Amputations

Metabolic Cost of Amputation

  • Increases the more proximal the amputation
  • Inversely proportional to length of stump or number of functional joints

Soft Tissue Envelope

  • Provides cover for the bony stump
  • Ideally should have:
    • A mobile muscle mass
    • Full thickness skin
    • Mobility reduces shear stress on the prosthesis
      • Reduces skin ulceration or breakdown

Load Transfer

  • Refers to how the body’s load is transferred to the prosthetic socket

Direct or Indirect

  • Direct:
    • For end-bearing stumps – symes or through knee
    • Prosthetic socket fit allows suspension
  • Indirect:
    • Load is not transferred directly to the socket from the stump
    • Load transferred by the total contact method
    • Refers to amputations through long bones
    • To work, the indirect method needs:
      • 10 degrees flexion in knee for a trans-tibial
      • 10 degrees adduction & flexion in hip for a transfemoral

Pre-requisites for Stump Healing

  1. Nutrition
  2. Vascularity
  3. Stumps heal by collateral flow
  4. Blood Oxygenation
  5. Stable well-oxygenated patient with Hb >10

Ischaemic Index

  • Ratio of Systolic BP at surgical level to the Brachial BP
  • Minimum required is 0.5 for wound healing
  • Ischaemia may occur if <0.8

Transcutaneous Oxygen Partial Pressure

  • Gold standard for measurement of vascular inflow to the skin
  • mare than 40 mmHg indicates good perfusion
  • <20 mmHg indicates wound healing will be poor

Paediatric Amputations

  • Main issue is bony overgrowth within a stump due to open physes
  • If occurs, needs stump revision
  • Most commonly occurs in the humerus and fibula

Amputation after Trauma

  • Amputation may provide better outcomes than salvage
  • See MESS score

Upper Limb

  • Sensation more important than lower limb
  • Prehensile function important also
  • Insensate upper limb may be better amputated
  • If prehensile function is possible and sensation intact, use salvage
  • Leave as much length as possible

Lower Limb

  • Plantar sensation loss is a relative indication to amputate
  • But – be very careful
    • The sensation could return if it is a neuropraxia
    • Therefore preserve if possible

Technical Considerations

  • Full thickness skin flaps
  • Do not dissect between tissue planes
  • Strip periosteum at amputation level – minimizes heterotopic bone
  • Perform a Myodesis rather than a myoplasty
  • Secure muscles to bone at resting length rather than to their antagonist
  • Nerves should be pulled and cut clean with a knife
  • All patients develop neuromas
  • Aim is to allow neuroma to sit away from skin, well covered and deep
  • Crushing nerve increases incidence of phantom pain

Complications

  1. Wound breakdown/infection
  2. Poor limb fitting of stump
  3. Phantom pain
  4. CRPS (Complex Regional Pain Syndrome)
  5. Localized stump pain
  6. Mechanical usually related to bone end
  7. May be from a neuroma
Amputation Level % Energy Above Baseline Speed (m/min) O2 Cost (mL/kg/m)
Long transtibial 10 70 0.17
Average transtibial 25 60 0.20
Short transtibial 40 50 0.20
Bilateral transtibial 41 50 0.20
Transfemoral 65 40 0.28
Wheelchair 0-8 70 0.16

Soft Tissue Coverage & Microsurgery

Reconstructive Ladder

  1. Primary closure
  2. Secondary intention
  3. STSG (Split Thickness Skin Graft)
  4. FTSG (Full Thickness Skin Graft)
  5. Local Flap coverage
  6. Free Flap coverage

Healing by Secondary Intention

  • Granulation tissue, epithelization, contracture of skin
  • Not advised if tendon, nerve, or bone is exposed in wound bed

Skin Grafting

  • Skin grafts receive their blood supply by diffusion from the wound bed
  • Failure of graft to take is due to:
    • Shear stress and hematoma formation

Split Thickness Skin Graft

  • Preferred for dorsal hand wounds
  • Meshing increases surface area and prevents hematoma accumulation
  • Typical donor site: anterolateral thigh
  • Thickness: 0.005-0.03 inches – 0.015 common
  • Thicker grafts contain hair follicles and sweat glands (may or may not be preferred)

Full Thickness Skin Graft

  • Higher chance of viability
  • Better re-innervation
  • Better cosmetic appearance; less scar contraction
  • Preferred for palmar defects
  • Typical donor site: volar wrist or forearm

Flaps

  • Tissue unit containing a blood supply taken from a donor site and re-implanted into the wound bed
  • Donor site where flap is taken from can be closed primarily or skin grafted
  • Flaps may be classified by:
    • Tissue type
    • Blood supply
    • Donor site location

Classification by Tissue Type

  • Cutaneous: contain skin and subcutaneous tissue
  • Fasciocutaneous: contain skin, SC tissue, and fascia
  • Musculocutaneous: skin, SC tissue, fascia, and muscle
  • Osteocutaneous: skin, SC tissue, fascia, muscle, and bone

Classification by Pattern of Blood Supply

  • Axial Pattern Supply Flap:
    • Blood supply is based on a named artery and its draining vein
    • Allows larger flaps to be grafted
    • More likely to take
    • Lower infection rate
  • Random Pattern Flap:
    • Vessels within the flap are allowed to micro-anastomose with those in the wound bed

