Mary K. Nagai, M.D., PhD
Frank Duerksen, M.D., FRCSC
Section of Orthopaedic Surgery, Department of Surgery
University of Manitoba,
Winnipeg, MB

Introduction
Neuropathic osteoarthropathy is a late complication of peripheral neuropathy of the foot and ankle. A Charcot foot has several distinct characteristics. It is a non-infective, destructive lesion of a bone and joint with collapse of joint spaces, often accompanied by a fracture and/or dislocation of one or more ankle and foot joints in a patient who has peripheral neuropathy.¹ The tarsal-metatarsal and tarsal joints are most commonly affected. It is a common and difficult complication of diabetes mellitus to treat. The Eichenholtz classification scheme for the Charcot foot is shown in Table 1.^1,2

Charcot Foot: Etiology
The cause of Charcot joints remains controversial. The traditional theory is that repetitive trauma to an insensitive foot causes the joint destruction. However, recent studies attribute the foot and ankle deformity(ies) to an increased vascularity secondary to abnormal sympathetic reflexes.³ Regardless of the cause of the Charcot joint, four factors are considered to be necessary in order for Charcot arthropathy to develop: (i) peripheral neuropathy; (ii) unrecognized injury; (iii) continued repetitive stress on injured structure; and (iv) increased local blood flow.⁴ The resulting gross deformity(ies) in the foot and ankle, specifically, large osseous prominences, places excess mechanical pressure and stresses on focal areas of soft tissue, which may ultimately lead to complications including, the development of foot ulcers and osteomyelitis and the need for subsequent operative intervention.¹ It has been reported that the presence of Charcot arthropathy was associated with an approximately 36 times greater risk for the development of a foot and/or ankle ulcer.^5,6,7

Goal of Operative and/or Nonoperative Management of Charcot Foot
The goal of operative and/or nonoperative management of the Charcot foot in the person with diabetes is to preserve as much useful functional morphology of the lower extremity. This will diminish future skin necrosis and ulceration by restoring the alignment of stability of the foot such that the patient may eventually be able to use custom footwear and/or a brace. Ultimately, the management goal is to prevent a potential amputation of the limb.¹ The available options are as follows:

Nonoperative Treatment
The standard initial treatment for Charcot arthropathy, regardless of the Eichenholtz stage, is immobilization with a non-weight-bearing total-contact cast until bone consolidation and joint stability are confirmed both clinically and radiographically.⁸ After successful treatment with a total-contact cast, an ankle-foot arthrosis may be used for 12-18 months or indefinitely for disease involving the ankle and/or hindfoot joints.¹ Extra-depth footwear and custom total-contact orthotics are used to treat Charcot foot involving the midfoot and forefoot.

 Operative Treatment
The severity of the Charcot foot and/or ankle deformity dictates the treatment plan. Operative treatment is indicated when, (i) the severity of the foot and/or ankle deformity is not amenable to conservative management (i.e. Prescription footwear and bracing); (ii) marked instability and/or malalignment (usually involving the hindfoot and ankle); (iii) for recurrent ulceration(s).¹ A painful Charcot joint is rarely the sole reason for operative treatment.

Timing of Operative Treatment
Prior to the commencement of any reconstructive procedure(s), the following clinical criteria should be met, (i) the foot and/or ankle should be in the resolution phase (Eichenholtz stage III); (ii) conservative treatment (i.e. Total contact casting, prescription footwear and bracing) has failed; and (iii) the skin of the overlying ulcer is closed so that the incision to remove the osseous prominence(s) can be made through intact skin. If osteomyelitis is present, treatment includes a thorough irrigation and debridement with accompanying antibiotic therapy. Once these criteria are met, the decision is not between nonoperative versus operative but rather involves operative treatment followed by prescription footwear and bracing.

Reconstructive Procedures
Ostectomy
Charcot arthropathy commonly affects the midfoot. As a result, the tarsal-metatarsal and tarsal joints are frequently destroyed leading to joint subluxation, symptomatic osseous prominences, and collapse of the midfoot. A characteristic "rocker-bottom" deformity in the midfoot develops and is a source of recurrent ulceration. The bony prominences are removed via ostectomy. Care must be taken not to resect excessive bone in the midfoot since removal of the plantar ligaments may cause progression of the rocker-bottom deformity. Many patients also have a co-existing contracture of the Achilles tendon.⁹ A percutaneous lengthening of the Achilles tendon is frequently performed at the time of plantar ostectomy. Postoperatively, a total-contact cast is applied to stabilize the soft tissues and to promote wound healing.

