Surgical management of neuropathic arthropathy (Charcot foot)

INTRODUCTION — Neuropathic arthropathy, named after French neurologist Jean-Martin Charcot (Charcot neuropathic arthropathy [CN], Charcot foot), is a progressive, denervation-induced degeneration of the weightbearing joints of the foot [1]. It is a serious problem for patients with peripheral neuropathy, and over 20 million patients throughout the United States are at risk. While it is most commonly associated with diabetes, any patient with loss of afferent proprioceptive fibers is susceptible to this degenerative process [2]. CN is present in approximately 10 percent of patients with diabetes.

CN typically presents as a unilateral, localized, inflammatory reaction in a focal area of the foot or ankle with erythema, warmth, and swelling that appears to be triggered by a trauma or repetitive microtrauma [2-4]. Once activated, a discrete period of destructive inflammation and osteoclastic activity occurs (algorithm 1). The localized osteopenic response in multiple bones leads to instability and collapse with weightbearing. The involved bone progresses through stages of destruction including fragmentation and coalescence through to consolidation, a process that can take months or even years to fully resolve.

The diagnosis of CN is based on clinical experience and radiographic changes. Distinct segments of the forefoot, midfoot, rearfoot, or ankle appear disorganized and osteopenic on plain radiographs, and joint spaces are often obliterated. CN is often initially misdiagnosed as cellulitis or osteomyelitis, which delays the diagnosis, allowing further bony destruction [5]. Detection of CN can also be made using magnetic resonance (MR) imaging, which shows bony edema in multiple bones. Bone scans can also provide evidence of active bone turnover [6].

While there is no cure, management includes strict offloading/casting and surgical reconstruction of the deformity [7]. Preservation of the integrity of the foot and ankle is vital to ensure optimal long-term outcomes. Surgical management of neuropathic arthropathy is reviewed. Nonsurgical treatments are presented separately. (See "Diabetic neuroarthropathy".)

ANATOMY AND CLASSIFICATION — Charcot neuropathic arthropathy (CN) most frequently involves the foot and ankle in the lower extremity (figure 1) [8]. CN typically affects one limb, although bilateral disease occurs in approximately 10 percent.

The ankle consists of the tibia, fibula, and talus. The foot is comprised of the talus, calcaneus, cuboid, navicular, cuneiforms, metatarsals, and the corresponding phalanges. CN most commonly involves the tarsometatarsal (Lisfranc) joint, which is affected in about 50 percent [9], but any joint in the foot or ankle can be involved [2].

The foot and ankle contain many soft tissue structures, including extrinsic and intrinsic tendons as well as various ligaments and support structures that transfer energy and ground-reactive forces during locomotion [10]. This motion and force plays a large role in the pathologic process of CN [11]. Under weakened conditions, these forces lead to structural failure and deformity of the foot and ankle (image 1) [11]. With ongoing pressure and the lack of pain signals as a result of the sensory neuropathy, soft and bony tissues are at risk for breakdown and infection [1].

Classification

Anatomic — CN is a progressive degeneration of the weightbearing joints of the foot that leads to multiple fragmented bones, dislocations, and distorted anatomy. Defining anatomic categories can aid in treatment. Surgical treatment for CN broadly distinguishes between disease that affects the "midfoot" or affects the "rearfoot and ankle." These two categories lump adjacent joints and those that act similarly during CN.

●The midfoot includes the Lisfranc or tarsometatarsal joint, as well as the naviculocuneiform joints. In general, midfoot CN appears to be more stable and may not require surgery in approximately 60 percent of patients [12-14]. However, with tarsal bone collapse and with the pull of the Achilles tendon, cuneiforms and the cuboid shift planarly due to ground reactive forces, frequently leading to chronic ulcerations and deformity.

●The rearfoot and ankle group includes the talocrural (ankle), subtalar, and talonavicular (or Chopart) joints. Ankle involvement in CN is less common but has a higher likelihood of significant deformity and so is more likely to require surgery [7]. Most experts agree, however, that rearfoot and ankle CN has a much higher likelihood of failure and need for surgical intervention [15].

CN has also been classified based on more specific anatomic location, including the Brodsky classification (table 1) and the similar Sanders and Frykberg classification (table 2) [16,17].

