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Study Design Small-diameter spinal rods were tested in fatigue loading before and after contouring in pedicle screw constructs using dynamic testing machines. Objective To characterize the change in fatigue performance of spinal rods resulting from contouring. Background Summary Spine surgeons have a variety of rod materials to choose from, and selecting the best rod depends on patient characteristics and rod material properties, including fatigue performance. Methods Four rod materials were tested, all 4.5 mm in diameter: titanium alloy (Ti), cobalt-chromium alloy (CoCr), and 2 different grades of stainless steel (SS and ultra SS). Three conditions were tested: straight (virgin rods), bent (rods bent to a radius of curvature of 100 mm), and re-bent (rods over-bent to a radius of 50 mm, then partially straightened to a 100-mm radius). Fatigue testing was conducted on unilateral vertebrectomy constructs with polyaxial screws. Results In all conditions, the endurance limit of the CoCr rods was at least 25% higher than the other materials but could not be determined because screw failure precluded rod failure. In the bent condition, the endurance limits of Ti, standard SS and ultra SS were reduced between 20% and 40%. In the re-bent condition, the endurance limit of Ti, standard SS, and ultra SS increased compared with the bent condition. Changes in fatigue performance are best explained by residual rod stresses induced during contouring. Conclusions It appears safe to over-bend and then re-bend, for 1 cycle, small-diameter spinal rods made of the materials tested in this study using tube benders, and CoCr rods were clearly superior for all conditions. However, larger rods, multiple cycles of bending and re-bending, and rods bent using other instruments such as French benders were not studied and may result in different performance under the same conditions.

Study design Observational. Objective To estimate the radiation dose imparted to patients during typical thoracolumbar spinal surgical scenarios. Summary of background data Minimally invasive techniques continue to become more common in spine surgery. Computer-assisted navigation systems coupled with intraoperative cone-beam computed tomography (CT) represent one such method used to aid in instrumented spinal procedures. Some studies indicate that cone-beam CT technology delivers a relatively low dose of radiation to patients compared with other x-ray-based imaging modalities. The goal of this study was to estimate the radiation exposure to the patient imparted during typical posterior thoracolumbar instrumented spinal procedures, using intraoperative cone-beam CT and to place these values in the context of standard CT doses. Methods Cone-beam CT scans were obtained using Medtronic O-arm (Medtronic, Minneapolis, MN). Thermoluminescence dosimeters were placed in a linear array on a foam-plastic thoracolumbar spine model centered above the radiation source for O-arm presets of lumbar scans for small or large patients. In-air dosimeter measurements were converted to skin surface measurements, using published conversion factors. Dose-length product was calculated from these values. Effective dose was estimated using published effective dose to dose-length product conversion factors. Results Calculated dosages for many full-length procedures using the small-patient setting fell within the range of published effective doses of abdominal CT scans (1-31 mSv). Calculated dosages for many full-length procedures using the large-patient setting fell within the range of published effective doses of abdominal CT scans when the number of scans did not exceed 3. Conclusion We have demonstrated that single cone-beam CT scans and most full-length posterior instrumented spinal procedures using O-arm in standard mode would likely impart a radiation dose within the range of those imparted by a single standard CT scan of the abdomen. Radiation dose increases with patient size, and the radiation dose received by larger patients as a result of more than 3 O-arm scans in standard mode may exceed the dose received during standard CT of the abdomen. Understanding radiation imparted to patients by cone-beam CT is important for assessing risks and benefits of this technology, especially when spinal surgical procedures require multiple intraoperative scans.

