The use of diffusion tensor imaging in spinal pathology: a comprehensive literature review.

STUDY DESIGN: We reviewed the available literature systematically without meta-analysis following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. OBJECTIVE: To evaluate contemporary literature on use of spinal diffusion tensor imaging(sDTI) in spinal pathology. BACKGROUND: sDTI reveals the location and functional state of critical long tracts and is a potentially useful adjunct in disease management. METHODS: Studies were included if they presented or discussed data from investigative or therapeutic procedures involving sDTI on human subjects in the setting of surgically amenable spinal pathology. Studies were excluded if they were (1) restricted to computational models investigating parameters using data not obtained clinically, (2) about cranial DTI methods, (3) about spinal pathology data not related to surgical management, (4) discussions or overviews of methods/techniques with minimal inclusion of objective experimental or clinical data. RESULTS: Degenerative pathologies of interest were restricted to either cervical myelopathy (22/29,75.9%) or lumbar spondylosis 7/29,24.1%). Mass-occupying lesions included intradural pathology and discussed preoperative (7/9,77.8%) and intraoperative imaging(2/9,22.2%) as an adjunct to surgery 22.2%. Traumatic pathology focused on spinal cord injury prognosis and severity grading. CONCLUSIONS: sDTI seems useful in surgical decision making and outcome measurements and in establishing clinical prognoses over a wide range of surgical pathologies. Further research is warranted with longer follow-up and larger population sizes in a prospective and controlled protocol.

What is the C2 pedicle, pars interarticularis, and isthmus? Anatomical study and review of the literature regarding these confusing terms with proposal of new nomenclature.

INTRODUCTION: The atypical anatomy of the C2 vertebra has led to terminological discrepancies within reports and studies in the literature regarding the location of its pedicle, pars interarticularis, and isthmus. These discrepancies not only limit the power of morphometric analyses, but they also confuse technical reports regarding operations involving C2, and thus confuse our ability to properly communicate this anatomy. Herein, we examine the variations in nomenclature regarding the pedicle, pars interarticularis, and isthmus of C2, and via an anatomical study, propose new terminology. METHODS: The articular surface and underlying superior and inferior articular processes and adjacent transverse processes were removed from 15 C2 vertebrae (30 sides). Specifically, the areas regarded as the pedicle, pars interarticularis, and isthmus were evaluated. Morphometrics were performed. RESULTS: Our results indicate that, anatomically, C2 has no "isthmus" and that a pars interarticularis for C2, when present, is very short. Deconstruction of the attached parts allowed for visualization of a bony arch extending from the anterior most aspect of the lamina to the body of C2. The arch is composed almost entirely of trabecular bone and without its attached parts, e.g., transverse process, really has no cortical bone laterally. CONCLUSIONS: We propose a more accurate terminology, the pedicle, for pars/pedicle screw placement of C2. Such a term more accurately describes this unique structure of the C2 vertebra and would alleviate terminological confusion in the future literature on this topic.

Technical advances in pediatric craniovertebral junction surgery.

Surgery for conditions in the craniovertebral junction in the pediatric population poses unique challenges. The posterior approach has emerged as the gold standard for arthrodesis in this region. Anterior fixation or decompression also may be indicated. Intraoperative image guidance and neurophysiological monitoring improve the safety and efficacy of these procedures. The specific technical advances in surgery of the craniovertebral junction that have improved patient outcomes are reviewed.

Intrafacet Spacer Placement as a Mobility-Sparing Bailout Option in Atlantoaxial Fusion Construct Salvage.

Background: Salvage revisions of atlantoaxial (AA) joint complex posterior segmental instrumented fusion constructs require careful individualized planning to prevent occipital extension. In this case report, we describe the use of bilateral intrafacet spacer placement as a mobility-sparing bailout option for the revision surgery. Case Report: A 64-year-old male with a history of diffuse idiopathic skeletal hyperostosis, extremely limited baseline cervical mobility, and prior AA posterior segmental instrumented fusion presented with increasing pain at his 6-month follow-up. Imaging showed fusion and hardware failures and dynamic instability. To prevent occipitocervical fixation, AA intra-articular fusion via a DTRAX spinal system (Providence Medical Technology, Inc) was used as an adjunct to a navigated C1 lateral mass and C2 pars screw posterior segmental instrumented fusion construct. The patient had an uneventful postoperative course and was discharged with resolution of symptoms. Three-month postoperative follow-up confirmed persistent resolution of symptoms and absence of complaints, along with successful arthrodesis on imaging. Conclusion: AA posterior segmental instrumented fusion revision is technically challenging, particularly when partial preservation of craniovertebral junction mobility is required. Bilateral intra-articular cages may be used as an adjunct to hardware revision in construct salvage when sturdy arthrodesis is desired without occipital extension and may represent a major potential strength of intra-articular cages.

