A tendon is a fibrous connective tissue that acts to transmit tensile forces between muscles and bones. It mainly consists of soluble substance, collagen and small volume of elastic fibres, which are produced by tenoblasts and tenocytes. The Achilles tendon is the thickest tendon in the human body that subjects to some of the highest tensile force, thus disorders and ruptures commonly happen. As the insoluble fibrous components in Achilles tendons, the collagen fibrils and elastic fibres have unique spatial structure that plays important functional roles. Despite this, the understanding of relationship between them is still limited due to the lack of imaging evidence. Using confocal and second harmonic generation microscopy, this study aims to comprehensively investigate the spatial relationship of collagen, elastic fibres and tenocytes in hydrated tendons.

Longitudinal sections of 50 µm thick and transverse sections of 20 µm thick were cryo-sectioned respectively from the mid-portion of ten rabbit Achilles tendons. Sections were stained with 0.03g/L Acridine Orange (AO) and 1mg/ml Sulforhodamine B (SRB) solution respectively for labelling the nucleus and elastic fibres. The Leica TCS SP2 multiphoton microscopy containing second harmonic generation microscopy can image collagen without labelling. The sections were scanned by the multiphoton microscopy, and images were processed and reconstructed into 3D images to study the spatial structure of collagen, elastic fibres and cells in Achilles tendons

A rabbit Achilles tendon consists of three sub-tendons named flexor digitorum superficialis tendon, medial gastrocnemius tendon and lateral gastrocnemius tendon. Loose connective tissue connects the three sub-tendons and ensures efficient sliding between sub-tendons. The 3D network shows that the mid-portion of Achilles tendons is composed of longitudinal collagen and elastic fibres, while spindle tenocytes rest along the collagen and elastic fibres. Tenocytes appear to have a closer microstructural relationship with the elastic fibres. In comparison with the collagen, tenocytes and elastic fibres only occupy a very small volume in the 3D network. The elastic fibres exist in both tendon proper and endotenons. The tendon sheath and loose connective tissue have a higher cell density, and the cells are large and round while compared with tenocytes.

As a component of the extracellular matrix (ECM) in Achilles tendons that closely mediates with the tenocytes, the elastin may participate in the force transition and interaction between tenocytes and the ECM. The elastic fibres may also endow Achilles tendons with unique mechanical properties to stand for tensile force.

Neck pain can be caused by pressure on the spinal cord or nerve roots from bone or disc impingement. This can be treated by surgically decompressing the cervical spine, which involves excising the bone or disc that is impinging on the nerves or widening the spinal canal or neural foramen. Conventional practise is to fuse the adjacent intervertebral joint after surgery to prevent intervertebral motion and subsequent recompression of the spinal cord or nerve root.

However fusion procedures cause physiological stress transfer to adjacent segments which may cause Adjacent Segment Degeneration (ASD), a rapid degeneration of the adjacent discs due to increased stress. ASD is more likely to occur in fusions of two or more levels than single level fusions and is more common where there is existing degeneration of the adjacent discs, which is not unusual in people over 30 years of age.

Partial dynamic stabilisation, which generally involves a semi-rigid spinal fixation, allows a controlled amount of intervertebral motion (less than physiological, but more than fusion) to prevent increased stress on the adjacent segments (potentially preventing ASD) whilst still preventing neural recompression. Partial dynamic stabilisation is suitable for treating spinal instability after decompression as well as certain degenerative instabilities and chronic pain syndromes.

Dynamic stabilisation and semi-rigid fixation systems for the spine are typically fixated posteriorly. However, choice of posterior surgical stabilisation techniques in the cervical spine is limited due to the size of the osseous material available for fixation and the close proximity of the neural structures and the vertebral artery. Posterior dynamic stabilisation systems for stabilisation of the lumbar spine often use the pedicle as an anchor point. Using the pedicle of the cervical spine as an anchor point is technically difficult because of its small size, angulation and proximity to neurovascular structures. Therefore, one of the main challenges to provide stabilisation in the cervical spine is the limitations of the anatomy.

This presentation will introduce a novel spinal implant (patent pending) which is proposed for the cervical spine to provide partial dynamic stabilisation in the C3 to T1 region from a posterior approach. The implant is a single unit with a safe and technically simple insertion technique into the lateral masses. The implant uses a simple mechanism to allow limited intervertebral motion at each instrumented level. It is hoped that the simplicity of the device and removing the need to provide a bone graft anteriorly may reduce the cost of the procedure compared to traditional fusion and competing surgeries.

Introduction and Aims: Conventional histology requires the traumatic removal of tissue from its native environment. This is not only a destructive process but also leads to tissue preparation artefact. We report on a novel arthroscopic instrument, the laser scanning confocal arthroscope (LSCA), which can image tissues of the knee at depth without the need for a damaging tissue biopsy.

Method: The new confocal arthroscope contains 4.4mm diameter with a 90-degree lens. Using three knee joints from two adult Merino sheep we imaged muscle, cartilage, ligament, tendon, synovium, meniscus and loose connective tissue. The knees were separately injected with three fluorophores (Acridine Orange, Acriflavine/Calcein-AM or Fluorescein) prior to imaging. Using a medial para-patellar incision, the contents of the knee were exposed and the confocal arthroscope was held directly on the tissue of interest. A second operator captured the images on a computer.

Results: We were able to demonstrate the common histological features of normal sheep articular cartilage, meniscus, synovium, ligament, tendon and muscle. Tissues were imaged to depths of 200 microns. Articular cartilage was characterised by a layer of dense superficial cells surrounded by extracellular matrix. There was no visible orderly arrangement of cells in this layer. Meniscus was characterised by closely packed circumferential collagen fibres. Synovium demonstrated a dense collection of cells in a thin membrane, typical of this secretory tissue. Ligament and tendon were characterised by bundles of parallel collagen fibres interspersed by scattered cells. Muscle revealed a typical arrangement of muscle fibres surrounded by a loose connective tissue and separated by capillaries and nerves. Eccentric nuclei were seen, however striations were beyond the imaging resolution of the arthroscope.

Conclusion: This study demonstrates the use of a novel arthroscopic instrument for the non-destructive examination of the components of the sheep knee joint. We foresee that the laser scanning confocal arthroscope will have future application in the assessment of cartilage grafting techniques and arthritis modifying drugs.