Lumbar spine orthosis wearing. I. Restriction of gross body motions

The effects of wearing commonly prescribed low-back braces and corsets on restriction of gross body motions were investigated. A lumbosacral corset, a chairback brace, and a molded plastic thoracolumbosacral orthosis (TLSO) were studied. Four trunk movements (flexion, extension, lateral bending, and twisting) were examined in five healthy adult men when standing and sitting. All three orthoses restricted at least some gross body motion to approximately two thirds to one half of no-orthosis values. All three orthoses failed to provide restrictions of at least 10% in at least one motion. Mean motion restriction across all eight movements studied in all five subjects were largest when wearing the TLSO and least when wearing the corset. Gross body motion restrictions relieve lumbar trunk muscle and spine loads.     

The influence of lordosis on axial trunk torque and trunk muscle myoelectric activity.

Force contributions from the facet complex and posterior ligaments during the generation of axial torque are a function of lordosis, and it has been speculated that these forces together with muscular contributions play a role in axial trunk twisting. This study investigated the electromyographic activity of the trunk musculature and torque-generating capacity of the lumbar spine under the conditions of normal lordosis, hyperlordosis, and hypolordosis. Eleven male subjects volunteered for this study. The subjects performed isometric twisting efforts and maximum dynamic twisting efforts at 30 degrees/sec. The myoelectric activity levels (normalized to maximal amplitude obtained from nontwist activities) were quite low despite maximal efforts to generate axial torque (for example: approximately 60% maximum voluntary contraction for latissimus dorsi and even lower for the abdominals). Furthermore, changes in lordosis did not produce any consistent changes in muscle activity, although a hyperlordotic spine produced significantly smaller axial torques, and a hypolordotic spine smaller still. Larger torques were measured during all three conditions of lordosis, as the subjects rotated toward an untwisted position, and lower torques as the subjects rotated away. The opposite trend was observed, however, in myoelectric activity of the agonistic side of latissimus dorsi, the thoracic level of erector spine, and the lumbar level of erector spinae, i.e., larger amplitudes were observed as the trunk was twisted away from the untwisted position. These data suggest that tissues other than muscle (i.e., passive tissue) contribute significantly to axial torque production and that the flexed and twisted spine is less able to resist applied axial torques, possibly increasing the risk of torsional injury.     

Quantitative analysis of the effect of lumbar orthosis on trunk muscle strength and muscle activity in normal subjects

 We studied the effect of lumbar orthosis on trunk muscle strength and muscle activity during flexion-extension bending of the trunk in 31 male volunteers. Trunk muscle strength was measured with a kinetic measurement system. Peak torque was calculated by using the mean torque of five repetitions. Trunk muscle activity was measured with commercially available equipment that has portable EMG data-collection units. The maximum level of the EMG signal was evaluated by employing the analyzing part of the computer's measuring program. With the application of the lumbar orthosis, the strength of the abdominal muscle and the back muscle increased; conversely, the activities of both muscles were decreased significantly. This might imply that lumbar orthosis reduces the load of the trunk muscles during performance. Received: October 5, 2001 / Accepted: February 12, 2002     

Lumbar trunk muscle use in standing isometric heavy exertions

A study was conducted to see whether a biomechanical model previously validated for predicting the lumbar spine internal loads imposed by the performance of easy and moderately strenuous physical tasks was also adequate for predicting loads imposed by heavy exertions. Lumbar trunk muscle myoelectric activities were measured in 10 healthy young adult men performing a variety of less strenuous and more strenuous tasks while standing upright, and these were compared to the lumbar muscle contraction magnitudes predicted by the model. For the less strenuous tasks, measured activities and predicted forces showed strong linear correlations, confirming the validity of the model at those load levels. Model predictions for the more strenuous tasks were often found to be inadequate. Contrary to model-incorporated assumptions, substantial antagonistic muscle contractions sometimes occurred, intraabdominal pressurization may sometimes have contributed substantially to the maintenance of structural equilibrium, and the ligamentous tissues of the trunk seemed sometimes to develop substantial passive resistances to bending and twisting moments.     

