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PubMed2000

Multifidus spasms elicited by prolonged lumbar flexion.

STUDY DESIGN: The electromyogram of the L1-L7 multifidus muscles of the in vivo cat were recorded while applying a prolonged steady displacement to the lumbar spine through the L4-L5 supraspinous ligament, simulating a moderate anterior flexion. OBJECTIVE: To demonstrate that tension-relaxation and laxity of the viscoelastic structures (ligaments, discs, and capsules) induced by prolonged static flexion of the spine results in loss of reflexive muscular stabilizing activity and in muscular disorders that may lead to or are associated with low back pain. SUMMARY OF BACKGROUND: Epidemiologic data show that prolonged loading of the spine, such as in some occupational activities, can cause low back pain and muscle spasms. Direct experimental evidence linking prolonged loading to a decrease in spinal stability, low back pain, and muscle spasms was not found. It was hypothesized, however, that mechanoreceptors in the viscoelastic structures, when strained, reflexively activate the multifidus muscles to maintain intervertebral stability; that the reflexive muscular activity decreases with stress-relaxation and laxity in the viscoelastic structures; and that when severe strain and possible damage of the viscoelastic structures occurs with time, nociceptive receptors elicit spasms in the musculature and possible pain. METHODS: The lumbar spine of seven in vivo cat preparations was displaced through the L4-L5 supraspinous ligament into moderate flexion that was steadily maintained for 50 minutes while intramuscular electromyograms were recorded from each of the multifidus muscles of L1-L2 through L6-L7. Load and electromyogram were continuously monitored and recorded. Five additional preparations were used as controls, in which dissection and recordings were identical, but the lumbar flexion was excluded. RESULTS: Prolonged flexion of the lumbar spine resulted in initial reflexive electromyogram from the multifidus muscles that decreased to approximately 5% of its initial value as tension-relaxation began in the viscoelastic structures within the first 3 minutes, after which, random and unpredictable electromyogram discharges (i.e., spasms) of high amplitude were recorded from different levels. In some preparations the spasms were present in L1-L4, and in others in all the levels. In other preparations the spasms were recorded only at L5 and L6. The onset of the spasms was also unpredictable, because they were initiated in some cases within 2-3 minutes after the spine was loaded. In other cases, the spasms were observed anytime during the test period and up to 20 minutes after the load was removed. Spasms were also observed in the spinalis and longissimus muscles. CONCLUSIONS: Prolonged flexion of the lumbar spine results in tension-relaxation and laxity of its viscoelastic structures, loss of reflexive muscular activity within 3 minutes and electromyogram spasms in the multifidus and other posterior muscles.

Animals↗
PubMed2002

Activation imbalances in lumbar spine muscles in the presence of chronic low back pain.

Paraspinal electromyographic (EMG) activity was recorded bilaterally from three lumbar levels during 30-s isometric trunk extensions [40 and 80% of maximum voluntary contraction (MVC)] in 20 healthy men and 14 chronic low back pain patients in pain. EMG parameters indicating neuromuscular fatigue and contralateral imbalances in EMG root-mean-square amplitude and median frequency were analyzed. Patients in pain showed less fatigue than controls at both contraction levels and produced only 55% of their MVC. Patients in pain likely did not produce a "true" maximum effort. A low MVC estimate would mean lower absolute contraction levels and less neuromuscular fatigue, thus explaining lower scores in the patients. Contralateral root-mean-square amplitude imbalances were present in both categories of subjects although such imbalances, when averaged across lumbar levels, were significantly larger in patients. Median frequency imbalances were significantly larger in the patients, at segmental as well as across lumbar levels. These results suggest that the presence of pain in these patients caused a redistribution of the activation behavior between synergistic muscles of the lumbar back.

Adult↗
PubMed1993

Trunk strength and lumbar paraspinal muscle activity during isometric exercise in chronic low-back pain patients and controls.

