Minimally Invasive Exostectomy for Charcot Neuroarthropathy

Background

Diabetic foot complications are the leading cause of amputations in the United States. Charcot neuroarthropathy is a destructive process, often seen in the foot, resulting from complications of diabetic vasculopathy and neuropathy. With Charcot disease progression, longitudinal arch collapse and bony prominence with plantar ulceration frequently occurs. Open reconstructive surgery is often avoided in the early stages of the disease process while a noninfected plantigrade foot is maintained.^1,5 However, with time, plantar protrusion of tarsal bones may occur, causing gait derangements and ulceration. Particularly, lateral column ulceration with plantar cuboid prominence has been shown to lead to amputation. Therefore, despite multiple medical comorbidities and advanced diabetes, surgery is sometimes recommended in an attempt to maintain a plantigrade foot or to prevent deep infection. ¹ Patients with disassociation of the hindfoot-forefoot continuity may be surgical candidates for external fixation or internal fixation beaming procedures to maintain structural alignment, as severe equinus and collapse present excessive impending risks. ³ Surgery ranges from soft tissue releases, exostectomies, osteotomies, and fusions. Even with experienced surgeons, complication rates remain high. ² Unhealthy patients with chronic infection, exceedingly high hemoglobin A_1c, or severe comorbidities may not be stable enough to undergo open surgery or heal large reconstructions. We suggest that in a subgroup of patients with progressive disease and impending ulceration, minimally invasive exostectomy may be a useful tool to preserve ambulation and limb salvage.^6,7 This technique mitigates infection risks and wound healing complications while facilitating patients’ return to activities of daily living. ⁸ Concomitant procedures such as Achilles lengthening can be added to further decrease equinus forces.

Indications and Contraindications

Patients with significant discomfort and previous or impending ulceration due to bony prominence can be considered for exostectomy. Stable patients with complete instability or more severe deformities may benefit from reconstructive surgery. Those with infection or lack of soft tissue coverage may require staged infection eradication and ulcer reepithelialization. A minimally invasive exostectomy may be successful long-term or can serve as a delay for larger reconstructive surgery.

Case Example

A 50-year-old man with poorly controlled insulin-dependent diabetes (HbA_1c of 13.8) presented with Charcot foot deformity. He was referred from wound care with recurrent neuropathic ulceration. Medical history included syncopal episodes secondary to autonomic insufficiency as well as pancreatitis and anxiety. He was a former heavy smoker, still actively using nicotine via vaping. Examination revealed a collapsed foot deformity with a recently healed lateral column plantar ulcer. Sensation was severely blunted from the midfoot distally, while improving proximal to the ankle. Conservative and surgical treatment options were discussed. It was felt, based on health and social concerns, that he was not an optimal candidate to tolerate a complete reconstruction with fusions. The decision was therefore made to proceed with minimally invasive tarsal exostectomy and percutaneous Achilles tenotomy.

Technique

The patient is placed supine on a radiolucent table with a bump and leg elevated on a foam wedge. The authors prefer a large C-arm to avoid moving the extremity. A tourniquet can be used for bleeding control. The authors recommend a 2-5 mm burr high torque and low speed (6000 rpm) with continuous irrigation for bone debridement. Accessibility with the hand-held burr can be achieved via a lateral 5-10 mm incision at the junction of the thick plantar skin and the softer lateral foot skin. Accessing the lateral or medial column through an adjacent incision nearest the plantar prominence is most reproducible. Avoiding incisions on the plantar aspect of the foot may better help in avoiding areas of ulceration and unhealthy tissue. It may also allow for more predictable healing in patients unable to comply with nonweightbearing recommendations (Figure 1).

Figure 1.

Left to right: Intraoperative photos demonstrating progressive removal of bony prominence using burr technique. The first photo reveals plantar retraction of soft tissues during resection, the middle photo reveals dorsal retraction of soft tissues during resection, and the final photo reveals intact surgical incision without soft tissue damage after completion.

Meticulous dissection is completed through skin and subcutaneous tissue. A soft tissue elevator or similar instrumentation can be used to elevate adhesive tissue and create a working portal. This helps to avoid vital structures or creating heat necrosis of overlying soft tissue. The affected foot can be held in a neutral or dorsiflexed position to palpate the plantar prominence in order to establish a planar weightbearing surface. Appropriate burr placement on the bony prominence can then be confirmed using a lateral view with intraoperative fluoroscopy. Gradual exostectomy with the burr can be performed with regular interval reexamination. Irrigation between episodic burring is employed to decrease any avoidable heat necrosis. A blunt-tip needle on a 30-mL syringe works well to access the working portal through the same incision. The bone reamings can then be pressure flushed from inside out using irrigation from the syringe. Intraoperative imaging should be used to ensure all reamings are evacuated. Routine palpation of the plantar foot helps ensure all pressure points are adequately relieved and that uniformity can be obtained for weightbearing (Figure 2).

Figure 2.

Intraoperative fluoroscopy images demonstrating (A) the plantar prominence necessitating excision, (B) progressive morselization of the prominence using burr technique, and (C) evidence of eradication of bony prominence with development of the planar surface after irrigation of reamings.

After complete irrigation and suction to remove residual bone fragmentation, the incision can be loosely closed. The final irrigation is performed with saline mixed with vancomycin powder. A splint is placed, and patients are recommended to remain nonweightbearing for the first 2 weeks. Patients should return to the clinic for a wound check at 10-14 days postoperatively. Depending on the circumstances, patients may begin transitioning into a weightbearing boot with custom insoles for no less than 12 weeks before wearing standard footwear. Charcot neuroarthropathy progression must still be monitored, and patients should be encouraged to perform regular foot checks to assist in preventing foot ulceration. Figure 3 demonstrates preoperative and 1-week postoperative radiographs of the case presented.

Figure 3.

Top to bottom: Preoperative lateral and anteroposterior (AP) weightbearing radiographs demonstrating plantar bony prominence, and 1 week postoperative lateral and AP radiographs demonstrating successful exostectomy without bony complications.

Conclusion

Minimally invasive exostectomy for Charcot foot deformity with pending or open ulceration may serve as an effective alternative to help delay or avoid more aggressive open surgical approaches. Minimally invasive surgery continues to be an increasingly popular tool within the field of foot and ankle surgery. ⁴ However, surgeon competency in minimally invasive techniques should be gained before employing this method. The proposed modified technique of minimally invasive exostectomy allows for accurate fluoroscopic identification of the ostectomy site while minimizing the risk of wound complications. We believe this serves as an additional method in the algorithm to prevent Charcot complications for selective patients.