Classification by Donor Location

Local Flaps
  • Transposition Flap:
    • Geometric in design and designed to close or lengthen a wound without having to actually free raise any tissue
    • Classic example: Z-plasty – used for:
      • Lengthening a scar (e.g., a scar within a flexion contracture)
      • Preventing formation of contracture (crossing creases)
      • Re-orientating a cosmetically bad scar (soft indication)
      • All limbs must be equal length
      • Full thickness skin flap raised
      • Tissues undermined enough to allow mobilization of limbs
      • Triangular flaps transposed around each other
      • 30-degree angle gives a 25% lengthening
      • 45-degree angle gives a 50% lengthening
      • 60-degree angle gives 75% lengthening
  • Rotation Flaps:
    • Random pattern with regard to blood supply
    • Length of flap should not exceed width of base
  • Advancement Flaps:
    • VY plasty and Moberg flaps
    • Proceed in a straight line to fill the defect
  • Axial Flag Flaps:
    • Based on the dorsal digital artery
    • Can be homodigital (used to fill defect on same digit) or heterodigital (transferred to an adjacent digit)
  • Fillet Flap:
    • Tissue taken from an amputated digit not for replantation
Distant Flaps
  • When there is inadequate local tissue for coverage
  • Example: placement of hand into a groin or abdominal pouch
Free Flaps
  • Distant axial pattern flap based on a named AV blood supply
  • Transferred and re-anastomosed to the local vasculature
  • Lat Dorsi Flap (Thoracodorsal artery) typical
  • Serratus Anterior (subscapular artery branch)

Flap Selection in the Hand

  • Finger Tip – Volar:
    • VY Advancement
  • Finger Tip – Volar oblique or Dorsal:
    • Cross Finger Flap (older patients)
    • Thenar Flap (young patients)
  • Volar Proximal Finger:
    • Cross Finger Flap
  • Dorsal Proximal Finger:
    • Reverse Cross Finger
  • Volar Thumb:
    • Moberg Advancement if <2cm defect
    • FDMA if 2-4cm
    • Neurovascular Island Flap if >4cm
  • Dorsal Thumb:
    • FDMA (First Dorsal Metacarpal Artery Flap)
  • 1st Web Space:
    • Z Plasty
  • Dorsal Hand:
    • Groin Flap

Traumatic Amputations

Indications for Replantation

  • Multiple Digits:
    • Will allow early ROM and rehab = good predictable result
  • Thumb
  • Any digit in child
  • Mid-Palmar amputation
  • Any proximal amputation:
    • Results with reimplantation better than prosthetic
    • Sensibility and coordinated function
  • Single digit distal to FDS insertion (within flexor zone 1):
    • Relative indication
    • Will be able to rehab better than proximal amputation

Contraindications

  • Single digit proximal to FDS (flexor zone 2)
  • Crush injury
  • Segmental amputation
  • Prolonged ischaemic time

Care of the Amputated Part

  • Place in saline-soaked gauze within a plastic bag in an ice bath
  • Transport at 4 degrees is ideal

Viable Ischaemic Time

  • Viable time is less for body parts containing muscle
  • Muscle very sensitive to ischaemia
  • Results in increased infection risk and necrosis
  • For Hand:
    • 12 hours warm ischemia and 24 hours cold ischemia time
  • Proximal to carpus:
    • 6 hours warm ischemia and 12 hours cold ischemia time

Order of Replantation for Hand and Digits

  1. Digit
  2. Thumb (provides 40% hand function)
  3. Middle
  4. Ring
  5. Little
  6. Index
  7. Structure:
  • Bone
  • Extensor Tendon
  • Flexor Tendon
  • Artery
  • Nerve
  • Vein
  • Skin

Technique

  • For multiple digital amputation use:
    • Structure by structure:
      • Faster
      • Higher viability rate
    • Digit by digit:
      • Slower
    • Transpositional Replantation:
      • Most viable digit re-planted to most important finger
      • Not as good as anatomic replantation if possible

Other Technical Points

  • Sympathetic block in axilla
  • Abx and tetanus cover
  • Dedicated replant team with practice in the lab gives best results
  • Use longitudinal mid-lateral incisions
  • Shorten bones before fixing – reduces tension on soft tissues
  • 10 nylon adventitial repair to artery
  • 10 epineureal repair for nerves – graft if irreparable (MCNF)

Post-operative Management

  • Hydrate patient
  • Keep warm
  • Anticoagulation:
    • Careful not to overdose – may cause hematoma
  • Avoid vasopressors (nicotine, caffeine etc.)
  • Monitor O2 sats and skin temperature:
    • Drop in temperature by 2 degrees in 1 hour or absolute temperature of 30 degrees indicates unsatisfactory perfusion

Complications

  • Failure:
    • Early:
      • Arterial thrombosis due to persistent vasospasm
      • Administer heparin, warm finger, stellate ganglion blockade
    • Late (>12 hours):
      • Venous thrombosis/congestion
      • Can be treated with leeches or heparin-soaked gauze
  • Re-perfusion injury:
    • Ischaemia induces hypoxanthine conversion to xanthine
    • Allopurinol given to prevent this
  • Myonecrosis and renal failure
  • Infection
  • Hypersensitivity
  • Cold intolerance

Results of Replantation

  • Best predictor of survival is:
    • Mechanism of injury (sharp better than blunt)
  • Following this:
    • Ischaemic time is main factor (<8 hours = optimal results)
  • Function:
    • Digital replantation can expect 50% ROM and 10mm 2PD

Forearm and Arm Replantation

  • Establish arterial flow first if possible
  • Minimizes warm ischaemia time
  • Prophylactic fasciotomies for all patients

Ring Avulsion Injuries

  • Avulsion of soft tissues and NV structures from finger
  • Type 1: NV viable – treat as soft tissue injury
  • Type 2: Vascular insufficiency – replant if bone/tendon intact
  • Type 3: Complete avulsion with bone exposed – amputated
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