Clinical — Classification based on clinical and radiographic changes is useful to differentiate the three traditional "stages" of CN [12,18]. A fourth stage, "stage 0," which is defined as a hyperthermic period immediately following injury, has also been added (table 2) [13]. Although patients in stage 0 have edema and erythema of the foot and ankle, no radiographic changes are yet visible. (See "Diabetic neuroarthropathy".)

●Stage 0: Early or inflammatory – There is localized swelling, erythema, and warmth with little or no radiological abnormalities.

●Stage 1: Development – Swelling, redness, and warmth persist, and bony changes such as fracture, subluxation/dislocation, and bony debris are apparent on plain radiographs.

●Stage 2: Coalescence – The clinical signs of inflammation decrease, and radiological signs of fracture healing, resorption of bony debris, and new bone formation are evident.

●Stage 3: Reconstruction – The redness, warmth, and swelling have resolved, and bony deformity, which may be stable or unstable, is present. Radiographs may show mature fracture callus and decreased sclerosis.

CN can be clinically classified as "active" (ie, stages 0, 1, 2) or "inactive" (ie, stage 3) to indicate if the process is in the acute stages or in the reconstruction (also known as remodeling or consolidation) phase, which has a bearing on the nature and timing of surgery. (See 'Indications for and timing of surgery' below.)

INDICATIONS FOR AND TIMING OF SURGERY — The timing of intervention for Charcot neuropathic arthropathy (CN) can be somewhat subjective. Available recommendations are mostly based on expert opinion with limited studies to provide evidence-based guidance [13]. In general, most agree that significant dislocation of any joint should be managed urgently [19]. Patients with concomitant soft tissue and/or bone infection with systemic signs or limb threat should also be considered for urgent surgical management.

Active disease — The patient with minimal deformity is immediately offloaded. Placement of a walking boot or cast should be attempted during consolidation [8]. These patients are monitored closely, making appropriate decisions regarding surgery in the months to come. Ankle CN seems more likely to fail attempts at nonsurgical correction and should be evaluated more frequently for the development of complications. Severe deformities should be handled quickly as with any other fracture or trauma.

Whether surgery in "active" disease (ie, ongoing inflammatory process with edema, erythema, and increased temperature) may be desirable or leads to higher complication rates is debated [20]. Even so, for the patient with active disease, the indications are mostly subjective and based on surgeon experience. Most surgeons consider the following to be surgical indications in "active" CN:

●Significant joint dislocations

●Significant instability

●Deformities that cannot be accommodated in a brace or orthotic device

●Deformities with impending ulcers or loss of skin integrity

●Deformities with active infection

Some experts believe that active CN may be the best timing for surgery since the deformities are fresh and flexible and are easy to reduce, similar to other acute fractures. Active disease may also offer the best bone quality when compared with later stages of CN. This belief stems from continued local osteoporotic effects of the ongoing disease process. In adult bone, activated osteocytes produce a cytokine called nuclear factor kappa-Β ligand (RANKL). Dysregulation of RANKL is associated with excessive osteoclastogenesis and net bone destruction such as in CN. Subsequent osteopenia is exacerbated by extended periods of nonweightbearing. For all of these reasons, bone quality in the active stages may be better compared with the inactive stage of CN.

Inactive disease — Traditionally, surgery has been delayed until the late stages of the disease (ie, inactive CN), once the bones have consolidated and inflammation has resolved [13]. Surgical intervention in this "inactive" CN stage has the benefit of less edema, less inflammatory product, and fewer soft tissue and wound complications. Similar to high-energy trauma to the foot and ankle, large amounts of edema and inflammation can increase the risk for postoperative wound complications [20]. Waiting for the later stages of CN may provide a better physiology for bone and skin healing. Unfortunately, the CN process can take several months or even longer to resolve [2]. Waiting for later stages means that the consolidated deformities are more difficult to reduce with an increased likelihood that an osteotomy will be required to correct the bony deformities [21]. In addition, during the waiting time, many deformities progress, during which time the skin and soft tissue can break down and become infected [12].

For "inactive" disease (ie, late stages with no inflammatory signs), treatment is based on the presence of wounds and nature of bony deformities.

●Stable, inactive CN that is not associated with a wound and is braceable does not require surgical intervention. If the plantigrade foot can be accommodated with appropriate shoe gear, inserts, or bracing, it can be monitored, which is performed at regular intervals (for life) [22,23].

