Definition
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Currently, diabetes mellitus (DM) is the most common predisposing medical condition for the development of Charcot arthropathy.
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The midfoot is most commonly affected in Charcot arthropathy and historically was treated with total contact casting in the acute phase with a later transition to accommodative bracing after resolution of symptoms. Prior studies have shown that bracing does not always correlate with a good patient outcome.
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Progressive bony deformity and resorption that may accompany Charcot arthropathy have led to advocating for surgical intervention. Recent literature has demonstrated successful operative corrections of midfoot deformity with improved quality of life for patients.
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Sammarco has described super construct concepts, which focus on four main factors:
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Extending the fusion beyond the zone of injury to the unaffected joints to improve fixation.
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Performing bony rection as needed to allow adequate deformity reduction without placing undue tension on the soft tissue envelop.
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Using the strongest device that can be tolerated by the soft tissue envelope.
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Application of the device in a position that maximizes mechanical function.
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Intramedullary beaming fixation is a more recently described technique which allows for decreased soft tissue dissection, simultaneous compression across multiple arthrodesis sites, minimally invasive insertion, and the ability to span across the zone of injury. The primary goal of surgery is an ulcer-free plantigrade foot.
Diagnosis
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Specific conditions for which such fusion is commonly indicated include:
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Inflammatory arthropathies
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Congenital deformity
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Neuropathic arthritis secondary to DM or inherited/acquired polyneuropathies
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Failed total ankle arthroplasty
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Severe pes planovalgus deformity
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Fracture malunion and nonunion
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Bone loss and collapse secondary to trauma, tumor, osteonecrosis, Charcot arthropathy, or infection.
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Patient factors that have been shown to affect outcomes of midfoot and hindfoot fusion include medical comorbidities such as DM, previous ulcerations, peripheral vascular disease, renal disease, immunosuppression, chronic steroid use, rheumatologic disease, malnutrition, and smoking.
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In addition, a history of surgical intervention, particularly with postoperative complications (e.g., deep infection, problems with wound healing) may affect postoperative outcomes.
Anatomy
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The midfoot includes the navicular, cuboid, and cuneiform bones and their articulations with the proximal metatarsal bones.
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The heads of the first and fifth metatarsal bones and the calcaneus constitute a tripod necessary for foot stability.
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The key joints in the foot for maintenance of mobility are the hindfoot joints, including the tibiotalar, subtalar, and talonavicular articulations. The lateral and fourth and fifth tarsometatarsal (TMT) joints that are important for normal foot function are more mobile than other TMT joints. The remaining hindfoot and midfoot joints, including the calcaneocuboid and the first, second, and third TMT joints, do not require a full range of motion to maintain function of the foot.
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The transverse tarsal joint (Chopart joint) is composed of the talonavicular and calcaneocuboid joints and acts in concert with the subtalar joint to control foot flexibility during gait.
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The talonavicular joint is supported by the spring ligament complex, which has two separate components: the superior medial calcaneonavicular ligament and the inferior calcaneonavicular ligament.
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The calcaneocuboid joint is saddle shaped. It is supported plantarly by the inferior calcaneocuboid ligaments (superficial and deep) and superiorly by the lateral limb of the bifurcate ligament.
Biomechanics
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TMT joints
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Little motion occurs through the intercuneiform and naviculocuneiform (NC) joints.
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The fourth and fifth TMT joints are the most mobile, with a range of motion from 5 to 17 degrees. The second TMT is the least mobile, with 1 degree of motion.
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Dorsiflexion of the metatarsal-phalangeal (MTP) joints during propulsion tightens the plantar fascia through a windlass effect, raising the longitudinal arch and inverting the heel.
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Pathogenesis
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Midfoot arthritis in the sensate foot
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The first, second, and third TMT joints of the midfoot may be viewed as nonessential joints, and if fused in anatomic alignment, physiologic foot function is generally anticipated.
