ORIGINAL ARTICLES
Personalized Orthoses as a Good Treatment Option for Charcot Neuro-osteoarthropathy of the Foot Maria Luz Gonza´lez Ferna´ndez, PhD* Rosario Morales Lozano, PhD* Carmen Martı´nez Rinco´n, PhD* David Martı´nez Herna´ndez, MD* Background: We sought to assess the biomechanical characteristics of the feet of patients with Charcot neuro-osteoarthropathy and to determine reulceration rates before and after personalized conservative orthotic treatment. Methods: A longitudinal prospective study was performed in 35 patients with Charcot’s foot. Although some patients had a history of ulcers, at the study outset no patient had ulcers. All of the patients underwent biomechanical testing and a radiographic study. A radiophotopodogram was prepared by superimposing an imprint of the sole on a plantar radiograph. Based on the results of these tests, an orthopedic insole was prepared and therapeutic footwear prescribed for each foot. The following variables were compared between the Charcot and unaffected feet: previous ulcers and ulcer sites, reulcerations produced after treatment, type of foot (neuropathic/neuroischemic), ankle mobility, firstray mobility, and relaxed calcaneal stance position. Treatment efficacy was determined by comparing ulcers presenting in patients in the year leading up to the study period and the year in which treatment was received. Results: In a 1-year period, 70 feet received orthotic treatment, of which 41 were Charcot’s feet. Ulceration rates before the study were 73.2% in feet with Charcot’s and 31.0% in those without. After 1 year of wearing the customized orthoses, rates fell significantly to 9.8% in the Charcot feet and 0% in the feet without this condition. Conclusions: Conservative customized orthotic treatment was effective at preventing ulcers and the complications that often lead these patients to surgery. (J Am Podiatr Med Assoc 104(4): 375-382, 2014)
Charcot neuro-osteoarthropathy (CN) is a noninfectious, chronic, degenerative disease of the foot.1 Although contributing factors for the disease are still largely unknown, CN has been linked to diseases that involve peripheral neuropathy or repeated trauma to the foot,2,3 and advances have been especially made regarding its etiology and treatment.2,4 Despite CN being considered a rare disease, it is estimated to affect 0.8% to 8% of diabetic patients,2 although its real prevalence in these patients is likely underestimated because many cases are incorrectly diagnosed.2,3,5 Moreover, given the increasing incidence of diabetes worldwide,6,7 we are likely to see a rise in the number of patients presenting with CN. In the diabetic patient, the deformation and destructive process that *Universidad Complutense de Madrid, Madrid, Spain. Corresponding author: Maria Luz Gonza´lez Ferna´ndez, PhD, Universidad Complutense Madrid, Avda Complutense s/n, Madrid, 28240, Spain. (E-mail: [email protected])
induces this disease may give rise to recurrent ulcers or amputations.2,5,8 Despite the many years since the first case of CN was described, its early diagnosis and adequate treatment remain a challenge.2 When treating CN, numerous considerations need to be made,2,3,5 such as how to obtain a stable plantigrade foot,2,9 what should be done if CN is complicated by an ulcer,5,10 and how to avoid its devastating morbidity and diminish mortality.11 This study was designed to assess the biomechanical features of feet with and without CN and then, based on the individual characteristics of each foot, to prescribe a personalized orthopodologic therapeutic option targeted at achieving the structural stability of the foot and, thus, prevent ulcers.
Research Design and Methods A descriptive longitudinal study with 1 year of follow-up was conducted of patients with CN
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associated with several etiologies: diabetic neuropathy in 31 patients (88.6%), leprosy in one (2.9%), and alcoholic neuropathy in three (8.6%). Neuropathy was diagnosed by examining ten sites on the foot using a 5.07/10-g Semmes-Weinstein monofilament (Sensifil-Novalab Ibe´rica, Madrid, Spain) and a neurotensiometer (Horwell 997; Sensifil-Novalab Ibe´rica).12,13 Neuroischemia was defined as an ankle-arm index lower than 0.8.14 The patients were referred from the Diabetic Foot Unit to the Orthopedics Unit of the University Podology Clinic of Universidad Complutense de Madrid (Madrid, Spain) for conservative orthotic treatment as prophylaxis for ulcers. From May 1, 2006 to April 30, 2009, 35 patients with CN were recruited (7 women [20%] and 28 men [80%]); in 6 patients, both feet were affected. Thus, 41 feet were treated (22 right, 19 left) and followed over a 1-year period. Although some patients had a history of ulcers, no patient had an ulcer at the study outset when treatment commenced. Before this study, ulcers in these patients had been treated by conservative surgery or using felt, bandaging, and cast walker boots. However, they had never received orthotic treatment to prevent reulcerations. All of the patients included in the study had been diagnosed as having CN according to a standardized protocol used at the University Podology Clinic based on the clinical and radiologic signs of Eichenholtz.2,10 These signs are used to define different stages (inflammatory or stage 0, progression or stage 1, coalescence or stage 2, and bone remodeling or stage 3). According to these criteria, all of the patients had stage 2 or 3 disease. Patterns of joint involvement were defined using the classification system adapted by Sanders and Frykberg3: involvement of the forefoot joints (pattern I), the ligament of Lisfranc (pattern II), Chopart’s joint (pattern III), the ankle and subtalar joint (pattern IV), and the calcaneus (pattern V). Participants were excluded if at the time of the study they had infections, ulcers, or critical ischemia as defined according to the Fontaine classification.15 The study protocol was approved by the institutional review board of Universidad Complutense de Madrid. Informed written consent was obtained from each patient. All of the patients’ feet were subjected to a biomechanical study. Dorsiflexion of the ankle was measured with the knee flexed and the heel in contact with the ground using a goniometer aligned with the floor (stable arm) according to the method of Bennell et al.16 Dorsiflexion of the first digit was
