Mechanisms and Anatomy of Anterior Shoulder Instability¶
The anatomy and pathomechanics of anterior shoulder instability involve a complex failure of the structures that normally maintain the humeral head within the glenoid fossa. Because the shoulder is the most mobile joint in the body, it is inherently the most unstable, relying on a delicate balance between static and dynamic stabilizers.
Anatomy of Shoulder Stability¶
The glenohumeral joint is often described as a ball-and-socket joint, but the "socket" (glenoid) is relatively small and shallow compared to the "ball" (humeral head). This lack of bony constraint allows for extensive range of motion but necessitates significant support from soft tissues.
Static Stabilizers:¶
◦ Glenoid Labrum: A fibrocartilaginous ring that surrounds the glenoid rim. It increases the depth of the socket by approximately 50%, deepens the concavity, and creates a "suction cup effect" that resists translational forces.
◦ Glenohumeral Ligaments (GHLs): These are thickenings of the joint capsule. The Inferior Glenohumeral Ligament (IGHL), specifically its anterior band, is the primary static restraint against anterior dislocation when the arm is in the high-risk position of 90° abduction and external rotation.
Knowledge Check
The anterior band of the IGHL is the primary static restraint against anterior dislocation in the high-risk position of 90° abduction and external rotation, which is the classic mechanism of anterior shoulder instability.
◦ Negative Intra-articular Pressure: This helps keep the humeral head centered through a vacuum-like effect.
◦ Bony Geometry: The native version and inclination of the glenoid provide a baseline framework for stability. An emerging concept in anterior and posterior instability is the acromial shape's relation to instability risk. While still early, these factors likely warrant attention when considering reinjury risk.
Acromial morphology differs significantly between patients with anterior and posterior shoulder instability, specifically regarding the height, orientation, and coverage the acromion provides to the humeral head.
Acromial Height and Sagittal Orientation¶
Posterior Instability: This condition is strongly associated with a higher and more horizontally oriented acromion in the sagittal plane, often referred to as a "flat roof" configuration. The posterior acromial height (PAH) is significantly greater in these patients, averaging approximately 30.9 mm. A cutoff value of 23 mm for PAH has been identified as a major risk factor; individuals exceeding this height have an odds ratio of 39 for the presence of posterior instability.
Knowledge Check
A PAH cutoff value of 23 mm has been identified as a major risk factor for posterior instability, with individuals exceeding this height having an odds ratio of 39 for posterior instability. This reflects a "flat roof" acromion configuration.
Anterior Instability**:** In contrast, the acromion in anteriorly unstable shoulders is typically lower and more vertically (steeply) oriented. This is frequently described as a "Swiss chalet roof" morphology. The mean PAH in patients with anterior instability is significantly lower, measured at approximately 19.5 mm.
Coverage and Tilt¶
• Posterior Coverage: Shoulders with posterior instability demonstrate significantly less posterior acromial coverage (PAC) compared to normal shoulders or those with anterior instability. One study found that static posterior instability (Walch B1) was associated with an average of 8.3° less posterior coverage and a flatter sagittal tilt compared to controls.
• Tilt: The acromion in static posterior instability may also be more externally rotated (axial tilt) and flatter (increased sagittal tilt) than in stable shoulders.
Functional and Biomechanical Differences¶
• Osseous Restraint: The low, steep acromion associated with anterior instability acts as a mechanical buttress that restricts posterior translation of the humeral head. Conversely, the high, horizontal acromion in posterior instability provides insufficient osseous restraint, which may lead to secondary plastic deformation of the posterior capsulolabral structures over time.
• Critical Shoulder Angle (CSA): While data are somewhat conflicting, some research indicates that the CSA is significantly smaller in patients with posterior instability (ranging from 25.2° to 28.0°) compared to those with anterior instability (30.1°) or healthy controls (31.7°). Other reports suggest that the critical shoulder angle in posterior instability does not differ significantly from normal shoulders.
