Lumbar disk herniation (LDH) is the pathologic condition most commonly responsible for radicular pain, and the condition for which lumbar surgery is performed most frequently. The first surgeons who performed excision of a ruptured intervertebral disk for LDH with knowledge of the pathophysiological causality between LDH and radicular pain were Mixter and Barr1 in 1934. Since this time, LDH is considered to be a surgical issue.
However, since Weber2 published his landmark paper in 1983, the pendulum with regard to the best treatment for LDH has shifted from surgery toward nonsurgical treatment options. In this prospective study, 126 patients were chosen from a series of 280 cases with LDH shown by myelographic assessment. These 126 patients were allocated randomly to surgical (60 patients) or conservative (66 patients) treatment. At 1-year follow-up, patients operated on for LDH showed better results compared to their conservative peers and the same was true at 4-year follow-up, but the difference between the 2 groups was no longer statistically significant. Interestingly, there was no difference between the 2 groups after 10 years. This study thus indicates that there is no significant difference at medium- and long-term follow-up between surgical and nonsurgical treatment for LDH.
Contrary, the long-term outcome of the prospective Maine Lumbar Spine Study revealed that surgically treated patients with LDH had more complete relief of leg pain and improved function and satisfaction compared with nonsurgically treated patients over a 10-year period.3
These 2 papers are symptomatic for the current controversy with regard to the best treatment of LDH, since their results vary widely suggesting that there is no general agreement on the preferred treatment method, or at what stage of the illness various invasive treatments should be initiated. This also might be the main reason why marked differences in the rate of surgery for LDH exist among western countries,4 reflecting distinct differences in attitudes of both physicians and patients. For instance the rate of back surgery in the United States was at least 40% higher than in any other country and was more than five-fold of that in England and Scotland.4 Moreover, countries with high back surgery rates also had high rates of other discretionary procedures such as tonsillectomy and hysterectomy.
When comparing surgical and nonsurgical treatment options the obvious advantage of conservative treatment is the absence of complications related to surgery. Any surgical procedure, no matter how carefully performed, carries risks. Common complications in diskectomy include wrong level surgery, missed pathology and/or retained herniation, dural leakage, epidural venous bleeding with epidural hematoma, iatrogenic instability with residual back pain, infection/diskitis, thromboembolism and postoperative epidural fibrosis.5 The reported intra- and postoperative complication rate varies between 3% and 25% for standard nucleotomy and between 2% and 11% in microsurgical diskectomy.6-10 An argument for nonoperative treatment is also the rate of reoperations after diskectomy. With regard to published data with sufficient follow-up and sound number of patients, the revision rate after diskectomy varies between 6% and 15% (Table 1).9,11-13
With these figures in mind there is no doubt that surgery should be restricted to patients who will not benefit from nonoperative treatment. However no general agreement exists that criteria support or justify indications for surgery.
The purpose of this article is to analyze diagnostic findings, which are often considered as reliable criteria for decision-making in patients with LDH. In particular the significance of the following diagnostic findings is analyzed in detail: (1) cauda equina syndrome, (2) paresis in general, (3) magnitude of paresis, (4) progression of paresis, (5) duration of paresis, (6) paralysis, (7) radicular pain, and (8) type of herniation.
At the end of each section an attempt was made to grade the level of available evidence and to conclude with a recommendation stating if there is good evidence, no evidence or poor support for a particular treatment. This assessment was based on the Scottish Intercollegiate Guidelines Network (SIGN) criteria,14 classifying 8 levels of evidence (1++, 1+, 1-, 2++, 2+, 2-, 3, and 4) as well as 4 grades of recommendation (A, B, C, and D) (Table 2).
