The magnitude of intramuscular deoxygenation during exercise is an unreliable measure to diagnose the cause of leg pain.

We measured intramuscular oxygenation in the anterior tibial muscle of 176 patients with exercise-induced leg pain by noninvasive near-infrared spectroscopy before, during, and after an exercise test that elicited the symptoms. Clinical investigation was performed after each test. Intramuscular pressure was measured in patients with nonconclusive findings. Chronic anterior compartment syndrome (CACS) was diagnosed in 47 patients, and other causes for the leg pain were diagnosed in 129 patients by clinical means. The mean level of oxygenation decreased to 33 ± 19% in patients with CACS and to 34 ± 19% in patients without CACS compared with baseline level (100%) at rest before exercise. The level of oxygenation was below 20% during the exercise test in 12 of 47 (26%) patients with CACS and in 30 of 129 (23%) patients without CACS. The time required for reoxygenation after the cessation of exercise was 61 ± 34 s in patients with CACS and 46 ± 20 s in patients without CACS (P < 0.05). We conclude that the magnitude of intramuscular deoxygenation during exercise is an unreliable measure to diagnose CACS. However, the time for reoxygenation returning to baseline level following an exercise test is a valuable adjunct in diagnosing CACS.

Simultaneous intramuscular pressure and surface electromyography measurement in diagnosing the chronic compartment syndrome.

We investigated the value of surface electromyography (EMG) as an aid to diagnosing the chronic compartment syndrome (CCS) by detecting elevated intramuscular pressure (IMP) at rest after an exercise test that was caused by remaining muscle contraction. IMP and EMG were measured in the anterior tibial muscle in 37 patients who were suspected to have CCS after an exercise test. At rest after the test, the EMG signal was positive in five of 37 (14%) patients, indicating that patients had remaining muscle contractions that elevated IMP. IMP exceeded 30 mmHg in 16 of 37 patients (43%). In 13 of these 16 patients, the EMG signal was silent, confirming that they had CCS. In the remaining three patients, the EMG signal was initially positive (5-34% of maximal voluntary contraction), and then became silent after communicating with the patients to relax their legs. Only one of the three patients was proven to have CCS. Other reasons for leg pain were diagnosed in 23 patients. The results demonstrated that simultaneous measurements of IMP and EMG differentiate elevated IMP at rest after exercise due to the volumetric load of the compartment muscles seen in patients with CCS and due to the remaining muscle contraction, thereby preventing a false diagnosis of CCS.

Transcapillary fluid shifts in tissues of the head and neck during and after simulated microgravity.

To understand the mechanism, magnitude, and time course of facial puffiness that occurs in microgravity, seven male subjects were tilted 6 degrees head-down for 8 h, and all four Starling transcapillary pressures were directly measured before, during, and after tilt. Head-down tilt (HDT) caused facial edema and a significant elevation of microvascular pressures measured in the lower lip: capillary pressures increased from 27.7 +/- 1.5 mmHg (mean +/- SE) pre-HDT to 33.9 +/- 1.7 mmHg by the end of tilt. Subcutaneous and intramuscular interstitial fluid pressures in the neck also increased as a result of HDT, whereas interstitial fluid colloid osmotic pressures remained unchanged. Plasma colloid osmotic pressure dropped significantly by 4 h of HDT (21.5 +/- 1.5 mmHg pre-HDT to 18.2 +/- 1.9 mmHg), suggesting a transition from fluid filtration to absorption in capillary beds between the heart and feet during HDT. After 4 h of seated recovery from HDT, microvascular pressures in the lip (capillary and venule pressures) remained significantly elevated by 5-8 mmHg above baseline values. During HDT, urine output was 126.5 ml/h compared with 46.7 ml/h during the control baseline period. These results suggest that facial edema resulting from HDT is caused primarily by elevated capillary pressures and decreased plasma colloid osmotic pressures. The negativity of interstitial fluid pressures above heart level also has implications for maintenance of tissue fluid balance in upright posture.

Intramuscular pressure and electromyography as indexes of force during isokinetic exercise.

