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Outcome After Microdiscectomy: Results of a Prospective Single Institutional Study
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Outcome After Microdiscectomy: Results of a Prospective Single Institutional Study Matthew R. Quigley, M.D.,* Jeffrey Bost, PA-C,* Joseph C. Maroon, M.D.,† Amr Elrifai, M.D.,† and Matthew Panahandeh, M.D.† *Allegheny General Hospital, and Allegheny University of the Health Sciences, Philadelphia, Pennsylvania and †Thomas Jefferson College of Medicine, Philadelphia, Pennsylvania
Quigley MR, Bost J, Maroon JC, Elrifai A, Panahandeh M. Outcome after microdiscectomy: results of a prospective single institutional study. Surg Neurol 1998;49:263– 8. BACKGROUND
Although lumbar microdiscectomy is one of the most frequently performed spinal procedures, little consensus exists in the literature regarding results. Whereas retrospective reports boast success rates as high as 98%, prospective studies are less sanguine with statistics in the 73–77% range. METHODS
Prospective single-institution outcome study of all patients undergoing virgin unilateral single-level microdiscectomies by study surgeons November 1990 to March 1992. Outcome determined by patient-reported responses to mail questionnaire or phone interview by a disinterested party. RESULTS
There were 374 patients operated on, average age 42.4 years with mean length of symptoms 9.4 months, and 31.5% were Workman’s Compensation cases. Total complication rate was less than 4%, and follow-up was accomplished for 86% of the patients. Overall success rate was 74% using a strict combination of patient-reported pain relief, work status not affected, absence of narcotic use, and satisfaction with the procedure. Using a multivariate logistic regression analysis, only Workman’s Compensation claim and length of symptoms (.6 months) were related to success, with a positive outcome in 86% of non-Compensation patients with brief symptoms contrasting with 29% in Compensation cases of greater than 6 months duration.
Workman’s Compensation claims. Science Inc.
© 1998 by Elsevier
KEY WORDS
Intervertebral disc, lumbar discectomy, microsurgery, nucleus pulposus, outcome, prospective.
urgery for the excision of herniated disc is widespread in spinal practice. The technique has evolved over time from a wide muscle/fascial exposure with generous bone removal to a minimally invasive microsurgical approach often aided by the operating microscope. Although frequently performed, no consensus exists in the literature regarding outcome of the microsurgical procedure. Whereas retrospective reviews frequently report success rates in excess of 90% [16], prospective analyses are less sanguine, with outcomes in the 75% range not uncommon [1]. Our practice represents a unique opportunity to evaluate this operation, consisting of five neurosurgeons performing essentially the identical, minimally invasive microsurgical operation on a uniform patient population. We therefore initiated a prospective analysis with self-reported outcome data to study this operation in as rigorous a manner as possible.
S
CONCLUSIONS
A prospective analysis of the frequency of success after microdiscectomy yields results lower than anticipated based on retrospective studies and finds success related to the non-anatomic factors of length of symptoms and This paper was presented at the 63rd Annual Meeting of the American Association of Neurological Surgeons, Orlando, FL; April 22–27, 1995. Address reprint requests to: Dr. Matthew R. Quigley, 420 East North Avenue, Suite 302, Pittsburgh, PA 15212. Received May 28, 1997; accepted August 26, 1997. © 1998 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
Materials and Methods All patients admitted to Allegheny General Hospital between November 1990 and March 1992 who were to undergo virgin, unilateral single-level lumbar microdiscectomies by study neurosurgeons (see acknowledgments) were included. All patients had at least 6 weeks of disabling symptoms, failed at least 0090-3019/98/$19.00 PII S0090-3019(97)00448-5
264 Surg Neurol 1998;49:263–8
1 month of supervised physical therapy, had a radicular component greater than back pain, and neurological signs and symptoms appropriate to a solitary unilateral herniation as evidenced on imaging studies. Demographics and examination data were collected by full-time Physician Assistants on admission, with radiographic and operating room data supplied by the surgeon at the time of the operation. Virtually all patients received preoperative prophylaxis with first-generation cephalosporins (Vancomycin in penicillin-allergic patients). Surgery consisted of a 1-inch skin incision, onethird medial facetectomy, and excision of disc fragment with limited disc space exenteration [12]. The microscope was used in all cases. Patients were examined by the treating physician at 1 month when surgical complications were assessed and contacted by letter or phone at 6 months for determination of long-term outcome. This consisted of a standardized series of questions relating to pain rating, job performance, analgesic use, and satisfaction. Up to three calls and letters were dispatched to maximize follow-up. Phone contact was from a disinterested party and not the treating physician. Success was strictly defined as a combination of all of the following: (1) no or minimal remaining pain; (2) work not adversely affected; (3) no narcotic usage; and (4) patient satisfied with procedure (Table 1). STATISTICS All data base items were entered into a desktop computer using World Health Organization EpiInfot software. Univariate and multivariate logistical regression analysis were performed with the SPSSt statistical package (SPSS Inc., Chicago, IL).
