Aggressive resection of the necrotic bone can result in shortening of the foot. Though it may not be visually appealing to the patient, biomechanically this can be advantageous. A shortened foot results in a smaller moment lever arm during the stance to propulsion phases of the gait and reduces the forefoot pressure. Though the maximum involvement in neuroarthropathy may be in the midfoot, Armstrong et al. have found that the peak pressure was in the forefoot [40]; therefore, reducing this pressure by shortening the foot may be biomechanically beneficial. It may also indirectly reduce the mechanical stress applied to the midfoot, contributing to the survival of the internal fixation devices. Though the patient needs to be aware of this potential shortening of the foot, because the reconstruction straightens the overlapped midfoot, the foot may not appear significantly shorter than preoperative length to many patients (Fig. 24.2). The patients should however be notified about digital deformities or non-purchasing digits that it may cause (Fig. 24.3).

It is not advisable to use nonviable osteobiologics to replace the necrotic Charcot bone. Not only the evidence for use of such products are lacking, replacing such a large defect and to achieve stable union is difficult even in healthy individuals. Because pathophysiology of neuroarthropathy involves inhibited anti-inflammatory process (Fig. 24.4), introduction of reactive foreign materials, excessive inflammatory cytokines, and growth factors may result in a vicious, uncontrolled, inflammatory cycle.

A minimal amount of nonreactive material may be indicated to fill a small void given that most of the arthrodesis sites are in close proximity. Some mesenchymal cell-based products are thought to have anti-inflammatory effect in the local tissue via paracrine signaling [41–43] though this phenomenon is yet to be tested in a Charcot clinical study. Research in this area is lacking understandably due to its relatively low prevalence of the disease.

Another caveat to aggressive resection of the necrotic tissue is that it often results in mismatching of the forefoot to the rearfoot. Because forefoot is wider than the rearfoot, it may not be possible to align both medial and lateral columns onto the remaining rearfoot (Fig. 24.5). If needs to be chosen, aligning the medial column is far more critical than the lateral column. It is advisable to align the first ray with the long axis of the talus even though the lateral column alignment may be compromised.

When resecting the midfoot, it is also important to avoid severe abduction or adduction. The midfoot often needs to be resected uniformly across from medial to lateral even when Charcot is affecting one side. When neuroarthropathy affects mainly the medial side and only the medial necrotic bone is aggressively resected, the significant shortening of the medial column can result in excessive forefoot adduction. This is biomechanically intolerable; therefore, resection of the healthy lateral column may be necessary to achieve balanced medial and lateral columns.

After arthrodesis sites are prepared, the forefoot is impacted onto the rearfoot and fixations are applied. Though it is a surgeon’s preference, some fundamental of fixation should be reviewed.

Many of the screws are positioning and beaming in nature in Charcot reconstruction rather than compression. It is more critical for the screws to be strong and resistant to bending. Unlike elective arthrodesis surgeries in non-neuroarthropathic patients, bone healing is expected to be prolonged, and patients are less likely to be able to off-load the operative foot effectively. It should be noted that stainless steel, solid screws are far stronger than titanium and cannulated screws given the same size. Additionally, the core diameter, rather than the outer diameter, of the screw determines the overall shearing and bending resistance.

One also needs to remember that fatigue property and ductility of the screws play a role in the long-term stability. Because of the cold-working process in stainless steel, the ductility is significantly compromised when compared to titanium. Therefore, once the metal is bent or contoured, it becomes more brittle. This concept is particularly important when considering plate fixation.

Pullout strength is significantly better with titanium since the friction is greater due to its osseointegration. Though it is a useful property for a rigid, long-term fixation, removal of such screws is more difficult. Biocompatibility is superior with titanium, yet that of stainless steel is still sufficient, and nickel allergy is rare. When a patient needs an MRI in the future, titanium avoids signal void effects.

For plate fixation, abovementioned metallurgy is still relevant. The plate fixation, however, requires more molding to a contour of the osseous structures; therefore, ductility of the metal cannot be over-emphasized.

