Biomedical subjects

Chien-Lin Liu

Publications and source records attributed to Chien-Lin Liu.

25 records · Page 2Linked to original sources

PubMed2003

Comparison of stabilities between obliquely and conventionally inserted Bagby and Kuslich cages as posterior lumbar interbody fusion in a cadaver model.

BACKGROUND: The Bagby and Kuslich (BAK) cage as posterior lumbar interbody fusion (PLIF) is reported to give satisfactory results in restoring spinal stability. Moreover, correction by obliquely inserting a single BAK cage has the advantages of reducing exposure, precise implantation, and lower cost. However, biomechanical data on this procedure are not abundant. This study was designed to compare the stability imparted by the cages placed using an oblique and posterior approaches and to determine the effects of supplementary posterior instrumentation. METHODS: After affixing nine human cadaveric spines (L2-S1) within a testing frame, load testing in several clinically relevant modes was performed sequentially for the intact and the following procedures across the L4-5 segments: posterior destabilization, stabilization using 2 parallel BAK cages (CBAK group) or 1 oblique BAK cage (OBAK group), and additional stabilization with posterior instrumentation. Spatial locations of vertebral bodies were recorded after each loading step using a 3-D motion measurement system. RESULTS: Except the OBAK group that had a lower stability in left axial rotation, there were no significant differences in the stability between both groups in all loading modes for the stabilization using cages alone. Compared with the intact cases, CBAK cages provide significant improvement in the stability in 5 displacement modes and OBAK cage may restore the stabilities of the specimens to the intact state in 5 modes and provide significant improvement in flexion. Addition of supplementary posterior instrumentation significantly reduced the angular displacements in both groups. CONCLUSIONS: Both methods of cage insertion have similar stability. Both implantations, alone or with posterior instrumentation, may improve the stability of the spine, although posterior instrumentation may further strengthen the stability. The oblique insertion is more favorable since it requires less exposure, enables precise implantation, and is less expensive.

Cadaver↗

PubMed2002

Surgical treatment of adult idiopathic scoliosis - comparison of two instrumentations.

In this study, 22 women patients with adult idiopathic scoliosis treated surgically with Cotrel-Dubousset instrumentation (CDI) or Texas Scottish Rite Hospital instrumentation (TSRHI) were followed up for 56.2+/-4.0 months. The overall immediate and final corrections were respectively 21.5+/-40 (58%) and 26.6+/-2.90 (48%), giving a loss of correction of 5.1+/-1.00 (10%). No significant differences were found in these two parameters between the two groups. The functional outcomes were good in 21 patients. There was no difference between CDI and TSRHI in deformity correction.

Adult↗

PubMed2002

A biomechanical comparison of posterolateral fusion and posterior fusion in the lumbar spine.

Late postoperative complications occurred after posterior fusion and posterolateral fusion as a result of biomechanical alterations. The stress change between the two fusion procedures has not been well reported. To differentiate the biomechanical alteration that occurs with posterior fusion and posterolateral fusion of the lumbar spine, the load sharing of the vertebrae, disc, facet joint, bone graft, and the range of motion were computed in a finite element model. Five finite element models, including the intact lumber spine, posterior fusion, posterior fusion with implant, posterolateral fusion, and posterolateral fusion with implant, were created for stress analysis. The finite element model estimated that the differences between these two fusion procedures were within 7% in stress of the adjacent disc, 3% in force of the facet joint above the fusion mass, and 5% in the range of motion. However, the stress of the pedicle in posterolateral fusion without an implant was at most two times greater than that in the intact lumbar spine under lateral bending. The stress of pars interarticularis in posterior fusion without an implant was also at most two times greater than that in the intact lumbar spine under lateral bending. After the implant was added, the discrepancy between the two fusion procedures decreased but still remained a relatively large difference. Therefore, the largest changes of posterior fusion and posterolateral fusion were in the pars interarticularis and pedicle, respectively.

Adult↗

PubMed2002

Biomechanical analysis of the lumbar spine with anterior interbody fusion on the different locations of the bone grafts.

The anterior lumbar interbody fusion is the common procedure in the management of the degenerated disc in the lumbar spine, but the biomechanical behavior of the fused segment would be changed because of the implantation of bone graft at the different locations. To investigate the biomechanical alteration, the study applied the finite element model to undergo the stress analysis.A three-dimensional finite element model of the lumbar spine was established, and modified to the three fusion models consisted of the bone graft at the anterior site, the middle site and the posterior site, respectively. The 12 N m flexion and the 10 N m torsion with pre-load 150 N were imposed on the L1 vertebral body. The results of the finite element model indicated that placing bone graft at anterior site could effectively resist flexion moment, and decreased the tensile force of the posterior ligaments about 15% above. Placing bone graft at posterior site could resist torsional moment, and also led to none of contact force of the facet joint in the fused segment. However, wherever the bone grafts were placed, stress slightly increased on the disc adjacent to interbody fusion about 5% below.

Bone Transplantation↗

PubMed1998

Biomechanical evaluation of a new anterior spinal implant.

