Diagnosis and surgical treatment of back pain originating from endplate

Fundamentals of intervertebral disc degeneration and related discogenic pain

Lumbar intervertebral disc degeneration is thought to be the main cause of low back pain, although the mechanisms by which it occurs and leads to pain remain unclear. In healthy adult discs, vessels and nerves are present only in the outer layer of the annulus fibrosus and in the bony endplate. Animal models, and histological and biomechanical studies have shown that annulus tear or endplate injury is the initiating factor for painful disc degeneration. Injury to the disc triggers a local inflammatory repair response that activates nociceptors and promotes the synthesis of neuropeptides such as substance P and calcitonin gene-related peptide, by dorsal root ganglion neurons. These neuropeptides are transported to injured discs and act as pro-inflammatory molecules, promoting the production of an "inflammatory soup" by inducing vasodilatation and plasma extravasation as well as by promoting the release of chemical mediators from disc cells and infiltrating immune cells, causing neurogenic inflammation that leads to progressive disc degeneration and discogenic pain.

Role of neurogenic inflammation in intervertebral disc degeneration

In healthy intervertebral discs (IVDs), nerves and blood vessels are present only in the outer annulus fibrosus, while in degenerative IVDs, a large amount of nerve and blood vessel tissue grows inward. Evidence supports that neurogenic inflammation produced by neuropeptides such as substance P and calcitonin gene related peptide released by the nociceptive nerve fibers innervating the IVDs plays a crucial role in the process of IVD degeneration. Recently, non-neuronal cells, including IVD cells and infiltrating immune cells, have emerged as important players in neurogenic inflammation. IVD cells and infiltrating immune cells express functional receptors for neuropeptides through which they receive signals from the nervous system. In return, IVD cells and immune cells produce neuropeptides and nerve growth factor, which stimulate nerve fibers. This communication generates a positive bidirectional feedback loop that can enhance the inflammatory response of the IVD. Recently emerging transient receptor potential channels have been recognized as contributors to neurogenic inflammation in the degenerative IVDs. These findings suggest that neurogenic inflammation involves complex pathophysiological interactions between sensory nerves and multiple cell types in the degenerative IVDs. Clarifying the mechanism of neurogenic inflammation in IVD degeneration may provide in-depth understanding of the pathology of discogenic low back pain.

Mrgprb2-mediated mast cell activation exacerbates Modic changes by regulating immune niches

Modic changes are radiographic features associated with microfracture, low-virulence organism infection and chronic inflammation with inflammatory cell infiltration in the vertebral endplate region. Mast cells, as innate immune cells similar to macrophages, are present in painful degenerated intervertebral discs. However, the involvement and mechanisms of mast cells in the development of Modic changes remain unclear. Herein, we found increased mast cell infiltration in samples from patients with Modic changes and in mouse models of Modic changes. To clarify the role of mast cells in the progression of Modic changes, we used mast cell-deficient (KITW-SH/W-SH) mice to construct a model of Modic changes and found that the severity of Modic changes in KITW-SH/W-SH mice was significantly lower than that in WT mice. These findings were further supported by the use of a mast cell-specific activator (compound 48/80) and a stabilizer (cromolyn). Furthermore, we found that mast cells were not activated via the classic IgE pathway in the Modic change models and that Mrgprb2 is the specific receptor for mast cell activation reported in recent studies. Then, we utilized Mrgprb2 knockout mice to demonstrate that Mrgprb2 knockout inhibited mast cell activation and thus reduced the degree of Modic changes. Transcriptomic sequencing revealed aberrant PI3K-AKT and MAPK pathway activation in the Mrgprb2-deficient mast cells. Additionally, Mrgpbrb2-activated mast cells regulate immune niches by recruiting macrophages, promoting M1 polarization and reducing M2 polarization, thereby promoting the progression of Modic changes. These findings suggest that mast cells may serve as a novel therapeutic target for addressing Modic changes.

Updates on Pathophysiology of Discogenic Back Pain

Discogenic back pain, a subset of chronic back pain, is caused by intervertebral disc (IVD) degeneration, and imparts a notable socioeconomic health burden on the population. However, degeneration by itself does not necessarily imply discogenic pain. In this review, we highlight the existing literature on the pathophysiology of discogenic back pain, focusing on the biomechanical and biochemical steps that lead to pain in the setting of IVD degeneration. Though the pathophysiology is incompletely characterized, the current evidence favors a framework where degeneration leads to IVD inflammation, and subsequent immune milieu recruitment. Chronic inflammation serves as a basis of penetrating neovascularization and neoinnervation into the IVD. Hence, nociceptive sensitization emerges, which manifests as discogenic back pain. Recent studies also highlight the complimentary roles of low virulence infections and central nervous system (CNS) metabolic state alteration. Targeted therapies that seek to disrupt inflammation, angiogenesis, and neurogenic pathways are being investigated. Regenerative therapy in the form of gene therapy and cell-based therapy are also being explored.

Thoracolumbar Vertebral Endplate Defect Morphology: A Descriptive Study of Human Cadaveric Spines Using Micro-Computed Tomography

STUDY DESIGN

A descriptive, cross-sectional cadaver study.

OBJECTIVE

This study aimed to provide a thorough depiction of vertebral endplate defects classified based on their morphologic features and reported with respect to size, location, and prevalence in the human cadaveric spines of older adults.

SUMMARY OF BACKGROUND DATA

Back pain has been associated with vertebral endplate defects; however, findings have been inconsistent. This is partially due to miscommunication surrounding the classification of endplate defects observed using clinical imaging, and limited knowledge of the types of defects present on the endplate and their prevalence. A comprehensive study of vertebral endplates is needed to clarify types of structural defects, their character, and prevalence.

MATERIALS AND METHODS

Using micro-computed tomography, 3-dimensional reconstructed images were created of 409 endplates from 19 cadaveric spines (9 men and 10 women; aged 62-91; T6-S1). Endplate defects were categorized based on their morphology, size, and location to investigate distribution patterns.

RESULTS

Seven types of endplate defects were identified: Schmorl nodes, corner fracture or limbus vertebra, other fractures, erosion, jagged surface, calcification, and depressions. Defects were identified on 63.6% of endplates. Multiple defects were present on 19.1% of endplates. Fracture and erosion were the most common defect types. Defects were more common on the endplate cranial to the intervertebral disc and in male specimens ( P = 0.01). Defects were larger in the lumbar spine and the "total area of endplate defect" was larger on the cranial than the caudal endplate in the thoracic spine ( P < 0.05).

CONCLUSION

This is the first study of which we are aware that provides a thorough depiction of the morphology and distribution of endplate defects across the entire lower thoracic and lumbar spine (T6-S1) using micro-computed tomography. Results support the presence of several distinct endplate defect phenotypes with different prevalence rates and provide a reference when considering endplate defects in the elderly.

Bone cement distribution may significantly affect the efficacy of percutaneous vertebroplasty in treating symptomatic Schmorl's nodes

PURPOSE

Percutaneous vertebroplasty(PVP) has been widely used in treating symptomatic Schmorl's nodes(SNs). However, there were still some patients with poor pain relief. At present, there is a lack of research to analyze the reasons for poor efficacy.

METHODS

Review the SNs patients treated with PVP in our hospital from November 2019 to June 2022, collect their baseline data. Reverse reconstruction software was used to calculate the filling rate of bone edema ring(R_f). NRS score was used to evaluate pain and ODI to evaluate function. The patients were divided into remission group(RG) and non remission group(n-RG) according to symptom. In addition, according to the R_f, they were divided into excellent, good and poor groups. Differences between groups were investigated.

