Surgery for the Neuropathic Foot and Ankle




Abstract


Charcot arthropathy is a very difficult condition to treat secondary to the severe deformity involved combined with medical comorbidities associated with this condition. The use of very rigid fixation distinct from that used in patients with routine arthritic conditions is required. Arthrodesis, not open reduction and internal fixation, is required.




Key Words

Charcot, neuroarthropathy, beaming, plantar, plate, diabetes

 


Although classifying the Charcot arthropathic process as acute, subacute, or chronic is helpful from a practical standpoint, the definitions of these stages have no value because treatment will depend on the clinical severity of the deformity and the presence of bone fragmentation and periosteal new bone formation. New bone formation is apparent a month or so after onset of the acute process, often associated with marked osteopenia and bone fragmentation. Surgery at this stage may be more complicated even if the deformity is amenable to open reduction and internal fixation (ORIF).


Once the process reaches the chronic phase, the midfoot is typically stable and is unlikely to deform further. However, bone prominence is often present on the plantar aspect of the midfoot, which may lead to ulceration or infection. In this context, “chronic” implies clinically stable, with an absence of swelling and inflammation ( Fig. 10.1 ). In these chronic arthropathies, the apex of the deformity is somewhere on the plantar foot. The chronic designation does not always equate with anatomic stability, however, because in a subgroup of midfoot arthropathies, the midfoot is quite unstable yet is not warm to touch. The deformity in such instances is very difficult to treat because of the very unstable rocker-bottom deformity of the midfoot ( Fig. 10.2 ).




Figure 10.1


Acute neuropathic arthropathy involving the right foot. (A) Swelling and erythema are evident. (B) The temperature of 95°F for the midfoot is indicative of severe inflammation.



Figure 10.2


(A and B) Midfoot subluxation in a patient with a neuroarthropathy of 5 years duration. The foot is grossly unstable in plantar flexion and dorsiflexion, but by definition this would be a “chronic” Charcot process. We prefer to consider this an unstable midfoot rather than a chronic arthropathy.


Occasionally, if the first metatarsal, cuneiform, or navicular dislocates medially, the forefoot abducts and the bone prominence is directly medial. This type of deformity is easier to treat with an ostectomy than those in which bone prominences are on the lateral or plantar midfoot. However, this ostectomy can only be performed when the midfoot is completely stable and quite rigid; otherwise, removing the bone will worsen the deformity. The lateral rocker-bottom deformity occurs when the navicular and cuneiforms dislocate dorsally (naviculocuneiform or talonavicular dislocation with fourth to fifth tarsometatarsal dislocation), leading to a shortening of the medial column and a laterally based prominent rocker-bottom deformity with the apex at the cuboid.


The rationale for operative treatment is to decrease the deformity, thereby minimizing the likelihood of complications, including infection and need for amputation, which otherwise may be imminent. Certainly, surgical reduction of acute dislocation makes sense, especially in patients with acute frank dislocation of the midfoot, who clearly will benefit from this more urgent operative treatment. By contrast, in patients with chronic but stable neuropathic deformity of the midfoot, use of appropriate shoes, orthoses, and braces can often restore adequate function, so the indication for surgery is more specific: deformity that cannot be controlled by nonsurgical means, associated with recurrent ulceration and infection. The key is to balance the surgical risks with the risk of ulceration for the patient with a persistent deformity ( Fig. 10.3 ).














Figure 10.3


Patient presented with acute midfoot Charcot affecting the tarsometatarsal joints (A–C). Given the deformity with pressure on the medial skin, it was felt that the patient would benefit from realignment and arthrodesis. Following appropriate total contact casting and elevation, surgical reconstruction resulted in what is felt to be satisfactory alignment (D and E). However, given the extent of the surgery, a wound complication over the dorsal distal foot with infection occurred. This resulted in amputation of the distal foot (F). The patient was satisfied and ambulated with a simple insole; however, this case emphasizes that surgery is not without risk in these patients.


Patients can experience pain from the deformity, and although neuropathy may be thought of as being complete and not associated with any sensation, some patients experience deep, aching discomfort. Accordingly, it is appropriate to indicate surgical reconstruction in such cases. Chronic deformity, recurrent ulceration, pain, and an unbraceable deformity are reasonable indications for reconstruction, but only if treatment-approach orthotics and prosthetics have failed to produce improvement or are unrealistic to begin with ( Figs. 10.4 and 10.5 ). There remains a gray zone in which the decision for performing reconstruction is more difficult, if not controversial. The experienced clinician, however, gains a “feel” for the foot that helps guide decisions about the type of treatment needed. Patient factors including compliance, weight, extent of neuropathy, perfusion, skin condition, family support, opposite limb function, mobility of the ankle, and travel distance required for foot care all need to be considered in planning surgery for either the acute or the chronic stage of neuroarthropathy. The importance of these factors must not be underestimated. No matter how skillful the surgeon, the surgery will be useless if the patient lacks the means to comply with the restrictions on weight bearing and personal care requirements during rehabilitation.




