Purpose: To evaluate the distribution and degree of radioactivity on sequential Tc-99m methylene diphosphonate (Tc-99m MDP) scans in the diagnosis of postoperative loosening in asymptomatic patients who underwent cementless total hip replacement. Material and Methods: Tc-99m MDP scans were obtained every three months where possible, for one year in those patients who underwent total hip replacement using a Harris Galante cementless prosthesis. Eighty-three scans from 45 patients were obtained. Uptake was assessed within the five periprosthetic zones (zone 1: greater trochanter; 2: lateral stem of the prosthesis; 3: tip of the prosthesis; 4: medial stem of the prosthesis; and 5: lesser trochanter) using an arbitrary 5-point grading system. Grade I indicated normal uptake and Grade 5 indicated highest uptake. The grade of uptake within each zone was then analyzed against their postoperative ages. Results: The radioactivity regressed to Grade 1 or 2 from Grade 4 or 5 within 12 months after cementless total hip replacement in 87.5% and 93.8% of patients in zones 2 and 4, respectively. Even though the radioactivity within zones 1, 3, and 5 tended to decrease, persistent elevation of activity (over grade 2) lasted up to 12 months after surgery in 31% or 37% of the patients. Conclusion: The radioactivity after cementless total hip replacement tended to regress in proportion to the postimplant age. The regression rate varied depending on the periprosthetic zones.
All Science Journal Classification (ASJC) codes
- Radiology Nuclear Medicine and imaging