PubMed Health⌕ Search

Biomedical subjects

J D Rubenstein

Publications and source records attributed to J D Rubenstein.

At least 19 recordsLinked to original sources
PubMed1997

Image resolution and signal-to-noise ratio requirements for MR imaging of degenerative cartilage.

OBJECTIVE: The purpose of this study was to determine the MR image resolution and signal-to-noise ratio (SNR) required to reveal morphologic abnormalities in degenerative cartilage. MATERIALS AND METHODS: In vitro MR microscopy of healthy bovine and degenerative human patellar cartilage was performed and image resolution degraded to simulate resolution achievable in routine and optimized clinical MR images. Noise was then added to images as in-plane resolution was increased to simulate the MR imaging appearance of cartilage with improved resolution, which is possible using a standard magnetic field strength. MR images of patellar cartilage from a healthy volunteer were also obtained to determine optimal SNR and image resolution achievable at 1.5 T; these images were compared with in vitro images to determine those features of abnormal cartilage that can be identified using available clinical MR imaging techniques. RESULTS: In-plane resolution of 39 microns exquisitely defines degenerative changes in articular cartilage. As in-plane resolution decreases to 600 microns, only gross cartilage thinning and signal intensity alterations are seen. MR images simulating progressively improved resolution using higher field strength gradients with conventional field strengths and RF coils provided suboptimal information because of low SNR. CONCLUSION: Routine clinical MR images do not accurately reveal early degenerative changes in articular cartilage; only large defects and distorted changes in the signal intensity of cartilage are seen.

Adult↗
PubMed1996

Effects of compression and recovery on bovine articular cartilage: appearance on MR images.

PURPOSE: To determine the influence of compression and decompression on bovine articular cartilage as it appears on magnetic resonance (MR) images. MATERIALS AND METHODS: Consecutive spin-echo MR images (repetition time msec/echo time msec = 800/33) of normal bovine cartilage were obtained with increasing increments of pressure, to a maximum of 4.14 MPa (600 psi); this was followed by consecutive MR imaging after release of the pressure. RESULTS: Before compression, cartilage showed a laminated appearance. After incremental pressure, cartilage thickness progressively decreased; a short T2, low-signal-intensity lamina became thicker and more distinct at the articular surface; signal intensity of the deep cartilage zone initially was high and then gradually decreased; and at maximum pressure, the cartilage showed uniform low signal intensity. After release of pressure, signal intensity changes in the cartilage were sequentially reversed from those observed with compression. Image resolution and echo time influenced the appearance of these findings, particularly the low-signal-intensity line at the cartilage interface. CONCLUSION: The varying appearance and signal intensity characteristics of cartilage under pressure are hypothesized to result from a combination of net water loss and alteration in collagen orientational structure.

Animals↗
PubMed1994

Investigating the genetic basis for ankylosing spondylitis. Linkage studies with the major histocompatibility complex region.

OBJECTIVE: To assess the hypothesis that B27 or a gene(s) in close proximity (e.g., within or near the major histocompatibility complex [MHC]) represents a disease-causing ankylosing spondylitis (AS) gene, and therefore contributes directly to the pathogenesis of this disorder. METHODS: MHC haplotypes were determined by both serologic and molecular analyses in 15 multiple-case AS families from Toronto and Newfoundland. Segregation of MHC haplotypes with AS within these families was examined by linkage and identity-by-descent analyses. Attributable risk estimates for various genetic markers and for sex were calculated. RESULTS: Linkage analyses established significant linkage between AS and the MHC, the maximal logarithm of odds (LOD) score being 3.48 at a recombination frequency (O) of 0.05. In a second analysis in which the population association of the MHC gene HLA-B27 with AS was taken into account, the maximal LOD score was 7.5 at O = 0.05. Identity-by-descent analyses showed a significant departure from random segregation among affected avuncular (P < 0.05) and cousin (P < 0.01) pairs. The presence of HLA-B40 in HLA-B27 positive individuals increased the risk for disease more than 3-fold, confirming previous reports. Disease susceptibility modeling suggested an autosomal dominant pattern of inheritance, with penetrance of approximately 20%. CONCLUSION: These data provide the first conclusive demonstration of linkage between the MHC region and AS, and confirm that genes within this region contribute directly to the genetic susceptibility for AS.

Adolescent↗
PubMed1993

Effects of collagen orientation on MR imaging characteristics of bovine articular cartilage.

