Muscle fiber types in thoracic erector spinae muscles. Fiber types in idiopathic and other forms of scoliosis

Histochemical studies of the thoracic part of the erector spinae muscles in scoliosis have shown a consistently higher proportion of Type 1 fibers on the convex side. The fiber distribution of the multifidus and semispinalis muscles was studied in adolescent idiopathic scoliosis (AIS). Compared with sex- and age-matched controls, a "normal" percentage of Type 1 fibers was found on the convex right side and significantly smaller percentage of Type 1 fibers on the concave side. Boys with AIS showed the same pattern as girls. In two patients with double major curves, the same pattern could be seen on the convexity of both curves. Patients with congenital scoliosis or scoliosis with early onset showed a different pattern with a "normal" percentage of Type 1 fibers on the concave side but a significantly greater percentage of Type 1 fibers on the convex side. In AIS, the deviation in the fiber distribution may constitute a primary factor in the pathogenesis of scoliosis. In congenital scoliosis the differences in fiber distribution between the convex and concave sides are considered secondary in the pathogenesis of the spinal curvature.     

Paraspinal muscle pathology in experimental scoliosis

Summary Paraspinal muscle biopsies from ten rabbits with experimentally induced scoliosis and from four healthy controls were analyzed histologically and histochemically. Scoliosis was induced by two different methods: six animals underwent unilateral damage of the dorsal column of the spinal cord (mean curve: 22°) and four costotransversectomy (mean curve: 47°). In eight scoliotic animals myopathic changes were detected on the muscles of the concave side. Only those animals which underwent costotransversectomy showed a neuropathic pattern with cronic denervation changes on the convex side. As regards the fiber type distribution, the control group showed a higher percentage of type-I fibers, which were similar on both sides of the spinal cord. No fiber proportion asymmetry could be detected in the muscles on the concave side in normal or scoliotic rabbits. There was a tendency to depart from normal values, in two different ways, on the convex side of scoliotic animals. Thus, in contrast to the medullary damage group, the muscles of the costotransversectomized rabbits showed an increased proportion of type-I fibers. Taken together, our findings support the hypothesis that myopathic changes as observed in human idiopathic scoliosis are a consequence of the postural deformity. Fiber type distribution does not appear to be related to the curvature in the same way.     

Morphological studies on the erector spinae muscle in sixty consecutive scoliotic patients

Paraspinal muscle biopsy was done on the erector spinae muscles in sixty consecutive scoliotic patients. Together with the clinical and muscle biopsy findings, these sixty patients were classified into thirty-two patients with idiopathic scoliosis, eleven patients with myopathic scoliosis, nine patients with neuropathic scoliosis, and eight patients with miscellaneous scoliosis. Of the thirty-two patients with idiopathic scoliosis, nineteen cases displayed neurogenic changes in the grouping of the Type 1 fibers and target fiber formation more common on the convex side back muscles. The myopathies consisted of central core disease, nemalin myopathy, congenital fiber type disproportion, mitochondrial myopathy, congenital muscular dystrophy, and myositis. Patients with neuropathic scoliosis all showed loss of the normal mosaic pattern and grouping of both Type 1 and 2 fibers in their muscle biopsies. This result indicates that there is a variety of neuromuscular diseases in scoliotic patients. The neurogenic changes observed more commonly on the convex side muscle of idiopathic scoliotic patients deserve further investigation.     

Morphologic and Morphometric Studies of Muscle in Idiopathic Scoliosis

The gluteus maximus and paraspinal muscles in IS cases of idiopathic scoliosis at the apex of the curve showed myopathic changes and a significant decrease in the type II fibers. Fiber type II atrophy was observed only on the concave side. Ultra-structure of paraspinal and gluteus muscle biopsies snowed disruption of myofilaments, Z band streaming and subsarcolemmal accumulation of glycogen, lipid and mitochondria. Quantitative estimation of these subcellular organelles pointed out that a higher glycogen content was significant in both paraspinal as well as the gluteus muscles while a higher mitochondrial content was significant only on the convex side and the gluteus muscle but not the concave side of the apex when compared to normal quadriceps muscle. These findings suggest that idiopathic scoliosis is a diffuse disease process and may be considered a primary muscle disease.     

