VALUE OF A SINGLE-SHOT TURBO SPIN-ECHO PULSE SEQUENCE FOR ASSESSING THE ARCHITECTURE OF THE SUBARACHNOID SPACE AND THE CONSTITUTIVE NATURE OF CEREBROSPINAL FLUID

Three case history reports are presented to illustrate the value of the single-shot turbo spin-echo pulse sequence for assessment of the subarachnoid space. The use of the single-shot turbo spin-echo pulse sequence, which is a heavily T2-weighted sequence, allows for a rapid, noninvasive evaluation of the subarachnoid space by using the high signal from cerebrospinal fluid. This sequence can be completed in seconds rather than the several minutes required for a T2-fast spin-echo sequence. Unlike the standard T2-fast spin-echo sequence, a single-shot turbo spin-echo pulse sequence also provides qualitative information about the protein and the cellular content of the cerebrospinal fluid, such as in patients with inflammatory debris or hemorrhage in the cerebrospinal fluid. Although the resolution of the single-shot turbo spin-echo pulse sequence images is relatively poor compared with more conventional sequences, the qualitative information about the subarachnoid space and cerebrospinal fluid and the rapid acquisition time, make it a useful sequence to include in standard protocols of spinal magnetic resonance imaging.     

Continuity and Change in an Old Industrial Region

Analysts have debated the extent to which recent economic changes represent a continuation of earlier patterns or a fundamental shift to a new industrial order. We trace and extend the spatial implications of this debate for a mature industrial region, the Ohio River Valley, part of the American Manufacturing Belt, for the 1980-90 period. The paper builds on recent research arguing that such regions had a diverse, rather than homogeneous, space-economy. Empirical findings clearly demonstrate diversity of economic structures, sectorally and spatially, emphasizing both continuity and change in an old industrial region, and the totality of economic activity rather than specific sectors identified with the rise or transformation of industrial capitalism. In terms of change, aggregate trends follow national ones, but do not wash evenly over the Ohio River Valley. Nor do they mirror, when considered at a sub-regional scale, patterns indicated by de-industrialization and post-Fordist transition frameworks. Findings provide implications for elaborating or augmenting these perspectives, and types of research needed to accomplish the task.     

THE EFFECT OF SEQUENCE SELECTION AND FIELD STRENGTH ON DETECTION OF OSTEOCHONDRAL DEFECTS IN THE METACARPOPHALANGEAL JOINT

Six cadaver forelimbs were imaged in two high‐field magnetic resonance (MR) systems and one low‐field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2^* gradient echo (GRE), T2‐weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low‐field system. PD fat saturated and 3D T1‐weighted spoiled GRE images with and without fat suppression were acquired with the high‐field systems. Lesions were measured and assigned a confidence score. The images obtained using high‐field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low‐field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low‐field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low‐field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high‐field systems when compared with the low‐field system.     

Evaluation of Fibular Head Transposition for Repair of Experimental Cranial Cruciate Ligament Injury in Dogs

Unilateral cranial cruciate ligament excision and fibular head transposition (FHT) were performed on 30 adult dogs. Vertical ground reaction forces were determined using force plate data before and after surgery. Cranial drawer motion, tibial rotation, and varus-valgus motion were measured at monthly intervals. Radiographic, gross, and histological examinations of the stifle joints that had been operated on were performed 3 weeks, 4 months, and 10 months after surgery. A scoring system was used to evaluate lameness, osteophyte formation, and meniscal damage. Rank correlation coefficients were calculated between variables tested in pairs. Cranial drawer motion and abnormal tibial rotation were present in all of the joints that had been operated on. Peak vertical force and associated impulse were not restored during the study time period. Meniscal damage was noted in 25% of the dogs at month 4 and in 50% of the dogs at month 10. Progressive gross and histological deterioration of the articular cartilage was observed in all joints. Positive correlations were noted between the degree of stifle joint instability and meniscal injury or radiographic changes. FHT did not control cranial drawer motion and rotational instability, was not successful in restoring limb function, and did not prevent joint degeneration, especially meniscal damage.     

