METALOSIS IN METAL-ON-METAL PPF TOTAL HIP ARTHROPLASTIES (THR)

Abstract

The development of metalosis is a not commonly reported complication after THR. The exact reasons are still unknown, but hypersensitivity reaction is favored ahead of toxic effects, immune defects and exogen causes. The phenomenon of metalosis occurred at an unpredictable time in situ and is often misinterpreted as a low grade infection.

In a retrospective study, we analysed all 173 (102 women and 71 men) primary and single cement less PPF THR (STRATEC®) with metal-on-metal (low carbide 0.08%) articulation of 1995. One patient was lost to follow-up, 18 patients were deceased. The average age at the time of surgery was 63.3 years and the follow-up time was 115 months.

40 (23.1%) metalosis cases were observed. Revision was done in 29 (16.8%) patients: three femur fractures, five cases of infection and 21 cases of metalosis. The median HHS at follow-up was 95. 18 cases (10.4%) had metalosis signs: six patients (3.2%) had periprosthetic osteolysis and pain, 16 patients (9.2%) had osteolysis without pain and nine patients (5.2%) had pain without osteolysis in the radiographs. Pain caused by metalosis typically occurred inguinal and at an average time of thirty months postoperatively. Dislocation was observed in 13 cases at an average time of 44 months with an average cup inclination of 48°. Extensive necrosis and diffuse lymphoplasmacytic infiltrates were noted. In most cases the bursa ileopectinea was highly filled and in this synovial fluid extremely elevated levels of chrome (32 – 46095 μg/l) and cobalt (30 – 67410 μg/l) were detected.

Since 2003, we do not implant or recommend metal-on-metal for THR anymore. Close radiographic and computertomographic monitoring with high mark on typical osteolysis and exact clinical evaluation is recommended for metal-on-metal THR. Patients without symptoms with severe osteolysis must be detected, and head and inlay changes must be performed.