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also measured using a goniometer, with the stable arm in the medial metatarsal region and the mobile arm in the medial region of the first digit according to the criteria described by Cleland.17 We also determined the calcaneal stance position according to the method of Sobel et al18 by measuring the position of the calcaneal bisection at right angles to the calcaneal stance plane and the Foot Posture Index.19 For each foot, we prepared a radiophotopodogram following a protocol standardized at the University Podology Clinic. An imprint of the sole is first obtained on radiographic paper, and this footprint is superimposed on a plantar radiograph. The radiophotopodogram provides additional information to the pressure points seen on the sole imprint. Thus, at these pressure points we can visualize the bone in a weightbearing position and get an idea of bone quality or whether there has been previous surgery. Besides allowing us to offload the anatomical zone with precision, extra information is provided on the zone where we are going to place pressure. A mold is then prepared using the impression of the sole made in a foam impression box. The individualized orthotic insole was then prepared based on a plaster cast mold on a moccasin shoe when deformity was severe or using the foam impression for a mild deformity. The orthotic insole used was heat-molded ethyl vinyl acetate, 1.5 to 2.0 cm thick, and of varying density according to patient weight. A shock-absorbing material, 6-mm Poron (Rogers Corp, Rogers, Connecticut), was used to off-load selective zones of bone prominences, seeking to maximize stability and evenly distribute plantar pressures across the floor while accommodating the deformity. In 2007, Paton et al20 published the results of a study examining the physical properties of 15 materials used to prevent ulcers in diabetic patients with neuropathy. Of these materials, 6-mm Poron offered the best results, and ethyl vinyl acetate was also cited as a material providing good results. We used this material for the base insole layer and then overlaid the base with further layers of decreasing density. Pieces such as pronation and supination wedges were sometimes needed to distribute pressures in patients requiring stabilization of the rearfoot or offloading of the forefoot. In patients with a large deformity at the medial foot level, the insole was reinforced using a medial prologation that continued until the end of the internal longitudinal arch. This longitudinal inner arch piece was designed to
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accommodate the deformity and was lined with 6mm Poron. Metatarsal off-loading mounds were used in patients with overloading at the plantar metatarsal level. This overloading was clinically identified by detecting callus zones and by quantitative analysis of pressures using a gait interface (footscan 7; RSscan International, Lammerdries, Belgium) 2-mlong F-system at a recording speed of 500 photograms per second. Each foot was prescribed therapeutic footwear with specific features according to the foot deformity, measuring foot width and length with calipers and a foot Heider Mass measurer. According to the algorithm described by Dahmen et al,21 extra-deep shoes were used in patients with a large deformity, and sometimes an anterior rocker was needed for propulsion during the push-off stage of gait.22,23 A descriptive analysis of the characteristics of the feet with and without CN was performed. In affected feet, the CN pattern and previous ulcer sites were recorded. The efficacy of treatment was assessed in terms of the presence or absence of a new ulcer or clinical evidence of an active episode of CN. Multivariate analysis was performed on the 70 feet to identify which factors could be related to a better prognosis in terms of an improved reulceration rate. The following variables were also compared using the Student t test between feet with and without CN: previous ulcers and ulcer sites, reulceration after treatment, type of foot (neuropathic/neuroischemic), ankle mobility, first-digit mobility, and relaxed calcaneal stance position. The McNemar test was used to compare the ulcers in each foot before and after 1 year of wearing the custom orthotic devices. Ulceration rates were calculated for the 1-year period leading up to treatment and for the 1 year of treatment. All of the statistical tests were performed using statistical analysis software (SPSS version 15.0; SPSS Inc, Chicago, Illinois). The level of significance was set at P , .05.
dL. Of the 41 affected feet, 19 (46.3%) had neuropathy and 22 (53.7%) had neuroischemia. The clinical records of the patients revealed that of the 41 feet with CN, 30 had ulcers in the year before the start of the study (ulceration rate, 73.2%), including 36 plantar ulcers. Of the 29 feet without CN, nine had presented plantar ulcers in the year before the study (ulceration rate, 31.0%). These two rates in the feet with and without CN differed significantly (P , .01). Ulcer sites on the feet with and without CN are provided in Table 1. Of the 30 feet with CN and a history of ulcers, 11 (36.7%) had needed conservative surgery involving partial amputations or resections and 19 (63.3%) had received standard wound care to treat their ulcers. No patient had had tendo Achillis lengthening or gastrocnemius recession. In addition, 21 patients (70.0%) had undergone temporary off-loading treatment using orthopedic felt and triple-layer bandages, and nine (30.0%) had been treated with felt, bandaging, and cast walker boots. Of the 11 feet that had not presented ulcers, eight (72.7%) had been treated with total-contact casts and three (27.3%) with standard footwear. The deformities experienced by the 41 feet with CN were collapse of the medial arch in 28 (68.3%), bone protrusion at the medial level with medial convexity in nine (22.0%), and rearfoot pronation and forefoot supination in four (9.8%). Of the unaffected contralateral feet in the 29 patients with only one foot affected, 11 (37.9%) showed subtalar joint pronation, six (20.7%) were flat feet due to inner longitudinal arch collapse, six (20.7%) showed a normal appearance, and five (17.2%) showed subtalar supination, three of which were cavus and one (3.4%) equinovarus. No differTable 1. Previous Ulcers by the Presence or Absence of CN and Ulcer Site Ulcers (No. [%]) Ulcer Site
Feet Feet with CN Without CN
Plantar metatarsal heads
9 (20)
Total
5 (11.1)
14 (31.1) 7 (15.6)
Plantar midfoot
Results In the 35 patients included in the study, CN affected 41 feet. In 6 patients (17.1%), both the right and left feet were affected. The mean 6 SD diabetes duration in the 31 diabetic patients (88.6%) was 20.13 6 12.1 years. Their mean 6 SD glucose level at the study outset was 164.07 6 44.9 mg/dL, and their glycosylated hemoglobin level was 8.5 6 1.8 g/
Medial
7 (15.6)
0
Central
4 (8.9)
0
4 (8.9)
Lateral
3 (6.7)
0
3 (6.7)
Plantar heel (calcaneocuboid) 1 (2.2) Dorsal toes Distal pulp Total
0
1 (2.2)
7 (15.6)
3 (6.7)
10 (22.2)
5 (11.1)
1 (2.2)
6 (13.3)
9 (20)
45 (100)
36 (80)
Abbreviation: CN, Charcot neuro-osteoarthropathy.