ULTRASONOGRAPHY OF HISTOLOGICALLY NORMAL PARATHYROID GLANDS AND THYROID LOBULES IN NORMOCALCEMIC DOGS

The purpose of this study is to characterize the sonographic appearance of canine parathyroid glands using high‐resolution ultrasonography. Ten cadaver dogs were studied after euthanasia for reasons not relating to the parathyroid. The cervical region was examined using a 13–5 MHz linear transducer in right and left recumbency. Ultrasonographic features of the parathyroid and thyroid glands were compared with the gross and histopathologic findings. Thirty‐five structures were identified sonographically as parathyroid glands but only 26 of 35 glands (74% positive predictive value) were proven to be normal parathyroid glands histopathologically. Of the nine false positives, five (14%) were proven to be lobular thyroid tissue. The remaining four (11%) structures were visible grossly or found histopathologically. There were no statistical differences between ultrasonographic and gross measurements of the parathyroid glands. The average size as seen sonographically was 3.3 × 2.2 × 1.7 mm and the average gross size was 3.7 × 2.6 × 1.6 mm (length, width, height). The average size of the thyroid lobules assessed sonographically was 2.3 × 1.6 × 0.8 mm (length, width, height). Normal parathyroid glands can be identified using high‐resolution ultrasonography. But some thyroid lobules will be misinterpreted as parathyroid glands; this will result in false positives when identifying parathyroid glands with ultrasonography.     

The Effects of Plate Type, Angle of Ilial Osteotomy, and Degree of Axial Rotation on the Structural Anatomy of the Pelvis

Unilateral triple pelvic osteotomy was performed with three variations in technique on canine cadaver pelves. The following variables were studied: the angle of the ilial osteotomy (perpendicular to the long axis of the ilium and 10d?, 20d?, and 30d? off perpendicular); the degree of axial rotation (20d?, 30d?, and 45d?); and the type of fixation (canine pelvic osteotomy plate [CPOP] or a 2.7-mm dynamic compression plate [DCP]). Structural changes measured were the pelvic inlet and acetabular area, interischiatic tuberosity distance, and degree of acetabular version. Means and standard error of the means were determined for all pelvic measurements and were analyzed by three-way analysis of variance (P < .05). As the axial rotation increased from 20d? to 45d? an ilial osteotomy angled 10d?, 20d?, or 30d? resulted in a significantly greater decrease in the pelvic inlet area and significantly less deviation of the interischiatic tuberosity distance and degree of acetabular version from normal than an osteotomy directed perpendicular to the long axis of the ilium. Compared with the CPOP, as the axial rotation increased from 20d? to 45d?, the DCP resulted in a significantly greater decrease in the pelvic inlet area, an increase in the interischiatic tuberosity distance and degree of acetabular version, and less of an increase in the acetabular area. The results of this study suggest that to maximize dorsal acetabular coverage, while minimizing disruption of normal pelvic architecture, a CPOP and an ilial osteotomy angled 10d? to 30d? are preferred for all degrees of axial rotation.     

Evaluation of the Lateral Collateral Ligament After Fibular Head Transposition in Dogs

Cranial transposition of the fibular head stabilizes the stifle joint by displacing the distal attachment of the lateral collateral ligament (LCL). The forces applied to the LCL after displacement may cause ligamentous elongation. This investigation evaluated the morphological, histological, and biomechanical changes of the LCL after fibular head transposition (FHT) in dogs. Unilateral cranial cruciate ligament (CCL) excision and FHT were performed on 25 dogs. Cross-sectional area, length, histological, and structural properties of the LCL were evaluated 3 weeks, 4 months, and 10 months after surgery. Ligament length means were significantly increased at week 3, month 4, and month 10 compared with intraoperative length means. No significant changes in elongation were observed after week 3. Fibrovascular proliferation within the LCL increased the cross-sectional area and associated structural properties.     

Suspensory Apparatus Prosthesis in the Horse Part 2: In Vivo Evaluation in a Suspensory Apparatus Disruption Model

The suspensory apparatus of one forelimb was surgically disrupted in six adult horses by transecting the distal sesamoidean ligaments. A double-braided prosthetic ligament made of aramid yarn was installed to support the flexor surface of the metacarpophalangeal joint. The prosthesis was routed through tunnels in the third metacarpal bone and proximal phalanx, and secured to bone with screws. Evaluation by radiography, synovial fluid analysis, cinematography, and dynamography was performed before surgery and at weeks 16 and 30. Supracondylar cortical lysis and periosteal proliferation were observed on postoperative radiographs. Synovitis and fragmentation of the prosthesis were apparent from synovial fluid evaluation. Weight bearing and metacarpophalangeal joint motion were decreased and loading was transferred in part to the opposite forelimb. Clinical lameness improved and weight bearing increased during the second half of the 30-week period. At necropsy, there was abrasion of the prosthesis and the articular surfaces in contact with the prosthesis. Diffuse granulomatous synovitis developed in response to aramid fiber fragments within the synovium.