Muscle functional MRI analysis of trunk muscle recruitment during extension exercises in asymptomatic individuals.

The present study examined the activity levels of the thoracic and lumbar extensor muscles during different extension exercise modalities in healthy individuals. Therefore, 14 subjects performed four different types of extension exercises in prone position: dynamic trunk extension, dynamic-static trunk extension, dynamic leg extension, and dynamic-static leg extension. Pre- and post-exercise muscle functional magnetic resonance imaging scans from the latissimus dorsi, the thoracic and lumbar parts of the longissimus, iliocostalis, and multifidus were performed. Differences in water relaxation values (T2-relaxation) before and after exercise were calculated (T2-shift) as a measure of muscle activity and compared between extension modalities. Linear mixed-model analysis revealed higher lumbar extensor activity during trunk extension compared with leg extension (T2-shift of 5.01 ms and 3.55 ms, respectively) and during the dynamic-static exercise performance compared with the dynamic exercise performance (T2-shift of 4.77 ms and 3.55 ms, respectively). No significant differences in the thoracic extensor activity between the exercises could be demonstrated. During all extension exercises, the latissimus dorsi was the least activated compared with the paraspinal muscles. While all extension exercises are equivalent effective to train the thoracic muscles, trunk extension exercises performed in a dynamic-static way are the most appropriate to enhance lumbar muscle strength.

Free radical scavengers have a preventive effect on heterotopic bone formation following manipulation of immobilized rabbit legs.

AIM: The pathogenesis of heterotopic ossification (HO) is still unclear and the preventive measures and therapies are usually insufficient. The authors compared free radical scavengers with placebo in order to assess the magnitude of their inhibitory effect on the development of HO. METHODS: A standard immobilization-manipulation model was used to induce HO in the hind legs of twenty female New Zealand albino rabbits. The animals were divided into two groups and received daily either placebo or a free radical scavenger (A/A) cocktail in a randomized double-blind fashion. Every four days an X-ray was taken and the thickness and length of new bone formation were measured at the thigh by two investigators independently. RESULTS: Fisher's exact test revealed a significant difference in the development of heterotopic ossification between the placebo group and the A/A group (70% versus none, respectively ; P=0.0031). CONCLUSION: The ischemia/reperfusion syndrome could be an important precipitating factor in the pathogenesis of heterotopic ossification and free radical scavengers were found to have a significant inhibitory effect on its development in a rabbit model. The results of this experimental model can be an impetus for further research into the prevention of heterotopic bone formation in humans.

Free radical scavengers are more effective than indomethacin in the prevention of experimentally induced heterotopic ossification.

The pathogenesis of heterotopic ossification is still unclear and the preventive therapies are usually insufficient. The present study was designed to investigate the possible preventive effect of free radical scavengers on the development of experimentally induced heterotopic ossification in a rabbit model and to compare free radical scavengers with indomethacin to determine whether they act synergistically. A standard immobilization-manipulation model was used to induce heterotopic ossification in the hind legs of 40 1-year-old female New Zealand albino rabbits. The animals were divided into four groups and received daily either placebo, a free radical scavenger cocktail [allopurinol and N-acetylcysteine (A/A)], indomethacin or the combination of A/A and indomethacin in a randomized double-blind fashion. Every 4 days an X-ray was taken and the thickness and length of new bone formation was measured at the thigh. A marked statistically significant difference was found between the four groups. In the groups that received A/A, either alone or combined with indomethacin, an inhibition of bone growth, both in thickness and in length was demonstrated. In this experimental model free radical scavengers had a superior inhibitory effect on heterotopic ossification than indomethacin. Free radicals could play an important role in the pathogenesis of heterotopic ossification.

Statistical modelling of fatigue-related electromyographic median frequency characteristics of back and hip muscles during a standardized isometric back extension test.

