High-resolution computerized tomography and nuclear bone scanning in the diagnosis of postoperative stress fractures of the mandible: a clinical report.

Root-form titanium dental implants are the treatment of choice for many partially and totally edentulous patients. The overall success rate is greater than 95%. Postoperative pain is usually the result of infection. This report presents two cases involving a sudden onset of jaw pain. Computerized tomographic scanning revealed that the pain was caused by stress fracture of the mandible.

Lumbar spinal fusion. Assessment of functional stability with magnetic resonance imaging.

Segmental spinal instability was evaluated with magnetic resonance (MR) imaging, computed tomography (CT), and conventional radiography in 33 patients who had undergone surgical spinal fusion. In 16 of the 19 patients who had a diagnosis of solid fusion, the immobilized vertebral bodies demonstrated areas of high signal intensity on images with short repetition time (TR) and echo time (TE). The signal intensity of these areas was either less intense or normal on images with long TR and TE. In 10 of the 14 patients with segmental instability at the fusion site, subchondral vertebral bands of low signal intensity were shown on short TR/TE images, which demonstrated high signal intensity on long TR/TE images. All but two of the patients showed vertebral signal changes 12 or more months past fusion or onset of clinical symptoms. The vertebral MR signal intensity in solid lumbar fusions might be related to marrow composition changes resulting from decreased biomechanical stress, while the vertebral signal intensities in patients with unstable fusions might be related to reparative granulation tissue, inflammation, edema, and hyperemic changes. Magnetic resonance imaging appears to be unique in its assessment of functional fusion stability. Magnetic resonance may be most useful in patients symptomatic of fusion pseudarthrosis in whom conventional radiography and CT fail to demonstrate anatomic disruption.

Computed tomography in dental implantation surgery.

High-resolution thin section CT with cross-sectional oblique and panoramic CT reconstructions has been shown to be an excellent tool for the preoperative evaluation of the mandible and maxilla for dental implant surgery. Oblique cross-sections throughout the entire surgical field allow visualization of osseous topography as well as related internal anatomic structures such as the inferior alveolar canal, the mental foramina, the incisive canal, and the maxillary sinuses. Armed with this knowledge, the surgeon-restorative dentist team can plan fixture positioning more effectively, thereby minimizing surprises in the operating room. Cases with inadequate buccolingual bone dimension are not attempted, whereas many other cases that do not appear to have adequate bone, as seen on conventional x-ray films, can be successfully implanted. The ultimate prosthesis is optimized because the surgeon can take full advantage of the available bone to achieve proper fixture alignment. It is quite likely that as future experience is obtained with maxillofacial CT, it may also be useful in diagnosis and treatment for a wide variety of other disorders of the jaw.

Differentiation between postoperative scar and recurrent disk herniation: prospective comparison of MR, CT, and contrast-enhanced CT.

Twenty-five symptomatic postlumbar surgery patients had findings on lumbar spinal noncontrast CT that were equivocal for distinguishing recurrent disk herniation from postoperative epidural fibrosis (scar). Contrast-enhanced CT and lumbar MR imaging were performed to differentiate these two conditions. Of the 14 levels, surgically explored, the diagnosis of scar or recurrent disk herniation was correct with contrast-enhanced CT at 10 levels and with MR imaging at 11 levels. At the levels operated on less than 2 years prior to MR imaging, scar more frequently demonstrated intermediate than low signal intensity. Scar older than 2 years most often showed low signal intensity. These preliminary findings suggest that MR may be useful in differentiating postoperative fibrosis from recurrent disk herniation in a significant proportion of patients whose unenhanced CT scans are equivocal.

[Magnetic resonance tomography in spondylolysis and spondylolisthesis]. / Magnetresonanztomographie bei Spondylolyse und Spondylolisthese.

