Does high BMI compromise outcomes following fixed bearing Partial Medial Knee Replacement

K Nicholls, K Wilcocks, K Shean, L Allsop, L Vachtsevanos

Salisbury NHS Foundation Trust

A high body mass index (BMI) has been associated with higher complication rates and poor outcomes following arthroplasty surgery. Our study investigates the effects of high BMI on patient outcomes following cemented fixed bearing partial medal knee replacement surgery.

Prospectively collected data on patients undergoing partial medial knee placement between 2018 and 2023 in Salisbury Hospital have been retrospectively analysed. Patients with a BMI of <30kg/m2 have been compared to those with a BMI of 30kg/m2 or above. Primary outcome was implant survivorship. Secondary outcomes included perioperative blood loss, length of stay, complications and readmissions.

61 patients were followed up for 5 years (0.5-5.1years) after partial medial knee replacement. 32 patients had a BMI of 30 or over (30-43.6,median:37.5) and 29 a BMI under 30 (19.8-29.8,median:23). Implant survivorship has been 100%. There have been no postoperative complications in either group. 2 patients in the low BMI group were readmitted with postoperative swelling and discharged with no intervention. Length of stay was similar between the 2 groups with a mean of 1.6 days in the low BMI group versus 1.9 days in the high BMI patients. Interestingly there was a statistically significant difference in mean haemoglobin drop in favour of the high BMI group (9.5g/l versus 15g/l). This difference was not clinically relevant and no patients required a blood transfusion.

A BMI of 30 or over does not appear to adversely affect outcomes within the first 5 years following cemented fixed bearing partial medial knee replacement surgery.