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IRCCS Istituto Ortopedico Galeazzi, via R. Galeazzi 4, 20126, Milan, Italy, stefania.vaga@hotmail.it.
The dynamic stabilization of lumbar spine is a non-fusion stabilization system that unloads the disc without the complete loss of motion at the treated motion segment. Clinical outcomes are promising but still not definitive, and the long-term effect on instrumented and adjacent levels is still a matter of discussion. Several experiments have been devised in order to gain a better understanding of the effect of the device on the intervertebral disc. One of the hypotheses was that while instrumented levels are partially relieved from loading, adjacent levels suffer from the increased stress. But this has not been proved yet. The aim of this study was to investigate the long-term effect of dynamic stabilization in vivo, through the quantification of glycosaminoglycans (GAG) concentration within instrumented and adjacent levels by means of the delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) protocol. Ten patients with low back pain, unresponsive to conservative treatment and scheduled for Dynesys implantation at one to three lumbar spine levels, underwent the dGEMRIC protocol to quantify GAG concentration before and 6 months after surgery. Each patient was also evaluated with visual analog scale (VAS), Oswestry, Prolo, Modic and Pfirrmann scales, both at pre-surgery and at follow-up. Six months after implantation, VAS, Prolo and Oswestry scales had improved in all patients. Pfirrmann scale could not detect any change, while dGEMRIC data already showed a general improvement in the instrumented levels: GAG was increased in 61% of the instrumented levels, while 68% of the non-instrumented levels showed a decrease in GAG, mainly in the posterior disc portion. In particular, seriously GAG-depleted discs seemed to have the greatest benefit from the Dynesys implantation, whereas less degenerated discs underwent a GAG depletion. dGEMRIC was able to visualize changes in both instrumented and non-instrumented levels. Our results suggest that the dynamic stabilization of lumbar spine is able to stop and partially reverse the disc degeneration, especially in seriously degenerated discs, while incrementing the stress on the adjacent levels, where it induces a matrix suffering and an early degeneration.
PMID: 19396475 [PubMed - as supplied by publisher]
1: Orthop Clin North Am. 2004 Jan;35(1):43-56.
William Beaumont Hospital, 3535 West Thirteen Mile Road, Suite 604, Royal Oak, MI 48073, USA. dsengupta@beaumont.edu
Soft stabilization has an important role in the treatment of the degenerative lumbar spine. Fusion of one or two motion segments may not make a big difference in the total range of motion of the lumbar spine, but preserving flexibility of a motion segment may prevent adjacent segment disease and may permit disc replacement, even when facet joints need to be excised. If a favorable environment is created in the motion segment by unloading the disc and permitting near normal motion, the disc may be able to repair itself or may supplement the reparative potential of gene therapy. Although soft stabilization seems promising, one should take a cautious approach to any new implant system. An implant for fusion only has to serve a temporary stabilization until fusion has taken place; on the other hand, a soft stabilization system has to provide stability throughout its life. Implant loosening following fusion surgery is common in the presence of pseudarthrosis. After soft stabilization, the implant has to stay anchored to the bone despite allowing movement. This sounds like a daunting task. The flexibility of the implant system, however, should be able to protect it from loosening at the anchor point into the bone. Finally, the soft stabilization system is intended to load-share with the disc and the facet joint only partially and unloads the motion segment. Any mismatch between the kinematics of the implant system and the motion segment, in particular any discrepancy between their IAR, would result in the implant bearing unexpected load at certain ranges of motion. If that happens, it would guarantee an early implant failure or loosening. The need for strict bench testing in the laboratory, therefore, cannot be over-emphasized. The few soft stabilization systems that have had clinical applications so far have produced a clinical outcome comparable to that of fusion. No prospective randomized controlled trial has been reported yet, which is an essential requirement for practice of evidence-based medicine.
1: Radiology. 2009 Mar;250(3):849-55.
Annapolis Spine Institute, 2002 Medical Pkwy, Suite 235, Annapolis, MD 21401, USA.
