The Mitchell brace

The Mitchell is a foot abduction brace: two shoes fixed to a bar, worn after the casting stage to hold the correction the casts achieved. It was developed specifically to be a more comfortable alternative, on the reasoning that a brace a family can actually live with is a brace that gets worn1.

The shoes are sandal-type leather with a molded soft thermoplastic elastomer lining, which is there to stop the foot sliding inside the shoe. They attach with a quick-release mechanism, so the shoes come off the bar without being unfastened from the foot1.

The heel carries a wedge that builds in the roughly 10 degrees of dorsiflexion the protocol calls for1. That detail matters more than it sounds: the brace is holding two things at once, abduction and dorsiflexion, and a boot that lets the heel drop has stopped doing half its job.

A series of 57 patients, 84 feet, followed after correction gives the clearest picture of the Mitchell on its own terms. Sixty percent complied with the protocol. Eight children, 14 percent, had skin problems, and in six of them that meant a superficial abrasion on the top of the foot1.

The outcomes in that series were good. At final follow-up every foot was plantigrade with at least 10 degrees of dorsiflexion, and none needed a surgical release. Of the 31 children followed for three years or more, 26, 84 percent, were still in the brace at three years1.

One study has compared the two designs directly on complications. Across 247 children and 374 feet at an Australian hospital, pressure sores occurred in 22.9 percent of children braced in a Mitchell and 12.6 percent of those in a Markell. A relative risk of 1.82, with a confidence interval running from 1.03 to 3.202.

What that means. On this one complication, at this one hospital, the Mitchell came out worse, and the difference was large enough not to be dismissed as chance.

What it might mean, and here you should be careful. That confidence interval very nearly touches 1.0, which is the line where an effect stops being distinguishable from none. It is retrospective, from a single center, and it does not tell you why. Children are not assigned a brace at random. A clinic may reach for one design for the harder feet, and harder feet get more complications. The study measured sores, not correction, and the Mitchell series above kept 84 percent of families braced at three years.

What nobody knows. Whether either design produces better feet. No comparison here measured that.

Every foot abduction brace in current use is an adaptation of the orthosis Denis Browne described in 19311. What separates them is the shoe, the bar, and whether the legs can move independently.

• Markell. Symmetrical shoes designed to work with a Denis Browne bar. Fewer pressure sores in the comparison above.
• Dobbs. A dynamic bar allowing independent leg movement, compatible with Mitchell or Markell shoes. Dorsiflexion can be harder to achieve with it, and it is relatively expensive1.
• Iowa. A fixed 60 degree abduction angle, a non-adjustable bar in three lengths, and a Flex Bar that gives limited movement and returns to position1.
• Steenbeek. Developed in Uganda, made with local tools, affordable, and used widely in clubfoot programs across Africa and Asia1.

The general finding on dynamic bars is worth knowing. In one series, non-compliance was 7.1 percent with a dynamic abduction brace against 41 percent with a traditional Denis Browne, and skin lesions 7 percent against 23.5 percent1. That is a different comparison from Mitchell versus Markell, and it is about the bar rather than the shoe.