The #1 Neglected Assessment Measurement

Most physical therapy assessments consist of passive ROM, active ROM, and functional strength. However, if these are the only tests you're performing, you're missing out on one particular measurement that may be the difference in getting your patient out of pain. This #1 neglected assessment measurement is the infrasternal angle (ISA). The ISA is a comprehensive topic, but this article will discuss a brief overview and provide three benefits when you include the ISA in your assessments!

I'll discuss the following topics in article:

• Basic ISA Overview
• Spinal Orientation
• Movement Bias
• Breathing Influence

If you're a visual learner, click the video below to watch the same concepts.

Basic ISA Overview

The infrasternal angle is the angle created between the lower rib cage's left and right sides as it meets the xiphoid process. These angles can be named either wide (> 90°) or narrow ( < 90°), which will produce different expectations based on the measurement. We'll now discuss the three expectations it creates.

Spinal Orientation

When assessing your patient in supine, have you ever noticed that one rib flares up more than the other? If so, what do you do with that information?

We often forget that the ribs are connected to the spine. So this asymmetrical rib flare you're observing is valuable information about your patient's posture. For example, if the left lower rib cage flared upwards compared to the right, the patient is rotating to the left. The rotation created the flare you're seeing (check it out yourself if you're having difficulty visualizing it). Furthermore, they most likely have a side-bent position on the right with a right shoulder lower than the left.

Why do you think?

The right side bend will contribute to the right ribs down and the left ribs up "look."

Make sure you consider this information when you're checking ROM measurements. For example, if the right shoulder is starting lower, it will run out of room faster. As a result, you'll see limited shoulder flexion compared to the left. Instead of quickly blaming a tight right shoulder, understand the influence that the ISA is playing on the measurement you're testing.

Movement Bias

 The angle created from the ISA will provide you with movement expectations. Yes, this means that when you're patient is lying in a supine position, you'll understand their natural movement biases and limitations before actually checking their movement.

To understand this better, you can see the expectations that cars create. For example, you would expect a Lamborghini to be fast, expensive, and bad on gas. Conversely, you would expect a smart car to be slow, inexpensive, and good on gas. Of course, they both have their pros and cons, but they have general expectations that come with the car.

Similarly, the infrasternal angle creates movement expectations and can be broken down like this:

Wide ISA:

• WNL: Internal rotation, adduction, and extension
• Limited: External rotation, abduction, and flexion

Narrow ISA:

• WNL: External rotation, abduction, and flexion
• Limited: Internal rotation, adduction, and extension

The various shape changes of the acetabulum and the glenoid for wide and narrows create these movement expectations at the hip and shoulder.

However, it's worth noting that with cars, there can be modifications to the engine. So, if you switch the engines of our two car examples, the outcomes wouldn't be exactly what you expect. However, the bias for a Lamborghini would always be a fast, expensive, and poor gas kind of car.

Likewise, the human body can adapt to secondary compensations depending on possible patterns it adapts to. But, as we saw with our car example, the wides will always have their internal rotation bias even if they show an external rotation ROM loss.

Breathing Patterns:

Let's get one thing straight — assessing breathing patterns should always be a part of your assessment! How your patient breathes is crucial to their range of motion restrictions and movement limitations and invaluable information you'll want to have.

The ISA provides a snapshot of how they manage air and how "patterned" they are. Someone that is more "patterned" has more difficulty opening and closing their ISA as we would want to see with normal respiration. As a quick reminder, airflow constantly moves from high to low concentrations. I like to think of air as being a "lazy person." They want to find the path of least resistance and do as little as possible. Similarly, the air will be "pushed" towards the open space (least resistance) and doesn't want to put up a fight against the resistance. Here are some breathing expectations for our two categories:

Wide ISA:

• Anterior-Posterior compression at the pump handle (think anterior chest and upper thorax being smooshed together)
• Lateral bucket handle expansion (think obliques being "weakened" and in a more lengthened position which increases in ISA)
• Thoracic and Pelvic diaphragm descended (take a big inhale and pause before you exhale — this is a wide ISA)
• Increased belly breathing (this is where the least amount of resistance is)
• Minimal lung expansion (to expand the chest i.e the lungs, it needs to be able to expand, but this is where the resistance is)

Narrow ISA:

• Lateral compression at the bucket handle (think more activation of obliques pushing the lower rib cage together)
• Anterior-Posterior expansion at the bucket handle (less resistance at the sternum allows for increased mobility a.k.a expansion)
• Thoracic and Pelvic diaphragm significantly descended (an increase in the pelvic floor ROM allows for further descension)
• Decreased belly breathing (increase in pump handle expansion allows lungs to expand easier than the Wide ISA's)
• Increased lung expansion (less resistance allows movement)

Overview

This article intends to increase your awareness of the ISA. First, it provides you with expectations, and then your full assessment will help rule in or out specific issues. But, if you'd like to dive significantly deeper to understand the ISA and these expectations further, I encourage you to join our Performance Redefined Program. This is our 8-week movement mastery course, which will go into significant details on topics like this to improve your assessments, exercise prescription, and overall comprehension of the human body!