A Multicenter Retrieval Study of the Taper Interfaces of Modular Hip Prostheses

Proximal Component Modularity in THA—At What Cost?: An Implant Retrieval Study

“…The patient demographics, time in situ, and clinical reasons for revision are summarized ( Table 2). The devices were retrieved from 33 men and 23 women with an average implantation age of 23 months (range, 1-204 months) with all devices included in the study regardless of time in situ, so as not to arbitrarily introduce a cutoff time in situ and inadvertently remove devices from the study with substantial degradation mechanisms, similar to other studies [6,8,12,16]. Mean time in situ was 19 months for the Co-Cr-Mo devices and 12 months for the Ti devices.…”

“…The machine surface finishes of the stem trunions and head trunions were either ground or gramophone ( Table 1). Evaluation of the devices incorporated the following: (1) qualitative macroanalysis of the retrieved components in terms of degradation mechanisms [1,6,8,12,16,21]; (2) optical microscopy [16]; (3) micro-CT scanning of tapers to determine taper ''fit''; and (4) microstructural assessment [16].…”

“…Two of the authors (AMK, ES) made qualitative observations, including assessing the corrosion, determining whether fretting was present, and correlating the clinically noted cold welding with surface-surface seizure. The trunions were assessed according to a modification of a previously described four-level scoring system [12]. That scoring system was modified to include an additional level between no corrosion and mild corrosion; thus, 0 = no corrosion; 1 = corrosion present but minimal; 2 = mild corrosion; 3 = moderate corrosion; and 4 = extensive corrosion of mating surfaces.…”

“…Numerous studies report failure mechanisms of modular hip designs with respect to the head-neck taper, the most common failure mechanisms being crevice corrosion and/ or fretting corrosion, particularly in devices with a titanium alloy (Ti) stem coupled with a cobalt-chromium-molybdenum (Co-Cr-Mo) femoral head [5,6,12,21,24,27]. The advantage of adding femoral head modularity, which facilitates revising an articulation while retaining a wellfixed stem, has outweighed the reported failures, albeit with some noted cases of femoral neck fracture [24].…”

Severe Metal-induced Osteolysis Many Years After Unipolar Hip Endoprosthesis

“…In vitro and finite element studies have shown that fretting would occur from micromotion at the interface [14,15,22,25]. Retrieval studies have documented corrosion of the headneck interface secondary to fretting [5,16,18,23]. Such corrosion can be potentiated by crevice corrosion, or that which occurs in spaces to which access of the working fluid from the environment is limited [5-8, 12, 14, 16, 18, 23].…”