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Show SPRING 2013 °™PS°nS) "' s^JsH ibe sliding V kd \" >oth bearing surface (Fig. 2). and the friction cocflki RESULTS The prendre pix.y.t) in the bearing between the tibial inse the textured femoral component is simulated ujiri; iiKompreuiblc two-dimensional Reynold* equation: Hf,y,ty local pacing height between the bearing surface* Wff. relative sliding velocity between the bearing surfaces ^efficient for the textured and smooth (average roughness SC ira per ISO 7206-2) CoCr cylinders is shown in Fig. 9: > A sharp drop in the normalized friction coefficient after the compared to the smooth CoCr cylinder (e.g. green circles). implants CONCLUSIONS hydrodynamic lubrication is established earlier i the cycle, Dt a lower sliding speed, and thus maintained over a larger portion of the gail cycle <• It is especially important that the texture reduci friction during the start and stop phases becau; daily h u m a n hip joint activities include frequei starts/stops, and it is during those typically higl friction periods that most wear tends to occur. FUTURE RESEARCH In future research, the patterned microte: be optimized in terms of maximizing pressure using the model discussed. experiments will validate the model, am proof of friction reduction over the entin cycle resulting from microtexture. 10 More than 200,000 total hip replacement (THR) surgeries are performed in the US each year. Presently, the statistical survivorship of these implants declines dramatically after 10 years of use [1 ]. This lack of durability has unacceptable effects, such as riskier revision surgery [2,3] or surgery postponement with its attendant pain and disability, which are rooted in the same cause: wear. Even short term wear can cause inflammatory reaction, tissue necrosis, osteolysis, and instability caused by wear debris [4]. This research focuses on the metal-on-polyethyl-ene (MOP) bearing type, which is most commonly used in the US. The current engineering paradigm for femoral head design is to manufacture ever smoother surfaces. This research aims to break this paradigm and attempts to achieve hydrodynamic lubrication in M O P hips using surface microtextur-ing. Our results suggest that with the microtexture, hydrodynamic lubrication is established earlier in the gait cycle, at a lower sliding speed, and thus is maintained over a larger portion of the reciprocating sliding cycle. This first prototype texture design demonstrates that reducing M O P hip wear using a microtextured femoral head is indeed feasible. [ CONTACT: bart.raeymaekers@utah.edu ) IMPROVING HIP IMPLANT DURABILITY BY MEANS OF MICRO-TEXTURED SURFACES Anthony Chyr (Bart Raeymaekers) Department of Mechanical Engineering University of Utah |