●Bony prominences on the plantar weightbearing surface of a foot can interfere with ambulation and are at risk for future skin breakdown and ulceration, and thus require surgical intervention [2].

●For patients with inactive CN who develop a wound, surgical decisions are based on whether the wound is likely to heal and risk for recurrence. For a wound that is not healing properly or a wound that recurs after initial closure with conservative care (ie, wound care, nonweightbearing, proper offloading), surgical intervention may be warranted to help reduce local pressure and manage the deformity. Surgery may also be needed to address infection.

●In the presence of wounds or infection, procedures need to be staged. The initial surgery aims to provide an environment conducive to wound healing, and at the subsequent surgery, definitive foot reconstruction is undertaken [24]. Using orthopedic hardware in association with concomitant wounds or infection contributes to higher complication rates and increases the likelihood of hardware failure, persistent infection, or amputation.

Contraindications — Patients with CN who have serious comorbidities (eg, cardiac disease, morbid obesity) may be poor surgical candidates. As an example, morbid obesity contributes to both short-term and long-term problems with wound healing. Following surgery, patients with obesity typically require intensive nursing care and assistance for daily activities and are at risk for remaining nonambulatory, with loss of functional status.

Poor glucose control may represent a relative contraindication to surgery. For the chronically affected patient with no acute need for intervention, hemoglobin A1c should be less than 8 [25]. For patients with Charcot arthropathy recovering from a severe infection, hemoglobin A1c levels should be monitored and improved before proceeding with definitive surgery. (See 'Patient optimization' below.)

Another relative surgical contraindication is a lack of appropriate postoperative social support. Having a support system clearly benefits patients. Those without social support might not be the best candidates for extensive reconstruction; however, patients without support should work with case manager for postacute care options.

PREOPERATIVE EVALUATION AND OPTIMIZATION — Preoperative evaluation requires a thorough history and clinical examination. It is important to determine the length of time the limb has been affected, though many patients may not remember a specific timeframe or inciting injury. In addition, for many patients, referral to a specialist may have been delayed due to Charcot neuropathic arthropathy (CN) having been initially diagnosed as another condition [4]. It is also important to know how well comorbidities are controlled.

Based on typically available data at the initial visit, a scoring system, the Charcot Reconstruction Preoperative Prognostic Score (CRPPS), can be used to help determine potential success [26]. The score can help guide limb salvage discussions with the patient.

Imaging — Following clinical examination, radiographs are typically obtained as many patients present to a specialist with no prior imaging. Radiographs determine the anatomic area involved (eg, midfoot, rearfoot, and ankle), but they also provide information about whether there is an urgent surgical issue (eg, significant dislocation) that may require immediate attention. Radiographs are also useful in surgical planning to help determine how best to reduce the deformity and realign the important bony relationships. In some cases, cross-sectional studies using computed tomographic (CT) or magnetic resonance (MR) imaging may be useful.

Weightbearing, rather than nonweightbearing, radiographs of the foot and ankle should be obtained, particularly in the chronic setting [27]. The use of nonweightbearing radiography is one of the most common early diagnostic errors in these patients. Radiographs can be misleading since they are typically not performed in a standard fashion. Weightbearing radiographs provide the best information about bone anatomy, joint congruity, and presence of any fractures. Weightbearing provides the sufficient downward stress required to show subluxations and frank dislocations that are often missed on nonweightbearing studies.

One of the most useful angles to identify on radiographs, in particular for midfoot CN, seems to be the lateral talar first metatarsal angle, which correlates with medial column issues. The angle should typically be zero. An angle greater than 27 degrees has been correlated with nonhealing wounds [28]. Cuboid height on lateral foot radiograph provides objective data about midfoot collapse and has also been correlated with nonhealing wounds [28]. If the cuboid is plantar to a line drawn from the plantar calcaneus to the plantar fifth metatarsal head, and correlates with wounds, the patient is more likely to require surgical intervention.

It can be difficult at times to quantify and qualify bone, particularly in a patient with CN. This is particularly true in the midfoot and rearfoot where the bones are small. As with most orthopedic planning, a CT scan may provide more information about bone quality and bone stock. At times destruction can be so severe that there is not enough bone to place the required hardware to salvage the foot, and in these cases, the CT scan may help make a decision for primary amputation rather than foot salvage.