The purpose of the present study was to evaluate which statistical model - linear, logarithmic, quadratic or exponential - best described the fatigue-related electromyographic (EMG) changes of back and hip muscles. Twenty healthy volunteers performed a modified Biering-Sorensen test. The EMG activity of the latissimus dorsi (LD), longissimus thoracis pars thoracis (LTT) and lumborum (LTL), iliocostalis lumborum pars thoracis (ILT) and lumborum (ILL), multifidus (MF), gluteus maximus (GM) and biceps femoris (BF) was measured bilaterally using surface electrodes. Higher R(2) values were found for the quadratic models (p<0.05 for all muscles), and lower R(2) values for the logarithmic models (p<0.05 for LTT, LTL, ILL, MF and GM). The exponential models generated higher R(2) values compared to the linear ones for the LTT, LTL and MF (all p<0.05). Further analyses revealed, however, that these models did not add useful additional information, and therefore would only increase the complexity. The findings of the current study validate the use of simple linear regression techniques when studying fatigue-related EMG median frequency characteristics of back and hip muscles during isometric contractions.

Evaluation of isokinetic force production and associated muscle activity in the scapular rotators during a protraction-retraction movement in overhead athletes with impingement symptoms.

OBJECTIVES: To determine if the muscle force and electromyographic activity in the scapular rotators of overhead athletes with impingement symptoms showed differences between the injured and non-injured sides. METHODS: Isokinetic peak force was evaluated during protraction and retraction of the shoulder girdle, with simultaneous recording of electromyographic activity of the three trapezius muscles and the serratus anterior muscle, in 19 overhead athletes with impingement symptoms. RESULTS: Paired t tests showed significantly lower peak force during isokinetic protraction at high velocity (p<0.05), a significantly lower protraction/retraction ratio (p<0.01), and significantly lower electromyographic activity in the lower trapezius muscle during isokinetic retraction on the injured side than on the non-injured side (p<0.05). CONCLUSION: These results confirm that patients with impingement symptoms show abnormal muscle performance at the scapulothoracic joint.

Differences in electromyographic activity in the multifidus muscle and the iliocostalis lumborum between healthy subjects and patients with sub-acute and chronic low back pain.

The present study was carried out to examine possible mechanisms of back muscle dysfunction by assessing a stabilising and a torque-producing back muscle, the multifidus (MF) and the iliocostalis lumborum pars thoracis (ICLT), respectively, in order to identify whether back pain patients showed altered recruitment patterns during different types of exercise. In a group of healthy subjects (n=77) and patients with sub-acute (n=24) and chronic (51) low back pain, the normalised electromyographic (EMG) activity of the MF and the ICLT (as a percentage of maximal voluntary contraction) were analysed during coordination, stabilisation and strength exercises. The results showed that, in comparison with the healthy subjects, the chronic low back pain patients displayed significantly lower (P=0.013) EMG activity of the MF during the coordination exercises, indicating that, over the long term, back pain patients have a reduced capacity to voluntarily recruit the MF in order to obtain a neutral lordosis. In contrast, during the stabilisation exercises, no significant differences between patients and controls were found for the normalised EMG activity of the two muscles. These findings indicated that, during low-load exercises, no insufficiencies in back muscle recruitment were evident in either subacute or chronic back pain patients. During the strength exercises, the normalised activity of both back muscles was significantly lower in chronic low back pain patients (P=0.017 and 0.003 for the MF and ICLT, respectively) than in healthy controls. Pain, pain avoidance and deconditioning may have contributed to these lower levels of EMG activity during intensive back muscle contraction. The possible dysfunction of the MF during coordination exercises and the altered activity of both muscles during strength exercises may be of importance in symptom generation, recurrence or maintenance of low back pain.

Intra-operator and inter-operator reliability of surface electromyography in the clinical evaluation of back muscles.

