Neurosurgery Blog

J Neurosurg Spine 16:107–113, 2012. DOI: 10.3171/2011.10.SPINE11199

The primary goal of this study was to review the immediate postoperative neurological function in patients surgically treated for symptomatic cervical spine disease without intraoperative neurophysiological monitoring. The secondary goal was to assess the economic impact of intraoperative monitoring (IOM) in this patient population.

Methods. This study is a retrospective review of 720 consecutively treated patients who underwent cervical spine procedures. The patients were identified and the data were collected by individuals who were not involved in their care.

Results. A total of 1534 cervical spine levels were treated in 720 patients using anterior, posterior, and combined (360°) approaches. Myelopathy was present preoperatively in 308 patients. There were 185 patients with increased signal intensity within the spinal cord on preoperative T2-weighted MR images, of whom 43 patients had no clinical evidence of myelopathy. Three patients (0.4%) exhibited a new neurological deficit postoperatively. Of these patients, 1 had a preoperative diagnosis of radiculopathy, while the other 2 were treated for myelopathy. The new postoperative deficits completely resolved in all 3 patients and did not require additional treatment. The Current Procedural Terminology (CPT) codes for IOM during cervical decompression include 95925 and 95926 for somatosensory evoked potential monitoring of the upper and lower extremities, respectively, as well as 95928 and 95929 for motor evoked potential monitoring of the upper and lower extremities. In addition to the charge for the baseline [monitoring] study, patients are charged hourly for ongoing electrophysiology testing and monitoring using the CPT code 95920. Based on these codes and assuming an average of 4 hours of monitoring time per surgical case, the savings realized in this group of patients was estimated to be $1,024,754.

Conclusions. With the continuing increase in health care costs, it is our responsibility as providers to minimize expenses when possible. This should be accomplished without compromising the quality of care to patients. This study demonstrates that decompression and reconstruction for symptomatic cervical spine disease without IOM may reduce the cost of treatment without adversely impacting patient safety.

Neurosurgery 70:264–277, 2012 DOI: 10.1227/NEU.0b013e3182305669

Controversy exists as to the best posterior operative procedure to treat multilevel compressive cervical spondylotic myelopathy.

OBJECTIVE: To determine clinical, radiological, and patient satisfaction outcomes between expansile cervical laminoplasty (ECL) and cervical laminectomy and fusion (CLF).

METHODS: We performed a prospective, randomized study of ECL vs CLF in patients suffering from cervical spondylotic myelopathy. End points included the Short Form-36, Neck Disability Index, Visual Analog Scale, modified Japanese Orthopedic Association score, Nurick score, and radiographic measures.

RESULTS: A survey of academic North American spine surgeons (n = 30) demonstrated that CLF is the most commonly used (70%) posterior procedure to treat multilevel spondylotic cervical myelopathy. A total of 16 patients were randomized: 7 to CLF and 9 to ECL. Both groups showed improvements in their Nurick grade and Japanese Orthopedic Association score postoperatively, but only the improvement in the Nurick grade for the ECL group was statistically significant (P < .05). The cervical range of motion between C2 and C7 was reduced by 75% in the CLF group and by only 20% in the ECL group in a comparison of preoperative and postoperative range of motion. The overall increase in canal area was significantly (P < .001) greater in the CLF group, but there was a suggestion that the adjacent level was more narrowed in the CLF group in as little as 1 year postoperatively.

CONCLUSION: In many respects, ECL compares favorably to CLF. Although the patient numbers were small, there were significant improvements in pain measures in the ECL group while still maintaining range of motion. Restoration of spinal canal area was superior in the CLF group.

J Neurosurg Spine 16:68–76, 2012. DOI: 10.3171/2011.7.SPINE11222

The aim of this study was to evaluate the results and effectiveness of bilateral decompression via a unilateral approach in the treatment of lumbar degenerative spondylolisthesis (DS).

Methods. Operations were performed in 84 selected patients (mean age 62.1 ± 10 years) with lumbar DS between the years 2001 and 2008. The selection criteria included lower back pain with or without sciatica, neurogenic claudication that had not improved after at least 6 months of conservative treatment, and a radiological diagnosis of Grade I DS and lumbar stenosis. Decompression was performed at 3 levels in 15.5%, 2 levels in 54.8%, and 1 level in 29.7% of the patients with 1 level of spondylolisthesis. All patients were followed up for at least 24 months. For clinical evaluations, a visual analog scale, Oswestry Disability Index (ODI), and Neurogenic Claudication Outcome Score (NCOS) were used. Spinal canal size and (neutral and dynamic) slip percentages were measured both pre- and postoperatively.

