Preoperative staging of osteosarcoma: efficacy of MR imaging in detecting joint involvement.
OBJECTIVE
Selecting the appropriate surgical procedure for treatment of patients with osteosarcoma requires accurate preoperative evaluation of tumor extent. Establishing the presence or absence of joint involvement is particularly important. Accordingly, we studied the efficacy of MR imaging for detecting joint involvement in 46 patients with osteosarcoma around joint spaces.


METHODS
Preoperative MR examinations were performed in 46 consecutive patients with osteosarcoma whose tumors were located around the knee (n = 33), the hip (n = 8), or the shoulder (n = 5). T2-weighted and unenhanced and contrast-enhanced T1-weighted spin-echo MR images were obtained for all patients. We assessed the presence or absence of tumor invasion of the intracapsular-intrasynovial joint space, either by disruption of the joint capsule or by intraarticular destruction of the cortical bone and articular cartilage or the intracapsular-extrasynovial cruciate ligaments of the knee. All patients subsequently had surgery. The MR findings were correlated with findings from macroscopic and microscopic pathologic examinations.


RESULTS
All 10 patients who subsequently proved to have tumor involvement of the joint were correctly identified (sensitivity, 100%). The tumor involved the knee joint in seven patients, the hip joint in two, and the shoulder joint in one. However, the MR diagnosis was false-positive in another 11 patients who did not have joint involvement at surgery (specificity, 69%). In the knee, MR imaging was more accurate in identifying tumor extension to the cruciate ligaments than to the intrasynovial joint space. Post-contrast T1-weighted images were most useful in detecting joint involvement.


CONCLUSIONS
MR imaging is highly sensitive for detecting joint invasion of osteosarcoma. However, false-positive diagnoses may lead to overstaging of tumor and result in unnecessarily radical surgical procedures.
Department of Radiology, University of Vienna, Austria.
W
W
Schima
G
G
Amann
R
R
Stiglbauer
R
R
Windhager
J
J
Kramer
M
M
Nicolakis
M T
MT
Farres
H
H
Imhof
D000293:Adolescent; D000328:Adult; D001859:Bone Neoplasms / Q000473:pathology*; D002648:Child; D005189:False Positive Reactions; D005260:Female; D006621:Hip Joint / Q000473:pathology*; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008023:Ligaments, Articular / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D012516:Osteosarcoma / Q000473:pathology*; D011300:Preoperative Care; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012785:Shoulder Joint / Q000473:pathology*; D013585:Synovitis / Q000175:diagnosis