Bearings for hip replacement
Wear occurs in all hip replacements, but is very much higher in patients with high activity levels, and is obviously more common the longer the implant is in use for. Hence it is the younger patient in whom this wear is a particular problem.
To address this problem alternative bearing materials have been developed that offer lower wear rates. However, potential problems in using all these different materials need to be carefully balanced against the potential benefits. (fig 2. depicts the relative wear rates for the various materials).
Below we summarise the latest evidence on bearing materials, and the rational for how we tailor the choice to each individual patient.
This newer material has performed extremely well so far.
Benefits of highly cross linked UHMWP:
- Relatively cheap
- Reduces wear by 90–95% compared to normal UHMWP
- Flexible options with head size and augments to improve stability
- Easy to revise
- Can be cemented
- No issues with metal allergy.
- Unknown performance after 15 years
- May have increased wear rates with head sizes over 32mm.
It is extremely hard wearing, due to its hardness, smoothness, and lubrication characteristics. A ceramic head can be used in combination with other materials such as UHMWP, ceramic cups, and most recently metal cups.
In the last few years, manufacturing techniques have dramatically improved allowing larger heads to be made, and reducing the risk of fracture.
Benefits of delta ceramic:
- Lowest wear rate of any bearing when combined with ceramic cup
- Inert wear debris
- 40 years of experience
- No issues with metal allergy.
- Limited size options of the head and cup, which may compromise stability
- Fracture risk (<1 in 1000)
- Squeaking (<1%)
- Limits options for revision due to taper damage and after fracture
- Very expensive.
Metal on metal
It is a very hardwearing material, and can be safely manufactured into relatively thin cups, allowing the use of very large heads and in hip resurfacing.
Benefits of MoM:
- Low wear
- >20 years experience of modern MoM bearings
- Allows use of very large heads and resurfacing.
- Metal allergy, and ALVAL/ARMD especially in young females
- Unexplained pain, especially in young females
- Worries over cancer risk (unfounded)
- Wear particles cross the placenta
- Sensitive to error in cup placement.
Despite the bigger incision required for this procedure, patients recover exceptionally quickly.
Benefits of hip resurfacing:
- Benefits of MoM bearings
- Very high activity possible
- Bone preservation
- Restores function.
- Problems of MoM bearings
- Neck fracture 1%
- Larger incision
- Neck thinning (usually females).
Our choices in bearing materials
Young (<60yrs) active males
Young males up to 65yrs
Young females (<60yrs)
There are many special cases, some of which require a variety of implants and bearings, and we will discuss the optimal choice for each individual before surgery.
- Pathway for total hip replacement and resurfacing hip replacement
- Bearings for hip replacement
- Hip replacement in the young
Pain Management after discharge
Advice following hip replacement surgery
DVT and PE
Anesthesia for Hip and Knee Surgery
Minimally Invasive Total Hip Replacement
Total Hip Replacement
Activities After Hip Replacement
Total Hip Replacement Exercise Guide
Surgery and Smoking
Deep Vein Thrombosis
Delta Motion ceramic hip replacement