Characterization of Lumbar Lordosis: Influence of Age, Sex, Vertebral Body Wedging, and L4-S1.

STUDY DESIGN: Retrospective radiographic review. OBJECTIVE: The objectives of the study were to determine the contributions to lumbar lordosis (LL) through both the vertebrae and the intervertebral disc (IVD), and to investigate the relationships between lumbar sagittal spine measurements and age and gender. SUMMARY OF BACKGROUND DATA: A small body of literature exists on the relative contributions of vertebral body and IVD morphology to LL, the effects of L4-S1 on overall LL, and the relationships/correlations between lumbar sagittal spine measurements. METHODS: Patients who met the inclusion criteria were retrospectively evaluated. Measurements included LL, pelvic incidence (PI), and % contributions of vertebral body wedging/IVD wedging/L4-S1 to LL. Patients were separated into groups by age and sex, demographic data were collected, and statistical analysis was completed. RESULTS: LL decreased with age, although PI remained similar. Females demonstrated increased LL and vertebral body wedging % than males. Males demonstrated increased L4-S1% than females. Despite a decrease in LL with age, patients maintained L4-S1% and IVD wedging %. There was a significant negative relationship between PI and IVD wedging, PI and L4-S1%, and LL and L4-S1%. CONCLUSIONS: During aging, the lumbar spine loses LL linearly. This occurs in the IVD and vertebral bodies. Females have increased LL compared with males, because of an increase in vertebral body wedging and IVD/vertebral wedging cranial to L4. In patients with high PI or LL, increased LL occurs from cranial to L4 and from vertebral body wedging.

The impact of minimally invasive surgical approaches on surgical-site infections.

We performed a literature review to describe the risk of surgical-site infection (SSI) in minimally invasive surgery (MIS) compared to standard open surgery. Most studies reported decreased SSI rates among patients undergoing MIS compared to open procedures. However, many were observational studies and may have been affected by selection bias. MIS is associated with reduced risk of surgical-site infection compared to standard open surgery and should be considered when feasible.

An Evidence-Based Algorithm for Determining Venous Thromboembolism Prophylaxis After Degenerative Spinal Surgery.

BACKGROUND: Although venous thromboembolism (VTE) is a potentially serious and life-threatening complication, there is no widely accepted protocol to guide VTE prophylaxis in adult degenerative spinal surgery, and pharmacologic overtreatment may result in hemorrhagic complications. Previously, we published the VTE Prophylaxis Risk/Benefit Score, an evidence-based algorithm that balances the risk and consequences of thrombotic versus hemorrhagic complications by taking consideration of patient-related risks, procedure-related risks, and the risk of neurological compromise to guide VTE prophylaxis. To objective of this study was to validate the VTE Prophylaxis Risk/Benefit Score. METHODS: From January 1, 2016, to December 31, 2017, VTE Prophylaxis Risk/Benefit Scores and corresponding prophylaxes were prospectively assigned. When indicated, chemoprophylaxis was dosed 24 to 36 hours postoperatively to allow for adequate surgical hemostasis. Patients were retrospectively evaluated for immediate and short-term complications. The Fisher exact test compared incidence of complications by VTE prophylaxis. Multinomial logistic regression modeled the probability of complication by prophylaxis type, demographics, and comorbidities. Significance was set at P < .05. RESULTS: Of the 266 patients who met inclusion criteria, 79.3% were given mechanical prophylaxis alone and 20.7% were given combined mechanical and chemical prophylaxis. Complications including VTE (0.38%), delayed wound healing or infection (2.26%), and hematoma (0.75%) were observed at rates similar to or lower than previously published studies with increased utilization of chemoprophylaxis. Use of chemoprophylaxis and continuation of perioperative aspirin were significantly associated with the development of a hemorrhagic complication. No patient developed persistent neurologic deficit from hematoma or pulmonary embolism. CONCLUSIONS: The VTE Prophylaxis Risk/Benefit Score comprehensively considers the risk of thrombotic, wound, and bleeding complications and is an effective tool for determining appropriate thromboprophylaxis in adult degenerative spinal surgery. LEVEL OF EVIDENCE: 3.

Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery.

