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Congenital hand differences
The upper limb develops in weeks 4 to 8 along three axes — the apical ectodermal ridge (AER) proximal to distal, the zone of polarising activity (ZPA, SHH) radial to ulnar, and Wnt7a dorsal to palmar — and hand anomalies are now classified by OMT; the commonest are syndactyly and polydactyly.
Why it matters in the exam
Syndactyly is commonest in the third web (between middle and ring fingers); it is simple (soft tissue only) or complex (bony fusion), complete or incomplete. Release is usually done at 12 to 18 months, and earlier when digits of unequal length are joined (thumb-index, ring-small) to prevent deformity. In each operation only one side of a digit is released to avoid endangering blood supply, and a full-thickness skin graft is usually needed. Ulnar (postaxial) polydactyly is common in people of African descent and usually isolated; thumb duplication (preaxial) is classified by Wassel, and type 4 (duplication at the proximal phalanx) is the commonest. A hypoplastic thumb is graded by Blauth: types 1 to 3A — thumb reconstruction; 3B, 4 ("floating thumb") and 5 (absent) — pollicisation of the index finger.
Radial longitudinal deficiency (radial club hand) requires a search for associated anomalies: VACTERL, Holt-Oram (heart defect), TAR (thrombocytopenia) and Fanconi anaemia — hence a blood count and a chromosomal breakage test. Further anomalies: camptodactyly (fixed PIP flexion of the small finger), clinodactyly (radial deviation of the small finger with a delta phalanx), trigger thumb in a child (often resolves; surgical release when it persists beyond about age 3), amniotic band syndrome with constriction rings, and symbrachydactyly — short and missing digits, sometimes with Poland syndrome. A child's fracture through the growth plate is classified by Salter-Harris from 1 to 5, and types 3 and 4 enter the joint.
Key points
- Syndactyly and polydactyly — the commonest.
- Syndactyly: 12 to 18 months, one side per operation.
- Blauth 3B to 5 — pollicisation.
- Radial deficiency — heart, platelets, Fanconi.
- AER, ZPA and Wnt7a set the axes of development.
Summary table
| Anomaly | Classification or feature | Treatment | Note |
|---|---|---|---|
| Syndactyly | Simple or complex; third web commonest | Release at 12 to 18 months, one side per operation | Earlier for digits of unequal length |
| Thumb duplication | Wassel; type 4 commonest | Excise the smaller thumb and reconstruct ligaments | Usually preserve the ulnar thumb |
| Hypoplastic thumb | Blauth 1 to 5 | 1 to 3A reconstruction; 3B to 5 pollicisation | CMC stability decides |
| Radial deficiency | VACTERL, Holt-Oram, TAR, Fanconi | Alignment and reconstruction | Blood count and chromosomal breakage |
| Paediatric trigger thumb | Nodule in the flexor tendon | Release if it persists beyond age 3 | Many resolve on their own |
A free exam question
בניתוחי הפרדת syndactyly , ידוע כי העצבים הדיגיטלים נפרדים מה- common digital nerve דיסטלית וכדי להפריד בין . האצבעות יש צורך להפריד את העצב. על איזה נתון מבני של העצב מסתמכים בהפרדה זו? (the question as examined, in Hebrew)
- א. ניתן להגדיר את הפסיקולים העצביים המיועדים לעצב הדיגיטלי הספציפי לכל אורך העצב, מחוט השדרה
- ב. כשמפרידים בניתוח עצב דיגיטלי משותף, מאבדים בהכרח פסיקולים
- ג. ככל שמתקדמים דיסטלית לאורך העצב מתמעטים ה"צמתים" והפסיקולים המשכיים וניתן להפריד ביניהם
- ד. ניתן להגדיר את הפסיקולים העצביים המיועדים לעצב הדיגיטלי הספציפי לכל אורך העצב המדיאני עצמו
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Sources
- Oberg-Manske-Tonkin (OMT) classification of congenital upper limb anomalies (IFSSH), 2020 update — Malformations, deformations, dysplasias
- Green's Operative Hand Surgery, 8th edition (2022) — Syndactyly; Polydactyly; Thumb hypoplasia; Radial longitudinal deficiency
- Blauth classification of thumb hypoplasia (modified by Manske), 1967 and 1995 — Types I to V
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.