UPTAKE OF 99mTC-MDP AFTER UNCEMENTED HIP ARTHROPLASTYA QUANTITATIVE ANALYSIS OF FINDINGS AROUND THE FEMORAL COMPONENT IN ASYMPTOMATIC PATIENTSR. N. Maniar, MS Orth, MCh Orth, FCPS, DNB, Consultant Orthopaedic SurgeonLilavati Hospital and Research Centre, A-791 Bandra Reclamation, Bandra (West), Bombay 400 050, India. R. C. Todd, FRCS, Consultant Orthopaedic Surgeon Colchester General Hospital and Black Notley Regional Orthopaedic Centre, Braintree, Essex CM7 8NF, UK. S. Robinson, BSc, MSc, Physicist Colchester Group of Hospitals, Turner Road, Colchester, Essex CO4 5JL, UK. M. Critchley, MD, FRCR, Head Department of Nuclear Medicine, Royal Liverpool University Hospital, Prescott Street, Liverpool L7 8XP, UK. Correspondence should be sent to Dr R. N. Maniar at The Nook Apartment, 51-B, S.V. Road, SantaCruz (W), Bombay 400 054, India. We studied the pattern of 99mTc-methylene diphosphonate uptake around uncemented femoral components in 44 asymptomatic hip arthroplasties, performing isotope scans at intervals from 4 to 48 months after operation. We used phase-III images obtained with a high-resolution gamma camera and measured the activity in various zones using a specially designed computer program. The components studied at 4, 6, 9 and 12 months were coated with hydroxyapatite (HA) and those studied at 18, 24, 36 and 48 months were not coated. We found a statistically significant fall in activity between four and six months around HA-coated prostheses in all five femoral periprosthetic zones. After six months activity was relatively uniform, but remained higher than that in normal femoral bone at 48 months in non-coated prostheses. We discuss the application of these patterns in the evaluation of painful cementless hip arthroplasties.
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