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This is the third edition of the Lumbar Disc Herniation Clinical Practice Guidelines, succeeding the first and second editions published in June 2005 and July 2011, respectively. Fourteen members selected from various regions of Japan and representatives of the Japanese Orthopaedic Association secretariat, the International Medical Information Center, and Nankodo Co., Ltd. participated in the kick-off meeting held on July 2, 2018 in the Japanese Orthopaedic Association secretariat meeting room. Decisions made were to search the MEDLINE, ICHUSHI, and Cochrane Reviews databases for new articles in ∼10 years from January 2008 and analyze them in the following five areas: epidemiology/natural course, pathological condition, diagnosis, treatment, and prognosis. At the first meeting, on August 11, 2018, Professor Masahiro Yoshida from Minds was invited and delivered a lecture, and the revision work finally started. In the epidemiology/natural course and pathological condition areas, four and five Back ground question (BQ)s were determined, respectively; these were developed based on the Questions in the second edition. While the diagnosis area was subdivided in the second edition, four BQs related to symptoms, diagnostics, diagnostic imaging, and other imaging/auxiliary diagnosis methodologies were determined. In the treatment area, three BQs, four Clinical question (CQ)s, and one Future research question (FRQ) were determined to cover advances after the second edition was published, such as advent of drugs for neuropathic pain and intradiscal treatment and wider use of endoscopic surgery; in the prognosis area, seven BQs were determined after examination of factors affecting the likelihood of return to work/sport, surgery results, and postoperative course. This edition is a product of many and long discussions among revision committee members to prepare guidelines that facilitate the current Japanese medical system to reflect facts based on scientific evidence supported by the latest knowledge collected from a large number of articles, and that are beneficial for healthcare professionals and patients. We hope that this edition of the guidelines finds effective use in various clinical settings.
1 Preparation organization/entity
A Preparation organization
Like the previous first and second editions, the present third edition of lumbar disc herniation clinical practice guidelines has been prepared by the "lumbar disc herniation clinical practice guidelines committee" organized after commission by the Japanese Orthopaedic Association. The committee had a total of 15 members, including a chairperson, an advisor, 12 members, and a member responsible for revision methodology. The committee members themselves conducted the systematic review.
B Preparation process
1) Preparation policy
These guidelines have been created according to the following basic policies.
(1)
The guidelines are beneficial not only for orthopedic surgeons but also for doctors in other clinical fields and patients.
(2)
We aim at guidelines that can be easily used by clinicians in clinical practice.
(3)
The guidelines are consistent with actual clinical practice in Japan.
(4)
The diagnostic criteria for lumbar disc herniation adhere to those proposed in the first edition.
(5)
Articles on lumbar disc herniation are included. Articles on sciatica are included if patients in the study do not have concomitant spinal stenosis. Articles on intervertebral disc degeneration are used as references.
2) Precautions for use
Since articles were evaluated according to Clinical Questions and outcomes in a cross-sectional manner to determine a body of evidence in this edition, the evidence level of each document as in the previous edition was not used for evaluation. However, the strength of a body of evidence for an outcome for which an interventional study such as a randomized controlled trial (RCT) was available was initially set as A, while the strength of a body of evidence for an outcome for which only observational studies were available was initially set as C; the rating was then adjusted according to bias risks.
3) Conflict of interest
・
Conflict of interest reporting
The conflict of interest (COI) status (fiscal 2015–2017) was confirmed through self-reporting for all members of the guidelines revision committee. COIs fall into two major classes: academic COIs and financial COIs. All directors in charge and committee members reported no companies that had a direct link to recommended Clinical Questions (no financial COIs). Academic COIs of committee members were also considered when the members voted to determine recommendation grades.
・
Measures against conflicts of interest
To minimize opinion bias, not only the members in charge of each chapter but all committee members voted to determine each recommendation, with an emphasis on the consensus of the entire committee.
4) Fund for guideline preparation
Costs for preparation of the guidelines were entirely covered by contributions from the Japanese Orthopaedic Association, and no support was received from other organizations or companies.
5) Organizational structure
Supervisor
The Japanese Orthopaedic Association
The third edition of lumbar disc herniation clinical practice guidelines preparation organization.
Tabled
1
<The Japanese Orthopaedic Association>
President
Morio Matsumoto
Keio University
Professor
<The Japanese Orthopaedic Association clinical practice guidelines committee>
These guidelines were prepared in accordance with the "Minds Handbook for Clinical Practice Guideline Development 2014." The "Handbook 2014," prepared by the medical information service project of the Japan Council for Quality Health Care, proposes a method considered desirable in Japan, based on proposed methods currently available publicly, such as the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system, the Cochrane Collaboration, the Agency for Healthcare Research and Quality (AHRQ), and the Oxford Evidenced Based Medicine (EBM) Center. This Handbook emphasizes the importance of "body of evidence." Preparation of clinical practice guidelines requires systematic review to systematically collect evidence such as research articles, and evaluation and integration of all the evidence adopted as a body of evidence. The Handbook also emphasizes the importance of "balance between benefit and harm." The clinical practice guidelines compare multiple intervention methods that may be selected in a certain clinical setting (such as diagnosis, treatment, and prevention) and recommend the methods considered to be the best options. The recommended methods are selected based on the benefit-harm difference resulting from the intervention, i.e., the "usefulness," with attention equally focused on adverse events due to the intervention as well as the efficacy of the intervention. Aside from patient outcomes as harms, the disadvantages for patients which were considered included increased costs and physical/mental burden.