PURPOSE: To assess the value of vertebral body endplate signal intensity (Modic) changes on magnetic resonance (MR) images in predicting a painful disk, with provocative diskography as the reference standard. MATERIALS AND METHODS: Lumbar spine diskograms and prediskogram MR images of 736 patients (2457 disks) were retrospectively reviewed as part of an institutional review board-approved HIPAA-compliant protocol. Each disk was assigned a Modic subtype: type 0, normal; type 1, nonfatty high signal intensity; type 2, fatty; and type 3, sclerosis. Statistical analysis involved use of a 2 x 2 contingency table of diskogram results for each of the subtypes. The subtype sensitivity, specificity, positive predictive value (PPV), negative predictive value, and confidence intervals (CIs) were calculated. Similar analyses of other MR variables (such as disk herniation, high signal intensity zone, and spondylolisthesis) and type 1 signal intensity changes also were performed. RESULTS: Type 1 changes (n = 155) had a high PPV (0.81; 95% CI: 0.74, 0.87) for a provocative diskogram. Type 2 changes (n = 126) had a lower PPV (0.64; 95% CI: 0.55, 0.72) for a positive diskogram. Type 3 changes (n = 21) had a PPV (0.57; 95% CI: 0.34, 0.78) that was not significant for a positive diskogram. The PPV of an endplate with a type 1 change (hereafter, type 1 endplate) for a tear in the annulus fibrosis of the disk was also insignificant (0.14; 95% CI: 0.09, 0.20). A similar analysis between a type 1 endplate and the presence of a disk herniation (PPV, 0.26; 95% CI: 0.19, 0.34) and between a type 1 endplate and vertebral body spondylolisthesis (PPV, 0.28; 95% CI: 0.20, 0.35) were significant. CONCLUSION: Type 1 signal intensity changes on MR images have a high positive predictive value in the identification of a pain generator. RSNA, 2009
1: Skeletal Radiol. 2009 Mar;38(3):237-44. Epub 2008 Dec 19.
Helsinki and Uudenmaa District University Hospitals, Helsinki University Central Hospital, HUS-röntgen, PL 340, 00029 HUS, Helsinki, Finland, katariina.luoma@hus.fi.
OBJECTIVE: The objective was to study the natural course of Modic type 1 change (M1) in relation to lumbar disc degeneration. MATERIALS AND METHODS: Twenty-four chronic low back pain (LBP) patients with M1 on lumbar spine were selected from 1,015 patients with magnetic resonance imaging from a follow-up study lasting for 18-74 months. Exclusion criteria were any other specific back disorder, age >/=60 years, or a recent spine operation. The association between the development of M1 and degenerative disc changes was studied using multivariate modeling (complex samples logistic regression). RESULTS: At baseline, 20 of 28 (71%) disc spaces with M1 had a decreased disc height (DH) and 16 of 28 (57%) a dark nucleus pulposus, but ten of 28 (36%) a very dark annulus fibrosus and a paradoxically bright nucleus pulposus albeit decreased DH. During follow-up, DH decreased in 13 of 28 (46%) and signal intensity of nucleus pulposus (DSI) in eight of 28 (29%) disc spaces with M1, but it increased in four (14%) discs. In those without M1, only few changes occurred. The larger the M1, the more likely was the DH low or decreased further. Both the presence and changes in M1 were associated with a decrease in DH and changes in DSI and bulges. CONCLUSION: The degenerative process in discs with adjacent M1 seems to be accelerated and leads to advanced and deforming changes with special morphologic features. M1 may be a sign of a pathologic degenerative process in the discovertebral unit
1: Eur Spine J. 2008 Nov;17(11):1407-22. Epub 2008 Sep 12.
