Retrospective analysis of preoperative embolization of spinal tumors.

BACKGROUND AND PURPOSE: Preoperative embolization of primary and metastatic spinal tumors is often performed to decrease intraoperative blood loss and facilitate surgical resection. The purpose of this study was to evaluate the safety of spinal tumor embolization and the variables that may influence intraoperative blood loss. MATERIALS AND METHODS: A retrospective analysis of 100 spinal tumor embolization procedures was performed. Multiple variables were evaluated with respect to intraoperative blood loss, including tumor pathology, degree of tumor embolization, embolization above/below the levels involved, PVA particle size, surgical approach, and invasiveness. RESULTS: There was 1 significant complication of the 100 embolization procedures performed. Evaluation of the entire set of embolization procedures demonstrated that RCC was associated with increased intraoperative blood loss (P = .009) relative to other tumor types, as were the surgical approach and invasiveness of the surgery performed. No other variables were found to be statistically significant predictors of intraoperative blood loss. Subset analysis of all RCCs demonstrated that complete embolization resulted in decreased blood loss compared with partial embolization (P = .03) and that male sex was associated with increased blood loss (P = .029). CONCLUSIONS: Preoperative embolization of spinal tumors is a safe procedure. Complete embolization of RCCs results in lower intraoperative blood loss compared with partial embolization. The effectiveness of preoperative embolization of non-RCCs is unclear. Using smaller embolic particles and embolizing beyond the levels affected by tumor may not provide added benefit.

The association of lumbar spondylolisthesis with collagen IX tryptophan alleles.

Two collagen type IX gene polymorphisms that introduce a tryptophan residue into the protein's triple-helical domain have been linked to an increased risk of lumbar disc disease. To determine whether a particular subset of symptomatic lumbar disease is specifically associated with these polymorphisms, we performed a prospective case-control study of 107 patients who underwent surgery of the lumbar spine. Patients were assigned to one of five clinical categories (fracture, disc degeneration, disc herniation, spinal stenosis without spondylolisthesis and spinal stenosis with spondylolisthesis) based on history, imaging results, and findings during surgery. Of the 11 tryptophan-positive patients, eight had spinal stenosis with spondylolisthesis and three had disc herniation. The presence of the tryptophan allele was significantly associated with African-American or Asian designation for race (odds ratio 4.61, 95% CI 0.63 to 25.35) and with the diagnosis of spinal stenosis with spondylolisthesis (odds ratio 6.81, 95% CI 1.47 to 41.95). Our findings indicate that tryptophan polymorphisms predispose carriers to the development of symptomatic spinal stenosis associated with spondylolisthesis which requires surgery.

A comparison of biomechanical mechanisms of whiplash injury from rear impacts.

Several hypotheses have been proposed to explain the mechanism of injury in whiplash including, pressure on nerve root ganglia, stretching of facet capsules, or damage to facet articular cartilage. These injury mechanisms have not been directly compared in the same study. A comparison could provide insight into the most likely mechanism of whiplash injury. Twenty eight volunteers underwent rear impacts with head and chest acceleration data collected. The same apparatus was used to test 11 cervico-thoracic human cadaveric spines with an instrumented headform attached. Head acceleration, individual vertebral kinematics from high speed video, local nerve root pressure, and facet joint contact pressures were collected during impacts. Each specimen was tested first at an impact acceleration similar to that of volunteers, who reported minimal or no symptoms after the test, then at double the acceleration. Head X (forward) and Z (upward) accelerations of cadaveric specimens were very similar in time sequence and magnitude to those of unprepared volunteers. Pressure around the lower cervical nerve roots ranged from 2.7kPa to 10kPa, and occurred generally after chest but before peak head acceleration. Facets at C4-5 and C5-6 had the highest probability (64% and 71% respectively) of pinching. Neither pressure rise nor pinching changed significantly with increased acceleration. Vertebral intersegmental extension rotations (4 ( o ) -9.5 ( o ) ) and posterior translations (3.7-8.9 mm) peaked near maximum head excursion into the head restraint, at the time of peak head acceleration. Vertebral shear translations showed the largest (and only significant) increases with increased impact acceleration. This data implies that facet shearing was most sensitive to the increased acceleration in this experiment and may be a primary mechanism of cervical spine injury in rear impacts.