• Contact Pressures: Biomechanical models show that a steeper acromion (low posterior acromial height) results in higher acromiohumeral contact pressure on the infraspinatus during posterior loading, suggesting the acromion actively bears load to prevent translation in stable configurations.
Dynamic Stabilizers:¶
◦ Rotator Cuff Muscles: The supraspinatus, infraspinatus, teres minor, and subscapularis provide "concavity compression," actively pulling the humeral head into the glenoid. The subscapularis is the most critical dynamic restraint against anterior humeral translation.
◦ Long Head of the Biceps (LHB): Acts as a humeral head depressor and resists translation during overhead activities.
◦ Scapular Stabilizers: Muscles such as the trapezius and serratus anterior maintain the scapula in an optimal position to support the humeral head during movement.
Pathomechanics of Anterior Instability¶
Anterior shoulder instability typically results from acute traumatic events or repetitive microtrauma.
• Mechanism of Injury: The classic mechanism involves forced abduction, external rotation, and extension. These positions create extreme leverage that forces the humeral head against the anterior glenoid rim, overwhelming the capsuloligamentous structures.
• Bankart Lesion: This is the hallmark of traumatic anterior shoulder instability, occurring in over 90% of cases. It involves the detachment of the anteroinferior labrum from the glenoid rim, often accompanied by damage to the IGHL and anterior capsule.
Knowledge Check
A Bankart lesion is the hallmark of traumatic anterior shoulder instability, occurring in over 90% of cases. It involves detachment of the anteroinferior labrum from the glenoid rim.
• Bipolar Bone Loss: Recurrent instability frequently leads to bone loss on both sides of the joint.
◦ Hill-Sachs Lesion: A compression fracture of the posterolateral humeral head caused by its impaction against the anterior glenoid rim during a dislocation.
◦ Bony Bankart: A fracture or chronic erosion of the anterior/inferior glenoid rim.
• The Glenoid Track Concept: The stability of the shoulder is determined by the interaction between glenoid bone loss and the size of the Hill-Sachs lesion. An "on-track" lesion stays within the contact area of the glenoid during motion, whereas an "off-track" (engaging) lesion extends medially past the glenoid rim, creating a high risk of recurrent dislocation.
• Soft Tissue Variants:
◦ ALPSA (Anterior Labral Ligamentous Periosteal Sleeve Avulsion): The labrum is displaced medially and rotated inferiorly, often scarring down in an abnormal position.
◦ HAGL (Humeral Avulsion of the Glenohumeral Ligaments): The IGHL detaches from its insertion on the humerus rather than the glenoid.
With every subsequent instability event, the risk of progressive bone and cartilage damage increases, further compromising the joint\'s biomechanical integrity and potentially leading to long-term arthropathy
Clinical presentations: first time anterior instability, young athlete¶
The clinical presentation of a first-time anterior shoulder instability event in a young athlete typically follows a distinct pattern characterized by a traumatic mechanism of injury followed by a high level of functional disability. Young age (particularly under 25 or 30 years) and participation in contact, collision, or overhead sports are the most significant risk factors identified for these events.
Clinical History¶
• Mechanism of Injury: The typical event involves an acute traumatic force applied to the shoulder while the arm is in a position of forced abduction, external rotation, and extension. This often occurs during a football tackle, a fall onto an outstretched arm, or the late cocking phase of a throwing motion.
• Chief Complaints: Patients usually report acute, severe shoulder pain and a distinct sensation of the joint "slipping," "popping," or "clunking" out of place.
• Initial Management Context: The history should document whether the shoulder required formal manual reduction (often in an emergency department) or if it reduced spontaneously or on the field.
• Associated Symptoms: Athletes may describe a "dead arm" sensation, which involves sudden sharp pain and a temporary loss of feeling or power in the extremity.
Physical Examination¶
Acute/On-Field Assessment
• Visual Inspection: In a frank dislocation, the athlete typically presents with a fixed deformity, holding the injured arm in slight abduction and external rotation. There is often a loss of the normal rounded deltoid contour, with the acromion appearing prominent and a palpable void beneath it.