To determine the influence of collagen orientation on the magnetic resonance (MR) imaging appearance of articular cartilage, spin-echo MR images of normal bovine patellar specimens were obtained with the specimens rotated in 5 degrees increments between +75 degrees and -130 degrees. Hyperintense superficial, hypointense middle, and intermediate-intensity deep laminae were observed. Results of polarized light microscopy of histologic specimens confirmed the three zones, and transmission electron microscopy showed different collagen arrangements in the zones. An anisotropic effect of rotation on signal intensity was evident, especially in the hypointense second lamina. Because of the preferential alignment of water molecules associated with collagen, angular rotation of the cartilage in the direction of minimum dipolar coupling (55 degrees to the magnetic field) caused the cartilage to have a homogeneous appearance. The MR imaging appearance of these layers is strongly influenced by an anisotropic arrangement of the collagen fibers and by the alignment of the specimen relative to the magnetic field.

Animals↗
PubMed1986

POEMS syndrome. Study of a patient with proteinuria, microangiopathic glomerulopathy, and renal enlargement.

We studied a patient with POEMS syndrome (plasma cell dyscrasia with polyneuropathy, organomegaly, endocrinopathy, monoclonal [M]-protein, skin changes) who was also found to have renal enlargement and microangiopathic glomerulopathy. The latter finding is unusual in POEMS syndrome patients, and the associated symptoms can lead to confusion in diagnosis. We emphasize the importance of considering POEMS syndrome in the differential diagnosis of patients who have unexplained neuropathy, scleroderma-like skin changes, and/or monoclonal gammopathy.

Adult↗
PubMed1986

Computerized tomography of the distal radioulnar joint: correlation with ligamentous pathology in a cadaveric model.

The kinematics of the normal distal radioulnar joint (DRUJ) and the stabilizing function of various structures about the DRUJ were investigated in a study involving six fresh frozen cadavers. Sequential division of the supporting structures was correlated with abnormalities detected by computerized tomography (CT). The infratendinous portion of the extensor carpi ulnaris is a major restraint against dorsal and palmar subluxation. Division of the radioulnar ligaments and triangular fibrocartilage alone produced only minor changes. Lateral displacement was controlled by the interosseous membrane and the pronator quadratus. CT is a useful method of gaining objective and quantifiable information regarding incongruity of the DRUJ. Three scans--one each in pronation, neutral, and supination--would be optimal. The pronation scan is likely to detect palmar subluxation, while the neutral scan is sensitive for dorsal subluxation and DRUJ diastasis. The supination view should confirm reduction of any subluxation. An important observation of this study was the spontaneous reduction of palmar, dorsal, and lateral displacement in supination. This suggests that immobilization in supination may be indicated in cases of acute DRUJ injury.

Cadaver↗
PubMed1986

Kinematics of the distal radioulnar joint.

The kinematics of the normal distal radioulnar joint (DRUJ) in five fresh frozen cadavers were investigated by means of computerized tomography (CT). Rotation of the radius about the ulna is accompanied by translation so that in supination the ulna is somewhat palmar, and in pronation the ulna is more dorsal relative to the radius. The average ranges of motion of the hand and DRUJ were 260 degrees and 190 degrees, respectively. Significant carpal and metacarpal rotation occurred with pronation-supination of the hand. The DRUJ has both rotational and translational components of movement and does not have a single center of rotation. The pathway of the instantaneous centers of rotation, or centrode, of the DRUJ has a characteristic pattern. The centrode moves in a direction opposite that of the DRUJ movement and is located near the center of the ulnar head. A prosthetic joint for the DRUJ should not have a fixed axis of rotation but should allow the normal translatory motion of the ulna and radius if early joint failure is to be prevented.

Biomechanical Phenomena↗
PubMed1986

False-normal bone imaging in spinal tuberculosis.

Tc-99m MDP bone imaging in spinal tuberculosis usually shows increased radioactivity at the sites of involvement. Uncommonly, the bone scan can be normal if the infection is low grade, indolent, or severely destructive. Two cases of spinal tuberculosis with normal bone imaging are reported. A normal bone image does not exclude tuberculous spondylitis. If there is clinical suspicion of this disease, further investigations, including tissue specimens, should be obtained.

Aged↗
PubMed1985

Computed tomography in the diagnosis of early ankylosing spondylitis.

