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Biomedical subjects

V K Goel

Publications and source records attributed to V K Goel.

139 records · Page 8Linked to original sources
PubMedDate not supplied

Development of spondylolytic olisthesis in adolescents.

BACKGROUND CONTEXT: Although it has been well documented that slippage in patients with spondylolysis is most prevalent during the growth period, the exact time when slippage initiates and halts during the growth period is still unknown. Moreover, the contribution of spinal deformities, such as wedging of the vertebral body to the slippage, remains controversial. PURPOSE: To clarify when slippage in pediatric spondylolysis initiates and halts. STUDY DESIGN: Retrospective study. PATIENT SAMPLE: We radiographically examined 46 athletes under 18 years of age with spondylolysis at the fifth lumbar vertebra (L5). The mean age at the first consultation was 13.3 years. The average follow-up period was 6.0 years. OUTCOME MEASURES: Longitudinal observation of slippage at L5 on radiogram in correlation with the maturity of the lumbar spine. METHODS: From a lateral radiogram of each patient, percent slippage, lumbar index (LI), and skeletal age of the affected vertebra were measured. Changes in the percent slippage over time were investigated, and the correlation between the percent slippage and LI was analyzed. RESULTS: From the cartilaginous stage to the apophyseal stage, the slippage increased in 80.0% of the patients (16 of 20). From the cartilaginous stage to the epiphyseal stage, slippage increased in 11.1% of the patients (3 of 27). None of the patients (0 of 22) showed an increase after the epiphyseal stage. In 20 patients in whom slippage increased during the follow-up period, the percent slippage at the final consultation and the LI at the first consultation showed no significant correlation; however, the percent slippage and the LI at the final consultation were significantly (p<.01) correlated. CONCLUSION: In conclusion, slippage was more prevalent in individuals of a younger skeletal age whose lumbar spine was immature, and it halted during the epiphyseal stage when the growth period was over and the vertebra matured. Furthermore, the results suggest that wedge deformity of an affected vertebra might be the result rather than the cause of slippage.

Adolescent↗
PubMedDate not supplied

Physiologic strains in the lumbar spinal ligaments. An in vitro biomechanical study 1981 Volvo Award in Biomechanics.

For understanding of the mechanical causes of low-back pain, knowledge of the biomechanics of the various spinal elements is essential. In this in vitro biomechanical study, in situ behavior of spinal ligaments of the L3-4 and L4-5 functional spinal units during physiologic activities was studied in a three-stage procedure. First, 72 load-displacement curves were obtained to determine the three-dimensional flexibility characteristics of the spinal units. Second, three-dimensional morphometric measurements were made of all the spinal ligament attachment points. Finally, a mathematical model was constructed to combine the flexibility and morphometric data and compute the ligament length changes and strains as functions of various spinal movements. In flexion movement, the interspinous and supra-spinous ligaments were found to be subjected to the highest strains, followed by the capsular ligaments and the ligamentum flavum. During extension, it is the anterior longitudinal ligament that has the maximum strain. In lateral bending, the contralateral transverse ligaments carried the highest strains, while the interspinous and supraspinous ligaments were relatively unstrained. In rotation, the capsular ligaments were by far the most strained ligaments.

Adult↗
PubMedDate not supplied

Kinematics of lumbar intervertebral foramen.

This in vitro study provides original data regarding the three-dimensional movements of the intervertebral foramen as the spine undergoes normal physiologic motions. Three-dimensional flexibility characteristics of fresh cadaver functional spinal units were determined. The same spinal units were fixed and thinly sectioned to yield quantitated anatomy of the soft and hard tissues of the specimen in three-dimensions. The flexibility and anatomic data were stored in a computer. A mathematical model was utilized to combine the two data sets, resulting in a precise three-dimensional description of the movements of the intervertebral foramen. Changes in foramen height, width, and area were obtained as functions of major spinal motions. Preliminary results indicate differences in intervertebral foramen kinematics of nondegenerated and degenerated spines. Such changes may affect the nerve root adversely and hence participate in pain production.

Biomechanical Phenomena↗
PubMedDate not supplied

The role of lumbar spinal elements in flexion.

