title: Three-dimensional joint reaction forces and moments at the low back during over-ground walking in persons with unilateral lower-extremity amputation.
abstract: BACKGROUND
  Abnormal mechanics of locomotion following lower-extremity amputation are associated with increases in trunk motion, which in turn may alter loads at the low back due to changes in inertial and gravitational demands on the spine and surrounding trunk musculature.
  
  
  METHODS
  Over-ground gait data were retrospectively compiled from two groups walking at similar self-selected speeds (~1.35m/s): 40 males with unilateral lower-extremity amputation (20 transtibial, 20 transfemoral) and 20 able-bodied male controls. Three-dimensional joint reaction forces and moments at the low back (L5/S1 spinal level) were calculated using top-down and bottom-up approaches. Peak values and the timings of these were determined and compared between and within (bilaterally) groups, and secondarily between approaches.
  
  
  RESULTS
  Peak laterally-directed joint reaction forces and lateral bend moments increased with increasing level of amputation, and were respectively 83% and 41% larger in prosthetic vs. intact stance among persons with transfemoral amputation. Peak anteriorly-directed reaction forces and extension moments were 31% and 55% larger, respectively, among persons with transtibial amputation compared to controls. Peak vertical reaction forces and axial twist moments were similar between and within groups. Peak joint reaction forces and moments were larger (3-14%), and the respective timing of these sooner (11-62ms), from the bottom-up vs. top-down approach.
  
  
  CONCLUSIONS
  Increased and asymmetric peak reaction forces and moments at the low back among persons with unilateral lower-extremity amputation, particularly in the frontal plane, suggest potential mechanistic pathways through which repeated exposure to altered trunk motion and spinal loading may contribute to low-back injury risk among persons with lower-extremity amputation.
authors.affiliation: Department of Rehabilitation, Walter Reed National Military Medical Center, Bethesda, MD 20889, USA; Center for Rehabilitation Sciences Research, Department of Physical Medicine and Rehabilitation, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA. Electronic address: bradford.d.hendershot.ctr@health.mil.
authors.forename: Brad D
authors.initials: BD
authors.lastname: Hendershot
authors.affiliation: Department of Rehabilitation, Walter Reed National Military Medical Center, Bethesda, MD 20889, USA; DOD - VA Extremity Trauma and Amputation Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD 20889, USA.
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Wolf
mesh_terms: D000328:Adult; D000673:Amputation, Traumatic / Q000503:physiopathology*; D001696:Biomechanical Phenomena / Q000502:physiology; D016022:Case-Control Studies; D005684:Gait / Q000502:physiology; D006801:Humans; D007866:Leg / Q000601:surgery; D008297:Male; D008889:Military Personnel; D012189:Retrospective Studies; D013131:Spine / Q000503:physiopathology*; D060726:Torso / Q000503:physiopathology*; D016138:Walking / Q000502:physiology*
keywords: Amputation; Biomechanics; Gait; Inverse dynamics; Low back pain; Lumbosacral