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ences were detected in these structural features between feet with and without CN (P . .05). Of the 41 feet with CN, toe flexion deformities were observed in 21 (51.2%) compared with 16 of the 29 feet without CN (55.2%). This difference was, however, not significant (P . .05). Further factors compared between feet with and without CN were the relaxed calcaneal stance position when loaded, dorsiflexion mobility of the ankle, and mobility of the first digit (Table 2). Table 3 provides the bone destruction patterns detected in the 41 feet with CN according to the classification system of Sanders and Frykberg.3 In the 24 feet with CN that presented a varus relaxed calcaneal stance position, this characteristic was found to be correlated with pattern II (P , .05). The study patients (70 feet) were prescribed individualized orthotic treatment. For 28 of the 41 feet with CN, a fenestration was made in the middle plantar zone of the insole to accommodate bone protrusion. This cutout was lined with 6-mm Poron. For nine feet, the medial side of the insole was reinforced with a flap lined with 6-mm Poron inserted with a 6-mm Poron inner lateral arch piece. For four feet, 6-mm Poron was embedded in the Table 2. Measurements Obtained in the Biomechanical Study According to the Presence or Absence of CN Feet (No. [%]) (N ¼ 70) Measurement
Without CN
With CN
Total
Relaxed calcaneal stance position Neutral (08) Valgus (18–58)
5 (7.1)
2 (2.9)
7 (10.0)
14 (20.0)
10 (14.3)
24 (34,3)
Valgus (.68)
3 (4.3)
5 (7.1)
8 (11.4)
Varus (.–18)
7 (10.0)
24 (34.3)
31 (44.3)
29 (41.4)
41 (58.6)
70 (100)
Total Ankle dorsiflexion mobility Normal (208–308) Limited (,198 Rigid (08) Total
4 (5.7)
6 (8.6)
10 (14.3)
22 (31.4)
28 (40.0)
50 (71.4)
3 (4.3)
7 (10.0)
10 (14.3)
29 (41.4)
41 (58.6)
70 (100)
First-ray dorsiflexion mobility Normal (658–508) Limited (,508)
2 (2.9)
2 (2.9)
13 (18.6)
15 (21.4)
4 (5.7) 28 (40)
Rigid (.158)
14 (20)
24 (34.3
38 (54.3)
Total
29 (41.4)
41 (58.6)
70 (100)
Note: P . .05 for all. Abbreviation: CN, Charcot neuro-osteoarthropathy.
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Table 3. Distribution of the Patterns of Bone Destruction Described by Sanders and Frykberg3 in 41 Feet with Charcot Neuro-osteoarthropathy Pattern/Combination
Frequency
Percentage (%)
I
4
9.8
II
3
7.3
III
4
9.8
IV
1
2.4
V
1
2.4
I and II
4
9.8
I and IV
1
2.4
II and III
5
12.2
III and IV
4
9.8
II, III, and IV
5
12.2
I, II, and III
7
17.1
II, III, and V
1
2.4
II, III, IV, and V
1
2.4
41
100
Total
forefoot part of the insole. In all 29 feet without CN, a heat-molded ethyl vinyl acetate insole was used, with 6-mm Poron as the longitudinal arch support; in 23 of these cases, the orthoses included metatarsal mounds. The footwear used in all of the patients was therapeutic; in 28 patients (80.0%), extra-depth shoes with a bilateral anterior rocker were prescribed. One year after personalized orthotic treatment, four reulcerations were produced in the feet with CN. This gave a reulceration rate at 1 year of 9.8% in feet with CN compared with 0% in feet without CN. Finally, the results of a multivariate analysis designed to identify factors indicating an improved prognosis of reulceration in the patients subjected to individualized orthotic treatment are presented as a decision tree (Fig. 1). The decision tree revealed that in 66 feet (94.3%), no reulcerations were produced and in four feet (5.7%), all with CN, reulcerations were produced during personalized orthotic treatment. For the 70 feet, reulceration could be correlated only with having neuroischemia (11.4%) or previous ulcers (22.2%). This finding suggests that patients with neuroischemia and a history of ulcers show a higher risk of reulceration. The descriptive analysis of the four reulcerations revealed that three presented in three of the 28 men (10.7%) and one in one of the seven women (14.3%) included in the study. Of these patients who ulcerated again, 100% were diabetic (three had type
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Figure 1. The decision tree displays the results of a probabilistic analysis in a way that helps identify factors
related to a better prognosis in patients receiving individualized orthotic treatment. The variables entered into the analysis were reulceration after orthotic treatment as the dependent variable and foot condition (neuropathic/neuroischemic), ankle dorsiflexion mobility, first-ray dorsiflexion, previous ulcers, relaxed calcaneal stance position, and presence or absence of Charcot’s disease as the independent variables. 2 and one had type 1 diabetes), with CN, neuroischemia, and a history of ulcers. The four reulcerations were classed as Wagner type l; three occurred during the first 6 months of treatment. Ulcer sites were the plantar fifth metatarsal in two cases, the midfoot plantar in a further case, and the lateral plantar in the last foot. Three of the reulcerations occurred in feet with a collapsed arch and varus relaxed calcaneus, and one in a supinated forefoot and relaxed calcaneal stance position that was 68 valgus. The Charcot patterns shown by the feet developing ulcers were one type 1, one type 3, one type 1/2 and one type 2/3/ 4. All four affected feet had limited ankle dorsiflexion mobility, and three showed rigid and one limited mobility of the first ray. Using the McNemar test for paired data, we determined the efficacy of the orthotic treatment regimen by comparing the number of reulcerations recorded in the year preceding treatment (30 ulcerations or affected feet) with those recorded
after treatment (four reulcerations or affected feet) (P , .01).
