Is TCC-EZ a Suitable Alternative to Gold Standard Total-Contact Casting?

Abstract

Background: The total-contact cast (TCC) is the gold standard for off-loading diabetic foot ulcers (DFUs) given its nonremovable nature. However, this modality remains underused in clinical settings due to the time and experience required for appropriate application. The TCC-EZ is an alternative off-loading modality marketed as being nonremovable and having faster and easier application. This study aims to investigate the potential of the TCC-EZ to reduce foot plantar pressures. Methods: Twelve healthy participants (six males, six females) were fitted with a removable cast walker, TCC, TCC-EZ, and TCC-EZ with accompanying brace removed. These off-loading modalities were tested against a control. Pedar-X technology measured peak plantar pressures in each condition. Statistical analysis of four regions of the foot (rearfoot, midfoot, forefoot, and hallux) was conducted with Friedman and Wilcoxon signed rank tests. Significance was set at P < .05. Results: All of the off-loading conditions significantly reduced pressure compared with the control, except the TCC-EZ without the brace in the hallux region. There was no statistically significant difference between TCC-EZ and TCC peak pressure in any foot region. The TCC-EZ without the brace obtained significantly higher peak pressures than with the brace. The removable cast walker produced similar peak pressure reduction in the midfoot and forefoot but significantly higher peak pressures in the rearfoot and hallux. Conclusions: The TCC-EZ is a viable alternative to the TCC. However, removal of the TCC-EZ brace results in minimal plantar pressure reduction, which might limit clinical applications of the TCC-EZ.

Globally, 26 million people are affected by diabetes-related foot ulceration [1]. Without appropriate care, diabetic foot ulcers (DFUs) increase health-related costs, morbidity, and mortality. This is the leading cause of lower-extremity amputation and diabetes-related hospitalization [1,2]. Hence, prompt healing of DFUs should be of the utmost importance [1,2]. A fundamental intervention for healing DFUs involves reducing plantar pressures [3-7]. Reduction is achieved by off-loading modalities fitted to the patient based on his or her function, ambulatory status, and activity level [3-7]. The gold standard intervention is a nonremovable knee-high off-loading device, ie, a total-contact cast (TCC) [1,2,8-16]. In Australia, however, removable off-loading devices are used more frequently than nonremovable devices [3,6,16-18]. The primary purpose of this study was to investigate the off-loading capacity of an alternative off-loading device.

The gold standard TCC achieves plantar pressure reduction by reducing stride length, decelerating the foot during gait, and redistributing the plantar forces along the walls of the cast and/or rearfoot [8,15]. The 2019 International Working Group for Diabetic Foot Guidelines reported that TCCs were 17% to 43% more likely to heal a neuropathic plantar forefoot ulcer and to reduce healing time by 8 to 12 days compared with removable devices [1]. The complete application of a TCC takes an average of 21 min, including setup, cast application, and drying time [13]. Continued off-loading management involves weekly removal and reapplication of the cast. Cost, time, and experience are factors that limit application of the TCC [10,13,19]. This may explain why it is underused in a clinical setting.

The TCC-EZ (Integra LifeScience Corp, Plainsboro, NJ) is a modified concept of the TCC in which a roll-on fiberglass cast is accompanied by a removable brace [2]. Compared with the traditional TCC, TCC-EZ has fewer application limitations: a marketed application time of 10 min inclusive of cast drying and less training for proper application [20]. Similar to the gold standard, TCC-EZ needs to be removed and reapplied weekly to optimize wound care [2,10,13,19]. Furthermore, the device has been reported to have similar healing rates; reduced rates of iatrogenic ulceration, amputations, and recurrent ulcerations; and overall good patient acceptance due to its lightweight nature compared with traditional TCCs [5,13]. The primary aim of this study was to assess in-shoe peak plantar pressures in a removable cast walker (RCW), a TCC, and the TCC-EZ with and without the brace. A reduction in plantar pressures confirms off-loading ability, which may present an alternative to the TCC. This could potentially pave the way for future research to close the gap between evidence and practice. We hypothesized that the TCC-EZ will provide equal plantar pressure off-loading to the TCC.

Methods

Participants

Twelve participants, six males and six females, older than age 18 years were recruited. Participants were excluded if they had any chronic disease or disability, including diabetes. Written and verbal informed consent was gained from all of the participants. Participants were able to withdraw at any point without consequence. This study was approved by the Human Ethics Office of Research Enterprise at The University of Western Australia (Crawley, Australia).

Outcome Measures

Foot characteristics were determined by the Foot Posture Index-6 [21-24]. Peak plantar pressures were measured using the Pedar-X system (novel GmbH, Munich, Germany) [25,26]. The Pedar-X insoles were calibrated using the Trublu calibration device (novel GmbH). Sensor threshold cutoff was set to 40 kPa to nullify constant pressure in the cast during the swing phase of gait.

