Correlation of pain with objective quantification of magnetic resonance images in older adults with chronic low back pain

Personalized Interventional Surgery of the Lumbar Spine: A Perspective on Minimally Invasive and Neuroendoscopic Decompression for Spinal Stenosis

Pain generator-based lumbar spinal decompression surgery is the backbone of modern spine care. In contrast to traditional image-based medical necessity criteria for spinal surgery, assessing the severity of neural element encroachment, instability, and deformity, staged management of common painful degenerative lumbar spine conditions is likely to be more durable and cost-effective. Targeting validated pain generators can be accomplished with simplified decompression procedures associated with lower perioperative complications and long-term revision rates. In this perspective article, the authors summarize the current concepts of successful management of spinal stenosis patients with modern transforaminal endoscopic and translaminar minimally invasive spinal surgery techniques. They represent the consensus statements of 14 international surgeon societies, who have worked in collaborative teams in an open peer-review model based on a systematic review of the existing literature and grading the strength of its clinical evidence. The authors found that personalized clinical care protocols for lumbar spinal stenosis rooted in validated pain generators can successfully treat most patients with sciatica-type back and leg pain including those who fail to meet traditional image-based medical necessity criteria for surgery since nearly half of the surgically treated pain generators are not shown on the preoperative MRI scan. Common pain generators in the lumbar spine include (a) an inflamed disc, (b) an inflamed nerve, (c) a hypervascular scar, (d) a hypertrophied superior articular process (SAP) and ligamentum flavum, (e) a tender capsule, (f) an impacting facet margin, (g) a superior foraminal facet osteophyte and cyst, (h) a superior foraminal ligament impingement, (i) a hidden shoulder osteophyte. The position of the key opinion authors of the perspective article is that further clinical research will continue to validate pain generator-based treatment protocols for lumbar spinal stenosis. The endoscopic technology platform enables spine surgeons to directly visualize pain generators, forming the basis for more simplified targeted surgical pain management therapies. Limitations of this care model are dictated by appropriate patient selection and mastering the learning curve of modern MIS procedures. Decompensated deformity and instability will likely continue to be treated with open corrective surgery. Vertically integrated outpatient spine care programs are the most suitable setting for executing such pain generator-focused programs.

A Proposed Personalized Spine Care Protocol (SpineScreen) to Treat Visualized Pain Generators: An Illustrative Study Comparing Clinical Outcomes and Postoperative Reoperations between Targeted Endoscopic Lumbar Decompression Surgery, Minimally Invasive TLIF and Open Laminectomy

