The Modified Boyd Fusion: An Uncommon Limb Salvage Procedure

Amputations of the lower extremity are among the most common and oldest surgical procedures. Approximately 185,000 amputations occur in the United States each year,¹ and nearly 2 million people live with limb loss in the United States.
The leading causes of limb loss are vascular disease (54%), which includes diabetes and peripheral arterial disease, trauma (45%), and cancer (less than 2%).² In 2009, hospital costs associated with amputation totaled more than $8.3 billion.³ Nearly half of those who undergo amputation due to vascular disease will die within 5 years, which is higher than the five-year mortality rates for breast cancer, colon cancer, and prostate cancer.⁴ Of persons with diabetes and a lower extremity amputation, up to 55% will require amputation of the second leg within 3 years.⁵

Studies show that the more distal the amputation site, the better the outcome for the patient.⁵ A more distal amputation’s primary benefits include decreased oxygen consumption and less energy requirement for postoperative ambulation. These salvage techniques contribute to a better prognosis for the patient, increasing the patient’s life span and quality of life.⁶

A modified Boyd fusion is a functional limb salvage technique that consists of a Chopart disarticulation at the midtarsal joint in conjunction with subtalar and ankle joint arthrodeses utilizing an intramedullary nail. The Chopart amputation, first described in 1792, has received criticism in the current literature due to the equinovarus deformity that results.⁷ Patients with both diabetes and neuropathy can develop this unbalanced deformity and resultant increased plantar pressures that ultimately cause a breakdown in the skin. This can then lead to a need for future procedures, along with increased morbidity and mortality.⁷

In this case series, we aim to share our surgical technique and surmise that the Boyd modification affords the patient a stable and functional platform that maintains maximal limb length while creating a weight-bearing surface for ambulation that prevents the uneven pressures seen in a standard Chopart amputation alone.

The Authors’ Experience With the Modified Boyd Fusion

Between 2013 and 2016, 4 patients underwent a combination of the two procedures that comprise the modified Boyd fusion. The surgeon performed the procedures separately or as an adjunct to a previous operation. Inclusion criteria consisted of any patient who had received a Chopart amputation in the past or who subsequently received one, with the subtalar and ankle joint arthrodesis planned as a staged procedure.

Two patients had received a Chopart amputation and developed chronic non-healing wounds to the plantar aspect of the foot due to the unbalanced equinovarus deformity. These 2 patients underwent a subtalar and ankle joint arthrodesis to salvage the distal stump. Two additional patients underwent a Chopart amputation and subsequent planned subtalar and ankle joint arthrodesis due to either infection or ischemic gangrene.

Two categories defined success after 1 year—the patient had to:
bear weight on the operative limb and ambulate short distances with or without a prosthetic device; and
have a wound-free and uninfected operative limb.

On the other hand, failure was defined as:
wound development on the operative limb with or without an equinovarus deformity; and
need for a more proximal amputation on the operative limb.

Key Aspects of the Surgical Technique: Case Reports

Case #1 is a 57-year-old female with a past medical history of type 2 diabetes with peripheral neuropathy and hypertension. She stepped on a piece of glass and self-treated with home wound care for several weeks before presenting to the emergency department. Admission took place in December 2012 with a white blood cell (WBC) count of 26,500, erythrocyte sedimentation rate (ESR) of 140, C-reactive protein (CRP) of 29, hemoglobin A1c (HbA1c) 6.3% and negative blood cultures. On physical exam, she had soft tissue emphysema to the dorsal aspect of the right foot from the Lisfranc joint extending proximally to the ankle joint with fluctuance of the second through fifth toes. Radiographs revealed edema and subcutaneous emphysema to the dorsum of the foot across all metatarsal heads (see Figure 1 and Figure 2). A bedside incision and drainage decompressed the abscess.

The patient was taken to the OR the following day where a full-thickness incision at the Lisfranc joint revealed deep liquefactive necrosis along the flexor sheath into the plantar midfoot, with abscess formation extending into the ankle joint dorsally. The surgeon converted the procedure to a modified Chopart amputation at calcaneocuboid and talonavicular levels. The wound was packed and left open.

In January 2013, the patient had purulence at the anterior ankle while in the hospital. She returned to the operating room for additional debridement and exploration of the wound. The wound was pulse lavaged and then packed with iodoform gauze. In March 2013, the patient returned to the operating room for an incision and drainage with a split-thickness skin graft.

The patient had extensive follow-up with infectious disease, received long-term IV antibiotics, and weekly wound care visits with negative pressure wound therapy (NPWT). The medicine and nutrition teams worked to help increase her prealbumin levels.

In May 2016, the patient was evaluated and diagnosed with osseous equinus deformity with a neurotrophic wound measuring 4cm x 4cm (see Figure 3) and uncontrolled diabetes with blood glucose in the 600s.

The patient underwent a tibial bone marrow aspiration, Achilles tenotomy, and a subtalar and ankle joint arthrodesis with a Panta 2 150mm intramedullary nail (Integra) (see Figure 4 and Figure 5). The surgeon also performed an excision of the wound with a bilobed rotational skin flap, an application of a three-ring multiplanar external fixation device (Orthofix), and removal of the navicular.

The patient continued to follow up in the wound care center, healed all wounds and incisions, and obtained a carbon fiber prosthetic device (see Figure 6 and Figure 7) for added stability. The patient followed up for approximately 1 year without wounds and the ability to ambulate without pain or recurrence.

Case #2 is a 62-year-old female who presented to the ED with pain in left lower extremity in January 2016, and had not seen a physician in over 20 years. Her labs showed a blood glucose of 391, CRP of 43.8, HbA1c of 12.8%. She began empiric antibiotics with vancomycin and pipercillin/tazobactam. Radiographs revealed an abscess in her left foot with evidence of gas gangrene.

