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Biomedical subjects

S L Weinstein

Publications and source records attributed to S L Weinstein.

At least 73 records · Page 4Linked to original sources
PubMed1990

The effects of contact pressure elevations and aseptic necrosis on the long-term outcome of congenital hip dislocation.

The relationship between excessive articular contact pressure, aseptic necrosis, and the long-term outcome with unilateral congenital dislocation of the hip (CDH) was studied in a series of 84 patients treated by closed reduction and followed for an average of 29.2 years. Contact stress was estimated from archived radiographs taken at the time of maturity and at several follow-up visits. At a recent review, each patient was rated both clinically for pain and function and radiographically for deformity, degeneration, and aseptic necrosis. For each of 431 archived films, articular contact stress (force/area) was estimated mathematically, based upon a frontal plane equilibrium (force) analysis and a landmark-based inference of three-dimensional head surface (area). Good correlation with final deformity (Spearman rho = 0.78) was obtained when the hips were ranked in terms of a new cumulative overpressure index Pc, defined as a time-pressure product involving years of pressure exposure beyond a 2 MPa pressure damage level. An unsatisfactory outcome occurred in 90.4% of the hips experiencing Pc greater than 10 MPa-years (most of which had aseptic necrosis involvement), whereas the outcome was satisfactory in 80.9% of hips with Pc less than 10 MPa-years.

Adolescent↗
PubMed1990

Validity and reliability testing of the Scoliometer.

This study was designed to evaluate the Scoliometer, an instrument that measures axial trunk rotation in individuals with scoliosis. The objectives included determining 1) the Scoliometer's screening capability and validity and 2) the intrarater and interrater reliability of Scoliometer measurements. Scoliometer measurements made by two raters on 65 persons with idiopathic scoliosis were correlated with radiographic assessment of vertebral (pedicle) rotation and lateral curvature (Cobb method). Correlation ranged from .32 to .46 with pedicle rotation and from .46 to .54 with the Cobb angle. Frequency analysis revealed relatively good specificity, sensitivity, and predictive capability of the Scoliometer. Intrarater and interrater reliability coefficients were high (r = .86-.97). These results indicate good measurement reproducibility. The less-than-optimal between-method correlation coefficients suggest that the validity of Scoliometer measurements is not sufficient to use this method alone for determining patient diagnosis and management. Based on the positive-frequency analysis, however, the use of this tool as a screening device would be appropriate.

Adolescent↗
PubMed1989

Compound muscle action potentials and spinal evoked potentials in experimental spine maneuver.

In this study, the authors evaluated the effects of spine manipulations, similar to those used in scoliosis surgery, on the compound muscle action potential (CMAP) and spinal evoked potential (SEP) in 25 cats: a distraction maneuver was performed in ten, a rotation in five, and a combined (distraction and rotation) procedure in ten cats. Compound muscle action potential was only minimally changed by the rotation maneuver alone in all five cats. Distraction resulted in earlier deterioration of CMAP than SEP; when CMAP was no longer elicitable in ten cats, seven still showed measurable SEP. All ten cats became paraplegic. With the combined procedure, both CMAP and SEP were abolished earlier than with distraction alone. This was observed in all ten cats becoming paraplegic. The authors further extended the study to ten rabbits having experimentally induced scoliosis. Following corrective surgery with distraction and derotation, eight rabbits lost both CMAP and SEP. Two lost CMAP with still recordable SEP. All ten rabbits became paraplegic. These findings suggest that monitoring CMAP is a more sensitive measure than SEP, and that the spinal cord is more vulnerable to a combined distraction and derotation maneuver than to either one alone.

Action Potentials↗
PubMed1989

Adolescent idiopathic scoliosis: prevalence and natural history.