Cauda Equina Syndrome
Cauda equina syndrome, which occurs in approximately 2% of patients with LDH,15 is thought to be the main absolute indication for a surgical intervention in patients with LDH.15-19 The clinical features can include low-back pain, unilateral or bilateral sciatica, saddle anesthesia, and motor weakness in the lower extremities that may progress to paraplegia with bowel and bladder incontinence.20-23
Ahn et al24 were the first to conduct a meta-analysis on the surgical outcome in patients with cauda equina syndrome. Forty-two articles met the criteria for inclusion, resulting in a total of 322 patients. In those studies, cauda equina syndrome was always secondary to LDH. Articles referring to patients with cauda equina syndrome caused by spinal stenosis, tumor, hematoma, fracture, infection, or ankylosing spondylitis were excluded from the meta-analysis. All patients had been treated with surgical decompression. Patients who refused surgery were excluded. Overall, no difference was noted in the outcome between patients treated within 24 hours after onset of cauda equina syndrome and those treated between 24 and 48 hours after onset of symptoms. However, there was a significant advantage in treating patients within the first 48 hours after clinical manifestation of cauda equina syndrome compared to a period longer than 48 hours, with improved outcome regarding the resolution of sensory and motor deficits as well as urinary and rectal function. Interestingly, preoperative chronic low-back pain was associated with continuing limited urinary and rectal function. Preoperative rectal dysfunction was associated with a worsened outcome regarding urinary continence as well as older patients were less likely to fully regain sexual function after surgery. Nevertheless, Kohles et al25 repeated this meta-analysis and found a different outcome in patients operated within 24 hours and those treated between 24 and 48 hours after onset of symptoms. They stated: “We conclude that a flawed methodology and misinterpretation of results are reported, understating the value of early surgical intervention.
Timing of surgery in patients with cauda equina syndrome due to LDH remains controversial even when considering recent evidence from McCarthy et al.26 These authors reported about the results of 42 patients with evidence of sphincter disturbance undergoing rapid surgery. Twenty-six patients underwent surgery within 48 hours after onset of sphincter symptoms, 5 of whom within 24 hours. Acute onset of sphincter symptoms and time to surgery did not influence the outcome after 2 years. In their conclusion the authors report that “in patients with cauda equina syndrome, the duration preoperatively and the speed of onset do not appear to influence the outcome 2 years postoperatively. Based on the Short Form 36 Health Survey Questionnaire, Low Back Outcome Score, and Oswestry Disability Index scores, patients who have had cauda equina syndrome do not return to a normal status.”26 However, the explosiveness of this entity is also emphasized by the authors since they report that the results of cauda equina syndrome studies could have significant medicolegal ramifications and that they advocate decompression at the earliest safe opportunity and would advise caution to the reader when interpreting the results of studies, including their own.
Apart from these recent findings controversy remains—in the clinical setting —with regard to the timing of decompression, especially because some reports show that delayed surgery may also provide satisfactory results.15,16,27-30 However, the main problem is the limited number of patients studied because of the rarity of this disorder. Most of the available data provide limited evidence because of an inability to achieve statistical significance; therefore, no study has clearly shown which factors influence outcome. Moreover, different types of cauda equina syndrome have been described (complete versus incomplete or rapid versus slow onset)28,31 and many papers on cauda equina syndrome cohorts do not specifically report about diagnostic criteria. With these limitations, the diagnosis of cauda equina syndrome is obvious in some patients and obscure in others.
A grade “A” recommendation for surgery cannot be given in patients with cauda equina syndrome secondary due to LDH because randomized trials are missing (and might not be ethical to undertake with our current knowledge). In addition, no final recommendation can be given with regard to timing of surgery, especially if surgical decompression should be performed within the first 24 or 48 hours after onset of symptoms. The main problem is that the 2 identical studies conducted by Ahn et al24 and Kohles et al25 with 2++ level of evidence came to totally different conclusions. Therefore, a grade “B” recommendation is not possible, neither for 24 hours nor for 48 hours. Despite these controversial results the authors of this article believe that an emergency operation for cauda equina syndrome is mandatory until proven otherwise.
Paresis in General
In addition to cauda equina syndrome, paresis is also regarded as a red flag symptom in patients with LDH. Therefore, some authors consider surgery as the therapy of choice if the mechanical pressure on the root can be relieved immediately after its appearance.32 But does paresis really justify surgery?
