Professor Boulton and Dr. Armstrong (1) argued recently that “all future trials of therapy should use a nonremovable off-loading device.” In doing so, they betray a failure to understand how the structure of trials must be determined by their purpose: those designed to determine the efficacy (“Can it work in ideal circumstances?”) may differ from those designed to determine effectiveness (“Does it work in practice?”). Two factors that underlie the capacity of a controlled trial to demonstrate efficacy are 1) the effect, or lack of it, of the intervention and 2) the effect of the control. Boulton and Armstrong concluded (with no evidence) that the failure of Veves et al. (2) to demonstrate any benefit of Promogran was “likely” to be the result of a failure to standardize off-loading techniques. Another interpretation is that the product is comparatively ineffective in routine practice.

The classical total contact cast (TCC) does not have a dressing window, and so how can it be used in trials of dressings and applications designed to be changed more often than the off-loading device? A TCC, but not their modified walker, can be modified by incorporating a dressing window, but dressing windows have their problems. If too small, they limit the ability to clean and dress the wound properly. If too large, they limit the effectiveness of off-loading by allowing the ulcerated area to prolapse.

Crucially, however, Boulton and Armstrong fail to satisfactorily address the questions of acceptability and safety. They acknowledge that TCCs have adverse effects and suggest that these may be overcome with their modified walker, but admit that relevant trials have not been completed. In truth, many people find nonremovable devices unacceptable, with reasons that include secondary ulceration of the index foot, abrasions on the contralateral foot, unsteadiness (especially in the elderly, those with postural hypotension or impaired proprioception), and falls from tripping, not to mention the ease—or lack of it—with which patients can shower or take a bath. Trials of nonremovable off-loading devices may be critically biased by population selection.

In conclusion, we emphasize our enormous respect for the work undertaken by Boulton and Armstrong but think that their arguments are simply not justified. The recent Cochrane review of off-loading (3) concluded that “there is very limited evidence of the effectiveness of total contact casts” and highlighted the fact that there has been no comparison undertaken between TCC and Scotchcast (or equivalent) removable boots, which are widely used in many countries. The TCC is an option, but not sine qua non in either clinical practice or future trials.

Boulton AJM, Armstrong DG: Trials in neuropathic diabetic foot ulceration: time for a paradigm shift? (Editorial).
Diabetes Care
Veves A, Sheehan P, Pham HT: A randomized controlled trial of promogran vs standard treatment in the management in the management of diabetic foot ulcers.
Arch Surg
Spencer S: Pressure relieving interventions for preventing and treating diabetic foot ulcers.
Cochrane Database Syst Rev