Discussion These data reveal a higher prevalence of CN in men (80%) than in women (20%), contrasting with other reports24 that have suggested no predilection for either sex. This discrepancy can be explained by the observed greater demand by men for orthopodologic conservative treatment at the University Podology Clinic, although the reason for this needs to be clarified in a future study. The mean 6 SD age of the patients with CN was 57.42 6 9.9 years, similar to that observed in other studies, in which its peak incidence was assigned to the fifth to sixth decades of life25 and diabetes duration was at least 10 years in 80% of patients.26 In the present study, 88.5% of patients showed a mean 6 SD diabetes duration of 20.13 6 12.1 years. Clinical and radiologic assessment of the 70 feet examined revealed that 17.1% of the cases were
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bilateral. This contrasts with the 9%27 reported in the literature, although several retrospective studies have identified up to 75% of cases of bilateral involvement by computed tomography.28 When the feet were stratified according to whether they had Charcot’s disease (58.6%) or not (41.4%), an ulceration rate of 73.2% was recorded for the feet with CN, which is clearly higher than the 31.0% observed for the unaffected feet. As argued by other researchers,5,9,29 we understand that the Charcot foot has a greater risk of developing ulcers than the unaffected foot owing to its greater deformities and larger number of pressure points. Moreover, a high susceptibility to ulceration poses a significant risk of a need for amputation,9 with repercussions for the integrity of the patient’s foot. This suggests that the risk of reulceration can be reduced by an orthopodologic treatment regimen that is able to maintain the foot in a plantigrade position with pressures well distributed.2,11 The present findings indicate that 1 year of personalized orthotic treatment was able to reduce the ulceration rate to 9.8% after a year in feet with CN and to 0% in feet without CN. This finding suggests that feet with CN receiving personalized orthotic treatment show a lower risk of reulceration. Indeed, ulcer prevention is critical for the recovery of complications derived from Charcot’s foot.9 All of the lesions produced during orthotic treatment occurred in diabetic patients with neuroischemic feet and a history of ulcers. As also mentioned by other investigators,2,29 we consider that the affected anatomical region is a determining factor for disease prognosis. However, we found it difficult to classify patterns of CN using the standard classification scheme4 because few patients presented a single pattern: 13 feet (31.7%) versus 28 feet (68.3%) being classified as showing mixed patterns. As in other reports,29 the most frequent presentation site of CN was the midfoot, especially the type 2 pattern. In contrast, in the present patients, besides type 2, we observed patients with combinations of different patterns, as may be seen in Table 2. This pattern (type 2) determines that the foot loses its normal architecture: the internal arch collapses and the forefoot abducts. In this type of foot, it is common to observe ulcers, soft-tissue infection, osteomyelitis, and even partial or complete foot amputations.11 In the present patients, three of the four reulcerations occurred in feet with a collapsed medial arch and a varus relaxed
380
calcaneal stance position. This type of foot shows the greatest risk of developing plantar ulcers.30 Of the 41 feet with Charcot’s disease, 58.5% were significantly correlated with a varus relaxed calcaneal stance position (P , .05). We have found no literature report with which to compare this finding. A possible explanation could be that arthrosis of the subtalar joint caused by CN could gradually modify its position as the biomechanics of the foot adapts to produce a varus calcaneal stance position. As far as we understand, biomechanically the distribution of pressures along the inner longitudinal arch will be affected by this situation, and this will compromise the stability of the lateral column. In turn, this could modify loads affecting the highest point of the arch and, thus, lead to its gradual collapse. The soft parts of the foot, the ligaments and tendons, may play an additional role in fixing the deformity, producing an equinus rearfoot in which the peroneal tendons lose their mechanical function. Clarifying this issue in future studies will help approach the treatment of Charcot’s foot before the arch collapses. When we examined the structural features of the foot contralateral to the Charcot foot, no relationship was detected between having CN and presenting a given type or other structural deformity of the unaffected foot. When designing the orthotic treatment, the contralateral foot was always taken into account because this foot will have to support a high amount of stress with possible consequences,2 such as contralateral fracture, which has been estimated to occur in 80% of patients. During this 1-year study, we observed no active CN episodes or contralateral fractures. The decision to undertake orthopodologic treatment based on off-loading pressures of the CN foot depends on numerous factors,2,5,6 such as clinical state, localization, and level of deformity, along with patient comorbidities.2,31 Several researchers describe orthotic treatments,1 but few studies have proposed different material and design options for orthotic devices. Some investigators2 have indicated the need for therapeutic footwear with customized modifications and reinforcement at the hindfoot. Others26,31,32 have reported that the use of therapeutic shoes in disease stage 32,10 with a rigid rod and a plantar rocker to reduce instability designed to relieve high pressures can provide joint stability and accommodate any existing deformity, such that gradual weightbearing by the affected foot carries no risk of ulcer formation or reactivation of CN.32 In this study, we adapted the materials, 6-mm
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Poron and heat-molded ethyl vinyl acetate, to the patient’s foot deformity in the form of an insole and chose the therapeutic footwear according to the foot architecture of each patient. As far as we know, the literature lacks a treatment prescription that specifies the different materials used for the insoles. The limitations of this study include the lack of a control group of untreated patients. As control data, we used retrospective data for the study participants corresponding to the year before treatment. A further limitation could be that the unit of analysis was the foot rather the patient. However, the design used served to provide information regarding the contralateral foot in patients with unilateral disease. The findings of this study suggest that conservative management involving personalized orthotic treatment based on off-loading insoles and therapeutic footwear according to the foot deformity is the best initial option in patients with CN, without forgetting to also consider the contralateral unaffected foot. We would recommend surgical treatment only when there are complications, such as osteomyelitis of a deformity, or when feet, given their deformity, cannot adapt to orthotic treatment. Indeed, conservative orthotic treatment of CN using accommodative methods has been reported to offer good outcomes, often avoiding the need for surgery.33 Acknowledgment: The staff of the University Podology Clinic, Universidad Complutense de Madrid, for their cooperation and Ana Burton, BSc, for translating the original manuscript. Financial Disclosure: None reported. Conflict of Interest: None reported.
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neuroarthropathy in diabetes mellitus. Diabetologia 45: 1085, 2002. PAKARINEN TK, LAINE HJ, MAENPAA H, ET AL: Long-term outcome and quality of life in patients with Charcot foot. Foot Ankle Surg 15: 187, 2009. VAN DER VEN A, CHAPMAN CB, BOWKER JH: Charcot neuroarthropathy of the foot and ankle. J Am Acad Orthop Surg 17: 562, 2009. PETROVA NL, EDMONDS ME: Charcot neuro-osteoarthropathy-current standards. Diabetes Metab Res Rev 24 (suppl 1): S58, 2008. PINZUR M: Surgical versus accommodative treatment for Charcot arthropathy of the midfoot. Foot Ankle Int 25: 545, 2004.
