Types of shoulder instabilities

There are many elements which need to be considered such as: 

• in which direction: anterior, posterior or inferior,

• in one or multiple directions,

• trauma induced or atraumatic,

• if there is identifiable structural damage(s) in the shoulder,

• any generalised joint laxity,

• any underlying neuromuscular or collagen disorder,

• abnormal muscle patterning,

• if the instability is volitional.

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 Many classification systems for shoulder instability had been put forward. The Thomas and Matsen system has the virtue of simplicity. [13] They termed the first group TUBS (traumatic, unidirectional, Bankart lesion and surgery). A second group was termed AMBRI (atraumatic, multidirectional, bilateral, rehabilitation and inferior capsular shift). More recently, the Stanmore system described a triangle with three poles of conditions based on presence of trauma, structural changes, and patterning of muscles. This gives a more comprehensive cover of the spectrum of shoulder instabilities. [14]

 

Treatments

The TUB and the AMBRI groups described in the above paragraph probably represent opposite ends of the spectrum of various types of shoulder instabilities. Reports of treatment results based on these groups help to give a practical guide.

In the TUB group, historically the re-dislocation rate after non-operative treatment is around 38-44%. [15, 16] Several cohort studies comparing recurrence rates between arthroscopic stabilisation and non operative management [17-20]. All of these studies demonstrated significant reductions in the rate of recurrence with operative stabilisation.

For patients in the AMBRI group, whether they fall into the Stanmore polar group 2 or group 3, a determined attempt at non-operative management is always indicated first. This should be delivered by physiotherapists with specialised experience in this area. Surgery should only be considered if there is a defined structural defect detected on imaging or arthroscopy and only after an initial period of physiotherapy. If there is no structural defect and the main pathology is suspected to be abnormal muscle recruitment (muscle patterning, Stanmore group 3) then surgery is contraindicated.

 

Treatment debate for first dislocation after reduction

Labrum repair was more effective than non-surgical treatment for first-time dislocation in terms of fewer redislocations. Arthroscopic lavage as an isolated treatment was no more effective at 2 years compared with non-surgical treatment, making arthroscopic lavage a candidate placebo surgical treatment in this context. Previous studies have suggested that delaying surgery and waiting to see whether the patient developed chronic instability after a first time traumatic shoulder dislocation did not lead to a less favourable prognosis of instability, quality of life or glenohumeral joint osteoarthritis. [21, 22]  Compared with routine surgery after a first time traumatic shoulder dislocation, waiting to see if a patient develops chronic instability despite rehabilitation might direct resources more efficiently and may save half of patients from unnecessary surgery.

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13. Thomas SC, Matsen FA. An approach to the repair of avulsion of the glenohumeral ligaments in the management of traumatic anterior glenohumeral instability. J Bone Joint Surg Am 1989; 71: 506-13

14. Lewis A, Kitamura T, Bayley JIL. The classification of shoulder instability: new light through old windows! Curr Orthop 2004; 18: 97-108

15. Rowe CD. Prognosis in dislocations of the shoulder. J Bone Joint Surg 1956; 38A: 957-77.

16. Hovelius L. Anterior dislocation of the shoulder in teenagers and young adults: Five year prognosis. J Bone Joint Surg Br 1987; 69A: 393-9

17. Wheeler JH, Ryan JB, Arciero RA, Molinari RN. Arthroscopic versus non-operative treatment of acute shoulder dislocations in young athletes. Arthroscopy 1989; 5: 213-7.

18. Arciero RA, Wheeler JH, Ryan JB, McBride JT. Arthroscopic Bankart repair versus non-operative treatment for acute, initial anterior shoulder dislocations. Am J Sports Med 1994; 22: 589-94.

19. DeBarardino TM, Arciero RA, Taylor DC, Uhorchak JM. Prospective evaluation of arthroscopic stabilization of acute, initial anterior shoulder dislocations in young athletes. Two to five year follow up. Am J Sports Med 2001; 29: 586-92.

20. Larrain MV, Botto GJ, Montenegro HJ, Mauas DM. Arthroscopic repair of acute traumatic anterior shoulder dislocation in young adults. Arthroscopy 2001; 23: 119-23.

21.  Kavaja L, Pajarinen J, Sinisaari I, et al. Arthrosis of glenohumeral joint after arthroscopic Bankart repair: a long-term follow-up of 13 years. J Shoulder Elbow Surg 2012;21:350–5.

22. Plath JE, Aboalata M, Seppel G, et al. Prevalence of and risk factors for dislocation arthropathy: radiological long-term outcome of arthroscopic bankart repair in 100 shoulders at an average 13-year follow-up. Am J Sports Med 2015;43:1084–90.