40 patients with spondylolisthesis and/or spondylolysis were studied by magnetic resonance imaging (MR), 12 of whom with correlation to CT. CT proved to be more sensitive in detecting pars defects than MR. Sagittal MR, however, was more accurate in assessing spondylolisthesis than axial CT. At present, CT is superior to MR in demonstrating bony abnormalities. MR appears indicated in the patient undergoing spinal fusion in whom detection of intervertebral disc degeneration in the levels above or below intended fusion may lead to extension of fusion to the degenerated levels. Lack of ionizing radiation makes MR an ideal diagnostic method in evaluating spondylolisthesis in children and adolescents.

Avascular necrosis of the femoral head: high-field-strength MR imaging with histologic correlation.

Magnetic resonance (MR) images, contact radiographs, and histologic sections of six femoral head specimens with avascular necrosis were correlated. A low-signal-intensity band or ring represented the repair tissue interface surrounding a high-signal-intensity necrotic marrow segment. Large segmental areas of low signal intensity were observed on T1-weighted images when the lesion consisted of necrotic bone with amorphous marrow debris and adjacent thickened trabecular bone with mesenchymal repair tissue infiltration. On intermediate-weighted images, however, mesenchymal repair tissue, which was located inferior to the necrotic zone, increased markedly in signal intensity, permitting distinction from low-intensity necrotic bone with amorphous marrow debris. When trabecular thickening with collapse predominated, segmental areas of low signal intensity with both sequences were found. MR signal intensities used in combination with anatomic configuration and location may provide information of potential therapeutic importance regarding tissue composition and stage of disease.

Neuromuscular thermography of the lumbar spine with CT correlation.

Fifteen asymptomatic volunteers and 19 patients with current CT (GE 8800 CT/T) scans demonstrating either thecal sac contour distortion or nerve root displacement from disc rupture or spinal stenosis of the L4-L5 or L5-S1 levels judged to be at least moderate in severity underwent lumbar thermography. All patients were studied with an infrared telethermographic unit (AGA model 720M) employing the technical standards recommended by the Academy of Neuromuscular Thermography. The thermographic exams were interpreted independently and in a blind fashion by two radiologists. Of the 15 exams of asymptomatic patients, six were interpreted as positive and consistent with nerve fiber irritation. Of the 19 exams of patients with demonstrated CT abnormalities, all had positive thermograms for nerve fiber irritation (specificity 60%, sensitivity 100%). It is concluded that lumbar thermography is a sensitive examination for detecting those patients who will demonstrate lumbar spinal CT abnormalities and should play an important role in the diagnostic screening of low-back pain syndrome patients.

Bayesean-deblurred Planar and SPECT nuclear bone imaging for the demonstration of facial anatomy and craniomandibular disorders.

Ambiguities in diagnoses can often be resolved when images from different imaging modalities are compared, and when images are processed with algorithms that improve resolution and contrast. Bayesean deblurring algorithms were developed and applied to Planar and SPECT images of the maxillofacial and temporomandibular joint regions. The combined use of Planar and SPECT imaging with Bayesean deblurring were complementary and provided more diagnostic information than either modality individually. A facial imaging protocol using Planar and SPECT imaging and Bayesean deblurring is described. SPECT maxillofacial anatomy is presented, as well as the application of the imaging protocol of craniomandibular dysfunction. Although not recommended for all patients with craniomandibular disorders, combined use of Planar and SPECT images and Bayesean deblurring techniques appears to be useful in diagnostically difficult or refractory cases.

Three-dimensional CT and MR imaging in congenital dislocation of the hip: clinical and technical considerations.

Three-dimensional (3D) CT and 3D magnetic resonance (MR) imaging were performed in four patients with congenital dysplasia of the hip. Two patients were studied by 3D CT and two by 3D MR. Prior to volume segmentation, two-dimensional (2D) MR image preprocessing was used to correct for nonuniform signal intensity distribution from local variations in field strength and coil response. An unsharp mask of the original MR scan was computed by extreme blurring of the image to suppress the details of the object. The unsharp mask was divided into the image on a pixel-by-pixel basis. For improved object contrast first and second echo images were combined in a 1:2 ratio. To add an additional feature for volume segmentation, 2D MR image homogeneity was computed based on 3 X 3 pixel neighborhoods. Volume segmentation was performed using one feature for CT, i.e., attenuation range, and two features for MR, i.e., signal intensity and image homogeneity range. Three dimensional CT and 3D MR demonstrated the 3D relationships of femoral heads and acetabula. Three-dimensional CT was limited to patients who had ossified femoral heads, whereas 3D MR demonstrated the cartilaginous femoral head. The extent of acetabular coverage on which the mode of therapy is based was shown. Three-dimensional MR permitted imaging without gonadal irradiation. The 2D MR image preprocessing described here should provide even better results in objects with greater contrast, i.e., nonosseus structures, and those of larger size with relation to image degradation from partial volume effect.

