Endplate Sclerosis Research Articles

Análise radiológica da degeneração discal experimental em coelhos

OBJETIVO: Validar a avaliação radiográfica da degeneração discal experimental em coelhos. MÉTODOS: Os discos intervertebrais lombares de coelhos New Zealand foram puncionados três vezes com uma agulha 18G com profundidade limitada de 5mm, através de abordagem lateral. Foram realizadas radiografias seriadas pré e pós-operatórias imediatas, e depois de quatro, oito e 12 semanas do procedimento, com posterior análise da altura discal, formação de osteófito, esclerose da placa vertebral e presença de degeneração discal. A análise estatística dos dados foi validada pelo coeficiente de concordância Kappa, com intervalo de confiança (IC) de 95%. RESULTADOS: Observou-se diminuição significativa do espaço discal nas radiografias em AP após 12 semanas de pós-operatório, com Kappa = 0,489 para IC 95% (0,25-0,72) com p < 0,001. Os sinais radiográficos de degeneração discal também apresentaram valor de Kappa = 0,63 para IC 95% (0,39-0,86) com p < 0,001. Os demais critérios avaliados tiveram resultados positivos, porém, com menor valor de Kappa. CONCLUSÃO: O modelo de degeneração discal em coelhos proposto neste estudo mostrou-se factível, com correlação radiológica positiva entre as imagens pré e pós-operatórias, validando a possibilidade de indução de degeneração discal nesse modelo animal para futuros estudos.

RADIOLOGICAL ANALYSIS OF EXPERIMENTAL DISC DEGENERATION IN RABBITS

Objective: To validate radiographic evaluation of a rabbit model for disc degeneration. Methods: Lumbar intervertebral discs of New Zealand rabbits were stabbed three times with a 18G needle at a limited depth of 5mm, through lateral approach. Serial radiographic images were taken on the early pre-and postoperative periods, and after four, eight and 12 weeks of the procedure, with subsequent analysis of disc height, osteophyte formation, endplate sclerosis, and presence of disc degeneration. The statistical analysis of data was validated by the Kappa coefficient, with a confidence interval (CI) of 95%. Results: A significant reduction of disc space was found on AP X-ray images after 12 postoperative weeks, with Kappa = 0.489 for CI 95% (0.25-0.72) with p < 0.001. X-ray signs of disc degeneration also presented Kappa = 0.63 for CI 95% (0.39-0.86) with p < 0.001. The remaining assessed criteria showed positive results, but with a lower Kappa value. Conclusion: The disc degeneration model using rabbits as proposed in this study was shown to be feasible, with positive X-ray correlation between pre- and postoperative images, validating the potential to induce disc degeneration in this animal model for future studies.

Qualitative and quantitative assessment of degeneration of cervical intervertebral discs and facet joints

Degeneration of intervertebral discs and facet joints is one of the most frequently encountered spinal disorders. In order to describe and quantify degeneration and evaluate a possible relationship between degeneration and biomechanical parameters, e.g., the intervertebral range of motion and intradiscal pressure, a scoring system for degeneration is mandatory. However, few scoring systems for the assessment of degeneration of the cervical spine exist. Therefore, two separate objective scoring systems to qualitatively and quantitatively assess the degree of cervical intervertebral disc and facet joint degeneration were developed and validated. The scoring system for cervical disc degeneration consists of three variables which are individually scored on neutral lateral radiographs: "height loss" (0-4 points), "anterior osteophytes" (0-3 points) and "endplate sclerosis" (0-2 points). The scoring system for facet joint degeneration consists of four variables which are individually scored on neutral computed tomography scans: "hypertrophy" (0-2 points), "osteophytes" (0-1 point), "irregularity" on the articular surface (0-1 point) and "joint space narrowing" (0-1 point). Each variable contributes with varying importance to the overall degeneration score (max 9 points for the scoring system of cervical disc degeneration and max 5 points for facet joint degeneration). Degeneration of 20 discs and facet joints of 20 patients was blindly assessed by four raters: two neurosurgeons (one senior and one junior) and two radiologists (one senior and one junior), firstly based on first subjective impression and secondly using the scoring systems. Measurement errors and inter- and intra-rater agreement were determined. The measurement error of the scoring system for cervical disc degeneration was 11.1 versus 17.9% of the subjective impression results. This scoring system showed excellent intra-rater agreement (ICC = 0.86, 0.75-0.93) and excellent inter-rater agreement (ICC = 0.78, 0.64-0.88). Surgeons as well as radiologists and seniors as well as juniors obtained excellent inter- and intra-rater agreement. The measurement error of the scoring system for cervical facet joint degeneration was 20.1 versus 24.2% of the subjective impression results. This scoring system showed good intra-rater agreement (ICC = 0.71, 0.42-0.89) and fair inter-rater agreement (ICC = 0.49, 0.26-0.74). Both scoring systems fulfilled the criteria for recommendation proposed by Kettler and Wilke. Our scoring systems can be reliable and objective tools for assessing cervical disc and facet joint degeneration. Moreover, the scoring system of cervical disc degeneration was shown to be experience- and discipline-independent.