Background: C5 nerve palsy is a known complication of cervical spine surgery. The development and etiology of this complication are not completely understood. The purpose of the present study was to determine whether rotation of the cervical spinal cord predicts the development of a C5 palsy. Methods: We performed a retrospective review of prospectively collected spine registry data as well as magnetic resonance images. We reviewed the records for 176 patients with degenerative disorders of the cervical spine who underwent anterior cervical decompression or corpectomy within the C4 to C6 levels. Our measurements included area for the spinal cord, space available for the cord, and rotation of the cord with respect to the vertebral body. Results: There was a 6.8% prevalence of postoperative C5 nerve palsy as defined by deltoid motor strength of ≤3 of 5. The average rotation of the spinal cord (and standard deviation) was 2.8° ± 3.0°. A significant association was detected between the degree of rotation (0° to 5° versus 6° to 10° versus ≥11°) and palsy (point-biserial correlation = 0.94; p < 0.001). A diagnostic criterion of 6° of rotation could identify patients who had a C5 palsy (sensitivity = 1.00 [95% confidence interval, 0.70 to 1.00], specificity = 0.97 [95% confidence interval, 0.93 to 0.99], positive predictive value = 0.71 [95% confidence interval, 0.44 to 0.89], negative predictive value = 1.00 [95% confidence interval, 0.97 to 1.00]). Conclusions: Our evidence suggests that spinal cord rotation is a strong and significant predictor of C5 palsy postoperatively. Patients can be classified into three types, with Type 1 representing mild rotation (0° to 5°), Type 2 representing moderate rotation (6° to 10°), and Type 3 representing severe rotation (≥11°). The rate of C5 palsy was zero of 159 in the Type-1 group, eight of thirteen in the Type-2 group, and four of four in the Type-3 group. This information may be valuable for surgeons and patients considering anterior surgery in the C4 to C6 levels. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Full article available online at Healio.com/Orthopedics. Search: 20120725-23 The incidence of pedicle screw breech varies based on anatomic location, body habitus, surgeon experience, spinal deformity, and surgical technique. Pedicle breeches have been reported to occur in up to 40% of screws. The purpose of this retrospective study was to compare the rates of revision of pedicle screw placement when using intraoperative C-arm vs O-arm (Medtronic, Memphis, Tennessee) assessment of pedicle screws. An economic analysis was also performed based on the estimated cost of pedicle screw revision. Four (1%) of 386 control patients required pedicle screw revision for a breeched pedicle screw not identified with intraoperative C-arm fluoroscopy. In the study group, none of the 331 patients returned to the operating room when O-arm was used to assess pedicle screw placement. Based on the 1% rate of returning to the operating room in the control group, the annual rate of cases nationwide requiring pedicle screw revision would be approximately 2300, with a cost of approximately $40,595,000. These results suggest that the use of intraoperative O-arm can reduce the need for revision of a breeched pedicle screw. This can potentially lead to a major cost savings.

Posterior cervical decompression and fusion can be performed for various spinal conditions. Previous rates of pseudoarthrosis have been reported in up to 38% of patients. The use of bone morphogenic protein (BMP) has been approved for use in certain anterior lumbar interbody fusion techniques to decrease the incidence of pseudoarthrosis. Bone morphogenic protein in the anterior cervical spine carries a potential increased risk of airway complications; however, few data exist on the safety and efficacy of BMP in the posterior cervical spine. The purpose of this study was to evaluate fusion success, safety, and heterotopic bone formation using BMP in posterior cervical fusion. Twenty-nine patients who received posterior cervical fusion with BMP were followed for a minimum of 12 months. Computed tomography scans were obtained at a minimum of 12 months postoperatively to evaluate for solid arthrodesis and the presence of heterotopic bone formation. Patients’ demographic data and adverse events were evaluated. All patients underwent posterior cervical decompression and instrumented fusion of at least 1 level between 2006 and 2008. Of 37 patients eligible for the study, 29 agreed to participate. Three (10.3%) of 29 patients developed pseudoarthrosis, as found on computed tomography scan. None of these went on to further surgery. No evidence existed of heterotopic bone formation outside of the lateral masses or bone growth over the spinal canal or neuroforamen. No adverse events were related to the use of BMP in this series of posterior cervical fusions. Bone morphogenic protein can be used safely in posterior cervical spine fusion, but additional larger studies are recommended. Even with the use of bone morphogenic protein, the possibility of pseudoarthrosis exists.