The Back Research Center, Lindevej 5, Ringe, Denmark. Tue.Secher.Jensen@shf.regionsyddanmark.dk
The prevalence of "vertebral endplate signal changes" (VESC) and its association with low back pain (LBP) varies greatly between studies. This wide range in reported prevalence rates and associations with LBP could be explained by differences in the definitions of VESC, LBP, or study sample. The objectives of this systematic critical review were to investigate the current literature in relation to the prevalence of VESC (including Modic changes) and the association with non-specific low back pain (LBP). The MEDLINE, EMBASE, and SveMED databases were searched for the period 1984 to November 2007. Included were the articles that reported the prevalence of VESC in non-LBP, general, working, and clinical populations. Included were also articles that investigated the association between VESC and LBP. Articles on specific LBP conditions were excluded. A checklist including items related to the research questions and overall quality of the articles was used for data collection and quality assessment. The reported prevalence rates were studied in relation to mean age, gender, study sample, year of publication, country of study, and quality score. To estimate the association between VESC and LBP, 2 x 2 tables were created to calculate the exact odds ratio (OR) with 95% confidence intervals. Eighty-two study samples from 77 original articles were identified and included in the analysis. The median of the reported prevalence rates for any type of VESC was 43% in patients with non-specific LBP and/or sciatica and 6% in non-clinical populations. The prevalence was positively associated with age and was negatively associated with the overall quality of the studies. A positive association between VESC and non-specific LBP was found in seven of ten studies from the general, working, and clinical populations with ORs from 2.0 to 19.9. This systematic review shows that VESC is a common MRI-finding in patients with non-specific LBP and is associated with pain. However, it should be noted that VESC may be present in individuals without LBP.
1: J Manipulative Physiol Ther. 2007 Jan;30(1):5-10.
Department of Radiology and Chief of Clinical Radiology, Canadian Memorial Chiropractic College, Toronto, Ontario, Canada. cpeterson@cmcc.ca
OBJECTIVE: The prevalence and distribution of Modic degenerative marrow changes as seen on magnetic resonance imaging scans have been reported for the lumbar spine, and research suggests that type 1 Modic changes are linked to low back pain. The purpose of this study was to report on the prevalence, types, and distribution of the changes found for the cervical spine. METHODS: One hundred thirty-three cervical spine T1-weighted and T2-weighted sagittal magnetic resonance imaging scans were viewed retrospectively by two radiologists. Data were recorded for patient age, patient sex, and the presence or absence of Modic changes. If Modic changes were present, then the precise vertebral levels of these changes and the specific Modic type were recorded. Descriptive statistics were calculated for the prevalence of Modic changes overall, the prevalence of types 1, 2, and 3 changes, and the prevalence in male vs female patients. The frequency of these changes by spinal level was also determined. RESULTS: One hundred eighteen patients met the inclusion criteria. Modic changes were seen in 19 patients (16%), with 4 showing changes in more than one segmental level. The most common Modic change observed was type 1. Type 3 marrow changes were the second most common category to be noted. Only 3 patients had Modic type 2 marrow changes. The most common cervical spinal level to show Modic changes was C5-6. CONCLUSIONS: Modic degenerative bone marrow changes are observed in the cervical spine, with the C5-6 level being the most commonly involved. Unlike in the lumbar spine in which Modic type 2 changes predominate, type 1 marrow changes were far more common in the cervical spine. Further studies should focus on the clinical relevance of these findings.
1: Eur Spine J. 1998;7(5):363-8.
Department of Spinal Surgery, The Royal National Orthopaedic Hospital Trust, Stanmore, Middlesex, UK.
The vertebral end-plate has been identified as a possible source of discogenic low back pain. MRI demonstrates end-plate (Modic) changes in 20-50% of patients with low back pain. The aim of this study was to investigate the association between Modic changes on MRI and discogenic back pain on lumbar discography. The MRI studies and discograms of 58 patients with a clinical diagnosis of discogenic back pain were reviewed and the presence of a Modic change was correlated with pain reproduction at 152 disc levels. Twenty-three discs with adjacent Modic changes were injected, 21 of which were associated with pain reproduction. However, pain was also reproduced at 69 levels where no Modic change was seen. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for a Modic change as a marker of a painful disc were 23.3%, 96.8%, 91.3% and 46.5% respectively. Modic changes, therefore, appear to be a relatively specific but insensitive sign of a painful lumbar disc in patients with discogenic low back pain.
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