A direct method for measuring force production of specific muscles during dynamic exercise is presently unavailable. Previous studies indicate that both intramuscular pressure (IMP) and electromyography (EMG) correlate linearly with muscle contraction force during isometric exercise. The objective of this study was to compare IMP and EMG as linear assessors of muscle contraction force during dynamic exercise. IMP and surface EMG activity were recorded during concentric and eccentric isokinetic plantarflexion and dorsiflexion of the ankle joint from the tibialis anterior (TA) and soleus (SOL) muscles of nine male volunteers (28-54 yr). Ankle torque was measured using a dynamometer, and IMP was measured via catheterization. IMP exhibited better linear correlation than EMG with ankle joint torque during concentric contractions of the SOL (IMP R2 = 0.97, EMG R2 = 0.81) and the TA (IMP R2 = 0.97, EMG R2 = 0.90), as well as during eccentric contractions (SOL: IMP R2 = 0.91, EMG R2 = 0.51; TA: IMP R2 = 0.94, EMG R2 = 0.73). IMP provides a better index of muscle contraction force than EMG during concentric and eccentric exercise through the entire range of torque. IMP reflects intrinsic mechanical properties of individual muscles, such as length-tension relationships, which EMG is unable to assess.

Evaluation of injection techniques in recording of intramuscular pressure.

Recording of intramuscular pressure by using the injection technique in different ways has been evaluated in 12 healthy subjects and 12 patients with medial tibial syndrome. Pressure recording with an injection needle was compared to the recording by a Teflon catheter with multiple side holes at its tip. Following an injection of 0.07 ml, the intramuscular pressure was significantly higher when it was recorded with the injection needle. Pressure recorded with an injection needle by the "meniscus method" was found to be significantly closer to the preinjection pressure compared to the injection technique described by Whitesides et al. Pressure readings by the "meniscus method" after injection, and by a catheter or needle with multiple side holes, decrease the drawbacks of the injection technique.

Effects of isokinetic muscle activity on pressure in the supraspinatus muscle and shoulder torque.

Work-related shoulder pain is an increasing problem. Work in overhead positions, which causes high pressure in the supraspinatus muscle, has been shown to increase the shoulder load. It is not known how different types of muscle activity in the shoulder affect pressure in the muscle. The aim of this study was to investigate the difference between contraction modes. This has not been done before for shoulder muscles. The results are relevant from several aspects, both clinical and experimental. Pressure in the supraspinatus muscle and torque generation in the shoulder during isokinetic concentric and eccentric activity were measured in nine healthy human subjects. Torque and arm position were measured continuously with a computerized ergonometer. The contraction velocity was 60 degrees per second, and the range of movement was 0-120 degrees of abduction. Electromyographic measurements were recorded with a surface electrode above the supraspinatus muscle belly. Intramuscular pressure was recorded with a microcapillary infusion technique. Peak intramuscular pressure did not differ significantly between the two modes of contraction, but the peak was reached at 115 degrees (SD = 15 degrees) of abduction during concentric activity and at 6 degrees (SD = 7 degrees) of abduction during eccentric activity. The ratio between intramuscular pressure and torque was 3.0 mm Hg/Nm (0.40 kPa/Nm) during concentric activity and 2.3 mm Hg/Nm (0.31 kPa/Nm) during eccentric activity. The peak torque occurred at 44 degrees of abduction during concentric muscle activity and at 74 degrees of abduction during eccentric activity. Intramuscular pressure was higher during isometric contraction than during eccentric and concentric activity, and the torque was in between the two latter contraction modes. We conclude that the supraspinatus muscle is heavily loaded not only in high arm positions during concentric contraction but also during eccentric contraction in arm positions of 0-30 degrees of abduction.

Pressure recording in the subacromial bursa.