Specific steps in the process were as follows.
①
Clarification of purpose of guideline preparation
②
Determination of the preparing entity
③
Establishment of the secretariat/clinical practice guideline preparation organization
Publication of the clinical practice guidelines is followed by dissemination, introduction, and evaluation.
A Scope
1) Basic characteristics of the illness topic
(1)
Clinical characteristics
The condition often develops suddenly, with intense pain accompanied by radiating pain to the lower extremities and lumbar pain. Symptomatic lumbar disc herniation shows regressive changes on images accompanied by symptomatic improvements in 60% or more of cases.
(2)
Epidemiological characteristics
The prevalence is about 1%, and the most common affected levels are L4-5 and L5-S lumbar discs. It occurs commonly among men in their 20s–40s. About 20 to 50% of patients who received conservative treatment require surgical treatment later. There are genetic and environmental background factors.
(3)
Overall clinical practice flow of the illness topic
The condition is diagnosed comprehensively using symptoms, neurological findings, and imaging findings (mainly MRI). In general, conservative treatment is used in the acute phase, including medication, block, and physical therapy. However, surgical treatment is administered to patients who are nonresponsive to conservative treatment or when severe, progressive motor paralysis and cauda equina syndrome emerge.
2) Matters concerning the contents of the clinical practice guidelines
In the treatment area, Clinical Questions (CQs) about drug therapy, epidural corticosteroid injection therapy, physical therapy and alternative therapy, comparison of surgical treatment and conservative treatment, and recommended surgical treatment procedures were formulated. Other matters were described as Background Questions (BQs).
3) Matters concerning systematic reviews
a.
Literature search and results
During the present revision work, we used search formulas to search for articles between January 1, 2008 and October 24, 2019 and identified 4,234 articles from MEDLINE, 954 articles from Cochrane, and 1,288 articles in ICHUSHI. Furthermore, the following exclusion and inclusion criteria were used in the primary selection.
(1)
Exclusion criteria: Articles without abstract, abstracts of presentations at academic meetings, communication, and articles not containing lumbar disc herniation (lumbar disk herniation, lumbar herniated nucleus, lumbar disc herniation, lumbar discectomy, or lumbar herniotomy) in the title.
(2)
Inclusion criteria: ① RCTs (at least 50 cases), ② observational studies (at least 100 cases), ③ case series studies (at least 500 cases), ④ systematic reviews, meta-analyses, ⑤ articles for which Cochrane Database of Systematic Reviews (CDSR) is available, and ⑥ Japanese articles on RCT or higher.
A total of 911 articles were selected in the primary selection. Furthermore, textbook descriptions were considered in addition to the searched articles to formulate treatment BQ1, BQ2, and BQ3. For preparation of structured abstracts, 593 articles were selected from 1,131 articles, and 296 articles were selected finally. Additionally, 31 articles were identified by hand searching.
Table 1-1Search formula Cochrane (Search period: January 2008–October 24, 2018).
#1
[mh ˆ"INTERVERTEBRAL DISC DISPLACEMENT"]
#2
(INTERVERTEBR∗ or INTRAVERTEBR∗ or (INTER or INTRA) next VERTEBR∗) near/2 (DISK or DISC) near/2 DISPLACE∗
#3
(HERNIA∗ or PROLAPS∗ or SLIPP∗ or SLID∗) near/2 (DISK or DISC)
#4
HERNIA∗ near/2 NUCLE∗ next PULPOS∗
#5
HERNIA∗
#6
[mh ˆ"INTERVERTEBRAL DISC CHEMOLYSIS"] or [mh ˆCHYMOPAPAIN] or [mh "INTERVERTEBRAL DISC"]
((椎間板ヘルニア(Herniated disc,Intervertebral disc herniation)/TH or 椎間板ヘルニア(Herniated disc,Intervertebral disc herniation)/AL) and (腰椎/TH or 腰椎/AL)) or ((椎間板ヘルニア(Herniated disc,Intervertebral disc herniation)/TH or 椎間板ヘルニア(Herniated disc,Intervertebral disc herniation)/AL) not ((頸椎/TH or 頸椎/AL) or (胸椎/TH or 胸椎/AL)))
＃2
#1 and (PT=原著論文 and IDAT=2008/1/1:2018/10/22 and DT=2007:2019)
※1 The number of hit articles in literature search after removal of duplicates between databases.※2 Inclusion/exclusion criteria.１) Articles studying the effect of a drug that is not indicated currently for lumbar disc herniation on sciatica are to be examined; however, studies in lumbar disc herniation patients without spinal canal stenosis are to be included in the primary selection and used for preparation of structured abstracts.There is no consensus about diagnosis of lumbar disc herniation in Japan or other countries, and the illness criteria for lumbar disc herniation was first determined in the first edition. The same diagnostic criteria were used for the present revision of the guidelines, and lumbar disc herniation is to be the focus in selection of articles and recommendations.2) Exclusion criteria: Articles without abstract, abstracts of presentations at academic meetings, communications, and articles not containing lumbar disk herniation, lumbar herniated nucleus, lumbar disc herniation, lumbar discectomy, or lumbar herniotomy in the title.3) Inclusion criteria.① RCTs (at least 50 cases).② Observational studies (at least 100 cases).③ Case series studies (at least 500 cases).④ Systematic reviews, meta-analyses.⑤ Articles for which Cochrane Database of Systematic Reviews (CDSR) is available.⑥ Japanese articles on RCT or higher.4) Additional considerations.In addition to the searched articles, textbook descriptions are considered to prepare the following.(1) Chapter 4 Treatment BQ1 Concept of conservative therapy.(2) Chapter 4 Treatment BQ2 Concepts of and differences among various procedures.(3) Chapter 4 Treatment BQ3 (Emergency) Surgery indications.※3: Additions by hand searching.・Citations from existing versions are excluded.・Articles restored during the primary and secondary selection steps are excluded.