Background: Endoscopically visualized spine surgery has become an essential tool that aids in identifying and treating anatomical spine pathologies that are not well demonstrated by traditional advanced imaging, including MRI. These pathologies may be visualized during endoscopic lumbar decompression (ELD) and categorized into primary pain generators (PPG). Identifying these PPGs provides crucial information for a successful outcome with ELD and forms the basis for our proposed personalized spine care protocol (SpineScreen). Methods: a prospective study of 412 patients from 7 endoscopic practices consisting of 207 (50.2%) males and 205 (49.8%) females with an average age of 63.67 years and an average follow-up of 69.27 months was performed to compare the durability of targeted ELD based on validated primary pain generators versus image-based open lumbar laminectomy, and minimally invasive lumbar transforaminal interbody fusion (TLIF) using Kaplan-Meier median survival calculations. The serial time was determined as the interval between index surgery and when patients were censored for additional interventional and surgical treatments for low back-related symptoms. A control group was recruited from patients referred for a surgical consultation but declined interventional and surgical treatment and continued on medical care. Control group patients were censored when they crossed over into any surgical or interventional treatment group. Results: of the 412 study patients, 206 underwent ELD (50.0%), 61 laminectomy (14.8%), and 78 (18.9%) TLIF. There were 67 patients in the control group (16.3% of 412 patients). The most common surgical levels were L4/5 (41.3%), L5/S1 (25.0%), and L4-S1 (16.3%). At two-year f/u, excellent and good Macnab outcomes were reported by 346 of the 412 study patients (84.0%). The VAS leg pain score reduction was 4.250 ± 1.691 (p < 0.001). No other treatment during the available follow-up was required in 60.7% (125/206) of the ELD, 39.9% (31/78) of the TLIF, and 19.7% (12/61 of the laminectomy patients. In control patients, only 15 of the 67 (22.4%) control patients continued with conservative care until final follow-up, all of which had fair and poor functional Macnab outcomes. In patients with Excellent Macnab outcomes, the median durability was 62 months in ELD, 43 in TLIF, and 31 months in laminectomy patients (p < 0.001). The overall survival time in control patients was eight months with a standard error of 0.942, a lower boundary of 6.154, and an upper boundary of 9.846 months. In patients with excellent Macnab outcomes, the median durability was 62 months in ELD, 43 in TLIF, and 31 months in laminectomy patients versus control patients at seven months (p < 0.001). The most common new-onset symptom for censoring was dysesthesia ELD (9.4%; 20/206), axial back pain in TLIF (25.6%;20/78), and recurrent pain in laminectomy (65.6%; 40/61) patients (p < 0.001). Transforaminal epidural steroid injections were tried in 11.7% (24/206) of ELD, 23.1% (18/78) of TLIF, and 36.1% (22/61) of the laminectomy patients. The secondary fusion rate among ELD patients was 8.8% (18/206). Among TLIF patients, the most common additional treatments were revision fusion (19.2%; 15/78) and multilevel rhizotomy (10.3%; 8/78). Common follow-up procedures in laminectomy patients included revision laminectomy (16.4%; 10/61), revision ELD (11.5%; 7/61), and multilevel rhizotomy (11.5%; 7/61). Control patients crossed over into ELD (13.4%), TLIF (13.4%), laminectomy (10.4%) and interventional treatment (40.3%) arms at high rates. Most control patients treated with spinal injections (55.5%) had excellent and good functional outcomes versus 40.7% with fair and poor (3.7%), respectively. The control patients (93.3%) who remained in medical management without surgery or interventional care (14/67) had the worst functional outcomes and were rated as fair and poor. Conclusions: clinical outcomes were more favorable with lumbar surgeries than with non-surgical control groups. Of the control patients, the crossover rate into interventional and surgical care was 40.3% and 37.2%, respectively. There are longer symptom-free intervals after targeted ELD than with TLIF or laminectomy. Additional intervention and surgical treatments are more often needed to manage new-onset postoperative symptoms in TLIF- and laminectomy compared to ELD patients. Few ELD patients will require fusion in the future. Considering the rising cost of surgical spine care, we offer SpineScreen as a simplified and less costly alternative to traditional image-based care models by focusing on primary pain generators rather than image-based criteria derived from the preoperative lumbar MRI scan.

A comparative study to evaluate disc degeneration on magnetic resonance imaging in patients with chronic low back pain and asymptomatic individuals

Objectives

The present study aimed to investigate the association of disc degeneration with low back pain and the effect of ageing on disc degeneration in low back pain versus asymptomatic individuals.

Methodology

A total of 50 patients with chronic low back pain (Group A) were compared to 25 healthy controls (Group B). Both the groups were subjected to magnetic resonance imaging of the lumbar spine and the disc degeneration was measured by the Pfirrmann grading system. The study group (Group A) was further sub-grouped into A1 (lumbar spondylosis, n = 11), A2 (mechanical back pain, n = –13) and A3 (lumbar disc herniation, n = 26).

