A Guide To Bracing For Charcot
Charcot neuroarthropathy is a progressive deterioration of a joint characterized by a loss of sensation. When left untreated, this condition can lead to pathological fractures, joint dislocation/subluxation and deformity. This condition reportedly affects an estimated 0.8 percent to 7.5 percent of people with diabetes. The prevalence of this condition increases dramatically among patients with diabetes and peripheral neuropathy, ranging from 29 to 35 percent in this specific population.1,2 However, this disorder is not limited to patients with diabetes as it can also afflict patients with other neurological disorders such as syringomyelia, congenital insensitivity to pain, leprosy, syphilis, myelomeningocele and alcoholic neuropathy. The exact pathogenesis of this condition is unknown, but there are two leading theories. The neurotraumatic theory hypothesizes that the neuropathic foot is subjected to repetitive microtrauma, which leads to progressive destruction and deformity. The neurovascular theory hypothesizes that autonomic dysfunction leads to arteriovenous shunting and demineralization of bone. However, Charcot is more likely to result from a combination of the two. Early diagnosis and initiation of treatment is crucial for the patient with acute Charcot. The goal of treatment is maintaining a stable foot (i.e., one that has no tendency to subluxate or dislocate without support) and ensuring that it fits in a shoe or brace without a tendency to recurrent ulceration and infection.3 In the acute setting, nonweightbearing of the affected extremity is recommended until there is resolution of edema and radiographic evidence of coalescence. However, there is a difference in opinion on the best way to accomplish this. While nonweightbearing is the gold standard of treatment for acute Charcot, one must consider many variables before initiating treatment for those with chronic Charcot. These factors include the degree of deformity, abnormal foot and ankle mechanics, patient compliance and satisfaction, and the presence of concurrent ulceration. Custom footwear and bracing devices are important considerations for patients with Charcot but one must choose from a wide variety of bracing devices and footwear that are currently available. Ideally, these devices should help protect the extremity from repetitive microtrauma, prevent skin breakdown or recurrence of the disease process, supplement wound healing of any ulcerations and assist the patient during ambulation. The choice of the device or shoe will change according to the stage of disease. Additionally, one must decide when it is appropriate to treat with over-the-counter (OTC) prefabricated devices/shoes versus custom-made devices. For the purposes of this article, we will assume the majority of patients have some degree of osseous deformity present. When this is the case, choosing an appropriate device is dependent upon the degree of deformity and its location. If you recognize the disease process early and promptly initiate treatment, the hope is that only minimal changes have occurred to the architecture of the foot and ankle. However, you often may see a patient present with an advanced stage of the disease and significant deformity. One may have to sacrifice functional stability of an orthosis in order to accommodate for this deformity. What The Literature Reveals About Total Contact Casting Total contact casting (TCC) is currently the mainstay of treatment for acute Charcot. Pinzur, et. al., found that TCC was the initial treatment for 49 percent of patients treated for acute Charcot.4 The effectiveness of this cast lies in its ability to reduce plantar pressures, which is accomplished by spreading the weightbearing forces over an increased surface area of the leg and foot.5 Lavery, et. al., found TCC to be the most effective modality for reducing forefoot pressures, citing up to an 84 percent decrease.6 A separate investigation demonstrated the average forefoot pressure in a TCC was 4.47 N/cm2 compared to 12.96 N/cm2 in a running shoe.7 Another advantage of using the TCC is the ability to almost ensure patient compliance. On the downside, the TCC requires a skilled technician and a relatively long application time with numerous applications needed over the duration of healing. The TCC also tends to be unpopular with patients. Furthermore, there is no predetermined duration of treatment. It is agreed the patient should remain in the TCC until the developmental stage (Eichenholz Stage I) has resolved and radiographic evidence of coalescence occurs (Eichenholz Stage II). However, this period can vary considerably from patient to patient. Armstrong, et. al., introduced the “Instant Total Contact Cast”in an attempt to help ensure patient compliance.8 They quoted an earlier study in which an Internet-based continuous activity monitor showed only 15 percent of patients wore their protective shoe gear at home, where they conducted more than 50 percent of their daily activity.9 This technique rapidly converts a removable cast walker to one that is less easily removed. They stated that