Effectiveness of Microdiscectomy for Lumbar Disc Herniation

Transcription

1 Effectiveness of Microdiscectomy for Lumbar Disc Herniation A Randomized Controlled Trial With 2 Years of Follow-up Heikki Österman, MD,* Seppo Seitsalo, MD, PhD,* Jaro Karppinen, MD, PhD, and Antti Malmivaara, MD, PhD SPINE Volume 31, Number 21, pp , Lippincott Williams & Wilkins, Inc. Study Design. Prospective randomized controlled trial. Objective. To assess effectiveness of microdiscectomy in lumbar disc herniation patients with 6 to 12 weeks of symptoms but no absolute indication for surgery. Summary of Background Data. There is limited evidence in favor of discectomy for prolonged symptoms of lumbar disc herniation. However, only one randomized trial has directly compared discectomy with conservative treatment. Methods. Fifty-six patients (age range, years) with a lumbar disc herniation, clinical findings of nerve root compression, and radicular pain lasting 6 to 12 weeks were randomized to microdiscectomy or conservative management. Fifty patients (89%) were available at the 2-year follow-up. Leg pain intensity was the primary outcome measure. Results. There were no clinically significant differences between the groups in leg or back pain intensity, subjective disability, or health-related quality of life over the 2-year follow-up, although discectomy seemed to be associated with a more rapid initial recovery. In a subgroup analysis, discectomy was superior to conservative treatment when the herniation was at L4 L5. Conclusions. Lumbar microdiscectomy offered only modest short-term benefits in patients with sciatica due to disc extrusion or sequester. Spinal level of the herniation may be an important factor modifying effectiveness of surgery, but this hypothesis needs verification. Key words: lumbar disc herniation, microdiscectomy, spinal surgery, randomized trial. Spine 2006;31: Elective discectomy is regarded as a good treatment option for lumbar disc herniation if severe pain or neurologic deficit persist after 4 to 6 weeks of conservative From the *Orton Orthopaedic Hospital of the Invalid Foundation, Helsinki, Finland; Jorvi Hospital, Helsinki and Uusimaa Hospital District, Espoo, Finland; Finnish Institute of Occupational Health, Helsinki, Finland; and Finnish Office for Health Care Technology Assessment, National Research and Development Centre for Welfare and Health, Helsinki, Finland. Supported by the Finnish Office for Health Technology Assessment at National Research and Development Centre for Welfare and Health; Jorvi Hospital, Helsinki and Uusimaa Hospital District, Espoo, Finland. Acknowledgment date: May 4, First revision date: November 2, Second revision date: December 20, Acceptance date: January 4, The manuscript submitted does not contain information about medical device(s)/drug(s). Institutional funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Address correspondence to and requests for reprints: Heikki Österman, MD, Kaavintie 24 D, Vantaa, Finland; heikki.osterman@ kolumbus.fi therapy. 1 Standard open discectomy and microdiscectomy seem to be equally effective. 2 Wide regional variations in lumbar discectomy rates reflect insufficient knowledge of effectiveness of discectomy. 3 5 Since 1934, when Mixter and Barr reported on the first series of operated patients, only one randomized trial has compared discectomy with conservative treatment. 6,7 The clinical outcome in surgical patients was superior at 1 year, but after 4 years there were no significant differences between the treatment groups. The Weber study remains a classic despite methodologic critique presented, but it has become outdated. 8 In a prospective cohort study, surgical treatment was associated with greater improvement than nonsurgical treatment, although relative benefit of surgery decreased over time. 9,10 We aimed to assess effectiveness of modern microdiscectomy in patients with lumbar disc herniation and symptoms prolonged enough to merit elective operation by current clinical treatment guidelines. Materials and Methods The study was conducted from November 1996 to December 1999 at the Jorvi Hospital (a primary referral center with a catchment population of 220,000 inhabitants situated in Espoo in southern Finland) and at the Finnish university hospitals of Kuopio, Tampere, and Oulu. Patients. Eligible patients had been referred to elective orthopedic consultation because of sciatica. They were 20 to 50 years of age and had to have radiating pain below the knee with clinical findings suggestive of nerve root compression. At the first visit, the patients were informed of the aims and content of the study, and a minimum follow-up of 2 