Results

There was a statistically significant difference in degeneration at the L4-L5 ( p = 0.001) and L5-S1 disc levels ( p = 0.001) between the two groups and contiguous disc involvement was more in low back pain patients. The subgroups of group A showed no statistically significant difference. Age showed a strong positive correlation ( r > 0.5) at all the lumbar levels (except at the L5-S1, r = 0.487) with Pfirrmann grading in Group A ( p = 0.001). There was a weak positive correlation ( r = 0.414) between age and Pfirrmann grade in the controls ( p = 0.04) at the L4-L5 level only.

Conclusions

Significantly higher Pfirrmann grading on magnetic resonance imaging was found at the L4-5 and L5-S1 levels in symptomatic patients suggesting higher involvement of these levels. Progressive disc degeneration is seen with ageing but in patients with low back pain, it is significantly accelerated.

Risk Factors for Axial Symptoms After Anterior Surgery Treating for Multilevel Cervical Disorder with kyphosis

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to investigate the risk factors associated with axial symptoms (AS) after anterior surgery in treatment of multilevel cervical disorder with kyphosis based on subgroup of follow-up time.

SUMMARY OF BACKGROUND DATA

Although many scholars reported on AS after cervical surgery, the risk factors associated with AS are controversial. Few studies have investigated the risk factors of AS after anterior cervical surgery treating multilevel cervical disorder with kyphosis.

METHODS

Totally, 103 patients who suffered from multilevel cervical disorder with kyphosis receiving anterior surgery from July 2015 to June 2017 were reviewed for clinical and radiological outcomes. These data were collected at the time of before surgery, 1 week, 3 months, 6 months, 1 year, and 2 years after surgery. Data were performed to compare between the patients with and without AS.

RESULTS

In our study, the occurrence of AS was 46.6%, 34.0%, 20.4%, 12.6%, and 10.7% at the time of 1 week, 3 months, 6 months,1 year, and 2 years after surgery, respectively. Our findings showed that patients with smoking, disease duration, preoperative Modic changes (Mcs), post-operative Cobb angle of C2-7, cervical range of motion (ROM) and T1 slope, and change of Cobb angle of C2-7, cervical ROM and T1 slope were associated with AS within 1 year after surgery. However, patients with smoking and preoperative Mcs were found to be risk factors associated with AS at at any follow-up.

CONCLUSION

In the present study, many factors were related to AS during 1-year after surgery. What's more, patients with smoking and preoperative Mcs were associated with AS at any follow-up. We hope this article can provide a reference for spinal surgeons to predict which patients were susceptible to suffer from AS after anterior surgery in treatment of multilevel cervical disorder with kyphosis.Level of Evidence: 3.

Accurate prediction of lumbar microdecompression level with an automated MRI grading system

OBJECTIVE

Lumbar spine MRI interpretations have high variability reducing utility for surgical planning. This study evaluated a convolutional neural network (CNN) framework that generates automated MRI grading for its ability to predict the level that was surgically decompressed.

MATERIALS AND METHODS

Patients who had single-level decompression were retrospectively evaluated. Sagittal T2 images were processed by a CNN (SpineNet), which provided grading for the following: central canal stenosis, disc narrowing, disc degeneration, spondylolisthesis, upper/lower endplate morphologic changes, and upper/lower marrow changes. The grades were used to calculate an aggregate score. The variables and the aggregate score were analyzed for their ability to predict the surgical level. For each surgical level subgroup, the surgical level aggregate scores were compared with the non-surgical levels.

RESULTS

A total of 141 patients met the inclusion criteria (82 women, 59 men; mean age 64 years; age range 28-89 years). SpineNet did not identify central canal stenosis in 32 patients. Of the remaining 109, 96 (88%) patients had a decompression at the level of greatest stenosis. The higher stenotic grade was present only at the surgical level in 82/96 (85%) patients. The level with the highest aggregate score matched the surgical level in 103/141 (73%) patients and was unique to the surgical level in 91/103 (88%) patients. Overall, the highest aggregate score identified the surgical level in 91/141 (65%) patients. The aggregate MRI score mean was significantly higher for the L3-S1 surgical levels.

