Polysyndactyly
| Classification according to ICD-10 | |
|---|---|
| Q70.4 | Polysyndactyly |
| ICD-10 online (WHO version 2019) | |
As polysyndactyly (from ancient Greek πολύς polys , much ', σύν syn , together' and δάκτυλος daktylos , finger ', more commonly called synpolydactyly) is a congenital physical deformity of limbs ( Dysmelia designated) by foot or hand by the simultaneous occurrence of Polydactyly (presence of an unusually large number of fingers or toes ) and syndactyly (coalescence of fingers or toes).
Synpolydactyly is a rare hereditary malformation that predominantly affects the third and fourth toes and the fifth finger. This results in complete or partial duplication of the affected fingers and toes, but not always complete polydactyly. No malformations outside of the extremities are associated, there are no gender-specific differences.
genetics
The cause is an autosomal dominant gene mutation in the transcription factor HOX-D13 gene, which is of decisive importance for the formation of postaxial toes and fingers in the context of extremity development . In the homozygous (hypoplastic) form, there are severe and complex malformations, often with an oversized and prominent big toe with a malalignment in the sense of hallux valgus or hallux varus and a supination malalignment , plus hypoplastic synpolydactyly of the smaller toes. On the other hand, the heterozygous form does not show any hypoplasia of the toes or fused ( synostotic ) toes, but mostly pure syndactyly or synpolydactyly. The classic form is that of the duplication of the fourth metatarsal with polydactyly or synpolydactyly of the fourth toe. Syndactylia without polydactyly or duplication of the metatarsals can also be present.
The change in the HOX-D13 gene is an extension of a poly- alanine chain, which normally has fifteen repeats. The more repetitions there are due to mutations, the more complex the malformation. The HOX-D13 protein activates the expression of the enzyme Radhl2 that for the synthesis of retinoic acid from vitamin A is responsible. Retinoic acid is of great importance for the formation of the interdigital spaces and is less expressed the longer the poly-alanine chain in HOX-13D, which leads to poly- and syndactylia. On the other hand, HOX-13D inhibits cartilage formation, which is responsible for hypoplasia. On the other hand, if the HOX-13D gene is missing in the mouse model (spdh mouse), no synpolydactyly is formed, since other Hox genes can take over the function of HOX-D13.
treatment
The treatment usually involves amputation of the excess toe or finger, for aesthetic reasons and to narrow an excessively wide forefoot. In the case of a duplication of the fourth toe including the fourth metatarsal (metatarsal heterozygous form), in the Sahin technique, the base of the duplicated fourth metatarsal is usually resected, as it is usually dysplastic, and the base of the fifth metatarsal is preserved, which is also the insertion of an important pronating Tendon, of the peroneus brevis muscle . In addition, the distal half of the fifth metatarsal bone including the fifth toe is removed and the base of the fifth metatarsal bone is connected to the distal half of the fourth duplicated metatarsal bone including the duplicated fourth toe, by means of osteosynthesis with K-wire or by intramedullary positioning of the dysplastic and thinner distal part of the fourth metatarsal.
Syndromes
Polysyndactyly also occurs in the context of syndromes such as:
Individual evidence
- ^ Wilhelm Gemoll : Greek-German school and hand dictionary . G. Freytag Verlag / Hölder-Pichler-Tempsky, Munich / Vienna 1965.
- ↑ Pia kiss: give me five! Or six? Or seven? Research report from Webservice 2010 - Max Planck Institute for Molecular Genetics, [1]
- ↑ O. Sahin, I. Kuru, RC Akgun, B. S; Sahin, ID Canbeylio, I. C; Tuncay: Metatarsal transfer for the treatment of postaxial metatarsal-type foot synpolydaktyly . The Bone and Joint Journal 2013, Volume 95-B, Issue 7, July 2013, pages 929-934; DOI: 10.1302 / 0301-620X.95B7.31708