RESULTS

A total of 26 vertebrae were included in 24 patients. When grouped according to symptoms, patients in n-RG were older, and surgical segments were tend to locate in lower lumbar spine. The proportion of Poor distribution was significantly higher. When grouped according to the cement distribution, the preoperative NRS and ODI of the three groups were comparable, but the NRS and ODI of Poor group were significantly worse than the Excellent and Good groups postoperatively and at the last follow-up.

CONCLUSIONS

The cement distribution may significantly affect the efficacy of PVP in treating symptomatic SNs. We suggest that the bone edema ring should be filled as fully as possible to ensure the efficacy. In addition, advanced age and low lumbar lesions are also adverse factors for clinical outcomes.

A systematic review of anterior lumbar interbody fusion (ALIF) versus posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), posterolateral lumbar fusion (PLF)

PURPOSE

The rate of elective lumbar fusion has continued to increase over the past two decades. However, there remains to be a consensus on the optimal fusion technique. This study aims to compare stand-alone anterior lumbar interbody fusion (ALIF) with posterior fusion techniques in patients with spondylolisthesis and degenerative disc disease through a systematic review and meta-analysis of the available literature.

METHODS

A systematic review was performed by searching the Cochrane Register of Trials, MEDLINE, and EMBASE from inception to 2022. In the two-stage screening process, three reviewers independently reviewed titles and abstracts. The full-text reports of the remaining studies were then inspected for eligibility. Conflicts were resolved through consensus discussion. Two reviewers then extracted study data, assessed it for quality, and analysed it.

RESULTS

After the initial search and removal of duplicate records, 16,435 studies were screened. Twenty-one eligible studies (3686 patients) were ultimately included, which compared stand-alone ALIF with posterior approaches such as posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), and posterolateral lumbar fusion (PLF). A meta-analysis showed surgical time and blood loss was significantly lower in ALIF than in TLIF/PLIF, but not in those who underwent PLF (p = 0.08). The length of hospital stay was significantly shorter in ALIF than in TLIF, but not in PLIF or PLF. Fusion rates were similar between the ALIF and posterior approaches. The Visual Analogue Scale (VAS) scores for back and leg pain were not significantly different between the ALIF and PLIF/TLIF groups. However, VAS back pain favoured ALIF over PLF at one year (n = 21, MD - 1.00, CI - 1.47, - 0.53), and at two years (2 studies, n = 67, MD - 1.39, CI - 1.67, - 1.11). The VAS leg pain scores (n = 46, MD 0.50, CI 0.12 to 0.88) at two years significantly favoured PLF. The Oswestry Disability Index (ODI) scores at one year were not significantly different between ALIF and the posterior approaches. At two years, ODI scores were also similar between the ALIF and the TLIF/PLIF. However, the ODI scores at two years (2 studies, n = 67, MD - 7.59, CI - 13.33, - 1.85) significantly favoured ALIF over PLF (I2 = 70%). The Japanese Orthopaedic Association Score (JOAS) for low back pain at one year (n = 21, MD - 0.50, CI - 0.78) and two years (two studies, n = 67, MD - 0.36, CI - 0.65, - 0.07) significantly favoured ALIF over PLF. No significant differences were found in leg pain at the 2-year follow-up. Adverse events displayed no significant differences between the ALIF and posterior approaches.

CONCLUSIONS

Stand-alone-ALIF demonstrated a shorter operative time and less blood loss than the PLIF/TLIF approach. Hospitalisation time is reduced with ALIF compared with TLIF. Patient-reported outcome measures were equivocal with PLIF or TLIF. VAS and JOAS, back pain, and ODI scores mainly favoured ALIF over PLF. Adverse events were equivocal between the ALIF and posterior fusion approaches.

What can we learn from long-term studies on chronic low back pain? A scoping review

PURPOSE

A scoping review was conducted with the objective to identify and map the available evidence from long-term studies on chronic non-specific low back pain (LBP), to examine how these studies are conducted, and to address potential knowledge gaps.

METHOD

We searched MEDLINE and EMBASE up to march 2021, not restricted by date or language. Experimental and observational study types were included. Inclusion criteria were: participants between 18 and 65 years old with non-specific sub-acute or chronic LBP, minimum average follow-up of > 2 years, and studies had to report at least one of the following outcome measures: disability, quality of life, work participation, or health care utilization. Methodological quality was assessed using the Effective Public Health Practice Project quality assessment. Data were extracted, tabulated, and reported thematically.

RESULTS

Ninety studies met the inclusion criteria. Studies examined invasive treatments (72%), conservative (21%), or a comparison of both (7%). No natural cohorts were included. Methodological quality was weak (16% of studies), moderate (63%), or strong (21%) and generally improved after 2010. Disability (92%) and pain (86%) outcomes were most commonly reported, followed by work (25%), quality of life (15%), and health care utilization (4%). Most studies reported significant improvement at long-term follow-up (median 51 months, range 26 months-18 years). Only 10 (11%) studies took more than one measurement > 2 year after baseline.

CONCLUSION

Patients with persistent non-specific LBP seem to experience improvement in pain, disability and quality of life years after seeking treatment. However, it remains unclear what factors might have influenced these improvements, and whether they are treatment-related. Studies varied greatly in design, patient population, and methods of data collection. There is still little insight into the long-term natural course of LBP. Additionally, few studies perform repeated measurements during long-term follow-up or report on patient-centered outcomes other than pain or disability.

Biomechanical comparison of vertebral augmentation and cement discoplasty for the treatment of symptomatic Schmorl's node: a finite element analysis

Percutaneous vertebral augmentation (PVA) and percutaneous cement discoplasty (PCD) are two relatively new minimally invasive surgeries for symptomatic Schmorl's reported in recent decade. However, the clinical evidence for the effectiveness of these two surgeries is insufficient. The purpose of this study was to compare the biomechanical benefits and risks of the two surgeries in order to analyze their biomechanical differences and effectiveness. We reconstructed Five lumbar finite element models via computed tomography data, including control model, PVA-ideal model, PVA-nonideal model, PCD-ideal model, and PCD-nonideal model. The stress and strain of Schmorl's nodes, bone marrow edema zone (BMEZ), affected endplate, and the overall stability of segment were analyzed and compared. The validity of our models was confirmed. As a result, the PVA-ideal model can significantly reduce the stress of Schmorl's node and the strain of BMEZ, while this effect is inappreciable in PVA-nonideal model. The PCD-ideal model significantly reduced the strain of Schmorl's nodes and BMEZ, and significantly improve segmental stability, but also resulted in a significant increase in the stress of Schmorl's nodes, BMEZ and endplates. The PCD-nonideal model not only lacks blocking effect, but also sharply increases the strain of Schmorl's nodes and BMEZ. Thus, We recommend that both PVA and PCD surgeries in ideal distribution facilitated a more stable paranodular biomechanical microenvironment. However, due to the possibility of poor biomechanical outcomes caused by the non-ideal cement distribution, the non-ideal distribution of bone cement needs to be remedied in practice.

The Effectiveness of Intraosseous Basivertebral Nerve Radiofrequency Neurotomy for the Treatment of Chronic Low Back Pain in Patients with Modic Changes: A Systematic Review

OBJECTIVE

Determine the effectiveness of intraosseous basivertebral nerve radiofrequency neurotomy for the treatment of chronic low back pain with type 1 or 2 Modic changes.

DESIGN

Systematic review.

POPULATION

Persons aged ≥18 years with chronic low back pain with type 1 or 2 Modic changes.

