Nicolas Dea

Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation

BACKGROUND CONTEXT Imaging modalities used to visualize spinal anatomy intraoperatively include X-ray studies, fluoroscopy, and computed tomography (CT). All of these emit ionizing radiation. PURPOSE Radiation emitted to the patient and the surgical team when performing surgeries using intraoperative CT-based spine navigation was compared. STUDY DESIGN/SETTING This is a retrospective cohort case-control study. PATIENT SAMPLE Seventy-three patients underwent CT-navigated spinal instrumentation and 73 matched controls underwent spinal instrumentation with conventional fluoroscopy. OUTCOME MEASURES Effective doses of radiation to the patient when the surgical team was inside and outside of the room were analyzed. The number of postoperative imaging investigations between navigated and non-navigated cases was compared. METHODS Intraoperative X-ray imaging, fluoroscopy, and CT dosages were recorded and standardized to effective doses. The number of postoperative imaging investigations was compared with the matched cohort of surgical cases. A literature review identified historical radiation exposure values for fluoroscopic-guided spinal instrumentation. RESULTS The 73 navigated operations involved an average of 5.44 levels of instrumentation. Thoracic and lumbar instrumentations had higher radiation emission from all modalities (CT, X-ray imaging, and fluoroscopy) compared with cervical cases (6.93 millisievert [mSv] vs. 2.34 mSv). Major deformity and degenerative cases involved more radiation emission than trauma or oncology cases (7.05 mSv vs. 4.20 mSv). On average, the total radiation dose to the patient was 8.7 times more than the radiation emitted when the surgical team was inside the operating room. Total radiation exposure to the patient was 2.77 times the values reported in the literature for thoracolumbar instrumentations performed without navigation. In comparison, the radiation emitted to the patient when the surgical team was inside the operating room was 2.50 lower than non-navigated thoracolumbar instrumentations. The average total radiation exposure to the patient was 5.69 mSv, a value less than a single routine lumbar CT scan (7.5 mSv). The average radiation exposure to the patient in the present study was approximately one quarter the recommended annual occupational radiation exposure. Navigation did not reduce the number of postoperative X-rays or CT scans obtained. CONCLUSIONS Intraoperative CT navigation increases the radiation exposure to the patient and reduces the radiation exposure to the surgeon when compared with values reported in the literature. Intraoperative CT navigation improves the accuracy of spine instrumentation with acceptable patient radiation exposure and reduced surgical team exposure. Surgeons should be aware of the implications of radiation exposure to both the patient and the surgical team when using intraoperative CT navigation.

Early clinical results with cortically based pedicle screw trajectory for fusion of the degenerative lumbar spine

This study reviews the outcomes and revision rates of degenerative lumbar fusion surgery using cortical trajectory pedicle screws in lieu of traditional pedicle screw instrumentation. Pedicle screw fixation can be a challenge in patients with low bone mineral density. Wide posterior approaches to the lumbar spine exposing lateral to the facet joints and onto transverse processes causes an additional degree of muscular damage and blood loss not present with a simple laminectomy. A cortical bone trajectory pedicle screw has been proposed as an alternative to prevent screw pullout and decrease the morbidity associated with the wide posterior approach to the spine. We present a series of eight consecutive patients using a cortical bone trajectory instead of traditional pedicle screw fixation for degenerative conditions of the lumbar spine. A retrospective review of our institutional registry data identified eight patients who had cortical screws placed with the assistance of O-arm Stealth navigation (Medtronic Sofamor Danek, Memphis, TN, USA) from 2010-2013. We analyzed the need for revision, the maintenance of reduction and the incidence of screw pullout or breakage. Our review demonstrated that two of eight patients were revised at an average of 12months. The reasons for these revisions were pseudarthrosis and caudal adjacent segment failure. All patients who were revised had frank screw loosening. We present early clinical results of a new technique that has been shown to have a better fixation profile in laboratory testing. Our less than favorable early clinical results should be interpreted with caution and highlight important technical issues which should be considered.