The natural history presented in this chapter applies only to AIS. Other types of scoliosis have their own natural history and associated problems that may significantly affect the ability of the patient to meet the demands of daily life. Increased public awareness and screening clinics have resulted in an increased number of children referred for orthopaedic opinion, less severe curve magnitude at initial detection, and earlier institution of treatment. Treatment of each patient must be individualized, taking into consideration the probability of curve progression based on curve magnitude, skeletal maturity, sexual maturity, and age (Table 6-7). Overdiagnosis and unnecessary treatment must be avoided. As our knowledge of the natural history of AIS expands, treatment decisions can be based on objective rather than subjective data. Any proposed treatment of this condition must have a reasonable chance of altering the natural history in a positive way. The information available on natural history has been accumulated on relatively small groups of patients and the conclusions presented represent generalities. There are probably many "natural histories" for AIS, especially with reference to curve progression; therefore, treatment decisions must be individualized. Long-term results of various treatments for scoliosis must take into consideration the natural history of the disorder.

Adolescent↗
PubMed1989

[Idiopathic scoliosis in adolescence. Incidence and progression of untreated scoliosis].

Decision making in adolescent idiopathic scoliosis (AIS) requires a thorough knowledge of the natural history. Treatment decisions must be individualized based on the probabilities of progression. Any treatment for AIS must influence the "natural history" in a positive way. The natural history of AIS with reference to back pain, effects on pulmonary function, psychosocial effects, mortality, effect on pregnancy and risks of progression in the immature and mature patient are presented.

Adolescent↗
PubMed1988

Dissociation of muscle action potentials and spinal somatosensory evoked potentials after ischemic damage of spinal cord.

In patients undergoing spinal fusion and Cotrel-Dubousset instrumentation we recorded compound muscle action potentials (CMAP) from the lower limb and spinal somatosensory evoked potentials (SSEP) from the caudal epidural space after direct stimulation of rostral spinal cord via epidural electrodes. In three of 30 patients tested, the derotation maneuver altered CMAP but not SSEP. In ten dogs, we observed similar dissociation with decrease or disappearance of CMAP amplitude and unchanged SSEP after ligation of the thoracoabdominal aorta or intercostal arteries at each level. In contrast, both CMAP and SSEP were unchanged by clamping the artery at the lumbar level. This is likely due to the lack of collateral vascular flow at the thoracic cord level, the anterior cord in particular, which is mainly supplied by a single large radicular artery (Adamkiewicz artery). These findings support that the CMAP and SSEP are mediated through two independent pathways located in the anterior and posterior spinal cord, respectively. We postulate that the dissociate alteration of CMAP and SSEP by derotation maneuver is due to greater vulnerability of the anterior cord or motor tract to ischemia caused by the displacement of anterior spinal or radiculomedullary artery. Therefore, the patients requiring major derotation procedure would benefit from CMAP monitoring, which provides more sensitive measure of anterior cord function that the conventional SSEP monitoring.

Action Potentials↗
PubMed1988

The possible role of dopamine autoreceptors in neuroleptic atypicality.

Different brain pathways have been shown to subserve the therapeutic effects of neuroleptics and their extrapyramidal side effects. Agents which can discriminate between these pathways, therefore, might be able to produce 'atypical' clinical effects. Molindone, a novel neuroleptic of the indoleamine class, has been shown in basic paradigms to discriminate between brain dopaminergic systems by virtue of its ability to preferentially inhibit dopamine autoreceptors (DARs). Clinical studies suggest that molindone may be less likely than traditional neuroleptics to induce tardive dyskinesia and that molindone may preferentially ameliorate some negative schizophrenic symptoms. We suggest that the distinct clinical effects of molindone result from its ability to block DARs.

Animals↗
PubMed1988

Spike osteotomy for angular deformities of the long bones in children.

We reviewed the results of fifty consecutive spike osteotomies that were performed in thirty-five children for the treatment of angular deformity of a long bone. After forty-three of the procedures, the radiographs were adequate to assess the stability of the fragments. At the time of healing, the average loss of correction from the position that had been accepted at operation was 2 degrees in the anterior-posterior plane and 1.2 degrees in the lateral plane. In four limbs, more than 5 degrees of correction had been lost. No patient lost more than 10 degrees of correction. The rates of complications and of recurrence were similar to those of other reported series. We concluded that the spike osteotomy is safe and effective.

Adolescent↗
PubMed1988

Monitoring of motor action potentials after stimulation of the spinal cord.

