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Context: Although poor paraspinal muscle endurance has been associated with less quadriceps activation (QA) in persons with a history of low back pain, no authors have addressed the acute neuromuscular response after lumbar paraspinal fatiguing exercise.

Objective: To compare QA after lumbar paraspinal fatiguing exercise in healthy individuals and those with a history of low back pain.

Design: A 2 × 4 repeated-measures, time-series design.

Setting: Exercise and Sport Injury Laboratory.

Patients or Other Participants: Sixteen volunteers participated (9 males, 7 females; 8 controls and 8 with a history of low back pain; age = 24.1 ± 3.1 years, height = 173.4 ± 7.1 cm, mass = 72.4 ± 12.1 kg).

Intervention(s): Subjects performed 3 sets of isometric lumbar paraspinal fatiguing muscle contractions. Exercise sets continued until the desired shift in lumbar paraspinal electromyographic median power frequency was observed. Baseline QA was compared with QA after each exercise set.

Main Outcome Measure(s): An electric burst was superimposed while subjects performed a maximal quadriceps contraction. We used the central activation ratio to calculate QA = (FMVIC/[FMVIC + FBurst])* 100, where F = force and MVIC = maximal voluntary isometric contractions. Quadriceps electromyographic activity was collected at the same time as QA measurements to permit calculation of median frequency during MVIC.

Results: Average QA decreased from baseline (87.4% ± 8.2%) after the first (84.5% ± 10.5%), second (81.4% ± 11.0%), and third (78.2% ± 12.7%) fatiguing exercise sets. On average, the group with a history of low back pain showed significantly more QA than controls. No significant change in quadriceps median frequency was noted during the quadriceps MVICs.

Conclusions: The quadriceps muscle group was inhibited after lumbar paraspinal fatiguing exercise in the absence of quadriceps fatigue. This effect may be different for people with a history of low back pain compared with healthy controls.

In this study, we compared the paramedian interfascial approach (PIA) and the traditional midline approach (MA) for lumbar fusion to determine which approach resulted in the least amount of postoperative back muscle atrophy. We performed unilateral transforaminal posterior lumbar interbody fusion via MA on the symptomatic side and pedicle screw fixation via PIA on the other side in the same patient. We evaluated the damage to the paraspinal muscle after MA and PIA by measuring the preoperative and postoperative paraspinal muscle volume in 26 patients. The preoperative and postoperative cross-sectional area, thickness, and width of the multifidus muscle were measured by computed tomography. The degree of postoperative paraspinal muscle atrophy was significantly greater on the MA side than on the contralateral PIA side (-20.7% and -4.8%, respectively, p<0.01). In conclusion, the PIA for lumbar fusion yielded successful outcomes for the preservation of paraspinal muscle in these 26 patients. We suggest that the success of PIA is due to less manipulation and retraction of the paraspinal muscle and further studies on this technique may help confirm whether less muscle injury has positive effects on the long-term clinical outcome.

Background

Females have a higher risk of experiencing low back pain or injury than males. One possible reason for this might be altered reflexes since longer paraspinal reflex latencies exist in injured patients versus healthy controls. Gender differences have been reported in paraspinal reflex latency, yet findings are inconsistent. The goal here was to investigate gender differences in paraspinal reflex latency, avoiding and accounting for potentially gender-confounding experimental factors.

Methods

Ten males and ten females underwent repeated trunk flexion perturbations. Paraspinal muscle activity and trunk kinematics were recorded to calculate reflex latency and maximum trunk flexion velocity. Two-way mixed model ANOVAs were used to determine the effects of gender on reflex latency and maximum trunk flexion velocity.

Findings

Reflex latency was 18.7% shorter in females than in males (P=0.02) when exposed to identical trunk perturbations, and did not vary by impulse (P=0.38). However, maximum trunk flexion velocity was 35.3% faster in females than males (P=0.01) when exposed to identical trunk perturbations, and increased with impulse (P<0.01). While controlling for differences in maximum trunk flexion velocity, reflex latency was 16.4% shorter in females than males (P=0.04).

Implications

The higher prevalence of low back pain and injury among females does not appear to result from slower paraspinal reflexes.

Background

Muscle metabolism in horses has been studied mainly by analysis of substances in blood or plasma and muscle biopsy specimens. By using microdialysis, real-time monitoring of the metabolic events in local tissue with a minimum of trauma is possible. There is limited information about muscle metabolism in the early recovery period after anaesthesia in horses and especially in the colic horse. The aims were to evaluate the microdialysis technique as a complement to plasma analysis and to study the concentration changes in lactate, pyruvate, glucose, glycerol, and urea during anaesthesia and in the recovery period in colic horses undergoing abdominal surgery and in healthy horses not subjected to surgery.

Methods

Ten healthy university-owned horses given anaesthesia alone and ten client-owned colic horses subjected to emergency abdominal surgery were anaesthetised for a mean (range) of 230 min (193–273) and 208 min (145–300) respectively. Venous blood samples were taken before anaesthesia. Venous blood sampling and microdialysis in the gluteal muscle were performed during anaesthesia and until 24 h after anaesthesia. Temporal changes and differences between groups were analysed with an ANOVA for repeated measures followed by Tukey Post Hoc test or Planned Comparisons.

