 population: 144 248). Participants: All individuals with incident TFA (N = 96), knee disarticulation, and transfemoral amputation residing in Olmsted County between 1987 and 2014. Each was matched (1:10 ratio) with non-TFA adults on age, sex, and duration of residency. Individuals were divided by etiology of amputation: dysvascular and trauma/cancer. Interventions: Not applicable. Main Outcome Measurements: Death and presentation for evaluation of LBP (LBP event) while residing in Olmsted County. LBP events were identified using validated International Classification of Diseases, Ninth Revision (ICD-9) codes and corresponding Berkson, Hospital International Classification of Diseases Adapted (HICDA), and ICD-10 diagnostic codes. Hurdle and competing-risk Cox proportional hazard models were used. Results: Having a TFA of either etiology did appear to correlate with increased frequency of LBP events, although this association was only statistically significant within the dysvascular TFA cohort (dysvascular TFA cohort: relative risk [RR] 1.80, 95% confidence interval [CI] 1.07-3.03, median follow-up 0.78 years; trauma/cancer TFA cohort: RR 1.14, 95% CI 0.58-2.22, median follow-up 7.95 years). In time to event analysis, dysvascular TFA had an increased risk of death and event. Obesity did not significantly correlate with increased frequency of LBP events or time to event for either cohort. At any given point in time, individuals with TFA of either etiology who had phantom limb pain were 90% more likely to have an LBP event (hazard ratio [HR] 1.91, 95% CI 1.11-3.31). Conditional on not dying and no LBP event within the first 2.5 years, individuals with prosthesis had a decreased risk of LBP events in subsequent years. Conclusions: Risk of LBP events appears to vary by TFA etiology. Obesity did not correlate significantly with increased frequency of LBP event or time to event. Phantom limb pain correlated with decreased time to LBP event after amputation. The association between prosthesis receipt and LBP events is ambiguous. Level of Evidence: III.