Figure 10.4


(A–C) Chronic deformity of the left foot in a 69-year-old patient that had been present for 7 years. Chronic callus was present but never broke down with ulceration, and no surgery was necessary.









Figure 10.5


Stable midfoot Charcot with a focus at the tarsometatarsal joints (A–C). Although the patient has medial prominence, the sagittal alignment demonstrates that the collapse is in line with the floor and poses very little risk of ulceration (C). Given the stability of the foot on examination, without significant plantar prominence, the patient can be managed in a custom diabetic shoe (D).




Correction of Neuropathic Deformity of the Midfoot


During the acute phase, some absolute indications for surgery exist, including medial dislocation of the cuneiform or navicular, which will lead to skin necrosis ( Fig. 10.6 ). Initially, the associated swelling masks the bone prominence, but with resolution of swelling, a pressure sore develops or full-thickness skin loss occurs ( Fig. 10.7 ). Our experience suggests that if the dislocation is diagnosed early on in the evolution of the arthropathy, surgery will minimize the likelihood of deformity. The patient has to remain non–weight bearing regardless of the type of treatment, and provided that the foot is not ischemic, surgery is preferable. With complete bone extrusion, operative reduction and stabilization will be necessary to prevent subsequent deformity. In patients with these acute fracture-dislocations, the issue is whether the potential morbidity of surgery outweighs the likelihood of later complications ( Fig. 10.8 ).




Figure 10.6


Radiographs of an acute forefoot injury. (A) The patient was monitored for neuropathy and acute swelling of the foot, but no fracture was evident. (B and C) One week later the dislocation became apparent.



Figure 10.7


(A and B) Acute dislocation of the medial cuneiform and lateral dislocation of the tarsometatarsal joint in a patient with neuropathy and diabetes. Eschar formation was the result of pressure of the cuneiform and the dislocation on the skin. (C) At surgery, the cuneiform was rotated 90 degrees; the anterior tibial tendon remained attached. (D) A primary arthrodesis of the medial column was performed.



Figure 10.8


(A) An acute midfoot dislocation of the left foot. (B and C) Radiographic appearance. (D and E) Treatment consisted of application of plantar plates and primary arthrodesis of the midfoot.


The key to operative treatment, however, is to take careful note of the quality of the bone. From a practical standpoint, knowing the onset of the injury is difficult, because many patients are unaware of the initial event anyway. It is preferable to use the appearance of the bone as an indicator of both the onset of the neuropathic injury and also the possibility for surgery. Performing surgery on the midfoot when the bones are crumbling as a result of osteopenia is difficult, if not frustrating, and complicated. Therefore we are more inclined to correct a subluxation or dislocation than multiple fractures around the midfoot. The traditional methods of reduction and fixation of these injuries do not work well here because they are associated with recurrence of deformity. In the setting of Charcot, arthrodesis is required following reduction in all cases, as approaching these patients as one would approach trauma with an ORIF will predictably fail.


In the chronic stage, a complete transverse tarsal joint dislocation with dorsal dislocation of the cuneiform commonly leads to a floppy, unstable forefoot. This deformity results because the forefoot is placed into dorsiflexion by the pull of the tibialis anterior tendon while the Achilles tendon forces the hindfoot into equinus. The combination of these deformities results in a foot that is ineffective at both heel strike and toe-off, and the midfoot is at risk for ulceration.


A second deformity that frequently requires surgery in the chronic phase is the midfoot rocker-bottom deformity that is associated with supination of the forefoot. This deformity results from the heel cord pulling the foot into equinus and subsequent weight bearing on the lateral aspect of the foot.




