Heel ulcers are a life-altering condition associated with a substantial risk for delayed healing, infection, amputation, or death.1 The quality-of-life impact is noteworthy; patients with diabetes who have experienced foot ulcers have a better quality of life with healed than with open ulcers and a lower quality of life if amputation was required.2-4 Among pressure ulcers, the heel is the second most common anatomical ulcer site after the sacral area.5 The incidence of heel ulcers has been reported to be between 19% and 32% in patients with and without diabetes in acute and residential care facilities, respectively.1 Improving ulcer healing, reducing amputations, and preventing ulcer reoccurrence requires knowledge of the etiology of heel ulcers and critical evaluation of efficacy of interventions.
Anatomy of the heel. Plantar soft tissue, a specialized, pressure-absorbing, closed-cell structure of fibrous septae-containing adipocytes, serves to protect the structures of the foot.6 Just below the dermis, this tissue is organized into microchambers; deeper in the foot, over bone or tendon, plantar soft tissue is organized into macrochambers. The plantar soft tissue covering the calcaneus is commonly known as the heel pad. The soft tissue layer covering the calcaneus, lateral foot, metatarsal heads, distal phalanges, and distal hallux is thicker than over the medial foot, proximal hallux, and proximal and intermediate phalanges (see Figure 1). When a person is standing, pressure is unevenly distributed over the plantar surface, with the highest pressure over the heel; the first, second, and third metatarsal heads; and the hallux.
The principal arteries supplying the heel are the posterior tibial and peroneal arteries.7 The subdermal plexus and periosteal plexus are well vascularized, with vessels within the fibrous septae that travel between the 2 arteries. The panniculus canosus muscle, located in the subcutaneous tissue, is sensitive to damage from pressure, mechanical trauma, and shear. These forces also may injure blood vessels and other tissues of the foot. A unique feature of plantar adipose tissue is that it is not replaced after injury or loss, and maintenance of the resilient, shock-absorbing heel tissue depends on pressure absorption, adequate arterial supply, and prevention of injury.
Risk factors for heel ulcers. Reviews of the literature1,5 list the causes of heel ulcers as callus, trauma, diabetes, foot deformities, neuropathy, peripheral arterial disease, reduced joint mobility, and limb immobility. Hsu et al8 studied a convenience sample of 33 volunteers with no heel problems to determine the effect of age on the mechanical properties of the heel pad. Two groups, divided by age into young (18–36 years) and elderly (62–78 years), were provided ultrasound examination of the heel pad during sequential loading and unloading using increments of 0.5 kg to a maximum of 3 kg to produce a load-displacement curve. Heel pads were found to be significantly thicker, more compressible, and less elastic in the elderly (all P <0.001). The combination of these findings, along with the increased fragmentation of elastic fibers and collagen reduction occurring with age, may help explain the reduced pressure absorbency of the heel pad and higher risk of tissue injury in older individuals.
Multiple factors may be linked to diabetic foot ulcer development. Reiber et al9 used the Rothman model of causation, a blinded multidisciplinary group of foot specialists, and a modified Delphi process to identify causal pathways for 92 persons with diabetes and diabetic foot ulcers from Manchester, United Kingdom and 56 from Seattle, WA. The process identified a critical triad of neuropathy, minor foot trauma, and foot deformity in the causal pathway of 63% of patients. Edema and ischemia were present in more than one third of cases. Single causes were callus formation (30%), trauma (6%), and edema (1%).
Descriptive studies10-12 focusing on preventing heel ulcers or characterizing patients with heel ulcers, conducted in inpatient and community settings, indicate risk assessment tools, such as the Braden Scale for Predicting Pressure Sore Risk, appear to be relatively insensitive to risks associated with heel ulcer development, at times placing patients with ulcers in the mild or not-at-risk categories.
Pressure Offloading in Heel Ulcer Management
A Cochrane review found nonremovable, pressure-relieving casts are more effective in healing foot ulcers in persons with diabetes mellitus than removable casts or dressings alone.13 A systematic review and meta-analysis14 of the clinical effectiveness of different offloading devices found any type of nonremovable offloading device to be more effective than removable devices in the treatment of diabetic foot ulcers, likely because patient adherence is facilitated. At this time, pressure offloading with a total contact cast (TCC) or instant total contact cast (iTCC) is considered the optimal method of pressure management in patients with foot ulcers; both options are considered equally effective.15,16 Although TCC and iTCC are effective for offloading, these devices may be associated with clinical disadvantages, including joint stiffness, muscle atrophy, and the risk of new ulceration; elderly, frail, or immobile patients may not tolerate TCC.17-19 An additional concern is the need to transition offloading effectively to maintenance footwear (both shoes and slippers) to prevent recurrence.17 However, in terms of heel ulcer prevention, a systematic review20 of pressure redistribution strategies and heel protection devices found insufficient evidence to select any particular device over a foam pillow.
A prospective pilot study21 compared a “football” dressing (consisting of a topical silver primary wound dressing, cast padding, and a self-adhesive wrap) with TCC or iTCC in 15 patients with chronic neuropathic ulcers that had a mean duration of 6 weeks. All 15 patients healed in 3.80 ± 2.60 weeks (range 1–10 weeks), but pressure relief over the metatarsal heads was 30% less with the football dressing than with TCC or iTCC. The incidence of infection was similar in both groups, and no dressing-related injuries were reported. A retrospective, multicenter analysis22 of the football dressing confirmed these findings and concluded the wound outcomes, coupled with ease of application and low cost, made the football dressing a useful choice in managing foot ulcers.