The microcapillary infusion (MCI) technique was evaluated in monitoring pressure in the subacromial bursa in 30 shoulders in healthy volunteers. The total pressure in the bursa was studied as the volunteers held their arms at rest and as they lifted their arms and held them lifted with or without a weight of 1 kg in the hands. The pressure in the bursae at rest averaged 8 mm Hg and was found stable during a 40-min period. When the arms were lifted, the average bursa pressure increased from 8 to 39 mm Hg. As the arms were held up, the weights were put in the hands, and the average bursa pressure then further increased to 56 mm Hg. When the infusion catheters were repeatedly flushed, during a period of 5 min and with a total of 1.2 ml of saline, the average bursa pressure doubled regardless of arm position and load in the hands. The compliance of the bursae decreased from 0.09 to 0.04 ml/mm Hg when the arms were lifted and from 0.04 to 0.02 ml/mm Hg when the arms were lifted and the hands were loaded. The MCI method was found suitable for recording pressure in the subacromial bursa during exercise.

Intramuscular pressure in the supraspinatus muscle.

Shoulder pain correlated to manual labour is an increasing problem. The etiology is multifactorial and often unclear. High local muscle load and muscle ischemia in the supraspinatus muscle is present in elevated arm positions, as shown in several electromyographic studies. The purpose of this study was to evaluate intramuscular pressure (IMP) as a way to describe local muscle load in the supraspinatus muscle. Measurements were made in 15 arm positions, and with hand loads of 0, 1, or 2 kg weight, in 12 shoulders. The IMP was recorded with microcapillary infusion technique. The method was found to be suitable in recording IMP at rest and during exercise. High intramuscular pressures, i.e., above 50 mm Hg (6.7 kPa), were seen in moderate humeral abduction. The IMP increased further in abduction up to 90 degrees, where mean IMP was 122 mm Hg (16.2 kPa). Added hand load increased intramuscular pressure in all positions except in shoulder flexion of 135 degrees. The study thus demonstrated that intramuscular pressure offers important information about the load on the supraspinatus muscle in different positions of the arm. The results indicate that fatigue and shoulder pain related to elevated arm positions may be caused by muscle ischemia induced by the high intramuscular pressure present in these positions.

A new "transducer-tipped" fiber optic catheter for measuring intramuscular pressures.

Laboratory and clinical tests were used to determine the efficacy of a new fiber optic "transducer-tipped" catheter for measuring intramuscular pressures. When pressures ranging from 0 to 250 mm Hg were applied by a mercury manometer, the fiber optic system accurately recorded the pressures. In addition, the fiber optic system showed long-term stability by accurately recording the manometer pressure over a 3 day period. The Slit system showed a higher magnitude of hydrostatic pressure artifacts with catheter tip movement as compared to the fiber optic system. The two catheters showed no difference when measuring pressures in pig muscle at rest or when being compressed throughout a range of 0 to 250 mm Hg. In human volunteers, both catheters measured essentially equal pressures at rest, during venous stasis, and during a combination of venous stasis and compression. For long-term assessment, the Slit system required as many as three saline flushes, whereas the fiber optic system measured pressures continuously without manipulation. We conclude that the fiber optic system is as accurate as the Slit catheter for measuring tissue fluid pressures at rest. In addition, the fiber optic system offers distinct advantages over conventional fluid-filled systems for measuring intramuscular pressures due to a lack of hydrostatic pressure artifacts caused by limb position and to the lack of flushing for long-term measurements.

Chronic exercise-induced pain in the anterior aspect of the lower leg. An overview of diagnosis.

Clinical examination following an exercise test that elicits the symptoms of lower leg pain is most helpful in diagnosing the causes. Location of swelling, pain, impaired muscle function and impaired nerve function should all be analysed. History and clinical signs alone are insufficient to establish the diagnosis of chronic anterior compartment syndrome, and for this reason intramuscular pressure recordings have an important role in diagnosis. Different techniques for pressure recording and different pressure parameters are reviewed. Muscle relaxation pressure during exercise and intramuscular pressure at rest after exercise are the best parameters to study. Fasciotomy relieves pain in between 60% and 100% of patients. Closure of a fascial defect is never indicated, because it decreases the compartment size and may precipitate an acute compartment syndrome. Recording of nerve conduction velocity is a helpful complement in the diagnosis and evaluation of superficial peroneal nerve compression. Decompression by local fasciectomy and fasciotomy of the lateral compartment gives good results in more than 50% of patients. The value of periostitis as a clinical sign and the possibility of chronic pain following eccentric exercise are discussed.

