HEAD SIZE IN RELATION TO NOISE OCCURRENCE IN CERAMIC ON CERAMIC BEARINGS

Abstract

Introduction: With ceramic on ceramic bearing surfaces in total hip arthroplasty audible noise is a frequently documented problem. With increasing head size, there is less chance of component-on-component impingement and therefore a decreased risk of chipping, breaking and maybe noise occurrence.

Material and Methods: Prospective multicentre follow-up study of n=149 cases (91 males and 58 females). All patients were treated with either 32 or 36mm ceramic on ceramic articulation (Bionit^®) in combination with the non-cemented modular pressfit cup seleXys^® (Mathys Ltd Bettlach, Switzerland). There were n=4 patients with bilateral surgery. 56 patients received a 32mm head whereas 93 patients were treated with a 36mm head. In the group with 32 mm head diameter 79% were women, whereas in the 36 mm group only 16% were women. Patients were operated between December 2005 and January 2007. The mean age at surgery was 67.2 years (range, 46.3 – 86.4 years). Mean body mass index was 28.0 kg/m2 (range, 17.1 – 45.4 kg/m2). Patients were followed clinically and radiographically at three and six months, then after one and two years.

Results: 5 patients died and 2 patients were lost to follow-up. Only one patient reported squeaking noise immediately after the operation. At the one year follow-up the patient reported a feeling of subluxation and the noise turned into a clicking. The patient had to be revised after 14 months with a polyethylene inlay. No other revisions had taken place.

Patients with femoral heads of 32 mm and 36 mm diameter had excellent clinical results after 2 years follow-up for flexion angle, range of motion and Harris Hip Score. The Harris Hip Score increased from a pre-operative mean of 48.7 points to 93.5 points. Hip flex-ion increased from 91° to 113°. The Visual Analogue Scale for pain decreased from 6.7 to 0.9 and VAS for satisfaction increased from 3.2 to 9.3.

Conclusion: Compared to other studies the occurrence of noise and resulting revision procedures is very low. We assume that the insertion of bigger heads may reduce this problem and simultaneously allow the patient a better range of motion. The non-cemented modular cup combined with a ceramic inlay and a ceramic femoral head is a safe implant with excellent clinical results after two years.