William F. Conway

Radiology of maxillofacial trauma

There has been a rising incidence of maxillofacial injuries during the past decade as a result of an increasing number of assaults and motor vehicle accidents. The maxillofacial region is one of the most complex areas of the human body, and the radiographic imaging of this region becomes even more difficult in traumatized patients because of their clinical condition and their inability to cooperate. Imaging modalities used in the evaluation of the traumatized maxillofacial region include conventional (plain) films, tomography, panoramic radiography, computed tomography, three-dimensional computed tomography, DentaScan, and magnetic resonance imaging. Each modality is discussed with regard to technique, advantages, and disadvantages. Plain films and computed tomography, the modalities that are used most in evaluating maxillofacial structures, are discussed in more detail. The normal anatomy and radiologic features are presented for both of these modalities. Radiographic evaluation of maxillofacial injury begins with a knowledge of the direct and indirect radiographic signs of injury seen on most imaging modalities. Computed tomography also has allowed a method of classifying facial fractures that is based on the involvement of the facial buttresses or struts. Three horizontal, two coronal, and five sagittal oriented struts are described. Limited fractures are differentiated from transfacial fractures by the lack of involvement of the pterygoid plates in the limited fractures. Limited fractures also can be subclassified as solitary (fracture of a single strut) or complex (fractures of multiple struts). A portion of the orbit is involved in almost every form of facial fracture; therefore, evaluation of facial injuries should always include the orbital structures. Although both can occur simultaneously, orbital injuries can be divided into soft tissue and bony vault injuries. Similar to midface fractures, orbital fractures also can be classified as solitary (fracture involves a single wall) or complex (fracture involves more than one wall or a part of a midface fracture). Computed tomography is of great value in evaluating both forms of injury. Magnetic resonance imaging is becoming increasingly important in the evaluation of orbital soft tissue injuries. Classification of midface injuries includes the solitary strut fractures and the complex strut fractures. Solitary strut fractures include fractures of the nasal arch, zygomatic arch, and isolated sinus wall fractures. Complex strut fractures include the nasal complex fractures, zygomatic (tripod) and zygomaticomaxillary fractures, transfacial fractures (LeFort fractures), and facial smash fractures. Each fracture type and its radiographic appearance are discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

Dynamic Magnetic Resonance Imaging of the Temporomandibular Joint Using FLASH Sequences

Magnetic resonance imaging (MRI) is a suitable modality for the visualization of the temporomandibular joint (TMJ) in both normal and pathologic conditions. Until recently, MRI had been unable to provide diagnostic dynamic images of the TMJ during opening. A series of 30 TMJ MRI examinations of 17 symptomatic patients and two normal volunteers (15 to 43 years old; 14 men and five women) was performed. Fast low angle shot (FLASH) sequences were used to provide a series of dynamic images of the TMJ in various phases of opening. In 30% of the joint examined, FLASH sequences contributed clinically significant information not available with standard T1-weighted sequences. These results suggest that FLASH images are particularly useful in distinguishing normal disc variants from pathologic conditions in which the disc is displaced anteriorly to a mild extent. The short imaging time of FLASH sequences decreases motion artifact in patients who have difficulty remaining still during the examination.

Case report 738

Fig. 2A, B. Tl-weighted sagittal (A) and axial (B) magnetic resonance (MR) images of the patella reveal an area of low signal intensity involving the inferior pole of the patella. Faintly seen within this region is a lower signal ring (7 mm in diameter) with an inter~ mediate signal interior (arrow). At the center is a tiny area of low signal. The adjacent infrapatellar fat pad demonstrates decreased signal intensity

Controversies in Magnetic Resonance Imaging of the Hip

One of the first musculoskeletal areas to be imaged by magnetic resonance (MR) was the hip. Early on, and even today, the most frequent indication for imaging of the hip has been for the evaluation of osteonecrosis and related diseases. Despite the long history of MR imaging of osteonecrosis, there still exist many controversies. This article will look at three of these: (a) What is the best way of imaging early osteonecrosis? This question has proven to be particularly important in the evaluation of the posttraumatic patient. We provide some preliminary evidence that the use of gadolinium-enhanced MR imaging may be helpful. Specifically, gadolinium fails to enhance areas of early osteonecrosis while surrounding uninvolved areas do enhance, (b) How should the patient with “MR bone marrow edema of the hip” be evaluated and treated? If there is radiographic osteopenia, the assumption is that this represents transient osteoporosis (a self-limited disease) and no treatment is necessary. However, if no osteopenia is present, the diagnosis and treatment become more problematic. A decision-making algorithm is presented to help overcome this dilemma. (c) Is documented osteonecrosis of the hip ever reversible without surgical intervention? Work done with renal transplant patients suggests that the answer to this question is yes, but work reported from Europe casts some doubt on this conclusion.

Normal Anatomy and Magnetic Resonance Appearance of the Knee

This article discusses the normal magnetic resonance (MR) appearance, functional anatomy, and biomechanics of the knee joint. Technical considerations of MR imaging of the knee are covered first: coil selection, positioning, and pulse sequences. Useful sequences for both routine examinations and specific clinical situations are suggested. This is followed by a discussion of the biomechanics and functional anatomy of the knee. The typical MR appearance of various key structures in the knee is discussed. The final section of the article is an atlas of normal MR anatomy of the knee, covering the sagittal, coronal, and axial planes.