Objectives:
To evaluate the clinical outcome and complication rates between the use of fixed bearing (Zimmer) and domed (Phase III Oxford (Biomet)) lateral unicompartmental knee replacements

Patients and Methods:
All lateral unicompartmental knee replacements were evaluated with a minimum follow up period of 12 months. Patients completed a subjective score from 0-10 and an Oxford knee score

Results

27 lateral unicompartmental knee replacements were performed from October 2007-August 2011. Mean follow up is 34 (SD 18) months. Oxford Knee Scores and satisfaction scores were collected from 22 patients (82%).
Of the 12 domed procedures, 2 required a further procedure (1 patient dislocated the bearing requiring a revision and 1 patient required a manipulation under anaesthetic). In the 15 fixed bearing procedures, 1 patient, who is on warfarin required aspiration for a haemarthrosis. 1 patient is been currently investigated for unexplained pain.
The average Oxford Knee Score was 37 (SD 11) for the patients receiving a domed knee with a mean satisfaction score of 7.8 (SD 2.3). The average Oxford Knee Score was 29 (SD 15) for the fixed bearing knees with a mean satisfaction score of 7.0 (SD 4.3).

Discussion

The domed prosthesis showed marginally better functional results however this was not statistically significant (P>0.05). The domed design is known to predispose to dislocation; in our series we had one dislocation and which is sufficient to suggest exercising caution. Overstuffing the replacing tibio-femoral compartment is another problem which should be watched for in any unicompartment knee replacement surgery.