The dual mobility cup was introduced in the 1970s to allow extensive range of motion associated with great stability thanks to double articulation; the first between the head and polyethylene, the second between the polyethylene and the cup. The original plan was to install a stainless-steel uncemented cup coated with a thin layer of alumina and a metal head of 22,2 mm with a polyethylene liner of first generation. Long term follow-up case studies are cited in the literature showing excellent results in reducing dislocations; however wearing and aseptic loosening are noted. The new dual-mobility cups, with reticular polyethylene and titanium and hydroxyapatite coating are proving as reliable as the older ones in terms of stability whilst they appear to be more durable. Furthermore, cemented dual-mobility cups are available, these are the topic of this study. One of the most frequent complications in the major revisions of hip replacement is dislocation. This study summarises our experience gathered in the use of dual-mobility cups during revisions of complex cases (GIR III-IV femoral or acetabular). Between July 2014 to March 2015, we have implanted 13 cemented cups with dual-mobility (Avantage® Biomet) each in different patients, who have undergone revision with severe ostheolysis (GIR III-IV femoral or acetabular). The mean age of patients was 71.5 years old (46 to 89). Indications for revisions were: aseptic loosening in 7 patients (two at third surgery), recurrent dislocation in 3 patients, 1 septic loosening, 1 revision after spacer removal e 1 post-traumatic. We used dual-mobility cup in revision surgery when implant stability could have been compromised due to difficult positioning of acetabular component in cases of walls defects or muscolar laxity. The patients have been evaluated clinically and radiographically.Introduction
Materials and Methods
Periprosthetic joint infection (PJI) is considered one of the most feared causes of implant failure, due to the difficulty in formulating a proper and timely diagnosis. In the diagnostic workup are often used test with a low specificity, such as the dosage of ESR and CRP, or sensitivity, such as cultures or the leukocyte count of the synovial fluid. Radiological investigations are expensive and unreliable to play a direct role in the diagnosis of PJI. The alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens and it is an ideal biomarker for the diagnosis of PJI. It is now possible to verify the presence of alpha-defensin in periprosthetic synovial fluid with an ELISA (Synovasure® PJI, Zimmer) that provides results in 10 minutes, with a sensitivity of 97% and a specificity of 96%, without being affected by systemic inflammatory diseases or by the assumption of antibiotics. The purpose of this study is to assess the applicability and reliability of Synovasure® PJI, correlating its results with microbiological analyzes, laboratory tests and imaging studies of the patient. Patients recruited are those who have undergone a previous total hip or knee arthroplasty where there is suspicion of PJI. The test can be performed either during surgery or during the diagnostic iter, through the execution of an arthrocentesis. The synovial fluid is partly used for Synovasure® PJI and partly put in culture for microbiological analyzes. Once ready, culture results are compared with the results of the test to get a confirmation of its reliability or reference to identify the microorganism responsible for PJI. These data are then compared, with laboratory tests and radiological investigations performed by the patient.Introduction
Materials and Methods
