Reliability of Human Lumbar Facet Joint Degeneration Severity Assessed by Magnetic Resonance Imaging.

OBJECTIVE: The purpose of this study was to determine the reliability of the assessment of lumbar facet joint degeneration severity by analyzing degeneration subscales using magnetic resonance imaging (MRI) in human participants. METHODS: The reliability of articular cartilage degeneration, subchondral bone sclerosis, and osteophyte formation subscales of lumbar facet joint degeneration severity was assessed in MRI images from n = 10 human participants. Each scale was applied to n = 20 lumbar facet joints (L4/5 level). Three examiners were trained. A first assessment of MRI images was provided by the examiners followed by a second assessment 30 days later. Intraobserver and interobserver reliability were determined using percent agreement, the weighted kappa coefficient κw for paired comparisons, and the overall weighted kappa κo. The minimum threshold for reliability was set at moderate levels of agreement, κw > 0.40, based upon previous recommendations. RESULTS: The articular cartilage subscale had acceptable intraobserver (κo = 0.51) and interobserver (κo = 0.41) reliability. Scales for subchondral bone sclerosis (intraobserver κo = 0.28; interobserver κo = 0.10) and osteophyte formation (intraobserver κo = 0.26; interobserver κo = 0.20) did not achieve acceptable reliability. CONCLUSION: Of the 3 subcategories of lumbar facet joint degeneration, only articular cartilage degeneration demonstrated acceptable reliability. Subscales of lumbar facet joint degeneration should be considered independently for reliability before combining subscales for a global degeneration score. Owing to the inherent difficulty of assessing lumbar facet joint degeneration, the use of multiple examiners independently assessing degeneration with reliable scales and then coming to a consensus score upon any disagreements is recommended for future clinical studies.

Contrast enhanced µCT imaging of early articular changes in a pre-clinical model of osteoarthritis.

OBJECTIVE: The objective of this study was to characterize early osteoarthritis (OA) development in cartilage and bone tissues in the rat medial meniscus transection (MMT) model using non-destructive equilibrium partitioning of an ionic contrast agent micro-computed tomography (EPIC-µCT) imaging. Cartilage fibrillation, one of the first physiological developments in OA, was quantified in the rat tibial plateau as three-dimensional (3D) cartilage surface roughness using a custom surface-rendering algorithm. METHODS: Male Lewis rats underwent MMT or sham-operation in the left leg. At 1- and 3-weeks post-surgery, the animals (n = 7-8 per group) were euthanized and the left legs were scanned using EPIC-µCT imaging to quantify cartilage and bone parameters. In addition, a custom algorithm was developed to measure the roughness of 3D surfaces. This algorithm was validated and used to quantify cartilage surface roughness changes as a function of time post-surgery. RESULTS: MMT surgery resulted in significantly greater cartilage damage and subchondral bone sclerosis with the damage increasing in both severity and area from 1- to 3-weeks post-surgery. Analysis of rendered 3D surfaces could accurately distinguish early changes in joints developing OA, detecting significant increases of 45% and 124% in surface roughness at 1- and 3-weeks post-surgery respectively. CONCLUSION: Disease progression in the MMT model progresses sequentially through changes in the cartilage articular surface, extracellular matrix composition, and then osteophyte mineralization and subchondral bone sclerosis. Cartilage surface roughness is a quantitative, early indicator of degenerative joint disease in small animal OA models and can potentially be used to evaluate therapeutic strategies.

Potential mechanism of alendronate inhibition of osteophyte formation in the rat model of post-traumatic osteoarthritis: evaluation of elemental strontium as a molecular tracer of bone formation.

OBJECTIVE: To employ elemental Strontium as a tracer of bone turnover, in the presence (or absence) of the bisphosphonate drug Alendronate, in order to spatially map osteophytogenesis and other bone turnover in rats developing post-traumatic secondary osteoarthritis (PTOA). METHODS: PTOA was induced in rats by medial meniscectomy surgery. We utilized in-vivo microfocal computed tomography (CT) to follow bony adaptations in groups for 8 weeks after surgery, either with or without alendronate treatment. Electron probe microanalysis (EPMA) was used to detect Strontium incorporation in mineralizing tissues. Histologic studies were conducted on the same samples using Safranin-O/fast green and Tetrachrome staining of decalcified sections to examine articular cartilage health and osteophyte formation at the sites of elemental Strontium deposition. RESULTS: EPMA revealed uniform incorporation of Strontium over actively remodeling trabecular surfaces in normal control rats. That pattern was significantly altered after meniscectomy surgery resulting in greater Strontium signal at the developing osteophyte margins. Alendronate treatment inhibited osteophyte development by 40% and 51% quantified by micro-CT volumetric measurements at 4 and 8 weeks after surgery, respectively. Osteophytes in the alendronate group were more cartilaginous in composition [i.e., lower bone mineral density (BMD)] compared to the untreated group. Histological analysis confirmed the osteophyte inhibitory effect of alendronate, and also verified reduced degeneration of the articular cartilage compared to untreated rats. CONCLUSION: Our study confirmed that alendronate administration will reduce osteophyte formation in a rat model of post-traumatic osteoarthritis, partially through the inhibition of secondary remodeling of osteophytes. Our study is the first to employ elemental Strontium as a tracer of bone turnover in the pathogenesis of osteoarthritis and to assess the efficacy of bisphosphonate antiresorptive drug interventions on osteophytogenesis.