you can use any removable cast walker for this technique and should apply the cast in the following manner.8 If warranted, you may apply cast padding to the patient’s leg. Then proceed to apply two layers of 4-inch cohesive bandage or plaster of Paris around the removable cast walker. Where Do Diabetic Boots Fit Into The Equation? Bledsoe Brace Systems recently introduced the Bledsoe Conformer Diabetic Boot. This boot features a fully enclosed, thick but breathable foam cocoon, which encases the foot and lower leg to provide maximum protection. The boot also features a unique Automold™ Dual Density footbed, which is designed to distribute body weight evenly across the entire bottom surface of the foot and up to 1 inch high on all sides of the foot. While the Charcot condition is not a contraindication for the Bledsoe Conformer Diabetic Boot, excessive deviation in shape and size from the normal anatomy is a contraindication. Therefore, if the patient has the beginning of Charcot without too much deformity, one may recommend the Conformer Boot for supporting the arch in an attempt to prevent the formation of a rocker bottom foot. However, if the foot has already become subluxed, the boot should not be used as excess pressure is likely to develop in the misfitted areas. Pollo, et. al., compared plantar pressures in fiberglass TCCs versus the Bledsoe Conformer Diabetic Boot.10 They showed at statistically significant levels that those wearing the boot had a greater reduction of peak pressure, maximum force and pressure time interval than those who wore the TCC. However, these findings were based on healthy individuals who did not have clinical foot deformity.10 Is The CROW A Viable Alternative To TCC For Acute Charcot? The Charcot Restraint Orthotic Walker (CROW) is a custom ankle-foot orthosis (AFO) prescribed for patients with distal sensory neuropathy and foot ulceration. One may employ this device during the remodeling stage of the disease in order to support the osteoarticular structures of the foot and ankle, and prevent further destruction of the architecture to the extremity. The CROW may be an effective alternative for the patient who cannot tolerate a TCC due to claustrophobia or a highly exudative wound that requires frequent dressing changes. In a study of 18 patients, Morgan, et. al., reported all patients rated their satisfaction with the CROW as good to excellent.11 They added that no one reported significant activity restrictions and all believed that their lifestyle was markedly improved by the CROW in comparison to cast immobilization. This bivalved orthosis covers the entire foot and leg. The boot is lined with perforated Plastazote® to provide cushioning and ventilation. The plantar surface of the foot is lined with a PPT shock-absorbing innersole and a rocker sole accommodates a solid ankle construct. When casting for a CROW, you usually want the patient to be seated with the leg 90 degrees to the thigh and the foot resting on a casting pad or platform in a semi-weightbearing fashion. Place the extremity in the angle and base of gait. When it comes to obtaining the best impression of the foot and leg, one should use either traditional plaster of Paris or an STS Bermuda Sock. Avoid using fiberglass as it usually does not sufficiently capture the anatomical landmarks of the extremity. Keep in mind that the CROW often needs additional modifications. If you do not have the availability to make changes to the polypropylene or plastazote lining, it might be advisable to refer the patient to a local orthotist or pedorthist. Can The Functional Foot Orthosis Have An Impact In Cases Of Chronic Charcot? What about devices for treating chronic Charcot neuroarthropathy? One may consider a functional foot orthosis (FFO) when seeking to eliminate the excessive deforming forces placed about the foot and ankle complex, and achieve a plantigrade biomechanically stable foot that is not prone to subluxation. Alternatively, one may use an accommodative orthosis to offload an area of ulceration or bony prominence. However, this can be a problem if the patient has a biomechanical abnormality with plantar ulceration and a rocker bottom foot. Keep in mind that the number of accommodations one makes to an orthotic device in or around the midtarsal joint may compromise the device’s functional stability. Also be aware that orthotic devices with multiple insole layers may require an extra-depth shoe to accommodate for the added bulk and presence of foot deformity. When casting for either a functional or accommodative foot orthosis, one should use either plaster of Paris, impression foam boxes or the STS slipper cast. The casting position for these orthoses is up to you. When Are Custom-Molded Shoes Appropriate? It may be necessary to prescribe either an extra-depth orthopedic shoe or custom molded shoe gear for the patient with varying degrees of bony deformity. Extra-depth shoes are often recommended for patients with mild deformity that requires accommodative insoles. Extra-depth shoes may also be required for patients wearing other devices such as a custom gauntlet