We recorded motor action potentials in cats, using surface electrodes placed over the soleus muscle. The action potentials were generated by stimulating the spinal cord with electrodes in the epidural space at the level of the fifth or sixth thoracic vertebra. This also was done in humans, using the same methods of stimulating and recording, but the intensity of the stimulus was adjusted to produce little or no twitch of the paraspinal muscles. In the animal experiment, the motor action potential was abolished after transection of the pyramidal tract and was progressively attenuated with effective doses of a curare-like agent. We also tested the effect of distraction, using the same technique as is used in Harrington instrumentation, and found that the amount of distraction that caused reduction of the amplitude of the motor action potential of more than 50 per cent, when sustained for longer than seven minutes, caused permanent paraplegia in two cats. The evaluation of spinal evoked potentials that were obtained from epidural electrodes placed caudad to the level of distraction, and of motor action potentials that were recorded over the soleus muscle, following the same stimulus, showed a similar pattern of reduction after distraction in five of seven cats. The other two cats had irreversible reduction of motor action potential associated with unchanged spinal evoked potential, and both cats became paraplegic.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1987

Natural history of congenital hip dislocation (CDH) and hip dysplasia.

For normal development of the hip joint to occur, there must be a delicate, genetically determined balance between growth of the acetabular and triradiate cartilages and a well-centered femoral head. This balance may be profoundly affected by the intrauterine environment. Without treatment, it is uncertain how many dysplastic, unstable hips will retain their dysplastic features throughout life. The natural history of untreated complete dislocation varies considerably and is affected by societal considerations. There may be little, if any, functional disability in many cases. Significant roentgenographic degenerative disease and poor clinical results, however, may develop in completely dislocated hips with well developed false acetabulae. In unilateral cases, ipsilateral knee deformity and pain may develop. Congenital subluxations have a particularly poor long-term outcome. A significant percentage of these patients have roentgenographic degenerative joint disease and clinical disability. The age of symptom onset and roentgenographic degenerative joint disease is related to the amount of subluxation and dysplasia. The natural history of acetabular dysplasia in the absence of subluxation is difficult to predict. Physical signs may be absent, and the diagnosis only established with symptom onset or as an incidental roentgenographic finding. While degenerative joint disease may ensue, current roentgenographic parameters are not predictive.

Adult↗
PubMed1987

Long-term follow-up of patients with grade-III and IV spondylolisthesis. Treatment with and without posterior fusion.

The outcome in eleven patients in whom Grade-III and IV spondylolisthesis was treated non-operatively (Group I) was compared with that in twenty-one patients in whom the same degrees of spondylolisthesis were treated by posterior interlaminar fusion (Group II). At an average eighteen-year follow-up of the eleven patients in Group I, four (36 per cent) were asymptomatic, six (55 per cent) had mild symptoms, and only one had significant symptoms. Five (45 per cent) had one or more neurological findings, but none were incontinent. All of the patients in this group led an active life, and all had required only minor adjustments in their life-style. At an average twenty-four-year follow-up of the twenty-one patients in Group II, twelve (57 per cent) were asymptomatic, eight (38 per cent) had mild symptoms, and only one had significant symptoms. Nine (50 per cent) of the eighteen patients who had a physical examination had one or more neurological findings. Roentgenographically demonstrated failure of fusion did not adversely affect the results, and the patients remained asymptomatic despite the development of pseudarthrosis in one patient and bending of the fusion mass in three (14 per cent). In situ arthrodesis provides acceptable results for the patient who has Grade-III or IV spondylolisthesis and pain that interferes with life-style and that is unresponsive to non-operative treatment. In the skeletally immature patient, in situ fusion is recommended for disturbances of gait secondary to tight hamstrings and when the spondylolisthesis progresses.

Adolescent↗
PubMed1986

Idiopathic scoliosis. Natural history.

This study reviews the prognostic factors in curve progression in untreated idiopathic scoliosis patients followed an average of 40 years. A select group of 54 patients with 67 curves with complete radiographs from initial presentation, skeletal maturity, 30-year follow-up and 40-year follow-up were analyzed for radiographic factors leading to curve progression. Analysis of these patients confirmed that the radiographic factors identified at skeletal maturity leading to curve progression apply to the skeletally immature patient as well.