Cervical spine injuries in patients 65 years old and older: epidemiologic analysis regarding the effects of age and injury mechanism on distribution, type, and stability of injuries.

OBJECTIVE: Our objective was to describe types and distribution of cervical spine injuries in elderly patients in regard to causative trauma mechanism and patient age. MATERIALS AND METHODS: The distribution and type of 225 cervical spine injuries in 149 consecutive patients 65 years old and older over a 5-year interval were retrospectively assessed. For each patient, initial admission imaging studies were reviewed, and injuries were classified. Trauma mechanism (falls from standing or seated height vs higher energy mechanisms) and initial clinical and neurologic status were recorded. Data were correlated according to patients' age (65-75 years and >75 years) and causative trauma mechanism. RESULTS: Ninety-five (64%) of 149 patients had upper cervical spine injuries. Fifty-nine (40%) of 149 patients had multilevel injuries. Main causes for cervical spine injuries were motor vehicle crashes in "young elderly" (65-75 years old; 36/59, 61%) and falls from standing or seated height in "old elderly" (>75 years old; 36/90, 40%). Fracture patterns at risk for neurologic deterioration were common (>50%), even in the absence of acute myelopathy or radiculopathy. Patients older than 75 years, independent of causative mechanism, and patients who fell from standing height, independent of age, were more likely to have injuries of the upper cervical spine (p = 0.026 and p = 0.006, respectively). CONCLUSION: Cervical spine injuries in elderly patients tend to involve more than one level with consistent clinical instability and commonly occur at the atlantoaxial complex. Old elderly patients and patients who fall from standing height are more prone to injuries of the upper cervical spine.

Percutaneous stabilization of U-shaped sacral fractures using iliosacral screws: technique and early results.

PURPOSE: To present the technique and early results of percutaneous stabilization of U-shaped sacral fractures with attention to neurologic recovery and maintenance of fracture reduction of the sacrum. DESIGN: Retrospective clinical study. SETTING: Level I trauma center. PATIENTS: During a thirty-eight-month period, 442 patients with pelvic ring disruptions were treated at a Level I trauma center. Thirteen (2.9 percent) of these patients had displaced U-shaped sacral fractures treated with percutaneous stabilization. INTERVENTION: Fracture stabilization was accomplished using fluoroscopically guided iliosacral screws inserted percutaneously with the patient positioned supine. Neurodiagnostic monitoring was not used during screw insertions. This technique was limited to patients with sacral kyphotic deformities, which allowed in situ fixation. Sacral neurologic decompression was not performed. MAIN OUTCOME MEASUREMENTS: Fracture healing and the stability of fixation were assessed on inlet and outlet radiographs and a lateral sacral view. Detailed neurologic examinations were performed at injury and at follow-up. RESULTS: The sacral fractures were classified based on plain pelvic radiographs and computed tomography scans and included one Type 1, eight Type 2, and four Type 3 fracture patterns. Twenty-five fully threaded cancellous 7.0-millimeter cannulated screws were used. Eleven patients had bilateral screw fixations; one patient had unilateral double screw fixation; and one patient had unilateral single screw fixation. Operative time for screw insertion averaged forty-eight minutes, with 2.1 minutes of fluoroscopy per screw. Accurate screw insertions without neuroforaminal or sacral spinal canal violations were confirmed in all patients with postoperative pelvic plain radiographs and computed tomography scans. A paradoxical inlet view of the upper sacral segments on the injury anteroposterior pelvis was seen in twelve of thirteen patients (92.3 percent), and the diagnosis was confirmed with the lateral sacral view in all thirteen (100 percent) patients. Preoperatively, sacral kyphosis averaged 29 degrees, whereas postoperative sacral kyphosis averaged 28 degrees. Screw disengagement occurred without a change in position of the sacral fracture in the only patient treated with a single unilateral screw. All fractures healed clinically and radiographically. Of the nine patients with preoperative neurologic abnormalities, two (22 percent) patients had residual neurologic deficits. Both patients had associated multiple level lumbar burst fractures, which required decompression and instrumented stabilization. CONCLUSIONS: These sacral fractures are rare and occur after significant spinal axial loading. A paradoxic inlet view of the upper sacrum on the anteroposterior plain pelvic radiograph heralds the diagnosis. Delayed diagnosis is avoided by a high clinical suspicion, early lateral sacral radiographs, and pelvic computed tomography scans. Surgical stabilization may assist in early mobilization of the patient from recumbency and prevents progressive deformity with associated nerve root injury. Percutaneous fixation diminishes potential blood loss and operative times, yet still allows subsequent sacral decompression of the local neural elements using open techniques when necessary. Early percutaneous iliosacral screw fixation is effective treatment for these injuries.