Morphologic and histochemical characteristics of skeletal muscle after long-term intramuscular electrical stimulation.

The purpose of this investigation was to examine the morphologic and histochemical characteristics of paraspinal muscles in patients with scoliosis after long-term electrical stimulation. Thirty-six children with idiopathic scoliosis, who had been treated with implantable muscle stimulators, had paraspinal muscle biopsies at the time of implantable muscle stimulator removal. Group A patients whose curve did not progress, had 2.9 years of stimulation stopped at skeletal maturity, with a further 1.5 years of nonstimulation before implant removal and biopsy. In group B patients, who had an average of 2.3 years of stimulation, the curve progressed and stimulation was continued until fusion and biopsy. Neither group showed any increase in the frequency of pathologic changes of paraspinal muscles contrasted with values reported in the literature for scoliotic muscle. In group A patients there was an increased proportion of type 1 fibers on the convex side of the curve compared to the concavity. Despite this finding the curves did not require fusion, suggesting that the increased percentage of type 1 fibers was not the cause of the scoliosis. In group B patients there was an even higher type 1 concentration on the convex side contrasted to the convex side of group A patients.     

Paraspinal muscle imbalance in adolescent idiopathic scoliosis

Twelve muscle biopsy samples were taken at operation for spinal instrumentation from each of seven patients suffering from idiopathic scoliosis (one male and six female patients; mean age 14.3 years). The samples were collected from two specific sites (superficial and deep) on both sides on the vertebral column at the level of the apex of the primary curve and two vertebral levels above and below the apex. The results of this study support and extend the findings of other workers. Not only was a significantly larger percentage of Type I fibers found in multifidus muscle at the apex on the curve on the convex side as other workers have found but also in the superficial muscles above and below the apex of the curve on the convex side. These results present a complex picture of muscle fiber characteristics associated with idiopathic scoliosis.     

A study of trunk muscle in idiopathic scoliosis

Isometric and isokinetic parameters related to trunk muscle function in patients with idiopathic scoliosis were measured by Cybex dynamometer with a trunk stabilization system. Activities of the paraspinal muscles were also determined by electromyographic observations. In scoliotic patients some parameters, especially endurance in lateral bending to the concave side of the trunk, were predominant. In electromyographic analysis, neurogenic changes were observed in 25.9% of patients with idiopathic scoliosis. In nonprogressive scoliosis, the mean amplitude of EMG did not differ between the convex and the concave. In progressive scoliosis, however, the mean amplitude of EMG was higher on the convex side than on the concave side. Thus, the compensatory reaction on the curvature of the spine caused higher amplitude of action potential of the back muscles on the convex side than in the concave side. These data suggest that the trunk muscle imbalance is one of the most important factors in the onset and progression of idiopathic scoliosis.     

An evaluation of muscle pathology in idiopathic scoliosis

This study assessed the degree of longissimus muscle pathology in 15 patients with idiopathic scoliosis. Bilateral muscle biopsy specimens were taken at the apex of the scoliotic curve and from five control subjects and processed histochemically. All biopsy specimens were free of muscle pathology. However, patients had a higher proportion of Type I fibers on the convex than the concave side of the curve (70.2 vs. 59.5%), whereas the controls had no difference. Fiber type imbalance in patients with idiopathic scoliosis is thought to result from compensatory stretching of muscle and not to be the cause of the deformity.     

Pathology and morphometry of the paraspinous muscles in nonidiopathic scoliosis

The muscle fibers in 19 patients with nonidiopathic scoliosis were generally small, especially on the concave side of the curve. Type 1 fibers were more frequently atrophic than type 2 fibers, but the former usually remained larger than the latter. Type 1 preponderance was greater on the convex side of the curve; type 2A preponderance occurred bilaterally. These changes are similar to those of idiopathic scoliosis. They resemble those of endurance training or stretch and are interpreted as secondary to the curve.     

