Charcot neuropathic osteoarthropathy of the foot is a relatively common complication of diabetic neuropathy. Incorrect diagnosis and improper treatment often result in the extremity having to be amputated. This paper summarises the current view on the etiology, diagnostics, and treatment of diabetic Charcot neuropathic osteoarthropathy, with particular focus on preserving the extremity through surgical intervention from our own experiences.
Charcot neuropathic osteoarthropathy (CN) is a chronic, progressive condition of bones, joints, and soft tissues, most commonly occurring in the area of the foot and ankle as a result of peripheral neuropathy. It is characterized by a local inflammatory process in the early stages and gradual development of bone loss, joint dislocation, and fixed deformities. These deformities can secondary lead to infected ulcerations and eventually to osteomyelitis. In general, any part of skeleton can be affected.
Diabetes mellitus, together with neuropathy, is currently considered the main cause of CN. Data indicating the prevalence and incidence of the condition suggest that it often goes undiagnosed among sufferers of diabetes, with figures ranging from 0.4 to 13% among diabetics [
The common issue is an early diagnosis and an appropriate treatment, in case of an acute phase where it is difficult to differentiate an acute osteomyelitis. Even though the treatment of CN is mostly conservative, the surgical options might be beneficial for the patients. However, the crucial question is when, where, and how a surgical therapy has to be used.
A PubMed search was done with the key word “Charcot foot, neuropathic arthropathy, Charcot arthropathy.” We could trace about 400 up-to-date papers on the subject. Electronic database was systematically searched for literature discussing the history, pathophysiology, assessment, imaging methods, diagnosis including osteomyelitis, classification, and management of CN. We applied no restrictions on publication date. Article eligibility was assessed independently by all authors. Reasons for exclusion of articles based on title or abstract were (1) nonoriginal data (e.g., editorials, guidelines, and comments), (2) nonclinical articles (e.g., technical or animal studies), (3) case reports, and (4) articles not written in English language. All authors independently chose the most up-to-date papers with regard to target topics resulting in the identification of 59 “most pertinent” articles. Together we discussed and compared the relevant information from all these sources with our clinical practice and included them in this review.
Musgrave first described neuropathic osteoarthropathy in 1703 as an arthralgia caused by venereal disease [
Numerous factors contribute to the development of CN. Two main theories concerning the origin of the condition have been discussed in the past. The neurotraumatic theory is based upon damage to sensory feedback resulting from progressive destruction of bones and joints brought about by repeated trauma. The neurovascular theory highlights the changes in blood supply caused by neuropathy, most of all lesions in the sympathetic nerves which affect bone resorption [
The diagnosis is based on patient’s history, clinical examination, and imaging methods. Patients are quite often not aware of any injury as a result of their lowered perception of pain. Another triggering factor can be previous surgery of the foot [
For further prognosis and therapy it is necessary to examine the foot’s stability. Instability of the forefoot can be assessed according to Assal and Stern: the pressure on the foot in the sagittal plane dorsally when the ankle joint is locked in dorsiflexion [
Clinical image of the right foot (CN) with contraction of m. triceps surae and plantar inclination of calcaneus (black arrow), instability of the foot, and dorsal collapse of the forefoot (white arrow).
