Emphasizing a comprehensive approach to diabetic foot ulcer healing, these authors contend that in some cases, careful consideration of amputation at the appropriate level may lead to less complications than less definitive approaches.
There are approximately 34.2 million Americans with diabetes and these numbers increase each year.1 As many as 7.3 million Americans over the age of 18 years old are not aware they have diabetes.1 One of the major complications of diabetes are diabetic foot ulcers (DFUs) that may unfortunately lead to toe, foot and limb amputations. When it comes to people with diabetes in the United States, there are approximately 73,000 non-traumatic lower extremity amputations each year.1
Diabetic foot ulcers are multifactorial. It is important to understand the nature of the wounds as well as a patient’s medical history to expedite healing and ultimately close the wound as soon as possible.2 Contributing factors with non-healing wounds often include multiple components of vascular, neuropathic, persistent pressure and/or infectious processes. If there is a greater than 50 percent reduction in wound area within four weeks of a wound care regimen, one can project that the wound may close within 12 weeks.3,4 If this is not the case, either one did not fully address the non-healing factor or the worsening condition of the soft tissue and/or bone may be far too advanced for tissue preservation.
Although most DFUs heal successfully with local wound care and offloading, elective toe or foot amputation may provide timely treatment options for chronic DFUs. The main indications for nontraumatic lower extremity amputations in patients with DFUs are to eliminate soft tissue and bone infections (see first photo to right).
Emphasizing Earlier Ambulation To Reduce Potential Muscle Wasting And Cardiovascular Risks
However, as foot and ankle specialists, our goal is to not only eliminate infection but allow the patient to walk and return to daily activities as soon as possible. Doing so provides a stable and walkable foot and helps prevent deconditioning and deterioration of cardiovascular health. Patients with a DFU tend to ambulate less in efforts to heal the wound, which is contradictory from a cardiovascular perspective. In a recent study published in the Journal of the American Medical Association, researchers found that the greater the number of steps taken not only statistically-significantly reduces cardiovascular disease but is associated with a lower all-cause mortality risk.5 Walking as little as 4,400 steps a day has proven beneficial among older women.6 However, in many cases, patients with DFUs may be discouraged to take these many steps in a day.
Individuals 65 years and older are at increased risk for the development of chronic illnesses, especially with risk factors such as tobacco smoking, alcohol intake and inactivity, to name a few.7 In a study analyzing 4,207 United States men and women with a mean age of 73 years, researchers found that greater physical activity is inversely related to heart disease, stroke and overall cardiovascular disease.8 As people age and chronic diseases become more common, it is important for physicians to stress the importance of daily ambulation for aerobic fitness as well as prevention of the muscle wasting phenomenon called sarcopenia.8
Measuring skin perfusion pressures in 1,125 lower extremity wounds in 998 patients, Suzuki and colleagues found that patients without peripheral arterial disease (PAD) and skin perfusion pressures over 50 mmHg averaged 52 days for wound closure.9 In the same study, patients with PAD who had skin perfusion pressures below 30 mmHg and between 31mmHg to 50 mmHg on average healed in 235 days and 98 days respectively.9 Keeping these patients minimally- to non-ambulatory to promote the healing of plantar foot wounds may translate to several months of steady deconditioning, which is a risk factor for cardiovascular morbidity and mortality not only in geriatric patients but middle-aged adults as well.10
A common misconception among our patients is that they may not be able to ambulate properly after toe or partial foot amputations. Although Dillon and colleagues showed altered ambulation between amputees and non-amputees, those with forefoot amputations still may walk very well post-operatively.11 In fact, modifying shoe gear with customized inserts effectively improves gait in patients with amputations, making their gait comparable to the gait pattern of the non-amputated side for forefoot amputations.12 A patient undergoing a toe or foot amputation can be fully ambulatory in as little as two to four weeks after surgery, provided he or she has adequate blood flow to the extremity. The goal for our patients is to facilitate early ambulation, which one may achieve with timely and appropriate application of lower extremity amputation procedures.
