Mallet finger and Swann neck deformities

Question 1

What is a mallet finger?

Answer 1

A finger deformity caused by

• A DISRUPTION of the TERMINAL EXTENSOR TENDON DISTAL TO DIPJ
• The disruption may be BONY or LIGAMENTOUS

Question 2

What is the aetiology of mallet finger?

Answer 2

• Traumatic impaction blow with finger in extended position-> forced flexion at DIPJ
• Dorsal laceration

Question 3

what is the signs and symtpoms of mallet deformity?

Answer 3

Symptoms

Pain and swelling around DIPJ following impact/injury

Signs

• DIPJ held in flexion 45⁰
• Lack of active extension at DIPJ

Question 4

what investigations are helpful?

Answer 4

Xray

• exclude a bony component as may just be a l_igamentous injury_

Question 5

What is the treatment of Mallet deformity?

Answer 5

Non op

• For soft tissue/ non displaced bony mallet injury Extension splint DIPJ for 6-8 wks
  
  • Maintain free rom of pipj avoid hyperextension
  • Volar splint less complications cf dorsal
  • Begin progression flexion exercise at 6 wks

Operative

• Closed reduction precutaneous pinning vs ORIF-
  
  • for volar subluxation of distal phalanx
  • or > 50% articular surface involved
  • or >2mm articular gap
  • simple pin fixation/ dorsal blocking wire
• Surgical reconstruction of terminal tendon
  
  • for > 12 weeks old chronic injury
  • direct repair/tendon advancement
  • high complication rate- 50%
• DIPJ Arthrodesis- for stiff/arthritic joint

Question 6

When is surgery required? what is your technique?

Answer 6

• Volar subluxation of distal phalanx
• realtive Indcations
  
  • >50% articular surface invovled
  • >2mm articular gap
• Tx by Simple pin fixation or dorsal blocking wire

Question 7

How would you tx a chronic injury?

Answer 7

• Surgical reconstruction of terminal tendon injury >12 weeks old from injury
• Done with direct repair/ tendon advancement
  
  • high complication rate 50%
• DIPJ arthrodesis for painful, stiff , arthritic dipj

Question 8

What are the complications of mallet fingers?

Answer 8

• Extensor lag - slight residual of <10^o may be apparent
• Swan neck deformities
  
  • Attenuation of volar plate & Transverse retinaculum at pipj
  • dorsal subluxation of lateral bands
  • -> pipj hyperextension
  • Contracture of traingular ligament maintains deformity

Question 9

What is this?

Answer 9

A Swan neck deformity

deformity of the phalanx characterise by

• Hyperextension at PIPJ
• Flexion at DIPJ
• NB a swan extends its long neck when gliding and its head is flexed :)

Question 10

How do swan neck deformities occur?

Answer 10

• 1) Laxity of the VOLAR PLATE -> PIPJ HYPEREXTENSION caused by
  
  • trauma
  • generalised ligament laxity
  • Rheuamtoid Arthritis

then….

• 2) imbalance of muscles- pipj extens> flexion due to
  
  • mallet injury- transfer of dipj exten to pipj
  • FDS rupture- unopposed PIPj extension
  • Intrinsic contracture-tethering of lateral bands by transverse retinacular lig as result of pipj extension
  • MCPJ volar subluxation- RA

Question 11

What are the symptoms and signs of Swan neck deformity?

Answer 11

Symptoms

Locking of fingers

Signs

Hyperextension at PIPJ and flexion at DIPJ

Question 12

How can swan neck deformity be tx?

Answer 12

Non op

• Double ring splint- prevents hyperextension of PIPJ

Operative

• volar plate advancement and PIP balancing with central slip tenotomy- for progressive deformity
  
  • volar plate advancement for volar plate laxity
  • Imbalance- FDS tendodesis if fds rupture
  • lateral band tenodesis
  • spiral oblique retinaculum ligament reconstruction
  • Central slip tenotomy- Fowler