• Palpation: The humeral head may be palpable anteriorly in the subcoracoid region. The provider should also check for crepitus or step-offs that might indicate an associated fracture of the humerus, clavicle, or scapula.
• Neurovascular Exam: It is critical to perform a thorough neurovascular assessment, with specific attention to the axillary nerve. This involves testing for sensation over the lateral shoulder (the "regimental badge" area) and assessing deltoid muscle contraction.
Subacute/Clinical Assessment¶
• Provocative Testing:
◦ Apprehension Test: This is the most diagnostic maneuver, where the arm is placed in 90° abduction and external rotation; a positive result is the patient\'s reported fear or resistance to further movement.
◦ Relocation (Jobe) Test: While in the apprehension position, a posteriorly directed force is applied to the humeral head; the test is positive if the athlete's pain or apprehension is relieved.
◦ Load-and-Shift Test: The clinician grasps the humeral head and translates it anteriorly and posteriorly relative to the glenoid to quantify translational laxity.
• Assessment of Hyperlaxity: The Beighton score is used to identify generalized ligamentous hypermobility (e.g., thumb-to-forearm apposition, knee hyperextension), while the sulcus sign evaluates for inferior capsular laxity.
• Functional Assessment: Evaluation includes testing rotator cuff strength and observing for scapular dyskinesis, which may either result from or contribute to the instability
Clinical presentations: recurrent anterior instability in an athlete¶
The typical clinical presentation of recurrent anterior shoulder instability in an athletic patient is defined by a history of multiple instability events and a physical examination that identifies both structural laxity and dynamic control deficits.
Clinical History¶
The history of a patient with recurrent instability is generally more complex than that of a first-time dislocator, focusing on the evolution of the condition.
• Instability Patterns: Patients report multiple episodes of subluxation or dislocation. While the initial event is typically traumatic, subsequent episodes often occur with decreasing levels of external force.
• Triggers and Complexity: Apprehension or instability events occurring with low-energy mechanisms, such as during sleep or at lower degrees of abduction (below shoulder level), are often harbingers of significant bone loss.
• Athletic Demands: In contact and collision sports, repetitive high-impact forces exacerbate structural damage to the labrum and capsule. Conversely, overhead athletes (e.g., baseball pitchers) are more likely to report a history of subtle subluxations rather than frank dislocations.
• Associated Symptoms: Athletes frequently describe a "dead arm" sensation, characterised by sudden sharp pain and a temporary loss of feeling or power in the extremity. Chronic cases are also more likely to be associated with persistent pain compared to acute presentations.
• Key Historical Factors: A thorough history should document the age at the first instability event, the total number of episodes, hand dominance, and whether the shoulder requires manual reduction or can be self-reduced.
Physical Examination¶
The physical examination aims to differentiate between physiologic laxity and symptomatic instability while assessing for progressive damage to the joint.
• Provocative Testing:
◦ Apprehension and Relocation Tests: These remain the most diagnostic manoeuvres, with high sensitivity and specificity for detecting anterior instability. A positive result reproduces the patient's specific symptoms of "slipping" or fear.
◦ Load-and-Shift Test: This is used to quantify the degree of translational laxity in the anterior and posterior directions.
• Assessment of Hyperlaxity: It is essential to screen for generalized ligamentous hypermobility using the Beighton score. Additional tests include the sulcus sign for inferior laxity and the Gagey test for hyperabduction.
• Muscular and Scapular Evaluation:
◦ Scapular Dyskinesis: Abnormal scapular motion (winging or dysrhythmia) is frequently identified and can unmask or exacerbate underlying instability.
◦ Dynamic Stabilisers: Evaluation of rotator cuff strength is critical, particularly the subscapularis, which provides primary dynamic restraint to anterior translation.
• Kinematic Alterations: Recurrently unstable shoulders often demonstrate decreased rotation range of motion and altered 3D kinematics, such as increased anterior translation of the humeral head during movement.
