Titanium-titanium modular neck for primary THA. Result of a prospective series of 170 cemented THA with a minimum follow-up of 5 years

BackgroundAlthough they have been in use since the end of the 1980s, modular titanium neck components are associated with a risk of wear or fracture, and their safety has recently become a subject of debate and has never been evaluated in a consecutive series of patients. The goal of this study was to evaluate: revision-free survival of these implants after a minimum follow-up of 5 years; clinical and radiographic results; and the potential complications associated with the use of modular titanium neck components.HypothesisThe use of titanium modular neck on cemented titanium THA is safe at a minimum follow-up of 5 years.Patients and methodsBetween January 2006 and December 2008, we prospectively followed 170 patients (170 hips) who underwent primary anatomical THA with a modular cemented titanium stem design implant. The indications were unilateral THA for primary (n = 160) or secondary (n = 10) hip osteoarthritis (aseptic osteonecrosis of the femoral head or hip dysplasia). Mean age of patients was 75.4 ± 5.8 years old (52–85), and mean BMI was 26.1 ± 4.5 kg/m2 (16.6–42.1). Patients were operated on by a modified Watson-Jones anterolateral approach based on preoperative 2D planning. All patients underwent annual clinical and radiological follow-up by an independent observer.ResultsAt a mean follow-up of 71 ± 8 months (60–84), 5 patients died and 7 were lost to follow-up. There was no revision of THA after a maximum follow-up of 84 months. The Harris score improved significantly from 50.4 ± 11.3 (0–76) preoperatively to 84.5 ± 15.2 (14–100) at the final follow-up. There was no difference in postoperative femoral offset or the position of the center of rotation compared to the opposite side. On the other hand, the neck-shaft angle (NSA) and limb length were corrected (2 ± 5° [−11 to +14°] and 2.16 ± 3.6 mm [−7.4 to +12.7 mm]) respectively. Fifteen patients (9%) had limb length discrepancies of more than 5 mm and 4 patients (2%) of more than 10 mm. There were no complications due to the modular implant design.DiscussionOur study suggests that the use of cemented titanium implants with a modular titanium stem is safe at a follow-up of 5 years. The modular design does not prevent limb length discrepancies but restores femoral offset.Level of evidenceIV: prospective, non-comparative study.