Protocol

Baseline descriptive data were collected (Table 1). The appropriately sized Pedar-X insole was applied to both of the participant's feet and secured with hypoallergenic micropore tape around the forefoot and at the insole attachment points. These insoles remained in place throughout the testing process. Then, each of the modalities was fitted to the participant's right foot, and Volley International (Brand Collective Pty Ltd, Port Melbourne, Victoria, Australia) footwear (control) was worn on the contralateral foot. A standard 5-min familiarization period was provided to all of the participants in each of the modalities. The Pedar-X system was used according to the manufacturer's specifications [27]. The participants were then asked to walk 12 steps in each of the modalities. Recording of plantar pressures began on the second step to eliminate initial gait acceleration pressures, allowing for five steps on the right foot to be recorded for analysis.

Table 1. Baseline Characteristics of the Study Participants

Table 1. Baseline Characteristics of the Study Participants

Each participant's plantar pressures were measured in each of the following modalities:

• Volley International (control): A baseline for comparison of the normal plantar pressures on each participant's foot.
• Össur Formfit walker (Össur; (Össur hf., Reykjavík, Iceland): A removable knee-high walker with adjustable straps, a rocker sole, and a seamless liner. This walker was fitted consistently by a final-year podiatric medical student (U.K.B.)
• TCC: A knee-high Delta Terry-Net stockinette (BSN Medical GmbH, Hamburg, Germany) was applied, followed by two rolls of Webril (Covidien Kendall Webril II undercast padding, Covidien/Medtronic, Dublin, Ireland), which were applied to the lower limb, followed by 10 mm semicompressed felt (Hapla, Cuxson Gerrard & Co. Ltd. Oldbury, West Midlands, UK) on the anterior aspect of the tibia, dorsum of the foot and both malleoli.
• Next, one roll of fiberglass tape (4 inch) (Delta-Cast Elite; BSN Medical GmbH) was applied, after which one roll was used to form the back slab of the cast, with one further roll used to complete the cast (three rolls in total). Each cast was applied by the same experienced and qualified podiatric physician (J.C.H.) from Royal Perth Hospital (Perth, Australia). The same podiatric student assisted in maintaining a plantigrade foot position throughout the casting process. A standard 15-min drying time was stipulated for each cast. An open-toe cast boot (Darco CBO; Darco International, Huntington, WV) was then fitted before pressure measurements were taken.
• TCC-EZ with brace: Applied as per manufacturer specifications, all of the consumables for each cast were supplied in the TCC-EZ packaging. The cast sock was allowed to dry for a standard 15 min per manufacturer specifications.
• TCC-EZ without brace: See the TCC-EZ protocol. The brace was removed for this off-loading modality.

Statistical Analysis

Because this was a pilot study, a power calculation was not performed. A previous study comparing plantar pressures in different off-loading modalities required seven participants to achieve a power of 0.8; however, they chose to use 16 participants to increase statistical robustness [28]. Based on this information, we opted to use 12 participants. The software program Creation of Any Masks (novel GmbH) [27]. was used to create the mask replicating used by Searle Mosteo and colleagues [29]. to validate ankle equinus in diabetic patients. These masks divided the foot into the rearfoot, midfoot, forefoot, and hallux regions, allowing distinct analysis. The peak plantar pressures measured were exported to a spreadsheet program (Microsoft Excel; Microsoft Corp, Redmond, Washington) before analysis with IBM SPSS Statistics for Windows, Version 25.0 (IBM Corp, Armonk, New York). All of the data were assessed for normal distribution. Because not all peak pressures were normally distributed, the nonparametric alternative to the repeated-measures analysis of variance, the Friedman rank analysis, was conducted. To isolate the differences in peak plantar pressure, the Wilcoxon signed rank test was used. Significance was set at P < .05.

Results

Twelve participants were recruited, with baseline characteristics collected (Table 1). Fifty percent of the participants were female and 50% were male, with a median age of 23 years (interquartile range [IQR] = 6 years). Of the 12 participants, seven (58.3%) had a neutral Foot Posture Index-6 score. No participants showed severely supinated or pronated foot postures.

Normality tests were run, and according to the Shapiro-Wilk test, not all of the variables were normally distributed (P < .05). As such, nonparametric tests were used to compare median peak pressures between the off-loading modalities. Friedman and Wilcoxon signed rank tests were performed. For further analysis, median values were converted to percentage reductions from the control shoe and the TCC.