The incidence of intraoperative complications during cervical spine surgery is low; however, if they do occur, intraoperative complications have the potential to cause considerable morbidity and mortality. Spine surgeons should be familiar with methods to minimize intraoperative complications. If they do occur, surgeons must be prepared to immediately treat each potential complication to reduce any associated morbidity.

Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery.

The incidence of intraoperative complications in cervical spine surgery is low. However, when they do occur, such complications have the potential for causing considerable morbidity and mortality. Spine surgeons should be familiar with methods of minimizing such complications. Furthermore, if they do occur, surgeons must be prepared to immediately treat each potential complication to reduce any associated morbidity.

An Algorithmic Approach to Venous Thromboembolism Prophylaxis in Spine Surgery.

Venous thromboembolic embolism (VTE) is a potentially serious and life-threatening complication in spine surgery. However, VTE incidence and prophylaxis in spine surgery remains controversial. Current recommendations for VTE prophylaxis address "spine surgery" as a single broad category and mainly consider patient factors when determining risk. We performed a literature review to determine the varying VTE and bleeding risks within spine surgery to develop an individualized prophylactic algorithm. Our review suggests that the current guidelines on VTE prophylaxis for spine surgery from NASS and ACCP are suboptimal. Consideration of (1) patient-related VTE risks, (2) procedure-related VTE risks, and (3) the risk of neurological compromise from bleeding complications will more appropriately balance safety and effectiveness when choosing a VTE prophylaxis method. To better individualize VTE prophylaxis, we have developed the VTE Prophylaxis Risk/Benefit Score that considers this currently available best evidence to arrive at a recommendation for the most appropriate form of VTE prophylaxis. This algorithm informs the surgeon to help make a more nuanced and individualized determination of prophylaxis.

Lumbar Radiculopathy Confounded: Total Knee Arthroplasty Diminishes the Patellar Tendon Reflex.

STUDY DESIGN: Patellar tendon reflexes were elicited among patients who had had a unilateral total knee replacement, those planned for unilateral total knee replacement, and a cohort of controlled patients. Patellar tendon reflex (PTR) response was measured with surface electromyography. OBJECTIVE: The aim of this study was to determine if total knee arthroplasty significantly alters the PTR. SUMMARY OF BACKGROUND DATA: As part of the clinical evaluation of the spine, extremity reflexes are provoked. Reflex variation between right and left extremities can be a pathological finding in disease of the spine. It has been noted that in patients who have undergone total knee arthroplasty (TKA), the PTR is diminished on the operative side compared with the contralateral nonoperative side. PTR is part of the clinical exam when evaluating a patient for lumbar radiculopathy. METHODS: The right and left patellar tendon reflex intensities were measured by quadriceps surface electromyography in 3 groups of patients. Group 1 consisted of 21 patients with unilateral TKA who were at least 6 months postoperative. Group 2 consisted of 18 patients with unilateral severe knee arthritis indicated for TKA. Group 3, serving as the control group, included 20 patients with no evidence of knee arthritis in either knee. The average reflex response for each group was recorded and comparisons were then made between each group. RESULTS: Patients who have undergone unilateral TKA have a PTR on average of 55.1% of their contralateral uninvolved side. This is statistically significant when compared with reflexes in patients who are planned for unilateral total knee arthroplasty, 96.03% (P = 0.001) and when compared with patients without evidence for knee arthritis, 102.2% (P < 0.001). CONCLUSION: The results of this case control study show that TKAs do significantly diminish PTRs when compared with a contralateral uninvolved knee in the same patient. LEVEL OF EVIDENCE: 3.

Risk factors for persistent dysphagia after anterior cervical spine surgery.