Effect of a thoracolumbosacral orthosis on lateral trunk shift in idiopathic scoliosis

The effect of the Wilmington brace on lateral trunk shift in adolescent idiopathic scoliosis was studied in 80 patients. With an average follow-up of 1 year 10 months after completion of brace treatment, improvement was seen in 58% of those patients with thoracic curves, 65% with thoracolumbar-lumbar curves, and 88% with double major curves. Lateral trunk shift decreased an average of 0.8 cm in patients with thoracic curves and 1.0 cm in patients with thoracolumbar-lumbar or double major curves. Improvement of existing lateral trunk shift was an additional consideration for instituting brace treatment in idiopathic scoliosis.     

Intramuscular myoelectric activity and selective coactivation of trunk muscles during lateral flexion with and without load.

STUDY DESIGN: Myoelectric activity of trunk muscles was measured intramuscularly in six healthy subjects as they maintained static trunk postures at 0 degrees, 15 degrees, and 30 degrees of lateral bending, unloaded or holding a 20-kg load in one hand alongside the body. OBJECTIVE: To determine the position and load dependency of the agonistic and antagonistic myoelectric responses of deep and superficial trunk lateral flexor muscles. SUMMARY OF BACKGROUND DATA: Loading of the trunk in lateral bending is associated with incidences of low back pain. The neuromotor control of muscles surrounding the spine may be decisive for its vulnerability. Earlier documentation of the activation pattern of trunk muscles, particularly those situated deeply, is incomplete. METHODS: Trunk angle was measured between S1-C7 and the vertical with a protractor. Electromyographic activity was recorded unilaterally from eight trunk muscles using intramuscular fine-wire electrodes inserted under the guidance of ultrasound. RESULTS: The electromyographic data showed that all muscles on the side contralateral to the load, except rectus abdominis, had their highest activity while loaded in the position most laterally flexed to the loaded side. The degree of bilateral coactivation was greater for the ventral than for the dorsal muscles. CONCLUSIONS: The myoelectric responses of most lumbar trunk muscles to static lateral flexion were dependent on trunk position and loading. The abdominal muscles demonstrated more coactivation than the other trunk muscles, and thus appeared to contribute more to trunk stabilization in laterally bent and loaded trunk positions.     

Effect of trunk flexion on cervical muscle EMG to rear impacts.

OBJECTIVE: To determine the effect of occupant positioning on the response of the cervical muscles to whiplash-type posterolateral impacts. METHODS: Twenty healthy volunteers underwent left posterolateral whiplash-type impacts with the volunteers seated "out-of-position". Electromyograms of the cervical muscles were recorded. RESULTS: Whether having the trunk flexed to the left or right at the time of impact, the muscle responses were low in magnitude, showing a trend to increasing EMG responses with increasing acceleration (P>0.05). The time to onset and time to peak electromyogram for most muscles showed a trend to progressively decrease with increasing levels of acceleration. With the subject flexed to the left, all muscles generated 31% or less of the maximal voluntary contraction electromyogram. With the subject flexed to the right, all muscles generated 27% or less of their maximal electromyogram. In both positions, the trapezii were the most active (P<0.05). Thus, having the trunk flexed out of neutral posture at the time of impact produces a very low magnitude cervical muscle response compared to impacts with the trunk in neutral posture. CONCLUSIONS: In the absence of bodily impact, the flexed trunk posture appears to produce a biomechanical response that would probably decrease the likelihood of cervical muscle injury in low velocity posterolateral impacts.     