MR imaging can also be useful in managing CN. As an example, if a neuropathic patient presents after a recent injury with foot or ankle erythema and edema, but no wounds or significant radiographic changes, MR can show early disease (stage 0) by demonstrating edema in multiple bones. MR can also be useful for identifying infection or abscess formation.

Patient optimization — Recovery after Charcot reconstruction is prolonged, so patient preparation prior to surgery is critical. This includes optimization of interim management strategies (offloading, wound care, management of infection), medical comorbidities, glucose control, and other metabolic issues and requires a team approach including internists, hospitalists, endocrinologists, cardiologists, vascular surgeons, anesthesia, and many times, infectious disease specialists to help aid in the preparations.

Once wounds have closed, infections have been satisfactorily managed with antibiotics, and long-term glucose as well as other laboratory values have come into more acceptable ranges or normalized, definitive surgery can be undertaken to control of the deformity long-term. (See 'Surgical approach' below.)

Patient optimization includes the following:

●Vascular evaluation – Many patients with CN have peripheral artery disease (PAD) and require vascular evaluation [12]. Noninvasive arterial studies should be included in the surgical intervention of any patient with CN. Referral to vascular surgery may be necessary. Invasive procedures to manage ischemia may be needed before, or in conjunction with, surgery for CN to salvage the limb. If possible, perfusion should be improved prior to CN surgery. (See "Management of chronic limb-threatening ischemia".)

●Markers of inflammation – Given that white cell count may not change even in the face of active infection, laboratory studies including inflammatory markers such as C-reactive protein and erythrocyte sedimentation rate may be useful to help guide the use and duration of antibiotics [29,30].

●Glycemic control – Perioperative glucose control is important. Glucose the morning of surgery should be controlled to be no greater than 200 mg/dL [31]. Long-term glucose should ideally be targeted to a hemoglobin A1c of less than 8 gm/dL [25]. Unfortunately, this may not be attainable in the setting of acute issues such as infection. (See "Perioperative management of blood glucose in adults with diabetes mellitus".)

●Nutritional status – Proper nutrition is important for wound healing. Thus, nutritional status should be evaluated and dietary supplements provided, if needed [32]. (See "Overview of perioperative nutrition support".)

SURGICAL APPROACH — Limited objective data are available to help guide the surgeon as to the timing and the best techniques to use for Charcot neuropathic arthropathy (CN). Unfortunately, CN is less common, and while many deformities are similar, there are unique aspects to each patient, which make comparisons difficult. In general, the first factor governing the approach for CN surgery is whether the disease is in an active or inactive stage. A staged approach may be necessary depending on the presence of wounds or infection. (See 'Classification' above.)

●For active disease, patients require surgical intervention if there is either significant instability or joint dislocation, or in the presence of wound and infection. When a deep space abscess or infection is present, staged surgical management is warranted. Initial irrigation and debridement are essential and appropriate cultures should be taken. Once acute infection is controlled, deformities are reduced, and any residual wounds are debrided. Antibiotic beads or cement can be used in conjunction to address any residual infection. External fixation allows the deformities to be held in a more appropriate and reduced position for maintaining nonweightbearing and helps protect any wounds. The stability afforded by the external fixator helps lessen soft tissue inflammation and aids management of infection. Once these issues have normalized, a more formal definitive surgery, typically an extended arthrodesis, can be performed, which provides long-term stability. The arthrodesis is extended past the area of injury to allow for better definitive fixation. (See 'Surgical techniques' below.)

●For inactive disease, the approach depends on the presence of wound or infection. For nonhealing or recurrent wounds, deformities are typically treated with osteotomies to correct angular deformities as well as remove infected bone [24]. Many times, the foot is held with external fixation to promote wound healing for the reasons described in the above paragraph [33]. Once inflammation has subsided, definitive surgery, typically an extended arthrodesis, which provides long-term stability, can be performed [34]. If there are no wounds, then the deformities can be addressed in a single-stage fashion. Osteotomies are performed, but internal fixation can be used at the primary surgery since there is no wound and less concern for infection. (See 'Surgical techniques' below.)

