Handbook on Flaps in Crush Injuries of the Hand Dhiren Mahida
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Introduction1

 
TERMINOLOGY
An understanding of the terms degloving, avulsion, and crush injury is essential before discussing the surgical aspects of hand injury.
 
Degloving Injury
Degloving (Figure 1.1) involves the skin and fascia. The superficial fascia is completely disrupted and usually deep fascia is also involved. Blood vessels are completely disrupted.
 
Avulsion Injury
Avulsion (Figure 1.2) involves deeper tissues, typically as part of a combined degloving/avulsion injury.
Part of tendon/muscle belly/nerve is pulled along with skin and deep fascia.
 
Crush Injury
Crush injury (Figure 1.3) involves an element of crushing and compressive force that leads to devitalization of tissues and may include skin, fascia, muscles, tendons, bones and neurovascular structures either singly or in combination.
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Fig. 1.1: Degloving
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Fig. 1.2: Avulsion
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Fig. 1.3: Crushed hand
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Flap Terminology
  • Flap is tissue used in surgical grafting that is only partially detached from its donor site so that it continues to be nourished during transfer to the recipient site.
  • Skin flap is a full-thickness mass or flap of tissue containing epidermis, dermis, and subcutaneous tissue. A standard technique in skin grafting; based on the part isolation of a graft by creation of a flap which retains its original circulation while becoming established at the new site on the new blood supply. Many types of flap are used, e.g. axial pattern, bipedicle, composite, delayed tube, direct, interpolating, reverse saphenous conduit.
  • Fasciocutaneous flap is a full-thickness mass or flap of tissue containing epidermis, dermis, and subcutaneous tissue along with deep fascia.
  • Myocutaneous flap is a compound flap of skin and muscle with adequate vascularity to permit sufficient tissue to be transferred to the recipient site.
  • Composite flap consists of skin with muscle, bone or cartilage.
  • Pedicle flap is a flap consisting of the full thickness of the skin and the subcutaneous tissue, attached by tissue through which it receives its blood supply. The proximal segment of a flap that has been entirely inset into the defect is referred as its base. Frequently only the distal segment of the flap may be inset into the defect, its central segment and base remaining unattached. The base is then referred to as the pedicle of the flap and the central segment as its bridge segment the pedicle of a skin flap usually consists like the rest of the flap of skin and subcutaneous tissue but is occasionally reduced to its subcutaneous component. In such circumstances it is the distal segment with a full component of skin and subcutaneous tissue, which is transferred and referred to as an island flap.
  • Random pattern flaps are not based on any specific blood supply.
  • Axial pattern flaps are based on a specific arterial supply delineated for that flap.
  • Rope flap or tube flap is one made by elevating a long strip of tissue from its bed except at its two ends, the cut edges then being sutured together to form a tube.
  • Rotation flap is a local pedicle flap whose width is increased by having the edge distal to the defect form a curved line; the flap is then rotated and a counter incision is made at the base of the curved line to increase mobility of the flap.
  • Transposition flap is a rectangular flap of skin repositioned to fill a defect like pedicle graft with intact blood supply.
  • Advancement flap or sliding flap is a flap carried to its new position by a sliding technique after release of a portion of tissue and reattachment at an advanced position technique for closing skin wounds where there is a large deficiency of skin. Includes sliding-H flap and Z-flap or Z-plasty. Skin around the defect is separated from its subcutis and the defect repaired by strategic additional incisions and the use of tension sutures.
  • Jump flap is one cut from the abdomen and attached to a flap of the same size on the forearm. The forearm flap is transferred later to some other part of the body to fill a defect there.
  • Free flap is an island flap detached from the body and reattached at the distant recipient site by microvascular anastomosis.
  • V-Y flap is one in which the incision is shaped like a V and after closure like a Y, to lengthen a localized area of tissue.
  • Bipedicle flap is one where the space created by undermining skin between two parallel incisions can be used to reconstruct skin defects, usually onto a distal limb, which is inserted into the space also called pouch flap.
  • Neurovascular island flap refers to flap elevated along with an intact artery and nerve supply. With the advent of microsurgical technique, a better understanding of vascular supply of most flaps and the use of Doppler study that help delineate local vessels most random pattern flaps can now be termed axial pattern.
 
Indications for Pedicle Flap
A pedicle flap is required in the following circumstances namely:
  • Finger injuries with exposed bone, joints or tendons
  • Soft tissue padding
  • Preserve length
  • Secondary reconstruction anticipated
  • Improve function and appearance
  • Facilitate wearing of prosthesis
  • Bare bone in electrical burns.3
 
Contraindications for Pedicle Flap
  • Elderly patient
  • Arthritic or degenerative changes
  • Circulatory problems
  • Scarring on donor area
  • Infection
  • Contused donor skin.
 
Classification of Degloving Injuries by Different Authors
Author
Date
Classification
Thomson
1968
Type A—Simple laceration
Type B—Avulsion of soft tissue + neurovascular injury
Type C—Tendon injury + cutaneous avulsion and neurovascular injury
Larrou
1974
Type I—Skin without injury to nerve and vessels
Type II—Skin + 1 pedicle
Type III—Avulsion + tendon + 2 pedicle
Type IV—Avulsion + tendon + 2 pedicle + fracture/dislocation
Michon and Merle
1979
Stage I—Pure cutaneous injury
Stage II—Partial vascular injury
Stage III Total devascularization
Stage IVa—Proximal disarticulation
Stage IVb—2nd phalange or distal interphalangeal neck fracture
Stage IVc—Cutaneous denuding without skeletal injury
Urbaniak
1981
Type I—Adequate circulation, treatment of soft tissues
Type II—Immediate vascular repair required
Type III—Denuded or amputated finger
Loda
1983
Stage I—Ring compression and pure cutaneous injury
Stage II—Dorsal vascular and cutaneous injury
Stage III—Palmar vascular and cutaneous injury
Stage IV—Dorsal and palmar vascular and cutaneous injury
without amputation
Stage V—Complete amputation with fracture or disarticulation (typical degloving injury).
 