Arthrodesis
Realignment arthrodesis has been described as an effective method of limb salvage. These patients often have severe midfoot (collapse) with bony prominences, hindfoot (fixed varus or valgus malalignment and secondary bony prominences) and/or deformity(ies) and instability associated with recurrent ulceration, that are not amenable to custom footwear and bracing. As previously noted, the goal of surgical intervention is to restore the alignment and stability of the foot so the patient may eventually be able to obtain custom footwear and/or a brace to enable weightbearing and ambulation. An arthrodesis is not intended to substitute for appropriate footwear and/or use of a brace.^10,11 Patients with severe foot and ankle deformity(ies) frequently present with a concomitant contracture of their Achilles tendon. An Achilles tendon lengthening procedure is frequently performed at the time of realignment arthrodesis.⁹ Autologous bone graft is used to fill any defects and to provide both an intra- and extra- articular arthrodesis when possible.

Arthrodesis is not without its complications, as it has been noted that an arthrodesis of the ankle, hindfoot or midfoot is prone to Charcot changes at adjacent joints.¹² Furthermore, active patients may be prone to stress fractures in the distal part of the tibia because the foot  acts as a long rigid lever arm and places added stress across the tibia. To prevent stress fractures, the stability provided by the arthrodesis itself is enhanced by the use of a brace and extra-depth footwear with a total contact orthotic and extended steel shank and rocker-bottom sole worn indefinitely.

Early reports suggested that realignment arthrodesis for Charcot foot and ankle deformities be approached with great caution due to the high rates of non-union and infection.^13,14

In contrast, a series of 8 clinical studies published more recently, involving 143 patients treated with an arthrodesis of the foot and ankle for Charcot arthropathy report an average rate of union of 70% (range, 54%-100%).^{8,11,14,15,16,17,18,19} In 87% of these patients, regardless of whether or not a solid union or a stable non-union had been achieved, were eventually able to mobilize using custom-made footwear or a brace or both. Operative treatment in all cases was carried out during the quiescent/resolution phase of the Charcot foot (Eichenholtz stage III). Overall, patient satisfaction was high in all of these latter studies. In contrast to the earlier studies, all of the more recent reports documented improved methods of internal fixation and prolonged immobilization.^{13, 14}

In a recent study, all 14 persons with diabetes who had clinical and radiographic evidence of Eichenholtz stage I Charcot arthropathy underwent successful realignment arthrodesis procedures to restore anatomical alignment and functional improvement.⁴ Clinically, none of the patients had immediate or long term complications postoperatively. No patients reported ulceration(s) postoperatively. Operating during Eichenholtz stage I did not appear to alter healing time but did appear to expedite the reversal of the destructive process. Eventually all of the patients regained their pre-arthropathy level of ambulation. This study is the first to clearly report the concept that early arthrodesis for Charcot arthropathy may be a treatment option and not a limb salvage procedure.⁴

Reconstruction Versus Amputation
Many patients with severe Charcot foot and ankle deformity(ies) are offered amputations rather than reconstructive surgical options. In the past, reports strongly supported this avenue of treatment, given the increased risk of complication and our lack of understanding of the disease itself. However, recent advances in our understanding of this disease, drug therapy, cardiology, ophthalmology and transplantation procedures, have now improved the quality of life and extended the life expectancy for persons with diabetes.

The ultimate goal of managing diabetic feet and ankles is to avoid lower extremity complications associated with diabetic peripheral neuropathy (especially if the patient has had a contralateral amputation).

Human kinetic studies examining energy expenditure clearly demonstrate that more cardiovascular work is required to ambulate with a prosthetic limb.^20,21 The energy cost of prosthetic walking in 70 patients with unilateral amputations (either above the knee, below the knee, or at the Syme's level) versus a controlled group of 40 normal subjects was compared.²⁰ In all groups of amputees, performance and energy expenditure was significantly greater than the control group of normal subjects. More importantly, the more distal of the level of the amputation, the lower the energy cost of ambulation.^{20, 21} These findings support the hypothesis that a patient with compromised cardiovascular function due to an underlying disease process such as diabetes, would expend less energy ambulating following an early foot and/or ankle reconstructive operative procedure as compared to an amputation. Furthermore, uncertainty about the future status of the contralateral foot provides stronger support for an early reconstruction procedure as opposed to an amputation in a patient who is a candidate for a reconstructive surgical procedure.

The psychosocial impact of an amputation versus an arthrodesis must also be considered. Persons with diabetes who have had a unilateral lower-limb amputation have a much poorer psychosocial adjustment to illness than do persons with diabetes who have not had an amputation.⁴ Moreover, persons with diabetes who have had a previous amputation are much more likely to require amputation of the contralateral limb.²²

Summary
Charcot foot and ankle deformities are progressive and complicated conditions. The ultimate goal of nonoperative and operative treatment is to stabilize and realign the foot and ankle to allow the patient a functional limb so that custom-made footwear and/or a brace may be used, thus lessening the risk of an amputation. Ultimately, patient satisfaction must be the goal.

