This document discusses posterior shoulder instability. It begins by describing the anatomy and biomechanics of the shoulder. Posterior instability is less common than anterior instability and can be caused by trauma or repetitive microtrauma. Clinical examination is important for diagnosis and may reveal posterior shoulder pain with flexion and internal rotation. Imaging such as x-rays, CT, and MRI can identify bony lesions. Surgical treatment options depend on the specific soft tissue or bony injuries identified and may include arthroscopic or open stabilization procedures like posterior capsulolabral repair. Rehabilitation is important after surgery.

1. ΤΑ Κ Τ Ι Κ Ό Μ Ε Τ Ε Κ Π Α Ι Δ Ε Υ Τ Ι Κ Ό Π Ρ Ό Γ ΡΑ Μ Μ Α Κ Ε ΟΧ
Π Α Θ ΟΛ Ο Γ Ί Α - Χ Ε Ι Ρ ΟΥ Ρ Γ Ι Κ Ή Ώ Μ ΟΥ
POSTERIOR SHOULDER
INSTABILITY
PRESENTED BY:
MANOS ANTONOGIANNAKIS
Κολλέγιο Ελλήνων Ορθοπαιδικών Χειρουργών
Ελληνική Εταιρεία Χειρουργικής Ορθοπαιδικής και Τραυματολογίας
9/5/2014w w w. s h o u l d e r. g r

2. The Shoulder
 Greatest Range of Motion in the Body
 Motion in all 3 planes of movement
 Prone to instability
Sacrifices stability for mobility

3. What is Instability
 Biomechanical Dysfunction
 Failure of static and dynamic stabilizers
 Ranges from mild subluxation to
traumatic dislocation

4. Contributors to stability
Static stabilizers
1. ligamentous structures labrum and
capsule
2. bony configuration of glenoid and
humeral head
Dynamic stabilizers
1. rotator cuff
2. scapula muscles

5. HISTORY
Hippocrates
First described reduction for posterior
dislocation of the shoulder
Sir Astley Cooper
First described posterior dislocation in a patient
with a seizure
Malgaigne
First described a series of 37 patients with
posterior instability in 1855
before the advent of radiology

6. POSTERIOR RESTRAINTS
1. Glenoid (version and shape)
Abnormalities in the glenoid shape and
version has been described as more common
in patients with atraumatic posterior
instability. (Weishaupt,2000).
The greater the retroversion of the glenoid
the more prone it is to posterior dislocation.

7. POSTERIOR RESTRAINTS
2. Capsule
IGHL plays a significant role at the extremes of internal humeral rotation.
Unlike the anterior structures, the posterior capsule is relatively thin with less
clearly defined ligamentous components, especially superiorly above the
equator.

8. POSTERIOR RESTRAINTS
3. Rotator Interval
Plays an important role with the humerus in neutral rotation
Incision of the rotator interval capsule increased posterior translation by 50%
and inferior translations by 100%, suggesting resultant overlap in magnitude
and direction of the various capsular regions to the overall instability pattern
(Harryman, 1992).

9. POSTERIOR RESTRAINTS
4. Labrum
Usually torn in Traumatic dislocations, with the formation of a posterior
Bankart lesion. The importance of the posterior labrum in posterior instability
has been neglected in the past. Since the advent of arthroscopy posterior
labral lesions have been more commonly found and treated.
Recent posterior labral lesions described:
POPSLA lesion – posterior Periosteal Sleeve labral Avulsion
(Yu et al. Skel Radiol. 2002. 31:396-9)
Kim’s Lesion – Incomplete & concealed avulsion posteroinferior labrum
(Kim, 2001)

10. POSTERIOR RESTRAINTS
Posterior inferior
Bankart lesion

11. POSTERIOR RESTRAINTS
5. Subscapularis
Blasier et al identified the subscapularis as being the muscle providing the
greatest resistance to posterior subluxation of the humerus
J Bone Joint Surg Am, 1997

12. AETIOLOGY
Traumatic instability
typically follows a distinct history of dislocation or subluxation, sustained
during a significant injury.
Patients with atraumatic instability often have no history of true dislocations,
but on probing there often is a history of minor trauma or repetitive
microtrauma (sports). This is usually associated with capsular laxity

13. Posterior instability
clinical presentation
in forward flexion and internal rotation sometimes
after an anterior repair of a lux shoulder
2. Locked posterior dislocation after acute trauma .
1. Sense of insecurity and feeling of instability

14. Atraumatic posterior instability
clinical presentation
Frank dislocations with minimum violence often reduced by
the patient
Subluxations and positive apprehension sign in forward
flexion and internal rotation in a loose joint individual
usually teenager
Pain and functional impairment in a loose joint individual,
the patient mainly complaining for posterior pain in flexion
internal rotation and not for instability

15. HISTORY
These patients often don’t present with a typical history of true
dislocations
Symptoms of posterior joint pain and/or clicking.
Often this the pain occurs when loading the flexed and internally rotated shoulder.
This can be confused with subacromial impingement
Therefore careful clinical examination is essential.

