Posterior Glenohumeral Instability
||Classification / Treatment
|Etiology / Epidemiology / Natural History
||Associated Injuries / Differential Diagnosis
|Xray / Diagnositc Tests
synonyms: posterior GH instability, posterior shoulder dislocation, posterior laxity.
Posterior GH Instability ICD-9
Posterior GH Instability Etiology / Epidemiology / Natural History
- Occurs in <5% of shoulder instability patients.
- Usually men 20-30y/o active in competitive overhead or contact sports.
- 50% report discrete injury that initiated symptoms
- Associated with locked, straight-arm pass-blocking techniques in football, bench pressing, and overhead sports such as baseball, tennis, swimming.
- Seizures, electric shock, chronic alchohol abuse
- May result from a posterior capsulolabral avulsion or stretching of the posteroinferior capsulolabrum. Most consistent finding is redundant posterior capsule.
- May have preceeding traumatic dislocation, repetitive microtrauma with overhead acitivity, or generalzed ligamentous laxity.
- Acute posterior dislocations occur with force applied to arm in a flexed, adducted and IR position.
Posterior GH Instability Anatomy
- May involve: posteroinferior capsulolabral tear(reverse Bankart) including posterior band of inferior GH ligament; patulous posteroinferior capsule; reverse humeral avulsion of GH ligaments(RHAGL lesion); posterior labrocapsular periosteal sleeve avulsion (POLPSA lesion); osseous avulsion of posteror aspect of glenoid rim; posterior capsule or RTC tear.
- Subscapularis is the primary restraint to posterior translation.
- Posterior band of the inferior glenohumeral ligament complex is the primarly restraint to posterior translation with the arm in abduction.
- Superior glenohumeral ligament and coracohumeral ligament are the primary restraints to posterior translation with the arm flexed, adducted and internally rotated.
- Bone: glenoid retroversion, posterior glenoid erosion, engaging anterior humeral head defect, posteriorinferior glenoid hypoplasia, humeral head retrotorsion
- Kim lesion = incomplete and concealed avulsion of the posteroinferior aspect of the labrum. (Kim SH, Arthroscopy 2004;20:712).
- See also Shoulder Anatomy.
Posterior GH Instability Clinical Evaluation
- Slips out with forward elevation/IR such as removing book from overhead shelf, blocking for football linemen.
- Pain or instability sensation with the arm in flexion, internal rotation and adduction.
- Aching over posterior shoulder with sense of shoulder instability
- May have no symptoms of instability, but have poorly localized posterior shoulder ache when arm is placed in provocative position; reaching across the body with arm in internal rotation; doing bench press or push-ups.
- Baseball players may complain of fatigue, loss of pitch velocity, pain with cocking or with follow-through.
- Acute posterior dislocation presents with arm in adduction and internal rotation with an inability to externally rotate.
- Provacative Position: Instability with flexion, adduction and IR. As arm is moved into abduction from this position, the shoulder may visibly and audibly relocate.
- Circumduction Test: patient actively rotates the shoulder from an internally rotated and cross-body adducted position fully elevated and then to an abducted, externally rotated position and then back. Positive result is felling the joint subluxate in the interally rotated, cross-body adducted position.
- Posterior Apprehension Test: apply a posterior force to the humeral head with the arm in a forward flexed and internaly rotated position.
- Jahnke Test: posteriorly directed force is applied to the forward flexed shoulder which is then into the coronal plane as an anteriorly directed force is applied to the humeral head. Positive result is a clunk / subluxation felt as the joint reduces from the subluxated position.
- Jerk Test:
- Kim Test:
- Load and Shift:
- Sulcus Sign: distraction force is applied to the arm with the patient seated with arm at the side. The magnitude of displaced and any apprehension sensations are compared to the contralateral limb. Any abnormalities indicate inferior instability.
- Evaluate for anterior instability with Apprehension and Relocation tests.
- Posterior instability typically subluxates with shoulder flexed to 80-90°, whereas bidirectional instability typically is worst at 110-120° of flexion.
- Evaluate generalized joint laxity
- Evaluate axillary nerve function
- Assessments of generalized ligamentous laxity: ability to touch ipsilateral forearm with the thumb, place palms of hands on floor with knees locked, elbow/knee/MCP hyperextension.
