Pertinent Pearls On Using A Hexapod Frame For Charcot Fixation

Noting the increasing utility of hexapod frames for Charcot, these authors detail hexapod frame use in a 63-year-old patient with subtalar joint subluxation secondary to Charcot.

Charcot neuroarthropathy is a complication of longstanding peripheral neuropathy. Uncontrolled diabetes is the most common cause of peripheral neuropathy.¹ The effect of this disease on the lower extremity can be debilitating.

Charcot joints can occur in the midfoot, hindfoot and ankle.² Charcot neuroarthropathy progresses through various stages that Eichenholtz noted with his classification system.³ During the acute stage (stage 1), there may not be any radiographic changes. However, during later stages (stages 2 and 3), the affected joints can have significant bony destruction, which can create ambulatory dysfunction or pedal wounds. These complications may require reconstructive surgery to avoid potential deleterious complications such as osteomyelitis and amputation.⁴

However, this “classical” presentation of bony destruction is not always evident. The disease can present as multilevel joint subluxation or dislocation without bone dissolution, which makes the treatment more challenging.⁵ In cases of dislocation and significant deformity, closing wedge and bone shortening osteotomies are powerful techniques to correct the alignment.⁶ However, this may leave the patient with a shortened limb or extremity or neurovascular compromise. The shortening can pose secondary challenges with shoe gear and or bracing.

Surgeons have successfully used the Ilizarov method, utilizing circular external fixation, to address traumatic, post-traumatic, infectious, congenital and numerous other deformities.⁷ Advancements in circular external fixation have resulted in the development of hexapod devices, which utilize a computer software to address multiplanar deformity. These new devices have decreased the complexity associated with the classic Ilizarov external fixation. Hexapod devices for correcting Charcot joints have gained popularity.⁸ Surgeons can employ this method to overcome some of the soft tissue and bony challenges they encounter during surgery. In cases of subluxation, without dissolution of bone, the hexapod frame can be powerful and decrease the need for large bone resection/shortening procedures.

A Closer Look At The Patient Presentation

In the following case, we describe the use of a hexapod frame in the treatment of subtalar joint subluxation secondary to Charcot neuroarthropathy at the Rubin Institute of Advanced Orthopedics at Sinai Hospital of Baltimore, Maryland.

A 63-year-old female with a history significant for diabetes with neuropathy, rheumatoid arthritis, pulmonary embolism, deep vein thrombosis and morbid obesity got a referral to the senior author at the limb preservation center. The patient had a chief complaint of a painful, deformed right foot and ankle. She reported having a dislocated foot for greater than one year and had been ambulating with the assistance of a walker and a brace on the affected side.

Upon clinical examination, the patient had non-reducible lateral subluxation of the foot with respect to the ankle. No open wounds were present. However, significant skin creases were visible laterally, making bony palpation difficult. Protective sensation was absent from the mid-tibia to the foot. However, she had excellent three-vessel flow to the foot, which we confirmed with non-invasive vascular testing. Radiographic evaluation supported the clinical presentation with a notable subluxation of the subtalar joint. The foot had translated laterally 4 cm and migrated proximally on the fibula approximately 5 cm with a valgus deformity of 45 degrees.

After ruling out any infectious process, we scheduled the patient for staged Charcot joint reconstruction. During the first stage, we performed gradual correction of the subtalar joint with the use of a hexapod external fixation device. This involved gradual distraction and translation of the foot under the ankle. At the second stage, utilizing a minimal lateral incisional approach, we prepared the ankle and foot joints for fusion. We converted the hexapod frame into a static configuration to allow for axial compression and weightbearing.

The patient had close follow-up and all incisions healed without difficulty. We treated local pin site infections with wound care and oral antibiotics. We removed the frame after three months once radiographic consolidation occurred.

Final Words

Researchers have classified Charcot joints by the most commonly affected joints.⁹ This case study illustrates a less commonly seen presentation of Charcot in the hindfoot. The patient had a complete dislocation and subluxation of the subtalar joint with minimal to no bone dissolution, which was complicated by multiple comorbid conditions. In addition, she had significant angular deformity with shortening, which made her an ideal candidate for external fixation.

