The Journal of Bone and Joint Surgery, Vol 65, Issue 8 1134-1143, Copyright © 1983 by Journal of Bone and Joint Surgery, Inc
Biplane radiographic measurements of reversible displacement (including clinical loosening) and migration of total joint replacements
DL Green, E Bahniuk, RA Liebelt, E Fender and P Mirkov
We studied nineteen total knee replacements and thirty-three total hip
replacements with simultaneous biplane radiography to measure in vivo
micromotion at the cement-bone interface. Spherical cobalt-chromium markers
were embedded in the cement and cortical bone. Relative motion of the
cement-markers was measured with respect to the markers in the cortical
bone. Reversible displacement (relative motion during a change from
non-weight-bearing to weight-bearing) and migration (relative motion over
time from one non-weight-bearing study to another) were calculated. The
resolution of the measuring system was 0.2 millimeter. The range for
symptomatic reversible displacement was 0.4 to 4.5 millimeters, while that
for asymptomatic reversible displacement was 0.3 to 1.9 millimeters. All
reversible displacement of less than 0.4 millimeter was asymptomatic.
Migration of as much as 2.1 millimeters occurred without concomitant
reversible displacement. All radiolucent lines correlated with measured
reversible displacement. Half of the patients who were evaluated two weeks
postoperatively had measurable reversible displacement. CLINICAL RELEVANCE:
Our findings were based on a small series from a selected population. The
incidence of measured reversible displacement (75 per cent) was based on in
vivo techniques and included symptomatic and asymptomatic reversible
displacement; therefore, it was higher than the incidence of clinical
loosening (9.6 per cent in our series). Simultaneous biplane radiography
may become an important adjunct in the postoperative management of patients
with a total joint replacement.