[3-dimensional computed tomography and multiplanar CT-reformations in lumbar spondylodesis]. / Dreidimensionale Computertomographie und multiplanare CT-Reformationen bei lumbalen Spondylodesen.

Three-dimensional computed tomography (3-D-CT) and multiplanar CT reformations were performed in 42 patients who were clinically suspected of spinal instability following posterior lumbar fusion. Sagittal and coronal CT reformations demonstrated fusion pseudarthrosis more frequently than axial CT or conventional radiography. Three-dimensional CT cuts through the fusion revealed pseudarthrosis in most patients with positive 2-D images. In 5 patients, however, fusion appeared to be artifactually stable or unstable on 3-D cuts contrasting the 2-D images. Three-dimensional surface reconstructions demonstrated the complex anatomy of the fusion and showed superficial breaks. They were helpful in preoperative planning as well as intraoperative localization. 3-D-CT is a clinically useful adjunctive imaging method.

Emission imaging of patients with craniomandibular dysfunction.

Signs and symptoms of craniomandibular dysfunction in 37 patients were compared with the results of corrected cephalometric tomography and an emission imaging protocol consisting of both planar and single photon emission computed tomography (SPECT) (7500 ZLC Orbiter) images. The planar images and the single photon emission computed tomography projection views were processed with a bayesian deblurring algorithm to improve image quality. The correlation of emission imaging with craniomandibular dysfunction, as indicated by temporomandibular joint pain and joint noise, showed a high sensitivity (93%) and a high specificity (86%), whereas the correlation of corrected cephalometric tomography with temporomandibular joint pain and joint noise showed a relatively high sensitivity (89%) but a low specificity (27%). These results indicate that emission imaging is a sensitive and accurate indicator of craniomandibular dysfunction.

Three-dimensional computed tomography and multiplanar reformations in the assessment of pseudarthrosis in posterior lumbar fusion patients.

Three-dimensional (3-D) surface reconstructions and multiplanar computed tomography (CT) reformations were obtained in 30 patients with clinically suspected spinal fusion pseudarthrosis. The imaging studies were blind-reviewed and the results were compared with the clinical and surgical findings. Sagittal, planar, and curved coronal two-dimensional (2-D) reformations were more useful in the detection of bony nonunion than were axial CT scans, as the latter required more extensive analysis. Three-dimensional surface "cuts" adequately demonstrated pseudarthrosis in most cases. In some instances, however, segmentation artifacts created artifactual clefts or implied solidity, which contrasted with the interpretation of the 2-D images. Sagittal 3-D cuts were helpful in demonstrating bony central and lateral stenosis. Three-dimensional surface reconstructions demonstrated superficial clefts and outlined the complex anatomy of the spinal fusions, thus facilitating pre- and intraoperative planning. The amount of bone stock available for pseudarthrosis repair at the fusion site and the need for additional harvesting of bone from the iliac crest also could be assessed easily. 3-D CT proved to be useful as an adjunctive imaging method in the evaluation of posterior lumbar fusion patients suspected of pseudarthrosis.

[Magnetic resonance tomography in the determination of the functional stability of posterolateral lumbar spondylodeses]. / Magnetresonanztomographie bei der Beurteilung funktioneller Stabilität posterolateraler lumbaler Spondylodesen.

