Evaluation of the rotator cuff and glenoid labrum using a 0.2-Tesla extremity magnetic resonance (MR) system: MR results compared to surgical findings.

The purpose of this investigation was to evaluate the diagnostic capabilities of magnetic resonance imaging (MRI) performed using a dedicated-extremity MR system in detecting lesions of the rotator cuff and glenoid labrum. This retrospective study compared the MR results obtained in 47 patients that underwent MRI using a 0.2-Tesla extremity MR system (E-scan) to the surgical findings. MR images of the shoulder were obtained as follows: shoulder coil, T1-weighted, coronal-oblique and axial images; short Tau inversion recovery (STIR), coronal-oblique images; and T2-weighted, coronal-oblique, sagittal-oblique, and axial images. The MR examinations were interpreted by three highly experienced, musculoskeletal radiologists. Open surgical (N = 26) or arthroscopic (N = 21) procedures were performed within a mean time of 33 days after MRI. The surgical findings revealed rotator cuff tears in 28 patients and labral lesions in 9 patients. For the rotator cuff tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 100%, 100%, and 90%, respectively. For the labral lesions, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 95%, 80%, and 97%, respectively. The findings indicated that there was good agreement comparing the MR results obtained using the low-field extremity MR system to the surgical findings for determination of lesions of the rotator cuff and glenoid labrum. Notably, the statistical values determined for the use of this MR system were comparable to those reported in the peer-reviewed literature for the use of whole-body, mid- and high-field-strength MR systems.

Real-time multiplex PCR assays.

The ability to multiplex PCR by probe color and melting temperature (T(m)) greatly expands the power of real-time analysis. Simple hybridization probes with only a single fluorescent dye can be used for quantification and allele typing. Different probes are labeled with dyes that have unique emission spectra. Spectral data are collected with discrete optics or dispersed onto an array for detection. Spectral overlap between dyes is corrected by using pure dye spectra to deconvolute the experimental data by matrix algebra. Since fluorescence is temperature dependent and depends on the dye, spectral overlap and color compensation constants are also temperature dependent. Single-labeled probes are easier to synthesize and purify than more complex probes with two or more dyes. In addition, the fluorescence of single-labeled probes is reversible and depends only on hybridization of the probe to the target, allowing study of the melting characteristics of the probe. Although melting curves can be obtained during PCR, data are usually acquired at near-equilibrium rates of 0.05-0.2 degrees C/s after PCR is complete. Using rapid-cycle PCR, amplification requires about 20 min followed by a 10-min melting curve, greatly reducing result turnaround time. In addition to dye color, melting temperature can be used for a second dimension of multiplexing. Multiplexing by color and T(m) creates a "virtual" two-dimensional multiplexing array without the need for an immobilized matrix of probes. Instead of physical separation along the X and Y axes, amplification products are identified by different fluorescence spectra and melting characteristics.

MR imaging of the spine in sports injuries.

MR imaging has afforded an ability to better visualize and characterize a whole host of spine abnormalities encountered in the athletic population. It remains the mainstay in the noninvasive diagnosis of most soft-tissue abnormalities occurring within and about the spine. Its role in the evaluation of central spinal stenosis, the central spinal canal, and the spinal cord is unsurpassed by other noninvasive imaging modalities. In the setting of underlying fractures, it is complementary to CT, particularly with respect to evaluating concomitant soft-tissue and ligamentous abnormalities. With its ability to image edema and reactive marrow changes, it is useful in the evaluation of osseous stress changes that may occur in the athletic population.

Rapid F508del and F508C assay using fluorescent hybridization probes.

Amplification and fluorescent genotyping of the cystic fibrosis F508del locus was achieved from human genomic DNA in less than 30 min. The hybridization of adjacent fluorescent probes at the mutation site was monitored by resonance energy transfer between fluorescein and Cy5 during heating or cooling. Characteristic curves were obtained for each genotype; the first derivative of these fluorescent curves has a maximum at an apparent hybridization temperature (Tm) that is specific for each probe/allele duplex. The direction and rate of temperature change determines the difference between the apparent Tm and the true equilibrium Tm. One hundred and five sample were genotyped for the F508del cystic fibrosis mutation by heating and cooling curve profiles. These genotypes were validated by allele-specific amplification. Two fluorescein hybridization probes were designed to match the wild-type sequence perfectly from either codons 502 to 513 or from 504 to 511 on the cystic fibrosis transconductance regulator gene of chromosome 7. While genotyping for the F508del, an allele with the F508C base change was detected. For both F508del and F508C variants, the Tm shift from wild type was greater with a 24-mer probe than with a 35-mer probe. Fluorescent monitoring of hybridization probes is a versatile technique that can detect unexpected sequence alterations.

