Lawrence Yao

Magnetic resonance imaging of plantar plate rupture

Degenerative plantar plate failure is an under-recognized cause of lesser metatarsalgia. We performed magnetic resonance imaging (MRI) with a small receiver coil in 13 patients in whom plantar plate ruptures of the second or third metatarsophalangeal joint were clinically suspected. In eight patients, MRI showed focal hyperintensity in the plantar plate that was interpreted as a rupture of the plate. Ruptures were confirmed in all five patients who underwent an operative procedure to treat the unstable, painful metatarsophalangeal joint. MRI is a noninvasive technique that can visualize plantar plate abnormalities and aid the clinical evaluation of problematic lesser metatarsalgia.

Partial ACL rupture: an MR diagnosis?

PurposeWe sought to clarify the ability of magnetic resonance imaging (MR) to show partial anterior cruciate ligament (ACL) ruptures and to allow distinction of partial from complete ACL ruptures.Materials and MethodsEighty-eight patients were studied by arthroscopy and MR (36 with normal ACLs, 21 with partial ACL ruptures, and 31 with complete ACL ruptures). MR studies were interpreted by an experienced, blinded reader. MR examinations were also independently scored with respect to four primary and seven secondary signs, and these data were analyzed using discriminant analysis.ResultsThe sensitivity of MR is lower for partial than for complete ACL ruptures. Most detected partial ACL ruptures resemble complete ruptures on MR. Secondary signs do not significantly improve detection of partial ACL ruptures, but they do help to distinguish partial from complete ACL ruptures. Displacement of the posterior horn of the lateral meniscus and popliteus muscle injury are indicative of complete ACL rupture.ConclusionsThe majority of partial ACL ruptures are shown by MR, but MR is less sensitive for partial than for complete ACL rupture. The distinction of partial from complete ACL rupture on MR examination, while problematic, is slightly improved by assessment of secondary signs.

MR-IMAGING OF TIBIAL COLLATERAL LIGAMENT INJURY - COMPARISON WITH CLINICAL EXAMINATION

We sought to clarify the capability of routine magnetic resonance (MR) imaging of the knee to detect and grade tibial collateral ligament (TCL) injury. We also wanted to define the exact MR findings that were the most important for diagnosis. Sixty-three patients were clinically evaluated for TCL injury prior to MR imaging of the knee on a 1.5-tesla system. MR studies were scored with respect to multiple direct and indirect findings. By discriminant analysis, the overall accuracy of classification (into clinical grades 1, 2, 3 and normal) on the basis of MR was 65%. Accuracy for detection of abnormal TCLs was 87%. The most useful MR findings for detection and grading of TCL injury were direct signs: subcutaneous edema over the TCL, focal disruption of the TCL, increased signal in the TCL on T2-weighted images, and longitudinal striations within the TCL. Indirect signs such as trabecular trauma were less useful for TCL evaluation. The presence of a tear of the anterior cruciate ligament, however, correlated with TCL injury of a higher grade. T2-weighted coronal images, by better depicting intraligamentous edema and fiber disruption, improved the MR assessment of the TCL.

Measurement of acetabular version on the axiolateral radiograph

There are 3 definitions of acetabular version: true (anatomic) version, planar (radiographic) version, and operative version. Although planar version can be measured on standard radiographs, the measurement may be inaccurate when applied to metal-backed acetabular components. However, another version angle is depicted clearly on an angled, cross-table lateral radiograph of the hip—the axiolateral view, and this angle readily distinguishes anteversion from retroversion. If the angle of the xray beam is known or is standardized, version measured on the axiolateral view can be converted to the other version angles. Nomograms for these conversions are presented. In most cases, acetabular version measured on the axiolateral radiograph closely approximates planar version.

Imaging shoulder impingement.

Appropriate imaging and clinical examinations may lead to early diagnosis and treatment of the shoulder impingement syndrome, thus preventing progression to a complete tear of the rotator cuff. In this article, we discuss the anatomic and pathophysiologic bases of the syndrome, and the rationale for certain imaging tests to evaluate it. Special radiographic projections to show the supraspinatus outlet and inferior surface of the anterior third of the acromion, combined with magnetic resonance images, usually provide the most useful information regarding the causes of impingement.

Case report 878

We discuss a patient with an occult, densely calcified synovial sarcoma of the hip who came to clinical attention because of pulmonary metastases. When synovial sarcomas present with dense and conglomerate calcification, they may be confused with benign processes such as myositis ossificans or tumoral calcinosis. Malignancies such as extraskeletal osteogenic sarcoma, extraskeletal chondrosarcoma, and mesenchymal chondrosarcoma must also be considered in the differential diagnosis.