The effects of functional knee bracing on muscle function and performance.

When applied, knee braces compress the soft tissues of the thigh and leg. External compression may abnormally elevate intramuscular pressure beneath the straps of the knee brace, decrease local muscle blood flow and muscular oxygenation, and induce premature muscle fatigue. Functional knee braces may give valuable support to athletes with unstable knees. They may also be a valuable rehabilitative tool in patients following surgery for knee joint instability. However, prophylactic and functional knee braces do not improve performance and may even inhibit performance in asymptomatic athletes. Athletes and coaches should be aware of the serious adverse effects of knee bracing.

Chronic anterior-compartment syndrome of the leg. Results of treatment by fasciotomy.

Thirty legs in nineteen patients, eleven with bilateral and eight with unilateral chronic anterior-compartment syndrome, were treated by fasciotomy. In addition, five of these patients (six legs) had compression of the superficial peroneal nerve: two before and three after fasciotomy. One patient also had lateral compartment syndrome in one leg. The patients who had compression of the superficial peroneal nerve were relieved by partial fasciectomy and fasciotomy of the lateral compartment. In one of these patients, with bilateral nerve compression, both superficial peroneal nerves were anomalous. The patient who had lateral compartment syndrome was relieved by fasciotomy of this compartment. Two patients required a second fasciotomy due to recurrence of the chronic compartment syndrome. At an average length of follow-up of twenty-five months after fasciotomy for anterior compartment syndrome, functional capacity was unlimited or increased in eighteen patients (twenty-eight legs) and was unchanged in one patient (two legs) who had had compression of the superficial peroneal nerve. The intramuscular pressures in the anterior compartment were normal at rest as well as during and after exercise eight months after the original fasciotomy in twenty-eight legs and eight months after the second fasciotomy in two legs.

Effect of ankle position and a plaster cast on intramuscular pressure in the human leg.

Intramuscular pressure was measured with transducer-tipped catheters that had been inserted into the anterior and deep posterior compartments of the leg in seven healthy adults. Intramuscular pressure increased three to sevenfold (depending on the position of the ankle) in both compartments after the application of a plaster cast from the proximal part of the thigh to the malleoli. While the cast was in place, the baseline intramuscular pressure was elevated by the inflation of a tourniquet, which was located on the proximal part of the thigh, to a pressure of sixty millimeters of mercury (8.00 kilopascals). The intramuscular pressure in both the anterior and the deep posterior compartments was found to be lowest when the ankle joint was between the neutral and the resting positions (between 0 and 37 degrees of flexion). After the cast was bivalved and the opening on each side was spread approximately one-half centimeter, there was a significant decrease in intramuscular pressure of 47 per cent in the anterior compartment and of 33 per cent in the deep posterior compartment (p < 0.05 for both).

Intramuscular deoxygenation during exercise in patients who have chronic anterior compartment syndrome of the leg.

