Lumbar facet joint subchondral bone density in low back pain and asymptomatic subjects.

OBJECTIVE: To report in vivo measurements of lumbar facet joint subchondral bone mineral density used in the description of facet joint loading patterns and to interrogate if low back pain is associated with changes in subchondral bone mineral density. MATERIALS AND METHODS: In vivo measurements of lumbar facet joint subchondral bone mineral density (L1/2 to L5/S1) in Hounsfield units were performed on 89 volunteers (56 controls and 33 with low back pain) by computed tomography osteoabsorptiometry at subchondral regions between 1.5 mm and 2.5 mm below the joint surface. The facet surface was divided into five topographic zones: cranial, lateral, caudal, medial, and central. RESULTS: We analyzed 1780 facet joint surfaces. Facets were denser (p < 0.0001) both in superior facets and in low back pain subjects (p < 0.0001). For the entire cohort, the facet center zone subchondral bone mineral density was higher (p < 0.0001) than that of the peripheral zones. The analyses indicate that subchondral bone mineral density is highest in patients with low back pain, the superior facets, and the center zone of the facets. CONCLUSIONS: Subchondral bone mineral density is thought to reflect cumulative, long-term distribution of stress acting on a joint. This work shows that higher subchondral bone mineral density values in the center zone indicate predominant stress transmission through the center of the facet joints. Finally, the greater subchondral bone mineral density in patients with low back pain may reflect both increased load bearing by the facets secondary to disc degeneration and misdistribution of loading within the joint.

Utilization of CT scanning associated with complex spine surgery.

BACKGROUND: Due to the risk associated with exposure to ionizing radiation, there is an urgent need to identify areas of CT scanning overutilization. While increased use of diagnostic spinal imaging has been documented, no previous research has estimated the magnitude of follow-up imaging used to evaluate the postoperative spine. METHODS: This retrospective cohort study quantifies the association between spinal surgery and CT utilization. An insurance database (Humana, Inc.) with ≈ 19 million enrollees was employed, representing 8 consecutive years (2007-2014). Surgical and imaging procedures were captured by anatomic-specific CPT codes. Complex surgeries included all cervical, thoracic and lumbar instrumented spine fusions. Simple surgeries included discectomy and laminectomy. Imaging was restricted to CT and MRI. Postoperative imaging frequency extended to 5-years post-surgery. RESULTS: There were 140,660 complex spinal procedures and 39,943 discectomies and 49,889 laminectomies. MRI was the predominate preoperative imaging modality for all surgical procedures (median: 80%; range: 73-82%). Postoperatively, CT prevalence following complex procedures increased more than two-fold from 6 months (18%) to 5 years (≥40%), and patients having a postoperative CT averaged two scans. For simple procedures, the prevalence of postoperative CT scanning never exceeded 30%. CONCLUSIONS: CT scanning is used frequently for follow-up imaging evaluation following complex spine surgery. There is emerging evidence of an increased cancer risk due to ionizing radiation exposure with CT. In the setting of complex spine surgery, actions to mitigate this risk should be considered and include reducing nonessential scans, using the lowest possible radiation dose protocols, exerting greater selectivity in monitoring the developing fusion construct, and adopting non-ferromagnetic implant biomaterials that facilitate MRI postoperatively.

Spatial geometric and magnetic resonance signal intensity changes with advancing stages of nucleus pulposus degeneration.

