Association between dorsolateral prefrontal N-acetyl aspartate and depression in chronic back pain: an in vivo proton magnetic resonance spectroscopy study.

Most studies of pain, including chronic pain, agree that depression and pain are interrelated, although the neurobiology of this relationship remains unknown. Neuroimaging studies suggest a specific role of the prefrontal brain regions in the mechanisms of mood disorders and chronic pain. The present study examines the interrelationships between regional brain N-Acetyl aspartate (NAA) levels (as identified by in vivo proton magnetic resonance spectroscopy in the right and left dorsolateral prefrontal cortex [DLPFC], orbitofrontal cortex, cingulate and thalamus), depression (as measured by the Beck Depression Inventory), and pain (as measured by short form of the McGill Pain Questionnaire) in 10 chronic back pain (CBP) patients with depression, and compared to the relationship between regional brain NAA levels and depression in 10 normal subjects (sex and age-matched). Reduction of NAA levels was demonstrated in the right DLPFC of CBP patients with depression, as compared to the normal controls (p < 0.02, two-tailed t-test). The depression levels in CBP patients were highly correlated with NAA levels in the right DLPFC (r = -0.99, p < 0.0001), and were unrelated to the other studied regional NAA in both groups, including the right DLPFC in normal subjects (p < 10(-6); comparing the difference between r values in the right DLPFC between the two groups). The pain levels in CBP patients were also associated with the right DLPFC (r = -0.62, p < 0.05), although these relationships were much weaker as compared to depression-NAA correlations (p < 0.0001; comparing the difference between r values). The interrelationships between NAA across brain regions were examined using correlation analysis, which detected different connectivity patterns between CBP patients with depression and normal subjects. These findings provide evidence for a stronger association of prefrontal NAA to depression than to pain in CBP, which may reflect the common neurobiological substrate underlying these conditions in CBP patients. Spectroscopic brain mapping of NAA, the marker of neuronal density and function, to the depression and pain measures might be used for segregation of their circuitries in the chronic pain brain.

Brain chemistry reflects dual states of pain and anxiety in chronic low back pain.

The neurobiology of the interaction between pain and anxiety is unknown. The present study examined interrelationships between: regional brain chemistry (as identified by in vivo proton magnetic resonance spectroscopy [(1)H-MRS] in dorsolateral prefrontal cortex [DLPFC], orbitofrontal cortex [OFC], cingulate and thalamus), pain (as measured by short form of the McGill Pain Questionnaire [SF-MPQ]), and anxiety (measured by the State-Trait Anxiety Inventory) in chronic low back pain (CLBP) patients, and contrasted to the relationship between brain chemistry and anxiety in sex and age-matched normal subjects. The results show that brain chemistry depends on a 3-way interaction of brain regions examined, subject groups (normal vs. CLBP), and anxiety levels (high vs. low). The concentration of N-Acetyl aspartate (the largest peak in (1)H-MRS) in OFC could distinguish between anxiety levels and between subject groups. Chemical-perceptual relationships were analyzed by calculating correlations between regional chemicals and perceptual measures of pain and anxiety. To isolate pain from anxiety, these maps were subdivided based on anxiety and, in the CLBP patients along anxiety-more-related vs. anxiety-less-related pain descriptors and along sensory vs. affective pain descriptors. There was a precise relationship between perception and brain chemistry. The chemical-perceptual network best related to pain in CLBP patients was comprised of the DLPFC and OFC; the chemical-anxiety network was best related to the OFC chemistry in normals and to all four regions studied in CLBP patients; and the cingulate was best related to the affective component of pain. We conclude that the chemical-perceptual mapping differentiates between closely related perceptual states of pain and anxiety in chronic pain and provides a brain regional-chemical-perceptual description of the long-term reorganization that occurs with chronic pain.

Imaging the pain of low back pain: functional magnetic resonance imaging in combination with monitoring subjective pain perception allows the study of clinical pain states.

