Arthrogryposis Multiplex Congenita | Multiple Contractures
- Definition: Non-progressive condition with multiple congenital joint contractures.
- Pathogenesis: Fetal akinesia (lack of movement) from any cause leads to contractures.
- Amyoplasia (30%): Classic type. Symmetric. Normal intelligence. Sporadic.
- Foot: Clubfoot is most common foot deformity (-rigid, needs extensive surgery).
- Upper Limb Goal: Elbow flexion + Hand to mouth. Elbow is key.
- “Arthrogryposis is a DESCRIPTION, not a diagnosis. Find the underlying cause.
- “Amyoplasia children are intelligent - treat like normal children cognitively.
- “Clubfoot in AMC is RIGID - Often needs extensive surgery (PMR, Talectomy).
- “Prioritize function over appearance. Elbow flexion is key for UL function.
AMC Contractures are RIGID. Do not expect Ponseti-level success with serial casting alone. Surgery is often needed.
Address Multiple Joints. AMC involves many joints. Prioritize for function (Elbows, Knees, Hips, Feet).
In Amyoplasia. Do not assume cognitive impairment. These children are typically intelligent and motivated.
Poor Skin Creases. AMC skin does not have normal creases. Incision planning is important.
- Features
- Symmetric limb contractures, 'Waiter's Tip'
- Inheritance
- Sporadic
- Intelligence
- Normal
- Features
- Hands and Feet primarily
- Inheritance
- AD
- Intelligence
- Normal
- Features
- CNS involvement
- Inheritance
- Variable
- Intelligence
- Often impaired
- Features
- Muscle disease
- Inheritance
- Variable
- Intelligence
- Variable
CONGENITALAMC Features
Hook:Key features of AMC.
ELBOWUpper Limb Priority
Hook:Elbow Flexion is KEY.
RIGIDClubfoot in AMC
Hook:AMC Clubfoot is RIGID.
Overview and Epidemiology
Arthrogryposis Multiplex Congenita (AMC) is a descriptive term for conditions characterized by multiple congenital joint contractures affecting two or more body areas. It is NOT a specific diagnosis but a clinical finding.
- Incidence: 1 in 3000 live births.
- Amyoplasia: ~30% of AMC cases (most common recognizable type).
Any condition causing decreased fetal movement leads to contractures:
- Neurogenic: Spinal muscular atrophy, Myelomeningocele.
- Myopathic: Congenital myopathies, Muscular dystrophies.
- Connective Tissue: Diastrophic dysplasia.
- Mechanical: Oligohydramnios, Multiple pregnancy.
- Vascular: Anterior horn cell ischemia (Amyoplasia).
Anatomy and Joint-Specific Considerations
The pathology is periarticular soft tissue, not bone. Fibro-fatty replacement of muscle, capsular fibrosis, and ligamentous shortening fix the joint, while the underlying articular surfaces and ossification centres are usually structurally normal at birth. Bony deformity is secondary and develops with growth against unbalanced soft tissues.
Joint-by-joint pattern (classic Amyoplasia):
- Typical position
- Internal rotation, adduction
- Limiting structure
- Subscapularis, capsule
- Functional priority
- Low – usually accommodated
- Typical position
- Extension (most common)
- Limiting structure
- Triceps, posterior capsule
- Functional priority
- High – flexion for hand-to-mouth
- Typical position
- Flexion, ulnar deviation
- Limiting structure
- Flexor tendons, volar capsule
- Functional priority
- Moderate – position for grasp
- Typical position
- Thumb-in-palm, camptodactyly
- Limiting structure
- Intrinsics, skin, A1 region
- Functional priority
- Moderate – pinch and release
- Typical position
- Flexion, abduction, ext rotation; dislocation
- Limiting structure
- Capsule, iliopsoas, adductors
- Functional priority
- High – stable base for sitting/standing
- Typical position
- Flexion or extension contracture
- Limiting structure
- Hamstrings or quadriceps/capsule
- Functional priority
- High – determines bracing and gait
- Typical position
- Rigid equinovarus (or vertical talus)
- Limiting structure
- Posteromedial structures, talus
- Functional priority
- High – plantigrade, braceable foot
- Typical position
- Neuromuscular scoliosis
- Limiting structure
- –
- Functional priority
- Monitor; affects sitting balance
Pathomechanics: Because muscle is deficient rather than merely tight, deforming forces are weak but corrected positions are also poorly maintained by active power. This dual problem (rigid contracture plus weak motors) is why recurrence is high and why surgery aims for a balanced, braceable position rather than a normal arc of motion.