Effect of abdominal surgery on intestinal myoelectric activity in the dog

The effect of cholecystectomy and small bowel transection on the myoelectric activity of the small intestine was determined in conscious dogs. Three animals were implanted with electrodes spaced approximately 25 cm apart along the serosal surface of the small intestine. Recordings were made with dogs in the unanesthetized fasted state. After completion of control recordings, the gallbladder was removed from each animal. Recordings were made each day after surgery for a period of one week and then periodically during the next two weeks. At the end of three weeks, transection and end-to-end anastomosis of the mid-ileum was done. Once again recordings were obtained each day for one week and periodically for two subsequent weeks to insure return to normal fasted patterns. Neither cholecystectomy nor transection and anastomosis had any inhibitory effects of the myoelectric activity of the small intestine.     

Lumbar multifidus muscle degenerates in individuals with chronic degenerative lumbar spine pathology

Histological and cell‐level changes in the lumbar musculature in individuals with chronic lumbar spine degenerative conditions are not well characterized. Although prior literature supports evidence of changes in fiber type and size, little information exists describing the tissue quality and biology of pathological features of muscle in this population. The purpose of this study was to quantify multifidus tissue composition and structure, inflammation, vascularity, and degeneration in individuals with chronic degenerative lumbar spine pathology. Human multifidus biopsies were acquired from 22 consecutive patients undergoing surgery for chronic degenerative lumbar spine pathology. Relative fractions of muscle, adipose, and extracellular matrix were quantified along with muscle fiber type and cross‐sectional area (CSA) and markers of inflammation, vascularity, satellite cell density, and muscle degeneration. On average, multifidus biopsies contained 48.5% muscle, 11.7% adipose tissue, and 26.1% collagen tissue. Elevated inflammatory cell counts (48.5 ± 30.0 macrophages/mm²) and decreased vascularity (275.6 ± 69.4 vessels/mm²) were also observed compared to normative values. Satellite cell densities were on average 13 ± 9 cells per every 100 muscle fibers. Large fiber CSA (3,996.0 ± 1,909.2 µm²) and a predominance of type I fibers (61.8 ± 18.0%) were observed in addition to evidence of pathological degeneration‐regeneration cycling (18.8 ± 9.4% centrally nucleated fibers, and 55.2 ± 24.2% of muscle regions containing degeneration). High levels of muscle degeneration, inflammation, and decreased vascularity were commonly seen in human multifidus biopsies of individuals with lumbar spine pathology in comparison to normative data. Evidence of active muscle degeneration suggests that changes in muscle tissue are more complex than simple atrophy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2700–2706, 2017.

     

Lumbar spine pain originating from vertebral osteophytes.

BACKGROUND AND OBJECTIVES: Axial spine pain originates from a number of structures. Putative pain generators include facet joints, intervertebral disks, sacroiliac joints, and myofascial structures. Osteophytes originating from lumbar vertebral bodies in the area of the intervertebral disks may be a source of nociceptive low back pain which may respond to local injection. METHODS: Five patients with axial low back pain unresponsive to traditional treatment modalities were treated with fluoroscopic guided injection of local anesthetic and corticosteroid near large intervertebral osteophytes. RESULTS: All 5 patients experienced relief. CONCLUSION: Vertebral osteophytes may be a source of axial spine pain. Injection of painful osteophytes with a local anesthetic and corticosteroid solution may produce pain relief.     

Effect of paraspinal muscle vibration on position sense of the lumbosacral spine.

