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Commentary: Advantages of percutaneous pedicle screws in the obese: What is the clinical evidence?
The Spine Journal 11 (2011) 925–926
Commentary
Commentary: Advantages of percutaneous pedicle screws in the obese: What is the clinical evidence? Ajay Jawahar, MD, MS*, Pierce D. Nunley, MD Spine Institute of Louisiana, 1500 Line Ave., Suite 200, Shreveport, LA 71101, USA Received 9 August 2011; accepted 30 August 2011
COMMENTARY ON: Park Y, Ha JW, Lee YT, Sung NY. Percutaneous placement of pedicle screws in overweight and obese patients. Spine J 2011;11:919–24 (in this issue).
Obesity has inarguably become the most prevalent medical condition in the Western nations. With more than a 100 million overweight or obese adults in the United States alone [1], and the incidence of obesity doubling in the past two decades, this condition has been increasingly implicated not only in the high incidence of diseases directly associated with it but also to higher complications after all surgical procedures [2,3]. Because of the erect posture of the human body, the lumbar spine is particularly susceptible to the ill effects of excessive weight gain, because the altered mechanics and dynamics of added stress are likely to exacerbate the process of degeneration. It is intuitive, therefore, to assume that the complications after lumbar spine surgery in overweight or obese patients could be more frequent and severe than in those within the normal weight range. However, several previously published studies have failed to establish a direct correlation between obesity and complications associated with lumbar spine surgery [4–6]. A careful analysis of the published literature brings to light several inconsistencies in the different authors’ DOI of original article: 10.1016/j.spinee.2011.07.029. FDA device/drug status: Not applicable. Author disclosures: AJ: Consulting: K2Medical (B, Paid directly to institution/employer), Sea Spine (B); Board of Directors: American College of Spine Surgeons (Nonfinancial, Vice President). PDN: Royalties: BioMet/EBI (B), Osprey Biomedical (B), LDR Spine (C), K2M (C); Stock Ownership: Amedica (50,000 shares, 1%), Paradigm Spine (18,728 shares, 1%), Spineology (62,500 shares, 1%); Speaking/Teaching Arrangements: K2M (C), Spinal Motion (A), NuVasive (B), OrthoFix (B); Scientific Advisory Board: K2M (B), Spinal Motion (10,000 options). The disclosure key can be found on the Table of Contents and at www. TheSpineJournalOnline.com. * Corresponding author. Spine Institute of Louisiana, 1500 Line Ave., Suite 200, Shreveport, LA 71101, USA. Tel.: (318) 629-5555; fax: (318) 629-5556. E-mail address: [email protected] (A. Jawahar) 1529-9430/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2011.08.430
approach and methodology that could have possibly contributed to such diverse conclusions regarding the role of obesity in complicating spinal surgery. The first issue that has yet to be clarified is the identification of the ‘‘obese patient population.’’ Literature review shows that the studies had quite a heterogenous group of patients within the broad purview of obesity. Andreshak et al. [4] reported a mean weight of 226 lb in their ‘‘obese’’ population, which, although satisfied their criteria of greater than 20% ideal body weight, can hardly be considered extraordinary by the current demographic standards of the United States. Patel et al. [7] had a 95% confidence interval of 24.4 to 30.3 body mass index (BMI) in their patient cohort. They pooled all patients with a BMI greater than 25 in a single group of ‘‘overweight or obese.’’ Such diversity in the inclusion criteria is likely to bring bias into the calculations of correlating postoperative complication rates within the patient population. The second issue that can significantly affect the analyses is the definition of the ‘‘complications’’ per se. Can prolonged odds ratio time, longer duration of the exposure, or longer length of the incision be considered true complications? Yadla et al. [6] used a simple binary definition of major and minor complications previously validated by Ratliff et al. [8] in their analysis and concluded that perioperative outcomes in obese and nonobese patients were comparable, whereas Patel et al. [7] arbitrated their own criteria for ‘‘significant complications’’ and found a positive correlation between increasing BMI and risk of such complications. The third major issue that can potentially affect the analyses is the period for which the complication data are being gathered. Although some series limited their focus to the perioperative period of up to 30 days after surgery, others have considered extended period after surgery to include
926
A. Jawahar and P.D. Nunley / The Spine Journal 11 (2011) 925–926