Results A total of 374 patients were operated on (M:F/295: 119), with an average age of 42.4 years. Mean length of symptoms was 9.4 months, and 31.5% were covered under Workman’s Compensation. Table 2 lists the affected levels. The size of each patient’s disc herniation was assessed pre-operatively from axial, computed tomography, or magnetic resonance images by comparing the ventral excursion from disc to vertebral body and dividing it by the width of the canal (Figure 1); 68% were ,30%, 26% were 30 – 60% and 6% were .60% of the canal diameter. Findings at surgery are presented in Table 3. One month follow-up was accomplished in all patients. Average length of hospital stay was 1.96 days. Surgical complications included six wound
Quigley et al
1
Patient Standardized Questionnaire
1. Describe current pain compared to before surgery. a None b Pain improved but doesn’t limit activity (work and leisure) c Pain improved but does limit activity (work and leisure) d Same pain as pre-op e Worse pain than pre-op 2. Current Working Situation a Same job as before back problem b Same job but light duty compared to before back problem c Working different job because of back problem d Not working because I am not employed or always stay at home e Not working because of back problems 3. How do you feel about the operation? a Pleased, would go through again b Pleased, but would not go through again c Displeased 4. Describe your analgesic (pain pill) use a Daily narcotic used b Non-daily narcotic use c Anti-inflammatory use only d None Standardized questionnaire administered to patient at 6 month follow-up by mail or phone. Success defined by the following responses to each question: 1 (a or b) and 2 (a or b or d) and 3 (a or b) and 4 (c or d).
and three disc space infections, three CSF leaks with two requiring re-exploration, and two reoperations for recurrent/residual disc herniations yielding a total complication rate of 3.7%. There were no major medical complications, root injuries, or deaths. No patient required a blood transfusion. Long-term follow-up at 6 months was accomplished in 322 patients (86%). Using the strict criteria previously outlined, 239 patients (74.2%) out of the total were deemed a success. Using a univariate analysis, a number of clinical and social factors correlated with outcome (Table 4). However, only two factors remained significant when subjecting the data to multivariate logistic regression analysis: Workman’s Compensation claim and length of symptoms (p , 0.0001 for both). Table 5 provides a
2 L1-2 L2-3 L3-4 L4-5 L5-S1
Levels Operated On 1% 1% 7% 44% 47%
Microdisc Outcome
Surg Neurol 265 1998;49:263–8
Schematic of technique used to judge size of disc herniation in relation to canal size as seen on axial CT or MR images. Herniation size was the ratio of B/A.
1
breakdown of surgical success rates segregated by the two significant factors.
4
Discussion “Success” after a microdiscectomy demonstrates marked variation, with the current study falling within the lower range of reported outcomes. Although this may represent differences in patient population or surgical technique, these explana-
3
Findings at Surgery
Bulge without fragment Contained fragment Free fragment
tions are unlikely. Rather, as noted by Pappas and colleagues [13] as well as Howe and Frymoyer [9], outcome differences are probably best attributed to experimental design, end-point measured, length of follow-up, and the agent used to measure the outcome. The current investigation was constructed accordingly so as to minimize controllable sources of bias. A less sanguine success rate is the predictable end result. Few studies have examined microdiscectomy on a prospective basis. The largest, conducted under the auspices of the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Spine section enrolled 740 patients but obtained follow-up on less than 60% at 12 months [1]. Success, as defined by return to pre-morbid activity and absence of narcotic use, was 77% and 73% determined by the surgeon or patient, respectively. The lumbar discectomy operation (as opposed to microdiscectomy) had been prospectively analyzed by Weir [18] as well as Kosteljanetz et al [10]. Improvement in preoperative pain symptoms (success) was recorded in 73% and 77% cases, respectively, both measured at about 1 year postoperatively. A host of retrospective, often single authored, papers concerning microdiscectomy have been published within the last two decades, documenting good outcome 72–98% of the time [5,6,15,19,20]. Vague definitions of “success,” often surgeon-determined, make comparisons of these efforts with our prospective study problematic. The definition of success employed in the present investigation is one of the most rigorous in the literature and in many ways corresponds to the Prolo scale [14] popularized in recent publications [2,13], but with the addition of patient satisfaction and absence of narcotic use. We selected 6 months
13% 30% 57%
Factors Related to Surgical Success (Univariate Analysis) P
Age Findings (degree herniation) Length of symptoms (.6 mos) Level Occupation (professional) Percent canal compromise Preoperative neuro deficit Sex Surgeon Surgical complications Work-related injury Working at presentation Workman’s Compensation claim