As a prerequisite to the use of a test battery based on electromyographic (EMG) analysis of the paraspinal muscles for identifying and remedying back muscle dysfunction, the intra- and inter-operator reliability was assessed. Fifteen volunteers underwent EMG tests on three occasions. The test subjects were asked to perform 22 exercises, subdivided into four categories: coordination, stabilization, balance and strength exercises. The time interval between the tests was one week. The myoelectric signals of the multifidus (MF) and iliocostalis lumborum pars thoracis (ICLT) were analysed with regard to amplitude (averaged EMG) and frequency (zero cross rate). The results indicated that the reliability was better for the MF than for the ICLT, and also for exercises at higher loads (strength exercises). In the intra-operator condition, the reproducibility of the averaged EMG was good (ICC>0.75), except for the balance exercises (ICC = 0.40-0.74). In general, the averaged EMG in the inter-operator condition and the zero cross rate in both the intra- and inter-operator conditions are less or poorly reliable. These results demonstrate that when back muscle function is evaluated during coordination, stabilization and strength exercises, only the averaged EMG parameter has acceptable reproducibility over time when assessed by the same operator.

Effects of three different training modalities on the cross sectional area of the lumbar multifidus muscle in patients with chronic low back pain.

OBJECTIVES: To determine the effect of different training schedules on the cross sectional area (CSA) of the lumbar multifidus muscle in patients with chronic low back pain. METHODS: Each of 59 nine patients was randomly assigned to one of three programmes: 10 weeks of stabilisation training (group 1; n = 19); 10 weeks of stabilisation training combined with dynamic resistance training (group 2; n = 20); 10 weeks of stabilisation training combined with dynamic-static resistance training (group 3; n = 20). Before and after 10 weeks of training, multifidus CSAs were measured from standard computed tomography images at three different levels (upper end plate of L3 and L4, and lower end plate of L4). RESULTS: The CSA of the multifidus muscle was significantly increased at all levels after training in group 3. In contrast, no significant differences were found in groups 1 and 2. CONCLUSIONS: General stabilisation exercises and dynamic intensive lumbar resistance training have no significant effect on the CSA of the lumbar multifidus muscle in patients with chronic low back pain. The static holding component between the concentric and eccentric phase was found to be critical in inducing muscle hypertrophy during the first 10 weeks. Treatment consisting of stabilisation training combined with an intensive lumbar dynamic-static strengthening programme seems to be the most appropriate method of restoring the size of the multifidus muscle.

A functional subdivision of hip, abdominal, and back muscles during asymmetric lifting.

STUDY DESIGN: An experimental study of muscle recruitment patterns during asymmetric lifting in healthy individuals. OBJECTIVE: To investigate muscle recruitment patterns during asymmetric lifting, representing a common daily living activity, to determine whether systematic differences exist between functioning of the local and global muscle systems. SUMMARY OF BACKGROUND DATA: The normal function of the local muscle system is to provide sufficient segmental stability to the spine. The global muscle system provides general trunk stabilization and enables the static and dynamic work necessary for daily living and sports activities. Current knowledge about these two muscle groups appears to be specifically derived from anatomic findings and experiments conducted under artificial circumstances. To the authors' knowledge, the recruitment patterns of both muscle groups have not been investigated in daily living activities. METHODS: Twenty-nine healthy individuals performed different variants of asymmetric lifting activities. Electromyographic data were collected from seven hip, abdominal, and back muscle pairs. In addition, trunk kinematics were measured by means of an ultrasonic movement analysis system. RESULTS: The left and right obliquus internus, rectus femoris, and multifidus showed symmetric co-contraction in all variants of activities. In contrast, significant left/right differences were observed in the external oblique, gluteus maximus, iliocostalis lumborum pars thoracis, and latissimus dorsi. CONCLUSIONS: The results of this study show a symmetric activation of the local muscles during the performance of low-load, asymmetric lifting tasks, which suggests that these muscles play a stabilizing role during these manoeuvres. The global muscles, however, hand show asymmetric patterns of activation during the same tasks, supporting their role as global stabilizers and prime movers.

The effects of three different training modalities on the cross-sectional area of the paravertebral muscles.

