Biomedical subjects

Serena Hu

Publications and source records attributed to Serena Hu.

4 recordsLinked to original sources

PubMed2005

Pedicle screw fixation of the thoracic spine: an in vitro biomechanical study on different configurations.

STUDY DESIGN: An in vitro biomechanical study of different pedicle screw configuration usage on the thoracic spine using a cadaveric model. OBJECTIVES: To investigate the degree of motion afforded different pedicle screw configurations in the thoracic spine using a cadaveric model with 2 different degrees of intrinsic stability. SUMMARY OF BACKGROUND DATA: Recently, thoracic pedicle screws have become an alternative to hook and wire fixation, and have gained popularity. Clinically, pedicle screw use has ranged from application to every segment, to skipping every other level. There exists no clear consensus as to which strategy is most appropriate. METHODS: The load-displacement behavior of 6 different constructs was determined on 8 fresh frozen cadaver spine specimens (T4-T12). Each construct was evaluated on 2 destabilization models, including minimum destabilization (bilateral facetectomy) and maximum destabilization (facetectomy and annulotomy). Pure moments were applied, and the resultant range of motion for each scenario was determined. RESULTS: Facetectomy did not significantly destabilize the thoracic spine. Annulotomy and facetectomy created gross instability that rendered testing of this destabilization model impossible. All constructs significantly reduced the range of motion compared to intact or facetectomized specimens (P < or = 0.001). When different constructs were compared to each other, a pattern of continuously increasing stability emerged, with the "maximum" construct being the most stable and "minimum" configuration being the least, with varying degrees of statistical significance. CONCLUSIONS: Our results suggest that the most important factor for the acute postoperative stability of spinal fixation is the degree of preoperative or iatrogenic destabilization. The minimum amount of pedicle screws provides adequate stability when there is minimal destabilization of the spine. On the other hand, when anterior column release has been performed or instability exists before surgery, segmental pedicle screw fixation may be necessary to achieve adequate stability.

Aged↗

PubMed2004

Intervertebral disc replacement maintains cervical spine kinetics.

STUDY DESIGN: An in vitro biomechanical study of C4-C5 intervertebral disc replacement using a cadaveric model. OBJECTIVES: To investigate the degree of motion afforded by a ball-and-socket cervical intervertebral disc prosthesis design. SUMMARY OF BACKGROUND DATA: Intervertebral disc prostheses designs attempt to restore or maintain cervical disc motion after anterior cervical discectomy and reduce the likelihood of accelerated degeneration in adjacent discs by maintaining normal motion at the affected disc level. Surprisingly, the actual kinetic and biomechanical effects that cervical disc arthroplasty imparts on the spine have not been widely reported. Accordingly, we investigated what effect implanting a cervical disc prosthesis has on the range of motion at the affected level as well as how it changes the coupled motion patterns at the level of implantation. METHODS: Six fresh-frozen human cadaveric cervical spines (C2-C7) were used in this study. We evaluated two different spinal conditions: intact and after disc replacement at C4-C5. Compression (using the follower load concept) and pure moment loading were applied to the specimen. Range of motion was measured using an optical tracking system. Statistical differences between the intact and replaced condition range of motion was determined using analysis of variance with post hoc comparisons (alpha = 0.05). RESULTS: The data indicate that the intervertebral disc prosthesis approximated the intact motion in all three rotation planes at the affected level. Finally, changes in cervical coupled rotations, specifically lateral bending during axial rotation loading and axial rotation during lateral bending loading, were not statistically significant between the two tested conditions. CONCLUSIONS: Our data demonstrate that a ball-and-socket design can replicate physiologic motion at the affected and adjacent levels. More importantly, the data indicate that motion coupling, which is most dramatic in the cervical spine and plays an important biomechanical role, is maintained.

Arthroplasty, Replacement↗

PubMed2004

Strategies for managing decreased motor evoked potential signals while distracting the spine during correction of scoliosis.

Surgical correction of kyphoscoliosis may result in spinal cord injury and neurologic deficits. Monitoring somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (MEPs) intraoperatively may allow for early detection and reversal of spinal cord injury. Controlled hypotension and isovolemic hemodilution are often used during these cases to reduce blood loss and transfusion. However, these physiologic parameters may affect the quality of SSEP and MEP signals. Acute reduction or loss of MEP or SSEP signals during spinal distraction presents a crisis for the operative team: should distraction be immediately relieved? The authors describe three patients who showed a decrease in evoked potential signals under hypotensive, hemodiluted conditions at the stage of spinal distraction. Each case illustrates a different strategy for successful management of these patients.

Adolescent↗

PubMed2003

Treatment of thoracic pseudarthrosis in the adult: is combined surgery necessary?

In deformity surgery in adults, pseudarthrosis remains an important cause of progressive deformity and postoperative pain. Revision surgery for pseudarthrosis in the lumbar spine is a difficult challenge with failure rates of as much as 50% using posterior surgery alone. Treatment of pseudarthrosis of the thoracic spine has not been well-described. The purpose of the current study was to review the long-term clinical and radiographic results of posterior-only surgery for the treatment of pseudarthrosis in the thoracic spine. Using a posterior extension osteotomy through the identified pseudarthrosis with reinstrumentation and autogenous bone grafting, an improvement of regional sagittal balance was shown and reliable clinical outcomes were obtained. A single-stage posterior revision surgery with extension osteotomies through the regions of pseudarthrosis coupled with rigid internal fixation and autogenous bone grafting is an effective technique for treatment of pseudarthrosis of the thoracic spine. This technique improves regional sagittal deformity and leads to reliable arthrodesis. Combined anterior and posterior surgery was not necessary for effective treatment of thoracic pseudarthrosis in this series.

Adolescent↗