Pathophysiology of Fetal Akinesia
The Central Mechanism: Fetal Immobility
All forms of arthrogryposis share a common final pathway: fetal akinesia (decreased fetal movement) during critical periods of joint development.
Normal Joint Development (Weeks 8-12):
- Joints form through cavitation of mesenchyme
- Movement is essential for normal joint cavity formation
- Fetal movement shapes articular surfaces and prevents contractures
- Muscles develop in response to neural input and use
Consequences of Akinesia:
- Gestational Age
- Early
- Consequence
- Mild contractures (correctable)
- Gestational Age
- Early (8-12 weeks)
- Consequence
- Severe fixed contractures
- Gestational Age
- Third trimester
- Consequence
- Milder deformities
Causes of Fetal Akinesia
1. Neurogenic Causes (Most Common)
- Anterior horn cell dysfunction (Amyoplasia - vascular insult)
- Spinal muscular atrophy
- Myelomeningocele
- CNS malformations
2. Myopathic Causes
- Congenital myopathies (Nemaline, Central Core)
- Congenital muscular dystrophy
- Myotonic dystrophy (maternal)
3. Mechanical Restriction
- Oligohydramnios (renal agenesis, PROM)
- Multiple pregnancy
- Uterine anomalies
- Amniotic bands
4. Connective Tissue Disorders
- Diastrophic dysplasia
- Larsen syndrome
Amyoplasia-Specific Pathophysiology
Amyoplasia is caused by anterior horn cell ischemia during early gestation:
- Sporadic occurrence (no inheritance)
- Symmetric involvement suggests vascular etiology
- Anterior horn cells are particularly vulnerable to hypoxia
- Results in muscle hypoplasia/aplasia with fatty replacement
- Preserved sensory function (posterior horn spared)
In AMC, the lack of fetal movement leads to:
- Failure of joint cavity formation (ankylosis)
- Capsular and ligamentous contracture
- Muscle fibrosis and shortening
- Secondary bony deformity
This explains why contractures are RIGID and resistant to simple stretching.
Amyoplasia Is More Than the Limbs: Associated Anomalies and Birth Fractures
The evidence base notes that amyoplasia comes with "vascular-compromise anomalies (bowel atresia, gastroschisis, digit loss)", but the body never develops them — and they change the newborn work-up and the way you handle the child.
The unifying idea — a vascular disruption. Amyoplasia is thought to follow an early vascular insult (the same compromise that depletes anterior horn cells and replaces muscle with fibro-fat). That insult produces a recognised cluster of associated anomalies elsewhere, so the amyoplasia newborn needs a whole-child screen, not just a limb assessment. According to PubMed (Hall et al., 560 individuals — the defining series):
- Approximate frequency
- About 9%
- Why it matters
- Needs abdominal examination/imaging in the neonate
- Approximate frequency
- Roughly 12% and 4%
- Why it matters
- Count and document digits; part of the disruption picture
- Approximate frequency
- About 3%
- Why it matters
- Affects core strength and surgical planning
- Approximate frequency
- About 10%
- Why it matters
- The fragile osteopenic limb can FRACTURE at birth or on handling/casting
- Approximate frequency
- About 7% (odds ratio ~11)
- Why it matters
- Supports a vascular/twin-related pathogenesis; reassure on recurrence
The midline frontal capillary haemangioma (noted in the differential) belongs to the same vascular picture.
The orthopaedic take-home: the amyoplasia limb is osteopenic and fragile — perinatal long-bone fractures occur in around a tenth of cases — so the limb must be handled and cast gently, and a fresh "deformity" at birth may actually be a fracture. Screen the abdomen for an atresia or wall defect, count the digits, and remember that, despite the cluster of anomalies, amyoplasia is sporadic with negligible recurrence risk.
Q: Beyond the contractures, what must you check for in a newborn with amyoplasia? A: A vascular-disruption cluster — gastrointestinal atresia/gastroschisis (~9%), digit loss/constriction rings, abdominal-wall muscle defects, and the midline facial haemangioma — plus the orthopaedically critical point that the fragile limb fractures perinatally in ~10%, so handle and cast it gently. The condition is still sporadic with negligible recurrence risk.
Classification
Amyoplasia (Classic AMC)
Most common recognizable type (~30%).
Features:
- Sporadic (No inheritance).
- Normal Intelligence.
- Symmetric limb involvement.
- Upper Limb: Internal rotation, Elbow extension, Wrist flexion ('Waiter's Tip').