STUDY DESIGN: A two-group experimental design with repeated measures on one factor was used. OBJECTIVES: To investigate the role of the muscle spindles of the paraspinal muscles in lumbosacral position sense of healthy individuals. SUMMARY OF BACKGROUND DATA: Muscle spindles are recognized to be important mediators for position and movement sense in peripheral joints, and they are very sensitive to mechanical vibration. However, little is known about their role in the control of lumbosacral spine positioning. METHODS: Twenty-five young individuals with no low back pain were assigned at random to an experimental or control group. Proprioceptive information of the multifidus muscle spindles was distorted in half of the trials in 16 individuals by manually applying vibration (70 Hz, 0.5 mm amplitude) for approximately 5 seconds. The control group (n = 9) only heard the vibrator noise during repositioning of the lumbosacral spine. Repositioning accuracy in the sitting position was estimated by calculating the mean absolute error, constant error, and variable error among six criteria and reproduction sacral tilt angles. RESULTS: Multifidus muscle vibration induced a significant muscle lengthening illusion through which the members of the experimental group undershot the target position (F(1,15) = 30.77, P < 0.0001). The position sense scores of the control group displayed no significant differences across trials (F(1,8) = 0.56, P > 0.05). CONCLUSIONS: The findings suggest that precise muscle spindle input of the paraspinal muscles is essential for accurate positioning of the pelvis and lumbosacral spine in a sitting posture.     

Lumbar spine listhesis in older African American women.

BACKGROUND CONTEXT: Degenerative changes in the lumbar spine may result in a loss of spinal stability and subluxation of one vertebra relative to another. Cadaveric studies and clinical case series have suggested that listhesis may be much more common in African Americans than in whites. PURPOSE: To determine the prevalence of lumbar spine listhesis (anterolisthesis and retrolisthesis) among African American women aged 65 years and older and the relationship of listhesis to low back pain, physical function and quality of life. STUDY DESIGN/SETTING: Cross-sectional study. PATIENT SAMPLE: A total of 481 African American women aged 65 years and older who were enrolled in the Study of Osteoporotic Fractures. These women were recruited from population-based listings in Baltimore, MD, Minneapolis, MN, Pittsburgh, PA, and Portland, OR. OUTCOME MEASURES: Not applicable. METHODS: Lateral radiographs of the lumbar spine were digitized, and listhesis (anterolisthesis and retrolisthesis) was assessed at spinal levels L3-L4, L4-L5 and L5-S1. Usable data were obtained for 470 women. Listhesis was defined as present when the subluxation (antero or retro) was 3 mm or more. RESULTS: The overall prevalence of anterolisthesis was 58.3% and varied by spinal level (13.2% at L3-L4, 36.5% at L4-L5 and 29.6% at L5-S1). The prevalence increased with age but was lower among oophorectomized women and those currently on estrogen replacement therapy. Anterolisthesis was not associated (p>.05) with disc height nor was it related to back function. Retrolisthesis occurred in 4% of women and was associated with decreased disc height and an increased prevalence of spinal problems and walking problems. CONCLUSIONS: The prevalence of anterolisthesis among older African American women living in the community was two to three times greater than that found in white women of a similar age. This condition was not related to an increased frequency of back problems nor did it adversely affect general physical function. Retrolisthesis was relatively rare but was associated with decreased back function.     

Effect of alcohol on cyclical myoelectric activity of the opossum sphincter of Oddi

Ethyl alcohol may adversely affect pancreatic function by perturbing sphincter of Oddi (SO) or duodenal motor activity. The aim of this study was to identify the effect of ingested alcohol on the SO, duodenal, and gastric myoelectric activity in conscious opossums. In five adult opossums bipolar stranded stainless-steel wire electrodes were implanted on the SO, gastric antrum, and duodenum. After a 2-week recovery period, each animal underwent eight 8-hr recording sessions while fasted and awake. After two fasting cycles of the migrating myoelectric complex, animals were randomly fed either 10 ml of a 30% ethyl alcohol solution or 10 ml of water via an esophageal tube, and recordings continued for 4-6 hr. During the control state, cyclical myoelectric spike activity was recorded from the SO, gastric antrum, and duodenum with a mean +/- SD cycle length of 7.35 +/- 15.0 min, 74.3 +/- 10.1 min, and 94.8 +/- 8.7 min, respectively. With alcohol, SO and duodenal cycle lengths were unchanged while gastric cycle length decreased. However, alcohol effected a significant increase in peak SO spike burst frequency with no corresponding change in gastric or duodenal spike burst frequency. An equivalent volume of water had no influence on sphincter of Oddi myoelectric activity. It is concluded that ingested alcohol induces increased myoelectric activity from the opossum SO, independent of changes in activity of the duodenum or stomach. Since the SO plays a major role in metering bile and pancreatic flow into the duodenum, this may be a factor in alcohol-induced pancreatitis.     

