Bed design and its effect on chronic low back pain--a limited controlled trial.

This study examines the effect of 4 different types of beds on chronic low back pain patients' symptoms and signs. The beds employed were an "orthopedic" hard bed with 720 reinforced coils and a built-in bed board, a softer 500 coil bed, a standard 10 in. thick waterbed, and a hybrid bed of foam and water. Subjectively the majority of patients preferred the hard bed and felt that their back pain improved to a greater extent after 2 weeks on the hard bed as compared to the other beds. The next largest group of patients to show improvement used the waterbed. Limitations in performing the straight leg raising test coincided with the subjective complaints. Significantly improved straight leg raising was observed after use of the hard bed or waterbed in 25% of the patients using those beds. No other objective signs were altered. The 500 coil bed and the hybrid bed proved of no benefit to any patient in this study group. This limited study indicates that hard beds should remain the first choice of patients with chronic low back pain. However, if relief is not obtained for these chronic pain patients, a trial on a waterbed may prove beneficial.

Effects of noradrenergic and serotonergic antidepressants on chronic low back pain intensity.

To understand the relative efficacy of noradrenergic and serotonergic antidepressants as analgesics in chronic back pain without depression, we conducted a randomized, double-blind, placebo-control head-to-head comparison of maprotiline (a norepinephrine reuptake blocker) and paroxetine (a serotonin reuptake blocker) in 103 patients with chronic low back pain. Of these 74 completed the trial; of the 29 who did not complete, 19 were withdrawn because of adverse effects. The intervention consisted of an 8-week course of maprotiline (up to 150 mg daily) or paroxetine (up to 30 mg daily) or an active placebo, diphenhydramine hydrochloride (up to 37.5 mg daily). Patients were excluded for current major depression. Reduction in pain intensity (Descriptor Differential Scale scores) was significantly greater for study completers randomized to maprotiline compared to placebo (P=0.023), and to paroxetine (P=0.013), with a reduction of pain by 45% compared to 27% on placebo and 26% on paroxetine. These results suggest that at standard dosages noradrenergic agents may provide more effective analgesia in back pain than do selective serotonergic reuptake inhibitors.

Negative and positive cognition in depressed and nondepressed chronic-pain patients.

Several studies have suggested that depressed pain patients evidence more cognitive distortion than nondepressed pain patients and healthy controls. Although these studies have generally supported notions relating cognitive distortion to depressive functioning, other aspects of dysfunctional cognition have not been assessed in the chronic-pain population. The present study examined negative and positive automatic thoughts and attributional style in depressed pain patients, nondepressed pain patients, and healthy controls. Depressed chronic-pain patients were found to exhibit significantly more negative automatic thoughts than nondepressed pain patients and healthy controls. Conversely, nondepressed chronic-pain patients reported significantly more positive automatic thoughts than did depressed patients and healthy controls. No significant differences were found for attributional style. These results suggest that different cognitive-behavioral interventions might be considered for depressed compared to nondepressed chronic-pain patients.

Reliability after repeated use of a torque screwdriver employed for halo pin fixation.

It has been recommended that halo torque screwdrivers be used only once. To determine if this advice is justified on biomechanical grounds, five commercially available torque screwdrivers were cycled 1,600 times each in an Instron testing machine over a 7-day period. The screwdrivers displayed an initial error from the dial reading at both 6 and 10 in-lb of only +/- 0.3 in-lb. After cyclic loading and retesting, the percent deviation from original calibration was 8% at both 6 and 10 in-lb. These data demonstrate the accuracy and dependability of the torque screwdrivers and imply that repeated use of these devices should be safe.

An in vitro mechanical and histological study of acute stretching on rabbit tibial nerve.