INTERVENTION

Intraosseous basivertebral nerve radiofrequency neurotomy.

COMPARISON

Sham, placebo procedure, active standard care treatment, or none.

OUTCOMES

The primary outcome of interest was the proportion of individuals with ≥50% pain reduction. Secondary outcomes included ≥10-point improvement in function as measured by Oswestry Disability Index as well as ≥2-point reduction in pain score on the Visual Analog Scale or Numeric Rating Scale, and decreased use of pain medication.

METHODS

Three reviewers independently assessed publications before May 15, 2020, in MEDLINE and Embase and the quality of evidence was evaluated using the Grades of Recommendation, Assessment, Development, and Evaluation framework.

RESULTS

Of the 725 publications screened, seven publications with 321 participants were ultimately included. The reported 3-month success rate for ≥50% pain reduction ranged from 45% to 63%. Rates of functional improvement (≥10-point Oswestry Disability Index improvement threshold) ranged from 75% to 93%. For comparison to sham treatment, the relative risk of treatment success defined by ≥50% pain reduction and ≥10-point Oswestry Disability Index improvement was 1.25 (95% confidence interval [CI]: .88-1.77) and 1.38 (95% CI: 1.10-1.73), respectively. For comparison to continued standard care treatment the relative risk of treatment success defined by ≥50% pain reduction and ≥10-point Oswestry Disability Index improvement was 4.16 (95% CI: 2.12-8.14) and 2.32 (95% CI: 1.52-3.55), respectively.

CONCLUSIONS

There is moderate-quality evidence that suggests this procedure is effective in reducing pain and disability in patients with chronic low back pain who are selected based on type 1 or 2 Modic changes, among other inclusion and exclusion criteria used in the published literature to date. Success of the procedure appears to be dependent on effective targeting of the BVN. Non-industry funded high-quality, large prospective studies are needed to confirm these findings.

Percutaneous vertebroplasty (PVP) to treat specialized type of endplate fractures around the Schmorl's node: a prospective study of 65 patients

BACKGROUND

The Schmorl's nodes (SNs) are defined as the herniation of the intervertebral disc into the vertebral body. Endplate fractures around the Schmorl's node could result in severe back pain that is similar to vertebral compression fractures. The objective of this study was to prospectively analyze the surgical effectiveness and safety of percutaneous vertebroplasty (PVP) for endplate fractures around the SNs.

METHODS

Seventy-one consecutive patients with the fresh endplate fracture around SNs from October 2017 to February 2018 were enrolled in this study. The visual analog scale (VAS) and Oswestry disability index (ODI) scores of low back pain were evaluated in all patients preoperatively, postoperatively, and at 1 month, 6 months, and 1 year after primary single level PVP. Surgery-related data including duration of the operation, injected cement volumes, and surgical complications were recorded.

RESULTS

Sixty-five patients with fresh endplate fractures around the SNs were treated successfully via percutaneous vertebroplasty. Our study showed that the VAS scores and ODI scores of patients were obviously improved after operation. Cement leakage into the disc space occurred in 5 patients (7.7%), and adjacent segment refractures occurred in 2 patients (3.1%). No other surgical complications, including infections or nerve root injuries were encountered.

CONCLUSIONS

Based on the results of this prospective study, PVP was an effective and safe procedure for endplate fractures around the SNs.

TRIAL REGISTRATION

ChiCTR, ChiCTR1800016453 . Registered 2 June 2018-retrospectively registered, http://www.chictr.org.cn/com/25/historyversionpuben.aspx?regno=ChiCTR1800017602.

Infected Schmorl's node: a case report

Background

Schmorls node (SN) are mostly asymptomatic and incidental findings on MRI. However, sometimes they present like acute onset low back pain or acute exacerbation of chronic back pain after minor trauma.

Case presentation

We present rare case of symptomatic infected SN in 67 years female patient presented with complains of low back pain radiating to right buttock. After initial conservative treatment failed subsequent imaging showed significant increase in size of lesion with focal signal changes in disc space gave suspicion of underlying secondary pathology. Patient operated for complete excision of lesion. Histopathological report was suggestive of pyogenic vertebral osteomyelitis. Patient improved well postoperatively.

Conclusion

Most of the time acute SN responds well to conservative treatment; however rapid deterioration of symptoms or persistent severe pain should give suspicion of underlying secondary pathology.

Lubricin expression in the lumbar endplate and its association with Modic changes

Objective

To explore the expression of lubricin in the lumbar endplate and its association with Modic changes (MCs).

Methods

Human endplate specimens harvested from patients undergoing surgery for thoracolumbar spine fractures ​or lumbar interbody fusion were divided into two groups: MCs group and normal group. Lubricin expression was examined by immunohistochemistry, and differences between the groups were analysed using quantitative polymerase chain reaction (qPCR). Lubricin expression and differences between endplates with MCs and normal endplates were confirmed using a rabbit model. In a final experiment, rabbit endplate chondrocytes were cocultured with Propionibacteria acnes (P. acnes) supernatant, and the expression of lubricin and endplate degeneration related genes were evaluated. In addition, the expression of matrix metalloproteinase 1(MMP-1), A disintegrin-like and metalloproteinase with thrombospondin type 5 motif (ADAMTS5) and inflammatory factors (Interleukin- 1β (IL-1β) and Interleukin-6 (IL-6)) were evaluated after lubricin overexpression.

Results

Lubricin was found in human lumbar endplates and its expression was lower in the MCs group compared to the normal group. In the rabbit model, lubricin was also found in the endplate. In rabbits injected with P. acnes (the MCs group), lubricin expression of endplate decreased compared to the normal group. In the culture of rabbit endplate chondrocytes with P. acnes supernatant, the expression of lubricin, aggrecan, sox9 and collagen type-II decreased significantly, while that of MMP-1 and ADAMTS5 increased significantly. Moreover, lubricin overexpression could downregulate the expression of MMP-1, ADAMTS5 and inflammatory factors (IL-1β and IL-6) compared to negative control.

Conclusion

Lubricin is present in the lumbar endplate where it may have an anti-inflammatory role. P. acnes infection inhibits lubricin expression by cartilage endplate cells and this may facilitate the progression of MCs and endplate degeneration.

The translational potential of this article

Lubricin may have an anti-inflammatory role. P. acnes infection inhibits lubricin expression by cartilage endplate cells and this may facilitate the progression of MCs and endplate degeneration.

The Chinese Association for the Study of Pain (CASP): Consensus on the Assessment and Management of Chronic Nonspecific Low Back Pain

Chronic nonspecific low back pain (CNLBP) is defined as pain or discomfort originating from the waist, which lasts for at least 12 weeks, but no radiculopathy or specific spinal diseases. CNLBP is a complicated medical problem and places a huge burden on healthcare systems. Clinical manifestation of CNLBP includes discogenic LBP, zygapophyseal joint pain, sacroiliac joint pain, and lumbar muscle strain. Further evaluation should be completed to confirm the diagnosis including auxiliary examination, functional assessment, and clinical assessment. The principle of the management is to relieve pain, restore function, and avoid recurrence. Treatment includes conservative treatment, minimally invasive treatment, and rehabilitation. Pharmacologic therapy is the first-line treatment of nonspecific LBP, and it is most widely used in clinical practice. Interventional therapy should be considered only after failure of medication and physical therapy. Multidisciplinary rehabilitation can improve physical function and alleviate short-term and long-term pain. The emphasis should be put on the prevention of NLBP and reducing relevant risk factors.

