Down Syndrome Orthopaedic
Ligamentous Laxity and Orthopaedic Challenges
Key Orthopaedic Issues
Critical Must-Knows
- Atlantoaxial Instability: ADI greater than 5mm on lateral flexion-extension.
- Ligamentous Laxity: Universal - affects all joints.
- Hip Instability: Late onset common. May develop in childhood.
- Cervical Clearance: Before anesthesia, contact sports.
- Os Odontoideum: Associated with AAI.
Examiner's Pearls
- "ADI greater than 5mm is abnormal
- "Cervical clearance before intubation
- "Hip instability is late onset
- "Ligamentous laxity universal
Clinical Imaging
Imaging Gallery
Atlantoaxial Instability (AAI)
Diagnostic Criterion
ADI > 5mm on lateral flexion-extension X-ray is abnormal. AAI incidence is 10-20%.
Screening Indications
Screen before Anesthesia (intubation risk) or Contact Sports/Special Olympics.
Symptomatic AAI
Neck pain, torticollis, or myelopathy mandates C1-C2 Fusion to prevent cord injury.
Orthopaedic Issues in Down Syndrome
| Issue | Incidence | Management |
|---|---|---|
| 10-20% | Screening, C1-C2 fusion if symptomatic | |
| 10-20% | Reconstruction or salvage | |
| Common | Realignment surgery | |
| 90% | Orthotics, rare surgery |
Down Syndrome Ortho Issues
Memory Hook:AHKF - Atlas, Hips, Knees, Feet.
AAI Features
Memory Hook:ASS - ADI, Symptomatic, Screening.
Hip Issues
Memory Hook:LAS - Late, AVN, Salvage.
Overview/Epidemiology
Down Syndrome (Trisomy 21) is the most common chromosomal abnormality.
- Genetics: Extra chromosome 21 (Trisomy 21).
- Incidence: 1 in 700-1000 live births.
- Key Feature: Generalized ligamentous laxity affecting all joints.
- Associated Conditions: Cardiac defects, hypothyroidism, leukemia, cognitive impairment.
Pathophysiology and Mechanisms
Ligamentous Laxity
- Collagen abnormalities lead to ligamentous laxity.
- All joints are hypermobile.
- Transverse ligament of C1 is lax → atlantoaxial instability.
Why Hip Instability Develops
- Unlike DDH which is present at birth, hip instability in DS may develop later.
- Lax capsule and ligaments allow progressive subluxation.
- May present at 2-10 years with painful limp.
Classification Systems
Atlantoaxial Instability
- Radiographic: ADI greater than 5mm on lateral flexion-extension.
- Os Odontoideum: Associated finding.
- Asymptomatic: Most. Still at risk.
- Symptomatic: Myelopathy, gait changes, torticollis.
Clinical Assessment
History:
- Developmental milestones.
- Walking age.
- Any neck pain, gait changes.
- Hip or knee symptoms.
Physical Exam:
- General: Hypotonia, short stature.
- Cervical Spine: ROM (limited may indicate instability), neurological exam.
- Hips: Stability, ROM.
- Knees: Patella tracking, apprehension.
- Feet: Arch, alignment.
- Generalized Laxity: Beighton score often high.
Investigations
Cervical Spine:
- Lateral Flexion-Extension X-ray: ADI measurement.
- CT: Os odontoideum, bony anomalies.
- MRI: If symptomatic, assess cord compression.
Hips:
- X-ray: AP pelvis, lateral.
- MRI: If AVN suspected.
Management Algorithm
Atlantoaxial Instability
- Asymptomatic with ADI 5-10mm: Restrict contact sports. Monitor.
- Symptomatic OR ADI greater than 10mm: C1-C2 fusion.
- Pre-operative Screening: Flexion-extension X-ray before anesthesia.
Surgical Techniques
C1-C2 Fusion
Indications: Symptomatic AAI, progressive instability.
Technique: Posterior approach. Gallie or Brooks wiring, or Harms (C1 lateral mass screws, C2 pedicle screws) with bone graft.
Post-op: Halo or rigid collar.