AIMS OF MANAGEMENT IN HAND INJURIES
The aim of management in hand injuries requiring skin coverage is four fold:
  1. Providing durable cover.
  2. Rapid healing and early return to work.
  3. Pain free scar and minimizing discomfort.
  4. Sensate flap preserving sensation and length.
Also remember the 4 Rs of fracture management:
  1. Recognition
  2. Reduction
  3. Retention of reduction
  4. Restoration of function.
The treatment is directed in ensuring wound healing in the shortest period of time and providing a hand that was almost similar to the uninjured hand, in terms of function, sensation and cosmetics. Different classes require different levels of functional capabilities and this must be carefully assessed before surgery. For example, a manual worker will be highly satisfied with a cross-finger flap over a thumb or index finger tip injury, whereas a pianist or stenographer will find the same to still lack in quality and function in many ways.
 
Order of Priority for Open Wound Management
This is as follows:
  1. The patient as a person and body as a whole
  2. Other injuries, resuscitation
  3. History and physical examination
  4. Tetanus prophylaxis and antibiotics
  5. Debridement
  6. Fasciotomy, if required
  7. Skeletal stability
  8. Restoring adequate blood supply
  9. Repair of damaged structures
  10. Proper dressing and elevation
  11. Appropriate timing of closure or coverage
  12. Secondary reconstruction: flap re-implantation, delay of flap, flap release, etc.4
  13. Rehabilitation; start as early as possible, preferably while the hand is still in the primary dressing stage.
  14. Defattening of flap, release of syndactyly, if one has been created during reconstruction. This is done 6–8 weeks after flap release and defattening of 30–40% is done at a time.
 
ASSESSMENT OF INJURY
A good history is essential and includes when, where and how.
 
 
When?
The time elapsed from injury is important. Many times reimplantation and/or primary closure of wound is dangerous and fraught with complications, especially when the patient presents six hours after injury.
 
Where?
Will indicate the environment and potential level of contamination of open wounds. Clean environment requires less debridement, whereas battlefield and sewage side injuries require extensive debridement.
 
How?
Reveals magnitude of force and degree of tissue damage.
For example, crush injury/high pressure injection injury require extensive debridement and compartment release. Glass injury can easily cause tendon and neurovascular damage.
 
Type of Injury
The surgical procedure is often dictated by the type of injury. Injury type includes the following:
  1. Cutting
  2. Slicing
  3. Crushing
  4. Degloving
  5. Avulsion.
 
Part of Injury
Anatomical structures involved in isolation or as a group.
 
Skin
Assess the amount of and extent of cut and crush of the skin edges.
 
Superficial/Deep Fascia
In a clean wound, primary skin grafting can be done on an intact fascia. Fascia has to be released in a developing compartment syndrome.
 
Tendon
An inability to extend fingers indicates extensor tendon injury. An inability to flex a fully extended and stabilized interphalangeal joint indicates flexor tendon injury. Position of ‘hangout’ in unconscious patients and children also indicates flexor tendon injury.
 
Blood Vessels
Distal pulse, capillary refill in nail bed, color of injured tissue is evaluated. Pulse oxymetry and free flow of blood to pin prick help assessment. A white hand implies arterial impairment and blue discoloration indicates venous stasis. Restoration of blood supply has the highest priority in treatment plan. Major arteries and a vein are repaired if deemed necessary. Compartment release is essential to prevent ischemia.
 
Muscles
Look for the extent of cut and crush element and assess the amount of nonviable muscles that have to be excised.
 
Bone
Clinical examination and X-rays help determine bony injury. Fractures can be stabilized by kirchner wires. Nonviable bones devoid of soft tissue attachment are preferably removed. Remember the 4 Rs of fracture management: Recognition, Reduction, Retention of reduction and Restoration of function.
 
Nerves
Discrimination of dull and sharp sensation to pinprick and two-point discrimination is carried out. Lack of pain indicates nerve damage (psychic problems excluded) and progressively increasing pain indicates developing compartment syndrome.
 
SURGICAL PROCEDURES/OPTIONS AVAILABLE
The following procedures are available to treat crush injury in increasing order of complexity. On evaluating 5the injury any one or a combination of the following will be required in treating hand injuries:
  1. Debridement with or without primary closure
  2. Healing by secondary intention
  3. Fasciotomy, if required
  4. Skin grafting
  5. Flaps
  6. Vacuum-assisted closure
  7. Amputations.
  8. Stabilization with Kirchner wires/fixators/plates/sutures, etc.
    As a primary or secondary procedure or in combination with the above.
  9. Microvascular repair and reimplantation of pulp/digits/hand.
    Majority of the discussion in the following chapters will be restricted to the first six procedures. Stabilization with Kirchner wires/implants/fixators, free flaps and microvascular repair are major topics in themselves and the reader can refer to authoritative textbooks devoted to these topics.
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Flow chart 1.1: Algorithm evaluating injury and available treatment options. Pre-requisites: Clean cut and debrided wound
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Flow chart 1.2: Evaluating treatment options for finger tip amputation
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Flow chart 1.3: Volar oblique finger amputation