Perspectives Commentary on: An Assessment of the Key Predictors of Perioperative Complications in Patients with Cervical Spondylotic Myelopathy Undergoing Surgical Treatment: Results from a Survey of 916 AOSpine International Members by Tetreault et al. World Neurosurg 2015 http://dx.doi.org/10.1016/j.wneu.2015.01.021
Predicting Complications after Cervical Spondylotic Myelopathy Surgery: Perception Equals Reality? Daniel J. Hoh
T
he current era in medicine has prioritized, above all else, health care quality and patient safety. Institutions, hospitals, and physicians are assessed on the basis of their performance with respect to delivery of health care to populations and individual patients. Although the highest quality of health care is ideally determined by optimal patient outcomes, the reality is that hospital and physician performance are largely measured by their overall safety of patient care. Evaluating patient safety currently relies on metrics that monitor the occurrence of in-hospital complications. Hospital-acquired complications can directly impact health status, alter patient disease course and/or management, or merely pose the potential threat of unintended negative consequences. Complications can occur randomly, due to individual patient factors, system inadequacies, human error, or often the unfortunate simultaneous alignment of multiple failures. Although the ultimate patient safety goal for hospitals and physicians is zero complications, it is clear that medical errors are an expected reality. The 1999 Institute of Medicine report “To Err is Human” calculated that an estimated 44,000e98,000 deaths occur annually in U.S. hospitals due to medical errors (12). In response, the subsequent report “The Quality Chasm” was a patient safety mandate urging the medical community to reduce medical errors in half. Value-based reimbursement has emerged as a strategy to improve patient safety by rewarding low-complication hospitals with financial incentives and penalizing higher complication hospitals by withholding reimbursement.
Key words Cervical spondylotic myelopathy - Postoperative complications - Prediction - Spine - Surgery - Survey -
Abbreviations and Acronyms ACS: American College of Surgeons CSM: cervical spondylotic myelopathy RCT: Randomized-controlled trial
WORLD NEUROSURGERY - [-]: ---, MONTH 2015
Until now, the spine surgical literature has predominantly focused on demonstrating surgical benefit on improving neurologic and functional outcomes. Moving forward, one can expect an increased need to study specifically surgical complications. Determining the incidence of complications and, perhaps more importantly, identifying predictors of occurrence are essential for measuring health care performance, engaging patients and caregivers in shared decision making, and, ultimately, improving overall health care delivery and resource utilization. Traditionally, evidence for patient outcomes has been borne out of clinical trials. Randomized-controlled trials (RCTs) for surgery, while the gold standard for comparing effectiveness between two interventions, frequently demonstrate poor generalizability across the broad spectrum of real-world patients. Strict inclusion and exclusion criteria often deliberately define a limited study population in order to show a true differential in treatment benefit. Studying a relatively homogeneous patient population, however, can significantly underestimate complication rates when applied to the general population. Lower-level evidence such as retrospective case series may encompass a more realworld surgical population. Interpreting clinical outcomes from single surgeon/institution case series, particularly with respect to negative results and complications, however, are often scrutinized due to the significant potential for reporting bias. The lure of “Big Data” has provided a new avenue in the science of studying patient outcomes, particularly with respect to complications. Large administrative databases, such as the National
From the Department of Neurosurgery, University of Florida, Gainesville, Florida, USA To whom correspondence should be addressed: Daniel J. Hoh, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015). http://dx.doi.org/10.1016/j.wneu.2015.04.034
www.WORLDNEUROSURGERY.org
1
PERSPECTIVES