BACKGROUND: With advancing stages of degeneration, denaturation and degradation of proteoglycans in the nucleus pulposus (NP) lead to tissue dehydration and signal intensity loss on T2-weighted MR images. Pfirrmann grading is widely used for grading degeneration of intervertebral discs (IVDs). The criterion to differentiate IVDs of Pfirrmann Grade I from the other grades is NP homogeneity. Pfirrmann grading is qualitative and its assessment may be subjective. Therefore, assessment of quantitative objective measures correlating with early disc degeneration may complement the grading. This study aimed to evaluate the applicability of the distance between the center weighted by signal intensity (weighted center) and the geometric center as a parameter of NP homogeneity. Other phenomena related to advancing stages of degeneration were also investigated. METHODS: MR images of 65 asymptomatic volunteers with a total of 288 lumbar IVDs with clearly identifiable nucleus pulposus boundary (Pfirrmann Grade I, II and III) were included in this study. A custom-written program was developed to determine the IVD longitudinal axis, define the NP boundary, and to locate the coordinates of geometric and weighted NP centers on the mid-sagittal image of each studied IVD. The distances between the weighted and geometric centers on the longitudinal axis and the perpendicular axis of each IVD were calculated. RESULTS: The weighted center located posterior to the geometric center, which indicated the signal intensity was lower at the anterior portion of the NP, in 85.8% of studied IVDs. The distance between the weighted and geometric center on the longitudinal axis was significantly shorter in homogeneous (Pfirrmann Grade I) than in inhomogeneous (Grade II) IVDs. The distance on the perpendicular axis in Grade III IVDs was significantly larger than that in Grade I and Grade II IVDs. CONCLUSION: The relationship between the weighted and geometric centers can serve as an indicator for NP homogeneity. The distance between both centers through advancing stages of degeneration demonstrated decrease of signal intensity progressing along the longitudinal axis initially and then along the cranio-caudal direction at later stages. These findings could provide insights of initiation and subsequent progression of degenerative changes in IVDs.

Effects of Axial Torsion on Disc Height Distribution: An In Vivo Study.

OBJECTIVES: Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positions on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo. METHODS: Eighty-one volunteers were computed tomography-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each "disc" set as the reference surface and separated into 5 anatomical zones: 4 peripheral and 1 central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions and were compared against each other with analysis of variance, with significance set at P < .05. RESULTS: Mean neutral disc height was 7.32 mm (1.59 mm). With 50° rotation, a small but significant increase to 7.44 mm (1.52 mm) (P < .0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (P < .0001), whereas the left, anterior, and central decreased. CONCLUSIONS: This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown.

Presentation and management of infection in total disc replacement: A review.

Background: Total disc replacement (TDR) is widely used in the treatment of cervical and lumbar spine pathologies. Although TDR infection, particularly delayed infection, is uncommon, the results can be devastating, and consensus on clinical management remains elusive. In this review of the literature, we asked: (1) What are the reported rates of TDR infection; (2) What are the clinical characteristics of TDR infection; and (3) How has infection been managed for TDR patients? Methods: We performed a search of the literature using PubMed and Embase to identify studies that reported TDR infection rates, the identification and management of TDR infection, or TDR failures with positive cultures. Twenty database studies (17 focusing on the cervical spine and 3 on the lumbar spine) and 10 case reports representing 15 patients were reviewed along with device Summary of Safety and Effectiveness Data reports. Results: We found a lack of clarity regarding how infection was diagnosed, indicating a variation in clinical approach and highlighting the need for a standard definition of TDR infection. Furthermore, while reported infection rates were low, the absence of a clear definition prevented robust data analysis and may contribute to underreporting in the literature. We found that treatment strategy and success rely on several factors including patient symptoms and time to onset, microorganism type, and implant positioning/stability. Conclusions: Although treatment strategies varied throughout the extant literature, common practices in eliminating infection and reconstructing the spine emerged. The results will inform future work on the creation of a more robust definition of TDR infection and as well as recommendations for management.

Utilization of Bone-Anchored Annular Defect Closure to Prevent Reherniation Following Lumbar Discectomy: Overcoming Barriers to Clinical Adoption and Market Access.

While achieving premarket approval from the US Food and Drug Administration represents a significant milestone in the development and commercialization of a Class III medical device, the aftermath endeavor of gaining market access can be daunting. This article provides a case study of the Barricaid annular closure device (Barricaid), a reherniation reduction device, which has been demonstrated to decrease the risk of suffering a recurrent lumbar intervertebral disc herniation. Following Food and Drug Administration approval, clinical adoption has been slow due to barriers to market access, including the perception of low-quality clinical evidence, questionable significance of the medical necessity of the procedure, and imaging evidence of increased likelihood of vertebral endplate changes. The aim of this article is to provide appropriate examination, rationale, and rebuttal of these concerns. Weighing the compendium of evidence, we offer a definition of a separate and unique current procedural terminology code to delineate this procedure. Adoption of this code will help to streamline the processing of claims and support the conduct of research, the evaluation of health care utilization, and the development of appropriate medical guidelines.

