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Symptomatic, MRI Confirmed, Lumbar Disc Herniations: A Comparison of Outcomes Depending on the Type and Anatomical Axial Location of the Hernia in Patients Treated With High-Velocity, Low-Amplitude Spinal Manipulation
Chiropractic Medicine Student, Chiropractic Medicine Department, Faculty of Medicine, Orthopaedic University Hospital Balgrist, University of Zürich, Zürich, Switzerland
Professor and Department Head, Chiropractic Medicine Department, Faculty of Medicine, Orthopaedic University Hospital Balgrist, University of Zürich, Zürich, Switzerland
The purpose of this study was to evaluate whether specific MRI features, such as axial location and type of herniation, are associated with outcomes of symptomatic lumbar disc herniation patients treated with spinal manipulation therapy (SMT).
Methods
MRI and treatment outcome data from 68 patients were included in this prospective outcomes study. Pain numerical rating scale (NRS) and Oswestry physical disability questionnaire (OPDQ) levels were measured at baseline. The Patients Global Impression of Change scale, the NRS and the OPDQ were collected at 2 weeks, 1, 3, 6 months and 1 year. One radiologist and 2 chiropractic medicine master’s degree students analyzed the MRI scans blinded to treatment outcomes. κ statistics assessed inter-rater reliability of MRI diagnosis. The proportion of patients reporting relevant improvement at each time point was compared based on MRI findings using the chi-square test. The t test and ANOVA compared the NRS and OPDQ change scores between patients with various MRI abnormalities.
Results
A higher proportion of patients with disc sequestration reported relevant improvement at each time point but this did not quite reach statistical significance. Patients with disc sequestration had significantly higher reduction in leg pain at 1 month compared to those with extrusion (P = .02). Reliability of MRI diagnosis ranged from substantial to perfect (K = .733-1.0).
Conclusions
Patients with sequestered herniations treated with SMT to the level of herniation reported significantly higher levels of leg pain reduction at 1 month and a higher proportion reported improvement at all data collection time points but this did not reach statistical significance.
Lumbar disc herniations (LDH) occur commonly in the population. Not all people with herniations are symptomatic and the diagnosis and therapy must correlate with the patient’s complaints, physical examination findings and clinical history.
Clinical correlation of magnetic resonance imaging with symptom complex in prolapsed intervertebral disc disease: A cross-sectional double blind analysis.
Potential of magnetic resonance imaging findings to refine case definition for mechanical low back pain in epidemiological studies: a systematic review.
The symptomatic herniations cause restrictions of functioning, suffering and costs and therefore deserve attention. Van Tulder et al state that LDHs can be the source of the most severe and disabling forms of back pain.
This also applies to patients suffering with chronic LDH.
There are different causes and risk factors known for LDH. Genetics, family history, lumbar load, hard-working and time urgency are the major risk factors.
Poor stabilization due to weak muscles and other instabilities are additional possible explanations for a herniated disc. Physical exercises therefore may be protective.
To confirm that someone’s symptoms are likely due to a herniated disc a magnetic resonance imaging scan (MRI) is necessary with the abnormal imaging findings compatible with the specific complaints of the patient. The indication for such an image is given by the anamnesis (patient history) and the presentation of the patient along with specific physical examination procedures including lumbar range of motion, dermatomal, myotomal and reflex changes and Lasègue sign.
To treat the condition it is essential to know what its effects are and where the herniation is located in terms of spinal level(s) as well as location in the axial plane. On the MRI scan the specific characteristics of the disc herniation are visualized as well as whether a nerve root is compressed.
Throughout the years different nomenclatures for classifying LDH were used. Today there are recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.
Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.
There are five different types or classifications of disc herniation: bulging, protrusion, extrusion, sequestration and intravertebral herniation (Schmorl’s node). The last one (Schmorl’s node) is of less interest, since these are usually not symptomatic and of relatively little clinical significance as they do not cause nerve root compression.
The association of combination of disc degeneration, end plate signal change, and Schmorl node with low back pain in a large population study: the Wakayama Spine Study.
The other four will be described under the Methods section.
There are many different therapies available for the treatment of patients with symptomatic LDH. They can be grouped in the two categories surgical and conservative care. The outcomes from treatment of patients with symptomatic herniations are quite variable. So far there are no predictors for treatment outcome such as size, shape or location of the hernia. On the contrary, Masui et al showed, that clinical outcomes did not depend on the size of herniation or the grade of degeneration of the intervertebral disc.