Inpatient Sample, offer the promise of mining patient hospital encounters for complication occurrence on a magnitude of scale not feasible for conventional clinical trials. Complex statistical models can determine incidence and predictors of complications by stratifying various individual patient factors, hospital type and size, geographic region, and payer. Using the American College of Surgeons (ACS) multicenter database, the ACS National Quality Improvement Program has created an online preoperative surgical risk assessment tool that calculates the probability of complication or death for a given procedure on the basis of individual patient health history (1). The recent surge in administrative database studies has certainly answered the call for providing a large-scale “30,000-foot view” of complication occurrence across a broad spectrum of individual patients and hospital systems (4, 8, 10, 13). Because of the manner in which coding data are entered and reported in many administrative databases, these studies, however, often lack real granularity in identifying causal relationships, failing to definitively link a given complication to an intervention. Medical societies and collaborative efforts among surgeons and institutions have turned toward initiating multicenter prospective registries to provide missing answers (2, 3, 9, 11). Prospective registries study patients, surgeons, procedures, and clinical outcome in real time as they exist in real-world, practical application. Unlike RCTs, prospective registry patients do not sign up for random assignment to one of two interventions (which the null hypothesis would suggest demonstrate clinical equipoise). Prospective registries are designed to be generally more broadly inclusive. Ideally, surgeons counsel patients and through shared decision making ultimately proceed with the procedure that best serves the individual patient’s needs. Inherent in this process is an equal assessment of surgical benefit versus complication and risk avoidance, based on both the individual patient and surgeon’s profile. As one may expect, patient and surgeon perception, perspective, and expectation are integral to this shared decision making. Fehlings and others studied clinical outcomes after surgical treatment for cervical spondylotic myelopathy (CSM) in the AOSpine North American multicenter registry (5, 6). CSM is a common disease with potentially significant neurologic and functional sequelae and affects individuals worldwide without particular ethnic or geographic discrimination. The indications for surgical treatment of CSM are generally well agreed upon, but it is also commonly accepted that types of surgical intervention can vary widely among surgeons by generation, institution, health care system, and country. From this registry, Fehlings et al. were able to demonstrate that despite wide variation in practice patterns, surgical outcomes for the treatment of CSM are largely beneficial with respect to improving neurologic function, pain, and disability (6). Interestingly, also in spite of wide variation in surgical procedures, the incidence of major complications and predictors of complication were relatively limited (5). Advanced age, combined anterior-posterior surgery, and increased operative time and blood loss were the only factors associated with occurrence of perioperative complications. Multivariate analysis of factors associated with major complications only identified age and combined anterior-posterior surgery. Surprisingly, individual patient characteristics such as comorbidities, body mass index, degree of myelopathy, smoking status, and anterior versus
2
www.SCIENCEDIRECT.com
posterior surgery did not impact complication rate, as has been seen in other clinical and administrative database studies. These results beg the inevitable questions: Were the surgeons in this registry highly adept with respect to perceived risk when determining which patients to treat, and what procedure was best indicated? The current study by Tetreault et al., “An Assessment of the Key Predictors of Perioperative Complications in Patients with Cervical Spondylotic Myelopathy Undergoing Surgical Treatment: Results from a Survey of 916 AOSpine International Members,” seeks to provide insight into this question. The authors sought to shed light on surgeon perception by asking the AOSpine community their perspective on important clinical and surgical predictors of complications after CSM surgery. One must assume that the survey responses were subject to potentially significant individual, generational, health care system, and regional bias. Because of these biases, expert opinion defines the lowest tier in the hierarchy of evidence-based medicine. Real-world, practical medicine, however, intuitively places a premium on expert judgment. Past patient experiences, wisdom passed by mentors and colleagues, and personal expertise instinctively combine on equal footing with interpretation of the medical literature to help inform clinical decision making. As Greenhalgh et al. suggest, “real evidence-based medicine is not bound by rules,” and ultimately “rule following” should give way “to expert judgments (7).” They further state that “quality in clinical care” should not “overlook the evidence on the more sophisticated process of advanced expertise.” The results of this survey study are not entirely surprising. The majority of respondents indicated that they perceived the presence of comorbidities to be the most important predictor of complications, with specifically diabetes posing a higher risk of cardiac issues and wound infections. Many respondents also generally perceived that posterior surgery is associated with a higher rate of complications than anterior