Results. Neutral and dynamic slip percentages did not significantly change after surgery (p = 0.67 and p = 0.63, respectively). Spinal canal size increased from 50.6 ± 5.9 to 102.8 ± 9.5 mm2 (p < 0.001). The ODI decreased significantly in both the early and late follow-up evaluations, and good or excellent results were obtained in 64 cases (80%). The NCOS demonstrated significant improvement in the late follow-up results (p < 0.001). One patient (1.2%) required secondary fusion during the follow-up period.

Conclusions. Postoperative clinical improvement and radiological findings clearly demonstrated that the unilateral approach for treating 1-level and multilevel lumbar spinal stenosis with DS is a safe, effective, and minimally invasive method in terms of reducing the need for stabilization.

J Neurosurg Spine 16:37–43, 2012. DOI: 10.3171/2011.9.SPINE11283

Present attempts to control health care costs focus on reducing the incidence of complications and hospital-acquired conditions (HACs). One approach uses restriction or elimination of hospital payments for HACs. Present approaches assume that all HACs are created equal and that payment restrictions should be applied uniformly. Patient factors, and especially patient comorbidities, likely impact complication incidence. The relationship of patient comorbidities and complication incidence in spine surgery has not been prospectively reported.

METHODS: The authors conducted a prospective assessment of complications in spine surgery during a 6-month period; an independent auditor and a validated definition of perioperative complications were used. Initial demographics captured relevant patient comorbidities. The authors constructed a model of relative risk assessment based on the presence of a variety of comorbidities. They examined the impact of specific comorbidities and the cumulative effect of multiple comorbidities on complication incidence.

RESULTS: Two hundred forty-nine patients undergoing 259 procedures at a tertiary care facility were evaluated during the 6-month duration of the study. Eighty percent of the patients underwent fusion procedures. One hundred thirty patients (52.2%) experienced at least 1 complication, with major complications occurring in 21.4% and minor complications in 46.4% of the cohort. Major complications doubled the median duration of hospital stay, from 6 to 12 days in cervical spine patients and from 7 to 14 days in thoracolumbar spine patients. At least 1 comorbid condition was present in 86% of the patients. An increasing number of comorbidities strongly correlated with increased risk of major, minor, and any complications (p = 0.017, p < 0.0001, and p < 0.0001, respectively). Patient factors correlating with increased risk of specific complications included systemic malignancy and cardiac conditions other than hypertension.

CONCLUSIONS: Comorbidities significantly increase the risk of perioperative complications. An increasing number of comorbidities in an individual patient significantly increases the risk of a perioperative adverse event. Patient factors significantly impact the relative risk of HACs and perioperative complications.

J Neurosurg Spine 16:44–50, 2012. DOI: 10.3171/2011.9.SPINE11373

Since its original description in 1982, transforaminal lumbar interbody fusion (TLIF) has grown in popularity as a means for achieving circumferential fusion. The authors sought to define the perioperative complication rates of the TLIF procedure at a large academic medical center.

Methods. For all eligible patients from a consecutive series of 531 TLIF procedures, the institution’s complication database and the medical record were reviewed to identify complications. Medical, nonprocedure-related complications such as myocardial infarction and pulmonary embolism were excluded due to inconsistency in the recording of these complications in the database. Rates were calculated for each type of complication, and subgroup analysis was performed to investigate the effect of previous lumbar surgery, and of multilevel versus single-level interbody fusion on complication rates. Odds ratios were calculated and evaluated using chi-square analysis.

Results. Five hundred thirty-one patients underwent a TLIF procedure during the study period. Two hundred forty-four patients (46%) had undergone a previous lumbar operation. Interbody fusion was performed at 1 level in 317 patients, at 2 levels in 188 patients, at 3 levels in 24 patients, and at 4 levels in 2 patients. One hundred thirty-five patients (25.4%) had at least one procedure-related complication. The most common complications were durotomy (14.3% of patients) and infection (3.8% of patients). Symptomatic screw misplacement (2.1% of patients) and interbody cage migration (1.8% of patients) were less common complications. The overall complication rate was greater in those patients who had undergone a previous operation (OR 1.75, 95% CI 1.18–2.59; p < 0.01) and in those who had multilevel surgery (OR 1.54, 95 % CI 1.04–2.28; p = 0.03), and the incidence of durotomy was higher in patients who had a previous operation (OR 1.75, 95% CI 1.07–2.87; p = 0.03). These differences were statistically significant. Durotomy also occurred more frequently in patients who had multilevel interbody fusion (OR 1.49, 95% CI 0.92–2.43; p = 0.13). A trend toward higher infection rates in those patients who underwent multilevel interbody fusion was observed (OR 1.5, 95% CI 0.62–3.68; p = 0.49), but this was not statistically significant. Infection rates did not differ between revision and first-time surgeries.