Results

Lactate, glucose and urea, in both dialysate and plasma, were higher in the colic horses than in the healthy horses for several hours after recovery to standing. In the colic horses, lactate, glucose, and urea in dialysate, and lactate in plasma increased during the attempts to stand. The lactate-to-pyruvate ratio was initially high in sampled colic horses but decreased over time. In the colic horses, dialysate glycerol concentrations varied considerably whereas in the healthy horses, dialysate glycerol was elevated during anaesthesia but decreased after standing. In both groups, lactate concentration was higher in dialysate than in plasma. The correspondence between dialysate and plasma concentrations of glucose, urea and glycerol varied.

Conclusion

Microdialysis proved to be suitable in the clinical setting for monitoring of the metabolic events during anaesthesia and recovery. It was possible with this technique to show greater muscle metabolic alterations in the colic horses compared to the healthy horses in response to regaining the standing position.

Objective

Both the paraspinal muscle sparing approach and percutaneous screw fixation are less traumatic procedures in comparison with the conventional midline approach. These techniques have been used with the goal of reducing muscle injury. The purpose of this study was to evaluate and to compare the safety and efficacy of the paraspinal muscle sparing technique and percutaneous screw fixation for the treatment of L5-S1 spondylolisthesis.

Methods

Twenty patients who had undergone posterior lumbar interbody fusion (PLIF) at the L5-S1 segment for spondylolisthesis were prospectively studied. They were divided into two groups by screw fixation technique (Group I : paraspinal muscle sparing approach and Group II: percutaneous screw fixation). Clinical outcomes were assessed by Low Back Outcome Score (LBOS) and Visual Analogue Scale (VAS) for back and leg pain at different times after surgery. In addition, modified MacNab's grading criteria were used to assess subjective patients' outcomes 6 months after surgery. Postoperative midline surgical scarring, intraoperative blood loss, mean operation time, and procedure-related complications were analyzed.

Results

Excellent or good results were observed in all patients in both groups 6 months after surgery. Patients in both groups showed marked improvement in terms of LBOSs all over time intervals. Postoperative midline surgical scarring and intraoperative blood loss were lower in Group II compared to Group I although these differences were not statistically significant. Low back pain (LBP) and leg pain in both groups also showed significant improvement when compared to preoperative scores. However, at 7 days and 1 month after surgery, patients in Group II had significantly better LBP scores compared to Group I.

Conclusion

In terms of LBP during the early postoperative period, patients who underwent percutaneous screw fixation showed better results compared to ones who underwent screw fixation via the paraspinal muscle sparing approach. Our results indicate that the percutaneous screw fixation procedure is the preferable minimally invasive technique for reducing LBP associated with L5-S1 spondylolisthesis.

Study Design

Prospective controlled study.

Purpose

The results of conventional open surgery was compared with those from minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) for lumbar fusion to determine which approach resulted in less postoperative paraspinal muscle degeneration.

Overview of Literature

MI TLIF is new surgical technique that appears to minimize iatrogenic injury. However, there aren't any reports yet that have quantitatively analyzed and proved whether there's difference in back muscle injury and degeneration between the minimally invasive surgery and conventional open surgery in more than 1 year follow-up after surgery.

Methods

This study examined a consecutive series of 48 patients who underwent lumbar fusion in our hospital during the period, March 2006 to March 2008, with a 1-year follow-up evaluation using MRI. There were 17 cases of conventional open surgery and 31 cases of MI-TLIF (31 cases of single segment fusion and 17 cases of multi-segment fusion). The digital images of the paravertebral back muscles were analyzed and compared using the T2-weighted axial images. The point of interest was the paraspinal muscle of the intervertebral disc level from L1 to L5. Picture archiving and communication system viewing software was used for quantitative analysis of the change in fat infiltration percentage and the change in cross-sectional area of the paraspinal muscle, before and after surgery.

Results

A comparison of the traditional posterior fusion method with MI-TLIF revealed single segment fusion to result in an average increase in fat infiltration in the paraspinal muscle of 4.30% and 1.37% and a decrease in cross-sectional area of 0.10 and 0.07 before and after surgery, respectively. Multi-segment fusion showed an average 7.90% and 2.79% increase in fat infiltration and a 0.16 and 0.10 decrease in cross-sectional area, respectively. Both single and multi segment fusion showed less change in the fat infiltration percentage and cross-sectional area, particularly in multi segment fusion. There was no significant difference between the two groups in terms of the radiologic results.

Conclusions

A comparison of conventional open surgery with MI-TLIF upon degeneration of the paraspinal muscle with a 1 year follow-up evaluation revealed that both single and multi segment fusion showed less change in fat infiltration percentage and cross-sectional area in the MI-TLIF but there was no significant difference between the two groups. This suggests that as time passes after surgery, there is no significant difference in the level of degeneration of the paraspinal muscle between surgical techniques.