Clip Ligation and Disconnection of a Ruptured Ventral Subaxial Cervical Isolated Spinal Aneurysm Using Tailored Access Osteotomies: An Operative Technique.

BACKGROUND: Isolated spinal aneurysms (iSAs) are lesions of the spinal vasculature with no associated vascular malformation with difficult management paradigms limited by safe access. OBJECTIVE: To describe a case of an irregular fusiform ruptured distal subaxial cervical spine iSA with a complex angioarchitecture intimately associated with the ventral pial plexus (VPP), treated using open clip ligation and disconnection. METHODS: A 51-year-old woman presented with complete spinal cord injury with a C8 sensory level and ventral subarachnoid hemorrhage at the C6-T1 vertebral levels. After emergent anterior evacuation and fusion, angiography revealed a small iSA around the VPP. A total laminectomy spanning C5 to T3 was completed, and bilateral C7 pedicle resections were performed. A temporary clip was placed from the left for proximal control, and a permanent clip was placed across the dome of the distal vessel for disconnection. The dura was then closed, and a cervicothoracic fusion completed. RESULTS: Postoperative angiography confirmed iSA disconnection and obliteration with anterior spinal artery preservation. The patient had intermittent numbness in the right C8 dermatome. On postoperative day 1, she regained proprioception in the right foot and movement in the lower extremities on command. On postoperative day 3, she regained full sensation and voluntary movement in both lower extremities. CONCLUSION: iSA is a rare and morbid condition with nonstandardized guidelines regarding management. We promote the concept of using tailored osteotomies to establish safe corridors for the open treatment of difficult subaxial cervical ventral lesions not amenable to transarterial treatment. Multidisciplinary collaboration is promising, and further investigation is highly warranted.

Ventral Subaxial Cervical Access Using Tailored Access Osteotomies, A Cadaveric Study.

BACKGROUND: Ventral lesions of the subaxial cervical spine are challenging because approaches must circumvent endodermal and neurovascular structures. OBJECTIVE: To use cadaveric study to describe 4 posterolateral approaches to the ventral subaxial cervical spine with various facilitating techniques and osteotomies. METHODS: Three cadaveric specimens of the cervical spine were sequentially subjected to multilevel laminectomy (Type 1), transfacet (Type 2), transpedicular (Type 3), and extreme lateral transforaminal (Type 4) approaches. Approach working angles and proportion of visualized zones were compared, the former calculated using trigonometric methods. RESULTS: There was a significant stepwise increase in working angle in the ventral space, associated with increasing osteotomy type, from an average of 3.7° in single-level type 1 to 19.47° in the type 4 osteotomy. Regarding anatomic zones, proportional partial and total visualization achieved with Type 2 to 4 approaches were significantly greater than with Type 1. Complex osteotomies allowed superior access to be obtained to contributing and adjacent vessels of the ventral spinal axis. CONCLUSION: Ventral subaxial cervical lesions are difficult to access. We report increased working angles using quantified cadaveric data in increasingly complex posterior and posterolateral approaches graded as type 1 through 4. We advocate continued translational research in such approaches to lesions often considered to lie in surgically inaccessible locations.

Patient-reported outcome measures in spine surgery: A systematic review.

Background: Steadily increasing expenditure in the United States health-care system has led to a shift toward a value-based model that focuses on quality of care and cost-effectiveness. Operations involving the spine rank among some of the most common and expensive procedures performed in operating rooms nationwide. Patient-reported outcomes measures (PROMs) are a useful tool for reporting levels of outcome and analyzing patient recovery but are both under-utilized and nonstandardized in spine surgery. Methods: We conducted a systematic review of the literature using the PubMed database, focusing on the most commonly utilized PROMs for spine disease as well as spinal deformity. The benefits and drawbacks of these PROMs were then summarized and compared. Results: Spine-specific PROMs were based on the class of disease. The most frequently utilized PROMs were the Neck Disability Index and the modified Japanese Orthopaedic Association scale; the Oswestry Disability Index and the Roland-Morris Disability Questionnaire; and the Scoliosis Research Society 22-item questionnaire (SRS-22) for cervicothoracic spine disease, lumbar spine disease, and spinal deformity, respectively. Conclusion: We found limited, though effective, use of PROMs targeting specific classes of disease within spine surgery. Therefore, we advocate for increased use of PROMs in spine surgery, in both the research and clinical settings. PROM usage can help physicians assess subjective outcomes in standard ways that can be compared across patients and institutions, more uniquely tailor treatment to individual patients, and engage patients in their own medical care.