Magnetic resonance imaging of the musculoskeletal system: the spine.

Magnetic resonance imaging in the patient who has had surgery is discussed. The most common indication for postoperative imaging is in the distinction between postoperative fibrosis and recurrent disc herniation. Magnetic resonance imaging is invaluable in the assessment of potential causes of failed back surgery syndrome such as postoperative infection, arachnoiditis and adjacent segment degeneration. Magnetic resonance imaging assumes a less important role in postoperative patients with metal hardware owing to image degradation secondary to metal artifact. Magnetic resonance imaging has a complementary role with computed tomography evaluation of spinal trauma. It excels at the noninvasive evaluation of spinal deformities and neoplasms.

Magnetic resonance imaging of the musculoskeletal system. Part 8. The spine, section 2.

Magnetic resonance imaging has revolutionized the noninvasive evaluation of degenerative disc disease and its complications. Compared with computed tomography and computed tomographic myelography, magnetic resonance allows specific determination of the nature of disc protrusions and other degenerative related soft tissues about the spine. Magnetic resonance offers the most complete evaluation of specific degenerative disorders including degenerative facet disease, spondylolysis, spondylolisthesis, spontaneous lumbar epidural hematomas, and juvenile discogenic disease.

Magnetic resonance imaging of the musculoskeletal system. Part 8. The spine, section 1.

Magnetic resonance has assumed a preeminent role in the imaging evaluation of the spine. Owing to its multiplanar capability and superior soft tissue contrast, magnetic resonance imaging is the procedure of choice for a host of spinal disorders including degenerative disc disease, tumor evaluation, trauma, and spinal deformities. It represents the most accurate means of distinguishing between recurrent disc herniation and epidural fibrosis, and it excels at the assessment of many postoperative abnormalities such as infection, adjacent segment disc degeneration, and arachnoiditis. Magnetic resonance imaging is also helpful in the evaluation of numerous diagnostic challenges that are less well resolved by other means. This includes the distinction between disc herniation and epidural hematoma, synovial cyst from nonspecific fibrous thickening of a facet capsule, and the evaluation of numerous other soft tissue abnormalities. Computed tomography, computed tomography myelography, and scintigraphy continue to be useful for numerous specific disorders and in those patients with metal hardware or contraindications to magnetic resonance scanning. Overall, however, magnetic resonance is the imaging procedure preferred for many spinal disorders. This article is the first installment of a 3-part series discussing the role of magnetic resonance imaging of spinal disorders. Section 1 will describe the varying imaging modalities available and their relative advantages and disadvantages. A consideration of magnetic resonance imaging techniques will follow, followed by a discussion of the imaging manifestations of early degenerative disc disease. Section 2 will be devoted to an in depth discussion of specific pathologic processes encountered in patients with degenerative disc disease. Section 3 will end the series with a consideration of postoperative imaging followed by a discussion of spinal deformities, trauma, and neoplasms.

The natural history of asymptomatic thoracic disc herniations.