• Associated Injuries: The examiner should also screen for concomitant pathologies, such as SLAP lesions (via O\'Brien\'s or Crank tests) or biceps-related pain, which are common in chronic instability cases
Clinical presentations: first time anterior instability in a patient aged 25 and older¶
The clinical presentation of a first-time anterior shoulder instability event in a middle-aged athletic patient (typically defined as the 25--50 age bracket) is distinct from that of younger patients due to a shift in the primary structures injured during the trauma. While younger athletes often suffer from failures of static stabilizers like the labrum, middle-aged patients are significantly more prone to failures of dynamic stabilizers, most notably the rotator cuff.
Clinical History¶
• Mechanism of Injury: The event is typically initiated by an acute traumatic force, such as a fall onto an outstretched arm or a collision during sporting activities. In patients over the age of 40, dislocations may even occur with relatively trivial trauma compared to the high-energy forces required in younger populations, often suggesting pre-existing tendon weakening.
• Chief Complaints: Patients usually report acute, severe shoulder pain and a significant loss of function. In this age group, the primary complaint may be an inability to abduct the arm following the injury, which can be a sign of either neurological damage or a massive rotator cuff tear.
• Recurrence and Risk Factors: Unlike younger patients, middle-aged athletes have a lower risk of recurrent instability; however, they face a much higher risk of prolonged morbidity from associated injuries. It is essential to document the patient\'s age, occupation, and the specific sport and competition level to assess their functional demands.
• Associated Conditions: A history of seizures or electric shocks should be noted, as these can cause violent muscle contractions leading to dislocations.
Physical Examination¶
• Visual Inspection and Palpation: In cases of acute dislocation, there is often a visible deformity with flattening of the normal deltoid contour and an empty-feeling space beneath the acromion. The clinician should also check for crepitus or step-offs that might indicate a concomitant fracture of the glenoid or humerus.
• Rotator Cuff Assessment: Testing the strength and integrity of the rotator cuff is the most critical part of the examination for this age group. Traumatic rotator cuff tears occur in approximately 7% to 32% of dislocations in older adults, and this incidence increases significantly with age.
• Neurovascular Examination: There is a high index of clinical suspicion for nerve injury, particularly involving the axillary nerve, which occurs in up to 18% of cases. A thorough exam must check for deltoid muscle contraction and sensation over the lateral shoulder.
• Provocative Instability Testing:
◦ Apprehension and Relocation Tests: These remain standard for confirming anterior instability, where a positive result is defined by the patient\'s report of apprehension or fear when the arm is moved into abduction and external rotation.
◦ Load-and-Shift Test: This maneuver evaluates the degree of translational laxity of the humeral head relative to the glenoid.
◦ Hyperlaxity Assessment: The Beighton score and Gagey test should be used to rule out generalized ligamentous hypermobility or inferior capsular laxity.
• Differential Diagnosis: Clinicians must be careful not to misdiagnose an inability to abduct the arm as exclusively being an axillary nerve palsy, as it frequently masks a ruptured rotator cuff
Clinical management¶
The clinical management of anterior shoulder instability (ASI) is a multi-stage process involving immediate on-field reduction, diagnostic evaluation, and the selection of either conservative or surgical pathways based on the patient's risk profile and specific pathology. While the overall goal is to restore stability and function, management varies significantly across patient demographics due to differences in injury mechanisms and recurrence risks.
Management Pathways by Patient Category¶
1. Young First-Time Dislocators (Age \< 25--30)¶
This group presents the greatest management dilemma due to their high demand for sports and an alarming recurrence rate of 60--94% following conservative treatment.
Knowledge Check
Young first-time dislocators have an alarming recurrence rate of 60-94% following conservative treatment, which is why early surgical stabilization is increasingly recommended for this population, particularly males under 25 and contact athletes.