Peripheral nerves are often mechanically stretched in association with trauma to extremities, resulting in varying degrees of impairment of nerve function. However, little is known about the biomechanical properties of peripheral nerves and limits of stretching that the nerve may undergo before structural changes occur. Also, the injury pattern of nerves under stretching is poorly understood. In the present study, fresh rabbit tibial nerves (n = 18) were harvested. Nine nerves were stretched to failure in an INSTRON materials testing machine at a rate of 1 cm/min (strain rate of 0.5%/s). Load-deformation and stress-strain curves were determined. Histological examination by light microscopy of the stretched nerves as well as six normal control nerves and three clamped nonstretched control nerves was performed. The results show that the rabbit tibial nerves have an in situ strain of 11.0 +/- 1.5% and exhibit a nonlinear stress-strain relationship. After 20% strain, the curve becomes linear up to failure. The ultimate strain and tensile strength of the nerves were 38.5 +/- 2.0% and 11.7 +/- 0.7 MPa, respectively. At failure, the load dropped suddenly, but the specimens remained grossly intact. Histological analysis of the stretched nerves showed multiple ruptures of perineurial sheaths when compared to controls.

A new technique for the in vitro measurement of nucleus pulposus swelling pressure.

Swelling of the intervertebral disc nucleus pulposus may be a contributing factor in lower back pain syndromes. We have designed and tested a new osmometer for in vitro determination of nucleus pulposus swelling pressure. The functional principle of the osmometer involves compressing a sample of nucleus pulposus with nitrogen gas until saline pressure gradients across a 0.45-micron Millipore filter are eliminated. Swelling pressures of both pooled dog and pooled pig lumbar disc nucleus pulposus were measured on the new osmometer and were compared with swelling pressure determined using the equilibrium dialysis technique. The osmometer measured swelling pressures comparable to those obtained by the dialysis technique. This osmometer provides a rapid, direct, and accurate measurement of swelling pressure of the nucleus pulposus.

Kappa Delta Award paper. Tissue fluid pressures: from basic research tools to clinical applications.

The two basic research tools developed to measure tissue fluid pressure (wick catheter) and osmotic pressure (colloid osmometer) have undergone extensive validation and refinement over the past 20 years. Using these techniques, basic science investigations were undertaken of edema in Amazon reptiles, pressure-volume relations in animals and plants, adaptive physiology of Antarctic penguins and fishes, edema in spawning salmon, tissue fluid balance in humans under normal conditions and during simulated weightlessness, and orthostatic adaptation in a mammal with high and variable blood pressures--the giraffe. Following and sometimes paralleling this basic research have been several clinical applications related to use of our colloid osmometer and wick technique. Applications of the osmometer have included insights into (a) reduced osmotic pressure of sickle-cell hemoglobin with deoxygenation and (b) reduced swelling pressure of human nucleus pulposus with hydration or certain enzymes. Clinical uses of the wick technique have included (a) improvement of diagnosis and treatment of acute and chronic compartment syndromes, (b) elucidation of tissue pressure thresholds for neuromuscular dysfunction, and (c) development of a better tourniquet design for orthopaedics. This article demonstrates that basic research tools open up areas of basic, applied, and clinical research.

Rattlesnake bites and surgical decompression: results using a laboratory model.

Studies were performed on the hind limbs of dogs and their anterolateral compartments to evaluate the effect of fasciotomy on tissue pressure and necrosis following pit viper envenomation. Venom from the southern Pacific rattlesnake, Crotalus viridis helleri, was injected into either the subcutaneous tissues, the intact anterolateral compartment or the anterolateral compartment following fasciectomy. Interstitial fluid pressure measurements, as well as limb girth and surface temperatures, were obtained over the first 48 hr following venom injection, after which time the compartment contents were examined microscopically. The results demonstrated intracompartment tissue pressure elevations only following intracompartment injections. Fasciectomy prior to injection did not prevent muscle necrosis, though it did reduce maximum compartment pressures. Clinically the limbs in each group could not be differentiated. Intracompartment pressure measurements were able to distinguish between muscle and subcutaneous envenomations by the differences in compartment pressures. These results demonstrate the value of tissue pressure measurements in the evaluation of patients envenomated by rattlesnakes. They also indicate the objectivity necessary to determine the need for surgical decompression.

The effect of antivenin on intramuscular pressure elevations induced by rattlesnake venom.