Primarily it must be emphasized that the changes on the X-ray are typically delayed and have low sensitivity [
A basic examination is an X-ray of the talus and the weight bearing foot in the anteroposterior and dorsoplantar lateral projection. During the initial stage the X-ray finding can be negative or only minor bone infractions and joint incongruence are present. In a developed stage fractures and subluxations or luxations are clearly observed. The X-ray finding depends on the specific type of CN. In a typical rocker bottom deformity a plantar dislocation of the navicular and cuboid bone is visible. A lateral projection defines inclination of the calcaneus. In CN we often find a negative inclination with a plantar tilt of the calcaneus. This deformity arises due to deformed midtarsal bones and the shortening of the Achilles tendon, which loses its elasticity during glycosylation [
Lateral X-ray image of the weight bearing left foot, visible negative inclination of calcaneus (white line), and collapse of middle part of tarsus (angle
Examination using magnetic resonance imaging is a very valuable method for the early stages of the illness when X-ray imaging alone results in practically normal findings. An important finding is oedema of the bone marrow of two or more bones, oedema of the adjacent soft tissues, and fluid in several joints or cortical fractures. If conservative treatment is begun during this phase the condition is reversible [
Certain methods of nuclear medicine can be helpful not only as an alternative diagnostic method, for example, in revealing the presence of osteomyelitis, but also for monitoring the progress of the treatment. These methods, however, introduce certain difficulties. Three- or four-phase bone scintigraphy (
The diagnostics of osteomyelitis in CN is difficult primarily in the active stage of the disease when clinical symptoms are practically the same both in osteomyelitis and in CN. On the contrary, in the chronic stage symptoms in osteomyelitis due to ischaemia and immunodeficiency may be masked. Diagnosing osteomyelitis is not possible on the basis of one examination alone. In general, for the differential diagnosis of osteomyelitis and CN, an important role plays a complex view of inflammatory markers and clinical manifestations of infection. The origin of osteomyelitis is in most cases caused by spread of infection from the soft tissues. History of ulceration or presence of ulceration and/or previous amputation in the area of the foot are possible factors to weigh when suspecting osteomyelitis. Osteomyelitis in CN without ulceration has a very small probability. On the contrary, a high predictive value for the presence of osteomyelitis is ulcerations bigger than two cm2 and deeper than three mm [
Typical ischaemic symptoms like claudication and pains at rest, which would normally appear in the history, might be unrecognised because of the presence of neuropathy. During a physical examination pulsation can be impalpable and trophic changes are often found. An example of a noninvasive diagnostic method that can be also used would be measuring blood pressure in the ankle using a Doppler probe (it carries a higher risk of artificially higher pressures in the case of mediocalcinosis). In our department we use measure pressure on the big toes or transcutaneous oxygen tension (this method carries a risk of artificially lower pressures in the case of oedema) [
The most commonly used classification according to Eichenholtz was published in 1966 (Table
Eichenholtz classification.
Stage | Radiographic finding | Clinical finding |
---|---|---|
I | Osteopenia, osseous fragmentation, joint subluxation or dislocation | Swelling, erythema, warmth, ligamentous laxity |
II | Absorption of debris, sclerosis, fusion of larger fragments | Decreased warmth, decreased swelling, decreased erythema |
III | Consolidation of deformity, fibrous ankylosis, rounding and smoothing of bone fragments | Absence of warmth, absence of swelling, absence of erythema, fixed deformity |
Currently, in spite of the quite widespread usage of this classification, it is necessary to consider and search for new alternative methods of imaging. Eichenholtz evaluated X-ray images in 68 patients (altogether 94 joints) of whom only 12 were diabetic [
Classification of CN based upon MR imaging. Source: [
Stage | Severity grade | |
---|---|---|
Low severity: grade 0 (without cortical fracture) | High severity: grade 1 (with cortical fracture) | |
Active arthropathy (acute stage) | Mild inflammation/soft tissue oedema | Severe inflammation/soft tissue oedema |
No skeletal deformity | Severe skeletal deformity | |
X-ray: normal | X-ray: abnormal | |
MRI: abnormal (bone marrow oedema, microfractures, bone bruise) | MRI: abnormal (bone marrow oedema, macrofractures, bone bruise) | |
| ||
Inactive arthropathy (becalmed stage) | No inflammation | No inflammation |
No skeletal deformity | Severe skeletal deformity | |
X-ray: normal | X-ray: abnormal (past macrofractures) | |
MRI: no significant bone marrow oedema | MRI: no significant bone marrow oedema |
The treatment of CN is mostly conservative. This method is based on immobilisation and the complete absence of weight bearing for the affected extremity in the active stage. There are various opinions concerning the type of immobilisation and the period of nonweight bearing for the foot. The most common immobilisation used is a total contact cast (TCC) changed three days after the initial application and then every week. Alternatively, it is possible to use Charcot Restraint Orthotic Walker (CROW) prefab orthoses. The period of fixation depends on the reduction in oedema and a drop in skin temperature below 2°C compared to the contralateral extremity [
To support healing some medicaments have been used, bisphosphonates, which inhibit osteoplastic bone resorption, and intranasal calcitonin, which has had fewer complications [
Besides conservative treatment, the possibilities of surgical treatment have also been looked into and the benefits and risks of such treatment have been considered. Saltzman et al. [
Indications of the surgical treatment.