Complications
Cervical Spine Complications
| Complication | Risk | Prevention | Management |
|---|---|---|---|
| Spinal Cord Injury | With AAI + trauma/intubation | Activity restriction, careful intubation | Fusion, rehabilitation |
| Neurological Deterioration | Progressive myelopathy | Early fusion for symptomatic AAI | Emergency stabilisation |
| Atlantoaxial Rotatory Subluxation | Post-trauma | Avoid high-risk activities | Traction, fusion if recurrent |
| Pseudarthrosis | After fusion | Proper technique, bone graft | Revision fusion |
| Hardware Failure | Osteoporosis, hypotonia | Adequate fixation | Revision with reinforcement |
Hip Surgery Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Avascular Necrosis | 20-40% | Open reduction, age over 2 | Monitor, salvage procedures |
| Re-dislocation | 15-30% | Inadequate soft tissue, hypotonia | Revision, muscle transfers |
| Stiffness | Variable | Prolonged immobilisation | Physiotherapy, releases |
| Residual Dysplasia | Common | Inadequate correction | Pelvic osteotomy |
| Infection | Higher than typical | Immune dysfunction | Aggressive treatment |
Anaesthetic and Perioperative Risks
Critical considerations for surgery in Down Syndrome:
- Difficult Airway: Macroglossia, small trachea, atlantoaxial instability
- Cardiac Disease: 40-50% have congenital heart defects - preoperative echo essential
- Respiratory Issues: Subglottic stenosis, sleep apnoea - postoperative monitoring crucial
- Immune Dysfunction: Higher infection risk - meticulous sterile technique
- Osteoporosis: Hardware complications more common - adequate fixation
Long-term Orthopaedic Issues
- Progressive Hypotonia: May affect rehabilitation outcomes
- Joint Laxity: Leads to instability, recurrent dislocations
- Accelerated Osteoarthritis: Hip and knee arthritis in young adults
- Cervical Degeneration: Early spondylosis due to laxity
- Pes Planus Progression: May require orthotic support lifelong
Postoperative Care
Cervical Fusion Rehabilitation
- Immobilisation: Halo or rigid collar for 3-6 months
- Activity Restriction: No contact sports, high-risk activities indefinitely
- Monitoring: Clinical and radiographic follow-up until fusion confirmed
- Long-term: Annual surveillance for adjacent segment disease
Hip Surgery Recovery
| Phase | Duration | Management |
|---|---|---|
| Immobilisation | 6-12 weeks | Spica cast or abduction brace |
| Protected Mobilisation | 3-6 months | Walking aids, physiotherapy |
| Strengthening | 6-12 months | Progressive muscle strengthening |
| Long-term | Ongoing | Monitor for AVN, dysplasia |
Special Considerations
- Communication: Adapt instructions for cognitive level
- Family Support: Essential for compliance with bracing
- School/Therapy: Coordinate with educational services
- Cardiac Monitoring: If heart disease present
Follow-up Protocol
- Early: 2, 6, 12 weeks for wound, neurological status
- Medium-term: 3, 6 months for radiographic healing
- Long-term: Annual for skeletal maturity, late complications
- Transition: Plan adult care by age 16-18
Outcomes/Prognosis
Cervical Spine Outcomes
| Presentation | Treatment | Expected Outcome |
|---|---|---|
| Asymptomatic AAI | Activity restriction | Usually stable, rare progression |
| Myelopathy (Early) | Fusion | 70-80% neurological improvement |
| Myelopathy (Established) | Fusion | Stabilisation, limited recovery |
| Quadriplegia | Supportive | Poor prognosis |
Hip Outcomes
- Open Reduction (Under 2yrs): 60-70% satisfactory long-term
- Open Reduction (Over 2yrs): Higher AVN, redislocation rates
- Pelvic Osteotomy: Improves coverage when hip reducible
- Salvage Procedures: Palliative for failed reconstruction
Functional Outcomes
| Domain | Expectation | Factors |
|---|---|---|
| Ambulation | 90% community ambulators | Hip stability, hypotonia degree |
| Independence | Variable | Cognitive level, orthopaedic status |
| Quality of Life | Generally good | Family support, access to services |
Key Prognostic Points
- AAI Fusion: Good outcomes if done for symptomatic patients before permanent deficit
- Hip Reconstruction: High failure rate (30-40%), AVN common, but function often maintained
- Early Intervention: Better outcomes for both spine and hip issues
- Overall: Most orthopaedic issues manageable with good quality of life achievable
Evidence Base
- Updated guidelines for DS
- AAI screening controversial
- Clinical assessment important
- AAI natural history
- Most asymptomatic
- Fusion for symptomatic
- Hip dislocation in DS
- Different from DDH
- Later onset
- Hip surgery in DS
- High complication rate
- AVN common
- Comprehensive DS orthopaedics
- Ligamentous laxity key
- Multidisciplinary care
Viva Scenarios
Practice these scenarios to excel in your viva examination
Pre-Operative AAI Screening
"5-year-old with Down Syndrome requires general anesthesia for dental work. How do you assess cervical spine?"
