Selective Hip Aspiration
We recommend a selective approach to aspiration of the hip based on the patient’s probability of periprosthetic joint infection and the results of the erythrocyte sedimentation rate (ESR) AND C-reactive protein (CRP). We recommend that the aspirated fluid be sent for microbiologic culture, synovial fluid white blood cell count and differential.

Rationale
AAOS conducted a systematic review that identified six Level I hip,4, 27, 57, 65, 68, 111 and one hip and knee study35 on the diagnostic performance of hip aspiration and culture. (Please see Recommendation 3 for data supporting knee patients.) These studies did not stratify patients as to whether they were at higher or lower probability for infection, and all patients underwent re-operation. The indications for patients having an aspiration varied between studies, with aspiration often a routine part of preoperative investigations. Our meta-analysis indicated that hip aspiration for culture has a moderate to large ability to “rule in” infection but a small to moderate ability to “rule out” infection (positive likelihood ratio 9.8, negative LR 0.33). Based on the meta-analysis, hip aspiration is a useful test to diagnose periprosthetic hip infection. Therefore, we recommend hip aspiration in all “higher probability or lower probability” patients undergoing reoperation of the hip with abnormal ESR and/or CRP results. 4, 27, 35, 57, 65, 68, 111

Given the potential problems with instituting treatment and missing the diagnosis of infection, “higher probability” patients with an abnormal ESR AND/OR CRP without planned reoperation should also receive hip aspiration.

There is no reliable evidence, however, on the diagnostic performance of hip aspirations in patients who are not to undergo reoperation. Possible harms include the possibility of false positive results, the possibility of the introduction of bacteria into the joint during the procedure and patient pain and/or discomfort while undergoing the procedure.4 There are also concerns about the cost of the procedure.4 Therefore, universal hip aspiration does not seem indicated. Aspiration is indicated for lower probability hip patients without planned reoperation only if both ESR AND CRP levels are abnormal. Lower probability hip arthroplasty patients without planned reoperation who have an abnormal ESR OR CRP are addressed in Recommendation 6.

We do not recommend that “higher or lower probability” patients with normal ESR and CRP have hip aspiration prior to planned reoperation.