STUDY DESIGN: Magnetic resonance imaging was used to determine the natural history of asymptomatic thoracic disc herniations. OBJECTIVES: To determine whether thoracic disc herniations change in size over time. SUMMARY OF BACKGROUND DATA: Based on previous work by the authors of the present study, the incidence of asymptomatic thoracic disc herniations is approximately 37%. The natural history of thoracic disc herniations is unknown. The natural history of lumbar and cervical disc herniations in symptomatic individuals who become asymptomatic has been shown in multiple studies frequently to result in a decrease in size of the herniation. METHODS: Twenty patients with 48 asymptomatic thoracic herniations previously diagnosed with magnetic resonance imaging underwent repeat magnetic resonance imaging using sagittal T1-weighted spine echo and axial multiplanar gradient refocused images at each thoracic disc level from T1 to T12 for a mean follow-up period of 26 months. Midsagittal canal diameter was recorded, and disc herniation square area was measured using a computer-assisted digitizing program. Disc herniations were categorized according to percentage of canal compromise. The change in size of the disc herniations over time was analyzed. RESULTS: All patients remained asymptomatic during the follow-up period. A total of 48 disc herniations were identified from the original magnetic resonance images. There were 21 small (0-10% canal compromise) disc herniations, 20 medium (> 10-20%) disc herniations, and seven large (> 20%) disc herniations. Of the 21 small disc herniations, 18 showed no significant change in size, whereas three showed a measurable increase in size. Of the 20 medium-sized disc herniations, 16 showed either a small or no change in size, one showed a significant increase in size, and three showed a significant decrease in size. Of the seven large disc herniations, three demonstrated no change in size, and four demonstrated a significant decrease in size. In addition, five new disc herniations were detected in four patients; one was small, and four were moderate in size. CONCLUSIONS: Based on the results of this study, the authors believe that asymptomatic disc herniations may well exist in a state of relative flux, yet exhibit little change in size and remain asymptomatic. There was a trend, however, for small disc herniations either to remain unchanged or increase in size and for large disc herniations often to decrease in size.

Magnetic resonance imaging and biological changes in injured intervertebral discs under normal and increased mechanical demands.

STUDY DESIGN: An animal model was used to examine the short-term tissue response to changes in the mechanical environment after the structure (disc) is mechanically injured. OBJECTIVES: To observe changes in an injured intervertebral disc and the corresponding motion segment when the mechanical demands of the disc were increased by fusion of the adjacent motion segments. SUMMARY OF BACKGROUND DATA: Disc degeneration has been modeled in animals by producing a tear in the anulus via laminectomy, laparotomy, or posterolaterally. Methods of altering and quantifying the mechanics of the intervertebral joint by use of internal fixation and fusion in the canine have been developed. METHODS: Eight dogs divided into two groups (a study and a control group) had anular stab wounds (L2-L3). The study group was surgically instrumented posteriorly from L3 to L7. Magnetic resonance imaging studies were conducted for all animals before and periodically after the surgical procedures. At the end of the study, the segments were processed histologically and biochemically. RESULTS: Anular bulging was seen on magnetic resonance imaging in all control animals 4 months after injury and did not progress out until 6 months after injury. Similar changes were seen in study animals, but 75% were herniated by 6 months. Histologic changes correlated with magnetic resonance imaging changes. No significant difference in water or proteoglycan content of the disc tissue between groups was found. CONCLUSIONS: Progression from the bulging of the anulus to herniation was not evident in damaged discs not subjected to adjacent fusions. No change in water or proteoglycan content as a function of altered mechanical state was found, suggesting the short-term effect of the altered mechanics is on the mechanical structure and not on the cells or extracellular matrix.

Cervical discogenic pain. Prospective correlation of magnetic resonance imaging and discography in asymptomatic subjects and pain sufferers.

STUDY DESIGN: Asymptomatic subjects and chronic head/neck pain sufferers were studied with high-field magnetic resonance imaging and cervical discography to compare and correlate both tests. OBJECTIVES: To assess the accuracy of magnetic resonance imaging and discography in identifying the source(s) of cervical discogenic pain. SUMMARY OF BACKGROUND DATA: Previous retrospective studies describe a generally poor correlation between magnetic resonance imaging and provocative discography in the cervical spine. METHODS: Ten lifelong asymptomatic subjects and 10 nonlitigious chronic neck/head pain patients underwent discography at C3-C4 through C6-C7 after magnetic resonance imaging. Disc morphology and provoked responses were recorded at each level studied. RESULTS: Of 20 normal discs by magnetic resonance from the asymptomatic volunteers, 17 proved to have painless anular tears discographically. The average response per disc (N = 40) for this group was 2.42, compared to 5.2 (N = 40) for the neck pain group. In the pain patients, 11 discs appeared normal at magnetic resonance imaging, whereas 10 of these proved to have anular tears discographically. Two of these 10 proved concordantly painful with intensity ratings of at least 7/10. Discographically normal discs (N = 8) were never painful (both groups), whereas intensely painful discs all exhibited tears of both the inner and outer aspects of the anulus. CONCLUSIONS: Significant cervical disc anular tears often escape magnetic resonance imaging detection, and magnetic resonance imaging cannot reliably identify the source(s) of cervical discogenic pain.