Comparing effects of kyphoplasty, vertebroplasty, and non-surgical management in a systematic review of randomized and non-randomized controlled studies.

PURPOSE: To determine if differences in safety or efficacy exist between balloon kyphoplasty (BKP), vertebroplasty (VP) and non-surgical management (NSM) for the treatment of osteoporotic vertebral compression fractures (VCFs). METHODS: As of February 1, 2011, a PubMed search (key words: kyphoplasty, vertebroplasty) resulted in 1,587 articles out of which 27 met basic selection criteria (prospective multiple-arm studies with cohorts of ≥ 20 patients). This systematic review adheres to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. RESULTS: Pain reduction in both BKP (-5.07/10 points, P < 0.01) and VP (-4.55/10, P < 0.01) was superior to that for NSM (-2.17/10), while no difference was found between BKP/VP (P = 0.35). Subsequent fractures occurred more frequently in the NSM group (22 %) compared with VP (11 %, P = 0.04) and BKP (11 %, P = 0.01). BKP resulted in greater kyphosis reduction than VP (4.8º vs. 1.7°, P < 0.01). Quality of life (QOL) improvement showed superiority of BKP over VP (P = 0.04), along with a trend for disability improvement (P = 0.08). Cement extravasation was less frequent in the BKP (P = 0.01). Surgical intervention within the first 7 weeks yielded greater pain reduction than VCFs treated later. CONCLUSIONS: BKP/VP provided greater pain relief and fewer subsequent fractures than NSM in osteoporotic VCFs. BKP is marginally favored over VP in disability improvement, and significantly favored in QOL improvement. BKP had a lower risk of cement extravasation and resulted in greater kyphosis correction. Despite this analysis being restricted to Level I and II studies, significant heterogeneity suggests that the current literature is delivering inconsistent messages and further trials are needed to delineate confounding variables.

Posterior facet load changes in adjacent segments due to moderate and severe degeneration in C5-C6 disc: a poroelastic C3-T1 finite element model study.

STUDY DESIGN: Biomechanics of normal vertebral segments adjacent to a degenerated segment in the cervical spine. OBJECTIVE: To test the hypothesis that posterior facet joints of adjacent segments are loaded more when degeneration occurs in the intermediate disc segment. SUMMARY OF BACKGROUND DATA: Degeneration progression in adjacent segments is a clinical concern. Literature studies that have documented the effects of a degenerated segment on the adjacent-segment discs have not addressed these effects on adjacent-segment posterior facets. Moreover, these biomechanical studies are performed mainly on the lumbar spine or the tissue quality of the cadavers is poor because of degenerated segments. Retrospectively, it is difficult to decipher to what extent degeneration in a single disc induces biomechanical changes in facet joints along the posterior spinal column. To date, no cervical spine biomechanical study investigated the facet joints response of adjacent segments when the disc in between those segments degenerates. METHODS: An earlier validated poroelastic, 3-dimensional finite element model of a normal C3-T1 segment was used. Two stages of degeneration (moderate and severe) were simulated in the C5-C6 disc. Disc geometry and tissue material properties were modified to simulate C5-C6 disc degeneration. For the 3 C3-T1 models, loads on the posterior facets at 3 levels (C4-C5, C5-C6, and C6-C7) were computed under moment loads. RESULTS: With progressive degeneration in the C5-C6 disc, posterior facet loading in adjacent segments and in the intermediate degenerated disc segment increased. Changes in facet loading in the inferior C6-C7 segment were greater than the corresponding changes in the superior C4-C5 segment. These changes were highest in lateral bending and lowest in axial rotation. CONCLUSIONS: Higher changes in facet loads along the posterior spinal column may contribute to altered biomechanics in neighboring segments. Future biomechanical experiments are required to develop a more clear understanding of the posterior facet joints response in neighboring segments because of degeneration in a cervical disc.