MR tomography was used to assess functional lumbar stability in 30 patients with posterolateral fusions. The vertebral bodies of 9 of the 12 patients with unstable lumbar fusions presented with areas of decreased signal intensity on T1- and intermediately weighted images, which increased on T2-weighting. The vertebrae of 15 of the 18 patients with stable fusions demonstrated zones of increased signal intensity on T1- and intermediately weighted images, which were less intense or invisible on T2-weighing. Surgical correlation was available in 11 of the 30 patients studied. Hyperemia and inflammation appear to be responsible for the abnormal signal intensities in the patients with stable fusions, whereas an increase in adipose marrow due to decreased biomechanical stress is thought to account for the atypical signal intensities in the vertebral bodies of the patients with stable fusions. MR tomography seems to be a potential method for evaluating functional lumbar fusion stability. MR tomography may be particularly helpful in those patients with multiple back surgeries and possible instability, recurrent disc herniation, or postoperative fibrosis. MR is recommended in the patient, who appears clinically unstable, whose radiographs and CT, however, do not demonstrate fusion failure.

Pseudarthrosis following lumbar fusion: detection by direct coronal CT scanning.

Twenty patients with fusions of the lumbar spine (seven with pseudarthrosis, 11 with solid bony fusions, and two with fusions that appeared solid but assessment was complicated by the presence of surgical hardware) underwent computed tomographic (CT) scanning in the supine position in the axial plane and, employing a specially designed seat, in the coronal plane. Three-millimeter contiguous sections were acquired. The direct coronal images were compared with those reformated from the axial images. The higher-resolution direct coronal images facilitated the diagnosis of pseudarthrosis and increased confidence in interpretation of normal studies. Direct coronal imaging is easy to perform and in many cases requires fewer scans and less radiation than reformations. Because it provides more useful diagnostic information, direct coronal imaging should replace current methods for evaluating fusions of the lumbar spine.

Subsidence of the femoral prosthesis. A stereophotogrammetric evaluation.

A quantitative three-dimensional measurement method, radiographic stereophotogrammetry (SPG), was employed to assess the relation between early subsidence of the femoral prosthesis after total hip arthroplasty (THA) and subsequent clinical course. The SPG technique and the authors' error control mechanisms are described in 15 patients in the early postoperative period, and the findings are correlated with those of follow-up clinical examinations. Among the 12 patients who remained clinically asymptomatic with respect to pain, only one had an SPG estimate of subsidence in excess of 1 mm at any point in time. Each of the three patients who later became symptomatic had SPG estimates of subsidence in excess of 1.75 mm within six months of the operation. Thus far, the patient with the largest estimate of subsidence is the only one who required surgical revision.

CT in low back pain syndrome.

CT has become the imaging modality of choice for diagnosing the specific cause of low back pain syndrome. This article describes and illustrates those abnormalities commonly associated with low back pain: disk herniation, spinal stenoses, facet joint abnormalities, spondylosis, inflammatory conditions of the lumbar spine, and sacroiliitis.

Multinuclide digital subtraction imaging in symptomatic prosthetic joints.

One hundred eleven patients with symptomatic prosthetic joints (86 hips, 23 knees, and two shoulders) were evaluated for prosthetic loosening and infection by combined technetium-99m-MDP/gallium-67 digital subtraction imaging. Clinical correlation was based on the assessment of loosening and bacterial cultures obtained at the time of surgery in 54 patients, joint aspiration cultures obtained in 37 patients, and long-term clinical follow-up for greater than 1.5 years in an additional 15 patients. Results revealed an 80%-90% predictive value of a positive test for loosening, and a 95% predictive value of a negative test for infection. However, because of the low sensitivities and specificities observed, this approach to the evaluation of symptomatic prosthetic joints does not seem cost effective.

Stereophotogrammetry of the lumbar spine. A technique for the detection of pseudarthrosis.

A computer-assisted photogrammetric method for the detection of pseudarthrosis following spinal fusion is described. This radiologic method is quantitative and noninvasive and requires a minimum of clinician time. Results of tests with a phantom specimen are presented. Preliminary indications are that the method may prove to be a useful adjunct to the clinician in monitoring the postoperative course of patients requiring fusion procedures.