Honda sign and variants in patients suspected of having a sacral insufficiency fracture.

Purpose: The purpose of this study was to reassess whether the Honda sign (HS) and its variants on bone scans can be used to differentiate an insufficiency fracture (IF) of the sacrum from a metastasis and to evaluate extrapelvic tracer accumulation in patients suspected of having a sacral IF. Methods and Materials: We retrospectively reviewed 34 bone scans of 26 patients suspected of having a sacral IF between January 1998 and June 2003. Results: Twenty-four of the patients had a sacral IF and 1 had a sacral metastasis from prostate cancer and another from lung cancer. The bone scans of only 15 (63%) of the 24 patients with a sacral IF exhibited the HS, 8 (33%) scans exhibited variants, and 4 (4%) scans showed whole-sacrum uptake. One of the 2 patients with metastasis exhibited the HS and the other exhibited a variant. The sensitivity and positive predictive value of HS plus its variants as diagnostic criteria for sacral IF were 96% and 92%, respectively. Seventeen patients (71%) had extrasacral accumulation. The most common site was the pubic bone (50%, 12 of 24), and the second most common site was the spine (46%, 11 of 24), where the accumulation was the result of a compression fracture or degenerative joint disease of the spine. Conclusions: A "Honda sign or variation" with evidence of fractures elsewhere or no evidence of other metastatic disease should be strong evidence for a sacral insufficiency fracture. The likelihood of having a solitary metastasis to the sacrum is small.