AFO, solid AFO or patella tendon bearing brace (PTBB). An extra-depth shoe with a steel shank is recommended for the patient who is wearing a PTBB. The goal of any shoe gear is providing the patient with the ability to ambulate with minimal difficulty. If the bony architecture is so deformed that it cannot be placed in OTC orthopedic shoes, then one should consider custom-molded shoe gear or make a referral to a certified pedorthist. Manufacturers of custom-molded orthopedic shoes can often incorporate supra-malleolar bracing, extended shanks, rigid counters and other modifications to meet the needs of the individual patient. When casting for a custom shoe, you usually want to have the patient seated with his or her leg 90 degrees to the thigh and the foot placed on a casting pad or platform with a 1/2-inch heel elevation. The patient’s foot should be in a semi-weightbearing fashion in the normal angle and base of gait. You can best obtain the impression of the foot and leg with either traditional plaster of Paris in a bivalved technique or an STS Ankle Casting Sock. Again, one should avoid using fiberglass because it fails to accurately capture the anatomical landmarks of the foot and ankle. A Closer Look At The Benefits Of Ankle-Foot Orthoses One may employ a custom gauntlet AFO for the patient who has severe pronation and abnormal foot and ankle mechanics secondary to the destructive nature of Charcot neuroarthropathy. The Total Control Orthosis (TCO) by Langer is a custom-molded AFO that is constructed with a leather outer shell, a lightweight plastic stabilizing heel cup and 1/8-inch Aliplast® foam insert. The TCO’s plastic shell provides maximum control of the foot and ankle complex, and supports the foot in all three planes. The Arizona AFO™ is custom-molded, leather AFO that stabilizes the ankle, talocalcaneal, midtarsal and subtalar joints while providing medial and lateral stability. There is also an Extended Arizona AFO™ available for the “rocker foot.” When it comes to casting for the custom gauntlet AFO, the patient should be seated with the leg 90 degrees to the thigh and the foot placed on a casting pad or platform with a 1/2-inch heel elevation in a semi-weightbearing fashion in the base and angle of gait. In order to obtain the best impression of the foot and leg, one should use traditional plaster of Paris, a STS Mid-Leg Casting Sock or a STS 17-inch Tubular Casting Sock. A solid AFO is indicated for the patient who has severe pronation and subluxation of the STJ and/or ankle joint with instability of the knee joint. Always perform a complete history and physical examination to determine muscle strength and tone, paying particular attention to the quadriceps/hamstrings. You may note genu recurvatum in these patients and a supra-malleolar device will fail to provide needed stability. Therefore, an AFO that extends proximally is indicated. Examples include the aforementioned Extended Arizona AFO and the traditional solid ankle AFO. A solid ankle AFO is typically constructed of polypropylene. This device extends proximally from the mid-gastroc-soleal complex to just proximal to the metatarsal heads. Secure this device to the leg proximally by a velcro strap with added pelite to prevent skin abrasion. Using an extra depth shoe or a custom shoe with a rocker sole in conjunction with a solid AFO is recommended for aiding the propulsive phase of gait. When casting for a solid AFO, have the patient seated with the leg 90 degrees to the thigh and his or her foot placed on a casting pad or platform in a semi-weightbearing fashion in the angle and base of gait. For the best impression of the foot and leg, use either traditional plaster of Paris or an STS Bermuda Sock. A Pertinent Guide To Patellar Tendon Bearing Braces One may employ the patellar tendon bearing brace (PTBB) to offload the distal extremity as the brace redistributes the weightbearing forces you normally see in the foot and ankle to the patellar tendon.11 The PTBB has a laced, molded leather cuff, aluminum uprights and stirrup, leather extra-depth shoes and a custom plastazote insert. Researchers have reported that a properly fitted PTBB reduces mean peak force to the distal extremity by 32 to 90 percent.12 A preliminary study by Saltzman, et. al., found that a properly fitted PTBB could reduce load transmission to the Charcot foot. Specifically, they noted that load transmission was reduced to the hindfoot, but not the midfoot or forefoot.13 This may be a useful alternative to TCC for the patient who has a hindfoot Charcot. Studies have shown that while TCC reduces forefoot pressures by 63.72 percent, loading under the heel is increased 37.09 percent.14 Rubin and Staros believe the results from the Saltzman study would have been quite different if they had fabricated the PTBB orthosis with an absent motion solid ankle rather than with a free motion ankle. They state that any ankle motion will be directly related to a decrease in weight bypass effectiveness.15 Trepman, et. al., described a PTBB orthosis that was modified with a patten-bottom caliper in order to eliminate all weightbearing