The purpose of this study was to describe trunk strength and lumbar paraspinal muscle activity across five angles of flexion during isometric exercise and rest in chronic low-back pain patients and control subjects. High muscle tension as measured by surface integrated electromyography is predicted by a muscle spasm model, and low muscle tension is predicted by a muscle deficiency model. Prior lumbar surgery had no affect on peak torque or maximum surface integrated electromyography data. Both groups produced greater torque and less surface integrated electromyography in more flexed positions. Chronic low-back pain patients exhibited lower peak torque and lower maximum surface integrated electromyography bilaterally during isometric extension effort across all angles. A muscle deficiency model of chronic low back pain was supported by these data and a muscle spasm model was not supported. Discriminant analyses indicated that monitoring maximum surface integrated electromyography of lumbar muscles during isometric effort facilitates classification of chronic low-back pain patients. Future directions are discussed in terms of applying psychophysiologic methods to pain rehabilitation.

Adult↗
PubMed2002

Myolysis of the erector spinae muscles as the cause of scoliosis in osteoid osteoma of the spine.

STUDY DESIGN: A case of an osteoid osteoma at the lower thoracic spine with scoliosis is reported. OBJECTIVES: To suggest that myolysis of the erector spinae muscles reflected by signal abnormalities on magnetic resonance images causes back pain, protective muscle contraction, and scoliosis. SUMMARY OF BACKGROUND DATA: Osteoid osteomas of the spine are frequently accompanied by scoliosis. The proposed mechanism of the scoliosis has been explained as a postural adaptation of the spine through predominant muscle spasm on the concave side. METHODS: The history of the patient and radiologic, magnetic resonance imaging, and histologic findings of the peritumoral area were reviewed. RESULTS: Magnetic resonance images showed signal abnormalities on muscles surrounding the tumor, and use of gadopentetate dimeglumine resulted in an enhancement. The microscopic examination of the erector spinae muscles that demonstrated high intensities on T2-weighted images showed derangement or destruction of the muscle fibers and replacement of the muscle fibers with fat tissue and infiltrating inflammatory cells. CONCLUSION: These findings were interpreted as those of myolysis. The suggested mechanism of the induction of scoliosis by the present osteoid osteoma is that the unaffected iliocostalis and quadratus lumborum muscles on the tumor side predominantly contracted over those on the opposite side to decrease the tension of the erector spinae muscles involved in myolysis, thereby producing a functional scoliosis.

Adult↗
PubMed1994

Electromyographic median frequency changes during isometric contraction of the back extensors to fatigue.

STUDY DESIGN: This was a cross-sectional study involving 229 healthy, back pain-free individuals. OBJECTIVES: To examine the relationship between electromyographic manifestations of fatigue and endurance time during isometric contraction of the back extensors to fatigue. SUMMARY OF BACKGROUND DATA: Despite the wide-spread use of electromyography to monitor muscle fatigue, its relationship with endurance time has not been well investigated. METHODS: Using skin-surface electrodes, electromyographic signals were recorded from thoracic (T10) and lumbar (L3) regions of erector spinae during an isometric endurance test, and the rate of change in median frequency of the electromyographic power spectrum (MFGRAD) was calculated. RESULTS: MFGRAD was significantly higher at L3 than at T10. The best predictor of endurance time was given by the greater MFGRAD observed at either region. MFGRAD calculated over a submaximal time period (50% total time or 60 sec) also correlated significantly with endurance time. Women displayed a significantly longer endurance time and lower MFGRAD than men. CONCLUSIONS: Endurance appears to be limited by the most fatigable region of the muscle group. MFGRAD is a suitable technique for monitoring back muscle fatigue, even when it is determined over a submaximal time period. The back extensors of women are less fatigable than those of men when the same task is performed.

Adult↗
PubMedDate not supplied

Quantitative-topographic and temporal characterization of myoelectrical activation patterns: new diagnostic possibilities in neurology, physiotherapy and orthopaedics.

