CORRELATION BETWEEN THE MODIC I SIGN AND IMAGES OF VERTEBRAL INSTABILITY

The lumbar region is highly affected by degenerative diseases and can be symptomatic as a result of inflammatory processes of the disc or segmental vertebral instability (SVI), according to concepts by White and Panjabi. Magnetic resonance imaging (MRI) and dynamic radiographs can be used to evaluate it. Objective: To determine whether images of Modic type I lesions are compatible with radiological vertebral instability. Methods: The MRIs and dynamic radiographs of 100 patients with a mean age of 46.94 years, 65 of whom were women and 35 of whom were men, were studied to evaluate the reaction of endplates according to Modic and SVI at levels L2-L3, L3-L4, L4-L5 and L5-S1. They were divided into 3 groups: A-Modic I and SVI; B-Modic I without SVI; and C-Without Modic I and SVI. Sex, age and type of disc were evaluated. Result: 46 Modic I lesions and 24 cases of SVI were recognized. There were 5 patients in Group A (OR 0.23, p=0.006), 38 in Group B; and 19 in Group C. No direct relationship between age and Modic I and/or SVI was observed. Pfirrmann grade 5 discs are 4.6 times more likely to present a Modic I signal. The most affected disc was L3-L4 for the Modic signal and L4-L5 with respect to the SVI, translational instability being more frequent. Conclusions: Modic type changes, identified by magnetic resonance, are clinically relevant in relation to low back pain, but their presence does not confirm either translational or angular instability. Level of evidence III; Cross-sectional cohort.


INTRODUCTION
The lumbar region of the spine is one of the areas most frequently affected by degenerative pathology and it is often associated with pain. 1,2][5][6] Lumbar spine instability is associated with lumbar pain and is strongly related to degenerative changes of the discs and joints and to the presence of morphological and structural changes of the yellow ligament; 1,2 and it is difficult to diagnose. 7valuation using neutral lateral and anteroposterior radiographs is recommended in all patients with lumbar symptoms that persist for more than 4 to 6 weeks. 2,8ateral radiographs of flexion and extension are performed to assess dynamic vertebral instability 8 and have been interpreted by White and Panjabi, 9 in which translation or hypermobility during flexion-extension can be signs of segmental instability. 1,10owever, MRI continues to be the most sensitive and specific method for evaluating intervertebral disc pathology, and even more so if a dynamic resonator is available. 1,5,11ur objective was to determine whether images of Modic type I lesions are compatible with radiological vertebral instability.

METHODS
An observational, analytical, cohort-type evaluation of patients with mechanical low back pain was performed using both magnetic resonance images (MRI) of the lumbosacral spine and lateral radiographs of the same segment in maximum flexion (LMF) and maximum extension (LME).A cohort study of 100 patients, 65 of them women and 35 men, ranging in age from 16 to 84 years of age (mean of 46.94) was conducted.
The following parameters were used as inclusion criteria: mechanical low back pain, the presence of a Modic type I (inflammatory) magnetic resonance image, and segmental vertebral instability values in dynamic radiographs (difference in displacement >3 mm and/or in angulation >12°).
Patients with fractures, tumors, infections and prior surgeries were excluded.
The patients were divided into three groups: Group A: Modic I patients with instability parameters; Group B: Modic I patients without instability parameters; and Group C: Patients without Modic I with instability parameters.Patient age, sex, and disc type according to the Pfirrmann scale (Table 1) were recorded for each group.
The data were loaded into an Access database and analyzed using Epi Info 3.3.2and evaluated using chi-squared, the odds ratio, and the student's t-test.
Forty-six Modic I lesions and 24 radiological instabilities were identified.
Only 5 patients presented Modic I associated with instability (Group A).Of these, 4 were in the 40-60 years of age group and one was in the 20-40 years of age group.The L3-L4 disc was affected in one case and the L4-L5 level in the other four.The L3-L4 disc was a Pfirrmann classification grade 3. Of the four L4-L5 discs, three were Pfirrmann classification grade 5 and one was grade 4. Four in this group presented instability from translation and one from angular instability.(Table 2) In Group B, 38 levels presented Modic I lesions without instability.There were three Modic lesions at level L2-L3, with one disc each of grades 1, 4, and 5.At the L3-L4 level, there were a total of five Modic lesions, two grade 3, one grade 4, and two grade 5.At level L4-L5 there were sixteen Modic lesions, with two grade 3, five grade 4, and six grade 5.At the L5-S1 level, there were 17 Modic lesions, one with disc grade 1, two grade 3, four grade 4, and ten grade 5. (Table 3) There were 19 patients in Group C, the instability without Modic group.Eighteen of them had transitional instability and one had angular instability.There were 16 instabilities at level L4-L5, 10 of which were classified as Pfirrmann grade 3, three as grade 4 and two as grade 5.At level L3-L4 there were three instabilities, with two grade 3 discs and one grade 4 disc.There was only one unstable L5-S1 with a grade 5 disc.(Table 4) The statistical analysis performed showed that there is a 4.6 times greater chance of having an inflammatory Modic signal (Modic I) in the presence of a Pfirrmann grade 5 disc (odds ratio of 4.670 with p=0.0001).
The possibility of presenting a Modic lesion and SVI at the same level is very low (odds ratio of 0.26 with p=0.006).
We did not observe any direct relationship between age and the Modic lesion and/or the SVI.