A longitudinal investigation of the endplate cystic lesion effect on oblique lumbar interbody fusion

OBJECTIVE

To determine longitudinal effects of changes in endplate cystic lesions on oblique lumbar interbody fusion (OLIF), the relationship between bone healing and endplate cystic lesion changes, and clinical significance of cyst formation.

PATIENTS AND METHODS

A total of 107 segments in 67 patients who underwent OLIF between January 2013 and July 2016 were examined in this retrospective study. Using computed tomography, radiographic examinations of endplate cystic lesion, positive or negative cyst formation, cage subsidence, and fusion status were performed. Clinical outcomes were measured using visual analogue scale (VAS) pain scores, Oswestry disability index (ODI), and modified Macnab criteria. Outcomes were compared with preoperatively and postoperatively. A logistic regression analysis was performed to evaluate the relationship between measurements for endplate cysts.

RESULTS

The fusion rate after OLIF was 94.4% at 2-year follow-up, with 86% of cases reporting satisfactory outcome (based on modified Macnab criteria). A significantly higher (P <  0.01) VAS score for back pain was observed in the cystic lesion group than non-cystic lesion group at 6-month follow-up. Cage subsidence significantly increased the risk of non-union (odds ratio [OR]: 17.24; 95% confidence interval [CI]: 1.67-178.09). Positive cyst sign was a significant risk factor for cage subsidence (OR: 8.52; 95% CI: 2.73-26.62) while cage subsidence was also a significant risk factor for positive cyst formation (OR: 8.37; 95% CI: 2.71-25.89).

CONCLUSIONS

Cystic lesion may increase back pain in the early postoperative period. However, the preoperative cystic lesion does not aggravate a positive cyst formation or affect the final clinical result. Positive cyst formation was a significant risk factor for cage subsidence. In addition, cage subsidence was a significant predictor of non-union. Thus, the authors can speculate that positive cyst sign was potentially an indirect predictor of non-union.

Defects of the vertebral end plate: implications for disc degeneration depend on size

BACKGROUND CONTEXT

Bony vertebral end plates must be porous to allow metabolite transport into the disc, and yet strong to resist high intradiscal pressure (IDP). End plate defects may therefore have nutritional and mechanical consequences for the disc, depending on their size and type. We hypothesize that broad, diffuse defects are more closely associated with disc decompression and degeneration than are focal Schmorl's node-type defects.

PURPOSE

This study aimed to determine how the size and type of end plate defects are related to decompression and degeneration in the adjacent intervertebral disc.

STUDY DESIGN

Mechanical, histologic, and micro-computed tomographic investigations were carried out in cadaver spines.

METHODS

The study involved 40 motion segments (T8-T9 to L4-L5) dissected from 23 cadavers aged 48-98 years. Intradiscal stresses were measured, under 1 kN compression, by pulling a pressure transducer along the disc's midsagittal diameter. The resulting "stress profiles" revealed nucleus pressure (IDP) and maximum stresses in the anterior and posterior annulus. Micro-computed tomography was then used to examine all 40 discs, with 5 mm of adjacent bone on either side, so that end plate defects could be characterized at a resolution of 35 µm. Cross-sectional area (in the transverse plane), volume, location, and morphologic type were determined for all bony defects in the 80 end plates. Finally, discs from each motion segment (with hyaline cartilage and bone attached) were sectioned (undecalcified) at 7 µm for histology to allow degeneration to be assessed.

RESULTS

Substantial defects were identified in 24 of 40 specimens (35 of 80 end plates). Of these, 83% was centrally located, and 17% was laterally located. Defects occurred more frequently in male than female specimens (p=.043), and were more common in thoracic than lumbar end plates (p=.002), although lumbar defects were greater in volume (p=.05). Defect area and volume increased with decreasing IDP, with decreasing peak stress in the annulus, and with increasing tissue degeneration. Stepwise multiple regression showed that average defect area depended most strongly on IDP, whereas maximum defect area and volume depended most strongly on peak stress in the anterior annulus. Multiple end plate defects were associated with lower values of IDP and higher degeneration scores when compared with erosions and Schmorl's nodes.

CONCLUSIONS

Disc degeneration has a stronger association with large or multiple end plate defects than with small or single defects (of any type). Large end plate defects probably allow greater volume changes within the disc, leading to greater nucleus decompression.

An Unusual Cause of Back Pain in a 10-Year-Old Girl

A 10-year-old girl with a 2-week history of atraumatic back pain presented to the emergency department with difficulty ambulating and a history of 2 episodes of urinary incontinence in the past week. Her examination was significant for pain with movement, tenderness to palpation in the lower thoracic spine, and no neurological deficits. In this case, the child was found to have a Schmorl node at T8 in the superior aspect of the vertebral body. Schmorl nodes are protrusions of the cartilage of the intervertebral disc through the vertebral body endplate and into the adjacent that is more commonly reported in the adult population. In this child, radiographic findings were normal, with no evidence of the Schmorl node. The diagnosis was made by magnetic resonance imaging. The child's symptoms significantly resolved with ibuprofen anti-inflammatory therapy. In children with atraumatic back pain lasting greater than 2 weeks with a sudden increase in severity and associated with a neurological deficit, advanced imaging is strongly recommended.

Significance of Vertebral Endplate Failure in Symptomatic Lumbar Disc Herniation

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

Endplate lesions though have been implicated in the genesis of lumbar disc herniation (LDH), very little is known regarding their clinical course. Thus, the present study is aimed to investigate the incidence and types of endplate failure (EPF) in LDH and its correlation with the clinical symptoms and prognosis.

METHODS

Clinical and magnetic resonance imaging (MRI) features of 66 patients with isolated single level LDH were studied. Three-dimensional fast spoiled gradient (3D FSPGR) MRI and computed tomography scans were used to identify the bony and cartilaginous EPF. Twenty-five patients were operated on and 41 patients were treated conservatively. Changes in the pain score, function and neurology were noted at 3, 6, 12, 24, and 36 weeks.

RESULTS

Endplate lesions were observed in 64 patients (96.9%), including bony endplate failure (bony failure) in 47 patients (71.2%) and isolated cartilaginous endplate lesions in 17 patients (25.7%). Bony failure group had similar pain and functional scores but more severe neurological deficit at the initial evaluation. Clinical parameters improved in all groups, but the recovery was lesser in conservatively treated bony failure patients.

CONCLUSION

Endplate lesions are commonly associated with symptomatic LDH. Presence of bony failure can increase neurological deficit and reduce the chance of recovery with conservative management. The 3D FSPGR sequence of MRI can be successfully used for detection of the endplate lesions in the herniated disc.

Painful Schmorl's nodes treated by discography and discoblock

PURPOSE

To determine the efficacy of discography and discoblock in the treatment of low back pain (LBP) associated with painful Schmorl's nodes (SNs).

METHODS

Between January 2010 and February 2015, 46 patients were studied who had LBP suspected to be secondary to SNs. There were 34 men and 12 women, and mean age was 54.2 years (range 42-68 years). All patients underwent provocation discography, and discoblock was given to positive patients (confirmed to have painful SNs). Visual analogue scores (VAS) and the Oswestry Disability Index (ODI) were evaluated at 4 h and 1, 3, 6, and 12 months post-operatively. MRI was also used to evaluate the SNs at 12 months.