b.
Preparation of structured abstracts and evaluation of articles
Members of the guideline preparation committee prepared structured abstracts and evaluated articles, using a structured abstract preparation form (not shown). Articles describing outcomes set by committee members were included in review preparation and meta-analysis.
c.
Evidence levels/recommendation grades
All articles collected and selected for a CQ are evaluated for each outcome in a cross-sectional manner and are assessed in terms of bias risks, indirectness, inconsistency, imprecision, publication bias, and so on according to Table (not shown) to determine a "body of evidence." Evidence levels of bodies of evidence and their definitions were determined according to Table 3. Then a recommendation statement for each CQ was prepared, and recommendation grades were determined through voting by the committee members (GRADE grid) according to the definition in Table 4. In addition to evidence levels, benefit–harm balance was also considered in determination of recommendation grades. After evaluating whether benefits outweigh harms, burdens and costs were also considered in evaluation of the balance between benefits and disadvantages (harms, burdens, and costs). Moreover, patients' values/preferences and cost-effectiveness were also examined as much as possible. In voting, an opinion with which at least 70% of voters agreed was considered a consensus of the committee (recommendation decision). When less than 70% of voters agreed, members voted again after the voting result was disclosed and sufficient discussion was held.
4) From recommendation decision to finalization and introduction policy
Third-party assessments of a draft revised version of the guidelines (public comments) were solicited. After all the comments received were reviewed individually and necessary modifications/additions were made, the final version was prepared. We requested the following academic societies to submit public comments and third-party assessments.
・
The Japanese Orthopaedic Association (Collection period: September 16, 2020–October 15, 2020)
・
Japanese Society of Lumbar Spine Disorders (Collection period: September 15, 2020–October 15, 2020)
・
The Japanese Society for Spine Surgery and Related Research (Collection period: September 17, 2020–October 15, 2020)
The Japanese Association for the Study of Musculoskeletal Pain (Collection period: September 15, 2020–October 15, 2020).
Regarding epidemiology/natural course of lumbar disc herniation, no epidemiological studies in general populations have been reported, and details, including the prevalence, male/female ratio, frequencies of affected intervertebral levels, and time to resolution/resorption, remain to be clarified. Therefore, overall epidemiology of lumbar disc herniation needs to be deduced from the results of studies in patients who visited medical institutions, such as those who underwent surgical treatment or conservative treatment or patients with low back pain. In the present revision, the following four BQs were set for literature search, and newly identified articles were selected. The contents of the first and second editions were retained for invariable matters and matters for which new articles were not obtained.
BQ1 Epidemiology of lumbar disc herniation.
BQ2 Natural course of lumbar disc herniation (type, size, imaging findings, time to regression/resorption)
BQ3 How many patients undergo surgical treatment?
BQ4 Relationship between lumbar disc herniation and sports (preventive factor or pathogenic trigger?)
Summary of this chapter
From among a total of 5,934 articles identified, 44 were selected for preparation of this chapter in the primary selection. Then the structured abstracts were prepared to evaluate the articles, and five articles were selected for BQ1. In addition, three articles included in the first and second editions were retained. For BQ2, a total of eight articles were selected; five from the present literature search and three from the first/second editions. For BQ3, one article was selected from the present search, and seven articles from the first/second editions were retained. For BQ4, three new articles and one article from the first/second editions were selected.
In the present revision, the prevalence in 19-year-old South Korean men was found to be 0.6%. Taking other reports into consideration, the prevalence of lumbar disc herniation appeared to be around 1%. The prevalence was slightly higher among people in their 20s–40s and among men, as was the case in the first/second editions. Regarding resorption/resolution of hernia, resorption rates for different types of hernia are newly shown in this edition. No clear answers about time to hernia resorption were obtained in the present revision. The frequency of requiring surgery varies from a report to another, ranging from 20–50% depending on the severity. Since all previous reports have dealt with patients who visited a medical institution, the overall surgery rate for lumbar disc herniation, including those with mild symptoms who did not seek medical attention or were not diagnosed, is predicted to be lower. No articles showing a clear relationship between lumbar disc herniation and the sports activity were found also in the present literature search, and no conclusive statements can be made as to whether the sports activity induces or prevents herniation. While there are many issues, such as the absence of standardized diagnostic criteria for lumbar disc herniation and the necessity of clear distinction between lumbar disc herniation with clinical findings and lumbar disc herniation found only on imaging, data from large-scale epidemiological studies in general populations are awaited.
