Amputations

KEY FACTS

General

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Amputation and disarticulation should be viewed as reconstructive procedures and not a failure of treatment.
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  In this manner, one realizes that it is the initial step in getting patients back to their previous functional status.
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Indications for amputation include ischemia, trauma, infection, tumor, and painful dysfunction of the foot and ankle not amenable to further conservative management.
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The goal is to create a modified limb that has a comfortable interface with a prosthesis and offers the most efficient energy-conserving gait as possible.
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A team effort, with a team composed of different medical specialists, is the best way to ensure a good result and restore patients to their optimal level of function.
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It is important to be aware of the psychosocial recovery of the patient with an amputation.
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Functional outcome is generally worse in patients with diabetes or end-stage renal disease.

Important Points for Surgical Approach to Amputation

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Team assessment
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Atraumatic soft tissue handling
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Adequate skin flaps
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Myodesis or myoplasty whenever possible
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Nerve transection sharp and at level well above amputation
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Artery and vein dissected free and double ligated
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Closure without tension
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No “dog ear” resection
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Accept delayed primary closure if there is tension

Indications

Peripheral Vascular Disease

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Peripheral vascular disease (PVD) is the most common reason for amputation.
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  Affects mainly geriatric patients and those with diabetes mellitus.
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Up to 20% of patients with diabetes mellitus will suffer from PVD.
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  Patients are prone to develop foot ulcers leading to lower extremity amputation.
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Peripheral neuropathy increases risk of complications.
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  Loss of protective sensation compromises the likelihood of healing ulcers.
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Prior to considering amputation, vascular studies are useful to determine the following:
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  Possibility of revascularization
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  Level of amputation
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25% of diabetics who undergo amputation will require an amputation on the contralateral limb within the following 3 years.
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Because of the medical complexity of these patients, optimal management is multidisciplinary with a team composed of a primary care physician, internist, surgeon, physiatrist, physical therapist, prosthetist, and social worker.
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  The input of an infectious diseases specialist may also be required.
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PVD accounts for 90% of amputations with 97% of dysvascular amputations performed on the lower limb.
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African American males are at greatest risk for dysvascular amputation.
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  They are 2-4x more likely to lose a limb than white persons of similar age and gender.
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In amputees with PVD, the 5-year survival rate is between 70-90% with heart disease as the leading cause of death (51%).
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  This is possibly because the coronary heart vessels are subject to the same occlusions as the peripheral arteries.
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Approximately 50% of dysvascular amputees are diabetic.

Civilian Trauma

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Several well-established scoring systems have been developed to help in arriving at a decision to perform an immediate amputation following lower extremity trauma.
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A commonly used scoring system is the Mangled Extremity Severity Score, which consists of 4 categories: Skeletal/soft tissue injury, limb ischemia, shock, and age.
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  A lower number of points indicates a less severe injury.
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  A total score of 7 or below is almost always compatible with limb salvage.
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It is felt by some that soft tissue injury severity has the greatest impact on decision-making regarding limb salvage vs. amputation.
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There are several other proposed limb salvage scoring systems.
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While they may provide guidance for a treating surgeon, none of the scoring systems are considered very reliable in predicting need for amputation.
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In cases of severe limb damage, primary amputation at first surgery may be best for the patient’s physical and psychologic well-being.
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In other cases, it may be better to plan an initial attempt at limb salvage and observe.
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  Prolonged attempts at limb salvage lead to severe psychologic and economic burdens on the patient and the family.
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If it is thought that amputation is inevitable, it should be performed as a delayed primary amputation within the first 10-14 days after injury.
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Almost 70% of trauma-related amputations are upper limb amputation.
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The most common causes of lower extremity trauma requiring amputation are lawn mower injuries and motorcycle accidents.
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Traumatic amputees have a better functional prognosis than dysvascular amputees.

