How to Identify, Assess and Provide Treatment for Subacromial Impingement Syndrome

This week’s guest blog is from Tyler Pearce

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The space between the scapula’s acromion, coracoid process and the humeral head is referred to as the “subacromial space” or the “coracoacromial arch”. Impingement is the mechanism of injury, not the diagnosis, and implies the structures that pass through the subacromial space will experience unwanted compression and shearing forces causing inflammation and injury (Houglum P. A., 2016; Tripp et al., 2023). The pathology changes depending on which structure is irritated between the space. Structures that are commonly compressed include the supraspinatus, infraspinatus, subscapularis tendons, subacromial bursa and the long head of the bicep tendon (Houglum P. A., 2016; Tripp et al., 2023). The three types of impingements commonly known are “primary subacromial impingement”, “secondary subacromial impingement”, and “internal impingement” (Tripp et al., 2023). 

The less common type of impingement is called “primary subacromial impingement syndrome” (SIS) and is the result of a structural change. An example of a primary impingement can be an abnormally long acromion or the development of a growth on the tip of the acromion that can be classified into four shapes as listed below (Houglum P. A., 2016; Tripp et al., 2023). Other possible causes of primary SIS can include a smaller than normal subacromial space, abnormally large tendons and/or bursa (Houglum P. A., 2016). The subacromial space is about the width of a pencil so if any structures in the subacromial space are larger than usual, they are at a greater risk of experiencing signs and symptoms of an impingement (Houglum P. A., 2016).

Acromion Shape Classifications (Tripp et al., 2023):

1. The acromion is flat and does not protrude further than normal
2. The acromion starts to protrude further with a slight curve resulting in a higher chance of impingement
3. The acromion is now hooked, the risk of tissue impingement increases 
4. Lastly, the distal end of the acromion has osteophyte growths or bone spurs projecting from the acromion

Secondary subacromial impingement syndrome is the more common impingement and is a result of someone experiencing functional changes that develop over time. Possible causes for secondary SIS include joint capsule laxity or tightness, postural changes, rotator cuff muscle injury, fatigue or weakness and shoulder dyskinesis (Michener et al., 2003). Shoulder or scapular dyskinesis is commonly defined as abnormal or poor scapular movement along the rib cage. Shoulder dyskinesis can be seen in people experiencing many injuries such as impingement, rotator cuff pathologies, frozen shoulder, or instability post-dislocation or subluxation (Struyf et al., 2014). In theory, subacromial impingement syndrome can occur acutely as a result of a hard fall causing a fracture or displacement of a bone but it is more likely to be a subacute or chronic injury that develops over time. Internal impingement is often the primary cause for posterosuperior shoulder pain in athletes who compete in sports requiring excessive shoulder abduction and external rotation (Seitz et al., 2011) such as during the cocking phase of a throwing motion (Castagna et al., 2010). The most common pathology of internal impingement is when the tendons of the infraspinatus and supraspinatus are compressed against the glenoid process during repetitive overhead motions (Seitz et al., 2011). 

Now that you have a general idea on what subacromial impingement is, let’s dive into how to determine whether someone is suffering from subacromial impingement syndrome. First, you want to consider the history of your patient asking questions about pain, aggravators, mechanism of injury, symptom relief and so much more. Your patient will likely report gradual increase of symptoms with no specific mechanism of injury. They will likely report pain along the anterolateral and/or posterosuperior shoulder during palpation, activity and rest. The client may also report a popping or clicking sound during activity (Tripp et al., 2023). Your client may report symptoms during overhead tasks such as washing their hair, putting on their shirt, or putting dishes away on the top shelf. Athletes who compete in sports involving a lot of overhead movement such as during swimming, volleyball, pitchers in baseball, or Olympic weightlifters may be more susceptible to an impingement. Someone that works as a manual labourer who paints a lot for work may also be prone to impingement.

During observation, you may notice forward-rounded shoulders, abnormally positioned scapulas on the thorax, anterior head tilt and a hyperkyphotic thoracic spine among other observations. When palpating the shoulder, you may find point tenderness along the rotator cuff tendons, long head of the bicep tendon through the bicipital groove and along the acromioclavicular joint (Tripp et al., 2023). During your functional testing, your patient may report increased pain between 60° to 120° of active shoulder abduction otherwise known as the painful arc. Your client may have muscle weakness and pain during the empty can test, shoulder abduction or external rotation. You may find your client has tightness in their pectoralis muscles, specifically the pectoralis minor (Tripp et al., 2023). Research has shown a positive Hawkins-Kennedy test and/or symptoms present within the painful arc with weak and/or painful shoulder external rotation indicates there is a higher chance of an impingement (Park et al., 2005). When forming your clinical impression, it’s important to make a list of differential diagnoses. Other conditions to consider include rotator cuff or acromioclavicular joint pathologies, SLAP lesions or labral tears, frozen shoulder and bursitis (Tripp, B. L. et al., 2023; Vizniak & Macdonald, 2018).

Treatment of subacromial impingement syndrome starts and continues throughout the treatment plan with education on lifestyle modification, pain, and their injury. It’s also important to be honest and encourage your client to take responsibility of their rehab. Unless your client can afford to pay you to receive treatment daily, then your client needs to feel empowered to demonstrate autonomy in the rehab process. It’s also critical to set realistic goals and objectives because this dictates when the treatment plan is concluded. Based on your patients’ goals, you want to break the treatment plan into phases. Below is how I like to break down my client’s treatment plans. 

Phase 1: Create an environment that allows for your client’s body to heal optimally. 

• Lifestyle and sport modification
  • Posture correction and symptom management
  • Manual therapy for pain desensitization 

   

  Phase 2: Build tolerance back, reintroduce activities of daily living or sport that previously provoked symptoms.

  • Reintroduce aggravating activities in a controlled way
  • Perform single plane to multi-planar movement exercises emphasizing scapular strengthening and stamina 
  • Manually treat tissues that were inflamed in the early stages 

   

  Phase 3: Self-management, early identification and prevention strategies to reduce the likeliness of this injury happening again or identify earlier to seek treatment faster. 

  • Modalities as needed for symptom management 
  • Larger compound movements that translate into activities of daily living and sport 
  • Maintenance and full return to activities of daily living and/or sport 

   

  It’s important to note that every therapist treats differently and every patient is different. Generic program may work for some people and may be great at the start but remember to treat the individual, not just the injury. In conclusion, subacromial impingement syndrome is multifactorial in nature so it’s important to understand the different types of impingements, how to identify subacromial impingement and differentiate from other pathologies, as well as how to treat the specific tissue that may be impinged.