Economic evaluation comparing intraoperative cone beam CT-based navigation and conventional fluoroscopy for the placement of spinal pedicle screws: a patient-level data cost-effectiveness analysis

BACKGROUND CONTEXT Pedicle screws are routinely used in contemporary spinal surgery. Screw misplacement may be asymptomatic but is also correlated with potential adverse events. Computer-assisted surgery (CAS) has been associated with improved screw placement accuracy rates. However, this technology has substantial acquisition and maintenance costs. Despite its increasing usage, no rigorous full economic evaluation comparing this technology to current standard of care has been reported. PURPOSE Medical costs are exploding in an unsustainable way. Health economic theory requires that medical equipment costs be compared with expected benefits. To answer this question for computer-assisted spinal surgery, we present an economic evaluation looking specifically at symptomatic misplaced screws leading to reoperation secondary to neurologic deficits or biomechanical concerns. STUDY DESIGN/SETTING The study design was an observational case-control study from prospectively collected data of consecutive patients treated with the aid of CAS (treatment group) compared with a matched historical cohort of patients treated with conventional fluoroscopy (control group). PATIENT SAMPLE The patient sample consisted of consecutive patients treated surgically at a quaternary academic center. OUTCOME MEASURES The primary effectiveness measure studied was the number of reoperations for misplaced screws within 1 year of the index surgery. Secondary outcome measures included were total adverse event rate and postoperative computed tomography usage for pedicle screw examination. METHODS A patient-level data cost-effectiveness analysis from the hospital perspective was conducted to determine the value of a navigation system coupled with intraoperative 3-D imaging (O-arm Imaging and the StealthStation S7 Navigation Systems, Medtronic, Louisville, CO, USA) in adult spinal surgery. The capital costs for both alternatives were reported as equivalent annual costs based on the annuitization of capital expenditures method using a 3% discount rate and a 7-year amortization period. Annual maintenance costs were also added. Finally, reoperation costs using a micro-costing approach were calculated for both groups. An incremental cost-effectiveness ratio was calculated and reported as cost per reoperation avoided. Based on reoperation costs in Canada and in the United States, a minimal caseload was calculated for the more expensive alternative to be cost saving. Sensitivity analyses were also conducted. RESULTS A total of 5,132 pedicle screws were inserted in 502 patients during the study period: 2,682 screws in 253 patients in the treatment group and 2,450 screws in 249 patients in the control group. Overall accuracy rates were 95.2% for the treatment group and 86.9% for the control group. Within 1 year post treatment, two patients (0.8%) required a revision surgery in the treatment group compared with 15 patients (6%) in the control group. An incremental cost-effectiveness ratio of

Does Extent of Resection Impact Survival in Patients Bearing Glioblastoma

15,961 per reoperation avoided was calculated for the CAS group. Based on a reoperation cost of

Surgical Management of Spinal Chondrosarcomas

12,618, this new technology becomes cost saving for centers performing more than 254 instrumented spinal procedures per year. CONCLUSIONS Computer-assisted spinal surgery has the potential to reduce reoperation rates and thus to have serious cost-effectiveness and policy implications. High acquisition and maintenance costs of this technology can be offset by equally high reoperation costs. Our cost-effectiveness analysis showed that for high-volume centers with a similar case complexity to the studied population, this technology is economically justified.

Dressings and drains in posterior spine surgery and their effect on wound complications