Anterior cervical discectomy and fusion in the setting of kissing carotids: A technical report and literature review.

BACKGROUND: The "kissing carotids" (KCS) phenomenon refers to bilateral retropharyngeal displacement of the internal carotid arteries (ICA). This anomalous anatomy can impose a significant surgical challenge to spine surgeons. OBJECTIVE: In this report, we describe our approach for an anterior cervical discectomy and fusion in the setting of kissing carotids. METHODS: We discuss our case, surgical technique, rationale, and outcome. Additionally, we conducted a systematic review of the literature. CASE DESCRIPTION: An 82-year-old female presented to our service with progressive myelopathy. Cervical spinal imaging revealed a large disc herniation at C3-C4 and severe spinal canal stenosis. Vascular imaging showed anomalous ICAs bilaterally overlying the prevertebral fascia at the midline. The patient received aspirin preoperatively and underwent a multidisciplinary approach with neurosurgery and otolaryngology. A standard transcervical approach centered on the C5-C6 disc space, where the carotid arteries splayed most from midline, allowed for facilitated visualization and mobilization of the vessels. Prevertebral dissection was then performed rostrally to the C3-C4 disc space. The patient was put into burst suppression prior to retraction and underwent uncomplicated anterior discectomy and fusion. CONCLUSIONS: KCS is a rare but critical presentation of extreme medial displacement of bilateral ICAs. Few cases have been reported in the spinal surgery literature. Knowledge of this rare variant is important to avoid iatrogenic injury and complications.

Novel Technique of Coregistered Intraoperative Computed Tomography and Preoperative Magnetic Resonance Imaging and Diffusion Tensor Imaging Navigation in Spinal Cord Tumor Resection.

Background: Intradural spinal tumors are surgically challenging lesions, and intraoperative spinal navigation offers clear potential assistance. While intraoperative computed tomography (iCT) of bony anatomy is routinely performed, coregistration with magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) to facilitate intradural spinal tumor resection is not widely described. We present 2 cases in which iCT was coregistered with MRI and DTI for navigational guidance in the resection of intradural spinal tumors to assess technical feasibility and surgical efficacy. Case Series: Navigation using coregistered iCT/MRI was used in the resection of one extramedullary and one intramedullary cervicomedullary tumor. The iCT was obtained following open midline exposure of bony anatomy. The images were then coregistered with preoperative MRI sequences to allow for optical tracking navigation via an optical tracking station (Brainlab). For the intramedullary tumor, preoperative DTI sequences were also coregistered for enhanced identification of relevant anatomy. Navigational accuracy for all cases was confirmed to be acceptable at the level of the posterior bony elements, the dura, and the tumor-parenchyma interface. Conclusion: The coregistration of preoperative MRI sequences and iCT images allowed for meaningfully enhanced navigation during resection. In the case involving the intramedullary cervicomedullary tumor with marked distortion of longitudinal tracts, iCT/DTI navigation allowed for accurate visualization of critical structures and facilitated delineation of tumor margins that otherwise would have been difficult. The use of combined iCT and preoperative MRI/DTI neuronavigational guidance is an effective approach in the resection of intradural extramedullary and intramedullary spinal cord tumors.

Doppler ultrasonography screening of poor-grade subarachnoid hemorrhage patients increases the diagnosis of deep venous thrombosis.

