EFFECT OF NAVIGATION ON LOW VOLUME OXFORD MEDIAL UNI COMPARTMENTAL KNEE REPLACEMENT SURGEONS.

Abstract

Oxford medial uni compartmental knee replacement is a common and widely accepted procedure that relies on accurate positioning and alignment of the implants for optimal outcome and longevity. Posterior slope of the tibial base plate has been shown to be an important factor affecting long term survivorship.

The aim of the study was to evaluate whether navigation increased the accuracy of Oxford knee replacements using the posterior slope of the tibial component as an index measure.

The posterior slope of tibial trays from 58 sequential Oxford medial unicondylar knee replacements over a two year period was checked on standard lateral x-rays against the recommended range.

There were 12 cases in the navigated and 46 in the conventional group across six Orthopaedic firms. The mean posterior slope for navigated and conventional implantations was 4.75 and 3.3 degrees respectively with the difference not being statistically significant. However, when considering the data for low volume surgeons, the mean posterior slope with and without navigation was 4.75 and 1.83 degrees respectively which was significant with a p value of 0.017. Navigation was also found to significantly decrease the chance of implanting the knee with the posterior slope outside the acceptable range (p=0.024). In both analyses the navigated cohort had a narrower data spread and fewer outliers compared to the conventional group. No other factors were found to significantly correlate with the posterior slope.

The study suggests that navigation might help low volume surgeons in increasing the accuracy and decreasing the incidence of extreme variations from the desirable range of implant positioning for unicompartmental knee replacements.