Clinodactyly

Clinodactyly is defined as angular deviation of a digit in the coronal (radioulnar) plane, most commonly affecting the small finger with radial deviation.

Definition and Terminology

• Clinodactyly: From Greek "klinein" (to bend) and "daktylos" (finger)
• Coronal plane deviation: Angular deviation in radioulnar direction
• Distinguish from: Camptodactyly (flexion deformity in sagittal plane)
• Kirner deformity: Specific form affecting small finger distal phalanx with volar-radial curvature

Epidemiology

• General Population: 1-10% incidence (variable based on diagnostic threshold)
• Down Syndrome: Over 50% affected (strongest association)
• Gender: Equal distribution male to female
• Bilaterality: Often bilateral (60-70% of cases)
• Inheritance: Often autosomal dominant with variable penetrance

Associated Conditions

Embryology

• Digital formation occurs at weeks 4-8 of gestation
• Phalangeal development involves chondrification (week 5-6)
• Normal physes form as straight transverse plates
• Delta phalanx results from abnormal chondrification
• Bracket epiphysis develops instead of normal linear physis

Normal Phalangeal Anatomy

• Rectangular bone: Tubular shape with parallel sides
• Linear physis: Straight transverse growth plate on ONE end
• Symmetric growth: Equal growth on radial and ulnar sides
• Normal alignment: Straight digital cascade in coronal plane

Delta Phalanx Pathoanatomy

Key Features:

1. Triangular/wedge shape: Instead of rectangular phalanx
2. C-shaped bracket epiphysis: Curves around and spans TWO sides of bone
3. Asymmetric growth: Shorter side (usually radial) grows less
4. Progressive deformity: Angular deviation increases with skeletal growth

Radiographic Appearance:

• AP view (best): Triangular bone outline, C-shaped physis visible
• Lateral view: May appear relatively normal
• Physeal shape: C or bracket configuration pathognomonic
• Adjacent bones: Usually normal morphology

Biomechanics of Deformity

• Hueter-Volkmann principle: Compression inhibits growth, tension stimulates
• Bracket physis: Tethers one side while allowing growth on other
• Progressive nature: Deformity worsens during growth spurts
• Growth cessation: Deformity stabilizes after skeletal maturity
• Remodeling potential: Limited in coronal plane deformities

Location Distribution

Most Common: Small Finger (5th Digit)

• Middle phalanx involvement (most frequent)
• Radial deviation typical
• Often bilateral
• Associated with Down syndrome

Less Common: Other Digits

• Index finger (2nd most common)
• Thumb (rare, when present often syndromic)
• Multiple digits (syndromic associations)

History

Key Questions:

• Age when deformity first noticed
• Progressive vs stable deformity
• Family history (autosomal dominant pattern)
• Functional limitations (overlapping, grip problems)
• Syndromic features (developmental delay, cardiac issues)
• Cosmetic concerns (patient/parent perspective)

Physical Examination

Measurement of Deformity

Clinical Measurement:

• Use goniometer with digit in extension
• Measure angle of deviation from longitudinal axis
• Document in degrees
• Compare with contralateral side if bilateral

Radiographic Measurement:

• More accurate than clinical measurement
• Measure angle between proximal and distal phalanx longitudinal axes
• Use AP radiograph with hand flat
• Document progression over time if serial films

Severity Classification:

• Mild: Under 10 degrees (observation)
• Moderate: 10-30 degrees (observation vs surgery)
• Severe: Over 30 degrees (surgery usually indicated)

Radiographic Imaging

Standard Views:

• AP hand: Essential - shows angular deformity and delta phalanx
• Lateral hand: Supplementary - may miss deformity in coronal plane
• Oblique: Sometimes helpful for bracket epiphysis visualization

Key Radiographic Features:

1. Delta phalanx identification

   • Triangular or wedge-shaped bone
   • C-shaped or bracket epiphysis
   • Best seen on AP view

2. Angular measurement

   • Measure angle between adjacent phalanges
   • Document severity
   • Serial films to assess progression

3. Growth plate assessment

   • Open vs closing physis (affects surgical options)
   • Bracket configuration
   • Physeal asymmetry

4. Adjacent structures

   • Joint congruity
   • Collateral ligament stress
   • Rotation component

Additional Imaging

• Advanced imaging rarely needed: Plain radiographs sufficient in most cases
• CT scan: Reserved for complex deformities or preoperative planning
• MRI: Not routinely indicated

Other Investigations

If Syndromic Features Present:

• Genetic testing: Karyotype for Down syndrome
• Cardiac echo: Congenital heart disease in syndromes
• Developmental assessment: Global development evaluation
• Genetic counseling: Familial cases

Isolated Clinodactyly:

• No additional testing required
• X-rays confirm diagnosis
• Monitor for progression

Intraoperative Complications

• Neurovascular injury: Digital nerves at risk - stay dorsal, identify and protect
• Complete osteotomy: Loss of hinge - leads to instability
• Inadequate correction: Undercorrection - may need revision
• Overcorrection: Usually minor, can remodel
• Bone graft dislodgment: Ensure stable graft position

Early Postoperative Complications (under 6 weeks)

Late Complications (over 6 weeks)

Recurrent Deformity:

