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Biomedical subjects

Edward C Benzel

Publications and source records attributed to Edward C Benzel.

At least 19 recordsLinked to original sources
PubMed2007

Cervical spondylosis anatomy: pathophysiology and biomechanics.

Cervical spondylosis is the most common progressive disorder in the aging cervical spine. It results from the process of degeneration of the intervertebral discs and facet joints of the cervical spine. Biomechanically, the disc and the facets are the connecting structures between the vertebrae for the transmission of external forces. They also facilitate cervical spine mobility. Symptoms related to myelopathy and radiculopathy are caused by the formation of osteophytes, which compromise the diameter of the spinal canal. This compromise may also be partially developmental. The developmental process, together with the degenerative process, may cause mechanical pressure on the spinal cord at one or multiple levels. This pressure may produce direct neurological damage or ischemic changes and, thus, lead to spinal cord disturbances. A thorough understanding of the biomechanics, the pathology, the clinical presentation, the radiological evaluation, as well as the surgical indications of cervical spondylosis, is essential for the management of patients with cervical spondylosis.

Biomechanical Phenomena↗
PubMed2007

Cervical deformity correction.

Subaxial cervical deformities most often occur in the sagittal plane, primarily as kyphosis. Kyphosis may develop secondary to advanced degenerative disease, trauma, neoplastic disease, or after surgery. Whatever the cause, the development of cervical deformity should be avoided and corrected when appropriate because the greater the deformity, the greater the probability of an associated neurological deficit or chronic pain. Patients usually present with mechanical type cervical pain, with or without neurological deficit (i.e., myelopathy). They may also be relatively asymptomatic. Work-up includes appropriate imaging studies, such as radiographs, including dynamic images, and magnetic resonance imaging or computed tomography myelography. The deformity may be accurately assessed and an appropriate surgical strategy undertaken. Depending on flexibility of the deformity and the presence or absence of facet ankylosis, a dorsal, ventral, or combined approach may be used. All approaches are unique in their ability to correct a deformity and in their associated complications. A comprehensive discussion of each is undertaken.

Cervical Vertebrae↗
PubMed2007

Multiple level discectomy and fusion.

The ventrolateral approach for surgical decompression of the cervical spine is widely used and well known to most spinal surgeons. Because compression of the spinal cord and nerve roots usually occurs ventral to the spinal cord, and the spinal cord does not tolerate traction, this approach allows safe and direct decompression of most compressive pathology. This article reviews the indications, diagnostic evaluation, and technique for multiple level discectomy and fusion. It further addresses the advantages and disadvantages of this technique compared with alternate surgical procedures.

Cervical Vertebrae↗
PubMed2007

Decision making process: problem-based decision making.

Clinical problems are often complex. Problems of great complexity are usually associated with a commensurately greater degree of difficulty with respect to the decision making process. This is most certainly true regarding the management of cervical spondylosis. Usually, clinicians make clinically appropriate decisions. However, more often than realized, suboptimal decisions may be made. Therefore, an assessment of the types of errors regarding clinical decision making are worthy of consideration. In this article, a scheme for decision making regarding the management of cervical spondylosis is presented.

Cervical Vertebrae↗
PubMed2006

Neurosurgery in the elderly: brain tumors and subdural hematomas.

Primary malignant brain tumors present a formidable challenge to surgeons, patients, and families. Although the prognosis in elderly patients approaches only 6 months, aggressive resection and adjuvant treatment may be indicated in a select group of patients who have preserved functional status. Subdural hematomas in the geriatric population usually are chronic. Patients often benefit from evacuation but their advanced age and significant comorbidities often increase perioperative morbidity and mortality. Minimally invasive evacuation, possibly under local anesthesia, often is indicated as an initial treatment.

Aged↗
PubMed2006

Bone-mounted miniature robotic guidance for pedicle screw and translaminar facet screw placement: Part I--Technical development and a test case result.