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Personalized Orthoses as a Good Treatment Option for Charcot Neuro-osteoarthropathy of the Foot Maria Luz Gonza´lez Ferna´ndez, PhD* Rosario Morales Lozano, PhD* Carmen Martı´nez Rinco´n, PhD* David Martı´nez Herna´ndez, MD* Background: We sought to assess the biomechanical characteristics of the feet of patients with Charcot neuro-osteoarthropathy and to determine reulceration rates before and after personalized conservative orthotic treatment. Methods: A longitudinal prospective study was performed in 35 patients with Charcot’s foot. Although some patients had a history of ulcers, at the study outset no patient had ulcers. All of the patients underwent biomechanical testing and a radiographic study. A radiophotopodogram was prepared by superimposing an imprint of the sole on a plantar radiograph. Based on the results of these tests, an orthopedic insole was prepared and therapeutic footwear prescribed for each foot. The following variables were compared between the Charcot and unaffected feet: previous ulcers and ulcer sites, reulcerations produced after treatment, type of foot (neuropathic/neuroischemic), ankle mobility, firstray mobility, and relaxed calcaneal stance position. Treatment efficacy was determined by comparing ulcers presenting in patients in the year leading up to the study period and the year in which treatment was received. Results: In a 1-year period, 70 feet received orthotic treatment, of which 41 were Charcot’s feet. Ulceration rates before the study were 73.2% in feet with Charcot’s and 31.0% in those without. After 1 year of wearing the customized orthoses, rates fell significantly to 9.8% in the Charcot feet and 0% in the feet without this condition. Conclusions: Conservative customized orthotic treatment was effective at preventing ulcers and the complications that often lead these patients to surgery. (J Am Podiatr Med Assoc 104(4): 375-382, 2014)
Charcot neuro-osteoarthropathy (CN) is a noninfectious, chronic, degenerative disease of the foot.1 Although contributing factors for the disease are still largely unknown, CN has been linked to diseases that involve peripheral neuropathy or repeated trauma to the foot,2,3 and advances have been especially made regarding its etiology and treatment.2,4 Despite CN being considered a rare disease, it is estimated to affect 0.8% to 8% of diabetic patients,2 although its real prevalence in these patients is likely underestimated because many cases are incorrectly diagnosed.2,3,5 Moreover, given the increasing incidence of diabetes worldwide,6,7 we are likely to see a rise in the number of patients presenting with CN. In the diabetic patient, the deformation and destructive process that *Universidad Complutense de Madrid, Madrid, Spain. Corresponding author: Maria Luz Gonza´lez Ferna´ndez, PhD, Universidad Complutense Madrid, Avda Complutense s/n, Madrid, 28240, Spain. (E-mail: [email protected])
induces this disease may give rise to recurrent ulcers or amputations.2,5,8 Despite the many years since the first case of CN was described, its early diagnosis and adequate treatment remain a challenge.2 When treating CN, numerous considerations need to be made,2,3,5 such as how to obtain a stable plantigrade foot,2,9 what should be done if CN is complicated by an ulcer,5,10 and how to avoid its devastating morbidity and diminish mortality.11 This study was designed to assess the biomechanical features of feet with and without CN and then, based on the individual characteristics of each foot, to prescribe a personalized orthopodologic therapeutic option targeted at achieving the structural stability of the foot and, thus, prevent ulcers.
Research Design and Methods A descriptive longitudinal study with 1 year of follow-up was conducted of patients with CN
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associated with several etiologies: diabetic neuropathy in 31 patients (88.6%), leprosy in one (2.9%), and alcoholic neuropathy in three (8.6%). Neuropathy was diagnosed by examining ten sites on the foot using a 5.07/10-g Semmes-Weinstein monofilament (Sensifil-Novalab Ibe´rica, Madrid, Spain) and a neurotensiometer (Horwell 997; Sensifil-Novalab Ibe´rica).12,13 Neuroischemia was defined as an ankle-arm index lower than 0.8.14 The patients were referred from the Diabetic Foot Unit to the Orthopedics Unit of the University Podology Clinic of Universidad Complutense de Madrid (Madrid, Spain) for conservative orthotic treatment as prophylaxis for ulcers. From May 1, 2006 to April 30, 2009, 35 patients with CN were recruited (7 women [20%] and 28 men [80%]); in 6 patients, both feet were affected. Thus, 41 feet were treated (22 right, 19 left) and followed over a 1-year period. Although some patients had a history of ulcers, no patient had an ulcer at the study outset when treatment commenced. Before this study, ulcers in these patients had been treated by conservative surgery or using felt, bandaging, and cast walker boots. However, they had never received orthotic treatment to prevent reulcerations. All of the patients included in the study had been diagnosed as having CN according to a standardized protocol used at the University Podology Clinic based on the clinical and radiologic signs of Eichenholtz.2,10 These signs are used to define different stages (inflammatory or stage 0, progression or stage 1, coalescence or stage 2, and bone remodeling or stage 3). According to these criteria, all of the patients had stage 2 or 3 disease. Patterns of joint involvement were defined using the classification system adapted by Sanders and Frykberg3: involvement of the forefoot joints (pattern I), the ligament of Lisfranc (pattern II), Chopart’s joint (pattern III), the ankle and subtalar joint (pattern IV), and the calcaneus (pattern V). Participants were excluded if at the time of the study they had infections, ulcers, or critical ischemia as defined according to the Fontaine classification.15 The study protocol was approved by the institutional review board of Universidad Complutense de Madrid. Informed written consent was obtained from each patient. All of the patients’ feet were subjected to a biomechanical study. Dorsiflexion of the ankle was measured with the knee flexed and the heel in contact with the ground using a goniometer aligned with the floor (stable arm) according to the method of Bennell et al.16 Dorsiflexion of the first digit was
376