Modic changes in vertebral endplates: a comparison of MR imaging and multislice CT

This paper aims to evaluate the presence of endplate sclerosis in different types of Modic changes and to assess the capability of MRI in detecting endplate sclerosis within these changes. The lumbar spines (L3-S1) of 70 patients were retrospectively reviewed to determine Modic changes and disc degeneration from MRI and endplate sclerosis from CT. T1- and T2-weighted signal intensity and Hounsfield unit (HU) measurements of type I and II Modic changes were recorded and the association of both Modic types I and II with endplate sclerosis was analyzed with a Mann-Whitney test. Altogether 82 Modic changes in 36 subjects were recorded: 13% were type I, 12% mixed type I/II, 65% type II, 9% mixed type II/III, and 1% type III. Thirty-eight percent of the endplates with Modic changes had sclerosis in CT. Of specific Modic types, mixed I/II and II/III associated significantly with endplate sclerosis. Endplate sclerosis was not detected in MRI in a quantitative analysis. Endplate sclerosis exists in all types of Modic changes, especially in mixed Modic types, and not only in type III changes, as previously assumed. Endplate sclerosis was not detected in MRI, which may depend on the amount of mineralization of the bone marrow.

Association of a Single Nucleotide Polymorphism in the Insulin-Like Growth Factor-1 Receptor Gene With Spinal Disc Degeneration in Postmenopausal Japanese Women

An association study investigating the genetic etiology for spinal disc degeneration. To determine the association of single-nucleotide polymorphism (SNP) in the insulin-like growth factor-1 receptor (IGF1R) with spinal disc degeneration. Insulin-like growth factor-1 (IGF-1) signaling pathway is involved in cartilage development and homeostasis, suggesting that genetic variations of genes involved in this pathway may affect the pathogenesis of cartilage-related diseases, such as disc degeneration. We evaluated the presence of endplate sclerosis, osteophytes, and narrowing of disc spaces in 434 Japanese postmenopausal women. A SNP in the IGF1R gene at intron 1 was determined using TaqMan polymerase chain reaction method. We compared those who carried the G allele (GG or GC, n = 290) with those who did not (CC, n = 144). We found that the subjects with the G allele (GG or GC) were significantly over-represented in the subjects having higher disc narrowing score (P = 0.0033; odds ratio, 2.04; 95% confidence interval, 1.27-3.29 by logistic regression analysis). We suggest that a genetic variation at the IGF1R gene locus is associated with spinal disc degeneration, in line with the involvement of the IGF1R gene in the cartilage metabolism.

Relationship between disc injury and manual lifting: A poroelastic finite element model study

Understanding how failure originates in a lumbar motion segment subjected to loading conditions that are representative of manual lifting is important because it will pave the way for a better formulation of the exposure-injury relationship. The aim of the current investigation was to use a poroelastic finite element model of a human lumbar disc to determine its biomechanical characteristics under loading conditions that corresponded to three different, commonly occurring lifting activities and to identify the most hazardous type of loading with regard to damage to the disc. The current study showed that asymmetric lifting may increase the risk of back injury and pain. Lifting that involved lateral bending (asymmetric lifting) of the trunk was found to produce stresses at a localized area in the annulus, annuluar fibres, end plates, and facet joints that were higher than their respective tissue failure strength. Thus asymmetric lifting, if performed over a large number of cycles, might help to propagate this localized failure of the disc tissue to a larger area, owing to fatigue. The analyses also showed that largest fluid exchange between the nucleus and the end plates occurred during asymmetric lifting. If the fluid exchange is restricted owing to end plate calcification or sclerosis of the subchondral bone, high intradiscal pressure might develop, leading to higher disc bulge causing back pain.

