In vitro investigation of friction under edge‐loading conditions for ceramic‐on‐ceramic total hip prosthesis

Abstract

Edge-loading generates higher wear rates in ceramic-on-ceramic total hip prosthesis (THP). To investigate the friction coefficient (FC) in these conditions, three alumina ceramic (Biolox Forte) 32 mm-diameter components were tested using a hip friction simulator. The cup was positioned with a 758 abduction angle to achieve edge-loading conditions. The motion was first applied along the edge and then across the edge of the cup. First, tests were conducted under lubricated conditions with 25% bovine serum. Next, to simulate an extremely high contact pressure, the tests were run with the addition of a third body alumina ceramic chip inserted between the edge of the cup and the head. Engineering blue was used to analyze the contact area. Reference values were determined using a 08 cup abduction angle. Edge loading was achieved. The FC increased by three-to sixfold when the motion was applied along the edge, and by 70% when the motion was applied across the edge. However, the FC value was still low (about 0.1), which is similar to metal-on-metal THP. With the third body alumina ceramic particle inserted, the FC was 26 times higher than in the ideal conditions and intermittent squeaking occurred. High cup abduction angles may generate edge-loading and an increase in the friction coefficient for ceramic THP. Keywords: friction coefficient; ceramic; hip prosthesis; edge loading; squeaking Ceramic-on-ceramic retrievals from total hip prostheses (THP) show higher wear rates than those predicted on simulators under normal conditions. 1 This discrepancy is related to edge loading that can occur clinically due to lateralization (microseparation) of the femoral head relative to the acetabular cup, causing a localized increase in stress and wear. Although a number of experimental wear simulator studies have been conducted that reproduce edge loading under microseparation conditions, the general tribological mechanism under this adverse condition is unclear. Friction levels, for example, have not been reported under these edgeloading conditions. We hypothesized that the friction coefficient (FC) increases under edge-loading conditions. A study to test such an hypothesis is important as it may assist in the understanding of clinical hip noises such as squeaking. 2,3 In addition, FC values are needed to develop computational models of contact mechanics and wear prediction under edge loading conditions, which can help improve implant design. Our goals were to determine the FC under edge loading for alumina ceramic-on-ceramic THP and to investigate the effect of the addition of alumina debris on the FC and the generation of squeaking. MATERIALS AND METHODS SpecimensThree Biolox Forte heads and liners were tested on the Leeds PROSIM 1 friction simulator. The components had a diameter of 32 mm, with a radial clearance of 30 mm. All specimens were manufactured by Ceramtec (Plochingen, Germany). Before testing, specimens were cleaned with a washing-up liquid, rinsed in water, and then ultrasonically cleaned in an isopropanol ...

What Factors Affect Posterior Dislocation Distance in THA?

“…The negative PHDD values indicate that the posterior wall of the resurfacing cup was medial to the head center, implying a risk for edge loading during chair rise with low inclination angles. There have been several reports of high cup inclination angles leading to edge loading and increased wear of metal-on-metal hip arthroplasties [17,27,30,32,41,49]. Based on the present study, it also appears that excessively closed cup positions may also lead to negative wear characteristics.…”

“…Many basic science [3,11,14,16,41] and clinical studies [8, 13-15, 29, 37, 42-45] support the notion that larger head sizes correlate with increased jump distance and therefore decrease THA dislocation risk. For example, in one of the first cadaver studies on this topic by the Harris Orthopaedic Laboratory, 36-mm heads had decreased dislocation rates compared with 26-and 32-mm heads, which was attributed solely to jump distance [11].…”

“…When evaluating jump distance, most studies have used purely mathematical techniques for assessments in either two or three dimensions coupled with characterization of typically one other factor such as acetabular abduction angle or head size [14,41]. Recently, Sariali et al [41] evaluated lateral jump distance according to implant characteristics, increasing head size, and head offset as well as a function of cup anteversion and abduction angle.…”

“…Recently, Sariali et al [41] evaluated lateral jump distance according to implant characteristics, increasing head size, and head offset as well as a function of cup anteversion and abduction angle. They found that the jump distance decreased as cup abduction angles increased and increased with increasing anteversion angles.…”

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