- Lower Limb: Hip dislocation (30%), Knee flexion or extension, Clubfoot.
- Facial: Micrognathia, Depressed nasal bridge.
- Skin: Dimpling, Lack of creases.
Prognosis: Excellent with appropriate management. Normal lifespan.
Good outcomes are expected with comprehensive multidisciplinary care.
Clinical Assessment
- Pregnancy: Decreased fetal movements? Oligohydramnios?
- Birth: Breech? Complications?
- Family History: Any inheritance pattern?
- Development: Milestones? Intelligence?
- General: Facies (Micrognathia), Skin (Dimpling, Lack of creases).
- Upper Limb:
- Shoulder: Internal rotation contracture.
- Elbow: Extension contracture (most common) or Flexion.
- Wrist: Flexion/Ulnar deviation.
- Hand: Thumb-in-palm, Camptodactyly.
- Lower Limb:
- Hip: Dislocated (30% in Amyoplasia), Flexion contracture.
- Knee: Extension or Flexion contracture.
- Foot: Clubfoot (rigid), Vertical Talus, Congenital Knee dislocation.
- Spine: Scoliosis (common).
- Neurological: Assess muscle bulk, Tone, Reflexes.
Differential Diagnosis
Arthrogryposis is a sign, not a diagnosis. The task is to place the child into a prognostic and genetic category.
- Distinguishing Features
- Symmetric, 4-limb, extended elbows, midline facial haemangioma, fatty muscle replacement
- Intelligence
- Normal
- Inheritance
- Sporadic
- Distinguishing Features
- Hands/feet predominant, proximal sparing, camptodactyly + clubfoot
- Intelligence
- Normal
- Inheritance
- Autosomal dominant
- Distinguishing Features
- Whistling face, microstomia, ulnar deviation; MYH3 mutation
- Intelligence
- Usually normal
- Inheritance
- Autosomal dominant
- Distinguishing Features
- Multiple large-joint dislocations, flat facies, cervical kyphosis (cord risk)
- Intelligence
- Normal
- Inheritance
- AD (FLNB)
- Distinguishing Features
- Short limbs, hitchhiker thumb, cauliflower ear, cleft palate
- Intelligence
- Normal
- Inheritance
- AR (SLC26A2)
- Distinguishing Features
- CNS signs, progressive weakness, abnormal imaging/EMG
- Intelligence
- Often impaired
- Inheritance
- Variable
Symmetric four-limb contractures + midline frontal capillary haemangioma + normal cognition strongly suggests amyoplasia. Hall's 2014 series of 560 patients confirmed this is the single most common recognisable form and is entirely sporadic — reassure parents regarding recurrence risk.
The Waiter's Tip Trap: Amyoplasia versus Obstetric Brachial Plexus (Erb's) Palsy
The classic amyoplasia upper limb is repeatedly described as the "Waiter's Tip" posture — internally-rotated adducted shoulder, extended elbow, pronated forearm, flexed wrist. That is exactly the posture of an obstetric brachial plexus (Erb's, C5-6) palsy, so the two are a classic neonatal trap, and getting it wrong sends the child down the wrong pathway entirely.
The single best discriminator is the joints: in amyoplasia they are stiff (a fixed contracture limiting passive as well as active motion); in Erb's palsy the limb is floppy with full passive motion (a paralysis, not a contracture).
- Amyoplasia
- Fixed joint CONTRACTURE
- Erb's palsy (obstetric brachial plexus)
- Flaccid NERVE palsy (C5-6)
- Amyoplasia
- Limited / stiff
- Erb's palsy (obstetric brachial plexus)
- Full and free (the joints are not contracted)
- Amyoplasia
- Bilateral and symmetric
- Erb's palsy (obstetric brachial plexus)
- Usually unilateral
- Amyoplasia
- Multiple — feet, hips, knees also involved
- Erb's palsy (obstetric brachial plexus)
- Isolated to the affected arm
- Amyoplasia
- No birth trauma; reduced fatty muscle bulk, sensation preserved
- Erb's palsy (obstetric brachial plexus)
- Difficult/instrumented delivery, shoulder dystocia; hypotonic, absent Moro/biceps reflex
Why it matters: the management diverges completely. Erb's palsy is treated with physiotherapy and often partially recovers, with microsurgical nerve reconstruction for those that do not — it is a nerve problem. Amyoplasia needs contracture management (stretching, serial casting, and later tendon transfers such as triceps-to-biceps). A "waiter's tip" arm that is bilateral, stiff and accompanied by clubfeet is amyoplasia until proven otherwise — never label it a birth palsy.
