Shape memory staples have several uses in both hand and foot and ankle surgery. There is relatively little data available regarding the biomechanical properties of staples, in terms of both the compression achieved and potential decay of mechanical advantage with time. An understanding of these properties is therefore important for the surgeon. Two blocks of synthetic polyurethane mimicking properties of cancellous bone were fixed in jigs to both the actuator and 6 degree-of-freedom load cell of an MTS servohydraulic testing machine. With the displacement between the blocks held constant the peak value and subsequent decay in compressive force applied by both the smooth and barbed version of the nitinol OSStaple (Biomedical Enterprises), Easyclip (LMT), Herbert
Introduction. Uncemented press-fit cups provide bone fixation in primary total hip replacement (THR). However, sometimes screws are needed to achieve primary stability of the socket. We analyzed biomechanical factors related to press-fit in seven cup designs and assessed whether screw use provides similar loosening rates to those of the press-fit technique. Materials y Methods. From a series of 1,350 primary uncemented THRs using seven different press-fit cup designs (a dome loading hemispheric cup and bi- or tri- radius cups), we only analyzed the 889 diagnosed of primary osteoarthritis. All cases were operated by the same surgical team. The use of screws was decided intraoperatively based on cup stability according to the pull-out test. There were 399 female and 490 male patients with a mean age of 65 years old. The mean follow-up was 8.6 years (5–13 years). The reconstruction of the hip rotation center was evaluated according to Ranawat. Results. Screws were required in 223 (25.1%) of the surgeries: 35% of all dome-loaded cups and less frequently with other cup designs (range 18%-24%) (p<0.001) All hips showed good clinical results and radiological
