Neck modularity in total hip arthroplasty: a retrospective study of nine hundred twenty-eight titanium neck implants with a maximum follow-up of eighteen years

Purpose Neck modularity was introduced to improve total hip arthroplasty (THA) accuracy, but it has been associated with early breakages and corrosion issues. In our hospital, modular necks have been in clinical use since the 1990s. We retrospectively analysed the occurrence of these sequelae in implants placed between January 2000 and December 2014. Methods Survival data from patients operated on in our hospital were obtained from the regional arthroplasty registry (Registro dell'Impiantologia Protesica Ortopedica, RIPO). The cohort comprised 928 THAs on 908 patients. The average patient age was 67.8 years. Main indications were primary osteoarthritis (71.4%), fracture (9.2%), congenital dysplasia or congenital luxation (7.8%), and idiopathic osteonecrosis (6.4%). All femoral stems were cementless, with 318 anatomically shaped (34.3%), 579 straight (62.4%), and 31 short stems (3.3%). All necks used were made of titanium alloy. The average follow-up time was 9.6 years (range, 4-18 years). Results In total, 66 revisions were reported. The main revision causes were periprosthetic fractures (33.3%), aseptic stem loosening (19.7%), luxation (18.2%), and implant breakage (12.1%). Five modular neck breakages were recorded. The overall survival rate was 87.7% at 17 years. We did not observe any component corrosion. The neck breakage rate was 0.5%, and the luxation rate was 1.3%. Conclusions Our experience suggests that neck modularity is a safe, effective way to reconstruct the proximal femur in THA patients. We attribute the absence of corrosion to the exclusive use of titanium necks.