Table 2.

Risk of insert exchange. Crude and adjusted hazard ratios (HR) for insert exchange derived from the Cox-regression comparing 6-mm inserts to inserts of 8 mm or more

Parameter	Hazard ratio	95% CI
Crude	11	1.4–93
Adjusted for:
Age	11	1.4–94
Gender	10	1.1–79
Weighta	85	4.1–1758
BMIa	39	3–511
Diagnosis	21	2.3–196
Medial / Lateral	10	1.3–87
Post-operative FTA angle	15	1.7–143
Post-operative KSS	12	1.4–102
Difference in femoral and tibial component size [23]	13	1.5–106

Note the 6-mm inserts have a significant 11 times higher revision risk compared to the inserts of 8 mm or more. This increased risk remains when adjusting for confounders

^a When adjusting for weight or BMI the HR increases to 39 and 85, respectively, with a very wide confidence interval. This is due to the fact that BMI and weight are strong confounders and the cohort is relatively small with only eight insert exchanges