RESULTS

Discography was performed on a total of 60 discs without infection or other complications. Positive findings were found in 71.7% discs; 20.0% were negative, and 8.3% were indeterminate. Among the positive patients who underwent discoblock, 89.2% reported an improvement in their LBP, and none reported worsening symptoms. VAS and ODI scores decreased significantly after discoblock, and there were no significant differences between 4 h and 1, 3, 6, and 12 months post-operatively. In patients with painful SNs, the vertebral body bone marrow surrounding the SN was characterized by low T1 and high T2 signals on MRI. At 12 months, the node demonstrated either high T1 and T2 signals or low T1 and T2 signals. The SNs tended to remain stable in size over time.

CONCLUSIONS

Painful SNs refractory to medical or physical therapy should be an indication for treatment with discography and discoblock.

A regenerative approach towards recovering the mechanical properties of degenerated intervertebral discs: Genipin and platelet-rich plasma therapies

Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are hence of great interest to both research and clinical communities alike. Exogenous crosslinking, such as Genipin, and platelet-rich plasma therapies have been recently demonstrated encouraging results for the repair and regeneration of degenerated discs, but there remains a knowledge gap regarding the quantitative degree of effectiveness and particular influence on the mechanical properties of the disc. This study aimed to investigate and quantify the material properties of intact (N = 8), trypsin-denatured (N = 8), Genipin-treated (N = 8), and platelet-rich plasma-treated (N = 8) discs in 32 porcine thoracic motion segments. A poroelastic finite element model was used to describe the mechanical properties during different treatments, while a meta-model analytical approach was used in combination with ex vivo experiments to extract the poroelastic material properties. The results revealed that both Genipin and platelet-rich plasma are able to recover the mechanical properties of denatured discs, thereby affording promising therapeutic modalities. However, platelet-rich plasma-treated discs fared slightly, but not significantly, better than Genipin in terms of recovering the glycosaminoglycans content, an essential building block for healthy discs. In addition to investigating these particular degenerative disc disease therapies, this study provides a systematic methodology for quantifying the detailed poroelastic mechanical properties of intervertebral disc.

Classification of Schmorl's nodes of the lumbar spine and association with disc degeneration: a large-scale population-based MRI study

OBJECTIVE

Schmorl's nodes (SN) are highly associated with lumbar disc degeneration (DD). However, SN present with different morphologies/topographies that may be associated with varying degrees of DD. This study proposed a classification of SN to determine their morphological/topographical prevalence and association with the severity of DD.

METHODS

Sagittal T2-weighted MRIs were assessed to identify SN and additional imaging findings from L1-S1 in 2,449 individuals. SN characteristics were classified by six criteria: disc level; endplate involvement; shape; size; location of endplate zone; and the presence of marrow changes. Hierarchical clustering was performed to identify distinct SN characteristics with endplate patterns.

RESULTS

Good to excellent observer classification reliability was noted. SN most commonly presented at the L1 and L2 disc levels, and entailed one-third of the endplate, predominantly the middle zone. Round shape (39.2%) was the most common SN shape. Four specific SN and endplate linkage patterns were identified. 8.3% of identified SN (n = 960) were "Atypical SN". Multivariable regression showed that "Typical SN" and "Atypical SN", depending on levels, were associated with an adjusted 2- to 4-fold and a 5- to 13-fold higher risk of increased severity of DD, respectively (p < 0.05).

CONCLUSIONS

This is the first large-scale magnetic resonance imaging (MRI) study to propose a novel SN classification. Specific SN-types were identified, which were associated with more severe DD. This study further broadens our understanding of the role of SN and degrees of DD, further expanding on the SN phenotyping that can be internationally adopted for utility assessment.

Neural innervation patterns in the sacral vertebral body

PURPOSE

To characterize the distribution of nerves within a single S1 vertebral body, with particular emphasis on the superior endplate that interfaces with the L5/S1 disc.

METHODS

Musculature and connective tissue surrounding the sacrum was carefully dissected away for close visual inspection of penetrating nerve fibers. The S1 vertebral body was then isolated for histology and serial coronal sections were cut and stained with a ubiquitous neural antibody marker (PGP 9.5). Slides were analyzed and nerves were manually marked on high resolution, composite captured images, rendering 3D depictions of internal nerve distribution.

RESULTS

The vast majority of nerves were closely associated with blood vessels within the marrow space with a uniform distribution in both the superior and inferior endplates of the S1 vertebral body. The highest nerve density was seen at the centrum (anatomic center) of the S1 vertebral body with smaller peaks seen at the lateral borders. Nerve fibers were observed branching from anterior sacral nerves and penetrating the lateral border of the S1 (during dissection), corresponding with peaks on nerve density maps.

CONCLUSIONS

Our results demonstrate that the S1 body and endplate are densely innervated and the peak in nerve density at the vertebral center coincides with vasculature patterns previously described in lumbar vertebral bodies. In the sacrum, however, there is no posterior nutrient foramen that facilitates nerve penetration through the vertebral cortex. Rather, our data indicate that nerves penetrate the S1 via the lateral aspects, consistent with being branches of the anterior sacral nerve. Since PGP 9.5 is a ubiquitous neural marker these identified nerves are likely composed of a mixed population of nociceptive and autonomic fibers.

Porosity and Thickness of the Vertebral Endplate Depend on Local Mechanical Loading

STUDY DESIGN

Mechanical and microcomputed tomography (micro-CT) study of cadaver spines.

OBJECTIVE

To compare porosity and thickness of vertebral endplates with (1) compressive stresses measured in adjacent intervertebral discs and (2) grade of disc degeneration.

SUMMARY OF BACKGROUND DATA

Endplate porosity is important for disc metabolite transport, and yet porosity increases with age and disc degeneration. We hypothesize that porosity is largely determined by mechanical loading from adjacent discs.

METHODS

Forty motion segments (T8-9 to L4-5) were dissected from 23 cadavers aged 48 to 98 years. Each was subjected to 1 kN compression during which time intradiscal stresses were measured by pulling a pressure transducer along the disc's midsagittal diameter. "Stress profiles" revealed the average pressure in the nucleus, and the maximum stress in the anterior and posterior annulus. Specimens were further dissected to obtain discs with endplates (and 5 mm of bone) on either side. Microcomputed tomography scans (resolution 35 μm) were analyzed to calculate thickness and porosity in the midsagittal regions of all 80 endplates. Average values for the anterior, central, and posterior regions of each endplate were obtained. Disc degeneration was assessed macroscopically and microscopically.

RESULTS

Endplate porosity was inversely related to its thickness, being greatest in the central region opposite the nucleus, and least near the periphery. Superior endplates (relative to the disc) were 14% thicker (P < 0.001) and 4% less porous (P = 0.008) than inferior. In each of the 3 endplate regions (anterior, central, and posterior), porosity was inversely and significantly related to mechanical loading (pressure or maximum stress) in the adjacent disc region (P < 0.01 in all cases). Disc degeneration was best predicted by (reduced) nucleus pressure (R = 0.46, P < 0.001) and (reduced) maximum stress in the anterior annulus (R = 0.31, P < 0.001).

CONCLUSION

Mechanical loading is a major determinant of endplate thickness and porosity. Disc degeneration is more closely related to reduced disc stresses than to endplate thickness or porosity.

LEVEL OF EVIDENCE

N/A.

ISSLS Prize winner: Mechanical influences in progressive intervertebral disc degeneration

STUDY DESIGN

Mechanical study on cadaver motion segments.

OBJECTIVE

To determine whether high gradients of compressive stress within the intervertebral disc are associated with progressive disc degeneration.

SUMMARY OF BACKGROUND DATA

Mechanical loading can initiate disc degeneration but may be unimportant in disease progression, because degenerative changes cause the disc to be increasingly "stress-shielded" by the neural arch. However, the most typical feature of advanced disc degeneration (delamination and collapse of the annulus) may not depend on absolute values of compressive stress but on gradients of compressive stress that act to shear annulus lamellae.