Dysphagia is a relatively common complication of anterior cervical spine surgery. Smoking has not been definitively assessed as a risk factor for dysphagia. This study examined risk factors for dysphagia, including smoking and pain severity. The authors performed a cross-sectional cohort study of 100 patients who underwent anterior cervical diskectomy and fusion (ACDF). Dysphagia was assessed with the Yoo-Bazaz questionnaire. Clinical notes were reviewed for demographic information, diagnosis, preoperative pain severity, preoperative smoking status, and operative details. The dysphagia questionnaire was administered via telephone. The rate of dysphagia at an average of 2.75 years (33 months) was 26%. Rare and mild dysphagia were reported by 2% and 7% of patients, respectively. Moderate dysphagia was reported by 12% patients, and severe dysphagia was reported by 5% of patients. Smokers were more likely to report dysphagia symptoms, and their dysphagia scores were more severe than those in nonsmokers (1.17 vs 0.54; P=.02). Patients undergoing revision surgery (n=7) had dysphagia at a rate of 71% compared with 23% of patients undergoing primary surgery (P<.004). Age, sex, diagnosis, severity of preoperative pain, and number of levels treated did not reach statistical significance. The prevalence of persistent dysphagia at an average of 33 months after ACDF was 23% in primary cases. To the authors' knowledge, the severity of dysphagia in smokers has not been reported previously. These data confirm previous reports that dysphagia symptoms persist in a significant proportion of patients more than 1 year after anterior cervical spine surgery.

Lateral mass versus hybrid construct for cervical laminectomy and fusion.

Spine stabilization after C3-C7 laminectomy can be accomplished with many instrumentation options. A hybrid construct using lateral mass screws from C3 to C5 and pedicle screws at C7 can potentially maximize strength and solve the spatial constraints introduced by the placement of C6 lateral mass screws and C7 pedicle screws. Seven cadaveric cervical spines from C2 to T2 were potted in a custom testing apparatus. Differential variable reluctance transducers were placed on C6 and C7 to measure linear displacement. Specimens were loaded in flexion, extension, lateral bending, and axial torque at 1.5 Nm. A wide laminectomy was then performed, and specimens were randomized to first receive either the bilateral C3-C7 lateral mass screw construct or a hybrid construct with C3-C5 lateral mass screws and C7 pedicle screws. All specimens were tested with both constructs. Normalized deformation (mean±SD) for the lateral mass screw vs the hybrid pedicle screw constructs in the sagittal plane was 7.46%±5.48% vs 5.68%±3.67%, respectively (P=.237). Coronal deformation for lateral mass screw vs the hybrid pedicle screw constructs was 19.2%±10.9% vs 13.6%±9.53% (P=.237). Axial rotation deformation for lateral mass vs pedical screw constructs was 85.9%±83.3% vs 74.7%±58.1%, respectively (P=.868). Despite data reported in the literature indicating a higher pullout strength of pedicle screws and improved strength of hybrid pedicle screw constructs compared with lateral mass screw constructs, a hybrid construct taking spatial constraints and increased danger of pedicle screw placement above C7 into account showed no improvement in motion compared with a lateral mass screw construct.

Does incorrect level needle localization during anterior cervical discectomy and fusion lead to accelerated disc degeneration?

STUDY DESIGN: Retrospective radiographic analysis. OBJECTIVE: To retrospectively review a group of patients undergoing anterior cervical discectomy and fusion (ACDF) to determine the relative risk of adjacent level disc degeneration after incorrect needle localization. SUMMARY OF BACKGROUND DATA: The needle puncture technique is a well-established method to cause disc degeneration in experimental animal studies. The risk for accelerated degeneration because of needle puncture in humans is unknown. METHODS: A retrospective radiographic analysis of 87 consecutive patients after single or 2-level ACDF with anterior plate instrumentation was performed. Perioperative and follow-up radiographs were used to grade disc degeneration according to a previously described scale. RESULTS: Eighty-seven patients were included in the study (36 underwent 1-level ACDF, and 51 underwent 2-level ACDF). Seventy-two had correct needle localization at the level of planned surgery; 15 had incorrect needle localization (1 level above the operative level). There were no differences between the 2 groups in age, sex and length of follow-up. Patients in the incorrectly marked group were statistically more likely to demonstrate progressive disc degeneration with an odds ratio of 3.2. There was no correlation between age and length of follow-up with development of disc degeneration. CONCLUSION: There is a 3-fold increase in risk of developing adjacent level disc degeneration in incorrectly marked discs after ACDF at short-term follow-up. This may indicate that either needle related trauma or unnecessary surgical dissection contributes to accelerated adjacent segment degeneration.

Financial incentives for lumbar surgery: a critical analysis of physician reimbursement for decompression and fusion procedures.

