How should a junior radiology resident approach his/her first shoulder MRI?
Look at what is known first: How old is the patient? Is this an in-patient or out-patient scan? Who is the referring physician? What is the history?
Believe it or not, but by the time you become a practicing radiologist with 5-10 years of experience, you will be able to “pre-fill” the report based on the answers to these questions, and be quite accurate for most scans without looking at a single image.
How is this possible? The age of the patient and clinical history tell the majority of the story. Remember, “treat the patient,” “don’t treat the images.” With common pathologies being common, an elderly patient with “shoulder pain” being referred to an outpatient imaging by a shoulder surgeon is most likely being considered for total shoulder replacement. The surgeon is usually trying to assess the integrity of the supporting structures and is probably not looking for “type VII vs type IIB” labral tears-centered report. Typical presentation in this elderly patient scenario will include pathologies such as acromioclavicular osteoarthritis, subacromial bursitis, either partial or complete rotator cuff tear, rotator cuff tendinosis, and very likely, degenerative changes and chronic tears in the glenoid labrum. The examination of bones will reveal degenerative changes in the greater tuberosity of the humerus.
Your report will be very different for an MRI of a young baseball pitcher with shoulder clicking or pain. Here you would spend majority of your time describing labral tear in detail. While not impossible, full thickness rotator cuff tears would be much less likely in a younger person.
Should shoulder MRI include intra-articular contrast?
The answer to this question depends on preferences of referring surgeons, radiologists and the available equipment. Some common sense points: if a massive rotator cuff tear is suspected, there is not much benefit in putting the patient through trouble of contrast injection into the joint. On the other hand, if a question comes up on “Whether a full thickness microtear is present?” or “Is this a scar or a new tear in a post surgical labrum?” intra-articular contrast can help to problem solve.
How do you describe rotator cuff tears?
Let’s start with an example: “1.5 cm distal, partial, articular surface tear of the supraspinatus tendon with inferior fibers retraction to the level of superior humeral head.” This achieves the following goals:
- Describe the size of the tear. In case of a full thickness tear, two dimensions are helpful. If you qualify with anteroposterior and mediolateral specifics, the surgeons will thank you.
- Explain where the location is – what tendon and whether distal, mid(critical) or proximal zone is involved
- The tear needs to be qualified as partial or complete. If partial, explain whether articular surface or bursal surface is involved. True intra-substance partial tears are also tears, but may be impossible to see during arthroscopy or surgery.
- Describe how far the torn tendon or tendon fibers are retracted.
Why are the acromion types important? How do you approach acromion types?
There are anatomical and developmental variations in the configuration and fusion of acromion process of the scapula. Os acromiale and hook-type acromion may predispose the patient to rotator cuff tendinosis and eventual tear.
Look at the acromion on sagittal, coronal and axial sequences at least a centimeter lateral to the acromioclavicular joint. The first observation to make here is whether the acromion is flat (type I) or curved (type II). The osseous spurs from the acromion should be evaluated separately from the inferiorly-projecting osteophytes of the acromioclavicular joint. The descriptive terms to use here are “large” or “small,” and”traction,” “keel,” “heel,” and “bird beak” types.
Any quick points on the glenoid labrum?
Let’s discuss two points here:
There are many sub types of labral tears, but one of the commonly asked questions by the surgeons is whether labral anchor is involved. When you describe superior labral tear, it helps to measure it or describe the clock face position. If you see that tear extends into the labral anchor, specify so.
The second point is to look for paralabral cysts. These are usually associated with labral tears even when MRI is not clearly showing a tear. Paralabral cysts can become quite large and may result in mass effect on suprascapular nerve or quadrilateral space.
What is a labral anchor?
The site of long head of the biceps tendon attachment onto the labrum.