Background question 1 Epidemiology of lumbar disc herniation
Summary
・
The prevalence of lumbar disc herniation is around 1%.
・
The most common affected levels are L4-5 and L5-S.
・
The surgical treatment is slightly more common among patients in their 20s–40s and among men.
Commentary
No epidemiological studies of lumbar disc herniation in a general population have been reported to date. A previous study has shown the prevalence of hernia in 39,673 19-year-old South Korean men who were examined for military service [
]. In this study, medical records and imaging findings (MRI or CT) for those who submitted medical certificates for lumbar disc herniation were retrospectively examined. As a result, lumbar disc herniation was found in 237 cases (0.6％), of which 44.3% and 55.7% were accounted for by single-level herniation and multilevel herniation, respectively. The affected intervertebral disc was L5/S in 40.8% of cases, L4-5 in 50.6%, L3-4 in 6.4%, L2-3 in 1.8%, and L1-2 in 0.4%; herniation at L4-5 and L5-S accounted for the vast majority of cases.
The following reports describe studies in patients who visited medical institutions or patients who underwent surgery. Results of these studies were treated as reference information because of selection bias. In particular, the results in surgery cases are likely to differ depending on institutions and countries because differences in perception of conservative treatment and healthcare systems have effects on surgery indications.
A study in Taiwan using insurance records (covering 99% of the population) has reported a prevalence rate of 1.5–2% for lumbar disc herniation diagnosed at medical institutions [
Physicians as well as nonphysician health care professionals in Taiwan have higher risk for lumbar herniated intervertebral disc than general population.
]. The male-female ratio, common age of development, and commonly affected levels shown are as reference information from studies in surgically treated cases. A study in 15,631 cases registered with SweSpine, a surgery case registration system in Sweden has reported that about 20 surgeries per 100,000 population were operated annually in Sweden between 2000 and 2010. Of these cases, 44% and 56% involved female patients (mean age 45 ± 13 years) and male patients (mean age 44 ± 13 years), respectively, showing that slightly more male patients underwent surgical treatment [
]. A study in the United Kingdom has analyzed 390 patients who underwent surgery after dividing them into age-based groups. Of 233 cases (59.7％) in young patients aged 25–45 years, 97% had herniation at L4/5 or L5/S. Meanwhile, 29 cases (7.4%) were in patients aged ≥65 years; among them, the male-female ratio was 1:1, only 12 cases (40％) were herniation of the L4/5 or L5/S disc, and more than half had upper levels of lumbar disc herniation [
]. An analysis of 1,431 cases from the Netherlands has shown a relationship between the affected level and mean age; mean patient ages in cases of herniation at L2-3, L3-4, L4-5, and L5/S were 59.6, 59.5, 49.5, and 44.1 years, respectively, showing that lumbar disc herniation at upper levels than L4/5 increased with age [
]. A study in 4,695 patients of lumbar disc herniation in China has focused on young patients aged 13–20 years, including 121 patients (2.6%) undergoing surgery. The affected disc was L4-5 in 50.4% and L5-S in 34.7%, and two levels of L4-5 and L5-S were affected in 10.7%; the data indicate that most of young patients had lower lumbar disc herniation [
]. A narrative review of pediatric lumbar disc herniation has reported that pediatric lumbar disc herniation is rare, accounting for 0.4–15.4% of all hernia cases [
]. Furthermore, cases in patients under 10 years of age have been described only in case reports.
In summary, these previous reports have shown that lumbar disc herniation requiring surgery is slightly more common in men and is more common at L4-5 or L5-S. The mean age of patients is in their 40s in many reports, and the disease is rarely found among elderly people or young people. Upper Lumbar disc herniation at upper level above L4-5 increases with age.
Background Question 2 Natural course of lumbar disc herniation (type, size, imaging findings, time to regression/resorption)
Summary
・
Regression on imaging is found in ≥60% of symptomatic cases of lumbar disc herniation.
・
Sequestration and extrusion types of herniation are prone to resorption.
・
Hernias imaged in a ring shape on contrast-enhanced MRI are prone to resorption.
・
The time when resorption starts is unknown; however, resorption within 3 months is not rare.
Commentary
A meta-analysis of 587 patients who underwent conservative treatment from 11 cohort studies has reported a spontaneous resorption of 66.6% [
]. Meanwhile, a study in residents observing asymptomatic lumbar disc herniation, detected on images, in a longitudinal manner has shown that regression, no changes, and size increases were found after 4 years in 14%, 81%, and 5%, respectively. After 8 years, regression, no changes, and size increases were found in 17.5%, 65%, and 12.5%, respectively; the majority of hernias remained unchanged in size [
Progression of lumbar disc herniations over an eight-year period in a group of adult Danes from the general population--a longitudinal MRI study using quantitative measures.