0.34 0.70 0.00001 0.79 0.00003 0.31 0.61 0.14 0.83 0.20 0.0001 0.00017 0.0001
266 Surg Neurol 1998;49:263–8
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Surgical Success by Significant Factors
WORKMAN’S COMPENSATION CLAIM Length of symptoms #6 months .6 months
No 86% 67%
Yes 58% 29%
to determine outcome to balance adequate patient accrual with a meaningfully long follow-up. Abramovitz and Neff [1] had shown 3-month outcome to be nearly identical to that at 12 months, but realized a follow-up rate of only 63.4% at 3 months and 53.5% at 1 year. It was thought, therefore, that for this study 6 months represented a valid endpoint compromise. Although diminishing success rates would be anticipated at longer follow-up, Lewis et al found this effect at 5–10 years to be modest [11]. In addition, the relative contribution of the various factors relating to success should not be altered. Finally, in our mobile society, obtaining follow-up in an otherwise healthy, young population remains a vexing problem, as attested to by the 86% rate we achieved despite extensive efforts. The adverse effect of a Workman’s Compensation claim on outcome after discectomy has been previously noted. Sander and Meyers [16] examined 37 patients with comparable initial injuries undergoing discectomy, half of which occurred off-duty. Return to work averaged 9.3 months for compensable cases versus 4.4 months for those that were not, the difference being significant. In their prospective trial, Abramovitz and Neff [1] also found a compensable injury to be statistically related to surgical failure as did Davis in his retrospective review [2]. Others have found fewer successes among compensation cases, but the differences were either not significant or not analyzed for significance [3,4,7,8]. Risk of surgical failure increased with extended length of symptoms (.6 months) in the study of Dvorak et al [3], although the relationship was not statistically significant. Dzioba and Doxey [4] found just the opposite, volunteering that their findings contradicted intuition. Ours is the first study to provide a statistical correlation between length of symptoms and outcome, but admittedly few authors have sought such a link. Clearly, our data do not suggest the cause for this detrimental effect, whether it is physiologic or just an artifact of patient selection. Owing to the relatively brief follow-up (6 months), it is difficult to gauge the significance of two re-operations for recurrence among 374 pa-
tients (0.6%) as it relates to the long term. Although others have found recurrences in 2–18% of operations, follow-up was considerably longer [11,19,20]. Total wound complication rate (3.2%) is comparable to other recent series such as Davis [2] with 3.1% and Pappas [13] at 8.5%; other series range from 0 –7% [5,6,13,15,17,19,20]. The series is also notable for an absence of post-operative neurologic deficits, bowel/arterial injuries, or mortalities. The length of hospital stay (1.96 days), to our knowledge is the shortest reported. In addition, current critical pathway management programs have further reduced our stay to 1.2 days. Surprising was the absence of the correlation of any technical (surgeon) or physical factors (level, sex, size of herniation, findings at surgery) with outcome. Only Abramovitz and Neff analyzed surgical findings (free fragment) against results and also found no relationship [1]. To our knowledge, no other manuscript has addressed the question of disc size (compared with canal width) and outcome, a factor we also found not correlated with success. In conclusion, microdiscectomy is a safe, minimally morbid procedure with a success rate which is markedly disparate depending only on compensation status and length of symptoms. The authors wish to thank their associates, Drs. Julian Bailes, Richard Douglas, and Jack Wilberger for allowing their patients to be enrolled in this study. They also wish to express their gratitude to Barbara Berry for secretarial support and to Joseph Bloch for providing the illustrations.
REFERENCES 1. Abramovitz JN, Neff S. Lumbar disc surgery: Results of the prospective lumbar discectomy study of the Joint Section on Disorders of the Spine and Peripheral Nerves of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons. Neurosurgery 1991;29:301– 8. 2. Davis RA. A long-term outcome analysis of 984 surgically treated herniated lumbar discs. J Neurosurg 1994;80:415–21. 3. Dvorak J, Gauchat M-H, Valach L. The outcome of surgery for lumbar disc herniation. 1.A 4 –17 years’ follow-up with emphasis on somatic aspects. Spine 1988;13:1418 –22. 4. Dzioba RB, Doxey NC. Prospective investigation into the orthopaedic and psychologic predictors of outcome of first lumbar surgery following industrial injury. Spine 1984;9:614 –23. 5. Ebeling U, Reichenberg W, Reulen HJ. Results of microsurgical lumbar discectomy. Review on 485 patients. Acta Neurochir 1986;81:45–52. 6. Goald HJ. Microlumbar discectomy: Follow-up of 477 patients. J Microsurg 1980;2:95–100. 7. Greenough CG, Fraser RD. The effects of compensa-
Microdisc Outcome
8. 9. 10.
11. 12. 13. 14.
15. 16. 17. 18. 19. 20.
