Intraoperative femur fracture during non-cemented total hip arthroplasty: The effect of cerclage wiring technique on micromotion

Abstract

INTRAOPERATIVE FEMUR FRACTURE DURING NON-CEMENTED TOTAL HIP ARTHROPLASTY: THE EFFECT OF CERCLAGE WIRING TECHNIQUE ON MICROMOTION Steven H. Elder, John J. Callaghan, and Thomas D. Brown Orthopaedic Biomechanics Lab, University of Iowa, Iowa City, IA 52242 Intraoperative fracture is not uncommon during non-cemented total hip arthroplasty, and the role of cerclage wiring in management of these fractures is controversial. The purpose of this study was to investigate the efficacy of cerclage wiring for component stabilization, given the occurence of a typical anteromedial longitudinal fracture. An intraoperative fracture was simulated by a saw cut in seven cadaver femurs implanted with a Harris-Galante porous ingrowth component. Three treatment options were studied: 1) fracture cerclage wired with prosthesis in place, 2) prosthesis removal followed by wiring prior to prosthesis reinsertion, and 3) non-wired. Prostheses were loaded through a simulated hemipelvis mounted in an MTS servohydraulic testing machine. The three dimensional micromotion of the prosthesis relative to bone was measured using an array of seven liquid metal strain gages. There were no statistically significant differences among the three treatment options with respect to micromotion. Cerclage wiring did limit micromotion in some cases , and thus may be important for keeping interface motion below the threshold for bone ingrowth. Furthermore, cerclage wiring is certainly a deterrent to crack propagation. Overall, however, it appears that cerclage wiring is relatively ineffective in reducing micromotion, and that the choice between in-place versus pre-reinsertion wiring techniques is of little consequence. A Technique to Measure Relative Motion Between Two Rigid Bodies with Application to Implanted Femoral Prosthetic Components Alan Litsky, MD, ScD; Andrew Ryan, MD; Thomas Hickey, BS’; Douglas Mackay, BS Orthopaedic BioMaterials Laboratory and *Department of Chemistry The Ohio State University, Columbus, Ohio 43210, USA A new technique and device are described for measuring the relative motion between two rigid bodies. The first rigid body is immobilely fixed to the testing apparatus while the mobile second rigid body is connected to a frame which serves as an antenna to amplify relative motion. The points of the frame are known in a global coordinate system, and points on the second rigid body are known in a local coordinate system. By converting from local to global coordinates, the motion of points on the second body can be determined to the same accuracy that motion of points on the frame can be measured in the global coordinate system. In our first application of this technique, a femoral prosthesis is implanted into a composite artificial femur, and motion of the prosthesisframe unit is measured by LVDT’s with accuracy on the order of 50 microns. FLOW STUDIES ON ATRIOPULMONARY AND CAVOPULMONARY CONNECTIONS OF THE FONTAN OPERATIONS FOR TRICUSPID ATRESIA H.T.Low, Y.T.Chew and C.N.Lee* Mechanical and Production Engineering Department. National University of Singapore *Cardiac Department, National University Hospital Two main types of Fontan operations are performed as treatment for tricuspid astresia. The atriopulmonary connection is performed by anastomising the right atrium with the pulmonary artery, bypassing the right ventricle. In the cavopulmonary connection, both the superior and inferior vena cavae are anastomised with the pulmonary artery, bypassing the right atrium. The objective of the present paper is to investigate the pressure and power loss coefficients of in-vitro models of these two surgical connections. The study will be conducted at steady flow rates of 3 to 9 l/m using glycerol solution. The results show that the pressure loss from the vena cavae to the pulmonary artery is generally much lower in the cavopulmonary connection. The additional losses in the atriopulmonary connection are attributed to the sudden flow-area enlargement in the atrium and the larger dynamic pressure from the atrium. The lower flow losses in the cavopulmonary connection is also reflected as a lower power loss coefficient.