surgery, and that types of complications significantly vary between anterior and posterior procedures. When comparing this survey of the AOSpine community to the AOSpine North American registry (5), the remarkable difference is that individual patient factors like comorbidities and anterior versus posterior surgery did not prove to be significant predictors of complications in the actual prospective registry. If one assumes that the registry represents a higher level of evidence, then one must conclude that surgeons (via survey) generally overestimate the impact of certain factors in predicting complications. Alternatively, one may attribute higher value to the “advanced expertise” as represented by the survey responses. Perhaps most indicative of expert judgment in practice, the surgeons in the registry presumably anticipated risk appropriately and made seemingly highly accurate clinical decisions in determining whom and how to treat. Unfortunately, with these two studies alone we cannot definitively distinguish the true answer. Interpreting them side by side, however, we must assume that expert judgment (as informed partially by perception) has a significant role in daily clinical decision making and positively impacts patient outcomes. We avoid or minimize risks that we perceive to be real and, in a way, further cement the reality of our perception. Patients not only expect but also value this kind of personal expertise from their
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.034
PERSPECTIVES
surgeon. Moving forward in the quality and patient safety era, hopefully health care systems will also appropriately assess and
REFERENCES 1. ACS NSQIP Surgical Risk Calculator. Available at: http://riskcalculator.facs.org. Accessed April 13, 2015. 2. Asher AL, McCormick PC, Selden NR, Ghogawala Z, McGirt MJ: The National Neurosurgery Quality and Outcomes Database and NeuroPoint Alliance: rationale, development, and implementation. Neurosurg Focus 34:E2, 2013. 3. Asher AL, Speroff T, Dittus RS, Parker SL, Davies JM, Selden N, Nian H, Glassman S, Mummaneni P, Shaffrey C, Watridge C, Cheng JS, McGirt MJ: The National Neurosurgery Quality and Outcomes Database (N2QOD): a collaborative North American outcomes registry to advance value-based spine care. Spine (Phila Pa 1976) 39(22 Suppl 1):S106-S116, 2014. 4. Boakye M, Patil CG, Santarelli J, Ho C, Tian W, Lad SP: Cervical spondylotic myelopathy: complications and outcomes after spinal fusion. Neurosurgery 62:455-461; discussion 461-462, 2008. 5. Fehlings MG, Smith JS, Kopjar B, Arnold PM, Yoon ST, Vaccaro AR, Brodke DS, Janssen ME, Chapman JR, Sasso RC, Woodard EJ, Banco RJ, Massicotte EM, Dekutoski MB, Gokaslan ZL, Bono CM, Shaffrey CI: Perioperative and delayed complications associated with the surgical treatment of cervical spondylotic myelopathy based on 302 patients from the AOSpine North America
place value on physician expert judgment as a part of shared decision making.
Cervical Spondylotic Myelopathy J Neurosurg Spine 16:425-432, 2012.
Study.
6. Fehlings MG, Wilson JR, Kopjar B, Yoon ST, Arnold PM, Massicotte EM, Vaccaro AR, Brodke DS, Shaffrey CI, Smith JS, Woodard EJ, Banco RJ, Chapman JR, Janssen ME, Bono CM, Sasso RC, Dekutoski MB, Gokaslan ZL: Efficacy and safety of surgical decompression in patients with cervical spondylotic myelopathy: results of the AOSpine North America prospective multi-center study. J Bone Joint Surg Am 95:1651-1658, 2013. 7. Greenhalgh T, Howick J, Maskrey N: Evidencebased medicine: a movement in crisis? BMJ 348: g3725, 2014. 8. King JT Jr, Abbed KM, Gould GC, Benzel EC, Ghogawala Z: Cervical spine reoperation rates and hospital resource utilization after initial surgery for degenerative cervical spine disease in 12,338 patients in Washington State. Neurosurgery 65: 1011-1022; discussion 1022-1023, 2009. 9. McGirt MJ, Speroff T, Dittus RS, Harrell FE Jr, Asher AL: The National Neurosurgery Quality and Outcomes Database (N2QOD): general overview and pilot-year project description. Neurosurg Focus 34:E6, 2013. 10. Memtsoudis SG, Hughes A, Ma Y, Chiu YL, Sama AA, Girardi FP: Increased in-hospital complications after primary posterior versus primary anterior cervical fusion. Clin Orthop Relat Res 469:649-657, 2011.
WORLD NEUROSURGERY - [-]: ---, MONTH 2015
11. Mummaneni PV, Whitmore RG, Curran JN, Ziewacz JE, Wadhwa R, Shaffrey CI, Asher AL, Heary RF, Cheng JS, Hurlbert RJ, Douglas AF, Smith JS, Malhotra NR, Dante SJ, Magge SN, Kaiser MG, Abbed KM, Resnick DK, Ghogawala Z: Cost-effectiveness of lumbar discectomy and single-level fusion for spondylolisthesis: experience with the NeuroPoint-SD registry. Neurosurg Focus 36: E3, 2014. 12. Stelfox HT, Palmisani S, Scurlock C, Orav EJ, Bates DW: The “To Err Is Human” report and the patient safety literature. Qual Saf Health Care 15: 174-178, 2006. 13. Wang MC, Chan L, Maiman DJ, Kreuter W, Deyo RA: Complications and mortality associated with cervical spine surgery for degenerative disease in the United States. Spine (Phila Pa 1976) 32: 342-347, 2007.