External fixation has been popular in Charcot reconstruction [44–47]. It can provide extra stability, dynamic compression if necessary, potential earlier weight-bearing, postoperative deformity correction, and bypassing of an infected area via spanning/bridging (Fig. 24.6). One always however needs to remember that the use of such fixation, especially with combination of other internal fixations and osteobiologics, is very expensive. Cost effectiveness of such construct has not been thoroughly studied. In addition, when it is used as a sole fixation, one has to remember that the external fixation may need to be removed prematurely to avoid pin tract infection prior to bone healing. In combination with internal fixation, it may add extra stability, but a long-term clinical benefit is in question [48]. Pin tract infection is also common [49], yet for a more salvage-type procedure where internal fixation is already attempted or not feasible, external fixation may be the only option (Fig. 24.7).

Gradual correction with dynamic multiplanar external fixation may be another option (Fig. 24.8); however, pin tract infection can be even more prevalent in these immunocompromised patients, especially with the motion and potential loosening of the transfixation wires. Internal fixation can be applied in the second stage with a minimally invasive approach after deformity is corrected [46].

Besides types of fixation, orientation of fixation is also important. The weakest point of fixation will be at the level of Charcot bone or the fusion site. The purpose of fixation is normally to stabilize the area until union. However, in Charcot patients, pseudoarthrosis or nonunion is not uncommon. Therefore, fixations need to withstand the weight-bearing force for a long period of time. A long-term structural support may be more important than short-term rigidity in this population.

For midfoot neuroarthropathy , it is important to establish a stable medial column. An unstable medial column can result in a recurrent collapse and/or abduction or adduction of the forefoot. There are several ways to establish long-term stabilization of the medial column. The most common methods are the beaming techniques that are established by an intramedullary screw or a plate-screw construct. An intramedullary screw is inserted in the first ray through the first metatarsal phalangeal joint, through the posterior aspect of the talus or base of the first metatarsal (Fig. 24.9). While a cannulated screw will allow much easier and precise insertion, such a screw is significantly weaker than a solid one. A solid, large core diameter screw is recommended for a stronger construct. If inserted in a retrograding fashion through the first metatarsophalangeal joint, a headless screw is needed. An approximately 3 cm incision can be made plantar to the first metatarsophalangeal joint longitudinally. The joint is then dorsiflexed, and the plantar plate and capsule are incised to expose the head of the first metatarsal bone from the plantar surgical wound. Once exposed, the midfoot is reduced to the plantigrade orientation, and a guide wire is inserted though the first ray before reaming. The reaming can be performed over the guide wire utilizing cannulated instruments that are appropriate for the solid screw size. A good reaming is necessary to insert a large diameter screw without fracturing the first metatarsal.

In order to achieve stability, the beaming screw often needs to reach all the way to the talus even if the talonavicular joint is not affected by neuroarthropathy nor prepared for arthrodesis (Fig. 24.10). The navicular or medial cuneiform is not robust enough to hold the beaming screw in a Charcot patient (Fig. 24.10). As mentioned earlier, when extensive resection of the midfoot is done, the first metatarsal may not align with the long axis of the talus as the first metatarsal may sit medial to the talus in the transverse plane. The first ray may need to be translated laterally or angulated medially to capture the talus.

Alternatively, a plate fixation can be utilized to “beam” the medial column. Often a locking plate-screw construct is utilized for this purpose as it can achieve stronger angular stability at the plate-screw interface. A locking plate-screw construct does not rely on friction created on the plate-bone interface; therefore, preservation of periosteal vascular supply can be managed. With minimally invasive dissection technique, this theoretically aids in bone healing. Yet, clinical benefit of locking plate in Charcot surgery is not extensively studied.

An additional interfragmentary screw may aid more rigidity by achieving absolute stability via compression across the fusion site rather than relying solely on locking plate-screw construct, often used for relative stability. Relative stability, with flexible fixation without compression, in theory can result in secondary bone healing via more biological fixation. However, this needs to rely on natural bone callus formation. In these high-risk neuropathic patients with abnormal biology, this may be difficult. It is unknown at this point which of the healing process, between primary and secondary bone healing, is better in Charcot patients. Yet, it should be reminded that bone healing in neuropathic patients is significantly prolonged, and the fixation devices may fail prior to bone callus formation. On the other hand, excessive rigidity may transfer the stress or strain to other areas and can cause a fracture or acute Charcot process (Fig. 24.11).

Orientation of the plate significantly changes the strength of the beam. A plate applied to the dorsal aspect of the first ray is more subject to bending and fatiguing than one placed on the medial aspect (Fig. 24.12). When the plate is placed in a vertical orientation, like a floor joist, it is much harder to fail with weight-bearing.

