Modular control of gait after incomplete spinal cord injury: differences between sides.

STUDY DESIGN: This is an analytical descriptive study. OBJECTIVES: The main goal of this study was to compare the modular organization of bilateral lower limb control in incomplete spinal cord injury (iSCI) patients during overground walking, using muscle synergies analysis. The secondary goal was to determine whether the similarity between the patients and control group correlate with clinical indicators of walking performance. SETTING: This study was conducted in National Hospital for Spinal Cord Injury (Toledo, Spain). METHODS: Eight iSCI patients and eight healthy subjects completed 10 walking trials at matched speed. For each trial, three-dimensional motion analysis and surface electromyography (sEMG) analysis of seven leg muscles from both limbs were performed. Muscle synergies were extracted from sEMG signals using a non-negative matrix factorization algorithm. The optimal number of synergies has been defined as the minimum number needed to obtain variability accounted for (VAF) ⩾90%. RESULTS: When compared with healthy references, iSCI patients showed fewer muscle synergies in the most affected side and, in both sides, significant differences in the composition of synergy 2. The degree of similarity of these variables with the healthy reference, together with the composition of synergy 3 of the most affected side, presented significant correlations (P<0.05) with walking performance. CONCLUSION: The analysis of muscle synergies shows potential to detect differences between the two sides in patients with iSCI. Specifically, the VAF may constitute a new neurophysiological metric to assess and monitor patients' condition throughout the gait recovery process.

Shoulder joint kinetics during wheelchair propulsion on a treadmill at two different speeds in spinal cord injury patients.

STUDY DESIGN: Prospective study using biomechanics patient data. OBJECTIVES: To analyze shoulder joint kinetics while propelling a wheelchair placed on a treadmill and compare shoulder joint net forces and moments when changing the speed of wheelchair propulsion on the treadmill. SETTING: National Hospital for Spinal Cord Injury, Toledo, Spain. METHODS: Sixteen subjects with thoracic spinal cord injury participated. A kinematic analysis system consisting of four camcorders (Kinescan-IBV) and a kinetic device that registered the contact force of the hand on the pushrim (SMART(Wheel)) were used. The wheelchair was propelled at 3 and 4 km h(-1) without any ramp. An inverse dynamic model allowed shoulder joint net forces and moments to be calculated from the contact force of the hand on the pushrim and kinematic data. RESULTS: Increasing propulsion speed increased most of the temporal parameters of propulsion and pushrim kinetics and shoulder joint net forces and moments. Compared with other studies that used an ergometer or dynamometer at the same speed, the magnitude of the shoulder joint net forces and moments elicited by wheelchair propulsion on the treadmill were lower than obtained by wheelchair propulsion on other devices. CONCLUSION: Lower magnitude of shoulder joint forces and moments found on the treadmill may be due to the lower friction compared with the other devices reviewed. Shoulder joint forces and moments depended strongly on the propulsion speed, increasing in magnitude when speed increased from 3 to 4 km h(-1).

Comparative biomechanical gait analysis of patients with central cord syndrome walking with one crutch and two crutches.

BACKGROUND: Ambulatory people with central cord syndrome often require assistive devices. The selection of a suitable assistive device should be based on an objective assessment. Our objective in this study was to determine whether there was any difference in using two crutches over one crutch, considering that these patients have bilateral upper-limb involvement. METHODS: Kinematic gait analysis was conducted in 12 patients with central cord syndrome of more than one year of evolution and functional capacity for walking with one crutch or without crutches. Patients were asked to walk with one crutch and with two crutches at a freely chosen walking speed through a 10-m walkway. Three-dimensional kinematic equipment based on active markers was used to analyze temporospatial and articular parameters (maximum, minimum, and range of motion, ROM, throughout the cycle) FINDINGS: During two-crutch versus one-crutch walking, speed was lower (P=0041), stride time and step time were longer (P=0.004 and P=0.005) and there were fewer strides/minute and steps/minute (P=0.005 and P=0.006). The duration of the single support stance was longer during two-crutch walking (P=0.008). With respect to the articular parameters, both ankle ROMs (dorsi-plantar flexion P=0.003 and pronation-supination P=0.004) were greater with one-crutch walking than with two-crutch walking. INTERPRETATION: In patients with central cord syndrome capable of walking with one crutch or without crutches, walking with two crutches decreases speed, increases stride time and step time and improves stability by increasing single support, and diminishes ankle plantar flexion during swing phase.