tion on recovery from low-back injury. Spine 1989;14: 947–55. Haddad GH. Analysis of 2,932 worker’s compensation back injury cases. The impact on the cost of the system. Spine 1987;12:765–9. Howe J, Frymoyer JW. The effects of questionnaire design on the determination of end results in lumbar spinal surgery. Spine 1984;10:804 –5. Kosteljanetz M, Epersen JO, Halaburt H, Miletic T. Predictive value of clinical and surgical findings in patients with lumbago-sciatica. Acta Neurochir 1984; 73:67–76. Lewis PJ, Weir BKA, Borad RW, Grace MG. Long-term prospective study of lumbosacral discectomy. J Neurosurg 1987;67:49 –53. Maroon JC, Abla AA. Microlumbar discectomy. Clin Neurosurg 1985;33:407–17. Pappas CTE, Harrington T, Sonntag VKH. Outcome analysis of 654 surgically treated lumbar disc herniations. Neurosurgery 1992;30:862– 866. Prolo DJ, Oklund SA, Butcher M. Toward uniformity in evaluating results of lumbar spine operations. A paradigm applied to posterior lumbar interbody fusions. Spine 1986;11:601– 6. Sachdev VP. Microsurgical lumbar discectomy: a personal series of 300 patients with at least 1 year of follow-up. Microsurgery 1986;7:55– 62. Sander RA, Meyers JE. The relationship of disability to compensation status in railroad workers. Spine 1986;11:141–3. Silvers HR. Microsurgical versus standard lumbar discectomy. Neurosurgery 1988;22:837– 41. Weir BKA. Prospective study of 100 lumbosacral discectomies. J Neurosurg 1979;50:283–9. Williams RW. Microlumbar discectomy. A conservative surgical approach to the virgin herniated lumbar disc. Spine 1978;3:175– 82. Wilson DH, Harbaugh R. Microsurgical and standard removal of the protruded lumbar disc: A comparative study. Neurosurgery 1981;8:422–7.
COMMENTARY
Dr. Quigley and his colleagues from Allegheny General Hospital have provided their results after lumbar microdiscectomy on a series of patients with single-level disease thought to be compatible with the clinical presentation. The procedures were done between November 1990 and March 1992; outcome was determined in the usual fashion by asking the individual how he or she fared after the surgical convalescence. Approximately one-third of the individuals operated on had pending Workman’s Compensation claims, and that group was segregated as to results, as is commonly done in studying the efficacy of low back surgery. The authors found that in the Workman’s Compensation group, patients who delayed surgery beyond 6 months resulted in approximately a one-third success rate, whereas 9 of 10 noncompensation claimants with a brief history of sciatica did well. Their results in
Surg Neurol 267 1998;49:263–8
these two population groups are not incompatible with previously published reports. All patients submitted to surgery had unilateral disc herniations, had never been previously operated upon, and had failed to improve with the passage of time. There was a single postoperative visit 1 month after discharge. Success was defined as little in the way of residual pain complaints without any adverse effect on work, the absence of any narcotic usage, and patient satisfaction with the outcome. The usual lower two lumbar levels were predominantly involved and there did not appear to be any significant impact on outcome related to the size or degree of the disc herniation. There were six wound infections and three disc space infections. There were also three CSF leaks, which the authors thought was comparable to other series; the use of the operating microscope may, however, be a contributing factor. The authors provide some basic demographic data, but tell us little about the patients. The 70% failure rate in Workman’s Compensation claimants operated on who have had more than 6 months of symptoms is not related to the technical failure of the procedure, but to a number of other factors ranging from childhood abuse to job satisfaction. Compensation claimants operated on 6 months after the onset of symptoms are seven times more likely to have “failed” the surgical procedure than are nonlitigants operated on in less than 6 months. No data are provided as to preoperative management or, perhaps more significantly, postoperative management, particularly in the Workman’s Compensation group, where results tend to be significantly affected by physician attitude and behavior. Patients tend to behave as directed, and a single postoperative visit 1 month after surgery may simply not be adequate in influencing patient behavior. It is generally accepted that very few operative failures are related to surgical misadventures, such as a missed fragment or illdirected operative approach, and that failure to improve in large part is related to behavioral and/or secondary gain issues. This is particularly significant when self-assessment is the only methodology available for determining whether or not an operative procedure on the lower back has been successful. Experienced spine surgeons will find little new information in this report of a prospective analysis of outcome after single-level microdiscectomy. A great deal more attention, in my opinion, will have to be directed at those factors—medical as well as societal—that promote the behavioral abnormalities that seem to represent the basis for continuing
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Quigley et al
complaints that have been equated with operative failure. Marshall I. Matz, M.D., FACS Neurosurgeon Chicago, Illinois Prospective studies are important and very few have been performed in the area of spinal surgery and outcome. Surgical outcome as determined by patient functioning and patient determination of outcome as monitored by a disinterested third party are key points in assessing the actual outcome of surgery. The fact that this series demonstrates that a positive outcome in cases with no secondary gain issues, such as socioeconomic issues surrounding Workman’s Compensation cases, is not as high as many series have reported in the past, but is still acceptably high (near 70 – 85% of patients without compensation claims). The rate of positive outcomes in compensation cases in whom
