Shoulder Anterior Impingement Syndrome...aka SAIS

Next up in our fantastic three-part series all about the shoulder, we are going to dive into shoulder anterior impingement syndrome, more commonly known as just SAIS. If you haven’t read our first blog on Upper Crossed Syndrome (UCS)- check it out here. You’ll want to be familiar with UCS as this is usually a precursor to the development of SAIS.

SAIS is caused when the supraspinatus tendon becomes entrapped between the acromion and the greater tuberosity of the humerus during elevation (shoulder shrug) and/or internal rotation (turning your shoulder to the inside) of the arm. (3) To put it more simply, SAIS occurs when there is an impingement of tendons (or bursa) in the shoulder. Impingements are most often caused by overuse. The repeated use of the shoulder can cause tendons to swell, leading them to catch on to the upper shoulder bone.

SAIS can also be caused due to a lack of subacromial space. (4) This is the space located above the shoulder’s ball-and-socket joint and below the acromion (the top-most bone of the shoulder). There are a couple conditions that can lead to a diminished subacromial space: degeneration of the AC joint (the joint that connects the clavicle to the acromion/shoulder blade), bone spurs, or the thickening of the coracoacromial ligament.

One of the biggest threats to subacromial space comes from having misshapen acromion. There are three different acromial types. Type I is “flat,” type II is “curved,” and type III is “beaked.” Approximately 20% of the population has a “flat” type, with 55% having a “curved” type, and finally 25% of the population has a “beaked” type acromion. (1) Type I has a larger space available for tendons and bursa when compared to Types II and III. With less space available for tendons and bursa, impingements become more likely. It has been found that Type III is more common in males and is present in 75% of patients with a rotator cuff tear.

Upper crossed syndrome and scapular dyskinesis (more simply the abnormal mobility or function of the shoulder blade) have also been known to be predisposing factors for SAIS.

SAIS is by far the most common disorder for the shoulder, accounting for up to 44-65% of all shoulder complaints. (2)

SAIS is typically found more frequently in younger and middle-aged populations, those who perform repetitive overhand activity for athletics or work.

SAIS can be categorized into three different categories, as the degeneration increases, so do the stages.

Stage 1- most common in younger patients, categorized by intense but reversible pain, and swelling

Stage 2- typically affects patients between ages of 25-40 who have suffered with SAIS for months/years, characterized by tendonitis and permanent scarring of connective tissues, may require surgical intervention

Stage 3- affect patients over 40, significant tendon degeneration/scarring result of prolonged irritation, characterized by irreversible disruption of rotator cuff tendon, biceps tendon degeneration/rupture common at this stage, acrimoplasty or rotator cuff most likely required for management (5)

There is a range of testing that can be done to evaluate the severity of a patient’s SAIS diagnosis. Differential diagnoses include: a partial or full thickness rotator cuff tear, adhesive capsulitis (frozen shoulder), biceps tendon rupture, A/C or glenohumeral (shoulder joint) osteoarthritis, labral injury, calcific tendonitis, cervical radiculopathy (“pinched nerve” in your neck), inflammatory arthropathy, avascular necrosis (death of bone tissue due to lack of blood), neoplasm (tumor), suprascapular nerve entrapment and thoracic outlet syndrome. (5)

Now that we have that long and very depressing list out of the way, let’s move onto treatments!!!

The first focus of SAIS management is restoring a patient’s range of motion, while also avoiding movements that aggravate the shoulder. This means avoidance of overhead presses, lateral raises and push-ups. This is one of the rare exceptions where we ask our patients to avoid various activity. Don’t worry- it’s only temporary!

In the office treatment will most likely include soft tissue manipulation or myofascial release. IASTM and manual manipulation may also be performed- that’s right, the “torture tools”. (6) Additionally, kinesiology tape can be applied to help aid in scapular movement. (7) You’ll also get some exercises to do from home.

Return to work/play will begin gradually with a full release after range of motion is full and free of any pain and strength testing reveals no significant weaknesses.

Got something funky in your shoulder going on? Don’t put it off- give us a call and get it checked out! Until next time, Dr. Amy