Although in favour many years ago as part of Hip Resurfacing procedures, the use of metal on metal has been steadily dropping as hip resurfacings are phased out overall. Although very occasionally still used, hip resurfacing and metal on metal implants are no longer common place due to the requirement to monitor cobalt and chromium levels, due to the development of metal nano particles that can destroy local tissue and enter the blood stream. This has been seen in many types of metal on metal implants, and particular with 1 particular implant that was used over 10 years ago. It is not used in our offering, due to the risks posed by this articulation.

The standard of implant articulation that is used currently is a metal ball, matched with a plastic liner. This is the most cost effective version of a hip articulation, and is the easiest to place within the hip, as the plastic is tolerant to less accurate insertion techniques than ceramic. Plastics have changed over the years, and are now extremely durable. It is a theory that newer plastics may not cause the same particulate damage to the bone as it wears, due to the decreased wear of newed plastics over older ones. For our practice, plastics are only used when a dual mobility implant is selected, which is where a small ceramic ball is connected to a large ceramic ball to decrease dislocation risk in complex revision scenarios generally. 

Cement is utilised in all Total Knee Replacements by Dr Chien-Wen Liew. The type of cement is usually one called Palacos, and has antibiotics within it. It has a 6 minute working time, and fully cures hard in 12 minutes. Cementation of the implant for knee replacements is different to that of hip replacements as the risks of cement embolisation is almost negligible in knee replacements as opposed to in hip replacements, where it is required to be pressurised into the femoral canal. Cement during knee replacement is mixed in a vacuum device and injected directly into prepared bone surfaces. Cement is Poly Methyl Methacrylate and is a light green in colour when used during surgery. 

Although not implanted, patient specific technology utilises a specific plastic and resin created for each and every patient. This custom made device is used to be a rigid guide during surgery to ensure accuracy during bony preparation. The individualised moulds are removed prior to the final implants are inserted. 

Not used in our inventory  are other articulations in knee replacements. Again, ceramicised metal can be used, but is only available in limited designs. Trials of ceramics have largely been unsuccessful due to the differing nature of the forces going through the knee compared to the hip joint. Plastics have made different additives with many having been discarded over time. In general, the material composition of knee replacements has been relatively stable over the years when compared to the choices for hip replacement surgery. 

Dr Chien-Wen Liew has a dedicated practice in only total hip and total knee replacements. He no longer accepts new referrals for sports injury, trauma or other conditions of the hip and knee. This allows a dedicated focus to optimising all efforts towards a successful total hip replacemnt or total knee replacement. 

For over 8 years, all total hip replacements have been performed using the Direct Anterior Approach. This is an approach where no muscles or tendons are cut or detached during surgery.  A cementless stem and socket combined with a ceramic on ceramic articulation will be used in most cases. 

There are minimal restrictions, and early mobility. As part of the procedure, patient specific technology is utilised – meaning that a 3 dimensional scan is performed 2 months prior to surgery in order to create customised cutting jigs and accurate planning to ensure an accurate outcome and to decrease the amount of soft tissue damage during surgery. A specialised table is used during surgery to minimise touching any part of the leg except for the small operative field. During surgery an intra-operative scan is performed to double check that the procedure has matched with the Xrays, as well as the 3 dimensional plan as well as the individualised modelling. This ensures an accurate procedure in an effort to never return to the same hip again. There are no movement restrictions post operatively. Most procedures are performed under a spinal anaesthetic.  No local anaesthetic is used during the procedure within the hip. 

The medial pivot design of the knee replacement has been a defining part of our practice. This allows the knee to glide in a natural movement. Combined with Kinematic Alignment, the procedure is now extremely planned using Patient Specific Technology. Kinematic alignment is where the final knee replacement is placed in a position to match a patient’s pre-arthritic anatomy rather than placed in what traditionally has been considered to be the “optimal” position for all patients. This means that each and every person will receive a position that mimics their own anatomy. Part of the benefit of this, is that there are no tendon, capsular, or ligamentous releases required, to balance the knee as we used to perform many years ago when each knee was aligned to be “straight”. This means that if you have been bow legged or knock kneed, pigeon toed or duck footed prior to developing knee osteoarthritis, then you will most likely be placed back into that position after surgery. This is done to regain the “forgotten knee” goal once recovery is completed. For every case, disposable instruments are used as part of the individualised patient equipment in order to decrease the risk of infection. We aim to walk our patients the same day, if surgery is performed in the morning, or first thing the following morning if performed in the afternoon. Most procedures are performed under a spinal anaesthetic.  A nerve block is performed (adductor canal) in addition to a small amount of local anaesthetic at the back of the knee during surgery.