However, spinal manipulative therapy (SMT) was not one of the treatments included in their evaluation. The recent study by Leemann et al showed that the vast majority of both acute and chronic MRI confirmed LDH patients treated with high-velocity, low-amplitude SMT reported clinically relevant improvement in their condition at multiple follow-up time periods up to 1 year, with no adverse events reported.
Outcomes of acute and chronic patients with magnetic resonance imaging-confirmed symptomatic lumbar disc herniations receiving high-velocity, low-amplitude, spinal manipulative therapy: a prospective observational cohort study with one-year follow-up.
This current study is a follow-up to the Leemann et al study with the purpose to investigate whether the specific MRI features, such as axial location or type of herniation as identified on the MRI scans are associated with outcomes of patients treated with SMT to their spinal level of herniation.
Methods
Sixty eight acute and chronic low back pain patients with magnetic resonance imaging-confirmed symptomatic LDH who were treated with high-velocity, low-amplitude SMT were included. All patients provided informed consent. Since this study is a follow-up study and only used already available data, there was no new ethics approval needed. The ethics approval number is EK 22/2009 from the Canton of Zürich, Switzerland.
From the original 148 patients with baseline data in the original study, 68 patients had their MRI scans readily available on the chiropractic practice computer records and were included in this study. Thus this is a convenience sample. The MRI scans for the other patients were not easily accessible being on the computer records of various hospitals and imaging centers. All patients were between the ages of 18 and 65 years, experiencing back pain and moderate to severe leg pain and had at least one neurological deficit (dermatome, myotome or reflex change) consistent with the level of disc herniation noted on their MRI scans. All patients were treated with high-velocity low amplitude side posture SMT at the level of the herniated disc. There were two different adjustments used depending on the axial location of the herniation. A modified push adjustment with a kick was used for foraminal disc herniations and a pull adjustment with a kick was used for paramedian disc herniations. For detailed explanations of these techniques see the study by Leemann et al.
Outcomes of acute and chronic patients with magnetic resonance imaging-confirmed symptomatic lumbar disc herniations receiving high-velocity, low-amplitude, spinal manipulative therapy: a prospective observational cohort study with one-year follow-up.
To objectify pain and disability levels the numeric rating scale (NRS) and Oswestry pain and disability questionnaire (OPDQ) were used before treatment (baseline) and at 2 weeks, 1, 3, 6 and 12 months after treatment. For the NRS score, the patient had to rate his pain on a scale from no pain (score of 0) to the worst pain imaginable (score of 10). NRS scores were collected for the low back pain and the leg pain separately. In the OPDQ the patient had to answer questions about the level of pain and disability. For the post treatment time frames noted above the patients also reported about their overall improvement using the Patients Global Impression of Change (PGIC) scale. This scale has 7 options ranging from much better to much worse. Clinically relevant improvement was considered with the responses much better or better whereas worsening was considered with the responses slightly worse, worse and much worse, which is the usual format used in other studies.
The response slightly better was not considered as improved. The PGIC was the primary outcome measure. The NRS and OPDQ were secondary outcome measures. It did occur that patients did not report on their scores at one of the data collection time points. In this case they were not excluded from the study if data from the other time points were present.
The MRI scans were independently analyzed by 3 persons, two year 5 chiropractic medicine students trained in the diagnosis and description of lumbar disc herniations on MRI (for the inter-rater reliability part of this study) and one musculoskeletal radiologist. The MRI readings were done blinded to the clinical outcomes. The two year 5 students were blinded to each other’s and the radiologist’s MRI analysis. Axial and sagittal T1 and T2-weighted slices were evaluated. Once the individual MRI analyses were completed, the team of 3 readers came to a consensus reading for each patient for ease of data analysis. The specific level or levels of disc herniation were determined first (ie, L4-L5). To determine where a herniation was located in the axial plane the raters categorized the MRI findings according to the recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology which suggest the categories of central, paracentral, foraminal and extraforaminal (Fig 1).
Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.
We also used a fifth option, which was a combination of paracentral and foraminal because some herniations were too large to categorize in only one of the two areas.
Fig 1Axial T2-weighted lumbar MRI slice showing the anatomic zones for classifying the location of disc herniation according to the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology. This patient has a paracentral herniation (b). a = central; b = paracentral; c = foraminal; d = extraforaminal.
We also used the following nomenclature for the disc herniation type according to the recommendations above: Bulging, protrusion, extrusion and sequestration. Bulging is present if the herniation is greater than 50% of the circumference of the disc or vertebral body. Protrusion is present if the greatest distance between the edges of the disc material presenting outside the disc space is less than the distance between the edges of the base of that disc material extending outside the disc space. Extrusion is present when, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base of the disc material beyond the disc space (Fig 2). Sequestration is present if the displaced disc material has lost continuity completely with the parent disc (Fig 3).
Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.
The study by Pfirrmann et al states that this grading system is a reliable method for evaluating and reporting compromise of intraspinal extradural nerve roots in both clinical and research settings.
Fig 2A, B, and C: Sagittal T2 (A) and T1 (B)-weighted and axial T2 (C)-weighted MRI slices showing a paracentral disc extrusion. Particularly on the T2-weighted sagittal slice the disc extends superior to the level of the disc indicating that this is an extrusion. This patient was included in this study.
Fig 3Sagittal and axial T2-weighted slices showing a large disc sequestration at the L5-S1 level. The fragment extends inferiorly behind the S1 vertebral body. Modic changes are also present at the inferior end plate of L5. This patient was included in this study.
Descriptive statistics were calculated for the age and sex of the patients as well as the percentage of disc herniations by spinal level, axial location and type. The PGIC scores (primary outcome measure) were dichotomized to improved yes/no. Responses of much better and better were improved (yes), while responses slightly better, no change, slightly worse, worse, much worse were not improved (no). The percentage of patients reporting clinically relevant improvement at each of the data collection time points was calculated. To evaluate whether or not individual MRI abnormalities of spinal level, axial location or type (bulge, protrusion, extrusion, sequestration) of herniation were related to clinically relevant improvement for each of the data collection time points, the Chi-square test was done. NRS and Oswestry change scores were calculated (baseline score − follow-up score) for each data collection time point and compared for differences based on disc herniation spinal level, axial location and type (bulge, protrusion, extrusion, sequestration) using the ANOVA test for all of the data collection time points. Post-hoc analysis then compared patients with disc herniation types of either extrusion or sequestration only due to the fact that the vast majority of patients fell into these 2 categories. The unpaired Student t test was used to compare NRS and Oswestry change scores and the χ2 test was used to compare the two groups for improvement at all data collection time points. P < .05 was considered statistically significant.
For the inter-rater reliability of the MRI diagnosis the κ statistics were done as well as percent agreement.
Statistical analyses were done with SPSS version 21.0 (Chicago, IL).
Results
The mean patient age was 41.9 (SD, 11.35) and 76.4% were male. Fifty percent of lumbar disc herniations were at the L5/S1 level and the majority of herniations were paracentral in location (Fig 1). Sixty percent of the herniations were classified as extrusions (Fig 2) with nearly one third being sequestrations (Fig 3, Fig 4).
Fig 4Distribution of disc herniation level, location and morphology.
For the inter-rater reliability part of this study an agreement of 100% and a κ of 1.0 for spinal level of the herniation was found, which is perfect. For the axial location of herniation an agreement of 82.8% and a κ of 0.733 was found, which is substantial agreement. For the type of herniation an agreement of 86.1% and a κ of 0.745 was calculated, which is also substantial (Table 1).
There were no significant relationships, between the spinal level of disc herniation, the location in the axial plane or the type of herniation and improvement for any of the data collection time points (Table 2, Table 3). A higher percentage of patients with disc sequestration reported improvement at 1 month (77.3%) compared to patients with disc extrusion (66.7%) but this did not quite meet statistical significance (P = .056). In general, a higher proportion of patients with sequestration reported improvement at all of the other time points but none reached statistical significance (Table 2).
Table 2Comparison of Improvement and Secondary Outcomes Between the Disc Herniation Types
Regarding the location of disc herniation in the axial plane (ie, central, paracentral, foraminal, extraforaminal and the combination of paracentral plus foraminal) there was a statistically significant difference in the 2 week NRS back pain change scores when comparing patients with paracentral plus foraminal herniations with patients having only foraminal herniations (P = .04) (Table 3). Patients with paracentral plus foraminal herniation had a pain reduction of 3.7 (SD = 2.3) NRS back pain points compared to only 1.0 (SD = 1.2) point for patients with foraminal herniations only. However, there were no significant differences between these two groups for any of the other data collection time points or for leg pain or Oswestry change scores at any data collection period. Only 4 patients had a purely foraminal herniation however.
