Sequential Tc-99m MDP bone scans after cementless total hip arthroplasty in asymptomatic patients.
OBJECTIVE
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.


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 1 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.


CONCLUSIONS
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.
Kim
H S
HS
Department of Diagnostic Radiology, Medical College of Yonsei University, Seoul, South Korea.
Suh
J S
JS
Han
C D
CD
Kim
Y H
YH
Lee
J D
JD
D001843:Bone Cements; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011475:Prosthesis Failure; D013669:Technetium Tc 99m Medronate; D013997:Time Factors
D001843:Bone Cements; D013669:Technetium Tc 99m Medronate