Biomedical subjects
Publications and source records attributed to E D Simmons.
Guidelines for radiographs of the lumbar spine are established. In general, radiographs are not believed to be necessary for a first episode of low back pain present for less than 7 weeks. Exceptions to this include various medical or physical findings, which are listed. In general, anteroposterior and lateral views only should be done initially. Indications for other views are discussed.
With the current emphasis on cost containment, it is important to order the single best diagnostic test when clinical uncertainties must be resolved. Magnetic resonance imaging is currently the optimal imaging modality to provide the maximum amount of information when evaluating patients with suspected spinal disorders. A comprehensive magnetic resonance imaging study is needed along with a subspecialty interpretation to provide the greatest amount of useful clinical information.
A retrospective review was carried out on 40 patients who met the criteria of 1) having a significant lumbar scoliosis associated with spinal stenosis, with symptoms of neurogenic claudication; and 2) having been treated with posterior decompression and pedicular screw fixation techniques. The average age of the patients was 61.5 years (range, 38-77 years), and 25 of the 40 patients were female. Eighty-eight percent of the patients had significant back pain in addition to lower extremity pain. All patients had pedicular screw fixation at all levels. Zielke instrumentation was used in 24 patients, Cotrel-Dubousset instrumentation in 8 patients, and Texas Scottish Rite Hospital instrumentation in the remaining 8 patients. After surgery, there was marked improvement in regard to pain status: 34 patients (83%) had severe pain before surgery, with 38 patients (93%) reporting mild or no pain at follow-up. Average length of follow-up was 44 months (range, 24-61 months). There were no deaths and no instrument-related failures or pseudarthroses noted in this series. A mean correction of the deformity of 19 degrees was obtained. Average scoliosis was 37 degrees before surgery and 18 degrees at follow-up.
A 44-year-old man had acute tumor lysis syndrome after a single dose of intrathecal methotrexate was administered for lymphomatous meningitis (high-grade, small noncleaved B-cell) in the setting of untreated systemic disease. The metabolic derangements reversed completely with conservative therapy and did not recur with subsequent treatment. Intrathecal methotrexate administration results in potentially toxic systemic methotrexate levels which persist longer than an equivalent systemic dose. Active central nervous system lymphoma may increase the duration of toxic levels in the circulation and contribute to the peripheral effects of the drug. The pathogenesis of tumor lysis syndrome in this patient and the mechanisms of systemic toxicity of intrathecal methotrexate are discussed.
Bone undergoes structural changes with aging, but the nature of qualitative changes remains to be established. Blocks of midshaft femur were taken at autopsy from men of four different age groups: 20-25 years, 40-45 years, 60-65 years, and 80-85 years. Each femoral specimen was analyzed by density fractionation, a technique that allows the separation of bone by extent of mineralization and maturity. In the 20-25 group, lower density bone predominates. The 40-45 group is characterized by more highly mineralized bone with an increase in the 2.1-2.2 g/cc fraction. At 60-65 years, an increase in the lower density fraction was found, indicating an increase in new bone formation. At 80-85 years, there is an increase in the highest density bone (2.2-2.3 g/cc), which may represent regions of interstitial bone not properly removed through remodeling processes. Chemical studies did not reveal any change in Ca, P, Ca + PO4, or Ca/P molar ratio with respect to age. X-ray diffraction studies show no changes in apatite crystal size with respect to age or degree of mineralization. Morphological studies documented increased remodeling activity and endosteal trabecularization in the older age groups, as well as increased intracortical porosity. An increase in the highest density fraction with aging may represent a pool of bone mineral that is less accessible to remodeling, which may be the interstitial bone.
The accuracy of a tibial medullary alignment device is assessed radiographically in 30 varus and 30 valgus knees undergoing total knee arthroplasty. The results suggest that although the device is reliable and accurate for varus knees, it may lead to malalignment of up to 5 degrees in valgus knees. Overall neutral alignment was achieved in 83% of the varus knees and 37% of the valgus knees. Tibial bowing was the main source of error and was present in 66% of the valgus knees, with mean of 3 degrees. Preoperative long films or cross-checking with external alignment devices is recommended to assure neutral alignment in genu valgus deformity.
Fifteen independent observers of three levels of experience (consultant staff, fellows, residents) assessed 40 radiographs of children presenting with Perthes' disease using the Catterall and the Salter-Thompson grading systems. Each observer was supplied with descriptions and illustrations of the classifications and each hip was grouped by both systems by each observer. The results were statistically analysed using 'kappa' statistics. The level of interobserver agreement was higher for the Salter-Thompson system and correlated with the level of experience of the observer. Both systems can give acceptable levels of interobserver agreement, but the Salter-Thompson grouping is simpler and easier to apply in the earlier stages of the disease when treatment must be decided, and has a higher degree of reproducibility amongst more experienced observers.
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The effects of castration on cortical bone structure and chemistry were studied in male Wistar rats of two age groups, 8 and 24 months. Some rats were castrated and some were sham operated (control) in each group. All animals were killed after 4 months. Although no changes in serum chemistry, bone chemistry, or bone histology could be found, the young castrated animals versus controls showed less density of bone mineral as determined by the density fractionation technique and smaller crystallite size of mineral particles as determined by x-ray diffraction line-broadening analysis. These changes, indicative of less mature bone formation, were not observed in mature castrated or control rats despite a decreased amount of bone compared with young rats. In this model, castration appears to affect bone mineral quality in young but not in old animals.