Paraspinal muscle fibre type alterations associated with scoliosis: an old problem revisited with new evidence

To establish the extent to which the paraspinal muscles are affected in idiopathic scoliosis, samples from patients must be compared with controls of a similar gender and age. To date, insufficient control data has been available for these purposes. The aim of this study was to redress this tissue, in order to identify whether one side of the apex of the scoliotic curve showed greater muscular abnormalities than the other. Bilateral samples of the paraspinal muscles were obtained during surgery from 14 female scoliosis patients, at the apex of the scoliotic curve at T9–T11. Percutaneous muscle biopsy samples were obtained from nine female volunteers, on the left side of the spine at T10. Samples were prepared for routine histochemistry for the identification of muscle fibre types. Fibre size was measured using computerised image analysis. Compared with control muscle, there was a significantly lower proportion of type I (slow-twitch oxidative) fibres in the muscle on the concave side of the scoliotic curve, but no difference on the convex side. The proportion of type IIB (fast-twitch, glycolytic) fibres was higher on both sides of the curve compared with controls, with the effect being significantly more marked on the concave side. The percentage of type IIA (slow-twitch, oxidative-glycolytic) fibres did not differ between the groups, and neither did fibre size (although there was a tendency for the controls to have larger type IIA fibres than the patients). Collectively, the differences in fibre type size and distribution meant that on the concave side the relative area of the muscle occupied by type I fibres was smaller, and on both sides of the curve the relative area occupied by type IIB fibres was greater and by type IIA fibres smaller, in comparison with controls. In scoliosis, the spinal musculature is most affected on the concave side of the curve’s apex. The muscle adopts a ‘faster’, or more ‘glycolytic’ profile, which would be consistent with a reduced low-level tonic activity of the muscle, perhaps consequent to a local change in activity on this side of the spine following progression of the curve. Less marked changes, in the same direction, are also evident on the convex side; these may be the result of general disuse of the paraspinal muscles associated with the spinal deformity. Received: 12 November 1997 Accepted: 2 March 1998     

Electromyography of the paravertebral muscles in idiopathic scoliosis: Measurements of amplitude and spectral changes under load

The myoelectric activity of the paraspinal muscles was recorded in girls with idiopathic scoliosis and in healthy controls. The muscles of the back were loaded isometrically and the signals recorded at the T8 and L3 levels were analysed as regards amplitude and frequency. A comparatively higher signal amplitude was found on the convex side of the scoliosis curve. This was found to be due to a lower amplitude on the concave side when the scoliosis group was compared to the controls. The amplitude difference was correlated to the degree of scoliosis. A shift in the myoelectric spectrum toward lower frequencies occurred during the loading period. There were no differences in this respect between the sides of the scoliosis, nor were there differences between the scoliosis patients and the controls.

Secondary adaptation to the higher load demand by the muscles on the convex side in scoliosis is the most probable explanation for our observations.     

Recovery from exercise-induced desaturation in the paraspinal muscles in idiopathic scoliosis.

STUDY DESIGN: A study using near-infrared light spectroscopy to measure recovery from exercise-induced desaturation in the paraspinal muscles of patients with idiopathic scoliosis. OBJECTIVES: To measure oxygenation of the paraspinal muscles and obtain differences between the convex and concave sides. SUMMARY OF BACKGROUND DATA: Authors of previous studies have reported that some patients experience pain on the convex side of the paraspinal muscles. The muscles on the convex side are more stretched and stressed than those on the concave side. The current authors investigated the degree of stress by measuring oxygenation and blood volume changes. METHODS: Paraspinal muscle spectral properties at L3 were investigated using near-infrared light spectroscopy. Thirty-six patients (8 men and 28 women) underwent this procedure. To assess a level of peripheral adaptations to exercise, the half-time of Oxyhemoglobin/Myoglobin recovery was measured, which indicates the recovery from energy deficit after exercise. RESULTS: The average half-time recovery on the convex side was 3.38 seconds (range, 1.5-5.5 seconds), whereas that on the concave side was 1.51 seconds (range, 0.7-4.0 seconds). The average difference between the convex side and the concave side was 1.87 seconds (range, 0.9-3.5 seconds). CONCLUSIONS: Half-time recovery on the convex side in the patients with idiopathic scoliosis was slower than that in healthy adults (P < 0.05). Half-time recovery on the concave side in such patients was faster than that on the convex side (P < 0.01). The authors consider half-time recovery an indication of back muscle stress.     