Surgical treatment | Indications |
---|---|
Reconstruction | Stable, nonplantigrade foot |
Resection of bony prominences | Isolated bony prominences in a stable plantigrade foot |
Major amputations | Severe peripheral vascular disease |
Major amputations in CN (generally we prefer the below-the-knee amputation) are still the current solution. If carried out properly, if the healing is complete, and if the patient is equipped in the prosthetic and rehabilitation department with a suitable prosthesis and has an adequate walking regime as part of the rehabilitation, then we know from experience that these patients, though initially perhaps unwilling to undergo surgery, are more satisfied compared to those who use orthosis for a long time, who required constant dressings of ulcerations and repeated visits to hospital. Based on our personal experiences, we use transcutaneous oxygen tension more than 35 mmHg as a predictive factor for successful healing of below-knee amputation. In dialysis patients we deal with problem of a suitable prosthesis after major amputation due to changes of extremity volume between dialyses.
Bone resections are done as a separate intervention in isolated bone prominences, mostly in cases of a high bony pressure that cannot be accommodated with orthotic and prosthetic means and in stable plantigrade foot [
With regard to poor bone quality and the presence of neuropathy in long-term healing, the so-called superconstruction principles for reconstruction operations have been set up: (a) extending arthrodesis beyond the affected area on neighbouring joints, (b) resection of the bone for mild shortening of the foot enabling adequate repositioning of the deformity without excessive tension of soft tissues, thus helping prevent secondary ischaemisation, (c) usage of the strongest possible implant which can be tolerated, and (d) introduction of an implant that can maximally increase mechanic stability, which is the main goal [
In general we can use different types of external fixators or internal fixators according to the type of deformity and preference of the surgeon. In the case of external fixators, the most suitable enabling gradual correction seems to be ankle-foot fixators of the Ilizarov type or the Taylor Spatial Frame. Their disadvantage is the relatively high purchase cost. Mostly, a three-plane fixation that combines common types of external fixators is used. An advantage of this method is the absence of internal implant that may increase the risk of infection and the possibility of earlier weight bearing on the foot. As for the internal fixations, plates are recommended if the implantation is from the plantar side, although nowadays angle stable plates are used more often. They enable good stability in an osteoporotic bone and greater variability from the point of view of plate placement. The disadvantage is the need for a wider surgical approach and problematic healing with the exposed implant [
Most of the earlier operations have been carried out only in the chronic, inactive stage. In the active stage, an inflammatory reaction with oedema and osteoporosis are present, thus increasing the risk of complicated healing. On the other hand, this stage enables easier corrections than in the fixed deformity as it is possible to use the remodeling capacity of the bone. Indications for surgery in the active stage are heavy instability, progression of the deformity, prevention of the dislocation of fragments by muscle contraction, and the general failure of conservative treatment. An external fixator is used exclusively. Usually within three to six weeks the position of the foot is gradually corrected by this external fixator into the correct plantigrade position, then an arthrodesis of joints is carried out, and the fixator is left in place for at least three more months [
Sanders and Frykberg classified individual localizations of CN on the foot (Table
Sanders and Frykberg classification.
Type | Localization |
---|---|
I | Metatarsophalangeal and interphalangeal joints |
II | Tarsometatarsal articulations (Lisfranc) |
III | Midtarsal joint line (Chopart) |
IV | Ankle joint and subtalar joint |
V | Calcaneus |
In this case prevailing resorptive changes were creating deformities of the metatarsal bones of the so-called candy bar type (Figure
Dorsoplantar X-ray image of the left foot. Resorptive changes I–III MTP of the joints.
Translation of metatarsi medially or laterally is usually associated with lowering the medial column and valgus heel. A frequent consequence is abduction of the forefoot, which includes a perinavicular affection with the talus and navicular bone in plantar flection while the cuneiform bone is dislocated dorsally with the I metatarsus. The contraction of the tibialis anterior muscle worsens the deformity and practically excludes successful conservative treatment. This type of CN is very often combined with the following type III, which is why surgical treatment of both these types will be described together. Moreover, a normal position of the hindfoot is a prerequisite for the correction of the forefoot.
This is a typical rocker bottom foot with the cuboid bone in plantar prominence. This plantar bone prominence causes chronic ulcerations which do not respond to conservative therapy (Figure
3D CT of the left foot: plantar prominence of tarsal bones and in this case plantar prominence of cuboid bone.
It is necessary to do reconstruction and stabilisation of the medial and lateral column and, in case of persistent instability, subtalar arthrodesis as well.
