Given the complexities of Charcot neuroarthropathy and involvement in the hindfoot and ankle, these authors review appropriate staging, keys to choosing optimal fixation and pertinent pearls in performing tibiotalocalcaneal fusion with intramedullary nailing.
Charcot neuroarthropathy of the foot and ankle is a destructive joint disorder resulting in severe and debilitating deformity of the foot and ankle secondary to pathologic fracture and dislocation. Although Charcot neuroarthropathy affects approximately 13 percent of patients with diabetes mellitus, this disorder may also occur in patients suffering from a multitude of conditions, such as syringomyelia, alcohol use disorder and leprosy, that can lead to advanced peripheral neuropathy.1-3 Regardless of the underlying condition, peripheral neuropathy is universally present in all patients suffering from Charcot neuroarthropathy.4,5
When it comes to hindfoot and ankle Charcot cases, in particular, surgical reconstruction with tibiotalocalcaneal fusion with intramedullary nailing may be a viable treatment option for restoring lower extremity stability and function.
To date, researchers have proposed several theories to explain the development of Charcot neuroarthropathy. These theories include: an increase in bone perfusion secondary to sympathetic denervation; repetitive microtrauma; and, most recently, dysregulation of pro-inflammatory cytokines and over-expression of the RANKL pathway leading to an uncontrolled inflammatory state.6,7 While a final consensus on etiology remains elusive at this time, the prevailing belief is these theories do not take place in isolation but instead occur simultaneously.
There are several classification systems for staging Charcot neuroarthropathy. The radiographically-based Eichenholtz system emphasizes development, coalescence and reconstruction.8 Eichenholtz believed that stage I was optimal for surgical reconstruction due to the relative lack of inflammation and late stage III was also favorable due to osseous structures becoming more stable.8 Shibata later described an additional stage (which precedes stage I) and is characterized by swelling, local warmth and clinical instability due to laxity of the ligaments.9 Radiographically, this stage is unremarkable. One must exercise a high index of suspicion in order to recognize the relatively subtle changes associated with early Charcot to prevent deformity progression and ulcer formation.
Additional classifications focus on the anatomic location of the Charcot deformity. Many sources cite the tarsometatarsal joints as the most common location of fracture and dislocation.10-12 Involvement of the ankle and hindfoot reportedly occurs in approximately 10 percent of Charcot neuroarthropathy cases.10,11
Addressing The Unstable Charcot Ankle And Hindfoot With Fusion And IM Nailing
Charcot neuroarthropathy associated with the ankle and hindfoot represents the most unstable of the Charcot deformities. This instability is likely a result of its multiplanar nature, which can lead to deformity in the sagittal, frontal and transverse planes. In addition to the multiplanar deformity, Charcot neuroarthropathy occurring at the ankle and hindfoot can often result in a shortened limb secondary to osseous resorption and collapse of the periarticular structures, most notably, the talus. Due to this instability, these patients are often at higher risk for associated ulcerations of the ankle and foot.
In the foot, ulceration is common due to the ankle deformity, leading to abnormally elevated pressures of the medial or lateral forefoot. In the ankle, ulceration often occurs due to increased pressure from exceptionally prominent malleoli secondary to local deformity. Due to the gross instability, bracing can be difficult with a high potential for wound complications. Due to the difficulties associated with conservative therapies, when appropriate, one can perform surgical reconstruction with tibiotalocalcaneal fusion via intramedullary nailing.
In addition to restoring lower extremity stability and function with arthrodesis of the hindfoot and ankle, Shibata and colleagues demonstrated relative protection of the midfoot joints in patients who underwent tibiotalar and tibiocalcaneal arthrodesis.9 Of the 15 patients in their series who achieved solid fusion, they reported no remarkable degenerative changes to the midfoot joints at final follow-up at an average of greater than nine years postoperatively. Additionally, Shibata and coworkers reported resolution of all clinical symptomatology, with exception of minor ulceration, in all patients who achieved successful arthrodesis.