weeks was organized to rule out eventual spontaneous resolution of the symptoms. If the symptoms were not resolving at the follow-up visit, enrollment into the study was considered. Inclusion criteria were 1) below knee radicular pain of 6 to 12 weeks duration at randomization, 2) a CT finding of intervertebral disc extrusion or sequester, and 3) at least one specific physical finding (a positive straight leg raising test 70, muscle weakness, altered deep tendon reflex, or a dermatomal sensory change). Exclusion criteria were 1) previous back surgery, 2) spondylolisthesis, 3) symptomatic spinal stenosis, 4) over 3 months continuous sick leave because of low back pain or leg pain preceding randomization, 5) a condition confounding evaluation of treatment outcomes (vascular claudication, symptomatic osteoarthritis, previous major trauma, diabetic polyneuropathy), or 6) a contraindication to conservative treatment (cauda equina syndrome, progressive neurologic deficit, or intolerable pain). 2409

2 2410 Spine Volume 31 Number One patient assigned to the surgical group was withdrawn because he did not fulfill the inclusion criteria. All the participants gave their written consent in accordance to the Helsinki Declaration. 11 The study was approved by the ethical research committees of all the participating hospitals and by the Finnish National Research and Development Centre for Welfare and Health. Protocol. Patients completed a baseline questionnaire gathering data on demographic characteristics, potential confounders, and factors related to sciatica (Table 1). Clinical examinations throughout the study were carried out by an independent research physiotherapist. Straight leg Table 1. Personal and Clinical Characteristics of Patients With Sciatica of 6 to 12 Weeks Duration at Baseline Surgery Control No. of patients No. of men/women 15/13 19/9 Age (yr) 37 (7) 38 (7) Body mass index (kg/m 2 ) 24 (4) 26 (5) Height (cm) 177 (10) 175 (7) No. of patients with college education 9 6 No. of smokers Work-related features No. currently employed No. with physically demanding work 8 10 No. with mentally demanding work 5 7 Subjective work ability (scale 0 100) 44 (26) 37 (30) Previous pain and disability No. with no previous leg or back pain 11 5 No. with 3 mo of back pain during the preceding year No. with 3 mo of leg pain during 10 9 the preceding year No. with 3 mo sick leave during the 0 2 preceding year Current pain and disability Duration of leg pain (days) 77 (32) 60 (21)* Duration of back pain (days) 94 (47) 73 (32) Intensity of leg pain (scale 0 100) 61 (20) 57 (21) Intensity of back pain (scale 0 100) 53 (25) 47 (28) Duration of current sick leave (days) 36 (26) 46 (37) Oswestry Low Back Disability Score 39 (15) 39 (14) Health-Related Quality of Life15D 0.83 (0.07) 0.84 (0.06) DEPS Risk of Depression 10 (5) 8 (5) Modified Schober (cm)# 19 (2) 20 (2) Lateral bending (cm)** 16 (5) 16 (5) No. with Waddell signs No. of SLR positive SLR elevation angle ( ) 46 (14) 43 (15) No. with muscle weakness No. with dermatomal sensory alteration No. with L4 L5 level herniation No. with L5 S1 level herniation No. with right-/left-sided symptoms 10/18 13/15 Values are mean (SD) unless stated otherwise. SLR Straight leg raising test, elevation angle given for patients with a positive test result. *P mm VAS (Visual Analog Scale) on a scale 0 (unable to work) to 100 (best possible work ability). 100 mm VAS (Visual Analog Scale) on a scale 0 (no pain) to 100 (worst possible pain). Oswestry scale 0 to 100, increasing score indicates greater low back pain related disability. 15-D scale 0 to 1.0, increasing score indicates better subjective general health and function. DEPS scale 0 to 30, increasing score indicates greater risk of depression. #Modified Schober (15 cm). **Right and left bendings measured, the more limited value reported. raising was recorded with a goniometer to the nearest 5. Lumbar flexion (modified Schober 15 cm) and lateral bendings were measured. Great toe and ankle extension strengths were estimated on a standard scale from 0 to 5. Deep tendon reflexes and sensation were tested and Waddell tests performed. 12 The physiotherapist encouraged early physical activity within pain limits and gave instructions on isometric muscle exercises. Plain radiographs and a CT scan of the lumbar spine were obtained. Disc findings in the CT were graded as normal, protrusion, extrusion, or sequester. A research assistant at the National Research and Development Centre for Welfare and Health performed randomization based on computer generated random blocks of variable size and placed the assignments in sealed opaque envelopes with running numbers. Every participating center had its own series of envelopes. Randomization took place after the baseline examination and questionnaires were completed. The treating physician phoned the central office, gave the identification data, and received the concealed treatment allocation. A microdiscectomy by a spinal orthopedic surgeon was performed within 2 weeks of randomization in the surgical group. 