What is shoulder instability?
Shoulder instability is a shoulder pathology that occurs when the humerus separates from the shoulder socket or glenoid. Shoulder instability occurs after sustaining damage to the shoulder joint, such as from a sudden fall. After an initial episode of dislocation, the shoulder is prone to repeat episodes, leading to chronic shoulder instability. Two different types of shoulder instability include complete dislocation, when the humerus comes out of the socket entirely and requires assistance to reduce the shoulder, or subluxation, when the humerus separate’s from the joint and immediately reduces.
Causes and symptoms of shoulder instability:
Shoulder dislocation: severe acute trauma to the shoulder may cause dislocation, often also resulting in tears of the ligaments and cartilage around the rim of the glenoid. The cartilage is referred to as the labrum, and a tear of the labrum is called a Bankart lesion. Symptoms include pain, weakness, and dysfunction of the shoulder.
Hyperlaxity: patients with loose ligaments experience hyperlaxity. Repetitive overhead potions may cause hyperlaxity, making the shoulder prone to instability. Some patients experience hyperlaxity without repetitive motions and will experience dislocation underneath the socket, behind the socket, and in front of the socket, also known as multidirectional stability. Other patients experience hyperlaxity naturally and are alternatively referred to as being double jointed.
Who is more susceptible to experiencing shoulder instability?
The younger, athletic population is susceptible to shoulder instability. Patients who are 20-years-old and younger, males, have joint hyperlaxity, are high-level athletes, have a history of shoulder instability, or have lesions on the glenoid or humerus are susceptible to recurring shoulder instability.
How is shoulder instability assessed?
Physicians may order X-rays to identify any possible injuries of the bones of the shoulder joint. An MRI can be used to obtain a more detailed image as well as show the soft tissue surrounding the shoulder joint and assess for labral tears. A CT scan can be used to show any bone loss.
During a shoulder examination, the physician will look for any asymmetry between the two shoulders, including the shoulder girdle (the shoulder blade and collarbone) and muscle mass, protrusion of the shoulder blade or winged scapula, and any signs of atrophy. Patients with chronic shoulder instability have some asymmetry between the two shoulders, with the deltoid muscle having some degree of atrophy. Depending on whether the instability occurs to the front or back of the shoulder, the examiner will feel fullness at the front of the shoulder in front shoulder instability and at the back of the shoulder for back shoulder instability.
Anterior Apprehension Test:
The patient lays on their back, with the affected arm held at a 90° angle from their torso and elbow bent at 90°. The examiner will apply pressure to the upward face of the arm, slightly before the elbow joint, with one hand and turn the arm and elbow towards the ground with the other hand. The test is positive if the motion produces shoulder dislocation or subluxation.
Jobe Relocation Test:
The Jobe’s Relocation test is a continuation of the Anterior Apprehension Test. Once the Anterior Apprehension Test is positive, the examiner will then apply push from underneath the arm rather than apply force to the underside of the arm while keeping it in the same position as the Anterior Apprehension Test. If symptoms of shoulder dislocation produced by the Anterior Apprehension Test are resolved, the test is positive.
Load-and-shift Test:
The patient is lying on their back, upper arm 0° from the torso, while the examiner holds the shoulder blade with one hand and holds the arm at the elbow bent at 90°. The examiner centers the humerus in the socket by applying force to the elbow. The examiner then uses the arm on the shoulder blade to push the shoulder downwards and then upwards. This is repeated with the upper arm held at 45° and then at 90° from the body. If the force applied by the examiner causes the humerus to slide, or translate, out of the shoulder socket by a greater extent than the unaffected shoulder, the test is indicative of shoulder instability. There are three different grades of humeral translation:
Grade 1: the humerus slides further in comparison to the unaffected shoulder.
Grade 2: the humerus slides up to the rim of the shoulder socket.
Grade 3: the humerus slides past the shoulder socket.