Muscle study in experimental scoliosis in rabbits with costotransversectomy: evidence of ischemic process

Scoliosis involves the central nervous system diseases, ligaments, articulations and skeletal muscles, but there is no consensus on its pathogeny and progression of muscle abnormalities. In this study, we investigate the morphologic changes in the muscle of rabbit submitted to experimental scoliosis, with special emphasis on abnormalities related to blood supply. We studied 26 rabbits subjected to costotransversectomy by pulling out six transverse processes at thoracic level and six rabbits were used as controls. All the animals operated upon developed scoliosis showing an average angle of 29.1° on the 60th day, with its apices located at T4 and T12 when they were subjected to paraspinal muscle biopsy on both sides. The muscle biopsies were subjected to histological stains and histochemical reactions, as well as to a morphometric study. On the concave side, the changes were not statistically significant regarding the control group. On the convex side conjunctive tissue proliferation, infiltration by adipose tissue, central nucleus excess, inflammatory reaction, segmental fibrosis, type 1 fiber hypertrophy, type 2 fiber hypertrophy and atrophic angular dark fibers in the unspecific esterase were statistically significant. The segmental fibrosis reached a circumscribed muscle segment, compatible with an ischemic phenomenon. The histological diagnoses on the concave side of the animals had unspecific alterations (atrophy and hypertrophy) in 13, myopathy in 3, denervation in 3 and normal in 7. The convex side diagnoses were myopathy in 14, denervation in 8, mixed in 3 and normal in 1. The procedure determined morphologic changes on the convex side indicating possible denervation or myopathy of ischemic origin.     

Spinal muscle evaluation in healthy individuals and low-back-pain patients: a literature review

This article reviews available techniques for spinal muscle investigation, as well as data on spinal muscles in healthy individuals and in patients with low back pain. In patients with chronic low back pain, medical imaging studies show paraspinal muscle wasting with reductions in cross-sectional surface area and fiber density. In healthy individuals, the paraspinal muscles contain a high proportion of slow-twitch fibers (Type I), reflecting their role in maintaining posture. The proportion of Type I fibers is higher in females, leading to better adaptation to aerobic exertion compared to males. Abnormalities seen in paraspinal muscles from patients with chronic low back pain include marked Type II fiber atrophy, conversion of Type I to Type II fibers, and an increased number of nonspecific abnormalities. Limited data are available from magnetic resonance spectroscopy used to investigate muscle metabolism and from near infrared spectroscopy used to measure oxygen uptake by the paraspinal muscles. Surface electromyography in patients with chronic low back pain shows increased paraspinal muscle fatigability, often with abolition of the flexion-relaxation phenomenon.     

Ⅱ型胶原、转化生长因子β1和碱性成纤维细胞生长因子在脊柱侧凸患者关节突软骨中分布及表达的实验研究

目的研究青少年特发性脊柱侧凸（AIS）和先天性脊柱侧凸（CS）畸形最严重部位一顶椎凸、凹侧下关节突软骨中Ⅱ型胶原、转化生长因子β1（TGF—β1）和碱性成纤维细胞生长因子（bFGF）的表达特点。方法22例AIS患者,18例CS患者作为研究对象。取两组患者的顶椎和端椎凸、凹侧的下关节突,采用苏木素-伊红（HE）染色、免疫组化和原位杂交方法观察关节突的病理改变和Ⅱ型胶原、TGF-β1及bFGF在关节突中分布的特点。将所得的免疫组化和原位杂交图像输入图像分析系统,进行半定量分析,并作统计学分析。结果Ⅱ型胶原、TGF-β1、bFGF在AIS和CS中的有基本相似的表达特点,免疫组化和原位杂交方法均显示顶椎凹侧的表达高于凸侧,差异有统计学意义（P〈0．05）;上下端椎的凸凹侧之间及凸凹侧的上下端椎之间的表达差异无统计学意义,顶椎、上下端椎各对应部位在AIS与CS之间的表达差异无统计学意义;Ⅱ型胶原在凸侧与凹侧顶椎的表达高于同侧上、下端椎,差异有统计学意义（P〈0．05）。结论AIS和CS顶椎关节突软骨呈现退变及发育不全等征象,凹侧较凸侧明显。AIS和CS中Ⅱ型胶原、TGF—β1及bFGF在顶椎凹侧表达的增高可能为脊柱畸形后异常的生物力学引起了关节突细胞间基质重建而进行代偿的结果。压应力可引起TGF—β1及bFGF的表达增高;压应力和张应力均可以引起Ⅱ型胶原的表达增高,但顶椎凹侧压应力比凸侧张应力的影响更大。     

