Progressive Sublesional Bone Loss Extends into the Second Decade After Spinal Cord Injury

Objective: The rate of areal bone mineral density (aBMD) loss at the knee (distal femur (DF) and proximal tibia) and hip (femoral neck (FN) and total hip (TH)) was determined in persons with traumatic spinal cord injury (SCI) who were stratified into subgroups based on time since injury (TSI). Design: Cross-sectional retrospective review. Setting: Department of Veterans Affairs Medical Center and Private Rehabilitation Hospital. Participants: Data on 105 individuals with SCI (TSI <= 12 months, n = 19; TSI 1-5 years, n = 35; 6-10 years, n = 19; TSI 11-20 years, n = 16; TSI >20 years, n = 15) and 17 able-bodied reference (AB(ref)) controls. Interventions: NA Main Outcome Measures: The knee and hip aBMD values were obtained by dual energy X-ray absorptiometry (GE Lunar iDXA) using standard clinical software for the proximal femur employed in conjunction with proprietary research orthopedic knee software applications. Young-normal (T-score) and age-matched (Z-scores) standardized scores for the FN and TH were obtained using the combined GE Lunar/National Health and Nutrition Examination Survey (NHANES III) combined reference database. Results: When groups were stratified and compared as epochs of TSI, significantly lower mean aBMD and reference scores were observed as TSI increased, despite similar mean ages of participants among the majority of TSI epoch subgroups. Loss in aBMD occurred at the distal femur (DF), proximal tibia (PT), FN, and TH with 46%, 49%, 32%, and 43% of the variance in loss, respectively, described by the exponential decay curves with a time to steady state (t(ss)) occurring at 14.6, 11.3, 14, and 6.2 years, respectively, after SCI. Conclusions: Sublesional bone loss after SCI was marked and occurred as an inverse function of TSI. For aBMD at the hip and knee, t(ss) extended into the second decade after SCI.