Both types of sesamoid bones are closely associated with a synovial lining and articular cartilage, the key components of a synovial joint 4. In Type B, the sesamoid is located at sites where tendons are angled about bony surfaces and separated from the underlying bone by a bursa (i.e., sesamoid of the peroneus longus tendon). In Type A, the sesamoid bone is located adjacent to an articulation, with its tendon incorporated into the joint capsule (i.e., patella and the hallucis and pollicis sesamoids). There are two types of sesamoid bones, designated Type A and Type B 5. The sesamoid osseous surfaces are covered by cartilage and are intimate with a synovial-lined cavity 4. They accomplish this as part of a gliding mechanism by modifying pressure, decreasing friction, and altering muscle pull. Sesamoid bones not only protect tendons from damage, but also can increase the efficiency or mechanical advantage of their associated muscle. Sesamoid bones are small round or ovoid bones embedded in certain tendons, usually related to joint surfaces 3. Inconstant sesamoids may be located about any metacarpophalangeal, metatarsophalangeal, or interphalangeal joint. Sesamoids are most constantly present about the metacarpophalangeal joint and interphalangeal joint of the thumb, and the metatarsophalangeal joint and interphalangeal joint of the great toe. This web clinic will review sesamoid bones as well as accessory ossicles, with an emphasis on the MR imaging findings.ģD graphics of the sesamoid distribution in the hand and foot. The most common sesamoid bones are those of the foot, including the hallucal sesamoids, lesser metatarsal sesamoids, interphalangeal joint sesamoid of the great toe, os peroneum, sesamoid within the anterior tibial tendon, and sesamoid within the posterior tibial tendon those of the hand, including the pollicis sesamoids, second and fifth metacarpal sesamoids, interphalangeal joint sesamoid of the thumb, and pisiform as well as the patella and fabella. As many as 42 sesamoid bones can be found within a single person 2. Sesamoid bones are common in humans, and vary in number. The term sesamoid is used for certain small nodular foci composed of bone, cartilage, or both that are shaped like a sesame seed 1. A sagittal T1-weighted MR image of the first metatarsophalangeal joint shows corresponding low signal intensity within the medial sesamoid (arrow) and adjacent soft tissues.ĭiagnosis: Sesamoiditis of the medial sesamoid of the first metatarsophalangeal joint.
0 kommentar(er)