Dressing-related and offloading device-related injury. In the authors’ clinic, dressings and offloading devices have been linked with adverse events contributing to patient injury. Dressing-related injuries observed included periwound maceration, skin stripping, and pressure injury (see Figure 2).
Offloading devices may contribute to pressure ulcer development, foot-drop, or lower limb rotation; thorough patient assessment is essential before selecting a device to reduce these risks. It is critical to consider the impact of the loss of protective sensation, peripheral arterial disease, infection, and exudate management.17 It is also important to examine patients while they are using the device and to assess comfort and any impact on their ability to reposition, stand, or walk.
Adverse events and patient intolerance may be associated with interventions such as the use of pillows to “float” the heel, heel protectors, and nonremovable or removable pressure-relief devices. Although clinical guidelines recommend the use of pillows to float the heel, it is essential to ensure adequate calf support to prevent Achilles pressure ulcers.23 Incorrect placement or displacement because of patient movement may result in Achilles tendon pressure ulcer development, especially in the presence of peripheral arterial disease. Removable devices, such as the Aircast® (Aircast Inc, Vista, CA) or ankle foot orthoses, have been noted in the authors’ clinic to cause pressure injury, trauma to the unaffected limb, and patient complaints of back or hip pain. Figure 3 illustrates pressure injuries associated with offloading interventions.
Evolution of the Padded Heel Dressing
The padded heel dressing (PHD) was conceived at the Foot and Leg Ulcer Clinic in Victoria, British Columbia (BC), when one of the authors, a clinical wound specialist, wrapped a heel ulcer in a patient with advanced peripheral arterial disease with cast padding in an attempt to relieve his intractable pain. The patient experienced immediate pain relief and was able to ambulate wearing running shoes with laces adjusted for the dressing size. Previously, he had been unable to tolerate use of an Aircast because of back and hip pain experienced with the device. Protected by the PHD, the ulcer healed in 2 months.
Pressure mapping. The clinic team then performed a pressure mapping study in 5 healthy adult volunteers (2 men, 3 women) to determine if the PHD affected heel pressure. The volunteer sat on a plinth at 45˚ with the foot straight in a natural comfortable extension. A CONFORMat® (Tekscan, Boston, MA) was placed under the heel. Measurements were performed for a bare heel as a baseline and for 1-roll and 2-roll padding with 4-inch Zimmer Orthopedic Cast Padding (Zimmer Orthopedic Surgical Products, Dover, OH) to determine appropriate dressing recommendations. Compared with the baseline pressure for a bare heel, average pressure reductions were 23% with 1 roll of padding and 39% with 2 rolls of padding (see Figure 4). This pressure-mapping result indicates the PHD may reduce heel pressure.
Pilot project. To address existing issues with standard dressings (including adverse events), facilitate offloading for heel ulcers, and potentially provide PHD pain relief, the clinic team decided to conduct a pilot study of the PHD among primary care nurses treating patients in both community and residential care settings. The team trained the nurses on dressing application procedure (see Table 1) and evaluated outcomes after the first 10 cases. Nurses reported the PHD was easy to apply, stayed intact between twice-weekly dressing changes, improved exudate control, facilitated wound healing, resolved the problem of periwound skin stripping, required fewer dressing changes, and reduced confusion about dressing selection. With a cost of between $6 and $8 CAN, the PHD was less expensive than previously used heel dressing of various types (eg, hydrocolloid, foam, alginate) with or without a topical antimicrobial product that ranged from $12.50 to $25.00 per change except for adhesive bandages, gauze, and gauze wrap, which cost $0.50 to $5.00. Patients using the PHD could wear loose clothing and resume social activities. Ambulatory patients could use footwear modified by an occupational therapist or pedorthist to ambulate at their previous level; nonambulatory patients could reposition themselves independently; and immobile patients were easier for staff to reposition. Community and residential management reported reductions in nursing time, number of dressing changes, and dressing product inventory.
Based on the results of the community and residential pilot of the PHD, in 2004 the Foot and Leg Ulcer Clinic decided to recommend the PHD for heel ulcers, and in 2007 a quality improvement review was approved.
Quality Improvement Review
The quality improvement review analyzed data from a retrospective chart review to answer the following questions:
- Did patient characteristics (age, peripheral arterial disease, diabetes, and neuropathy) differ between the PHD use and nonuse groups?
- Did ulcer outcomes (closure, amputation, and lost to review), weeks of care, number of nursing visits, nursing costs, and cost-efficiency ratio (CER) differ between the PHD use and nonuse groups?
- What were the average weeks of care, nursing costs, and CER for the PHD use and nonuse groups by depth of tissue involved (superficial skin and muscle, heel pad or tendon, and bone)?
- What was the feedback from primary care nurses and management about adverse events, utility, cost, and satisfaction for the PHD use and nonuse groups?
- What feedback did patients in the PHD use and nonuse groups provide about dressings and offloading devices, dressing experience, pain relief, comfort, physical activity, social interaction, and quality of life?