Invasive Treatments for Low Back Disorders.

OBJECTIVE: This abbreviated version of the American College of Occupational and Environmental Medicine's Low Back Disorders guideline reviews the evidence and recommendations developed for invasive treatments used to manage low back disorders. METHODS: Comprehensive systematic literature reviews were accomplished with article abstraction, critiquing, grading, evidence table compilation, and guideline finalization by a multidisciplinary expert panel and extensive peer-review to develop evidence-based guidance. Consensus recommendations were formulated when evidence was lacking and often relied on analogy to other disorders for which evidence exists. A total of 47 high-quality and 321 moderate-quality trials were identified for invasive management of low back disorders. RESULTS: Guidance has been developed for the invasive management of acute, subacute, and chronic low back disorders and rehabilitation. This includes 49 specific recommendations. CONCLUSION: Quality evidence should guide invasive treatment for all phases of managing low back disorders.

Non-Invasive and Minimally Invasive Management of Low Back Disorders.

OBJECTIVE: This abbreviated version of the American College of Occupational and Environmental Medicine's (ACOEM) Low Back Disorders Guideline reviews the evidence and recommendations developed for non-invasive and minimally invasive management of low back disorders. METHODS: Systematic literature reviews were accomplished with article abstraction, critiquing, grading, evidence table compilation, and guideline finalization by a multidisciplinary expert panel and extensive peer-review to develop evidence-based guidance. Consensus recommendations were formulated when evidence was lacking. A total of 70 high-quality and 564 moderate-quality trials were identified for non-invasive low back disorders. Detailed algorithms were developed. RESULTS: Guidance has been developed for the management of acute, subacute, and chronic low back disorders and rehabilitation. This includes 121 specific recommendations. CONCLUSION: Quality evidence should guide treatment for all phases of managing low back disorders.

Intradiscal electrothermal therapy (IDET) for the treatment of discogenic low back pain: patient selection and indications for use.

Discogenic low back pain resulting from internal disc disruption can be severely disabling, clinically challenging, and expensive to treat. Previously, when conservative care had been exhausted, open surgical intervention such as spinal fusion or artificial disc replacement was the only treatment option for these patients. Intradiscal electrothermal therapy (IDET), a minimally-invasive technique performed in the outpatient setting, offers an intermediate intervention between conservative care and surgery. Specific selection criteria have been refined that identify patients for treatment with IDET, ensuring maximal clinical benefit and appropriate use of healthcare resources. Indications for use were developed from review of selection criteria from published clinical reports and review articles of IDET, and further refined by identifying components with the strongest positive predictive value and by direct physician feedback. Final indications for use consist of clinical and imaging criteria. There are 5 compulsory indications for use: 1) persistent axial low back pain +/- leg pain and non-responsive to > or = 6 weeks of conservative care; 2) history consistent with discogenic low back pain without marked lower extremity neurological deficit; 3) one to 3 desiccated discs with or without small, contained herniated nucleus pulposus by T2-weighted magnetic resonance imaging, with at least 50% remaining disc height; 4) concordant pain provocation by low pressure (< 50 psi above opening pressure) discography; and, 5) posterior annular disruption by post-discography computed tomography. Using these patient selection characteristics, approximately 3 of 4 IDET-treated patients should achieve a minimal clinically important improvement in pain and disability.

Changes in Lumbar Endplate Area and Concavity Associated With Disc Degeneration.