STUDY DESIGN: Retrospective case-control study/economic analysis. OBJECTIVE: To determine the treatment times required for isolated lumbar decompressions and for combined decompression and instrumented fusion procedures to compare the relative reimbursements for each type of operation as a function of time expenditure by the surgeon. SUMMARY OF BACKGROUND DATA: Under current Medicare fee schedules, the payment for a fusion procedure is higher than of an isolated decompression. It has been recently suggested in the lay press that the greater reimbursement for a lumbar arthrodesis may inappropriately influence the manner in which surgeons elect to treat lumbar degenerative conditions, resulting in what they believe to be a substantial number of unnecessary spinal fusions. METHODS: A consecutive series of 50 single-level decompression cases performed by single surgeon were retrospectively analyzed and compared with an equivalent cohort of subjects who underwent single-level decompression and instrumented posterolateral fusion with autogenous iliac crest bone grafting. The operative reports, office charts, and billing records were reviewed to determine the total clinical time invested by the surgeon and the Medicare reimbursement for each surgery. RESULTS: Relative to the corresponding values of the decompression group, combined decompression and fusion procedures were associated with a longer mean surgical time (134.6 min vs. 47.3 min, P<0.0001), a greater number of postoperative visits (1.0 vs. 3.2, P<0.0001), a higher mean total clinical time expenditure (186.6 min vs. 62.2 min, P<0.0001), and a lower mean dollars received per minute of surgeon time ($12.51 vs. $15.51, P<0.001). CONCLUSIONS: These findings challenge the assertion that spine surgeons have an undue financial incentive to recommend a combined decompression and instrumented fusion procedure over an isolated decompression to patients with symptomatic lumbar degeneration, especially when considering the greater time, effort, and risk characteristic of this more complex operation.

The surgeon as a consultant for medical device manufacturers: what do our patients think?

STUDY DESIGN: Patient survey. OBJECTIVE: To evaluate patient perspective on surgeons as consultants for industry and medical device manufacturers. SUMMARY OF BACKGROUND DATA: Relationships between surgeons and medical device manufacturers are becoming increasingly common. Little is known, however, about how patients perceive these relationships. METHODS: Patients in the waiting area of an orthopedic surgery clinic were given a simple 1-page, 8-question anonymous questionnaire. Their responses were tabulated and analyzed for 3 variables: gender, age, and education level. RESULTS: A total of 245 patients completed the questionnaire. An overwhelming majority (94.3%) believed that surgeon-industry relationship is beneficial to patients, and a majority (66.5%) of patients thought that physicians should be compensated for this role. Women were more likely than men to want this relationship to be regulated by physicians instead of the government or hospitals. Patients older than 55 years were less likely to be in favor of physicians being compensated than younger patients. The more educated the patient, the less likely he/she was in favor of allowing physicians to regulate physician-industry relationship. CONCLUSION: Patients support surgeons in the role of consultants for industry. Gender, age, and education level influence the way that patients perceive this issue.

Regional variability in use of a novel assessment of thoracolumbar spine fractures: United States versus international surgeons.

BACKGROUND: Considerable variability exists in clinical approaches to thoracolumbar fractures. Controversy in evaluation and nomenclature contribute to this confusion, with significant differences found between physicians, between different specialties, and in different geographic regions. A new classification system for thoracolumbar injuries, the Thoracolumbar Injury Severity Score (TLISS), was recently described by Vaccaro. No assessment of regional differences has been described. We report regional variability in use of the TLISS system between United States and non-US surgeons. METHODS: Twenty-eight spine surgeons (8 neurosurgeons and 20 orthopedic surgeons) reviewed 56 clinical thoracolumbar injury case histories, which included pertinent imaging studies. Cases were classified and scored using the TLISS system. After a three month period, the case histories were re-ordered and the physicians repeated the exercise; 22 physicians completed both surveys and were used to assess intra-rater reliability. The reliability and treatment validity of the TLISS was assessed. Surgeons were grouped into US (n = 15) and non-US (n = 13) cohorts. Inter-rater (both within and between different geographic groups) and intra-rater reliability was assessed by percent agreement, Cohen's kappa, kappa with linear weighting, and Spearman's rank-order correlation. CONCLUSION: Non-US surgeons were found to have greater inter-rater reliability in injury mechanism, while agreement on neurological status and posterior ligamentous complex integrity tended to be higher among US surgeons. Inter-rater agreement on management was moderate, although it tended to be higher in US-surgeons. Inter-rater agreement between US and non-US surgeons was similar to within group inter-rater agreement for all categories. While intra-rater agreement for mechanism tended to be higher among US surgeons, intra-rater reliability for neurological status and PLC was slightly higher among non-US surgeons. Intra-rater reliability for management was substantial in both US and non-US surgeons. The TLISS incorporates generally accepted features of spinal injury assessment into a simple patient evaluation tool. The management recommendation of the treatment algorithm component of the TLISS shows good inter-rater and substantial intra-rater reliability in both non-US and US based spine surgeons. The TLISS may improve communication between health providers and may contribute to more efficient management of thoracolumbar injuries.

