Diabetic foot ulcerations (DFUs) are a common yet often complicated problem. Ulcerations precede amputations 85 percent of the time in those with diabetes.1 Prevention and early treatment are of the utmost importance in order to achieve functional limb salvage. Biomechanical abnormalities and irregular foot structure lead to areas of increased pressure that are often the etiologies behind DFUs.2 Addressing underlying deformity is essential for long-term success and wound healing.
Common locations of DFUs are the plantar first metatarsal head, sub-styloid (fifth metatarsal base), plantar heel, dorsal proximal interphalangeal joint and the distal tips of lesser digits with hammertoe contractures. Accordingly, let us take a closer look at the abundance of treatment options for correcting the specific biomechanical deformities that lead to these ulcerations.
Essential Surgical Considerations For Plantar First Metatarsal Ulcerations
In those with diabetes, 33 to 35 percent of ulcerations occur at the plantar first metatarsal.3,4 Surgical reconstruction is often required to successfully manage such plantar forefoot ulcerations in these high-risk patients with complex comorbidities.5,6 Traditional surgical management includes wound debridement, sesamoidectomy, metatarsal head resection and Achilles tendon lengthening.7,8
Important surgical considerations include assessment of wound contamination as well as reducibility of the deformity. The distinction between clean or contaminated wounds will aid in the decision to introduce a foreign body such as hardware to supplement the correction.9 If the wound environment contains devitalized tissue or evidence of bacterial colonization, the risk for potentiating biofilm development, worsening infection and osteomyelitis increases.10 A biomechanical exam will also enable one to assess if the first ray is rigid or flexible, if there is a forefoot, rearfoot or global cavus deformity, and whether there is an associated equinus contracture.
In the case of a flexible or rigid first ray, one initiates surgical correction after ensuring a clean wound bed in the plantar first metatarsal ulceration and evaluating contributing etiologies for increased sub-first metatarsal pressure. Causes vary and include first metatarsal declination (metatarsus primus equinus), cavus foot deformity, equinus contracture, and/or hallux limitus and rigidus.11 One assesses each etiology independently and performs surgical correction as necessary.
Equinus treatment may include either an Achilles tendon lengthening or Baumann gastrocnemius recession based on the results of the Silfverskiold test.12 One can employ a Steindler stripping release of the plantar fascia for a flexible forefoot cavus deformity. A flexible or rigid plantarflexed first ray can benefit from a dorsiflexory wedge osteotomy (see first set of images above).
In regard to our surgical techniques for addressing these etiologies, we utilize minimal skin incisions in order to mitigate the risk of wound healing complications. Our treatment of choice incorporates a combination of the aforementioned procedures in those with diabetes or high-risk insensate patients with plantar first metatarsal ulcerations, particularly in the setting of pes cavus.
In cases with a contaminated wound and exposed bone or concern for osteomyelitis, there is a decreased ability to perform osseous and tendon reconstruction for fear of infection. The goal in these instances is to resect the affected bone to decrease pressure in this area and remove the source of infection. When the wound involves exposure of the sesamoids, one may perform sesamoidectomy of either or both affected bones. However, removal of these accessory bones can lead to tendon imbalance and subsequent new deformities such as dorsal phalangeal subluxation.13 Furthermore, Giurini and colleagues have noted a decrease in osseous pressure to the plantar first metatarsal head after sesamoidectomy.14 When there is concern for osteomyelitis in the first metatarsal in addition to the sesamoids, a metatarsal head resection is a more aggressive option to clear infection.
Plantar Fifth Metatarsal Base Ulcerations: What You Should Know
Cavovarus deformities have a high propensity for increased plantar lateral peak pressures of the foot and can ultimately lead to ulceration.15 Neuropathic ulcerations under the fifth metatarsal carry a high risk for osteomyelitis and often require osseous resection.16 Surgical intervention for fifth metatarsal osteomyelitis often includes loss of the fifth metatarsal base and therefore loss of eversion by the peroneus brevis, further propagating cavovarus deformity.17-19 The pull of the anterior and posterior tibial tendons without apposition of the peroneus brevis can cause greater varus deformity of the forefoot, resulting in elevated plantar lateral foot pressures.
One can categorize these treatment options into osseous resection, tendon transfers and tendon lengthenings. Tendon transfers include that of the peroneus brevis, peroneus longus or posterior tibialis tendon whereas tendon lengthenings involve the anterior tibial tendon or posterior muscle/tendon group. The split anterior tibial tendon transfer, unlike other transfers, is in-phase and is possible as either a single or staged procedure. Insertion of the hemisected tendon into the dorsolateral cuneiform avoids placement of implants or foreign materials near the ulceration.