In controls and patients with different syndromes (spastic/flaccid paresis, low back pain syndrome), the myoelectrical activation patterns of complex muscles (M. biceps brachii, M. quadriceps femoris, M. masseter) or synergistic/antagonistic muscle groups in the back region during isometric muscle contractions and defined movements were determined by monopolar 16 (32) channel surface EMG recordings. On the basis of these recordings, maps of myoelectrical activation ("EMG-maps") were calculated. This method permits a detailed quantitative-topographic EMG analysis including the characterization of therapy effects.

Adult↗
PubMed1996

[The courses and the segmental origins of the cutaneous branches of the thoracic dorsal rami].

It is described in many textbooks that the medial cutaneous branches (RCM) from the medial branches of the upper six thoracic dorsal rami supply the upper half of the back of the body, the lateral cutaneous branches (RCL) from the lateral branches of the lower six thoracic dorsal rami supply the lower half of it, and the area supplied by both branches is limited to a few segments. Unlike those descriptions, we had frequently observed RCL from the second or the third thoracic dorsal ramus penetrating the rhomboideus muscle during previous research concerning the double innervation of the superficial muscles of the back by both the ventral and the dorsal rami (Kumaki et al., 1984). To make clear the origin of the discrepancy between the description in the textbooks and our observations, we examined the segmental origins, the courses, and the distributions of both the medial and the lateral branches of the thoracic dorsal rami on 20 sides of 11 bodies dissected in the years 1986 and 1989. Consequently, RCL from the second thoracic dorsal ramus (Th 2) was observed in 25% of the cases and RCL from Th 3 and Th 4 were observed in 50% and in 70%, respectively. The highest segment of RCL was Th 2 in 25%, Th 3 in 25%, Th 4 in 35%, Th 6 in 10%, or Th 8 in 5%, and the mean was Th 3.65 +/- 1.53. On the other hand, the lowest segment of RCM was Th 6 (15%), Th 7 (35%), Th 8 (25%), Th 9 (15%), or Th 10 (10%), and the mean was Th 7.70 +/- 1.19. The mean number of the segments at which the dorsal ramus of the thoracic nerve sent both RCM and RCL was 4.55 +/- 1.50 (Max: 9 segments). Thus, we made clear that RCL from the upper thoracic nerves were commonly observed and that the number of segments sending both RCM and RCL was larger than hitherto described. The course of the upper RCL was bent at the points where the RCL penetrated the superficial muscles of the back forming a "Z"-shape, i.e., RCL changed its course from an infero-lateral to an infero-medial direction at the point of penetrating the rhomboid muscle and from an infero-medial to a lateral direction at the point of penetrating the trapezius muscle or the latissimus dorsi muscle. These directions might be associated with the development of the muscles. Sometimes RCL was sharply pulled in a medial direction by the trapezius muscle to penetrate the muscle near the median plane and appeared as RCM. Therefore, we supposed that the main reason why the upper RCL had been overlooked was because the complicated zigzag course of the RCL was damaged by the inadequate dissection or RCL was mistaken for the RCM. While the points where the cutaneous branches penetrated the superficial muscles were variable, the points where they penetrated the thoraco-lumbar fascia were relatively stable. This point of the RCM was generally near the tip of the spinal process of the same segmental number of the nerve, and the same point of RCL was generally at the gap between the longissimus and the iliocostal muscles in the intercostal space one segment lower than the segment of the RCL. The RCL from the last thoracic to the third lumbar dorsal rami communicated with one another to form a nerve plexus under the lumbo-dorsal aponeurosis, then penetrated that aponeurosis forming several nerve bundles, crossed over the iliac crest and supplied the hip skin as the superior cluneal nerves. Therefore, each bundle was not equivalent to each segment, but was composed of two or more segments.

Humans↗
PubMed2005

Presence of neurotrophic factors in skeletal muscle correlates with survival of spinal cord motor neurons.

