MRI phenotypes of herniated discs associated with adjacent disc degeneration.

Adjacent segment degeneration is commonly observed in patients after fusion surgery. Among the associated risk factors is the preoperative presence of adjacent disc degeneration (ADD). The risk factors and other spine phenotypes associated with preoperative ADD is critical to understand the pathological process and better prognosis postsurgery. Current study aims to assess and compare the magnetic resonance imaging (MRI) spinal phenotype of herniated level with and without ADD. Preoperative T2W sagittal lumbar MRI images of 155 lumbar disc herniated patients were analyzed for the presence of ADD (Pfirrmann grade III and above). The herniated disc level was assessed for the presence and absence of vertebral endplate (VEP) defects, Modic changes, and high intensity zone (HIZ). Mean age of patients was 38 ± 2 years, almost 62% were males. ADD was found in 57%, VEP defects were seen in 62% of the herniated level, 24.5% showed Modic changes, 3.8% showed spondylolishthesis, and 15.5% revealed HIZ. Age and other demographic factors did not have any significant effect on the presence of ADD, the patients with extruded and sequestered discs had more ADD (p = 0.02). VEP defects were significantly higher in levels with ADD (p = 0.02). Patients with ADD had significantly VEP defect scores (p = 0.01), Modic score (p = 0.002), HIZ score (0.02), and posterior bulge score (p < 0.001). Findings suggest that affected levels with VEP defects and severe grade of disc herniation have the greater likelihood of having ADD. Once developed this ADD may also affect the other spinal levels, and also can affect postoperative prognosis.

Computational modeling of lumbar disc degeneration before and after spinal fusion.

BACKGROUND: Advancing age and degeneration frequently lead to low back pain, which is the most prevalent musculoskeletal disorder worldwide. Degenerative changes in intervertebral discs and musculo-ligamentous incapacity to compensate sagittal imbalance are typically amongst the sources of instability, with spinal fusion techniques being the main treatment options to relieve pain. The aims of this work were to: (i) assess the link between ligament degeneration and spinal instability by determining the role of each ligament per movement, (ii) evaluate the impact of disc height reduction in degenerative changes, and (iii) unveil the most advantageous type of posterior fixation in Oblique Lumbar Interbody Fusion to prevent adjacent disc degeneration. METHODS: Two L3-L5 finite element models were developed, being the first in healthy condition and the second having reduced L4-L5 height. Different degrees of degeneration were tested, combined with different fixation configurations for Oblique Lumbar Interbody Fusion. FINDINGS: Facet capsular ligament and anterior longitudinal ligament were the most influential ligaments for spinal stability, particularly with increasing degeneration and disc height reduction. Pre-existent degeneration had lower influence than the fusion procedure for the risk of adjacent disc degeneration, being the highest stability and minimal degeneration achieved with bilateral fixation. Right unilateral fixation was more suited to reduce disc stress than left unilateral fixation. INTERPRETATION: Bilateral fixation is the best option to stabilize the spinal segment, but unilateral right fixation may suffice. This has direct implications for clinical practice, and the extension to a population-based study will allow for more efficient fusion surgeries.

Effect of Interbody Fusion on the Remaining Discs of the Lumbar Spine in Subjects with Disc Degeneration.