CONCLUSION

A previously developed CNN framework accurately predicts the level of microdecompression for degenerative spinal stenosis in most patients.

Feasibility of Using Intraoperative Neuromonitoring in the Prophylaxis of Dysesthesia in Transforaminal Endoscopic Discectomies of the Lumbar Spine

(1) Background: Postoperative nerve root injury with dysesthesia is the most frequent sequela following lumbar endoscopic transforaminal discectomy. At times, it may be accompanied by transient and rarely by permanent motor weakness. The authors hypothesized that direct compression of the exiting nerve root and its dorsal root ganglion (DRG) by manipulating the working cannula or endoscopic instruments may play a role. (2) Objective: To assess whether intraoperative neurophysiological monitoring can help prevent nerve root injury by identifying neurophysiological events during the initial placement of the endoscopic working cannula and the directly visualized video endoscopic procedure. (3) Methods: The authors performed a retrospective chart review of 65 (35 female and 30 male) patients who underwent transforaminal endoscopic decompression for failed non-operative treatment of lumbar disc herniation from 2012 to 2020. The patients’ age ranged from 22 to 86 years, with an average of 51.75 years. Patients in the experimental group (32 patients) had intraoperative neurophysiological monitoring recordings using sensory evoked (SSEP), and transcranial motor evoked potentials (TCEP), those in the control group (32 patients) did not. The SSEP and TCMEP data were analyzed and correlated to the postoperative course, including dysesthesia and clinical outcomes using modified Macnab criteria, Oswestry disability index (ODI), visual analog scale (VAS) for leg and back pain. (4) Results: The surgical levels were L4/L5 in 44.6%, L5/S1 in 23.1%, and L3/L4 in 9.2%. Of the 65 patients, 56.9% (37/65) had surgery on the left, 36.9% (24/65) on the right, and the remaining 6.2% (4/65) underwent bilateral decompression. Postoperative dysesthesia occurred in 2 patients in the experimental and six patients in the control group. In the experimental neuromonitoring group, there was electrodiagnostic evidence of compression of the exiting nerve root’s DRG in 24 (72.7%) of the 32 patients after initial transforaminal placement of the working cannula. A 5% or more decrease and a 50% or more decrease in amplitude of SSEPs and TCEPs recordings of the exiting nerve root were resolved by repositioning the working cannula or by pausing the root manipulation until recovery to baseline, which typically occurred within an average of 1.15 min. In 15 of the 24 patients with such latency and amplitude changes, a foraminoplasty was performed before advancing the endoscopic working cannula via the transforaminal approach into the neuroforamen to avoid an impeding nerve root injury and postoperative dysesthesia. (5) Conclusion: Neuromonitoring enabled the intraoperative diagnosis of DRG compression during the initial transforaminal placement of the endoscopic working cannula. Future studies with more statistical power will have to investigate whether employing neuromonitoring to avoid intraoperative compression of the exiting nerve root is predictive of lower postoperative dysesthesia rates in patients undergoing videoendoscopic transforaminal discectomy.

Proposal for a new scoring system for spinal degeneration: Mo-Fi-Disc

OBJECTIVE

We aimed to develop a new scoring system for spinal degeneration including Modic changes, fatty infiltration (fi) in the paraspinal muscles, and intervertebral disc degeneration (IVDD), briefly Mo-fi-disc, using current radiological classification systems. We also aimed to understand whether Mo-fi-disc could predict patients with more intense low back pain (LBP).

PATIENTS AND METHODS

We conducted a cross-sectional analysis of a retrospective database between March 2018 and July 2020. We evaluated patients in terms of Modic changes, fatty infiltration in the paraspinal muscles, and IVDD at all lumbar levels on lumbar spine MRI. We grouped patients based on their LBP intensity. Visual analog scale (VAS) scores were used for LBP intensity.

