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A synostosis (" bone-like "), Latin synostosis , is the bony connection (fusion) of two bones that were previously connected by cartilage or connective tissue.

However, if there is ossification of a previous joint, such as in the end stage of osteoarthritis , after an infection or a joint injury, this is referred to as ankylosis . If the bony build-up of a previous joint is the result of a stiffening operation, an arthrodesis is present.

Synostosis can be normal in human development, e.g. B. the bony connection of the sacrum to the sacrum or the formation of a bone from several fusing bone nuclei , z. B. the three parts of the pelvis to the hip bone .

Synostosis can rarely occur between two usually separate bones. This can lead to serious illnesses or it can be an incidental finding without clinical problems. Synostosis can already occur intrauterine, e.g. B. at the cranial sutures - known as craniosynostosis -, or appear only during further growth, and can occasionally be part of a complex clinical syndrome :

  • Radioulnar synostosis with fusion of the head of the spoke with the base of the ulnar and the resulting inability to rotate the forearm.
  • Radiohumeral synostosis predominantly associated with syndromic malformations.
  • Synostoses in the wrist area and resulting finger malformations.
  • Rückfußsynostosen can choose between the calcaneus , the talus , the cuboid and the navicular exist and are often only in prepubertal age by a deformity or pain in the rearfoot striking. They are often collectively referred to as the Tarsal Coalition .
  • A terminal joint synostosis with the fusing of the terminal and middle phalanx of the fifth toe is relatively common and is considered an asymptomatic incidental finding.
  • A synostosis between two vertebral bodies is known as a block vertebra and, when it occurs individually, is usually asymptomatic and an incidental finding.
  • Synostoses of several cervical vertebrae are found more frequently in Klippel-Feil syndrome .
  • Synostosis cranio-facialis (with progeny due to a smaller upper jaw)

Synostoses are only surgically resolved in the case of problems that can clearly be traced back to the synostosis, especially in the case of craniosynostoses. Radioulnar synostoses and those of the rear foot are also usually removed surgically to improve mobility.

See also


  • W. Pschyrembel: Clinical Dictionary. Verlag Walter de Gruyter, 265th edition (2014) ISBN 3-11-018534-2

Individual proof

  1. Flexicon Synostosis
  2. ^ Alfred Kantorowicz : Inhibition and promotion of the growth of the jaw. In: Dental World. No. 6, 1949, pp. 141-148 and 151 f.