Y. Raja Rampersaud

Radiation exposure to the spine surgeon during fluoroscopically assisted pedicle screw insertion.

Study Design. In vitro study to determine occupational radiation exposure during lumbar fluoroscopy. Objectives. To assess radiation exposure to the spine surgeon during fluoroscopically assisted thoracolumbar pedicle screw placement. Summary of Background Data. Occupational radiation exposure during a variety of fluoroscopically assisted musculoskeletal procedures has been previously evaluated. No prior study has assessed fluoroscopy-related radiation exposure to the spine surgeon. Methods. Bilateral pedicle screw placement (T11–S1) was performed in six cadavers using lateral fluoroscopic imaging. Radiation dose rates to the surgeon’s neck, torso, and dominant hand were measured with dosimeter badges and thermolucent dosimeter (TLD) rings. Radiation levels were also quantified at various distances from the dorsal lumbar surface using an ion chamber radiation survey meter. Results. The mean dose rate to the neck was 8.3 mrem/min. The dose rate to the torso was greatest when the surgeon was positioned ipsilateral to the beam source (53.3 mrem/min, compared with 2.2 mrem/min on the contralateral side). The average hand dose rate was 58.2 mrem/min. A significant increase in hand dose rate was associated with placement of screws ipsilateral to the beam source (P = 0.0005) and larger specimens (P = 0.0007). Radiation levels significantly decreased as distance from the beam source and dorsal body surface increased. The greatest levels of radiation were noted on the side where the primary radiograph beam entered the cadaver. Conclusion. Fluoroscopically assisted thoracolumbar pedicle screw placement exposes the spine surgeon to significantly greater radiation levels than other, nonspinal musculoskeletal procedures that involve the use of a fluoroscope. In fact, dose rates are up to 10–12 times greater. Spine surgeons performing fluoroscopically assisted thoracolumbar procedures should monitor their annual radiation exposure. Measures to reduce radiation exposure and surgeon awareness of high-exposure body and hand positions are certainly called for.

Virtual fluoroscopy : Computer-assisted fluoroscopic navigation

Study Design In vitro accuracy assessment of a novel virtual fluoroscopy system. Objectives To investigate a new technology combining image-guided surgery with C-arm fluoroscopy. Summary of Background Data Fluoroscopy is a useful and familiar technology to all musculoskeletal surgeons. Its limitations include radiation exposure to the patient and operating team and the need to reposition the fluoroscope repeatedly to obtain surgical guidance in multiple planes. Methods Fluoroscopic images of the lumbar spine of an intact, unembalmed cadaver were obtained, calibrated, and saved to an image-guided surgery system (StealthStation; Medtronic Sofamor–Danek, Memphis, TN). A virtual fluoroscopy system (FluoroNav; Medtronic Surgical Navigation Technologies, Broomfield, CO) was used for the sequential insertion of a light-emitting diode–fitted probe into the pedicles of L1–S1 bilaterally. The trajectory of a “virtual tool” corresponding to the tracked tool was overlaid onto the saved fluoroscopic views in real time. Live fluoroscopic images of the inserted pedicle probe were then obtained. Distances between the tips of the virtual and fluoroscopically displayed probes were quantified using the image-guided computer’s measurement tool. Trajectory angle differences were measured using a standard goniometer and printed copies of the workstation computer display. The surgeon’s radiation exposure was measured using thermolucent dosimeter rings. Results Excellent correlation between the virtual fluoroscopic images and live fluoroscopy was observed. Mean probe tip error was 0.97 ± 0.40 mm. Mean trajectory angle difference between the virtual and fluoroscopically displayed probes was 2.7° ± 0.6°. The thermolucent dosimeter rings measured no detectable radiation exposure for the surgeon. Conclusions Virtual fluoroscopy offers several advantages over conventional fluoroscopy while providing acceptable targeting accuracy. It enables a single C-arm to provide real-time, multiplanar procedural guidance. It also dramatically reduces radiation exposure to the patient and surgical team by eliminating the need for repetitive fluoroscopic imaging for tool placement.