Lumbar disc high-intensity zone. Correlation of magnetic resonance imaging and discography.

STUDY DESIGN: This study correlated a specific lumbar disc abnormality described as the high-intensity zone observed on high-field magnetic resonance imaging with discography. OBJECTIVES: To analyze the significance of high-intensity zones in lumbar discs of symptomatic patients with low back/radicular pain. SUMMARY OF BACKGROUND DATA: Aprill and Bogduk described an 86% incidence of concordantly painful discography in lumbar discs exhibiting a posterior high-intensity zone on T2-weighted magnetic resonance imaging studies performed on back pain sufferers. They assert that the high-intensity zone is a reliable marker of discogenic pain in symptomatic subjects. METHODS: Consecutive cases of lumbar spine high-field magnetic resonance imaging using T2-weighted images on symptomatic patients followed by discography at all high-intensity zone levels and at non-high-intensity zone control levels were reviewed until 100 high-intensity zone discs in 63 patients were found. Seventeen lifelong asymptomatic (for low back/radicular pain) adults were also scanned as magnetic resonance imaging controls. All magnetic resonance scans and discograms were agreed on by at least two of the radiologist authors. RESULTS: Eighty-seven of 100 of the high-intensity zone discs proved concordantly painful at discography. All 87 painful and concordant discs exhibited abnormal morphology with anular tears extending either well into or through the outer third of the anulus fibrosus. Sixty-five of 67 non-high-intensity zone control discs were nonconcordant and of lower sensation intensity than the high-intensity zone discs. Only one high-intensity zone was found in the control subjects. CONCLUSIONS: In patients with symptomatic low back pain, the high-intensity zone is a reliable marker of painful outer anular disruption.

Magnetic resonance imaging of the thoracic spine. Evaluation of asymptomatic individuals.

We reviewed magnetic resonance imaging studies of the thoracic spines of ninety asymptomatic individuals to determine the prevalence of abnormal anatomical findings. This group included sixty individuals who had no history of any thoracic or lumbar pain and thirty individuals who had a history of low-back pain only. In addition, we reviewed imaging studies of eighteen patients who had an operatively proved herniation of a thoracic disc and studies of thirty-one patients who had been seen with thoracic pain. Sagittal T1-weighted spin-echo and axial multiplanar gradient refocused images at each disc level were interpreted by us (two neuroradiologists and two orthopaedic spine surgeons); we had no clinical information about the patients. Sixty-six (73 percent) of the ninety asymptomatic individuals had positive anatomical findings at one level or more. These findings included herniation of a disc in thirty-three subjects (37 percent), bulging of a disc in forty-eight (53 percent), an annular tear in fifty-two (58 percent), deformation of the spinal cord in twenty-six (29 percent), and Scheuermann end-plate irregularities or kyphosis in thirty-four (38 percent). This study documents the high prevalence of anatomical irregularities, including herniation of a disc and deformation of the spinal cord, on the magnetic resonance images of the thoracic spine in asymptomatic individuals. We emphasize that these findings represent roentgenographic abnormalities only, and any clinical decisions concerning the treatment of pain in the thoracic spine usually require additional studies.

Imaging evaluation of patients with spinal deformity.

CT myelography and MRI provide the best means of preoperatively assessing patients with spinal deformities. Owing to its noninvasive nature and its superior soft-tissue contrast, MRI represents the single best modality in the evaluation of a patient with any deformity. MRI allows complete preoperative surgical planning and obviates the need for any additional studies. Screening of the entire cord in a patient with a deformity is best accomplished with sagittal and coronal (as needed) T1W images. These images allow assessment of the cord for compression, tethering, syrinx, enlargement, and Arnold-Chiari malformation. Evaluation of cord compression at the apex of a curve is the single most important consideration other than the diagnosis of intrinsic cord abnormality. Subsequent sagittal or axial T2W images may be helpful if specific abnormalities are noted on T1W screening images. Coronal images are particularly helpful in patients with prominent curves or in those with vertebral anomalies. Additionally, coronal images may be useful in assessing patients with suspected diastematomyelia. Advances in hardware and software design have resulted in marked improvements in the ability to satisfactorily image all aspects of patients with spinal deformities. New phased array coils allow rapid imaging of larger portions of the spine. For instance, a complete MRI of the spine can be performed in a child in the same length of time that would have been necessary for a single lumbar examination when MRI was in it's infancy. The use of fast spin-echo imaging also permits more rapid acquisition times. CT myelography remains useful for those patients who cannot undergo MRI or for those with specific abnormalities such as multilevel central spinal stenosis when dynamic information obtained during the myelogram might be helpful. CT myelography represents the only means of assessing the central spinal canal of patients with metallic instrumentation in place. With the exception of these limited applications, MRI has replaced CT myelography as the imaging study of choice in the evaluation and examination of patients with spinal deformities.

