How To Determine The Appropriate Level Of Amputation

By Kathleen Satterfield, DPM

   One should not view an amputation as a failure but as an opportunity to give a patient a chance to improve his or her quality of life.1-3 If the amputation is a definitive procedure, it may allow the patient freedom from the continuing wound care that chronic ulcerations tend to require. While the amputation is often thought of as a simple procedure, one should only perform this procedure after careful consideration of factors that will lead to a successful long-term outcome for each patient.    Selecting an inappropriate level of amputation can doom a procedure to failure from the start, even if the surgeon has performed the technical aspects of the surgery flawlessly. The pre-planning of a successful procedure should, in fact, comprise the majority of effort in a well-performed amputation.4    Surgeons must weigh many considerations in order to successfully plan the appropriate level of amputation. These factors include: tissue viability (the presence of ulcerations, skin anomalies, tissue deficits); micro- and macro-vascular circulation; anatomy and biomechanical function (residual deformities); cardiac demand and energy expenditure; and rehabilitation potential.

Tissue Viability: Why It Is Essential To Evaluate For Possible Infection

   While it is of paramount importance to leave only viable tissue when performing an amputation, it is not always an easy call to make. The decision to leave “marginal” tissue has been the cause of many failed surgeries. Infection, ulcerations, necrosis and fibrotic tissue or dysvascular tissue can all predispose the surgery to fail. A failed amputation can mean the need for revision and exposing the compromised patient to further risk of anesthesia.2    There is an inherent desire on the part of the surgeon, and indeed the patient, to leave as much length as possible during an amputation. However, leaving even any question of potentially infected tissue within the wound is inadvisable and foolhardy. That said, identifying affected tissue can be difficult in cases that are marginal.5-7    There are some important signs to consider when evaluating patients. Strep infections, which are most destructive to tissue of all origins, cause hemorrhagic changes that are clearly visible as dark red, maroon and/or black color changes to connective tissues, blood vessels and muscle tissue.    Staph infections may be more commonly represented by purulence. While the adjacent tissue may not have become compromised, it is necessary in this case to perform an atraumatic exploration of all potential spaces for further presence of infection. This is a learned skill that requires considerable caution and care. By exploring adjacent spaces, the surgeon may inadvertently spread infection. It is important to not only have an ingress into a compartment, but also to have an egress to allow for drainage of potentially infected materials.8-10    It is imperative to visualize all tissue that may have been contiguous with known areas of infection. Under pressure, infectious fluids will extrude from one compartment to the next along anatomic lines.11, 12    Van Baal states in Clinics of Infectious Disease that “Proper debridement and drainage of the infection requires a sound knowledge of foot anatomy. The usual routes of progression of the infection along anatomic pathways must be understood.”13 Reviewing the compartments of the foot will aid both novice and experienced surgeons in ensuring a knowledgeable exploration of potential areas of infection progression.

How Ulcerations Affect Planning For Amputations

   While the presence of ulcerations guides the surgeon in the planning of incisions, it may not require a more proximal level of amputation. However, the existence of ulceration does require one to explore structures through which the ulcer extends. The surgeon must examine for non-viable tissue, infection, extension to bone and osteomyelitis. All of these represent tissues that may require excision. It is possible, though, to have an ulceration that has not progressed to the level that allows for deep infection. In that case, isolated remodeling of the ulceration can allow for a more distal amputation (more distal than the site of the ulceration), which is almost always preferable.    Utilizing simple techniques of plastic surgery — rotation advancement flaps and pedicle flaps — one may remodel ulcers at the surface while leaving the structures below intact.    One must consider the reality that one amputation can lead to another in the future due to the creation of biomechanical abnormalities or a worsening of disease. Given this possibility, one must perform initial incisions for an initial amputation in such a way as to avert difficult scenarios in future surgeries, if at all possible.    The classic example is when one has to address an infected ulcer directly plantar to a metatarsal head. Often, surgeons may extend their incision from the metatarsal head to the proximal arch. If this presenting complaint subsequently becomes worse and progresses into an infected deep plantar space, the linear incision from distal to proximal through the arch may present the surgeon with a dilemma when he or she tries to convert this to a Loeffler and Ballard incision to view those compartments.14    This is the pitfall of seeing a problem in isolation when one knows the natural history of the amputation.2 For example, the natural history of the hallux amputation was well documented in the article by Murdoch, et. al., in The Journal of Foot and Ankle Surgery.15 In this retrospective study of 90 patients over a 10-year period, 60 percent of the patients had a subsequent second amputation, 21 percent had a third and 7 percent had a fourth. Seventeen percent underwent a below-the-knee amputation and 11 percent had a transmetatarsal amputation. There were also contralateral limb amputations with 3 percent below the knee and 2 percent undergoing transmetatarsal amputation.    Therefore, it is obviously important that at each step of the way, surgeons should not plan any incisions that will limit their ability to complete the next procedure in an efficacious and skillful manner, preserving skin coverage and circulation.

