Sborník vědeckých prací Vysoké školy báňské – Technické univerzity Ostrava číslo 1, rok 2008, ročník LI, řada hutnická článek č. 1386 160 MODELLING OF THE NEEDLE-PALISADE FIXATION SYSTEM FOR THE TOTAL HIP RESURFACING ARTHROPLASTY ENDOPROSTHESIS J. MIELNICZUK 1 , P. ROGALA 2 , R. UKLEJEWSKI 3 , M. WINIECKI 3 *, G. JOKŚ 1 , A. AUGUŚCIŃSKI 1 , M. BERDYCHOWSKI 1 1 Chair of Fundamentals of Machine Design, Poznan University of Technology, Poznań, Poland 2 Department of Spine Surgery, Orthopaedics and Traumatology, Poznan University of Medical Sciences, Poznań, Poland 3 *Department of Fundamentals of Medical Bioengineering, Institute of Technology, Kazimierz Wielki University of Bydgoszcz, Bydgoszcz, Poland, winiecki@ukw.edu.pl ABSTRACT: In this paper there is presented the geometrical model of the endoprosthesis with needle-palisade fixation system for minimal invasive total hip resurfacing arthroplasty (THRA) corresponding with the concept and assumptions of the Rogala’s patent [16, 17], also presented in papers [14, 15]. The most advantageous needle-palisade fixation system variant according to adhesive properties optimization is here under discussion. Authors also present early pre-prototypes of the endoprosthesis manufactured by CNC Controlled Electrical Discharge Machining and Selective Laser Melting with discussion about the technological possibilities for the further endoprosthesis prototypes manufacturing. KEY WORDS: joint replacement, bone-implant fixation, low invasive arthroplasty 1. INTRODUCTION The total hip resurfacing arthroplasty concept (THRA) is the epiphyseal cancellous bone preserving alternative to commonly used long stem total hip replacement (THR). It restores normal joint biomechanics and close-to-natural load transfer ensuring artificial joint stability. During the traditional THR with the long stem endoprosthesis (Fig. 1a) the head and neck of the femur are removed. To the femur cavity there is inserted the metallic stem while the cup is placed into the socket in pelvis which has been reamed to shape. Both components of endoprosthesis are bonded to surrounding bone by either bone tissue in-growth or with polymer cement. The high invasiveness of traditional endoprosthesis leads to non-physiological load transfer (stress shielding phenomenon) resulting in bone atrophy and extensive destruction of surrounding bone tissue (Fig. 1b). a) b) Fig. 1: a) Traditional long-stem hip endoprosthesis; b) the roentgenogram showing the destruction in femoral bone with bone resorption caused by the stress shielding phenomenon