Reconstruction of the foot consists of several phases. One advantage is regional anaesthesia and minimal usage of a tourniquet. In the case of pes equinus, the first phase, according to the preoperative assessment, involves either the Strayer procedure or, more frequently, prolongation of the Achilles tendon, which can be carried out using either a Z-plasty or a technique of three mini-incisions three cm apart from each other and up to one-half of the tendon diameter (most frequently a lateral-medial-lateral incision). The position of the sole is corrected up to 90 degrees in respect to the long axis of the fibula, with the knee in full extension. This procedure restores the positive inclination of the calcaneus and facilitates the reconstruction of the medial part of the tarsus. Care must be taken to avoid pes calcaneus by overextended prolongation; this position causes heel ulcerations that do not heal, leading to the necessity for below-knee amputation. We temporarily fix the corrected position of the hindfoot with the help of the Kirschner wire from the calcaneus to the tibia.
In the next phase we make a slightly S-shaped incision on the medial side of the foot from the talus to the base of the I metatarsus, where we identify individual joint dislocations. Earlier we used the approach to the lateral column according to Ollier which led to a higher percent of secondary healing. That is why, in a deformity where the cuboid bone is the lowest bone, the callus is excised from a plantar approach. Reconstruction of the Lisfranc joint follows, and we correct abduction or adduction deformity performing osteotomy using the previously introduced Kirschner wires. We temporarily fix the corrected position with the help of Kirschner wire.
In the third phase we reconstruct the middle part of the tarsus. The navicular and cuboid bones are usually plantarly dislocated, with the goal being resectional talonavicular, naviculocuneiform, and calcaneocuboid arthrodesis in the corrected position, which is again temporarily fixed by the Kirschner wires.
A final fixation with a Midfoot Fusion Bolt of 6.5 mm (DePuy/Synthes) is the last step. We introduce the implant medially over the head of the I metatarsus according to the deformity of the hallux from a dorsal or plantar approach up to the talus bone. Laterally we introduce the implant from the mini-incision from the area of base of the IV metatarsus through the cuboid bone to the calcaneus. To date we did not have to address residual instability between the talus and calcaneus, for which subtalar arthrodesis with the same implant is recommended [
(a) Clinical image of CN with collapsed middle part of tarsus and plantar sinus (right foot). (b) Preoperative X-ray image of collapsed arch in the middle part of tarsus. (c) Clinical image immediately after reconstruction with reconstructed longitudinal arch. (d) Lateral X-ray image demonstrates reconstruction of both columns two months after surgery.
In this type the ankle and frequently a subtalar joint are most affected. Because of the instability the deformity progresses and calluses and ulcerations emerge. We indicate arthrodesis of the ankle and the subtalar joint along with an external fixation (Figure
(a) AP X-ray image of the right ankle: inveterate neuropathic fractures of both malleoli. (b) A primary arthrodesis using an external fixation carried out.
In the case of severe deformities we prefer astragalectomy before performing prospective transtibial amputation. After the tibiocalcaneal arthrodesis is healed it is necessary to use an orthosis for several months (Figure
(a) A clinical image of a left foot deformity with complete dislocation of talus plantolaterally (arrow). (b) A clinical image after astragalectomy and completed healing of tibiocalcaneal fusion. (c) Individual plastic orthosis into shoes.
This is the least frequent type affecting the calcaneus (Figure
A lateral X-ray image of calcaneus: the pull of the Achilles tendon causes the fragment to be dislocated, with incongruence in the subtalar joint.
Postoperative care depends on the type of corrected deformity, the implant used (internal or external fixation), the course of healing, whether or not the contralateral extremity is affected, and the ability of nonweight bearing on the operated extremity. In general a great deal of attention must be paid to the appropriate off-loading in the early and subacute postoperative stage and in the case of chronic CN in terms of localization. The advantage of external fixation is the possibility of earlier weight bearing; internal fixation is supplemented by a plaster cast usually for three to four months. After the external fixator or plaster cast fixation is removed, individual orthoses are applied, and weight bearing is gradually increased by reduction in limitation of walking time and speed. A suitable time for using the orthosis is up to one year. After this period individual orthopaedic shoes are usually made. A lifelong follow-up including diabetes, nutrition, and infection control by antibiotic treatment if necessary is essential.
The treatment of CN is mostly conservative. Thanks to new findings from the aetiopathogenesis of the condition and its biomechanics it is possible, in indicated cases, to supplement CN treatment with reconstructive procedures along with suitable implants, thus avoiding major amputation. Nevertheless, to evaluate the benefits and risks of these procedures further evidence-based studies will be necessary.
The authors declare that there are no competing interests.
This work was supported by the programme PRVOUK P 37/04.