The dose of an antivenin required to neutralize a clinical case of venom poisoning, as well as determining the timing or need to initiate antivenin treatment, is frequently difficult to objectively ascertain. In this study, venom from the southern Pacific rattlesnake, Crotalus viridis helleri, was injected into 29 dog hind limb anterolateral compartments. A solution of C. v. helleri venom (15 mg/ml) was prepared using dessicated venom and saline; 0.2 ml were injected sub-fascially so that each of the compartments received 3 mg of venom. In one group no antivenin was given, in a second group four vials of antivenin were administered i.v. 1 hr post-injection, and in the final group eight vials of antivenin were administered i.v. 1 hr following venom injection. In all groups intracompartment pressures, limb girth and surface temperature were measured at regular intervals over the first 48 hr. In the group receiving eight vials of antivenin the intracompartment pressure reached a peak mean pressure of 49 mm Hg at 2 - 4 hr, and then rapidly fell. In those treated with none or four vials the pressure rose to 70 and 60 mm Hg, respectively, and remained elevated over the first 24 hr. The difference between the former and latter two groups is statistically significant. The findings indicate that the intracompartmental pressure, and presumably destructive damage of the venom, can be controlled by adequate levels of i.v. antivenin. Intracompartmental pressure measurements should be considered as an adjunct in the monitoring and decision-making processes for the treatment of patients bitten by rattlesnakes.

The effect of pin location on the rigidity of the halo pin-bone interface.

Optimal insertion of halo fixation pins to maximize the rigidity of the interface between the halo pins and the outer table of the skull is important in reducing the incidence of pin loosening. An in vitro biomechanical study was performed using cadaver skulls to investigate the effects of pin location on the rigidity of this pin-bone interface. Halo pins were inserted at nine positions within a recommended "safe zone" for pin insertion. It was found that the rigidity of the pin-bone interface progressively decreased as pins were inserted more superiorly on the calvaria. The rigidity of the interface did not change significantly when the location of the pins was varied in the horizontal axis. This reduction in interface rigidity associated with inserting pins more superiorly on the skull may be related to an increase in the angle of insertion of the pins with respect to the surface of the calvaria. Based on this study, a change in the technique of halo pin insertion is recommended. Pins should be placed as inferiorly as possible, close to the supraorbital ridge, to achieve the most perpendicular angle of insertion and thus the most rigid fixation. The improved rigidity obtained with perpendicular pin insertion may minimize the rate of pin loosening and other complications associated with use of the halo orthosis.

Deterioration following spinal cord injury. A multicenter study.

The results are presented of a prospective study of the course of 283 spinal cord-injured patients who were consecutively admitted to five trauma centers participating in the Comprehensive Central Nervous System Injury Centers' program of the National Institutes of Health. Of the 283 patients, 14 deteriorated neurologically during acute hospital management. In 12 of the 14, the decline in neurological function could be associated with a specific management event, and in nine of these 12 the injury involved the cervical cord. Nine of the 14 patients who deteriorated had cervical injuries, three had thoracic cord injuries, and two had thoracolumbar junction injuries. Management intervention was identified as the cause of deterioration in four of 134 patients undergoing operative intervention, in three of 60 with skeletal traction application, in two of 68 with halo vest application, in two of 56 undergoing Stryker frame rotation, and in one of 57 undergoing rotobed rotation. Early surgery on the cervical spine when cord injury is present appears hazardous, since each of the three patients with a cervical cord injury who deteriorated was operated on within the first 5 days. No such deterioration was observed following surgery performed from the 6th day on. In two other patients, deterioration did not appear to be related to management but was a direct product of the underlying disease or of systemic complications. Deterioration following hospitalization for spinal cord injury is relatively uncommon--4.9% in this large series. In most instances, decline in function could be attributed to specific management procedures. These changes must not be interpreted as representing failure to provide optimal care but rather should be seen as the inevitable product of an attempt to manage patients with spinal cord and column injuries, many of which are clearly unstable.

Application of the halo device for immobilization of the cervical spine utilizing an increased torque pressure.