Most brain imaging studies of pain are done using a two-state subtraction design (state-related design). More recently event-related functional magnetic reasonance imaging (fMRI) has also been used for studying pain. Both designs severely limit the application of the technology to clinical pain states. Recently we demonstrated that monitoring time fluctuations of perceived pain could be used with fMRI to identify brain regions involved in conscious, subjective perception of pain. Here we extend the methodology to demonstrate that the same approach can be used to study clinical pain states. Subjects are equipped with a finger-spanning device to continuously rate and log their perceived pain during fMRI data collection. These ratings are convolved with a canonical hemodynamic response function to generate predictor waveforms with which related brain activity can be identified. Chronic low back pain patients and a normal volunteer were used. In one series of fMRI scans the patient simply lies in the scanner and indicates spontaneous fluctuations of the subjective pain. In other fMRI scans, a straight-leg raising procedure is performed to exacerbate the back pain. In the normal volunteer, fMRI scans were done during painful and non-painful straight-leg raisings. The results indicate the feasibility of differentiating between different pain states. We argue that the approach can be generalized to identify brain circuitry underlying diverse clinical pain conditions.

Functional outcome of low lumbar burst fractures. A multicenter review of operative and nonoperative treatment of L3-L5.

STUDY DESIGN: A retrospective review of 42 patients treated at three major medical centers for burst fractures of L3, L4, and L5. This is the largest low lumbar (L3-L5) burst fracture study in the literature to date. The study was designed to assess both radiographic and clinical outcomes in a cohort of patients treated during a 16-year period. OBJECTIVES: The objective of this study was to determine whether conservatively treated patients with low lumbar burst fractures had satisfactory outcomes compared with those in a surgically treated cohort of patients. The study included patients with and without neurologic deficits. SUMMARY OF BACKGROUND DATA: Burst fractures of the low lumbar spine (L3-L5) represent a small percentage of all spine fractures. The iliolumbar ligaments and location below the pelvic brim are two stabilizing factors that are unique to these fractures when compared with burst fractures at the thoracolumbar junction. METHODS: Forty-two (n = 42) patients with low lumbar burst fractures were identified from 1980 through 1996. Medical records, radiographs, and follow-up Dallas Pain Questionnaires were obtained. Loss of anterior vertebral height, kyphotic angulation, and amount of retropulsion were recorded at several phases of treatment. Mean follow-up time was 45.2 months (range, 5-132 months). Twenty patients were treated without surgery (18 were neurologically intact, and 2 had isolated nerve root injury), and 22 underwent surgery (14 had neurologic injury, 8 were intact). RESULTS: No patient showed neurologic deterioration, regardless of treatment. Fracture of the third lumbar segment showed the greatest tendency toward kyphotic collapse and loss of height in the nonoperative group, although this was not reflected in the final functional outcome of both groups. The ability to return to work and achieve a good-to-excellent long-term result was not significantly different among fracture levels or between surgical and nonsurgical treatments. CONCLUSIONS: The results of nonoperative treatment of low lumbar burst fractures were comparable with those of operative treatment. The rate of repeat surgery (41%) and absence of a clearly definable long-term functional or radiographic benefit in patients without neurologic compromise may make surgery less appealing.

Surgical treatment of internal disc disruption: an outcome study of four fusion techniques.

Surgical treatment for internal disc disruption remains controversial in terms of efficacy of spinal fusion and optimal fusion method. The present study was carried out in 56 consecutive patients, with the diagnosis confirmed by computed tomographic (CT) discography, who were operated with one of four different lumbar fusion procedures. Outcomes were determined by postoperative pain questionnaires, independent clinical assessment, and radiographic evaluation. Simultaneous anterior interbody fusion using BAK cage and posterior facet fusion provided the highest rate of fusion (88%) and clinical satisfaction (63%). Pain scores were also significantly lower than facet screw augmented posterolateral fusion, and anterior interbody fusion with fibula allograft, but not significantly different from pedicle screw instrumented posterolateral fusion. Patients who achieved successful lumbar fusion had better clinical outcomes and a better chance of work resumption.

