Arthrogryposis
Arthrogryposis Multiplex Congenita | Multiple Contractures
AMC Classification
Critical Must-Knows
- 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.
Examiner's Pearls
- "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.
Clinical Imaging
Imaging Gallery
AMC Orthopaedic Pitfalls
Rigid Deformities
AMC Contractures are RIGID. Do not expect Ponseti-level success with serial casting alone. Surgery is often needed.
Multiple Joints
Address Multiple Joints. AMC involves many joints. Prioritize for function (Elbows, Knees, Hips, Feet).
Intelligence is Normal
In Amyoplasia. Do not assume cognitive impairment. These children are typically intelligent and motivated.
Skin Issues
Poor Skin Creases. AMC skin does not have normal creases. Incision planning is important.
At a Glance: AMC Types
| Type | Features | Inheritance | Intelligence |
|---|---|---|---|
| Amyoplasia (Classic) | Symmetric limb contractures, 'Waiter's Tip' | Sporadic | Normal |
| Distal Arthrogryposis | Hands and Feet primarily | AD | Normal |
| Syndromic (Neurogenic) | CNS involvement | Variable | Often impaired |
| Syndromic (Myopathic) | Muscle disease | Variable | Variable |
CONGENITALAMC Features
Memory Hook:Key features of AMC.
ELBOWUpper Limb Priority
Memory Hook:Elbow Flexion is KEY.
RIGIDClubfoot in AMC
Memory Hook:AMC Clubfoot is RIGID.
Overview and Epidemiology
Definition: 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.
Epidemiology:
- Incidence: 1 in 3000 live births.
- Amyoplasia: ~30% of AMC cases (most common recognizable type).
Pathogenesis (Fetal Akinesia): 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).
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:
| Duration | Gestational Age | Consequence |
|---|---|---|
| Brief | Early | Mild contractures (correctable) |
| Prolonged | Early (8-12 weeks) | Severe fixed contractures |
| Late onset | Third trimester | 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)
Why Contractures Are Fixed
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.
Anatomy and Joint-Specific Considerations
Key Anatomy: Understanding the relevant anatomy is crucial for diagnosis and management. The structures involved include the osseous architecture and surrounding soft tissues.
Pathomechanics: The injury mechanism often involves specific loading patterns that disrupt the structural integrity.
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
History:
- Pregnancy: Decreased fetal movements? Oligohydramnios?
- Birth: Breech? Complications?
- Family History: Any inheritance pattern?
- Development: Milestones? Intelligence?
Physical Examination:
- 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.
Investigations
Diagnosis (Clinical):
- Diagnosis is clinical (multiple congenital contractures).
- Investigations aim to find the underlying cause.
Investigations:
- 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.
Orthopaedic Imaging:
- 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.
Management Algorithm
Complications
Complications
| Complication | Risk Factor | Management |
|---|---|---|
| Recurrence (Clubfoot) | Rigid deformity | Revision surgery |
| Stiffness | Inherent in AMC | Accept / Physio |
| AVN (Hip Reduction) | Forced reduction | Avoid aggressive reduction |
| Skin Issues | Atypical creases | Careful incision planning |
| Scoliosis Progression | Natural history | Monitor / Fusion |
Postoperative Care
After Clubfoot Surgery:
- Cast 6-8 weeks.
- Bracing long-term (AFO, UCBL).
- Monitor for recurrence.
After Elbow Surgery:
- 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.
Evidence Base
Amyoplasia Description
- Defined Amyoplasia as a distinct entity.
- Sporadic, Not inherited.
- Normal intelligence.
Clubfoot in AMC
- Clubfoot in AMC is rigid and resistant to conservative treatment.
- Often requires extensive surgery (PMR, Talectomy).
- Recurrence is common.
Elbow Reconstruction
- Triceps to Biceps transfer effective for elbow flexion.
- Achieves functional elbow flexion.
- Improves self-care.
Hip Management
- Bilateral hip dislocation in AMC may not need reduction.
- Unilateral dislocation should be reduced.
- Forced reduction risks AVN.
Talectomy for Severe Clubfoot
- Talectomy creates a plantigrade foot in rigid clubfoot.
- Useful when other methods fail.
- Accepts reduced range of motion.
Viva Scenarios
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
The Newborn with Stiff Joints
"What is your diagnosis and approach?"
The Clubfoot Question
"What are your options?"
The Elbow Problem
"How would you help this child?"
MCQ Practice Points
Definition
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.
Most Common Type
Q: What is the most common recognizable type of AMC? A: Amyoplasia (~30% of cases). Sporadic, Normal intelligence, Symmetric limb involvement.
Clubfoot Treatment
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).
Upper Limb Priority
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.
Elbow Surgery
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.
Australian Context
- MDT Clinics: Pediatric hospitals have arthrogryposis clinics.
- NDIS: Supports therapy, equipment, orthotics.
- Genetic Services: State genetics services for testing and counseling.
High-Yield Exam Summary
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