Malignant mesenchymoma of the thigh

Skeletal Radiol (1995) 24:301-304 Skeletal Radiology Malignant mesenchymoma of the thigh Alan D. MassengUl, M.D. 1, Leanne L. Seeger, M.D. 1, Lawrence Yao, M.D. 1, Joseph M. Mirra, M.D. 2, Jeffrey J. Eckardt, M.D. 3 l Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, California, USA 2 Department of Pathology, Orthopaedic Hospital, Los Angeles, California, USA 3 Department of Orthopaedic Surgery, UCLA School of Medicine, Los Angeles, California, USA Clinical information A 39-year-old radiation oncology technologist presented to her physi- cian after noting a painless mass in the anterior aspect of her right thigh for several weeks. She stated that the mass was exactly at the height of her therapy table, and she repeatedly bumped the table with her thigh when positioning patients. Radio- graphs and computed tomography (CT) revealed a homogeneously en- hancing 6x2.5x2.5 cm mass within the rectus femoris muscle, with min- eralization in portions of the periph- eral margin (Fig. 1). On the basis of the history of chronic repetitive trau- ma and the peripheral mineralization, the mass was believed to represent heterotopic ossification (myositis os- sificans). Periodic radiographic sur- veillance was suggested to follow the lesion to maturity. Two years after initial presenta- tion, the patient returned and stated that the mass had continued to grow slowly but had recently become tender and was growing more rapid- ly. During this time, she reported continued trauma to the area during her daily work. Radiographs at this time showed enlargement of the mass and increased peripheral ossification (Fig. 2A). CT images confirmed en- largement of the mass and further os- sification confined exclusively to the Correspondence to: A.D. Massengill, De- partment of Radiology, University of Texas HSC/Houston, 6431 Fannin, 2.100 MSMB, Houston, TX 77030, USA periphery of the lesion (Fig. 2B). Due to the progressive enlargement and increased symptoms, tissue con- firmation was recommended. An excisional biopsy was per- formed. At surgery, a 10.6x6.5x6 cm mass was found which was confined to the central portion of the rectus femoris muscle. Grossly, the lesion was of a variegated yellow-tan color and had a gelatinous consistency. Multifocal areas of ossification were Fig. 1. A Lateral radiograph of the right thigh. Distinct ossification is seen in the periphery of a soft tissue mass in the anterior segment of the thigh. B CT image showing the enhanc- ing mass within the rectus femoris muscle. The mass shows incomplete peripheral miner- alization Fig. 2. A Twenty-two months later, the size of the mass and the peripheral ossification have increased. B Corresponding CT image at the same level as Fig. lB. The ossification remains confined to the periphery 9 1995 International Skeletal Society

Case report 715

We present a giant cell tumor of the distal end of the femur that exhibited unusual diaphyseal extension and atypical MRI features. MRI demonstrated differing zonal signal characteristics in the distal metaphyseal/epiphyseal versus the diaphyseal components of the tumor. It also depicted an irregular, proximal tumor margin with an unusual, enhancing, peripheral zone. The atypical MRI features may be related to the unusual finding at pathological examination of an almost entirely necrotic giant cell tumor. This massive necrosis may illustrate a stage in the evolution of some giant cell tumors to fibrous histiocytoma-like variants of giant cell tumor or to conventional, benign fibrous histiocytoma of bone.

Epiphyseal growth arrest lines MR findings

We present two cases in which MR exams revealed unusual, low signal intensity lines in the marrow space of epiphyses. These epiphyseal lines were smooth and regular, creating a bone-in-bone appearance. These lines were much more conspicuous on MR than on radiographs, partly because of adjacent alterations in trabecular architecture. A history of prolonged immobilization during childhood in both cases suggests that these lines represent growth arrest lines persisting in the epiphyses.

Saline versus gadolinium-enhanced magnetic resonance arthrography of porcine cartilage

RATIONALE AND OBJECTIVES The authors compared saline and dilute gadopentetate dimeglumine as injectants for magnetic resonance (MR) arthrography. METHODS Sixty-three lesions were created on the joint surfaces of six pig patellas. MR arthrography (1.5 T) was performed with the specimens in saline and then in 2 mmol gadopentetate dimeglumine by using fat-saturated two-dimensional (2D) and three-dimensional (3D) sequences. Two musculoskeletal radiologists independently interpreted the images. RESULTS At 2D MR arthrography, reader 1 performed equally well with saline and gadolinium solutes, whereas reader 2 had better sensitivity with the saline solute (P < .05); interobserver agreement was equivalent for saline and gadolinium solutes. With 3D MR arthrography, reader 2 performed equally well with saline and gadolinium solutes, whereas reader 1 had better sensitivity (P < .0001) but poorer specificity (P < .001) with the gadolinium solute; interobserver agreement was significantly better for saline than for gadopentetate dimeglumine (P < .05). CONCLUSION In this initial evaluation, there was no clear advantage to using gadolinium-enhanced MR arthrography over saline MR arthrography for detecting lesions in porcine hyaline cartilage.