13 The operation was carried out under general anesthesia in a genupectoral position with fluoroscopic control of the spinal level before draping. The patients were usually discharged from the hospital on the second or third postoperative day. Sick leave and analgesia were prescribed according to individual requirements. Surgical patients were advised to continue with isometric exercises while waiting for the operation and also after discharge from the hospital. At follow-up visits, this group received active physiotherapeutic instructions, including stretching, bending, and muscle strengthening exercises. Passive forms of treatment were not recommended. The control group received similar physiotherapeutic instructions initially and continued with isometric exercises after randomization. At follow-up visits, as with the surgical group, activity was encouraged. Patients in the control group were informed of symptoms meriting operation, and they were advised to contact the treating physician if the symptoms should get worse. Clinical follow-up took place at 6 weeks, 3 months, and 1 year. At 6 months and 2 years, the patients received a mailed questionnaire. Outcome Measures. Leg pain intensity was the primary outcome measure. Secondary outcomes measured at every follow-up included back pain and work ability (100 mm visual analog scales [VAS]), a generic health-related quality of life measure 15D, and the Oswestry Low Back Disability Score. 14,15 Risk of depression was assessed at 6 weeks, 3 months, 1 year, and 2 years. 16 Satisfaction with treatment (100 mm VAS) was assessed at every follow-up. Global assessment of healing was recorded at 6 weeks, 3 months, and 1 year. Clinical examinations similar to the baseline examination took place at 6 weeks, 3 months, and 1 year. Statistical Analysis. Power calculations to obtain a power of at least 0.80 at a significance level of 0.05 were done assuming a standard deviation of 20 mm for leg pain intensity (the primary outcome measure). Considering a clinically significant difference in pain intensity to be 10 or15 mm would necessitate a sample size of 80 to 56 patients, respectively. Change in outcome measures from baseline during the entire follow-up was assessed with a general linear model for

3 Microdiscectomy for Lumbar Disc Herniation Österman et al 2411 repeated measures (SPSS, version ). The baseline measurement of the outcome variable was entered as a covariant into the model, which included group and time effects and their interaction. Efficacy variables were analyzed on an intentionto-treat basis. The last observation was carried forward for patients who did not complete the study or who had missing values at follow-up. Differences between the groups at different times of follow-up were checked for with the Mann-Whitney U test, 2 test, or Fisher s exact test. Additional analyses included an on-treatment analysis according to the actual treatment and subgroup analyses based on gender, age, intensity of sciatica at baseline, and spinal level of disc herniation. Differences between subgroups were tested with one-way analysis of variance using the Bonferroni method for multiple comparisons. Results Patients The final study population consisted of 56 patients (Figure 1). The baseline data for patients recruited at different hospitals did not differ. Twenty-eight patients were randomized to the surgical group and 28 to the control group. The groups were similar in all baseline characteristics except for the duration of sciatica, which was greater in the surgical group (Table 1). The follow-up information at 2 years was obtained for 50 patients (89%) (Figure 1). Adherence and Cointerventions All the 28 patients in the surgical group underwent surgery. There were two reoperations because of recurring symptoms on the same side and level. The reoperations took place 6 weeks and 19 months after initial surgery. Eleven patients in the control group crossed over to surgery eventually. Indications for surgery were unbearable continuing pain (in 7), recurring symptoms after initial improvement (in 3), and progressive motor weakness (in 1). The local study orthopedist made the decision Figure 1. Patient flowchart. about operation. Three operations were performed before the 6-week follow-up (unbearable pain), 4 between the 6-week and 3-month follow-up (unbearable pain in 2, 1 progressive motor weakness, 1 recurrence), 3 between the 3-month and 6-month follow-up (unbearable pain in 2, 1 recurrence), and 1 between the 6-month and 1-year follow-up (recurrence). Fifteen patients in the control group and eight in the surgical group reported having had additional physical therapy during the follow-up. The average number of visits was 12 (range, 1 34) in the control group and 9 (range, 1 25) in the surgical group. One patient in the surgical group had urosepsis needing intravenous antibiotics and prolonged stay in the hospital. No other operative complications were noted. Patient and Physician Expectations Because of the surgical intervention, it was not possible to blind the patients or the treating personnel. To assess any possible preferences toward the treatments, both the patients and the physicians were asked immediately after randomization on a scale from 0 to 6 how confident they were that the treatment would help (0 no confidence, 6 maximal confidence). In addition, patients were asked to what extent they believed to become symptomfree and able to work eventually (6 indicating complete disappearance of symptoms and full recovery of work ability). Patients median expectations on getting help, becoming symptom-free, and recovering work ability were 6.0, 5.0, and 6.0 in the surgical group and 5.0 (P 0.041), 5.0, and 5.0 in the control group. Physicians median expectations on the treatment effect were 5.0 in the surgical group and 3.5 (P 0.001) in the control group. Outcomes The repeated measures model showed no statistically significant differences between the groups for leg pain intensity, back pain intensity, Oswestry disability, healthrelated quality of life 15D, work ability, or risk of depression (Table 2). At each follow-up, the surgical group fared better, but the differences in group means were statistically significant only for leg pain intensity at 6 weeks and for satisfaction with treatment at 6 weeks, 6 months, and 2 years. At 6 weeks, 5 patients in the surgical group reported complete recovery (Table 2). Lumbar flexion and lateral bending, straight leg raising positivity, and muscle weakness displayed no differences between the groups (Table 2). Additional Analyses The on-treatment analysis compared all the operated patients (28 initially allocated to surgery, 11 crossing over from the control group) with patients who stayed in the control group throughout the follow-up. There were no statistically significant differences between the ontreatment groups. In the subgroup analyses, men and women did not differ from each other, neither were there any differences

4 2412 Spine Volume 31 Number Table 2. Outcomes of Microdiscectomy at 6 Weeks, 3 and 6 Months, and 1 and 2 Years After Randomization Outcome Group Baseline 6 Weeks 3 Months 6 Months 1 Year 2 Years Difference in Group Means (95% CI) Leg pain Surgery 61 (20) 12 (20)** 9 (16) 9 (20) 6 (11) 6 (11) Control 57 (21) 25 (27) 16 (25) 18 (29) 9 (19) 15 (24) 9 ( 1 to 20) Back pain Surgery 53 (25) 21 (25) 15 (20) 13 (22) 19 (25) 11 (18) Control 47 (28) 28 (24) 22 (23) 20 (28) 17 (23) 21 (27) 7 ( 3 to 17) Oswestry Low Back Disability Score Surgery 39 (15) 16 (16) 8 (11) 8 (12) 10 (13) 6 (9) Control 39 (14) 22 (16) 14 (14) 12 (15) 11 (14) 11 (16) 3 ( 4 to 10) 15D Health-Related Quality of Life Surgery 0.83 (0.07) 0.92 (0.07) 0.94 (0.06) 0.95 (0.06) 0.95 (0.05) 0.95 (0.08) Control 0.84 (0.06) 0.89 (0.09) 0.91 (0.09) 0.90 (0.13) 0.94 (0.07) 0.93 (0.12) 0.03 ( 0.01 to 0.07) Subjective work ability Surgery 44 (26) 68 (27) 84 (14) 87 (18) 82 (26) 89 (16) Control 37 (30) 63 (32) 70 (31) 75 (30) 81 (27) 79 (28) 5 ( 7 to 18) DEPS Surgery 10 (5) 6 (5) 3 (5) NA 3 (4) 3 (4) Control 8 (5) 6 (5) 3 (4) NA 3 (4) 4 (6) 1 ( 1 to 3) Forward bending (cm) Surgery 19 (2) 19 (2) 20 (1) NA 21 (2) NA Control 20 (2) 20 (2) 20 (2) NA 21 (2) NA 0.1 ( 0.8 to 0.6) Lateral bending (cm) Surgery 16 (5) 18 (4) 19 (3) NA 19 (3) NA Control 16 (5) 18 (4) 17 (4) NA 18 (4) NA 0.7 ( 1.0 to 2.4) SLR positivity (n) Surgery NA 1 NA Control NA 3 NA Muscle weakness (n) Surgery NA 6 NA Control NA 6 NA Patients reporting full recovery Surgery NA 5* 5 NA 7 NA Control NA 0 4 NA 5 NA Satisfaction with treatment Surgery NA 93 (10)** 93 (11) 88 (22)** 89 (20) 89 (19)* Control NA 79 (23) 88 (17) 74 (28) 85 (20) 79 (28) Values are mean (SD) unless stated otherwise. NA not assessed; CI confidence interval. Difference in group means is expressed as surgery minus control and indicates the difference in mean improvement from baseline during the follow-up analyzed with repeated-measures model and adjusted for baseline values. Between-group differences at different times of follow-up analyzed with Mann-Whitney U test, ² test, or Fisher s exact test and statistically significant differences reported. *P 0.05, **P See Table 1 for definition. No. of patients reporting full global recovery. 