Morphologically, lumbar disc herniation falls into bulging type, protrusion type, extrusion type (with complete tear in the annulus fibrosus), and sequestration type (migrated disc) (see Chapter 2). Regarding the relationship between the type of lumbar disc herniation and natural course, a report has described analysis of 53 cases of sequestration-type herniation from 12 articles. In this group, symptoms improved 1.3 months after the onset on average. On imaging, hernia regression was confirmed in 9.3 months on average [
]. A systematic review of 361 cases in nine articles about resorption of lumbar disc herniation has shown that hernia regression was found in 96% (52/54) of sequestration-type cases, 70% (108/154) of extrusion-type cases, 41% (38/93) of protrusion-type cases, and 13% (8/60) of bulging-type cases [
]. The complete resorption rate was 43% (18/42) in sequestration-type cases, 15% (16/91) in extrusion-type cases, 0% (0/7) in protrusion-type cases, and 11% (3/24) in bulging-type cases. A study in 77 patients who underwent conservative treatment in Japan has reported that protrusion-type herniated discs are resistant to resorption, and sequestration-type herniated discs are prone to resorption. In particular, marked resorption or disappearance of herniated discs was observed in 84% of cases in which lumbar disc herniation migrated more than 1/3 of lower vertebrae in sagittal sections. Moreover, hernia resorption was observed within 3 months in 46% of cases [
]. In a longitudinal study in 505 patients in South Korea, hernia resorption and ≥50% regression were observed in 486 patients (96.2％) and 220 patients, respectively, during follow up for about 1 year on average. Resorption has been reported to be facilitated when herniation is extrusion-type or sequestration-type or when the initial hernia is larger [
]. In this study, an MRI examination after 2 months showed ≥40% hernia resorption in 28 of 74 cases (37.8％).
Therefore, symptomatic herniated discs are prone to resorption, and sequestration-type and extrusion-type herniated discs, craniocaudally extruded discs, and large herniation are more prone to resorption. Meanwhile, asymptomatic, accidentally discovered hernias often undergo no changes in size and may represent a different pathological condition. Currently, there are no reports clarifying when hernia resorption starts; however, it has been reported that marked resorption occurs within 2–3 months in some cases.
Background Question 3 How many patients undergo surgical treatment?
Summary
・
Surgery is required at varying rates depending on symptoms and morphological types of herniation.
・
The proportion of patients who underwent conservative treatment and require surgical treatment later ranges widely from 20–50% and is related, to some extent, to the intensity of preoperative symptoms.
Commentary
Lumbar disc herniation improves spontaneously or only with conservative treatment in many cases, but surgical treatment is required in some cases. Knowing what percentage of herniation patients are likely to require surgery is also helpful to explain conditions to patients immediately after the onset.
During preparation of the third edition, no new relevant articles with high-level evidence were found. Attempts were made to answer the question "How many patients undergo surgical treatment?" based on results in the first/second editions and reference information: percentages of patients who previously underwent conservative treatment and required surgery later in case series studies and percentages of patients who underwent surgery among those assigned to conservative treatment in randomized controlled trials (RCT). Results as the third edition are shown below.
Out of 100,000 people, the number of patients who underwent surgery for lumbar disc herniation was 50–70 in the United States, 40 in Finland, and 10 in the United Kingdom. According to 1987–1996 survey data, the number in Sweden was 24 out of 100,000 people and decreased from 32 in 1993 to 20 in 1999. These data show differences depending on geographic region and age [
]. In the first reported RCT comparing conservative treatment and surgical treatment, 126 relatively mild patients were divided into the conservative treatment group and the surgical treatment group after two weeks of bed rest; in the conservative treatment group, 17 patients (28％) underwent surgery within 1 year due to pain [
]. In an RCT in which patients who did not respond to 6-week conservative treatment were allocated to the early surgery group and the continued conservative treatment group, 54% of patients in the continued conservative treatment group underwent surgery within 13 months [
], a large-scale study, 1,244 patients who had persisted leg pain after 6-week or longer conservative treatment for lumbar disc herniation were divided into 501 patients who participated in an RCT and 743 patients who refused to participate in the RCT and participated in a cohort study. While the mean Oswestry Disability Index (ODI) in RCT participants was 46.9, indicating moderate to severe symptoms, 30% and 45% of patients assigned to conservative treatment underwent surgery within 3 months and within 2 years, respectively. Among patients who refused the RCT and preferred conservative treatment, 9% and 22% underwent surgery within 3 months and within 2 years, respectively, while they had a low mean ODI of 35.9 and most of them were mild cases. These data suggest that the percentage of requiring surgery varies considerably widely depending on the patient's background but is associated with the intensity of symptoms to some extent. In an article investigating the preoperative pain intensity in 194 patients (81 women and 113 men, mean age 38.3 ± 11.2 years) who underwent herniotomy, the mean preoperative ODI and Visual Analog Scale (VAS) (㎝) were 56.7 and 6.1, respectively, indicating moderate to severe pain. The data have shown that the percentage of patients undergoing surgery tends to be high among patients with moderate to severe pain even during conservative treatment [
In a report comparing the group of patients encouraged to undergo early surgery and the group of patients undergoing 2–3-week extended conservative treatment, the percentage of patients who underwent surgery in the extended conservative treatment group decreased to 46.4% compared to 69.8% in the early surgery group. The decreased rate of undergoing surgery in the extended conservative treatment group was attributed to non-contained-type herniation, in which the tip of the herniated disc is extruded into the epidural space, as no changes were observed for the contained type, in which the herniated disc is separated from the epidural space by the posterior longitudinal ligament and other structures. These data indicate that the frequency of surgery is also associated with the morphological type [
Therefore, the percentage of patients undergoing surgery for lumbar disc herniation varies from 20–50% among patients who underwent conservative treatment for a certain period and depends on symptoms and morphological types.