Accuracy requirements for image-guided spinal pedicle screw placement

Study Design Accuracy requirement analysis for image-guided pedicle screw placement. Objectives To derive theoretical accuracy requirements for image-guided spinal pedicle screw placement. Summary of Background Data Underlying causes of inaccuracy in image-guided surgical systems and methods for quantifying this inaccuracy have been studied. However, accuracy requirements for specific spinal surgical procedures have not been delineated. In particular, the accuracy requirements for image-guided spinal pedicle screw placement have not been previously reported. Methods A geometric model was developed relating spinal pedicle anatomy to accuracy requirements for image-guided surgery. This model was used to derive error tolerances for pedicle screw placement when using clinically relevant screw diameters in the cervical (3.5 mm), thoracic (5.0 mm), and thoracolumbar spine (6.5 mm). The error tolerances were represented as the permissible rotational and translational deviations from the ideal screw trajectory that would avoid pedicle wall perforation. The relevant dimensions of the pedicle model were extracted from existing morphometric data. Results As anticipated, accuracy requirements were greatest at spinal levels where the relevant screw diameter approximated the dimensions of the pedicle. These requirements were highest for T5, followed in descending order by T4, T7, T6, T3, T12, L1, T8, T11, C4, L2, C3, T10, C5, T2, T9, C6, L3, C2, T1, C7, L4, and L5. Maximum permissible translational/rotational error tolerances ranged from 0.0 mm/0.0° at T5 to 3.8 mm/12.7° at L5. Conclusions These results, obtained by mathematical analysis, demonstrate that extremely high accuracy is necessary to place pedicle screws at certain levels of the spine without perforating the pedicle wall. These accuracy requirements exceed the accuracy of current image-guided surgical systems, based on clinical utility errors reported in the literature. In actual use, however, these systems have been shown to improve the accuracy of pedicle screw placement. This dichotomy indicates that other factors, such as the surgeon’s visual and tactile feedback, may be operative.

Intraoperative adverse events and related postoperative complications in spine surgery: implications for enhancing patient safety founded on evidence-based protocols.

Study Design. Prospective observational study. Objective. To assess the incidence and clinical consequence of intraoperative adverse events from a wide variety of spinal surgical procedures. Summary of Background Data. In this study, adverse events were defined as any unexpected or undesirable event(s) occurring as a result of spinal surgery. A complication was defined as a disease or disorder, which, as a consequence of a surgical procedure, will negatively affect the outcome of the patient. We hypothesized that most adverse events would not result in complications that would be normally flagged through traditional practice audit approaches. By defining the incidence and types of adverse events seen in a spine surgical practice, we hope to develop preventative approaches to enhance patient safety. Methods. All postoperative clinical sequelae (i.e., complications) were prospectively identified, classified as to type, and graded (0 [none] to IV [death]) in 700 consecutive patients who underwent spine surgery (excluding >300-day surgery microdiscectomies) at a university center from January 2002 to June 2003. To confirm data accuracy and assess the clinical sequelae of any adverse events, the medical records of these 700 patients were reviewed. Results. The overall incidence of intraoperative adverse events was 14% (98/700). A total of 23 adverse events led to postoperative clinical sequelae for an overall intraoperative complication incidence of 3.2% (23/700). Specific adverse events included dural tears (n = 58), spinal instrumentation-related events (n = 12), blood loss exceeding 5000 mL (n = 10), anesthesia/medical (n = 4), suspected or actual vertebral artery injury (n = 3), approach-related events (n = 3), esophageal/pharyngeal injury (n = 2), and miscellaneous (n = 6). Conclusions. Adverse events can frequently occur (14%) during spinal surgery, however, the majority (76.5%) are not associated with complications. Improved patient safety can only be maximized by independent practice audit and the development of prospective methods to record adverse event data so that enhanced, evidence-based, clinical protocols can be developed.

The surgical approach to subaxial cervical spine injuries: an evidence-based algorithm based on the SLIC classification system.

Study Design. Systematic review of literature and expert clinical opinions of the members of the Spine Trauma Study Group were combined to develop and refine this algorithm. Obejctive. To develop an evidence-based algorithm for surgical approaches to manage subaxial cervical injuries using a systematic review of the literature, expert opinion, and anticipated patient preferences. Summary of Background Data. There is lack of consensus in the management of subaxial cervical spine trauma, in part, because of the lack of a clinically relevant system for classifying these injuries. The newly developed Subaxial Injury Classification scoring system categorizes injury morphology into 3 broad groups, includes an assessment of the integrity of the discoligamentous soft tissue structures and the patients neurologic status, and thus guides surgical or nonsurgical treatment. The choice of a specific surgical technique and approach is currently not evidence based, and this gap in knowledge is one which the current article seeks to address. Methods. A literature review followed by a consensus of experts approach was used to develop the algorithm and to ensure face and content validity. Results. An algorithm is presented to guide the choice of surgical approach in cervical subaxial burst fractures, distraction injuries, and translation or rotation injuries. The burst or compression injuries and distraction injuries are more likely to be treated with a single anterior approach, whereas the more severe translation or rotation injuries may more commonly be approached posteriorly or with combined anterior and posterior surgery. Conclusion. This algorithm; derived from the Subaxial Injury Classification scoring system, will assist surgeons in answering the 2 most common questions they face when managing subaxial cervical spine trauma: “Should I operate?” and “Which surgical approach should I select?”

Use of minimally invasive surgical techniques in the management of thoracolumbar trauma: current concepts.