100 mm VAS (Visual Analog Scale) on a scale 0 (completely dissatisfied) to 100 (as satisfied as possible). when patients with more than median leg pain at baseline (40/100 mm VAS) were compared with patients with less than median pain. There were, however, significant differences associated with the age of the patients and the level of disc herniation. Surgical treatment was associated with less leg pain, less disability, and improved generic health-related quality of life in patients older than median (37 years). Surgical treatment was also associated with statistically significantly improved leg and back pain, Oswestry disability, generic health-related quality of life, and subjective work ability when the disc herniation was at L4 L5. For disc herniations at L5 S1, however, there were no significant differences in these outcomes. Patients with a primary discectomy both at L4 L5 and L5 S1 had good results at 2 years (average leg pain, 2 4 and 11 16, respectively). Good results were likewise seen at 2 years in both L4 L5 and L5 S1 patients who had remained in the control group (average leg pain, 6 11 and 6 9, respectively). Crossover patients pain and disability at 2 years were significantly worse when the herniation was at L4 L5 (7 patients, average leg pain, 41 35) but not when it was at L5 S1 (4 patients, average leg pain, 5 10). Discussion The repeated measures model displayed no statistically significant differences in clinical outcomes between the surgical and the control group over the entire 2-year follow-up. Both groups improved significantly over time. However, at 6 weeks, discectomy patients had less leg pain and 5 of 28 patients reported full global recovery, which suggests a faster initial recovery after discectomy. Our results suggest a rather small benefit from surgery in comparison to other reports. 7,9,10 The Maine Lumbar Spine Cohort Study noted a greater improvement with surgical than nonsurgical management of disc herniation. On the other hand, the cohort of surgical patients had more severe symptoms initially, and they may be expected to gain more from surgery. 9,10 The only randomized trial comparing discectomy and conservative management reported statistically significantly better 1-year results after discectomy. 7 The outcome measure in the study is problematic, however. Weber had a single outcome measure composed of several parameters of which patient satisfaction was of substantial significance. 7 Only satisfied patients could be graded as good or fair. This kind of outcome is potentially biased if surgical patients, as well as treating physicians, have more favorable expectations about their treatment as we noted in our study. Surgical patients were better satisfied with their treatment even if the clinical outcomes did not differ, which seems to reflect more optimistic expectations. Our results must be interpreted with caution because of our small sample size and the large number of crossover operations. Because of the slow rate of recruitment, enrollment of patients was discontinued at a stage when

5 Microdiscectomy for Lumbar Disc Herniation Österman et al 2413 the study sample was big enough to show a difference of 15 mm in pain intensity. It is possible that a smaller difference may have existed and gone unnoticed. However, minimal clinically important difference in pain on visual analog scale for lumbar surgery patients is considered to be 20 mm. 17 Actual differences noted in this study were less than 15 mm; hence, increasing the study sample would probably have contributed little to the clinical significance of the findings. Ten patients in the control group crossed over to surgery because of unrelenting or recurring pain, and one because of progressive motor weakness. The crossover patients are problematic methodically but in a setting like this they are hard to avoid. Some of the patients may have had herniations poorly suited to conservative management, whereas in others more subjective factors may have been important. Most of the operations were performed because of unrelenting pain, which is a highly subjective indication. The reason for the operation notwithstanding, the fact remains that 40% of the control group had surgery in the end. With the intention-to-treat analysis, these patients were analyzed belonging to the control group, which might modify the results. In an effort to control for