Mechanical failure of modular hip stems due to titanium alloy neck breakage: a single-center case series

Modular neck implants in total hip arthroplasty (THA) allow control of length, offset, and version. However, these implants showed problems such as implant fracture and adverse reactions due to metal debris. This study aims to analyze our modular titanium-titanium neck THA stems, focus on mechanical complications related to its breakage, conduct a metallurgical analysis on these broken implants, and report revision surgery outcomes.

We performed a retrospective review to identify patients who had undergone THA with a specific modular (H2M-C2F Implants) implant at our institute (Fondazione Policlinico Universitario Campus Bio-Medico, Rome). Patient demographics, implant characteristics, clinical follow-up, and revision outcomes were obtained. A metallurgical examination was conducted on the broken implants.

Out of thirty-eight patients eligible patients, seventeen had a titanium alloy neck, whereas the remaining twenty-one had CrCo necks. Thirteen of seventeen patients with titanium necks reported spontaneous ruptures of the neck due to fretting corrosion phenomena. Revision surgery was offered to all patients, including the ones who did not experience spontaneous rupture (four patients). Neither intraoperative nor long-term complications were reported, except for one patient who showed gluteal insufficiency. No clinical differences were reported between the patients who underwent revision surgery and those who were revised preventively.

Using modular implants should be limited to strict indications. Patients' characteristics are vital in selecting the ideal candidate for a modular THA. Modular implants should answer all the questions regarding durability and fracture risk to become a valid alternative to fixed-neck stems.