More On-Off(loading) from Dr Frykberg.

Offloading Diabetic Foot Ulcers
Still the Primary Treatment 

Despite all the recent advances in our understanding of the etiology, pathophysiology, and treatments for diabetic foot ulcers (DFU), the basic tenets of ulcer care remain the same (Table 1). Appropriate treatment, of course, is predicated upon proper assessment of the wound. This is not difficult in most circumstances. The clinician simply needs to perform a systematic and thorough evaluation of each and every ulcer to be able to determine important underlying characteristics and perturbations that can impair normal healing.

 

Table 1. BASIC TENETS OF DFU CARE

Determine Etiology Medical Management of Co-morbidities Vascular Assessment and Management Infection Management

Offloading Wound Debridement Therapeutic Agents and Dressings

 

Although all facets of the patient and wound assessment are critical components of care (as we have previously discussed several times), this month we will concentrate on the aspect of DFU treatment that is often under-appreciated – that of offloading. There are likely three most common reasons why foot ulcers remain unhealed, even when under the care of a health care practitioner:

1. Unrecognized vascular insufficiency
2. Occult underlying osteomyelitis
3. Inadequate offloading.

Much attention is given to the former two aspects in diverse circles, but the simpler (and perhaps the most commonly neglected) of the three problems to address is certainly pressure relief through appropriate offloading. 

We have long recognized that DFUs are frequently the result of high pressures causing injury to the skin envelope of neuropathic (or ischemic) individuals. For plantar ulcers, of course, this comes from walking in improperly fitted shoes or in footwear without sufficient protection for the sole of the foot. (Here we are excluding those wounds resulting from barefooted walking or due to other types of trauma).  One 1999 multicenter study determined that a specific triad of component causes were present in 63% of the pathways leading to DFU in their patients: neuropathy, deformity, and trauma .  These findings are certainly biologically plausible wherein the neuropathic foot is both prone to unrecognized trauma as well as to the development of deformities (hammertoes, Charcot foot, etc.). Neuropathic feet are also subsequently prone to higher plantar foot pressures, especially with increasing number of deformities or with greater risk level (see the 2008 Comprehensive foot examination paper by Boulton et al for specifics of risk identification and classification).  Since high plantar foot pressures underlie the etiology of the large majority of DFUs, it makes absolute sense that such pressures need to be ameliorated in order to successfully treat these chronic wounds.

Total contact casts (TCC) remain the “gold standard” for offloading plantar ulcers, at least in terms of their effectiveness in reducing plantar pressures and promoting healing of ulcers. (Fig 1 ) Partly due to their non-removability, as well as due to their ability to distribute pressures even to the leg, TCCs in the appropriate patients will generally lead to faster healing rates than any other modality (approximately 6 weeks or so depending upon the study).  Unfortunately, time, cost, fear of complications, and inexperience often deter clinicians from routinely applying casts to their ulcerated patients. A newer version of the TCC provides an easier solution, wherein a fiberglass cast can be “rolled” onto the extremity in a minimum of time and safely offer the same benefits as the traditional TCC.

Figure 1: Total Contact Cast

 

Because of the aforementioned impediments (real or perceived) to the routine use of the TCC, alternative devices have been used for many years. The recent Cochrane review by Lewis and Lipp provides a comprehensive literature review of the efficacy of many approaches to offloading DFUs.  All modalities are aimed at reducing plantar pressures under or around the site of ulceration, recognizing that pressure must be removed from the equation if the wound is to heal. Alternative offloading devices and modalities are found throughout the world’s literature including felt or foam aperture pads, rolled foam buttress pads, modified surgical shoes with cut-out pressure relieving foot beds, “half shoes” or forefoot wedge shoes, prefabricated and custom fabricated splints or braces, and various types of prefabricated removable “cast walkers” (RCW). (Fig 2)

Figure 2: Removable cast walker

 

