S09.4 CLINICAL ASSESSMENT OF PATIENTS WITH PROSTHETIC LOOSENING

Abstract

Aims: The symptoms of aseptic and septic prosthetic joint loosening may be similar, and identification of low-grade prosthetic infection based only on clinical history and physical examination has a reported low sensitivity. In a prospective study we explored to what extent a thorough examination of the patient’s history of sickness and a standardized preoperative clinical examination could help the surgeon to identify cases of septic loosening.

Methods: We included 54 patients undergoing revision surgery due to loosening of a total hip or knee prosthesis. Preoperatively a standardized form which included data regarding the patient’s history of sickness was obtained and a physical examination was performed.

Postoperatively a final diagnose was made based on microbiological testing, which in addition to routine culture, included sonication of the prosthesis and nucleic acid based diagnostics (PCR). Data from the preoperative examination was evaluated in relation to the final diagnose (chi-square test and Student’s t-test), and the sensitivity and specificity for diagnosing a septic loosening was calculated for each preoperative finding.

Results: According to the final diagnose, 21 patients had a septic loosening and 33 patients had an aseptic loosening. In the septic group and aseptic group the following anamnestic data was registered: Pain during rest: 16/21 vs. 7/33 (p < 0.001). Prior history of soft tissue debridement: 11/21 vs. 4/33 (p = 0.001). Prior prosthetic revision surgery: 13/21 vs. 8/33 (p = 0.006). Time from index operation to revision: 45 (5 – 144) moths vs. 159 (22–390) moths, (p = 0.02). Time from index operation to debut of prosthetic assosiated dyscomfort: 10 (0–110) moths vs. 120 (0–240) moths, (p < 0.001). The calculated sensitivity (se) and spesifisity (sp) for the pre-operative findings were: Existence of prosthetic related pain during rest: 79% se, 79% sp; history of soft tissue revision in the affected joint 52% se, 88% sp; history of prior exchange prosthetic revision in the affected joint 62% se, 76% sp, respectively.

Conclusion: We advise a carefully obtained history from every patient presenting with loosening of implanted prosthetic components for identification of a potential low grade infection. In particular, pain during rest has a notable sensitivity and specificity. A prior history of soft tissue revision also strongly indicates a septic prosthetic loosening.