- Assess for history of Ehlers-Danlos or Marfan Syndrome.
Posterior GH Instability Xray / Diagnositc Tests
- A/P and Lateral view in the plane of the scapula, and axillary view. Look for anterior impression defects in humeral head, or posterior lesions on glenoid.
- CT scan is best to evaluate bony anatomy. Evaluate for reverse Hill-Sachs or bony reverese Bankart lesion.
- MRI is best to evaluate for capsulolabral lesions and associated pathlogy. 86% demontrate reverse Hills-Sachs lesions; 60% posterocaudal labrocapsular lesions; 20% full-thickness RTC tear (Saupe N, Radiology, 2008;248:185).
Posterior GH Instability Classification / Treatment
- Classification: Acute: <6wks vs Chronic: >6wks; traumatic vs atraumatic; voluntary vs involuntary. Initial treatment is nearly always non-operative
- Nonoperative treatment: Physical therapy with exercise program designed to strengthen the posterior deltoid, the infraspinatus, and the teres minor, as well as the dynamic glenohumeral and scapular stabilizers. activitiy modifications for 6 months. Avoid elevation in the sagittal plane with arm in internal rotation. 2/3 of patients are successfully treated non-operatively. (Tibone J, CORR 1993;291:124).
- Chronic posterior instability without bone loss: Open posterior capsular shift vs arthroscopic posterior stabilization (Savioe RH, Arthroscopy. 2008;24:389). Ensure there is not a glenoid or humeral head lesion requiring bone graft or OATS.
- Chronic posterior instability with humeral head bone loss: lesser tuberosity transfer; allograft; Cap hemiarthroplasty; consider grafting defect arthrscopically using synthetic bone plugs (Smith& Nephew); Modified McLaughlin procedure (Charalambous CP, Arch Orthop Trauma Surg. 2008 Aug).
- Chronic posterior instability with glenoid bone loss: glenoid osteotomy; ICBG; acromial bone graft.
- May consider earlier surgery after discrete traumatic injury which has been associated with a poor responce to nonoperative treatment.
- Surgery is contraindicated for voluntary, habitual instability due to psychological problems.
Posterior GH Instability Associated Injuries / Differential Diagnosis
Posterior GH Instability Complications
- Recurrent instability
- Inability to return to competition in high-level athletes.
- Hardware failure / Anchor pull-out
- Nerve injury: Axillary nerve, Brachial plexus
- Fluid Extravasation:
- Chondrolysis: though to be related to heat from electo cautery or radiofrequency probes used during capsular release or capsular shrinkage.
- Chondral Injury / arthritis
Posterior GH Instability Follow-up Care
- Post-op: Place in shoulder immobilizer in slight abduction, slight extension and slight external rotation. Avoid flexion and internal rotation to protect repair. Perform elbow, wrist, hand ROM/strengthening,
- 7-10 Days: Wound check, continue immobilization,
- 6 Weeks: Discontinue immobilizer; begin cross-body adduction and light progressive resistive exercises / PT.
- 3 Months: Begin sport specific training.
- 4 Months: May return to non-contact sports.
- 6 Months: May return to contact/collision sports.
- Open Posteroinferior Capsular shift outcomes: 50% excellent; 32% good; 2% fair; 18% poor. 12% recurrent instability (Bibliani LU, JBJS 1995;77A:1011). 19% recurrence, 84% patient satisfaction. Significantly poorer satisfaction/outcomes in shoulders with chondral defects at the time of stabilization and in patients aged <37 years at the time of surgery. No progressive radiographic signs of glenohumeral arthritis were seen up to 22 years after surgery. (Wolf BR, JSES 2005;14:157).
- Arthroscopic Posterior Repair outcomes: 89% return to sport (67% at same level) with arthroscopic repair (Bradley JP, AJSM 2006;34:1061).
- Shoulder Outcome measures
Posterior GH Instability Review References
- Burkhart SS, A Cowboy's Guide to Advanced Shoulder Arthroscopy, 2006
- Millet PJ, JAAOS 2006;14:464
- Robinson CM, JBJS 2005;87A:883