Some authors report in retrospective studies superior results by means of better motor recovery following surgery. Bloch-Michel et al33 reported a recovery/improvement rate of the paresis in 64% of their surgically treated patients. In contrast the recovery/improvement rate was only 56% after nonoperative treatment. The same tendency was reported by Weigert32 with 77% motor recovery/improvement in surgically treated patients compared to 53% in nonsurgically treated patients. However data exist that display contrasting findings. De Seze et al34 reported in a retrospective study about a lower recovery rate in patients treated operatively (54% versus 63%). But none of these studies was prospective and randomized and included any meaningful statistical analysis. Moreover these studies did not specify clear criteria for recovery.
In contrast to the studies mentioned before, the prospective study of Weber2 reported a similar recovery rate of 70% in surgically and nonsurgically treated patients. However, this study also has limitations, since both treatment groups do not represent a true randomized population. Patients who presented with significant symptoms of radiculopathy were excluded from the randomization process. Another problem is that neither criteria for recovery and improvement were defined nor the magnitude of paresis was considered. However, the best available evidence is in this study, since this is the only clinical trial with a “1-” level of evidence. Therefore, based on this study, the recommendation that clinical presentation of paresis in general does not constitute an indication for (early) surgery can be classified as “B.”
Magnitude of Paresis
Assuming that paresis in general does not justify early surgical intervention, it is also questionable if the magnitude of paresis might be indicative for early surgery.
Dubourg et al35 attempted to address this problem in a prospective multi-center study. They enrolled patients with diskogenic sciatica and paresis that had been present for <1 month and was rated <3 on a 5-point scale. Bilateral testing of 11 lower limb muscles or muscle groups was performed. Recovery and improvement were defined by pain not exceeding 20 mm on a visual analog scale or <50% of the initial pain score and a score of either 5 (recovery) or 4 (improvement) for the weakest muscle at inclusion. At 6-month follow-up, 14 of 25 patients (56%) treated nonoperatively had an improvement of the paresis and 10 (40%) even a recovery. Seventeen of 32 patients (53%) treated by diskectomy had an improvement and 8 (25%) showed signs of recovery.35 However, the major weakness of this study is the short follow-up of 6 months. However, Jonsson and Stromqvist36 reported a neurological recovery in half of their patients 2 years postoperatively, with the main part of this improvement occurring within 4 months postoperatively.
Eysel et al37 retrospectively analyzed the neurological recovery of 240 patients with radicular paralytic symptoms with regard to the intensity of the paresis, which had been treated surgically. The degree of the intensity of the paresis was a good prognostic indicator for the postoperative course. Paresis grade 3 and 4 receded in >70% of the cases within 6 months, whereas the recovery rate in paresis grade 2 was 40%, and in total paresis no complete neurological recovery was registered.
Although several factors could have affected the results of Dubourg et al,35 such as lack of randomization, missing evaluation of the intra- and interobserver reproducibility of muscle testing and the fact that patients undergoing surgery had a longer duration of sciatica, it is the only article (to the best knowledge of the authors) that addresses the parameter of paresis magnitude in surgically and nonoperatively treated patients and forms the basis for further randomized studies.
Based on the study of Dubourg et al35 with its “2-” level of evidence, the magnitude of paresis may not be a reliable indicator for surgical intervention since the neurological outcome did not differ between surgical and nonsurgical treatment, regardless of the magnitude of the paresis.
Progression of Paresis
In addition to paresis and its magnitude, another indicative parameter for surgical intervention, which was proposed in the literature, is that of the progression of paresis.
Eysel et al37 attempted to analyze in a retrospective study prognostic criteria of diskogenic paresis in 240 patients with radicular symptoms. Although no analysis was conducted with regard to the progression of paralytic symptoms itself, at the end of their paper the authors stated: “In the case of deterioration of the paresis, an operation should be performed quickly.”37
The same recommendation was given by Marshall38 in his annotation to the article of Mariconda et al.39 Although this study did not clearly address paresis progression,39 Marshall38 reported: “Except for the cauda equina syndrome and with clearly evolving motor weakness, unrelenting radicular pain (sciatica and cruralgia) must be considered to be the main indication for diskectomy.”38 However, since there is no clear evidence for this recommendation it can be considered as expert opinion only (level of evidence: 4; grade of recommendation: “D”).