OBJECTIVE: To introduce a new miniature robot (SpineAssist; MAZOR Surgical Technologies, Caesarea, Israel) that has been developed and tested as a surgical assistant for accurate percutaneous placement of pedicle screws and translaminar facet screws. METHODS: Virtual projections in three planes-axial, lateral, and anteroposterior-are reconstructed for each vertebra from a preoperative computed tomographic (CT) scan. On a specially designed graphic user interface with proprietary software, the surgeon plans the trajectory of the screws. Intraoperative fluoroscopic x-rays with targeting devices are then matched with the CT-based virtual images, as well as the surgeon's plan. A clamp is attached to the spinous process or a minimally invasive frame (Hover-T frame; MAZOR Surgical Technologies) is mounted to the iliac crest and one spinous process. The miniature robot is then attached to the clamp and/or frame. On the basis of combined CT scan and fluoroscopic data, the robot aligns itself to the desired entry point and trajectory, as dictated by the surgeon's preoperative plan. RESULTS: A test case in a cadaver lumbar spine was performed in which four screws and two rods were inserted, using a minimally invasive technique, combining the SpineAssist system and Hover-T frame in conjunction with the PathFinder system (Spinal Concept Inc., Austin, TX). The discrepancy between the planned and actual screw trajectories was measured by means of postprocedural CT scan. Overall, the four screws were implanted with an average deviation of 1.02 +/- 0.56 mm (range, 0-1.5 mm) from the surgeon's plan. CONCLUSION: These preliminary results confirm the system's accuracy and support its use in minimally invasive spine surgery applications.

Bone Screws↗
PubMed2006

Axially dynamic implants for stabilization of the cervical spine.

OBJECTIVE: Subsidence is a naturally occurring process that is observed during aging and after spine surgery. Rigid cervical spine instrumentation is excellent for stabilizing the spine. These devices, however, also retard subsidence after surgery. Thus, the implant carries much of the axial load, rather than sharing the axial load with the bone graft. This results in an increased incidence of construct failures, pseudoarthrosis, or both, which often occur late in the postoperative course. METHODS: In contrast, dynamic implants allow normal (natural) subsidence to occur, while effectively stabilizing the spine by preventing translation, rotation, and angular deformation. Load sharing, which works with, instead of against, the normal biology of bone healing, occurs with axially dynamic implants, resulting in more robust and earlier fusions. RESULTS: Diminished incidences of construct failures have been reported with dynamic implants. CONCLUSION: Dynamic implants seem to be the system of choice for ventral cervical stabilization in selected patients.

Cervical Vertebrae↗
PubMed2006

Biomechanical evaluation of the ventral and lateral surface shear strain distributions in central compared with dorsolateral placement of cages for lumbar interbody fusion.

OBJECT: The purpose of this study was to measure and compare the ventral and lateral surface strain distributions and stiffness for two types of interbody cage placement: 1) central placement for anterior lumbar interbody fusion (ALIF); and 2) dorsolateral placement for extraforaminal lumbar interbody fusion (ELIF). METHODS: Two functional spine units were obtained for testing in each of 13 cadaveric spines, yielding 26 segments (three of which were not used because of bone abnormalities). Bilateral strain gauges were mounted adjacent to the endplate on the lateral and ventral walls of each vertebral body in the 23 motion segments. Each segment was cyclically tested in compression, flexion, and extension in the following conditions: while intact, postdiscectomy, and instrumented with interbody fusion cages placed using both insertion techniques. No significant differences were observed between ALIF and ELIF in compressive stiffness, bending stiffness in flexion and extension (p > or = 0.1), ventral and lateral strain distribution during the intact tests (p > or = 0.24), and during the flexion tests after fusion (p > or = 0.22). In compression, higher ventral and lower lateral strain was observed in the ALIF than in the ELIF group (ventral, p = 0.05; lateral, p = 0.04), and in extension, higher ventral (p = 0.01) and higher lateral strain (p = 0.002) was observed in the ELIF than in the ALIF group. CONCLUSIONS: Preservation of the ventral anulus and dorsolateral placement of the interbody cages during ELIF allow alternate load transfer pathways through the dorsolateral vertebral wall and ventral anulus that are not observed following ALIF. These may be associated with a lower incidence of subsidence and a higher rate of fusion due to a more concentrated application of bone healing-enhancing compression forces during the fusion and healing process.