Use of structural allografts in spinal osteomyelitis: a review of 47 cases.

OBJECT: The use of structural allografts in spinal osteomyelitis remains controversial because of the perceived risk of persistent infection related to a devitalized graft and spinal hardware. The authors have identified 47 patients over the last 3.5 years who underwent a surgical decompression and stabilization procedure in which fresh-frozen allografts were used after aggressive removal of infected and devitalized tissue. The patients subsequently underwent 6 weeks of postoperative antibiotic therapy (12 months for those with tuberculosis [TB]). METHODS: Follow-up data included results of serial clinical examinations, radiography, laboratory analysis (erythrocyte sedimentation rate and white blood cell count), and clinical outcome questionnaires. Of the original 47 patients (14 women and 33 men, aged 14-83 years), 39 were available for follow up. The average follow-up period at the time this article was submitted was 17 +/- 9 months (median 14 months, range 6-45 months). In the majority of cases (57%), a Staphylococcus species was the infectious organism. Predisposing risk factors included intravenous drug abuse (IVDA), previous surgery, diabetes, TB, and concurrent infections. During the follow-up period only two patients suffered recurrent infection at a contiguous level; both had a history of IVDA and one also had a chronic excoriating skin condition. No other recurrent infections have been identified, and no patient has required reoperation for persistent infection or allograft/hardware failure. CONCLUSIONS: It is the authors' opinion that the use of structural allografts in combination with aggressive tissue debridement and adjuvant antibiotic therapy provide a safe and effective therapy in cases of spinal osteomyelitis requiring surgery.

Canal geometry changes associated with axial compressive cervical spine fracture.

STUDY DESIGN: A laboratory study using isolated ligamentous human cadaveric cervical spines to investigate canal occlusion during (transient) and after (steady-state) axial compressive fracture. OBJECTIVES: To determine whether differences exist between transient and postinjury canal occlusion under axial compressive loading, and to examine the effect of loading rate on canal occlusion. SUMMARY OF BACKGROUND DATA: Prior studies have shown no correlation between neurologic deficit and canal occlusion measurements made on radiographs and computed tomography scans. The authors hypothesized that postinjury radiographic assessment does not provide an appreciation for the transient occlusion that occurs during the traumatic fracture event, which may significantly affect the neurologic outcome. METHODS: Twelve human cervical spines were instrumented with a specially designed canal occlusion transducer, which dynamically monitored canal occlusion during axial compressive impact. Six specimens were subjected to a fast-loading rate (time to peak load, approximately 20 msec), and the other six were subjected to a slow-loading rate (time to peak load, approximately 250 msec). After impact, two different postinjury canal occlusion measurements were performed. RESULTS: Each of the six specimens subjected to the fast-loading rate incurred burst fractures, whereas the slow-loading rate produced six wedge-compression fractures. For the fast-rate group, the postinjury occlusion-measurements were significantly smaller than the transient occlusion. In contrast, transient occlusion was not found to be significantly different from postinjury occlusion in the slow-rate group. All of the comparisons between loading rate groups showed significant differences, with the fast-rate fractures producing larger amounts of canal occlusion in every category. CONCLUSIONS: The findings indicate that even if canal occlusion could be measured immediately after axial compressive trauma, the measurement would underestimate the maximal amount of transient canal occlusion. Therefore, postinjury measurement of canal occlusion may indicate a smaller degree of neurologic deficit than what might be expected if the transient occlusion could be measured.