RESULTS

We evaluated 134 patients (female: 66, male: 68; mean age: 35.44 ± 6.5 years). Patients with higher VAS scores had significantly higher 'Mo-disc' scores and higher 'fi' scores compared to those with lower VAS scores (3.54 ± 2.7 vs. 2.55 ± 2.8, p = 0.0075; 6.85 ± 3.2 vs. 5.25 ± 2.9, p = 0.0092). Patients with higher VAS scores had significantly higher 'Mo-fi-disc' scores compared to those with lower VAS scores (10.4 ± 4.2 vs. 7.94 ± 3.8, p = 0.0003). The most significant predictor for patients with higher VAS scores was 'Mo-fi-disc' scoring system with an OR of 1.193 (95 % CI: 1.055-1.349, p = 0.005).

CONCLUSION

Patients with more intense LBP had higher 'Mo-fi-disc' scores. This scoring system suggests an easy and objective classification to evaluate the spinal degeneration.

Significance of the Association between Disc Degeneration Changes on Imaging and Low Back Pain: A Review Article

Low back pain (LBP) is a major health issue resulting in a huge economic burden on the community. It not only increases the medical costs directly, but also raises the disability and loss of productivity in the general population. Symptoms include local pain over the spinal area, pain radiating to the lower leg, stiffness, and muscle tension. LBP is strongly linked with intervertebral disc degeneration that is further associated with the disruption of the complex anatomy of nucleus pulposus, annulus fibrosus, and adjacent supporting structures of the spine. Change in the shape and intensity of nucleus pulposus, decreased disc height, disc herniation, vertebral endplate changes, presence of osteophyte, and posterior high intensity zones are degenerative changes found in imaging studies. Every feature is considered while grading the severity score. Modic changes, DEBIT (disc extension beyond interspace) score, and Pfirrmann criteria are some of the scoring criteria used for evaluating disc degeneration severity. Moreover, the total number and contiguous pattern of affected discs play a crucial role in symptom generation of back pain. Many studies have reported asymptomatic patients. Thus, the correlation between degeneration severity found in imaging study and symptom severity of LBP remain unclear. This review discusses and summarizes the available literature on the significance of the association between the severity of degenerative changes found in imaging study with the presence and intensity of LBP.

Reduced nucleotomy-induced intervertebral disc disruption through spontaneous spheroid formation by the Low Adhesive Scaffold Collagen (LASCol)

Back pain is a global health problem with a high morbidity and socioeconomic burden. Intervertebral disc herniation and degeneration are its primary cause, further associated with neurological radiculopathy, myelopathy, and paralysis. The current surgical treatment is principally discectomy, resulting in the loss of spinal movement and shock absorption. Therefore, the development of disc regenerative therapies is essential. Here we show reduced disc damage by a new collagen type I-based scaffold through actinidain hydrolysis-Low Adhesive Scaffold Collagen (LASCol)-with a high 3D spheroid-forming capability, water-solubility, and biodegradability and low antigenicity. In human disc nucleus pulposus and annulus fibrosus cells surgically obtained, time-dependent spheroid formation with increased expression of phenotypic markers and matrix components was observed on LASCol but not atelocollagen (AC). In a rat tail nucleotomy model, LASCol-injected and AC-injected discs presented relatively similar radiographic and MRI damage control; however, LASCol, distinct from AC, decelerated histological disc disruption, showing collagen type I-comprising LASCol degradation, aggrecan-positive and collagen type II-positive endogenous cell migration, and M1-polarized and also M2-polarized macrophage infiltration. Reduced nucleotomy-induced disc disruption through spontaneous spheroid formation by LASCol warrants further investigations of whether it may be an effective treatment without stem cells and/or growth factors for intervertebral disc disease.

Magnetic resonance imaging analysis of work-related chronic low back pain: comparisons of different lumbar disc patterns

Background

Currently, there is a lack of comparative research about different lumbar disc patterns in patients with work-related chronic low back pain (CLBP) based on magnetic resonance imaging (MRI) analysis. Therefore, this study, on different patterns of lumbar disc degeneration or herniation in patients with CLBP, is valuable. In this study, we retrospectively investigated lumbar degenerative changes in patients with CLBP by using MRI analysis.