Treatment:
First, the physician will reduce the dislocated shoulder, if needed, in order to bring the humerus back into the shoulder socket. The arm will then be immobilized in a sling and the patient will be advised to discontinue use until further assessment. Treatment may be surgical or nonsurgical.
Nonsurgical treatment:
Nonsurgical treatment is used for patients with first-time dislocations, defects to the head of the humerus or the shoulder socket are less than 25%, the patient would like to return to the sport in-season, the sport is non-contact or there is no overhead throwing, and/or the patient can wear a brace and has no instability while playing.
After 1 to 2 weeks of immobilization and cryotherapy, the application of extreme cold to the shoulder, patients will gradually stop using a sling and begin physical therapy to regain strength and range of motion. After about 2 to 3 weeks, the patient can return to regular activities using a brace.
Surgical treatment:
Candidates for surgical treatment include patients who also experience a rotator cuff tear, have large Blankart lesions, Hill-Sachs lesions or humeral head defects greater than 25%, humeral fractures near the shoulder, have a dislocated humerus than cannot be brought back into the socket, have dislocated the shoulder for the first time and are less than 20-years-old, play contact or overhead-throwing sports, experience instability after returning to a sport, are unable to wear a brace while playing, conservative treatment fails to bring the patient’s performance back to baseline, or the patient seeks surgical treatment sooner.
Surgeries can be open or use an arthroscope. An arthroscope is a small camera that is inserted into the joint, displaying images on a monitor. This allows the surgeon to survey the inside of the joint and avoid making large incisions. An open surgery does not use an arthroscope and therefore requires larger incisions.
The following surgeries may be used for patients with shoulder instability:
-Arthroscopic Bankart Repair: The primary aim of this procedure is to repair labral tears and reattach the labrum onto the glenoid rim through the use of an arthroscope.
-Remplissage: an arthroscopic procedure that is utilized when the Hill-Sachs lesion is very large and causes the shoulder to easily dislocate with little overhead movement.This technique helps prevent the recurrence of shoulder instability postoperatively by anchoring the infraspinatus tendon of the rotator cuff, a group of tendons and muscles that attach the humerus to the shoulder blade, into the lesion in order to fill it in.
-Latarjet: used to repair lesions in the front of the glenoid. Bone is transferred from a part of the shoulder blade called the coracoid process to fill in the lesion, preventing further dislocations.
The following algorithm is used to determine the type of procedure:
-Group 1 patients: patients that have a less than 25% defect to the glenoid and Hill-Sachs lesion that does not engage with the front of the glenoid. These patients undergo Arthroscopic Bankart repairs.
-Group 2 patients: patients with a glenoid defect of less than 25% and have a large Hill-Sachs lesion that engages with the front of the glenoid (i.e a lesion that gets caught on the front glenoid rim). These patients are treated with an Arthroscopic Bankart repair and a remplissage.
-Group 3 patients: patients with a greater than 25% glenoid defect and a non-engaging Hill-Sachs lesion. These patients are treated with a Latarjet procedure.
-Group 4 patients: patients with a glenoid defect greater than 25% and an engaging Hill-Sachs lesion. The glenoid lesion is addressed first using the Latarjet procedure followed by the Remplissage procedure and other humeral bone grafting procedures.
Postoperative recovery: The patient is kept in a sling for 4 to 6 weeks and is encouraged to avoid stiffness by doing elbow, wrist, and finger range of motion exercises. Once the patient is weaned off of using the sling, the patient can then do passive - movement with assistance - and active - patient moves shoulder on their own- range of motion exercises. Extreme positions are avoided until 8 weeks postoperatively, with full active range of motion being achieved by the 8 week period. The patient will then begin strengthening and resistance exercises 10 or 12 weeks postoperatively. The length of time it takes for patient to return to a sport or work depends on the demands of the position. Patients will return to a sport no sooner than 3 months and may even return after 6 months for high-impact sports. Patients can return to work as soon as 1 to 4 weeks to up to 10 months after surgery.