Lumbopelvic kinematics and trunk muscle activity during sitting on stable and unstable surfaces

STUDY DESIGN: A single-group comparative study. OBJECTIVES: To compare lumbopelvic kinematics and muscle activation patterns while sitting on stable and unstable surfaces. BACKGROUND: Unstable surfaces are commonly used during the rehabilitation of certain low back pain disorders. The benefits postulated are increased muscle activity and facilitation of sustainable midrange positions via neuromuscular control. The use of unstable sitting devices in the workplace is controversial, as the postulated increase in muscle activity is thought to lead to a muscle fatigue/pain response. However, little evidence exists for or against the ability of these devices to alleviate or prevent spinal pain. METHODS AND MEASURES: This study included 26 healthy adults (14 male, 12 female). Fastrak 3-dimensional motion analysis detected lumbar curvature, pelvic tilt, and postural sway during sitting on a stable and unstable surface over 5-minute periods. Surface electromyography was used to measure activity in the superficial lumbar multifidus, transverse fibers of internal oblique, and iliocostalis lumborum pars thoracis. RESULTS: Spinal postures were similar for sitting on a stable and unstable surface. Significant increases in postural sway were detected (P = .013) in 3 dimensions of movement during sitting on an unstable surface. Gender differences were noted. No EMG amplitude or variance differences were detected between seating conditions. CONCLUSIONS: Preliminary data show that sitting on unstable surfaces induces greater spinal motion, but does not significantly alter the lumbosacral posture nor the amount of activity in the superficial trunk muscles under investigation.     

Effects of specific exercise instructions on abdominal muscle activity during trunk curl exercises

STUDY DESIGN: A repeated-measures, counterbalanced design. OBJECTIVES: To test whether subjects could learn and retain the ability to alter the relative activity of abdominal muscle groups when performing trunk curl exercises. BACKGROUND: Although trunk curl exercises are widely prescribed, a disadvantage of trunk curls is that they primarily activate rectus abdominis, while the internal and external oblique abdominis muscles are considered to be more important contributors to lumbar stability. METHODS AND MEASURES: A convenience sample of 25 subjects performed trunk curl exercises in accordance with 3 different sets of instructions: nonspecific instructions (NS), instructions intended to emphasize rectus abdominis activity (RE), and instructions intended to emphasize oblique abdominis activity (OE). Electromyographic (EMG) activity was recorded from the upper and lower rectus and the internal and external oblique abdominis muscles while a physical target was used to insure that the trunk was raised to the same height for all conditions. Normalized root-mean-square EMG amplitude measures were used to test for instruction-dependent changes in the relative EMG activity of the rectus and oblique muscle groups. RESULTS: Following a single, brief, instruction session, subjects performing trunk curls had significantly greater normalized oblique:rectus EMG ratios when following OE instructions (mean [+/- SD] oblique-rectus ratio, 1.45 +/- 0.34) than when following RE (mean [+/- SD] oblique-rectus ratio, 0.76 +/- 0.24) or NS (mean [ISD] oblique-rectus ratio, 0.63 +/- 0.23) instructions. Retesting 1 week later indicated that subjects retained this skill. CONCLUSIONS: With minimal instruction, subjects are able to volitionally alter the relative activity of the oblique and rectus abdominis muscles when performing trunk curls. Incorporating instructions emphasizing oblique abdominis activity into lumbar stabilization programs appears promising and has potential advantages over other approaches to altering abdominal muscle activity during trunk