Assessment of injury to the thoracolumbar posterior ligamentous complex in the setting of normal-appearing plain radiography.

BACKGROUND CONTEXT: The posterior ligamentous complex (PLC) is thought to contribute significantly to the stability of thoracolumbar spine. Obvious translation or dislocation of an interspace clearly denotes injury to the PLC. A recent survey of the Spine Trauma Study Group indicated that plain radiographic findings, if present, are most helpful in determining PLC injury. However, confusion exists when plain radiography shows injury to the anterior spinal column without significant kyphosis or widening of the posterior interspinous space. PURPOSE: The objective of this study is to identify imaging parameters that may suggest a disruption of the posterior ligamentous complex of the thoracolumbar spine in the setting of normal-appearing plain radiographs. This study was performed, in part, as a pilot study to determine critical imaging parameters to be included in a future prospective, randomized, multicenter study. STUDY DESIGN/SETTING: Survey analysis of the Spine Trauma Study Group. PATIENT SAMPLE: None. OUTCOME MEASURES: Compilation and statistical analysis of survey results. METHODS: Based on a systematic review of the English literature from 1949 to present, we identified a series of traits not found on plain X-rays that were consistent with PLC injury. This included five imaging findings on either computed tomography (CT) scans or magnetic resonance imaging (MRI) and several physical examination features. These items were placed on a survey and sent to the members of the Spine Trauma Study Group. They were asked to rank the items from most important to least important in representing an injury to the PLC in the setting of normal-appearing plain radiographs. RESULTS: Thirty-three of 47 surveys were returned for final analysis. Thirty-nine percent (13/33) of the members ranked "disrupted PLC components (i.e., interspinous ligament, supraspinous ligament, ligamentum flavum) on T1 sagittal MRI" as the most important factor in determining disruption of PLC. When analyzed with a point-weighted system, "diastasis of the facet joints on CT" received the most points, indicating that this category was ranked high by the majority of the members of the group. The members were also given freedom to add other criteria that they believed were important in determining PLC integrity in the setting of normal-appearing plain radiograph. Of the other criteria suggested, one included a physical finding and the other a variant of MR sequencing. CONCLUSIONS: In a setting of normal-appearing plain radiographs, PLC injury as displayed on T1-weighted MRI and diastasis of the facet joints on CT scan seem to be the most popular determinants of probable PLC injury among members of the Spine Trauma Study Group. Between MRI and CT scan, most members feel that various characteristics on MRI studies were more helpful.

Bioabsorbable interbody spacers.

Bioabsorbable polymers have been used in surgery for more than four decades. With increased reliability and decreased incidence of complications, their application has become widespread. Although their role in spinal surgery continues to evolve, the theoretic biomechanical and biologic advantages over contemporary metallic and composite implant materials make bioabsorbable interbody spacers an attractive alternative. The lack of artifact on postoperative imaging studies and the ability to load share across fusion sites in a time-dependent manner can lead to more accurate fusion assessment and increased fusion rates. The preliminary data from small, short-term studies are promising. However, larger studies with long-term follow-up are lacking. The theoretic advantages of bioabsorbable materials must be tempered by the lack of long-term clinical evidence of their benefit. Until the results of more studies in human spinal applications become available, the precise indications for the use of bioabsorbable interbody spacers will continue to evolve.

Evaluation of the elderly patient with an abnormal gait.