BACKGROUND The impact of malignant glioma resection on survival is still a matter of controversy. The lack of well-designed prospective studies as well as control of all factors in retrospective studies plays an important role in this debate. Amongst some of these uncontrolled factors, are the inclusion of different histological grades, the lack of objective methods to estimate the extent of resection and unspecified delays in post-operative imaging. METHODS We retrospectively reviewed 126 consecutive patients with glioblastoma, operated on by the senior authors at the Centre Hospitalier Universitaire de Sherbrooke, who met the following criteria: >18 years of age, newly diagnosed glioblastoma, pre-operative magnetic resonance imaging (MRI) within 2 weeks prior to surgery, and a post-operative MRI within 72 hours after surgery. Extent of tumour resection was calculated using pre and post-operative tumour delimitation on gadolinium-enhanced T1 MRI in a volumetric analysis. RESULTS Applying stringent specific inclusion criteria, 126 patients were retained in the analysis. The median overall survival was 271 days and the median extent of resection was 65%. Patients with more than 90% of tumour resection had a significantly better outcome, improving median survival from 225 to 519 days (P=0.006). Other factors that significantly improved survival were the use of radiotherapy, the number of regimens and type of chemotherapy used. CONCLUSION A more aggressive approach combining maximal safe resection and use of salvage chemotherapy seems to confer a survival advantage for glioblastoma patients.

Spinal cord perfusion pressure predicts neurologic recovery in acute spinal cord injury

Study Design. An ambispective cohort study. Objective. The aim of this study was to determine whether the application of the Enneking classification in the management of spinal chondrosarcomas influences local recurrence and survival. Summary of Background Data. Primary spinal chondrosarcomas are rare. Best available evidence is based on small case series, thus making it difficult to determine optimal management and risk factors for local recurrence and survival. Methods. The AOSpine Knowledge Forum Tumor developed a multicenter ambispective database of surgically treated patients with spinal chondrosarcoma. Patient data pertaining to demographics, diagnosis, treatment, cross-sectional survival, and local recurrence were collected. Tumors were classified according to the Enneking classification. Patients were divided into two cohorts: Enneking appropriate (EA) and Enneking inappropriate (EI). They were categorized as EA when the final pathological assessment of the margin matched the Enneking recommendation, and otherwise, they were categorized as EI. Results. Between 1987 and 2011, 111 patients (37 female; 74 male) received surgical treatment for a primary spinal chondrosarcoma at a mean age of 47.4 ± 15.8 years. Patients were followed for a median period of 3.1 years (range = 203 d–18.7 yrs). Median survival for the entire cohort was 8.4 years postoperative. After 10 years postoperative, 36 (32%) patients died and 37 (35%) patients suffered a local recurrence. Twenty-three of these 37 patients who suffered a local recurrence died. Sixty (58%) patients received an EA procedure while 44 (42%) received an EI procedure. EI patients had a higher hazard ratio for local recurrence than those who received an EA procedure (P = 0.052). Local recurrence was strongly associated with chondrosarcoma-related death (risk ratio = 3.6, P < 0.010). Conclusion. This is the largest multicenter cohort of spinal chondrosarcomas. EA surgical management appeared to correlate with a decreased risk of local recurrence, yet no relationship with survival was found. Where possible, surgeons should strive to achieve EA margins to minimize the risk of local recurrence. Level of Evidence: 4

Adverse events in surgically treated cervical spondylopathic myelopathy: a prospective validated observational study.

The purpose of this study was to systematically search, critically appraise and summarize published randomized control trials (RCT) and non-RCT examining the effect of drains and dressings on wound healing rates and complications in posterior spine surgery. The use of post-operative drains and the type of post-operative dressing is at the discretion of the treating surgeon with no available clinical guidelines. Drains will theoretically decrease incidence of post-operative hematoma and therefore, potentially decrease the risk of neurologic compromise when the neural elements have been exposed. Occlusive dressings have more recently been advocated, potentially maintaining a sterile barrier for longer time periods post-operatively. A systematic review of databases from 1969-2013 was undertaken. All papers examining drains in spine surgery and dressings in primary healing of surgical wounds were included. Revman (version 5.2; The Nordic Cochrane Centre, The Cochrane Collaboration, Oxford, UK) was used to test for overall treatment effect, clinical heterogeneity and risk of bias. Of the papers identified, 1348 examined post-operative drains in spine surgery and 979 wound dressings for primary wound healing of all surgical wounds. Seven studies were included for analysis for post-operative drains and 10 studies were analyzed for primary wound healing. The use of a post-operative drain did not influence healing rates and had no effect secondarily on infection (odds ratio [OR] 1.33; 95% confidence interval [CI] 0.76-2.30). We were not able to establish whether surgical drains prevent hematomas causing neurologic compromise. There was a slight advantage to using occlusive dressings versus non-occlusive dressings in wound healing (OR 2.09; 95% CI 1.44-3.02). Incisional vacuum dressings as both an occlusive barrier and superficial drainage system have shown promise for wounds at risk of dehiscence. There is a relatively high risk of bias in the methodology of many of the studies reviewed. We recommend favoring of occlusive dressings based on heterogeneous and potentially biased evidence. Drain use does not affect wound healing based on similar evidence. Incisional vacuum dressings have shown promise in managing potentially vulnerable wounds.