SURGICAL TECHNIQUES — In general, surgical intervention aims to align the bones of the foot to a near-normal anatomic relationship. The rearfoot should be rectus, but more often than not, it is equinus in patients with Charcot neuropathic arthropathy (CN) and needs to be reduced. In addition, the talus and first metatarsal should be in line, with no fault along the medial column. To achieve proper alignment, a combination of bone debridement (exostectomy) or removal (osteotomy) and bony fixation (external, internal) or fusion (arthrodesis) is used.

In a review of 214 patients treated over a 12 year period, patients with a valgus deformity pattern were most likely to achieve a favorable clinical outcome (87 percent) [35]. The overall success rate was 70.3 percent among patients with a dislocation pattern deformity and 56.3 percent with a varus deformity pattern. Patients who failed surgical intervention went on to require amputation.

Exostectomy — Exostectomy is the removal or planing of prominent bone to prevent ulceration or promote wound healing. It does not require any internal hardware and is considered the most conservative surgical intervention [36]. Exostectomy is appropriate and has the highest success rate in midfoot CN [36]. Planing should only be performed during the inactive stage of CN since bones can continue to shift and further instability can occur with planing [37].

Major drawbacks include lack of deformity correction, further hypertrophic bone formation, wound recurrence, and the need for further surgery. Following exostectomy, weightbearing can be immediate with protective casting or controlled ankle movement (CAM) boot.

A concomitant Achilles tendon lengthening should always be considered with this procedure [19]. Lengthening of the Achilles tendon or gastrocnemius tendon recession can decrease forefoot pressures and improve the alignment of the ankle/rearfoot to the midfoot/forefoot [13].

Osteotomy — Osteotomies are used to correct angular deformities as well as to remove infected bone if there is an active wound that cannot be healed, or for recurrent wounds [24]. Many times a staged approach is used with the bones held using external fixation to promote wound healing [33]. Once things have normalized, a definitive procedure is performed to provide long-term stability.

For patients with inactive CN and no wound or concern for infection, the deformities can be addressed typically in a single-stage fashion. Similar osteotomies are performed, but internal fixation can be used at the primary surgery.

Arthrodesis — Arthrodesis or joint fusion is useful in patients with significant instability, recurrent ulcerations, and pain. It is often the only alternative to amputation in severe deformities. Fusion includes midfoot osteotomy-arthrodesis, triple arthrodesis, or tibio-talo-calcaneal arthrodesis [19]. If infection or wound is present, staged procedures are required before providing definitive internal fixation. The location of CN is another consideration. Midfoot CN typically requires an extended arthrodesis through the entire midfoot and rearfoot. In the ankle, CN tends to be much more unstable, and arthrodesis often needs to be extended to include the ankle joint as well [34].

Progressive bony deformity and bone resorption in CN make bony fusion difficult. Surgeons often use a "superconstruct" technique to improve arthrodesis outcomes [38]. This means that the fusion is extended beyond the zone of injury to include adjacent joints, which allows for physically larger implants. Correction includes osteotomy and preparation of adjacent joints for increased stability. Implants, such as an intermedullary nail or plates, can span multiple joints to incorporate the surrounding healthier bone, thereby improving long-term stability and outcomes. The strongest device that can be tolerated by the soft tissue envelope is used, and the devices are applied to maximize mechanical function. In addition, bone resection is performed to shorten the extremity to allow for adequate reduction of deformity without undue tension on the soft tissue envelope.

Fixation types — Fixation can be internal, external, or a combination of both. Internal fixation uses pins, screws, intramedullary nails, and plates applied directly to the bone. External fixation holds the bone in place using pins that are connected to a stabilizing structure outside the body.

External fixation is used in the presence of severe deformity, infection, or ulcerations. This technique allows for the monitoring of soft tissue healing and access to the wound [33]. The benefits of external fixation include its minimally invasive placement and dissection, and the ability to gradually and accurately realign the anatomy of dislocated or subluxated joints [23]. Using external fixation in a staged approach also limits neurovascular compromise because of the gradual and slow correction [21,33]. External fixation techniques can also be used in patients with comorbidities not suited for internal fixation as an alternative to amputation.

A combination approach begins with osseous realignment using an external circular multiplane fixator using the principles of ligamentotaxis (ie, continuous longitudinal force or distraction) [39]. After external fixation removal, the second step is arthrodesis of the affected joints with internal fixation.