Several subsequent studies support these findings, including a recent study from Siebachmeyer and team, who demonstrated a 100 percent limb salvage rate and 80 percent resolution of ulceration in their 20-patient cohort following correction of multiplanar deformities of the ankle and hindfoot via arthrodesis with intramedullary (IM) nailing.13
Essential Considerations In Choosing Between IM Nailing And External Fixation
For patients presenting with Charcot neuroarthropathy, the primary indication for surgical reconstruction is a non-braceable deformity with associated instability.14 Other factors include inability to heal an ulcer or recurrent ulceration secondary to deformity, impending ulceration or the presence of osteomyelitis or significant pain. Discussion of perioperative risks, benefits and alternatives as well as postoperative complications (including the risk of minor or major amputation) are particularly important in this patient population. In addition, patient education should include discussion of possible changes in functional status and activity level as well as the need for aggressive rehabilitation. Ultimately, the decision for reconstruction hinges upon the aforementioned indications as well as the patient’s desire for limb salvage.
The decision to utilize intramedullary nailing versus external fixation for arthrodesis depends on several factors. We limit the use of internal fixation in the presence of active soft tissue infection or acute osteomyelitis in our practice. Evaluation of the soft tissue envelope is also important when determining the fixation modality. Surgeons may utilize intramedullary nailing in the presence of non-infected ulceration when the ulceration is not in close proximity to areas of surgical incision. One may employ external fixation for patients who are deemed poor candidates for intramedullary nailing or other forms of internal fixation.
Several studies evaluate the outcomes associated with tibiotalocalcaneal arthrodesis using external fixation versus intramedullary nailing versus superconstructs with combined internal and external fixation. In a recent meta-analysis involving 117 patients, Yammine and Assi compared TTC fusion with intramedullary nailing versus external fixation.15 They demonstrated statistically significant differences in fusion rates as the group with intramedullary nailing had a fusion rate two times greater than that achieved in patients who had external fixation. In addition, patients who had intramedullary nailing achieved radiographic fusion five weeks sooner than those treated with external fixation. The intramedullary nailing group also outperformed the external fixation group in regard to lower rates of hardware infection and wound infection.
However, Yammine and Assi found no significant difference in rates of amputation or reoperation.15 Of note, the authors do acknowledge that traditionally those patients who have a tibiotalocalcaneal arthrodesis with external fixation tend to have higher rates of open ulcerations, infection and osteomyelitis that may have led to distortion of their results.
Key Insights On Preoperative Testing And Evaluation
In an overwhelming majority of cases, patients with Charcot neuroarthropathy also have a plethora of medical issues and comorbidities. Accordingly, a thorough preoperative workup with optimization and laboratory testing is essential in this patient population.
Evaluation of the patient’s peripheral vascular system is paramount and standard in our practice. Even in the presence of palpable pedal pulses, non-invasive vascular studies, consisting of a minimum of ankle brachial indices (ABIs) and toe brachial indices (TBIs), are mandatory for all patients undergoing surgical reconstruction. When severe peripheral vascular disease is present, we commonly refer these patients to the appropriate surgical provider for preoperative optimization of blood flow and intervention as necessary prior to any elective or even semi-urgent lower extremity reconstruction. We also routinely emphasize the importance of tobacco cessation prior to surgical reconstruction to facilitate optimal soft tissue and bone healing.
Evaluation of perioperative nutritional status is also standard in our practice. Previous studies as early as 1986 demonstrate suboptimal healing and poor surgical outcomes in patients with malnutrition as defined by a decrease in serum albumin and total lymphocyte count.16 While early studies evaluated patients undergoing minor lower extremity amputation, more recent studies continue to evaluate the significance of preoperative nutritional status in both elective and non-elective surgeries, and demonstrate significant increases in postoperative complications in malnourished patients.17 Furthermore, these studies show that deficiencies in serum pre-albumin and transferrin levels are also significant markers of nutritional status impacting perioperative complications. Given these findings, we ensure preoperative screening of patients undergoing Charcot reconstruction for malnutrition by using the aforementioned protein markers and making appropriate referrals to nutritional specialists when necessary for preoperative optimization.