Cavernous hemangioma consists mainly of congenital vascular malformations present before birth and gradually increasing in size with skeletal growth. A small number of patients with cavernous hemangioma develop scoliosis, and surgical treatment for the scoliosis in such cases has not been reported to date. Here we report a 12-year-old male patient with severe progressive scoliosis due to a huge subcutaneous cavernous hemangioma, who underwent posterior correction and fusion surgery. Upon referral to our department, radiographs revealed a scoliosis of 85° at T6-L1 and a kyphosis of 58° at T4-T10. CT and MR images revealed a huge hemangioma extending from the subcutaneous region to the paraspinal muscles and the retroperitoneal space and invading the spinal canal. Posterior correction and fusion surgery using pedicle screws between T2 and L3 were performed. Massive hemorrhage from the hemangioma occurred during the surgery, with intraoperative blood loss reaching 2800 ml. The scoliosis was corrected to 59°, and the kyphosis to 45° after surgery. Seven hours after surgery, the patient suffered from hypovolemic shock and disseminated intravascular coagulation due to postoperative hemorrhage from the hemangioma. The patient developed sensory and conduction aphasia caused by cerebral hypoxia during the shock on the day of the surgery. At present, two years after the surgery, although the patient has completely recovered from the aphasia. This case illustrates that, in correction surgery for scoliosis due to huge subcutaneous cavernous hemangioma, intraoperative and postoperative intensive care for hemodynamics should be performed, since massive hemorrhage can occur during the postoperative period as well as the intraoperative period.

The original description of the paraspinal posterior approach to the lumbar spine was for spinal fusion, especially regarding lumbosacral spondylolisthesis treatment. In spite of the technical details described by Wiltse, exact location of the area where the sacrospinalis muscle has to be split remains somewhat unclear. The goal of this study was to provide topographic landmarks to facilitate this surgical approach. Thirty cadavers were dissected in order to precisely describe the anatomy of the trans-muscular paraspinal approach. The level of the natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was noted and measurements were done between this level and the midline at the level of the spinous process of L4. A natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was present in all cases. There was a fibrous separation between the two muscular parts in 55 out of 60 cases. The mean distance between the level of the cleavage plane and the midline was 4 cm (2.4–5.5 cm). In all cases, small arteries and veins were present, precisely at the level of the cleavage plane. We found it possible to easily localize the anatomical cleavage plane between the multifidus part and the longissimus part of the sacrospinalis muscle. First the superficial muscular fascia is opened near the midline, exposing the posterior aspect of the sacrospinalis muscle. Then, the location of the muscular cleft can be found by identifying the perforating vessels leaving the anatomical inter-muscular space.

Purpose

Ischemia-reperfusion injury induced by the Pringle maneuver is a well-known problem after liver surgery. The aim of this study was to monitor metabolic changes in the pig liver during warm ischemia and the following reperfusion preceded by ischemic preconditioning (IPC).

Methods

Eight Landrace pigs underwent laparotomy. Two microdialysis catheters were inserted in the liver, one in the left lobe and another in the right lobe. A reference catheter was inserted in the right biceps femoris muscle. Microdialysis samples were collected every 30 min during the study. After 2 h of baseline measurement, IPC was performed by subjecting pigs to 10 min of ischemia, followed by 10 min of reperfusion. Total ischemia for 60 min was followed by 3 h of reperfusion. The samples were analyzed for glucose, lactate, pyruvate, and glycerol. Blood samples were drawn three times to determine standard liver parameters.

Results

All parameters remained stable during baseline. Glycerol and glucose levels increased significantly during ischemia, followed by a decrease from the start of reperfusion. During the ischemic period, lactate levels increased significantly and decreased during reperfusion. The lactate–pyruvate ratio increased significantly during ischemia and decreased rapidly during reperfusion. Only minor changes were observed in standard liver parameters.

Conclusions

The present study demonstrated profound metabolic changes before, during, and after warm liver ischemia under the influence of IPC. Compared with a similar study without IPC, the metabolic changes seem to be unaffected by preconditioning.

BACKGROUND CONTEXT

Findings on imaging of noncontractile anatomic abnormalities and the intensity of low back pain have weak associations because of false-positive rates among asymptomatic individuals. This association might be stronger for contractile tissues.

PURPOSE

The purpose of this study was to examine the relationship between location and reports of pain intensity in the low back and exercise-induced muscle damage to the lumbar paraspinal muscles.

STUDY DESIGN

Nondiagnostic observational study in a laboratory setting.

METHODS

Delayed onset muscle soreness was induced in the low back of healthy pain-free volunteers. Measures of pain intensity (100-mm visual analog scale [VAS]) and location (area on the pain diagram) were taken before and 48 hours after exercise. Muscle damage was quantified using mechanical pain thresholds, motor performance deficits, and transverse relaxation time (T2)–weighted magnetic resonance imaging (MRI). Changes pre- to postexercise in signal intensity on T2-weighted imaging within the erector spinae, pain intensity, pain area, mechanical pain threshold, and isometric torque were assessed using paired t tests. Bivariate correlations were conducted to assess associations among muscle damage, pain intensity, and pain drawing area.

RESULTS

Twenty participants volunteered (11 women; average age, 22.3 years; average body mass index, 23.5) for study participation. Reports of pain intensity at 48 hours ranged from 0 to 59 mm on the VAS. Muscle damage was confirmed by reductions in mechanical threshold (p=.011) and motor performance (p<.001) and by changes in T2-weighted MRI (p=.007). This study was powered to find an association of at least r=0.5 to be statistically significant. Correlations of continuous variables revealed no significant correlations between pain intensity and measures of muscle damage (ranging between −0.075 and 0.151). There was a significant association between the remaining torque deficit at 48 hours and pain area.