To present a case report of a patient with an ASIA B spinal cord injury with partially intact baseline IONM who made a complete functional recovery postoperatively. A thirty-three year old male presented after a motor vehicle accident. Imaging studies revealed a C4–C5 bilateral facet dislocation. On presentation the patient had 4/5 strength in bilateral biceps and wrist extensors, 3/5 strength in bilateral triceps, and 0/5 strength in the finger flexors, intrinsics and all lower extremity muscles. Motor level was C7. Sensation was grossly intact to light touch throughout all extremities, intact to pinprick from C2 to T7, and absent to pinprick caudal to T7. Rectal tone and contraction were absent. After attempts at closed reduction failed the patient underwent an open reduction and posterior C4–C5 fusion. Intraoperative neurophysiologic monitoring (IONM) revealed the presence of baseline responses to the posterior tibial nerve using somatosensory evoked potentials and to the right abductor hallucis using transcranial motor evoked potentials. At the 6 weeks postoperative visit the patient had full 5/5 motor strength to all muscles except the left deltoid that was 4/5 due to a rotator cuff injury. This case illustrates a potential prognostic value of IONM. Despite lack of clinical motor function at the time of surgery, IONM was able to illicit a motor response in the right lower extremity. Further prospective studies are needed for further investigation.

STUDY DESIGN: This is a prospective study. OBJECTIVE: The aim of our study is to identify whether vertebral arteries (VA), normal or aberrant, are routinely described in cervical spine magnetic resonance imaging (MRI) interpretations. SUMMARY OF BACKGROUND DATA: VA injury is a serious complication of anterior cervical spine surgery. Aberrant VA anatomy is a potential cause of such complications. Therefore, VA anatomy should be evaluated in cervical MRIs. METHODS: Six neuroradiologists were blinded to the study design and were asked to interpret 79 cervical MRIs. Of these, 39 had aberrant VAs, whereas 40 had normal VAs. Initially, the indications for the study included only a description of patient's symptoms. The radiologists were then given the same MRIs with different indications. This time, the indications included the patient's symptoms, a request for annotations on the VA, and a definition of VA anomaly. All of the MRI interpretations were then evaluated for the frequency and accuracy of VA description. RESULTS: When the indications for the study did not specifically request a comment on VAs, the VA was never described (0%). When the indications included the specific request and definition, all 6 commented on the VA (100%). Three of the 6 radiologists were 100% accurate in identifying all 40 normal and 39 aberrant VAs, whereas the other 3 identified all 40 normal and 38 of 39 aberrant VAs. CONCLUSION: This study demonstrates that the VA is not a standard component of cervical spine MRI interpretations. Because of the significant complications related to its injury, VA anatomy, whether normal or variant, needs to be evaluated in cervical MRIs. When ordering a cervical MRI, surgeons should request a description of the VA and any anomalies.

STUDY DESIGN Meta-analysis. OBJECTIVE Meta-analysis of the data to determine the effect of magnetic resonance imaging (MRI) signal change on preoperative and postoperative Japanese Orthopedic Association (JOA) scores and on recovery rate after surgery. SUMMARY OF BACKGROUND DATA MRI signal changes are commonly found in myelopathy. There is often an increased T2 signal with or without a decreased T1 signal. The clinical significance of these signal changes remains debated. METHODS A comprehensive review of the literature was performed to identify all published studies with data on the presence of MRI signal change and JOA scores in myelopathic patients. T tests were performed to determine if there were significant differences between preoperative and postoperative JOA scores in patients with or without MRI signal change. The recovery rate was calculated for all patients undergoing surgery. T tests were performed to determine whether significant differences occurred in recovery rate in patients with or without MRI signal change. RESULTS A total of 16 studies were used for the meta-analysis. The total population included 886 patients: 659 with MRI signal change, and 227 without MRI signal change. Preoperative and postoperative JOA scores and the recovery rates were significantly better in patients without MRI signal changes (P < 0.05). The mean preoperative JOA scores were 10.63 and 11.37 for patients with and without MRI signal changes, respectively. The mean postoperative JOA scores were 13.37 and 14.19 for patients with and without MRI signal changes, respectively. The mean recovery rates were 43.87% and 49.31% for patients with and without MRI signal changes, respectively. CONCLUSION A meta-analysis of the literature revealed statistically better preoperative and postoperative JOA scores and recovery rates following surgery in myelopathic patients without MRI signal change. Although the data were statistically significant, the clinical significance of the differences might be less due to the relatively small differences in actual values.

