Dennis L. Janzen

Three-dimensional CT measurement of adult acetabular dysplasia: technique, preliminary results in normal subjects, and potential applications

Abstractu2002Objective. To assess a three-dimensional computed tomography (3DCT) technique for measurement of acetabular coverage in adults.nDesign. We used 3DCT to define the geometric centre of the femoral head and to measure centre-edge angles (CEAs) at 10° rotational increments around the acetabular rim. The means, ranges, standard deviations and 95% confidence intervals for the CEAs at the various rotational increments were determined. Inter- and intra-observer variability was measured. The normal values are compared with two example cases of acetabular dysplasia.nPatients. The normal hips of 15 subjects aged 19–49 years (mean 34.2 years) were measured.nResults. The 3DCT measurements are reproducible (mean difference inter-observer, 1.7°–7.9°; mean difference intra-observer, 0.6°–6.9°). Mean normal CEA at the lateral rim was 33° with a 95% confidence interval of 23°–43°. Mean normal CEAs at 10° rotational increments from anterior to posterior rim were determined, and graphed as a ’normal curve’.nConclusion. This new 3DCT method of assessing acetabular dysplasia is simple, reproducible, and applicable to diagnosis, quantification and surgical planning for adult acetabular dysplasia patients.

CT evaluation of periacetabular osteotomies

We have previously described a simple and reproducible three-dimensional technique of CT for the measurement of the cover of the femoral head in acetabular dysplasia in adults. We now describe the application of this technique in ten patients with symptomatic dysplasia to assess the degree and direction of dysplasia and to measure the cover obtained at acetabular osteotomy. The indices obtained gave a useful indication of the degree and direction of the dysplasia and confirmed which components had been used most efficiently to achieve cover. The information is easily presented in graphical form and gives a clearer indication of the cover obtained than the indices derived from plain radiographs.

Malignant Fibrous Histiocytoma of Soft Tissue Imaging with Emphasis on MRI

Malignant fibrous histiocytoma (MFH) is the most common soft tissue sarcoma in adults. This pictorial essay describes and illustrates the clinical, pathologic, and radiologic features of MFH. The cross-sectional imaging features on CT and MRI are emphasized in relation to the diagnosis and staging of MFH.

Improving the detection of radiographically occult ankle fractures : Positive predictive value of an ankle joint effusion

OBJECTIVEnTo assess the value of an ankle effusion on plain radiographs as a predictor of radiographically occult fracture after acute ankle trauma.nnnPATIENTSnConsecutive patients with acute ankle trauma and radiographic evidence of an ankle joint effusion. Patients were excluded if ankle trauma was sustained more than 48 h previously or if a fracture was visible on initial photographs.nnnMETHODSnAll subjects (n = 26) underwent computed tomography (CT) of the ankle in sagittal and coronal planes. Ankle effusion size was measured from initial lateral ankle radiographs.nnnRESULTSnTwelve patients (46%) had radiographically occult fractures identified with CT. Fracture sites included: posterior or lateral malleoli (n = 4), calcaneus (n = 1), or talus (n = 7). Ankle effusion size was 11.2 mm in the group without fracture and 17.1 mm in the group with fracture (P < 0.0001). The positive predictive value of an effusion 15 mm or greater was 83%. CT detected significant soft-tissue injuries in four (15%) patients including peroneal retinaculum tear (n = 1), anterior talofibular ligament avulsion (n = 1), and tears of the peroneus longus (n = 1) and tibialis posterior (n = 1) tendons.nnnCONCLUSIONSnThe presence of a large ankle effusion of radiographs after acute ankle trauma suggests an underlying fracture. An ankle effusion of > or = 15 mm is a reasonable threshold to prompt additional imaging. Computed tomography provides good visualization of subtle bone injuries and may detect clinically imported soft-tissue injuries.

Using tomography to diagnose occult ankle fractures.

STUDY OBJECTIVESnTo determine the incidence of occult ankle fractures and to determine whether an ankle effusion identified radiographically correlated with the presence of an occult fracture.nnnMETHODSnAttending physicians in the emergency department of a university hospital prospectively identified patients with acute ankle injuries that produced ecchymosis or edema over two or more major ligaments of the ankle. Plain radiographs of these patients demonstrated ankle effusions without fractures. A consecutive sample of patients with acute ankle injuries was selected. Thirty-six of 1,151 patients were eligible to enter the study; 2 of these patients subsequently were excluded from the data analysis. All eligible patients underwent plain ankle tomography at 3-mm intervals in the coronal and sagittal planes. The types and frequencies of occult ankle fractures identified on plain film tomography were noted. The distention of the ankle joint capsule of enrolled patients was measured to determine if the degree of effusion correlated with the presence of an occult fracture.nnnRESULTSnThe minimum incidence of occult fractures in the general population with ankle injuries was 1%. Twelve of 34 patients (35%) with acute, severe injuries had occult fractures. Depending on the size, an effusion was correlated with the presence of an occult fracture in 35% to 85% of the study population.nnnCONCLUSIONnPlain film tomography should be used when evaluating ankle injuries if both edema or ecchymosis over two or more stabilizing ligaments and radiographic evidence of an effusion are present simultaneously.

Occult ankle fracture detected by an ankle effusion on plain radiography: A case report

Subtle ankle fractures may escape detection on plain radiography. These occult fractures can cause prolonged disability and pain. We present a case of blunt ankle trauma where plain radiography failed to reveal any bony abnormalities. The recognition of an ankle effusion on plain radiographs prompted us to perform a computed tomography (CT) scan of the ankle. The CT scan demonstrated an anterior plafond fracture of the distal tibia, which required surgical fixation. Had the fracture not been identified, our patient would have been treated inappropriately for a ligament sprain. An occult fracture should be suspected if an ankle is grossly swollen after blunt trauma, and plain radiography demonstrates an effusion. In this circumstance, performance of further imaging studies, such as conventional or CT, are advised to rule out an occult ankle fracture.