Fracture of the polyethylene tibial post in the posterior-stabilized total knee prosthesis: arthrographic and CT arthrographic diagnosis.

Fracture of the polyethylene tibial post in the posterior-stabilized total knee prosthesis is often delayed in diagnosis due to its nonspecific symptoms and the radiolucent characteristic of polyethylene on conventional radiography. Therefore, the diagnosis is always established by arthroscopy. Notwithstanding recent advances in imaging modalities, we are presently aware of only two related case reports on MRI and even no reports about arthrographic or CT-arthrographic diagnosis of fractured tibial post. We hereby report a case of a 58-year-old female patient who developed recurrent knee pain during the third year after total knee arthroplasty. The displaced polyethylene tibial post was clearly outlined by administered contrast material in the posterior knee. Under the diagnosis of fracture of the tibial post, the patient underwent isolated replacement of the broken polyethylene insert. Her knee pain significantly improved after the operation.

Differentiation between Glioblastoma Multiforme and Primary Cerebral Lymphoma: Additional Benefits of Quantitative Diffusion-Weighted MR Imaging.

The differentiation between glioblastoma multiforme (GBM) and primary cerebral lymphoma (PCL) is important because the treatments are substantially different. The purpose of this article is to describe the MR imaging characteristics of GBM and PCL with emphasis on the quantitative ADC analysis in the tumor necrosis, the most strongly-enhanced tumor area, and the peritumoral edema. This retrospective cohort study collected 104 GBM (WHO grade IV) patients and 22 immune-competent PCL (diffuse large B cell lymphoma) patients. All these patients had pretreatment brain MR DWI and ADC imaging. Analysis of conventional MR imaging and quantitative ADC measurement including the tumor necrosis (ADCn), the most strongly-enhanced tumor area (ADCt), and the peritumoral edema (ADCe) were done. ROC analysis with optimal cut-off values and area-under-the ROC curve (AUC) was performed. For conventional MR imaging, there are statistical differences in tumor size, tumor location, tumor margin, and the presence of tumor necrosis between GBM and PCL. Quantitative ADC analysis shows that GBM tended to have significantly (P<0.05) higher ADC in the most strongly-enhanced area (ADCt) and lower ADC in the peritumoral edema (ADCe) as compared with PCL. Excellent AUC (0.94) with optimal sensitivity of 90% and specificity of 86% for differentiating between GBM and PCL was obtained by combination of ADC in the tumor necrosis (ADCn), the most strongly-enhanced tumor area (ADCt), and the peritumoral edema (ADCe). Besides, there are positive ADC gradients in the peritumoral edema in a subset of GBMs but not in the PCLs. Quantitative ADC analysis in these three areas can thus be implemented to improve diagnostic accuracy for these two brain tumor types. The histological correlation of the ADC difference deserves further investigation.

Fibrodysplasia ossificans progressiva: initial presentation with a preosseous lesion of the scalp and its MRI appearance.

This case subject is a 1-year-old girl presenting with recurrent diffuse soft-tissue swelling of the scalp and periorbital region. Her family denied any known history of trauma. There was no obvious discoloration or local heat at the lesion. Magnetic resonance imaging (MRI) revealed diffuse soft tissue swelling of the scalp manifesting as high signal intensity on T2-weighted images and low signal intensity on T1-weighted images with diffuse enhancement after gadolinium-contrast administration. Biopsy yielded inconclusive pathological results. Fibrodysplasia ossificans progressiva (FOP) was not suspected until malformation of the patient's toes was noticed. The scalp lesion underwent spontaneous regression, and subsequent radiographs of the chest and cervical spine revealed heterotopic ossifications of the neck and thorax. Early diagnosis of FOP is vital because trauma, unnecessary biopsy and intramuscular injection are known to cause acceleration of heterotopic ossifications. Previous studies reported diffuse soft tissue swelling at the posterior neck, thoracic wall or paraspinal region as preosseous lesions of FOP (Shiva Kumar et al. Neurology. 2010;74(6):e20, Merchant et al. Pediatr Radiol. 2006;36(10):1108-11, Hagiwara et al. AJR Am J Roentgenol. 2003;181(4):1145-7). To our knowledge, diffuse soft tissue swelling of the scalp as a preosseous lesion of FOP and associated MRI findings have not yet been reported. We believe that awareness of preosseous lesions presenting as diffuse soft tissue swelling, in addition to shortening and valgus deformity of the great toes, is an important diagnostic clue for establishing FOP.

Posteromedial olecranon impingement of the pitching elbow: Additional findings provided by CT.

PURPOSE: Posteromedial olecranon impingement (PMOI) is the most common diagnosis in baseball players with throwing-induced elbow injuries. CT imaging manifestations of PMOI have seldom been previously reported. Our purpose is to investigate the additional value of CT imaging in the evaluation of PMOI. MATERIALS AND METHODS: From July 2010 to December 2013, 47 baseball players with throwing-induced elbow pain received imaging studies (CT and/or MRI) of the elbow at our institution. After retrospectively reviewing the clinical records and imaging studies, 31 of the 47 players were diagnosed with PMOI by the criteria of posteromedial elbow pain with clinical consistency for PMOI and characteristic osteoarthrosis at the posteromedial ulnotrochlear articulation (posteromedial olecranon space, PMOS) detected by CT and/or MRI. The imaging modalities of these 31 players including radiography, CT, and MRI were reviewed by 2 experienced musculoskeletal radiologists. RESULTS: The most common imaging manifestations of PMOI by CT or MRI include joint space narrowing, subchondral sclerosis, and osteophytes at the PMOS. CT was superior to MRI with a statistically significant (P<0.05) difference in detecting joint space narrowing, medial olecranon subluxation, as well as the number of loose bodies. In contrast, bone marrow edema and associated soft tissue injuries in PMOI are more readily observed on MRI. CONCLUSIONS: CT is superior in identifying some imaging features of PMOI. Whenever PMOI is diagnosed in the pitching elbow of a baseball player, CT should be considered prior to surgical intervention as it will often provide additional information to the surgeon that may alter surgical management.