Biomechanical Phenomena↗
PubMed2006

Regional instability following cervicothoracic junction surgery.

OBJECT: The cervicothoracic junction (CTJ) is the transitional region between the cervical and thoracic sections of the spinal axis. Because it is a transitional zone between the mobile lordotic cervical and rigid kyphotic thoracic spines, the CTJ is a region of potential instability. This potential for instability may be exaggerated by surgical intervention. METHODS: A retrospective review of all patients who underwent surgery involving the CTJ in the Department of Neurosurgery at the Cleveland Clinic Foundation during a 5-year period was performed. The CTJ was strictly defined as encompassing the C-7 vertebra and C7-T1 disc interspace. Patients were examined after surgery to determine if treatment had failed. Failure was defined as construct failure, deformity (progression or de novo), or instability. Variables possibly associated with treatment failure were analyzed. Statistical comparisons were performed using the Fisher exact test. Between January 1998 and November 2003, 593 CTJ operations were performed. Treatment failed in 14 patients. Of all variables studied, failure was statistically associated with laminectomy and multilevel ventral corpectomies with fusion across the CTJ. Other factors statistically associated with treatment failure included histories of cervical surgery, tobacco use, and surgery for the correction of deformity. CONCLUSIONS: The CTJ is a vulnerable region, and this vulnerability is exacerbated by surgery. Results of the present study indicate that laminectomy across the CTJ should be supplemented with instrumentation (and fusion). Multilevel ventral corpectomies across the CTJ should also be supplemented with dorsal instrumentation. Supplemental instrumentation should be considered for patients who have undergone prior cervical surgery, have a history of tobacco use, or are undergoing surgery for deformity correction.

Adult↗
PubMed2005

Acute low back pain and radiculopathy: MR imaging findings and their prognostic role and effect on outcome.

PURPOSE: To prospectively determine in patients with acute low back pain (LBP) or radiculopathy, the magnetic resonance (MR) imaging findings, prognostic role of these findings, and effect of diagnostic information on outcome. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. This study was HIPAA compliant. A total of 246 patients with acute-onset LBP or radiculopathy were randomized to either the early information arm of the study, with MR results provided within 48 hours, or the second arm of the study, where both patients and physicians were blinded to MR results, unless this information was critical to patient care. Patients underwent 6 weeks of conservative care. Roland function scoring, visual pain analog, Short Form 36 health status survey, self-efficacy scoring, and a fear avoidance questionnaire were completed at presentation; at 2-, 4-, 6-, and 8-week follow-up; and at 6-, 12-, and 24-month follow-up. A second MR imaging examination was performed at 6-week follow-up. Multivariate logistic regression analysis was used to determine which imaging and nonimaging variables can be used to predict improvement in Roland function and patient satisfaction. The chi(2) test and repeated-measures analysis of variance were used to compare outcome of blinded and unblinded patients. RESULTS: Herniation was identified in 60% (n = 147) of patients at the initial examination. The prevalence of herniations in patients with LBP (57%) (n = 85) and those with radiculopathy (65%) (n = 62) were similar (P = .217), although patients with radiculopathy were more likely to have stenosis and nerve root compression (P < .006). There was no relationship between herniation type, size, and behavior over time with outcome. An improvement of 50% or more in Roland function score at 6-week follow-up occurred 2.7 times as often among patients with a herniation at baseline (P = .003). Improvement at 6-week follow-up was similar in unblinded (60%) (n = 55) and blinded (67%) (n = 57) patients (P = .397). Self-efficacy, fear avoidance beliefs, and the Short Form 36 subscales were similar for blinded and unblinded patients. CONCLUSION: In typical patients with LBP or radiculopathy, MR imaging does not appear to have measurable value in terms of planning conservative care. Patient knowledge of imaging findings does not alter outcome and is associated with a lesser sense of well-being.

Acute Disease↗
PubMed2005

Techniques for the ventral correction of postsurgical cervical kyphotic deformity.