Distinguishing between the normal gait of the elderly and pathologic gaits is often difficult. Pathologic gaits with neurologic causes include frontal gait, spastic hemiparetic gait, parkinsonian gait, cerebellar ataxic gait, and sensory ataxic gait. Pathologic gaits with combined neurologic and musculoskeletal causes include myelopathic gait, stooped gait of lumbar spinal stenosis, and steppage gait. Pathologic gaits with musculoskeletal causes include antalgic gait, coxalgic gait, Trendelenburg gait, knee hyperextension gait, and other gaits caused by inadequate joint mobility. A working knowledge of the characteristics of these gaits and a systematic approach to observational gait examination can help identify the causes of abnormal gait. Patients with abnormal gait can benefit from the treatment of the primary cause of the disorder as well as by general fall-prevention interventions. Treatable causes of gait disturbance are found in a substantial proportion of patients and include normal-pressure hydrocephalus, vitamin B(12) deficiency, Parkinson's disease, alcoholism, medication toxicity, cervical spondylotic myelopathy, lumbar spinal stenosis, joint contractures, and painful disorders of the lower extremity.

"Normal" prevertebral soft tissue swelling following elective anterior cervical decompression and fusion.

INTRODUCTION: Prevertebral soft tissue swelling (PSTS) has been evaluated in the setting of traumatic cervical spine injuries. However, no study to date has quantified the PSTS following elective anterior cervical decompression and fusion or the time course to resolution of that swelling. METHODS: From May 2002 to May 2005 the senior author performed 193 elective 1- or 2-level anterior cervical decompression and fusions. Patients who underwent corpectomies and anterior cervical fusions for trauma or tumor were excluded. Preoperative, 2-week postoperative and 6-week postoperative radiographs were available on 100 patients. The prevertebral soft tissue stripe was measured on the neutral lateral radiographs for the 3 time points. The mean swelling (mm) for each time point was calculated and stratified by cervical level. Repeated measures analysis of variance with the Tukey-Kramer multiple comparisons test was used to compare the measured swelling at the various time points. RESULTS: The average PSTS was calculated for each cervical level, for each of the 3 time points, preoperative, 2- and 6-week postoperative. There was a significant increase in PSTS between the preoperative and 2-week postoperative measurements at all levels. There is a significant decrease in PSTS between 2- and 6-week postoperatively at all cervical levels. There is no significant change in PSTS at C2, C3, and C5, when comparing the preoperative and 6-week postoperative measurements. There is significant PSTS at C4, C6, and C7, when comparing preoperative and 6-week postoperative measurements. CONCLUSIONS: The "normal" range for PSTS at 2 weeks and at 6 weeks after elective 1- and 2- level anterior cervical decompression and fusions is described. Our data demonstrates that edema persists at the 2-week follow-up. By 6 weeks postoperative, the increased PSTS has greatly dissipated.

Assessment of injury to the posterior ligamentous complex in thoracolumbar spine trauma.

BACKGROUND CONTEXT: Posterior ligamentous complex (PLC), consisting of supraspinous ligament (SSL), interspinous ligament (ISL), ligamentum flavum (LF), and the facet joint capsules is thought to contribute significantly to the stability of thoracolumbar spine. Currently, no consensus exists on radiographic imaging parameters that may indicate injury to the posterior ligamentous complex. PURPOSE: To identify imaging parameters that may suggest a disruption of the PLC of the thoracolumbar spine. STUDY DESIGN/SETTING: A survey analysis of members of the Spine Trauma Study Group. PATIENT SAMPLE: None. OUTCOMES MEASURES: Compilation of survey results. METHODS: An extensive review of the literature from 1949 to the present was performed to identify key radiographic elements that have been suggested as indicators of PLC injury. Twelve items identified as such were placed on a survey and sent to the members of the Spine Trauma Study Group. They were asked to rank the items from most important to least important, and the results were compiled for analysis. RESULTS: Twenty-eight surveys were returned for final analysis. Fifty-percent (14/28) of the members ranked "vertebral body translation" on plain radiographs as the most important factor in determining disruption of PLC. Plain radiographic signs were ranked higher than computed tomography or magnetic resonance imaging indicators, and history of the mechanism ranked lowest. The members were also given freedom to add other criteria that they felt were important in determining PLC integrity. "Interspinous spacing 7 mm greater than that of level above or below on antero posterior plain X-rays" was the only new category that was suggested. CONCLUSION: Plain radiographic findings were felt to be most helpful in determining PLC injury by the members of the Spine Trauma Study Group. Physical examination findings and history of the mechanism of injury were ranked lower than imaging studies. Future analysis should focus on indicators of PLC injury when plain radiographic findings are either subtle or not present.

