BKA – 25% increased energy expenditure
ï¿½ decrease in push-off is compensated by increased work for hip extensors.
ï¿½ increased quadriceps contraction for knee stabilization with increased work by hamstrings.
AKA – 65% increased energy expenditure
ï¿½ primary concern is in knee stability.
ï¿½ hip extensors have increased demand to maintain knee stability in stance phase.
ï¿½ hip flexors have increased demand to accelerate the leg forward in pre-swing phase due to lack of plantar-flexion power.
Stump pain remains a difficult problem in amputees, both in the early post-operative period and in the long-term.
Continuous Regional Analgesia
Malawer et al. 1991, Clinical Orthopaedics and Related Research
ï¿½ Bupivacaine infusions into peripheral nerve sheaths via catheters placed intraoperatively. 23 patients compared against matched controls. 11 required no supplemental narcotics; the remainder required a third of the narcotics that the controls required. An overall 80% reduction in narcotic requirement was seen.
LONG TERM MANAGEMENT
ï¿½ By far the most common cause of persistent stump pain.
ï¿½ Meticulous prosthetic fitting with appropriate training and follow-up is critical
ï¿½ Usually from neuroma formation.
ï¿½ Can be treated with surgical excision, chemical ablation, electrical stimulation, or anticonvulsant medications.
ï¿½ Phenol injection provides a relatively non-invasive, long-term solution.
ï¿½ Common in the knee joint of BKA’s, and hip joint or SI joints of AKA’s
ï¿½ Requires optimization of gait via prosthesis adjustment.
ï¿½ Will benefit from sympathetic block when identified early
Abnormal Stump Tissue
ï¿½ Bony exostoses, heterotopic ossification, adherent scar, ischemia,
ï¿½ Meticulous surgical detail and careful wound care postoperatively.
AMPUTATION IN THE SETTING OF TRAUMA
Is there a certain population of patients with such severe injuries that they are better off with an amputation and immediate rehabilitation rather than multiple reconstructive procedures with prolonged recovery?
If so, how does one identify these patients?
In an attempt to prognosticate injuries: SCORING SYSTEMS
Mangled Extremity Syndrome Index (MESI)
Gregory et al. 1985 – Retrospective review of 17 patients
> 20 predicted amputation
Limb Salvage Index (LSI)
Russel et al. 1991 – Retrospective review of 70 patients
> 6 predicted amputation
Mangled Extremity Severity Score (MESS)
Johanson et al. 1990 – Retrospective review of 26 patients
>7 predicted amputation
Predictive Salvage Index (PSI)
Howe et al. 1987 – Retrospective review of 21 patients
> 8 predicted amputation
All represent GUIDELINES – None replace clinical judgment.
Based on poorly defined injury criteria, cumbersome application, small numbers, retrospective data, little functional outcome data.
Factors to Consider:
Vascular injury – location, duration of warm ischemia
Bony injury – severity of fracture
Soft tissue injury – crush component, reconstructive requirements,
Nerve injury – partial vs complete transection
Injury severity score – ie. Other injuries, particularly to ipsilateral limb
Pre-existing health of patient
Time to operating room
Most agree that complete loss of sciatic or posterior tibial nerve function is an absolute indication for primary amputation.
AMPUTATION IN THE SETTING OF TUMOUR
Obtain wide margins
– 5-7 cm margin of normal bone marrow
Plan the amputation to ensure viable flaps remain after resection.
Plan to excise the biopsy site and tract in entirety.
Individualize the therapy:
n Sarcomas of bone in lower extremities – often require
hemipelvectomy, hip disarticulation, or AKA
n Soft tissue tumours in lower extremities – may get away with BKA but will require AKA if popliteal neurovascular structures involved (esp. Posterior tibial nerve).