Duration of Paresis
Although published data support the finding that paresis magnitude is not of relevant importance with regard to the treatment, the duration of paresis until surgery might be of crucial importance for the extent of neurological recovery.
Therefore the question in the article by Eysel et al37: “Should a patient with an acute paresis be treated surgically in an emergency procedure or is there any time left for a conservative attempt?” is of substantial interest in the clinical setting. With regard to the published data in cauda equina syndrome one could argue that the interval between neurological impairment and subsequent surgery should have a considerable effect on motor recovery.
Knutsson40 addressed this problem in 110 patients with paresis of the extensor of the great toe. Postoperatively the paresis persisted in 26 patients, but the time from the first occurrence of the paresis did not influence the motor recovery. Eysel et al37 also analyzed the neurological recovery of 240 patients with radicular paralytic symptoms with regard to the time elapsed since the occurrence of the paresis. The time that elapsed since the occurrence of the paresis did not show any significant influence on motor recovery.37
An influence of the time interval between onset of the paresis and surgical treatment was reported by Weigert.32 Fifty-eight of 344 patients treated surgically for L5 or S1 root compression had a paresis preoperatively. In 77% of the patients complete recovery was registered postoperatively. Regarding the duration of paresis there was no influence within the first year (recovery rate 80%) whether the paresis had existed for 1 month or 1 year, respectively. Only in patients with a duration of the paresis longer than 1 year the recovery rate worsened (65%).32
Although the duration of paralytic symptoms had no influence on the amount of motor recovery postoperatively in their study group, Woertgen et al41 reported that duration of paralysis is highly valuable as a general predictive factor with regard to the clinical outcome after lumbar disk surgery. They assessed in a prospective study 121 patients after lumbar disk surgery with 4 different outcome measures (Prolo Scale, Low Back Outcome Score, Pain Grading Scale and Quality of Life) and concluded that the preoperative duration of paresis seems to be a good general predictive factor for poor outcome.41
Summarizing the available data, there is no striking evidence that the duration of paresis influences the amount of neurological recovery following surgical intervention when considering paresis duration up to 1 year (level of evidence: 2+ / 2-; grade of recommendation: “B-C”).
When analyzing the prognostic value of paresis with regard to different treatment options, one possible rationale could be that paralysis instead of paresis is a good indicator for surgical intervention.
When searching for evidence, it is important to remember that no comparative study ever has been performed, comparing surgical and nonsurgical treatment in diskogenically induced paralysis. This may be based on the perception that paralysis is a severe complication of LDH, which needs to be addressed surgically. Therefore it seems neither practical nor ethical to undertake such a prospective randomized clinical trial.
The second problem is that a precise definition of paralysis has not been established yet in the literature. The classification of paralysis incorporates, depending on the study group, severe motor loss (“fair” or less by manual muscle test [“fair” means muscle strength by which complete range of motion against gravity can be obtained]) up to marked extensor weakness, especially painless foot drop. Therefore the comparison of different studies is limited.
In the aforementioned study of Dubourg et al35 only 6 patients had sciatic diskogenic paralysis (rated 0 on a 5-point scale).35 Three of these patients were treated surgically and another 3 nonsurgically. But the results for these few patients were not reported, which prevents any clinically meaningful interpretation. When considering the study of Eysel et al,37 only 6 of 240 patients had a paralysis that did not show a complete resolution at latest follow-up. Due to the fact that only a small number of patients had paralysis and no control group was established, this study also does not provide evidence for the pending question, if surgical intervention might be more effective compared to conservative measures in paralysis.
The prognosis in complete paralysis after surgical intervention has been evaluated by Andersson and Carlsson.42 After exclusion of cases with cauda equina syndrome, they found evidence of foot drop in 65 patients following 372 operations for LDH over a 10-year period. The paralysis persisted in 50%, and the outcome was not related to the onset of symptoms, the time interval to the intervention, and the age of the patients.42 However, the main shortcoming of this study is the lack of a control group (with conservative treatment). Considering the basic problem of paralysis definition the results of Andersson and Carlsson,42 with only 50% of paralysis persistence, might be an underestimation, when assuming that patients with marked extensor weakness (including complete foot drop) were also defined as complete paralysis and inclusion criteria were not exclusively complete “painless-paralysis,” which means lack of any visible or palpable muscle contraction.