Ketorolac is a nonopioid, anti-inflammatory drug commonly used for postoperative analgesia. Its effectiveness has been previously documented in various orthopedic procedures and more recently in spinal surgery. It remains uncertain if ketorolac has an effect on wound healing. The purpose of this study was to determine if the use of postoperative ketorolac induced deleterious effects on wound healing in a simulated spinal surgery incision using a rat model. A 4-cm dorsal midline incision was made and closed in 36 rats. Rats were divided into 3 groups: (1) 5 mg/kg ketorolac given every 6 hours for 24 hours; (2) 5 mg/kg ketorolac given every 6 hours for 48 hours; and (3) control group given dextrose 5% in water every 6 hours for 48 hours. On postoperative day 14, sutures were removed. Wounds were removed and loaded to failure in tension. The mean+/-SD loads to failure were 9.8+/-1.8 N for group 1, 9.0+/-2.4 N for group 2, and 9.5+/-4.5 N for group 3. The differences among the 3 groups were not statistically significant (P>.05). The use of ketorolac in the immediate postoperative period produces no increased risk of wound complications in this rat model.

A 54-year-old woman presented with neck pain and bilateral shoulder pain. The pain was of varying intensity and was present with activity as well as at night and at rest. She had weakness of her triceps and finger intrinsic muscles. Her past medical history included stage IV melanoma for which she underwent an excision from the right flank area 25 years ago. She was cleared from any disease 5 years after the excision. Magnetic resonance imaging of the cervical spine revealed increased signal intensity in the C7 vertebral body with soft tissue extension into the epidural space. Two weeks after initial presentation the patient underwent a C7 corpectomy and fusion. The C7 vertebral body was grossly pathologic and tissue samples revealed metastatic malignant melanoma. During the 2 weeks following the fusion the patient developed increasing pain and generalized weakness. Repeat MRI of the cervical spine revealed a large soft tissue intensity extending in the spinal canal from C6 to T2. Several days later the patient developed an acute onset of lower extremity weakness as well as urinary incontinence. The patient opted to pursue hospice care, and she died 3 weeks later, 8 weeks after the initial presentation.

Study design Experimental dog model of acute spinal cord injury. Objective To compare the relative value of methylprednisolone, surgical decompression, or both for the treatment of traumatic spinal cord injury. Summary of background data Acute spinal cord injury results from both primary damage to the spinal cord at the time of the initial injury as well as a deleterious secondary cascade of events, which leads to further damage. Surgical decompression is known to improve clinical outcomes, but the timing of surgical decompression remains controversial. Methods A nylon tie was used to constrict the spinal cord in 18 adult male beagle dogs. The animals were then prospectively randomized to 3 groups: 1) surgical decompression at 6 hours and intravenous methylprednisolone; 2) surgical decompression at 6 hours and intravenous saline; and 3) intravenous methylprednisolone without surgical decompression. Each animal was evaluated by somatosensory-evoked potentials, daily neurologic assessment, and histologic examination at 2 weeks following injury. Results Immediately following spinal cord constriction, all animals were paraplegic, incontinent, and the somatosensory-evoked potentials were abolished. Surgical decompression 6 hours after injury, with or without methylprednisolone, led to significantly better neurologic function at 2 weeks than methylprednisolone alone. Conclusion In the setting of acute and persistent spinal cord compression in beagle dogs, surgical decompression 6 hours after injury, with or without methylprednisolone, is more effective for improving neurologic recovery than methylprednisolone alone.

Background context Cervical spine dislocations represent an area of great controversy among spine surgeons. Purpose The purpose of this review is to present the specific areas of controversy and to provide a review of the literature. Study design A case of cervical spine dislocation is presented to illustrate the major controversies related to the treatment of cervical spine dislocations. Methods A review of the literature is presented regarding the major controversial aspects of the treatment of cervical spine dislocations. Results The major areas of controversy include the choice of imaging, closed versus open reduction and surgical approach. Conclusions Guidelines for the management of cervical spine dislocations are presented based on evidence-based medicine.

Degenerative changes in the cervical spinal column are ubiquitous in the adult population, but infrequently symptomatic. The evaluation of patients with symptoms is facilitated by classifying the resulting clinical syndromes into axial neck pain, cervical radiculopathy, cervical myelopathy, or a combination of these conditions. Although most patients with axial neck pain, cervical radiculopathy, or mild cervical myelopathy respond well to initial nonsurgical treatment, those who continue to have symptoms or patients with clinically evident myelopathy are candidates for surgical intervention.