BACKGROUND: Prophylactic anticoagulation greatly decreases the prevalence of deep venous thrombosis (DVT) in neurosurgical patients. Using Doppler ultrasonography (USG), recent studies demonstrate a 1% DVT detection rate following microsurgery or endovascular treatment for aneurysmal subarachnoid hemorrhage (aSAH). We hypothesize that reported statistics underestimate the DVT detection rate in this high risk cohort by accounting for only symptomatic thromboses. This study utilizes Doppler USG to examine the prevalence of DVT in a large population of aSAH patients and attempts to identify a high-risk subgroup within this cohort. METHODS: We retrospectively examined 178 aSAH patients who underwent screening lower extremity Dopplers (LEDs) and 57 who did not undergo screening LEDs. All received pharmacologic and mechanical DVT prophylaxis. We analysed DVT prevalence within these two groups and compared rates to the literature. We then segregated patients according to Hunt-Hess grade and determined DVT prevalence within subgroups. RESULTS: Patients who underwent LED screening demonstrated a 3.4% (6/178) DVT rate, compared to 0% (0/57) in the unscreened cohort. Our screening protocol yielded a thrombosis rate almost triple that reported in the literature (3.4% versus 1.2%). A significantly greater (p<0.05) percentage of screened Hunt-Hess III-V patients (6.5%, 6/93) had positive LEDs compared to Hunt-Hess I-II patients (0%, 0/85). CONCLUSION: These data suggest that while pharmacologic prophylaxis lowers the prevalence of symptomatic DVTs in aSAH patients, the number of asymptomatic DVTs remains significant, particularly in patients with formidable neurological deficits. While a formal cost-effective analysis is warranted, our data suggest that screening high-risk patients may increase the diagnosis of asymptomatic DVTs and potentially prevent serious medical complications.

Patellofemoral evaluation after total knee arthroplasty. Validation of a new weight-bearing axial radiographic view.

BACKGROUND: Radiographic assessment of the patella after total knee arthroplasty is typically performed with use of static, unloaded views that may not reproduce the in vivo patellofemoral kinematics. The purpose of the present study was to evaluate and validate the reliability and reproducibility of a weight-bearing radiographic assessment of the patellofemoral joint in patients who have undergone total knee arthroplasty. METHODS: Radiographs were made for 100 knees in sixty-nine patients who had undergone total knee arthroplasty. Radiographic assessment of the patellofemoral joint was performed with use of both the standard Merchant axial view and a modification of that view. The Merchant axial view was modified by positioning the standing patient in the semi-squatted position with the knees in 45 degrees of flexion. The relationship between the x-ray source, the angle of incidence on the joint, and the cassette position was kept unchanged from the original view. The standing position and consequent muscle involvement were the only differences. RESULTS: Compared with the standard Merchant axial view, the weight-bearing axial view showed a number of patellofemoral tracking changes. Specifically, lateral tilt and subluxation of the patella were significantly reduced; the rate of exposed, uncovered patellar bone contact with the femoral trochlea was significantly increased; and radiographic evidence of maltracking was more closely correlated with clinical symptoms. CONCLUSIONS: An axial weight-bearing radiographic view with the patient in the semi-squatting position was developed to reproduce patellofemoral joint loading. This view demonstrates that the position of the patella, as seen on the standard unloaded Merchant view, changes during squatting. Utilization of this axial weight-bearing view to evaluate total knee arthroplasty may provide additional information over standard radiographic views.

Indications and Techniques for Spinal Instrumentation in Thoracic Disk Surgery.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To identify the indications, techniques, and outcomes for instrumented fusion during thoracic discectomy. SUMMARY OF BACKGROUND DATA: Thoracic discectomy may require extensive bone removal to avoid spinal cord manipulation, but the indications and techniques for instrumented fusion during thoracic discectomy remain poorly delineated. METHODS: The authors identified 220 consecutive patients who underwent thoracic discectomy between 1992 and 2012. Clinical and radiographic variables were compared between patients who underwent instrumented fusion and patients without instrumentation, and among surgical approaches utilized for discectomy. RESULTS: Patient age for the entire cohort averaged 49±13.01 years, and mean clinical follow-up was 45 months (range, 1-218 mo). Patients underwent 226 thoracic discectomy procedures, including 48 thoracotomy, 136 thoracoscopy, and 42 posterolateral approaches. Seventy-eight patients required instrumented fusion and, compared with patients without instrumentation, were more likely to present with myelopathy (P<0.0001) and harbor giant (P=0.0012), calcified (P=0.019), or transdural (P=0.0004) herniated disks. Surgery with instrumentation resulted in greater blood loss (P<0.0001), longer hospital stay (P<0.0001), and a higher complication rate (22% vs. 9.9%), yet patients in both cohorts had similar rates of symptom resolution postoperatively. Of the patients who underwent thoracic discectomy without instrumentation, 3 (2.1%) developed delayed deformity or instability and required subsequent surgery for fixation and fusion at an average 6.3 months postoperatively (range, 4-8 mo). Patients who underwent instrumented fusion exhibited no nonunions or delayed deformity. CONCLUSIONS: Thoracic discectomy without fixation is a reasonable clinical option in carefully selected patients, but instrumented fusion is safe and effective in other patients. Indications for fixation and fusion are thus proposed.

Surgical management and clinical outcomes of multiple-level symptomatic herniated thoracic discs.

