Swan neck deformity vs Boutonniere deformity

Alterations in the relationships between the balanced extrinsic and intrinsic musculature of the hand due to trauma or secondary to the effects of systemic disease may cause the development of functional deformities such as a boutonnière or swan-neck deformity.

rheumatoid hand
Swan-neck deformityBoutonniere deformity
ThumbNot affectedMay be affected
FunctionImpairedInability to make fist due to PIPJ hyperextensionMore of aesthetic concernAble to make fists
Causes and BiomechanicsWrist synovitisCarpal collapse, supination and ulnar translation lengthens/weakens extrinsic tendons which are then overpowered by intrinsic tendons resulting in MCPJ flexion and PIPJ extensionCentral slip dysfunction from tear (trauma) or attenuation (synovitis in RA)Triangular ligament stretches
MCPJ synovitisWeakened extensor tendon insertion at P1 increases extensor force on P2 leading to PIPJ hyperextensionLateral bands sublux in volar direction maintaining a persistent PIPJ flexion
MCPJ volar plateWeakened volar plate leads to MCPJ subluxation and shortened intrinsics which causes PIPJ hyperextensionConcentration of extensor force on DIPJ
PIPJ synovitisAttenuates volar plate and triangular retinacular ligament (TRL) resulting in dorsal translation of lateral band and destruction of FDS insertion leading to PIPJ hyperextension and DIPJ flexion due to increase in FDP tension and decrease in lateral band tensionIn chronic cases, fixed contracture develops
PIPJ volar plateLax volar plate allows for PIPJ hyperextension
DIPJ mallet injuryExtensor power is concentrated on the central slip resulting in PIPJ hyperextension and volar plate weakens over time
Classification and managementNalebuff’sNalebuff and Miller’s
1Flexible1. PIPJ extension block splints (Figure of 8 or Murphy ring)

2. FDS sling/tenodesis i.e. Beckenbaugh technique (FDS slip is transected and brought over A2 pulley and sutured back to itself)

3. Littler ORL reconstruction (creation of ORL using lateral band)

4. Lateral band mobilization and skin release (Nalebuff and Millender)
Extensor lag of 10-15 degrees, passively correctable1. Splinting (DIP in full extension)

2. Dolphin or Folwer tenotomy (Releasing lateral tendons near their insertion into distal phalanx)
2Intrinsic tightnessIntrinsic release at MCPJExtensor lag of 30-40 degrees, passively correctableShorten central slip or Centralize lateral bands
3Fixed hyperextension deformity of PIP1. MUA

2. Intrinsic release
Fixed flexion deformity with retinacular tightness (ORL and TRL)ORL (which maintains DIP extension and prevents flexion) stretching and then proceed as in stage 2 when PIP is fully extended
4Arthritic1. Arthrodesis of PIPJ

2. Arthroplasty
ArthriticArthrodesis or Swanson type arthroplasty

Acronyms used:

  1. MCPJ: Metacarpophalangeal joint
  2. PIPJ: Proximal interphalangeal joint
  3. DIPJ: Distal interphalangeal joint
  4. TRL: Triangular retinacular ligament
  5. ORL: Oblique retinacular ligament
  6. P1: Proximal phalanx
  7. P2: Middle phalanx
  8. FDS: Flexor digitorum superficialis
  9. MUA: Manipulation under anesthesia

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