Q: A neonate has the 'waiter's tip' posture — how do you tell amyoplasia from an Erb's palsy? A: Test passive motion and look at the other limbs. Amyoplasia is a stiff, fixed contracture, usually bilateral and symmetric with other joints involved (clubfeet, hips), sensation preserved and no birth trauma. Erb's palsy is a flaccid C5-6 nerve injury — usually unilateral, with full passive motion, an absent Moro/biceps reflex and a difficult-delivery history that often partially recovers.
Investigations
- Diagnosis is clinical (multiple congenital contractures).
- Investigations aim to find the underlying cause.
- Genetic Testing: Gene panels for distal arthrogryposis, SMA, etc.
- MRI Brain/Spine: If neurogenic cause suspected.
- EMG/NCS: Differentiate myopathic vs neurogenic.
- Muscle Biopsy: If myopathy suspected.
- Ophthalmology Review: Associated eye anomalies.
- Cardiac Echo: Associated cardiac anomalies.
- Hip X-ray/Ultrasound: Assess dislocation.
- Spine X-ray: Scoliosis.
- Foot X-ray: Clubfoot assessment.
Management Algorithm
Surgical Technique
Clubfoot Treatment in AMC
Initial: Serial casting (Ponseti-style).
- Often achieves partial correction.
- More casts may be needed than idiopathic.
Achilles Tenotomy: Almost always needed.
If Residual Deformity (Common):
- Posteromedial Release (PMR): Extensive release of hindfoot soft tissues.
- Talectomy: Removal of talus for severe rigid clubfoot. Creates a plantigrade foot.
Goal: Plantigrade foot that can be braced and shoe-fitted.
Complications
- Risk Factor
- Rigid deformity
- Management
- Revision surgery
- Risk Factor
- Inherent in AMC
- Management
- Accept / Physio
- Risk Factor
- Forced reduction
- Management
- Avoid aggressive reduction
- Risk Factor
- Atypical creases
- Management
- Careful incision planning
- Risk Factor
- Natural history
- Management
- Monitor / Fusion
Postoperative Care
- Cast 6-8 weeks.
- Bracing long-term (AFO, UCBL).
- Monitor for recurrence.
- Splint in flexion 6 weeks.
- Gradual ROM.
- Long-term PT.
Outcomes
- Amyoplasia: Excellent outcomes. Most walk. Normal intelligence and lifespan.
- Syndromic: Depends on underlying condition.
- Function: Children adapt remarkably and achieve independence.
Guidelines, Registries & Global Practice
Global epidemiology: Arthrogryposis affects roughly 1 in 3,000 to 1 in 5,000 live births worldwide; amyoplasia is the most common recognisable form (Hall 2014, N=560). Distribution is broadly similar across regions; apparent variation reflects ascertainment rather than true geography.
Side-by-side guidance:
- Position relevant to AMC
- Multidisciplinary, function-led care; Ponseti casting first-line for clubfoot of any aetiology
- Position relevant to AMC
- Casting-first with rigorous foot-abduction bracing; surgery reserved for relapse/failure
- Position relevant to AMC
- Soft-tissue balancing and staged correction; aim for a plantigrade, braceable foot, not a normal arc
- Position relevant to AMC
- Early genetic work-up to define subtype and recurrence risk before committing to a surgical plan
There is no dedicated AMC implant registry; arthroplasty registries (NJR, AJRR, AOANJRR) are not relevant in childhood. Outcome data come from specialist-centre cohorts and clubfoot relapse audits, which consistently identify brace non-compliance as the dominant predictor of recurrence.
In high-resource settings, early MDT clinics (orthopaedics, physiotherapy, occupational therapy, genetics) and serial casting from the neonatal period are standard. In limited-resource settings, late presentation is common, Ponseti programmes are the most scalable and cost-effective intervention, and talectomy remains a valuable single-stage salvage where staged reconstruction and long-term bracing are impractical.
Controversies and Areas of Uncertainty
No consensus. Bilateral teratologic dislocations are often left unreduced if symmetric and painless, as motion may matter more than location for sitting and gait. Others reduce via the medial approach citing satisfactory acetabular development (Szöke 1996). AVN risk is the deciding factor.
Historically AMC clubfoot went straight to extensive release. Boehm/Dobbs (2008) showed Ponseti casting works (more casts, strict bracing), shifting practice toward casting-first. Talectomy/release is now reserved for true failure.