Comorbidities can make diabetic wound healing extremely challenging. Estimates suggest that PAD occurs in 40 percent of patients with diabetic foot ulcers.13 Patients with diabetes chronically experience an altered angiogenic and pro-thrombotic state. When these patients do not have adequate vascular supply, their lower extremity wounds will not heal.14 Even once a patient’s wound heals, as many as 40 percent of patients have a recurrence within one year.15 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 test results show any worse than “mild ischemia,” a swift consultation with your vascular specialist colleagues for an angiogram is indicated. We encourage readers to develop a close working relationship with local vascular specialists. Successful limb preservation depends on solid referral and communication channels between the two specialties.
Key Considerations With Toe Amputations And Trans-Metatarsal Amputations
Toe amputation (see second photo to right). Surgeons can often perform a partial or complete toe amputation at the interphalangeal joint or the metatarsophalangeal joint safely in the office setting with local anesthesia. One may find this procedure useful in addressing a toe tip ulceration when bone is exposed, which is a clinical diagnosis of osteomyelitis.
Another indication is for correction of a painful hammertoe deformity, especially when it is dislocated and no longer functional. We often see this deformity in elderly patients. Alternatively, one may perform a flexor tenotomy to address the flexible or semi-rigid hammertoe deformity, either in the office or in the operating room. After post-op healing, the patient will not require a toe prosthesis although some patients may use a silicone toe spacer to fill in the gap while in regular shoes.
Trans-Metatarsal Amputation (TMA) (see third photo to right). This procedure is a workhorse in treating forefoot ischemia and infection in our profession. The TMA is a very durable procedure with a stable construct that may last a decade or longer without skin breakdown in our clinical experience. The TMA eliminates the forefoot tissue under the dual threat of ischemia and traumatic injury from ambulation by shortening the length and the leverage. This procedure makes foot ulcer recurrence much less likely once healed.
Once the patient has healed a TMA procedure, he or she may have shortened stride length but many of our patients continue to stay active by walking leisurely, playing golf or driving independently as one still retains plantarflexion of the foot.
Due to the need for hemostasis and pain control, we recommend performing TMA or higher foot amputations as inpatient procedures in the hospital setting. One may concurrently perform this procedure as necessary with a tendo-Achilles lengthening in order to release a tightened Achilles and prevent ulcerations at the distal stump. We recommend our TMA patients ambulate in high-top lace-up shoes with a forefoot filler orthosis although some may just use a balled-up sock to fill the forefoot space.
In one recent case, a 49-year-old male with a past medical history of type II diabetes mellitus, peripheral arterial disease, hypertension, obesity, previous opioid abuse and current tobacco use presented to the emergency room with a left foot infection (see fifth photo to right). He previously had a right above-knee amputation secondary to trauma 15 years ago, a left partial second ray resection a year ago and has battled several left foot wounds and infections. Laboratory workup and vitals revealed sepsis, and radiographic imaging revealed soft tissue emphysema requiring an urgent incision and drainage.
We promptly took the patient to the operating room due to severe infection requiring an open trans metatarsal amputation (see sixth photo to right). We obtained wound cultures in order to determine appropriate definitive antibiotic therapy. Three days later, we returned to the operating room for another wash-out procedure with removal of nonviable soft tissue and bone (see seventh photo to right), and a wound closure with advancement flaps (see eighth photo to right). Postoperatively, the patient’s lab results improved and he was discharged with culture-directed oral antibiotics for 10 days and plans for postoperative follow-up. One may suggest that below-knee amputation had an application here, however, we maintain that preserving 2/3 of his foot to allow him to ambulate and drive independently was worthwhile in this relatively young and very active 49-year-old.
When Other Partial Amputation Procedures Are Warranted
Chopart or Lisfranc amputation. One would reserve these procedures, more aggressive versions of the TMA, for cases involving overwhelming forefoot ischemia and infection, or revision of a TMA stump when the incision breaks down postoperatively. Chopart amputation is the last resort to save the hindfoot for ambulation purposes and is functionally less desirable to a TMA. As with the TMA, we recommend high-top lace-up shoes for extra support, either off-the-shelf footwear or custom-made shoes. A Charcot Restraint Orthotic Walkers (CROW) boots may prove useful if you find the patient to be a fall risk from a shortened foot.