Citation: World Neurosurg. (2015). http://dx.doi.org/10.1016/j.wneu.2015.04.034 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
3
Predicting Complications after Cervical Spondylotic Myelopathy Surgery: Perception Equals Reality? Daniel J. Hoh
T
he current era in medicine has prioritized, above all else, health care quality and patient safety. Institutions, hospitals, and physicians are assessed on the basis of their performance with respect to delivery of health care to populations and individual patients. Although the highest quality of health care is ideally determined by optimal patient outcomes, the reality is that hospital and physician performance are largely measured by their overall safety of patient care. Evaluating patient safety currently relies on metrics that monitor the occurrence of in-hospital complications. Hospital-acquired complications can directly impact health status, alter patient disease course and/or management, or merely pose the potential threat of unintended negative consequences. Complications can occur randomly, due to individual patient factors, system inadequacies, human error, or often the unfortunate simultaneous alignment of multiple failures. Although the ultimate patient safety goal for hospitals and physicians is zero complications, it is clear that medical errors are an expected reality. The 1999 Institute of Medicine report “To Err is Human” calculated that an estimated 44,000e98,000 deaths occur annually in U.S. hospitals due to medical errors (12). In response, the subsequent report “The Quality Chasm” was a patient safety mandate urging the medical community to reduce medical errors in half. Value-based reimbursement has emerged as a strategy to improve patient safety by rewarding low-complication hospitals with financial incentives and penalizing higher complication hospitals by withholding reimbursement.
Key words Cervical spondylotic myelopathy - Postoperative complications - Prediction - Spine - Surgery - Survey -
Abbreviations and Acronyms ACS: American College of Surgeons CSM: cervical spondylotic myelopathy RCT: Randomized-controlled trial
WORLD NEUROSURGERY - [-]: ---, MONTH 2015
Until now, the spine surgical literature has predominantly focused on demonstrating surgical benefit on improving neurologic and functional outcomes. Moving forward, one can expect an increased need to study specifically surgical complications. Determining the incidence of complications and, perhaps more importantly, identifying predictors of occurrence are essential for measuring health care performance, engaging patients and caregivers in shared decision making, and, ultimately, improving overall health care delivery and resource utilization. Traditionally, evidence for patient outcomes has been borne out of clinical trials. Randomized-controlled trials (RCTs) for surgery, while the gold standard for comparing effectiveness between two interventions, frequently demonstrate poor generalizability across the broad spectrum of real-world patients. Strict inclusion and exclusion criteria often deliberately define a limited study population in order to show a true differential in treatment benefit. Studying a relatively homogeneous patient population, however, can significantly underestimate complication rates when applied to the general population. Lower-level evidence such as retrospective case series may encompass a more realworld surgical population. Interpreting clinical outcomes from single surgeon/institution case series, particularly with respect to negative results and complications, however, are often scrutinized due to the significant potential for reporting bias. The lure of “Big Data” has provided a new avenue in the science of studying patient outcomes, particularly with respect to complications. Large administrative databases, such as the National
From the Department of Neurosurgery, University of Florida, Gainesville, Florida, USA To whom correspondence should be addressed: Daniel J. Hoh, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015). http://dx.doi.org/10.1016/j.wneu.2015.04.034
www.WORLDNEUROSURGERY.org
1
PERSPECTIVES
Inpatient Sample, offer the promise of mining patient hospital encounters for complication occurrence on a magnitude of scale not feasible for conventional clinical trials. Complex statistical models can determine incidence and predictors of complications by stratifying various individual patient factors, hospital type and size, geographic region, and payer. Using the American College of Surgeons (ACS) multicenter database, the ACS National Quality Improvement Program has created an online preoperative surgical risk assessment tool that calculates the probability of complication or death for a given procedure on the basis of individual patient health history (1). The recent surge in administrative database studies has certainly answered the call for providing a large-scale “30,000-foot view” of complication occurrence across a broad spectrum of individual patients and hospital systems (4, 8, 