CONCLUSIONS

The results of this study indicate that there was no association between the magnitude of muscle damage in the lumbar erector spinae and reported pain intensity in the low back. In future studies, larger cohorts may report statistically significant associations, but our data suggest that there will be low magnitude potentially indicating limited clinical relevance.

Objectives: The objective of this study is to introduce modifications in paraspinous muscle flap surgery and compare this new variation's ability to salvage infected hardware with the classic technique. Infected posterior spine wounds are a difficult problem for reconstructive surgeons. As per experience, hardware retention in infected wounds maintains spinal stability, decreases length of stay, and decreases the wound healing complication rate. Methods: An 11-year retrospective office and hospital chart review was conducted between July 1996 and August 2007. All patients who underwent paraspinous muscle flap reconstruction for postspine surgery wound infections during this time period were included. There were 51 patients in the study representing the largest reported series, to date, for this procedure. Twenty-two patients underwent treatment using the modified technique and 29 patients were treated using the classic technique. Results: There was no statistical difference between the 2 groups in demographics, medical history, or reason for initial spine surgery. The hardware salvage rate associated with the modified technique was greater than the rate associated with the classic technique (95.4% vs 75.8%; P = .03). There were fewer postreconstruction wound healing complications requiring hospital readmission in the modified technique group than the classic group (13.6% vs 44.8%; P = .04). Patients in the modified technique group demonstrated a shorter mean length of stay than the patients in the classic group (23.7 days vs 29.7; P = .25). Conclusions: The modified paraspinous muscle flap technique is an excellent option for spinal wound reconstruction, preservation of spinal hardware, and local infection control.

Paraspinal muscle fatigability during various trunk extension tests has been widely investigated by electromyography (EMG), and its task-dependency is established recently. Hip extensor muscle fatigability during the Sorensen test has been reported. The aim of the present experiments was to evaluate the task-dependency of back and hip extensor muscle fatigue during two variants of the Sorensen test. We hypothesized that the rate of muscular fatigue of the hip and back extensor muscles varies according to the test position. Twenty healthy young males with no history of low back pain volunteered to participate in this cross-sectional study. They were asked to perform two body weight-dependent isometric back extension tests (S1 = Sorensen test; S2 = modified Sorensen on a 45° Roman chair). Surface EMG activity of the paraspinal muscles (T10 and L5 levels) and hip extensor muscles (gluteus maximus; biceps femoris) was recorded, and muscular fatigue was assessed through power spectral analysis of the EMG data by calculating the rate of median power frequency change. We observed hip extensor muscle fatigue simultaneously with paraspinal muscle fatigue during both Sorensen variants. However, only L5 level EMG fatigue indices showed a task-dependency effect between S1 and S2. Hip extensor muscles appear to contribute to load sharing of the upper body mass during both Sorensen variants, but to a different extent because L5 level fatigue differs between the Sorensen variants. Our findings suggest that task-dependency has to be considered when EMG variables are compared between two types of lumbar muscle-fatiguing tasks.

Objective

To investigate the prognostic value of cross-sectional areas (CSA) of paraspinal (multifidus and erector spinae) and psoas muscles on magnetic resonance imaging (MRI) in chronicity of low back pain.

Method

Thirty-eight subjects who visited our hospital for acute low back pain were enrolled. Review of their medical records and telephone interviews were done. Subjects were divided into two groups; chronic back pain group (CBP) and a group showing improvement within 6 months after onset of pain (IBP). The CSA of paraspinal and psoas muscles were obtained at the level of the lower margin of L3 and L5 vertebrae using MRI.

Results

CSA of erector spinae muscle and the proportion of the area to lumbar muscles (paraspinal and psoas muscles) at L5 level in the CBP group were significantly smaller than that of the IBP group (p<0.05). The mean value of CSA of multifidus muscle at L5 level in the CBP group was smaller than that of the IBP group, but was not statistically significant (p>0.05). CSA of psoas muscle at L5 level and all values measured at L3 level were not significantly different between the groups (p>0.05).

Conclusion

CSA of erector spinae muscle at the lower lumbar level and the proportion of the area to the lumbar muscles at the L5 level can be considered to be prognostic factors of chronicity of low back pain.

Most spine fusion procedures involve the use of prosthetic fixation devices combined with autologous bone grafts rather than biological treatment. We had shown that spine fusion could be achieved by injection of bone morphogenetic protein-2 (BMP-2)-expressing mesenchymal stem cells (MSCs) into the paraspinal muscle. In this study, we hypothesized that posterior spinal fusion achieved using genetically modified MSCs would be mechanically comparable to that realized using a mechanical fixation. BMP-2-expressing MSCs were injected bilaterally into paravertebral muscles of the mouse lumbar spine. In one control group BMP-2 expression was inhibited. Microcomputed tomography and histological analyses were used to evaluate bone formation. For comparison, a group of mouse spines were bilaterally fused with stainless steel pins. The harvested spines were later tested using a custom four-point bending apparatus and structural bending stiffness was estimated. To assess the degree to which MSC vertebral fusion was targeted and to quantify the effects of fusion on adjacent spinal segments, images of the loaded spine curvature were analyzed to extract rigidity of the individual spinal segments. Bone bridging of the targeted vertebrae was observed in the BMP-2-expressing MSC group, whereas no bone formation was noted in any control group. The biomechanical tests showed that MSC-mediated spinal fusion was as effective as stainless steel pin-based fusion and significantly more rigid than the control groups. Local analysis showed that the distribution of stiffness in the MSC-based fusion group was similar to that in the steel pin fusion group, with the majority of spinal stiffness contributed by the targeted fusion at L3–L5. Our findings demonstrate that MSC-induced spinal fusion can convey biomechanical rigidity to a targeted segment that is comparable to that achieved using an instrumental fixation.