Background Question 4 Relationship between lumbar disc herniation and sports (preventive factor or pathogenic trigger?)
Summary
・
No clear relationships between lumbar disc herniation and sports have been shown thus far, and we cannot determine whether sports induce or prevent the development of hernia.
Commentary
Various factors have previously been considered to be risk factors for the development of lumbar disc herniation. Based on previous reports, we clarify what environmental factors have been identified to date.
Articles on the relationship between lumbar disc herniation and sports newly found during preparation of the third edition are described below along with opinions in the first/second editions.
A study comparing effects of major sports (baseball, softball, golf, swimming, diving, aerobics, racket sports) in 287 hernia patients and the same number of controls matched in terms of age, sex, and regional characteristics showed no significant differences in the incidence of herniation between the two groups [
An epidemiologic study of sports and weight lifting as possible risk factors for herniated lumbar and cervical discs. The Northeast Collaborative Group on Low Back Pain.
]. In a study investigating effects of swimming on lumbar disc degeneration, a comparison between 100 elite swimmers (mean age: 20 years) and 96 people with no history of sports participation showed that prevalence rates of MRI-based intervertebral disc degeneration, intervertebral disc bulging, and intervertebral disc herniation in the two groups were comparable [
There is a study investigating 275 NFL professional American football players who newly developed intervertebral disc herniation in 12 seasons (2000–2012). The study showed that the lumbar spine was affected in 76%, and the most frequently affected level was L5/S1. The position associated with the highest prevalence was offensive lineman, and the blocking play was associated with the highest injury rate [
The findings in these articles suggest that specific position and play only in American football may have effects on the development of intervertebral disc herniation. Reports also have shown that intervertebral disc degeneration tends to be more common among baseball players and swimmers. However, for all findings, evidence levels are insufficient. Therefore, no definitive conclusion can be made currently about the presence of relationship between the development of lumbar disc herniation and sports.
Lumbar disc herniation is a condition in which the annulus fibrosus is ruptured primarily by the degenerated nucleus pulposus of an intervertebral disc, and the intervertebral disc tissue extruded or protruded into the spinal canal applies direct compression to nerves, causing lumbar pain and neurological symptoms. Previous histological examinations have revealed that the extruded tissue consists of not only components of the degenerated nucleus pulposus but also the annulus fibrosus and endplate components and that infiltration of inflammatory cells into the hernia and neovascularization are involved in spontaneous regression. However, mechanisms underlying development and spontaneous regression of hernia largely remain unclear.
Macnab et al. classified hernias into the following four types: protruded type, prolapsed type (with partial tear in the annulus fibrosus), extrusion type (with complete tear in the annulus fibrosus), and sequestrated type (migrated disc) (Canad J Surg 14:280-289, 1971). In 1980, the American Academy of Orthopaedic Surgeons (AAOS) revised the classification system as follows: intraspongy nuclear herniation, protrusion type, extrusion type, and sequestration type. In the classification system used currently, the extrusion-type herniation is subdivided into subligamentous extrusion type, in which the posterior longitudinal ligament is not ruptured, and transligamentous extrusion type, in which the posterior longitudinal ligament is ruptured, and intraspongy nuclear herniation is referred to as bulging type.
A very large number of factors interacting with each other in a complex manner, such as daily living/working environments, mechanical factors, and genetic factors, are involved in the development of lumbar disc herniation. In the present revision, separate background questions (BQs) for ① pathogenic mechanism (including age-associated differences in pathological condition), ② morphology and clinical symptoms, ③ environmental factors, ④ genetic factors, and ⑤ regression mechanism that have effects on the development of lumbar disc herniation were created for better clarification of the pathological condition, including relationships of pathogenic mechanism and morphology with symptoms and the process of regression.
Clarification of these pathological conditions provides a guide for making treatment-related decisions in daily clinical practice and is essential to give correct explanations to patients. In this chapter, 66 articles selected from 143 articles extracted during preparation of structured abstracts were used to prepare guidelines for the pathological condition of lumbar disc herniation.
BQ1. Pathogenic mechanism of lumbar disc herniation.
BQ2. Morphology and clinical symptoms of lumbar disc herniation.
BQ3. Environmental factors that have effects on the development of lumbar disc herniation.
BQ4. Genetic factors that have effects on the development of lumbar disc herniation.
BQ5. Regression mechanism of lumbar disc herniation.
