Knox Orthopaedic Group

262 Mountain Highway,
Wantirna 3152
Victoria, Australia

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What’s new in hip surgery

Ultra-cross-linked Polyethylene

The Australian Orthopaedic Association manages the Australian Joint Replacement Registry and has done so for fourteen years. This registry collects data on all joint replacements performed in Australia and is regarded as one of the best registries of its kind in the world. This registry provides two benefits to patients.

  • It identifies prostheses that have a high revision rate and surgeons make choices about the prostheses they use based on this information. This has led to a decrease in revision rate as surgeons use the available data to choose better performing prostheses.
  • The data collected by the registry has demonstrated that only 5% of hip replacements have required revision at ten years post operatively. Fourteen years after surgery 7.8% of hip replacements require revision.

Each year the registry publishes its annual report highlighting interesting trends in joint replacement surgery. In the 2015 report an interesting account was given of the results of different bearing surfaces in hip joint replacement. (See Hip Replacement Surgery on this website – link) The vast majority of hip replacements performed in Australia use a metal on polyethylene articulation. This has demonstrated very good results for over thirty years. There is however a group of patients who continue to require revision surgery due to higher than expected wear of the polyethylene. Approximately fifteen years ago a newer form of polyethylene was developed in order to improve its wear rate. This is called ultra-crosslinked polyethylene and is used in the majority of current prostheses.

The registry has demonstrated a significantly lower revision rate for prostheses using the newer polyethylene. In addition, they have compared the revision rate between this bearing surface and ceramic on ceramic bearing surfaces. At 14 years after surgery there is no statistical difference between the two groups. This is surprising, as it has been traditionally thought that the ceramic on ceramic bearing would produce lower wear than any other articulation. Time will tell whether ceramic on ceramic bearing surfaces will produce better results after twenty to thirty years.

Learning Curve for Anterior Hip Replacement

There was an interesting study published in an American orthopaedic journal that looked at the learning curve for surgeons using the anterior approach for hip replacement surgery.

Most of the data in this article came from the Australian National Joint Replacement Registry. It demonstrated that it takes surgeons using this approach at least fifty cases to reduce their revision rate to those of surgeons who are more experienced.

Surgeons performing their first fifteen cases had a revision rate of 6% at four years compared with a revision rate of 2% for surgeons who had performed over a hundred cases. There are no comparable figures published for other approaches for hip replacement.

The surgeons at KOG who perform anterior hip replacement surgery have all completed more than a hundred cases and have had extensive training and mentorship during their learning curve.