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Displacement of Fat Pads in Disease and Injury of the Elbow

1959; Radiological Society of North America; Volume: 73; Issue: 5 Linguagem: Inglês

10.1148/73.5.717

1527-1315

Raleigh Bledsoe, I. L. Izenstark,

Shoulder Injury and Treatment

Injuries, particularly linear fractures of the radial head, may be difficult to detect in the routine radiographic study of the elbow (1). Kulowski (4) has expressed the need for more accurate diagnoses in elbow fractures. Meschan (8), without elaborating, has stated that the periarticular soft tissues may show evidence of swelling. Norell (9), in an excellent observation, has described fat pad displacement about the humeral fossae in the presence of fractures involving the elbow joint, although he erroneously described the fat as "extracapsular." A survey of the American radiological and orthopedic literature fails to reveal any report of this "fat pad sign." The purpose of the present paper is to show that the pads described by Norell are "extrasynovial" and "intracapsular," and to demonstrate further their value in radiographic interpretation of obscure elbow joint injuries. Displacement of these pads can also be of aid in evaluating the elbow in those local and generalized disease processes which result in hydrarthrosis. Anatomy A knowledge of the anatomy of the elbow is pertinent to radiographic interpretation. Gray (6) and other anatomists (2, 3, 7, 11) depict the fat pads as intracapsular and extrasynovial in contradistinction to the "extracapsular" location cited by Norell. According to Gray's Textbook of Anatomy (6) the articular capsule is a thin, broad, fibrous covering attached anteriorly to the medial epicondyle, and to the front of the humerus immediately above the coronoid and radial fossae; below to the anterior surface of the coronoid process of the ulna, and to the annular ligament. The posterior part is thin and membranous attached above to the humerus immediately behind the capitellum and close to the medial margin of the trochlea, to the margins of the olecranon fossa, and to the back of the lateral epicondyle. Below it is fixed to the upper and lateral margins of the olecranon, to the posterior part of the annular ligament, and to the ulna behind the radial notch. Transverse fibers form a strong band which bridges the olecranon fossa. Under cover of this band, a pouch of synovial membrane and a pad of fat project into the upper part of the fossa when the joint is extended. The capsule is in relation posteriorly with the tendon of the triceps brachii and the anconeus. The synovial membrane is described by Gray as extending from the margin of the articular surface of the humerus to line the coronoid, radial, and olecranon fossae of that bone. It is then reflected over the deep surface of the tendinous capsule of the joint to form a pouch between the radial notch, the deep surface of the annular ligament, and the circumference of the radial head. The radial head is thus surrounded almost completely by synovial membrane, although not actually within the synovial sac.