Offloading Diabetic Foot Wounds Using the Scotchcast Boot: A Retrospective Study
One of the central tenets of care in the treatment of plantar diabetic foot wounds is reduction of pressure through various devices. One of the most popular of these devices in use in many parts of the world is the Scotchcast boot.
Although the Scotchcast boot has been used successfully for nearly two decades in several clinics in the United Kingdom and elsewhere, evidence of treatment outcomes in large populations is sparse.1,2 The purpose of this study was to evaluate time to healing associated with treatment of diabetic foot ulcers of varying depth using the Scotchcast boot.
Materials and Methods
Data were extracted from the records of 180 patients, 150 (83.3%) male, with a mean age of 55.3 ±10.9 years, who underwent treatment for neuropathic diabetic foot wounds at a university teaching hospital's tertiary care outpatient clinic. Data were abstracted for consecutive patients seeking care at the facility who were treated with the Scotchcast boot. All patients included in the study had been previously diagnosed with diabetes mellitus by their attending physicians. Wounds were described and classified using the University of Texas diabetic foot wound classification system3 and all patients had loss of plantar sensory protective threshold based on biothesiometer test results and the method and criteria defined by Young et al.4,5 Vascular status was evaluated by pedal pulse palpation. Data from patients were excluded from analysis if acute soft tissue, bone infection, or ischemia had been diagnosed by the treating physician at the time of assessment. The diagnosis of ischemia was made by the absence of more than one foot pulse or a nonaudible signal on Doppler ultrasonography of the dorsalis pedis or posterior tibial pulses the affected extremity.
All patients were treated with the Scotchcast boot as the sole form of pressure relief. Data from patients who received multiple forms of pressure relief during their treatment were not included. The boot was applied using the technique described by Knowles et al6 and Burden et al.1
The Scotchcast boot is a well-padded cast cut away at the ankle (see Figures 1 and 2). It is made removable by cutting away the cast over the dorsum of the foot and making a closure of padding and tape with Velcro® straps. Windows are cut over the ulcers as needed. For large heel ulcers, a removable heel-cap of fiberglass is added. The boot is worn with a cast sandal to increase patient mobility; the Scotchcast protects the ulcer from any pressure while keeping the patient ambulant. Patients were followed at weekly intervals, at which time the wounds were evaluated and debrided if necessary.
Statistical analysis. All descriptive data are presented as mean ± standard deviation. An Analysis of Variance (ANOVA) was used to compare mean age, duration of diabetes, and healing time based on depth. Post hoc tests (Tukey's Studentized Range Test) were used to test differences between different variables. Pearson's test was used to analyze the association between continuous variables (time to healing and wound size) and Student's t-test for independent samples compared differences in time to healing by gender. For all analyses, an alpha level of 0.05 was considered statistically significant.7
The average follow-up for each patient was 85.9 ± 30.6 months (range 34.2 to 147.7 months) (see Table 1). The mean time to healing for all patients was 130.5 ± 106.7 days (see Figure 3). Although no statistically significant difference in healing time between Grade 1 and Grade 2 wounds (P= 0.7) was noted, superficial (Grade 1) wounds healed significantly faster than deep (Grade 3) wounds (111.5 ± 98.2 days versus 180.8 ± 138.8 days, P = 0.01) (see Figure 4). No statistically significant difference was observed for gender and time to healing (P = 0.2). As this is a retrospective study over several years, the authors did not feel comfortable with using wound area as a variable in time to healing.
During the long follow-up period, 144 (80%) wounds healed. Of the 36 (20%) that did not heal with Scotchcast boot therapy, 10 went on to more proximal amputation (5.6% of total population), two required surgical intervention to heal their wounds (0.6% of total population), one patient died with an unhealed wound (0.6% of total population), and 23 patients (12.8% of total population) were lost to follow-up in the National Health Service district in which the study was performed. During the mean 7.2-year follow-up period, 47 patients died (26.1% of total population).
To the authors' knowledge, this is the first report of outcomes obtained in a large number of patients treated with this mode of pressure relief. Time to healing appears comparable to other types of offloading modalities such as the half shoe.8 However, when reviewing the results of other studies, the treatment used in this data set did not achieve the same healing results as the traditional gold-standard treatment, the total contact cast (TCC). Studies evaluating the TCC consistently report mean times to healing of 6 to 10 weeks.9-19
The main purported advantage of the Scotchcast boot over the total contact cast is that it is removable, allowing regular inspection and redressing of the wound, an advantage for outpatient care and the management of deep and/or infected wounds. Removability also can be an important disadvantage, particularly for noninfected superficial wounds in people who may opt to remove and not reapply the boot. An alternative method of application for the noncompliant patient with a superficial wound would be fabrication of a non-removable Scotchcast boot. This was not evaluated in the present study, but healing times potentially might have been more favorable if the boots were made non-removable; thereby, forcing compliance.
Review of long-term outcomes of patients treated with the Scotchcast boot suggest that this modality may be useful in outpatient care of deeper or complex wounds that require frequent inspection, but treatment of superficial wounds may be better suited to a device that ensures compliance. In this era of promising advanced wound healing modalities, the central focus of treatment continues to be debridement and pressure reduction. Therefore, further work is required both to report on and compare various methods of offloading the diabetic foot wound. Only then can informed, evidence-based decisions on this most important aspect of treatment be reached.