Bone has a number of different functions in the skeleton including the physical roles of support, protection and sound wave conduction. The mechanical properties, required for these different functions varies and can be achieved by compositional adaption of the bone material, in addition to changes in shape and architecture. A number of previous studies have demonstrated the relationship between mechanical function and mineral to collagen ratio in bones from different species. The aim of this study is to test the hypothesis that the mineral to collagen ratio is higher in bone with a mechanically harder matrix within a species. The red deer The results showed that the hardness (Indentation Distance Increase) was lowest in the metacarpal (8.5µm), followed by the bulla bone (9.4µm) and highest in the antler (14.5µm). Raman spectroscopy showed a mineral:collagen ratio of 1:0.10 (bulla), 1:0.13 (metacarpal) and 1:0.15 (antler) for the different bones. This does not follow the more linear trend previously shown between young's modulus and the mineral:collagen ratio. The location of the mineral appeared to differ between bone types with pQCT revealing locations of concentrated density and banding patterns in antler. Interestingly, Raman spectra showed differences in the amide peaks revealing differences in protein structure. The results reject the hypothesis but also suggest that the organisation of mineral and collagen has an impact on the hardness modulus. We demonstrate that the red deer provides a good model for studying bone specialisation. This work will provide the basis for further investigation into collagen as a controlling factor in mineral deposition.
Energy storing tendons such as the equine superficial digital flexor tendon (SDFT) stretch and recoil with each stride and therefore require a high degree of compliance compared to tendons with a purely positional function, such as the equine common digital extensor tendon (CDET). This extra extensibility is provided by a specialised interfascicular matrix (IFM), which provides greater sliding and recoil between adjacent fascicles in energy storing tendons. However, the composition of the IFM remains largely undefined. We hypothesised that the IFM in the SDFT has a distinct composition, with a greater abundance of proteoglycans and elastin which facilitate extension and recoil. Transverse and longitudinal sections were cut from the mid-metacarpal regions of SDFTs and CDETs from 5 horses aged 3–7 years. Sections were stained using Alcian blue/Periodic acid Schiff to detect proteoglycans, elastic Van Giesson's to detect elastin, and immunohistochemistry was performed using antibodies for decorin, biglycan, fibromodulin, lumican and lubricin. Resultant images were graded by blinded observers to assess staining intensity in the IFM and fascicular matrix (FM), and statistical significance determined using ANOVA.Introduction
Materials and Methods
Regular, repeated stretching increases joint range of movement (RoM), however the physiology underlying this is not well understood. The traditional view is that increased flexibility after stretching is due to an increase in muscle length or stiffness whereas recent research suggests that increased flexibility is due to modification of tolerance to stretching discomfort/pain. If the pain tolerance theory is correct the same degree of micro-damage to muscle fibres should be demonstrable at the end of RoM before and after a period of stretch training. We hypothesise that increased RoM following a 3 weeks hamstrings static stretching exercise programme may partly be due to adaptive changes in the muscle/tendon tissue. Knee angle and torque were recorded in healthy male subjects (n=18) during a maximum knee extension to sensation of pain. Muscle soreness (pain, creatine kinase activity, isometric active torque, RoM) was assessed before knee extension, and 24 and 48 hours after maximum stretch. An exercise group (n=10) was given a daily home hamstring stretching programme and reassessed after 3 weeks and compared to a control group (n=8). At reassessment each subject's hamstring muscles were stretched to the same maximum knee extension joint angle as determined on the first testing occasion. After 24 hours, a reassessment of maximum knee extension angle was made.Introduction
Materials and Methods
Whilst all tendons connect muscle to bone, energy storing (ES) tendons, such as the equine superficial digital flexor tendon (SDFT) play an additional role, storing energy to improve locomotion efficiency. ES tendons experience significantly higher strains during locomotion than other positional tendons, such as the common digital extensor tendon (CDET). Our previous work has demonstrated that the interfascicular matrix (IFM) is more extensible in ES tendons, allowing ES tendons to stretch further during use. However, ES tendons must also recoil efficiently to perform their energy storing function. It has not been yet established if the IFM is able to recoil and recover after loading. Thus, this project aimed to determine the recoil capacity of the IFM in both the ES and positional tendons from young and old horses. Five young (3–7 years) and five old (17–20 years) SDFTs and CDETs were dissected from the forelimbs of 10 euthanized horses. Groups of 2 intact fascicles (bounded by IFM) were dissected from each tendon. Using a custom-made dissection rig and a polarised light microscope, samples were dissected, and the opposing end of each fascicle was cut transversely, leaving a 10 mm length of IFM. IFM samples were tested in shear, by preconditioning with 10 loading cycles then pulling to failure. The hysteresis and stress relaxation that occurred during preconditioning were calculated.Introduction