STUDY DESIGN: Retrospective image-based analysis. OBJECTIVE: To measure endplate three-dimensional (3D) geometry, endplate changes in vivo and to investigate correlations between disc degeneration and endplate 3D geometry dependent on symptoms of low back pain (LBP). SUMMARY OF BACKGROUND DATA: It has been hypothesized that alteration of load transmission from the nucleus pulposus to the annulus fibrosus affects vertebral endplate geometry. METHODS: 3D surface models of inferior/superior lumbar endplates were created from computed tomography scans of n = 92 volunteers with and without LBP. Disc degeneration was evaluated using Pfirrmann scale. Concavity in both coronal and sagittal planes was assessed with the Concavity Index (unitless; larger than 1: concave; flat: 1; and less than 1: convex, respectively). Endplate area and disc height distribution were computed and the effects from demographics and spinal degeneration were sought with an analysis of variance model. RESULTS: Both sagittal and coronal planes revealed significantly decreased concavity in those with terminal grade 5 disc degeneration (mean 0.833 ±â€Š0.235) compared to the other grades in the cohort. Older subjects presented with larger endplate areas than the younger subjects (P = 0.0148) at L4-S1. Overall, symptomatic subjects had significantly larger endplate areas (P = 0.022), especially at the lower lumbar levels (P < 0.001). Analysis of variance showed that sex, disc level, disc degeneration grade, and disc height reached significance (P < 0.0001) as influential parameters in both Concavity Index cases. CONCLUSION: With advancing intervertebral disc degeneration, endplates become more convex over time in both sagittal and coronal planes. Our findings implicate the endplate changes with advancing disc degeneration in the shift in load transmission from the nucleus pulposus to the annulus fibrosus, resulting in changes within the curvature of the endplates. This is also the first study to describe the direct impact of age, sex, and LBP on vertebral endplate anatomy. LEVEL OF EVIDENCE: 5.

Participation in occupational health longitudinal studies: predictors of missed visits and dropouts.

PURPOSE: The purpose of this study is to determine whether demographics, health, and job factors influence continued participation of employed persons in a longitudinal intervention study of tertiary prevention for work-related low-back disorders (WR-LBDs). METHODS: Four hundred fifty-four actively employed persons had enrolled in an intervention study of back supports and education to promote recovery from a WR-LBD. Baseline values were examined according to whether individuals continued in the study, missed a visit, or dropped out; frequency of missed visits; and early or late dropouts at follow-up intervals of 1, 2, 6, and 12 months. RESULTS: Workers who did not complete all study visits were significantly more likely to be younger and have poorer self-reported health. Individuals with a greater percentage of body fat dropped out early. Significantly more missed visits were observed among those who had arthritis and longer duration of low-back pain symptoms. Job factors did not influence study participation. CONCLUSIONS: Continued participation in a longitudinal study of working adults was influenced by age, health status, and factors related to the primary condition targeted by the intervention study. Strategies aimed at those who report lower levels of health and symptoms related to the condition under study may promote follow-up participation in longitudinal studies. Thus, even among actively employed persons, one should not assume that all workers are "healthy."

Inclusion of regional poroelastic material properties better predicts biomechanical behavior of lumbar discs subjected to dynamic loading.

Understanding the relationship between repetitive lifting and the breakdown of disc tissue over several years of exposure is difficult to study in vivo and in vitro. The aim of this investigation was to develop a three-dimensional poroelastic finite element model of a lumbar motion segment that reflects the biological properties and behaviors of in vivo disc tissues including swelling pressure due to the proteoglycans and strain-dependent permeability and porosity. It was hypothesized that when modeling the annulus, prescribing tissue specific material properties will not be adequate for studying the in vivo loading and unloading behavior of the disc. Rather, regional variations of these properties, which are known to exist within the annulus, must also be included. Finite element predictions were compared to in vivo measurements published by Tyrrell et al. (1985) of percent change in total stature for two loading protocols, short-term creep loading and standing recovery and short-term cyclic loading with standing recovery. The model in which the regional variations of material properties in the annulus had been included provided an overall better prediction of the in vivo behavior as compared to the model in which the annulus properties were assumed to be homogenous. This model will now be used to study the relationship between repetitive lifting and disc degeneration.

Novel model to analyze the effect of a large compressive follower pre-load on range of motions in a lumbar spine.