Partial calcanectomy (see fourth photo to right). Severe heel ulcers that one typically sees in bed-bound neuropathic patients can lead to a calcaneal bone infection. Surgeons may address these ulcers with a partial calcanectomy and subsequent negative pressure wound therapy (NPWT) and skin grafting, performed in two stages. This procedure preserves most of the foot and one may attempt this procedure when the patient wishes to avoid a major leg amputation. As with the aforementioned partial foot amputations, the post-op patient would benefit from a custom filler for the heel defect and a high-top shoe for mechanical support with or without a custom ankle brace or CROW boot.
A Few Thoughts About Major Leg Amputations
Below-knee amputation (BKA)/above-knee amputation (AKA)/hip disarticulation. When infection and ischemia of lower extremity are overwhelming, or the patient has severe ischemic rest pain due to uncorrectable ischemia, a major leg amputation may be the most appropriate option. Although major leg amputation is most helpful in clearing foot infections, many of our geriatric patients may not return to ambulation as this requires extensive physical therapy and an adequate aerobic capacity to ambulate well with a BKA or AKA prosthetic. Indeed, we have witnessed many patients who failed to use a BKA prosthesis even once, due to lack of motivation and strength. Conversely, younger and healthier patients, who have traumatic amputations may do very well in regaining ambulation once they are introduced to a good rehabilitation program and work with prosthetists and physical therapists. Also, BKA or AKA may be desirable options if the patient suffers from devastating compound foot fractures like one sees in cases of advanced Charcot joint disease as opposed to complex reconstruction attempts that may be doomed to fail.
Important Aspects Of Amputation Aftercare
After amputations, there are a variety of shoe modifications, orthotics and prostheses that are possible for each patient. As ”diabetic socks” do not have a well-defined specification, we recommend multilayer cushioned socks (similar to hiking socks) to reduce shear forces and direct trauma. Typically for toe amputations, modifications are not necessary but it is important to get the patient in properly fitting shoes to prevent further ulceration while encouraging early mobilization. In our experience, off-the-shelf stability or motion-control running shoes may work (in place of custom diabetic shoes) if the clinician confirms appropriate fit.
For a TMA or Chopart amputations, we begin with a long-leg controlled ankle motion (CAM) walker postoperatively. Once the surgical site heals in four weeks, we recommend forefoot filler insoles with well-fitting mid-cut or high-cut shoes. In the event of a calcanectomy, a long-leg CAM walker can be beneficial postoperatively with subsequent transition into a CROW boot or custom-molded insole to protect the heel. For patients requiring a below-knee amputation or above-knee amputation, a postoperative stump shrinker and cast prevents the leg muscles from contracting. Then the patients are fitted for prosthesis for ambulation.16
Life does not have to stop after amputations and appropriate coordination with physical therapists/orthotists/prosthetists can make the rehabilitation process successful after surgery.
With the increased prevalence of diabetes in America, it is important to educate not only patients but 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 greater potential increase in mortality due to cardiovascular deconditioning. If bone infection from DFUs requires long-term use of IV antibiotics, you also need to consider the deleterious effects to kidney function, possibly leading to dialysis as well. Appropriate application of foot amputations may result in returning to daily life faster with improved quality of life and cardiovascular health. When a DFU is not progressively improving during each doctor visit, it may be time 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 Multi-Specialty Medical Group Wound Care Clinic in Los Angeles. He is also a member of the attending staff of Cedars-Sinai Medical Center in Los Angeles. He can be reached at Kazu.Suzuki@ cshs.org.
Dr. Chin is a second-year resident at the Cedars- Sinai Medical Center in Los Angeles.
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This article has been adapted with permission from a previously published article that ran in the July 2020 issue of Today’s Wound Clinic.