Shoulder Instability Series (Part 1): Dislocations, Labral Tears and the Bankart Lesion
The shoulder joint, or glenohumeral joint, is made up of three bones. The shoulder blade (scapula), arm bone (humerus) and the collar bone (clavicle).
For those that didn’t know, or perhaps never thought about it – the shoulder joint creates the most movement in the human body. It’s clear superiority of range, results in the joint becoming prone to pain, injury and instability.
Shoulder instability is a common restriction/injury, especially in young athletes and/or those that play contact sports. In these population groups, shoulder instability represents 23% of total shoulder injuries (9).
Shoulder instability branches a wide range of conditions, most commonly, it occurs following a shoulder subluxation or dislocation (2). However, it can also occur genetically or following repetitive overhead use of the shoulder (2). Before we go any further, let’s define the difference between subluxation and dislocation.
Subluxation – partial dislocation of the shoulder where part of the ball of the upper arm moves out of its socket. It occurs usually following the compromisation of the joint’s mechanical integrity. This integrity is impeded by weakness of the rotator cuff muscles, laxity of the glenohumeral ligaments or from a traumatic episode to the shoulder.
Dislocation – a complete dislocation means the ball comes all the way out of the socket (1). Following this, ligaments, muscles or the socket itself that are responsible for keeping the arm (humerus) in the socket (glenoid) are usually injured to some degree. Following a dislocation, these structures are often compromised – resulting in shoulder instability and therefore causes the shoulder to be susceptible to future dislocation.
Prevalence – The prevalence of shoulder dislocations is shown in figure 1. The incidence in males is higher than females across almost all age groups, with young males (17-21 years old) the clear leader. Majority of the younger dislocations are due to a traumatic episode with the older groups usually occurring from an isolated event typically influenced by age-related degeneration (3).
Labral Tears – Following a shoulder dislocation, the rim (labrum), which helps hold the ball by deepening the socket, is often torn – these are called labral tears. Labral tears often result in residual pain, popping, clicking or rotator cuff weakness that continues even after the shoulder has been put back into the socket (4). The labrum has no blood supply, this results in a lack of recovery of the soft tissue with subsequent reduction in shoulder stability. The most common labral tear is the SLAP lesion (Superior Labrum tear from Anterior to Posterior). Small labral tears, such as grade 1 and 2 SLAP lesions, can be managed well through physiotherapy by strengthening the dynamic stability (muscles) of the shoulder. However, severe tears, such as grade 3 and 4 SLAP lesions are often required to be operated on.
Common causes of labral tears:
- Falling onto an outstretched arm
- Traction injury or arm pulled out of socket
- Repetitive overhead activities
- Landing on shoulder/direct trauma
- Shoulder hyperextension
- Heavy lifting
Recurrent shoulder dislocation
Whether someone, following a shoulder subluxation or dislocation, is at risk of recurrence is largely dependent on the management they received following the initial injury. However, even with optimal management and intense rehabilitation – an individual may still experience future episodes of shoulder instability (3). This is due to other factors such as the residual damage to stabilising structures, the individual’s genetic make-up, their age and the sport or physical activity they return to.
A summary of recurrent dislocations is evident in table 1.
The pathology of recurrent shoulder dislocations has been investigated for decades. In the 1930’s a British surgeon named Bankart described and performed a surgical repair on a recurring lesion he found in the anterior labrum (3). This lesion and repair was then named after him.
The Bankart lesion remains to be the most consistently found abnormality in shoulder arthroscopy of those with recurrent dislocations, along with capsular laxity (loose ligaments) (3). More modern studies and surgeons involve the repair of ligament(s) as well as the Bankart lesion as the Bankart lesion alone has later been proven insufficient to cause shoulder dislocations (3).
Bankart lesions are evident when a tear occurs on the bottom/front of the labrum. Due to 96% of shoulder dislocations occuring out the front (anterior) of the labrum/shoulder – the Bankart lesion is very common following a shoulder dislocation and is typically involved with those that are traumatic. If a Bankart lesion is not repaired or compensated for correctly – the injured person will likely experience future dislocations, instability and pain (4).
Typically, a Bankart will be repaired via an arthroscopy (4). This procedure involves two small incisions where the repair is guided by a small camera lens. Tears in the labrum or injured muscles are repaired and damaged tissues removed (4). Both the arthroscopic and open procedures have been proven to be effective in the management of Bankart lesions (4).
