RESUMO
PURPOSE: The purpose of this study is to evaluate the rate and direction of subsidence that occurred after anterior cervical discectomy and fusion using the polyetheretherketone (PEEK) cage and to analyze the risk factors of subsidence. MATERIALS AND METHODS: Thirty two patients (36 segments) who underwent anterior cervical discectomy and fusion using the PEEK cage and autologous cancellous iliac bone graft from July 2003 to November 2011 were enrolled in this study. anterior segmental height (ASH), posterior segmental height (PSH) and cage corner distance (CCD) were measured on plain radiographs. Subsidence was defined as > or =2 mm decrease in the average of ASH and PSH at the final follow up compared to that measured in the immediate postoperative period. A decrease of more than 3 mm was defined as severe subsidence for further statistical analysis. RESULTS: Subsidence of more than 2 mm was observed in 14 segments (38.9%) and severe subsidence (> or =3 mm) was observed in seven segments (19.4%). The direction of subsidence was examined by comparison of means of decreased ASH and PSH and anterior subsidence outweighed posterior subsidence (p<0.001). Examination of CCD showed that inferior subsidence was more frequent than superior subsidence (p<0.001, p=0.047). Among the suspicious risk factors for subsidence, intraoperative disc space distraction (anterior distraction: p=0.031, posterior distraction: p=0.007) and height of inserted cage (p=0.032) showed statistical significance. CONCLUSION: Considerable incidence of subsidence was observed after use of the cage. Using a cage of appropriate height and prevention of intraoperative over-distraction of disc space will be helpful to prevention of subsidence of the cage after anterior cervical discectomy and fusion using the PEEK cage.