Page 82 - HA Convention 2015

Masterclasses

MC4.3 Advances in Joint Replacement 13:15 Convention Hall C

Monday, 18 May Total Knee Replacement in Octogenarians — Dilemma and Challenges
Ng CFY
Department of Orthopaedics and Traumatology – Division of Joint Replacement Surgery, Queen Mary Hospital, Hong Kong

The octogenarian population in Hong Kong is growing. The life expectancy at birth for both sexes have steadily increased.
In 1971, life expectancy for males was 67.8 years and 75.3 years for females; In 2013, 81.1 years for males and 86.7 years
for females. As a result of the ageing population, the demand for medical healthcare among elderly patients increase
significantly. Degenerative knee joint disease is prevalent in our population and the demand for total knee replacement is
especially enormous. In 2014, 2,363 elective total knee replacements were performed in public hospitals in Hong Kong, while
217 patients (9.2%) were over 80 years of age. The number of octogenarian patients receiving total knee replacement has
already doubled comparing to the figure in 2009. Previous studies have shown that total knee replacement in octogenarian
population led to higher complication rates, peri-operative mortality and increase in length of stay. As a result, this may
potentially increase medical expenditure. This lecture aims to provide the updated information and current evidence-based
practice on how morbidity and mortality can be reduced in this age group receiving elective total knee replacement.

MC4.4 Advances in Joint Replacement 13:15 Convention Hall C

HOSPITAL AUTHORITY CONVENTION 2015 Materials Used in Total Joint Replacement
Yeung EST
Department of Orthopaedics and Traumatology, Queen Elizabeth Hospital, Hong Kong

The biomaterials used in total joint replacement have undergone a major evolution since its development from the last
century. Biocompatibility is paramount for the materials used in the implant structure and the various different bearing
surfaces. Over the last few decades, significant improvements have been made to enhance their structural strength,
compatibility with host tissue and wear properties, in the hope that the implants will have better longevity.

In order to get the optimum properties required to incorporate within the host bone, several types of metal alloys namely
stainless steel, titanium-based and cobalt-based alloys have been developed for use in the implants. Fixation method
can be a cemented or cementless type. The cemented type prosthesis employs the use of specific polymer (polymethyl
methacrylate) as a grouting agent to hold the implant within bone. Cementless type of fixation employs a coating of porous
metal or a calcium phosphate ceramic (hydroxyapatite) over the implant surface to allow the bone to grow into and develop a
firm fixation.

However, the wearing properties of the material at the bearing surfaces play a significant role in joint replacement as it is
a common reason for the implants to fail. In modern types of joint prosthesis, a metal on plastic type is the most common
form of bearing surface, with a metal component articulating with a polymer (polyethylene) on the other side. Other bearing
surfaces such as metal on metal (between two cobalt chrome alloy implants) and ceramic on ceramic (aluminium oxide) have
also been developed because of their high wear resistance. However, the cost and brittleness of ceramic, and the concern of
increased metal ions in the systemic circulation have limited the popularity of these bearing material choices.

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