16. CLINICAL EXAMINATION
It should include all of the followin
 Laxity (both the shoulder and general)
 Stability
 Proprioception
 Psychology

17. Clinical examination
www.shoulder.gr

18. POSTERIOR DISLOCATION
Much less common than anterior (3-5 %)
May be difficult to diagnose and may often be missed
on up to 50% standard AP view
Electric shock
Seizures
Trauma (alchoholics)

19. MECHANISM OF INJURY
 Axial loading of the adducted, internally rotated arm
because the internal rotator muscles are approx twice as powerful as the exernal
rotator muscles, a sudden contraction (such as from a seizure or shock) will cause
the humeral head to dislocate
 Involuntary recurrent posterior subluxation may be associated w/ high
forces generated during follow thru phase of various sports activities
this develops as humerus is in adduction, flexion, and internal rotation, & maximal
contractions of subscapularis and deltoid
 Voluntary dislocation
Internal rotation – Adduction – Flexion

20. ASSOCIATED LESIONS
 Reverse Bankart lesion
 Reverse Hill-Sachs deformity
 Lesser tuberosity fx
 Posterior HAGL lesion
 POLPSA lesion

21. ASSOCIATED LESIONS
Reverse Bankart lesion

22. Reverse Hill-Sachs deformity

23. POSTERIOR DISLOCATION
Athletes, such as weight lifters, throwers, racket sport athletes,
rugby players, and swimmers at higher risk.
inherently lax shoulders (advantage for their sports but prone to instability)
repetitive trauma (chronic instability)

24. CLINICAL EXAMINATION

25. CLINICAL EXAMINATION
 Attempted abduction and external rotation are painful
 The arm cannot be externally rotated to a neutral position
 There is inability to supinate
 Examination may resemble a frozen shoulder, especially
with a chronic, unreduced dislocation
 Nerve and vascular injury are not common

26. CLINICAL EXAMINATION

27. CLINICAL EXAMINATION

28. CLINICAL EXAMINATION

29. Locked posterior dislocation is easily
missed

30. POSTERIOR DISLOCATION

31. CLINICAL EXAMINATION

32. EVALUATION
 Radiographs (AP and axillary views)
 CT with 3D reconstruction (bony lesions)
 MR Arthrogram
.
Examination under anesthesia and arthroscopy aids the diagnosis, although
one should have most of the information before this.

33. X-RAYS

34. HELPFUL RADIOGRAPHIC SIGNS
Lightbulb sign
humeral head internally rotated
tuberosity no longer project laterally

35. HELPFUL RADIOGRAPHIC SIGNS
Trough line sign
2 parallel lines of cortical bone are seen on
medial cortex of HH, one line is medial
cortex of HH other line is “trough of
impaction fx (reverse Ηill-Sachs) anterior
articular surface of HH

36. CT

37. CT

38. DECISION MAKING
If the primary abnormality is found to be
structural (eg. Bankart lesion, bony lesion or
capsular injury) then surgery is often required
early and the rehab follows accordingly

39. POSTERIOR INSTABILITY SURGERY
It depends on the injuries
It is essential to identify the pathology and treat
accordingly

40. POSTERIOR INSTABILITY SURGERY
Soft Tissue Injuries
Soft tissue injuries are much more common than bony.
Posterior Capsulolabral Repair: repair of the soft tissue posterior bony Bankart
lesion, often combined with a capsular shift.
Capsular Shift: A posterior capsular shift may be required for a hyperlax posterior
capsule in the absence of a labral injury

41. POSTERIOR INSTABILITY SURGERY
Bony Injuries
Bony abnormalities are rare, but should always be considered, especially in
patients with failed soft tissue surgery
Subscapularis Transfer
Glenoid Osteotomy: a glenoid retroversion of above 20 degrees should be
considered for glenoid osteotomy.
Posterior Bone Block: This procedure is only considered in extreme cases as a
bony block to posterior translation of the humeral head. High failure rates

42. ARTHROSCOPIC REPAIR
 Lower morbidity
 Easily assess the entire joint and treat associated pathology
SLAP lesion, Rotator Interval lesions and anterior labral injuries
 Easier revision

43. ARTHROSCOPIC REPAIR
Arthroscopic instability repair is considered
a technically difficult operation
How to make it easier ?
Follow always standard steps

44. ARTHROSCOPIC REPAIR OF
POSTERIOR INSTABILITY
Arthroscopic repair of posterior dislocation although rare is not
so difficult
The only think needed is just to reverse the portals

45. EXAMINATION UNDER ANESTHESIA
You must have a feel of the joint

46. ARTHROSCOPIC REPAIR
 Anesthesia
 Patient positioning
 Surgeons Position
 Portals
 Haemostasis
 Instrumentation
 Suture management

47. ARTHROSCOPIC MANAGEMENT

48. ARTHROSCOPIC MANAGEMENT
Anchor placement

49. ARTHROSCOPIC MANAGEMENT
Knot tying

50. ARTHROSCOPIC MANAGEMENT
Knot tying

51. ARTHROSCOPIC MANAGEMENT

52. ARTHROSCOPIC MANAGEMENT

53. 3 MONTHS POST-OP

54. 3 MONTHS POST-OP

55. 3 MONTHS POST-OP

56. 3 MONTHS POST-OP

57. 3 MONTHS POST-OP

58. REHABILITATION

59. CONCLUSION
Unidirectional posterior shoulder instability
 Is much less common than anterior instability
 It should be strongly suspected in those high risk group of
athletes with posterior shoulder pain and/or clicking
 The treatment involves a combination of skilled therapy and
surgery for optimal outcome

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