Hip Replacement Diagnosis
For anyone with a total hip replacement (THR), hip pain is a red flag. Medical evaluation is important because of the risk of joint infection. Treatment depends on knowing if there is (or isn't) an infection.
But there isn't one single or individual test that works best to diagnose or rule out infection. To avoid the high cost of multiple tests, it would be useful for the surgeon to know which tests to order. Cultures of the joint taken directly from the area during surgery are the most accurate.
But this type of testing is not practical for the patient who doesn't have an infection or who doesn't need surgery. And there is a fair amount of false-positive test results with intraoperative cultures due to errors in sampling technique. Not only that, but sometimes patients are given antibiotics before the operation (affecting test results) and the surgeon doesn't know it.
So which tests are sensitive, reliable, and accurate with a low false-positive and high true-positive results? That was the focus of this study on over 200 patients with painful total hip implants. The tests they evaluated included:
Values for test results are always listed with suggested normal reference ranges. The surgeon must use the test results along with patient history and clinical presentation when making the final diagnosis of infection. Until now, the physician has relied upon three things: positive intraoperative culture, visible pus in or around the joint, and the pathology report confirming that the culture was infected.
But now, the authors present data to support the combined use of several lab tests to make the diagnosis. This provides surgeons with a low-cost method of screening for infection of the hip in patients with a total hip replacement. Here's what they found:
Using these guidelines, the surgeon can consistently and accurately diagnose hip infection. White blood cell count is very useful and highly accurate in diagnosing hip infection when combined with values for SED rate and CRP.
Mark F. Schinsky, MD, et al. Perioperative Testing for Joint Infection in Patients Undergoing Revision Total Hip Arthroplasty. In The Journal of Bone and Joint Surgery. September 2008. Vol. 90. No. 9. Pp. 1869-1875.'