Materials and Methods
Fatigue loading has an age-specific effect on tendon fascicle micro-mechanics, with greater fibre sliding in aged samples indicating a decreased mechanical integrity, and a reduced ability to withstand cyclic loading, which may partially explain the age-related risk of tendon injury. The human Achilles and equine superficial digital flexor (SDFT) tendons function as energy stores, experiencing large, repetitive stresses and strains1 and are therefore highly susceptible to injury, particularly in aged individuals. We have previously observed rotation within SDFT fascicles in response to applied strain, which indicates the presence of helical sub-structures within this tendon. Further, we have shown that this rotation decreases with ageing, suggesting alterations to the helix sub-structure and a difference in the extension mechanisms in aged tendons. We therefore hypothesise that cyclic fatigue loading (FL) will result in alterations in fascicle extension mechanisms which are age specific.Summary Statement
Introduction
Osteoarthritis is associated with changes to the matrix composition of subchondral bone. Raman spectroscopy has the potential to detect in vivo the molecular changes in osteoarthritic subchondral bone. The objectives were to determine the levels of mineralisation, carbonate accumulation and bone remodelling in osteoarthritic subchondral bone, which we defined as within 3mm of articular cartilage. This was compared to the proximal-compartment (10mm distal to articular cartilage) and the head-neck junction. Five osteoarthritic (average age: 76 years) and five normal cadaveric femoral heads (average age: 72 years) were scanned using peripheral quantitative computed tomography and then sectioned coronally. Raman spectroscopy was then used to scan the femoral heads. All scans were done in the plane of the longitudinal axis of the diaphysis. Cores were subsequently extracted and sodium dodecyl sulphate polyacrylamide gel electrophoresis performed to determine the levels of homotrimeric collagen. The phosphate-to-amide I ratio, from the Raman spectra, in osteoarthritic subchondral bone was significantly greater than controls (p=0.023). Within osteoarthritic specimens, the phosphate-to-amide I ratio increased proximally. The density in osteoarthritic subchondral bone was 89mg/cm3 higher than controls (p=0.022), and 494mg/cm3 higher than the osteoarthritic proximal-compartment (p<0.001). Moreover, carbonate substitution into the apatite crystals decreased in osteoarthritic specimens. The carbonate-to-amide I ratio was highest in osteoarthritic subchondral bone. Furthermore, the median α1-to-α2-chain ratio in osteoarthritic specimens was 2:1. The changes found in subchondral bone are important in the pathogenesis of osteoarthritis. This study shows that Raman spectroscopy can detect differences between osteoarthritic specimens and controls, further supporting its potential use in diagnosing bone disorders.
Osteoarthritis (OA) is a common, debilitating joint disease involving degeneration of cartilage and bone. It has been suggested that subtle changes in the molecular structure of subchondral bone may precede cartilaginous changes in the osteoarthritic joint. To explore these changes Raman spectroscopy was employed as a diagnostic tool. Raman spectroscopy measures inelastic scattered laser light produced when photons interact with chemical materials. Resultant changes in wavelength form spectra relative to the chemical composition of the given sample: with bone this includes the mineral and matrix components, unlike conventional X-rays. The aim of our study is to explore the hypothesis: Changes in matrix composition of osteoarthritic subchondral bone can be detected with Raman spectroscopy. pQCT and Raman spectroscopy were employed to determine the bone mineral density (BMD) and bone quality, respectively. Ten medial compartment OA and five control (non-OA) tibial plateaus were interrogated and analysis performed to compare OA to control, and medial to lateral compartments. The subchondral bone of the medial OA compartments had higher BMD (p=0.05) and thickness compared to lateral and control samples. Spectral analysis revealed there is no difference between the medial and lateral compartments within either cohort. However, there is a statistically significant (p=0.02) spectral difference between the OA and control specimens. The detection of bone matrix changes in osteoarthritis using Raman spectroscopy contributes to the understanding of the biochemical signature of subchondral bone across diseased and control tibial plateaus. This technique has potential to shed light on the role of bone in osteoarthritis.