pseudarthrosis, repeat fusion, and so on as potential complications. Considering the above-mentioned issues along with several others, it is very easy to comprehend the diversity of conclusions by different study groups that have tried to correlate obesity with the incidence of postoperative complications in the patient undergoing elective surgery for lumbar spine diseases. Park et al. [9], in their present work titled ‘‘Percutaneous placement of pedicle screws in overweight and obese patients’’ have analyzed their experience with percutaneous pedicle screw placement in overweight and obese patients needing lumbar spine surgery. Their focus, however, is on the incidence of misplaced screws because of these patients’ relatively large body habitus. I agree with the authors that such a study has not been published in the literature so far, most studies being focused on the clinical outcome and fusion rates. One of the reasons why the results of such an analysis could be questioned is the lack of direct quantitative attribute that the patient’s body habitus could have on the screws being misplaced. Minimally invasive spine surgery (MISS) is recognized as an art and science that is known to improve considerably with proper training, repeated exposure, and hands-on experience of the surgeon. Most surgeons agree that there is a definite learning curve attributable to MISS with reduced complications and better outcome rates with growing experience. One potential way that such a bias could be eliminated would be to design a prospective analysis of patients who have been operated by the same surgeon(s) within a comparable time frame. Even such an exercise may not be without bias as the selection of approach and technique for hardware placement (minimally invasive surgery [MIS] or open) depends on the surgeon’s decision for individual patients. Such a decision could usually be based on a variety of factors including, but not necessarily limited to, the patient’s body habitus. So, a true analysis of the effect of body habitus and screw mishaps could only be decided in a prospective randomized trial conducted within a specified period. It has been the general experience in the field of spine surgery that such trials are very few and far between because of factors ranging from patient safety to individual surgeon philosophy. Results of the present work also have a potential of being influenced by the above-mentioned biases. Although the authors state that it is a ‘‘prospective study,’’ I do not necessarily agree with this statement. The cohort consists of patients who already had pedicle screw fixation between 2004 and 2007 via MIS technique for different indications. When the authors make a statement about
contraindications, it is not clear whether these contraindications were for the lumbar fusion surgery itself or just the MIS pedicle screw placement. If these contraindications were exclusively for MIS approach for pedicle screws, then a reason for such an exclusion needs to be elaborated by the authors. The authors report 16.5% incidence of misplaced screws overall with most pedicle violations being less than 2 mm (Grade B). It is not clear in the report, but I strongly suspect that if a year-wise analysis was done, relatively larger incidence could be in the patients who had surgery during the initial 1 or 2 years of this analysis. Nevertheless, the authors concluded that the incidence of screw misplacement has no statistical relationship with the body habitus of the patients in this retrospective review. This result is in agreement with the clinical outcome studies performed for lumbar spine surgeries [5,6]. In absence of any previous Class 1 or Class 2 studies, the present work adds to the growing belief among spine surgeons that MIS pedicle screw placement is a technique that gets refined with individual surgeon’s hands-on experience but certainly offers no additional advantage based on the patient’s body habitus. Prospective randomized trials with multiple outcome parameters will be needed to truly compare the open versus MIS pedicle screw placement techniques for lumbar spine fusion. References [1] Flegal K, Caroll MD, Kuczmarski RJ, et al. Overweight and obesity in the United States: prevalence and trends, 1960-1994. Int J Obes Relat Metab Disord 1998;22:39–47. [2] Chapman GW Jr, Mailhes JB, Thompson HE. Morbidity in obese and nonobese patients following gynecologic surgery for cancer. J Natl Med Assoc 1988;80:417–20. [3] DeMaria EJ, Carmody BJ. Perioperative management of special populations: obesity. Surg Clin North Am 2005;85:1283–9. [4] Andreshak TG, An HS, Hall J, et al. Lumbar spine surgery in the obese patient. J Spinal Disord 1997;10:267–9. [5] Peng CW, Bendo JA, Goldstein JA, et al. Perioperative outcomes of anterior lumbar surgery in obese versus non-obese patients. Spine J 2009;9:715–20. [6] Yadla S, Malone J, Campbell PG, et al. Obesity and spine surgery: reassessment based on a prospective evaluation of perioperative complications in elective degenerative thoracolumbar procedures. Spine J 2010;10:581–7. [7] Patel N, Bagan B, Vadera S, et al. Obesity and spine surgery: relation to perioperative complications. J Neurosurg Spine 2007;6:291–7. [8] Ratliff J, Lebude B, Albert T, et al. Complications in spine surgery: comparative survey of spine surgeons and patients who underwent spine surgery. J Neurosurg Spine 2009;10:578–84. [9] Park Y, Ha JW, Lee YT, Sung NY, et al. Percutaneous placement of pedicle screws in overweight and obese patients. Spine J 2011;11: 919–24.