this, we performed an additional on-treatment analysis where all the discectomy patients were compared with patients remaining in the control group. The ontreatment analysis did not show any statistically significant differences between the groups, which suggests that the crossover operations probably did not have a major effect on the results. Reasons for crossover operations remain controversial, but we think that at least in some cases spinal level of the herniation may be important. According to the subgroup analysis operative treatment resulted in a superior outcome at L4 L5, whereas no difference was noted at L5 S1. The worst outcome at 2 years was seen in the 7 crossover patients with a L4 L5 herniation. These patients may have had a worse prognosis right from the start, hence the poor response to any care. On the other hand, it is possible that they were poorly suited to conservative treatment and the delay in their operation may have contributed to the poor result. The better surgical result at L4 L5 is, to our knowledge, a new finding that needs to be verified in further studies. Anatomically and biomechanically, the two motion segments are different and biologically it is plausible that herniations at L4 L5 and L5 S1 could be separate entities. Spinal level may be a more important factor than previously thought, and the issue merits more research. Patients older than median (37 years) seemed to benefit more from surgery. This finding may be independent, but it may also be linked with spinal level. L4 L5 herniation patients were older than L5 S1 patients. Consequently, the apparent benefit from surgery in the older patients may simply reflect the larger number of L4 L5 herniations in this age group. The Maine Study suggested that patients with more severe symptoms may benefit more from surgery. 9,10 We excluded patients with intolerable pain as their randomization would have been unethical; thus, our study results are applicable only to patients with tolerable pain. On the other hand, this group of patients is precisely the one where clinical decision-making is often difficult and good-quality evidence needed. Within this context, our subgroup analysis suggested that surgical patients with more than median leg pain did not differ from conservatively treated patients or patients with less pain. The randomized setting and an acceptable rate of follow-up can be counted as merits of this study. The patients enrolled from elective orthopedic outpatient clinics all had an indication for surgery and their baseline characteristics compared well with previously published operative series. 18 Our study protocol was designed to compare microdiscectomy with natural course of disc herniation; therefore, the conservative treatment regimen was similar in both groups. It has to be noted, however, that the patients in our study were fairly young and they could not have been on a sick leave for more than 3 months. Consequently, our findings must be regarded with caution when dealing with older patients or patients receiving Workers Compensation for a longer period of time. Conclusion Lumbar microdiscectomy may be associated with a more rapid initial recovery in patients with sciatica due to disc extrusion or sequester and a history of less than 12 weeks. Otherwise, benefit from surgery is rather modest during the first 2 years and conservative therapy is a reasonable option for these patients. Spinal level of the herniation may be an important factor modifying effectiveness of surgery, but this hypothesis needs verification. Key Points Effectiveness of microdiscectomy was assessed in lumbar disc herniation patients with 6 to 12 weeks of symptoms but no absolute indication for operation. Discectomy seemed to be associated with a more rapid initial recovery. Over the 2-year follow-up, there were no clinically significant differences between discectomy and conservative treatment in leg or back pain intensity, subjective disability, or health-related quality of life. Spinal level of the herniation may be a factor of importance in modifying effectiveness of surgery. Acknowledgments The authors thank our research assistants Seija Puro and Satu Kerppilä at the National Research and Development Centre for Welfare and Health, our research physiotherapist Kirsti Pasanen, research nurse Eija Merta-Saari in Jorvi Hospital, and orthopedic surgeons Veli Turunen (Kuopio University Hospital), Kimmo Vihtonen (Tampere University Hospital), and Timo Niinimäki (Oulu University Hospital) for their contribution, as well as all the personnel involved with the study at the participating hospitals.

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