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The use of focus rigidity casts as pressure-relieving devices for foot wound healing

Focus rigidity casts (FRCs) are commonly used in the wound-care community and are primarily provided for sites of heel ulceration. The aim of this audit was to determine whether FRCs can reduce the size of ulcerations on various pressure sites of the foot and ankle, as well as the heel. Retrospective data from 21 patient records were collected. Wound size was measured at baseline before the use of FRC, 4 and 8 weeks post intervention. In a sample of 12 wounds located on the heel; 1 ulcer healed entirely, 10 reduced in at least one measurement parameter, and 1 increased in size. In a sample of 10 wounds on the bony prominence of the ankle, midfoot and forefoot, 3 ulcers healed entirely, 7 reduced in at least one measurement parameter and 2 patients showed an increased the wound size. This audit would suggest FRCs provide clinical benefit in the treatment of foot and ankle wounds, with a greater reduction in wound size at the heel; further study is required.

Focus rigidity casts (FRCs) have been suggested for use in wound healing since 1998 (Petty and Wardman, 1998). The innovative use of FRCs in the treatment of heel ulcers has been outlined in a number of studies (Stuart et al, 2008; Malone et al, 2011). These studies are by no means comprehensive, the largest multi-centre UK study (Jeffcoate et al, 2014) has been completed and their results are due March 2016. The use of the FRCs for heel ulcers, however, continued with anecdotal evidence and some professionals have started using the heel cast regimen on other pressure sites of the feet and ankles (Dagg, 2013).

The FRCs are manufactured using an impregnated resin bandage that is moulded to the shape of the foot overlying dressings and soft bandages. After a reinforced 4 layer region overlying the area of ulceration is added before the resin dries and takes its permanent shape.

How the FRC works and provides clinical benefit is not fully understood. There is evidence to show, in healthy participants, a significant reduction in forefoot pressures when using FRCs compared with a control canvas shoe (Dagg, 2013). The FRC may also reduce shearing and stretching of the tissues rather than the usual ‘offloading’ notion of addressing vertical forces only (Jeffcoate et al, 2014), although this remains to be demonstrated.

There have been a number of positive results for the use of FRCs heel cup on heel ulceration (Malone et al, 2011; Dagg, 2013; Stuart et al, 2008) and this prompted expansion into using it on other pressure areas of the foot and ankle. The aim of this audit was to measure whether applying an FRCs was beneficial in reducing the size of the wounds that were overlying the medial metatarsophalangeal joint (MTPJ), the lateral MTPJ, the medial malleoli, lateral malleoli, the styloid process and the calcaneum.

A retrospective audit of patient records kept in the hospital and community of Salford Royal NHS Foundation Trust was undertaken. The record of the FRCs made during the last 6 months formed the basis of the audit.

Method to manufacture the FRCs was consistent in the trust. Using the same technique for the FRCs, a cup was made for ulcers at the heel, an extended slipper cast to include the MTPJs for medial and lateral bunion ulcers and a slipper cast extended above the ankle for malleoli ulcers. The procedure is illustrated in Figures 1–5.

The wounds were measured in millimetres using a disposable paper ruler or a firm ruler (on a scalpel handle), the length and width was measured at widest points of the wound. Depth was not measured as this was not constantly recorded within the notes. The measurements were recorded at the date of manufacture of the cast and the nearest date to 4 weeks and 8 weeks after the intervention was initiated.

The percentage difference was calculated using Excel (Windows Office 2010) between start date and 4 weeks (week 4 − week 0), 4 weeks and 8 weeks (week 8 − week 4) and the overall start date to 8 weeks (week 8 − week 0).

Data were gathered on 21 patients and 24 wounds. In 11 patients and 12 wounds were situated on the heel (Table 1) 6 patients had type 2 diabetes (DM T2), 1 patient had type 1 diabetes (DM T1), 1 patient had multiple sclerosis (MS), 1 patient had rheumatoid arthritis (RA) and 2 patients (none) had no specific associated disease.

The results of the heel ulcers over 8 weeks showed 1 wound healed completely, 9 wounds had a reduction in size in both length and width and 1 wound showed a reduction in a single parameter. One wound stayed the same size. Decreases in wound size ranged from 14% to 100% from baseline to 8 weeks, while increases occurred in 2 cases and ranged from 0 to 15% in size.