Materials and methods

Two hundred and eighty-three patients (110 women and 173 men) with work-related CLBP were enrolled and divided into four groups based on intervertebral disc morphology from MRI analysis, including normal discs (ND) group, degenerative discs (DD) group, bulging discs (BD) group, and herniated discs (HD) group. Demographic characteristics, occupational information, Visual Analog Scale (VAS) scores, and Oswestry Disability Index (ODI) scores were analyzed. Moreover, multiple parameters were investigated in the MRI analysis.

Results

The mean age of all 283 patients was 41.8±12.0 years (range, 18-80) and the mean duration of CLBP for all patients was 24.5±24.9 months. There were no significant differences in the patients' BMI, history of smoking, and education level (P>0.05). The three most common occupational types were manual worker, desk worker, and technician. The VAS and ODI scores of patients with CLBP in the DD, BD, and HD groups were significantly higher than those of patients in the ND group (P<0.05). The degrees of degeneration of L4/5 and L5/S1 were significantly higher than those of other intervertebral discs (P<0.05). The disc heights of L4/5 in the BD and HD groups were significantly lower than those of the ND group (P<0.05) and the disc height of L5/S1 in the HD group was significantly lower than that of the ND group (P<0.05). At the neutral position, the distances of L3/4, L4/5, and L5/S1 discs' bulge/herniation in the BD and HD groups were significantly higher than those in the ND and DD groups (P<0.05).

Conclusion

In summary, more severe degenerative changes of lower lumbar discs (L4/5 and L5/S1) such as higher degree of degeneration of disc, lower disc height, and significant displacement of disc were found in patients with work-related CLBP based on MRI analysis.

Characteristics of Modic changes in cervical kyphosis and their association with axial neck pain

BACKGROUND

The purpose of this study was to evaluate characteristics of Modic changes in cervical kyphosis (CK) and their association with axial neck pain.

METHODS

Study participants included 286 asymptomatic or symptomatic patients with CK (mean age = 54.2 ± 12.2 years) who were consecutively enrolled from March 2009 to October 2015. Clinical and radiographic evaluations were performed at a university outpatient department. CK was classified as global type, reverse sigmoid type, or sigmoid type.

RESULTS

There were 138 participants with global type CK, 103 with reverse sigmoid type CK, and 45 with sigmoid type CK. Of the 286 participants, 102 had Modic changes (Modic-1 in 38 segments and Modic-2 in 75 segments). Spinal cord compression grade and disc degeneration occurred more frequently in the group with axial neck pain compared to the group without pain. Angular motion was decreased in those with axial neck pain (mean ± standard deviation [SD] 7.8°±4.6°) compared to those who were asymptomatic (mean ± SD 8.9°±5.1°; P<0.001). In multivariate logistic regression analysis, Modic changes were associated with axial neck pain (odds ratio =5.356; 95% confidence interval =1.314-12.800; P<0.001).

CONCLUSION

Modic changes occur most commonly in association with CK global type and less commonly with reverse sigmoid type and sigmoid type. Modic changes are associated with axial neck pain in patients with CK.

The Long-term Clinical Effect of Minimal-Invasive TLIF Technique in 1-Segment Lumbar Disease

STUDY DESIGN

A prospective cohort double-center study.

OBJECTIVE

To assess the clinical effect of minimally invasive transforaminal lumbar interbody fusion (miTLIF) using the tunnel technique.

SUMMARY OF BACKGROUND DATA

A series of short-term studies have indicated that miTLIF could reduce blood loss and improve clinical results. However, long-term clinical study and magnetic resonance imaging research are still scare.