Conclusions. Transforaminal lumbar interbody fusion has gained widespread popularity as a procedure for achieving arthrodesis in the lumbar spine. Complications occurred more often in patients undergoing revision surgery or multilevel interbody fusion. Durotomy and infection were the most common complications in this series.

J Neurosurg Spine 16:31–36, 2012. DOI: 10.3171/2011.8.SPINE11303

The purpose of cervical total disc replacement (TDR) is to decrease the incidence of adjacent segment disease through motion preservation. Heterotopic ossification (HO) is a well-known complication after hip and knee arthroplasties. There are few reports regarding HO in patients undergoing cervical TDR, however; and the occurrence of HO and its effects on cervical motion have rarely been reported. Moreover, temporal progression of HO has not been fully addressed. One goal of this study involved determining the incidence of HO following cervical TDR, as identified from plain radiographs, and demonstrating the progression of HO during the follow-up period. A second goal consisted of determining whether segmental motion could be preserved and identifying the relationship between HO and clinical outcomes.

Methods. The authors conducted a retrospective clinical and radiological study of 28 consecutive patients who underwent cervical TDR with Mobi-C prostheses (LDR Medical) between September 2006 and October 2008. Radiological outcomes were evaluated using lateral dynamic radiographs obtained preoperatively and at 1, 3, 6, 12, and 24 months postoperatively. The occurrence of HO was interpreted on lateral radiographs using the McAfee classification. Cervical range of motion (ROM) was also measured. The visual analog scale (VAS) and Neck Disability Index (NDI) were used to evaluate clinical outcome.

Results. The mean follow-up period was 21.6 ± 7.0 months, and the mean occurrence of HO was at 8.0 ± 6.6 months postoperatively. At the last follow-up, 18 (64.3%) of 28 patients had HO: Grade I, 6 patients; Grade II, 8 patients; Grade III, 3 patients; and Grade IV, 1 patient. Heterotopic ossification progression was proportional to the duration of follow-up; HO was present in 3 (10.7%) of 28 patients at 1 month; 7 (25.0%) of 28 patients at 3 months; 11 (42.3%) of 26 patients at 6 months; 15 (62.5%) of 24 patients at 12 months; and 17 (77.3%) of 22 patients at 24 months. Cervical ROM was preserved in Grades I and II HO but was restricted in Grades III and IV HO. Clinical improvement according to the VAS and NDI was not significantly correlated with the occurrence of HO.

Conclusions. The overall incidence of HO after cervical TDR was relatively high. Moreover, HO began unexpectedly to appear early after surgery. Heterotopic ossification progression was proportional to the time that had elapsed postoperatively. Grade III or IV HO can restrict the cervical ROM and may lead to spontaneous fusion; however, the occurrence of HO did not affect clinical outcome. The results of this study indicate that a high incidence of HO with the possibility of spontaneous fusion is to be expected during long-term follow-up and should be considered before performing cervical TDR.

Neurosurgery 70:211–219, 2012 DOI: 10.1227/NEU.0b013e31822d5f17

This second part of a comprehensive review of primary vertebral tumors focuses on locally aggressive and malignant tumors. As discussed in the earlier part of the review, both benign and malignant types of these tumors affect the adult and the pediatric population, and an understanding of their subtleties may increase their effective resection. In this review, we discuss the epidemiologic, histological, and imaging features of the most common locally aggressive primary vertebral tumors (chordoma and giantcell tumor) and malignant tumors (chondrosarcoma, Ewing sarcoma, multiple myeloma or plasmacytoma, and osteosarcoma). The figures used for illustration are from operative patients of the senior authors (Z.L.G. and J.H.C.). Taken together, parts 1 and 2 of this article provide a thorough and illustrative review of primary vertebral tumors.

