Assessing the effectiveness of semi-rigid casting for alternative pressure areas on the foot: A Clinical Audit

Trisha Barker Specialist Podiatrist, Samantha Haycocks, Advanced Podiatrist, Paul Chadwick, Consultant Podiatrist, Jill Halstead, Principle Podiatrist. Salford Royal NHS Foundation Trust.

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Introduction

A semi-rigid cast is a device made out of resin impregnated bandage. This is made chair side by the clinician, with reinforced layers overlying the wound area to protect the wound site. Semi-rigid devices for heel ulcers are increasingly being utilised in the NHS (Stuart et el, 2008), although there is limited evidence. This is currently being addressed; a randomised controlled trial to investigate the clinic efficacy of semi-rigid casts for heel ulcers has recently being conducted across the UK. Semi-rigid casts are also being used in other pressure sites of the foot and ankle particularly over bony prominences. Semi-rigid casts are applied with anecdotal evidence they can reduce wound size via mediating foot pressures (Dagg et al., 2011). The aim of this audit was to present a case series of patients who were given Benecast Flex casts for ulcer sites other than the heel.

Method

Benecast Flex semi-rigid slipper casts were provided for patients with foot and ankle wounds at Salford Royal NHS Foundation Trust over a 3 month period. Using Benecast flex, four members of staff used a standardised technique to make a semi-rigid cast by producing a slipper with four layer reinforcement over the wound site (see Figures 1 to 7). A single researcher (TB) undertook a retrospective audit of standardised clinical measurements of wound size. These perimeters included length and width of wound at baseline, four weeks and eight weeks. It wasn’t possible to measure wound depth due to inconsistent use of perimeters, e.g. depth was recorded in some cases using a probe and measured in millimetres, while in other cases a descriptor was used, i.e. deep, moderate, shallow. To analyse the data, descriptive analysis was undertaken. The ulcer size (length x width in mm) was compared by assessing the percentage increase or decrease after 4 weeks, 8 weeks and finally baseline to final measurement at 8 weeks. No statistical inference was undertaken due to the small sample size.

Results

Out of 10 patients 3 wounds healed entirely. In 7 out of the 10 patients there was a reduction in a least one measurement perimeter. We showed 4 patients had a reduction in both size perimeters (length and width) and 3 had reduction in one perimeter and no change in the other. Over the 8 weeks, 2 patients showed an overall increase in one measurement perimeter (length or width). The majority of cases in this clinical audit showed an improvement in wound size. Reductions ranged from 10% to 100%. While increases occurred in 2 cases from 14% to 27%. Case 9 showed an increase in initial wound size followed by a decrease due to irregular application of the semi-rigid cast. Clinically this was thought to be associated with the complex medical needs, as the patient had dementia and application depended on various staff providing the application of the soft cast (see Table).

Discussion

The results of this clinical audit suggest a benefit of using semi-rigid cast at sites of foot ulceration at the metatarsal head, styloid process and malleoli. This would suggest that sites of foot ulceration on the medial and lateral border may benefit from further protection using a semi-rigid cast.  Those wounds that healed completely were smaller and of potentially shorter duration. A limitation of this audit would be the use of different clinical staff measuring wounds. Therefore some of these results may be attributed to measurement error. Studies suggest repeatability of distance measured by a ruler is 11% in small wounds (defined as <10cm2) (Plassmann & Peters 2002). This would suggest a minimum change of 10%, the lowest reduction found in our audit maybe due to measurement error. This would suggest that the wound size reductions shown in this study reflect real patient benefit.

Conclusion

This small wound care audit suggests that semi-rigid casts used in pressure areas other than the heel are a beneficial clinical device. Further studies are now needed in order to test the clinical efficiency in a feasibility study and ultimately in a large multi centre randomized controlled trial.

DFU Salford Study Table

Table shows the wound measurements of all the cases included in this audit at baseline, 4 weeks and 8 weeks.

  • Figure 1 Original ulceration
  • Figure 2 Ulceration 12 weeks later
  • Figure 3-6 Stages of manufacturing and shaping of Benecast Flex
  • Figure 7 Use of cast sandal to allow ambulation

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This study was presented at the Wounds UK Conference 2015.

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References:

Stuart, L., Berry, M., Gordon, H., Wiles, P. The Manchester Martini Cast: Anytime, anyplace. Poster presentation, 4th Foot In Diabetes Conference, 2008

Dagg, A.R., Chockalingam, N., Branthwaite, H. The effects of focused-rigidity casts on forefoot plantar pressures: a pilot investigation. Journal of wound Care 2013; Vol 22 (5): 237-243.

Plassmann P. & Peters J.M. Recording wound care effectiveness. Journal of Tissue Viability 2002; 12(1): 24-8.