In regard to the posterior tibial tendon transfer, while this tendon is not inserted into the site of ulceration, this is an out-of-phase transfer and therefore has a less effective muscular pull, requiring significant postoperative rehabilitation.20 While the peroneus brevis tendon transfer is in-phase, it does involve securing the tendon into the site of the ulceration and the foreign bodies needed to secure the tendon can be a nidus for colonization of bacteria and subsequent infection.9,10 Lengthening of either the anterior tibial or Achilles tendons may help mitigate excessive inversion forces and offload lateral foot pressure, but fails to increase the everting forces required to reduce a cavovarus deformity.
Split anterior tibial tendon transfers rebalance the foot and ankle by increasing the everting forces and weakening the strong inversion forces. This transfer maintains the lever arm of the tendon and reestablishes eversion, leading to a decrease in plantar lateral foot pressure, which aids in wound healing.21 The surgeon inserts the hemisected tendon into the dorsolateral cuneiform or cuboid. There is limited associated morbidity as this tendon transfer maintains the medial portion of the anterior tibial tendon. Furthermore, if bioburden contamination or infection is a concern, one can obviate the need for biocomposite interference screws and perform a pull-through technique with an external button and sponge.
How To Approach Plantar Central Heel Ulcerations
Heel wounds are difficult to treat based on their location and are the most likely diabetic foot ulcerations to lead to proximal lower extremity amputation. Researchers have demonstrated that 85 percent of heel ulcerations result in proximal amputation.22,23
Early treatment is imperative for limb salvage and good functional outcomes. When considering treatment options, one can group heel ulcerations into those with osseous extension and those without. When there is osseous exposure and risk for osteomyelitis, osseous resection is vital to eliminate infection. This bony resection also creates a mobile soft tissue envelope for osseous coverage and ease with primary closure.24-26 The vertical contour calcanectomy is the treatment of choice for patients with calcaneal osteomyelitis as the aggressive removal of bone paired with separation of the tendo-Achilles from its insertion helps to decrease calcaneal fracture risk (see second set of images above).
Despite the concomitant Achilles tenectomy paired with the procedure, 69 percent of patients maintain or improve their ambulatory status postoperatively due to the offloading of plantar heel pressures.24 Unfortunately, after a surgeon has performed a vertical contour calcanectomy, there remains a 29 percent rate of progression to proximal limb amputation.26 Other studies have shown a decrease in the total lower extremity amputation rate to 18.8 percent when utilizing this procedure in comparison to a traditional partial calcanectomy.24
When there is no osseous involvement and the etiology of the heel ulceration is solely from calcaneal gait, the surgical treatment needs to include tensioning of the Achilles tendon.27 Our treatment method to effectively shorten the Achilles is to imbricate the tissue, thus removing the redundant tendon.
We perform percutaneous Achilles repair to the proximal tendon just distal to the myotendinous junction with percutaneous insertion of the sutures and suture anchors into the calcaneus (see third set of photos above). We do not perform a full transection or removal of the Achilles tendon. This method allows for the native tendon to regain function in a shortened and imbricated fashion, alleviating the existing calcaneal gait.28
Pertinent Aspects Of Addressing Distal Digital Ulcerations
With hammertoe and mallet toe contractures, there can be increased pressure on either the dorsal proximal interphalangeal joint or the distal aspect of the digit respectively. Traditional treatment options for these flexion contractures include arthrodesis or arthroplasty of the proximal interphalangeal joint. Surgical procedures to avoid hardware placement with dorsal suspension sutures after PIPJ resection exist in the literature.29 Additionally, the flexor tenotomy is a possible alternative as a percutaneous in-office procedure to reduce the flexion contracture, therefore reducing pressure to the distal aspect of the digit.30
Although flexible hammertoe deformities respond more favorably, surgeons may still consider flexor tenotomies for some rigid deformities prior to traditional surgical intervention. In cases in which there is deformity recurrence or limited overall correction leading to continued wound formation, operative intervention becomes the only plan of treatment. Flexor tenotomies demonstrate high wound healing rates up to 96 percent with few instances of wound recurrence.31
Through surgical reconstruction of diabetic ulcerations, it is imperative to incorporate a pathomechanics-based approach to these deformities. Plantar first metatarsal ulcerations are commonly the result of a combination of biomechanical abnormalities, including a plantarflexed first metatarsal, cavus deformity and equinus contracture. Sub-styloid ulcerations result from the biomechanical deformity of cavovarus, leading to increased plantar lateral pressure. Heel ulcerations can manifest from calcaneal gait. Mallet toe contractures often develop due to overpowering of the flexor tendons.
By using a pragmatic approach to assessing and treating these etiologies, surgeons with a strong awareness of the aforementioned surgical considerations and treatment options can help facilitate optimal healing in these complex patients.
Dr. Cates is a Limb Preservation and Deformity Correction Fellow in the Department of Orthopaedics at the University of Maryland School of Medicine in Baltimore.
Dr. Kavanagh is a second-year podiatry resident at MedStar Georgetown University Hospital in Washington, D.C.
Dr. Wynes is an Assistant Professor and Fellowship Program Director in the Department of Orthopaedics at the University of Maryland School of Medicine in Baltimore.
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