Congenital Hand

• Anatomy and Development of the Upper Extremity
• The upper extremity consists of mesenchyme covered by ectoderm
• Limb growth = proliferation of mesenchyme
• Embryologic development
• 4^th week (26 days)—limb bud appears
• 6 weeks—finger buds visible
• Hand initially forms with webbed digits, 
• Interdigital tissue must undergo program cell death 
• 6-8 weeks (44-54 days)—separation of the digits
• 8-12 weeks—ossification occurs 

• Genetics of upper extremity development
• HOX Genes
• Regulate patterning in limb development
• Apical (ecto)dermal ridge (AER)
• Important for proximodistal development of the upper limb
• AER failure results in limb truncation
• Fibroblast growth factors (FGF) 
• Secreted by AER and aids in differentiation and limb bud outgrowth (IE finger buds)
• FGF failure results in syndactyly
• Bone morphogenetic protein (BMP)
• Plays a role in cell death during hand formation 
• BMP failure results in syndactyly
• Zone of polarizing activity (ZPA)
• Present in the posterior aspect of the developing upper limb and helps direct the anteroposterior(radio/ulnar) axis 
• Sonic the hedgehog protein (SHH) 
• SHH expression results from ZPA and also directs radio-ulnar axis
• Failure results in mirror hand deformity (IE a central finger with identical flanking fingers)
• WNT7 and wingless-type are responsible for dorsoventral development
• EN-1 results in ventral differentiation
• LMX1B results in dorsal differentiation

• Types of Failure in Embryonic development 
• Failure of formation cleft hand and longitudinal deficiencies
• Failure of differentiation syndactyly, symbrachydactyly,* camptodactyly, and clinodactyly
• *Associated with Poland syndrome (IE absent pectoralis muscle, breast development)
• Duplication includes mirror hand deformity, polydactyly
• Overgrowth includes macrodactyly
• Undergrowth includes brachydactyly

• Radial longitudinal deficiency: Hypoplasia and dysplasia of radius and or thumb
• Associated syndromes
• Thrombocytopenia absent radius (TAR) syndrome
• Autosomal recessive disorder characterized by absent radius with relatively normal thumb and thrombocytopenia
• Holt Oram Syndrome
• Autosomal dominant disorder with radial longitudinal deficiency accompanied by either atrial or a ventricular septal defect
• VACTERL
• Vertebral deformities, Anal atresia, Cardiac abnormalities,** Tracheoesophageal fistula, Renal agenesis, and Limb deformities
• ** greatest predictor of inpatient mortality is cardiac disease
• Fanconi Anemia
• Autosomal recessive pancytopenia, invariably fatal, treated with bone marrow transplantation
• Additional screening with spinal X-rays, cardiac echocardiography, renal ultrasonography, CBC
• Does not manifest with aplastic anemia on routine blood testing until after 3 years
• Patients with radial longitudinal deficiency should undergo chromosomal breakage test for earlier detection

• Polydactyly
• Preaxial polydactyly describes thumb duplication
• Wassel classification: I-V- to correctly classify count the number of affected bones.
• Wassel I: incomplete distal phalanx duplication (1 bone)
• Wassel II: complete distal phalanx duplication (2 bones) 
• Treatment includes excision of the radial portion of the bone and stabilization with collateral ligament reconstruction via a ligamentous and periosteal flap
• Other options include Bilhaut-Cloquet: excision of central bone and soft tissue
• Wassel III: incomplete proximal phalanx duplication (3 bones)
• Wassel IV: complete proximal and distal duplication (4 bones) 
• This is the most common thumb duplication
• Treatment is to excise the radial portion of the bone and stabilize with collateral ligament reconstruction
• Most important to maintain the ulnar collateral ligament
• Also need reposition of eccentric flexor and extensor tendons, as well as identify and reattach the abductor pollicis brevis
• Wassel V: incomplete duplicated metacarpal
• Wassel VI: duplicated metacarpals
• Wassel VII: triphalangeal thumb (7 bones)
• 3 on normal side and 4 on other (triphalangeal duplication)