• Incidence: 10-20% after physiolysis (higher than osteotomy)
• Causes: Incomplete physeal excision, growth recurrence
• Management: Observation vs revision osteotomy

Nonunion:

• Rare: under 5% with adequate bone graft
• Risk factors: Inadequate graft, excessive motion
• Management: Revision grafting if symptomatic

Angular Deformity:

• Undercorrection: Most common issue (10-15%)
• Overcorrection: Less common, usually minor
• Management: Revision osteotomy if severe, observe if mild

Stiffness:

• PIPJ stiffness: 10-20% have some stiffness
• Usually mild: 10-20 degree loss
• Prevention: Early ROM after K-wire removal
• Management: Hand therapy, rare need for manipulation

Growth Disturbance:

• Physeal damage: Rare with careful technique
• Shortening: Expected with closing wedge (2-3mm)
• Angular deformity: From asymmetric growth arrest

Immediate Postoperative (0-4 weeks)

Immobilization:

• Dorsal blocking splint
• Include MCPJ, PIPJ, and DIPJ of affected digit
• Buddy tape to adjacent digit for stability
• Elevate hand for first 48-72 hours

Wound Care:

• K-wires left protruding through skin
• Pin site care: Clean with saline daily
• Monitor for infection signs
• Keep splint clean and dry

Pain Management:

• Usually minimal pain after first 2-3 days
• Paracetamol or ibuprofen sufficient
• Ice therapy for swelling

Intermediate Phase (4-6 weeks)

Radiographic Assessment:

• X-ray at 4 weeks to assess healing
• Check alignment maintenance
• Assess bone graft incorporation

K-wire Removal:

• Usually 4-6 weeks postoperatively
• Once radiographic union evident
• Can remove in clinic (no anesthesia usually needed in cooperative child)
• Continue splinting part-time after removal

Late Phase (6 weeks to 3 months)

Splint Weaning:

• Gradual weaning after K-wire removal
• Night splinting for additional 2-4 weeks
• Progressive return to activities

Range of Motion:

• Begin gentle active ROM after K-wire removal
• Focus on PIPJ and DIPJ motion
• Buddy tape during activities
• Hand therapy if significant stiffness

Strengthening:

• Progressive strengthening at 8-10 weeks
• Age-appropriate activities
• Return to unrestricted activity at 12 weeks

Long-term Follow-up

• 3 months: Clinical and radiographic assessment
• 6 months: Assess final alignment and function
• Annual: Monitor through skeletal maturity for recurrence
• Skeletal maturity: Final assessment, discharge if stable

Expected Outcomes

Opening Wedge Osteotomy:

• Correction: Excellent angular correction in over 90%
• Recurrence: Low (under 5%) with adequate technique
• Function: Minimal impact, good ROM
• Satisfaction: High patient/parent satisfaction

Physiolysis:

• Correction: Variable, 60-80% achieve satisfactory correction
• Recurrence: Higher (10-20%) than osteotomy
• Gradual: Correction occurs over 2-3 years
• May need secondary procedure: 15-20% require later osteotomy

Non-operative (Observation):

• Mild deformity (under 30 degrees): Usually stable, good function
• Progression: 10-20% progress during growth spurts
• Functional impact: Minimal in most cases
• Satisfaction: Good for mild deformities

Prognostic Factors

Functional Outcomes

• Range of Motion: Usually normal or near-normal (within 10 degrees of contralateral)
• Grip Strength: Not affected by surgery
• Fine Motor: Returns to baseline
• Cosmesis: Significant improvement, scar usually inconspicuous
• Patient Satisfaction: High (over 85% satisfied or very satisfied)

Long-term Prognosis

• Excellent prognosis for isolated clinodactyly with surgery
• Low risk of recurrence with opening wedge technique
• Normal hand function expected
• No increased risk of arthritis from surgery
• Psychosocial impact: Improved confidence with correction

Clinodactyly management in Australia follows international best practice guidelines. Pediatric hand surgery services are available through major metropolitan children's hospitals in Sydney, Melbourne, Brisbane, Adelaide, and Perth. Regional centers may have visiting pediatric hand surgeons or utilize telehealth for initial consultation.

The association between Down syndrome and clinodactyly is well-recognized in Australian practice, with screening and developmental follow-up provided through specialized Down syndrome clinics in public hospital systems. Early genetic diagnosis and multidisciplinary care facilitate appropriate referral for hand surgery assessment when clinodactyly is functionally or cosmetically significant.

Surgical correction with opening wedge osteotomy is typically performed as a day surgery procedure under general anesthesia. Bone graft harvest from iliac crest is standard practice in Australian centers. Postoperative hand therapy services are available through public hospital occupational therapy departments and private hand therapy clinics for cases requiring ROM rehabilitation.

Public hospital waiting lists for elective pediatric hand surgery may be 3-6 months depending on location and urgency. Private sector option provides earlier access. Medicare coverage applies for functionally indicated surgery (over 30 degrees or progressive deformity), while purely cosmetic cases may have limited rebates.

Long-term follow-up through skeletal maturity is standard practice to monitor for recurrence or growth-related issues. Telehealth has improved access for regional families requiring serial radiographic and clinical monitoring.