Spine 2012 ; 37 : 48 – 56

Study Design. A prospective study evaluating a cohort of patients with spondylotic cervical spine compression.

Objective. To analyze the potential of diffusion tensor imaging (DTI) of the cervical spinal cord in the detection of changes associated with spondylotic myelopathy, with particular reference to clinical and electrophysiological fi ndings.

Summary of Background Data. Conventional magnetic resonance imaging (MRI) may provide confusing fi ndings because of a frequent disproportion between the degree of the spinal cord compression and clinical symptoms . The DTI is known to be more sensitive to subtle pathological changes of the spinal cord compared with conventional MRI. Methods. The DTI of the cervical spinal cord was performed within a group of 52 patients with spondylotic spinal cord compression and 13 healthy volunteers on a 1.5-T MRI scanner. All patients underwent clinical examination that differentiated between asymptomatic and symptomatic myelopathy subgroups, and 45 patients underwent electrophysiological examination. We measured the apparent diffusion coeffi cient and fractional anisotropy of the spinal cord at C2/C3 level without compression and at the maximal compression level (MCL). Sagittal spinal canal diameter, cross-sectional spinal cord area, and presence of T2 hyperintensity at the MCL were also recorded. Nonparametric statistical testing was used for comparison of controls with subgroups of patients.

Results. Significant differences in both the DTI parameters measured at the MCL, between patients with compression and control group, were found, while no difference was observed at the noncompression level. Moreover, fractional anisotropy values were lower and apparent diffusion coeffi cient values were higher at the MCL in the symptomatic patients than in the asymptomatic patients. The DTI showed higher potential to discriminate between clinical subgroups in comparison with standard MRI parameters and electrophysiological fi ndings.

Conclusion. The DTI appears to be a promising imaging modality in patients with spondylotic spinal cord compression. It refl ects the presence of symptomatic myelopathy and shows considerable potential for discriminating between symptomatic and asymptomatic patients.

Spine 2012 ; 37 : 35 – 40

Study Design. Retrospective review of a prospectively maintained surgical database.

Objective. To report the indications, surgical procedures performed, and outcomes from the largest series of thoracoscopically treated herniated thoracic discs (HTDs). We also compared approach-related complications with an unmatched cohort undergoing thoracotomy for HTD.

Summary of Background Data. Symptomatic HTDs are rare, and their surgical management is technically challenging.

Methods. A prospectively maintained surgical database of all patients undergoing surgery for symptomatic HTDs by the senior author (blinded for review) was reviewed. As needed, the database was supplemented with hospital and clinic charts and telephone conversations with patients. A triportal method of thoracoscopic discectomy was performed in all cases.

Results. Between 1994 and 2008, 121 patients underwent 125 thoracoscopic-assisted operations for 139 HTDs. Their mean age at surgery was 46.6 years. Indications for thoracoscopic resection currently include small symptomatic disc, anterior location, nonmorbidly obese patient, favorable chest anatomy, and T4–T11 location. Symptom duration averaged 32 months. Radiculopathy was the most common presentation, followed by myelopathy and pain (radiculopathic or back). The mean hospital stay was 4.8 days. Chest tubes remained in place for a mean of 3.2 days. At a mean follow-up of 2.4 years, myelopathy, radiculopathy, and back pain had resolved or improved at a rate of 91.1%, 97.6%, and 86.5%,of cases, respectively. Most patients (97.4%) would be willing to undergo the operation again. The complication rate was acceptable. Patients undergoing thoracoscopic excision had less approachrelated morbidity than an unmatched cohort undergoing excision using thoracotomy.

Conclusion. Thoracoscopic-assisted microsurgical resection is a safe, effective, and minimally invasive method of treating symptomatic HTDs in appropriately selected patients. The symptoms of most patients improve or resolve with minimal morbidity.

Neurosurgery 69:1181–1187, 2011 DOI: 10.1227/NEU.0b013e31822a9aeb

Management approaches for adult scoliosis are primarily based on adults with idiopathic scoliosis and extrapolated to adults with degenerative scoliosis. However, the often substantially, but poorly defined, greater degenerative changes present in degenerative scoliosis impact the management of these patients.

OBJECTIVE: To assess the prevalence, severity, and impact of canal and foraminal stenosis in adults with degenerative scoliosis seeking operative treatment.