The purpose of this study was to determine the effect of different training schedules on the cross-sectional area (CSA) of the paravertebral muscles (PA) in chronic low back pain (CLBP) patients. To achieve this goal 59 patients were randomly assigned to three different 10-week rehabilitation programs: stabilization training (group 1, n=19), stabilization training combined with dynamic resistance training (group 2, n=20) and stabilization training combined with dynamic-static resistance training (group 3, n=20). The CSA of the PA was derived from standard computerized tomography (CT) images at three different levels. The CSA of the PA was found to increase statistically in group 2 (upper end-plate of L4) and group 3 (upper end-plate of L3 and lower end-plate of L4). In contrast, no statistical differences over time were found in group 1. Since stabilization exercises have no effect on the CSA of the PA, intensive lumbar resistance training seems to be necessary to restore the size of the PA in CLBP patients with atrophied back muscles. No systematic difference in hypertrophy between dynamic and dynamic-static strengthening training modes was found.

CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects.

Increasing documentation on the size and appearance of muscles in the lumbar spine of low back pain (LBP) patients is available in the literature. However, a comparative study between unoperated chronic low back pain (CLBP) patients and matched (age, gender, physical activity, height and weight) healthy controls with regard to muscle cross-sectional area (CSA) and the amount of fat deposits at different levels has never been undertaken. Moreover, since a recent focus in the physiotherapy management of patients with LBP has been the specific training of the stabilizing muscles, there is a need for quantifying and qualifying the multifidus. A comparative study between unoperated CLBP patients and matched control subjects was conducted. Twenty-three healthy volunteers and 32 patients were studied. The muscle and fat CSAs were derived from standard computed tomography (CT) images at three different levels, using computerized image analysis techniques. The muscles studied were: the total paraspinal muscle mass, the isolated multifidus and the psoas. The results showed that only the CSA of the multifidus and only at the lowest level (lower end-plate of L4) was found to be statistically smaller in LBP patients. As regards amount of fat, in none of the three studied muscles was a significant difference found between the two groups. An aetiological relationship between atrophy of the multifidus and the occurrence of LBP can not be ruled out as a possible explanation. Alternatively, atrophy may be the consequence of LBP: after the onset of pain and possible long-loop inhibition of the multifidus a combination of reflex inhibition and substitution patterns of the trunk muscles may work together and could cause a selective atrophy of the multifidus. Since this muscle is considered important for lumbar segmental stability, the phenomenon of atrophy may be a reason for the high recurrence rate of LBP.

Sensory nerve repair in perforator flaps for autologous breast reconstruction: sensational or senseless?

The spontaneous return of sensation in autologously reconstructed breasts, especially in the Transverse Rectus Abdominis Myocutaneous (TRAM) flap, generated the belief that sensory reinnervation by nerve repair of the flap would be superfluous. This study compares the sensation of the following non-reconstructed and reconstructed breasts: (1) non-operated breasts; (2) flaps of patients reconstructed with the Deep Inferior Epigastric Perforator (DIEP) flap with sensory nerve repair; (3) flaps of patients reconstructed with the Deep Inferior Epigastric Perforator (DIEP) flap without nerve repair; and (4) flaps of patients reconstructed with the free TRAM flap without nerve repair. Statistically significant lower pressure thresholds were found for DIEP flaps with nerve repair through Semmes-Weinstein testing. More segments of the DIEP flaps with nerve repair reacted to cold, warm and vibratory stimuli compared to flaps without nerve repair. Delayed but satisfactory sensory evoked potential responses were obtained for all reconstructed breasts, but in 46% of TRAM flaps no response could be registered compared with 23% and 0% for DIEP flaps without and with nerve repair, respectively. Questionnaires confirmed the objective data and showed return of erogenous sensation in 30% of the patients with DIEP flaps with nerve repair. Our data reconfirm the possibility of spontaneous return of sensation in pedicled and/or free lower abdominal flaps without nerve repair. Nerve repair in free DIEP flaps nevertheless does restore sensation earlier postoperatively, increases the quality and quantity of sensation in the flap and has a higher chance of providing erogenous sensation. The benefits obtained outweigh the disadvantages of the increased operating time.

The fate of the oblique abdominal muscles after free TRAM flap surgery.