To determine which combination of skeletal muscle-derived neurotrophic factors may be important for the survival of specific subpopulations of developing spinal cord motor neurons, we used Myf5 and MyoD (myogenic regulatory factors) knockouts, containing differentially committed myogenic precursor cells (MPCc) and immunohistochemistry against several muscle-secreted neurotrophic factors. At the peak of motor neuron cell death, skeletal muscle development is delayed in the back and body wall muscles of Myf5-/- embryos and in the limb muscles of MyoD-/- embryos. We hypothesized that, if the skeletal muscle was indeed an important source of survival factors for motor neurons, the back, the abdominal wall, and the forelimb MPCs of Myf5-/- or MyoD-/- embryos should produce at least some neurotrophic factors necessary for the survival of motor neurons. In this report, we demonstrate that (1) different MPCs lacking Myf5, MyoD, or Myf5/MyoD have different capabilities in providing factors potentially required for the survival of motor neurons and intramuscular nerve branching, (2) MPCs in double-mutant embryos do not contain neurotrophic factors in the absence of myogenic specification, and (3) different subpopulations of MPCs contain different combinations of neurotrophic factors potentially required for the survival of the specific subpopulations of innervating motor neurons.

Animals↗
PubMed1999

Neuronal pathways from low-threshold hindlimb cutaneous afferents to motoneurons innervating trunk muscles in low-spinal cats.

Postsynaptic potentials (PSPs) evoked in motoneurons innervating the back and abdominal muscles in the lumbar part of the body by stimulating hindlimb cutaneous afferents were investigated in unanesthetized decerebate and spinal cats. Various types of PSP: pure excitatory postsynaptic potential (EPSP), pure inhibitory postsynaptic potential (IPSP), and mixed PSP (i.e., EPSP followed by IPSP, EPSP/IPSP; and IPSP followed by EPSP, IPSP/EPSP) were observed. The weak stimulation at 2 times threshold (2T) produced predominantly the EPSP, while at 5T the incidence of IPSP or EPSP followed by IPSP was increased. In about 20-50% of the various groups of motoneurons, PSPs evoked by ipsi- and contralateral nerves were qualitatively and quantitatively similar. For the other motoneurons, PSPs evoked by ipsi- and contralateral nerves were markedly different with respect to magnitude and/or polarity. These findings suggest that, within each motoneuron pool, some neurons act to increase stiffness of the trunk or to move vertically in response to an increased activity of cutaneous afferents, while the other motoneurons act to produce lateral bending of the trunk.

Afferent Pathways↗
PubMed2003

Muscle energy technique in patients with acute low back pain: a pilot clinical trial.

STUDY DESIGN: A prospective, pilot clinical trial. OBJECTIVE: Examining the outcomes of Muscle Energy Technique (MET) in patients with acute low back pain. BACKGROUND: MET is commonly used to treat patients with acute low back pain. No randomized controlled trials examining the outcomes of this treatment in symptomatic populations has been reported in the literature. METHODS AND MEASURES: Ten men and 9 women diagnosed with acute low back pain were randomly assigned with stratification to 1 of 2 treatment groups. Patients were matched according to age, gender, and initial Oswestry score. The control group received supervised neuromuscular re-education and resistance training while the experimental group received the same exercises coupled with MET. Both groups received the selected treatment 8 times over a 4-week period (2 times per week). Patients completed an Oswestry Disability Index on their first and eighth visits and change scores were calculated. RESULTS: A 2-tailed t test (P < .05) demonstrated a statistically significant difference with the experimental group showing greater improvement in the Oswestry Disability Index score than the control group. CONCLUSION: MET combined with supervised motor control and resistance exercises may be superior to neuromuscular re-education and resistance training for decreasing disability and improving function in patients with acute low back pain.

Acute Disease↗
PubMed1986

Discharge patterns of reticulospinal and other reticular neurons in chronic, unrestrained cats walking on a treadmill.