METHODS: A prospectively collected database of adult patients with deformity was reviewed for consecutive patients with degenerative scoliosis seeking surgical treatment, without prior corrective surgery. Patients completed the Oswestry Disability Index, SF-12, Scoliosis Research Society 22 questionnaire, and a pain numeric rating scale (0-10). Based on MRI or CT myelogram, the central canal and foraminae from T6 to S1 were graded for stenosis (normal or minimal/mild/moderate/severe).

RESULTS: Thirty-six patients were included (mean age, 68.9 years; range, 51-85). The mean leg pain numeric rating scale was 6.5, and the mean Oswestry Disability Index score was 53.2. At least 1 level of severe foraminal stenosis was identified in 97% of patients; 83% had maximum foraminal stenosis in the curve concavity. All but 1 patient reported significant radicular pain, including 78% with discrete and 19% with multiple radiculopathies. Of those with discrete radiculopathies, 76% had pain corresponding to areas of the most severe foraminal stenosis, and 24% had pain corresponding to areas of moderate stenosis.

CONCLUSION: Significant foraminal stenosis was prevalent in patients with degenerative scoliosis, and the distribution of leg pain corresponded to levels of moderate or severe foraminal stenosis. Failure to address symptomatic foraminal stenosis when surgically treating adult degenerative scoliosis may negatively impact clinical outcomes.

Neurosurgery 69[ONS Suppl 2]:ons156–ons160, 2011 DOI: 10.1227/NEU.0b013e318219565f

Retraction injury might explain the soft tissue complications seen after anterior cervical surgery. A novel retractor system (Seex retractor system [SRS]) that uses a principle of bone fixation with rotation has been shown to reduce retraction pressure in a cadaveric model of anterior cervical decompression and fusion.

OBJECTIVE: To compare the conventional Cloward-style retractor (CRS) with the SRS in a prospective randomized clinical trial.

METHODS: After ethics and study registration (ACTRN 12608000430336), eligible patients were randomized to either the CRS or SRS before 1- or 2-level anterior cervical decompression and fusion. The pressure beneath the medial retractor blade was recorded with a thin pressure transducer strip. Postoperative sore throat, dysphagia, and dysphonia were assessed after 1, 7, and 28 days.

RESULTS: Twenty-six patients were randomized. There were no serious complications. Complication rates were low with a trend favoring SRS that was not statistically different. Average retraction pressure with SRS was 1.9 mm Hg and with CRS was 5.6 mm Hg (P , .001 on F test; P = .002 on 2-tailed t test). Mean average peak retraction pressure with the SRS was 3.4 mm Hg and with the CRS was 20 mmHg (P , .001 on F test; P = .005 on 2-tailed t test).

CONCLUSION: The new retractor is safe, and statistically similar complication rates were observed with the 2 systems. The SRS generated significantly less retraction pressure compared with the CRS. This difference can be explained by the different principles governing the function of these retractors. Bone fixation gives stability and rotation reduces tissue pressure, both desirable in a retractor.

J Neurosurg Spine 15:648–653, 2011.DOI: 10.3171/2011.7.SPINE10843

The authors assessed the role of 3D anisotropy contrast (3DAC) in evaluating specific ascending tract degeneration in patients with cervical spondylotic myelopathy (CSM).

Methods. The authors studied 10 patients (2 women, 8 men; mean age 59.8 ± 14.6 years) with CSM and spinal cord compression below the C2–3 disc level, as well as 10 healthy control individuals (3 women, 7 men; mean age 42.0 ± 24.1 years). Images of the cervical cord at the C2–3 level were obtained using a 3.0-T MR imaging system.

Results. Three-dimensional anisotropy contrast imaging clearly made possible tract-by-tract analysis of the fas- ciculus cuneatus, fasciculus gracilis, and spinocerebellar tract. Tract degeneration identified using 3DAC showed good correlation with a decline in fractional anisotropy. Degeneration of the fasciculus gracilis detected by “vector contrast” demonstrated a good correlation with Nurick grades.

Conclusions. The study unambiguously demonstrated that 3DAC imaging is capable of assessing ascending tract degeneration in patients with CSM. Degeneration of an individual tract can be easily identified as a vector con- trast change on the 3DAC image, a reflection of quantitative changes in anisotropism, similar to fractional anisotropy. Excellent correlation between Nurick grades and fasciculus gracilis degeneration suggests potential application of 3DAC imaging for tract-by-tract clinical correlation.

