1350 THE BONE & JOINT JOURNAL  HIP Quantification of material loss from the neck piece taper junctions of a bimodular primary hip prosthesis. A retrieval study from 27 failed Rejuvenate bimodular hip arthroplasties D. Buente, G. Huber, N. Bishop, M. Morlock From TUHH Hamburg University of Technology, Hamburg, Germany  D. Buente, Dipl.-Ing., Research Assistant  G. Huber, Dr.-Ing., Senior Researcher  M. Morlock, Prof Dr.-Ing. habil., PhD, Professor TUHH Hamburg University of Technology, Denickestraße 15, 21073 Hamburg, Germany.  N. Bishop, Prof Dr-Ing. habil., Professor Hamburg University of Applied Sciences, Ulmenliet 20, 21033 Hamburg, Germany. Correspondence should be sent to Mr D. Buente; e-mail: dennis.buente@tuhh.de ©2015 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.97B10. 35342 $2.00 Bone Joint J 2015;97-B:1350–7. Received 28 October 2014; Accepted after revision 5 June 2015 The early failure and revision of bimodular primary total hip arthroplasty prostheses requires the identification of the risk factors for material loss and wear at the taper junctions through taper wear analysis. Deviations in taper geometries between revised and pristine modular neck tapers were determined using high resolution tactile measurements. A new algorithm was developed and validated to allow the quantitative analysis of material loss, complementing the standard visual inspection currently used. The algorithm was applied to a sample of 27 retrievals (in situ from 2.9 to 38.1 months) of the withdrawn Rejuvenate modular prosthesis. The mean wear volumes on the flat distal neck piece taper was 3.35 mm 3 (0.55 to 7.57), mainly occurring in a characteristic pattern in areas with high mechanical loading. Wear volume tended to increase with time to revision (r² = 0.423, p = 0.001). Implant and patient specific data (offset, stem size, patient’s mass, age and body mass index) did not correlate with the amount of material loss observed (p > 0.078). Bilaterally revised implants showed higher amounts of combined total material loss and similar wear patterns on both sides. The consistent wear pattern found in this study has not been reported previously, suggesting that the device design and materials are associated with the failure of this prosthesis. Cite this article: Bone Joint J 2015;97-B:1350–7. The risk of early revision of primary bimodular total hip arthroplasty prostheses with modular necks has been identified as a significant clini- cal problem. High early failure rates have resulted in the withdrawal of certain designs from clinical use. 1 Several studies have reported corrosion and wear at modular neck taper junctions, leading either to implant frac- ture (mostly in titanium alloy combinations) 2 or elevation of serum cobalt (Co) and chro- mium (Cr) ion concentrations arising from implantation of prostheses with a combination of titanium and CoCr components. 3-7 The sys- temic release of Co and Cr ions can be associ- ated with adverse tissue reactions, causing symptoms such as severe pain, soft-tissue necrosis or pseudo-tumour formation. 3,8,9 The explanation for differing concentrations of metal ions and the relationship with symptoms are unclear. 10 Co and Cr ion production can result from material loss from any interface of the CoCr components of the implant system. In the case of the Rejuvenate prosthesis (Stryker Ortho- paedics, Mahwah, New Jersey), the modular neck was the common CoCr component in all cases studied requiring revision (Fig. 1). Increased Co and Cr levels have been associ- ated with early clinical failure and revision with this design. In the literature the time to revision has varied between 15.2 months and 32.4 months. 4-6 Presently, the amount of taper corrosion from non-circular tapers is evaluated using the qualitative Goldberg or Cook scales, which are based on visual estimations and analyses. 11 The amount of material loss is not reflected well by these scores. 12 This method also does not quantify the risk to which patients might be exposed from released ionic CoCr. 13 A method of quantifying the amount of material lost from the implant interfaces and the ability to correlate with clinical outcome is desirable. The aim of this study was to develop a method to quantify wear of non-circular tapers, and to apply it to a cohort of retrievals from one specific bimodular primary hip arthroplasty design, the Rejuvenate prosthesis. Materials and Methods Measurement method. All prostheses were cleaned in an ultrasound bath (Elmasonic P, Elma, Singen, Germany) using soap (Edisonite 5%) and a tooth brush, for mechanical