also measured using a goniometer, with the stable arm in the medial metatarsal region and the mobile arm in the medial region of the first digit according to the criteria described by Cleland.17 We also determined the calcaneal stance position according to the method of Sobel et al18 by measuring the position of the calcaneal bisection at right angles to the calcaneal stance plane and the Foot Posture Index.19 For each foot, we prepared a radiophotopodogram following a protocol standardized at the University Podology Clinic. An imprint of the sole is first obtained on radiographic paper, and this footprint is superimposed on a plantar radiograph. The radiophotopodogram provides additional information to the pressure points seen on the sole imprint. Thus, at these pressure points we can visualize the bone in a weightbearing position and get an idea of bone quality or whether there has been previous surgery. Besides allowing us to offload the anatomical zone with precision, extra information is provided on the zone where we are going to place pressure. A mold is then prepared using the impression of the sole made in a foam impression box. The individualized orthotic insole was then prepared based on a plaster cast mold on a moccasin shoe when deformity was severe or using the foam impression for a mild deformity. The orthotic insole used was heat-molded ethyl vinyl acetate, 1.5 to 2.0 cm thick, and of varying density according to patient weight. A shock-absorbing material, 6-mm Poron (Rogers Corp, Rogers, Connecticut), was used to off-load selective zones of bone prominences, seeking to maximize stability and evenly distribute plantar pressures across the floor while accommodating the deformity. In 2007, Paton et al20 published the results of a study examining the physical properties of 15 materials used to prevent ulcers in diabetic patients with neuropathy. Of these materials, 6-mm Poron offered the best results, and ethyl vinyl acetate was also cited as a material providing good results. We used this material for the base insole layer and then overlaid the base with further layers of decreasing density. Pieces such as pronation and supination wedges were sometimes needed to distribute pressures in patients requiring stabilization of the rearfoot or offloading of the forefoot. In patients with a large deformity at the medial foot level, the insole was reinforced using a medial prologation that continued until the end of the internal longitudinal arch. This longitudinal inner arch piece was designed to
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accommodate the deformity and was lined with 6mm Poron. Metatarsal off-loading mounds were used in patients with overloading at the plantar metatarsal level. This overloading was clinically identified by detecting callus zones and by quantitative analysis of pressures using a gait interface (footscan 7; RSscan International, Lammerdries, Belgium) 2-mlong F-system at a recording speed of 500 photograms per second. Each foot was prescribed therapeutic footwear with specific features according to the foot deformity, measuring foot width and length with calipers and a foot Heider Mass measurer. According to the algorithm described by Dahmen et al,21 extra-deep shoes were used in patients with a large deformity, and sometimes an anterior rocker was needed for propulsion during the push-off stage of gait.22,23 A descriptive analysis of the characteristics of the feet with and without CN was performed. In affected feet, the CN pattern and previous ulcer sites were recorded. The efficacy of treatment was assessed in terms of the presence or absence of a new ulcer or clinical evidence of an active episode of CN. Multivariate analysis was performed on the 70 feet to identify which factors could be related to a better prognosis in terms of an improved reulceration rate. The following variables were also compared using the Student t test between feet with and without CN: previous ulcers and ulcer sites, reulceration after treatment, type of foot (neuropathic/neuroischemic), ankle mobility, first-digit mobility, and relaxed calcaneal stance position. The McNemar test was used to compare the ulcers in each foot before and after 1 year of wearing the custom orthotic devices. Ulceration rates were calculated for the 1-year period leading up to treatment and for the 1 year of treatment. All of the statistical tests were performed using statistical analysis software (SPSS version 15.0; SPSS Inc, Chicago, Illinois). The level of significance was set at P , .05.
dL. Of the 41 affected feet, 19 (46.3%) had neuropathy and 22 (53.7%) had neuroischemia. The clinical records of the patients revealed that of the 41 feet with CN, 30 had ulcers in the year before the start of the study (ulceration rate, 73.2%), including 36 plantar ulcers. Of the 29 feet without CN, nine had presented plantar ulcers in the year before the study (ulceration rate, 31.0%). These two rates in the feet with and without CN differed significantly (P , .01). Ulcer sites on the feet with and without CN are provided in Table 1. Of the 30 feet with CN and a history of ulcers, 11 (36.7%) had needed conservative surgery involving partial amputations or resections and 19 (63.3%) had received standard wound care to treat their ulcers. No patient had had tendo Achillis lengthening or gastrocnemius recession. In addition, 21 patients (70.0%) had undergone temporary off-loading treatment using orthopedic felt and triple-layer bandages, and nine (30.0%) had been treated with felt, bandaging, and cast walker boots. Of the 11 feet that had not presented ulcers, eight (72.7%) had been treated with total-contact casts and three (27.3%) with standard footwear. The deformities experienced by the 41 feet with CN were collapse of the medial arch in 28 (68.3%), bone protrusion at the medial level with medial convexity in nine (22.0%), and rearfoot pronation and forefoot supination in four (9.8%). Of the unaffected contralateral feet in the 29 patients with only one foot affected, 11 (37.9%) showed subtalar joint pronation, six (20.7%) were flat feet due to inner longitudinal arch collapse, six (20.7%) showed a normal appearance, and five (17.2%) showed subtalar supination, three of which were cavus and one (3.4%) equinovarus. No differTable 1. Previous Ulcers by the Presence or Absence of CN and Ulcer Site Ulcers (No. [%]) Ulcer Site
Feet Feet with CN Without CN
Plantar metatarsal heads
9 (20)
Total
5 (11.1)
14 (31.1) 7 (15.6)
Plantar midfoot
Results In the 35 patients included in the study, CN affected 41 feet. In 6 patients (17.1%), both the right and left feet were affected. The mean 6 SD diabetes duration in the 31 diabetic patients (88.6%) was 20.13 6 12.1 years. Their mean 6 SD glucose level at the study outset was 164.07 6 44.9 mg/dL, and their glycosylated hemoglobin level was 8.5 6 1.8 g/
Medial
7 (15.6)
0
Central
4 (8.9)
0
4 (8.9)
Lateral
3 (6.7)
0
3 (6.7)
Plantar heel (calcaneocuboid) 1 (2.2) Dorsal toes Distal pulp Total
0
1 (2.2)
7 (15.6)
3 (6.7)
10 (22.2)
5 (11.1)
1 (2.2)
6 (13.3)
9 (20)
45 (100)
36 (80)
Abbreviation: CN, Charcot neuro-osteoarthropathy.