The rates for loosening and infection of the pins used in the halo apparatus are unfortunately high. The commonly recommended amount of torque to be used in applying the pins is 0.68 newton-meter (six inch-pounds). Forty-two adult patients underwent application of a halo device for immobilization of the cervical spine using an increased torque of 0.90 newton-meter (eight inch-pounds). The rate for loosening of the pins and the rate for infection at the pin site dropped from 36 per cent to 7 per cent and 20 per cent to 2 per cent, respectively.

Subdural abscess associated with halo-pin traction.

Osteomyelitis and intracranial abscess are among the most serious complications that have been reported in association with the use of the halo device. The cases of five patients who had formation of an intracranial abscess related to the use of a halo cervical immobilizer are described. All of the infections resolved after drainage of the abscess, débridement, and parenteral administration of antibiotics. Meticulous care of the pin sites is essential to avoid this serious complication. Additionally, since all of the infections were associated with prolonged halo-skeletal traction, this technique should be used with caution and with an awareness of the possible increased risks of pin-site infection and of formation of a subdural abscess.

Organization of intrathecal nerve roots at the level of the conus medullaris.

The three-dimensional organization of the spinal nerve roots at the level of the conus medullaris has not been described previously, to our knowledge. In this study, we used a newly developed technique of in situ fixation and embedding to define the cross-sectional anatomy at the level of the conus medullaris in ten fresh human cadavera. A highly organized overlapping pattern of nerve roots was demonstrated in all specimens. The nerve roots form a peripheral rim around the spinal cord at the levels of the tenth and eleventh and the eleventh and twelfth thoracic intervertebral discs. More caudally, the cord diminishes in size and the nerve roots predominate. The most cephalad roots lie laterally, with the motor roots ventral to their sensory counterparts. The more caudad roots overlap toward the midline, and the motor and sensory portions of each root are separated by spinal cord tissue. An intricate web of arachnoid membrane holds the nerve roots in a fixed relationship to each other.

The use of computerized tomography in evaluating non-visualized vertebral levels caudad to a complete block on a lumbar myelogram. A review of thirty-two cases.

In thirty-two patients who demonstrated a complete or almost complete block on a lumbar myelogram, computerized tomography of the non-visualized vertebral levels caudad to the block was performed prior to surgical intervention. The purpose of this study was to evaluate the clinical value of computerized tomography in detecting a lesion that is caudad to the level of a myelographic block. For twenty-three patients the cause of the myelographic block was stenosis of the spine; for five patients, a combination of stenosis of the spine and herniation of a disc; for one patient, herniation of a disc between the fourth and fifth lumbar vertebrae alone; for two patients, arachnoiditis; and for one patient, kyphosis secondary to fracture. A total of fifty vertebral levels that could not be visualized because of the block were evaluated. Thirty (60 per cent) of the non-visualized vertebral levels, in nineteen (59 per cent) of the thirty-two patients, demonstrated stenosis of the spine or a herniated disc that was confirmed at the time of surgical treatment. The value of computerized tomography for the evaluation of the vertebral levels caudad to the level of a complete or almost complete block on a lumbar myelogram was threefold. First, it provided visualization of the vertebral levels that could not be evaluated by the myelography. Second, the findings on computerized tomography provided information that was essential for preoperative planning and it removed the so-called exploratory element from the operative procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of intracompartmental pressure and volume under plaster casts.

UNLABELLED: Infusion lines (to elevate intracompartmental pressure experimentally) and wick catheters (to monitor the pressure produced) were inserted into hind-limb muscle compartments in twenty-six dogs. A padded plaster cast was then applied. The effect of the cast on intracompartmental pressure and volume and the effect of first splitting the cast and then cutting the padding were determined. Three different padding were used: dry Webril, Webril soaked in blood and Betadine (povidone-iodine), and Webril soaked in blood and Betadine and then dried. The cast was found to restrict expansion of the compartment volume by approximately 40 per cent. The most significant reductions in pressure in all groups occurred after the cast was cut and spread (mean reduction, 65 per cent). An additional pressure reduction of 10 to 20 per cent occurred after cutting the Webril. After removal of the cast, all limbs maintained some residual elevation of the intracompartmental pressure. CLINICAL RELEVANCE: This study demonstrates the need in clinical practice for continued evaluation and monitoring of a limb even after the cast has been completely removed because of signs and symptoms of a compartmental syndrome.