Ostectomy


Ulcers may develop as a result of rubbing of anatomic bony prominences, or those produced during weight bearing in unstable joints, against shoes or other points of contact. If ulcers are intractable, ostectomy should be considered to resect the bone prominence. This procedure works well in such instances, provided that there is no associated instability of the adjacent joints. In general, ostectomy is effective for midfoot Charcot, and is not indicated for hindfoot Charcot as those are inherently unstable ( Fig. 10.9 ). If the bone prominence is resected and the midfoot is unstable, then recurrent ulceration will occur. Ostectomy can be performed only if stability (rigidity) of the midfoot is present. Because this is a much easier and quicker procedure to recover from, with less morbidity, we prefer to perform an ostectomy, as opposed to an arthrodesis, if possible. If the ulcer fails to heal with use of a total contact cast, the ostectomy is not contraindicated. The incision has to be made carefully, however, to avoid extension of the ulcer and the possibility of infection.






Figure 10.9


Chronic stable midfoot Charcot that presented with a large plantar ulceration directly over the bony prominence (A). Unlike the patient presented in Fig. 10.5 , the deformity has bony prominence plantar to the plane of the foot, which puts this patient at risk. A debridement of the wound with a plantar exostectomy with application of a wound vac resulted in healing of the soft tissue, resulting in limb salvage without the need for a large osteotomy/arthrodesis (B).


Technically, the ostectomy is not difficult to perform, and the only issue is to try to minimize postoperative soft tissue problems. Rarely, we approach the ostectomy through the open ulcer. Usually, the skin has healed over the ulcer from a total contact cast program, and the incision is made off the weight-bearing surface of the foot, either medially or laterally. Large skin flaps are preserved, and full-thickness dissection using a broad periosteal elevator should be performed to reach the prominence. We use a combination of an oscillating saw, osteotomes, and a rongeur to create a contoured surface of the plantar weight-bearing foot amenable to ambulation ( Fig. 10.10 ). It is imperative not to resect too much bone, or the result will be instability, which is particularly likely on the inferior aspect of the midfoot joints. A large, solid neuropathic bone mass may be present but is uncommonly seen; resection of the undersurface of unfused midfoot joints may have the effect of worsening the deformity and secondarily exacerbating the deformity.



Techniques, Tips, And Pitfalls




  • •

    We prefer to leave large segments of the subchondral bone of the midfoot bones intact.


  • •

    If bone quality is sufficient, the medial column length can be maintained with bridge plating from the talus to the cuneiforms or first metatarsal ( Fig. 10.11 ).




    Figure 10.11


    (A and B) This severe acute neuropathic fracture of the navicular was treated with open reduction and primary talonavicular arthrodesis. Note the segmental bone loss at the talonavicular joint. (C and D) Instead of a chisel or osteotome, a burr was used to denude cartilage, to prevent further bone fragmentation. (E) Fixation was accomplished with a combination of cannulated screws and a medially applied plate.


  • •

    Neuropathic fracture, dislocation, or fracture-dislocation of the midfoot results in loss of medial column length secondary to comminution of an intercalary segment. Caution is indicated, because any further shortening of the medial column would cause a lateral “rocker,” or adduction, of the midfoot with the apex at the calcaneocuboid joint.


  • •

    We use a burr to remove selected portions of the articular surface, rather than a chisel or an osteotome, because the ligamentous support is friable and tenuous, and with less than delicate handling, bone may literally fall out ( Fig. 10.12 ).




    Figure 10.12


    (A and B) Chronic dislocation of the midfoot with plantar and medial subluxation of the navicular (outlined area) led to ulceration of the medial foot, which was refractory to all methods of nonsurgical care. The dislocation of the navicular (outlined area) was associated with a flatfoot and a rocker-bottom deformity. (C and D) Correction was accomplished with open reduction, combined with arthrodesis of the medial column of the foot with a plantar plate.


  • •

    Primary arthrodesis of these acute midfoot dislocations must be performed, with the joint surfaces denuded using a burr applied to subchondral bone.


  • •

    If a talonavicular-cuneiform arthrodesis is performed, do not shorten the medial column. It may be preferable to include the calcaneocuboid joint in the arthrodesis, to avoid a lateral rocker-bottom deformity created by slight shortening of the medial column.


  • •

    If hindfoot valgus and forefoot abduction are associated with the acute midfoot Charcot arthropathy, a triple arthrodesis should be performed using lag screw fixation, but because of bone loss, plates are often necessary.


  • •

    If the navicular is fragmented and unable to be maintained as a part of the fusion mass, a naviculectomy with subsequent talocuneiform arthrodesis with similar surgical principles should be performed.


  • •

    To minimize the effect of the equinus contracture that is always present, we routinely perform a lengthening of the Achilles tendon.


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Apr 18, 2019 | Posted by in RHEUMATOLOGY | Comments Off on Surgery for the Neuropathic Foot and Ankle

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