Fracture of the cobalt-chromium modular femoral neck component in total hip arthroplasty

Abstract

Total hip prostheses using cervico-metaphyseal modularity were designed to better replicate the geometry of the native extra-medullary femur. However, they are associated with numerous complications including corrosion, disassembly, pseudotumours and, most notably, fractures of the modular neck. All reported cases of modular neck fractures occurred with titanium components (Ti-6Al-4V). To prevent this weakness, manufacturers developed modular necks made of cobalt-chromium (Co-Cr). We report a fracture of a long, 8° varus, Co-Cr modular neck connected to a 36-mm short (-3.5mm) femoral head. The fracture occurred 22 months post-implantation in a woman who had a low level of physical activity and a body mass index of 28.7 kg/m(2). To our knowledge, this case is the first reported instance of Co-Cr modular neck fracture. It may challenge the wisdom of further developing this modularity design, as our patient had none of the known risk factors for modular neck fracture. In addition, cases of pseudotumour have been reported with Co-Cr modular necks subjected to fretting corrosion, which contributed to the fracture in our patient.

High Risk of Failure With Bimodular Femoral Components in THA

“…The other method of failure in our study was bimodular neck fracture in approximately 5.6% of the PROFEMUR 1 Z stems (six of 107) and 0.6% of PROFEMUR 1 E stems (one of 170). There are several case reports regarding bimodular neck fracture of PROFEMUR 1 femoral stems [7,21,26]. Our data also suggest that long neck lengths, greater offset, and larger head diameters may potentiate failure of bimodular neck junctions.…”

Failure mechanisms in CoCrMo modular femoral stems for revision total hip arthroplasty

“…Fretting fatigue is widely reported in the fracture of Ti alloy components in modular hip systems . However, fretting corrosion induced fracture on modular CoCrMo stem is less commonly documented in literature . The role of fretting in crack formation in current Revitan hip system is not straight forward.…”

“…[30][31][32][33] However, fretting corrosion induced fracture on modular CoCrMo stem is less commonly documented in literature. 19 The role of fretting in crack formation in current Revitan hip system is not straight forward. Since no fretting marks were observed together with the microcracks in Area 2 [ Figure 5(b,c)], fretting was probably not involved in the process of crack coalescence and propagation.…”

“…Another possible reason for fatigue fracture of CoCrMo stem is the overload due to undersized component in some designs. 13,18 Corrosion such as fretting corrosion 19 and intergranular corrosion 20 was also reported to be involved in fatigue cracking. In the report on the failed Revitan modular femoral stems, Norman et al concluded that the fracture was caused by corrosion-fatigue based on their microscopic analyses of the fractured surfaces.…”

Inovacijska past: izmenljivi vrat totalne kolčne endoproteze

“…Menciere in sod. so poročali o zlomu izmenljivega kobalt-kromovega vratu le 22 mesecev po totalni artroplastiki kolka z modelom Profemur L pri bolnici z ITM 28,7 kg/m2 in nizko ravnijo telesne dejavnosti (23). Tudi pri naših bolnikih se je prvi zlom kobalt-kromovega izmenljivega vratu dogodil le dve leti po vsaditvi in to pri bolniku z minimalno povišanim ITM (26 kg/m2).…”