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The etiology of midfoot arthritis can be primary, inflammatory, or posttraumatic ( Fig. 15.1 ).
• Fig. 15.1
Pes planovalgus foot alignment secondary to posttraumatic midfoot arthritis.
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Primary osteoarthritis of the midfoot is the most common type of midfoot arthritis.
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Untreated TMT joint (Lisfranc) fracture-dislocation typically leads to loss of the longitudinal arch and forefoot abduction.
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The pathogenesis of Charcot arthropathy (also termed Charcot foot or Charcot neuroarthropathy [CN]) has been explained using two major theories:
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The neurotraumatic theory attributes bone destruction to the loss of pain sensation and proprioception, combined with repetitive and mechanical trauma to the foot.
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The neurovascular theory suggests that joint destruction is secondary to an autonomic stimulated vascular reflex causing hyperemia and periarticular osteopenia with contributory trauma.
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There is a growing body of evidence that dysregulation of inflammatory and bone metabolism pathways, with upregulation of receptor activator of nuclear factor K-B ligand (RANK-L), lead to osteoclast overactivation and bone resorption. , ,
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Clinically, midfoot osteoarthropathy manifests as a noninfectious, osteolytic process that may ultimately result in profound deformity and instability from bone and joint collapse. Deformity with neuropathy may lead to ulceration and potentially to a limb-threatening condition.
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In 1966, orthopedic surgeon Sidney N. Eichenholtz (1909–2000) published a monograph entitled “Charcot Joints” in which the clinical, radiographic, and pathologic data of 68 consecutive patients were used to define three stages of Charcot arthropathy based on the natural history of the condition. The three stages he described were (1) development, (2) coalescence, and (3) reconstruction and reconstitution.
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Clinical signs (such as swelling, warmth, and erythema) regularly precede the radiographic findings seen with Eichenholtz stage I arthropathy. As such, in 1990 Shibata et al. added a fourth stage, Charcot foot stage 0, to the conventional Eichenholtz classification ( Table 15.1 ).
TABLE 15.1
Charcot Neuroarthropathy Staging Based on Eichenholtz and Shibata et al. ,
Stage
Characteristic
0: Acute inflammatory phase
Foot is swollen, erythematous, warm, hyperemic; radiographs reveal periarticular soft tissue swelling and varying degrees of osteopenia
1: Developmental or fragmentation
Periarticular fracture and joint subluxation with risk of instability and deformity
2: Coalescence stage; subacute
Resorption of bone debris and soft tissue homeostasis
3: Consolidation or reparative stage; chronic
Restabilization of the foot with fibrous or bony arthrodesis of the involved joints
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Patient history and physical exam findings
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Patients reports midfoot/arch pain with weight bearing, particularly with push-off during gait. Pain is elicited with palpation or stress. Bone prominences of the midfoot may be present.
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Examination of the patient should begin with assessment of the skin and pedal pulses. If there is any question about the vascular status of the limb in which surgery is being considered, further workup is warranted and may include vascular studies or consultation with a vascular surgeon. A neurologic evaluation should include sensation testing with a 5.07-gauge monofilament and an evaluation of the muscular strength in all planes of the leg that is to be treated.
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Assessment of the alignment of the foot and ankle begins with an evaluation of the standing alignment and during gait. Loss of the longitudinal arch (often associated with forefoot abduction) is frequently seen on weight bearing and with radiographic alignment. Midfoot arthritis is the second most common cause of longitudinal arch loss behind posterior tibial tendon dysfunction.
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Special attention should be paid to the alignment in both the sagittal and coronal planes. An equinus posture (i.e., fixed ankle plantar flexion) is important to detect, along with any varus or valgus positioning of the hindfoot. Attention should then be turned to the forefoot. To assess the need for forefoot correction, the hindfoot can be held in the corrected position while the clinician assesses the position of the forefoot in the coronal plane relative to the long axis of the tibia while the patient is seated.