There was a tendency for disc herniation type (ie, bulge, protrusion, extrusion and sequestration) to be linked to the 2 week change in NRS back pain scores (P = .053). Table 2 shows the outcomes for patients with extrusion (n = 42) and sequestration (n = 22) only as there were only 2 patients with a bulge and 2 with a protrusion. Patients with extrusion reported a mean pain reduction of 3.32 (SD = 3.0) points compared to 1.78 (SD = 2.69) points for patients with disc sequestration. Furthermore, there was a statistically significant difference between patients with extrusion and sequestration for the 1 month NRS leg pain change score (P = .02). Patients with sequestration had a significantly higher amount of leg pain reduction of 4.34 NRS points compared to only 2.39 points for patients with extrusion. A similar trend was noted for NRS leg pain change scores at the 3 month time period (Table 2) but this did not reach statistical significance.
Discussion
The purpose of this study was to evaluate whether specific MRI features, specifically axial location and type (bulge, protrusion, extrusion, sequestration) of a herniated disc, are associated with the short and long term outcomes of patients treated with high-velocity, low-amplitude SMT specifically to the level of the symptomatic, MRI confirmed, herniation. This is the first study to address this question. Studies searching for predictors of improvement after treatment in previous low back pain patients did not target type and axial location of the herniated discs.
The Nordic Back Pain Subpopulation Program: validation and improvement of a predictive model for treatment outcome in patients with low back pain receiving chiropractic treatment.
Additionally, patients with disc sequestration were not excluded from this study as was done in the randomized controlled clinical trial (RCT) by Santilli et al on SMT in patients with disc herniation.
Chiropractic manipulation in the treatment of acute back pain and sciatica with disc protrusion: a randomized double-blind clinical trial of active and simulated spinal manipulations.
The only other RCT evaluating SMT in lumbar disc herniation patients does not even mention the issue of disc sequestration at all in their small sample size.
Importantly, in terms of type of the herniated disc, we found that leg pain reduction at 1 month after the first treatment in patients with sequestration is significantly higher compared to patients with extrusion as well as a nearly significant difference between these two groups in the percentage of patients reporting clinically relevant improvement. Over 77% of patients with disc sequestration reported clinically relevant “improvement” compared to 66.7% of patients with extrusion. Although not statistically significant, 100% of patients with sequestration reported clinically relevant improvement at the 3 month data collection time point and at all data collection time points a higher proportion of patients with sequestration reported clinically relevant improvement. There were no significant differences for disc herniation location either by spinal level or in the axial plane for any of the data collection time points. This now calls into question the traditional thinking that disc sequestrations are more dangerous than herniations that remain attached to the parent disc and are more likely to require surgery.
However, the studies reporting this did not consider chiropractic spinal manipulative therapy as a treatment option.
Although patients with foraminal location of their disc herniation had significantly less low back pain reduction at the 2 week time point compared to patients whose disc herniations were paracentral plus foraminal in location, it must be noted that only 4 of the 68 patients had a foraminal only disc herniation. Linking a patient’s clinical symptoms with MRI findings is important when determining appropriate treatments rather than basing treatment on MRI findings alone.
Clinical correlation of magnetic resonance imaging with symptom complex in prolapsed intervertebral disc disease: A cross-sectional double blind analysis.
Potential of magnetic resonance imaging findings to refine case definition for mechanical low back pain in epidemiological studies: a systematic review.
Little research has been done on this but is starting to emerge. The recent study by Bensler et al found that patients with cervical disc extrusions compared to the other disc morphologies had less pain relief when treated with indirect nerve-root-blocks and were 4 times more likely to subsequently require surgery.
However, only 1 of the 112 patients in that study had a disc sequestration so direct comparisons between this lumbar disc herniation study, which had 22 patients with disc sequestration, and the Bensler et al study on cervical disc herniations cannot be done.
The mechanism as to why patients with sequestered disc herniations had better treatment outcomes compared to patients with disc extrusions is currently unknown and should be investigated. Perhaps these patients with disc sequestration have more normal biomechanics at the affected motion segment compared to patients whose herniations remain attached to the parent disc.
This current study supports SMT as a treatment in patients with all locations and types of disc herniation providing there are no signs of cauda equina compression or deteriorating neurology between treatments.
It is interesting to note that two different SMT procedures were used depending on the location of the disc herniation in the axial plane as determined by the MRI scans. These SMT procedures were developed based on the clinical experience and reflection of the senior treating chiropractor over time and then taught to the younger clinicians. After the 2 week data collection time point there were no significant differences in the proportion of patients reporting clinically relevant improvement based on the location of the herniation in the axial plane. This may indeed support the use of different SMT procedures based on the location of herniation but it does not prove that the improvement was due to the specific manipulative procedure. An RCT would be needed to randomly assign one of the two SMT procedures irrespective of the axial location of the disc herniation.
