~ 810 ~ International Journal of Orthopaedics Sciences 2018; 4(1): 810-815 ISSN: 2395-1958 IJOS 2018; 4(1): 810-815 © 2018 IJOS www.orthopaper.com Received: 07-11-2017 Accepted: 08-12-2017 Dr. Jai Thilak D’orth D’Orth, MS Ortho Professor Arthroplasty and Arthroscopy Unit, Department of Orthopaedics, Amrita Institute of Medical Sciences, Kochi, Kerala, India Dr. Aravind Madanan Senior Resident, Department of Orthopaedics, Amrita Institute of Medical Sciences, Kochi, Kerala, India Correspondence Dr. Jai Thilak D’orth D’Orth, MS Ortho Professor Arthroplasty and Arthroscopy Unit, Department of Orthopaedics, Amrita Institute of Medical Sciences, Kochi, Kerala, India Midterm follow-up study of metal on metal total hip replacement Dr. Jai Thilak and Dr. Aravind Madanan DOI: https://doi.org/10.22271/ortho.2018.v4.i1l.118 Abstract Background: Metallosis and pseudotumors are long discussed complications with metal on metal bearing total hip replacement which has increased the rate of revision total hip replacements in these patients. Aims and Objective: To evaluate the levels of metal ion (Cobalt and Chromium), factors affecting theses metal ion levels and incidence of pseudotumors in metal on metal total hip replacement patients. Materials and Methods: Prospective descriptive study done on 25 patients who had metal on metal bearing surface replacement and total hip replacement with a mean post-op period of 6 years. Serum metal ion levels (Cobalt and Chromium), MARS-MRI (Metal Artifact Reduction Sequence) and acetabular cup inclination angle on X-rays and functional score were recorded in theses patients on two follow-up visits with mean follow-up period of 1 year. Result: Mean cobalt was 1.64 and mean chromium was 3.06. 28% of the study population showed asymptomatic pseudotumors but were less than 5cm. Mean cup inclination angle was 41.8* on X-rays which did not have any influence on serum metal ions and functional score. Gender (Male / Female) and type of arthroplasty (Articular surface replacement / Total hip replacement) has no affect on serum metal ions. Functional scores of these metal on metal patients comparable to metal on polyethylene bearing patients. Revison total hip replacement done in one metal on metal THR patient who had a dislocated cup in his second follow-up. Conclusion: Metal on metal hip arthroplasty patients were functionally doing well like the regular metal on polyethylene patients. Chromium values were significant and higher than cobalt. Incidence of asymptomatic pseudotumors was 28%. Keywords: Midterm follow-up, metal, hip replacement, asymptomatic pseudotumors Introduction Hip replacement has become the commonest treatment in most of the hip pathologies in adults in this era. In metal-on-metal implants increased head-neck ratio provides increased range of motion, decreased potential for femoral neck impingement, decreased dislocation rates, and greater stability compared to smaller head metal-on-polyethylene (MoP) implants [1] . However, complications that can develop with MoM implants such as increase in metal ions in the body, aseptic lymphocytic vasculitis associated lesion (ALVAL) and pseudotumor. Theses metal particles and ions disseminate throughout the body and are nanometers in size and high in number [2] . Increases in cobalt and chromium ions in serum, urine, and red blood cells of patients with a metal-on- metal bearing hip due to these metal particle dissolution [3] . Hypersensitivity, carcinogenicity and fetal exposure to metallic ions in pregnant women are great concerns regarding the effects of prolonged exposure to increased metal ion levels [4, 5] . Pseudotumors, defined as a solid or fluid mass which has developed in the peri-prosthetic soft tissue, are considered a severe complication of these MoM implants, which may cause pain, swelling, deep vein thrombosis and extensive soft tissue damage [6, 7] . Interestingly, not all MoM prostheses seem to develop these pseudotumor sequelae, and a debate exists on the prevalence of these pseudotumors, which ranges from less than 1% to 39% [7, 8] . Currently the only treatment option in case of pseudotumors is revision surgery, during which the MoM articulation is replaced by a non-MoM articulation. However, outcome of revision surgery for pseudotumor is poor compared to MoM revision surgery for other reasons [9] .