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ences were detected in these structural features between feet with and without CN (P . .05). Of the 41 feet with CN, toe flexion deformities were observed in 21 (51.2%) compared with 16 of the 29 feet without CN (55.2%). This difference was, however, not significant (P . .05). Further factors compared between feet with and without CN were the relaxed calcaneal stance position when loaded, dorsiflexion mobility of the ankle, and mobility of the first digit (Table 2). Table 3 provides the bone destruction patterns detected in the 41 feet with CN according to the classification system of Sanders and Frykberg.3 In the 24 feet with CN that presented a varus relaxed calcaneal stance position, this characteristic was found to be correlated with pattern II (P , .05). The study patients (70 feet) were prescribed individualized orthotic treatment. For 28 of the 41 feet with CN, a fenestration was made in the middle plantar zone of the insole to accommodate bone protrusion. This cutout was lined with 6-mm Poron. For nine feet, the medial side of the insole was reinforced with a flap lined with 6-mm Poron inserted with a 6-mm Poron inner lateral arch piece. For four feet, 6-mm Poron was embedded in the Table 2. Measurements Obtained in the Biomechanical Study According to the Presence or Absence of CN Feet (No. [%]) (N ¼ 70) Measurement
Without CN
With CN
Total
Relaxed calcaneal stance position Neutral (08) Valgus (18–58)
5 (7.1)
2 (2.9)
7 (10.0)
14 (20.0)
10 (14.3)
24 (34,3)
Valgus (.68)
3 (4.3)
5 (7.1)
8 (11.4)
Varus (.–18)
7 (10.0)
24 (34.3)
31 (44.3)
29 (41.4)
41 (58.6)
70 (100)
Total Ankle dorsiflexion mobility Normal (208–308) Limited (,198 Rigid (08) Total
4 (5.7)
6 (8.6)
10 (14.3)
22 (31.4)
28 (40.0)
50 (71.4)
3 (4.3)
7 (10.0)
10 (14.3)
29 (41.4)
41 (58.6)
70 (100)
First-ray dorsiflexion mobility Normal (658–508) Limited (,508)
2 (2.9)
2 (2.9)
13 (18.6)
15 (21.4)
4 (5.7) 28 (40)
Rigid (.158)
14 (20)
24 (34.3
38 (54.3)
Total
29 (41.4)
41 (58.6)
70 (100)
Note: P . .05 for all. Abbreviation: CN, Charcot neuro-osteoarthropathy.
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Table 3. Distribution of the Patterns of Bone Destruction Described by Sanders and Frykberg3 in 41 Feet with Charcot Neuro-osteoarthropathy Pattern/Combination
Frequency
Percentage (%)
I
4
9.8
II
3
7.3
III
4
9.8
IV
1
2.4
V
1
2.4
I and II
4
9.8
I and IV
1
2.4
II and III
5
12.2
III and IV
4
9.8
II, III, and IV
5
12.2
I, II, and III
7
17.1
II, III, and V
1
2.4
II, III, IV, and V
1
2.4
41
100
Total
forefoot part of the insole. In all 29 feet without CN, a heat-molded ethyl vinyl acetate insole was used, with 6-mm Poron as the longitudinal arch support; in 23 of these cases, the orthoses included metatarsal mounds. The footwear used in all of the patients was therapeutic; in 28 patients (80.0%), extra-depth shoes with a bilateral anterior rocker were prescribed. One year after personalized orthotic treatment, four reulcerations were produced in the feet with CN. This gave a reulceration rate at 1 year of 9.8% in feet with CN compared with 0% in feet without CN. Finally, the results of a multivariate analysis designed to identify factors indicating an improved prognosis of reulceration in the patients subjected to individualized orthotic treatment are presented as a decision tree (Fig. 1). The decision tree revealed that in 66 feet (94.3%), no reulcerations were produced and in four feet (5.7%), all with CN, reulcerations were produced during personalized orthotic treatment. For the 70 feet, reulceration could be correlated only with having neuroischemia (11.4%) or previous ulcers (22.2%). This finding suggests that patients with neuroischemia and a history of ulcers show a higher risk of reulceration. The descriptive analysis of the four reulcerations revealed that three presented in three of the 28 men (10.7%) and one in one of the seven women (14.3%) included in the study. Of these patients who ulcerated again, 100% were diabetic (three had type
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Figure 1. The decision tree displays the results of a probabilistic analysis in a way that helps identify factors
related to a better prognosis in patients receiving individualized orthotic treatment. The variables entered into the analysis were reulceration after orthotic treatment as the dependent variable and foot condition (neuropathic/neuroischemic), ankle dorsiflexion mobility, first-ray dorsiflexion, previous ulcers, relaxed calcaneal stance position, and presence or absence of Charcot’s disease as the independent variables. 2 and one had type 1 diabetes), with CN, neuroischemia, and a history of ulcers. The four reulcerations were classed as Wagner type l; three occurred during the first 6 months of treatment. Ulcer sites were the plantar fifth metatarsal in two cases, the midfoot plantar in a further case, and the lateral plantar in the last foot. Three of the reulcerations occurred in feet with a collapsed arch and varus relaxed calcaneus, and one in a supinated forefoot and relaxed calcaneal stance position that was 68 valgus. The Charcot patterns shown by the feet developing ulcers were one type 1, one type 3, one type 1/2 and one type 2/3/ 4. All four affected feet had limited ankle dorsiflexion mobility, and three showed rigid and one limited mobility of the first ray. Using the McNemar test for paired data, we determined the efficacy of the orthotic treatment regimen by comparing the number of reulcerations recorded in the year preceding treatment (30 ulcerations or affected feet) with those recorded
after treatment (four reulcerations or affected feet) (P , .01).