Table 1 shows the measurements of the heel ulcers at time points 0, 4, 8 weeks.

For sites of ulceration other than the heel, in 10 patients 12 wounds were located at bony prominences at the ankle, midfoot and forefoot (Table 2). These bony prominences were identified as the medial metatarsophalangeal joint (MTPJ), the lateral MTPJ, the medial malleoli, lateral malleoli and the styloid process. In this group 4 had type 2 diabetes, 2 had type 1 diabetes and 4 had no associated diseases.

Out of 10 patients with ulcers measured at the forefoot, midfoot and ankle (not including the heel), 3 wounds healed entirely. In 7 out the 10 patients, there was a reduction in at least one measurement parameter. We showed 4 patients had a reduction in both size parameters (length and width). Over the 8 weeks, 2 patients showed an overall increase in one measurement parameter (length or width). Decrease in size ranged from 10% to 100%, while increases occurred in 2 cases and ranged from 14% to 27%. Case 9 showed an increase in initial wound size followed by a decrease due to irregular application of the soft cast. Clinically this was thought to be associated with the patient’s complex medical needs, as the patient had dementia and application depended compliance from a variety of care staff.

Table 2 shows the measurements of the forefoot, midfoot and ankle ulcers at time points 0, 4, 8 weeks.

The application of FRC for pressure ulcers of the foot and ankle did not cause any abrasions and were not removed prematurely by clinical staff.

This audit was undertaken to investigate whether applying FRCs at the traditional site at the heel and at other ulcers at sites of bony prominence is a safe practice and can show clinical benefit. This small audit showed for the first time a reduction in wound size for the majority of ulcers located at the heel and bony prominences in the forefoot, midfoot and ankle.

There were some indications that a greater proportion of wounds reduced in size at the heel although, this may be due to the size of the wound and audit methodology. Limits imposed by being a retrospective study meant only a small section of data could be compared across numerous case records.

Reductions in the wounds were measured by different clinicians using paper ruler and stiff ruler on the sides of scalpel handles, but there was no information on which was used in each individual entry. This may have affected the outcomes shown this audit due to measurement errors.

The repeatability of distance measured by a ruler in millimetres is 11% in small wounds (defined as <10cm2) (Plassmann and Peters, 2002). This would suggest a minimum change of 10% is beyond measurement error, which was the smallest measurement change found in this audit. Therefore, the wound size reduction in this study is likely to reflect real patient benefit.

This audit is limited by methodological rigor (lack of control group and lack of randomisation) and comparison between ulcer size at the heel and other sites was limited. Further studies to compare the use of FRCs in sites of ulcers other than the heel is now needed.

The use of FRCs may have a role to play in contributing to the healing of ulcers in pressure areas of the foot and ankle. The audit would suggest a reduction in wound size was more consistent in the heel. Further investigation is needed to understand the efficacy and mechanism of action. A larger prospective study with a control group would be needed to understand the role of FRC in pressures sites across the foot and ankle and not just the heel. This will also allow for uniformity in measurement methods and the inclusion of greater detail regarding wound appearance, wound depth and any adverse effects of the use of this method.

Dagg AR, Chockalingam N, Branthwaite H (2013a) Focused rigidity casts: an overview. J Wound Care 22: 53–4, 56–7
Dagg AR, Chockalingam N, Branthwaite H (2013b) The effects of focused-rigidity casts on forefoot plantar pressures: a pilot investigation. J Wound Care 22: 237–43
Jeffcoate W, Game F, Price P (2014)Evaluation of lightweight fibreglass heel casts in the management of ulcers of the heel in diabetes: study protocol for a randomised controlled trial. Trials 15: 462
Malone M, Gannass AA, Bowling F (2011) Flexible and rigid casting tape as a novel approach to offloading diabetic foot ulcers. J Wound Care 20: 335–6, 338–9
Plassmann P, Peters JM (2002) Recording wound care effectiveness. J Tissue Viability 12: 24–8
Petty AC, Wardman C (1998) A randomized, controlled comparison of adjustable focused rigidity primary casting technique with standard plaster of Paris/synthetic casting technique in the management of fractures and other injuries. Journal of Orthopaedic Nursing 2: 95–102
Stuart L, Berry M, Gordon H, Wiles P (2008) The Manchester Martini Cast: Anytime, Anyplace. Poster presented at 4th Foot In Diabetes Conference, Harrogate

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