Clinical Results and Changes of Adjacent Segment after Whole Lumbosacral Fusion

Purpose: To analyze the clinical and radiological results of whole lumbosacral fusion, and to identify whether an extension of the fusion level is required. Materials and Methods: A retrospective review was carried out on 40 patients who had undergone whole lumbosacral fusion. The adjacent segment changes were evaluated by the radiological findings including intervertebral space narrowing, traction spur, endplate sclerosis and vacuum phenomenon. The clinical results were evaluated using a visual analogue scale (VAS) and Oswestry disability index (ODI). Results: The mean age was 63.8 years and the mean follow-up period was 41.7 months. At the last follow-up, adjacent segment changes were observed in 12 cases of intervertebral space narrowing, 15 cases of traction spur, 20 cases of endplate sclerosis and 8 cases of vacuum phenomenon. In the clinical results, the VAS was improved to 4.0 points from 7.6 points, and the ODI improved to 43.9% from 86.0%. There were no revision cases due to adjacent segment problems. Conclusion: Whole lumbosacral fusion in spinal stenosis with degenerative lumbar scoliosis was concomitant with some adjacent segment problems, but presented favorable outcomes. For the prevention of junctional problem, caution should be taken when extending the fusion level to the proximal level in whole lumbosacral fusion.

Vertebral Endplate and Disc Changes in the Aging Sand Rat Lumbar Spine

Lumbar vertebral segments from a large cross-sectional population of male and female sand rats were assessed for quantitative determination of lumbar endplate bone mineral density (BMD) and radiologic features. To determine radiologic and BMD characteristics in the lumbar spines of males and females ranging in age from 1.5 to 46.0 months. The sand rat provides an excellent economical model in which disc degeneration is reliable and well characterized. A major advantage of this model is that disc degeneration is spontaneous and does not need to be induced by stab surgical procedures. Previous work has only examined a small group of male sand rats for radiologic and BMD features of the lumbar spine; more complete data on both genders and a wider age range are lacking. BMD data were obtained for 99 male or female sand rats aged 1.5 to 46.0 months using the GE Lunar PIXImus bone densitometer; results were assessed for changes related to age, weight, gender, lumbar vertebral site, and radiologic characteristics of disc degeneration (disc space narrowing, wedging, and endplate calcification). Four age groups were studied: Group 1, 1 to 3.9 months of age; Group 2, 4 to 11.9 months of age; Group 3, 12 to 23.9 months of age, and Group 4, 24 to 46 months of age. Group 1 females showed a greater incidence of radiologic disc space narrowing and wedging at L1-L2, L2-L3, L3-L4, L4-L5, and of wedging at sites L5-L6, L6-L7, and L7-S. Group 2 females had significantly greater disc space narrowing at L3-L4 and L4-L5. By the time animals reached the age of Groups 3 and 4, males showed more wedging at L1-L2 and L3-L4. BMD data showed that Group 1 females had significantly lower BMD than Groups 2, 3 and 4 at all lumbar levels, and Group 4 had significantly higher BMD than Group 3. For males, there were no differences in younger animals, but older Group 3 and 4 animals had significantly greater BMD than Groups 1 and 2. Caudal BMD values were generally significantly higher than cranial values. Averaged BMD levels correlated significantly with both age and body weight, but the correlation with age at each lumbar level accounted for much more of the variation than did weight. Averaged BMD was significantly greater in disc sites showing disc space narrowing than in sites without narrowing for L1-L2 and L3-L4 through L7-S (P < or = 0.002 for each spinal level). Results expand our understanding of the association of age and gender to endplate sclerosis patterns in the lumbar spine, and support the hypothesis that endplate sclerosis may play a role in disc degeneration.

