Abstract
Aim
The knee radiograph is a commonly requested investigation as the knee joint is commonly injured. Each radiograph exposes 0.01mSv of radiation to the patient that is equivalent to 1.5 days of natural background radiation. Also, each knee radiograph costs approximately £37.16 to produce.
The aim of the clinical audit was to use the Pittsburgh knee rules to attempt to reduce the number of knee radiographs taken in patients with acute knee injuries and hence reduce the dose of ionising radiation the patient receives.
Method
A retrospective audit was undertaken. 149 knee requests and radiographs taken during October 2016 were evaluated. Each knee radiograph request including patient history and clinical examination was graded against the Pittsburgh knee rules to give a qualifying score. The Pittsburgh knee rules assigns 1 point for each of the following; blunt trauma or a fall, age less than 12 years or over 50 years, and unable to take 4 limping weight bearing steps in the emergency department. A Pittsburgh knee rule qualifying score warranting a knee radiograph is 2 or more points, where the patient must have had blunt trauma or a fall. A Pittsburgh knee rule score less than 2 points predicts a non-fractured knee and hence no radiograph warranted. Each radiograph was reviewed if a fracture was present or not.
Results
The clinical audit identified 85 true negative patients where their Pittsburgh knee rule score was less than 2 points and they did not have a fracture of the knee joint. The Pittsburgh knee rule score of less than 2 points did not warrant obtaining knee radiographs. Therefore, a total of 85 knee radiographs were unnecessary which is equivalent to 127.5 days of background radiation. The financial burden of these unnecessary radiographs is £2648.60. The negative predictive value of the Pittsburgh knee rules in this audit was 93.4%.
Discussion
The clinical audit shows that the use of the Pittsburgh knee rules scoring system can reduce the number of knee radiographs obtained by 57.4% and hence the doses of ionising radiation patients are exposed to. The audit also showed this clinical scoring system has a high negative predictive value that when utilised can discern patients with a normal knee joint who do not require a knee radiograph. In conclusion employing the Pittsburgh knee rule scoring system can improve patient safety by reducing ionising radiation exposure and can reduce financial costs of patient encounters.