OBJECTIVE: To biomechanically evaluate the construct of a new anterior spinal implant for osteoporotic patients. DESIGN: Mechanical tests and finite element analysis were designed to evaluate the spinal implant. BACKGROUND: Many osteoporotic thoracolumbar spine fractures often need surgical intervention to relieve pains, stabilize progressive kyphosis or improve neurologic impairment. Progressive kyphosis, instrumentation failure and pseudoarthrosis are often seen post-operatively. These results may be due to insufficient bonding between the screw and the vertebral body. As the end-plate is the most rigid part of the vertebral body, the spinal implant was designed so that the end-block would fix onto the end-plates of the vertebral bodies. METHODS: Two biomechanical evaluations of the new anterior spinal implant were conducted to evaluate the construct stiffness and the bonding strength between the spinal implant and the vertebral body. In the evaluation of the construct stiffness, the biomechanical tests between the new spinal implant and the Kaneda device were performed on six fresh intact porcine spines at the thoracolumbar region. In the prediction of the loading transfer between the spinal implant and the vertebral body, a three-dimensional finite element model (FEM) was built to simulate the osteoporotic vertebral body and the new anterior spinal implant. RESULTS: The results of the mechanical tests showed that the compressive stiffnesses of the Kaneda device and the new implant were 357 +/- 37 N mm(-1) and 297 +/- 98 N mm(-1). Their flexional stiffnesses were 0.339 +/- 0.126 N-m mm(-1) and 0.364 +/- 0.107 N-m mm(-1), respectively. Their torsional stiffnesses were 6.37 +/- 0.28 N-m deg(-1) and 5.30 +/- 0.71 N-m deg(-1), respectively. There were no significant differences (p > 0.01). The results of FEM showed that the new implant had high stress concentration on the junction of the screw and plate, screw and end-blocks, and between the end-plate and the end-blocks. CONCLUSIONS: The stabilization effect of the new implant was similar to that of the Kaneda device. With less rigid mechanical properties, the new implant can be more beneficial to the remodeling process of the spinal structure after instrumentation. The new anterior spinal implant showed a high potential for application to osteoporotic patients.

Journal Article↗

PubMed1998

A three-dimensional mathematical model for predicting spinal joint force distribution during manual liftings.

OBJECTIVE: A three-dimensional dynamic mathematical model was developed to discover what loads are imposed on the lumbar structures by performance of asymmetric manual liftings. DESIGN: An external model was used to estimate the intersegmental resultant forces and moments at the L(5)/S(1) joint in this dynamic biomechanical model. Using an optimization algorithm, an internal model then distributed the intersegmental resultants to forces of muscle, disc, facet joints, and ligaments. BACKGROUND: To study the relation between large loads and low-back disorders, many biomechanical models have been developed. Most of the models were two-dimensional models discussed with symmetric activities. Some three-dimensional biomechanical models were static models or only included limited elements of the disc and muscles in the model. METHODS: A healthy young male subject was asked to perform asymmetric lift with bent knees. Dynamic data of body motion and ground reaction forces were monitored, and the EMG of six muscles were recorded simultaneously. A Newtonian equation was used to calculate the joint intersegmental resultant forces and moments. In the internal model, three components of the disc force, eight muscle forces, two ligament forces and two facet joint forces were computed. RESULTS: The correlation between the reaction moments from the upper and lower models of the external part were generally above 0.94, and the root mean square differences were below 19 Nm. In this internal model, the maximal disc compression was close to the data showed on the literature, and the estimation of muscle forces corresponded to the EMG activities. CONCLUSIONS: A three-dimensional biomechanical model has been developed and evaluated to estimate the spinal joint force distribution during asymmetric manual lifting activities.

Journal Article↗

PubMed1998

Isokinetic evaluation of the ankle before and after surgical treatment of the lumbar disc herniation.

OBJECTIVE: To quantitatively evaluate the ankle strength before and after surgical treatment for herniated lumbar intervertebral disc. DESIGN: Isokinetic test of ankle joint and statistical analysis were designed to evaluate the results before and after surgery. BACKGROUND: Assessments of the results before and after treatment of lumbar herniation of intervertebral discs (HIVD) in previous papers were all based on patients' symptoms, activity, working condition, the angle of straight leg raising test, and requirement of pain medication. We designed a prospective study of isokinetic measurement of the ankle joints in those patients with HIVD to try to find a quantitative method of evaluation. METHODS: The criteria of selecting patients were single level disc herniation of lumber spine, without associated major neuromuscular or musculoskeletal disorder, normal mental status and cooperative, clinically evident radiculopathy, failure of conservative treatment, and age under 45. The isokinetic strengths of the ankle joints, of both involved and uninvolved limbs, were evaluated with plantarflexion or dorsiflexion, in the velocities of 30, 60, 120, and 180 degrees s(-1), according to their affected levels. Standard laminotomy with removal of intervertebral disc was undertaken for all patients under general anesthesia. The isokinetic strength of the ankle joints were evaluated with Kin-Com dynamometer before surgery, and post-operatively at 1 week, 2 weeks, 4 weeks, 2 months, and 3 months. All data were collected and analyzed with linear mixed model for analysis of variance with repeated measures. RESULTS: From January, 1996, 5 patients entered this study, 2 patients were L4-L5 herniation, and 3 for L5-S1. The estimated mean strength ratio and standard error was 55.04 +/- 2.21% preoperatively, 46.42 +/- 2.22% postoperatively at 1 week, 64.35 +/- 2.23% postoperatively at 2 weeks, 73.93 +/- 2.23% postoperatively at 4 weeks, 100.40 +/- 2.22% postoperatively at 2 months, and 104.55 +/- 2.21% postoperatively at 3 months. CONCLUSIONS: In this preliminary prospective study, there seems no correlation between duration of the symptoms and isokinetic strength of the ankle joint. There is, however, marked improvement of isokinetic strength of ankle joint postoperatively at 2 months, which was statistically significant.

Journal Article↗