Predictive signs of discogenic lumbar pain on magnetic resonance imaging with discography correlation.

STUDY DESIGN: The correlation between discogenic lumbar pain and disc morphology was investigated by using magnetic resonance imaging and discography. OBJECTIVES: To assess the various pathologic parameters seen on magnetic resonance imaging in patients with discogenic lumbar pain and to correlate them with observations on discography. SUMMARY OF BACKGROUND DATA: Although numerous previous studies on the subject have been performed, the correlations between various pathologic findings on magnetic resonance imaging and pain reproduction by provoked discography have not been explained fully. METHODS: One hundred and one lumbar discs in 39 patients were studied with magnetic resonance imaging and pain provocation discography. When pain reproduction under discography was concordant, various pathologic parameters on magnetic resonance imaging were analyzed by three statistical parameters to determine the associated magnetic resonance imaging findings. RESULTS: Radial tears commonly are demonstrated on magnetic resonance imaging in discs with concordant pain on discography. The presence of these tears is not a reliable predictor of a painful disc on discography. Although a high-intensity zone on T2-weighted images is a relatively reliable predictor of pain, the statistical values were lower than those in previous studies. Massive degeneration and severe disc height loss were rare in this population. These findings were good predictors of pain on disc injection. CONCLUSIONS: Although the lumbar intervertebral discs with posterior combined anular tears are likely to produce pain, the validity of these signs for predicting discogenic lumbar pain is limited.

Thoracolumbar spine injuries.

This article reviews some of the anatomic and mechanical aspects of thoracolumbar injuries as they relate to classification systems and stability. In addition, an overview of the initial management including surgical and conservative treatment options is provided.

Interference screw fixation of cervical grafts. A combined in vitro biomechanical and in vivo animal study.

The dislodgement of an anterior bone graft in the cervical spine is a frequent complication of attempted fusion following discectomy or corpectomy. It has been hypothesized that fixation augmented with interference screws may increase the pullout strength of the construct and decrease the rate of these complications. In vitro mechanical tests and in vivo sheep studies were conducted to compare interference screw fixation methods for enhancing the fixation between the bone graft and the adjacent vertebra. Using human cadaver cervical spines, the anterior pullout strengths of cervical bone grafts were compared using fixation with and without the addition of interference screws for the in vitro mechanical testing. The mean pullout forces for a Smith-Robinson type bone graft alone was 58.1 N (SD 11.4 N); for the graft augmented with two 3.5 mm cancellous bone screws, 153.9 N (58.9 N); and for the graft with four 3.5 mm screws, 217.1 N (SD 69.9 N). The pullout strengths of the two- and four-3.5 mm screw constructs were significantly greater than the strength of the graft alone (P < 0.05). Similarly placed 2.7 mm cortical screws of the same length provided increased pullout strength (123.7 N 38.6 N and 142.5 N 38.2 N for two- and four-screw constructs, respectively); however, in comparison to the graft alone, these differences were not statistically significant. For both screw types, the four-screw fixations were stronger than the two-screw fixations, although these differences were not statistically significant. For the in vivo portion of the study, a single-level anterior cervical discectomy and fusion were performed on 20 sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of Harrington rod treatment of spinal trauma.

Harrington rod treatment for spinal trauma has become the gold standard against which other treatment modalities are judged. A review of the results of Harrington rod treatment is essential to establish a baseline level of efficiency in terms of rehabilitation time, correction of deformity, canal decompression, motion segment loss, and device-related complications. With economic concerns becoming more important in medical treatment, the value of newer techniques must be clearly superior to established methods. Harrington rod-augmented spine fusion is reliable and cost-effective in the thoracic and thoracolumbar spine. The risks of rod failure and late complications related to lost motion segments in the lumbar spine make pedicle screw systems a better option in this region.

Mechanics of anatomic reduction of thoracolumbar burst fractures. Comparison of distraction versus distraction plus lordosis, in the anatomic reduction of the thoracolumbar burst fracture.

