What makes the safe position safe? Part 1
Vita TU, Occupational Therapist and Project Manager
Sunshine Social Welfare Foundation
We all know safe position is the basis of good positioning in burns…
It’s common knowledge that when immobilizing the burned hand, we must position it in the safe position. The wrist in 10 to 15 degree extension, while the fingers are positioned with MP joints in 70 to 90 degree flexion, and PIP and DIP joints are in extension. The thumb’s CMC joint is in radial and palmar abduction, while the thumb’s MP joint is in extension [1]. But have you ever wondered why this position is actually safe? In this first post, we’ll tell you why, starting with the MP and IP joints.
It’s the anatomy, dummy!
There’s an anatomical explanation to why we position the MP joint in flexion and the IP joints in extension. First, let’s look at the MP joint.
There are two structures that ensure stability of the MP joint: the collateral ligaments and the volar plate.
Why is it safer to put MP joints in flexion instead of extension? The shape of the articular surface of the metacarpal head is eccentric, cam-shaped so it extends farther volarly than dorsally, and it is wider volarly than dorsally. When the metacarpophalangeal joint is in flexion, we can see the difference. The distance in extension is shorter than the distance in flexion. This in turn will affect the soft tissues that surround the MP joint and ensure its stability: the collateral ligaments and the volar plate. When the MP joint is at 90 degrees, the collateral ligament will be at its tightest.