Ground Walking in Chronic Complete Spinal Cord Injury

Abstract

THE AIM OF THE ARTICLE This article aims to foster methodological reflections on previous researches making causal inferences between biological interventions and behavioral outcomes. In a thorough study, electrical lumbar epidural stimulation added to an intense and prolonged exercise program seemed to be effective in allowing independent standing and assisted overground gait in two of four chronic complete spinal cord injury subjects. The conclusions from this research are debatable and therefore potentially misleading as the message that some chronic complete paraplegic persons can return to walk strongly appeals to patients and professionals. A warning is provided against overconfidence in deterministic, bottom-up modeling of treatment effects across the many functional levels linking the body’s biology to a person’s behavior. OUTCOME MAY NOT BE THE EFFECT OF THE HYPOTHESIZED CAUSE Gait Training and Recovery of Patients With Chronic Motor Complete Spinal Cord Injury A recent article in New England Journal of Medicine1 reported a case series of four chronic spinal cord injury patients (aged 22–32 yrs; 2.5–3.3 yrs after trauma). Two patients (participants P1 and P2, gender unspecified) were motor and sensory complete (grade A, ASIA Impairment Scale-AIS, 2011 Version2), both at the T4 level. Two other participants (P3 and P4), a man and a woman, as observed in the supplementary videos,1 were motor complete and sensory incomplete (AIS B), at level C5 and T1, respectively. An intense training program was initiated, consistent with the patients’ progress and focused on three types of training sessions: stepping on a treadmill, overground standing, and overground walking. “Core” exercises (ie, exercises targeting force and coordination of trunk and lower limb muscles) were also associated. Stepping on a treadmill was performed “with bodyweight support and manual facilitation of stepping.” Bodyweight was supported on the treadmill through the use of a custom-built apparatus. Trainers moved the patients’ “legs through the step cycle if needed, during which the participant made voluntary attempts to perform elements of the step cycle” (Appendix1). Training also included assistance to overground standing” and to overground walking, which occurred only if the former skill was attained. The subjects were allowed to use their arms to aid in posture and balance. Manual assistance for the knees and hips was supplied as needed. During overground walking, patients were allowed to use walkers, and parallel bars were held by two therapists. The exercise program was applied daily, in one or two 1-hr sessions. All four participants failed to attain independent standing and walking either on the treadmill or overground after the initial training period that lasted for 2 hrs per day, 5 days a week, for 8–9 wks. Subsequently, an epidural stimulator was implanted in all subjects. A 16-electrode array was placed over spinal segments L2 to S1-S2. Details can be found in the original article (main text and supplements). Thus, the selected anode-cathode pairs and stimulation parameters presumably induced the “rhythmic activation of ensembles of leg muscles that simulated walking movements” and the “combinations were selected that enhanced standing and stepping movements while participants focused on each of these tasks.”1(p1247) The participants resumed an intensive training program (one to two 1-hr session per day, 5 days a week) during which the epidural stimulation was continuously provided. “Both standing and stepping stimulation configurations were modified every 2–4 wks to determine whether adjustments resulted in better standing and stepping, on the basis of observation and electromyographic (EMG) activity” (Appendix1). The number of training sessions with epidural stimulation and the treatment duration were as follows: 375 sessions and 52 wks for P1 (with a 1-yr gap because of a spontaneous hip fracture while stepping on the treadmill in week 2