Multidirectional Shoulder Instability (MDI)?

The shoulder is the most flexible joint in the body with a complex arrangement of structures working together to provide necessary movement in daily life. This also makes it vulnerable to many serious injuries. 

Although the prevalence of MDI (atraumatic shoulder instability) is rare, it is generally common in women. 

Many patients affected with MDI are involved in overhead sports such as gymnastics, swimming, weightlifting, or volleyball that repetitively stretches the shoulder to extreme ranges of motion.


What is Multidirectional Shoulder Instability?

MDI is characterized as the laxity of the shoulder’s glenohumeral joint in multiple directions. The glenoid, glenoid labrum complex, and the glenohumeral ligaments as well as the negative pressure created in the joints play an important role in static stabilization of the shoulder. The rotator cuff, long head of the biceps, periscapular muscles, and deltoid muscles all act in maintaining the dynamic stabilization. The interaction between the static and the dynamic stabilizers is responsible for the overall stability of the shoulder. 

MDI is recognized as the condition where the static and dynamic stabilizers are no longer able to maintain the sufficient harmony of the glenohumeral joint. 

MDI is also known as atraumatic shoulder instability. 

Causes of Multidirectional Shoulder Instability

There are three factors that majorly cause MDI, these are:

  1. Bone anatomy: The bones of the shoulder help very little in stabilizing the joint. The shoulder socket is shallow and without any proper structures to hold it in place, the ball will not stay in position. 
  2. Static stabilizers: The ligaments around the joints are known as static stabilizers. These connect the bones. The ligaments are flexible but not stretchable. Shoulder instability is caused because of ligament tear. MDI is often caused by loose ligaments.
  3. Dynamic stabilizers: The muscles and tendons around the joints are known as dynamic stabilizers. This includes the rotator cuff. Dynamic stabilizers are flexible but not elastic. 

MDI is also caused by traumatic or atraumatic injuries; poor coordination of the rotator cuff muscles, having loose joints and genetic conditions.


Symptoms of Multidirectional Shoulder Instability

  • Discomfort or pain when performing overhead movements
  • Difficulty in performing daily simple tasks such as lifting objects or pushing doors
  • Feeling as if the shoulder might slip out of place
  • Stiffness and lack of strength in the shoulder
  • Inflammation and pain in the shoulder 
  • Pain while sleeping at night due to persistent pain in the shoulder 
  • Popping sound in the joint

Patients may also show signs of injury in the labrum or rotator cuff muscles. 


Diagnosis of Multidirectional Shoulder Instability

The diagnosis of MDI is a complex process as it lacks substantial findings. Thus, it is a problem that is present with vague activity-related shoulder pain. Generally, MDI is characterized by an atraumatic event. 

The doctor will look into the medical history of the patient and past injury to the shoulder if any. 

The doctor will then proceed to carry out a physical examination of the affected shoulder. The diagnosis requires instability in 2 or more planes in the anterior, posterior, or inferior region. Two tests that make it easier to evaluate are: 

  1. Sulcus Test: The examiner will apply downward force on the elbow while the arm is in a neutral position resting at the patient’s side. If a depression greater than the fingerbreadth is found between the lateral acromion and the head of the humerus, it is considered as the sulcus sign and the test is positive. 
  2. Apprehension test: The examiner will flex the patient’s elbow to 90 degrees and adduct the patient’s shoulder to 90 degrees while maintaining a neutral position. Then the examiner will slowly apply force to perform the external motion. The patient’s apprehensiveness to perform this motion is considered a positive result. 

After completing the physical examination, the doctor will follow it up with X-rays and MRI scans to understand the issue with more clarity. X-rays help in ruling out the possibility of other injuries and may also reveal any abnormality causing instability. MRI scans show the damage that happened to the labrum and also show the laxity of the ligaments and tendons. 

While coming to a diagnosis it is necessary to consider the psychological component present that might make the patient voluntarily induce shoulder dislocation.


Treatment for Multidirectional Shoulder Instability

Nonsurgical treatment is the first choice in the line of treatment options. 

Treatment should emphasize on strengthening the dynamic stabilizers of the shoulder joint.

  • Ample rest is advised and excessive intense overhead motions of the arm should be avoided. 
  • Nonsteroidal inflammatory drugs as prescribed by the doctor should be taken to reduce inflammation and relieve pain. 
  • Physical therapy that focuses on strengthening the shoulders and restoring scapular motions and improving ROM should be performed under the guidance of a trained professional to yield positive results. 

It is found that about 85% of the patients recover and are able to resume their daily life activities with nonsurgical treatments. However, some patients may not benefit from nonsurgical treatments and may ultimately have to opt for surgery. 

The best surgery for MDI is capsular plication which involves tightening the shoulder capsule. Tightening of the ligaments around the shoulder and closing the gap between the rotator cuff muscles are also some other surgical methods that can be performed arthroscopically or with standard incisions