A 3-D finite element model (FEM) of the lumbar spine (L1-S1) was used to determine the effect of a large compressive follower pre-load on range of motions (ROM) in all three planes. The follower load modeled in the FEM produced minimal vertebral rotations in all the three planes. The model was validated by comparing the disc compression at all levels in the lumbar spine with the corresponding results obtained by compressing 10 cadevaric lumbar spines (L1-S1) using the follower load technique described by Patwardhan et al. [1999. A follower load increases the load-carrying capacity of the lumbar spine in compression. Spine 24(10), 1003-1009]. Further validation of the model was performed by comparing the lateral bending and torsion response without pre-load and the flexion-extension response without pre-load and with an 800 N follower pre-load with those obtained using cadaver lumbar spines. Following validation, the FEM was subjected to bending moments in all three planes with and without compressive follower pre-loads of up to 1200 N. Disc compression values and the flexion-extension range of motion under 800 N follower pre-load predicted by the FEM compared well with in vitro results. The current model showed that compressive follower pre-load decreased total as well as segmental ROM in flexion-extension by up to 18%, lateral bending by up to 42%, and torsion by up to 26%.

Matrix replenishment by intervertebral disc cells after chemonucleolysis in vitro with chondroitinase ABC and chymopapain.

BACKGROUND CONTEXT: One of the advantages of chemonucleolysis for the treatment of a herniated intervertebral disc is the potential for the disc to self-repair. It has been suggested that the enzymes used for chemonucleolysis differentially affect the potential of the disc cells to promote repair. PURPOSE: To test the ability of nucleus pulposus and anulus fibrosus cells to repair the extracellular matrix degraded in vitro by either chondroitinase ABC or chymopapain. STUDY DESIGN: An alginate cell culture system was used to monitor the progress of matrix repair after chemonucleolysis in vitro. METHODS: Rabbit nucleus pulposus or anulus fibrosus cells precultured for 10 days in alginate gel were briefly exposed to low concentrations of chondroitinase ABC or chymopapain and then returned to normal culture conditions for up to 4 weeks. At each time point, the contents of DNA and matrix macromolecules and proteoglycan synthesis were measured. RESULTS: The DNA content of enzyme-treated alginate beads during the following 4 weeks of culture was higher in the chondroitinase ABC group than in the chymopapain group (NP, p<.01, and AF, p<.05). The content of proteoglycan in beads containing nucleus pulposus and anulus fibrosus cells in the chondroitinase ABC group was higher than that in the chymopapain group (NP and AF, p<.001). The rate of proteoglycan synthesis and the content of collagen did not, however, differ between those two groups. CONCLUSIONS: Intervertebral disc cells exposed to chondroitinase ABC reestablish a matrix richer in proteoglycan than cells exposed to chymopapain. This may be because of differences in the substrate spectrum of each enzyme. Although these results cannot be translated directly to the in vivo situation, they suggest the possibility that cells in discs subjected to chondroitinase ABC-induced chemonucleolysis retain a greater ability to replenish their extracellular matrix with proteoglycans than cells in discs exposed to chymopapain.

Lumbar disc degeneration is an equally important risk factor as lumbar fusion for causing adjacent segment disc disease.

Treatment of degenerative spinal disorders by fusion produces abnormal mechanical conditions at mobile segments above or below the site of spinal disorders and is clinically referred to as adjacent segments disc disease (ASDD) or transition syndrome in the case of a previous surgical treatment. The aim of the current study is to understand with the help of poro-elastic finite element models how single or two level degeneration of lower lumbar levels influences motions at adjacent levels and compare the findings to motions produced by single or two level fusions when the adjacent disk has varying degree of degeneration. Validated grade-specific finite element models including varying grades of disc degeneration at lower lumbar levels with and without fusion were developed and used to determine motions at all levels of the lumbar spine due to applied moment loads. Results showed that adjacent disc motions do depend on severity of disc degeneration, number of disc degenerated or fused, and level at which degeneration or fusion occurred. Furthermore, single level degeneration and single level fusion produced similar amount of adjacent disc motions. The pattern of increase in adjacent segment motions due to disc degeneration and increase in motions at segment adjacent to fusion was similar. Based on the current study, it can be concluded that disc degeneration should also be considered as a risk factor in addition to fusion for generating adjacent disc degeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:123-130, 2017.