What You Should Know About Assessing Circulation

   Failure to appropriately assess healing potential from a vascular standpoint may be the single most critical error made in pre-planning for amputation level. If the surgeon considers the surgery as an “inciting event” for the patient, it is easier to view it as an event that will require increased metabolic demand to heal.    Methods for assessing the patient’s ability to heal from a vascular standpoint include the ankle-brachial index (ABI), the toe-brachial index (TBI), transcutaneous oxygen pressure monitoring (TCPO2) and angiograms.    The ABI (the ratio of the systolic pressure in the ankle to that in the arm) is known to be a poor predictor of healing when it is at a level of greater than 1.1, indicating calcification of the vessels in the diabetic. Perfusion is better indicated by the TBI (the ratio of the systolic pressure in the hallux to that in the arm).16, 17    In the works by Bacharach, Rooke and Osmundson, a TCPO2 greater than or equal to 40 was associated with primary or delayed healing in 98 percent of limbs undergoing amputation while a TCPO2 value of less than 20 was “universally associated with failure.”18    Angiograms remain the central tool for intervention if one anticipates the need for vascular reconstruction. Modern techniques that target smaller vessels in patients with lower limb vascular disease require very precise imaging of the peripheral vessels preoperatively.19 Several studies have shown that a positive outcome of these distal bypass procedures is governed by exacting determination of adequate pedal perfusion, requiring preoperative identification of the vessels.20,21 Failure to do so can result in further, unnecessary amputations.    One may successfully limit surgery to an anatomic area with fair circulation while the rest of the foot is compromised. For example, no palpable posterior tibial pulse would predispose a plantar flap to failure but a strong dorsalis pedis might allow for healing of a distal toe amputation.    In the case of the scheduled amputation, one must assess vascular disease (both focal microvascular and macrovascular) prior to the surgery. For the emergency case, the infection requires attention before the need for vascular assessment. In this setting, a revisional amputation may be required if the vascular test results do not indicate healing potential at the previously chosen level of amputation.    It is important to remember that a palpable pedal pulse does not guarantee adequate circulation and perfusion is necessary to heal a surgery. Keep in mind that patients with diabetes commonly have calcified vessels, giving falsely elevated indicators of circulation.    When it comes to patients with gangrene and diabetic complications, researchers have suggested amputating at a level with good, documented circulation.22    Another research group had success in assessing healing potential by using the amount of intraoperative bleeding from the skin flap. If it did not bleed sufficiently, they revised the amputation to a higher level.23 This technique is commonly used and highlights one reason for not employing a tourniquet during amputation procedures or at least letting the tourniquet down upon completion and prior to dressing.

Addressing Anatomical And Biomechanical Issues

   Abnormal foot biomechanics is a major factor in the development of ulcerations in the neuropathic patient. This often leads to the initial amputation.24    Distal amputations of isolated toes present several potential complications that one should consider. Amputating a toe at the metatarsophalangeal joint leaves a deficit that allows for drifting of the remaining toes into that space. This new anatomical position is often biomechanically unstable and presents a prominence that could ulcerate. For instance, an absent second toe usually results in the hallux transitioning into an abducted position. After amputation of a lesser digit, the adjacent ones may drift toward that open position as they no longer have a counterforce. If it is possible to do a more distal amputation through the phalanx, the remaining bone of the digit provides a spacer to prevent drifting.22    The powerful, deforming force of unopposed tendons is another source of complications that can occur. If the surgeon judges that a proximal transmetatarsal amputation is needed, leaving too little of the fifth metatarsal base can create a catastrophic deformity. The pull of the peroneals can reorient a short length of metatarsal bone, rotating it plantarly.    A proximal transmetatarsal amputation may also create an equino varus deformity with the loss of the plantar medial structures and allowing for the anterior tibial tendon to pull the foot into the varus position. One can revise this at a later date via a tendo-Achilles lengthening and anterior tibial tendon transection.

Assessing The Patient’s Cardiac Demand And Energy Expenditure

   Researchers have noted that survival rates after a lower-extremity amputation (limb amputation) range between 50 and 60 percent.2,25 In all likelihood, the patient who requires an amputation already has vascular disease as a contributing factor. Therefore, placing an even greater demand on the cardiovascular system of the patient after amputation often negatively affects mortality.    Surgeons who believe that a distal amputation, such as a transmetatarsal amputation, will not cause increased energy expenditure with ambulation are incorrect. While it creates less of an energy demand than the below knee or above knee amputation, it still affects the cardiovascular system. Due to the patient’s decreased capability of generating adequate plantarflexory motion, the leg is mobilized by the hip flexors, which requires considerable energy.26-31    It was historically accepted that the increase in energy was due to the weight of a prosthesis and the length of the residual limb but this was disproved. Instead, the socket shape appears to be the primary source. One should carefully consider this before asking the patient to continue to ambulate with assistive devices after rehabilitation. There is also a very high potential for loss of the contralateral limb.32,33

