Covering Plantar Wounds With An Abductor Digiti Minimi Muscle Flap

These authors discuss using the abductor digiti minimi muscle flap to help facilitate limb salvage in a 63-year-old patient with Charcot neuroarthopathy and a diabetic plantar ulcer.

Treating wounds of the lower extremity requires adherence to a multifactorial algorithm, which provides patients with the greatest healing potential while mitigating health cost burdens and wound recurrence. The basic steps in the management of most lower extremity wounds include eradication of infection, optimization of tissue perfusion and adequate offloading of pressure-prone areas. Often these wounds require staged surgical débridement, parenteral antibiotics and vascular intervention.

Additionally, we must consider medical and nutritional optimization as part of the comprehensive wound treatment algorithm. After optimizing the patient and wound, multiple treatment options are available for wound closure. These options, which respect the tenets of the soft tissue reconstruction ladder, include secondary intention, direct closure, skin grafting, local tissue transfers, regional tissue transfers and free tissue transfers. A variety of factors play a role in determining which method of wound closure is best, the most important factors being wound location and topography.¹

In addition to using pectoralis minor muscle flaps for breast reconstruction, authors have also described local muscle flaps in the lower extremity. In the 1960s, Ger pioneered soft tissue reconstruction in the lower extremity for post-traumatic and venous stasis wounds with the use of pedicled soleus and flexor digitorum longus muscle flaps.² Historically speaking, advances in anesthesia, antibiotics and wound healing gradually popularized the use of these flaps and, in doing so, improved postoperative outcomes.

Local muscle flaps are especially advantageous for bone coverage secondary to their robust vascularity. Transposing the muscle frees it from the surrounding tissues but the muscle remains attached to its blood supply, thus enhancing the chances of appropriate wound healing.³ Muscle flaps offer lower donor site morbidity than more complex regional and free tissue transfers, require shorter operative time, and require a less intensive postoperative course. Intrinsic muscle flaps of the foot are well-vascularized tissue flaps with adequate composition that are capable of filling soft tissue defects while having the ability to withstand the high impact forces of ambulation.⁴

Local muscle transposition flaps improve the blood supply to the recipient region, which may also enhance antibiotic delivery and promote wound healing, including to the underlying bone.⁵ The abductor digiti minimi muscle is located in the first layer of the lateral foot between the flexor digitorum brevis medially and the fifth metatarsal and cuboid laterally. It takes its origin from the medial and lateral calcaneal tubercles and its adjacent intermuscular septum, and inserts onto the lateral aspect of the base of the fifth proximal phalanx. The main vascular supply is the proximal branch of the lateral plantar artery, which is its dominant pedicle, inserting medial to the muscle’s origin on the calcaneus with one or more minor pedicles also noted (Mathes and Nahai Type II).^3,6 When raised, the muscle survives based on the single dominant vessel supply.⁶ The abductor digiti minimi muscle is useful for small coverage of plantar and lateral defects of the foot including the calcaneus.

What You Should Know About The Patient’s Surgical Course

A 63-year-old male with a past medical history of longstanding diabetes presented with a left plantar foot ulcer and foot deformity. The patient was afebrile and without constitutional symptoms. Pedal pulses were palpable and the neurologic assessment confirmed loss of protective sensation. The plantar midfoot ulcer was a full-thickness fissure with a hyperkeratotic border and a positive probe-to-bone test. There was no surrounding erythema or edema. Plain radiographs revealed hindfoot collapse consistent with late-stage Charcot neuroarthropathy without evidence of osteomyelitis. Initial laboratory analysis revealed leukocytosis (12,500/L) and hyperglycemia (239 mg/dL).

Following admission, the patient started on empiric broad spectrum parenteral antibiotic therapy. Non-invasive vascular testing demonstrated no occlusive arterial disease. The patient had a staged debridement, which included plantar exostectomy of the exposed calcaneus. Negative pressure wound therapy with instillation of normal saline and retention suture placement augmented therapy. Once post-debridement cultures confirmed eradication of infection, we utilized an abductor digiti minimi muscle flap and proceeded to perform primary closure of the plantar defect.

We revised the wound edges with semi-elliptical incisions, extending distal and proximal at the apices. After identifying the abductor digiti minimi muscle belly along the lateral aspect of the wound, we mobilized it from its fascia and bone.

We then transposed the abductor digiti minimi muscle belly medially to cover the exposed plantar calcaneus. Utilizing a monofilament polypropylene suture to oppose the muscle to the fascia on the medial aspect of the wound, we closed the skin atop the local muscle flap in a vertical mattress configuration. We placed a micro-drain as prophylaxis against hematoma formation, which can compress against the traumatized muscle and induce necrosis. The patient wore a non-weightbearing posterior splint. The drain was removed the day after the surgery and we discharged the patient the following day.

In Conclusion

Surgeons should consider local muscle flaps as a reconstructive option for wound closure about the foot and ankle. Pedicled muscle flaps offer a solution to soft tissue defects and are an alternative to free tissue transfers, especially in high-risk surgical patients with exposed bone or osteomyelitis in the foot and ankle.

Knowledge of anatomy and surgical technique makes the transposition of intrinsic foot muscles like the abductor digiti minimi a practical procedure for the podiatric surgeon. The treatment of exposed bone with intrinsic muscle flaps makes it possible to obtain coverage of exposed structures while potentially reducing hospital length of stay. This is one of many solutions to a common but challenging problem, and one should regard this as a valuable limb salvage tool.

Dr. Atves is a second-year resident in the Division of Podiatric Surgery at MedStar Washington Hospital Center in Washington, DC.

Dr. Elmarsafi is a Fellow of Diabetic Limb Salvage in the Department of Plastic Surgery at MedStar Georgetown University Hospital in Washington, DC.

Dr. Attinger is a Professor in the Department of Plastic Surgery at MedStar Washington Hospital Center in Washington, DC.

Dr. Steinberg is a Professor in the Department of Plastic Surgery at MedStar Washington Hospital Center in Washington, DC.

References

1. Attinger, CE, Clemens, MW, Ducic I, Levin, MM, Zelen, C. The use of local muscle flaps in foot and ankle reconstruction. In: Dockery GD, ed. Lower Extremity Soft Tissue & Cutaneous Plastic Surgery, Second Edition, Ch. 23. Elsevier Science, Kidlington, 2011.
2. Attinger CE, Ducic I, Zelen C. The use of local muscle flaps in foot and ankle reconstruction. Clin Podiatr Med Surg. 2000;17(4):681-711.
3. Ger R. The technique of muscle transposition and the operative treatment of traumatic and ulcerative lesions of the leg. J Trauma. 1971;11(6):502–510.
4. Ramanujam C, Zgonis T. Muscle flaps for the diabetic Charcot foot. Clin Podiatr Med Surg. 2012; 29(2):323-326.
5. D’Avila F, Franco D, D’Avila B, Arnaut Jr M. Use of local muscle flaps to cover leg bone exposures. Rev Col Bras Cir. 2014; 41(6):434–9.
6. Mathes SJ, Nahai F. Reconstructive Surgery: Principles, Anatomy and Technique. Churchill Livingstone and Quality Medical Publishing, Inc., New York, NY, 1997.