We analysed the clinical data of 858 consecutive primary total hip and knee replacement patients to establish how age, ASA grade, body mass index and a simplified cognitive score correlate with the length of hospital stay and early complication rates. We further used statistical regression analysis to study how hospital stay and complication rates correlate with different pre-operative grading systems based on combinations of age, ASA grade, body mass index and a cognitive score.

The results indicate that age and ASA grade correlate significantly with both length of hospital stay and complication rates, while body mass index correlated poorly with both. A grading system based on a combination of age and ASA grade (the AA Grade) correlated significantly with both length of hospital stay and complication rates. Adding body mass index or a cognitive score did not significantly add to the correlation.

We discuss the relevance of this simple grading system and how it might contribute to pre-operative risk assessment and peri-operative planning.