The “Safe Position” for the Hand

safe-position

People can be whiners sometimes. Their hand will be in a cast for some break and you’ll take it off and they will say, “my hand is stiiiiifffff

It’s not just them, the mechanics of their hand is working against them and if the cast wasn’t positioned properly, it can make matters much worse as far as stiffness is concerned. This is why when a hand or wrist is being casted or splinted, care is taken to put it in the position that will minimize stiffness.

The “safe position” is also known as the intrinsic plus position as it favours the weaker motions of MCP flexion and IP extension that are difficult to recover.

Wrist: The weight of your hand, gravity and resting muscle tension all work together to pull the wrist into flexion. When the wrist is flexed, there is more tension on the extrinsic extensor muscles and they pull the MCP joints into extension. The extrinsic flexors are stronger than the extensors and pull the IP joints into flexion.ย Taking the tension off the extensors limits their pull across the MCP joints.

The position of flexed wrist, extended MCP joints and flexed IP joints is known as intrinsic minus.

Metacarpal Phalangeal (MCP) Joint: These joints are a little funny due to the collateral ligaments on either side. These ligaments pass slightly above the axis of rotation of the joint, this means that when the joint is flexed, they’re at their longest and when the joint is extended, they’re at their shortest. This is due to the famed “CAM EFFECT.” Though often quoted, you have to wonder, what is a cam*? This website explains it well.

* This does not apply to all those people who remember basic mechanical principles or were trained in something more hands-on than neuroscience

Interphalangeal (IP) Joints: The ligaments around the IP joints are at maximum stretch when they are fully extended (aka 0 degrees)

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