Study Design. Literature review and expert opinion. Objective. To provide an overview of the current concepts of minimally invasive surgical (MIS) techniques for the management of thoracolumbar (TL) spinal trauma. Summary of Background Data. Current surgical treatment of thoracolumbar trauma typically involves open placement of spinal instrumentation with fusion. Conventional open spinal exposures can be associated with significant muscle morbidity that can lead to subsequent paraspinal muscular atrophy, scarring, decreased extensor strength and endurance, as well as pain. This approach-related morbidity is the main impetus for application MIS techniques to spinal procedures including trauma. Methods. A review of the relevant English literature was performed. Results. The current rationale, clinical applications, outcomes, and limitation of MIS management of TL injuries are summarized. Conclusion. The application of MIS techniques to spinal trauma is theoretically sound. However, the indications and technology are currently in evolution. Although very limited information is available, the results of current MIS techniques for the management of TL trauma are encouraging.

Morbidity and mortality of major adult spinal surgery. A prospective cohort analysis of 942 consecutive patients

BACKGROUND CONTEXT To date, most reports on the incidence of adverse events (AEs) in spine surgery have been retrospective and dependent on data abstraction from hospital-based administrative databases. To our knowledge, there have been no previous rigorously performed prospective analysis of all AEs occurring in the entire population of patients presenting to an academic quaternary referral center. PURPOSE To determine the mortality and true incidence and severity of morbidity (major and minor, medical and surgical) in adults undergoing complex spinal surgery, both trauma and elective, in a quaternary referral center. To examine the influence of the introduction of a dedicated weekly multidisciplinary rounds, and a formal abstraction tool, on the recording of this prospective perioperative morbidity data. To examine the validity and inter- and intraobserver reliability of a dedicated Spine AdVerse Events Severity system, version 2 (SAVES V2) AE abstraction tool. STUDY DESIGN Ours is an academic quaternary referral center serving a population of 4.5 million people. Beginning in April 2008, a spine-specific AE-recording instrument, entitled SAVES V2, was introduced at our center for reporting, categorization, and classification of AEs. The use of this system remains an ongoing prospective study. PATIENT SAMPLE All adult patients admitted to the spine service of a quaternary referral center for a 12-month period. OUTCOME MEASURES A validity and an inter- and intraobserver reliability examination of the SAVES V2 system, as used at our institution. Morbidity and inhospital deaths, unplanned second surgeries during index admission, wound infections requiring reoperation, and readmissions during the same calendar year. We also examined in detail all intraoperative and nonsurgical postoperative AEs, as well as hospital length of stay (LOS). METHODS Data on all patients undergoing surgery over a 12-month period were prospectively collected using a perioperative morbidity abstraction tool at weekly dedicated mortality and morbidity rounds. This tool allows identification of each specific AE and grades the severity. Before the introduction of this system, and using the hospital inpatient database, our documented perioperative morbidity rate (major and minor, medical and surgical) was 23%. Diagnosis, operative data, hospital data, major and minor complications both medical and surgical, and deaths were recorded. RESULTS One hundred percent of all patients discharged from the unit had complete data available for analysis. Nine hundred forty-two patients with an age range of 16 to 90 years (mean, 54 years; mode, 38 years) were identified. There were 552 males and 390 females. Around 58.5% of patients had undergone elective surgery. Thirty percent of patients were American Spinal Injury Association class D or worse on admission. The average LOS was 13.5 days (range, 1-221 days). Eight hundred twenty-two (87%) patients had at least one documented complication. Thirty-nine percent of these adversely affected hospital LOS. There were 14 mortalities during the study period. The rate of intraoperative surgical complication was 10.5% (4.5% incidental durotomy and 1.9% hardware malposition requiring revision and 2.2% blood loss >2 L). The incidence of postoperative complication was 73.5% (wound complications, 13.5%; delerium, 8%; pneumonia, 7%; neuropathic pain, 5%; dysphagia, 4.5%; and neurological deterioration, 3%). CONCLUSIONS Major spinal surgery in the adult is associated with a high incidence of intra- and postoperative complications. We identified a very high rate of previously unrecognized postoperative complications, which adversely affect LOS. Without strict adherence to a prospective data collection system, the true complexity of this surgery may be greatly underestimated.