Summary of this chapter
Regarding the pathogenic mechanism of lumbar disc herniation, the possible involvement of different mechanisms has been newly reported based on age-dependent differences in the incidence and the affected level in addition to previous histological examinations. It has been pointed out that the incidence rates in children and elderly people are lower than the rate in adults and herniation occurs at higher intervertebral levels with aging. Although some new reports were found regarding the risk for lumbar disc herniation in patients differing in background factors, such as the involvement of spinopelvic alignment, the direct pathogenic mechanism largely remains unclear.
An increasing number of reports have documented factors that have effects on the development of lumbar disc herniation; reported risks include occupations, such as helicopter pilot, astronaut, and healthcare professionals, and smoking. Aside from smoking, reports have shown causal relationships with body mass index (BMI), fat disorder, blood viscosity, and so on; however, more evidence should be built through, for example, validation of these factors and exploration for more factors.
The involvement of genetic factors has been pointed out based on studies in twins and familial occurrence, and various disease susceptibility genes have been reported. These findings support that lumbar disc herniation is a multifactorial illness. Differences in the disease susceptibility genes among races have also been reported recently. In this chapter, reports on the disease susceptibility genes for lumbar disc herniation and genes related to associated pain are listed in a table format and reviewed.
Regarding the mechanism of spontaneous regression of herniation, there are reports on differences in diagnostic imaging depending on herniation types and those using molecular biological approach. Regarding the relationship between the herniation type and regression, extrusion and sequestration types have been reported to be significantly more prone to spontaneous regression than bulging and protruding types, and the sequestration type has been shown to be more prone to complete resolution than the extrusion type. Regarding the regression mechanism, vascular endothelial growth factor (VEGF) may induce neovascularization of herniated discs and infiltration of inflammatory cells and promote spontaneous regression of herniation through the action of matrix metalloproteinases 3 and 7 derived from macrophages.
Future issues
Although the number of reports on the pathogenic mechanism of herniation and influential factors is increasing, specific mechanisms underlying pathogenesis largely remain unclear. In the previous edition, age-associated characteristics have been described, including: lumbar disc herniation in young patients may be accompanied by dissociation of the epiphyseal nucleus; the nucleus pulposus is the main component in adolescents; and annulus fibrosus and endplate fragments are often found in lumbar disc herniation in elderly patients. In the present revision, only a small number of articles describing molecular biological mechanisms, such as pathogenic mechanisms, were newly identified; however, affected intervertebral levels associated with age are being identified, and reports based on new concepts, such as spinal alignment, blood viscosity, and fat disorder, were added. More studies on triggers of pathogenic mechanisms based on new concepts are awaited.
Regarding genetic factors, many gene regions have been reported; however, given the fact that lumbar disc herniation is unlikely to be attributable to a specific single gene and is a multifactorial illness, there may be no genes that can be called causative genes. Mechanistic studies to elucidate how genetic factors are involved in pathogenesis of herniation may drive the development of treatments.
Regarding regression, extrusion and sequestration types have previously been reported to be prone to resorption; however, accurate prediction based solely on imaging data is still difficult. We hope for the advent of new concepts, such as new diagnostic imaging procedures.
This chapter is very important from the viewpoint of primary care requiring provision of correct information to patients and prevention of herniation from occurring. The development of new therapeutic agents based on yet-to-be-defined pathogenic mechanisms of herniation and more therapeutic agents promoting regression is awaited.
Background Question 1 Pathogenic mechanism of lumbar disc herniation
Summary
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Lumbar disc herniation occurs relatively less frequently in childhood and in elderly people.
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Upper lumbar discs are often affected in elderly people, while lower lumbar discs are often affected in children, as in adults.
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Various patient background factors have been reported as onset risks for herniation, but it remains to be clarified whether these factors are directly involved in the pathogenic mechanism.
Commentary
The pathogenic mechanism of lumbar disc herniation largely remains unclear, and there may be differences in the pathogenic mechanism and affected intervertebral level particularly between children and elderly people. Here, we discuss differences in the pathogenic mechanism depending on age and patient background.
a.
Age-associated differences
Studies have shown that the incidence and affected level differ depending on patient age, suggesting age-associated variations in the pathogenic mechanism (see Chapter 1 Epidemiology BQ1). Upper lumbar disc herniation increases with age. A study investigating histological differences among removed herniated discs has reported that the number of cases of hernias containing cartilage endplates increased with age; cartilage endplates were found in 70% of patients in their 60s and 80% of patients over 70 years of age [
Onset risk associated with different patient background factors
Abnormally large lumbar intervertebral disc mobility has been reported to be a risk for the development of herniation as general joint laxity was observed in 13.2% of hernia patients and this rate was significantly higher than 5.1% in the control group [
A study analyzing the pathogenic mechanism in 154 patients with lumbar disc herniation has reported that 62% of the cases were spontaneous without clear causes of injury, such as carrying heavy loads, suggesting that contribution of external factors is likely to be limited [
In some recent reports, the involvement of global spinal alignment in lumbar disc herniation was studied. In patients with lumbar disc herniation, sacral slope (SS), pelvic incidence (PI), and lumbar lordosis (LL) were smaller and thoracic kyphosis (TK) and sagittal vertical axis (SVA) were larger, compared to corresponding values in non-herniation patients; however, it remains unclear whether these differences have direct relevance to the pathogenic mechanism [
Bacterial biofilms: a possible mechanism for chronic infection in patients with lumbar disc herniation - a prospective proof-of-concept study using fluorescence in situ hybridization.