Progressive kyphotic deformity of the cervical spine may be a late sequela of congenital cervical anomalies, degenerative disc disease, neoplasm, cervical trauma, and surgical procedures. Of these, postsurgical kyphosis is the most common and can occur after ventral and dorsal surgeries of the cervical spine. The purpose of this article is to review the causes and clinical presentation of postsurgical cervical kyphosis and to focus on the operative planning and ventral correction techniques.

Cervical Vertebrae↗
PubMed2005

Nonoperative management of vertical C2 body fractures.

OBJECTIVE: To estimate the incidence and to describe the clinical results of the nonoperative management of vertical C2 body fractures. METHODS: An 8-year retrospective review of upper cervical spine injuries from the registry of a level I trauma center identified 21 patients with a vertical C2 body fracture. RESULTS: Sixteen coronally oriented Type 1 vertical C2 body fractures and 5 sagittally oriented Type 2 vertical C2 body fractures were identified. These fractures account for approximately 10% of the upper cervical spine fractures identified over this period of time. One elderly patient with a Type 1 fracture died as a result of pneumonia, and two patients with Type 2 fractures died from severe closed-head injuries. One patient had evidence of spinal cord injury. This was not related to the C2 body fracture but rather to a subaxial cervical spine injury. Of the surviving 18 patients, all were managed nonoperatively (with external orthoses) and showed evidence of fusion (union of fracture fragments) at the time of the last follow-up. CONCLUSION: Vertical C2 body fractures are not rare injuries and can account for up to 10% of upper cervical spine injuries. In general, vertical C2 body fractures are amenable to nonoperative treatment with external orthoses.

Accidents, Traffic↗
PubMed2005

Surgical management of osseous hemangioblastoma of the thoracic spine: technical case report.

OBJECTIVE AND IMPORTANCE: Spinal hemangioblastomas usually occur as isolated, intramedullary, central nervous system masses, often as a component of von Hippel-Lindau syndrome. They may occasionally occur extradurally and give the appearance of vertebral hemangioma. Rarely, they may be purely osseous lesions. The surgical management of these lesions has not been elaborated. We present a case and discuss the management of multilevel osseous hemangioblastoma of the thoracic spine. CLINICAL PRESENTATION: A 50-year-old woman with a history of thoracic hemangioblastoma 3 years earlier presented with progressive paraparesis. Imaging revealed circumferential tumor involvement of T7 to T9, inclusive. There was severe spinal cord compression. INTERVENTION: The patient underwent surgery via a bilateral lateral extracavitary approach to the tumor. This permitted a complete spondylectomy of T7, T8, and T9; complete tumor removal; and decompression of the spinal cord. Pathological analysis confirmed hemangioblastoma. The spine was reconstructed with an interbody expandable cage and pedicle screw fixation, all placed via the dorsal approach. The patient improved neurologically after the operation. CONCLUSION: Although extremely rare, hemangioblastomas may occur in a purely osseous location. They may resemble vertebral hemangioma. Treatment should include aggressive surgical removal, although arduous, if appropriate. A bilateral lateral extracavitary approach is ideal for complete spondylectomy. With this technique, ventral and dorsal reconstruction of the spine through the same incision is possible.

Female↗
PubMed2005

Effects of age on the perioperative characteristics and short-term outcome of posterior lumbar fusion surgery.

OBJECT: Although advances in patient care have enabled surgeons to perform posterior lumbar decompression and fusion (PLDF), increased age remains a major concern when designing a treatment strategy. The authors conducted a study to evaluate if increased age has any effect on lumbar fusion surgery in terms of perioperative events. METHODS: This retrospective study comprised 129 patients (age range 25-91 years) with spondylolisthesis, lumbar stenosis and/or disc degeneration/herniation with instability, or unsuccessful results after a failed previous PLDF. The patients were stratified by age: those younger than 65 years of age (85 patients) and those at least 65 years of age (44 patients). The parameters reviewed included comorbid conditions, American Society of Anesthesiologists score, instrumentation technique (pedicle screws, a combination of pedicle screw fixation [PSF] and posterior lumbar interbody fusion [PLIF], or noninstrumented fusions), number of fused levels, operative time, estimated blood loss (EBL), complications, and hospital length of stay (LOS). Fusion strategies in the elderly tended to be more conservative. Repeated operations and PSF/PLIF procedures were less frequent in the older age group. Older age did not result in increased complications, EBL, and operative time. Longer hospital LOS was observed in the older age group (7 +/- 3.5 days) compared with the younger age group (5.5 +/- 1.9 days) (p = 0.022). CONCLUSIONS: Complications and perioperative events following PLDF in the elderly are comparable with those observed in younger patients. Withholding lumbar spine fusion solely based on advanced age is not warranted.