The latter have undergone the most study, in various designs from several different companies, each showing their ability to promote healing of ulcers when compared to less restrictive weight bearing devices.  In fact, most current wound healing trials for DFUs use RCWs as their standard of care device incorporated into their protocols. The problem with these devices, as in most alternative devices, is that they are indeed removable and patients prefer to walk without them- especially at home. To address this deficiency, the concept of a non-removable RCW was introduced and termed as an “instant” Total Contact Cast (iTCC) by simply affixing fiberglass or a bandage to the standard device to deter removal. (Fig 3)

Figure 3: Irremovable cast walker

 

As might be anticipated, when directly comparing healing rates between removable and irremovable RCWs, the latter iTCC devices were more effective because they also removed patient non-adherence from the offloading prescription. Finally, several authors have compared efficacy of non-removable cast walkers with TCC and found essentially equal healing rates between the two types of devices. From these studies, we now recognize the superiority of nonremovable devices for offloading DFUs and generally recommend this approach for the management of the majority of plantar DFUs when TCC is not used as a first line offloading therapy. Nonetheless, the aforementioned Cochrane review supports the important benefits and efficacy of the TCC.

Healing sandals, modified surgical shoes, or insole modifications in patients’ shoes are no longer considered adequate pressure relieving interventions for plantar foot ulcers (although for non-plantar wounds such therapies might be sufficient). Become familiar with cast application techniques and pitfalls. Remember that the TCC is still considered the ‘gold standard” for offloading, but when not feasible, a removable or preferably irremovable RCW will do the best job for your patients.  Remember that the pressure is on to always take the pressure off your diabetic foot ulcers – and your diligence in this regard will be reflected in improved healing rates.

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We welcome your opinions, concerns, and suggestions.  If you have an interesting case or a troubling circumstance that you would like to share with fellow PRESENT Diabetes members,  please feel free to comment on eTalk. 
 

Best regards,

Robert Frykberg, DPM, MPH
PRESENT Editor, 
Diabetic Limb Salvage

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References:

1. Veves A, Murray HJ, Young MJ, Boulton AJ. The risk of foot ulceration in diabetic patients with high foot pressure: a prospective study. Diabetologia. 1992;35(7):660-663.

2. Frykberg RG, Zgonis T, Armstrong DG, et al. Diabetic foot disorders. A clinical practice guideline (2006 revision). J Foot Ankle Surg. Sep-Oct 2006;45(5 Suppl):S1-66.

3. Lavery LA, Armstrong DG, Wunderlich RP, Tredwell J, Boulton AJ. Predictive value of foot
   pressure assessment as part of a population-based diabetes disease management program. Diabetes Care. Apr 2003;26(4):1069-1073.

4. Reiber GE, Vileikyte L, Boyko EJ, et al. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999;22(1):157-162.

5. Boulton AJ, Armstrong DG, Albert SF, et al. Comprehensive foot examination and risk assessment: a report of the task force of the foot care interest group of the American Diabetes Association, with endorsement by the American Association of Clinical Endocrinologists.Diabetes Care. Aug 2008;31(8):1679-1685.

6. Mueller MJ, Diamond JE, Sinacore DR, Delitto A, Blair VP, 3rd, Drury DA and Rose SJ: Total contact casting in treatment of diabetic plantar ulcers. Controlled clinical trial. Diabetes Care12:384-8, 1989

7. Lewis J and Lipp A: Pressure-relieving interventions for treating diabetic foot ulcers. Cochrane Database Syst Rev 1:CD002302, 2013

8. Shaw JE, Hsi WL, Ulbrecht JS, Norkitis A, Becker MB and Cavanagh PR: The mechanism of plantar unloading in total contact casts: implications for design and clinical use. Foot Ankle Int18:809-17, 1997

9. Armstrong DG, Short B, Nixon BP and Boulton AJM: Technique for Fabrication of an "Instant" Total Contact Cast for Treatment of Neuropathic Diabetic Foot Ulcers. J Amer Podiatr Med Assn 92:405-408, 2002

10. Katz IA, Harlan A, Miranda-Palma B, Prieto-Sanchez L, Armstrong DG, Bowker JH, Mizel MS and Boulton AJM: A Randomized Trial of Two Irremovable Offloading Devices in the Management of Neuropathic Diabetic Foot Ulcers. Diabetes Care 28:555-559, 2005

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