Asymptomatic intraprosthetic dual mobility cup dislocation with increased metal ion levels

Abstract

With the increased use of dual-mobility cups (DMCs) in total-and revision hip arthroplasties, surgeons can expect an increase of known and new complications. During routine follow-up, we observed an asymptomatic patient with an intraprosthetic-dislocation (IPD) and elevated levels of serum metal ions (1.8 ppb of cobalt and 28.0 ppb of chromium). Revision surgery was inevitable. Perioperative metallosis and severe wear of the metal shell and metal femoral head supported the IPD. Literature showed that the modularity of the DMC can result in increased serum metal ions, create excessive wear, and possibly affect implant survival. Our case and review of the literature may form an argument not to consider DMC for primary cases. Furthermore, we advise yearly clinical and radiological follow-up and, on indication, metal ion testing for DMCs.

Keywords: Dual mobility cup; Intraprosthetic dislocation; Metal ions; Revision surgery; Total hip arthroplasty.

Figure 1

Anteroposterior radiograph (a) before the first revision of the left total hip prosthesis. The eccentric head of the Charnley prosthesis clearly demonstrates wear. Anteroposterior radiograph (b) after the first total revision and placement of the Avantage cemented dual mobility cup.

Figure 2

Regular control shows an eccentric femoral metal head caused by an intraprosthetic dislocation. There is no total dislocated hip, and there is no sign of polyethylene component outside the metal shell (bubble sign). (a) Anteroposterior view. (b) Adduction view. (c) Abduction view. (d) Lateral view.

Figure 3

Perioperative photograph of the revision operation. The black tissue around the prosthesis shows the amount of metallic debris. An intraprosthetic dislocation was found as shown by the dislodged femoral metal head from the high molecular weight cross-linked polyethylene liner.

Figure 4

(a) Metal head and shell with cement immediately after the revision. (b) The undamaged highly cross-linked polyethylene liner. (c) Surface abrasions of the articulating part of the metal head. (d) Close up of the severe wear in the metal shell.

Figure 5

Direct postoperative radiograph after the second revision of the left total hip prosthesis. (a) Anteroposterior view. (b) Lateral view.

Figure 6

(a) Light micrograph showing typical histologic features of dense lymphohistiocytic aggregates (stain, hematoxylin and eosin, original magnification ×400). (b) Polarized micrograph showing black birefringent crystalline material (original magnification ×400). This received an ALVAL score of 8 (3 for synovial lining, 3 for inflammatory infiltrate, and 2 for tissue organization). ALVAL, aseptic lymphocytic vasculitis-associated lesion.