The forces induced in the disc and ligaments of a lumbar motion segment in resisting a quasi-static external load, using a semi-experimental approach, are presented. The lines of action of ligaments (direction cosines) and disc center for the initial position of the specimen were determined using a morphometer. The changes in these lines of action for a known external load were computed by using the three-dimensional load-deformation characteristics of an intact motion segment. The load-deformation behavior were obtained by applying a known load to the motion segment's superior vertebra and recording the motion produced. A seven dial gauge motion measuring system was used for this purpose. The six equations of equilibrium yielded a statically indeterminate model. A linear optimization technique in conjunction with a cost function enabled the computation of forces in the ligaments as well as forces and moments in the disc. This approach made it possible to determine the component forces without a priori knowledge of the structural properties of ligaments. Typically for an external flexion moment of 6.9 Nm the supraspinous ligament experienced the most force (60 N), followed by capsular ligaments (25 N), and transverse ligaments (15 N). A compressive force of 100 N within the disc was predicted. The load-deformation curve, obtained from this study, for the supraspinous ligament was nonlinear and is in agreement with published experimental results.

Aged↗
PubMedDate not supplied

Kinematics of the whole lumbar spine. Effect of discectomy.

The biomechanical effects of discectomy on the motion behavior of whole lumbar spine are investigated using a Selspot II system. Fresh human ligamentous specimens were potted at the sacrum and clinically relevant loads (flexion/extension, right/left lateral bending, and right/left axial torsion moments) applied through a loading frame attached rigidly to the topmost vertebra of the specimen. The resulting three-dimensional motions of each vertebra for the intact specimen were recorded. The specimen was injured sequentially on the right side of the L4-5 level: partial laminectomy, partial facetectomy, subtotal discectomy, and total discectomy. The motion behavior of the specimen after each injury was recorded. The results of the injured tests were normalized with respect to the corresponding intact results. The normalized data for eight specimens were pooled for statistical analysis. Subtotal discectomy induced significantly less motion at the injury site than total discectomy, in all loading modes. At L3-4, the motion segment above the injury level, anteroposterior translation in flexion and lateral translation in left lateral bending show significant increases irrespective of the amount of nucleus excised. The clinical relevance of these findings are discussed.

Aged↗
PubMedDate not supplied

Parameters of MOD cavity preparations: a 3-D FEM study, Part II.

Stresses induced by the influence of variations in the dimensions of three different parameters of MOD cavity preparations were studied using the finite element technique. The parameters studied were the depth, isthmus width, and the thickness of the remaining interaxial dentin. A total of eight different cavity designs, divided into three groups, were compared with the normal (unprepared) tooth and other cavity designs in the same group. Enamel and dentin experienced large regional variations in compressive stresses even in normal teeth. Teeth with prepared cavities showed even more variation, and stress combinations became critical from a tooth fracture point of view. It was seen that narrow but deep cavity preparations and wide and equally deep cavity preparations experienced a similar, damaging combination of stresses. It was deduced from the stress patterns observed in this study that the depth of the cavity preparations is the most critical factor in fracture of the tooth or cusps, whereas the width of the isthmus alone is the least critical.

Dental Cavity Preparation↗
PubMedDate not supplied

Selection of an animal model for implant fixation studies: anatomical aspects.

A number of different animal models have been employed by investigators to study the biology of the bone-cement interface as it relates to the problem of hip implant loosening in humans. This study compares to the human three species (baboon, dog, and sheep) currently under use as experimental animal models from an anatomical point of view. A number of parameters, important for the dimensional design of a femoral prosthesis, loads at the hip joint and its subsequent performance, were used for comparing external and internal femoral anatomy. The baboon and dog femora were found to be most similar to the human femur in their external anatomy. The quantification of cancellous bone distribution within the medullary canal revealed that, of the species studied, the sheep femur provided the least support to the prosthesis. The results suggest that the dog and baboon are anatomically appropriate for studying hip implant biomechanics experimentally. Thus, from an anatomical point of view, the current extensive use of the dog as an experimental animal appears appropriate.

Animals↗