Synostosis (plural: synostoses) is fusion of two or more bones. It can be normal in puberty, fusion of the

epiphyseal plate The epiphyseal plate (or epiphysial plate, physis, or growth plate) is a hyaline cartilage plate in the metaphysis at each end of a long bone. It is the part of a long bone where new bone growth takes place; that is, the whole bone is alive, wit ...

to become the epiphyseal line, or abnormal. When synostosis is abnormal it is a type of

dysostosis A dysostosis is a disorder of the development of bone, in particular affecting ossification. Examples include craniofacial dysostosis, Klippel–Feil syndrome, and Rubinstein–Taybi syndrome. It is one of the two categories of constitutional di ...

. Examples of synostoses include: * craniosynostosis – an abnormal fusion of two or more cranial bones; *

radioulnar synostosis Radioulnar synostosis is a rare condition where there is an abnormal connection between the radius and ulna bones of the forearm. This can be present at birth (congenital), when it is a result of a failure of the bones to form separately, or follo ...

– the abnormal fusion of the radius and ulna bones of the forearm; *

tarsal coalition Tarsal coalition is an abnormal connecting bridge of tissue between two normally-separate tarsal bones. The term 'coalition' means a coming together of two or more entities to merge into one mass. The tissue connecting the bones, often referred ...

– a failure to separately form all seven bones of the tarsus (the hind part of the foot) resulting in an amalgamation of two bones; and *

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δά� ...

– the abnormal fusion of neighboring digits. Synostosis within

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

s can cause

ankylosis Ankylosis is a stiffness of a joint due to abnormal adhesion and rigidity of the bones of the joint, which may be the result of injury or disease. The rigidity may be complete or partial and may be due to inflammation of the tendinous or muscular ...

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Clinical significance

Radioulnar synostosis Radioulnar synostosis is a rare condition where there is an abnormal connection between the radius and ulna bones of the forearm. This can be present at birth (congenital), when it is a result of a failure of the bones to form separately, or follo ...

is one of the more common failures of separation of parts of the upper limb. There are two general types: one is characterized by fusion of the radius and ulna at their proximal borders and the other is fused distal to the proximal radial epiphysis. Most cases are sporadic, congenital (due to a defect in longitudinal segmentation at the 7th week of development) and less often post-traumatic, bilateral in 60%, and more common in males. Familial cases in association with autosomal dominant transmission appear to be concentrated in certain geographic regions, such as

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

. The condition frequently is not noted until late childhood, as function may be normal, especially in unilateral cases. Increased wrist motion may compensate for the absent forearm motion. It has been suggested that individuals whose forearms are fixed in greater amounts of pronation (over 60 degrees) face more problems with function than those with around 20 degrees of fixation. Pain is generally not a problem, unless radial head dislocation should occur. Most examples of radioulnar synostosis are isolated (non-syndromic). Syndromes that may be accompanied by radioulnar synostosis include X chromosome polyploidy (e.g., XXXY) and other chromosome disorders (e.g., 4p- syndrome,

Williams syndrome Williams syndrome (WS) is a genetic disorder that affects many parts of the body. Facial features frequently include a broad forehead, underdeveloped chin, short nose, and full cheeks. Mild to moderate intellectual disability is observed in people ...

), acrofacial dysostosis,

Antley–Bixler syndrome Antley–Bixler syndrome is a rare, severe autosomal recessive congenital disorder characterized by malformations and deformities affecting the majority of the skeleton and other areas of the body. Presentation Antley–Bixler syndrome presents i ...

genitopatellar syndrome Genitopatellar syndrome is a rare disorder consisting of congenital flexion contractures of the lower extremities, abnormal or missing patellae, and urogenital anomalies. Additional symptoms include microcephaly, severe psychomotor disability. I ...

Greig cephalopolysyndactyly syndrome Greig cephalopolysyndactyly syndrome is a disorder that affects development of the limbs, head, and face. The features of this syndrome are highly variable, ranging from very mild to severe. People with this condition typically have one or more ...

, hereditary multiple osteochondromas (

hereditary multiple exostoses Hereditary multiple osteochondromas (HMO), also known as hereditary multiple exostoses, is a disorder characterized by the development of multiple benign osteocartilaginous masses ( exostoses) in relation to the ends of long bones of the lower li ...

limb-body wall complex Limb body wall complex (LBWC) is a rare fetal malformation of unknown origins. Traditionally diagnosis has been based on the Van Allen et al., criteria, i.e. the presence of two out of three of the following anomalies: # Exencephaly or encephaloce ...

, and Nievergelt syndrome. Craniosynostosis (from cranio, cranium; + syn, together; + ostosis relating to bone) is a condition in which one or more of the fibrous sutures in an infant skull prematurely fuses by turning into

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

(ossification). Craniosynostosis Craniosynostosis has following kinds:

scaphocephaly Scaphocephaly is a type of cephalic disorder which occurs when there is a premature fusion of the sagittal suture. The sagittal suture joins together the two parietal bones of the skull. Scaphocephaly is the most common of the craniosynostosis con ...

trigonocephaly Trigonocephaly is a congenital condition of premature fusion of the metopic suture (from the Greek , "forehead"), leading to a triangular forehead. The merging of the two frontal bones leads to transverse growth restriction and parallel growth ex ...

plagiocephaly Plagiocephaly, also known as flat head syndrome, is a condition characterized by an asymmetrical distortion (flattening of one side) of the skull. A mild and widespread form is characterized by a flat spot on the back or one side of the head cause ...

, anterior plagiocephaly, posterior plagiocephaly,

brachycephaly Brachycephaly (derived from the Ancient Greek '' βραχύς'', 'short' and '' κεφαλή'', 'head') is the shape of a skull shorter than typical for its species. It is perceived as a desirable trait in some domesticated dog and cat breeds, ...

oxycephaly Turricephaly is a type of cephalic disorder where the head appears tall with a small length and width. It is due to premature closure of the coronal suture plus any other suture, like the lambdoid, or it may be used to describe the premature fusi ...

, pansynostosis.

References

External links

* {{Congenital malformations and deformations of musculoskeletal system Congenital disorders of musculoskeletal system