Biomaterials for hip replacement prosthesis arthroplasty
The hip is a vital joint that support the body. it is frequently subjected to high stresses, such as lifting of heavy objects etc; as it bears the load of the upper region of the body.
The term “Osteoarthritis of the hip” is a condition that subjects the body (hip region) to a very intense pain due to stiffening.
Recalling from foundational / basic knowledge, the hip joint is a ball and socket type of joint, which consist of:
- Femoral stem.
- Femoral head.
- Acetabular component.
- Plastic liner.
Orgination of biomaterials was with the primary aim to improve the quality of life, via the repair or replacement of a body part or it’s function in the body in a reliable, economically and physiologically accepted manner.
Formerly, materials like wood, glue, rubber, iron, gold, since etc, w were used as biomaterials for repairing or replacing damaged, malfunctioning, or disfigured hip joints.
Damages in the hip region causes disability and subjects the body to difficulty to walk.
Thus, the essence of designing, developing and manufacturing Biomaterials for medical implants so as to repair or replace damaged body parts or organs, especially with the ageing population, cannot be over emphasised.
From recent statistics, it’s observed that over a million hip replacement surgical operations are being carried out annually, with strong signals that by the year 2024, the number might increase by over double.
The Biomaterials for hip replacement must be inert, safe, and mechanically fit to bear loads, and overall, must be biocompatible with the body.
Apart from repair and replacement of damaged or diseased body parts (ie:- hip / knee joint replacement), they are also used for improving functionality (ie:- cardiac peace maker), they also assist healing (ie:- use of plates and screws, stutures), they are also used to aid diagnosis (ie:- probes and catheres).
Puting materials for total hip replacement into consideration, we consider the age of the patient, his or her work environment.
Did you know that daily activities subjects the bones to stresses upto 4MPa, and the mean load on the hip is thrice the weight of the weight of the body.
Total hip replacement replacement have been recorded successful over years, but is currently reviewed following limitations such as wearing of implants as a result of friction and load bearing, thus result in bone loss and implant loosening. Another is limited service life of about 15years, thus being a future disadvantage to patients under 40years.
To overcome these limitations, Biomaterials are designed and manufactured to posses properties such as wear resistance, inertness, biocompatible, biodegradable so as to mitigate implant loss, and also ease degradation of implant loss without any further detrimental effects on the bones or tissues.
Biomaterials for hip prosthesis arthroplasty replacement
Materials for hip replacement:-
Listed below are materials for hip replacement:-
- Metal materials
- Polymer materials
- Ceramic materials
Metallic materials often used for biomaterials for hip replacement include:-
- Stainless Steel
- Colbalt Chromium Molybdenum based alloys
- Titanium alloys
Stainless steel and colbalt chromium molybdeunm metallic materials are highly corrosion resistance due to the presence of chromium content. The have other properties such as high strength, good wear resistance, hardness and high toughness. Their limitation is that they degrade due to pitting, fretting, corrosion fatigue, etc in the body.
Titanium based alloys introduced as biomaterials for total hip replacement because they are much less dense. They have high strength, good corrosion resistance. In the case of corrosion mitigation, they form self protective oxide films TiO² on reacting with oxygen in the presence on a corrosive environment. The limitation of using titanium based alloys is that they lead to health challenges in a long run. Problems such as Alzheimer disease and neuropathy, due to the release of aluminum and vanadium.
Also Read:- Materials and Metallurgical Engineering
Because of high module of elasticity as a unique property of metals, there is difficulty in the distribution of stress between the biomaterial implant and the bones. This issue led to the drifting of materials manufacturing into metallic material modification and advancement, as metals with low module of elasticity, coupled with high corrosion and wear resistance are being designed and produced.
Another metal alloys for hip replacement that overcome the problem of Biomaterials implant to bone stress distribution, with low module of elasticity and great hardness are:-
- Ti – 5Al – 2.5Fe
- Ti – 6Al – 7Nb
Both alloys were obtained from Ti – 6Al – 4V. The Iron Fe and Nobeium Nb were used to replace the Vanadium V. Vanadium was observed to have a high level of toxicity, making it non-biocompatible.
Ceramics as Biomaterials for hip replacement was introduced to overcome the problem of wearing, low strength etc. Some ceramic materials used as Biomaterials for hip replacement Prostheses are:-
- Yttria Stabilizing Oxide
- Zirconia toughned alumina
The alumina was introduced as a biomaterial for hip replacement arthroplasty in 1971, following the observation made by Boutin. Boutin noted that alumina has good tribological properties such as favourable friction behavior, wear resistance and hardness. Alumina is the most commonly used ceramic material for the hip replacement arthroplasty.
Zircona is yet another ceramic material used for total hip replacement. It has good mechanical properties with high toughness. It has an outstanding property of being crack resistance. It’s a widespread alternative to alumina.
Initially, magnesia partially stablised Zirconia (MgPSZ) was being focused on, but was limited to not satisfying the problem of wear resistance properly. The focus later drifted to Yttria Stabilizing Oxide (Y–TZP) due to advancement and further developments.
The Y–TZP is totaly formed by submicron sized grains, representing the current standard for clinical application.
Features of the Y–TZP:-
- tetragonal sized grains less than 0.5microns
- It has superior wettability property that ease fluid formation between the biomaterial implant and the articulating surface.
The Zircona toughned alumina (ZTA) is a ceramic based composite Biomaterial. It was achieved by introducing about 25%Wt of Zircona as reinforcement to the alumina matrix. This composite material formulation yeilded an increase in toughness. It agglomerated the good properties of alumina (ie:- high strength and toughness), with the excellent wear resistance, hydrothermal and chemical stability of Zircona.
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