This child needs **cervical spine assessment before intubation**. I would order **lateral flexion-extension X-rays** and measure the **ADI (Atlantodental Interval)**. If ADI is **less than 5mm**, intubation can proceed with care (avoid hyperflexion). If **5-10mm**, intubation should be cautious with in-line stabilization. If **greater than 10mm or symptomatic**, I would refer to a spine surgeon before elective procedure.
Late Onset Hip Dislocation
"8-year-old with DS presents with a limp. X-ray shows subluxated left hip. Walking milestone was normal. No trauma."
This is **late-onset hip instability** characteristic of Down Syndrome (unlike DDH which is present at birth). It develops due to ligamentous laxity. Management is challenging. Options: (1) **Observe** if asymptomatic. (2) **Reconstruction** (open reduction, pelvic/femoral osteotomy) if reducible and cartilage intact, but warn of high failure and AVN risk. (3) **Salvage** (Girdlestone or shelf) if unreducible or failed reconstruction. I would discuss with the family that outcomes are often poor.
Symptomatic AAI
"Same child develops neck pain and gait changes. ADI is 8mm. What is your management?"
This child has **symptomatic atlantoaxial instability**. Symptoms (neck pain, gait changes) indicate cord compression. Management: **MRI to assess cord**. If cord compression or myelopathy, urgent **C1-C2 fusion** is needed. I would admit the child, immobilize the cervical spine with a hard collar, and refer urgently to a pediatric spine surgeon.
MCQ Practice Points
AAI MCQ
Q: What ADI is abnormal in Down Syndrome? A: Greater than 5mm on lateral flexion-extension X-ray.
Hip MCQ
Q: How does hip instability in DS differ from DDH? A: It is late-onset (develops in childhood), unlike DDH which is present at birth.
Screening MCQ
Q: When should cervical spine screening be done? A: Before anesthesia (intubation) and contact sports.
Foot MCQ
Q: What is the common foot deformity in DS? A: Pes planovalgus (flatfoot). Usually managed with orthotics.
Hip Surgery MCQ
Q: What is the prognosis for hip surgery in Down Syndrome? A: High failure rate with AVN common. Salvage procedures often needed.
Os Odontoideum MCQ
Q: What cervical anomaly is associated with AAI in DS? A: Os odontoideum - separate ossicle at tip of odontoid.
Australian Context
- Special Olympics: Cervical clearance required before participation.
- Anesthesia Guidelines: AAI screening recommended.
- Multidisciplinary Care: Down Syndrome Association support.
- Orthopaedic Follow-Up: Regular assessment for hip and spine.
DOWN SYNDROME ORTHOPAEDIC
High-Yield Exam Summary
CERVICAL
- •AAI 10-20%
- •ADI greater than 5mm abnormal
- •Screen before anesthesia
- •C1-C2 fusion if symptomatic
HIP
- •Late onset
- •High failure rate
- •AVN common
- •Salvage may be needed
KNEE/FOOT
- •Patella instability
- •Pes planovalgus 90%
- •Orthotics usually enough
- •Surgery rarely needed
KEY CONCEPT
- •Ligamentous laxity
- •All joints affected
- •Generalized hypermobility
- •Beighton score high
SCREENING
- •Before anesthesia
- •Before contact sports
- •Special Olympics clearance
- •Clinical symptoms first
EXAM PEARLS
- •Os odontoideum association
- •Hip differs from DDH
- •MRI for cord compression
- •Multidisciplinary care
Self-Assessment Quiz
Differential Diagnosis
Other Causes of Generalized Ligamentous Laxity:
- Ehlers-Danlos Syndrome: Skin hyperelasticity, joint hypermobility, different genetics.
- Marfan Syndrome: Tall stature, arachnodactyly, aortic root dilatation.
- Larsen Syndrome: Multiple joint dislocations at birth.
Key Differentiators for Down Syndrome:
- Characteristic facial features.
- Cognitive impairment.
- Chromosome analysis confirms Trisomy 21.
- Cardiac defects (40-50%).
Red Flags:
- Any neurological symptoms → urgent cervical spine assessment.
- New limp → hip instability developing.
- Patellar dislocation → realignment may be needed.
Associated Medical Conditions:
- Cardiac defects (40-50%) - AV canal defects.
- Hypothyroidism - screen regularly.
- Leukemia - increased risk.
- Hearing impairment - assess.