Association of a single nucleotide polymorphism in the WISP1 gene with spinal osteoarthritis in postmenopausal Japanese women

The Wnt-beta-catenin signaling pathway that regulates bone density is also involved in cartilage development and homeostasis in vivo. Here, we assumed that genetic variation in Wnt-beta-catenin signaling genes can affect the pathogenesis of cartilage related diseases, such as osteoarthritis. Wnt-1-induced secreted protein 1 (WISP1) is a target of the Wnt pathway and directly regulated by beta-catenin. In the present study, we analyzed the association of a single nucleotide polymorphism (SNP) in the WISP1 3'-UTR region with the development of radiographically observable osteoarthritis of the spine. For this purpose, we evaluated the presence of osteophytes, endplate sclerosis, and narrowing of disc spaces in 304 postmenopausal Japanese women. We compared those who carried the G allele (GG or GA, n = 184) with those who did not (AA, n = 120). We found that the subjects without the G allele (AA) were significantly over-represented in the subjects having higher endplate sclerosis score (P = 0.0069; odds ratio, 2.91; 95% confidence interval, 1.34-6.30 by logistic regression analysis). On the other hand, the occurrence of disc narrowing and osteophyte formation did not significantly differ between those with and without at least one G allele. Thus, we suggest that a genetic variation in the WISP1 gene locus is associated with spinal osteoarthritis, in line with the involvement of the Wnt-beta-catenin-regulated gene in bone and cartilage metabolism.

Answer to the letter to the editor of Dr. D.E. Harrison et al. regarding “The association between cervical spine curvature and neck pain” (D. Grob et al., Eur Spine J, published online Nov 18, 2006)

Answer to the letter to the editor of Dr. D.E. Harrison et al. regarding “The association between cervical spine curvature and neck pain” (D. Grob et al., Eur Spine J, published online Nov 18, 2006)

The influence of magnetic resonance imaging findings of degenerative disease on dual-energy X-ray absorptiometry measurements in middle-aged men

To examine degenerative features based on magnetic resonance imaging (MRI) measurements at the lumbar spine in relation to dual-energy X-ray absorptiometry (DXA), and to investigate whether bone mineral density (BMD) is reflected in the substitution of bone trabecular structure by fat at the vertebral body level indicated by MRI T1 relaxation time, endplate concavity, and hypertrophic (osteophytes and endplate sclerosis) MRI findings. The sample for this cross-sectional study was composed of 102 subjects, 35-70 years old, from a population-based cohort. Data collection included DXA in the anterior-posterior projection at the L1-L4 vertebrae and right femoral neck, and MRI of the lumbar spine in the midsagittal plane. Age, vertebral signal intensity, osteophytes, and endplate concavity collectively explained 20% of the variance in spine BMD. The study findings suggest that degenerative findings based on MRI measurements at the lumbar spine have an influence on bone assessment using DXA. Therefore, an overall bone assessment such as DXA might not offer an accurate measure of BMD.

Analysis of cell death and vertebral end plate bone mineral density in the annulus of the aging sand rat

Background context The relationship between disc degeneration and end plate sclerosis is poorly understood. The sand rat is an excellent, economical small-animal model in which disc degeneration is age related, spontaneous, reliable, and well characterized. This model is used here to evaluate disc degeneration, disc cell viability, and vertebral end plate bone mineral density (BMD) in lumbar sites. Purpose To determine the proportion of live and dead cells and end plate bone mineral density in the aging sand rat annulus. Study design Young and old sand rats were used in work approved by the Institutional Animal Care and Use Committee. Outcome measures were the percentage of live/dead annulus cells in the disc and the BMD of cranial and caudal end plates of lumbar vertebrae. Methods Bone densitometry was used to obtain endplate BMD on lumbar spines of 16 young sand rats aged 2 to 6 months and 26 older animals aged 22 to 46 months. X-ray films were analyzed for wedging, end plate calcification, and disc-space narrowing. Additional discs were also harvested and incubated with fluorochromes, and the percentage of live or dead cells were determined for the outer, inner annulus, and entire annulus. Results Radiographically old animals had significantly greater incidence of lumbar wedging (p<0.004) and a significantly greater incidence of end plate calcification and disc-space narrowing (p<0.01). In the live-dead study, the mean percentage of dead annulus cells for the three age groups were significantly different for the outer annulus (p<0.001), inner annulus (p=0.005), and total annulus (p<0.0001). The percentages of dead cells for the entire annulus were 46.14%±7.99% (age 2–6 months), 48.13%±17.32% (age, 13–19 months), and 76.80%±7.27% (age 26–38 months). The percentage of dead disc cells correlated significantly with age for outer annulus, inner annulus, and total annulus (p<0.006). The percentage of dead cells in the entire annulus and the inner annulus correlated significantly with end plate BMD (p<0.02). Conclusions Data are novel and show that in very aged sand rats, end plate BMD is significantly greater than that of young animals. Live/dead cell analyses showed increasing cell death in both outer and inner annulus, which correlated significantly with age and with end plate BMD.