Commentary
Commentary: Advantages of percutaneous pedicle screws in the obese: What is the clinical evidence? Ajay Jawahar, MD, MS*, Pierce D. Nunley, MD Spine Institute of Louisiana, 1500 Line Ave., Suite 200, Shreveport, LA 71101, USA Received 9 August 2011; accepted 30 August 2011
COMMENTARY ON: Park Y, Ha JW, Lee YT, Sung NY. Percutaneous placement of pedicle screws in overweight and obese patients. Spine J 2011;11:919–24 (in this issue).
Obesity has inarguably become the most prevalent medical condition in the Western nations. With more than a 100 million overweight or obese adults in the United States alone [1], and the incidence of obesity doubling in the past two decades, this condition has been increasingly implicated not only in the high incidence of diseases directly associated with it but also to higher complications after all surgical procedures [2,3]. Because of the erect posture of the human body, the lumbar spine is particularly susceptible to the ill effects of excessive weight gain, because the altered mechanics and dynamics of added stress are likely to exacerbate the process of degeneration. It is intuitive, therefore, to assume that the complications after lumbar spine surgery in overweight or obese patients could be more frequent and severe than in those within the normal weight range. However, several previously published studies have failed to establish a direct correlation between obesity and complications associated with lumbar spine surgery [4–6]. A careful analysis of the published literature brings to light several inconsistencies in the different authors’ DOI of original article: 10.1016/j.spinee.2011.07.029. FDA device/drug status: Not applicable. Author disclosures: AJ: Consulting: K2Medical (B, Paid directly to institution/employer), Sea Spine (B); Board of Directors: American College of Spine Surgeons (Nonfinancial, Vice President). PDN: Royalties: BioMet/EBI (B), Osprey Biomedical (B), LDR Spine (C), K2M (C); Stock Ownership: Amedica (50,000 shares, 1%), Paradigm Spine (18,728 shares, 1%), Spineology (62,500 shares, 1%); Speaking/Teaching Arrangements: K2M (C), Spinal Motion (A), NuVasive (B), OrthoFix (B); Scientific Advisory Board: K2M (B), Spinal Motion (10,000 options). The disclosure key can be found on the Table of Contents and at www. TheSpineJournalOnline.com. * Corresponding author. Spine Institute of Louisiana, 1500 Line Ave., Suite 200, Shreveport, LA 71101, USA. Tel.: (318) 629-5555; fax: (318) 629-5556. E-mail address: [email protected] (A. Jawahar) 1529-9430/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2011.08.430
approach and methodology that could have possibly contributed to such diverse conclusions regarding the role of obesity in complicating spinal surgery. The first issue that has yet to be clarified is the identification of the ‘‘obese patient population.’’ Literature review shows that the studies had quite a heterogenous group of patients within the broad purview of obesity. Andreshak et al. [4] reported a mean weight of 226 lb in their ‘‘obese’’ population, which, although satisfied their criteria of greater than 20% ideal body weight, can hardly be considered extraordinary by the current demographic standards of the United States. Patel et al. [7] had a 95% confidence interval of 24.4 to 30.3 body mass index (BMI) in their patient cohort. They pooled all patients with a BMI greater than 25 in a single group of ‘‘overweight or obese.’’ Such diversity in the inclusion criteria is likely to bring bias into the calculations of correlating postoperative complication rates within the patient population. The second issue that can significantly affect the analyses is the definition of the ‘‘complications’’ per se. Can prolonged odds ratio time, longer duration of the exposure, or longer length of the incision be considered true complications? Yadla et al. [6] used a simple binary definition of major and minor complications previously validated by Ratliff et al. [8] in their analysis and concluded that perioperative outcomes in obese and nonobese patients were comparable, whereas Patel et al. [7] arbitrated their own criteria for ‘‘significant complications’’ and found a positive correlation between increasing BMI and risk of such complications. The third major issue that can potentially affect the analyses is the period for which the complication data are being gathered. Although some series limited their focus to the perioperative period of up to 30 days after surgery, others have considered extended period after surgery to include
926
A. Jawahar and P.D. Nunley / The Spine Journal 11 (2011) 925–926