Currently, the definitive diagnosis of chronic compartment syndrome is based on invasive measurements of intracompartmental pressure. We measured the intramuscular pressure and the relative oxygenation in the anterior compartment of the leg in eighteen patients who were suspected of having chronic compartment syndrome as well as in ten control subjects before, during, and after exercise. Chronic compartment syndrome was considered to be present if the intramuscular pressure was at least fifteen millimeters of mercury (2.00 kilopascals) before exercise, at least thirty millimeters of mercury (4.00 kilopascals) one minute after exercise, or at least twenty millimeters of mercury (2.67 kilopascals) five minutes after exercise. Changes in relative oxygenation were measured with use of the non-invasive method of near-infrared spectroscopy. In all patients and subjects, there was rapid relative deoxygenation after the initiation of exercise, the level of oxygenation remained relatively stable during continued exercise, and there was reoxygenation to a level that exceeded the pre-exercise resting level after the cessation of exercise. During exercise, maximum relative deoxygenation in the patients who had chronic compartment syndrome (mean relative deoxygenation [and standard error], -290 +/- 39 millivolts) was significantly greater than that in the patients who did not have chronic compartment syndrome (-190 +/- 10 millivolts) and that in the control subjects (-179 +/- 14 millivolts) (p < 0.05 for both comparisons). In addition, the interval between the cessation of exercise and the recovery of the pre-exercise resting level of oxygenation was significantly longer for the patients who had chronic compartment syndrome (184 +/- 54 seconds) than for the patients who did not have chronic compartment syndrome (39 +/- 19 seconds) and the control subjects (33 +/- 10 seconds) (p < 0.05 for both comparisons).

Pressure in the erector spinae muscle during exercise.

The microcapillary infusion method was evaluated in recording intramuscular pressure during isometric and concentric exercise of the erector spinae muscle. Intramuscular pressure at rest was 6.1 (SD = 1.4) mm Hg without infusion and 8.3 with an infusion rate of 1.5 ml/hour. When the subject experienced muscle fatigue during exercise, the muscle relaxation pressure had increased to 14 mm Hg. The erector spinae muscle was found to be heavily loaded during exercise with an average muscle contraction pressure of 175 mm Hg. Recording of intramuscular pressure in the erector spinae muscle during exercise tests can be an additional method in the study of ergonomics and biomechanics of the spine as well as in the diagnosis of chronic compartment syndrome in this muscle.

Chronic compartment syndrome in the erector spinae muscle.

Intramuscular pressure in the erector spinae muscle was measured during exercise with the microcapillary infusion method in 12 highly selected patients with recurrent low-back pain. The criteria for selection were low-back pain induced only by exercise, relief of symptoms at rest, and no neurologic deficits in the lower extremities. During a 4-year period, 12 patients fulfilled these criteria. One patient had a unilateral chronic compartment syndrome. Fasciotomy of the erector spinae muscle normalized the intramuscular pressure during exercise and at rest after exercise, and relieved the pain. All the other patients with chronic low-back pain had normal intramuscular pressure findings. Chronic compartment syndrome in the erector spinae muscle seems to be an extremely uncommon cause of exercise-induced low-back pain.

The effects of external compression by three different retractors on pressure in the erector spine muscles during and after posterior lumbar spine surgery in humans.

STUDY DESIGN: An experimental study on patients undergoing posterior lumbar spine surgery. OBJECTIVES: To study the relation between external compression and muscle strain induced by spinal retractors and intramuscular pressure in the dorsolumbar compartment during posterior spinal surgery. SUMMARY OF BACKGROUND DATA: Pressures were studied as a function of the distance between the retractor blades during surgery. METHODS: Intramuscular pressure was measured bilaterally in the erector spinae muscle with intermittent microcapillary infusion technique in 12 patients undergoing posterior lumbar spine surgery during 271 (range 90-420) minutes. Three self-retaining retractors were tested; the McCulloch, the Viking, and the Richard retractors. RESULTS: Intramuscular pressure was 7.7 mm Hg before surgery. It varied between 35 mm Hg and 69 mm Hg during surgical exposure of the laminas and facet joints. Intramuscular pressure varied between 61 mm Hg and 158 mm Hg depending on which retractor was used and on the distance between the retractor blades. Intramuscular pressure never exceeded 30 mm Hg at rest after the operation. CONCLUSIONS: External compression and muscle strain from retractor blades during surgery increased intramuscular pressure in the paravertebral muscles to levels that, according to other studies, induce ischemia in the muscles.

Early active training after lumbar discectomy. A prospective, randomized, and controlled study.