Military Trauma

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The changing nature of military conflicts over the past few decades has lead to an increasing number of blast injuries.
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  A mangled extremity is a common combat injury.
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While advances have been made in limb salvage of complex injuries, amputation sometimes offers the best outcome.
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In several studies of wounded soldiers, immediate and delayed lower extremity amputation patients generally have better functional outcomes compared to limb salvage, both physically and psychologically.
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  This is not true for every patient but rather represents a trend for the groups as a whole.
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  Individual decisions are made based on the extent of injury, the experience of the surgeon, and the capabilities of the health care system.
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  Immediate amputation may be necessary for a critically ill patient in a combat zone, whereas the same injury in a stable patient at a tertiary center may be offered limb salvage.

Malignancies

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The most common malignant tumor found in the region of the foot and ankle is synovial sarcoma.
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While metastases to the feet are uncommon, any cancer can metastasize to bone, and any bone can be involved.
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The most common primary tumors that metastasize to the feet are as follows:
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  Carcinoma of lung
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  Adenocarcinoma of colon
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  Genitourinary carcinoma
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  Melanoma
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  Other undifferentiated tumors
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The development of limb salvage procedures, combined with chemotherapy, has reduced the incidence of amputation for primary malignancies of the lower extremity.

Infection

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Life-threatening infection of the lower extremity requires an open amputation.
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  The stump can be closed only when it is certain that the infectious process is under control.
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In some circumstances, repeated debridement and lavage in the operating room is required until the stump is clear of infection and necrotic tissue.
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Chronic osteomyelitis is not an absolute indication for amputation.
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  It can be managed with good preoperative planning and selective surgery, including fistulectomy, sequestrectomy, and similar less invasive procedures.
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  Plastic surgery is often required for coverage of soft tissue defects.
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The ultimate function of the salvaged limb should justify the physical and psychologic costs of the treatment.
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Recurrent infection points to the possibility of PVD.
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  It prevents adequate perfusion of the infected area.
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    Decreased efficacy of antibiotic therapy
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Recurrent infection is common in patients with diminished protective sensation combined with bony deformities leading to abnormal pressure points and recurrent ulcers.
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  Charcot neuroarthropathy involving the foot and ankle is a major cause of recurrent infection.

Dysfunctional Limb

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Painful dysfunction of the limb following several attempts at reconstruction is a rare indication for amputation.
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  A classic example might be a young patient with severe collapse of the talus with avascular necrosis following trauma.
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  If the patient wants to run distances, he or she is more likely to achieve that goal with a transtibial amputation than a pantalar fusion.
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In some cases, consultation with a pain management specialist and a psychiatrist is helpful.
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With the correct indication, a well-healed stump, and a properly fitted prosthesis, many patients with painful dysfunction of the limb will benefit from amputation and regain excellent function with significant pain relief.
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The most common level of amputation for a dysfunctional foot and ankle is a long transtibial amputation, provided that the soft tissues forming the stump are healthy.
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A well-functioning transtibial amputation in a healthy young person will lead to better function than a multiply fused foot and ankle (such as a pantalar fusion).