DISCUSSION
Only 5 patients had Modic I associated with instability (Group A).This result observed in the study was not adequately discussed.In the discussion, the authors stated that the Modic type I lesion is more often associated with lumbar pain than the other types and corresponds to a hypervascular inflammatory state in which some degree of microinstability may exist. 4egenerative disc disease is a common problem that often increases with age. 1,2,11,12firrmann suggests correlations between degenerative lesions and structural changes in the intervertebral endplates in cases of association between both pathologies, and proposed a classification of disc degeneration based on 5 grades. 13odic 3 formulated a simple and easy method for interpreting degenerative disc disease linked to changes in the bone marrow signal into three distinct types.5][6] This state of supposed instability may be a sign of active degeneration. 6Type I lesions commonly progress to type II, but they also may go into remission. 5,16However, the morphological differences do not always correlate with the symptoms. 15odic II is defined as a more stable state in which fat replacement is a continuation of the degenerative process. 6Braithwaite et al. report that the different Modic changes are the consequence of different states of the same pathology. 16,17 veral authors [4][5][6]8 indicate that the inflammatory lesions (I) are associated with SVI in 40% of cases and the degenerative lesions (II) in 20%. Inour study we only analyzed the patients with Modic I (Groups A and B) and 11.63% of these patients presented SVI, a number less than that reported in the international literature.Of the total patient sample analyzed, 38.71% presented the SVI sign and the relationship with Modic I was observed in 26.32% of these.
Malinin and Brown 18 conducted studies in primates and stated that vascular disruption of the endplate and the loss of disc support, as the result of microfractures and bone necrosis, explain the pathogenesis of the lesion. 6,18andhu et al. could not demonstrate any relationship between discography and these changes in the magnetic resonance imaging. 19egmental vertebral instability has been identified in several publications as responsible for low back pain, with degenerative disc pathology being one of those most responsible for low back pain. 11he use of dynamic radiographs remains a controversial method.However, it allows us to determine instabilities that could go unnoticed in static radiographs and magnetic resonance. 8ith technological advances, such as dynamic magnetic resonance imaging, it would be easier to research these pathologies. 1,11,10NCLUSIONS Segmental instability, especially translational instability, is often an important factor in determining surgical indications of spinal arthrodesis in patients submitted to decompression surgery.
Modic type changes, identified by magnetic resonance, are clinically relevant in relation to low back pain, but their presence does not confirm either translational or angular instability.Therefore, emphasis must be placed on an analysis of the axial instability of the lumbar spine in order to determine its relationship to this.
All authors declare no potential conflict of interest related to this article.

Table 2 .
List and characteristics of the Group A patients (Modic I and SVI).

Table 4 .
List and characteristics of the patients in Group C (Without Modic I and with SVI).