Recordings were made from single units in the medullary reticular formation (MRF) between AP-4.2 and AP-12.9 and from the midline to 3.7 mm lateral in chronically prepared, unrestrained cats walking on a treadmill. Recordings were made with rigid microelectrodes held in a microdrive, and reticulospinal neurons were identified by antidromic stimulation of their axons through microwires chronically implanted into the spinal cord at the L2 level. Electromyograms (EMGs) were recorded from flexor and extensor muscles of the fore- and hindlimbs as well as from back and neck muscles. In total, 295 cells were recorded from 40 penetrations in 4 cats; 252 of these cells were recorded from the more medial regions of the reticular formation encompassing the gigantocellular, magnocellular, and lateral tegmental fields; 38.5% of these (97/252) were antidromically identified from the spinal cord. The remaining 43 neurons (43/295) were recorded from a more lateral and ventral position. These medial and ventrolateral groups of neurons differed not only in position but also in aspects of their discharge during locomotion. Rank-ordered raster displays, triggered from the onset of each recorded muscle, were used to correlate neuronal and muscular activity. The discharge rate of 31% of the reticulospinal neurons (30/97) was modulated once or twice in each step cycle and was strictly related to one or more of the recorded EMGs (EMG-related neurons) on the basis of the pattern of discharge. The discharge of 33/97 (34%) of the neurons was modulated at the periodicity of the locomotor rhythm but could not be correlated with any of the recorded EMGs (locomotor-related cells), whereas the remaining 34/97 neurons (35%) were either silent, fired tonically, or were not related to the locomotor pattern (unrelated cells). Of the EMG-related neurons 27% were related to flexor muscles and the remaining 63% to extensor muscle activity. The discharge pattern of all except two of the flexor-related neurons was correlated with hindlimb muscle activity, whereas that of the extensor-related neurons was correlated almost equally with fore- and hindlimb muscles. Correlations were found with muscles lying both ipsilaterally and contralaterally to the site of the recordings. Although the locomotor-related neurons showed no preferential relation with any of the recorded EMGs, a comparison of the depth of modulation of their discharge measured from postevent histograms suggested that more of these cells were related to the forelimb than to the hindlimb.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

The pectoralis myocutaneous flap for salvage of necrotic wounds.

The authors have utilized six pectoralis major myocutaneous flaps in attempts to salvage extensive necrotic wounds of the pharynx and neck. The flap was employed in the following situations: massive necrosis of the entire neck skin with both carotid artery systems exposed, radiation necrosis of the neck skin with exposure of carotid artery, dehiscence of gastric pull-up from pharynx with resultant carotid exposure, failed trapezius flap in a radionecrotic oral cavity, and two cases of pharyngocutaneous fistula with extensive soft tissue necrosis. These flaps achieved healing in all cases. One death occurred 3 weeks following complete cutaneous healing secondary to a ruptured carotid pseudoaneurysm. One flap underwent total skin loss but the entirety of the muscle survived and the fistula was successfully closed with the back of the muscle being subsequently skin grafted. One case of dehiscence of the flap from oral mucosa resulted in a minor exposure of mandible with limited osteoradionecrosis controlled by topical means. This flap has performed extremely well in these precarious and difficult situations that previously may not have been salvageable. It has also been effective in abbreviating the required hospitalization and wound care. We conclude that the pectoralis myocutaneous flap should be the primary choice for the management of extensive postsurgical wound necrosis.

Aged↗
PubMed1984

Physical measurements as risk indicators for low-back trouble over a one-year period.

