Extremity Flap Reconstruction - Hand

Introduction

Definition of flap
- unit of tissue transferred from a donor site to a recipient site while maintaining its own vascular supply
Definition of pedicle
- vascular portion of the transferred tissue
- usually contains one artery and one or more veins
Indications for flap coverage
- soft tissue injury with exposed
  - bone
  - tendons
  - cartilage
  - orthopaedic implants
Prognosis
- free tissue transfer within 72 hours for severe trauma in the upper extremity has been shown to decrease complication rates

Classification

Blood supply classification
- axial pattern local flaps
  - contain single arteriovenous pedicle (a "named vessel")
  - indications
    - primary/secondary closure not advisable and
    - area cannot support STSG or FTSG and
    - length-width ratio needed > 2:1
- random pattern flaps
  - supported by numerous microcirculation with no single arteriovenous pedicle
  - indications
    - primary/secondary closure not advisable andarea cannot support STSG or FTSG and
    - length-width ratio needed < 2:1
- venous flap
  - uses veins as inflow and outflow of arterial blood
Tissue type classification
- cutaneous
  - include skin and subcutaneous tissue
- fascial flap
  - include fascia with no overlying skin
  - example
    - temporoparietal flap
- muscle flaps
  - usually requires additional transfer of a skin graft to cover muscle
  - alternatively, muscle can be transposed as part of a musculocutaneous flap (composite flap)
  - if motor nerve is not preserved the flap will atrophy to 50% of its original size
- bone flaps
  - free fibula
    - based on peroneal artery pedicle
    - useful for diaphyseal reconstruction
  - free iliac crest
    - based on deep circumflex iliac vessels
    - useful for metaphyseal reconstuction
- composite flaps
  - consists of multiple tissue types
    - examples
      - radial forearm flap (fasciocutaneous)
Mobilization type classification
- local flap
  - tissue transferred from an area adjacent to defect
- distal random pattern flap
  - transfer of tissue to a noncontiguous anatomic site
  - indications
    - surrounding tissue will not support a local flap
    - length-width ratio needed < 2:1
- distal axial pattern flap
  - indications
    - surrounding tissue will not support a local flap
    - length-width ratio needed > 2:1
- free tissue transfer
  - indicatoins
    - local or distant tissue not sufficient for distal axial and random pattern flaps

Techniques

Fingertips & Hand
See Finger amputation and Flaps
Arm Flaps
Lateral arm flap	• Lateral arm defects • Blood supply by posterior radial collateral artery (branch of profunda brachii)
Latissimus Dorsi myocutaneous flap	• For large defects around the elbow • Blood supply provided by perforators off of the thoracodorsal artery
Leg Muscle Flaps
Medial Gastroc flap	• Used for medial and midline defects over proximal third of tibia • Pedicle supplied bymedial sural artery
Lateral Gastroc flap	• Used for lateral defects over proximal third of tibia
Soleus	• Used for wounds over middle third of tibia • Supplied by branches of the popliteal artery trunk, the posterior tibial artery (medial), and the peroneal artery (proximal)
Gracilis	• Most common donor for free muscle transfer • Nerve isanterior division of obturator nerve • Artery is branch ofmedial femoral circumflex artery
Free flaps	• Used for wound coverage over distal third of tibia, or in the middle and proximal leg when soleus and gastrocnemius are damaged
Groin flap	• Axial flap that has been a mainstay of providing soft-tissue coverage of the upper extremity • Based on thesuperficial circumflex iliac artery • Risk of injury to lateral femoral cutaneous nerve
Bone Flaps
Free iliac crest	• Based on deep circumflex iliac vessels • Useful for metaphyseal reconstruction
Free fibula	• Useful for diaphyseal reconstruction • Based onperoneal artery pedicle
Vascular bone graft from radius	• Gaining popularity osteonecrosis of scaphoid fractures • Harvested from dorsal aspect of distal radius • Based on 1-2 intercompartmental superretinacular artery (branch of radial artery)
Index metacarpal transposition	• Indicated to reduce the space left between the index and ring finger following middle ray amputation. An alternative technique is deep transvers intermetacarpal ligament reconstruction.
Little metacarpal transposition	• Indicated to reduce the space left between the middle and little finger following ring ray amputation.

Technique

Ladder of reconstruction
- in order of increasing complexity
  - primary closure
  - secondary closure
    - healing by secondary intention
  - skin graft
  - local flap
  - regional flap
  - free tissue transfer

Complications

Flap Failure
- inadequate arterial flow
  - treatment
    - immediate return to operating room
- inadequate venous outflow
  - treatment
    - loosen dressings, removal of selected sutures
    - return to operating room if not relieved by above measure
Donor site morbidity
- may be cosmetically unacceptable
- pain related to grafting
- seroma
  - treatment
    - aspiration
    - excision if encapsulated
Nonunion for vascularized bone transfer
- incidence
  - may be as high as 32% if no additional bone graft is used