Control Shoe

In the control, the Volley International footwear, the median peak pressures obtained were 299 kPa (IQR = 94 kPa) in the rearfoot, 110 kPa (IQR = 85 kPa) in the midfoot, 315 kPa (IQR = 69 kPa) in the forefoot, and 204 kPa (IQR = 163 kPa) in the hallux (Table 2).

Table 2. Absolute Peak Pressure Values Compared with the Control

Table 2. Absolute Peak Pressure Values Compared with the Control

Total-Contact Cast

This gold standard modality was ranked as producing the lowest peak pressures in the rearfoot and hallux, with reductions of 44% and 74%, respectively (Table 2). The midfoot and forefoot also achieved reductions in peak pressure of 39% and 69%, respectively (Table 2). These reductions were significantly different from the control in all of the regions of the foot (P < .05).

Removable Cast Walker

The RCW was consistently ranked as the modality achieving the third lowest peak pressures. It also achieved significant reductions in peak pressure in all of the regions of the foot compared with the control (Table 2). Compared with the gold standard, TCC, the RCW showed significantly higher peak pressure in the rearfoot (P = .005) (Table 3). The midfoot showed no change in peak pressure with RCW compared with the TCC (0%; P = .783) (Table 3). In addition, despite pressure increases in the forefoot (4%) and hallux (79%), these were not statistically significant compared with TCC peak pressures (Table 3).

Table 3. Absolute Peak Pressure Values Compared with the TCC

Table 3. Absolute Peak Pressure Values Compared with the TCC

TCC-EZ

When worn with the accompanying brace the TCC-EZ achieved the lowest-ranking peak pressure in the midfoot and forefoot, with reductions of 44% and 69%, respectively (Table 2). These reductions where significant compared with the control (P < .05). When the TCC-EZ was compared with the gold standard, TCC, there was no significant difference in peak pressure between the two (Table 3).

TCC-EZ Without the Accompanying Brace

When the TCC-EZ without the accompanying brace was compared with the control, reduction in peak pressures were observed (Table 2). These reductions were significant in the rearfoot (–20%; P = .034), midfoot (–32%; P = .003), and forefoot (–28%; P = .003). However, the 4% reduction in peak pressure in the forefoot was not significantly different from the peak pressure measured when wearing the control footwear (P = .182). Compared with the TCC, the TCC-EZ without the accompanying brace increased peak pressures in the rearfoot by 43%, in the midfoot by 12%, in the forefoot by 130%, and in the hallux by 268% (Table 3). These were noted as significant increases in the rearfoot, forefoot, and hallux (P = .002). When the TCC-EZ was worn without the accompanying brace and compared with TCC-EZ when worn as directed, significantly higher peak pressures were recorded, with increases from 21% to 150% noted in all of the regions of the foot (P < .05) (Table 4).

Table 4. Absolute Peak Pressure Values Compared with TCC-EZ + Brace

Table 4. Absolute Peak Pressure Values Compared with TCC-EZ + Brace

In summary, the TCC-EZ achieved similar peak pressures as the gold standard TCC. However, when the accompanying brace was removed, the TCC-EZ had significantly higher peak pressures recorded.

Discussion

Off-loading of plantar wounds is a keystone in healing DFUs because pressure contributes to delayed wound healing in 94% of plantar foot ulcers [2]. Nonremovable knee-high off-loading is considered the gold standard [30]. but is used only 2% to 16% of the time in clinical practice when indicated [2,31-33]. Lack of use is attributed to disruption in clinical flow, difficulty in training staff for appropriate application, contraindications for patients with ischemia, and patients' ability to tolerate the device [2,30]. In contrast, shoes, felt, and foam are most commonly used to manage plantar foot ulcers [10,34]. This displays an apparent gap between evidence-based guidelines and clinical practice in the off-loading management of plantar DFUs that we aimed to close by testing the plantar pressure of a new off-loading device.

The findings of this study provide a snapshot of the peak pressures measured across four regions of the plantar foot in a variety of off-loading modalities. To have a consequential reduction in pressure, one of two things must occur: an overall decrease in force and/or an increase in the area in which the force is applied [18]. Therefore, devices that exhibit lower peak pressures can be described as superior off-loading modalities. To our knowledge, this is the first study comparing plantar pressure of the RCW, TCC, and TCC-EZ with and without the accompanying brace in different regions of the foot. Summarizing these findings, there was no statistical significance in pressure reductions between the TCC and TCC-EZ in all of the regions of the foot. The TCC and TCC-EZ provided the greatest reductions in pressure across all of the regions of the foot, thus confirming the off-loading potential of these devices. Hartsell and colleagues [35]. found that the TCC reduced plantar pressures by 38% compared with a running shoe, particularly through the forefoot and lateral midfoot region. Meanwhile, Armstrong and colleagues [36]. found that TCC-EZ reduces plantar pressures equally or better than TCC. Compared with the literature, the present findings support the hypothesis that TCC-EZ will provide equal plantar pressure off-loading.

