From Big Medical Encyclopedia

SESAMOIDS [ossa sesamoidea (PNA, JNA, BNA)] — the small sizes of a bone, being constants or non-constant additional educations of joints. Outer surfaces of S. to. are spliced with the joint capsule or a sinew of a muscle, and only the insignificant, covered with a cartilage their inner surface is turned into a joint cavity. Page to. have the rounded or discal shape, the size from 0,3 to 4,5 cm and meet in quantity from one to eight. The sesamoid is a peculiar block for a joint, to-ry increases a corner of an attachment of a sinew of a muscle to a bone that promotes strengthening of action of a muscle on this bone.

Page to. are put at a fruit in the form of connective tissue educations, after the birth they become cartilaginous, and in the course of further development of an organism there is their calcification or ossification. Time of emergence of ossification centers in S. to. serves as an indicator at establishment of age of the child (e.g., ossification centers in a patella appear at girls in 4 — 5 years, at boys in 5 — years, in a kneeboard — in 10 years, in a pea-shaped bone at girls in 9 — 10 years, at boys in 12 — 13 years). Separate S. to. can form up to 20 years.

Fig. 1. Bones of the right brush (palmar surface): 1 — a sesamoid at a head of the II metacarpal bone; 2 — a sesamoid of an interphalangeal joint of the I finger; 3 — sesamoids of the I metacarpophalangeal joint; 4 — a pea-shaped bone.

The greatest number of S. to. meets in brushes (see), to foot (see) and knee joint (see), in those places where there is considerable pressure upon the joint capsule or a sinew of a muscle. In S.'s brush to. constantly heads of the first metacarpal bone are located in the area I of a metacarpophalangeal joint lateralny and medialny. Rare option are three S.' presence to. in this joint. The head of the second metacarpal bone has one S. to. roundish forkhma; often S. meet to. in the capsule of an interphalangeal joint of the I finger and it is very rare in joints of the II finger of a brush (fig. 1).

Fig. 2. Bones of the right foot (bottom surface): 1 — a sesamoid of an interphalangeal joint of the I finger; 2 — sesamoids of the I metatarsophalangeal joint.

In foot is much less S. to., than in a brush. They, as a rule, are located in sinews of flexor muscles of the I metatarsophalangeal joint or at heads of plusnevy bones; S. is more rare to. meet in an interphalangeal joint of the I finger (fig. 2) and in the V metatarsophalangeal joint.

The largest S. to. are: a patella (patella) lying in the thickness of a sinew the four-head of a muscle of a hip, a kneeboard (fabella) located in a lateral head of a gastrocnemius muscle and a pea-shaped bone (os pisiforme), edges it is put in a sinew of an elbow sgibatel of a wrist (fig. 1). In a sinew of a medial head of a gastrocnemius muscle there are separate small stones, so-called sesamoids of Vezaliya, and in the thickness of a bottom calcaneonavicular sheaf or in a sinew of a back tibial muscle — an additional tibial bone (os tibiale externum) which is also relating to S. to. The separate centers of ossification meet in muscles of a hip, the capsule of a knee joint and a tricipital muscle of a shoulder. S.'s presence to. at the specified places easily it is found on roentgenograms.

S.'s blood supply to. carry out small arterial branches of the corresponding joint capsule, a sinew or muscle. A venous blood flows in nearby veins. A lymph from S. to. flows brushes on deep limf, vessels in elbow limf, nodes, and from S. to. feet — in a subnodal limf, a node, and also in front or back tibial limf. nodes. S. innervate to. the branches going from the next nerves.

On the roentgenogram S.'s image to. appears only after emergence of ossification centers in them. S.'s structure to. during formation when there is a calcification of a cartilage, it is presented on the roentgenogram in the form of a dense heterogeneous shadow. The created S. to. have the typical rounded or oval shape, equal and smooth contours, the sizes from 1 — 2 to 10 — 12 mm. Structure of the created S. to. has the nature of uniform melkopetlisty trabecular network.

Fig. 3. The roentgenogram of a distal part of the left foot (the tangential projection, fingers are bent): sesamoids of the I metatarsophalangeal joint are specified by shooters.
Fig. 4. Roentgenogram of area of the left knee joint (side projection): 1 — a patella; 2 — a kneeboard.

Page to. come to light rather accurately on roentgenograms of the brushes and feet made in standard projections. For a research C. to. The I metatarsophalangeal joint, it is recommended to make a X-ray analysis in a tangential projection (fig. 3). Page to. a knee joint — patella (see) and a kneeboard — come to light on survey roentgenograms of a knee joint in direct and side projections (fig. 4).

Sometimes merges of separate ossification centers of S. to. does not occur. In these cases of S. to. consist of two, three p more fragments (os sesamoideum bi-, tri-, multipartitum). At the same time each of components of S. to. has the correct structure, equal and smooth outlines that distinguishes them from S.'s changes to. Asymmetric S. are in rare instances observed to., to-rye sometimes mistakenly take for separations of particles of a bone at traumatic damages.

Pathology Page to. it is observed seldom. Most often it is secondary and arises at diseases of joints and their tendinous and copular device, the exception makes a patella, to-ry can initially be surprised.

At deforming arthrosis (see) nearby S.' defeat is sometimes observed to. (is more often on foot). Wedge, a picture is defined by basic process. Radiological find deformation and S.'s increase to. due to bone growths. S.'s structure to. in these cases it is uneven, cystous reorganization can be observed. Treatment is directed to elimination of a basic disease. Sometimes it is necessary to delete the struck S. to. At hundred-Tiko-functional disturbances of foot, e.g. Hallux valgus (see), flat-footedness (see), nearby S.' removals are possible to., causing additional morbidity. Treatment of deformations of feet usually interrupts patol. process in S. to. It is extremely seldom observed osteochondropathy (see) S. to., found usually accidentally at a X-ray analysis of joints. Sometimes changes of sesamoids and their separations from a sinew meet. The diagnosis is made on the basis of survey, by palpations (local morbidity is noted) and results of a X-ray analysis. Treatment conservative: rest, physical therapy.

Bibliography: Dyachenko of V. A. Rent-genoosteologiya, M., 1954; Kasatkin S. N. Sesamoids of a brush and foot of the person, Works of the 4th Vsesoyuz. congress of zoologists, annate. and gistol., page 248, Kiev, 1931; Lagunova I. G. Radioanatomy of a skeleton, M., 1981; M and y-kova-Stroganova V. S. and Rokhlin D. G. Bones and joints in the x-ray image, the Extremity, L., 1957: In i of k n e of R. Normal radiologic patterns and variances of the human skeleton, Baltimore — Mlinchen, 1978; Gaff ey J. Pediatric X-ray diagnosis, Chicago — L., 1978; Groskopff K. W. u. Ti ~ schendorf R. Das normale mensch-liche Skelett in Rontgenskizzen, Lpz., 1962.

V. Ya. Bocharov; M. K. Klimova (injuries.), I. P. Korolyuk (rents.).