Type II odontoid fractures in the elderly: early failure of nonsurgical treatment.

The optimum treatment of Type II odontoid fractures in the geriatric population remains controversial. Coexisting medical conditions encountered in the elderly patient often increase operative risk and make cervical immobilization difficult to tolerate. Previous studies have shown increased morbidity and mortality and decreased fusion rates for Type II odontoid fractures treated with cervical orthoses in the geriatric population, whereas low morbidity and mortality rates with operative management have recently been documented. To investigate the role of surgical and nonsurgical treatment, a retrospective analysis was performed of patients with Type II odontoid fractures who were at least 65 years old and were consecutively admitted to a single medical center from 1994 to 1998. Twenty patients met inclusion criteria. In 12 patients nonsurgical management with a cervical orthosis was attempted. The nonsurgical management failed early in six patients, with one associated death. Eleven patients were treated surgically with either anterior odontoid screw fixation or posterior C1-2 transarticular screw fixation and modified Gallie fusion. Postoperatively one patient required revision of the C1-2 transarticular screws, and there was one death. In conclusion Type II odontoid fractures in this elderly population were associated with early 10% morbidity and 20% mortality rates. Nonsurgical management of Type II odontoid fractures failed early in six (50%) of 12 patients, whereas surgical treatment failed early in one of 11 (9%) patients. Both the nonsurgical and surgical treatments resulted in approximately 10% morbidity and 10% mortality rates.

Risk of early closed reduction in cervical spine subluxation injuries.

OBJECT: The authors retrospectively reviewed 121 patients with traumatic cervical spine injuries to determine the risk of neurological deterioration following early closed reduction. METHODS: After excluding minor fractures and injuries without subluxation, the medical records and imaging studies (computerized tomography and magnetic resonance [MR] images) of 82 patients with bilateral and unilateral locked facet dislocations, burst fractures, extension injuries, or miscellaneous cervical fractures with subluxation were reviewed. Disc injury was defined on MR imaging as the presence of herniation or disruption: a herniation was described as deforming the thecal sac or nerve roots, and a disruption was defined as a disc with high T2-weighted signal characteristics in a widened disc space. Fifty-eight percent of patients presented with complete or incomplete spinal cord injuries. Thirteen percent of patients presented with a cervical radiculopathy, 22% were intact, and 9% had only transient neurological deficits in the field. Early, rapid closed reduction, using serial plain radiographs or fluoroscopy and Gardner-Wells craniocervical traction, was achieved in 97.6% of patients. In two patients (2.4%) closed reduction failed and they underwent emergency open surgical reduction. The average time to achieve closed reduction was 2.1+/-0.24 hours (standard error of the mean). The incidence of disc herniation and disruption in the 80 patients who underwent postreduction MR imaging was 22% and 24%, respectively. However, the presence of disc herniation or disruption did not affect the degree of neurological recovery, as measured by American Spinal Injury Association motor score and the Frankel scale following early closed reduction. Only one (1.3%) of 80 patients deteriorated, but that occurred more than 6 hours following closed reduction. CONCLUSIONS: Although disc herniation and disruption can occur following all types of traumatic cervical fracture subluxations, the incidence of neurological deterioration following closed reduction in these patients is rare. The authors recommend early closed reduction in patients presenting with significant motor deficits without prior MR imaging.

