Anterior Instability



Traumatic initial cause in 95%


M:F 2:1


Age of initial dislocation inversely related to recurrence rate

- patients younger than 20 have a redislocation rate of 90%

- between 20 - 40 years, redislocation rate of 60%

- patients > 40 years have a 10% rate of dislocation but a higher rate of cuff tears (up to 40% in patients > 60yrs)


Anatomy & Stability


1. Passive Stabilisers


Glenoid labrum 

- significant deepening by 50%

- labrum attaches capsule / ligaments / biceps


Negative intra-articular joint pressure


Joint fluid adhesion/ cohesion



- attaches to SNOH


Coracoacromial arch

- prevents superior displacement


Coracohumeral ligament

- attaches base of coracoid

- to lesser and greater tuberosity 

- passess through rotator interval between SS and SSC

- static restraint to anteroinferior translation in the adducted shoulder


Capsulo-ligamentous structures


1.  IGHL


Most important

- resists anterior translation in abduction and ER

- anterior & posterior band with sling between

- anteror band limits ER at abduction > 90°



- anterior band glenoid 3 o'clock

- posterior band 9 o'clock



- inferior anatomical neck / head


Arthroscopy Normal IGHL Humeral AttachmentIGHL


2.  MGHL


MGHL in Buford Complex



- behind SSC

- 2° restraint anterior translation

- limits ER at 45° Abduction

- present in 60% population



- supraglenoid tubercle below SGHL



- medial to LT


3.  SGHL





- adjacent to biceps tendon

- prevents inferior subluxation 

- functions only in adduction

- no function in decreasing anterior translation

- present 50% population



- supraglenoid Tubercle 



- LT


2. Dynamic Stabilisers


Rotator Cuff

- SSC resists anterior translation

- compresses head into glenoid socket


LH Biceps



- especially when arm is elevated 90o


Scapular Rotators 

- move glenoid into stable position




No essential pathological lesion responsible for every recurrent subluxation or dislocation


Thomas and Matsen Aetiology Classification



- Atraumatic, Multidirectional, Bilateral

- Rehabilitation, Inferior capsular shift, closure rotator Interval



- Traumatic, Unidirectional, Bankart, Surgery


1.  Labrum / Ligament / Capsule


A.  Bankart lesion



- described in 1938 

- humeral head forced through capsule

- humeral head tears fibrocartilaginous labrum from almost entire anterior 1/2 of glenoid rim 

- is an IGHL avulsion

- usually between 3 and 6 o'clock



- see detachment of anterior labrum


Anterior Bankart Lesion MRIShoulder MRI Anterior Bankart




Anterior bankart lesion ArthroscopyArthroscopy Soft Tissue Bankart



- present in 85% traumatic recurrent dislocations 

- may be associated with avulsion fracture of glenoid rim / bony bankart


B.  Excessive Capsular laxity 



- may be present alone or with Bankart lesion

- 30% have both

- 85% previous failed surgical procedures



- congenital collagen deficiency / MDI

- plastic deformation of capsuloligamentous complex

- single macro-traumatic event or repetitive micro-traumatic events


C. Capsular Tears


Capsular Tear 1Capsular Tear 2Capsular Tear 3


Capsular Repair 1Capsular Repair 2





- avulsion of IGHL from anterior humeral neck

- Humeral Avulsion of Glenohumeral Ligament



- 2 - 10%



- can be in combination with anterior bankart (Floating IGHL)

- association with subscapularis tear



- may see bony avulsion



- enlarged inferior  pouch

- discontinuity of IGHL / J sign


MRI Normal Humeral IGHL InsertionMRI HAGL J Sign



- will see exposed subscapularis muscle


Arthroscopy HAGL Normal Humeral attachment IGLH




A.  Open Repair

- take down SSC

- repair via bone anchors to inferior neck

- can cause limitation ER


B.  Arthroscopic repair

- 70o scope and 5 o'clock portal


E.  Bankart Variations



- anterior labrum periosteal sleeve avulsion

- labral-ligamentous structures shifted medially

- roll up under the periosteum


Perthes Lesion

- stripping of the scapular periosteum medially

- labrum may or may not be attached


Perthes Lesion MRI 1Perthes Lesion MRI 2Perthes Lesion MRI 3



- glenoid labrum articular disruption

- damage to the glenoid cartilage

- labrum undisplaced


Shoulder GLAD


F.  Muscle


Cuff Tears

- Present as pain or weakness 

- > 40 years = 30%

- > 60 years > 80% 


Increased Rotator Interval

- between SS and SSC

- tends to open up with AMBRI


2.  Bony


A.  Bony Bankart



- AP

- Garth (aim beam caudally)


