Functial Assessment of a Limb

How to Tell if a Broken Arm or Leg is Working

Doctors treating girl's leg with bandages
Bandaging a leg. Blend Images - ERproductions Ltd / Getty Images

When you think an arm or leg is injured or broken, one of the assessments you'll want to do is called a functional assessment. There are two parts of an assessment:

  1. Structural integrity, which includes issues like deformity or discoloration.
  2. Functional integrity, which measures circulation, sensation and motion (CSM)

Always Assess Distally

Distal refers to points on the arm or leg that are further away from the heart. The tips of the fingers or the tips of the toes are the most distal parts of the body. When we assess a limb after an injury, we always asses areas distal to the injury.

Assessing a spot more proximal to an injury (closer to the heart) doesn't matter. A broken wrist will not affect your shoulder's ability to feel or get blood flow, but it can cut off blood flow to your hand.


Checking bone density of teenage boys left foot
Capillary refill is one way to test circulation. Medic Image / Getty Images

Circulation (blood flow) in an injured limb is what will encourage healing. Blood brings nutrients and oxygen to damaged body tissues and removes waste products that come from repairing the damage.

Capillary Refill

There are two ways to assess circulation in an injured extremity. The first is known as capillary refill, which can be tested by blanching the nail of a finger or toe (squeeze the nail gently to make the blood leave the area) and waiting to see how quickly the color returns when you let go.

It should take less than 2 seconds for the capillaries to refill after being blanched. It just so happens that saying "capillary refill" takes about 2 seconds. So, blanch the nail bed and say capillary refill. If the color doesn't return before you finish saying it, the circulation of the limb is compromised.


The other option is to check the pulse in the injured extremity. Sometimes, it's not possible to check a pulse distal to the injury. For instance, checking a radial pulse (found at the wrist) is not feasible in a patient with a wrist injury. In that case, you have to use capillary refill.

When assessing circulation using the pulse, you are only looking for the pulse to be present. It doesn't really matter how fast or slow it is. We just want to know if there is blood flowing past the injury.


Nurse assisting boy with broken leg
Sensation should be done where the patient can't see what toe you're touching. Blend Images - ERproductions Ltd / Getty Images

Sensation tests the sensory nerve function in an injured limb. There are three things we can sense with skin: pain, heat and pressure. This isn't a test of how well each of these types of neurons works. This is a test of whether or not the patient can feel anything at all distal to the injury. To test it: touch a finger or a toe and ask the patient which one you're touching.

Our minds can play tricks on us, so it's important not to let the patient see which toe or finger you're touching. If the patient does see, he or she could perceive sensation even if it doesn't exist.


Boy in pain while having broken arm examined by nurse
Squeezing is one way to test motion of an extremity. Steve Debenport / Getty Images

Assessing the motor function of an extremity tests not only the motor neurons, but also the structural integrity of the limb. If an extremity is locked in place by displacement from a fracture, it's not the same as a damaged neuron. However, that doesn't change the fact that the extremity is not functioning.

Push and Pull

Assess motion by having the patient move his or her extremity. If it's a lower extremity, make the patient pull his or her toes upward (or push downward) against your hand.

If you are assessing the patient's hand, have him or her squeeze your hand to assess whether he or she can do it. Again, the test is to see if it can be done, not how well it can be done.

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