Abstract

Introduction. Foot offloading is the mainstay treatment for plantar diabetic foot ulcers (DFUs). Objective. This multicenter, single-blinded, randomized controlled trial evaluates the efficacy of a total offloading foot brace for healing plantar DFUs.Materials and Methods. Seventeen patients were randomized to standard therapy (ie, reducing stress and pressure via mechanical offloading) or offloading foot brace. Comparison of plantar pressures was performed using digital pressure sensing films. The ulcers were assessed by physical inspection and digital planimetry of photographs. Results. Reductions in peak plantar pressures ranged from 67.3% to 89.4% (P = .09). Healing at weeks 12 to 15 had minimal differences (brace vs. control: 71.7% vs. 80.3%, respectively). Although not significant, earlier periods of the brace versus the control demonstrated faster wound healing in weeks 2 to 5 (36.0% vs. 6.8%, respectively) and weeks 6 to 9 (50.7% vs. 17.0%, respectively). Conclusions. The total offloading foot brace minimizes plantar pressure, allowing for early healing of DFUs, and optimizations in brace design may enhance healing of plantar DFUs. 

Plantar diabetic foot ulcers (DFUs) are a serious burden to both patients and the health care system. Estimates predict the lifetime risk of a patient with diabetes developing a foot ulcer can approach 25%.1 Estimates also predict 50% of these patients will redevelop an ulcer within 3 years.2 As DFU severity worsens, an amputation due to gangrene or other complications may be required. In the United States, more than half of all amputations are associated with diabetes mellitus and its complications.3 

Current plantar DFU treatment focuses on alleviating pressure on contact with the foot. While irremovable total contact casts (TCCs) are considered the treatment gold standard, usage rates remain low.4-6 With the rate of diabetes growing worldwide,2 the prevalence of associated DFUs is expected to increase. Thus, there is a need to explore new treatment modalities. 

In this study, the investigators evaluate an offloading foot brace (Toad Anti-Gravity Brace; Toad Medical Corporation, Carson City, NV) as a new way to completely offload the foot (Figure 1) and determine whether the complete offloading from the foot brace would improve healing rates of plantar DFUs. wounds_0418_kashyap_figure1

MATERIALS AND METHODS

This was a multicenter, single-blinded, randomized controlled trial comparing the offloading foot brace to the current standard of care treatment for plantar DFUs. Following University Hospitals Cleveland Medical Center Institutional Review Board (Cleveland, OH) approval, patients were selected from 2 institutions: University Hospitals Cleveland Medical Center and the Cleveland Clinic (Cleveland, OH). Written informed consent was obtained from all participants prior to study enrollment. All wounds were plantar DFUs; typically, these wounds develop due to a loss of protective sensation following neuropathy.7 Basic demographic information was collected and catalogued. 

Patient inclusion criteria consisted of a University of Texas Grade 1A, 1C, 2A, or 2C wound of at least 2 weeks’ duration and well-controlled diabetes mellitus; hemoglobin A1c was assessed to determine if patients met inclusion criteria during the first office visit, but the values were not recorded in following visits. In addition, absence of limb ischemia was ensured by the presence of palpable pulses, an ankle-brachial index ≥ 0.7, and/or toe pressure > 30 mm Hg. Patients experiencing limb ischemia, active infection, wounds on calf or leg that contacted the offloading foot brace, active Charcot arthropathy, or an inability to ambulate were excluded from the study. 

The control group received routine standard of care (ie, reducing stress and pressure via mechanical offloading8) per a physician’s order. In agreement with this, patients in the control group received an offloading therapeutic shoe; no patient received an irremovable TCC or underwent surgery to correct abnormal biomechanics. 

Before using the offloading foot brace, patients walked barefoot in figure-eight patterns while a force-scanning device recorded their peak plantar pressures (F-Scan System; Tekscan Inc, South Boston, MA). Both the control and experimental groups had their average maximum pressure recorded while not wearing any device at all to allow for the establishment of a baseline pressure. In the experimental group, pressures were then recorded while patients replicated their figure-eight walking patterns while wearing the offloading foot brace. In the control group, the pressure was not recorded while the patient wore the traditional offloading shoe.