References

1.     Johnson, J.E.: Operative Treatment of Neuropathic Arthropathy of the Foot and Ankle.JBJS 80-A: 1700-1709, 1998.

2.     Wilson, M. : Charcot Foot Osteoarthropathy in Diabetes Mellitus. Military Med. 156 (10): 563-569, 1991.

3.     Wagner, F.W. Jr.: A Classification and Treatment Program for Diabetic, Neuropathic, and Dysvascular Foot Problems. Instr. Course Lect. 28: 143, 179.

4.     Simon S.R., Tejwani, S.G., Wilson D.L., Santner T.J., Denniston M.L.: Arthrodesis as an Early Alternative to Nonoperative Management of Charcot Arthropathy of the Diabetic Foot. JBJS 82-A: 939-950, 2000.

5.     Armstrong D.G., Lavery L.A., Harkless L.B.: Who is at Risk for Diabetic Foot Ulceration? Clin Podiat Med Surg 15: 11-19, 1988.

6.     Brand P.W.: Repetitive Stress in the Development of Diabetic Foot Ulcers. In Levin M.E., O'Neal L.W.: The Diabetic Foot. Edition 4 CV. Mosby St Louis 83-90, 1988.

7.     Myerson, M.S., Papa, J., Eaton K., Wilson, K.: The Total-contact Cast for Management of Neuropathic Plantar Ulceration of the Foot. JBJS 74-A: 261-269, 1992.

8.     Papa J., Myerson M., Firard P.: Salvage, with Arthrodesis, in Intractable Diabetic Neuropathic Arthropathy of the Foot and Ankle. JBJS 75-A 1056-1066, 1993.

9.     Armstrong D.G., Stacpoole-Shea S., Nguyen H., Harkless L.B.: Lengthening of the Achilles Tendon in Diabetic Patients Who are at High Risk for Ulceration of the Foot. JBJS 81-A: 535-538, 1999.

10.  Giurini J.M., Rosenblum B.I.: The Role of Foot Surgery in Patients with Diabetes. Clin Podiat Med Surg, 12: 119-127, 1995.

11.  Sammarco G.J., Conti S.F.: Surgical Treatment of Neuroarthropathic Foot Deformity. Foot Ankle Int, 19: 102-109, 1998.

12.  Mitchell, J.R., Johnson, J.E., Collier, B.D., Gould, J.S. Stress Fracture of the Tibia following Extensive Hindfoot and Ankle Arthrodesis: A Report of three cases. Foot and Ankle International 16: 445-448. 1995

13.  Cleveland, M. Surgical fusion of unstable joints due to neuropathic disturbance. Am. J. Surg. 43: 580-584. 1939.

14.  Stuart, M.J., Morrey, B.F., Arthrodesis of the diabetic neuropathic ankle joint. Clin. Orthop. 253: 209-211. 1990.

15.  Bono, J.V., Roger, D.J., Jacobs, R.L. Surgical arthrodesis of the neuropathic foot. Salvage procedure. Clin. Orthop. 296: 14-20. 1993

16.  Alvarez, R.G., Barbour, T.M., Perkins, T.D. Tibiocalcaneal arthrodesis for nonbraceable neuropathic ankle deformity. Foot and Ankle International 15: 354-359, 1994

17.  Tisdel, C.L., Marcus, R.E., Heiple, KG. Triple arthrodesis for diabetic peritalar neuroarthropathy. Foot and Ankle International 16: 332-338. 1995

18.  Early, J.S., Hansen, S.T. Surgical reconstruction of the diabetic foot: a salvage approach for midfoot collapse Foot and Ankle Internat. 17: 325-330. 1996

19.  Johnson, J.E., Kennedy, E.J., Shereff, M.J., Patel, N.C., Collier B.D. Prospective study of bone, indium-111 labeled white blood cell, and gallium-67 scanning for the evaluation of osteomyelitis in the diabetic foot. Foot and Ankle 17: 10-16. 1996

20.  Waters R.L., Perry J., Antonelli D., Hislop H.: Energy Cost of Walking of Amputees: The Influence of Level of Amputation. JBJS 58: 42-46, 1976.

21.  Pinzur, M.S., Gold, J., Schwartz, D., Gross, N. Energy demands for walking in Dysvascular amputees as related to the level of amputation. Orthopedics 15: 1033-1037. 1992.

Table 1: Classification System of Eichenholtz¹