• Syndactyly: variable fusion between two adjacent fingers
• Simple: fusion only through the skin
• Complex: fusion involving bone
• Complete: involves the entire commissure, including the nail bed.
• Treatment of syndactyly
• Surgery on simple syndactyly of toes (particularly 2^nd and 3^rd) are not required but can be done to avoid emotional and psychological problems
• Simple syndactyly can be reconstructed by dorsal rectangular flaps for the webspace
• Limit of dissection is at the bifurcation of the digital arteries
• Digits are separated by interdigitating skin flaps and full thickness skin grafts
• Staging of complete syndactyly separation includes 1^st and 4^th web spaces first, followed by the 2^nd and 3^rd spaces in two separate operations.
• Associated syndromes: Apert’s syndrome
• Thumb abnormalities: 
• Blauth classification
• I: minimal hypoplasia with full complement of neurovascular and musculoskeletal elements that are small in size
• No surgical treatment necessary
• II: all bones present, but hypoplastic. Instability of ulnar collateral ligament of the MCP joint and thenar hypoplasia 
• Treatment—MCP joint stabilization with opponensplasty and deepening of first web space.
• IIIA: CMC joint intact however there is poor active motion at MCP and IP joints
• Treatment—MCP joint stabilization with opponensplasty and deepening of first webspace.
• IIIB: deficient CMC joint with absence of trapezium, aplastic proximal first metacarpal head, absence of MP/IP joint motion
• Treatment—thumb amputation followed by index pollicization
• IV: pounce flottant or floating thumb. No muscular or skeletal attachments between thumb and hand
• Treatment—amputation of thumb followed by index pollicization
• V: absent thumb
• Treatment—index finger pollicization
• Index pollicization: for Blauth type IIIB or higher
• Performed between 3 months- 3 years 
• It is important to perform before child learns pinch.
• Procedure requires shortening the index finger metacarpal and repositioning of metacarpal head in hyperextension against the preserved metacarpal base (becomes CMC joint)
• Index MP joint becomes new thumb CMC joint, index PIP becomes thumbs MP joint and index DIP becomes thumbs IP joint
• EDC becomes APL, dorsal interosseous becomes abductor pollicis brevis, palmar interosseous becomes ADDuctor pollicis, EIP can become EPL
• Remember PAD/DAB to remember the intrinsic (palmar ADDucts, dorsal Abducts)
• For pollicization, do not need thumb metacarpal present 
• Other reconstruction options include great toe to thumb transfer (need metacarpal present)

• Amniotic Band Syndrome or constriction band syndrome
• Accepted cause from extrinsic theory which proposes low amniotic fluid and constriction rings
• Clinical manifestations vary from skin dimpling to digital amputation 
• Acrosyndactyly is pathognomonic for amniotic band syndrome
• Think limb and digital amputations along with constriction rings and fibrous bands
• Responsible for 12% of all congenital limb deformities 
• No known genetic transmission.
• Associated factors 
• Prematurity
• Low birth weight
• Young multigravida mothers
• Oligohydramnios
• Can result in compartment syndrome (edema, bullae, followed by compartment syndrome and volkmann’s contracture)
• Bullae is the sign to look for and is the sentinel lesion
• May excise 50% followed by the other 50% 3-6 months later 
• This results in rapid resolution of edema
• Treatment of compartment syndrome is constriction band excision

• Camptodactyly
• Painless and progressive nontraumatic contracture of the PIP joint
• Affects 1% population (will typically show Xray of contracted PIPJ)
• Typically treated with nonoperative treatment including static splinting
• Surgery should be last option!

• Clinodactyly
• Can be caused by a delta phalanx or bracketed epiphysis e
• Results in excessive radial or ulnar deviation of a digit

• Kirner deformity
• Progressive palmar and radial curvature of the distal phalanx of the little finger that presents in preadolescence

• Congenital Trigger Finger
• Differs from congenital trigger thumb
• Presents more commonly in the ulnar digits with associated malformations of superficial and deep flexors
• Presents as flexion at IP joint of thumb, sporadic locking
• Treatment
• Typically need A1 pulley release with tenoplasty of the chiasm and partial opening of the A2 pulley generally necessary
• Observation at 1 year, treatment after three years
• Thumb abnormality is known as “notta’s node”.

• Macrodactyly: congenital overgrowth disorder and represents 1% of upper extremity congenital anomalies. 
• Digital enlargement involves all tissue types and maintains patterns of growth and anatomic relationships within the affected portion of the hand
• Treatment
• If affected fingers are sensate, then debulking procedures and epiphysiodesis (premature closure of growth plates) are performed at IP and MP joints
• Can be associated with neurfibromatosis (von Recklinghausen’s disease)

• Brachydactyly
• Shortened fingers
• Treatment is aimed at keeping pinch
• Attempt to reconstruct small and ring fingers to facilitate grip and opposition
• Perform treatment at 8-12 months of age
• If there is no functional deficit then reconstruction is not necessary

• Miscellaneous
• Shoulder dystocia 
• Found to be the risk factor most associated with birth brachial plexus injuries (cesarean delivery protective)
• Salter Harris: fractures that involve the physis (extra octave if not involving the physis)
• I: transphyseal
• II: transphyseal but exit through metaphysis
• III: transphyseal but exit the epiphysis and joint
• IV: both epiphysis and physis, exiting through metaphysis
• V: crush injuries to physis
• Infants that undergo upper extremity reconstruction procedures should be placed in a long arm cast