METHODS

From January 2008 to January 2009, 187 patients with 1-segment lumbar disease requiring intervertebral fusion were enrolled in this study. Patients were divided into 2 groups according to the operative methods. Postoperative low back pain (LBP), postoperative lumbar function, the fusion rate, lower extremity pain relief, variation of lumbar lordosis, and implant failure were assessed. At 48 months postoperation, the cross-sectional area of the paraspinal muscle was measured using magnetic resonance imaging.

RESULTS

The mean duration of follow-up was 54.4±5.9 months. The intermuscular pressure generated by the tunnel in the miTLIF group was lower than that generated in the oTLIF group. Patients in the miTLIF group reported a lower degree of LBP at all timepoints. The ODI scores were similar to the VAS scores. No significant differences were found in fusion rate, lower extremity pain relief, lumbar lordosis, or implant failure rate. A significant difference was found between the 2 groups in postoperative cross-sectional area.

CONCLUSIONS

This study confirmed the advantages of miTLIF in reducing postoperative LBP, improving postoperative quality of life and preventing paraspinal muscle atrophy compared with oTLIF, while achieving a similar therapeutic outcome. The lower intermuscular pressure generated by minimally invasive tunnel and subsequent moderate muscle atrophy were presumed to be possible reasons for its superiority.

Behavioral signs of axial low back pain and motor impairment correlate with the severity of intervertebral disc degeneration in a mouse model

BACKGROUND CONTEXT

Chronic low back pain is debilitating and difficult to treat. Depending on the etiology, responses to treatments vary widely. Although chronic low back pain is frequently related to intervertebral disc degeneration, the relationship between disc degeneration severity and clinical symptoms are still poorly understood. In humans, studies investigating the relationship between disc degeneration severity and low back pain are limited by the difficulty of obtaining disc samples from well-characterized patients and pain-free controls. We have previously described the secreted protein, acidic, rich in cysteine (SPARC)-null mouse model of chronic low back pain. SPARC is a matricellular protein involved in regulating the assembly and composition of extracellular matrix. The SPARC-null mice develop age-dependent disc degeneration of increasing severity accompanied by behavioral signs suggestive of axial low back pain, radiating leg pain, and motor impairment. The existence of this model allows for examination of the relationships between clinical symptoms in vivo and pathological signs of disc degeneration ex vivo.

PURPOSE

The goal of this study was to explore the relationship between behavioral signs of pain and the severity of lumbar disc degeneration using the SPARC-null mouse model of disc degeneration-related low back pain.

STUDY DESIGN

This study used a cross-sectional, multiple-cohort behavioral and histological study of disc degeneration and behavioral symptoms in a mouse model of low back pain associated with disc degeneration.

METHODS

SPARC-null and wild-type control mice ranging from 6 to 78 weeks of age were used in this study. The severity of disc degeneration was determined by ex vivo analysis of the lumbar spine using colorimetric histological staining and a scoring system adapted from the Pfirrmann scale. Behavioral signs of axial low back pain, radiating leg pain, and motor impairment were quantified as tolerance to axial stretching in the grip force assay, hypersensitivity to cold or mechanical stimuli on the hindpaw (acetone and von Frey tests), and latency to fall in the rotarod assay, respectively.

RESULTS

The SPARC-null mice exhibited decreased tolerance to axial stretching, hindpaw cold hypersensitivity, and motor impairment compared with age-matched control mice. The severity of disc degeneration increased with age in both SPARC-null and control mice and by 78 weeks of age, the same proportion of lumbar discs were abnormal in SPARC-null and control mice. However, the degree of degeneration was more severe in the SPARC-null mice. In both SPARC-null and control mice, tolerance to axial stretching but not hindpaw cold sensitivity correlated with disc degeneration severity. Motor impairment correlated with degeneration severity in the SPARC-null mice only.

CONCLUSIONS

These data suggest that internal disc disruption contributes to axial low back pain and motor impairment but not to radiating leg pain. These results have implications for the optimization of mechanism-based treatments strategies.