]; however, further studies are required to attribute herniation to infection.
Background Question 2 Size and clinical symptoms of lumbar disc herniation
Summary
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The size and shape of lumbar disc herniation often correlate with leg pain and neurological symptoms. However, this is not always the case.
Commentary
Advances in diagnostic imaging have brought about improved understanding of morphology of lumbar disc herniation than before. Here, we review the relationship between morphology and clinical symptoms of herniation based on the relationship with spinal canal occupation ratio and classification of herniation.
The following articles were described in the previous edition. No new reports were found during the present revision.
a.
Relationship between the spinal canal occupation ratio and clinical symptoms
Three methods are available to measure the ratio of the lumbar disc herniation size to the spinal canal size: area ratio, product ratio of lateral diameter × anterior-posterior diameter, and anterior-posterior diameter ratio using CT. Regardless of the method used, the measured ratios have been shown to have tight positive correlations with the intensity of buttock/leg pain [
Describing the size of lumbar disc herniations using computed tomography. A comparison of different size index calculations and their relation to sciatica.
]. The results of a survey of 298 lumbar disc herniation patients aged ≤60 years have shown that the severity of lower limb muscle weakness increased with the spinal canal occupation ratio of herniation, and the incidence reached 80% when the occupation ratio was greater than 50% [
]. A study in 30 patients undergoing conservative treatment has reported a correlation between the size ratio of lumbar disc herniation to the spinal canal and the degree of alleviation of buttock/leg pain, suggesting that the size ratio can serve as an indicator of the efficacy of conservative treatment [
]. A study in 93 patients with lumbar disc herniation has shown that the herniation size affected sensory disturbance and bladder and rectal disturbance, and bladder and rectal disturbance tended to be more often associated with central herniation with a smaller area of the epidural space. However, no significant correlations were found between muscle weakness lower limb or the Japanese Orthopedic Association score for the lumbar spine (L-JOA score) and the herniation size, and the straight leg raising test (SLRT) score has been shown to be associated with the nerve root position and spinal canal morphology, rather than the size of herniated mass [
Relationship between hernia classification and clinical symptoms
Among different types of lumbar disc herniation, the extrusion and sequestration types have been reported to be associated with a higher SLRT-positive rate and an increased severity of motor/sensory disturbance in the damaged nerve root region compared with the protrusion type [
Background Question 3 Environmental factors that have effects on the development of lumbar disc herniation
Summary
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There are some reports on occupations posing risk.
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Regarding effects of smoking, smokers have been reported to be at increased risk for herniation.
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Many environmental factors associated with hernia patients have been reported; however, no factors other than smoking have been demonstrated to have a clear association.
Commentary
Lumbar disc herniation is a multifactorial illness, and environmental factors are among the important ones. Here, we review related occupations, effects of smoking, and other factors.
Physicians as well as nonphysician health care professionals in Taiwan have higher risk for lumbar herniated intervertebral disc than general population.
Regarding the relationship between smoking and the development of lumbar disc herniation, a systematic review has shown that the relative risk of smokers was 1.27; both male and female smokers have significantly increased risk for lumbar disc herniation. A study has reported that the risk in current smokers is higher than that in previous smokers, and the risk increases with the quantity of smoking [
The group of patients who required surgery for lumbar disc herniation had a significantly higher BMI than the group of age/sex-matched patients who did not require surgery [
]. In herniated patients, the whole blood viscosity, which tends to increase as the physical activity level decreases, was significantly higher than that in non-herniated patients [
] lumbar disc herniation. It remains unclear whether these factors directly increase the risk for herniation.
Background Question 4 Genetic factors that have effects on the development of lumbar disc herniation
Summary
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Familial aggregation has been detected for the occurrence of lumbar disc herniation, and differences in disease susceptibility genes among races have been reported recently.
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The involvement of genes of type IX and XI collagen, cartilage intermediate layer protein (CILP), thrombospondin, and matrix metalloproteinase (MMP)-9 has been reported previously; various disease susceptibility genes have been reported recently.
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Recently, genetic polymorphisms associated with hernia pain have also been reported.
Commentary
Young patients with lumbar disc herniation are known to show particularly high familial aggregation, and studies in twins have shown frequent simultaneous onset. Here, we review results of studies on genetic background factors in patients with lumbar disc herniation (excluding intervertebral disc degeneration and stenosis).
a.
Hereditability of hernias
Previous studies have reported familial occurrence of lumbar disc herniation [
], and familial aggregation is considered particularly clear for intervertebral disc herniation in young patients. A twin study has reported that the onset of intervertebral disc herniation in a twin is associated with a 10-fold increase in the onset risk in the other twin [
A functional polymorphism in COL11A1, which encodes the alpha 1 chain of type XI collagen, is associated with susceptibility to lumbar disc herniation.
]), which are expressed specifically in cartilages and intervertebral discs, genes constituting cartilage matrix (cartilage intermediate layer protein: CILP [