The adequate reduction of vertebral burst fractures is dependent on successful application of distractive forces in combination with the restoration of normal spinal lordosis. However, the optimal sequence of distraction in comparison to distraction plus lordosis in the anatomic restoration of the fractured thoracolumbar spine has not been described. Burst fractures of the L1 vertebra were first created and the reduced in vitro using three differing reduction techniques. In six fresh human cadaver spine specimens, the mean fracture severity based on the degree of canal compromise was 31% (SD +/- 20%) after fracture. Reductions were performed using the AO Fixator Intern, the Reduction Fixation (RF) Device, and the Steffee plate systems following standard clinical techniques. The AO Fixator Intern provided independent but variable control of distraction and lordosis, the RF device provided variable distraction with independent, but preset, correction of lordosis and the Steffee system provided set distraction and stabilization. Both the AO and RF devices restored the lordosis (7.6 degrees +/- 5.2 degrees and 9.7 degrees +/- 4.5 degrees, respectively) better than the Steffee plate system (0 degrees +/- 1.6 degrees). However, the AO device provided poorest restoration of the posterior vertebral body height (92% vs 96% for the RF device and 99% for the Steffee plate). The RF device, which restored both lordosis and posterior vertebral body height to the near anatomic prefracture level, provided significantly better canal clearance (9% +/- 8%) than the other techniques, P < 0.05. The study demonstrates that instrumentation systems that provide independent correction of distraction and lordosis can best restore anatomic alignment, with indirect neurodecompression of the compromised spinal canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Vertebral burst fractures: an experimental, morphologic, and radiographic study.

Spinal burst fractures are produced by rapid compressive loading, and may result in spinal cord injury from bone fragments forced from the vertebral body into the spinal canal. This fracture is one of the most difficult injuries of the spine to successfully treat, in part because the biomechanics of reduction and the exact mechanism by which the distraction forces are transmitted to the intracanal fragments of the burst fracture have not been adequately investigated. The authors developed a reproducible technique for creating these fractures in vitro. The fractures produced were identical to those observed in clinical practice, and were used for investigating the mechanics of this fracture and its reduction. This work describes the pathologic anatomy of the burst fracture both on the gross structure and also on microtome sections of the vertebrae, and examines the biomechanics of fracture reduction. The margins of the vertebral bone fragment, which was forced posteriorly into the spinal canal during fracture, were noted to extend far laterally beyond the pedicles. The authors also found extensive damage not only to the disc above the injured level, but also to that below, explaining the clinical observation that disc degeneration frequently occurs at both levels. Examination of anatomic data provided by microtome section supported the hypothesis that the fibers that actually reduce the intracanal fragment originate in the anulus of the superior vertebra in the midportion of the endplate and insert into the lateral margins of the intracanal fragment. Investigations using magnetic resonance imaging confirmed that these obliquely directed fibers account for the indirect reduction of the fragment. The authors' studies demonstrate that the posterior longitudinal ligament provides only a minor contribution in the reduction of the fracture in comparison to the attachments of the posterior portion of the anulus fibrosus. The forces required to reduce this fragment were studied. Distraction was found to be the predominant force required for indirect posterior reduction. This was confirmed by a series of tests using devices that provided segmental fixation. The application of uniform distraction forces was most effective in the posterior reduction of the intracanal fragment.

Interference screw fixation of cervical grafts: a biomechanical study of a new method of cervical fixation.