The problem of definition and interpretation of paralysis is highlighted in an annotation of Marshall38 to a publication of Mariconda et al.39 In his final conclusion Marshall38 reported: “Marked extensor weakness, including complete foot drop, occurs in 5% to 10% of cases, and there is a potential for recovery in approximately half, with or without treatment. In those with severe extensor weakness, especially painless foot-drop, diskectomy does not improve the outcome.” Discrimination between foot drop and severe extensor weakness may not be possible or reasonable.
No final recommendation can be given on the effect of surgical intervention compared to nonsurgical treatment in paralysis due to LDH, since no study with at least 2-level of evidence already addressed this problem. Nevertheless, there is no absolute indication for surgery of painless paralysis.
With regard to radicular pain general agreement exists that patients who undergo operative treatment will have more rapid resolution of symptoms, especially those who have an acute onset of severe sciatica.2,3,43 Moreover, patients treated operatively have a shorter recovery period, return to work in less time, and overall, place less of a financial and social burden on the health care system when compared with patients treated nonoperatively.5
Summarizing the available evidence, there is a 1+/ 2++ level of evidence that surgical treatment will provide a more rapid resolution of symptoms compared to nonsurgical treatment (grade of recommendation: “B”).
When analyzing the prognostic value of radicular pain, more questions need to be addressed: “When conservative treatment for symptomatic LDH is considered, what is a reasonable period for such measures? Is there a time limit when the results of subsequent surgery will deteriorate?”
In his landmark paper, Weber2 proposed a 3-month period to be sufficient to decide against surgery in four-fifths of the 60% conservatively treated patients with good and fair results. Nevertheless, he also reported that if all patients with doubtful surgical indications had to wait 3 months before a decision was made, 40% would spend this time in a more or less painful condition with possible psychosocial consequences. Therefore, Weber2 recommended better informing patients to enable them to participate in the decision-making process at an earlier stage. The 3-month time limit in the study by Weber2 is based on the sound personal experience of the author, but not proven by his data. The same is true for the 2- to 3-month period advocated by Postacchini,43 since he did not analyze the outcome with regard to the time until surgery.
In contrast, Nygaard et al44 prospectively analyzed 132 consecutive patients with regard to the prognostic value of preoperative leg pain. The authors concluded that leg pain lasting >8 months correlates with an unfavorable postoperative outcome and with a high risk of not returning to work. Ng and Sell45 proposed a threshold for the duration of sciatica of 12 months. Some of the reported thresholds of the duration of sciatica, which is associated with poor outcome, are listed in Table 3.
The different values reported in the literature for the duration of sciatica until the results of surgical intervention are expected to deteriorate may be illustrated by the results of the study of Woertgen et al.41 They analyzed the clinical results after diskectomy with 4 different outcome measurements and found that beside preoperative duration of paresis only the duration of preoperative pain was a predictive factor on all outcome scales. They divided the clinical results in a dichotomic manner into good or poor results. With regard to the used scoring system the average duration of pain in patients with poor results differed markedly. When looking at the clinical results obtained with the “Quality of Life Score,” patients with poor outcome had an average duration of pain of 209 days. In contrast, patients with poor results according to the “Low Back Outcome Score” had pain lasting for 159 days on average prior to surgery.41 These figures highlight the problem of adequately assessing the clinical outcome of patients with LDH. Korres et al49 already addressed this problem when they evaluated the results of lumbar diskectomy using 15 different evaluation methods in 92 patients who had undergone a primary excision of a lumbar disk. The satisfactory results ranged from 62% to 84% depending on the evaluation method used. Therefore most of the studies analyzing the threshold of the duration of sciatica, which is associated with poor outcome, are difficult to compare.
In view of the favorable course of nonoperative treatment in LDH, most authors recommend for a minimum 2-month period of conservative management (Table 2). With regard to the available evidence, this period should not exceed 12 months since the risk of poor functional outcome then increases (level of evidence: 2+; grade of recommendation: “B-C”).