symptoms have been present for more than 6 months is an unacceptably low 29%. This rate is not too different from the rate discovered by Schofferman et al in their study which demonstrated that the psychological profile of the patient with specific reference to childhood psychological trauma played a much more important role in the outcome of surgery than did the selection by a surgeon for surgical intervention. It is noteworthy that in the operative findings in the present series, 13% of patients were found to have a bulge without a fragment. It would be interesting to see the correlation between the outcome in those patients, the length of the symptoms, and the relationship to workman’s compensation cases as a subset. This might be a worthwhile investigation on its own. Ronald P. Pawl, M.D., FACS Neurosurgeon Lake Forest, Illinois
Outcome After Microdiscectomy: Results of a Prospective Single Institutional Study Matthew R. Quigley, M.D.,* Jeffrey Bost, PA-C,* Joseph C. Maroon, M.D.,† Amr Elrifai, M.D.,† and Matthew Panahandeh, M.D.† *Allegheny General Hospital, and Allegheny University of the Health Sciences, Philadelphia, Pennsylvania and †Thomas Jefferson College of Medicine, Philadelphia, Pennsylvania
Quigley MR, Bost J, Maroon JC, Elrifai A, Panahandeh M. Outcome after microdiscectomy: results of a prospective single institutional study. Surg Neurol 1998;49:263– 8. BACKGROUND
Although lumbar microdiscectomy is one of the most frequently performed spinal procedures, little consensus exists in the literature regarding results. Whereas retrospective reports boast success rates as high as 98%, prospective studies are less sanguine with statistics in the 73–77% range. METHODS
Prospective single-institution outcome study of all patients undergoing virgin unilateral single-level microdiscectomies by study surgeons November 1990 to March 1992. Outcome determined by patient-reported responses to mail questionnaire or phone interview by a disinterested party. RESULTS
There were 374 patients operated on, average age 42.4 years with mean length of symptoms 9.4 months, and 31.5% were Workman’s Compensation cases. Total complication rate was less than 4%, and follow-up was accomplished for 86% of the patients. Overall success rate was 74% using a strict combination of patient-reported pain relief, work status not affected, absence of narcotic use, and satisfaction with the procedure. Using a multivariate logistic regression analysis, only Workman’s Compensation claim and length of symptoms (.6 months) were related to success, with a positive outcome in 86% of non-Compensation patients with brief symptoms contrasting with 29% in Compensation cases of greater than 6 months duration.
Workman’s Compensation claims. Science Inc.
© 1998 by Elsevier
KEY WORDS
Intervertebral disc, lumbar discectomy, microsurgery, nucleus pulposus, outcome, prospective.
urgery for the excision of herniated disc is widespread in spinal practice. The technique has evolved over time from a wide muscle/fascial exposure with generous bone removal to a minimally invasive microsurgical approach often aided by the operating microscope. Although frequently performed, no consensus exists in the literature regarding outcome of the microsurgical procedure. Whereas retrospective reviews frequently report success rates in excess of 90% [16], prospective analyses are less sanguine, with outcomes in the 75% range not uncommon [1]. Our practice represents a unique opportunity to evaluate this operation, consisting of five neurosurgeons performing essentially the identical, minimally invasive microsurgical operation on a uniform patient population. We therefore initiated a prospective analysis with self-reported outcome data to study this operation in as rigorous a manner as possible.
S
CONCLUSIONS
A prospective analysis of the frequency of success after microdiscectomy yields results lower than anticipated based on retrospective studies and finds success related to the non-anatomic factors of length of symptoms and This paper was presented at the 63rd Annual Meeting of the American Association of Neurological Surgeons, Orlando, FL; April 22–27, 1995. Address reprint requests to: Dr. Matthew R. Quigley, 420 East North Avenue, Suite 302, Pittsburgh, PA 15212. Received May 28, 1997; accepted August 26, 1997. © 1998 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
Materials and Methods All patients admitted to Allegheny General Hospital between November 1990 and March 1992 who were to undergo virgin, unilateral single-level lumbar microdiscectomies by study neurosurgeons (see acknowledgments) were included. All patients had at least 6 weeks of disabling symptoms, failed at least 0090-3019/98/$19.00 PII S0090-3019(97)00448-5
264 Surg Neurol 1998;49:263–8
1 month of supervised physical therapy, had a radicular component greater than back pain, and neurological signs and symptoms appropriate to a solitary unilateral herniation as evidenced on imaging studies. Demographics and examination data were collected by full-time Physician Assistants on admission, with radiographic and operating room data supplied by the surgeon at the time of the operation. Virtually all patients received preoperative prophylaxis with first-generation cephalosporins (Vancomycin in penicillin-allergic patients). Surgery consisted of a 1-inch skin incision, onethird medial facetectomy, and excision of disc fragment with limited disc space exenteration [12]. The microscope was used in all cases. Patients were examined by the treating physician at 1 month when surgical complications were assessed and contacted by letter or phone at 6 months for determination of long-term outcome. This consisted of a standardized series of questions relating to pain rating, job performance, analgesic use, and satisfaction. Up to three calls and letters were dispatched to maximize follow-up. Phone contact was from a disinterested party and not the treating physician. Success was strictly defined as a combination of all of the following: (1) no or minimal remaining pain; (2) work not adversely affected; (3) no narcotic usage; and (4) patient satisfied with procedure (Table 1). STATISTICS All data base items were entered into a desktop computer using World Health Organization EpiInfot software. Univariate and multivariate logistical regression analysis were performed with the SPSSt statistical package (SPSS Inc., Chicago, IL).