• Conservative Pathway: Historically the standard, this involves immobilisation for 1--3 weeks (typically in internal rotation), followed by a structured physical therapy programme focusing on neuromuscular control. While conservative management allows a quick return to sport, it carries a high risk of subsequent events.
• Early Surgical Pathway: There is an emerging consensus to stabilise this group early---routinely recommended for males under 25 and contact athletes. Arthroscopic Bankart Repair is the preferred procedure, yielding a 7-fold lower recurrence rate compared to non-operative care in first-time dislocators.
• Exceptions: Skeletally immature patients (age \< 14 with open physes) are an exception; they have lower recurrence rates and should generally be managed conservatively first.
2. Young, Recurrent Instability¶
In patients with multiple episodes, the management focus shifts from soft tissue repair to addressing cumulative bone loss on both the glenoid and humeral head (bipolar lesions).
• Surgical Necessity: Surgical intervention is almost universally required as each subsequent event increases attritional glenoid bone loss and the size of Hill-Sachs lesions.
• Procedural Choice based on Bone Loss:
◦ \< 13.5--15% bone loss: Arthroscopic Bankart Repair is typically sufficient.
◦ 15--25% bone loss (Subcritical): Often requires ABR augmented with a Remplissage procedure (to fill humeral defects) or an Open Bankart repair, which is more reliable in collision athletes.
◦ > 20--25% bone loss (Critical): Mandates a bone block procedure, such as the Latarjet or Eden-Hybinette, to restore the glenoid arc and provide a "sling effect" via the conjoint tendon.
• Contact Athletes: Soft tissue repairs alone have failure rates up to 25% in this group; many surgeons recommend going straight to a Latarjet procedure for martial arts or rugby players even with less than 20% bone loss.
3. Middle-Aged First-Time Dislocators (Age 25--50)¶
Pathophysiology in this age group differs because the dynamic stabilizers (rotator cuff) are more likely to fail than the static labral restraints.
• Conservative Pathway: This group is generally more successful with non-operative management than younger patients because the recurrence risk decreases with age (around 12% for those >30).
• Diagnostic Urgency: The primary goal is to rule out traumatic rotator cuff tears, which occur in 7--32% of cases in this bracket. An MRI or arthrogram should be performed within 7--10 days post-reduction if significant weakness persists.
• Surgical Pathway: Indicated if a massive or full-thickness rotator cuff tear is identified. Unlike the young, where the labrum is the focus, the surgical priority here is often the cuff repair; Bankart repair may not even be necessary in older patients if the cuff is restored.
Comparison Summary¶
Feature Young 1st Time Young Recurrent 25--50 Years 1st Time
Primary Static Bony Dynamic (Rotator Failure (Labrum/Capsule) (Glenoid/Humerus) Cuff)
Recurrence Very High (60--94%) Inevitable without Lower (11--30%) Risk surgery
Management Stabilisation to Reconstruction of Rotator cuff Focus prevent bone loss bone defects integrity & nerve status
Gold ABR or Conservative Latarjet or ABR + Conservative or Standard Rx Remplissage Cuff Repair
Associated ALPSA lesions Chronic instability Massive cuff tears Risks arthropathy & axillary nerve palsy
Across all categories, return to sport (RTS) decisions should be based on objective criteria---symmetric strength and range of motion---rather than purely time-based milestones. Furthermore, psychological readiness (measured via the SIRSI scale) is a critical predictor of successful return to play, particularly in athletes fearing re-injury
Conservative rehabilitation of shoulder instability¶
A comprehensive rehabilitation programme for the conservative care of shoulder instability is a staged, criterion-based process that shifts from protecting injured tissues to restoring neuromuscular control, strength, and functional stability. The sources emphasize that because shoulder stability relies on a complex interplay between static and dynamic stabilizers, rehabilitation must be tailored to the specific direction of instability and the individual athlete\'s demands.
Phase 1: Acute Management and Tissue Protection¶
The initial phase (typically weeks 0--6) focuses on pain modulation and protecting healing structures.