Q89R Polymorphism in the LDL Receptor-Related Protein 5 Gene Is Associated With Spinal Osteoarthritis in Postmenopausal Japanese Women

An association study investigating the genetic etiology for spinal osteoarthritis. To determine the association of single-nucleotide polymorphism (SNP) causing an amino-acid change (Q89R) in the low-density lipoprotein receptor-related protein 5 (LRP5) coding region with spinal osteoarthritis. Wnt/beta-catenin signaling pathway regulates bone density through a Wnt coreceptor LRP5. This pathway is also involved in cartilage development and homeostasis, suggesting that genetic variation in LRP5 gene may affect the pathogenesis of cartilage-related diseases, such as osteoarthritis. We evaluated the presence of osteophytes, endplate sclerosis, and narrowing of disc spaces in 357 Japanese postmenopausal women. Missense coding SNP for Q89R of LRP5 gene was determined using TaqMan polymerase chain reaction (PCR) method. We found that subjects without the R allele (QQ; n = 321) had a significantly lower osteophyte formation score than did subjects bearing at least one R allele (QR + RR; n = 36) (7.80 vs. 10.89, P = 0.0019 by analysis of covariance). We suggest that a genetic variation at the LRP5 gene locus is associated with spinal osteoarthritis, in line with the involvement of the LRP5 gene in the bone and cartilage metabolism.

Osteopetrosis Type II

An asymptomatic 19-year-old man underwent a routine outpatient evaluation. He was born after a normal pregnancy and delivery. Both parents and two siblings (27 and 25 years of age) were in good health. His physical and mental development had been normal. He did not have visual or hearing disturbances. He had no history of fractures. The serum calcium, phosphorus, alkaline phosphatase, and creatinine levels were all within the normal range. Bone radiology demonstrated osteosclerosis primarily involving the axial and appendicular skeleton. A plain radiograph of the spine showed end-plate thickening and sclerosis producing the classic “sandwich vertebra” appearance. These findings . . .

Long-segment Posterolateral Fusion with Instrumentation of the Multi-level Spinal Stenosis: Long-term Followup over the 5 Years

Purpose : To evaluate the long-term results, and to analyze the clinical and radiological of long-segment posterolateral fusion with instrumentation in multi-level spinal stenosis. Materials and Methods : A retrospective review was carried out on 62 patients, who had undergone long-segment posterolateral fusion with instrumentation for the treatment of multi-level spinal stenosis from June, 1990 to May, 1998 with a minimal follow up of 5 years. The clinical outcomes were evaluated using the Katz's classification and the Oswestry disability scoring system (ODI). The radiological were evaluated by monitoring the changes in the adjacent segments and the Lenke's grade for bony union. Results : The mean follow-up duration was 94 (61-156) months. There were 14 males and 48 females. The mean age was 58.7 (37-78) years. The mean number of fused segments per person were 3.97 (3-8) and the fusion techniques used in this study were either the fixed fusion for 60 cases or floating fusion for 2. 48 (77.4%) cases showed beyond 'satisfaction'. The mean ODI was 30.0 (6-88%), which means moderate disability. The ODI according to the number of fusion segments was checked for results. Good were observed in 25.8%, 33.6%, and 25.9% of patients with 3, 4 or more than 5 fusion segments, respectively. There was no statistical difference. Regarding the changes in the adjacent segments, disc space narrowing, traction spur, endplate sclerosis and vacuum phenomenon was observed in 25 (40.3%), 26 (41.9%), 22 cases (35.5%) and 7 cases (11.3%), respectively. 34 (55.0%) cases had more than one change in the adjacent segments but the ODI was 38.0% for good results and 25 (74.0%) cases were satisfied. In all cases except for one, bony union showed Lenke's A or B degree by radiographs. Pseudarthrosis was detected in 1 (1.6%) case. Conclusion : In the analysis of long-term clinical and radiological for multi-level spinal stenosis treatment, posterolateral fusion with instrumentation might be irrespective of the fusion level and the change in adjacent segment.

