Oxford medial unicompartmental knee arthroplasty in patients younger and older than 60 years of age.

Price AJ, Dodd CAF, Svard UGC and DW Murray. J Bone Joint Surg (Br) 2005;87-B:1488-92.

This is the editor's interpretation of a paper published in the orthopaedic literature in 2005 - our attempt to make relevant medical articles accessible to lay readers. If you wish to read the original it is easy to ask your librarian to obtain a reprint for you from any medical library.


The Oxford unicompartmental knee arthroplasty is a 'mobile'bearing' partial knee prosthesis ('implant'). In this 2005 publication the authors set out to determine if age - in patients over 50 - is a contraindication for the Oxford medial unicompartmental knee replacement with respect to the durability of the implant.

 

Patient Group

Five hundred and sixty four knees  (447 patients) with Oxford medial unicompartmental knee replacements were included in the study -

  • 52 knees in patients less than 60 years old (all but one was over 50)
  • 512 knees in patients over 60 years old

Data was obtained from two centres -

  • Nuffield Orthopaedic Centre, Oxford, UK
  • Skaraborg Sjukhus, Skövde, Sweden

 

The Study

All patients had primary osteoarthritis (OA) of the medial compartment, with the lateral compartment unaffected and the cruciate ligament intact. Damage to the patellofemoral joint was not considered an exclusion criterion. The authors did exclude patients with a fixed flexion of greater than 15 degrees and non-correctable varus deformity.

The patients were followed up for a number of years, and in the younger age group there were 21 knees where patients had been followed up for at least 10 years. Twenty of the 21 had had X-rays to look for any migration or subsidence of the components as well as any OA changes in the good (lateral) compartment.

The Results

The 10-year results in the younger group showed an average of 91% survival of the prosthesis and an HSS score of 92 [Ed: which are excellent clinical results], suggesting that the Oxford medical unicompartmental arthroplasty functions well and is durable when used for younger patients. But despite the good results the percentage needing 'revision' (re-operating to change the prosthesis) was greater in the younger than in the older age group, suggesting that younger patients put increased demands on the prosthetic implants. [In their discussion, the authors refer to other similar studies using different prostheses - the interested reader may like to get the original article from a library and refer to these studies.]

Within the younger age group, of the four knees that required revision - two had failed because OA had developed in the lateral compartment - and the procedure was revised to a total knee replacement. Of the other two, one knee had developed a fracture of the meniscus, and in this case the prosthesis was exchanged to an open-bearing one. [The authors suggest that younger patients should not be given the thinner bearings.] The fourth had a loose femoral component, and was revised to a total knee replacement.

Alternative treatment in the younger age group with unicompartmental disease includes total knee replacement and high tibial osteotomy. The authors in the paper also review relevant literature here - and they conclude that the unicompartmental knee replacement leads to fewer problems and better function than total knee replacement in the younger patient.

 

Conclusion

Regarding this specific study, the authors conclude that for people in their 50s age is not a contraindication for using the Oxford unicompartmental arthroplasty to treat patients with anteromedial OA of the knee.

 

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