She was taken to the OR for a Chopart amputation of the left distal foot. Intraoperative findings included extensive necrotizing fasciitis to rays 2 through 5 with liquefactive necrosis to the dorsal and plantar muscles. As a result, the surgeon converted the procedure to an open guillotine amputation with NPWT application. Ten days later, she underwent incision and drainage of a localized abscess of the plantar flap with excisional debridement of a 4.0 x 5.0 cm wound and washout of a larger 10.0 x 10.0 cm wound.  

Twelve days later, she underwent a tibiotalocalcaneal fusion with an Panta 2 nail with two 5.0 calcaneal and two 4.0 tibial screws, a reverse peroneal brevis muscle flap with excisional wound debridement with excision of navicular and cuboid bones, application of Integra Meshed Bilayer Wound Matrix with a total area 36 cm² with the application of NPWT and application of an Orthofix five-ring multiplanar external fixator.

Another two weeks passed, and she then underwent excisional debridement of muscle totaling 6.0 x 6.0 cm and 12.0 x 12.0 cm with Versajet hydrosurgery system (Smith + Nephew), harvest of a split-thickness skin graft (total area 24 cm²), and application of the meshed bilayer (36 cm²) wound matrix. On March 25, we performed a harvest and application of the split-thickness skin graft. Over three months after initial presentation, we removed the external fixation and performed another application of the meshed bilayer wound matrix.

Case #3 involved a 64-year-old female with a benign past medical history except for hypertension. In June 2016, she underwent a bilateral iliac aortogram, including right superficial femoral artery (SFA) and popliteal angioplasty with stenting. She presented with acute onset of ischemic gangrene to the left distal plantar forefoot from emboli. In August 2016, she underwent an amputation of the fourth and fifth digits of the left foot with partial amputation of digits 1, 2, and 3 with extensive debridement of plantar skin due to gangrene. We also applied a meshed bilayer wound matrix and NPWT to the plantar foot. One month later, she underwent a Chopart amputation with flap closure and a tibiotalocalcaneal arthrodesis with the 150 mm Panta nail.

Case #4 focused on a 48-year-old male with a history of necrotizing fasciitis to the right lower extremity in August 2014 and underwent Chopart amputation at an outside hospital. The patient continued to have a chronic non-healing ulcer to the plantar aspect of the right foot. In May 2015, he underwent excisional debridement of the right foot ulcer and tibiotalocalcaneal arthrodesis with a 12mm ankle hindfoot (AHN) nail (Orthofix) and a complex wound closure with a rotational skin flap. An application of Orthofix multiplanar external fixation device with 2 rings and footplate was added for stability.

What Can Clinicians Learn From These Cases?

Patient ages ranged from 48 to 64 years of age (see Table 1 for demographics). Females outnumbered males in this case study 3 to 1. Follow-up time ranged from 7 to 23 months since the definitive operation. The patients’ preoperative diagnoses ranged from diabetes with peripheral neuropathy with forefoot gas gangrene, osteomyelitis, and necrotizing fasciitis to one ischemic gangrene from emboli. Several patients had wound complications after the definitive subtalar and ankle joint arthrodesis with an intramedullary nail and were treated in a local wound care center until they healed. All patients subsequently healed the wounds.

Table 2 shows the time difference from the original Chopart amputation date to the date of the subtalar and ankle joint arthrodesis with an intramedullary nail. The difference ranged from 0 to 29 months. Two patients had the subtalar and ankle joint arthrodesis staged as part of the original Chopart amputation, while the other two had the Chopart amputation previously and subsequently developed equinovarus deformity with plantar wounds.

The inherent muscle imbalance of the Achilles tendon on the rearfoot following a Chopart amputation inevitably causes an equinovarus deformity. This can eventually lead to uneven pressures on the residual stump, which, even with prosthetic support, can ultimately cause tissue breakdown. The combination of a Chopart amputation with a subtalar and ankle joint arthrodesis eliminated the unopposed pull of the Achilles tendon, thus counteracting the potential development of the equinovarus deformity. The significant advantage of this procedure is that it maintains a maximal limb length and affords a stable platform for the patient to ambulate.

All 4 of the patients had subtalar and ankle joint arthrodesis done with an intramedullary nail with the ability to compress the joints. It is important to note that the surgeon did not denude the subtalar and ankle joints of their cartilage surfaces before intramedullary nail placement. Compressing the cartilage with the nail eliminates any movement in these respective joints. This has two advantages in our experience: it decreases the overall anesthesia and operation time and any unnecessary soft tissue dissection and added wounds. All patients were monitored postoperatively with serial radiographs showing a stable subtalar and ankle joint. All 4 patients also had an external fixation device placed for added stability while the subtalar and ankle joint fused, allowing time for the soft tissue to heal and providing for earlier ambulation

Concluding Thoughts

The modified Boyd fusion, in our experience, is a valuable limb salvage procedure to have in your repertoire for a specific subset of patients. It affords the patient a functional and stable platform and maintains maximal limb length and weight-bearing surface for ambulation. We find this construct eliminates the equinovarus deformity and subsequent wound development typically seen in the Chopart amputation alone while increasing quality of life and longevity by reducing the energy expenditure needed to ambulate. Future studies with long-term follow-up, larger populations, energy expenditure data, and morbidity and mortality specific to this procedure would be an invaluable tool to help determine the benefit of this procedure. 

References
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6.    Taylor RP, Bouchard JL, Rabjohn LV. Amputations. In: Southerland JT, Boberg JS, Downey MS, Nakra A, Rabjohn LV (eds). McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery, 4th ed. Lippincott, Williams & Wilkins; 2013:1022-1035.
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