Vertebral Endplate Architecture and Vascularization: Application of Micro-Computerized Tomography, a Vascular Tracer, and Immunocytochemistry in Analyses of Disc Degeneration in the Aging Sand Rat

Lower lumbar vertebral endplates from young and old sand rats were assessed in an Institutional Animal Care and Use Committee approved study for architectural endplate features using micro-computerized tomography (CT) 3-dimensional (3D) models and vascularization studies by an in vivo vascular tracer or immunocytochemical identification of blood vessels. To assess endplate porosity and vascularization using microCT architectural analysis, an in vivo vascular tracer, and immunocytochemical identification of blood vessels in the endplate. The vertebral endplates, also called cartilage endplates, form the superior and inferior, or cranial and caudal, boundaries of the disc. In the human being and sand rat, the cartilaginous endplate undergoes calcification with aging and is replaced by bone. Endplate sclerosis has long been thought to play a role in disc degeneration by decreasing nutrient availability to the disc, but this is still poorly understood. Previous work has identified increasing bone mineral density with aging and disc degeneration in the sand rat model. microCT models of the lower lumbar endplates of vertebrae at L5-6 and L6-7 were constructed from 6 younger (mean age 11 months) and 21 older (mean age 25.6 months) sand rats. Architectural features were scored on a semiquantitative scale for smoothness of the endplate face, irregularities on the endplate margin, and endplate thickness. There were 2 smaller sets of animals (n = 18) evaluated for endplate vascularity following in vivo injection of a fluorescent vascular tracer or by the use of immunocytochemistry to identify blood vessels. microCT revealed a solid bony surface to the endplate, which was not penetrated by vasculature; with aging/disc degeneration, there was roughening and pitting of the plate surface, and the development of irregular margins. In L5-6 and L6-7, sites of prominent disc degeneration evident on radiographs, the proportion of abnormalities in surface smoothness, margin irregularity, and endplate thickening were all statistically significant in both younger and older animals (P < or = 0.0027). More severe changes were evident in the caudal versus cranial endplate surfaces. Histologic study of vascular tracer showed that there was no penetration of the disc by vascular supply from the endplate; this was verified by immunocytochemical identification of blood vessels. The canal system within the endplate was a complex 3D interconnected network. Findings show that disc degeneration in the sand rat occurs concomitantly with marked architectural bony changes on the endplate face, including loss of smoothness and development of irregular bony margins. Vascular connections were not present between the endplate and disc; this was verified with microCT studies, in vivo vascular tracers, and traditional immunocytochemistry. The canal system within the imaged endplate was revealed to consist of a complex 3D interconnected network.

The Changes of Adjacent Segments after Long Segment Posterolateral Fusion: Comparative Study of 3 year versus over the 7 year Follow-up Patients

Purpose: To compare the 3 year and over the 7 year results after long-segment posterolateral fusion and to analyze the changes of adjacent segments and the changes according to the segmental lordosis angle of the fusion segments. Materials and Methods: A retrospective review was carried out 62 patients of long segment fusion for 7 years follow up and compared that of the 3 year and over the 7 year results. The changes of adjacent segments were evaluated by simple radiography for disc space narrowing, traction spur, endplate sclerosis and vacuum phenomenon. In last follow-up, segmental lordosis angle of fusion level was evaluated by Gelb,s criteria and clinical results were analyzed by Katz,s classification. Results: In the changes of adjacent segments, disc space narrowing was increased 27.4% to 38.7%, traction spur was 22.6% to 35.5%, endplate sclerosis was 19.4% to 32.2% and vacuum phenomenon was 8.1% to 12.9%. The changes of adjacent segments were observed that from 3.4% to 20.7% in physiologic group and from 33.3% to 90.9% in un-physiologic group. The clinical results showed 83.9% satisfaction and 16.1% un-satisfaction.Conclusion: In long-term follow up of long-segment posterolateral fusion, physiologic segmental lordosis angle should be preserved for decrease of changes of adjacent segments in long-segment posterolateral fusion.

