Dear Sir,
Thank you for your interest in our study that assessed the accuracy and
value of radiographs in detecting pelvic osteolysis.
It is well recognized that the diagnosis of pelvic osteolysis
following total hip replacement is difficult and it was the intent of our
study to demonstrate and quantify the merits as well as the limitations of
standard radiographs in the detection of periacetabular osteolysis.
In our Discussion we noted that CT scans might represent an alternative
method to detect osteolysis. However, we did not suggest that CT scans be performed
for regular follow-up of patients with total hip replacement for several
reasons.
First, despite an encouraging report {1},
the accuracy of computed tomography in identifying
periacetabular lesions has yet to be determined.
Second, we share your concern that regular CT scans expose the patient to
high radiation. Additionally, the routine use of CT scans represents a cost-benefit dilemma
because an effective therapy for pelvic osteolysis in the setting of stable implants is not yet known. There is an ongoing discussion
about potential surveillance and treatment algorithms [2, 3, 4].
Based on our current knowledge we recommend using multiple
radiographic views--an AP pelvic view, an anteroposterior femoral view of the
affected hip and 45° iliac and obturator oblique views
for follow-ups.
When assessing these views for the presence of osteolysis, the
reviewer must be aware that identification of an osteolytic lesion in
any view, no matter what the other views show and no matter how
small the lesion is, establishes the likelihood that osteolysis is
present. Using this radiographic protocol, 75% of all lesions can be detected, but some lesions,particularly those located in the posterior column of the acetabulum, may go undetected.
If the radiographs indicate the presence of extensive periacetabular bone loss in the presence of a stable cup,
or the surgeon decides to perform revision surgery, one might then consider
performing a CT scan to obtain a three-
dimensional understanding of the extent of bone loss as a preparation for revision surgery. However, streak artifacts caused by a metal implant may limit the effectiveness of CT. The use of MRI to evaluate pelvic osteolysis in the presence of a stable implant is also affected by implant artifacts and its use for this indication is under current investigation [5].
We hope we have addressed your concerns regarding the problem of
detecting periacetabular osteolysis using radiographs.
Sincerely
Alexandra M. Claus, MD., PhD
1. Puri L, Wixson RL, Stern SH, Kohli J, Hendrix RW, Stulberg SD
Use of helical computed tomography for the assessment of acetabular
osteolysis after total hip arthroplasty.
J Bone Joint Surg Am. 2002 Apr;84-A(4):609-14
2. Stulberg SD, Wixson RL, Adams AD, Hendrix RW, Bernfield JB
Monitoring pelvic osteolysis following total hip replacement surgery:
an algorithm for surveillance
J Bone Joint Surg Am. 2002;84-A Suppl 2:116-22.
3. Claus AM, Walde TA, Leung SB, Wolf RL, Engh CA Sr
Management of patients with acetabular socket wear and pelvic
osteolysis
J Arthroplasty. 2003 Apr;18(3 Suppl 1):112-7
4. Maloney WJ, Paprosky W, Engh CA, Rubash H
Surgical treatment of pelvic osteolysis
Clin Orthop. 2001 Dec;(393):78-84.
5. Sofka CM, Potter HG
MR imaging of joint arthroplasty
Semin Musculoskelet Radiol. 2002 Mar;6(1):79-85
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