David G. Disler

Magnetic Resonance Imaging of Articular Cartilage

Magnetic resonance imaging is the optimal modality for assessing articular cartilage because of superior soft tissue contrast, direct visualization of articular cartilage, and multiplanar capability. Despite these advantages, there has been disagreement as to the efficacy of magnetic resonance imaging of articular cartilage. The reason for this controversy is multifactorial but in part is attributable to the lack of the use of optimized pulse sequences for articular cartilage. The current authors will review the current state of the art of magnetic resonance imaging of articular cartilage and cartilage repair procedures, discuss future new directions in imaging strategies and methods being developed to measure cartilage thickness and volume measurements, and propose a magnetic resonance imaging protocol to evaluate cartilage that is achievable on most magnetic resonance scanners, vendor independent, practical (time and cost efficient), and accepted and used by a majority of musculoskeletal radiologists.

In vitro simulation : Early results of stereotaxy for pedicle screw placement

Study Design. Frameless stereotaxy with doppler ultrasound and three dimensional computer model registration is assessed in vitro for pedicle screw placement. Objective. To identify feasibility of pedicle screw navigation and placement using this technology. Summary of Background Data. Inaccurate pedicle screw placement can lead to neurovascular injury or suboptimal fixation. Present techniques in pedicle screw placement involve only confirmation of hole orientation. Method. Forty‐four pedicle screws were placed in lumbosacral models and cadaver specimens. Accuracy was assessed with a computed tomography scan and vertebral cross sectioning. Results. All screws were intrapedicular. Accuracy of anterior cortical fixation was 1.5 mm, with a range of 2.5 mm. Conclusion. In vitro frameless stereotaxy is accurate for pedicle screw placement. This technology adds a component of navigation to pedicle screw placement.

Clinical magnetic resonance imaging of articular cartilage.

Magnetic resonance (MR) imaging of articular cartilage has recently become of intense interest because of new developments in the treatment of articular cartilage injury. Recent advances in MR imaging technology has allowed the development of imaging sequences tailored to the assessment of articular cartilage. Several clinical studies have validated the accuracy and reliability of high-resolution, fat-suppressed, three-dimensional, spoiled gradient-recalled MR imaging in the assessment of articular cartilage defects of the knee. The use of other MR imaging techniques is evolving, including the use of fast spin-echo imaging and anionic contrast-enhanced T1-weighted imaging. This article describes the background and rationale to MR imaging of articular cartilage and focuses on its clinical application. Because the knee has been the focus of most research in articular cartilage imaging, the discussion in this article will be largely restricted to this joint.

MRI imaging of tendon, ligament, and osseous abnormalities of the ankle and hindfoot

This article serves as an overview of the pathologic processes that are seen in the foot and ankle. MRI can play a pivotal role in making precise diagnoses and then guiding treatment decisions. MRI can be extremely helpful in determining response to therapy.

Bone marrow edema in the greater tuberosity of the humerus at MR imaging: association with rotator cuff tears and traumatic injury

UNLABELLED The purpose of this study was to determine the prevalence of bone marrow edema in the greater tuberosity of the humerus on MR imaging, the association with other findings at MR imaging and the injury mechanism which can lead to this finding. SUBJECTS AND METHODS MR reports from 863 patients referred for shoulder MRI over 74 months were reviewed to identify patients with marrow edema in the greater tuberosity. The MR images from patients with greater tuberosity marrow edema were reviewed by consensus of two radiologists for the extent of marrow edema and for associated injuries. Marrow edema in the greater tuberosity was seen in 11 of 863 patients (1.3%). Nine patients (82%) had associated rotator cuff tear by MR imaging (four full thickness and five partial thickness), one patient had avulsion of the greater tuberosity from the humerus, and one had no rotator cuff abnormality. History of trauma was reported by eight patients including fall without direct blow to the shoulder (6), car accident (1) and direct blow to the top of the shoulder (1). Marrow edema in the greater tuberosity is an infrequent finding. Marrow edema most often is associated with a history of trauma and with rotator cuff abnormalities including full thickness tears. The history of trauma without direct blow to the shoulder and the location of the edema indicates that marrow edema often results from avulsion injury by the supraspinatus tendon.

Osseous hemangiopericytomas of unsuspected intracranial origin

Abstract Two cases of osseous hemangiopericytoma are presented that were initially diagnosed as primary in origin, but later reclassified as metastases, after a history of resection for an intracranial tumor was discovered. An intracranial source should be excluded before an isolated osseous tumor is determined to be a primary hemangiopericytoma.

Imaging of the lower extremity

This issue of the Radiologic Clinics of North America is devoted to addressing current stateof-the-art applications of MR to musculoskeletal imaging of the lower extremity. Our expert panel of contributors has provided reviews of various topics useful to the practicing radiologist. The articles are designed to be reviews of specific topics that will allow the reader to organize the information in a meaningful fashion. We hope that the information contained within this issue will help practicing radiologists provide clinically relevant interpretations to referring clinicians and in so doing become relevant to the care of the patient. Musculoskeletal imaging has undergone rapid and dramatic change with the advent of MR imaging. The articles in this issue will highlight the unique advantages of MR imaging over other modalities. Topics covered in this issue include assessment of neoplastic disorders of the lower extremities, MR evaluation of articular disorders, MR imaging of bone marrow disorders and nonneoplastic muscle conditions, MR of postoperative knee assessment, and MR assessment in the setting of osteomyelititis. We would like to thank our colleagues for their outstanding contributions to this issue as well as the staff of W.B. Saunders, particularly Barton Dudlick, for their help in its assembly.