According to American Joint Replacement Registry, particle mediated osteolysis represents 13 % of the knee revision surgeries performed in the United States. The comprehension of mechanical and wear properties of materials envisioned for TJR is a key step in product development. Furthermore, the maintenance of UHMWPE mechanical properties after material modification is an important aspect of material success. Initial studies conducted by our research group demonstrated that the incorporation of ibuprofen in UHMWPE had a minor impact on UHMWPE physicochemical and mechanical properties. Drug release was also evaluated and resulted in an interesting profile as a material to be used as an anti-inflammatory system. Therefore, the present study investigated the effect of drug release on the mechanical and biological properties of ibuprofen-loaded UHMWPE. UHMWPE resin GUR 1020 from Ticona was for sample preparation. Samples with drug concentrations of 3% and 5% wt were consolidated as well as samples without anti-inflammatory addition through compression molding at 150 °C and 5 MPa for 15 minutes. Mechanical properties were evaluated via the tensile strength experiment (ASTM D638) and dynamic mechanic tests. Wear resistance was measured using the pin on disc (POD) apparatus. Finally, cytotoxicity analysis was conducted based on ISO 10993–5.Introduction
Experimental
Shoulder arthroplasty has been performed by many years for the treatment of several conditions such as osteoarthritis, umeral head avascular necrosis and proximal umeral fractures following traumas. Surgical site infection (SSI) following shoulder arthroplasty remains a challenge, which increases morbidity including reoperations, implant removal, poor mobility, and raises extra medical costs. Identification of risk factors may help implementing adequate strategies to prevent infection. We aim to identify pre- and intra-operative risk factors associated with deep infections in shoulder arthroplasty. An age and sex-matched case control study was conducted to describe the prevalence rate, clinical and microbiological findings and to evaluate patient and surgical risk factors for shoulder arthroplasty-associated infections (SAIs), among 158 patients who underwent shoulder replacement surgery due to any reason, from 1988 to 2011 at a tertiary public university institution. To evaluate risk factors from SAI we performed uni- and multivariate analysis by multiple logistic regression. We analyzed 168 prosthetic shoulder replacement surgeries from 158 patients, with an overall infection rate of 9.5%, (16/168 cases). Gram-positive cocci and Gran-negative bacilli were equally isolated in 50% of cases, however the most common bacteria detected (18.8%) was Pseudomonas aeruginosa. Univariate analysis identified neither specific comorbidity nor pre-operative risk factors, but American Society of Anesthesiologists (ASA) score higher than 2 (odds ratio [OR] = 5.30, 95% confidence interval [CI] = 1.58 to 17.79; p=0,013) to be significant preoperative patient-related predisposing factor for SAI. On univariate analysis, the only surgery-related factor significantly associated with higher risk of SAIs was the presence of surgical haematoma (OR = 7.1, 95% CI = 1.1 to 46; p=0.04). On multivariate analysis ASA score higher than two (OR = 4.7, 95% CI = 1.3 to 16.9; p=0.01) was the only independent predictor for periprosthetic shoulder infection. This study identified unusual pathogens and confirmed previously patient-related known factors such as higher ASA score that predispose to SAIs.
The problem of retained drain fragments is a well known but under reported complication in the literature. The authors present the case of a 66 years old male, who suffered a right distal humerus fracture luxation six years ago that was treated conservatively. He went to the emergency service with fever and right elbow purulent drainage. Physical examination showed deformity, swelling and fluctuation of the right elbow with purulent drainage through cutaneous fistula. The x-ray showed instable inveterate pseudarthrosis of the distal humerus. Leucocytosis and neutrophylia with increased CRP were presente in the blood tests and the patient started empiric treatment with Ceftiaxone IV. A MRSA was isolated in cultural exam of the exsudate, and a six weeks treatment with Vancomycin IV was iniciated. Exhaustive surgical cleaning was performed and two plastic foreing bodies (fragmented drains) were removed. At the time of discharge the patient was afebrile, with normal analytical parameters and negative culture tests. The orthopaedic surgeon should considerate the presence of a foreign body in patients with infected abcess and traumatic or surgery previous history.
