Metallosis Presenting as Knee Pain 26 years after Primary Total Knee Arthroplasty

Abstract

Introduction: Metallosis occurs when periprosthetic soft tissues, synovium, and/or bone is infiltrated by metallic debris secondary to metal-on-metal wear. This debris can cause a chronic inflammatory reaction leading to joint instability, pain, and swelling, and may cause osteolysis, implant looseningand ultimately implant failure.

Case report: An 81 year old female, with a history of primary left total knee arthroplasty, presented with a 6 month history of left knee pain, swelling, and limited range of motion following a fall. Radiographs and joint aspiration were performed, with results that showed no evidence of periprosthetic trauma or infection but were suspicious for chronic metallosis. The patient underwent revision total knee replacement of the left knee which revealed extensive necrotic black metal debris throughout the joint space. Histopathology confirmed the diagnosis of a foreign body reaction consistent with metallosis.

Conclusion: This case is a rare example of chronic metallosis presenting 26 years following total knee replacement. Treatment with revision total knee replacement is the consensus management choice to avoid further destruction of the bone and joint capsule that can occur with metal-induced inflammation.

Keywords: Aseptic loosening; Metal-induced synovitis; bubble sign; cloud sign; metal-line sign; metallosis; severe osteolysis.

Figure 1

a) Lateral radiograph of the left knee showing severe osteolysis beneath the tibial component (white arrowhead) and amorphous curved densities, known as “Cloud” sign (white arrows). b) Postero-anterior radiograph of the left knee showing semicircular radio densities representing metal deposition outlining the synovium and joint capsule, known as “Bubble” sign (black arrows)

Figure 2

Arthrocentesis of the joint pre - operatively yielded a black-tinged fluid suspicious for metallosis.

Figure 3

a) Black necrotic metallic debris material noted in the joint space. b) resected synovium with extensive black metallic debris material noted throughout

Figure 4

a) Extensive black metallic debris material noted over the distal femur and femoral canal upon removal of the femoral component, b) Extensive black metal debris material noted over the tibia following removal of the tibial component.

Figure 5

a) The femoral component showing metal wear and erosion. b) Metallic wear of the patella button, c) Erosion of the edge of the lateral tibial base plate.

Figure 6

a) Antero-posterior postoperative radiograph showing revision TKA b) lateral post operative radiograph showing revision TKA

Figure 7

Synovial microscopic histology showing : a) black pigment interspersed within extensive fibrosis (white arrows). b) black pigment (left) neighboring multiple histiocytes (white arrows)

Figure 8

Synovial microscopic histology showing a multinucleated giant cell (red arrow)