The relationship of Vitamin D levels and bone healing is well-known. Providers often evaluate Vitamin D levels prior to reconstructive surgery. Several studies demonstrate higher rates of non-union in patients with vitamin D deficiency who underwent fusion procedures in the foot and ankle.18
In addition, a recent study by Greenhagen and colleagues demonstrated an increasing rate of diabetic foot complications in patients with vitamin D deficiency.19 Vitamin D deficiency becomes increasingly relevant in the patient with Charcot neuroarthropathy due to the prevalence of diabetes and renal disease in this patient population.20 In order for vitamin D to achieve its active form, 1,25-dihydroxy-vitamin D3, bioactivation must occur in the kidney.21 In patients suffering from diabetes with impaired renal function, this process may arrest despite adequate exposure to sunlight and supplementation. Due to these factors, it is standard practice to obtain preoperative vitamin D levels in our patients undergoing Charcot reconstruction. In our practice, patients who have this deficiency, as defined by serum vitamin D levels less than 30 ng/mL, commonly receive vitamin D supplementation consisting of 50,000 IU/week for 12 weeks.
Careful management of long- and short-term control of blood glucose levels is critical in this patient population. Recent studies demonstrate increased rates of postoperative infection in patients with hemoglobin A1c (HbA1c) levels greater than eight percent undergoing surgical reconstruction in the foot and ankle.22,23 The need for tight glucose control is equally important in the postoperative window. A recent retrospective study demonstrated higher rates of postoperative infection in patients with even just one isolated occurrence of blood glucose over 200 mg/dL in comparison to patients who did not experience elevated blood sugars over 200 mg/ dL postoperatively.24
Given these findings, in our practice, we aim for an HbA1c of less than eight percent in all patients undergoing elective foot and ankle surgery, including diabetic Charcot reconstruction. We make exceptions to this guideline on a case-by-case basis, such as performing surgery on patients with an elevated HbA1c due to a severely unstable neuropathic fracture-dislocation or an increased risk of ulceration.
Additional testing includes preoperative complete blood count (CBC) and basic metabolic panel (BMP) that are routinely ordered by our service for all patients undergoing Charcot reconstruction, even in the absence of diabetes. The basic metabolic panel allows for assessment of not only glucose control but also evaluation of renal function, which can have further implications on a potential antibiotic regimen as well as the patient’s ability to appropriately synthesize bioactive vitamin D as I previously mentioned. The complete blood count helps to rule out leukocytosis, anemia or any other hematologic abnormalities that may increase risks of surgery or impair postoperative healing, If concern for active infection or osteomyelitis is present, one should order standard laboratory markers of infection in the form of white blood cell count (WBC), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).
Preoperative imaging is crucial for appropriate assessment of deformity and preoperative planning, including standard weightbearing films of the foot and ankle as well as hindfoot alignment views. In addition, advanced imaging often assists with further evaluation and preoperative planning. In the acute, early stages of Charcot neuroarthropathy, magnetic resonance imaging (MRI) is favored over computed tomography (CT) to allow for further evaluation and delineation of the affected osseous structures based on bone marrow edema and neuropathic changes that may not be evident on plain films.25,26 In addition, a recently developed fracture scoring system using MRIs obtained in acute Charcot is useful in better understanding the extent of osseous destruction.27 In patients presenting in the later chronic stages of Charcot neuroarthropathy, CT is superior to MRI as one may better appreciate subtle areas of fracture and fragmentation.25
Step-By-Step Surgical Pearls
One determines the surgical approach by the patient’s deformity as well as the presence or absence of soft tissue deficits. Traditionally, I prefer to utilize a lateral transfibular approach when feasible. Gastrocnemius recession or Achilles tendon lengthening may apply when appropriate. One approaches the ankle and subtalar joints from the lateral aspect with resection of the distal fibula, which the surgeon may employ later as an autogenous bone graft to augment the arthrodesis site. Using a combination of surgical instrumentation, the surgeon prepares the ankle and subtalar joints, removing all articular cartilage and necrotic bone.