Background:

Various modalities of treatment from standard discectomy, microdiscectomy, percutaneous discectomy, and transforaminal endoscopic discectomy have been in use for lumbar intervertebral disc prolapse. The access to spine is kept to a minimum without stripping paraspinal muscles minimizing muscle damage by posterior interlaminar endoscopic approach. The aim of this study was to evaluate technical problems, complications, and overall initial results of microendoscopic discectomy.

Materials and Methods:

First 100 consecutive cases aged 19-65 years operated by microendoscopic dissectomy between August 2002 – December 2005 are reported. All patients with single nerve root lesions including sequestrated or migrated and selected central disc at L4-5 and L5-S1 were included. The patients with bilateral radiculopathy were excluded. All patients had preoperative MRI and first 11 patients had postoperative MRI to check the adequacy of decompression. Diagnostic selective nerve root blocks were done in selective cases to isolate the single root lesion when MRI was inconclusive (n=7). All patients were operated by a single surgeon with the Metrx system (Medtronics). 97 were operated by 18-mm ports, and only three patients were operated by 16-mm ports. Postoperatively, all patients were mobilized as soon as the pain subsided and discharged within 24–48 h postsurgery. Patients were evaluated for technical problems, complications, and overall results by modified Macnab criteria. Patients were followed up at 2, 6, and 12 weeks.

Results:

The mean follow up was 12 months (range 3 months – 4 years). Open conversion was required in one patient with suspected root damage. Peroperatively single facet removal was done in 5 initial cases. Minor dural punctures occurred in seven cases and root damage in one case. The average surgical time was 70 min (range 25-210 min). Average blood loss was 20-30 ml. Technical difficulties encountered in initial 25 cases were insertion of guide pin, image orientation, peroperative dissection and bleeding problems, and reaching wrong levels suggestive of a definitive learning curve. Postoperative MRI (n=11) showed complete decompression. Overall 91% of patients had good-to-excellent results, with four patients having recurrence of whom three were reoperated. Four patients had postoperative discitis. One of the patients required fusion for discitis and rest were managed conservatively. One patient had root damage to L5 root that had paresthesia in L5 region even on 4 years of follow-up.

Conclusion:

Microendoscopic discectomy is minimally invasive procedure for discectomy with early encouraging results. Once definite learning curve was over and expertise is acquired, the results of this procedure are acceptable safe and effective.

The purpose of this study was to investigate the use of magnetic resonance (MR) imaging and image processing software to determine the functional cross-sectional area (FCSA) (the area of muscle isolated from fat) of the lumbar paraspinal muscles. The measurement of the morphology of the lumbar paraspinal muscles has become the focus of several recent investigations into the aetiology of low back pain. However, the reliability and validity of determining the FCSA of the lumbar paraspinal muscles using MR imaging are yet to be reported. T2 axial MR scans at the L1-S1 spinal levels of six subjects were obtained using identical MR systems and scanning parameters. Lean paraspinal muscle, vertebral body bone and intermuscular fat were manually segmented using image analysis software to assign a grey scale range to the MR signal intensity emitted by each tissue type. The resultant grey scale range for muscle was used to determine FCSA measurements for each of the paraspinal muscles, psoas, quadratus lumborum, erector spinae and lumbar multifidus on each scan slice. As various biological, instrument and measurement factors can affect MR signal intensity, a sensitivity analysis was conducted to determine the error associated in calculating FCSA for paraspinal muscle using a discrete grey scale range. Cross-sectional area and FCSA measurements were repeated three times and reliability indices for the FCSA measurements were obtained, showing excellent reliability, intra class correlation coefficient (mean=0.97, range 0.90–0.99) and %SEM (mean=2.6%, range 0.7–4.8%). In addition, the error associated with miscalculation of the grey scale range for the MR signal intensity of muscle was calculated and found to be low with an error of 20 grey scale units at the upper end of the muscle’s grey scale range resulting in a very small error in the measured muscle FCSA. The method presented in this paper has a variety of practical applications in areas such as evidence-based rehabilitation, biomechanical modelling and the determination of segmental inertial parameters.

Abstract

Context:

Isolated lumbar paraspinal muscle fatigue causes lower extremity and postural control deficits.

Objective:

To describe the change in body position during gait after fatiguing lumbar extension exercises in persons with recurrent episodes of low back pain compared with healthy controls.

Design:

Case-control study.

Setting:

Motion analysis laboratory.