stresses from the suspended foot while allowing ambulation without crutches.16 They studied six patients who had active Charcot with bony deformity involving the ankle and hindfoot. However, patient compliance was poor for four of the six patients and minor problems with the orthosis included superficial skin breakdown and downward positioning of the leg associated with improper, loose donning.16 Casting for PTBB usually follows the aforementioned protocols and one can obtain the best impression of the foot and leg with either traditional plaster of Paris or an STS Bermuda Sock. Practitioners may want to consult with a certified pedorthist or orthotist who can make the appropriate modifications in the shoe to facilitate acceptance of the double upright steel support. In Conclusion It is of utmost importance to diagnose Charcot neuroarthropathy early and initiate treatment before a significant deformity occurs. Unfortunately, patients often fail to seek treatment until it is too late. Treating these patients can be difficult and there is an array of challenging questions that one must consider when exploring treatment options. When should you allow weightbearing in the acute phase of the disease process? Are prefabricated devices as successful as the TCC in the acute phase? Should you opt for early surgical stabilization or accommodation when the deformity first develops? When treating the late stages of the deformity, should you pursue late reconstruction, accommodation or amputation?6 Currently, there are many different conservative treatment options available to the foot and ankle specialist. However, before you choose a treatment modality, it is essential to pay careful consideration to the degree and location of deformity, biomechanical instability, patient compliance and satisfaction with the device, and the presence of ulceration. Dr. Pollard is a first-year resident within the San Francisco Bay Area Foot and Ankle Residency Program. Dr. Stess is the Chief of Podiatry in the Department of Veterans Affairs Medical Center in San Francisco. He is also the President of STS Company.
References 1. Schon LC, Easley ME, Weinfeld SB. Charcot neuroarthropathy of the foot and ankle. Clin Orthop. 1998 Apr;(349):116-31. 2. Armstrong DC, Todd WF, Lavery LA, Harkless LB, Bushman TR. The natural history of acute Charcot arthropathy in the diabetic foot specialty clinic. Diab. Med. 24: 357, 1997. 3. Myerson MS. Evaluation of diabetic neuroarthropathy guides treatment. Biomechanics, 1999. 4. Pinzur MS, Shields N, Trepman E, Dawson P, Evans A. Current practice patterns in the treatment of Charcot foot. Foot Ankle Int. 2000 Nov;21(11):916-20. Review. PMID: 11103763 5. Dhalla R, Johnson JE, Engsberg J. Can the use of a terminal device augment plantar pressure reduction with a total contact cast? Foot Ankle Int. 2003 Jun;24(6):500-5. 6. Lavery LA, Vela SA, Fleischli JG, Armstrong DG, Lavery DC. Reducing plantar pressure in the neuropathic foot. A comparison of footwear. Diabetes Care. 1997 Nov;20(11):1706-10. PMID: 9353613 7. Fleischli JG, Lavery LA, Vela SA, Ashry H, Lavery DC. Comparison of strategies for reducing pressure at the site of neuropathic ulcers. J Am Podiatr Med Assoc. 1997 Oct;87(10):466-72. PMID: 9351316 8. Armstrong DG, Short B, Espensen EH, Abu-Rumman PL, Nixon BP, Boulton AJ. Technique for fabrication of an “instant total-contact cast” for treatment of neuropathic diabetic foot ulcers. J Am Podiatr Med Assoc. 2002 Jul-Aug;92(7):405-8. PMID: 12122129 9. Armstrong DG, Abu-Rumman PL, Nixon BP, Boulton AJ. Continuous activity monitoring in persons at high risk for diabetes-related lower-extremity amputation. J Am Podiatr Med Assoc. 2001 Oct;91(9):451-5. PMID: 11679626 10. Pollo FE, Brodsky JW, Crenshaw SJ, Kirksey C. Plantar pressures in fiberglass total contact casts vs. a new diabetic walking boot. Foot Ankle Int. 2003 Jan;24(1):45-9. PMID: 12540081 11. Morgan JM, Biehl WC 3rd, Wagner FW Jr. Management of neuropathic arthropathy with the Charcot Restraint Orthotic Walker. Clin Orthop. 1993 Nov;(296):58-63. PMID: 8222450 12. Guse ST, Alvine FG. Treatment of diabetic foot ulcers and Charcot neuroarthropathy using the patellar tendon-bearing brace. Foot Ankle Int. 1997 Oct;18(10):675-7. No abstract available. PMID: 9347309 13. Saltzman CL, Johnson KA, Goldstein RH, Donnelly RE. The patellar tendon-bearing brace as treatment for neurotrophic arthropathy: a dynamic force monitoring study. Foot Ankle. 1992 Jan;13(1):14-21. PMID: 1577336 14. Hartsell HD, Fellner C, Saltzman CL. Pneumatic bracing and total contact casting have equivocal effects on plantar pressure relief. Foot Ankle Int. 2001 Jun;22(6):502-6. PMID: 11475459 15. Rubin G, Staros A, Cohen-Sobel E. The patellar tendon-bearing brace as treatment for neurotropic arthropathy: a dynamic force monitoring study. Foot Ankle Int. 1994 Jan;15(1):56-7. No abstract available. PMID: 7981799 16. Trepman E, Donnelly P. Patellar tendon-bearing, patten-bottom caliper suspension orthosis in active Charcot arthropathy: crutch-free ambulation with no weight bearing in the foot. Foot Ankle Int. 2002 Apr;23(4):335-9. PMID: 11991480