Realignment of the calcaneus and foot under the tibia in the presence of significant soft tissue contracture (Achilles tendon, flexor compartment, extensor compartment and lateral compartment) is challenging without significant bone shortening procedures. Shortening the limb can result in neurovascular compromise and researchers have advocated limiting shortening to < 3 cm.^10,11

This gradual method of correction can be technically challenging. The senior author presented a case of a patient with significant deformity and numerous comorbidities. With the assistance of the hexapod device, the senior author was able to accomplish the goals of:

• minimal soft tissue/vascular disruption 
• maintaining bony length
• restoration of limb height
• clinical and radiographic realignment of limb and extremity
• maintaining ambulatory status during treatment

The pedal manifestations of Charcot neuroarthropathy can be one of the most challenging conditions for foot and ankle surgeons. The hexapod external fixation device can be a powerful tool in the armamentarium of the foot and ankle surgeon. Utilization of the device in this challenging population can assist in achieving successful outcomes and preservation of the limb.

Dr. Siddiqui is affiliated with the International Center for Limb Lengthening/Rubin Institute for Advanced Orthopedics at Sinai Hospital of Baltimore. He is the Director of Podiatry Services at the International Center for Limb Lengthening, and the Associate Residency Director of the Baltimore VA/Sinai Hospital Podiatric Surgery Residency Program. Dr. Siddiqui is also the Medical Director of Diabetic Limb Preservation at LifeBridge Health in Baltimore and the Division Chief of Podiatry at Northwest Hospital in Baltimore. Dr. Siddiqui is an Associate of the American College of Foot and Ankle Surgeons.

Dr. Wilczek is a second-year resident at Our Lady of Lourdes Hospital in Binghamton, NY.

References

1. Hughes RA. Clinical review: Peripheral neuropathy. Br Med J. 2002; 324(7335):466–469.

2. Sinha S, Munichoodapa CS, Kozak GP. Neuroarthropathy (Charcot joints) in diabetes mellitus (clinical study of 101 cases). Medicine (Baltimore). 1972; 51(3):191-210.

3. Eichenholtz SN. Charcot Joints. Charles C. Thomas, Springfield, IL, 1966.

4. Johnson JT. Neuropathic fractures and joint injuries. Pathogenesis and rationale of prevention and treatment. J Bone Joint Surg Am. 1967; 49(1):1-30.

5. Armstrong DG, Todd WF, Lavery LA, Harkless LB, Bushman TR. The natural history of acute Charcot’s arthropathy in a diabetic foot specialty clinic. Diabet Med. 1997; 14(5):357-63.

6. Zgonis T, Stapleton JJ, Jeffires LC, Girard-Powell VA, Foster LJ. Surgical treatment of Charcot neuroarthropathy. AORN J. 2008; 87(5):971-86.

7. Zgonis, Thomas. External Fixators of the Foot and Ankle. Wolters Kluwer/Lippincott Williams & Wilkins, Philadelphia, 2013.

8. Zgonis T, Roukis TS, Lamm BM. Charcot foot and ankle reconstruction: current thinking and surgical approaches. Clin Podiatr Med Surg. 2007; 24(3):505-17.

9. Sanders LJ, Mrdjenovich D. Anatomic patterns of bone and joint destruction in neuropathic diabetics. Diabetes. 1991; 40:529A.

10. Sen C, Kocaoglu M, Eralp L, Gulsen M, Cinar M. Bifocal compression distraction in the acute treatment of grade III open tibia fractures with bone and soft-tissue loss: a report of 24 cases. J Orthop Trauma. 2004; 18(3):150-7.

11. Saleh M, Rees A. Bifocal surgery for deformity and bone loss after lower-limb fractures: comparison of bone-transport and compression-distraction methods. J Bone Joint Surg Br. 1995; 77(3):429-34.