Bony bankart XrayShoulder Garth ViewBony Bankart



- large bony bankart increases risk of failure of soft tissue bankart repair



- may need CT to decide the size best


Burkhart and De Beer Arthroscopy 2000

- described the inverted pear appearance

- loss of bone antero-inferior




CT Sagittal Small Bony Bankart




CT Axial Large Bony BankartCT Axial Large Bony BankartLarge Bony Bankart


Size calculation


Bony Bankart Size CalculationGlenoid Bone Loss Measurement 1Glenoid Bone Loss Measurement 1


Lo Parten and Burkhart, Arthroscopy 2004

- calculation of percentage bone loss arthroscopically


1.  Inferior glenoid is nearly a perfect circle

- centre is the bare area of the glenoid

- measure anterior radius v posterior radius at this level


2.  Calculate the diameter of the inferior circle

- twice the posterior radius


3.  Calculate the difference between anterior and posterior radius


The average diameter is 24 mm

- hence 12 mm posterior and 12 mm anterior

- if lose 8 mm anteriorly

- 12 mm posterior and 4 mm anterior

- calculation is 8/24 = 30%




25% loss and above poor prognostically

- means approximately 7.5 mm anterior bone loss

< 4mm anterior to bare area

- > 30%

- likely not amenable to soft tissue bankart repair alone


Acute Bankart Repair


Sugaya et al JBJS Am 2005

- demonstrated union of fragment with arthroscopic restoration

- must mobilise fragment, restore anatomically

- otherwise bony procedure


Decision Making


A.  Small fragment < 15%

- arthroscopic bankart repair

- can attempt to include fragment


B.  Intermediate 15 - 25%


C.  > 25%

- must restore glenoid rim

- acute restoration of bony frament or

- bony procedure / Latarjet / Bristow


B.  Hills Sachs Lesion 



- lesion posterior aspect of head

- where head engages on anterior glenoid



- AP with IR

- Garth view


Hill Sachs XrayLarge Hill Sachs Xray




Hill Sachs CT



- cartilage each side of lesion

- this differentiates it from the normal bare area next to infraspinatous


Arthroscopy Hill Sachs LesionLarge Hill Sachs



- large lesion can contribute to dislocation

- head engages defect in external rotation & abduction


Large Hill Sachs MRICT Hill SachsHill Sachs


Dynamic CT

Dynamic CT 1Dynamic CT 2Dynamic CT 3




Estimate percentage of articular surface

- concern if 25% or more


Hill SachsHill Sachs Measurement


Hill SachsHill Sachs measured


Management options for engaging Hill Sachs


1.  Posterior capsular advancement / Remplissage

2.  Humeral head allograft

3.  Anterior Bony Procedure / Latarjet / Bristow

- Hill Sach's lesion unable to engage on anterior glenoid rim

4.  Humeral osteotomy





- described by Wolf Arthroscopy 2008

- advance IS into Hill Sachs lesion

- makes lesion extracapsular



- perform arthroscopic transtendinous advancement of IS and capsule into defect

- tie knots from subacromial space




Zhu et al Am J Sports Med 2011

- 8.2% failure in 42 cases


Humeral head allograft


Humeral Head Allograft APHumeral Head Allograft Lateral.jpg



- anterior deltopectoral approach

- ER shoulder

- debride base of Hill Sachs

- secure allograft with 2 x screws



- late resorption of graft with recurrent instability


Humeral Head Allograft Resorption


Humeral Head Osteotomy


Weber et al JBJS Am 1984

- series of 180 patients

- very low risk of recurrence


C.  Abnormal Version 


Glenoid or Head

- rarely a cause