Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 1. Ambulation performance and anthropometric measures.

OBJECTIVE: To describe performance parameters and effects on anthropometric measures in spinal cord injured subjects training with the Parastep 1 system. DESIGN: Before-after trial. SETTING: Human spinal cord injury applied research laboratory. PARTICIPANTS: Thirteen men and 3 women with thoracic (T4-T11) motor-complete spinal cord injury: mean age, 28.8yrs; mean duration postinjury, 3.8yrs. INTERVENTION: Thirty-two functional neuromuscular stimulation ambulation training sessions using a commercially available system (Parastep-1). The hybrid system consists of a microprocessor-controlled stimulator and a modified walking frame with finger-operated switches that permit the user to control the stimulation parameters and activate the stepping. OUTCOME MEASURES: Distance walked, time spent standing and walking, pace, circumferential (shoulders, chest, abdomen, waist, hips, upper arm, thigh, and calf) and skinfold (chest, triceps, axilla, subscapular, supraillium, abdomen, and thigh) measurements, body weight, thigh cross-sectional area, and calculated lean tissue. RESULTS: Statistically significant changes in distance, time standing and walking, and pace were found. Increases in thigh and calf girth, thigh cross-sectional area, and calculated lean tissue, as well as a decrease in thigh skinfold measure, were all statistically significant. CONCLUSIONS: The Parastep 1 system enables persons with thoracic-level spinal cord injuries to stand and ambulate short distances but with a high degree of performance variability across individuals. The factors that influence this variability have not been completely identified.

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 3. Lack of effect on bone mineral density.

OBJECTIVE: To determine if the bone mineral density loss seen after spinal cord injury (SCI) is reversed by a walking program using the Parastep 1 system. DESIGN: Before-after trial. SETTING: Human SCI applied research laboratory. PARTICIPANTS: Thirteen men and 3 women with thoracic motor- and sensory-complete SCI, mean age 28.8yrs, mean duration postinjury 3.8yrs. INTERVENTION: Thirty-two functional neuromuscular stimulation (FNS) ambulation training sessions using a commercially available system (Parastep 1). This system consists of a microprocessor-controlled stimulator and a modified walking frame with finger-operated switches that permit the user to control the stimulation parameters and activate the stepping. OUTCOME MEASURE: Bone mineral density at the femoral head, neck, and Ward's triangle measured using a Lunar DP3 dual-photon densitometer. RESULTS: No significant change in bone mineral density was found using repeated measures analyses of variance. CONCLUSIONS: Axial loading combined with muscle stimulation and resistive exercise does not result in significant changes in bone mineral density in persons with complete paraplegia.

Stimulus-evoked EMG monitoring during transpedicular lumbosacral spine instrumentation. Initial clinical results.

OBJECTIVES: The authors developed and evaluated an electrophysiologic method for minimizing the risk of nerve root trauma associated with the placement of pedicle screws during transpedicular lumbosacral fixation in humans. SUMMARY OF BACKGROUND DATA: Various methods have been evaluated to reduce the high complication rates associated with lumbosacral transpedicular fixation, but none are without significant limitations or drawbacks. Using a pig model, we previously developed a technique for assessing, by electrophysiologic means, the potential risk associated with placement of a screw at a given site. In this report, the authors describe their experience with this technique in patients. METHODS: Electromyogram (EMG) was monitored from eight lower extremity muscles bilaterally. Square-wave electrical shocks (200 microseconds, 7 mA) were delivered through the instruments used to form and evaluate each pedicle hole, and through the screw itself if placement was deemed safe. Provided that the instruments used (e.g., awl, tap, probe) do not exit from bone in any direction below the entry point, the resistance of bone to the 7 mA stimulus intensity is high enough such that no nerve roots are stimulated, and the EMG traces remain flat. Conversely if EMG is evoked, it warns of a potential perforation in a pedicle wall or in the anterior body. RESULTS: The authors evaluated this technique in 18 patients in whom a total of 102 screws were placed. Based on results of electrophysiologic and palpatory evaluation, 68% of the screws were placed in a satisfactory manner. Electrophysiologic evidence of a perforation, which could not be confirmed by palpation or visualization, was seen in another 13% of this total. The remaining 19% of screw placements involved sites where a defect was missed originally by palpation alone, but was located based on electrophysiological testing combined with palpation and visualization (11%), and where a perforation was initially palpated (8%). There was no postoperative morbidity associated with malpositioned screws. CONCLUSIONS: Our results indicate that the technique is sensitive and, based on early clinical results, reliable in the detection of perforations in pedicle screw placement. Moreover, the method is inexpensive, rapid, and easily implemented into a standard intraoperative monitoring protocol.