OBJECTIVE: To study effects (stress loads) of lumbar fusion on the remaining segments (adjacent or not) of the lumbar spine in the setting of degenerated adjacent discs. METHODS: A lumbar spine finite element model was built and validated. The full model of the lumbar spine was a parametric finite element model of segments L 1-5 . Numerous hypothetical combinations of one-level lumbar spine fusion and one-level disc degeneration were created. These models were subjected to 10 Nm flexion and extension moments and the stresses on the endplates and consequently on the intervertebral lumbar discs measured. These values were compared to the stresses on healthy lumbar spine discs under the same load and fusion scenarios. RESULTS: Increased stress at endplates was observed only in the settings of L4-5 fusion and L3-4 disc degeneration (8% stress elevation at L2,3 in flexion or extension, and 25% elevation at L3,4 in flexion only). All other combinations showed less endplate stress than did the control model. For fusion at L3-4 and degeneration at L4-5 , the stresses in the endplates at the adjacent level inferior to the fused disc decreased for both loading disc height reductions. Stresses in flexion decreased after fusion by 29.5% and 25.8% for degeneration I and II, respectively. Results for extension were similar. For fusion at L2-3 and degeneration at L4-5 , stresses in the endplates decreased more markedly at the degenerated (30%), than at the fused level (14%) in the presence of 25% disc height reduction and 10 Nm flexion, whereas in extension stresses decreased more at the fused (24.3%) than the degenerated level (5.86%). For fusion at L3-4 and degeneration at L2-3 , there were no increases in endplate stress in any scenario. For fusion at L4-5 and degeneration at L3-4 , progression of degeneration from I to II had a significant effect only in flexion. A dramatic increase in stress was noted in the endplates of the degenerated disc (L3-4 ) in flexion for degeneration II. CONCLUSIONS: Stresses are greater in flexion at the endplates of L3-4 and in flexion and extension at L2-3 in the presence of L3-4 disc disease and L4-5 fusion than in the control group. In all other combinations of fusion and disc disease, endplate stress was less for all levels tested than in the control model.

MRI Assessments of Adjacent Disc Degeneration Following Lumbar Fusion / 대한척추외과학회지

STUDY DESIGN: Retrospective case-control study OBJECTIVE: To use MRI to assess intervertebral disc degeneration at adjacent levels after spinal fusion and after discectomy. SUMMARY OF LITERATURE REVIEW: Degeneration of adjacent intervertebral discs following lumbar spinal fusion is one of the principal reasons for considering motion preservation techniques, such as placement of an artificial disc. Much attention has recently been directed toward disc morphometric studies using MRI. MATERIALS AND METHODS: Fifty-six patients who underwent spinal surgery for lumbar degenerative disease and who underwent a minimum of 2 years of follow-up MRIs were included in this study. Thirty-four patients were included in the lumbar fusion study group, and 22 patients were included in the discectomy control group. The MRI Thompson classification was used to grade both upper and lower adjacent disc degeneration preoperatively and at the time of last follow-up. RESULTS: There were significant changes in Thompson degenerative grade in the upper adjacent levels for both the fusion group patients and in the discectomy group patients. However, there was no statistically significant difference between the two groups with regard to either the upper or lower adjacent levels (p=0.146 and 0.350, respectively). CONCLUSIONS: In this short-term study comparing MRI outcomes in spinal fusion and discectomy patients, no significant difference in adjacent disc degeneration was observed between the two group.

Adjacent Segment Degeneration After Spinal Fusion In Lumbar Degenerative Disorders / 대한척추외과학회지

STUDY DESIGN: A retrospective radiological assessment was conducted. OBJECTIVES: An attempt to analyze the degenerative change of an intervertebral disc for adjacent segment degeneration in lumbar degenerative diseases. LITERATURE REVIEW SUMMARY: A review of the literature failed to uncover any documented study examining the quantitative analysis of the degenerative change of the intervertebral disc for adjacent segment degeneration. METHODS: This study was based on 45 patients, treated operatively or conservatively at this hospital, between April 1995 and July 2004. 39 and 6 cases of operative and conservative treatments, respectively, were performed. In the 39 operative treatments, there were 34 cases of fusion and 5 of discectomy. Dynamic X-ray and MRI were performed at the initial evaluation, and again more than 2 years later. In the 34 fusion cases, the upper and lower adjacent segments of the fused level were studied, and in the 11 non-fusion cases (conservative treatment or discectomy), the L3-4, L4-5 and L5-S1 level were studied. The instability of the dynamic X-ray and Thompson grade changes of the disc on MRI were also evaluated. Statistical analysis was carried out using the Wilcoxon signed rank test. RESULTS: Adjacent segment degeneration was found in 10 of the 34 cases (29.4%) on plain X-ray. The average Thompson grades of the 33 upper segment cases were 2.6 and 3.4 preoperatively and postoperatively (P=0.000), and for the 24 of the lower segment cases were 2.9and 3.2 (P=0.033), respectively. No statistical increase in the Thompson grade was found in the non-fusion group. CONCLUSIONS: The adjacent discs of the fusion group showed statistically meaningful degeneration on MRI, but this was not correlated with adjacent segment degeneration on plain X-ray. Various anatomical and functional factors must be considered in the evaluation of adjacent segment disease.