Biomechanical analysis of scoliosis and back muscles using CT evaluation and the finite element method

The CT observation of back muscles of an idiopathic scoliosis patient showed increased muscle volume and high CT value on the convex side. Following these muscles by digitizer showed that convex muscle volume increased as the vertebra shifted to convexity. These back muscles were suggested to be transversospinalis muscles. Biomechanical analysis using finite element method (FEM) was done to further investigate this increasing volume of back muscles. A Risser experiment using FEM revealed that initial lordosis configuration model only produces rotation to the convex side by unilateral loading. We, therefore, made the model adding posterior element, regarding contraction of M. transversospinalis. In a normal case, the upper vertebra is rotated over the lower towards the side opposite the muscle contraction. The scoliosis model, however, showed rotation towards the side of muscle contraction. M. transversospinalis can be considered as the agent of this rotation force.     

Idiopathic scoliosis: a clinical, morphometric, and histopathological correlation

At the time of spinal fusion, muscle biopsies were taken from both the convex and concave side at the apex of the curve from 27 patients with idiopathic scoliosis. Histochemical and morphometric studies showed generally small and atrophic type 1 muscle fibers on both sides, with preservation of the normal type 1 predominance. The most striking abnormality was a type 2A predominance over type 2B fibers, the reverse of normal in the paraspinous muscle. These changes showed no correlation with sex, age, or electrical stimulation but showed a significantly greater severity with the duration and severity of the curve. We conclude that these changes are a secondary muscle adaptation to the curve and not its primary etiology.     

Running training alters fiber type composition in spinal muscles

Summary The issue of whether exercise can induce changes in muscle fiber types has been long debated. Knowledge about the alterations in spinal muscle fiber types is scarce. In this study, the alterations initiated by long-distance running on spinal muscle fiber type distribution was studied. Ten young dogs were run on a treadmill for 55 weeks, 5 days a week, and ten dogs from the same litters served as controls. The daily running distance was gradually increased to 40 km and maintained at that level for the final 15 weeks. Histological sections were prepared from the cervical, thoracic, and lumbar multifidus muscles and the medial and lateral heads of triceps brachii and analyzed for the fiber type composition and cross-sectional area of fibers. In the lumbar multifidus, the numerical percentage of the muscle fibers with low oxidative capacity (type II) increased significantly in the running group. However, in the thoracic and cervical spine multifidus, the response to running resembled more of the significant shift from type II to type I fibers (with high oxidative capacity), which was also observed in the triceps brachii muscle. In these muscles, the quantitative image analysis of nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) reaction also demonstrated a shift towards a higher oxidative capacity within the type II fibers. The results show that training can induce changes in fiber type composition not only in limb muscles but also in the stabilizing spinal muscles. The additional stress induced by running exercise was apparently highest in the thoracic and cervical spine. It modulated the muscle fiber composition towards the types with high oxidative capacity and capable of tonic contraction. Comparison of the present results with earlier analyses on these dogs suggests that the recruitment of certain muscle fiber types predicts the influence of exercise on the intervertebral discs.     

用纤颤电位波幅衡量失神经肌肉萎缩程度的临床研究

目的研究失神经支配肱二头肌纤颤电位波幅的变化规律，并探索其与肌肉萎缩程度的关系。方法１９９５年８月～１９９６年１２月，检测１７３块因臂丛神经损伤致完全失神经支配的肱二头肌纤颤电位并计算其波幅；６３例在检测同一部位取肌组织送病理检查。被检肌肉行ＡＴＰ酶染色，测定Ｉ、Ｉ型肌纤维面积。结果纤颤电位的波幅和肌纤维的横断面积与失神经时间呈负相关；失神经后第５、６个月及１年以后为纤颤电位波幅的显著下降期；失神经后第４个月为肌纤维的显著萎缩期。纤颤电位的波幅与肌纤维的横截面积呈正相关；男性纤颤电位的波幅及ＩＩ型肌纤维面积均较女性为高（Ｐ＜０．０５）。结论纤颤电位波幅与肌纤维萎缩状态相一致，可作为评估肌肉萎缩程度的定量指标