Computed tomography (CT) was compared with plain radiography and quantitative sacroiliac (SI) scintigraphy in 28 patients with early ankylosing spondylitis (AS) of less than or equal to 10 years duration. Compared with conventional radiography, CT improved delineation of the SI joints and revealed more abnormalities and higher grades of sacroiliitis; this was significant in patients with early AS of less than or equal to 3 years duration. Quantitative sacroiliac scintigraphy showed higher SI joint: sacrum ratios of radioisotope uptake in patients with AS compared with controls. However, its diagnostic usefulness was limited by the frequency of inconsistent results and the lack of specificity. CT examination of the SI joints may be a useful adjunct in the diagnosis of early AS.

Adult↗
PubMed1985

Traumatic scapulothoracic dissociation.

Scapulothoracic dissociation represents a closed traumatic forequarter amputation associated with major neurovascular injury. Radiographic findings consist of lateral displacement of the scapula on a well-centered plain film of the chest. Associated abnormalities include disruption of the acromioclavicular joint or, as in our two cases, distracted fractures of the clavicle. Persons in whom scalpulothoracic dissociation is diagnosed should undergo emergency angiography and surgery.

Adult↗
PubMed1984

Radiographic assessment of Harrington rod instrumentation for spinal fractures.

The surgical procedure for Harrington stabilization of spinal fractures is described. A retrospective review was carried out on 36 patients who underwent Harrington instrumentation for spinal trauma. The group comprised 21 burst fractures, 11 fracture-dislocations and four wedge-compression fractures. Satisfactory reduction was achieved in 13 patients, unsatisfactory reduction in 19 patients, and no reduction in four patients. Loss of reduction later occurred in seven of the patients with satisfactory initial reduction. Further loss of reduction also developed in nine patients in the remaining group without satisfactory reduction initially. Radiographically demonstrable causes for loss of reduction included technical errors allowing slippage of the hooks, improper placement of the hooks, and laminar fractures.

Fracture Fixation, Internal↗
PubMed1983

Radiology of spinal trauma--practical experience in a trauma unit.

The early diagnostic management of patients with acute spinal canal trauma may be among the most difficult injuries referred to a trauma centre. No standardized protocol exists. Radiographic examinations commence with plain films, including special views. Further radiographic studies, if required, vary and include CT, myelography and conventional tomography. CT and metrizamide myelography are complementary. In more complicated fracture-dislocations, all of the above investigations may be necessary. Recent advances, including water-soluble contrast media, the lateral C1-2 puncture and CT, now offer faster, safer and more thorough follow-up investigations with less radiation exposure. Patients with multiple injuries, previously considered too severely injured to undergo further neurologic investigations, may now be more adequately assessed early in the acute phase of injury such that appropriate surgical decompression or stabilization may be performed. The maximum attainable neurologic improvement for such individuals may be better realized with the improved radio-diagnostic capabilities available.

Diagnosis, Differential↗
PubMed1983

Radiographic assessment of pelvic trauma.

Assessment of pelvic fractures requires an understanding of the bony and soft-tissue anatomy of the pelvis. Pelvic injuries may be classified into major and minor groups. Minor fractures usually result from athletic trauma in the young or falls in the elderly and can generally be adequately evaluated with routine radiography. Major fractures are most often caused by motor vehicle accidents, falls from a height or industrial accidents and require more sophisticated examination. However, the investigation of injuries in either category should be directed by a knowledge of the history and physical findings. The classification of pelvic injuries used at Sunnybrook Medical Centre is based on mechanisms of injury.

Accidents, Traffic↗
PubMedDate not supplied

Centrode patterns in the lumbar spine. Baseline studies in normal subjects.

Segmental spinal instability is a known cause of back pain, but no method of accurately quantifying instability exists. The movement of complex joints with rotational and translational components (such as the lumbar motion segment) is tracked by a pathway of instantaneous centers of rotation, or a centrode. Instability, ie, excessive and/or erratic movement, is reflected by increased centrode length in cadaver studies. This study describes an in vivo method that precisely determines the centrode pattern and reports the results for 21 normal male volunteers who were studied at the L4-5 and L5-S1 levels. Each volunteer underwent lateral radiographs of the lumbar spine. High speed films were used and six positions, from full extension to full flexion, were recorded. Acetate tracings and contour matching techniques recorded the relative positions of the vertebral bodies on each film. Multiple tracings of each radiograph, combined with a digitizer and computer, were used to improve precision in the calculated centrode patterns. Centrode lengths measured 43.7 mm and 55.9 mm, respectively, for the L4-5 and L5-S1 levels. This study demonstrates that precise centrode pattern analysis for sagittal plane motion of the lumbar spine is possible in vivo. Studies are under way to determine whether this technique will be useful as a clinical test in diagnosing early segmental instability of the lumbar spine in patients with low-back pain.

Adult↗