Biomedical subjects

I Zaltz

Publications and source records attributed to I Zaltz.

3 recordsLinked to original sources

PubMed1995

Does bracing affect bone density in adolescent scoliosis?

STUDY DESIGN: This is a case-control, cross-sectional analysis of bone density. OBJECTIVES: To determine if bracing during growth affects bone density in adolescent idiopathic scoliosis and whether the effect is local or systemic. SUMMARY OF BACKGROUND DATA: Data concerning the effect of bracing on bone mass in adolescents with idiopathic scoliosis are nonexistent. We were concerned that bone mass loss resulting from long-term brace use may be permanent and may predispose to problems with osteoporosis. METHODS: Healthy adolescent females (n = 85) with scoliosis measuring 20-45 degrees and treated either by brace or observation were studied. Dietary calcium, activity level, body mass index, and pubertal status were evaluated. Scoliosis was measured by Cobb angle. Bone mineral density at the hip and spine were measured by dual energy x-ray absorptiometry to differentiate local versus systemic effects of bracing. Lateral scans of the L3 vertebral body were used to minimize the influence of the pedicles, the effect of the scoliosis, and the interference of the ilium. RESULTS: Mean age, height, and weight were similar between braced and observed groups. After adjusting for curve, Cobb angle, body mass index, activity, and diet, two-way analysis of covariance showed L3 and femoral bone mineral density was the same for braced and observed patients, and pubertal status affected spinal bone mineral density but had no effect on femoral bone mineral density. Pubertal status and body mass index accounted for 53% of the variation in spine bone mineral density and was not affected by brace use. Cobb angle, curve pattern, activity, and diet were not associated with bone mineral density. CONCLUSION: Brace treatment does not adversely affect bone mass at the spine and hip in children with idiopathic scoliosis.

Absorptiometry, Photon↗

PubMed1995

Predicting the integrity of vertebral bone screw fixation in anterior spinal instrumentation.

STUDY DESIGN: Using 2-week-old calf lumbar vertebrae as a model for the human adolescent spine, the strength and rigidity of different methods of anterior spinal screw fixation and the use of noninvasive techniques for predicting bone screw stability before surgery and screw insertional torque intraoperatively were investigated. OBJECTIVES: The objectives were to determine what factors most affect the strength and rigidity of screw fixation, to determine the strongest and most rigid type of screw fixation for anterior spinal instrumentation, and to determine if noninvasive measurements of bone density before surgery by dual energy x-ray absorptiometry or quantitative computed tomography and if intraoperative measurement of screw insertional torque can be used to predict the in vivo strength and rigidity of vertebral screw fixation. SUMMARY OF BACKGROUND DATA: Anterior spinal instrumentation is an efficient method to correct spinal deformities in the thoracolumbar and lumbar spine. Fewer vertebrae are instrumented and arthrodesed, allowing for greater spine mobility. The forces transmitted to each vertebra are higher, perhaps accounting for the clinical failure rate of 13-30% at the metal bone interface from screw cut out. METHODS: Quantitative computed tomography and dual energy x-ray absorptiometry were used to assess the bone density of 24, 2-week-old calf lumbar vertebrae. Four different methods of vertebral screw fixation were evaluated: unicortical screw, bicortical screw, bicortical screw and washer, and bicortical screws and staple. The maximal screw insertional torque was measured for each specimen. Each vertebral body-screw construct failed in a mode simulating in vivo screw cut out. The applied moment and rotatory displacement were recorded. Ash density was measured for each vertebral body after removing all hardware. RESULTS: Noninvasive measures of bone density varied linearly with ash density (P < 0.01). Screw insertional torque varied linearly with bone mineral content and bone mineral density (r2 = 0.50) and was correlated with the yield moment for all types of fixation except the staple. Density measured by quantitative computed tomography did not affect rigidity or yield moment. Post hoc analysis showed that the screw-staple construct was the strongest and most rigid form of fixation. CONCLUSIONS: Measurement of bone density before surgery using dual energy x-ray absorptiometry and intraoperative measurement of screw insertional torque can be used to assess the stability of anterior spinal instrumentation. A bicortical screw inserted through a Dwyer-type staple provided the strongest and most rigid form of fixation.

Absorptiometry, Photon↗

PubMedDate not supplied

Ulnar nerve instability in children.

We carried out a cross-sectional study to define the prevalence of ulnar nerve instability and its relationship to ligamentous laxity in the pediatric population. Children were divided into three age groups: group I (0-5 years), group II (6-10 years), and group III (11-18 years). Of children in group I 17.7%, of children in group II 7.7%, and 5.7% of children in group III had dislocating ulnar nerves. With the exception of one patient, nerve instability was bilateral. Of those children possessing all five Wynne-Davies signs of ligamentous laxity, 25.4% had dislocating nerves, 71.9% had subluxing nerves, and 2.6% had stable nerves. Age, ulnar nerve instability, and ligamentous laxity were statistically associated (p < 0.0001).

Adolescent↗