Results A total of 374 patients were operated on (M:F/295: 119), with an average age of 42.4 years. Mean length of symptoms was 9.4 months, and 31.5% were covered under Workman’s Compensation. Table 2 lists the affected levels. The size of each patient’s disc herniation was assessed pre-operatively from axial, computed tomography, or magnetic resonance images by comparing the ventral excursion from disc to vertebral body and dividing it by the width of the canal (Figure 1); 68% were ,30%, 26% were 30 – 60% and 6% were .60% of the canal diameter. Findings at surgery are presented in Table 3. One month follow-up was accomplished in all patients. Average length of hospital stay was 1.96 days. Surgical complications included six wound
Quigley et al
1
Patient Standardized Questionnaire
1. Describe current pain compared to before surgery. a None b Pain improved but doesn’t limit activity (work and leisure) c Pain improved but does limit activity (work and leisure) d Same pain as pre-op e Worse pain than pre-op 2. Current Working Situation a Same job as before back problem b Same job but light duty compared to before back problem c Working different job because of back problem d Not working because I am not employed or always stay at home e Not working because of back problems 3. How do you feel about the operation? a Pleased, would go through again b Pleased, but would not go through again c Displeased 4. Describe your analgesic (pain pill) use a Daily narcotic used b Non-daily narcotic use c Anti-inflammatory use only d None Standardized questionnaire administered to patient at 6 month follow-up by mail or phone. Success defined by the following responses to each question: 1 (a or b) and 2 (a or b or d) and 3 (a or b) and 4 (c or d).
and three disc space infections, three CSF leaks with two requiring re-exploration, and two reoperations for recurrent/residual disc herniations yielding a total complication rate of 3.7%. There were no major medical complications, root injuries, or deaths. No patient required a blood transfusion. Long-term follow-up at 6 months was accomplished in 322 patients (86%). Using the strict criteria previously outlined, 239 patients (74.2%) out of the total were deemed a success. Using a univariate analysis, a number of clinical and social factors correlated with outcome (Table 4). However, only two factors remained significant when subjecting the data to multivariate logistic regression analysis: Workman’s Compensation claim and length of symptoms (p , 0.0001 for both). Table 5 provides a
2 L1-2 L2-3 L3-4 L4-5 L5-S1
Levels Operated On 1% 1% 7% 44% 47%
Microdisc Outcome
Surg Neurol 265 1998;49:263–8
Schematic of technique used to judge size of disc herniation in relation to canal size as seen on axial CT or MR images. Herniation size was the ratio of B/A.
1
breakdown of surgical success rates segregated by the two significant factors.
4
Discussion “Success” after a microdiscectomy demonstrates marked variation, with the current study falling within the lower range of reported outcomes. Although this may represent differences in patient population or surgical technique, these explana-
3
Findings at Surgery
Bulge without fragment Contained fragment Free fragment
tions are unlikely. Rather, as noted by Pappas and colleagues [13] as well as Howe and Frymoyer [9], outcome differences are probably best attributed to experimental design, end-point measured, length of follow-up, and the agent used to measure the outcome. The current investigation was constructed accordingly so as to minimize controllable sources of bias. A less sanguine success rate is the predictable end result. Few studies have examined microdiscectomy on a prospective basis. The largest, conducted under the auspices of the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Spine section enrolled 740 patients but obtained follow-up on less than 60% at 12 months [1]. Success, as defined by return to pre-morbid activity and absence of narcotic use, was 77% and 73% determined by the surgeon or patient, respectively. The lumbar discectomy operation (as opposed to microdiscectomy) had been prospectively analyzed by Weir [18] as well as Kosteljanetz et al [10]. Improvement in preoperative pain symptoms (success) was recorded in 73% and 77% cases, respectively, both measured at about 1 year postoperatively. A host of retrospective, often single authored, papers concerning microdiscectomy have been published within the last two decades, documenting good outcome 72–98% of the time [5,6,15,19,20]. Vague definitions of “success,” often surgeon-determined, make comparisons of these efforts with our prospective study problematic. The definition of success employed in the present investigation is one of the most rigorous in the literature and in many ways corresponds to the Prolo scale [14] popularized in recent publications [2,13], but with the addition of patient satisfaction and absence of narcotic use. We selected 6 months
13% 30% 57%
Factors Related to Surgical Success (Univariate Analysis) P
Age Findings (degree herniation) Length of symptoms (.6 mos) Level Occupation (professional) Percent canal compromise Preoperative neuro deficit Sex Surgeon Surgical complications Work-related injury Working at presentation Workman’s Compensation claim