10, 13). Because of the manner in which coding data are entered and reported in many administrative databases, these studies, however, often lack real granularity in identifying causal relationships, failing to definitively link a given complication to an intervention. Medical societies and collaborative efforts among surgeons and institutions have turned toward initiating multicenter prospective registries to provide missing answers (2, 3, 9, 11). Prospective registries study patients, surgeons, procedures, and clinical outcome in real time as they exist in real-world, practical application. Unlike RCTs, prospective registry patients do not sign up for random assignment to one of two interventions (which the null hypothesis would suggest demonstrate clinical equipoise). Prospective registries are designed to be generally more broadly inclusive. Ideally, surgeons counsel patients and through shared decision making ultimately proceed with the procedure that best serves the individual patient’s needs. Inherent in this process is an equal assessment of surgical benefit versus complication and risk avoidance, based on both the individual patient and surgeon’s profile. As one may expect, patient and surgeon perception, perspective, and expectation are integral to this shared decision making. Fehlings and others studied clinical outcomes after surgical treatment for cervical spondylotic myelopathy (CSM) in the AOSpine North American multicenter registry (5, 6). CSM is a common disease with potentially significant neurologic and functional sequelae and affects individuals worldwide without particular ethnic or geographic discrimination. The indications for surgical treatment of CSM are generally well agreed upon, but it is also commonly accepted that types of surgical intervention can vary widely among surgeons by generation, institution, health care system, and country. From this registry, Fehlings et al. were able to demonstrate that despite wide variation in practice patterns, surgical outcomes for the treatment of CSM are largely beneficial with respect to improving neurologic function, pain, and disability (6). Interestingly, also in spite of wide variation in surgical procedures, the incidence of major complications and predictors of complication were relatively limited (5). Advanced age, combined anterior-posterior surgery, and increased operative time and blood loss were the only factors associated with occurrence of perioperative complications. Multivariate analysis of factors associated with major complications only identified age and combined anterior-posterior surgery. Surprisingly, individual patient characteristics such as comorbidities, body mass index, degree of myelopathy, smoking status, and anterior versus
2
www.SCIENCEDIRECT.com
posterior surgery did not impact complication rate, as has been seen in other clinical and administrative database studies. These results beg the inevitable questions: Were the surgeons in this registry highly adept with respect to perceived risk when determining which patients to treat, and what procedure was best indicated? The current study by Tetreault et al., “An Assessment of the Key Predictors of Perioperative Complications in Patients with Cervical Spondylotic Myelopathy Undergoing Surgical Treatment: Results from a Survey of 916 AOSpine International Members,” seeks to provide insight into this question. The authors sought to shed light on surgeon perception by asking the AOSpine community their perspective on important clinical and surgical predictors of complications after CSM surgery. One must assume that the survey responses were subject to potentially significant individual, generational, health care system, and regional bias. Because of these biases, expert opinion defines the lowest tier in the hierarchy of evidence-based medicine. Real-world, practical medicine, however, intuitively places a premium on expert judgment. Past patient experiences, wisdom passed by mentors and colleagues, and personal expertise instinctively combine on equal footing with interpretation of the medical literature to help inform clinical decision making. As Greenhalgh et al. suggest, “real evidence-based medicine is not bound by rules,” and ultimately “rule following” should give way “to expert judgments (7).” They further state that “quality in clinical care” should not “overlook the evidence on the more sophisticated process of advanced expertise.” The results of this survey study are not entirely surprising. The majority of respondents indicated that they perceived the presence of comorbidities to be the most important predictor of complications, with specifically diabetes posing a higher risk of cardiac issues and wound infections. Many respondents also generally perceived that posterior surgery is associated with a higher rate of complications than anterior surgery, and that types of complications significantly vary between anterior and posterior procedures. When comparing this survey of the AOSpine community to the AOSpine North