Level of Amputation

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Determining the appropriate level of amputation or disarticulation is the most important, and probably the most difficult, part in the treatment of a patient who has no hope for limb preservation.
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If the indication for amputation is a malignant tumor, a life-threatening infection, or an irreparably damaged body part, then the level of amputation must be done proximal to the lesion, in healthy tissues.
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If amputation is performed for PVD, a thorough evaluation of arterial blood flow is essential.
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  Forefoot and toe blood pressure obtained using Doppler devices are of limited value.
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    Artificially high values may be obtained from heavily calcified, hence incompressible, vessels.
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Transcutaneous oxygen measurements (tc P o2) can assist in evaluating tissue oxygenation to the dorsal distal metatarsal level.
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  Greater than 30-40 mm Hg indicates wound healing is likely.
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  Less than 20 mm Hg indicates wound healing is unlikely to occur at that level.
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Hyperbaric oxygen chamber therapy with 100% oxygen at 2.5 atm may help wound healing for those patients who are able to increase their tc P o2 to 40 mm Hg under the administration of 100% normal baric oxygen via a snugly fitting mask for 20 minutes.
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The presence of palpable pulses does not guarantee healing of the stump.
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  The patient may have heavily calcified arteries or poor peripheral blood distribution due to microangiopathy.
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The presence of hair on the leg or the dorsum of the foot is a positive sign for adequate skin perfusion and secondary wound healing.
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The presence of a thermal gradient from proximal to distal, as well as skin trophic changes, is a clinical sign of poor vascular supply to the soft tissue envelope.
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Lack of protective sensation by itself should not be a factor in considering a more proximal amputation level.
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There is a 2.5x higher complication rate of infection and reamputation in patients who continue to smoke after amputation.
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Platelet function and fibrinogen levels require ~ 1 week of smoking cessation to return to normal levels.
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Perfusion should be optimized by avoidance of vasoconstrictors, such as nicotine and caffeine.
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Serum albumin level below 3.0 g/dL, total lymphocyte count < 1500/mm³, and poor glucose control in patients with diabetes (Hb A1-C > 7% or 8%) significantly decrease wound-healing potential.
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Partial foot amputation is associated with major advantages over higher amputation levels, including:
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  Preservation of weight bearing
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  Improved proprioceptive function
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  Decreased disruption of body image
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  In addition, requires only shoe modifications or limited prosthesis
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    Especially true in older patients or those with diabetes
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A determined effort should be made to save maximum length to enhance function.
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  At the same time, the likelihood of healing should be sufficiently high to avoid the need for repeat surgery.
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In cases of peripheral ischemia secondary to frostbite, vasoconstrictor administration for hypotension, and cryoglobulinemia, it is essential to allow time for completion of tissue demarcation and to keep the necrotic areas dry.
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  In many cases, maximum tissue preservation can be achieved by allowing autoamputation of the necrotic portions.
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  No urgent surgery should be done until the necrotic tissues are well demarcated and the ischemic wounds are dry.
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A contracted knee despite intensive physical therapy is an indication for a knee disarticulation instead of a transtibial amputation.
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  The prosthesis can only partially compensate for the lack of extension of the knee, thus making ambulation challenging.
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A nonambulatory patient requires a level of amputation that will ensure the best chance of healing whenever a lower level might be questionable.
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Split skin grafts should be avoided, especially on surfaces that experience significant shear forces, such as at the end of the stump, where they may ulcerate.
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  In younger children, there will be more remodeling of the soft tissues, and simple skin grafts may be more successful.
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Patients with significant gangrenous changes of the heel pad should have a transtibial amputation.

Physiology of Amputation: Energy Expenditure

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The metabolic demands of walking are increased by the following factors.
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  Decreasing residual limb length
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  Increasing number of amputated joints
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  Increasing number of amputated limbs
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  Dysvascular amputation
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The rates of metabolic energy expenditure ( V O2, mL/kg per minute) at various amputation levels were compared with those of nonamputees, demonstrating the increased metabolic costs.

Surgical Technique

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A well-planned amputation or disarticulation conserves all tissue possible according to the diagnosis and good function.
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The skin is the most important tissue for the healing of the amputation wound.
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  It therefore must be handled very carefully with the use of skin hooks.
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The transected muscles should provide an adequate soft tissue mantle for the residual extremity.
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The soft tissue envelope must be mobile, because it will absorb the normal and indirect shear forces during prosthetic usage.
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Myodesis consists of suturing the transected muscle to the bone through drill holes.
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Myoplasty refers to the suturing of the cut ends of the antagonistic muscle groups and their fascias together.
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Bony prominences, such as sharp edges and corners, must be removed and the cut surfaces properly contoured to prevent damage to the soft tissue envelope.
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All transected nerves develop a neuroma, which is painless in the vast majority of patients.
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Neuromas within the weight-bearing area can become painful.
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  Each nerve must be dissected free and sharply transected at a level well above the level of amputation.
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Arteries and veins must be dissected free and doubly ligated before transection.
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  They must be independently ligated in order to prevent the development of an aneurysm or arterial venous fistula.
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Split-thickness grafts may be used occasionally but only over soft tissues and not placed over bone or thick scars.
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Skin grafts are more successful in children than in adults.
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During wound closure, the flaps are trimmed to fit without tension.