Formation of a pseudotumor in total hip arthroplasty using a tribological metal-polyethylene pair / Formação de pseudotumor na artroplastia total do quadril com par tribológico metal-polietileno

The aim here was to report a case of a young adult patient who evolved with tumor formation in the left thigh, 14 years after revision surgery on hip arthroplasty. Davies in 2005 made the first description of this disease in patients undergoing metal-on-metal hip arthroplasty. Over the last decade, however, pseudotumors around metal-on-polyethylene surfaces have become more prevalent. Our patient presented with increased volume of the left thigh 8 years after hip arthroplasty revision surgery. Two years before the arising of the tumor in the thigh, a nodule in the inguinal region was investigated to rule out a malignant neoplastic process, but the results were inconclusive. The main preoperative complaints were pain, functional limitation and marked reduction in the range of motion of the left hip. Plain radiographs showed loosening of acetabular and femoral, and a large mass between the muscle planes was revealed through magnetic resonance imaging of the left thigh. The surgical procedure consisted of resection of the lesion and removal of the components through lateral approach. In respect of total hip arthroplasty, pseudotumors are benign neoplasms in which the bearing surface consists of metal-on-metal, but they can also occur in different tribological pairs, as presented in this case.

Relatar o caso de um paciente adulto jovem que evoluiu com tumoração na coxa esquerda após 14 anos de uma cirurgia de revisão de artroplastia do quadril. Davies em 2005 descreveu esta afecção em pacientes submetidos a atroplastia de quadril com par tribológico metal-metal, mas na última década é possível achar relatos de pseudotumores em superfície metal-polietileno. O paciente iniciou queixa de aumento de volume da coxa esquerda após oito anos da cirurgia de revisão da artroplastia do quadril. Dois anos antes do aparecimento da tumoração da coxa, a investigação para descartar um processo neoplásico maligno de um nódulo em região inguinal foi inconclusiva. Suas principais queixas pré-operatórias eram dor, limitação funcional e marcada redução da amplitude de movimento do quadril esquerdo. As radiografias do membro acometido evidenciavam soltura dos componentes acetabular e femoral, e uma grande massa entre os planos musculares se revelou à ressonância magnética da coxa esquerda. A abordagem cirúrgica consistiu de ressecção intralesional da coxa esquerda, seguida da retirada dos componentes pela via lateral direta. No âmbito da cirurgia de artroplastia de quadril, os pseudotumores são neoplasias benignas cujo par tribológico consiste em metal -metal, mas podem também ocorrer em diferentes pares tribológicos, como neste caso.

An in vitro comparison of nickel and chromium release from brackets

This study aimed at comparing amounts of nickel (Ni) and chromium (Cr) released from brackets from different manufacturers in simulated oral environments. 280 brackets were equally divided into 7 groups according to manufacturer. 6 groups of brackets were stainless steel, and 1 group of brackets was made of a cobalt-chromium alloy with low Ni content (0.5 percent). International standard ISO 10271/2001 was applied to provide test methods. Each bracket was immersed in 0.5 ml of synthetic saliva (SS) or artificial plaque fluid (PF) over a period of 28 days at 37ºC. Solutions were replaced every 7 days, and were analyzed by spectrometry. The Kruskal-Wallis test was applied. Amounts of Ni release in SS (µg L-1 per week) varied between groups from "bellow detection limits" to 694, and from 49 to 5,948.5 in PF. The group of brackets made of cobalt-chromium alloy, with the least nickel content, did not release the least amounts of Ni. Amounts of Cr detected in SS and in PF (µg L-1 per week) were from 1 to 10.4 and from 50.5 to 8,225, respectively. It was therefore concluded that brackets from different manufacturers present different corrosion behavior. Further studies are necessary to determine clinical implications of the findings.