OBJECT: Symptomatic herniated thoracic discs (HTDs) are rare, and patients infrequently require treatment of 2 or more disc levels. The authors assess the surgical management and outcomes of patients with multiple-level symptomatic HTDs. METHODS: A retrospective review of a prospectively maintained database was performed of 220 consecutive patients treated surgically for symptomatic HTDs. Clinical and surgical results were compared between patients with single-level disease and patients with multiple-level disease and also among the different approaches used for surgical decompression. RESULTS: Between 1992 and 2012, 56 patients (mean age 48 years; 26 male, 30 female) underwent 62 procedures for 130 HTDs. Forty-six patients (82%) had myelopathy, and 36 (64%) had thoracic radiculopathy; 24 patients had both conditions in varying degree. Symptom duration averaged 28 months. The surgical approach was dictated by disc size, consistency, and location. Twenty-three thoracotomy, 26 thoracoscopy, and 13 posterolateral procedures were performed. Five patients required a combination of approaches. Patients underwent 2-level (n = 44), 3-level (n = 7), 4-level (n = 4), or 5-level (n = 1) discectomies. Instrumented fusion was performed in 36 patients (64%). Thirteen patients harbored 19 additional discs, which were deemed asymptomatic/nonoperative. The mean hospital stay was 6.5 days. Complete disc resection was verified with postoperative imaging in every patient. The procedural complication rate was 23%, and the nature of complications differed based on approach. No patients had surgery-related spinal cord injury or new myelopathy. At a mean follow-up of 48 months, myelopathy and radiculopathy had resolved or improved at a rate of 85% and 92%, respectively. Using a general linear model, preoperative symptom duration (p = 0.037) and perioperative hospital length of stay (p = 0.004) emerged as negative predictors of myelopathy improvement. Most patients (96%) were satisfied with the surgical results. Compared with 164 patients who underwent single-level HTD decompression, patients requiring surgery for multiple-level HTDs were more often myelopathic (p = 0.012). Surgery for multiple-level HTDs was more likely to require a thoracotomy approach (p = 0.00055) and instrumented fusion (p < 0.0001) and resulted in greater blood loss (p = 0.0036) and higher complication rates (p = 0.0069). The rates of resolution for myelopathy (p = 0.24) and radiculopathy (p = 1.0), however, were similar between the 2 patient groups. CONCLUSIONS: The management of multiple-level symptomatic HTDs is complex, requiring individualized clinical decision making. The surgical approaches must be selected to minimize manipulation of the compressed thoracic spinal cord, and a patient may require a combination of approaches. Excellent surgical results can be achieved in this unique and challenging patient population.

Pupillary reactivity upon hospital admission predicts long-term outcome in poor grade aneurysmal subarachnoid hemorrhage patients.

BACKGROUND: Historically, the prognosis for poor grade subarachnoid hemorrhage patients has been considered dismal. As a result, many hospitals have chosen conservative management over aggressive therapy. This guarded approach, however, is based on studies that do not take into account newer, more effective, management protocols and more recent long-term evidence that significant neurological recovery occurs in the months to years following discharge. More accurate and predictive methods are needed to decide when aggressive therapy is warranted. METHODS: Two hundred and twenty-six grade aneurysmal subarachnoid hemorrhage (aSAH) patients of grades IV and V were admitted to Columbia University Medical Center and enrolled in our study. Demographics, clinical information (e.g. pupillary reactivity on admission), and treatment course (operative versus non-operative) were recorded. Rankin scores at 14 days, 3 months, and 1 year were also recorded. A favorable Rankin score was defined as 0-3. Unfavorable was defined as 4-6. RESULTS: Among all poor grade patients who received operative therapy, pupillary reactivity at admission was not predictive of a favorable Rankin score at day 14 (odds ratio = 3.3, P = 0.129). Pupillary reactivity, however, was predictive of Rankin score at 3 months (odds ratio = 4.57, P = 0.05) and 12 months (odds ratio = 6.44, P = 0.008). After constructing a Kaplan-Meiers survival curve, pupillary reactivity was a better predictor of survival at 12 months than H&H grade [Hazard ratio 3.342 (1.596-7.000) P = 0.001 versus 1.964 (1.016-3.798) P = 0.045]. CONCLUSIONS: This study demonstrates that significant recovery occurs in the weeks to months after poor grade aSAH. Pupillary reactivity on admission can be used as a predictor of survival and recovery at intermediate and long-term time points, more so than Hunt and Hess grade.