J Neurosurg Spine 15:630–635, 2011.DOI: 10.3171/2011.8.SPINE11273

Cervical arthroplasty has emerged as a means of preventing adjacent segment disease by preserving motion, restoring sagittal balance, and mimicking natural spinal kinematics. The purpose of this retrospective in vivo study was to characterize the impact of arthroplasty on sagittal balance and segmental kinematics of the cervical spine.

Methods. Sixty patients receiving the Bryan disc, ProDisc-C, or Prestige LP disc were retrospectively analyzed. Only single-level arthroplasty cases were included in this study. Lateral dynamic radiographs of the cervical spine were evaluated using quantitative measurement analysis software to determine the kinematics at the index level both preoperatively and 1 year postoperatively. Collected parameters included range of motion (ROM), disc angles, shell angles, anterior and posterior disc heights (ADHs/PDHs), translation, and center of rotation (COR). Preoperative and postoperative data were compared using the Student t-test, with p < 0.05 indicating significance.

Results. The Bryan and Prestige LP discs preserved motion, whereas the ProDisc-C increased segmental ROM from extension to flexion. Following surgery, the Bryan disc exhibited significant shell angle kyphosis, while Pro- Disc-C and Prestige LP retained lordosis. Both ADHs and PDHs decreased following insertion of the Bryan disc. In contrast, the ProDisc-C increased the ADHs and PDHs by 80% and 52%, respectively, and the Prestige LP disc increased the ADHs and PDHs by 20%. Only the ProDisc-C demonstrated significant translation of 0.7 mm. The ProDisc-C shifted the COR x by 0.9 mm anteriorly, while the Prestige LP disc demonstrated a significant superior shift of 2.2 mm in COR y.

Conclusions. All discs adequately maintained ROM at the surgical level. The greatest difference among the 3 devices was in the disc height and index angle measurements

J Neurosurg Spine 15:654–659, 2011. DOI: 10.3171/2011.8.SPINE11155

Digital subtraction (DS) angiography is the gold standard for diagnosing spinal vascular malformations. Recently, multidetector-row spiral CT and contrast-enhanced MR angiography have been introduced as screening examinations before DS angiography. These methods, however, do not always determine the accurate location of an arteriovenous shunt because the resulting images lack information about the spinal cord or the dura mater.

Methods. Between April 2009 and December 2010, 13 patients underwent imaging evaluations for spinal vascular malformations at the authors’ university hospital. This group included 8 patients with spinal dural arteriovenous fistulas (AVFs), 3 with perimedullary AVFs, and 2 with intramedullary arteriovenous malformations. Using data from these patients, the authors attempted to develop 3D computer graphics (CG) based upon the fusion of 3D rotational angiography and postmyelographic CT. They subsequently verified the accuracy of this imaging method. Ten of these 13 patients underwent surgical treatment for their lesions (11 AVFs), and for these 11 lesions the authors compared the diagnoses obtained using 3D CG with those obtained using conventional DS angiography.

Results. In all 13 cases, 3D CG images of the spinal lesions were successfully developed using the patients’ actual data. Four (36%) of 11 AVFs were correctly identified using DS angiography, whereas 10 (91%) were correctly identified using 3D CG. Results from 3D CG of spinal AVFs corresponded well with operative findings, and 3D CG was significantly better than conventional DS angiography at predicting AVF location (p = 0.024, Fisher exact test).

Conclusions. To the authors’ knowledge, this is the first reported case series in which 3D CG of spinal vascular malformations was used to provide simultaneous, stereoscopic visualization of the spinal vascular system, spinal cord, dura mater, and bone. The 3D CG method provides precise visual images for the diagnosis and treatment of these lesions.

Neurosurgery 69:1171–1180, 2011 DOI: 10.1227/NEU.0b013e31822b8107

Primary vertebral tumors, although less common than metastases to the spine, make up a heterogeneous group of neoplasms that can pose diagnostic and treatment challenges. They affect both the adult and the pediatric population and may be benign, locally aggressive, or malignant.

An understanding of typical imaging findings will aid in accurate diagnosis and help neurosurgeons appreciate anatomic subtleties that may increase their effective resection. An understanding of the histological similarities and differences between these tumors is imperative for all members of the clinical team caring for these patients. In this first review of 2 parts, we discuss the epidemiological, histological, and imaging features of the most common benign primary vertebral tumors— aneurysmal bone cyst, chondroma and enchondroma, hemangioma, osteoid osteoma, and osteoblastoma—and lesions related to eosinophilic granuloma and fibrous dysplasia.