METHODS

A total of 191 motion segments (T7-T8 to L5-S1) were dissected from 42 cadavers aged 19 to 92 years. Each was subjected to approximately 1 kN compression, while intradiscal stresses were measured by pulling a pressure transducer along the disc's midsagittal diameter. "Stress gradients" in the annulus were quantified as the average rate of increase in compressive stress (MPa/mm) between the nucleus and the region of maximum stress in the anterior or posterior annulus. Measurements were repeated before and after creep loading and in simulated flexed and erect postures. Disc degeneration was assessed macroscopically on a scale of 1 to 4.

RESULTS

As grade of disc degeneration increased from 2 to 4, nucleus pressure decreased by an average 68%, and maximum compressive stress in the annulus decreased by 48% to 64%, depending on location and posture. In contrast, stress gradients in the annulus increased by an average 75% in the anterior annulus (in flexed posture) and by 108% in the posterior annulus (in erect posture). Spearman rank correlation showed that these increases were statistically significant.

CONCLUSION

Despite stress-shielding by the neural arch, gradients of compressive stress increase with increasing grade of disc degeneration. Stress gradients act to shear adjacent lamellae and can explain progressive annulus delamination and collapse.

LEVEL OF EVIDENCE

N/A.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 7: Lumbar fusion for intractable low-back pain without stenosis or spondylolisthesis

Establishing an appropriate treatment strategy for patients presenting with low-back pain, in the absence of stenosis or spondylolisthesis, remains a controversial subject. Inherent to this situation is often an inability to adequately identify the source of low-back pain to justify various treatment recommendations, such as lumbar fusion. The current evidence does not identify a single best treatment alternative for these patients. Based on a number of prospective, randomized trials, comparable outcomes, for patients presenting with 1- or 2-level degenerative disc disease, have been demonstrated following either lumbar fusion or a comprehensive rehabilitation program with a cognitive element. Limited access to such comprehensive rehabilitative programs may prove problematic when pursuing this alternative. For patients whose pain is refractory to conservative care, lumbar fusion is recommended. Limitations of these studies preclude the ability to present the most robust recommendation in support of lumbar fusion. A number of lesser-quality studies, primarily case series, also support the use of lumbar fusion in this patient population.

Why do some intervertebral discs degenerate, when others (in the same spine) do not?

This review suggests why some discs degenerate rather than age normally. Intervertebral discs are avascular pads of fibrocartilage that allow movement between vertebral bodies. Human discs have a low cell density and a limited ability to adapt to mechanical demands. With increasing age, the matrix becomes yellowed, fibrous, and brittle, but if disc structure remains intact, there is little impairment in function, and minimal ingrowth of blood vessels or nerves. Approximately half of old lumbar discs degenerate in the sense of becoming physically disrupted. The posterior annulus and lower lumbar discs are most affected, presumably because they are most heavily loaded. Age and genetic inheritance can weaken discs to such an extent that they are physically disrupted during everyday activities. Damage to the endplate or annulus typically decompresses the nucleus, concentrates stress within the annulus, and allows ingrowth of nerves and blood vessels. Matrix disruption progresses by mechanical and biological means. The site of initial damage leads to two disc degeneration "phenotypes": endplate-driven degeneration is common in the upper lumbar and thoracic spine, and annulus-driven degeneration is common at L4-S1. Discogenic back pain can be initiated by tissue disruption, and amplified by inflammation and infection. Healing is possible in the outer annulus only, where cell density is highest. We conclude that some discs degenerate because they are disrupted by excessive mechanical loading. This can occur without trauma if tissues are weakened by age and genetic inheritance. Moderate mechanical loading, in contrast, strengthens all spinal tissues, including discs.

Persistent degenerative changes in the intervertebral disc after burst fracture in an in vitro model mimicking physiological post-traumatic conditions

PURPOSE

Post-traumatic disc degeneration (DD) is currently investigated with models not fully matching the clinical condition, in particular post-traumatic loading of the disc is not considered. Therefore, the aim was to establish an in vitro burst fracture model that more closely mimics the in vivo situation by including post-traumatic physiological loading and to investigate DD under these conditions.

METHODS

72 rabbit spinal segments (disc/endplates + 1/3 of adjacent vertebrae) were harvested from T8/9 to L5/6 and assigned to control (n = 36) or trauma groups (n = 36). Burst fractures were induced at day 0 in the trauma group using a dropped-weight device. From day 1 to 28, all specimens were cultured at 37 °C and were dynamically loaded daily (~1 MPa nominal pressure, 1 Hz, 2,500 cycles). At day 1, 7, 14, and 28, 9 specimens from each group were taken for analysis: histology (n = 2), total disc glycosaminoglycan (GAG) content (n = 3) normalized to DNA, and qPCR of DD marker genes (n = 4) in the nucleus pulposus and the annulus fibrosus.

RESULTS

Burst fracture with post-traumatic physiological loading resulted in a 65 % loss of GAG/DNA by day 28. Histological sections confirmed the remodeling of the matrix. Catabolic (MMP-1/-3), pro-apoptotic (TNF-α, fas ligand), and pro-inflammatory (IL-1/-6, iNOS) gene transcription was substantially up-regulated in the nucleus after the trauma and did not normalize to control within 28 days. Similar results were found for the annulus on lower levels.

CONCLUSION

An in vitro burst fracture model with physiological post-traumatic loading was established. Under these conditions, burst spinal segments undergo strong and persistent degenerative changes.

Delivery of small molecules for bone regenerative engineering: preclinical studies and potential clinical applications

Stimulation of bone regeneration using growth factors is a promising approach for musculoskeletal regenerative engineering. However, common limitations with protein growth factors, such as high manufacturing costs, protein instability, contamination issues, and unwanted immunogenic responses of the host reduce potential clinical applications. New strategies for bone regeneration that involve inexpensive and stable small molecules can obviate these problems and have a significant impact on the treatment of skeletal injury and diseases. Over the past decade, a large number of small molecules with the potential of regenerating skeletal tissue have been reported in the literature. Here, we review this literature, paying specific attention to the prospects for small molecule-based bone-regenerative engineering. We also review the preclinical study of small molecules associated with bone regeneration.

The role of the vertebral end plate in low back pain

End plates serve as the interface between rigid vertebral bodies and pliant intervertebral disks. Because the lumbar spine carries significant forces and disks don't have a dedicated blood supply, end plates must balance conflicting requirements of being strong to prevent vertebral fracture and porous to facilitate transport between disk cells and vertebral capillaries. Consequently, end plates are particularly susceptible to damage, which can increase communication between proinflammatory disk constituents and vascularized vertebral bone marrow. Damaged end plate regions can be sites of reactive bone marrow lesions that include proliferating nerves, which are susceptible to chemical sensitization and mechanical stimulation. Although several lines of evidence indicate that innervated end plate damage can be a source of chronic low back pain, its role in patients is likely underappreciated because innervated damage is poorly visualized with diagnostic imaging. This literature review summarizes end plate biophysical function and aspects of pathologic degeneration that can lead to vertebrogenic pain. Areas of future research are identified in the context of unmet clinical needs for patients with chronic low back pain.

