Gamma correction ^99mTc-hydroxymethylene diphosphonatepinhole bone scan diagnosis and histopathological verification of trabecular contusion in young rats

The aim of this rat experiment using gamma correction pinhole bone scan (GCPBS) was two-fold: first, to confirm whether specific unwashed micro ^99mTc-hydroxymethylene diphosphonate (^99mTc-HDP) uptake occurs in trabecular contusion (TC) and washed out uptake occurs in edema and/or hemorrhage-irritated trabeculae, and, second, to histopathologically identify the tissue in which the ^99mTc-HDP uptake is unwashed. Five young Sprague-Dawley rats were used for the contusion model and one rat was used as a control. Trauma was inflicted on the femoral shaft with a free-falling iron ball. The presence of injury was confirmed by means of ^99mTc-HDP pinhole bone scan and radiography with built-in scales. All rats were carefully killed for histopathologic verification. The size and shape of the unwashed high ^99mTc-HDP uptake in TC were assessed on a 50-fold magnified GCPBS (mGCPBS), and the findings were compared with those of hematoxylin eosin (H&E) stain findings. mGCPBS showed TC with osteoblastic rimming and high unwashed ^99mTc-HDP uptake. H&E stain findings showed osteoblastic rimming. The smallest TC was 0.03mm in transaxial diameter on both mGCPBS and H&E stain findings. The four shapes of TC were bar-like, round, ovoid, and pinpointed in the longitudinal, oblique, and transaxial sections. The size and shape shown on mGCPBS and H&E stain findings were in good accord, demonstrating that TC was coated with osteoblastic rimming, which is pathognomonic of contusion. This sign was not seen for the control rat. mGCPBS is useful in the diagnosis of TC because osteoblastic rimming, typically stained in the base, is marked with unwashed high ^99mTc-HDP uptake.