STUDY DESIGN: A prospective, randomized, and controlled study was conducted. OBJECTIVES: To evaluate two training programs, both of which started immediately after lumbar discectomy. SUMMARY OF BACKGROUND DATA: In previous studies, patients began physiotherapy between 4 weeks and 60 months after surgery. No studies have been conducted to evaluate a physiotherapy program that begins immediately after surgery. METHOD: Twenty-six patients were treated according to an early active training program. Twenty-six patients were treated with a traditional, less active training program (control group). All patients were examined immediately before and after surgery and 3, 6, 12, and 52 weeks after surgery by an unbiased observer. Two years after surgery, patients completed a questionnaire. Range of motion of the lumbar spine and straight leg raising were measured. pain intensity and location was measured by a visual analog scale. The duration of sick leave was documented. RESULTS: Six and 12 weeks after surgery, patients with dominating residual leg pain had significantly less intense pain in the early active training group than those in the control group (P < 0.05). Twelve weeks after surgery, range of motion of the lumbar spine was significantly more increased in the early active training group (P < 0.01). One year after surgery, there was no significant difference between the groups regarding the duration of sick leave, results in a positive straight leg raising, or pain intensity. Twenty-two (88%) patients in the early active training group and 16 (67%) in the control group were satisfied with the treatment outcome 2 years after surgery (P < 0.10). CONCLUSIONS: Patients rehabilitated according to the early active training program had a better short-term outcome of objective values. At 2 years' follow-up, more patients were satisfied with the result of the operation. The early active treatment program is recommended.

Back muscle injury after posterior lumbar spine surgery. Topographic evaluation of intramuscular pressure and blood flow in the porcine back muscle during surgery.

STUDY DESIGN: Intramuscular pressure and blood flow of the back muscles were evaluated topographically during posterior lumbar spine surgery. The topographic damage of the back muscle after surgery was studied. OBJECTIVE: To investigate the relationship between intramuscular pressure or blood flow during posterior lumbar surgery and the back muscle injury after surgery. SUMMARY OF BACKGROUND DATA: Latrogenic back muscle injury in an animal and human model has been reported previously. Changes of intramuscular pressure and blood flow during surgery might be related to the muscle injury. No previous study on this issue has been published. METHODS: The contact pressure between the retractor blade and muscle tissue was monitored in 10 pigs during posterior surgery of the lumbar spine. On one side, intramuscular pressure at 5, 10, and 20 mm lateral to the retractor and on the other side blood flow of the back muscle at 5 and 20 mm during surgery were measured. Histologic changes of the back muscle at 5, 10, and 20 mm to the midline were evaluated 3 hours after surgery. RESULTS: The contact pressure decreased exponentially with time. Intramuscular pressure 5 mm lateral to the retractor was 114 +/- 31 mm Hg and was significantly higher than at 10 mm and 20 mm. Blood flow markedly decreased during surgery and recovered incompletely after releasing the retractor at 5 mm and 20 mm lateral to the retractor. Blood flow at 5 mm was significantly lower than at 20 mm throughout surgery. The muscle damage 3 hours after surgery was more severe near the retractor blade. CONCLUSIONS: The back muscles were exposed to pathophysiologic condition by a retractor during posterior lumbar spine surgery. External compression by a retractor increases intramuscular pressure to levels that impede local muscle blood flow. The muscle degeneration after surgery could be explained by direct mechanical damage and by the increased intramuscular pressure of muscle tissue by the retractor.

Diagnosis of exercise-induced pain in the anterior aspect of the lower leg.

Ninety-eight patients with chronic exercise-induced pain in the anterior compartment of the lower leg underwent extensive clinical and laboratory investigations to establish the diagnosis. They all were referred because of a putative chronic compartment syndrome (CCS). Intramuscular pressure was recorded bilaterally during exercise in the anterior tibial muscle in all of them. Conduction-velocity recordings of the deep and superficial peroneal nerves were performed in 29 patients. Other investigations included radiography, plethysmography, and scintigraphy. CCS was diagnosed in 26 of the 98 patients. Other diagnoses included periostitis in 41 patients, compression of the superficial peroneal nerve in 13, and miscellaneous other diagnoses in 18. CCS seems to be an uncommon reason for anterior pain in the lower legs.