pseudarthrosis, repeat fusion, and so on as potential complications. Considering the above-mentioned issues along with several others, it is very easy to comprehend the diversity of conclusions by different study groups that have tried to correlate obesity with the incidence of postoperative complications in the patient undergoing elective surgery for lumbar spine diseases. Park et al. [9], in their present work titled ‘‘Percutaneous placement of pedicle screws in overweight and obese patients’’ have analyzed their experience with percutaneous pedicle screw placement in overweight and obese patients needing lumbar spine surgery. Their focus, however, is on the incidence of misplaced screws because of these patients’ relatively large body habitus. I agree with the authors that such a study has not been published in the literature so far, most studies being focused on the clinical outcome and fusion rates. One of the reasons why the results of such an analysis could be questioned is the lack of direct quantitative attribute that the patient’s body habitus could have on the screws being misplaced. Minimally invasive spine surgery (MISS) is recognized as an art and science that is known to improve considerably with proper training, repeated exposure, and hands-on experience of the surgeon. Most surgeons agree that there is a definite learning curve attributable to MISS with reduced complications and better outcome rates with growing experience. One potential way that such a bias could be eliminated would be to design a prospective analysis of patients who have been operated by the same surgeon(s) within a comparable time frame. Even such an exercise may not be without bias as the selection of approach and technique for hardware placement (minimally invasive surgery [MIS] or open) depends on the surgeon’s decision for individual patients. Such a decision could usually be based on a variety of factors including, but not necessarily limited to, the patient’s body habitus. So, a true analysis of the effect of body habitus and screw mishaps could only be decided in a prospective randomized trial conducted within a specified period. It has been the general experience in the field of spine surgery that such trials are very few and far between because of factors ranging from patient safety to individual surgeon philosophy. Results of the present work also have a potential of being influenced by the above-mentioned biases. Although the authors state that it is a ‘‘prospective study,’’ I do not necessarily agree with this statement. The cohort consists of patients who already had pedicle screw fixation between 2004 and 2007 via MIS technique for different indications. When the authors make a statement about
contraindications, it is not clear whether these contraindications were for the lumbar fusion surgery itself or just the MIS pedicle screw placement. If these contraindications were exclusively for MIS approach for pedicle screws, then a reason for such an exclusion needs to be elaborated by the authors. The authors report 16.5% incidence of misplaced screws overall with most pedicle violations being less than 2 mm (Grade B). It is not clear in the report, but I strongly suspect that if a year-wise analysis was done, relatively larger incidence could be in the patients who had surgery during the initial 1 or 2 years of this analysis. Nevertheless, the authors concluded that the incidence of screw misplacement has no statistical relationship with the body habitus of the patients in this retrospective review. This result is in agreement with the clinical outcome studies performed for lumbar spine surgeries [5,6]. In absence of any previous Class 1 or Class 2 studies, the present work adds to the growing belief among spine surgeons that MIS pedicle screw placement is a technique that gets refined with individual surgeon’s hands-on experience but certainly offers no additional advantage based on the patient’s body habitus. Prospective randomized trials with multiple outcome parameters will be needed to truly compare the open versus MIS pedicle screw placement techniques for lumbar spine fusion. References [1] Flegal K, Caroll MD, Kuczmarski RJ, et al. Overweight and obesity in the United States: prevalence and trends, 1960-1994. Int J Obes Relat Metab Disord 1998;22:39–47. [2] Chapman GW Jr, Mailhes JB, Thompson HE. Morbidity in obese and nonobese patients following gynecologic surgery for cancer. J Natl Med Assoc 1988;80:417–20. [3] DeMaria EJ, Carmody BJ. Perioperative management of special populations: obesity. Surg Clin North Am 2005;85:1283–9. [4] Andreshak TG, An HS, Hall J, et al. Lumbar spine surgery in the obese patient. J Spinal Disord 1997;10:267–9. [5] Peng CW, Bendo JA, Goldstein JA, et al. Perioperative outcomes of anterior lumbar surgery in obese versus non-obese patients. Spine J 2009;9:715–20. [6] Yadla S, Malone J, Campbell PG, et al. Obesity and spine surgery: reassessment based on a prospective evaluation of perioperative complications in elective degenerative thoracolumbar procedures. Spine J 2010;10:581–7. [7] Patel N, Bagan B, Vadera S, et al. Obesity and spine surgery: relation to perioperative complications. J Neurosurg Spine 2007;6:291–7. [8] Ratliff J, Lebude B, Albert T, et al. Complications in spine surgery: comparative survey of spine surgeons and patients who underwent spine surgery. J Neurosurg Spine 2009;10:578–84. [9] Park Y, Ha JW, Lee YT, Sung NY, et al. Percutaneous placement of pedicle screws in overweight and obese patients. Spine J 2011;11: 919–24.