Periprosthetic joint infection (PJI) is a devastating complication in revision total hip arthroplasty (THA). As preoperative diagnosis can be difficult, some patients who undergo planned aseptic revision surgery might have positive intraoperative cultures and later be classified as infected. In this retrospective study we analyzed the influence of intraoperative positive cultures and possible underlying risk factors in patients undergoing planned aseptic THA revision.
We retrospectively analyzed 276 cases of aseptic THA revision surgery between 2010 and 2017 who had a minimum follow-up period of 24 months. All patients underwent preoperative serum and synovial diagnostics according to the Center of Disease Control (CDC) (2010) or Musculoskeletal Infection Society (MSIS) Criteria (2011–2017) for PJI and were classified as aseptic prior to surgery. In all cases intraoperative tissue samples were taken and reviewed. Primary endpoint was defined as any complication leading to revision surgery. Secondary endpoint was explantation due to PJI or death. Revision free survival (RFS) and infection free survival (IFS) for intraoperative negative and positive cultures was calculated via Kaplan Meyer Method. Patients’ medical history was analyzed for possible risk factors for positive cultures.
In 96 (34.78%) cases positive cultures were found. 67 (24.28%) had a single positive culture and 29 (10.51%) had ≥ two positive cultures. Coagulase negative staphylococci were found in 57.69% of the positive cultures. While the revision free survivorship was not different in patients with single positive cultures compared to patients with negative cultures (72.86 (95%CI 60.08–85.64) vs 83.01 months (95%CI 75.42–90.60) p=0.201), patients with ≥ two positive cultures had a reduced mean RFS (38.46 (95%CI 20.16–50.76) vs. 83.01 months (95%CI 75.42–90.60) p<0.02). 22 (7.97%) patients underwent explantation of the THA due to PJI. The IFS was reduced if ≥ two cultures were positive compared to culture negative patients (56.48 (95%CI 46.20–66.75) vs 110.78 months (95%CI 106.78–114.77) p=0.001). Risk for explantation due to PJI increased if ≥ two cultures were positive (Odds Ratio (OR) 3.19 (95%CI 1.36–7.52). A BMI ≥ 30 was associated with the risk of ≥ two positive cultures (OR 2.85 (95%CI 1.40–5.78).
Occurrence of two or more positive cultures in aseptic revision THA has devastating influence on the revision free survival and infection free survival. As the risk for ≥ two positive cultures increase almost 3-fold in patients with a BMI ≥ 30, extended preoperative diagnostics in obese patients should be considered to detect possible low grade PJI before revision surgery.