Characterization of neurophysiologic alerts during anterior cervical spine surgery.

STUDY DESIGN: A retrospective review of neurophysiologic alerts during anterior cervical surgery. OBJECTIVES: To examine incidence and types of neurophysiologic alerts and their correlation with new postoperative neurologic deficits after anterior cervical discectomy or corpectomy procedures. SUMMARY OF BACKGROUND DATA: Although multimodality neurophysiologic monitoring has been shown to predict iatrogenic neurologic injuries in scoliosis surgeries, their role in degenerative or trauma-related anterior cervical spine surgery is still unclear. MATERIALS AND METHODS: We retrospectively reviewed 1,445 patients who underwent anterior cervical discectomy or corpectomy and arthrodesis with neurophysiologic monitoring that included transcranial electrical motor-evoked potentials (tceMEP), somatosensory-evoked potentials (SSEP), and spontaneous electromyography (EMG). Intraoperative alerts were analyzed for type, perceived cause, actions taken to reverse or minimize the possible spinal cord injury, and any new postoperative neurologic deficits. RESULTS: There were 267 (18.4%) procedures that had either minor (spontaneous, sustained EMG) or major (tceMEP/SSEP amplitude reduction) alerts. Patients who underwent corpectomies had 28% increased risk of having a major neurophysiologic alert compared with those who had discectomies. Diagnosis of cervical spondylotic myelopathy or trauma increased the risk of having a major neurophysiologic alert 30% and 76%, respectively, compared with cervical radiculopathy. Eight surgeries were aborted due to persistent tceMEP/SSEP amplitude loss, but none resulted in new postoperative neurologic deficits. Two patients had halo-vest applied due to early termination of surgery. One of these patients ultimately could not receive definitive surgical stabilization. DISCUSSION AND CONCLUSION: Diagnosis of cervical spondylotic myelopathy or trauma and cervical corpectomy procedures increase the risk for having major intraoperative alerts. In case of persistent tceMEP/SSEP amplitude loss, consider delaying potentially harmful interventions, such as premature termination of the procedure or methylprednisolone infusion, until a new neurologic deficit is verified with an awake-clinical examination.

Quantitative prediction of spinal cord drift after cervical laminectomy and arthrodesis.

STUDY DESIGN: Retrospective review of radiographic parameters. OBJECTIVES: To identify preoperative radiographic parameters that may be quantitatively predictive of postoperative spinal cord drift after cervical laminectomy and arthrodesis. SUMMARY OF BACKGROUND DATA: Cervical laminectomy and arthrodesis can be an effective method to treat anterior compressions of the spinal cord if there is a sufficient posterior spinal cord drift after surgery. Preoperative cervical alignment has shown some correlations to the degree of spinal cord shift, but whether this and other preoperative radiographic parameters can be used to quantitatively predict the amount of spinal cord drift is unclear. MATERIALS AND METHODS: Preoperative and postoperative radiographs (radiographs, MRIs, and CT) of patients who had cervical laminectomy and arthrodesis were reviewed retrospectively. Various radiographic parameters, including sagittal alignment, longitudinal distance index, space available for the spinal cord at cephalad or caudad levels, and distance from apex of the lordosis to the C2-C7 vertical line were measured. In the first cohort of patients, these parameters were correlated with mean postoperative spinal cord shift to identify any relationships. In the second cohort of patients, the identified association was used on preoperative imaging studies to attempt quantitative prediction of the postoperative spinal cord shift. RESULTS: Space available for the spinal cord at the level immediately cephalad to the laminectomized segments had high correlations (R = 0.94) to the postoperative spinal cord shift. This association was used to quantitatively predict postoperative spinal cord shift within 11% +/- 6% of the measured value. If 4 mm of mean postoperative spinal cord shift is desired, the ratio to the available space and anterior posterior diameter of the spinal cord should be approximately 2.0. CONCLUSION: Relative stenosis at the level directly cephalad to the laminectomized level can affect the degree of postoperative spinal cord shift. Preoperative axial imaging studies should be closely scrutinized to ensure that adequate space is available at the cephalad adjacent level to allow sufficient cord shift after decompressive laminectomy and arthrodesis.