Early adolescent lumbar intervertebral disc injury: a case study

This article describes and discusses the case of an adolescent male with lumbar intervertebral disc injury characterized by chronic low back pain (LBP) and antalgia. A 13-year-old boy presented for care with a complaint of chronic LBP and subsequent loss of quality of life. The patient was examined and diagnosed by means of history, clinical testing and use of imaging. He had showed failure in natural history and conservative management relief in both symptomatic and functional improvement, due to injury to the intervertebral joints of his lower lumbar spine. Discogenic LBP in the young adolescent population must be considered, particularly in cases involving even trivial minor trauma, and in those in which LBP becomes chronic. More research is needed regarding long-term implications of such disc injuries in young people, and how to best conservatively manage these patients. A discussion of discogenic LBP pertaining to adolescent disc injury is included.

Pathophysiology, diagnosis, and treatment of discogenic low back pain

Discogenic low back pain is a serious medical and social problem, and accounts for 26%-42% of the patients with chronic low back pain. Recent studies found that the pathologic features of discs obtained from the patients with discogenic low back pain were the formation of the zones of vascularized granulation tissue, with extensive innervation in fissures extending from the outer part of the annulus into the nucleus pulposus. Studies suggested that the degeneration of the painful disc might originate from the injury and subsequent repair of annulus fibrosus. Growth factors such as basic fibroblast growth factor, transforming growth factor β1, and connective tissue growth factor, macrophages and mast cells might play a key role in the repair of the injured annulus fibrosus and subsequent disc degeneration. Although there exist controversies about the role of discography as a diagnostic test, provocation discography still is the only available means by which to identify a painful disc. A recent study has classified discogenic low back pain into two types that were annular disruption-induced low back pain and internal endplate disruption-induced low back pain, which have been fully supported by clinical and theoretical bases. Current treatment options for discogenic back pain range from medicinal anti-inflammation strategy to invasive procedures including spine fusion and recently spinal arthroplasty. However, these treatments are limited to relieving symptoms, with no attempt to restore the disc's structure. Recently, there has been a growing interest in developing strategies that aim to repair or regenerate the degenerated disc biologically.

Spinal fusion for chronic low back pain: systematic review on the accuracy of tests for patient selection

BACKGROUND CONTEXT

Spinal fusion is a common but controversial treatment for chronic low back pain (LBP) with outcomes similar to those of programmed conservative care. To improve the results of fusion, tests for patient selection are used in clinical practice.

PURPOSE

To determine the prognostic accuracy of tests for patient selection that are currently used in clinical practice to identify those patients with chronic LBP who will benefit from spinal fusion.

STUDY DESIGN

Systematic review of the literature.

SAMPLE

Studies that compared the results of magnetic resonance imaging (MRI), provocative discography, facet joint blocks, orthosis immobilization, and temporary external fixation with the clinical outcome of patients who underwent spinal fusion for chronic LBP.

OUTCOME MEASURES

To determine the prognostic accuracy of tests to predict the clinical outcome of spinal fusion in terms of sensitivity, specificity, and likelihood ratios (LRs).

METHODS

Data sources PubMed (1966 to November 2010), EMBASE (1974 to November 2010), and reference lists were searched without restriction by language or publication status. Two reviewers independently selected studies for inclusion, extracted data for analysis, and assessed the risk of bias with the Quality Assessment of Diagnostic Accuracy Studies checklist, modified for prognostic studies. Discrepancies were resolved by consensus.

RESULTS

Ten studies met the eligibility criteria. Immobilization by an orthosis (median [range] positive LR, 1.10 [0.94-1.13] and negative LR, 0.92 [0.39-1.12]), provocative discography (median [range] positive LR, 1.18 [0.70-1.71] and negative LR, 0.74 [0.24-1.40]), and temporary external fixation (median [range] positive LR, 1.22 [1.02-1.74] and negative LR, 0.58 [0.15-0.94]) failed to show clinically useful prognostic accuracy. Statistical pooling was not feasible because of different test protocols, variability in outcome assessment, and heterogeneous patient populations. No studies reporting on facet joint blocks or MRI could satisfy the inclusion criteria. Obscure patient selection, high risk of verification bias, and outcome assessment with poorly validated instruments precluded strong conclusions for all tests.

CONCLUSIONS

No subset of patients with chronic LBP could be identified for whom spinal fusion is a predictable and effective treatment. Best evidence does not support the use of current tests for patient selection in clinical practice.

Decision making in surgical treatment of chronic low back pain: the performance of prognostic tests to select patients for lumbar spinal fusion