Safety and efficacy of Gamma Knife surgery for brain metastases in eloquent locations: Clinical article

Objective: To determine whether spinal cord perfusion pressure (SCPP) as measured with a lumbar intrathecal catheter is a more predictive measure of neurologic outcome than the conventionally measured mean arterial pressure (MAP). Methods: A total of 92 individuals with acute spinal cord injury were enrolled in this multicenter prospective observational clinical trial. MAP and CSF pressure (CSFP) were monitored during the first week postinjury. Neurologic impairment was assessed at baseline and at 6 months postinjury. We used logistic regression, systematic iterations of relative risk, and Cox proportional hazard models to examine hemodynamic patterns commensurate with neurologic outcome. Results: We found that SCPP (odds ratio 1.039, p = 0.002) is independently associated with positive neurologic recovery. The relative risk for not recovering neurologic function continually increased as individuals were exposed to SCPP below 50 mm Hg. Individuals who improved in neurologic grade dropped below SCPP of 50 mm Hg fewer times than those who did not improve (p = 0.012). This effect was not observed for MAP or CSFP. Those who were exposed to SCPP below 50 mm Hg were less likely to improve from their baseline neurologic impairment grade (p = 0.0056). Conclusions: We demonstrate that maintaining SCPP above 50 mm Hg is a strong predictor of improved neurologic recovery following spinal cord injury. This suggests that SCPP (the difference between MAP and CSFP) can provide useful information to guide the hemodynamic management of patients with acute spinal cord injury.

Changing the adverse event profile in metastatic spine surgery: An evidence based approach to target wound complications and instrumentation failure

Study Design. Prospective observational study. Objective. Using validated tools to accurately identify and quantify incidence of and risks for inpatient adverse events (AEs) associated with surgical management of cervical spondylopathic myelopathy (CSM) with the goal of assisting physicians and patients in decision making. To identify patient-/disease-/technique-specific, independent risk factors for developing AEs perioperatively and affecting length of stay for patients treated surgically for CSM. Summary of Background Data. Previous studies have reported an overall perioperative complication rate between 15.6% and 18.52%. Methods. A total of 104 patients underwent surgery for CSM in our academic quaternary referral center. The average age was 60.3 years (range, 34–86 yr) with a male preponderance (n = 77, 74%). The severity of myelopathy and significant comorbidities was measured and was in keeping with previously assessed populations. Surgical approach was anterior-alone (39.4%), posterior-alone (55.8%), or combined (4.8%) surgery. Inpatient AE data were collected in a rigorous, contemporaneous fashion using the previously validated Spine Adverse Events Severity System (SAVES) tool. Results. A total AE rate of 42.3% was documented in surgically managed patients with CSM (intraoperative = 13.5%, postoperative = 37.5%). Statistically significant risk factors for postoperative AEs were identified, including number of comorbidities (P = 0.012), anterior surgical approach (P = 0.003), and number of levels operated on (P = 0.031). Multiple risk factors for length of stay were also identified, including number of AEs (P < 0.0001), Nurick Score (P < 0.0001), number of levels operated on (P = 0.006), and occurrence of deep wound infection (P < 0.0001). Conclusion. We report higher perioperative AE rates than previously recognized, due to the use of a validated, rigorous data collection tool. Multiple novel patient/disease severity/surgical factors with high statistical significance on perioperative AEs have been identified. Level of Evidence: 3