• Immobilisation: Short-term use of a standard sling is recommended for comfort, usually limited to one week to prevent disuse atrophy and stiffness. There is no definitive consensus in the sources regarding whether immobilisation should be in internal or external rotation, though some advocate for a neutral position.
• Early Activation: Rehabilitation begins with submaximal isometric contractions of the rotator cuff and scapular muscles in pain-free positions.
• Range of Motion (ROM): Staged recovery of ROM is initiated, typically starting with passive exercises like pendulums or wands to restore physiologic joint motion without overstressing the capsule.
Phase 2: Restoration of Motor Control and Strength¶
As irritability subsides, the focus shifts to re-establishing neuromuscular coordination and foundational strength.
• Scapular Foundation: Scapular control must precede aggressive rotator cuff strengthening to avoid joint irritation. Targeted training focuses on the serratus anterior and trapezius to ensure optimal upward rotation and posterior tilting of the scapula.
• Direction-Specific Strategies:
◦ Anterior Instability: The subscapularis is the primary target for strengthening, as it is a critical dynamic anterior stabilizer. Training involves isolating its activity from the pectoralis major and latissimus dorsi to prevent excessive anterior translation forces.
◦ Posterior Instability: Focuses on the external rotators (infraspinatus and teres minor) while preventing compensatory scapular retraction.
◦ Multidirectional Instability (MDI): A cocontraction protocol is used to axially load the humerus, facilitating joint stability by training the anterior and posterior cuff to center the humeral head together.
Phase 3: Dynamic Loading and Integration
Once basic strength is achieved, the programme introduces dynamic exercises that vary in Position, Amplitude, Load, and Speed.
• Dynamic Stabilization: Exercises progress from the side to more provocative, functional positions (e.g., 90° abduction).
• Metronome Pacing: Speed is gradually increased using a metronome (e.g., starting at 30 beats/min and progressing to 120 beats/min) to improve the eccentric capacity of the rotator cuff.
• Kinetic Chain Integration: Effective rehabilitation incorporates the entire kinetic chain, including core, hip, and trunk stability, as these are foundational to overhead athletic motions.
Phase 4: Perturbation Training and Functional Readiness¶
The final stage prepares the athlete for the unexpected forces encountered in sport.
• Perturbations: Expected and unexpected directional forces (e.g., weighted ball drops) are applied to the arm, often with eyes closed, to stimulate high-level proprioceptive feedback.
• Plyometrics: These are introduced to develop power and prepare tissues for the deceleration forces of throwing or contact.
Return to Sport (RTS) Criteria¶
It's suggested that we should be using objective, criteria-based clearance rather than arbitrary time-based milestones, however we don't have much in terms of validated objective testing options, so all of the following should be viewed in that light.
• Physical Thresholds: Athletes should demonstrate symmetric ROM and strength (typically within 10% of the unaffected side) and an external-to-internal rotation strength ratio of at least 65--75%.
• Functional Tests: Standardized batteries like the Closed Kinetic Chain Upper Extremity Stability Test, the Y-balance test, and the seated shot-put test are used to validate readiness.
• Psychological Readiness: Assessment via the Shoulder Instability-Return to Sport after Injury (SIRSI) scale is critical, as fear of reinjury and low confidence are primary predictors of failed return to play
Post-operative rehabilitation after stabilisation surgery¶
Post-operative rehabilitation for shoulder instability is a staged, criteria-based process designed to protect healing structures while gradually restoring range of motion (ROM), strength, and functional stability. While general phases of recovery are similar across procedures, the specific restrictions and timelines vary significantly based on the surgical technique employed and the specific tissues repaired.
General Phases of Rehabilitation¶
Most protocols follow a four-to-five phase progression:
1. Phase I (Protection): Immediate post-operative period (typically 0--6 weeks) focused on tissue protection, symptom modulation, and early activation of scapular muscles.
