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Keys To Addressing Forefoot Plantar Ulcerations 

The Centers for Disease Control and Prevention (CDC) estimates one in ten Americans have diabetes and one in three have prediabetes.1 Diabetes is also increasing among younger populations and can lead to sleep apnea, cardiovascular disease, pulmonary disease and risk of cancer.2,3 One major complication of diabetes is diabetic peripheral neuropathy (DPN), seen in 50 percent of the geriatric population with diabetes.4 Although poor vascularity can cause diabetic foot ulcerations (DFUs), 80 percent of cases are a result of DPN.5 Once a patient acquires a DFU, they are at risk for infection and amputation. According to the National Diabetes Statistics Report, there are about 73,000 non-traumatic lower extremity amputations each year in the United States alone.1 This article aims to assist in medical and surgical decision making for patients with plantar diabetic foot ulcers. 

Pertinent Case Examples To Ponder 

We received a consultation request for an 85-year-old male with a past medical history significant for type 2 diabetes mellitus complicated by peripheral neuropathy. He presented with multiple acutely infected forefoot ulcers with signs of skin necrosis and bone exposure and a clinical diagnosis of osteomyelitis (see first photo above). Immediate hospital admission took place for IV antibiotic therapy. Due to sepsis, his chronic kidney disease progressed to end-stage renal disease requiring hemodialysis. His forefoot necrosis and infection eventually necessitated transmetatarsal amputation (TMA), which was successful (see second photo above).  

An additional case concerned a 47-year-old male with a past medical history significant for former alcohol abuse, type 2 diabetes mellitus complicated by peripheral neuropathy, a recurrent right foot plantar ulcer, infection and osteomyelitis. He previously had successful treatment with a right foot TMA. However, he gradually developed Achilles tendon contracture, with a subsequent and recurring plantar foot wound at the distal stump (see third photo above).  

After a year of local wound care, magnetic resonance imaging (MRI) displayed osteomyelitis in the forefoot stump, requiring further amputation. After reduction of the bony prominence and removal of the infected bone in a Chopart-type amputation, he was discharged with a 10 day course of oral antibiotics. He eventually healed from the surgery, obtained customized insoles and has experienced wound remission ever since for the past six months (see fourth photo above).

Overarching Considerations In Diabetic Forefoot Ulcerations 

Diabetic foot ulcers, no matter the location, are a multifactorial issue. One can consider a wound non-healing and chronic if the area does not reduce by more than 50 percent in four weeks and considered to carry poor prognosis.6,7 It is important that one understand the etiology of a wound, in order to address the underlying problem for optimized wound healing. Often, chronic ulcerations can give insight into a patient’s health before even exploring a patient’s history. In terms of comorbidities, patients with chronic diabetic foot wounds present with an 86.1 percent prevalence of diabetes-related kidney disease and a 90 percent prevalence of diabetic retinopathy.8 Understanding these underlying diseases may aid in antibiotic selection and comprehensive management of DFUs. 

The main goal of therapy is to provide a durable and healed, walkable foot, capable of walking and returning to daily activities as soon as possible. Another aim is to prevent deconditioning and cardiovascular deterioration for our patients. Patients with plantar DFUs tend to ambulate less in an effort to heal the wound, which can prove detrimental from a cardiovascular perspective. In a study published in the Journal of the American Medical Association, the greater the number of daily steps taken not only significantly reduces cardiovascular disease, but carries a lower all-cause mortality risk.9 It was previously believed that everyone should strive for 10,000 steps a day, while actually, walking as little as 4,400 steps a day shows direct correlation with lower mortality rates.10 In the latest large-scale 90,000 subject study published in 2021, physical activities (i.e. walking exercise) not only associate with lower risk for cardiovascular disease, but the greatest benefit is seen in those who are the most active, with no upper threshold for the positive health benefit.11 It bolsters the growing evidence that almost any amount of physical activity is good for cardiovascular health, with no apparent upper limit to the benefit.  

These findings support our treatment goals, which focuses on evidence-based wound treatment to heal the plantar foot ulcer in the shortest amount of time. In our experience, we achieve this by establishing a plantigrade foot via surgery when indicated. We also provide patient education and counseling on proper shoe gear and foot care to facilitate early return to vigorous ambulation, for the sake of optimal patient cardiovascular and mental health.  

Pertinent Pearls In Local Wound Care 

The basic treatment methods of local wound care for plantar forefoot ulcers are the same as with any lower extremity wounds; we suggest starting with a complete history and physical examination. Should the wound probe to bone or reveal acute infection, it is imperative to initiate antibiotic therapy and investigate the underlying cause. More often than not, these patients will have a vascular component that contributes to the non-healing wound, which one must address. If contributing ischemia is identified, we make a referral to our vascular specialist colleagues immediately. If one suspects skin and/or soft tissue infection, obtain a wound culture if possible, then place the patient on empiric oral antibiotics to cover gram-positive bacteria, the most common pathogen for skin and soft tissue infection.12 Moreover, we advocate for empiric coverage of community-acquired methicillin-resistant staphylococcus aureus (CA-MRSA), for example, doxycycline or trimethoprim/sulfamethoxazole, as it is increasingly more prevalent in the antibiogram for our region, as well as many urban hospitals in the United States today.12