Type of Herniation
The definition of the herniation type is based on magnetic resonance imaging (MRI) findings. Several definitions of disk herniation have been reported. These classifications compromise protrusion versus prolapse or contained versus noncontained herniation. Contained disks, which are wholly within an intact outer annulus or a capsule composed of the outer annulus and the posterior longitudinal ligament, are not in direct contact with epidural tissue, whereas noncontained herniations are in direct contact. The discrimination of different types of disk herniation with MRI seems to be possible with acceptable sensitivity, specificity, and accuracy.
Kim et al50 analyzed 211 patients with lumbar disk herniation at 242 levels and classified the type of herniation according to a 5 group classification system, defined by the MRI appearance. The comparison of radiological and clinical findings obtained at the time of the operation revealed 92% sensitivity, 91% specificity, and 92% accuracy of the MRI classification in distinguishing between protruded disks from other forms of LDH. For sequestrated disks the values were as follows: 92% sensitivity, 99% specificity, and 97% accuracy. In the extruded subligamentous type the values were 71% for sensitivity, 82% for specificity and 79% for accuracy and in the extruded transligamentous type 52% for sensitivity, 92% for specificity, and 81% for accuracy, respectively.50
Although the classification of different types of LDH is possible on MRI with sufficient accuracy, the clinical meaningfulness remains uncertain. Gaetani et al51 analyzed the records of 403 patients treated for LDH in a retrospective observational study to verify how 3 outcome measures (satisfaction with the outcome of surgery, degree of return to activities of daily living [ADL] including work, and duration of interruption of ADL) may be influenced by clinical variables. The results of this study suggested that age and type of disk herniation were among the most important factors to consider when deciding whether to operate on a patient for LDH. Favorable results (very satisfied or minor reservations) were observed in 100% of patients younger than 20 years, in 88.6% of patients between 21 and 30 years, in 80.1% of patients between 31 and 50 years, in 73.6% of patients between 51 and 65 years, and in 53.8% older than 65 years. With regard to the type of disk herniaton 86.8% of noncontained and 85.1% of contained disk herniation patients viewed the outcome of surgery favorably, whereas the rate was lower (65%) in the foraminal disk herniation patients. The observed differences for age and type of herniation were significant with regard to multivariate analysis and logistic regression considering “degree of return to activities of daily living including work” as the dependent variable.
However, the results of Gaetani et al51 are in contrast to the observations of Beattie et al,52 who compared in a cross-sectional study the relationship between clinical symptoms and anatomic impairment as shown by MRI in 408 symptomatic patients. The presence of disk extrusion and/or ipsilateral severe nerve compression at one or multiple sites was strongly associated with distal leg pain. Mild to moderate nerve compression, disk degeneration or bulging, and central spinal stenosis were not significantly associated with specific pain patterns. Boos et al53 confirmed these results in a prospective study of patients with symptomatic LDH and asymptomatic volunteers. They concluded that individuals with minor disk herniations (eg, protrusion, contained disk) are at a high risk that MRI does not provide a causal explanation of pain because a high rate of asymptomatic patients had similar morphological findings.53
The observations of Beattie et al52 and Boos et al53 are also supported when looking at the reported results postoperatively with regard to the type of herniation. Carragee et al54 analyzed the influence of annulus integrity and the type of herniation on postoperative clinical outcome following lumbar diskectomy. Based on intraoperative findings disk herniations were classified into 4 categories: (1) fragment-fissure herniations, (2) fragment-defect herniations, (3) fragment-contained herniations, and (4) no fragment-contained herniations. Patients in the fragment-fissure group, who had disk fragments and a small annular defect, had the best overall outcome and the lowest rate of re-herniation (1%) as well as re-operation (1%). In contrast, patients in the no fragment-contained group performed poorly with 38% having recurrent or persistent sciatica. Hirabayashi et al55 reported a higher incidence of secondary operations after lumbar microdiskectomy in patients with protrusion-type herniation than in those with extrusion-type or sequestration-type herniation (noncontained disks). Based on the results of Carregee et al54 and Hirabayashi et al,55 a noncontained disk herniation with corresponding radicular pain or paresis could be considered as indicative for a surgical intervention.
