Abstract. Objectives. Back pain will be experienced by 70–85% of all people at some point in their lives and is linked with intervertebral disc (IVD) degeneration. The aim of this study was to 1) compare 3D internal strains in degenerate and non-degenerate human IVD under axial compression and 2) to investigate whether there is a correlation between strain patterns and failure locations. Methods. 9.4T MR images were obtained of ten human lumbar IVD. Five were classed as degenerate (Pfirrmann = 3.6 ± 0.3) and five were classed as non-degenerate (Pfirrmann = 2.0 ± 0.2). MR Images were acquired before applying load (unloaded), after 1 kN of axial compression, and after compression to failure using a T2-weighted RARE sequence (resolution = 90 µm). Digital Volume Correlation was then used to quantify 3D strains within the IVDs, and failure locations were determined from analysis of the failure MRIs. Results. Average of axial strains were higher (p<0.05) in the degenerate samples compared to the non-degenerate (−3.4 vs-5.2%, respectively), particularly in the posterior and lateral annulus (−6.2 vs −3.6%, and −5.6 vs −3.5%, respectively). Maximum 3D compressive strains were higher (p<0.05) in the posterior annulus and nucleus regions of the degenerate discs compared to non-degenerate (−9.8 vs −6.2%, and −7.7 vs −5.5%, respectively). In all samples peak tensile and shear strains were observed close to the endplates. All samples failed through the endplates with fractures in the nucleus region in all non-degenerate samples, and fractures in the lateral annulus regions in all degenerate samples. Conclusion. Degeneration caused significant changes to strain distributions within IVDs, particularly at the lateral and posterior AF regions. A shift from endplate failure in the nucleus to the annulus region was observed which was also seen in peak axial internal strains demonstrating a possible correlation between internal IVD strains, and endplate failure locations. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

The biomechanical evaluation of tendon repair with collagen-based scaffolds in rat model is a common method to determine the functional outcome of the tested material. We introduced a magnetic resonance imaging (MRI) approach to verify the biomechanical test data. In present study different collagen scaffolds for tendon repair were examined. Two collagen test materials: based on bovine stabilized collagen, chemically cross-linked with oriented collagenous fibres (material 1) and based on porcine dermal extracellular matrix, with no cross-linking (material 2) were compared. The animal study was approved by the local review board. Surgery was performed on male Sprague-Dawley rats with a body weight of 400 ± 19 g. Each rat underwent a 5 mm transection of the right Achilles tendon. The M. plantaris tendon was removed. The remaining tendon ends were re-joined with a 5 mm scaffold of either the material 1 or 2. Each scaffold material was sutured into place with two single stiches (Vicryl 4–0, Ethicon) each end. A total of 16 rats (n= 8 each group) were observed for 28 days follow up. The animals were sacrificed and hind limbs were transected proximal to the knee joint. MRI was performed using a 7 Tesla scanner (BioSpec 70/30, Bruker). T2-weighted TurboRARE sequences with an in-plane resolution of 0.12 mm and a slice thickness of 0.7 mm were analysed. All soft and hard tissues were removed from the Achilles tendon-calcaneus-foot complex before biomechanical testing. Subsequently, the specimens were fixed in a materials testing machine (Z1.0, Zwick, Ulm, Germany) for tensile testing. All tendons were preloaded with 1 N and subsequently stretched at a rate of 1 mm/s until complete failure was observed. Non-operated tendons were used as a control (n=4). After 28 postoperative days, MRI demonstrated that four scaffolds (material 1: n=2, material 2: n=2) were slightly dislocated in the proximal part of hind limb. In total five failures of reconstruction could be detected in the tendon repairs (material 1: n=3, material 2: n=2). Tendons augmented with the bovine material 1 showed a maximum tensile load of 57.9 ± 17.9 N and tendons with porcine scaffold material 2 of 63.1 ± 19.5 N. The native tendons demonstrated only slightly higher loads of 76.6 ± 11.6 N. Maximum failure load of the tendon-scaffold construct in both groups did not differ significantly (p < 0.05). Stiffness of the tendons treated with the bovine scaffold (9.9 ± 3.6 N/mm) and with the porcine scaffold (10.7 ± 2.7 N/mm) showed no differences. Stiffness of the native healthy tendon of the contralateral site was significantly higher (20.2 ± 6.6 N/mm, p < 0.05). No differences in the mechanical properties between samples of both scaffold groups could be detected, regardless of whether the repaired tendon defect has failed or the scaffold has been dislocated. The results show that MRI is important as an auxiliary tool to verify the biomechanical outcome of tendon repair in animal models