Juvenile discogenic disease.

This study was undertaken to document an association of degenerative lumbar disc disease in patients with thoracolumbar Scheuermann's disease. During a 3-month period, 9% of 1419 of the persons referred to our center for magnetic resonance imaging of the lumbar spine demonstrated changes of both thoracolumbar Scheuermann's disease and degenerative disc disease in the lower lumbar spine. The disease was less commonly detected on computed tomography (2% of 1522 patients). The patients were relatively young: 81% were younger than 40 years and 9% were younger than 21 years. We theorize that the thoracolumbar Scheuermann's disease and the associated degenerative disc disease of the lower lumbar spine are manifestations of an intrinsic defect of the discs and/or cartilaginous end plates, which results in inadequate nutrition and structural weakness or a combination of both, and early degeneration.

Epidural hematoma of the lumbar spine: 18 surgically confirmed cases.

The authors report 18 cases of surgically proved spontaneous epidural hematoma of the lumbar spine. The clinical findings in spontaneous epidural hematoma were identical to those in acute disk herniation. Underlying disk abnormalities were common; the majority of hematomas (14 of 18, 78%) were associated with small concomitant disk herniations or underlying annular tears. The magnetic resonance imaging and computed tomographic findings were similar to those in extruded/free-fragment disk herniation. The strong coincidence between epidural hematoma and underlying disk disruption (annular tear or herniation) leads the authors to postulate that spontaneous epidural hematoma results from tearing of fragile epidural veins lying adjacent to the displaced anulus or nucleus.

Jogging causes acute changes in the knee joint: an MR study in normal volunteers.

As MR imaging allows evaluation of soft-tissue structures not previously possible with imaging techniques, we undertook a preliminary study to evaluate the effects of a popular form of exercise (jogging) on the knee. The specific question prompting our investigation was, does repetitive impulse loading produced by jogging cause acute structural changes within the knee that are visible by MR imaging? The knees of 10 healthy subjects were examined on a 1.5-T MR system before and immediately after 30 min of continuous jogging. The same extremity was examined each time, and the imaging sequences and photographic technique (meniscal windows) were identical for both examinations. Effusions developed in five of 10 subjects after exercise. In addition, five of 10 subjects had subtle increased signal intensity within their menisci. These results suggest that jogging frequently leads to acute changes in the knee that are visible on MR imaging. The significance of these changes is unknown.

Advanced imaging of the wrist.

Abnormalities of the wrist present a difficult diagnostic challenge requiring thorough evaluation of both osseous and soft-tissue structures. Advanced techniques such as scintigraphy, computed tomography, three-phase arthrography, and, most recently, magnetic resonance imaging have added greatly to our understanding of wrist pathology. This article discusses the application of these techniques in imaging the wrist.

Pseudopseudarthrosis in a patient with ankylosing spondylitis.

There is a growing consensus that the mechanism leading to extensive discovertebral destruction (type III) in most patients with ankylosing spondylitis relates to fracture and subsequent pseudarthrosis. We introduced the term "pseudopseudarthrosis" to describe (in our case) the occurrence of abnormal motion between 2 fused spinal segments, resulting in extensive discovertebral destruction without fracture or pseudarthrosis.

Dual-energy radiographic absorptiometry of the lumbar spine: clinical experience with two different systems.

Dual-energy radiographic absorptiometry (DRA) of the lumbar spine was performed in 222 subjects (aged 17-92 years) of both sexes with use of two different systems. In a sub-group of 21 patients, results were compared with those obtained by means of dual-photon absorptiometry (DPA) of the lumbar spine. There was a high correlation among the results obtained with three instruments (r = .9, P less than .0001), and interconversion factors were calculated. Data conversion based on these regression equations may be useful for comparing results from one laboratory to another.