In addition, we discuss the basic management paradigms for each of these diagnoses. In combination with part II of the review, which focuses on locally aggressive and malignant tumors, this article provides a comprehensive review of primary vertebral tumors

Neurosurgery 69:1307–1316, 2011 DOI: 10.1227/NEU.0b013e31822ba190

Image-guided spinal instrumentation may reduce complications in spinal instrumentation.

OBJECTIVE: To assess accuracy, time efficiency, and staff radiation exposure during thoracolumbar screw instrumentation guided by intraoperative computed tomography (iCT)-based neuronavigation (iCT-N).

METHODS: In 55 patients treated for idiopathic and degenerative deformities, 826 screws were inserted in the thoracic (T2–T12; n = 243) and lumbosacral (L1–S1; n = 545) spine, as well as ilium (n = 38) guided by iCT-N. Up to 17 segments were instrumented following a single automated registration sequence with the dynamic reference arc (DRA) uniformly attached to L5. Accuracy of iCT-N was assessed by calculating angular deviations between individual navigated tool trajectories and final implant positions. Final screw positions were also graded according to established classification systems. Clinical and radiological outcome was assessed at 12 to 14 months.

RESULTS: Additional intraoperative fluoroscopy was unnecessary, eliminating staff radiation exposure. Unisegmental K-wire insertion required 4.6 6 2.9 minutes. Of the thoracic pedicle screws 98.4% were assigned grades I to III according to the Heary classification, with 1.6% grade IV placement. In the lumbar spine, 94.4% of screws were completely contained (Gertzbein classification grade 0), 4.6% displayed minor pedicle breaches ,2 mm(grade 1), and 1% of lumbar screws deviated by.2 to,4 mm (grade 2). The accuracy of iCT-N progressively deteriorates with increasing distance from the DRA, but allows safe instrumentation of up to 12 segments.

CONCLUSION: iCT-N using automated referencing allows for safe, highly accurate multilevel instrumentation of the entire thoracolumbosacral spine and ilium, rendering additional intraoperative imaging dispensable. In addition, automated registration is time-efficient and significantly reduces the need for re-registration in multilevel surgery.

J Neurosurg Spine 15:472–478, 2011. DOI: 10.3171/2011.6.SPINE10809

The aim of this study was to retrospectively evaluate the reliability and accuracy of cervical pedicle screw (CPS) placement using an intraoperative, full-rotation, 3D image (O-arm)–based navigation system and to assess the advantages and disadvantages of the system.

Methods. The study involved 21 consecutive patients undergoing posterior stabilization surgery of the cervical spine between April and December 2009. The patients, in whom 108 CPSs had been inserted, underwent screw placement based on intraoperative 3D imaging and navigation using the O-arm system. Cervical pedicle screw positions were classified into 4 grades, according to pedicle-wall perforations, by using postoperative CT.

Results. Of the 108 CPSs, 96 (88.9%) were classified as Grade 0 (no perforation), 9 (8.3%) as Grade 1 (perforations < 2 mm, CPS exposed, and < 50% of screw diameter outside the pedicle), and 3 (2.8%) as Grade 2 (perforations between ≥ 2 and < 4 mm, CPS breached the pedicle wall, and > 50% of screw diameter outside the pedicle). No screw was classified as Grade 3 (perforation > 4 mm, complete perforation). No neurovascular complications occurred because of CPS placement.

Conclusions. The O-arm offers high-resolution 2D or 3D images, facilitates accurate and safe CPS insertion with high-quality navigation, and provides other substantial benefits for cervical spinal instrumentation. Even with current optimized technology, however, CPS perforation cannot be completely prevented, with 8.3% instances of minor violations, which do not cause significant complications, and 2.8% instances of major pedicle violations, which may cause catastrophic complications. Therefore, a combination of intraoperative 3D image–based navigation with other techniques may result in more accurate CPS placement.