Summary Statement. Conventional imaging techniques lack the ability to objectively assess early stages of intervertebral disc degeneration, characterised by glycosaminoglycan loss. This study shows that MRI T2∗ mapping correlates positively with GAG content and that it provides continuous measurements for disc degeneration. Introduction. Early degenerative changes arise in the nucleus pulposus (NP) and are characterised by a loss of glycosaminoglycans (GAG). Early disc degeneration (DD) could possibly be treated with upcoming regenerative therapies (e.g. with stem cells and/or growth factors). In order to evaluate degeneration and treatments, a sensitive diagnostic tool is needed. While conventional magnetic resonance imaging (MRI) and x-ray techniques can detect late stages of DD, these techniques lack the ability to detect early degenerative changes. Recently, T2∗ mapping has been proposed as a new technique to evaluate early IVD degeneration, yet the correlation with GAG content and histological features has not been previously investigated. The objective of this study was to determine the value of T2∗ mapping in diagnosing DD by correlating this technique with the biochemical composition of IVDs. Materials & Methods. Six caprine lumbar spines obtained from an in vivo study and two healthy goat spines from the local abattoir, encompassing a total of 48 IVDs, were examined using sagittal standard T2-weighted and T2∗ mapping MRI protocols at 1.5 Tesla. Regions of interest (ROIs) were drawn on the T2∗ maps, covering the IVD. Based on T2 weighted MRI, discs were morphologically classified using the Pfirrmann score. Histological and macroscopic features were evaluated based on grading scales adapted for goat DD. Finally, GAG content was determined using colorimetric analysis (DMMB assay). Correlations between variables were analysed using Pearson correlation (r) coefficients (parametric data) or Spearman's rho (ρ) coefficients (non-parametric data). Results. The mean GAG content in the NP was 450 μg/mg dry weight (range 20–730 μg/mg dry weight) and the mean histological grade was 2.2 (range 0–6), corresponding with relatively mild disc degeneration. A linear positive correlation was observed between T2∗ and NP GAG content (r = 0.65, p < 0.001). T2∗ in the NP decreased linearly with increasing degeneration as assessed with macroscopic (ρ = 0.33, p < 0.05) and histological (ρ = −0.45, p < 0.05) grading, as well as with the Pfirrmann scoring system (ρ = −0.67, p < 0.001). Discussion. T2∗ mapping is a relatively new MRI technique which allows for measurements on a continuous scale, is acquired in less time than T2 mapping and minimises observer bias compared to grading systems. Although limited by a small sample size (n=48), this study showed a relatively good, linear correlation between T2∗ and GAG content in the NP, suggesting that T2∗ mapping may be an efficient and reliable tool for the objective assessment of proteoglycan content in early DD. Furthermore, with minor software modifications, it can be implemented on a standard 1.5 Tesla clinical MRI scanner. Future research should aim at optimizing the efficiency and user-friendliness of the T2∗ mapping protocol as well as yielding an even stronger correlation between T2∗ mapping and glycosaminoglycan content in human IVD tissue

Objectives

The objectives of this study were: 1) to examine osteophyte formation, subchondral bone advance, and bone marrow lesions (BMLs) in osteoarthritis (OA)-prone Hartley guinea pigs; and 2) to assess the disease-modifying activity of an orally administered phosphocitrate ‘analogue’, Carolinas Molecule-01 (CM-01).

We released the infraspinatus tendons of six sheep, allowed retraction of the musculotendinous unit over a period of 40 weeks and then performed a repair. We studied retraction of the musculotendinous unit 35 weeks later using CT, MRI and macroscopic dissection.

The tendon was retracted by a mean of 4.7 cm (3.8 to 5.1) 40 weeks after release and remained at a mean of 4.2 cm (3.3 to 4.7) 35 weeks after the repair. Retraction of the muscle was only a mean of 2.7 cm (2.0 to 3.3) and 1.7 cm (1.1 to 2.2) respectively at these two points. Thus, the musculotendinous junction had shifted distally by a mean of 2.5 cm (2.0 to 2.8) relative to the tendon. Sheep muscle showed an ability to compensate for approximately 60% of the tendon retraction in a hitherto unknown fashion. Such retraction may not be a quantitatively reliable indicator of retraction of the muscle and may overestimate the need for elongation of the musculotendinous unit during repair.