Patients or Other Participants:

Twenty-five recreationally active participants with a history of recurrent episodes of low back pain, matched by sex, height, and mass with 25 healthy controls.

Intervention(s):

We measured 3-dimensional lower extremity and trunk kinematics before and after fatiguing isometric lumbar paraspinal exercise.

Main Outcome Measure(s):

Measurements were taken while participants jogged on a custom-built treadmill surrounded by a 10-camera motion analysis system.

Results:

Group-by-time interactions were observed for lumbar lordosis and trunk angles (P < .05). A reduced lumbar spine extension angle was noted, reflecting a loss of lordosis and an increase in trunk flexion angle, indicating increased forward trunk lean, in healthy controls after fatiguing lumbar extension exercise. In contrast, persons with a history of recurrent low back pain exhibited a slight increase in spine extension, indicating a slightly more lordotic position of the lumbar spine, and a decrease in trunk flexion angles after fatiguing exercise. Regardless of group, participants experienced, on average, greater peak hip extension after lumbar paraspinal fatigue.

Conclusions:

Small differences in response may represent a necessary adaptation used by persons with recurrent low back pain to preserve gait function by stabilizing the spine and preventing inappropriate trunk and lumbar spine positioning.

The high risk of sustaining subsequent vertebral fractures after an initial fracture cannot be explained solely by low bone mass. Extra-osseous factors, such as neuromuscular characteristics may help to explain this clinical dilemma. Elderly women with (n = 11) and without (n = 14) osteoporotic vertebral fractures performed rapid shoulder flexion to perturb the trunk while standing on a flat and short base. Neuromuscular postural responses of the paraspinal muscles at T6 and T12, and deep lumbar multifidus at L4 were recorded using intramuscular electromyography (EMG). Both groups demonstrated bursts of EMG that were initiated either before or shortly after the onset of shoulder flexion (P < 0.05). Paraspinal and multifidus onset occurred earlier in the non-fracture group (50–0 ms before deltoid onset) compared to the fracture group (25 ms before and 25 ms after deltoid onset) in the flat base condition. In the short base condition, EMG amplitude increased significantly above baseline earlier in the non-fracture group (75–25 ms before deltoid onset) compared to the fracture group (25–0 ms before deltoid onset) at T6 and T12; yet multifidus EMG increased above baseline earlier in the fracture group (50–25 ms before deltoid) compared to the non-fracture group (25–0 ms before deltoid). Time to reach maximum amplitude was shorter in the fracture group. Hypothetically, the longer time to initiate a postural response and shorter time to reach maximum amplitude in the fracture group may indicate a neuromuscular contribution towards subsequent fracture aetiology. This response could also be an adaptive characteristic of the central nervous system to minimise vertebral loading time.

Background Context

In neutral spinal postures with low loading moments the lumbar spine is not inherently stable. Small compromises in paraspinal muscle activity may affect lumbar spinal biomechanics. Proprioceptive feedback from muscle spindles is considered important for control of muscle activity. Because skeletal muscle and muscle spindles are thixotropic, their length history changes their physical properties. The present study explores a mechanism that can affect the responsiveness of paraspinal muscle spindles in the lumbar spine.

Purpose

This study had two aims: to extend our previous findings demonstrating the history dependent effects of vertebral position on the responsiveness of lumbar paraspinal muscle spindles; and to determine the time course for these effects. Based upon previous studies, if a crossbridge mechanism underlies these thixotropic effects, then the relationship between the magnitude of spindle discharge and the duration of the vertebral position will be one of exponential decay or growth.

Study Design/Setting

A neurophysiological study using the lumbar spine of a feline model.

Methods

The discharge from individual muscle spindles afferents innervating lumbar paraspinal muscles in response to the duration and direction of vertebral position were obtained from teased filaments in the L6 dorsal roots of 30 Nembutal-anesthetized cats. The L6 vertebra was controlled using a displacement-controlled feedback motor and was held in each of 3 different conditioning positions for durations of 0, 0.5, 1, 1.5, and 2 seconds. Two of the conditioning positions stretched or shortened the lumbar muscles relative to an intermediate conditioning position. Conditioning positions for all cats ranged from 0.9 – 2.0 mm dorsal and ventralward relative to the intermediate position. These magnitudes were determined based upon the displacement that loaded the L6 vertebra to 50–60% of the cat’s body weight. Conditioning was thought to simulate a motion segment’s position that might be passively maintained due to fixation, external load, a prolonged posture, or structural change. Following conditioning positions that stretched (hold-long) and shortened (hold-short) the spindle, the vertebra was repositioned identically and muscle spindle discharge at rest and to movement was compared with conditioning at the intermediate position.

Results

Lumbar vertebral positions maintained for less than 2 seconds were capable of evoking different discharge rates from lumbar paraspinal muscle spindles despite the vertebra having been returned to identical locations. Both resting spindle discharge and their responsiveness to movement were altered. Conditioning vertebral positions that stretched the spindles decreased spindle activity and positions that unloaded the spindles increased spindle activity upon returning the vertebra to identical original (intermediate) positions. The magnitude of these effects increased as conditioning duration increased to 2 seconds. These effects developed with a time course following a first order exponential reaching a maximal value after approximately 4 seconds of history. The time constant for a hold-short history was 2.6 seconds and for a hold-long history was approximately half of that at 1.1 seconds.