Microendoscopic approach to far-lateral lumbar disc herniation

The purpose of this study was to determine the feasibility of performing far-lateral lumbar discectomy by using the microendoscopic discectomy (MED) technique. The authors studied 11 consecutive patients with unilateral, single-level radiculopathy secondary to far-lateral disc herniation. There were eight men and three women, with an average age of 43 years. In all patients magnetic resonance imaging and/or computerized tomography scanning documented far-lateral disc herniations. Six patients experienced motor deficits, nine patients sensory abnormalities, and five depressed reflexes. All patients complained of radicular pain, which failed to improve with conservative care. After induction of epidural anesthesia, single-level, unilateral percutaneous discectomies were performed using the MED technique. Five discectomies were performed at L3-4 and six at L4-5. There were four contained and seven sequestered disc herniations. All surgeries were performed on an outpatient basis. Follow up ranged from for 12 to 27 months. Improvement was shown in all patients postoperatively. Using modified Macnab criteria to assess results of surgery, there were 10 excellent results and one good result. None of the patients experienced residual motor deficits, four had residual decreased sensation, and one still had some degree of nonradicular pain. There were no complications. Although various open techniques exist for the treatment of far-lateral disc herniation, MED is unique in that far-lateral pathological entities can be directly visualized and removed via a 15-mm paramedian incision. The percutaneous approach avoids larger, potentially denervating and destabilizing procedures. The need for general anesthesia can be avoided, and surgery is performed on an outpatient basis, thereby reducing hospital cost and length of stay.

PPARγ deficiency results in severe, accelerated osteoarthritis associated with aberrant mTOR signalling in the articular cartilage

Objectives We have previously shown that peroxisome proliferator-activated receptor gamma (PPARγ), a transcription factor, is essential for the normal growth and development of cartilage. In the present study, we created inducible cartilage-specific PPARγ knockout (KO) mice and subjected these mice to the destabilisation of medial meniscus (DMM) model of osteoarthritis (OA) to elucidate the specific in vivo role of PPARγ in OA pathophysiology. We further investigated the downstream PPARγ signalling pathway responsible for maintaining cartilage homeostasis. Methods Inducible cartilage-specific PPARγ KO mice were generated and subjected to DMM model of OA. We also created inducible cartilage-specific PPARγ/mammalian target for rapamycin (mTOR) double KO mice to dissect the PPARγ signalling pathway in OA. Results Compared with control mice, PPARγ KO mice exhibit accelerated OA phenotype with increased cartilage degradation, chondrocyte apoptosis, and the overproduction of OA inflammatory/catabolic factors associated with the increased expression of mTOR and the suppression of key autophagy markers. In vitro rescue experiments using PPARγ expression vector reduced mTOR expression, increased expression of autophagy markers and reduced the expression of OA inflammatory/catabolic factors, thus reversing the phenotype of PPARγ KO mice chondrocytes. To dissect the in vivo role of mTOR pathway in PPARγ signalling, we created and subjected PPARγ-mTOR double KO mice to the OA model to see if the genetic deletion of mTOR in PPARγ KO mice (double KO) can rescue the accelerated OA phenotype observed in PPARγ KO mice. Indeed, PPARγ-mTOR double KO mice exhibit significant protection/reversal from OA phenotype. Significance PPARγ maintains articular cartilage homeostasis, in part, by regulating mTOR pathway.

Comparative Outcomes of Minimally Invasive Surgery for Posterior Lumbar Fusion: A Systematic Review

BackgroundAlthough minimally invasive surgical (MIS) approaches to the lumbar spine for posterior fusion are increasingly being utilized, the comparative outcomes of MIS and open posterior lumbar fusion remain unclear.Questions/purposesIn this systematic review, we compared MIS and open transforaminal or posterior lumbar interbody fusion (TLIF/PLIF), specifically with respect to (1) surgical end points (including blood loss, surgical time, and fluoroscopy time), (2) clinical outcomes (Oswestry Disability Index [ODI] and VAS pain scores), and (3) adverse events.MethodsWe performed a systematic review of MEDLINE®, Embase, Web of Science, and Cochrane Library. Reference lists were manually searched. We included studies with 10 or more patients undergoing MIS compared to open TLIF/PLIF for degenerative lumbar disorders and reporting on surgical end points, clinical outcomes, or adverse events. Twenty-six studies of low- or very low-quality (GRADE protocol) met our inclusion criteria. No significant differences in patient demographics were identified between the cohorts (MIS: n = 856; open: n = 806).ResultsEquivalent operative times were observed between the cohorts, although patients undergoing MIS fusion tended to lose less blood, be exposed to more fluoroscopy, and leave the hospital sooner than their open counterparts. Patient-reported outcomes, including VAS pain scores and ODI values, were clinically equivalent between the MIS and open cohorts at 12 to 36 months postoperatively. Trends toward lower rates of surgical and medical adverse events were also identified in patients undergoing MIS procedures. However, in the absence of randomization, selection bias may have influenced these results in favor of MIS fusion.ConclusionsCurrent evidence examining MIS versus open TLIF/PLIF is of low to very low quality and therefore highly biased. Results of this systematic review suggest equipoise in surgical and clinical outcomes with equivalent rates of intraoperative surgical complications and perhaps a slight decrease in perioperative medical complications. However, the quality of the current literature precludes firm conclusions regarding the comparative effectiveness of MIS versus open posterior lumbar fusion from being drawn and further higher-quality studies are critically required.