Chronic low back pain (CLBP) is one of the main causes of disability in the western world with a huge economic burden to society. As yet, no specific underlying anatomic cause has been identified for CLBP. Imaging often reveals degenerative findings of the disc or facet joints of one or more lumbar motion segments. These findings, however, can also be observed in asymptomatic people. It has been suggested that pain in degenerated discs may be caused by the ingrowth of nerve fibers into tears or clefts of the annulus fibrosus or nucleus pulposus, and by reported high levels of pro-inflammatory mediators. As this so-called discogenic pain is often exacerbated by mechanical loading, the concept of relieving pain by spinal fusion to stabilise a painful spinal segment, has been developed. For some patients lumbar spinal fusion indeed is beneficial, but its results are highly variable and hard to predict for the individual patient. To identify those CLBP patients who will benefit from fusion, many surgeons rely on tests that are assumed to predict the outcome of spinal fusion. The three most commonly used prognostic tests in daily practice are immobilization in a lumbosacral orthosis, provocative discography and trial immobilization by temporary external transpedicular fixation. Aiming for consensus on the indications for lumbar fusion and in order to improve its results by better patient selection, it is essential to know the role and value of these prognostic tests for CLBP patients in clinical practice. The overall aims of the present thesis were: 1) to evaluate whether there is consensus among spine surgeons regarding the use and appreciation of prognostic tests for lumbar spinal fusion; 2) to verify whether a thoracolumbosacral orthosisis (TLSO) truly minimises lumbosacral motion; 3) to verify whether a TLSO can predict the clinical outcome of fusion for CLBP; 4) to assess whether provocative discography of adjacent segments actually predicts the long-term clinical outcome fusion; 5) to determine the incidence of postdiscography discitis, and whether there is a need for routine antibiotic prophylaxis; 6) to assess whether temporary external transpedicular fixation (TETF) can help to predict the outcome of spinal fusion; 7) to determine the prognostic accuracy of the most commonly used tests in clinical practice to predict the outcome of fusion for CLBP. The results of a national survey among spine surgeons in the Netherlands were presented in Study I. The surgeons were questioned about their opinion on prognostic factors and about the use of predictive tests for lumbar fusion in CLBP patients. The comments were compared with findings from the prevailing literature. The survey revealed a considerable lack of uniformity in the use and appreciation of predictive tests. Prognostic factors known from the literature were not consistently incorporated in the surgeons' decision making process either. This heterogeneity in strategy is most probably caused by the lack of sound scientific evidence for current predictive tests and it was concluded that currently there is not enough consensus among spine surgeons in the Netherlands to create national guidelines for surgical decision making in CLBP. In Study II, the hypothesized working mechanism of a pantaloon cast (i.e., minimisation of lumbosacral joint mobility) was studied. In patients who were admitted for a temporary external transpedicular fixation test (TETF), infrared light markers were rigidly attached to the protruding ends of Steinman pins that were fixed in two spinal levels. In this way three-dimensional motion between these levels could be analysed opto-electronically. During dynamic test conditions such as walking, a plaster cast, either with or without unilateral hip fixation, did not significantly decrease lumbosacral joint motion. Although not substantiated by sound scientific support, lumbosacral orthoses or pantaloon casts are often used in everyday practice as a predictor for the outcome of fusion. A systematic review of the literature supplemented with a prospective cohort study was performed (Study III) in order to assess the value of a pantaloon cast in surgical decision-making. It appeared that only in CLBP patients with no prior spine surgery, a pantaloon cast test with substantial pain relief suggests a favorable outcome of lumbar fusion compared to conservative treatment. In patients with prior spine surgery the test is of no value. It is believed by many spine surgeons that provocative discography, unlike plain radiographs or magnetic resonance imaging, is a physiologic test that can truly determine whether a disc is painful and relevant in a patient's pain syndrome, irrespective of the morphology of the disc. It has been suggested that in order to achieve a successful clinical outcome of lumbar fusion, suspect discs should be painful and adjacent control discs should elicit no pain on provocative discography. For this reason, a cohort of patients in whom the decision to perform lumbar fusion was based on an external fixation (TETF) trial, was analysed retrospectively in Study IV. The results of preoperative discography of solely the levels adjacent to the fusion were compared with the clinical results after spinal fusion. It appeared that in this select group of patients the discographic status of discs adjacent to a lumbar fusion did not have any effect on the clinical outcome. The most feared complication of lumbar discography is discitis. Although low in incidence, this is a serious complication for a diagnostic procedure and prevention by the use of prophylactic antibiotics has been advocated. In search for clinical guidelines, the risk of postdiscography discitis was assessed in Study V by means of a systematic literature review and a cohort of 200 consecutive patients. Without the use of prophylactic antibiotics, an overall incidence of postdiscography discitis of 0.25% was found. To prove that antibiotics would actually prevent discitis, a randomised trial of 9,000 patients would be needed to reach significance. Given the possible adverse effects of antibiotics, it was concluded that the routine use of prophylactic antibiotics in lumbar discography is not indicated. In Study VI, the middle- and long-term results of external fixation (TETF) as a test to predict the clinical outcome of lumbar fusion were studied in a group of back pain patients for whom there was doubt about the indication for surgery. The test included a placebo trial, in which the patients were unaware whether the lumbar segmental levels were fixed or dynamised. Using strict and objective criteria of pain reduction on a visual analogue scale, the TETF test failed to predict clinical outcome of fusion in this select group of patients. Pin track infection and nerve root irritation were registered as complications of this invasive test. It was concluded that in chronic low back pain patients with a doubtful indication for fusion, TETF is not recommended as a supplemental tool for surgical decision-making. In Study VII, a systematic literature review was performed regarding the prognostic accuracy of tests that are currently used in clinical practice and that are presumed to predict the outcome of lumbar spinal fusion for CLBP. The tests of interest were magnetic resonance imaging (MRI), TLSO immobilisation, TETF, provocative discography and facet joint infiltration. Only 10 studies reporting on three different index tests (discography, TLSO immobilisation and TETF) that truly reported on test qualifiers, such as sensitivity, specificity and likelihood ratios, could be selected. It appeared that the accuracy of all prognostic tests was low, which confirmed that in many clinical practices patients are scheduled for fusion on the basis of tests, of which the accuracy is insufficient or at best unknown. As the overall methodological quality of included studies was poor, higher quality trials that include negatively tested as well as positively tested patients for fusion, will be needed. It was concluded that at present, best evidence does not support the use of any prognostic test in clinical practice. No subset of patients with low back pain could be identified, for whom spinal fusion is a reliable and effective treatment. In literature, several studies have reported that cognitive behavioural therapy or intensive exercise programs have treatment results similar to those of spinal fusion, but with considerably less complications, morbidity and costs. As the findings of the present thesis show that the currently used tests do not improve the results of fusion by better patient selection, these tests should not be recommended for surgical decision making in standard care. Moreover, spinal fusion should not be proposed as a standard treatment for chronic low back pain. Causality of nonspecific spinal pain is complex and CLBP should not be regarded as a diagnosis, but rather as a symptom in patients with different stages of impairment and disability. Patients should be evaluated in a multidisciplinary setting or Spine Centre according to the so-called biopsychosocial model, which aims to identify underlying psychosocial factors as well as biological factors. Treatment should occur in a stepwise fashion starting with the least invasive treatment. The current approach of CLBP, in which emphasis is laid on self-management and empowerment of patients to take an active course of treatment in order to prevent long-term disability and chronicity, is recommended.

Intervertebral disc degeneration: evidence for two distinct phenotypes

We review the evidence that there are two types of disc degeneration. 'Endplate-driven' disc degeneration involves endplate defects and inwards collapse of the annulus, has a high heritability, mostly affects discs in the upper lumbar and thoracic spine, often starts to develop before age 30 years, usually leads to moderate back pain, and is associated with compressive injuries such as a fall on the buttocks. 'Annulus-driven' disc degeneration involves a radial fissure and/or a disc prolapse, has a low heritability, mostly affects discs in the lower lumbar spine, develops progressively after age 30 years, usually leads to severe back pain and sciatica, and is associated with repetitive bending and lifting. The structural defects which initiate the two processes both act to decompress the disc nucleus, making it less likely that the other defect could occur subsequently, and in this sense the two disc degeneration phenotypes can be viewed as distinct.

Schmorl's nodes

INTRODUCTION

First described in 1927, a Schmorl's node (SN) is the herniation of nucleus pulposus (NP) through the cartilaginous and bony end plate into the body of the adjacent vertebra. SNs are common findings on imaging, and although most SNs are asymptomatic, some have been shown to become painful lesions. In this manuscript, we review the literature regarding the epidemiology, clinical presentation, pathogenesis, imaging, and management of SNs.

MATERIALS AND METHODS

Using databases from the US National Library of Medicine and the National Institutes of Health, relevant articles were identified.

RESULTS

While several theories regarding the pathogenesis of SNs have been proposed, an axial load model appears to have the greatest supporting evidence. Symptomatic SNs are thought to be due to the inflammatory response solicited by the herniation of NP into the well-vascularized vertebral body. Management options for symptomatic SNs vary, ranging from medical management to surgical fusion.

CONCLUSION

SNs are common lesions that are often asymptomatic. In certain cases, SNs can cause back pain. No consensus on pathogenesis exists. There is no established treatment modality for symptomatic SNs.

Healing of a painful intervertebral disc should not be confused with reversing disc degeneration: implications for physical therapies for discogenic back pain

BACKGROUND

Much is known about intervertebral disc degeneration, but little effort has been made to relate this information to the clinical problem of discogenic back pain, and how it might be treated.

METHODS

We re-interpret the scientific literature in order to provide a rationale for physical therapy treatments for discogenic back pain.

INTERPRETATION

Intervertebral discs deteriorate over many years, from the nucleus outwards, to an extent that is influenced by genetic inheritance and metabolite transport. Age-related deterioration can be accelerated by physical disruption, which leads to disc "degeneration" or prolapse. Degeneration most often affects the lower lumbar discs, which are loaded most severely, and it is often painful because nerves in the peripheral anulus or vertebral endplate can be sensitised by inflammatory-like changes arising from contact with blood or displaced nucleus pulposus. Surgically-removed human discs show an active inflammatory process proceeding from the outside-in, and animal studies confirm that effective healing occurs only in the outer anulus and endplate, where cell density and metabolite transport are greatest. Healing of the disc periphery has the potential to relieve discogenic pain, by re-establishing a physical barrier between nucleus pulposus and nerves, and reducing inflammation.

CONCLUSION

Physical therapies should aim to promote healing in the disc periphery, by stimulating cells, boosting metabolite transport, and preventing adhesions and re-injury. Such an approach has the potential to accelerate pain relief in the disc periphery, even if it fails to reverse age-related degenerative changes in the nucleus.