One should base dressing selection on the wound characteristics as well as the amount of drainage. Careful evaluation for undermining, tunneling or fluctuance can reveal an abscess. In these cases, treatment involves incision and drainage along with trimethoprim/sulfamethoxazole or clindamycin for uncomplicated skin abscesses.13 We recommend, based on our experience, that ideal wound dressings be non-adherent to minimize the pain of dressing removal, while keeping the wound bed moist to facilitate faster granulation and epithelialization. We also recommend the use of antimicrobial dressings (despite the nominal added cost), as in our experience, chronic wounds tend to harbor wound colonization on the surface, and various antimicrobial wound dressings may suppress and control the bacterial count, preventing wound infection, although medical evidence in-vivo is scarce at this time. We also routinely use various collagen-based dressings, including biologic skin substitute grafts (cellular tissue products or CTPs) that mimic skin grafting, although CTPs may be cost-prohibitive in some cases. For more complex and difficult-to-heal wounds, as adjunct therapies, negative pressure wound therapy (NPWT) and hyperbaric oxygen therapy (HBOT) may be considerations, when clinical indications are met.    

Offloading may be the most important aspect of plantar forefoot ulcer treatment, as pressure and shearing force may often cause trauma that leads to skin injury. Various offloading shoe gear (postoperative surgical shoes, controlled ankle motion walking boots, custom-fitted Charcot restraint orthotic walkers) are available for effective offloading, allowing the patient to ambulate safely to some extent.14 One can also customize orthopedic felt pads of ¼-inch thickness with adhesive to the patient’s foot to create offloading “donuts” and “horse-shoe” padding (see fifth photo above).  

Employing Appropriate Surgical Options 

Once the we establish and address if possible, the underlying cause of the wound, we can then begin surgical planning as indicated. Plantar forefoot wounds often stem from repetitive trauma on a localized area, which causes increased pressure and tissue injury in a neuropathic foot. As we age, we tend to develop fat pad atrophy which can be from genetics, the force of gravity, multiple steroid injections in the area of concern, previous surgery or foot trauma.15 Losing such padding to the sole of the foot leads to more pressure in pressure points. Eliminating the osseous structure or biomechanical abnormality causing an ulceration may be addressed with various surgical techniques.  

The greatest battle of plantar forefoot ulcers, in our experience, is recurrence. Sharp, mechanical debridement to remove necrotic and devitalized tissue will allow for granulation tissue and re-epithelialization no matter the location of the wound.16 When a wound is at the distal tip of the toe, one might consider a flexor tenotomy to straighten the toe and improve the deformity. A flexible hammertoe contracture can be due to tendon imbalances, possibly addressable with a flexor tenotomy, extensor tendon lengthening and/or capsulotomies.17 For a more rigid hammertoe contracture, an arthroplasty or arthrodesis of the affected toe is indicated, as a tendon balancing procedure will not suffice.18 If the wound has been an issue for a long duration leading to bone infection, it is appropriate to offer a complete toe amputation as a definitive treatment option. 

Wounds under the metatarsal heads are very common in older patients and often go unnoticed as they can develop underneath a hyperkeratotic lesion. Upon debridement, physicians discover the wound that occurred due to the constant pressure from the weight of the body on the foot. After evaluating whether the wound probes to bone, one may consider removing the metatarsal head contributing to the lesion. This can help reduce the pressure on the soft tissue and allow for expedited healing.19 One caveat is the possibility of developing transfer lesions, which occurs in one in ten patients, as weight will redistribute to neighboring metatarsals.20 In these cases, we recommend getting patients in custom molded shoes as soon as possible.20 Whenever a forefoot plantar ulcer is present, consider Achilles tendon lengthening or a gastrocnemius recession for equinus after performing a Silfverskiold test, as this can help prevent excess force on the forefoot.21 

What Happens After The Forefoot Wound Heals? 

After plantar foot ulcers heal, we encourage through patient education and counseling for shoe modifications, orthotics or customized shoes. As “diabetic sock” descriptions do not have a proper definition, we recommend thick and well-padded socks, made of synthetic or wool fiber, to facilitate moisture transfer. One may also recommend off-the-shelf, motion-control or stability-type running or walking shoes if custom-made diabetic shoes are not readily available. Once fitting a patient with proper socks and shoes, periodic re-evaluation is in order to prevent further wounds or acknowledge initiation of a new wound.22,23 In our experience, we recommend every two months for most patients in this population, while higher-risk patients may necessitate visits as frequently as every two weeks, initially. Regardless of the procedure, evaluating gait may be helpful in counseling. Lastly, we encourage daily physical activity in the form of walking or low-impact exercise, such as swimming, stationary biking or yoga, as to optimize cardiovascular and mental health as described previously.  

Concluding Thoughts 

Plantar diabetic forefoot wounds are complex and require thoughtful evaluation of the underlying cause in order to expeditiously heal the wound and prevent recurrence. Any patient with a history of a diabetic neuropathic forefoot ulcer is at high risk for recurrence, and one should consider surgical options to eliminate deformity when indicated. Cardiovascular health and mortality is severely impacted with inactivity, therefore, it is essential to treat patients aggressively to heal wounds, while expediting return to early ambulation in proper shoe gear.  

Dr. Suzuki is the Medical Director of the Apex 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 podiatric medicine and surgery resident at Cedars-Sinai Medical Center in Los Angeles.

Features
By Kazu Suzuki, DPM and Tiffany M. Chin, DPM 
References
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