Current Concepts of Non-Traumatic Foot Amputation: Indications and Aftercare

Which level of amputation is appropriate for patients with diabetes? These authors review considerations when patients need non-traumatic amputation, including surgical indications and how to help patients function best postoperatively. 

According to the National Diabetes Statistics Report, as of 2018, there are roughly 34.2 million Americans with diabetes and these numbers are increasing each year.¹ As many as 7.3 million Americans over the age of 18 years old were not aware they had diabetes. One of the major complications of diabetes is diabetic foot ulcers (DFUs), which unfortunately may lead to toe and foot amputations. There are about 73,000 non-traumatic lower extremity amputations a year performed on people with diabetes in the United States.¹ These statistics may seem alarming, but it is the reality that podiatric physicians encounter daily across the country.

Diabetic foot ulcers are a multifactorial problem that does not always have a simple solution. Although most DFUs are treated successfully with local wound care, timely application of toe and foot amputation should be considered as a treatment option. The main indications for amputations of the lower extremity often seen in DFUs are to eliminate soft tissue and/or bone infections (Figure 1). However, as foot and ankle specialists, our goal is not only to eliminate infection, but also to get the patient walking and returning to daily activities as soon as possible, by providing a stable and walkable foot. Patients with a DFU tend to ambulate less in efforts to heal the wound, which has several disadvantages from a total body and cardiovascular perspective. In a recent study published in the Journal of the American Medical Association, the greater the number of steps taken not only significantly reduces cardiovascular disease, but is also associated with lower all-cause mortality risk.² Walking as little as 4,400 steps a day has proven to be beneficial among older patients.³ However, in many cases, diabetic patients with foot wounds are discouraged to take that many steps in a day.

A common misconception among our patients is that they may not be able to ambulate properly after toe or partial foot amputations. Though literature has shown ambulation between amputees and non-amputees is altered, amputees are still able to walk very well postoperatively.⁴ In fact, modifying shoe gear with customized inserts has proven to effectively improve gait in amputees, making their gait comparable to the gait pattern of the non-amputated side.⁵ Patients undergoing a toe or foot amputation can be fully ambulatory in as little as 2–4 weeks after surgery, provided they have adequate blood flow to the extremity. Toes are not vital organs like the heart or liver, and toe amputations are not a death sentence, contrary to the belief shared by many of our patients. The goal for all patients is to facilitate early ambulation, which may be achieved with a timely and appropriate application of lower extremity amputations.

A major hindrance of diabetic wound healing is comorbidities. Peripheral arterial disease (PAD) is estimated to occur in 40% of patients with diabetic foot ulcers.⁶ Patients with diabetes are chronically in an altered angiogenic state and without an adequate vascular supply, these lower extremity wounds will not heal.⁷ Patients with skin perfusion pressures (SPP) over 40 mmHg near the wound have been shown to have significantly shorter wound closure times, while SPP of 30 mmHg or lower may predict wound healing failure.⁸ Even once a patient’s wound heals, as many as 40% of patients have a recurrence of foot ulcers within 1 year.⁹ Especially in patients with diabetes and PAD, it is crucial to evaluate the patient with an arterial Doppler study prior to any surgical intervention. If these results are shown to be any worse than “mild ischemia,” it is generally recommended that you request a consultation with your vascular specialist colleagues.

Considerations With Foot Amputation Levels

Toe amputation (Figure 2). A partial or complete toe amputation at the interphalangeal or at the metatarsophalangeal joint can often be done safely in the office setting with local anesthesia. It may be useful in correcting a toe tip ulcer when a bone is exposed (clinical diagnosis of osteomyelitis). Another indication is to correct painful hammertoe deformity, which may be dislocated and no longer functional, often seen in elderly patients. Alternatively, flexor tenotomy can be performed to correct the hammertoe deformity, either in office or in the operating room.

