Lower Limb Amputations – Level Selection

Arvind LeeVascular FellowNepean Hospital

Overview

• Integral part of any surgical practice.

• The global lower extremity amputation study group

- wide variations in amputation rates worldwide

- similarities in age and sex distribution - very high correlation with diabetes (BJS 2000)

Overview

• Australian data – - 2629 diabetes related lower limb

amputations per year - 2:1 male: female ratio - majority in the 65-79 year age group - Highest incidence in SA and NT (MJA 2000)

Indications for amputation:

• PVD- Failed revascularisation- Extensive tissue loss- Unreconstructable- Excess surgical risk

Indications for amputation:

• Diabetes- Overwhelming sepsis- Extensive tissue loss- Excess surgical risk

Indications for amputation:

• Trauma- Crush- Nerve injuries

• Others- Spina bifida- Contractures- Neuropathy- Bed bound

Goals of amputation:

• Get rid of all infected, necrotic and painful tissue

• Attain successful wound healing• Have an adequate stump for a prosthetic

Attempt limb salvage or primary amputation?

• Extent of tissue loss in foot• Anatomy of reconstruction• Associated comorbidities

• ESRD with heel gangrene – maybe best treated with primary amputation

Natural history of major amputation:

• 10% perioperative mortality• 3 year survival after BKA – 57%; after AKA –

39%• Of 440 major amputations – 75 died in

hospital, 113 deemed unsuitable for prosthesis. Of 57% referred for prosthesis – at 3years follow up a further 54 died, only 10-15% were mobile at home. (BJS 1992)

Amputation levels and significance:

• Major amputation: above tarso metatarsal joint.

• Levels - BKA - Through knee - AKA - Hip disarticulation

Amputation levels and significance:

• BKA – maximal rehabilitation potential - 10-40% increase in energy expenditure - 15-20% of all BKAs go onto an AKA in 3

years (5% periop mortality)• AKA – less rehab potential - 50-70% extra energy expenditure - Better rates of healing

Level Selection:

• Subjective:- Clinical exam – skin quality, extent of

ischemia/ infection- Pulses – presence of a pulse immedietly above

the level of amputation – almost 100% chance of healing

- “Clinical judgment” alone 80% accurate in predicting healing with BKA and 90% in AKA.

Level Selection:

• Wagner et al (J vasc surgery 1988): clinical judgment superior to objective assessments. More distal amputations can be achieved with clinical measures over objective studies.

• Clinical judgment is central to amputation level selection.

Level Selection:

• Objective tests:- Non invasive1. Doppler pressures –

maybe unreliable in diabetics; ankle pressures >60mm – >50% chance of BKA healing.

Level Selection

• Non invasive2. Skin perfusion

pressures- Radio isotope washout- Laser doppler

velocimetry- <20mm Hg – 89%

failure of healing

Level Selection

• Non Invasive3. Transcutaneous

oximetry- Tested under local

hyperthermia- Correlates with true

PaO2- Threshold value –

30mm

Level Selection:

• Invasive – Angiographic scoring

• Poor correlation

Level Selection

Conclusions:

• Amputation is traumatic enough…poor level selection can make it worse.

• Clinical judgement central to proper level selection

• Patient factors are more important than objective testing

Case 1

• 93 yr old from NHBed bound after strokePainful heel ulcer on

stroke affected sidePalpable popliteal pulse

Case 2

• 68 yr old maleCRF on hemodialysisPost surgery for #NOF – bilateral heel ulcersPainful, non healing despite multiple

debridementsPalpable popliteal pulses