Whether to correct knee flexion before or after hip and foot is debated. Many correct the knee first because residual knee flexion undermines foot bracing and gait, but sequencing is individualised.
For fixed knee extension (hyperextension/dislocation), VY quadricepsplasty versus distal femoral extension osteotomy or shortening is unsettled; choice depends on age, severity and reducibility.
Viva Scenarios
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“What is your diagnosis and approach?”
“What are your options?”
“How would you help this child?”
MCQ Practice Points
Q: What is Arthrogryposis? A: A descriptive term for conditions with multiple congenital joint contractures affecting two or more body areas. It is NOT a specific diagnosis.
Q: What is the most common recognizable type of AMC? A: Amyoplasia (~30% of cases). Sporadic, Normal intelligence, Symmetric limb involvement.
Q: Why is clubfoot in AMC different from idiopathic clubfoot? A: AMC clubfoot is RIGID and resistant to conservative treatment. It often requires extensive surgery (Posteromedial Release or Talectomy).
Q: What is the priority for upper limb surgery in AMC? A: Elbow flexion - to allow hand-to-mouth function for feeding and self-care.
Q: What is the procedure to restore elbow flexion in AMC? A: Triceps to Biceps transfer - the triceps is detached and rerouted to act as an elbow flexor.
Key Features
- Multiple congenital contractures
- Fetal akinesia is cause
- Amyoplasia = Normal IQ
- Non-progressive
Lower Limb
- Clubfoot: Casting then PMR/Talectomy
- Hip: Bilateral may leave dislocated
- Knee: Serial casting, Release
- Goal: Independent Mobility
- Vertical Talus: Common, Surgical
Upper Limb
- Elbow Flexion = Priority
- Triceps to Biceps Transfer
- Wrist Fusion for function
- Thumb-in-Palm Release
Prognosis
- Amyoplasia: Excellent (Normal IQ)
- Most walk (85%+)
- Children adapt well
- Distal Arthrogryposis: Best outcomes
- Ongoing PT/OT essential for function
Evidence Base
Amyoplasia Revisited — the defining series
- 560 individuals collated from over 600 reports — the largest amyoplasia cohort.
- Most common recognisable form; 55.9% had symmetric four-limb involvement; equinovarus almost always present and elbows characteristically extended.
- Completely sporadic; fatty-fibrous muscle replacement and vascular-compromise anomalies (bowel atresia, gastroschisis, digit loss) support a vascular pathogenesis.
Foot deformities in AMC — surgery is usually needed
- 43 of 52 AMC patients had foot deformities; talipes equinovarus was the commonest (72 feet), bilateral in all cases.
- Primary treatment was operative in 52 patients; recurrence was frequent (36 reoperations across 15 feet).
- Talectomy and bony decancellation were both effective for recurrent deformity; knee/hip deformity influenced foot outcomes.
Ponseti method for distal arthrogrypotic clubfoot
- 12 infants (24 feet) with distal-arthrogryposis clubfoot; initial correction achieved in all feet.
- Required a mean of 6.9 casts versus 4.5 for idiopathic clubfeet (p=0.002) — more casts but still effective.
- All six relapses were linked to brace non-compliance; most were salvaged by repeat casting/tenotomy.
Tendon transfer to restore elbow flexion
- 18 tendon transfers in 14 children; triceps-to-biceps gave the best results (7 of 9 arms good).
- Capsulotomy with triceps lengthening improved the motion arc from 17° to 67°.
- Best candidates: age over 4 years, full passive elbow motion in the dominant arm, and at least grade-4 donor strength.
Medial-approach open reduction of the arthrogrypotic hip
- 40 dislocations in 26 amyoplasia patients; medial-approach open reduction at a mean 8.9 months.
- 92% good/fair outcomes with satisfactory acetabular development; bilateral cases showed no stiffness or asymmetry.
- AVN occurred in 4 of 25 hips — the principal risk to weigh against reduction.
Hip dislocation management — approach matters
- 18 of 131 arthrogryposis children had hip dislocation; 14 underwent open reduction.
- Medial-approach reduction gave better range of motion and acetabular development than anterolateral or bilateral closed reduction.
- Only one AVN and no redislocations after the medial approach.
BSCOS / AO consensus on paediatric clubfoot and neuromuscular foot
- Ponseti casting is first-line for all clubfoot types, including syndromic/arthrogrypotic, before any soft-tissue surgery.
- Bracing adherence is the dominant predictor of relapse across registries and cohorts.
- Soft-tissue release and talectomy are reserved for true Ponseti failure, not used as primary treatment.