Wear at the taper‐trunnion junction of contemporary ceramic‐on‐ceramic hips shown in a multistation hip simulator

Abstract

Ceramic-on-ceramic (CoC) total hip replacements (THR) have a substantially lower wear rate than metal-on-polyethylene (MoP) hips, as shown by hip simulator testing. However, the revision rates of CoC and MoP hips are comparable. To try and explain this discrepancy the wear, at both the bearing surfaces and taper-trunnion interface of 36 mm BIOLOXdelta CoC THRs, mounted on 12/14 titanium (Ti6Al4V) trunnions was investigated using a hip simulator (n = 3) and a dynamically loaded CoC sample in a separate test station. Wear was assessed gravimetrically and surface roughness measurements of the articulating and taper surfaces taken at regular intervals. Scanning electron microscopy, surface roughness, and gravimetric measurements of trunnions was performed. After 5 million cycles, the mean total wear from the ceramic articulating surfaces was 0.25 mm from the hip simulator test, and that from the titanium trunnions was 0.29 mm . This metal wear may provide an explanation for adverse reaction to metal debris found in contemporary CoC hip joints. It is therefore vital to consider taper-trunnion wear in preclinical testing of artificial hip joints. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B, 2018.

Hip simulator testing of the taper‐trunnion junction and bearing surfaces of contemporary metal‐on‐cross‐linked‐polyethylene hip prostheses

“…We feel that a second factor is the material combination involved at the bearing surfaces. A polymeric liner might serve to “soften the blow” of peak forces during gait and other activities, compared with a “hard‐on‐hard” material combination such as MoM. Third, Hothi et al found significantly less material loss from the taper‐trunnion junctions of retrieved MoP THRs compared with MoM THRs of the same design .…”

“…The impaction force applied during the assembly of the femoral head on the trunnion and the number of impactions were not measured during this current hip simulator test. However, the same author (RMB) carried out all impactions as per a previously used technique . Additionally, surface roughness of the trunnion was not measured as we were guided by previous retrieval studies, which show that the material loss arises mainly from the CoCrMo alloy femoral tapers rather than the Ti alloy trunnion, when CoCrMo/Ti alloy combinations are used for the taper‐trunnion junction.…”

“…Although the hip simulator had six test stations, only five were used in this wear test. All test specimens were subject to time‐varying double‐peak load with a minimum load value 400 N and a maximum load value 2000 N and relative articulating motion, generating an elliptical wear path . The articulating motion of the simulator comprised of sinusoidal flexion‐extension and abduction‐adduction with the excursions of 46° and 12°, respectively.…”

“…Fixation of the femoral head onto the trunnion was carried out by impacting a minimum of two firm blows in an axial direction in dry conditions, replicating surgical scenarios. All impactions were carried out using a previously published methodology . The estimated impaction force was 4–5 kN, based on separate measurements undertaken on CeramTec equipment.…”

“…Three‐dimensional (3D) surface roughness (Sa) of articulating bearing surfaces and the femoral tapers was measured using a noncontacting Zygo NewView 5000 white light interferometer . On each articulating specimen, 10 pre‐and 10 postwear test Sa measurements were acquired using the 10× objective lens and 2.0× manual zoom (area of view 317 μm × 238 μm).…”