Mallet Deformity

Epidemiology

  • M>F
  • MF most common followed by LF
  • ? familial predisposition

Aetiology

  • Usually due to forced flexion of the extended digit

Classification

Type 1: closed injury tendon disruption with or without small avulsion injury

Type 2: lacerated tendon

Type 3: deep abrasion with loss of skin/tendon

Type 4:

A = pediatric transepiphyseal fracture

B = fracture involving 20-50% articular surface

C = fracture involving >50% articular surface with subluxation

Considerations

  • Open vs closed
  • Paediatric
  • Amount of articular surface
  • Acute vs chronic
  • Fractures vs true mallet
  • Fractures of the base of distal phalanx will present with pseudomallet – thse should be treated as a fracture and not as a tendon injury

Management

Timing for closed injuries

  • Can be considered early if treated <4weeks
  • except where there is large>20% avulsion fragment
  • these need to be treated within 10-14days
Type 1
  • delayed closed treatment (up to 3-4 months after injury) has a high degree of success equal to or better than surgery
Nonoperative
  • Plaster cast
  • Classic method (Smille) is to immobile PIPJ in flexion (40-60deg) and DIPJ at slight hyperextension
  • Should only immobilise PIPJ flexion at 45deg in those with a swan neck deformity
  • Splints
  • Stack splints commonly used
  • Continuous splinting for 6 weeks then night splinting for 2 weeks
  • Poor results due to poor compliance or inadequate immobilisation
Operative
  • K wire
  • Tendon trapping method or K wire across joint
  • Complication – loss of DIPJ flexion due to adhesion of extensor/flexors over middle phalanx
  • External tendon suture (tenodermodesis)
  • Direct suture
  • Difficult as tendon thin and sutures frequently cut out
Complications
  • Due to splint – skin irritation, ulcers, maceration, allergy, pain, transverse nail groove
  • Surgical – nail deformities, joint incongruities, infection, pin site infections, loss of surgical reduction

Types II and III

  • Open repair
  • Type III treated with skin coverage in first stage and tendon graft or arthrodesis at second stage

Type IVA (children)

  • Closed reduction and splint in full extension for 4 weeks

Type IVB and IVC

  • Operative management usually recommended if involving greater than 1/3rd of joint surface
  • Some treat conservatively believing that remodelling of the articular surface will lead to near normal painless ROM despite presence of subluxation
  • Green recommends ORIF only in the presence of subluxation
  • Tendon may be reinserted with or without fragment – may need to use a volar tieover button or a Mitek bone anchor

Chronic Mallet Finger

  • Patient may present due to
  1. Failure of conservative management
  • Elicit reasons for failure – noncompliance or inadequate mobilisation
  • If due to above reasons, worth giving another trial of conservative management
  1. Aesthetic appearance
  2. Secondary swan neck deformity
  3. Gets in the way
  • Test for intrinsic tightness (usually secondary) as this will respond to stretching exercises

Surgical Options

  1. Dorsal dermodesis
  1. Tendon reconstruction
  • Indicated if joint surfaces are congruous and mobile
  • Neotendon formed in gap
  • Options:

a)Plicate normal extensor tendon proximally

b)Shorten extensor tendon proximally (2-3mm excised and end-end repair)

c)Divide insertion of neotendon and reinsert into distal phalanx

  • K wire across DIPJ and immobilise for 6-8 weeks
  • Difficult with associated subluxation as often the volar plate and collaterals are contracted and need releasing
  1. Fowler’s tenotomy
  • Central slip release
  • 2cm incision over PIPJ either laterally (need to divide and then repair transverse retinacular ligament) or mid-dorsal
  • Divide just proximal to its insertion, preserving the lateral slips
  • Splinted in flexion of PIPJ and extension of DIPJ for 2 weeks, then mallet splint for 4 weeks
  • Restores balance by allowing entire extensor expansion to slip proximally
  1. Spiral oblique retinacular reconstruction (Littler’s procedure)
  • Main indication if mallet has resulted in a secondary swan neck deformity
  • If early - treatment of the mallet alone may correct the soft tissue imbalance across the PIPJ
  • Useful as treats both joints

Method

  • Free tendon graft sutured to terminal tendon
  • Spiralled around the radial side of the middle phalanx deep to the neurovascular bundle passing superficial to the tendon sheath
  • Brought around the ulnar side and passed through a drill hole volar to Cleland’s ligament (keep below axis of rotation) in the distal proximal phalanx in 30-40deg of flexion
  • Perform a distal intrinsic release
  1. Arthrodesis
  • Indications
  1. Fixed joint
  2. Significant arthritis
  3. Incongruous joint surfaces
  • Arthrodesis in full extension
Mallet Thumb
  • Closed injuries rare
  • Studies have shown that conservative treatment with splintage of Zone 1 EPL injuries is effective
  • Similar protocol to fingers