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(A) Radiographs taken at 5-year follow-up (year 2000) showing a cementless Kotz modular femoral and tibial reconstruction (KMFTR) in an acceptable positioning. (B) An anteroposterior standing radiograph of the lower left limb showing fracturing of the proximal femoral stem (yellow arrow) and medial tibial plateau (red arrow).
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At the last follow-up there were no local recurrence of the oncologic disease and the prosthesis showed no signs of mobilization (Fig. 1A). The X-ray showed a two-point prosthesis breakage (femur and medial tibial plateau) and a femoral stem subsidence (Fig. 1B).
(A) Patient presented a large area of cutaneous metallosis characterized by dyspigmentation of the skin overlying the joint space affected. (B) anteroposterior standing radiograph demonstrating dismetry: left (surgical) leg was 2 cm shorter than the right with a deviation in varus of the knee. (C) A-P and L-L X-rays showing the typical amorphous, increased density material defined as "cloud sign" of metallosis.
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The clinical examination revealed a massive black dyspigmentation of the skin (Fig. 2C), moderate swelling, mild warmth and tenderness. Plain X-rays (Fig. 2A-B), that confirmed the lower limb discrepancy, were suspicious for metallosis: presence of radio-dense line ("cloudy sign"), associated with "the bubble sign" described by Su and the "metal-line sign" a thin rim of linear increased density in the suprapatellar pouch region described by Weissman.
Intraoperative photographs show (A-B) massive metallosis of the soft tissue adjacent to the prostheses, and (C-D) absence of osteolytic reaction with the femoral prosthetic stem well integrated to bone.
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Revision knee surgery confirmed the presence of massive soft tissue metallosis of the distal femur and the proximal tibia (Fig. 3A-B). However, there was not osteolysis, both prosthetic stems resulted still well bone-integrated (Fig. 3C-D).
Prosthesis after explantation: a femoral stem and medial tibial plateau breakage and extensive polyethylene wear and deformation distributed asymmetrically over the medial and lateral joint surfaces were detected.
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After prosthesis components removal, both femoral and medial tibial plateau fracture were confirmed and an extensive polyethylene wear and deformation distributed asymmetrically over the medial and lateral joint surfaces was detected (Fig. 4).
Extensive metallic particle deposition in the pseudo synovial tissue. H&E x 200.
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Inflammatory cells were composed predominantly of lymphoplasmacytes showing perivascular aggregates followed by macrophages and eosinophils Specimens were graded as 3+ (jet-black histiocytes/ > 100 visible metal particles/histiocytes) according to the modified Mirra classification for metallosis (Fig. 5).