Proceed to evaluate the viability of the talus based on its appearance. When appropriate, one may perform a talectomy with reimplantation of the resected talus as autograft. One may discard necrotic portions of the talus and use a femoral head allograft for restoration of height. Following joint preparation, the alignment of the hindfoot and ankle is important to evaluate in all planes. Planar resection and realignment osteotomies as necessary provide a stable and appropriate plantigrade foot. For augmentation of the arthrodesis site, surgeons typically use autograft, allograft or a combination of the two when appropriate.
Following satisfactory alignment, one inserts a guidewire for application of the intramedullary nail. Ensure appropriate positioning of the guide wire, which one can confirm via intraoperative fluoroscopy. Reaming of the intramedullary canal coincides with the length and diameter of the intramedullary nail. In my experience, selecting the intramedullary nail with the shortest length and smallest diameter that will allow for appropriate fixation is most desirable in order to allow for reinsertion of a larger intramedullary nail when a repeat operation is necessary. One performs proximal fixation of the intramedullary nail in such a fashion to allow for dynamization and compression at the arthrodesis site when appropriate. At the end of the procedure, one flushes the surgical incisions with copious amounts of sterile saline and disperses vancomycin powder throughout the surgical wound bed. One can perform a layered closure with absorbable and non-absorbable sutures.
What Is A Typical Postoperative Protocol For This Procedure?
Following reconstruction, one may apply a posterior splint with a Jones compression dressing and admit the patient for observation, management of comorbidities and evaluation by the physical therapy and occupational therapy teams. Upon discharge, the patient should maintain non-weightbearing status with the surgical lower extremity.
At two weeks post-op, the patient reports to the clinic for radiographic evaluation and suture removal when appropriate. At this time, one can apply a short leg fiberglass cast or CAM boot to the surgical lower extremity depending on the condition of the soft tissue envelope and presence of postoperative edema. At six weeks, the clinician obtains new radiographs and transitions the patient to partial weightbearing in the short-leg cast or CAM boot. At 10 weeks, after radiographs reflect adequate healing for the postoperative stage, the patient may transition to protected weightbearing in a CAM boot. At 14 weeks, the patient may proceed to full weightbearing as tolerated in a Charcot restraint orthotic walker (CROW) boot or extra-depth diabetic shoe gear with custom-molded inserts is likely possible.
Case Study: When A Patient With Diabetes Has Ongoing Pain And Swelling After An Ankle Inversion Injury
A 42-year-old female with a past medical history significant for type 2 diabetes mellitus presented to our clinic with concern for continued pain and swelling of her left ankle following a prior ankle inversion injury. The patient previously had treatment for a left ankle sprain at an outside facility with brace immobilization and non-steroidal anti-inflammatory medication, but has experienced minimal relief.
Of note, the patient does relate a history of uncontrolled diabetes with a previous HbA1c of 14.0 percent but maintains she is now addressing her medical condition more appropriately. She denies any history of prior injury to the extremity or any history of ulceration. Plain film radiographs demonstrate early Charcot neuroarthropathic changes to the left ankle joint. Significant instability was evident on the physical exam.
Ultimately, we decided to surgically address the Charcot neuroarthropathic ankle deformity with tibiotalocalcaneal fusion using a short intramedullary nail. After successful reconstruction with intramedullary nailing, the patient did have a post-op complication of a tibial fracture near the proximal aspect of the intramedullary nail. At this time, we removed the shorter nail and reinserted a larger nail in order to maintain stability of the fusion sites and address the new tibial fracture. Following resizing of the intramedullary nail, the patient went on to successful union of the tibiotalocalcaneal arthrodesis and tibial fracture without further complications in her postoperative course.
This case shows the important steps in evaluating the appropriateness of and approaches toward intramedullary nailing for tibiotalocalcaneal fusion in patients with hindfoot and ankle Charcot arthropathy.
Dr. McMillen is Chief of Podiatry at the Allegheny Health Network/Jefferson Hospital in Pittsburgh, Pa. He is board-certified by the American Board of Foot and Ankle Surgery.
Dr. Vacketta is a first-year resident at the Allegheny Health Network/Western Pennsylvania Hospital in Pittsburgh, Pa.
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