O2058 ANALYSIS OF POSTOPERATIVE COMPLICATIONS IN PRIMARY KNEE ARTHROPLASTY USING STATISTICAL CONTROL CHARTS

Abstract

Aims: To investigate whether normal statistical ßuctuation in the incidence of early complications of primary Knee Arthroplasty (TKA) follows the laws of statistical probability and can thus be amenable to analysis by standard Statistical Quality Control (SQC) methods. The þnal objective is to apply such techniques to distinguish random ßuctuation from real (undetected by traditional p value statistical methods) increase in the incidence of early complications in primary joint Arthroplasty. Methods: We employed statistical quality control charts (X-bar, p, c, u and np) to analyse postoperative complications and length of stay in 1,196 consecutive primary TKAs performed over a 20-quarter time period (October 1995 to September 2000). For all analyses (Minitab 12.1 software) the standard practice of employing ± 3 standard deviation upper and lower control limits and generally accepted criteria for determining the presence or absence of statistical control were used. Results: Deep infection, major thromboembolic incident, total number of complications per case and total number of complicated cases appeared to be in stable statistical control and followed the laws of statistical ßuctuation throughout the entire study period. However, patella mal-tracking, persistent knee stiffness, postoperative length of stay and total number of postoperative complications showed an (undetected by conventional postoperative audit methods) lack of control at various time periods with subsequent return to the statistically-controlled range. Conclusions: SQC methods may be employed in the audit of postoperative events in TKA and can be a valuable tool in continuous assessment of the statistical variability of postoperative complications, with the aim of reducing the variability and improving clinical outcome Arthritic knee imaging