The dislodgement of anterior bone graft in the cervical spine is a frequent complication of attempted fusion following discectomy or corpectomy. It has been hypothesized that fixation augmented with interference screws may increase the pull-out strength of the construct and decrease the rate of these complications. Mechanical tests were conducted to compare interference screw fixation methods for enhancing the fixation between the bone graft and the adjacent vertebra. The anterior pull-out strengths of cervical bone grafts were compared using fixation with and without the addition of interference screws. Both discectomy and corpectomy graft models were examined in vitro. The mean pull-out force for a Smith-Robinson type bone graft alone was 58.1 N (SD +/- 11.4 N); for the graft augmented with two 3.5 mm cancellous bone screws, 153.9 N (+/- 58.9 N); for the graft with four 3.5 mm screws, 217.1 N (SD +/- 69.9 N). The pull-out strengths of the two and four 3.5 mm screw constructs were significantly greater than the strength of the graft alone (p less than 0.05). Similarly placed 2.7 mm cortical screws of the same length provided increased pull-out strength (123.7 N +/- 38.6 N and 142.5 N +/- 38.2 N for two and four screws, respectively); however, in comparison to the graft alone, these differences were not statistically significant. For both screw types, the four screw fixations were stronger than the two-screw fixations, although these differences were not statistically different.(ABSTRACT TRUNCATED AT 250 WORDS)

The Syracuse I-plate.

The Syracuse I-Plate is a versatile neutralization plate for anterior spinal fixation following decompression for burst fractures and pathologic vertebral body destruction by tumor. In this article, the history, current use, and indications are discussed. The anterior approach and application of the I-plate to the lower thoracic and lumbar spine is presented, as well as a brief summary of a current clinical series of 34 patients. Fusion rates were high and hardware failure most frequent in patients with associated osteoporosis or extensive posterior disruption, such that the device was contraindicated in cases of extensive three-column injuries or significantly osteoporotic bone.

A biomechanical investigation of short segment spinal fixation for burst fractures with varying degrees of posterior disruption.

A biomechanical study was performed to evaluate the effectiveness of the Fixateur Interne pedicle screw system and the Syracuse I-Plate anterior fixation system. A total of 12 fresh frozen cadaver spines were tested intact, after burst fracture was created and application of a fixation device (six each), and after six serial transections of posterior ligaments and bony structures. Spines were loaded to a maximum of 10 N-m in flexion, extension, left and right lateral bending, and clockwise and counter-clockwise rotation. Results indicate that both systems reduce spinal flexibility in flexion, extension, and lateral bend loading when used to reduce and fix a classic burst fracture without posterior disruption. No decrease in flexibility was found in axial rotation for either device. After transection of all posterior elements, the I-Plate construct became much more flexible than the intact spine in flexion, extension, and axial rotation loading. The internal fixator construct retained more stability than the I-Plate construct after transection of posterior elements in flexion and extension loading, but was considerably more flexible than the intact spine in axial rotation loading. The results imply that the posterior internal fixator provides much better stabilization than the anterior I-Plate for those cases in which there is a large amount of posterior disruption in addition to an anterior burst injury. Neither device provides extensive support in axial rotation loading.

Variability of somatosensory cortical evoked potential monitoring during spinal surgery.

The intraoperative variability of somatosensory cortical evoked potentials (SCEPs) has been measured for 320 consecutive spinal surgeries and found to be a function of patient diagnosis, neuromuscular status, age, and procedural factors. In many cases, it is likely that this variability severely limits the reliability and usefulness of spinal cord monitoring in detecting early cord compromise. Patients with idiopathic scoliosis, spondylolisthesis, and pseudarthrosis have the smallest spontaneous variability and strongest amplitudes, while those with congenital, paralytic scoliosis, stenosis, or tumor have very variable, weak SCEPs. Patients with neurologic disorders, particularly cerebral palsy, myelomeningocele, Friedreich's ataxia, and peripheral deficits, also have high variability and weak amplitudes. A monitoring quality scoring system is proposed that may be useful during surgery in judging how well the SCEPs can discern surgically related changes in cord function from background variations.

Reduction of the intracanal fragment in experimental burst fractures.

An experimental investigation was carried out to create burst fractures and to evaluate the mechanisms and degree of reduction of the intracanal fragment with posterior instrumentation techniques in multisegmental human cadaver specimens. Reduction of the spinal fragment through kyphosis correction and distraction was evaluated using CT imaging. With kyphosis correction alone there was no decrease in canal compromise; in some cases there was a slight increase in canal compromise. Distraction, whether applied before or after kyphosis correction was the effective mechanism in reducing the fracture fragment. Kyphosis correction applied after distraction did not reduce the fragment further. Posterior devices that are used to treat burst fractures of the thoracolumbar spine with intracanal fragments should provide some form of distraction.