Adjacent Segment Degeneration After Spinal Fusion In Lumbar Degenerative Disorders / 대한척추외과학회지

STUDY DESIGN: A retrospective radiological assessment was conducted. OBJECTIVES: An attempt to analyze the degenerative change of an intervertebral disc for adjacent segment degeneration in lumbar degenerative diseases. LITERATURE REVIEW SUMMARY: A review of the literature failed to uncover any documented study examining the quantitative analysis of the degenerative change of the intervertebral disc for adjacent segment degeneration. METHODS: This study was based on 45 patients, treated operatively or conservatively at this hospital, between April 1995 and July 2004. 39 and 6 cases of operative and conservative treatments, respectively, were performed. In the 39 operative treatments, there were 34 cases of fusion and 5 of discectomy. Dynamic X-ray and MRI were performed at the initial evaluation, and again more than 2 years later. In the 34 fusion cases, the upper and lower adjacent segments of the fused level were studied, and in the 11 non-fusion cases (conservative treatment or discectomy), the L3-4, L4-5 and L5-S1 level were studied. The instability of the dynamic X-ray and Thompson grade changes of the disc on MRI were also evaluated. Statistical analysis was carried out using the Wilcoxon signed rank test. RESULTS: Adjacent segment degeneration was found in 10 of the 34 cases (29.4%) on plain X-ray. The average Thompson grades of the 33 upper segment cases were 2.6 and 3.4 preoperatively and postoperatively (P=0.000), and for the 24 of the lower segment cases were 2.9and 3.2 (P=0.033), respectively. No statistical increase in the Thompson grade was found in the non-fusion group. CONCLUSIONS: The adjacent discs of the fusion group showed statistically meaningful degeneration on MRI, but this was not correlated with adjacent segment degeneration on plain X-ray. Various anatomical and functional factors must be considered in the evaluation of adjacent segment disease.

Changes of Adjacent Segment in Anterior Cervical Fusion / 대한척추외과학회지

STUDY DESIGN: A retrospective radiographic and medical record analysis of 36 patients. OBJECTIVES: To describe the incidence and consequence of the distribution of sagittal plane motion, across the adjacent cervical motion segment, after cervical fusion. Furthermore, to find the cause of the progression of degenerative changes in intervertebral discs adjacent to the fused segment. SUMMARY OF LITERATURE REVIEW : Anterior cervical fusion has been widely used in the treatment of degenerative cervical spine. An increased incidence of degenerative disease may exist at the levels immediately adjacent to a cervical fusion. However, the frequency of these complications is probably overestimated, and their effect on clinical outcome remains unknown. MATERIALS AND METHODS: From 1990 to 1996, 36 patients who underwent anterior cervical spine fusion for degenerative disorders were reviewed retrospectively with an average follow up of 6.9 years. Lateral views in neutral position, in flexion, and in extension of the preoperative cervical roentgenograms were analyzed in comparison with the last follow-up films in the range of motion of the neck, and in the intervertebral angular mobility and anteroposterior displacement of the vertebral bodies, and finally to quantify the incidence of the spinal instability. RESULTS: Degenerative change in adjacent intervertebral level was observed in 16 of the 36 patients (44.4%), above the fusion in 10, below the fusion in 4, and both above and below the fusion in 2 cases. In addition, degenerative change in adjacent intervertebral level was observed in 68% of cases of loss of lordosis of the fused segment, and degenerative change occurred more frequently in younger patients to a statistically significant extent. CONCLUSIONS: Loss of lordosis of the fused segment and young age are two factors promoting degenerative changes in adjacent intervertebral levels after anterior cervical fusion.