American registry (5), the remarkable difference is that individual patient factors like comorbidities and anterior versus posterior surgery did not prove to be significant predictors of complications in the actual prospective registry. If one assumes that the registry represents a higher level of evidence, then one must conclude that surgeons (via survey) generally overestimate the impact of certain factors in predicting complications. Alternatively, one may attribute higher value to the “advanced expertise” as represented by the survey responses. Perhaps most indicative of expert judgment in practice, the surgeons in the registry presumably anticipated risk appropriately and made seemingly highly accurate clinical decisions in determining whom and how to treat. Unfortunately, with these two studies alone we cannot definitively distinguish the true answer. Interpreting them side by side, however, we must assume that expert judgment (as informed partially by perception) has a significant role in daily clinical decision making and positively impacts patient outcomes. We avoid or minimize risks that we perceive to be real and, in a way, further cement the reality of our perception. Patients not only expect but also value this kind of personal expertise from their
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.034
PERSPECTIVES
surgeon. Moving forward in the quality and patient safety era, hopefully health care systems will also appropriately assess and
REFERENCES 1. ACS NSQIP Surgical Risk Calculator. Available at: http://riskcalculator.facs.org. Accessed April 13, 2015. 2. Asher AL, McCormick PC, Selden NR, Ghogawala Z, McGirt MJ: The National Neurosurgery Quality and Outcomes Database and NeuroPoint Alliance: rationale, development, and implementation. Neurosurg Focus 34:E2, 2013. 3. Asher AL, Speroff T, Dittus RS, Parker SL, Davies JM, Selden N, Nian H, Glassman S, Mummaneni P, Shaffrey C, Watridge C, Cheng JS, McGirt MJ: The National Neurosurgery Quality and Outcomes Database (N2QOD): a collaborative North American outcomes registry to advance value-based spine care. Spine (Phila Pa 1976) 39(22 Suppl 1):S106-S116, 2014. 4. Boakye M, Patil CG, Santarelli J, Ho C, Tian W, Lad SP: Cervical spondylotic myelopathy: complications and outcomes after spinal fusion. Neurosurgery 62:455-461; discussion 461-462, 2008. 5. Fehlings MG, Smith JS, Kopjar B, Arnold PM, Yoon ST, Vaccaro AR, Brodke DS, Janssen ME, Chapman JR, Sasso RC, Woodard EJ, Banco RJ, Massicotte EM, Dekutoski MB, Gokaslan ZL, Bono CM, Shaffrey CI: Perioperative and delayed complications associated with the surgical treatment of cervical spondylotic myelopathy based on 302 patients from the AOSpine North America
place value on physician expert judgment as a part of shared decision making.
Cervical Spondylotic Myelopathy J Neurosurg Spine 16:425-432, 2012.
Study.
6. Fehlings MG, Wilson JR, Kopjar B, Yoon ST, Arnold PM, Massicotte EM, Vaccaro AR, Brodke DS, Shaffrey CI, Smith JS, Woodard EJ, Banco RJ, Chapman JR, Janssen ME, Bono CM, Sasso RC, Dekutoski MB, Gokaslan ZL: Efficacy and safety of surgical decompression in patients with cervical spondylotic myelopathy: results of the AOSpine North America prospective multi-center study. J Bone Joint Surg Am 95:1651-1658, 2013. 7. Greenhalgh T, Howick J, Maskrey N: Evidencebased medicine: a movement in crisis? BMJ 348: g3725, 2014. 8. King JT Jr, Abbed KM, Gould GC, Benzel EC, Ghogawala Z: Cervical spine reoperation rates and hospital resource utilization after initial surgery for degenerative cervical spine disease in 12,338 patients in Washington State. Neurosurgery 65: 1011-1022; discussion 1022-1023, 2009. 9. McGirt MJ, Speroff T, Dittus RS, Harrell FE Jr, Asher AL: The National Neurosurgery Quality and Outcomes Database (N2QOD): general overview and pilot-year project description. Neurosurg Focus 34:E6, 2013. 10. Memtsoudis SG, Hughes A, Ma Y, Chiu YL, Sama AA, Girardi FP: Increased in-hospital complications after primary posterior versus primary anterior cervical fusion. Clin Orthop Relat Res 469:649-657, 2011.
WORLD NEUROSURGERY - [-]: ---, MONTH 2015
11. Mummaneni PV, Whitmore RG, Curran JN, Ziewacz JE, Wadhwa R, Shaffrey CI, Asher AL, Heary RF, Cheng JS, Hurlbert RJ, Douglas AF, Smith JS, Malhotra NR, Dante SJ, Magge SN, Kaiser MG, Abbed KM, Resnick DK, Ghogawala Z: Cost-effectiveness of lumbar discectomy and single-level fusion for spondylolisthesis: experience with the NeuroPoint-SD registry. Neurosurg Focus 36: E3, 2014. 12. Stelfox HT, Palmisani S, Scurlock C, Orav EJ, Bates DW: The “To Err Is Human” report and the patient safety literature. Qual Saf Health Care 15: 174-178, 2006. 13. Wang MC, Chan L, Maiman DJ, Kreuter W, Deyo RA: Complications and mortality associated with cervical spine surgery for degenerative disease in the United States. Spine (Phila Pa 1976) 32: 342-347, 2007.
Citation: World Neurosurg. (2015). http://dx.doi.org/10.1016/j.wneu.2015.04.034 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
www.WORLDNEUROSURGERY.org
3