Primary or secondary amputation — Primary amputation may be indicated for patients with severe medical comorbidities. Secondary amputation may be needed if previous surgeries have failed and the patient has significant bony loss, deformity, recurrent deformity, or severe infections. The level of amputation is typically below the knee. (See 'Contraindications' above and "Techniques for lower extremity amputation", section on 'Below-knee amputation'.)

POSTOPERATIVE CARE — Patients are typically admitted to the hospital for one to two days after Charcot neuropathic arthropathy (CN) surgery for pain management and physical therapy. Specific postoperative patient care depends upon the nature of the surgery.

●For patients who have undergone internal fixation, the leg is placed in a splint or cast for three months, and the patient will be nonweightbearing during this time. Incisions are left covered and should remain clean and dry until they are removed at around three weeks postoperatively. Wound dressing changes are performed three times weekly. After three months, patients transition into a controlled ankle movement (CAM) boot and begin physical therapy for three additional months.

●For patients who have undergone external fixation, pin care begins on the second postoperative day. This involves cleaning pin sites (eg, betadine, half-strength hydrogen peroxide, or mild soap and water) [40]. Pin-tract infections can be avoided with home nursing, patient education, and compressive dressings. Tension must be released from all pin or wire insertions, and adjustments should be made at the first signs of irritation. The external fixator will stay in place for two to three months. Once it is removed, the patient is placed into a cast for an additional month of immobilization. At this time, the patient can be fit for a custom orthopedic boot, brace, or shoe.

COMPLICATIONS — Postoperative complications include development of new wounds, surgical dehiscence, nonunion, infection, and hardware failure. Complications are addressed with antibiotics for infection, surgical revision, bone grafting, application of antibiotic cement, or amputation [41]. Complication rates of patients who undergo surgery during active compared with inactive phases of Charcot neuropathic arthropathy (CN) are not well studied.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Diabetes mellitus in adults" and "Society guideline links: Chronic wound management".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Beyond the Basics topics (see "Patient education: Type 1 diabetes: Overview (Beyond the Basics)" and "Patient education: Type 2 diabetes: Overview (Beyond the Basics)" and "Patient education: Foot care for people with diabetes (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Neuropathic arthropathy – Neuropathic arthropathy is a progressive, denervation-induced degeneration of the weightbearing joints. Neuropathic arthropathy in the foot and ankle (Charcot neuropathic arthropathy [CN], Charcot foot) is a poorly understood process and is a devastating complication more commonly occurring in patients with diabetes, but any patient with loss of afferent proprioceptive fibers is susceptible to this degenerative process. (See 'Introduction' above.)

●Diagnosis and classification – The diagnosis is based on clinical evaluation and the radiographic appearance of the bones in the foot. CN can be classified clinically ("active," "inactive") or anatomically ("midfoot," "rearfoot and ankle"), and both are important for determining the surgical approach. (See 'Classification' above.)

●Perioperative care – Recovery after Charcot reconstruction is prolonged. As such, patient preparation and optimization prior to surgery is critical. This requires a team approach. (See 'Preoperative evaluation and optimization' above and 'Postoperative care' above.)

●Indications and timing of surgery – Early treatment prior to the development of deformity is essential to preserve function and improve outcomes. However, there are few guidelines regarding the timing of surgery in patients with CN. (See 'Indications for and timing of surgery' above.)

•For patients with "active" CN, surgery may be necessary to manage significant joint dislocation or instability, or deformities that cannot be braced, or are associated with skin breakdown or infection.

•For patients "inactive" CN (ie, no acute issues), surgery is often delayed until the bones have consolidated and inflammation has resolved. Proponents of delayed management note that there is less edema, which results in fewer soft tissue and wound complications.

•For patients with "inactive" CN who have a plantigrade foot that has no wounds and is stable and brace-able, surgery is not indicated.

●Surgical techniques – Surgery aims to align the foot bones to a near-normal anatomic relationship. To achieve proper alignment, a combination of bone debridement (exostectomy) or removal (osteotomy) and bony fixation (external, internal) or fusion (arthrodesis) is used. For CN associated with wounds, soft tissue infection, or osteomyelitis, a staged approach is required. In the initial stage, infection or wounds are managed, and, depending on pathology, external fixation may be necessary to offload and stabilize the bone. Once these issues have stabilized, a definitive procedure is performed to provide long-term stability. (See 'Surgical approach' above and 'Surgical techniques' above.)