ABSTRACT Purposes: Shoulder arthroplasty (SA) has been performed by many years for the treatment of several conditions, including osteoarthritis and proximal humeral fractures following trauma. Surgical site infection (SSI) following Shoulder arthroplasty remains a challenge, contributing to increased morbidity and costs. Identification of risk factors may help implementing adequate strategies to prevent infection. We aimed to identify pre- and intra-operative risk factors associated with deep infections after Shoulder arthroplasty. Methods: An unmatched case-control study was conducted to describe the prevalence, clinical and microbiological findings, and to evaluate patient and surgical risk factors for prosthetic shoulder infection (PSI), among 158 patients who underwent SA due to any reason, at a tertiary public university institution. Risk factors for PSI was assessed by uni- and multivariate analyses using multiple logistic regression. Results: 168 SA from 158 patients were analyzed, with an overall infection rate of 9.5% (16/168 cases). Subjects undergoing SA with American Society of Anesthesiologists (ASA) grade III or higher (odds ratio [OR] = 5.30, 95% confidence interval [CI] = 1.58-17.79, p < 0.013) and presenting local hematoma after surgery (odds ratio [OR] = 7.10, 95% confidence interval [CI] = 1.09-46.09, p = 0.04) had higher risk for PSI on univariate analysis. However, only ASA score grade III or higher remained significant on multivariate analysis (OR = 4.74, 95% CI = 1.33-16.92, p = 0.016). Gram-positive cocci and Gram-negative bacilli were equally isolated in 50% of cases; however, the most commonly detected bacterium was Pseudomonas aeruginosa (18.7%). Conclusion: This study provides evidence suggesting that patient-related known factors such as higher ASA score predisposes to shoulder arthroplasty-associated infection. Furthermore, unusual pathogens associated with PSI were identified.

OBJETIVO: Desenvolver uma porca para fixação óssea (PFO) com o objetivo de aumentar a estabilidade da osteossíntese interna. MÉTODOS: Foram utilizados 16 cadáveres frescos (32 extremidades proximais do úmero), sendo oito masculinos e oito femininos, com média de idade de 60,56 anos. Em cada um dos 16 cadáveres, o úmero de um dos braços foi fixado com sistema de placa-parafuso-PFO e o contralateral, com o sistema placa-parafuso-porca de metal convencional. Foi aplicada uma força sobre os sistemas, medida por meio de torquímetro, até que um dos elementos falhasse (porca de polietileno, porca convencional ou osso). Depois, foi medida a força usada individualmente por 20 ortopedistas para apertar parafusos até que acreditassem que o sistema podia ser considerado como estável. Todos os resultados foram anotados e avaliados estatisticamente. RESULTADOS: Na avaliação da força média utilizada para aperto de parafusos, nas fixações rotineiras, individualmente, por 20 ortopedistas experientes, registrou-se a força média de 3,18N.m, força esta inferior à resistência do sistema placa-parafuso-PFO, que foi de 6,37N.m. A falha do sistema no osso com a PFO ocorreu em três casos e do sistema no osso com a porca de metal, em 10. CONCLUSÃO: A porca PFO mostrou-se menos agressiva ao osso que a porca metálica convencional, apresentando menor índice de fratura no osso. A força média aplicada pelo ortopedista não é capaz de quebrar a porca e levar a falha do sistema.

OBJECTIVE: To develop a bone fixation nut (PFO) for the purpose of increasing the internal osteosynthesis stability. METHODS: 16 fresh cadavers were used (32 proximal humeral extremities), eight male and eight female, mean age of 60.56 years. In each of the 16 cadavers, the humerus of one of the arms was fixated with a PFO-plate-screw system, and the contralateral was fixated with the plate-screw-nut system made of conventional metal. A load was applied on the system and measured by a torquemeter till one of the elements failed (polyethylene nut, conventional nut, or bone). The load individually used by 20 orthopedists to tighten the screws till the point they believed that the system was stable was measured. All of the results were noted down and statistically evaluated. RESULTS: In the evaluation of the mean load used to tighten the screws, in routine fixations, individually, by 20 experienced orthopedists, a mean load of 3.18 N.m was found, this load being lower than the strength of the PFO-plate-screw system, that was 6.37 N.m. Failure of the system in the bone with the PFO occurred in three cases and failure of the system with the metal nut occurred in 10 cases. CONCLUSION: The PFO nut showed to be less aggressive to the bone than the conventional metal nut, and presented a lower incidence of bone fracture. The mean load applied by the orthopedist is not sufficient to break the nut and lead to a system failure.