Adult↗
PubMed2005

Thoracic transfacet pedicle screw fixation: a new instrumentation technique.

OBJECT: Pedicle screw instrumentation of the thoracic spine remains technically challenging. Transverse process and costotransverse screw fixation techniques have been described as alternatives to pedicle screw fixation (PSF). In this study, the authors introduce thoracic transfacet PSF and compare its experimental biomechanical results with those of standard PSF in short-term cyclic loading in cadaveric thoracic specimens. METHODS: Specimens were tested intact for six cycles at compressive loads of 250 N offset by 1 cm along appropriate axes to induce flexion, extension, and left and right lateral bending. The specimens were then fixed with either a pedicle screw/rod construct or transfacet pedicle screws and retested in the same fashion. After this sequence, specimens were loaded until failure in flexion mode at a rate of 5 mm/minute was observed. Both fixation constructs provided significantly greater stiffnesses than that demonstrated when the specimen was intact (p < 0.05, two-way analysis of variance). Additionally, the two constructs were statistically equivalent in terms of stiffness and load-to-failure values (p < 0.05, two-tailed nonpaired t-test). The only difference observed was that the low midthoracic region (T7-9) was biomechanically weaker than the upper midthoracic and lower thoracic areas in flexion after the destabilization and instrumentation-augmented stabilization procedures. CONCLUSIONS: In selected thoracic surgical procedures, transfacet PSF may, after analysis of long-term biomechanical data, potentially become a reasonable alternative to conventional PSF.

Adult↗
PubMed2005

Stretch-associated injury in cervical spondylotic myelopathy: new concept and review.

The simple pathoanatomic concept that a narrowed spinal canal causes compression of the enclosed cord, leading to local tissue ischemia, injury, and neurological impairment, fails to explain the entire spectrum of clinical findings observed in cervical spondylotic myelopathy. A growing body of evidence indicates that spondylotic narrowing of the spinal canal and abnormal or excessive motion of the cervical spine results in increased strain and shear forces that cause localized axonal injury within the spinal cord. During normal motion, significant axial strains occur in the cervical spinal cord. At the cervicothoracic junction, where flexion is greatest, the spinal cord stretches 24% of its length. This causes local spinal cord strain. In the presence of pathological displacement, strain can exceed the material properties of the spinal cord and cause transient or permanent neurological injury. Stretch-associated injury is now widely accepted as the principal etiological factor of myelopathy in experimental models of neural injury, tethered cord syndrome, and diffuse axonal injury. Axonal injury reproducibly occurs at sites of maximal tensile loading in a well-defined sequence of intracellular events: myelin stretch injury, altered axolemmal permeability, calcium entry, cytoskeletal collapse, compaction of neurofilaments and microtubules, disruption of anterograde axonal transport, accumulation of organelles, axon retraction bulb formation, and secondary axotomy. Stretch and shear forces generated within the spinal cord seem to be important factors in the pathogenesis of cervical spondylotic myelopathy.

Biomechanical Phenomena↗
PubMed2004

Biomechanics of metastatic spine cancer.

The spine is the most common site of skeletal metastases. Most of these occur within the vertebral body, thereby predisposing patients to pathologic fracture. The risk of fracture is related to the extent of bony destruction, location of the lesion, and inherent bone quality. The regional variation in spine anatomy exposes the cervical,thoracic, and lumbar spines to different forces,resulting in varying fracture types.

Biomechanical Phenomena↗