AN ASSESSMENT OF THE POSSUM SYSTEM IN ORTHOPAEDIC SURGERY

Abstract

The use of crude mortality and morbidity data to assess the outcome from surgical intervention can be both dangerous and misleading. Furthermore, differences in outcome when comparing differing units or surgeons may be explained merely by variations in case mix and the type of surgery.

In recent years there have been a number of attempts to devise a reliable method for assessing the outcome from surgical intervention. In the general surgical setting, the POSSUM system has proved to be the most reliable and accurate of all scoring systems so far devised. It is widely applicable in other specialities as it allows comparison based on the patient’s physiological status and the magnitude of surgery. It could be used in any hospital, in elective and emergency operations. The present study attempted to validate the application of this new method of assessing the outcome after orthopaedic surgery.

All consecutive patients admitted to the orthopaedic wards in a district general hospital during a 12 month period in which orthopaedic surgery was performed on a non-day case basis were assessed using the new orthopaedic POSSUM system. POSSUM is an acronym for Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity. POSSUM is a two-part system that scores both physiological and operative factors. It is developed of multivariate discriminate and logistic regression analysis of 62 variables reduced to: * 12 factors, 4 grade physiological score and * 6 factors, 4 grade operative severity score. When these are combined, a numerical estimate of both mortality and morbidity is obtained. Mortality prediction for individual patients was estimated using this equation: Log [risk − (1 − risk)] =−7.04 + (0.13 physiological score) + (0.16 operative severity score)

During the 12 month period, 2326 patients underwent orthopaedic surgery. 44% were in elective setting, 56% were in emergencies. Using the POSSUM logistic regression equations yielded an overall predicted mortality of 53 patients (versus 51 observed) and a predicted morbidity of 254 patients (versus 252 observed).

The present study indicates that orthopaedic POSSUM is accurate in assessing outcome after an orthopaedic operation and can be used as an audit aid to assess the quality of surgical care.