Evaluation of gait parameters and mechanical work on patients with lower extremity amputations

Introduction: Due to improved body armor and medical techniques, the rate of war-related amputations experienced by military personnel is now twice that of prior wars [1]. Previous research has examined amputee gait, but information on bilateral trans-femoral amputees as a group is lacking. Therefore, the aim of this study was to compare gait parameters and mechanical work of subjects with bilateral trans-femoral (BTF) amputations to those with unilateral trans-tibial (UTT) amputations, unilateral trans-femoral (UTF) amputations, and able-bodied controls. Patients/materials and methods: At Naval Medical Center San Diego, a retrospective review was conducted of active duty military members who had undergone a BTF, UTT, or UTF amputation due to trauma and had been walking unassisted for at least three months. All subjects were male and matched for age (25.6±4.0 years), height (176.9±5.5 cm), and weight (82.1±13.6 kg), resulting in groups of 14 UTTs, 9 UTFs, 9 BTFs, and 11 controls. Subjects wore their customized prosthesis(es) and walked at their selfselected pace as three dimensional gait data were collected with a 12-camera Motion Analysis Corporation (MAC) system (Motion Analysis Corp., Santa Rosa, CA) and four, floor-embedded AMTI force plates (AMTI, Watertown, MA). Trials were processed with Cortex (MAC) and OrthoTrak (MAC) software. Variables examined included gait velocity, cadence, stride length, step width, and mechanical work. Visual3D (C-Motion Inc., Germantown, MD) was used to calculate totalmechanical work as the sumof the potential, translational, and rotational energies of each body segment, integrated per stride length for both lower limbs and normalized per stride and body mass (J/kgm). Results: For each variable of interest, a 4 (condition)×1 (dependent variable) ANOVA with alpha=0.05 was run to detect significant differences. Age, height, and weight were not statistically different across groups, but post-hoc analyses using Bonferroni corrections showed the BTF group had significantly (p<0.05) greater mechanical work output and significantly (p<0.05) lower velocity, cadence, and stride length compared to the UTTs, UTFs, and controls. Step width post-hoc analysis using Games–Howell corrections found BTFs had a wider step width (p<0.05) than UTTs and controls but not UTFs. Linear regressions between mechanical work and velocity (R2 =0.91), cadence (R2 =0.70), step width (R2 =0.46), and residual limb length (R2 =0.29) were also performed. Discussion and conclusions: In summary, the BTF group had a significantly slowerwalking speed (0.95±0.12m/s), lower cadence (95.45±4.90 steps/min), shorter stride length (119.52±11.67 cm), and larger mechanical work output (11.12±1.17 J/kgm) as compared to theUTT,UTF, andcontrol groups. BTFsalsohadawider step width (22.19±6.13 cm) than UTTs and controls. The linear regression analysis showed slower walking speeds and lower cadences require higher mechanical work outputs. This is supported by the fact that the BTFs who had slower gait characteristics used approximately 45% more work per meter than the able bodied controls, 51%more than UTTs, and 35%more than UTFs. Although, no significant differenceswere found between UTFs, UTTs, and the controls, additional subjects could provide more power in order to detect differences across these groups. Views in the article are those of the authors and not of the DoN, DoD, or the US Government.