0.34 0.70 0.00001 0.79 0.00003 0.31 0.61 0.14 0.83 0.20 0.0001 0.00017 0.0001
266 Surg Neurol 1998;49:263–8
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Surgical Success by Significant Factors
WORKMAN’S COMPENSATION CLAIM Length of symptoms #6 months .6 months
No 86% 67%
Yes 58% 29%
to determine outcome to balance adequate patient accrual with a meaningfully long follow-up. Abramovitz and Neff [1] had shown 3-month outcome to be nearly identical to that at 12 months, but realized a follow-up rate of only 63.4% at 3 months and 53.5% at 1 year. It was thought, therefore, that for this study 6 months represented a valid endpoint compromise. Although diminishing success rates would be anticipated at longer follow-up, Lewis et al found this effect at 5–10 years to be modest [11]. In addition, the relative contribution of the various factors relating to success should not be altered. Finally, in our mobile society, obtaining follow-up in an otherwise healthy, young population remains a vexing problem, as attested to by the 86% rate we achieved despite extensive efforts. The adverse effect of a Workman’s Compensation claim on outcome after discectomy has been previously noted. Sander and Meyers [16] examined 37 patients with comparable initial injuries undergoing discectomy, half of which occurred off-duty. Return to work averaged 9.3 months for compensable cases versus 4.4 months for those that were not, the difference being significant. In their prospective trial, Abramovitz and Neff [1] also found a compensable injury to be statistically related to surgical failure as did Davis in his retrospective review [2]. Others have found fewer successes among compensation cases, but the differences were either not significant or not analyzed for significance [3,4,7,8]. Risk of surgical failure increased with extended length of symptoms (.6 months) in the study of Dvorak et al [3], although the relationship was not statistically significant. Dzioba and Doxey [4] found just the opposite, volunteering that their findings contradicted intuition. Ours is the first study to provide a statistical correlation between length of symptoms and outcome, but admittedly few authors have sought such a link. Clearly, our data do not suggest the cause for this detrimental effect, whether it is physiologic or just an artifact of patient selection. Owing to the relatively brief follow-up (6 months), it is difficult to gauge the significance of two re-operations for recurrence among 374 pa-
tients (0.6%) as it relates to the long term. Although others have found recurrences in 2–18% of operations, follow-up was considerably longer [11,19,20]. Total wound complication rate (3.2%) is comparable to other recent series such as Davis [2] with 3.1% and Pappas [13] at 8.5%; other series range from 0 –7% [5,6,13,15,17,19,20]. The series is also notable for an absence of post-operative neurologic deficits, bowel/arterial injuries, or mortalities. The length of hospital stay (1.96 days), to our knowledge is the shortest reported. In addition, current critical pathway management programs have further reduced our stay to 1.2 days. Surprising was the absence of the correlation of any technical (surgeon) or physical factors (level, sex, size of herniation, findings at surgery) with outcome. Only Abramovitz and Neff analyzed surgical findings (free fragment) against results and also found no relationship [1]. To our knowledge, no other manuscript has addressed the question of disc size (compared with canal width) and outcome, a factor we also found not correlated with success. In conclusion, microdiscectomy is a safe, minimally morbid procedure with a success rate which is markedly disparate depending only on compensation status and length of symptoms. The authors wish to thank their associates, Drs. Julian Bailes, Richard Douglas, and Jack Wilberger for allowing their patients to be enrolled in this study. They also wish to express their gratitude to Barbara Berry for secretarial support and to Joseph Bloch for providing the illustrations.
REFERENCES 1. Abramovitz JN, Neff S. Lumbar disc surgery: Results of the prospective lumbar discectomy study of the Joint Section on Disorders of the Spine and Peripheral Nerves of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons. Neurosurgery 1991;29:301– 8. 2. Davis RA. A long-term outcome analysis of 984 surgically treated herniated lumbar discs. J Neurosurg 1994;80:415–21. 3. Dvorak J, Gauchat M-H, Valach L. The outcome of surgery for lumbar disc herniation. 1.A 4 –17 years’ follow-up with emphasis on somatic aspects. Spine 1988;13:1418 –22. 4. Dzioba RB, Doxey NC. Prospective investigation into the orthopaedic and psychologic predictors of outcome of first lumbar surgery following industrial injury. Spine 1984;9:614 –23. 5. Ebeling U, Reichenberg W, Reulen HJ. Results of microsurgical lumbar discectomy. Review on 485 patients. Acta Neurochir 1986;81:45–52. 6. Goald HJ. Microlumbar discectomy: Follow-up of 477 patients. J Microsurg 1980;2:95–100. 7. Greenough CG, Fraser RD. The effects of compensa-
Microdisc Outcome
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11. 12. 13. 14.
15. 16. 17. 18. 19. 20.