Study design Biomechanical study of pullout strength of unicortical versus bicortical C1 lateral mass screws using a cadaveric cervical spine model. Objective To compare pullout strength of unicortical versus bicortical C1 lateral mass screws. Summary of background data The internal carotid artery and hypoglossal nerve lie over the anterior aspect of the lateral mass of the atlas and are at risk from bicortical C1 lateral mass screws. Unicortical screws would reduce the risk of injury to these neurovascular structures; however, no data are available on the relative strength of unicortical versus bicortical C1 lateral mass screws. Methods Fifteen cadaveric cervical spine specimens underwent axial pullout testing of C1 lateral mass screws. A unicortical C1 lateral mass screw was placed on 1 side with a contralateral bicortical screw. Results The mean pullout strengths of the unicortical screws and bicortical screws were 588 N (range, 212 to 1234 N) and 807 N (range, 163 to 1460 N), respectively (P=0.008). Conclusions Bicortical C1 lateral mass screws were significantly stronger than unicortical screws; however, the mean pullout strength of both the unicortical and bicortical C1 screws were greater than previously reported values for subaxial lateral mass screws. On the basis of these data, the clinical necessity for using bicortical screw fixation in all patients must be questioned. If similar strength can be achieved using unicortical C1 lateral mass screw to that currently accepted in the subaxial spine, bicortical screws might not be justified for the C1 lateral mass. However, the ability to extrapolate C1-C2 data to subaxial spine data is uncertain because of the difference in normal physiologic loading at these levels.

Minimally invasive techniques for lumbar spine fusion have been developed in an attempt to decrease the complications related to traditional open exposures (eg, infection, wound healing problems). Anterior minimally invasive procedures include laparoscopic and mini-open anterior lumbar interbody fusion as well as the lateral transpsoas and percutaneous presacral approaches. Posterior techniques typically use a tubular retractor system that avoids the muscle stripping associated with open procedures. These techniques can be applied to both posterior and transforaminal lumbar interbody fusion procedures. Many initial reports have shown similar clinical results in terms of spinal fusion rates for both traditional open and minimally invasive posterior approaches. However, the anterior minimally invasive procedures are often associated with significantly greater incidence of complications and technical difficulty than their associated open approaches. There is a steep learning curve associated with minimally invasive techniques, and surgeons should not expect to master them in the first several cases.

Rates of redundant publications in the general surgery literature are approximately 14%. This article identifies the rate of redundant publications in the orthopedic literature. All original articles published during the year 2000 in The Journal of Bone and Joint Surgery (American Volume), Journal of Orthopaedic Trauma, Journal of Spinal Disorders, and Spine were searched using PubMed. Redundancy rate was 4 (3.15%) of 127 for The Journal of Bone and Joint Surgery (American volume), zero (0%) of 70 for Journal of Orthopaedic Trauma, 2 (2.90%) of 69 for Journal of Spinal Disorders, and 11 (3.12%) of 353 for Spine.

Background context The internal carotid artery and hypoglossal nerve lie over the anterior aspect of the lateral mass of the atlas and are at risk from bicortical C1–C2 transarticular screws. This has led to the recommendation for unicortical screws if the neurovascular structures are in close proximity to the proposed exit point. No data are available on strength of unicortical versus bicortical C1–C2 transarticular screws. Purpose To compare the biomechanical pullout strength of unicortical versus bicortical C1–C2 transarticular screws in a cadaveric model. Study design Biomechanical study. Methods Fifteen cervical spine specimens underwent axial pullout testing. A unicortical C1–C2 transarticular screw was placed on one side with a contralateral bicortical screw. Data were analyzed to reveal any significant differences in strength. Results Mean pullout strength for the bicortical C1–C2 transarticular screws was 1,048.8 (±360.1) N versus 939.2 (±360.6) for unicortical screws (p=.22). There was no significant difference in the pullout strength of unicortical and bicortical screws. Conclusions In cases with satisfactory bone quality, it appears reasonable to use unicortical screws to avoid the risk of neurovascular injury from penetrating the anterior cortex of C1.