Conclusions

Thixotropic contributions to the responsiveness of muscles spindles in the low back are caused by the rapid, spontaneous formation of stable crossbridges. These sensory alterations due to vertebral history would represent a proprioceptive input not necessarily representative of the current state of intersegmental positioning. As such, they would constitute a source of inaccurate sensory feedback. Examples are presented suggesting ways in which this novel finding may affect spinal physiology.

Background

No consensus exists on how rehabilitation programs for lumbar discectomy patients with persistent complaints after surgery should be composed. A better understanding of normal and abnormal postoperative trunk muscle condition might help direct the treatment goals.

Methods

A three-dimensional CT scan of the lumbar spine was obtained in 18 symptomatic and 18 asymptomatic patients who had undergone a lumbar discectomy 42 months to 83 months (median 63 months) previously. The psoas muscle (PS), the paraspinal muscle mass (PA) and the multifidus muscle (MF) were outlined at the L3, L4 and L5 level. Of these muscles, fat free Cross Sectional Area (CSA) and fat CSA were determined. CSA of the lumbar erector spinae (LES = longissimus thoracis + iliocostalis lumborum) was calculated by subtracting MF CSA from PA CSA. Mean muscle CSA of the left and right sides was calculated at each level. To normalize the data for interpersonal comparison, the mean CSA was divided by the CSA of the L3 vertebral body (mCSA = normalized fat-free muscle CSA; fCSA = normalized fat CSA). Differences in CSA between the pain group and the pain free group were examined using a General Linear Model (GLM). Three levels were examined to investigate the possible role of the level of operation.

Results

In lumbar discectomy patients with pain, the mCSA of the MF was significantly smaller than in pain-free subjects (p = 0.009) independently of the level. The mCSA of the LES was significantly smaller in pain patients, but only on the L3 slice (p = 0.018). No significant difference in mCSA of the PS was found between pain patients and pain-free patients (p = 0.462). The fCSA of the MF (p = 0.186) and of the LES (p = 0.256) were not significantly different between both populations. However, the fCSA of the PS was significantly larger in pain patients than in pain-free patients. (p = 0.012).

The level of operation was never a significant factor.

Conclusions

CT comparison of MF, LES and PS muscle condition between lumbar discectomy patients without pain and patients with protracted postoperative pain showed a smaller fat-free muscle CSA of the MF at all levels examined, a smaller fat- free muscle CSA of the LES at the L3 level, and more fat in the PS in patients with pain. The level of operation was not found to be of importance. The present results suggest a general lumbar muscle dysfunction in the pain group, in particular of the deep stabilizing muscle system.

Abstract

Objective

This study examined a set of patients who were symptomatic for low back pain and who had significant lumbar hypolordosis as assessed by visual evaluation of magnetic resonance images to investigate the frequency of comorbid paraspinal muscle spasms as determined via history or physical examination.

Methods

A retrospective chart review was performed on 50 patients who had significant hypolordosis on magnetic resonance imaging (MRI) (Cobb angle <20°) to determine whether they were positive for paraspinal muscle spasms by either history or physical examination.

Results

Of the 50 patients with significant hypolordosis on MRI, 66% (33) had a history of paraspinal muscle spasms, 76% (38) had a positive physical examination for palpation of paraspinal muscle spasms, and 48% (24) were positive for both history and physical examination.

Conclusions

This retrospective study suggests that most symptomatic patients with significant hypolordosis on lumbar MRI have a positive history or physical examination for paraspinal muscle spasm. Thus, MRI finding of significant hypolordosis (Cobb angle <20°) could potentially be a valuable tool in addition to medical history and physical examination in aiding clinicians in diagnosing paraspinal muscle spasms in symptomatic patients and in helping them to formulate appropriate and effective treatments.

Introduction

Hyperlactatemia represents one prominent component of the metabolic response to sepsis. In critically ill patients, hyperlactatemia is related to the severity of the underlying condition. Both an increased production and a decreased utilization and clearance might be involved in this process, but their relative contribution remains unknown. The present study aimed at assessing systemic and muscle lactate production and systemic lactate clearance in healthy human volunteers, using intravenous endotoxin (LPS) challenge.

Methods

Fourteen healthy male volunteers were enrolled in 2 consecutive studies (n = 6 in trial 1 and n = 8 in trial 2). Each subject took part in one of two investigation days (LPS-day with endotoxin injection and placebo-day with saline injection) separated by one week at least and in a random order. In trial 1, their muscle lactate metabolism was monitored using microdialysis. In trial 2, their systemic lactate metabolism was monitored by means of a constant infusion of exogenous lactate. Energy metabolism was monitored by indirect calorimetry and glucose kinetics was measured with 6,6-H2 glucose.

Results

In both trials, LPS increased energy expenditure (p = 0.011), lipid oxidation (p<0.0001), and plasma lactate concentration (p = 0.016). In trial 1, lactate concentration in the muscle microdialysate was higher than in blood, indicating lactate production by muscles. This was, however, similar with and without LPS. In trial 2, calculated systemic lactate production increased after LPS (p = 0.031), while lactate clearance remained unchanged.