Eur Spine J (2011) 20:1899–1907. DOI 10.1007/s00586-011-1860-0
The purpose of this study was to assess the value of isocentric C-arm three-dimensional (Iso-C 3D) fluoroscopy for the insertion of an anterior odontoid screw. The results of the Iso-C 3D group were compared with that of an historic control group using conventional fluoroscopy.
Methods  Twenty-nine patients diagnosed with type II or rostral-type III odontoid fractures were treated with a single anterior screw fixation in this study. The Iso-C 3D group included 13 patients and the other 16 patients were in the historic control group. All operations were performed by a single surgeon using standard procedure and manner. The clinical and radiographic results were recorded and compared between the two groups.
Results  The fluoroscopy time in the Iso-C 3D group was 42.9 s as compared to 68.1 s in the control group (P\ 0.01). The mean operative time was 91.5 min in the Iso-C 3D group when compared with 81.6 min in the control group (P =  0.20). The rate of bony fusion was 96.6% (28/29), the failure rate of reduction or fixation was 13.8% (7.7% in Iso-C 3D group; 18.8% in control group). The Smiley–Webster scale showed that 90% of patients achieved good or better outcomes
Conclusions  In conclusion, this technique can be safely extended to the treatment of technically difficult to treat spinal injuries and at the same time reduce total radiation exposure time both for the patient and the surgeon.

Journal of Neurosurgery: Spine DOI: 10.3171/2011.3.SPINE10445.

The accurate intraoperative localization of the correct thoracic spine level remains a challenging problem in both open and minimally invasive spine surgery. The authors describe a technique of using preoperatively placed percutaneous fiducial screws to localize the area of interest in the thoracic spine, and they assess the safety and efficacy of the technique.

METHODS

To avoid wrong-level surgery in the thoracic spine, the authors preoperatively placed a percutaneous 5-mm fiducial screw at the level of intended surgery using CT guidance. Plain radiographs and CT images with reconstructed views can then be referenced in the operating room to verify the surgical level, and the fiducial screw is easily identified on intraoperative fluoroscopy. The authors compared a group of 26 patients who underwent preoperative (often outpatient) fiducial screw placement prior to open or minimally invasive thoracic spine surgery to a historical group of 26 patients who had intraoperative localization with fluoroscopy alone.

RESULTS

In the treatment group of 26 patients, no complications related to fiducial screw placement occurred, and there was no incidence of wrong-level surgery. In comparison, there were no wrong-level surgeries in the historical cohort of 26 patients who underwent mini-open or open thoracic spine surgery without placement of a fiducial screw. However, the authors found that the intraoperative localization fluoroscopy time was greatly reduced when a fiducial screw localization technique was employed.

CONCLUSIONS

The aforementioned technique for intraoperative localization is safe, efficient, and accurate for identifying the target level in thoracic spine exposures. The fiducial marker screw can be placed using CT guidance on an outpatient basis. There is a reduction in the amount of intraoperative fluoroscopy time needed for localization in the fiducial screw group.

Neurosurgical Focus Oct 2011 / Vol. 31 / No. 4 / Page E4

Recently, the minimally invasive, lateral retroperitoneal, transpsoas approach to the thoracolumbar spinal column has been described by various authors. This is known as the minimally invasive lateral lumbar interbody fusion. The purpose of this study is to elucidate the approach-related morbidity associated with the minimally invasive transpsoas approach to the lumbar spine. To date, there have been only a couple of reports regarding the morbidity of the transpsoas muscle approach.

METHODS

A nonrandomized, prospective study utilizing a self-reported patient questionnaire was conducted between January 2006 and June 2008 at Northwestern University. Data were collected in 53 patients with a follow-up period ranging from 6 months to 3.5 years. Only 2 patients were lost to follow-up.

RESULTS

Thirty-six percent (19 of 53) of patients reported subjective hip flexor weakness, 25% (13 of 53) anterior thigh numbness, and 23% (12 of 53) anterior thigh pain. However, 84% of the 19 patients reported complete resolution of their subjective hip flexor weakness by 6 months, and most experienced improved strength by 8 weeks. Of those reporting anterior thigh numbness and pain, 69% and 75% improved to their baseline function by the 6-month follow-up evaluations, respectively. All patients with self-reported subjective hip flexor weakness underwent examinations during subsequent clinic visits after surgery; however, these examinations did not confirm a motor deficit less than Grade 5. Subset analysis showed that the L3–4 and L4–5 levels were most often affected.

CONCLUSIONS

The minimally invasive, transpsoas muscle approach to the lumbar spine has a number of advantages. The data show that a percentage of the patients undergoing the transpsoas approach will have temporary sensory and motor symptoms related to this approach. The majority of the symptoms are thought to be related to psoas muscle inflammation and/or stretch injury to the genitofemoral nerve due to the surgical corridor traversed during the operation. No major injuries to the lumbar plexus were encountered. It is important to educate patients prior to surgery of the possibility of these largely transient symptoms.