Application of the plate more plantarly can result in conversion of the weight-bearing force into compression force via tension banding (Fig. 24.12). However, in order for tension banding to work, the bones must have a strong dorsal cortex. Many Charcot bones are fragile; therefore, a care must be taken to inspect the quality of the bone before attempting this technique.

For transfixation screws, longer screws with multiple cortical purchases are always more stable than unicortical purchases.

For the central rays and the lateral columns, the same principles are applied. While alignment of the lesser rays are not as critical in the transverse plane once the medial column is established, a patient will not be able to tolerate the malalignment in the frontal or sagittal planes. It can result in forefoot plantar ulceration secondary to increase in focal pressure or a fixation failure if bone healing is delayed.

In the ankle, fixation and deformity correction are little more forgiving. The larger structures with more parallel orientation of the joint to the ground surface afford more stable construct via fixations, such as retrograding intramedullary nail, multiplanar external fixation, and more robust plating systems.

Unlike the midfoot, shortening in the ankle is not beneficial however. Though a permanent brace, such as CROW or AFO, may add some height, a significantly shortened limb may not be any more functional than a proximally amputated extremity with a good prosthesis (Fig. 24.13).

Talectomy with tibiocalcaneal fusion (Boyd’s procedure) is often utilized for a severe ankle neuroarthropathy (Fig. 24.14). The procedure however results in significant shortening and operative trauma in the extremity. Despite, this can be the only option in many patients short of major amputation . For those with severe, chronic deformity, this may be the only feasible procedure since acute correction without significant shortening may compromise neurovascular structures (Fig. 24.15).

Addition of bone graft material even with osteobiologic supplementation is not advisable for the same reasons discussed earlier. Surgical trauma itself will “reactivate” the vicious inflammatory cycle (Fig. 24.4), and the bone substitute may be resorbed or “washed out” in the process (Fig. 24.16). An off-label use of bisphosphonates has been suggested to be useful in inhibiting the neuroarthropathic inflammatory process, but the clinical results are inconsistent [50–52].

For fixation in ankle Charcot reconstruction, an intramedullary nail can provide tremendous stability without needing to have significant foreign material underneath the surgical incision. Shah and De demonstrated that the union rate with a retrograde intramedullary nail was higher than that with a unilateral external fixation [53]. However, if infected, a salvage procedure is more difficult.

On the other hand, plate fixation may be better managed in a case of infection because intramedullary tracking of infection may be less likely. However, having the fixations right underneath the incision can be problematic, as postoperative dehiscence of the incision is not uncommon in a Charcot reconstructive surgery. Screw fixation is least stable. Yet, in cases of arthroscopic or minimal incision approach of the ankle arthrodesis, screw fixation can be executed via stab incisions, minimizing operative trauma.

A use of bone stimulator has been studied in Charcot patients [54, 55], yet the effectiveness of bone stimulator in this population is still questionable. Again, having meaningful statistics in a clinical study in this relatively rare disease is challenging.

There is no good evidence for use of prophylactic antibiotics in elective foot and ankle surgeries; however, in other areas, especially when hardware is utilized, a routine use of preoperative antibiotics is recommended [56]. There is no evidence for using antibiotics past 24 h after surgery. The Surgical Care Improvement Program (SCIP) guideline recommends against use of antibiotics for more than 24 h after the surgery [57]. Though the guideline was not derived from data in Charcot reconstructive surgeries, a justification to deviate from the guideline may be difficult.

Minimizing hematoma in the surgical site is highly recommended. Charcot reconstructive surgery can traumatic, and many patients often possess major bleeding disorders and/or calcified vessels. Coupled with prolonged surgery and creation of a dead space from extensive resection of necrotic soft tissue and bones, these patients are in high risk for developing hematoma. Hematoma can be minimized by utilizing a drain, releasing the tourniquet prior to closure to identify and eliminate major bleeding, managing medically for a bleeding disorder, adjusting pharmacological agents preoperatively, and applying a compressive dressing and cryotherapy.

Application of compressive dressing and cryotherapy should be done with caution since most of these patients have a significant sensory loss (Fig. 24.17). They are not able to detect abnormal pressure or extreme temperature even after the postoperative block wears off. Education regarding bandaging and cryotherapy and instruction for discontinuation or reporting adverse events are important. Frequent skin inspection and simple vascular examination should also be encouraged. Application of cryotherapy is not indicated at the level of sensory loss [58]. It needs to be proximal enough that the patient is able to feel any discomfort when too cold.