Cutaneous metal hypersensitivity syndrome in total knee arthroplasty with titanium-coated implant

Sir, Metal hypersensitivity syndrome is a type IV hypersensitivity reaction against metal ions through skin contact, lung inhalation or artificial implants.[1] It is a rare cause of failure of total knee arthroplasty (TKA) seen with the conventional cobalt-chromium implant, which should be suspected when other causes of implant failure such as infection, trauma and aseptic loosening have been ruled out. Our patient, a 73-year-old male, presented with uncontrollable itching over the knees associated with a burning sensation for two weeks. On enquiry, he gave a history of right knee arthroplasty for osteoarthritis two months back, following which he was asymptomatic for one and a half months. The implant used for the procedure was a titanium-coated cobalt-chromium alloy. Three weeks ago, he developed swelling and pain in the operated knee joint, which was not associated with constitutional symptoms. One week later, he developed itching over the operated site, which progressed to involve the other knee in a span of two days. Cutaneous examination revealed bilaterally symmetrical erythematous lichenified plaques with scaling and crusting extending from mid-thighs till the upper half of legs [Figure 1a]. There was periprosthetic swelling with a limitation of range of motion in the right knee [Figure 1b]. Post-operative surgical site infection was ruled out by negative joint aspirate culture and C-reactive protein. A preliminary diagnosis of metal hypersensitivity syndrome was made and the patient was started on systemic steroids following which the joint swelling and cutaneous symptoms resolved dramatically within two weeks. After the resolution of his symptoms, a skin patch test was performed with constituent metals and polymethyl-methacrylate, which was positive for nickel, cobalt and chromium [Figure 2a and b]. This corroborated with our initial diagnosis of metal hypersensitivity syndrome secondary to implant metal. He was symptom-free for the next one month; however, he had to subsequently undergo revision arthroplasty due to the aseptic loosening of the implant.Figure 1: (a) Erythematous lichenified plaques with crusting and scaling over bilateral knees. (b) Periprosthetic swelling over right knee with overlying dermatitisFigure 2: (a) Skin patch test: Well 3 (Titanium), Well 8 (Bone cement), Well 4 (Cobalt), Well 5 (Nickel), Well 10 (Chromium). (b) Patch test positive in Well 4 (Cobalt), 5 (Nickel), 10 (Chromium)Metal hypersensitivity syndrome secondary to implant material is a T cell-mediated immune response directed against corroded metal ions, polymethyl-methacrylate or in some cases, against antibiotic coating over the implant.[2] Patients present with periprosthetic synovitis, associated with a burning pain component, joint stiffness and limited range of motion. Less frequently, cutaneous manifestation is seen in the form of localised/generalised dermatitis.[2] Although no standard battery of investigations has been advised, skin patch test, lymphocyte migration inhibition test and lymphocyte transformation test have been utilised.[3] Management of symptomatic cases involves nonsteroidal anti-inflammatory drugs (NSAIDs), topical or systemic steroids for dermatitis and physiotherapy for joint stiffness. However, definitive management involves revision surgery for replacement with a tolerable implant material such as oxidised zirconium or a coating of titanium nitrite over the conventional cobalt-chromium implant to prevent corrosion of metal ions.[2,4,5] The manifestation of this rare complication with the use of hypoallergenic implant material has been reported in this case. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.