Following either operation, immobilisation of the shoulder with a sling is typically undertaken for 4 weeks (4). Physiotherapy is also undertaken during this time and continues after the sling is removed.
Conservative vs Surgical Management
Following a dislocation, there are conservative and surgical methods of management that have been investigated thoroughly. Essentially which option is best for you depends on a full history taking and physical examination by a health professional. However, typically the younger population (under 25) are likely to have recurring dislocations follow their first and, due to its link with shoulder osteoarthritis, are advised to have surgery. If a labral tear has occurred, conservative management can be limited in its effectiveness. This is, once again, due to the labrum’s lack of blood supply and healing properties.
For those that pursue conservative management following dislocation – a strong emphasis is placed on strengthening the dynamic stabilisers of the shoulder joint. Following the relocation of the shoulder, it is best practice to immobilise it. Traditionally the shoulder was in a sling or collar and cuff with adduction and internal rotation – as seen in figure 2. However, recent research from the USA and Japan now recommends that the shoulder is immobilised in external rotation – as seen in figure 3. This is due to a perceived superiority of recurrence rate found to be 0% in external rotation and 30% in those immobilised with internal rotation.
Conflicting research of late, however, has shown there to be no significant difference between the two positions, with internal rotation showing 24.7% and external rotation having a 30% recurrence rate in one particular study (6). And supports findings in a 2015 systematic review that looked at first time anterior shoulder dislocations that were managed with immobilisation only – no surgery or physiotherapy (5). The results showed that 58.9% of those immobilised in external rotation returned to preinjury sport activities with 42.6% of those immobilised in internal rotation returned to this level of activity (5).
Despite recent support for the external rotation sling, more research is required to determine which sling position has the best results, or whether there is no superiority between the two.
Figure 2 – Internal Rotation Sling Figure 3 – External Rotation Sling
Information regarding the rehabilitation of shoulder instability as well as return to sport exercises, will be provided in part 2 of the shoulder instability series.
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- American Academy of Orthopaedic Surgeons (2019). Chronic Shoulder Instability. Retrieved from https://orthoinfo.aaos.org/en/diseases–conditions/chronic-shoulder-instability/
- Antonio, G. E., Griffith, J. F., Yu, A. B., Yung, P. S. H., Chan, K. M., & Ahuja, A. T. (2007). First‐time shoulder dislocation: High prevalence of labral injury and age‐related differences revealed by MR arthrography. Journal of Magnetic Resonance Imaging, 26(4), 983-991. doi:10.1002/jmri.21092
- Cutts, S., Prempeh, M., & Drew, S. (2009). Anterior shoulder dislocation. England: The Royal College of Surgeons of England. doi:10.1308/003588409X359123
- Desio Sports Medicine (2019). Shoulder Dislocation and Bankart Repair. Retrieved from https://www.desiosportsmedicine.com/treatment-specialties/shoulder/shoulder-dislocation-bankart-repair/
- Dickens, J. F., Owens, B. D., Cameron, K. L., Kilcoyne, K., Allred, C. D., Svoboda, S. J., . . . Rue, J. (2014). Return to play and recurrent instability after in-season anterior shoulder instability: A prospective multicenter study. The American Journal of Sports Medicine, 42(12), 2842-2850. doi:10.1177/0363546514553181
- Immobilization in external rotation after primary shoulder dislocation did not reduce the risk of recurrence: A randomized controlled trial. (2012). Orthopedics, 35(7), 610-611. doi:10.3928/01477447-20120621-09
- Kim, D., Yoon, Y., & Yi, C. H. (2010). Prevalence comparison of accompanying lesions between primary and recurrent anterior dislocation in the shoulder. The American Journal of Sports Medicine, 38(10), 2071-2076. doi:10.1177/0363546510371607
- Polyzois, I., Dattani, R., Gupta, R., Levy, O., & Narvani, A. A. (2016). Traumatic first time shoulder dislocation: Surgery vs non-operative treatment. The Archives of Bone & Joint Surgery, 4(2), 104-108. doi:10.22038/abjs.2016.5305
- Soliaman, R. R., da Cunha, R. A., Pochini, A. d. C., Andreoli, C. V., Cohen, M., & Ejnisman, B. (2016). Less than 60% return to preinjury sports activities after primary anterior shoulder dislocation treated with immobilisation only. Journal of ISAKOS: Joint Disorders & Orthopaedic Sports Medicine, 1(4), 198-201. doi:10.1136/jisakos-2015-000034