Surveillance of Dual-Mobility Hip Systems: Damage Mode and Clinical Data Analysis.

BACKGROUND

Hip instability following total hip arthroplasty (THA) is among the most common indications for revision surgery. The implantation of dual-mobility (DM) systems, designed to improve stability, continues to rise, and thus, characterizing in vivo implant damage modes is paramount.

METHODS

Under an implant retrieval protocol, 51 DM THA systems were analyzed. Each component was examined for macroscopic damage and microscopically graded for fretting corrosion at the trunnion interface. Clinically relevant data were collected from medical records.

RESULTS

Revision indications included mechanical complications (n = 15, 27%), infection (n = 12, 22%), and dislocation (n = 9, 16%). The average duration of implantation was 12 months, which significantly correlated with summed femoral head taper corrosion (P = 0.044). Average summed fretting and corrosion scores were 2.9 and 3.0 for heads (two regions, 2 to 8 summed scores possible) and 7.6 and 7.1 for trunnions (four quadrants, 4 to 16 summed scores possible), respectively. Scratching (n = 26, 65.4%) was the most common damage mode on articular surfaces of acetabular cups, burnishing (n = 29, 55.2%) on metal liners, and edge deformation (n = 22, 45.5%) on polyethylene liners. Screw-liner corrosion was noted on 10.3% (n = 3) of available acetabular liners; an increased incidence of acetabular and femoral osteolysis was noted when this damage mode was present (P = 0.019 and P = 0.022, respectively).

CONCLUSIONS

This series demonstrated in vivo damage of DM THA components following short-term-to-midterm (zero to five years) implantation, with overall mild-to-moderate fretting and corrosion scores. Femoral head taper corrosion correlated with longer implantation, and amplified trunnion corrosion was observed in the setting of infection. Screw-liner corrosion may be related to acetabular and femoral osteolysis. This study indicates trends that merit further evaluation.