C7: Biomechanics

CARTILAGE CHANGES IN SHOULDER HEMIARTHOPLASTY


Maryam Imani Masouleh, Niloofar Ajdari, Ulrich Hansen, Daniele Dini


Imperial College London, UK


Osteoarthritis (OA) is a common form of arthritis that causes joint degradation and affects up to 15% of the adult population. It is characterized by chronic and irreversible degeneration of articular cartilage (AC). Hemiarthoplasty is a surgical procedure, where the diseased (OA) cartilage on one side of the joint is replaced with an implant, while the other side remains intact.

The main aim of this study is to analyse the mechanical and frictional response of different shoulder humeral component materials against the natural glenoid. This has been developed as a two stage process. Initially, friction and wear properties of four different grades of human osteoarthritic AC were measured using pin-ondisc technique against three major types of implant materials used in hemiarthoplasty including Cobalt-Chromium, ceramic and Polycarbonate-urethane (PCU) polymer. Mechanical and frictional properties of the samples were characterised by compression, shear tests and surface roughness measurements using white light interferometry (WLI). Results indicated that at the same stage of OA, the cartilage tribological and mechanical properties deteriorated when using COCR.

The second stage of this study focuses on creating a model more anatomically realistic of the hemi-replaced shoulder joint and assesses the cartilage mechanical behaviour. A custom made joint simulator has been built and will be used to investigate the response of shoulder joints under representative loads. The glenoid will be tested against different humeral component materials to understand the friction/wear response of the cartilage. The correlation between mechanically damaged and healthy cartilage will be investigated. Histological analysis will be performed on the tissue to observe any structural changes due to wear. The results from this study can aid the surgeons to choose the best possible material for hemiarthoplasty according to the disease state of the patient. 

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