May 2011, Vol. 40 No. 5
Orthopaedic Implant Technology: Biomaterials from Past to Future
Wilson Wang,1MBBS (London), FRCS (Glasg), Dphil (Oxford), Youheng Ouyang,1MBBS (Singapore), Chye Khoon Poh,1BSc (Singapore)
The orthopaedic implant sector forms a signifi cant
portion of the worldwide biomedical industry. In the US
alone, the orthopaedic implant market was estimated at
over US$14 billion in 2008, and this is projected to rise
to US$23 billion by the year 2012.1 Within this large
and diverse fi eld of orthopaedic surgical practice, there
are 4 major implant applications: (i) reconstructive joint
replacements, (ii) spinal implants, (iii) orthobiologics and
(iv) trauma implants. The clinical need in all of these areas
is anticipated to continue to grow for the foreseeable future,
boosted by local and worldwide ageing populations, as well
as increasing prevalence of physically active lifestyles and
higher expectations of quality of life in older age groups.
Success in the application of an orthopaedic implant
depends on the complex interplay of a number of factors.
In broad terms, these can be grouped into surgeon factors,
patient factors, and implant factors. The surgeon of
course plays a crucial role in determining the success of
a particular orthopaedic implant, not only through their
1 Department of Orthopaedic Surgery, National University Health System
Address for Correspondence: Dr Wilson Wang, Division of Hip & Knee Surgery, Department of Orthopaedic Surgery, National University Health System, 1E
Kent Ridge Road, Level 11, NUHS Tower, Singapore 119228.
Orthopaedic implant technology is heavily based on the development and use of biomaterials. These
are non-living materials (e.g. metals, polymers and ceramics) that are introduced into the human
body as constituents of implants that fulfi l or replace some important function. Examples would be
prosthetic joint replacements and fracture fi xation implants. For orthopaedic biomaterials to succeed
in their desired functions and outcomes in the body, a number of factors need to be considered.
The most obvious mechanical properties of the implants are that they need to suit their intended
function, and various classes and types of biomaterials have been developed and characterised for
use in different implant components depending on their demands. Less well understood but no less
important are the interactions that occur between the constituent biomaterials and the living cells
and tissues, both of the human host as well as pathogens such as bacteria. Biomaterials used for
orthopaedic applications are generally considered to be biocompatible. However, adverse effects
arising from interactions at the implant interface can result in various modes of implant failure,
such as aseptic loosening and implant infection. This review paper uses the illustrative example of
total hip replacement (which has been called the operation of the century) to highlight key points
in the evolution of orthopaedic biomaterials. It will also examine research strategies that seek to
address some of the major problems that orthopaedic implant surgery are facing today.
Ann Acad Med Singapore 2011;40:237-44
Keywords: Biocompatibility, Biomaterials, Joint Replacement, Orthopaedic Implants
surgical technique and expertise, but also by the choice of
implant type and design appropriate for a particular patient
and condition. Patient factors are no less important, as the
patient is not merely a passive recipient of the implant,
but an active end-user as well. Patients can thus affect the
outcome and long-term results of implant surgery not just
by their medical status and physiological responses to the
implant, but by their activities and compliance to medical
instructions that can affect implant survivorship. Within the
ambit of this review paper however, we shall be focusing
on the third factor of this triad: the implant itself.
Orthopaedic implants are manufactured devices that have
been designed and developed to fulfi l particular functions
when implanted into the living body, and usually for specifi c
indications. The non-living materials that are used in their
manufacture are termed biomaterials, as these materials are
intended to survive and function as foreign bodies within
a biological environment, i.e. in the living human system.
Implants may consist of a single type of biomaterial
Biomaterials in Orthopaedic Implant Technology—Wilson Wang et al
Annals Academy of Medicine
Biomaterials in Orthopaedic Implant Technology—Wilson Wang et al
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