Radiologic features of renal osteodystrophy in a patient with “normal” bone mineralization

A 10-year-old boy with a past history of progressive renal dysfunction on peritoneal dialysis because of prune belly syndrome was evaluated before renal transplant. Despite treatment with oral phosphate binding agents and 1,25-dihydroxyvitamin D3 analogs, the family described longstanding difficulties complying with a low-phosphorus diet. There was no history of fractures and previous bone densitometry scans had shown his bone mineral density to be normal. Recent complaints centered on worsening lower extremity bone pain and bilateral joint pain affecting the knees and ankles. On examination, the patient was <3rd percentile for stature and weight and exhibited significant genu varus as well profound Trandelenberg gait, resulting in painful ambulation. Laboratory evaluation revealed a low calcium of 2.27 mmol/L (2.4–2.64), elevated phosphorus of 2.13 mmol/L (1.19–1.42), elevated alkaline phosphatase (1648 U/L [415–945]), and parathyroid hormone (64 pmol/L [1–5.2]). Selected radiographs from the patient's skeletal survey are shown. Vertebral endplate sclerosis accounts for the “rugger jersey” appearance of the spine (Fig 1). The patient also exhibited diffuse metaphysical widening, lucency, and fraying with subperiosteal resorption along the middle phalanges of both hands (Fig 2, available at www.us.elsevierhealth.com/jpeds). Despite these and other radiographic findings, a dual energy x-ray absorptiometry (DEXA) scan (GE Lunar Prodigy) at the lumber spine, and both hips showed bone mineral densities within age-reported normal values. Download .jpg (.58 MB) Help with jpg files Fig 2 Renal osteodystrophy is a generic term that describes all skeletal disorders occurring in patients with renal failure. It describes bony changes as a result of phosphate retention, hypocalcemia, and reduced 1,25-dihydroxyvitamin D3 production leading to hyperparathyroidism. In cortical bone, this results in increased resorption at subperiosteal, endocortical, and intracortical sites, whereas thickening and sclerosis occur in trabecular bone.1.Parfitt M. A structural approach to renal bone disease.J Bone Miner Res. 1998; 13: 1213-1220Crossref PubMed Scopus (163) Google Scholar The end result of these changes is impaired bone strength and increased fracture risk, which is not reflected with integrated DEXA bone densitometry measurements.2.Leonard M.B. Bachrach L. Assessment of bone mineralization following renal transplantation in children: limitations of DEXA and confounding effects of delayed growth and development.Am J Transplant. 2001; 1: 193-196Crossref PubMed Scopus (34) Google Scholar This case reinforces the importance of obtaining and evaluating radiographs in patients with metabolic bone disease. These better allow clinicians to directly observe the structural changes of renal osteodystrophy and avoid interpretation of erroneous and conflicting bone densiometry scans.

Intervertebral disc degeneration adjacent to a lumbar fusion

Our study establishes a rabbit model of disc degeneration which requires neither a chemical nor physical injury to the disc. Disc degeneration similar to that seen in man was created at levels proximal (L4-L5) and caudal (L7-S1) to a simulated lumbar fusion and was studied for up to nine months after arthrodesis. Loss of the normal parallel arrangement of collagen bundles within the annular lamellae was observed in intervertebral discs adjacent to the fusion at three months. By six months there was further disorganisation as well as loss of distinction between the lamellae themselves. By nine months the structure of the disc had been replaced by disorganised fibrous tissue, and annular tears were seen. There was an initial cellular proliferative response followed by loss of chondrocytes and notochordal cells in the nucleus pulposus. Degeneration was accompanied by a decrease in the monomer size of proteoglycans. Narrowing of the disc space, endplate sclerosis and the formation of osteophytes at adjacent disc spaces were observed radiologically.

Intervertebral disc degeneration adjacent to a lumbar fusion. An experimental rabbit model.

Our study establishes a rabbit model of disc degeneration which requires neither a chemical nor physical injury to the disc. Disc degeneration similar to that seen in man was created at levels proximal (L4-L5) and caudal (L7-S1) to a simulated lumbar fusion and was studied for up to nine months after arthrodesis. Loss of the normal parallel arrangement of collagen bundles within the annular lamellae was observed in intervertebral discs adjacent to the fusion at three months. By six months there was further disorganisation as well as loss of distinction between the lamellae themselves. By nine months the structure of the disc had been replaced by disorganised fibrous tissue, and annular tears were seen. There was an initial cellular proliferative response followed by loss of chondrocytes and notochordal cells in the nucleus pulposus. Degeneration was accompanied by a decrease in the monomer size of proteoglycans. Narrowing of the disc space, endplate sclerosis and the formation of osteophytes at adjacent disc spaces were observed radiologically.