Lower-extremity sensibility testing in patients with herniated lumbar intervertebral discs.

The significance of sensory changes determined by pinprick and light touch in individuals with a herniated lumbar disc has been questioned. Discrepancies may be related to the subjectiveness of the test, failure to use dermatome-specific testing sites, overlap of areas that are innervated by different nerve roots, anatomical variations, or lack of sensitivity of the testing technique. For this study, we assessed the results of sensory examinations of twenty-five patients with documented herniation of a lumbar disc. The examinations were done using Semmes-Weinstein monofilaments, vibrometry, pinprick, and light touch in the autonomous skin areas supplied by the fourth and fifth lumbar and first sacral-nerve roots. Right-left differences in Semmes-Weinstein pressure thresholds of more than fifteen milligrams per square millimeter enabled us to localize disc lesions to a specific root in 100 per cent of patients and differences in vibratory thresholds of more than 3.5 micrometers, to localize the correct level in 88 per cent. Lesser differences in thresholds did not help to identify the involved root. The mean sensory threshold on the side of the disc lesion was found to be significantly greater than that on the opposite side by both vibrometry and pressure aesthesiometry (p less than 0.005). These findings were not duplicated using light touch or pinprick testing. Even with the most sophisticated sensibility-testing techniques, correct identification of the nerve root that was compressed by a herniated lumbar disc was accurate in only 50 per cent of patients.

Recurrent posterior dislocation of the shoulder: treatment using a bone block.

Acute posterior dislocations of the shoulder are uncommon. Recommended surgical treatments for recurrent posterior dislocation include soft-tissue advancement, posterior glenoid osteotomy, rotational osteotomy of the humerus, and posterior bone block. The posterior bone-block procedure successfully prevented recurrent dislocation in our series of five patients. The patients ranged in age from seventeen to forty-four years, and have been followed for two and one-half to eight years. All returned to unrestricted activity and recreational sports. The complications included a later anterior dislocation of the shoulder in one patient and an unsightly scar requiring revision in two patients. There were no complaints of pain. Radiographs showed decreased density of the bone block in two patients, but graft resorption did not occur.

Intraspinal synovial cyst causing sciatica.

Four patients who had low-back pain and sciatica were diagnosed as having a lumbar intraspinal extradural synovial cyst adjacent to a facet joint between the fourth and fifth lumbar vertebrae. The patients ranged in age from forty-nine to seventy-one years, and the symptoms and signs involved the fourth or fifth lumbar-nerve roots. Roentgenographically, degeneration of the intervertebral discs and facet joints was noted in every patient. Degenerative spondylolisthesis was also a frequent finding. Myelography and computed tomographic scans aided in diagnosis, revealing a soft-tissue lesion, occasionally rimmed with calcification, adjacent to the involved facet joint. The treatment was surgical excision of the cyst, as well as complete laminectomy if there was concomitant spinal stenosis. Follow-up, ranging from eighteen to twenty-five months, revealed complete resolution of the sciatica in all patients.

Complications in the use of the halo fixation device.

The medical records of 179 patients were reviewed to identify complications related to the use of the halo external skeletal-fixation device. The complications that were identified included pin-loosening in 36 per cent of the patients, pin-site infection in 20 per cent, pressure sores under either a plastic vest or a plaster cast in 11 per cent, nerve injury in 2 per cent, dural penetration in 1 per cent, dysphagia in 2 per cent, cosmetically disfiguring scars in 9 per cent, and severe pin discomfort in 18 per cent. One hundred and eighty (25 per cent) of the 716 pins used had become loose at least once, and an infection had developed at sixty-seven pin sites (9 per cent). Two-thirds of the pins that were loose or associated with infection required change or removal. These complication rates, particularly of pin-loosening and infection, are exceedingly high. Attention to details in pin application, pin maintenance, and proper pin-site care may minimize the number of complications.