Discussion These data reveal a higher prevalence of CN in men (80%) than in women (20%), contrasting with other reports24 that have suggested no predilection for either sex. This discrepancy can be explained by the observed greater demand by men for orthopodologic conservative treatment at the University Podology Clinic, although the reason for this needs to be clarified in a future study. The mean 6 SD age of the patients with CN was 57.42 6 9.9 years, similar to that observed in other studies, in which its peak incidence was assigned to the fifth to sixth decades of life25 and diabetes duration was at least 10 years in 80% of patients.26 In the present study, 88.5% of patients showed a mean 6 SD diabetes duration of 20.13 6 12.1 years. Clinical and radiologic assessment of the 70 feet examined revealed that 17.1% of the cases were
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bilateral. This contrasts with the 9%27 reported in the literature, although several retrospective studies have identified up to 75% of cases of bilateral involvement by computed tomography.28 When the feet were stratified according to whether they had Charcot’s disease (58.6%) or not (41.4%), an ulceration rate of 73.2% was recorded for the feet with CN, which is clearly higher than the 31.0% observed for the unaffected feet. As argued by other researchers,5,9,29 we understand that the Charcot foot has a greater risk of developing ulcers than the unaffected foot owing to its greater deformities and larger number of pressure points. Moreover, a high susceptibility to ulceration poses a significant risk of a need for amputation,9 with repercussions for the integrity of the patient’s foot. This suggests that the risk of reulceration can be reduced by an orthopodologic treatment regimen that is able to maintain the foot in a plantigrade position with pressures well distributed.2,11 The present findings indicate that 1 year of personalized orthotic treatment was able to reduce the ulceration rate to 9.8% after a year in feet with CN and to 0% in feet without CN. This finding suggests that feet with CN receiving personalized orthotic treatment show a lower risk of reulceration. Indeed, ulcer prevention is critical for the recovery of complications derived from Charcot’s foot.9 All of the lesions produced during orthotic treatment occurred in diabetic patients with neuroischemic feet and a history of ulcers. As also mentioned by other investigators,2,29 we consider that the affected anatomical region is a determining factor for disease prognosis. However, we found it difficult to classify patterns of CN using the standard classification scheme4 because few patients presented a single pattern: 13 feet (31.7%) versus 28 feet (68.3%) being classified as showing mixed patterns. As in other reports,29 the most frequent presentation site of CN was the midfoot, especially the type 2 pattern. In contrast, in the present patients, besides type 2, we observed patients with combinations of different patterns, as may be seen in Table 2. This pattern (type 2) determines that the foot loses its normal architecture: the internal arch collapses and the forefoot abducts. In this type of foot, it is common to observe ulcers, soft-tissue infection, osteomyelitis, and even partial or complete foot amputations.11 In the present patients, three of the four reulcerations occurred in feet with a collapsed medial arch and a varus relaxed
380
calcaneal stance position. This type of foot shows the greatest risk of developing plantar ulcers.30 Of the 41 feet with Charcot’s disease, 58.5% were significantly correlated with a varus relaxed calcaneal stance position (P , .05). We have found no literature report with which to compare this finding. A possible explanation could be that arthrosis of the subtalar joint caused by CN could gradually modify its position as the biomechanics of the foot adapts to produce a varus calcaneal stance position. As far as we understand, biomechanically the distribution of pressures along the inner longitudinal arch will be affected by this situation, and this will compromise the stability of the lateral column. In turn, this could modify loads affecting the highest point of the arch and, thus, lead to its gradual collapse. The soft parts of the foot, the ligaments and tendons, may play an additional role in fixing the deformity, producing an equinus rearfoot in which the peroneal tendons lose their mechanical function. Clarifying this issue in future studies will help approach the treatment of Charcot’s foot before the arch collapses. When we examined the structural features of the foot contralateral to the Charcot foot, no relationship was detected between having CN and presenting a given type or other structural deformity of the unaffected foot. When designing the orthotic treatment, the contralateral foot was always taken into account because this foot will have to support a high amount of stress with possible consequences,2 such as contralateral fracture, which has been estimated to occur in 80% of patients. During this 1-year study, we observed no active CN episodes or contralateral fractures. The decision to undertake orthopodologic treatment based on off-loading pressures of the CN foot depends on numerous factors,2,5,6 such as clinical state, localization, and level of deformity, along with patient comorbidities.2,31 Several researchers describe orthotic treatments,1 but few studies have proposed different material and design options for orthotic devices. Some investigators2 have indicated the need for therapeutic footwear with customized modifications and reinforcement at the hindfoot. Others26,31,32 have reported that the use of therapeutic shoes in disease stage 32,10 with a rigid rod and a plantar rocker to reduce instability designed to relieve high pressures can provide joint stability and accommodate any existing deformity, such that gradual weightbearing by the affected foot carries no risk of ulcer formation or reactivation of CN.32 In this study, we adapted the materials, 6-mm
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Poron and heat-molded ethyl vinyl acetate, to the patient’s foot deformity in the form of an insole and chose the therapeutic footwear according to the foot architecture of each patient. As far as we know, the literature lacks a treatment prescription that specifies the different materials used for the insoles. The limitations of this study include the lack of a control group of untreated patients. As control data, we used retrospective data for the study participants corresponding to the year before treatment. A further limitation could be that the unit of analysis was the foot rather the patient. However, the design used served to provide information regarding the contralateral foot in patients with unilateral disease. The findings of this study suggest that conservative management involving personalized orthotic treatment based on off-loading insoles and therapeutic footwear according to the foot deformity is the best initial option in patients with CN, without forgetting to also consider the contralateral unaffected foot. We would recommend surgical treatment only when there are complications, such as osteomyelitis of a deformity, or when feet, given their deformity, cannot adapt to orthotic treatment. Indeed, conservative orthotic treatment of CN using accommodative methods has been reported to offer good outcomes, often avoiding the need for surgery.33 Acknowledgment: The staff of the University Podology Clinic, Universidad Complutense de Madrid, for their cooperation and Ana Burton, BSc, for translating the original manuscript. Financial Disclosure: None reported. Conflict of Interest: None reported.
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July/August 2014 Vol 104 No 4 Journal of the American Podiatric Medical Association