During clinic visits, mechanical wound debridement using a sharp scalpel blade to remove all surrounding callus, wound debris, necrotic tissue, fibrin, eschar, and nonviable tissue was performed by the treating physician as necessary. Patients were treated with moist wound therapy using mostly alginate or hydrogel dressings. Compliance with study protocol was assessed at each visit.

After assessment by the treating physician, a digital photograph was taken to document ulcer status. Photographs were taken during the initial patient office visit to establish a baseline and then at follow-up appointments between weeks 2 to 5, weeks 6 to 9, and weeks 12 to 15 of the study period. Detailed analysis of wound healing was determined by blinded, computer-assisted planimetry (BioVisual Technologies, Elmwood Park, NJ). Wound area, length, and width were recorded. Areas of new epithelium or partial-thickness ulceration were excluded from assessment. Ulcers were considered healed once fully epithelialized with no drainage. 

Statistical analysis of continuous variables was performed using 2-tailed paired and unpaired t tests as appropriate. Categorical variables were analyzed by a Fisher’s exact test. A P value of .05 was deemed significant. An a priori power analysis was performed, assuming a 30% difference in wound area between patients assigned to the brace group and those in the control group at the 12-week conclusion. With an α of 0.05 and power of 80%, this suggested 21 patients were required per treatment group. 

RESULTS

Initial study goals aimed to recruit about 70 patients. Following exclusion criteria, 17 patients were enrolled. The exact number of patients who were considered for the study but ruled out based on exclusion criteria was not recorded. Patients were followed for 15 weeks. Overall study data collection spanned from December 13, 2013, to June 1, 2015.

Baseline demographics and clinical variables were collected from the primary referral institution. The investigators observed no statistically significant differences between demographics of the offloading foot brace and control groups. While the offloading foot brace group did have wounds with a smaller initial average surface area compared with the control (1.07 cm2 vs. 1.93 cm2, respectively), determination of healing focused on percentage of the wound healed. Of note, 2 participants (1/group) were removed from the study for failing to adhere to protocol procedure. Of the remaining 15 patients included in the calculations and statistics, 9 received the offloading foot brace and 6 were placed in the control group. 

Plantar pressure measurements were recorded at study initiation. A small subset of patients in both the offloading foot brace and control groups were elicited to provide data. Patients in the control group subset (n = 3) had an average initial plantar pressure of 514.67 kilopascal (kPa), while those in the offloading foot brace group subset (n = 4) had an average initial plantar pressure of 353.75 kPa. Subsequent measurements of brace group members wearing the device demonstrated a nonsignificant finding (P = .09) towards decreased plantar pressures with an average plantar pressure of 62.25 kPa. Overall, reductions in peak plantar pressures ranged from 67.3% to 89.4%.

A nonsignificant trend (Figure 2) was noted, demonstrating increased wound healing in patients assigned to the offloading foot brace group in comparison with the control during follow-up weeks 2 to 5 (36.0% vs. 6.8%, respectively) and weeks 6 to 9 (50.7% vs. 17.0%, respectively). This trend dissipated in weeks 12 to 15 (brace vs. control: 71.7% vs. 80.3%, respectively). Furthermore, the investigators analyzed rates of healing between patients deemed compliant versus noncompliant with study protocol. When stratified by compliance, patients in the compliant subgroup (n = 4) had compliance rates of 75% to 100%. Patients in the noncompliance subgroup (n = 4) had compliance rates of 50% to 75%. A nonsignificant trend favoring increased wound healing in compliant patients was observed. This trend was faint initially at weeks 6 to 9 (compliant vs. noncompliant: 50.8% vs. 52.0%, respectively). However, compliant patient’s trend of improved healing rates strengthened by the study’s conclusion at weeks 12 to 15 (compliant vs. noncompliant: 75.3% vs. 66.8%, respectively). wounds_0418_kashyap_figure2

Patients completed the RAND 36-Item Short-Form Health Survey (SF-36) at both the initiation and conclusion of the study. This allowed for assessment of quality of life improvements. Members of the offloading foot brace group reported improvements in social functioning, emotional well-being, energy, and limitations due to emotional and physical health. 