However, according to Kraemer56 a spontaneous resolution of symptoms and retraction of free fragments in disk herniation is possible. This mechanism works especially well, if the fragment is well hydrated (possibility of shrinkage), the whole volume of the fragment is less than 1/3 of spinal canal diameter, and the fragment has a contact to the epidural membrane, which has a good blood supply, inducing the process of resorption.56
Ito et al57 described an interesting phenomenon in their study population, which might support the hypothesis of Kraemer.56 Over 7 years, they noted that surgeries for disk herniation most frequently encountered free fragments when performed within 2 months after the onset of severe leg pain. In a subsequent, prospective series, they found that free extruded fragments seldomly were found at surgery, if the patient had been treated at least for 2 months conservatively.57 The author’s interpretation of these results was that disk re-absorption selectively targets these extruded fragments, which led them to conclude that patients with noncontained lumbar disk herniation can be treated without surgery, if they can tolerate the symptoms for the first 2 months.57 The spontaneous disappearance or diminution of herniated disks in the lumbar spinal canal has also been described by several others.58-62
Autio et al63 analyzed rim enhancement in LDH with gadolinium-enhanced MRI, since neovascularization in the outermost areas of the herniated nucleus pulposus presenting as an enhancing rim is thought to be a major determinant of spontaneous disk resorption. Thickness of rim enhancement was a stronger determinant of spontaneous resorption than the extent of rim enhancement. A higher baseline score of rim enhancement thickness, a higher degree of disk displacement in the Komori classification, and an age category between 41 and 50 years was associated with a higher resorption rate. Moreover, clinical symptom alleviation was correlated with a faster resorption rate. The final conclusion was that MRI is a useful prognostic tool for identifying patients with LDH-induced sciatica and at the same time a benign natural course.60
The type of herniation on MRI does not appear to be among the most important factors to consider when deciding whether or not to operate on a patient for symptomatic LDH (level of evidence: 2++; grade of recommendation: “B”). However, MRI is an indispensable tool in patients with radicular pain to delineate possible differential diagnoses.
The only clear and objective indication for early surgery in LDH is cauda equina syndrome. However, even this severe complication of LDH is not covered by striking evidence with regard to the necessity for immediate surgery. Nonetheless surgery should be performed as soon as possible and a delay should only be considered if the perioperative risk for the patient might be decreased markedly. Although paresis is regarded as a red flag symptom in patients with LDH, neither the magnitude nor the duration of paresis constitute an indication for early surgery.
In addition to cauda equina syndrome, pain as a subjective parameter seems to be the second important indication for surgery. According to the currently available literature, there is sufficient evidence that patients who undergo operative treatment will have more rapid resolution of symptoms compared to nonsurgically treated patients. If conservative treatment is intended, it should be considered for at least 2 months but should not be extended beyond 1 year if the patient shows only minimal improvement, since the result of surgery will diminish after this period. Nevertheless, if the patient reports devastating pain refractory to conservative measures, surgery should be initiated independent of the duration of conservative therapy.
The type of herniation on MRI does not appear to be a relevant parameter when deciding whether to operate on a patient for LDH. However, MRI is an indispensable tool in patients with radicular pain that delineates possible differential diagnoses and when surgery is scheduled. Evidence exists that gadolinium enhanced MRI as a noninvasive method might be a prognostic tool for identifying patients with LDH-induced sciatica with a benign natural course.
The statement of Dr John D. Lurie64 should always be in kept mind when treating patients with LDH: “It can be far more difficult to rigorously evaluate commonly used interventions than novel approaches. When interventions are more familiar, there is always the impression that we already know how they work and how well they work. Even when there are little data to support such impressions.”
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Drs Cakir, Reichel, and Käfer are from the Department of Orthopedic Surgery, University of Ulm, and Dr Schmidt is from the Department of Orthopedic and Trauma Surgery, University Medical Center Mannheim, Germany.
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Correspondence should be addressed to: Balkan Cakir, MD, Department of Orthopedic Surgery, University of Ulm, Oberer Eselsberg 45, 89081 Ulm, Germany.