Conclusions

LPS administration increases lactatemia by increasing lactate production rather than by decreasing lactate clearance. Muscle is, however, unlikely to be a major contributor to this increase in lactate production.

Trial registration

ClinicalTrials.gov NCT01647997

Background

Minimizing peritoneal tissue injury during abdominal surgery has the benefit of reducing postoperative inflammatory response, pain, and adhesion formation. Ultrasonic dissection seems to reduce tissue damage. This study aimed to compare electrocautery and ultrasonic dissection in terms of peritoneal tissue ischemia measured by microdialysis.

Methods

In this study, 18 Wistar rats underwent a median laparotomy and had a peritoneal microdialysis catheter implanted in the left lateral sidewall. The animals were randomly assigned to receive two standard peritoneal incisions parallel to the catheter by either ultrasonic dissection or electrocautery. After the operation, samples of microdialysis dialysate were taken every 2 h until 72 h postoperatively for measurements of pyruvate, lactate, glucose, and glycerol, and ratios were calculated.

Results

The mean lactate–pyruvate ratio (LPR), lactate–glucose ratio (LGR), and glycerol concentration were significantly higher in the electrocautery group than in the ultrasonic dissection group until respectively 34, 48, and 48 h after surgery. The mean areas under the curve (AUC) of LPR, LGR, and glycerol concentration also were higher in the electrocautery group than in the ultrasonic dissection group (4,387 vs. 1,639, P = 0.011; 59 vs. 21, P = 0.008; 7,438 vs. 4,169, P = 0.008, respectively).

Conclusion

Electrosurgery causes more ischemic peritoneal tissue damage than ultrasonic dissection.

Minimally invasive surgeries including endoscopic surgery and mini-open surgery are current trend of spine surgery, and its main advantages are shorter recovery time and cosmetic benefits, etc. However, mini-open surgery is easier and less technique demanding than endoscopic surgery. Besides, anterior spinal fusion is better than posterior spinal fusion while considering the physiological loading, back muscle function, etc. Therefore, we aimed to introduce the modified “mini-open anterior spine surgery” (MOASS) and to evaluate the feasibility, effectiveness and safety in the treatment of various anterior lumbar diseases with this technique. A total of 61 consecutive patients (46 female, 15 male; mean age 58.2 years) from 1997 to 2004 were included in this study, with an average follow-up of 24–52 (mean 43) months. The disease entities included vertebral fracture (20), failed back surgery (13), segmental instability or spondylolisthesis (10), infection (8), herniated disc (5), undetermined lesion for biopsy (4), and hemivertebra (1). Lesions involved 13 cases at T12–L1, 18 at L1–L2, 18 at L2–L3, 22 at L3–L4 and 11 at L4–L5 levels. All patients received a single stage anterior-only procedure for their anterior lumbar disease. We used the subjective clinical results, Oswestry disability index, fusion rate, and complications to evaluate our clinical outcome. Most patients (91.8%) were subjectively satisfied with the surgery and had good-to-excellent outcomes. Mean operation time was 85 (62–124) minutes, and mean blood loss was 136 (minimal-250) ml in the past 6 years. Hospital stay ranged from 4–26 (mean 10.6) days. Nearly all cases had improved back pain (87%), physical function (90%) and life quality (85%). Most cases (95%) achieved solid or probable solid bony fusion. There were no major complications. Therefore, MOASS is feasible, effective and safe for patients with various anterior lumbar diseases.

OBJECTIVE—To evaluate interstitial glycerol as a marker of ischaemia by studying the changes in glycerol in direct relation to changes in regional cerebral metabolic rate of oxygen (CMRO2), the lactate/pyruvate ratio (LP ratio), and glutamate.
METHODS—Transorbital 2 hour middle cerebral artery occlusion (MCAO) was performed in eight monkeys, which were studied with continuous microdialysis for 24 hours. Interstitial fluids were collected by microdialysis and analysed for glycerol, lactate, pyruvate, and glutamate with an enzymatic assay and high performance liquid chromatography. Sequential PET studies of cerebral blood flow (CBF), CMRO2, oxygen extraction ratio (OER), and cerebral blood volume (CBV) were performed. The microdialysis probe regions were classified as severe ischaemia or penumbra, depending on whether the mean CMRO2 side to side ratio was below or above 60%, respectively.
RESULTS—A nine-fold, sustained increase in glycerol was registered after MCAO in severe ischaemia regions. In penumbra regions, the increase in glycerol was five-fold, but the glycerol concentration returned to baseline within 8 hours of clip removal. The difference between severe ischaemia and penumbra glycerol values was statistically significant. As expected from previous studies, the interstitial LP ratio and glutamate increased markedly in severe ischaemia, with a less pronounced change in penumbra regions. There was a time lag between the biochemical changes in severe ischaemia regions, with the LP ratio preceding glutamate, followed by glycerol.
CONCLUSIONS—A marked, sustained increase in interstitial glycerol is indicative of severe ischaemia in this stroke model. A transient, diminutive increase in interstitial glycerol may reflect a penumbra situation. Interstitial glycerol in combination with other biochemical markers such as the LP ratio and glutamate may be useful for clinical monitoring of the ischaemic brain, reflecting a sequence of secondary pathophysiological events.