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When evaluating the patient with Charcot arthropathy of the midfoot, the location and severity of the deformity must be determined radiographically and clinically to decide which treatment will most likely lead to a good result.
Imaging and other diagnostic testing
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Weight-bearing radiographs of the ankle and foot are mandatory in the evaluation for deformity and alignment. Findings may include:
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A nonlinear talus-first metatarsal relationship with the apex of the deformity at the midfoot.
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Loss of longitudinal arch and forefoot abduction.
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Evidence of arthrosis, bone loss, shortening, or existing implants from prior surgeries (particularly broken screws).
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Bilateral weight-bearing anteroposterior (AP) view of both feet and ankles give an excellent indication of the degree of actual or functional shortening caused by bone loss or malalignment.
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Radiographic parameters examined include the lateral talo-first metatarsal angle (Meary’s angle), AP talo-first metatarsal angle, calcaneal pitch, and cuboid height—weight bearing preoperative and final postoperative data are collected for comparison.
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In addition to plain radiography, a CT scan may be indicated in patients with substantial disruption of the normal bone architecture of the foot and ankle, and it is also useful in revision arthrodesis for determining the status of a previous fusion.
Nonoperative management
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Nonsurgical treatment of arthritis of the ankle and foot include nonsteroidal antiinflammatories (systemic or topical), activity modification, corticosteroid injections, shoe modifications, and bracing treatment (ankle foot orthosis [AFO]). Most cases of acute Charcot arthropathy can be treated effectively with pressure-relieving methods such as total contact casting or a Charcot restraint orthotic walker (CROW).
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Longitudinal arch supports with rigid inserts.
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Typical advanced midfoot deformities require accommodative (not corrective) orthotics with recess to relieve pressure from prominences.
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Shoe modifications (rocker soles).
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Fixed ankle bracing treatment in combination with shoe modifications (rocker soles) may further unload the midfoot during gait.
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Early-stage Charcot arthropathy, where the arch is low and the foot is at risk, can often be managed with orthotics or accommodative shoes. Later stages, when the arch has collapsed, requires aggressive nonsurgical treatment such at total contact casting, and surgery may be required.
Traditional surgical management
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Prior studies have shown that bracing does not always correlate with a good patient outcome. Progressive bony deformity and resorption that may accompany CN have led to advocating for surgical intervention.
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Late-stage CN, where the arch is below the plane of the calcaneus and the metatarsal heads, has a poor prognosis and a high risk of chronic ulcers and osteomyelitis. These patients likely require surgery.
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The primary goal of surgery is an ulcer-free plantigrade foot.
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Surgical treatment consists of either an ostectomy or correction of the deformity and fusion. An ostectomy is indicated in patients who have continuous breakdown resulting from a bony prominence that prevents casting or bracing, as well as in patients who have sustained a fracture that has fragmented and consolidated into a stable deformity and now has symptomatic bony prominences. One caveat is that in completing the ostectomy you may destabilize the joint, as the resected, prominent bone may have been contributing to stability. An ostectomy is also indicated in patients who have recurrent ulcers owing to bony prominences, to allow the ulcers to heal before definitive correction and fusion.
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Operative intervention may be indicated to realign the midfoot, which is typically achieved in conjunction with internal plate/screw or circular external (thin-wire) fixation.
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In general, fusion should involve the joints that are most obviously affected. In more mild deformities a more limited fusion may suffice. In severe cases, a first through fifth tarso-metatarsal (TMT) fusion is required. Additionally, fixation without fusion of the NC, talonavicular, and calcaneocuboid joints may also be beneficial to gain stability in better bone stock.
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“Beaming,” which refers to a technique that utilizes intramedullary large-bolt fixation, has been described ( Fig. 15.2 ). Utilizing medial and lateral column beams across the midfoot may allow surgeons to decrease the amount of hardware required to achieve stability, provide improved compression, and do so with both less soft tissue stripping and a lower chance of hardware exposure in the event of wound breakdown.
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