Limitations
From the 148 patients at baseline in the study by Leemann et al we looked at the 68 patients whose MRI scans were available on the chiropractic practice computer system. This was a convenience sample and large enough to get some statistically relevant information but it is possible that with a larger sample size those results that were close to being statistically significant would indeed have become significant. Certainly important trends were noted. Thus, a larger sample size may have strengthened the relationship between herniation type, particularly sequestration, and treatment outcomes.
For outcome measures the NRS and OPDQ were used before treatment (baseline) as well as at 2 weeks, 1, 3, 6 and 12 months after treatment along with the primary outcome measure of the PGIC. For type and determination of axial location the recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology were used, which suggest using the terms bulging, protrusion, extrusion and sequestration and the categories of central, paracentral, foraminal and extraforaminal.
Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.
These methods therefore were very adequate. Today however, the Bournemouth Questionnaire would be the preferred outcome measure instead of the OPDQ for these particular types of patients. It gives a broader picture of the limitations of a condition including psychosocial aspects, which are not included in the OPDQ. At the time the study was conducted by Leemann et al the Bournemouth Questionnaire for low back pain was not yet translated and validated into German.
A possible limitation for the reliability part could be that the 3 persons interpreting the MRI slices were looking at the same screen simultaneously while one rater navigated through the MRI slides. Although none commented on what was seen until all 3 raters wrote down their findings, the way the navigator may have hesitated at certain slices could influence the other two observers. This study of course has some of the same limitations as the one by Leemann et al, which are that this is a cohort outcomes study rather than an RCT and that all patients were treated in a single chiropractic practice.
Outcomes of acute and chronic patients with magnetic resonance imaging-confirmed symptomatic lumbar disc herniations receiving high-velocity, low-amplitude, spinal manipulative therapy: a prospective observational cohort study with one-year follow-up.
In this current study, unlike the Leemann et al publication, we did not make a difference between chronic and acute patients because in the original study the proportion of chronic patients reporting improvement was nearly as high as for the acute patients.
Conclusions
The majority of patients in this study had either extruded or sequestered disc herniations. Patients with sequestered herniations treated with SMT to the level of herniation reported significantly higher levels of leg pain reduction at 1 month and a higher proportion reported improvement at all data collection time points compared to patients with extruded disc herniations but this did not reach statistical significance. Further investigation is needed to determine mechanisms for this finding. This also calls into question the seriousness of disc sequestration in determining appropriate treatment.
Funding Sources and Potential Conflicts of Interest
The European Chiropractors’ Union, the Balgrist Foundation, and the Uniscientia Foundation for providing funding for this study. No conflicts of interest were reported for this study.
Contributorship Information
Concept development (provided idea for the research): C.P., S.L., C.S., B.A., B.K.H.
Design (planned the methods to generate the results): C.P., S.L., C.S., B.A., B.K.H.
Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): C.P., B.K.H.
Data collection/processing (responsible for experiments, patient management, organization, or reporting data): S.L., C.S., B.A., M.E., C.P.
Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): C.P, M.E.
Literature search (performed the literature search): M.E., C.P.
Writing (responsible for writing a substantive part of the manuscript): M.E., C.P.
Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): B.K.H., S.L., C.S., B.A.
Other (list other specific novel contributions): B.K.H. (obtained funding)
Practical Applications
•
Most patients had either lumbar disc extrusions or sequestrations.
•
A higher proportion of patients with sequestration reported clinically relevant improvement at all data collection time points
•
Patients with disc sequestrations had significantly higher leg pain change scores (ie, greater pain reduction) at 1 month compared to patients with extruded disc herniations.
•
There were no adverse events from spinal manipulation to patients with symptomatic, MRI confirmed, lumbar disc herniations.
References
Bajpai J
Saini S
Singh R
Clinical correlation of magnetic resonance imaging with symptom complex in prolapsed intervertebral disc disease: A cross-sectional double blind analysis.
Potential of magnetic resonance imaging findings to refine case definition for mechanical low back pain in epidemiological studies: a systematic review.
Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology.
The association of combination of disc degeneration, end plate signal change, and Schmorl node with low back pain in a large population study: the Wakayama Spine Study.
Outcomes of acute and chronic patients with magnetic resonance imaging-confirmed symptomatic lumbar disc herniations receiving high-velocity, low-amplitude, spinal manipulative therapy: a prospective observational cohort study with one-year follow-up.
The Nordic Back Pain Subpopulation Program: validation and improvement of a predictive model for treatment outcome in patients with low back pain receiving chiropractic treatment.
Chiropractic manipulation in the treatment of acute back pain and sciatica with disc protrusion: a randomized double-blind clinical trial of active and simulated spinal manipulations.
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