• Numerous classification systems exist for upper extremity limb anomalies based on embryology, teratologic sequencing, and/or anatomy. Each proposal has merit at the time of its inception, although many systems become
|
Table 30-1: Signaling Pathways During Embryogenesis | ||
|
SIGNALING CENTER |
RESPONSIBLE SUBSTANCE |
ACTION |
|
Apical ectodermal ridge |
Fibroblast growth factors |
Proximal to distal limb development, interdigital necrosis |
|
Zone of polarizing activity |
Sonic hedgehog protein |
Radioulnar limb formation |
|
Wingless-type (Wnt) pathway |
Lmx-1 |
Dorsalization of the limb |
|
Table 30-2: Embryologic Classification of Congenital Anomalies | |||
|
CLASSIFICATION |
SUBHEADING |
SUBGROUP |
CATEGORY |
|
I. Failure of formation |
A. Transverse arrest |
1. Shoulder 2. Arm 3. Elbow 4. Forearm 5. Wrist 6. Carpal 7. Metacarpal 8. Phalanx | |
|
B. Longitudinal arrest |
1. Radial deficiency 2. Ulnar deficiency 3. Central deficiency 4. Intersegmental |
Phocomelia | |
|
II. Failure of differentiation |
A. Soft tissue |
1. Disseminated |
A. Arthrogryposis |
|
2. Shoulder 3. Elbow and forearm 4. Wrist and hand |
A. Cutaneous syndactyly B. Camptodactyly C. Thumb-in-palm D. Deviated/deformed digits | ||
|
B. Skeletal |
1. Shoulder | ||
|
2. Elbow |
Synostosis | ||
|
3. Forearm |
A. Proximal B. Distal | ||
|
4. Wrist and hand |
A. Osseous syndactyly B. Carpal bone synostosis C. Symphalangia D. Clinodactyly | ||
|
C. Tumorous conditions |
1. Hemangiotic 2. Lymphatic 3. Neurogenic 4. Connective tissue 5. Skeletal | ||
|
III. Duplication |
A. Whole limb B. Humeral C. Radial D. Ulnar |
1. Mirror hand | |
|
E. Digit |
1. Polydactyly |
A. Radial (preaxial) B. Central C. Ulnar (postaxial) | |
|
IV Overgrowth |
A. Whole limb B. Partial limb C. Digit |
1. Macrodactyly | |
|
V Undergrowth |
A. Whole limb B. Whole hand C. Metacarpal D. Digit |
1. Brachysyndactyly 2. Brachydactyly | |
|
VI. Constriction band syndrome | |||
|
VII. Generalized skeletal abnormalities |
Outdated as our understanding of embryogenesis and genetics expands.
The most widely accepted classification of congenital limb anomalies is based on embryonic failure during development and relies on clinical diagnosis for categorization. Each limb malformation is classified according to the most predominant anomaly and placed
Into one of seven categories (Table 30—2). Different clinical presentations within similar categories are explained by variable degrees of damage. This classification scheme represents a valiant attempt to comprehensively classify congenital anomalies.
• However, valid criticisms of this system have arisen concerning the difficulty with classifying the
“predominant” deformity and the inability to categorize peculiar anomalies. Also, several authors have noted numerous similarities and differences between various congenital anomalies, creating conflict within this embryologic failure classification scheme.4-6