Adolescent↗
PubMed1986

Renal handling of cadmium in perfused rat kidney and effects on renal function and tissue composition.

Isolated rat kidneys perfused with a Krebs-Ringer bicarbonate (KRB) solution containing 1 microM CdCl2 plus 6% substrate-free albumin (SFA) and a mixture of substrates accumulated substantially less cadmium in tissue than kidneys perfused with 1 microM CdCl2 in a protein-free KRB solution containing the same substrates: 11 vs. 205 nmol Cd/g dry wt. Decreasing the glomerular filtration rate (GFR) by occluding the ureters of kidneys perfused in the absence of albumin did not change the rate of net tissue uptake of cadmium (Cd), suggesting that the kidney can extract Cd from the peritubular capillary fluid and that net uptake of Cd is not dependent on the reabsorption of filtered Cd. The tissue accumulation of large quantities of Cd (1.8 mumol Cd/g dry wt), which established levels of non-metallothionein-bound Cd exceeding 1 mumol Cd/g dry wt, caused no changes in either GFR, perfusion flow rate, fractional reabsorption of Na+, fractional reabsorption of K+, fractional reabsorption of glucose, or free-water clearance. However, discrete changes in renal tissue K+ content were observed. Exposure to 1 microM CdCl2 resulted in a net loss of renal tissue K+ in rat kidneys perfused with substrate-enriched KRB containing 6% albumin. Exposure to 0.8 microM or 7 microM CdCl2 completely prevented K+ loss from kidneys perfused with a substrate-enriched, protein-free KRB solution.

Absorption↗
PubMed1985

QTc and R-R intervals in victims of the sudden infant death syndrome.

Electrocardiograms obtained during sleep within the first and/or fourth week postnatally were available on eight infants who subsequently died of the sudden infant death syndrome (SIDS). The corrected QT (QTc) and R-R intervals were compared with controls for the purpose of evaluating their relevance for SIDS. The QTc interval in controls increased with age and tended to be longer during sleep without rapid eye movements. The R-R interval decreased with age. None of the SIDS victims was found to have a prolonged QTc interval. However, the R-R interval during rapid eye movement epochs was significantly shorter in future SIDS victims compared with controls. These data were interpreted as being inconsistent with the congenital variants of the long-QT hypothesis but compatible with the growing conviction that infants who die of SIDS have a chronic underlying abnormality that has subtle manifestations within the immediate postnatal period.

Electrocardiography↗
PubMed1985

Spinal cord monitoring. Electrophysiological measures of sensory and motor function during spinal surgery.

Various recording methods were tested in 60 patients who underwent scoliosis surgery to find the most suitable technique for the spinal cord monitoring and to elucidate the neuroanatomic relationship of the evoked potentials recorded by these methods. Responses were recorded from the scalp and spine after stimulation of the tibial nerve or the spinal cord. The potentials from electrodes placed over the muscles and the tibial nerve after stimulation of the spinal cord were also recorded. Epidurally recorded spinal evoked potentials after stimulation of the tibial nerve generally consisted of two major negative peaks, NI and NII, and subsequent multiple waves. NI may be mediated through the spinocerebellar tract, and NII is most likely mediated through the dorsal column. The polyphasic waves are probably conducted through the slower sensory ascending pathways. The potentials recorded from the muscle after spinal cord stimulation may be mediated through the motor tract. Various recording techniques described in this study were mutually complimentary in confirming the results of tests recorded in the technically difficult environment of the operating room. In general, spinal cord stimulation recorded from the scalp or the spine was superior to peripheral nerve stimulation in yielding better defined responses. If the potential recorded from the muscle after stimulation of the spinal cord is indeed mediated through the motor pathway, this would be useful to assess motor function during surgery.

Action Potentials↗
PubMed1984

Adductor tenotomy-obturator neurectomy.

A 3.7-year follow-up study of 25 cerebral palsied children with 41 adductor tenotomies and obturator neurectomies showed significant improvement in hip abduction and acetabular development.

Cerebral Palsy↗