Evaluating The Patient’s Rehabilitation Potential And Quality Of Life Issues

   It is important to keep in mind that the higher the level of the amputation, the less likely the potential for rehabilitation success.34    It is often assumed that loss of a portion of a foot or limb will create a negative impact on quality of life and some researchers have found that to be true, but a recent study by researchers refutes this assertion. Peters, et. al., found that the psychosocial scores of patients who underwent amputations were not significantly different than those of the non-amputee diabetic patients.35 They found that the patients had in a sense disowned the body part prior to the amputation.    The more distal amputation (i.e. a toe) will probably be well perceived by the patient. In one study, researchers found no change in the quality of life of patients who underwent digital amputations. They noted that the quality of life of these patients was similar to that of patients who had a healed ulceration.36    When it comes to taking an aggressive approach to diabetic infection or vascular disease that leads to minor amputation, one should be aggressive because research shows only 63 percent of patients fully recover (have autonomic gait with limb prosthesis) after a major amputation. This speaks highly for the effort to do foot sparing surgeries with minor amputations as a hallmark.37

What The Statistics Reveal About Lower-Extremity Amputations

   Between 1997 and 1999, approximately 82,000 non-traumatic lower extremity amputations were reported in the United States and the most common link among these patients was foot ulceration.38 That figure will increase considerably in the coming decade given the rising number of patients with diabetes in this country. There are many factors that can lead to repetitive amputations at higher and higher anatomic levels. Poor planning is at the top of that list.    Unfortunately the fact that there has been an amputation already predisposes the patient to additional amputations because of altered biomechanical function. Revisional amputations are not uncommon. In several studies, the rate varies from 10 to 50 percent. Researchers have noted that the initial amputation has sometimes been performed at an inappropriate level.39-41

Final Notes

   Unfortunately, amputations are often relegated to the least experienced surgeon. While the technical aspects of the procedures are not usually challenging, the decision-making process behind the level of amputation requires a higher level of thought and training to achieve excellent results. Experienced surgeons will determine why the amputation is necessary in the first place, whether it is due to complications of neuropathy, vascular disease or a combination of the two.42-46    The ultimate outcome for the patient is a higher quality of life with a functional limb. Dr. Satterfield is an Associate Professor in the Department of Orthopaedics at the University of Texas Health Science Center in San Antonio, Texas. She is a Fellow of the American College of Foot and Ankle Orthopedics and Medicine, and the American Professional Wound Care Association. CE Exam #127 Choose the single best response to each question listed below: 1. In order to plan the appropriate level of amputation successfully, surgeons must consider factors like … a) tissue viability b) micro- and marcovascular circulation c) cardiac demand and energy expenditure d) anatomy and biomechanical function e) all of the above 2. Which of the following statements is false about Strep infections? a) They may cause hemorrhagic, dark red color changes to connective tissues, blood vessels and muscle tissue. b) These infections cause the least destruction to tissue of all origins. c) They may cause hemorrhagic, black color changes to connective tissues, blood vessels and muscle tissue. d) All of the above e) None of the above 3. Which of the following statements is true about Staph infections? a) These infections cause the most destruction to tissue of all origins. b) They may cause hemorrhagic, black color changes to connective tissues, blood vessels and muscle tissue. c) They may cause hemorrhagic, maroon changes to connective tissues, blood vessels and muscle tissue. d) They are more commonly represented by purulence. e) None of the above. 4. The presence of ulcerations … a) has no effect on the planning of incisions for an amputation. b) requires a more proximal level of amputation. c) requires surgeons to explore structures through which the ulcer extends. d) require the use of rotation advancement flaps in most cases of more distal amputations. e) None of the above 5. The ankle-brachial index (ABI) is … a) a poor predictor of healing when it is at a level of greater than 1.1. b) a better indicator of perfusion than the toe-brachial index (TBI). c) associated with delayed healing in 98 percent of limbs undergoing amputation. d) associated with primary healing in 60 percent of limbs undergoing amputation. e) None of the above 6. Which of the following statements is true? a) When the rest of the foot is compromised, one cannot successfully limit surgery to an anatomic area that has fair circulation. b) When a patient has no palpable posterior tibial pulse, this would likely predispose a plantar flap to failure. c) A strong dorsalis pedis may compromise healing of a distal toe amputation. d) Approximate determination of the patient’s pedal perfusion will help ensure a positive outcome with distal bypass procedures. e) None of the above. 7. Amputating a toe at the metatarsophalangeal joint … a) leaves a deficit that allows for drifting of the remaining toes into that space. b) may lead to biomechanical instability. c) may lead to a prominence that could ulcerate. d) all of the above e) none of the above 8. A proximal transmetatarsal amputation … a) has complications that may be revised at a later date with a tendo-Achilles-lengthening and anterior tibial tendon transection. b) may create an equino varus deformity. c) may lead to the anterior tibial tendon pulling the foot into the varus position. d) all of the above e) a and c 9. Survival rates after a lower-extremity limb amputation range from … a) 80 to 90 percent b) 20 to 30 percent c) 50 to 60 percent d) 30 to 40 percent e) None of the above Instructions for Submitting Exams Fill out the enclosed card that appears on the following page or fax the form to the NACCME at (610) 560-0502. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam. Responses will be accepted up to 12 months from the publication date.



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