During recent years, clinical research on the donor site morbidity after free or pedicled transverse rectus abdominis myocutaneous (TRAM) flap surgery has been focusing on the reduced flexion capacity of the abdominal wall. However, the rectus abdominis muscles have close interactions with their synergists and antagonists and collaborate with their neighbouring muscles. The purpose of this study was to examine the consequences of partially resecting the rectus abdominis muscle on the different muscle groups of the abdominal wall. Twenty free TRAM flap patients, 12-61 months (mean 32.1 months) after surgery, were clinically examined, evaluated for curl-up performance and underwent isokinetic dynamometry for flexion, extension and rotation. The patients were compared with 20 non-operated controls. Nineteen patients answered a questionnaire. Abdominal wall abnormalities occurred in 10 patients: umbilical asymmetry (n = 3), abdominal wall asymmetry (n = 4), lower abdominal bulging (n = 2) and hernia (n = 1). Curl-up performance was less in the TRAM flap patients (P = 0.001, Mann-Whitney). Isokinetic flexion, extension and rotation were also less in the TRAM flap patients (Fisher's exact test). This study indicates that what has been believed to be 'limited' surgical damage to the abdominal wall leads to an important reduction in flexion strength but to an even more important reduction of rotation strength due to bilateral displacement and damage of the insertion of the oblique muscles. Partial compensation by synergists is variable and unpredictable on an individual basis. These functional disorders can potentially lead to important changes in activities of daily life.

The donor site morbidity of free DIEP flaps and free TRAM flaps for breast reconstruction.

This study was undertaken to demonstrate that the deep inferior epigastric perforator (DIEP) flap can provide the well-known advantages of autologous breast reconstruction with lower abdominal tissue while avoiding the abdominal wall complications of the transverse rectus abdominis myocutaneous (TRAM) flap. Eighteen unilateral free DIEP flap breast reconstruction patients were assessed 12-30 months (mean 17.8 months) after surgery. Clinical examination, physical exercises and isokinetic dynamometry were performed preoperatively and two months and one year postoperatively. Intraoperative segmental nerve stimulation, visual evaluation and postoperative CT scans were also used to quantify the damage to the rectus muscle. The 18 patients were then compared with 20 free TRAM flap patients and 20 non-operated controls. Two DIEP flap patients presented with abdominal asymmetry. A limited decrease of trunk flexing strength was noticed but rotatory function was intact. Ten of the TRAM flap patients had umbilical or abdominal asymmetry, bulging or hernias. TRAM flap patients showed a statistically significant reduction in strength to flex and to rotate the upper trunk compared to both the one year postoperative DIEP flap group and the control group. The answers to a questionnaire revealed impairment of activities of daily living for some TRAM flap patients while the activities of all DIEP flap patients were unaffected. Our data demonstrate that the free DIEP flap can limit the surgical damage to the rectus abdominis and oblique muscles to an absolute minimum. We believe it is worthwhile to spend extra operative time, the main disadvantage of this technique, to limit late postoperative weakness of the lower abdominal wall.

Failure of therapeutic ultrasound in healing burn injuries.

Experimental observations suggest that therapeutic ultrasound stimulates wound healing. Despite the controversy concerning its efficiency, this procedure is commonly implemented. To study the effect of this treatment in burns, we conducted a randomized control trail in 20 Fischer rats. Two groups of 10 animals each were studied, In group 1 the experimental burn was treated with pulsed ultrasound (SATA 0.25 W/cm2), in group 2 with continuous ultrasound (0.3 W/cm2). No stimulating effect of ultrasound could be demonstrated in these two groups, monitored by histological examination and a size index. These results discourage the clinical administration of therapeutic ultrasound to enhance the healing of burns.

Motor evoked potentials of the respiratory muscles in tetraplegic patients.