Of all 30-, 40-, 50-, and 60-year-old inhabitants of Glostrup, a suburb of Copenhagen, 82% (449 men and 479 women) participated in a general health survey, which included a thorough physical examination relating to the lower back. The examination was constituted of anthropometric measurements, flexibility/elasticity measurements of the back and hamstrings, as well as tests for trunk muscle strength and endurance. The reproducibility of the tests was found to be satisfactory. Twelve months after the physical examination 99% of the participants completed a questionnaire sent by mail concerning low back trouble (LBT) in the intervening period. The prognostic value of the physical measurements was evaluated for first-time experience and for recurrence or persistence of LBT by analyses of the separate measurements and discriminant analyses. The main findings were that good isometric endurance of the back muscles may prevent first-time occurrence of LBT in men and that men with hypermobile backs are more liable to contract LBT. Recurrence or persistence of LBT was correlated primarily to the interval since last LBT-episode: the more LBT, the shorter the intervals had been. Weak trunk muscles and reduced flexibility/elasticity of the back and hamstrings were found as residual signs, in particular, among those with recurrence or persistence of LBT in the follow-up year.

Adult↗
PubMed2005

Relationship between erector spinae static endurance and muscle oxygenation-blood volume changes in healthy and low back pain subjects.

The purposes of this study were to: (1) compare the muscle blood volume (Mbv) and oxygenation (Mox) responses on the right and left side erector spinae during the Biering-Sorensen muscle endurance (BSME) test between healthy, low back pain active (LBP-A) and LBP-sedentary (LBP-S) subjects using near infrared spectroscopy (NIRS), and (2) determine the relationships between the BSME time and Mbv and Mox. Informed consent was obtained from 30 healthy and 30 chronic LBP subjects. The latter group was subdivided into an active (LBP-A; n = 18) and sedentary (LBP-S; n = 12) subgroups based on physical activity patterns. The groups were age and sex matched. The NIRS probes were placed bilaterally on the erector spinae muscle at the level of the third lumbar vertebrae. The testing protocol was: 2-min resting baseline, BSME to voluntary fatigue, and 4-min recovery. During the BSME Mbv immediately increased for approximately 30-60 s, then showed an asymptote, and a steady decline towards the baseline at termination. Mox demonstrated either an initial increase followed by a systematic decrease until the termination of the BSME, or a systematic decrease throughout the BSME until termination. The LBP-S subjects showed a reduced Mox-range and slower Mox (1/2) recovery time on the left side suggesting a reduced aerobic capacity of the erector spinae muscle in this group. Significant correlations were noted between BSME time and the pooled values of Mox-delta and-range only in the LBP-A group. These observations suggest that factors other than erector spinae aerobic capacity can influence BSME performance.

Adult↗
PubMed1997

Self-administration of over-the-counter medication for pain among adolescents.

OBJECTIVE: To examine over-the-counter (OTC) medication use and self-administration of medication among adolescents. DESIGN: In-person survey. SETTINGS: Three public junior high schools in Halifax, Nova Scotia. PARTICIPANTS: Six hundred fifty-one junior high school students (7th, 8th, and 9th grades). MAIN OUTCOME MEASURES: A questionnaire regarding OTC medication use and self-administration for head: stomach; ear and throat; muscle, joint, and back; and menstrual pains. RESULTS: Of those who reported taking medication, many adolescents (58.7%-95.9%) reported taking OTC medications for each pain. Medications and knowledge about medications were obtained from a variety of sources, primarily parents. Self-administration was widespread; 58.3% to 75.9% of adolescents reported taking an OTC medication for pain without first checking with an adult in the previous 3 months. Self-administration of medication without the knowledge of adults increased significantly from grades 7 to 9 for all types of pain. Girls tended to self-administer medication more than boys. Higher levels of pain frequency and intensity were related to higher levels of self-administration for all pains except muscle, joint, and back pain. Adolescents reported that they began to self-administer medication between the ages of 11 and 12 years. CONCLUSIONS: Although a relatively responsible picture of self-administration of medication emerges, some adolescents engaged in inappropriate OTC medication use (eg, the common use of aspirin), highlighting the importance of providing adolescents with correct information about these medications.

Adolescent↗