Nonadherence is a major consideration in off-loading [37,38], especially with removable parts such as the brace component of TCC-EZ. When worn without the brace, TCC-EZ showed the lowest percentage pressure reduction in all of the regions of the foot (Table 2). Clinically, if patients are nonadherent to medical advice and do not use the device as recommended, they will experience suboptimal off-loading.

Research has found that patients wear prescribed removable devices for only 30% of their daily activities and do not consistently wear the device in the home [30]. Although TCC-EZ is considered a TCC with its roll-on fiberglass sock [2,5,10,39], it lacks structural integrity when worn without the brace, with pressure increases ranging from 21% to 150% across the foot. Thus, our hypothesis is not supported when TCC-EZ is worn without the brace. Nevertheless, the TCC-EZ nonremovable sock component provides significant pressure reduction compared with the control. This indicates that TCC-EZ is preferred to a completely removable device, such as the RCW, in circumstances of nonadherence to the treatment plan.

Although this study did not find statistically greater off-loading using the RCW, it suggests that there was no difference in peak plantar pressure through the forefoot and midfoot regions compared with the TCC. This suggests that the RCW provides equal off-loading potential in these areas. The lack of significance achieved in the rearfoot in this study can be attributed to low power.

Baumhauer and colleagues [40]. found that an RCW reduced peak plantar pressures equally to the TCC, with significantly greater reductions at the fifth metatarsal head and base. Although the RCW and the TCC have similar off-loading capacities in the study by Baumhauer et al [40]. and the present study, Gutekunst and colleagues [41]. proved greater benefit in using a TCC over an RCW. Due to the TCC's nonremovable nature, it exhibits greater healing potential of plantar wounds in the literature [41]. Therefore, in situations in which a TCC is not available, rendering the RCW nonremovable (ie, instant TCC) is recommended [32,40].

Rendering the RCW nonremovable would potentially ease practitioners' concern regarding patient compliance and deliver close to optimal off-loading in the midfoot and forefoot at a minimal cost [42]. The greatest advantage of the RCW is its ease of application and removal. However, this is also its biggest downfall because it can encourage nonadherence, similar to TCC-EZ, when worn without the brace, directly hindering healing rates [30].

Limitations

A limitation of this study was low participant numbers, which contributed to low heterogeneity in the participant pool and lack of statistical power. This is attributed to the study design being a pilot study, and, consequently, no specific clinical recommendations have been made, rather only clinical suggestions. However, this study does confirm the feasibility for future studies to be conducted with greater power. Another factor noted while conducting the study was the application of both TCC and TCC-EZ casts, where the cast wall height was dictated by the vertical length of the insole cable. Although this limitation was minimized with appropriately sized insoles, variation in cast length is a significant limitation given that these casts are known to disperse plantar foot pressures through the walls of the cast.

Furthermore, a limitation concerning testing of the TCC-EZ was related to specific manufacturers' guidelines. They suggested 10 to 15 min of drying time after application and a curing time of 24 hours before ambulation. Due to time constraints, we could allow only 15 min of drying time before ambulation. In a clinical setting it would be difficult, or even impractical, to have a 24-hour cure time because it would involve sending the patient home in a wheelchair and completely nonweightbearing during that period.

Strengths

This study demonstrates some key strengths, with the most significant strength directly relating to trying to close the gap between evidence and clinical practice. This study is the first to analyze plantar pressure off-loading by TCC-EZ compared with other modalities commonly used in a clinical setting. These results can provide insight to podiatric physicians and other practitioners of the most suitable off-loading required for their patients.

To further cement and validate these findings, further studies should aim to have at least 26 to 30 participants according to the post hoc power analysis performed on G*Power [43,44]. In conjunction with this, researchers could look into recruiting diabetic patients, a more appropriate demographic group, to assess whether peak pressures are similar through the tested modalities; as in reality, these off-loading devices would be used on high-risk patients, particularly those with active DFUs.

Conclusions

These findings suggest that the TCC and TCC-EZ reduce plantar pressures to a similar extent. Thus, TCC-EZ is a viable alternative off-loading device to the gold standard. Removal of the external TCC-EZ brace resulted in significantly higher plantar pressures. We believe that the removable nature of the TCC-EZ brace may limit its application in clinical settings, and patient compliance should be deliberated before issue [35]. This study displays the feasibility of the TCC-EZ in reducing plantar pressures of the foot, paving the way for future investigation by further studies.