Early versus delayed surgery for acute cervical spinal cord injury.

The optimal timing of surgical intervention in cervical spinal cord injuries has not been defined. The goals of the study were to investigate changes in neurologic status, length of hospitalization, and acute complications associated with surgery within 3 days of injury versus surgery more than 3 days after the injury. All patients undergoing surgical treatment for an acute cervical spinal injury with neurologic deficit at two institutions between March 1989 and May 1991 were reviewed retrospectively. Forty-three patients initially were evaluated. At one institution, patients with neurologic spinal injuries had surgical intervention within 72 hours of injury. At the other institution, patients underwent immediate closed reduction with subsequent observation of neurologic status for 10 to 14 days before undergoing surgical stabilization. This study indicates that patients who sustain acute traumatic injuries of the cervical spine with associated neurologic deficit may benefit from surgical decompression and stabilization within 72 hours of injury. Surgery within 72 hours of injury in patients sustaining acute cervical spinal injuries with neurologic involvement is not associated with a higher complication rate. Early surgery may improve neurologic recovery and decrease hospitalization time in patients with cervical spinal cord injuries.

Stabilizing properties of the halo apparatus.

STUDY DESIGN: A cadaveric cervical spine specimen fixed between a fiberglass torso and a plastic skull was used as a model to determine the effect of halo structural parameters on motion at a lesion simulated at C5-C6. In a second part, nine commercially available halo devices were compared. OBJECTIVES: To define the contributions of the various components of the halo apparatus to reducing motion in an injured cervical spine and to compare the stability offered by a sample of commercially available halo devices. Controversy exists concerning the ability of the halo apparatus to stabilize the injured cervical spine. SUMMARY OF BACKGROUND DATA: The halo apparatus has been shown to be the most effective nonsurgical method for stabilizing the fractured spine. Nonetheless, several clinical studies have demonstrated that unacceptably large motions can occur at the injured spinal segment stabilized with a halo apparatus. METHODS: Each cadaveric cervical spine was mounted onto a fiberglass torso and a rigid plastic skull was attached to the base of the occiput. A posterior ligamentous lesion was created between C5 and C6. The halo ring was fitted to the skull and a vest to the torso. Loads were applied to the skull in flexion, extension, and lateral bending, and relative angulation between C5 and C6 was measured with electroinclinometers. In the first part, the effect of parameters such as vest tightness, vest-thorax friction, vest deformation, and connecting bar rigidity on spinal angulation were measured using one vest. In the second part, the stability offered by each of nine commercially available halo devices was compared. RESULTS: Increasing chest strap tightness and decreasing vest deformation reduced angulation at the spinal lesion. Once connecting bar joints were tightened to 25% of their recommended torque, increased tightening or adding additional bars had no effect on rigidity. Although specific vests permitted significantly greater motion in specific directions, no vest allowed greater angulation consistently in all loading planes. CONCLUSIONS: Increasing vest tightness, decreasing the deformability of the vest, and ensuring a good fit can reduce motion in the fractured spine. Most commercially available halo vests provide similar mechanical stability to the injured cervical spine.

Anatomy of intervertebral disc and pathophysiology of herniated disc disease.

This discussion reviews developments in normal and abnormal disc biology over the past decade. The anatomic and biochemical structure of the disc is reviewed. Emphasis is placed on recent neurochemical changes identified in disc degeneration and disc herniation. Biomechanical considerations for the normal disc are presented. Influence of mechanical factors on disc nutrition, disc degeneration and disc herniation is reviewed. Biologic events underlying the diagnostic methods used in evaluating disorders of the intervertebral disc are presented. The biologic consequences of iatrogenic disc injury in discectomy are also discussed.