Transmetatarsal amputation (TMA) (Figure 3). This procedure is a workhorse in treating forefoot ischemia and infection in our profession. TMA shortens the length of the foot by two-thirds by design, which makes the foot ulcer recurrence much less likely postoperatively. Once performed and healed correctly, this is a very durable procedure with a stable construct that may last a decade or longer without skin breakdown. TMA may alter the patient’s gait to be shorter, although many of our patients continue to be active by walking leisurely, playing golf or driving themselves as the TMA retains the plantarflexion of the foot. Because of the hemostasis and pain control purpose, we recommend performing TMA or higher foot amputation in the hospital setting. This procedure may be concurrently performed with a tendo-Achilles lengthening procedure in efforts to release a tightened Achilles tendon as needed, and to prevent ulcerations at the forefoot.

Chopart amputation. The Chopart is a shorter version of the TMA, which may be performed when forefoot ischemia and infection are overwhelming, or used as a revision of TMA stump when the skin breaks down. Chopart amputation would be the last resort to save the hindfoot and heel for an ambulation purpose, and it may be functionally less desirable to TMA.

Partial calcanectomy (Figure 4). Severe heel ulcers can lead to a bone infection of the calcaneus (heel bone), which can be corrected with a partial calcanectomy, possibly followed by negative pressure wound therapy and skin grafting. This procedure preserves most of the foot, and it may be desirable when the patient wishes to avoid a major leg amputation.

Below knee amputation/above knee amputation (BKA/AKA). When the infection and ischemia of lower extremity are overwhelming, or the patient has severe ischemic rest pain due to uncorrectable ischemia, a major leg amputation (as in BKA/AKA) may be the most appropriate option. Although a BKA/AKA is the most helpful in clearing foot infections, many of our geriatric patients may not return to ambulation as this amputation requires extensive physical therapy and aerobic capacity to ambulate well with a prosthetic. Conversely, younger and healthier patients may do very well in regaining ambulation once introduced to a good rehabilitation program and working with prosthetists and physical therapists. BKA/AKA may be a desirable option if the patient is faced with the devastating compound foot fracture often seen in Charcot foot disease.  

After amputations, there are a variety of shoe modifications, orthotics and prosthesis that can be custom made for each patient. Typically for toe amputations, modifications are not necessary, but it is important to get the patient in proper fitting shoes to prevent further ulcerations. For a TMA or Chopart amputations, we begin with a long-leg controlled ankle motion (CAM) walker postoperatively and then once the surgical site heals in 3 to 4 weeks, we recommend forefoot filler insoles with custom diabetic shoes. In the event of a calcanectomy, a long leg CAM walker can be beneficial postoperatively, followed by a Charcot restraint orthotic walker. Patients requiring a below knee amputation or above knee amputation, are placed in a postoperative shrinker and cast to prevent the muscles from contracting, then they are fitted for prosthesis for ambulation.¹⁰ Life does not have to stop after amputations and orthotists/prosthetists make this possible after surgery.

In Conclusion

With the uptrend of diabetes in America, it is important to educate not only patients with diabetes, but also their family members on the negative effects of diabetic foot ulcers from a total body perspective. The more time spent on local wound care and limited ambulation for the sake of healing DFUs, the increase in mortality is observed due to cardiovascular deconditioning. If the bone infection from DFUs requires long-term antibiotics, you also need to consider the deleterious effects to patients’ kidney function as well. Toes are not essential to walking and appropriate foot amputations may result in patients returning to daily life faster with improved cardiovascular health. When a DFU is not progressively improving during each doctor visit, it is imperative to consider a definitive solution to the problem, with surgical intervention involving an experienced foot and ankle surgeon.

Dr. Suzuki is the Medical Director of the Apex Wound Care Clinic in Los Angeles, CA. He is also a member of the attending staff of Cedars-Sinai Medical Center in Los Angeles, CA. He can be reached at Kazu.Suzuki@cshs.org.
 

Dr. Chin is a second-year resident at Cedars-Sinai Medical Center in Los Angeles, CA.

 

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