Evaluation of serum osteoblast mitogenic activity in spinal cord and head injury patients with acute heterotopic ossification.

STUDY DESIGN: This was a blind, prospective study of the effect of sera from patients with spinal cord and head injuries on osteoblast proliferation. OBJECTIVES: The authors studied whether a humoral factor that stimulates the formation of heterotopic bone is released into the circulation after a neural injury. BACKGROUND DATA: Other authors have shown that a humoral osteoinductive factor may be released after head and spinal cord injuries. METHODS: Serum was obtained at certain times throughout the first 12 weeks post-injury and from control subjects. It was incubated with osteoblasts harvested from fetal rats, as well as with fibroblast controls. RESULTS: There was a significant rise in serum mitogenic activity after injury in both groups. When patients that developed heterotopic ossification were compared to other patients and controls, no significant differences were seen. CONCLUSIONS: This in vitro study fails to support a humoral mechanism for heterotopic ossification after spinal cord or brain injuries.

Nonoperative management of stable thoracolumbar burst fractures with early ambulation and bracing.

Eighteen neurologically intact patients with burst fractures at the thoracolumbar junction were treated with early ambulation in a total contact orthosis. No attempt was made to reduce the associated deformity. Selection criteria excluded patients with posterior column disruption. Hospital stay averaged 10 days. Follow-up averaged 19 months. Mean kyphosis was 19 at time of injury and 20 at follow-up. At follow-up, 15 patients rated their pain as little or none. Seventeen patients had little or no restriction of activity. Follow-up computed tomography (CT) scans obtained in eight patients showed significant resorption of retropulsed bone. No deterioration of neurologic function developed in any patient. In patients with intact posterior elements and thoracolumbar burst fractures, early mobilization in a total contact TLSO can lead to satisfactory functional results. Prolonged bed rest was not required in this series. The authors attribute the good results of nonoperative management to the exclusion of patients with posterior column disruption.

Intraoperative evoked EMG monitoring in an animal model. A new technique for evaluating pedicle screw placement.

An electric drill was used to introduce holes in the L4 through L7 pedicles in pigs. Constant-voltage stimulating pulses (5.5 V, stimulus rate = 3/sec) were delivered through a ball-tipped probe used to palpate the walls of each pedicle, and observation was made of electromyogram (EMG) evoked from hind limb muscles. Screws were placed in each pedicle hole, and evaluated for absolute voltage necessary to evoke EMG (threshold). At the conclusion of each experiment, screw positions were ascertained by removal and dissection of the lumbosacral spine. Approximately 50% of screw placements resulted in defects of the pedicle. In each of these cases, 5.5 V stimuli delivered through the probe evoked EMG from muscles innervated by adjacent motor axons. Conversely, for those cases where the pedicle was intact, significantly higher voltages were needed to evoke EMG. The authors believe that this is a promising intraoperative technique to simply and reliably identify mispositioned screws, thereby minimizing neurologic complications.

Characterization and demonstration of human liver-specific protein (LSP) and apo-LSP.

Liver-specific protein (LSP) prepared by standard methods from five normal human livers showed significant variations in terms of quantitative yield, lipid/protein ratio and migration characteristics of different components on SDS-polyacrylamide gel electrophoresis. This heterogeneity is probably related to varying amounts of different molecular species in the LSP preparations. Delipidation and re-chromatography of the LSP preparation appeared to result in relative enrichment of apo-LSP which showed immunological identity with LSP. Rabbit antiserum to LSP gave a precipitin line of identity with standard antisera to human LSP (anti-LSP) from two other laboratories. After extensive absorption, anti-LSP showed selective reactivity with a surface membrane antigen on a human hepatocellular carcinoma cell line (PLC/PRF/5) that exhibits functional and morphological characteristics of differentiated hepatocytes. The antiserum did not react with cell lines derived from other organs as determined by the indirect fluorescent antibody technique. The surface staining of viable PLC/PRF/5 cells was eliminated by absorption with LSP and apo-LSP, but not with the equivalent kidney fractions. These findings support the concept of a liver-specific antigen and suggest that the PLC/PRF/5 cell line may serve as a source of homogeneous LSP.