Upon performance of a futility analysis, the trial was halted early. The results of the analysis showed that continuing patient enrollment was unlikely to make a significant difference in the study’s outcome. 

DISCUSSION

Plantar DFUs are difficult to heal and represent an enormous burden for the patients living with them.1,2,9 Due to the loss of protective pain that accompanies diabetic neuropathy, many patients are unable to detect repeated traumas to their feet.7 The gold standard of care, an irremovable TCC, has been shown to heal ulcers in an average time of 6 to 8 weeks.7 While total immobilization provided by a TCC allows for healing, its cost and complexity mean that it is only used by 1.6% to 6% of providers.4,5 

The present study was the first clinical trial to evaluate rates of wound healing for plantar DFUs in patients fitted with a specific offloading foot brace. This brace is unique for several reasons, but most notably for facilitating complete offloading of weight from the foot’s plantar surface. If needed, the foot can be suspended several inches above the brace’s surface. This allows for the accommodation of negative pressure dressings or bulky bandages, which is a crucial advantage for patients that require advanced wound care. 

The investigators discovered a nonsignificant trend demonstrating increased wound healing in patients assigned to the experimental group during weeks 2 to 5 and 6 to 9. However, this trend was lost during weeks 12 to 15. These findings may suggest the offloading foot brace promotes healing more efficiently during the early stages of the recovery period. Furthermore, they analyzed a subset of patients to determine healing rates between those deemed compliant versus noncompliant with the study protocol. A nonsignificant but positive trend in healing was noted among those compliant with study protocol. 

In addition, the authors catalogued and recorded a reduction in peak plantar pressures among patients using the offloading foot brace. Cavanagh and Bus7 determined that effective healing of plantar DFUs best occurs when peak plantar pressures are below 200 kPa. In patients who received force scan measurements while wearing the offloading foot brace (n = 4), all had reduced peak pressures below the therapeutic level of 200 kPa. 

LIMITATIONS 

A limitation of this study is the small sample size, which limits generalizability. However, it is important to note that the study was halted after futility analysis revealed that continuation would be unlikely to produce significant findings. Furthermore, it is possible that the 3-month follow-up was not of significant duration to incorporate relevant healing events.

Despite these limitations, continued investigation of total offloading foot devices remains warranted, specifically in relation to patient compliance with offloading devices.

CONCLUSIONS

This study represents an initial clinical trial to evaluate wound healing rates of plantar DFUs in patients fitted with a total offloading foot brace. The investigators catalogued and recorded a reduction in peak plantar pressures among patients using the offloading brace, suggesting the offloading brace may be of some value in clinical situations where reduced plantar pressure is desired. In addition, they identified a statistically nonsignificant trend that correlated with increased rates of healing during the initial weeks of the study period. However, this dissipated by the study’s conclusion. The study was halted after futility analysis demonstrated continuing patient enrollment was unlikely to make a significant difference. Moving forward, the authors suggest patient compliance with offloading devices be more closely studied. 

Acknowledgments

Affiliations: 1Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH; and 2Division of Vascular Surgery and Endovascular Therapy, University Hospitals Cleveland Medical Center, Cleveland, OH

Correspondence: Vikram S. Kashyap, MD, FACS, Chief, Division of Vascular Surgery and Endovascular Therapy, Harrington Heart & Vascular Institute, University Hospitals Case Medical Center, 11100 Euclid Avenue, LKS 7060, Cleveland, OH 44106; Vikram.kashyap@UHHospitals.org

Disclosure: Partial funding was provided by the Cleveland Clinic Global Cardiovascular Innovation Center (Cleveland, OH). The authors disclose no financial or other conflicts of interest.

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