Background:
Acetabular osteolysis is a major problem affecting long-term survival
of total hip prostheses. Since lytic lesions may be asymptomatic
until extensive bone loss has occurred, early detection of lytic
lesions is important. The purposes of this study were to determine
the efficacy and potential role of high-resolution helical (or spiral)
computed tomography with metal-artifact minimization in the early
detection of osteolysis of the pelvis and to use the method to determine
if there was a relationship between the extent of osteolysis and
the amount of polyethylene wear.
Methods:
Forty patients (fifty hips) who had undergone primary cementless
total hip arthroplasty between 1988 and 1994 were evaluated as part
of an ongoing prospective study. These patients had a history of
high-level activity that was believed to place them at increased
risk for accelerated polyethylene wear. The most recent follow-up
radiographs were compared with the three-month postoperative radiographs.
Helical computed tomography scans with metal-artifact minimization were
made, and evidence of osteolytic lesions on these scans was compared
with that on the radiographs. Two-dimensional wear analysis was
performed with use of digitized radiographs, and the results were
compared with loss of bone volume as calculated from the computed
tomography scans.
Results:
Acetabular lysis was identified on the radiographs of sixteen hips
and on the computed tomography scans of twenty-six hips. Radiographs
underestimated the extent of the lysis in thirteen of the sixteen
hips. There was no correlation (r = 0.036) between linear wear and
the measured volume of bone loss, with the numbers available. On
the basis of the amount of lysis seen on the computed tomography
scans, one patient underwent a revision procedure.
Conclusions:
Helical computed tomography with metal-artifact minimization is
more sensitive for identifying and quantifying osteolysis after
total hip arthroplasty than is plain radiography. Since computed
tomography scans show both the extent and the location of lytic
lesions, they are useful to guide treatment decisions as well as
to assist in planning for surgical intervention, when needed, in
patients with suspected osteolysis.