Biomechanical analysis of the Achilles tendon enthesis organ

• Main Author: Theobald, Peter
• Published: Cardiff University 2006
• Subjects: 617.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.583929

The tendon/ligament insertional region is a common site of injury, despite the protection offered by the surrounding tissues. These tissues, termed the enthesis organ, form a concept that has only recently been developed and thus has been the focus of only a few publications. The work in this thesis is the first study to perform a biomechanical analysis of the enthesis organ, providing information that may potentially improve injury management methods. A thorough assessment of the enthesis organ biomechanics was made using a number of techniques. Dissecting room cadavers allowed for micro- and macroscopic examination, whilst magnetic resonance imaging and ultrasound provided in vivo images and movie files. Specially fabricated apparatuses were also developed to investigate the load bearing and lubrication regime. A number of the structures within the enthesis organ were identified as being of biomechanical importance. The paratenon/deep fascia was recognised as influencing the insertional angle of the Achilles tendon, possibly in tandem with the superior tuberosity. It was Kager's fat pad, however, that appeared the most highly specialised and influential tissue. This is currently excised when performing arthroscopic ankle surgery, although microscopic examination revealed a highly specialised structure with 3 separate regions. These appeared to allow independent movement of its distal wedge into the retrocalcaneal bursa, a movement that was hypothesised to both equalise a pressure change and to lubricate the contacting surfaces of the enthesis organ. This work concludes that the surgical removal of Kager's fat pad is likely to starve the Achilles tendon enthesis organ of a number of biomechanical functions performed by this tissue, and thus may influence pain relief post-operatively. The excision of the superior tuberosity, however, appears insignificant as it not believed to increase the likelihood of enthesis failure, although preservation of both the superior tuberosity and the deep fascia/paratenon would ensure continued regulation of the Achilles tendon insertion angle.