We studied the respiratory muscles with magnetic transcranial stimulation (TCS) in four spinal cord injured (SCI) patients as compared to age-matched controls from a database of 40 healthy subjects. These SCI patients all had spinal cord lesions above C6 level with a clinically incomplete tetraplegia. One patient was artificially ventilated. Motor evoked potentials (MEPs) were recorded from the diaphragm, the scalenes, the parasternal intercostals and the expiratory rectus abdominis during inspiration and expiration. In patients with incomplete tetraplegia MEP latency times were significantly prolonged in the scalenes and the parasternal intercostals, both during inspiration and expiration, and were nearly normal for the diaphragm, which was found to be more or less preserved. The mean MEP amplitudes in these patients for all inspiratory muscles studied were significantly decreased in tetraplegic patients, in part due to a decreased number of innervating axons and muscle hypotrophy. No MEPs could be obtained from the abdominal muscles, except in one C3 tetraplegic patient, in whom only a very small response was seen during expiration, with a very delayed latency time. The much lower location of their innervating nerve roots (T10) and the much longer distance of their spinal exit zone from the level of injury at the cervical spinal cord might at least partially explain this phenomenon. In the ventilator-dependent tetraplegic patient no MEPs could be obtained from any of the muscles studied. Thus, magnetic TCS is a painless and easily applicable technique to investigate the central motor conduction properties of the respiratory muscles, both in healthy humans and in tetraplegic patients.

Sufentanil and nitrous oxide anaesthesia for the recording of transcranial magnetic motor evoked potentials in dogs.

Transcranial magnetic motor evoked potentials were recorded from the extensor carpi radialis muscle of the forelimbs and from the cranial tibial muscle of the hindlimbs of anaesthetised dogs. The dogs were premedicated with droperidol and fentanyl and a light plane of anaesthesia was induced and maintained with sufentanil and nitrous oxide. The potentials recorded under sufentanil and nitrous oxide anaesthesia were suppressed in comparison with baseline recordings under droperidol and fentanyl sedation: their latencies were significantly increased and their amplitudes significantly decreased (P < 0.05). However, the potentials could be recorded reliably in all the dogs and with very good reproducibility. This narcotic anaesthesia also allowed sensory evoked potentials to be recorded reliably.

Low-power laser and healing of burns: a preliminary assay.

A randomized preliminary study of 20 female Fischer rats was conducted to assess the effect of laser on healing in burns. Clinical use for this purpose seemed to be widely accepted and implemented, despite the few substantiating research reports. Two burns were inflicted on each animal; one was treated, and the other was left untreated. Two groups of 10 animals each were randomly organized. In group 1, the experimental burn was treated with a helium-neon laser; in group 2, with a gallium- arsenide laser. In neither group could any major stimulating effect be demonstrated on the basis of observation and a size index. The low statistically significant smaller size index in group 1 on day 20, in comparison with the controls, is intriguing but is of no relevance in view of the complete healing process. The practical feasibility and the weak differential power arouse doubts about the effectiveness of laser for this matter.

Comparison of two techniques of narcotic-induced anesthesia for use during recording of magnetic motor evoked potentials in dogs.

OBJECTIVE: To compare 2 types of narcotic-induced anesthesia for recording of transcranial magnetic motor evoked potentials (TMMEP) in dogs. DESIGN: The effect of different doses of sufentanil and midazolam and of sufentanil and nitrous oxide on onset latencies and peak-to-peak, amplitudes of TMMEP was evaluated and compared. ANIMALS: 18 neurologically normal dogs. PROCEDURE: Premedication with droperidol and fentanyl. Induction and maintenance of anesthesia either with sufentanil and midazolam or with sufentanil and nitrous oxide. Recording of TMMEP from the extensor carpi radialis muscle of the forelimb and from the cranial tibial muscle of the hind limb. RESULTS: Both types of narcotic anesthesia induced dose-dependent suppression of TMMEP; compared with baseline recordings, latencies increased, amplitudes decreased, and reproducibility became poorer with increasing dose of the anesthetics. Using surgical-depth doses of the anesthetics, TMMEP could still be recorded in all dogs with sufentanil and nitrous oxide, but not with sufentanil and midazolam anesthesia. CONCLUSIONS: Sufentanil and nitrous oxide anesthesia was superior to sufentanil and midazolam anesthesia for TMMEP recording. CLINICAL RELEVANCE: In small animal medicine, and in dogs in particular, spinal cord diseases are among the most frequently encountered neurologic disorders. The development of techniques for recording TMMEP in anesthetized dogs allows noninvasive evaluation of transmission along descending motor pathways of the spinal cord.