PREDICTORS OF LENGTH OF HOSPITAL STAY IN TOTAL KNEE REPLACEMENT PATIENTS

Introduction: In Scotland, the number of primary total knee replacements has been steadily increasing since 1992. It has been predicted that the number of total knee replacements performed annually will soon outstrip the number of hip replacements. The price of the implant is fixed but the length of hospital stay, and associated cost, is variable. An understanding of what currently influences length of hospital stay may be of paramount importance in order that we can influence some of these parameters, with resulting benefit to our patients as well as contributing significantly and favourably towards the health economics of this procedure. Materials and Methods: All patients who underwent primary unilateral total knee replacement in the region of Fife, Scotland, UK, during the period December 1994 to February 2007 were prospectively investigated. The following information was gathered: age, sex, body mass index (BMI), year of operation, day of operation, diagnosis, surgeon grade, consultant performing the operation, walking score, walking aids score, stair score, American Knee Society score (pain, stability and range of motion), length of operation, need for lateral release, patella replacement, urinary catheterisation, blood transfusion, presence of deep or superficial infection, pre and post-operative haemoglobin values, haemoglobin drop, and length of hospital stay. All the data was analysed using univariate and multiple linear regression statistical analysis. Results: Data on length of hospital stay was available from a total of 2105 unilateral total knee replacements. Length of stay varied from 4 to 70 days, with a mean of 9.4 and a median of 8.0. There were numerous highly significant predictors of increased length of hospital stay, when considered separately. Many of these independently significant factors remained significant when adjusted for the effects of the others. These included age of the patient, year of admission, consultant performing the operation, use of a walking aid, lateral release, deep and superficial infection, pre and post-operative haemoglobin values, urinary catheterisation and blood transfusion. Of note, the day of operation and high BMI did not influence the length of stay. Conclusion: Prolonged hospital stay following total knee replacement is associated with demographic, preoperative, intra-operative and post-operative factors. An awareness of these factors gives us the opportunity to make attempts to influence them favourably with resulting reduction in length of hospital stay and, therefore, the associated costs.