tion on recovery from low-back injury. Spine 1989;14: 947–55. Haddad GH. Analysis of 2,932 worker’s compensation back injury cases. The impact on the cost of the system. Spine 1987;12:765–9. Howe J, Frymoyer JW. The effects of questionnaire design on the determination of end results in lumbar spinal surgery. Spine 1984;10:804 –5. Kosteljanetz M, Epersen JO, Halaburt H, Miletic T. Predictive value of clinical and surgical findings in patients with lumbago-sciatica. Acta Neurochir 1984; 73:67–76. Lewis PJ, Weir BKA, Borad RW, Grace MG. Long-term prospective study of lumbosacral discectomy. J Neurosurg 1987;67:49 –53. Maroon JC, Abla AA. Microlumbar discectomy. Clin Neurosurg 1985;33:407–17. Pappas CTE, Harrington T, Sonntag VKH. Outcome analysis of 654 surgically treated lumbar disc herniations. Neurosurgery 1992;30:862– 866. Prolo DJ, Oklund SA, Butcher M. Toward uniformity in evaluating results of lumbar spine operations. A paradigm applied to posterior lumbar interbody fusions. Spine 1986;11:601– 6. Sachdev VP. Microsurgical lumbar discectomy: a personal series of 300 patients with at least 1 year of follow-up. Microsurgery 1986;7:55– 62. Sander RA, Meyers JE. The relationship of disability to compensation status in railroad workers. Spine 1986;11:141–3. Silvers HR. Microsurgical versus standard lumbar discectomy. Neurosurgery 1988;22:837– 41. Weir BKA. Prospective study of 100 lumbosacral discectomies. J Neurosurg 1979;50:283–9. Williams RW. Microlumbar discectomy. A conservative surgical approach to the virgin herniated lumbar disc. Spine 1978;3:175– 82. Wilson DH, Harbaugh R. Microsurgical and standard removal of the protruded lumbar disc: A comparative study. Neurosurgery 1981;8:422–7.
COMMENTARY
Dr. Quigley and his colleagues from Allegheny General Hospital have provided their results after lumbar microdiscectomy on a series of patients with single-level disease thought to be compatible with the clinical presentation. The procedures were done between November 1990 and March 1992; outcome was determined in the usual fashion by asking the individual how he or she fared after the surgical convalescence. Approximately one-third of the individuals operated on had pending Workman’s Compensation claims, and that group was segregated as to results, as is commonly done in studying the efficacy of low back surgery. The authors found that in the Workman’s Compensation group, patients who delayed surgery beyond 6 months resulted in approximately a one-third success rate, whereas 9 of 10 noncompensation claimants with a brief history of sciatica did well. Their results in
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these two population groups are not incompatible with previously published reports. All patients submitted to surgery had unilateral disc herniations, had never been previously operated upon, and had failed to improve with the passage of time. There was a single postoperative visit 1 month after discharge. Success was defined as little in the way of residual pain complaints without any adverse effect on work, the absence of any narcotic usage, and patient satisfaction with the outcome. The usual lower two lumbar levels were predominantly involved and there did not appear to be any significant impact on outcome related to the size or degree of the disc herniation. There were six wound infections and three disc space infections. There were also three CSF leaks, which the authors thought was comparable to other series; the use of the operating microscope may, however, be a contributing factor. The authors provide some basic demographic data, but tell us little about the patients. The 70% failure rate in Workman’s Compensation claimants operated on who have had more than 6 months of symptoms is not related to the technical failure of the procedure, but to a number of other factors ranging from childhood abuse to job satisfaction. Compensation claimants operated on 6 months after the onset of symptoms are seven times more likely to have “failed” the surgical procedure than are nonlitigants operated on in less than 6 months. No data are provided as to preoperative management or, perhaps more significantly, postoperative management, particularly in the Workman’s Compensation group, where results tend to be significantly affected by physician attitude and behavior. Patients tend to behave as directed, and a single postoperative visit 1 month after surgery may simply not be adequate in influencing patient behavior. It is generally accepted that very few operative failures are related to surgical misadventures, such as a missed fragment or illdirected operative approach, and that failure to improve in large part is related to behavioral and/or secondary gain issues. This is particularly significant when self-assessment is the only methodology available for determining whether or not an operative procedure on the lower back has been successful. Experienced spine surgeons will find little new information in this report of a prospective analysis of outcome after single-level microdiscectomy. A great deal more attention, in my opinion, will have to be directed at those factors—medical as well as societal—that promote the behavioral abnormalities that seem to represent the basis for continuing
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complaints that have been equated with operative failure. Marshall I. Matz, M.D., FACS Neurosurgeon Chicago, Illinois Prospective studies are important and very few have been performed in the area of spinal surgery and outcome. Surgical outcome as determined by patient functioning and patient determination of outcome as monitored by a disinterested third party are key points in assessing the actual outcome of surgery. The fact that this series demonstrates that a positive outcome in cases with no secondary gain issues, such as socioeconomic issues surrounding Workman’s Compensation cases, is not as high as many series have reported in the past, but is still acceptably high (near 70 – 85% of patients without compensation claims). The rate of positive outcomes in compensation cases in whom
symptoms have been present for more than 6 months is an unacceptably low 29%. This rate is not too different from the rate discovered by Schofferman et al in their study which demonstrated that the psychological profile of the patient with specific reference to childhood psychological trauma played a much more important role in the outcome of surgery than did the selection by a surgeon for surgical intervention. It is noteworthy that in the operative findings in the present series, 13% of patients were found to have a bulge without a fragment. It would be interesting to see the correlation between the outcome in those patients, the length of the symptoms, and the relationship to workman’s compensation cases as a subset. This might be a worthwhile investigation on its own. Ronald P. Pawl, M.D., FACS Neurosurgeon Lake Forest, Illinois