Early clinical experience with the Syracuse I-Plate: an anterior spinal fixation device.

Sixteen patients were treated with a new anterior internal fixation device after thoracolumbar or lumbar decompression, and fusion with bone grafting. Ten patients had acute burst fractures, four had metastatic tumors, and two had old, healed fractures with deformity. In the acute fracture group, eight patients had neurologic deficits and seven patients experienced improvement. Six patients had lesions of the conus medullaris, all of which improved. The four patients with metastatic tumors underwent surgery for back and leg pain and all gained significant relief. Two patients had correction of old fracture deformity with satisfactory outcome. Complications were minimal. The new anterior stabilization device provided early stability, allowed early patient mobilization, was easy to insert, and has a low profile. Late collapse, non-union, and kyphotic deformity have not been noted thusfar.

Rehabilitation of the patient with chronic back pain. A search for outcome predictors.

This prospective study was initiated 3 years ago to evaluate the outcome and to identify predictors of success or failure in patients admitted to a rehabilitation program for chronic low-back pain. Multiple parameters were evaluated, including psychologic data (MMPI, personal interview, pain drawing, etc.), physical measurements (flexibility, strength and endurance), and demographic data concerning the patient's home and working environment. Information was available on each patient admitted to the program prior to his admission, at completion of the program, 6 weeks following completion of the program and 3 months following completion of the program. A telephone interview was carried out 2 1/2 years following the patient's discharge from the program. Linear regression analysis was used to identify the important independent variables with regard to the dependent variables of relief of back pain, return to work and increased activities at home. Demographic data were of no value as a predictor with the exception of age and returning to work. The patients over the age of 50 returned to work with much less frequency than those less than 50. Psychologic information from the MMPI and similar tests were of no value. The personal preadmission interview of a trained psychologist, however, was a good predictor of an individual's eventual return to work and overall improvement. Worker's Compensation and other litigation was a negative factor in a patient's prognosis. The treatment team's prognosis at the time of discharge from the program was the best overall predictor of a patient's chance of success or failure in the longterm.

Conservative treatment of fractures of the thoracic and lumbar spine.

Patients with burst fractures of the thoracic and lumbar spines must receive individualized case analysis before a course of therapy can be decided. A consideration of fracture stability, degree of canal compromise, and patient evaluation becomes significant in determining operative or nonoperative treatment. In neurologically intact patients with selected fractures, nonoperative treatment can be successful in the functional rehabilitation of the patient.

Computed tomography of calcaneal fractures: anatomy, pathology, dosimetry, and clinical relevance.

Eighteen CT examinations were performed in 10 patients for the evaluation of acute intraarticular fractures and their follow-up. Fractures comparable to those in the patients were created in cadavers. The normal anatomy and the traumatically altered anatomy of the calcaneus in the axial, coronal, and sagittal planes are demonstrated by CT and corresponding anatomic sections. Scanning was performed in the axial plane, with subsequent reconstruction in the coronal and sagittal planes. The axial scans show disruption of the inferior part of the posterior facet, calcaneocuboid joint involvement, and widening of the calcaneus. The coronal scans show disruption of the superior part of the posterior facet, sustentaculum tali depression (involvement of middle and anterior facets), peroneal and flexor hallucis longus tendon impingement, and widening and height loss of the calcaneus. The sagittal scans show disruption of the posterior facet, calcaneocuboid joint involvement, and height loss of the calcaneus and allow the evaluation of Boehler's and Gissane's angles. All three planes show the position of major fracture fragments. Radiation dose to the foot was measured to be 0.1 rad (0.001 Gy) for plain film radiography (five exposures), 18 rad (0.18 Gy) for conventional tomography (20 cuts), and 2.6 rad (0.026 Gy) for axial CT examination.