2. Phase II (ROM Recovery): Gradual restoration of passive and active-assisted ROM.
3. Phase III (Strengthening): Restoration of muscle strength, endurance, and neuromuscular proprioception.
4. Phase IV (Functional Optimization): Targeted power development and sport-specific drills.
5. Phase V (Return to Sport): Objective testing to clear the athlete for full competition.
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Rehabilitation by Surgical Technique¶
1. Arthroscopic Bankart Repair¶
ABR focuses on reattaching the labrum to the glenoid.
• Immobilisation: Typically 4 weeks in a standard sling.
• ROM Restrictions: Early goals are often limited to 90° forward flexion, 30° external rotation (ER), and 45° internal rotation (IR) to avoid overstressing the repair.
• Accelerated Protocols: Some evidence suggests early accelerated rehabilitation (starting ROM within the first week) can reduce post-operative pain and hasten functional recovery without increasing recurrence rates.
2. Open Bankart Repair¶
Open repairs are more invasive and often involve the detachment or splitting of the subscapularis muscle to access the joint.
• Subscapularis Protection: If a subscapularis tenotomy or peel was performed, strict protection is required for 4--6 weeks. This includes avoiding forced IR and limiting passive/active-assisted ER to neutral or very low degrees.
• Compliance: Because of the higher risk of failure if restrictions are ignored, some surgeons mandate 6 weeks of continuous sling use in younger patients.
3. Remplissage (Added to Bankart Repair)¶
This procedure involves tenodesis of the infraspinatus into a humeral Hill-Sachs defect.
• Infraspinatus Protection: Strict limitation of aggressive stretching or tensioning of the infraspinatus is required for approximately 6 weeks.
• ER Caution: While it does not always alter the general Bankart protocol, clinicians must be more cautious with ER in the first few weeks to protect the healing tenodesis.
• Timeline: The addition of remplissage can extend the return-to-sport (RTS) timeline by approximately one month compared to isolated ABR.
4. Latarjet and Bone Block Procedures¶
These procedures involve bony augmentation (coracoid or iliac crest) and often a subscapularis split.
• Bony Union: The primary focus is protecting the graft until radiographic healing is confirmed, typically via CT scan at 3 months.
• Sling Use: Typically 4 weeks, with ER limited to \<30° to protect the subscapularis repair.
• ROM Deficits: FF often progresses faster than ER; ER deficits frequently persist and may require more aggressive stretching starting at 10 weeks.
• Accelerated Nature: Some surgeons utilize an accelerated protocol for Latarjet because the bony fixation (screws) is inherently more stable than soft tissue anchors.
Comparison of Key Milestones
Feature Arthroscopic **Open Bankart / **(Posterior Bankart Latarjet** Repair)**
Sling 4 weeks 4--6 weeks 4--6 weeks Duration
Strict ER (Abducted) Subscapularis Internal Limitation Load/ER Rotation
Strength 6--8 weeks 8--10 weeks 8 weeks Start
RTS ~12--16 weeks ~16--24 weeks ~4 months Assessment
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Surgical techniques commonly used in shoulder stabilisation¶
The management of anterior shoulder instability involves various surgical interventions, ranging from anatomic soft tissue repairs to non-anatomic bony reconstructions. The choice of procedure is primarily dictated by the degree of glenoid and humeral bone loss, the patient's athletic demands (e.g. contact vs overhead sports), and whether the case is a primary or revision stabilization.
Arthroscopic Bankart Repair (ABR)¶
ABR is currently the most commonly performed procedure for ASI worldwide.
• Mechanism: It involves reattaching the avulsed labrum to the glenoid rim using suture anchors to restore the static stabilizers of the joint.
• Indications: It is the standard for patients with minimal glenoid bone loss (<13.5--15%) and "on-track" Hill-Sachs lesions.
• Outcomes: In first-time dislocators, ABR results in a 7-fold lower recurrence rate compared to conservative management and has high return-to-sport (RTS) rates (approx. 88--92.8%).
• Limitations: Recurrence rates are significantly higher in contact athletes (up to 17--20%) or those with "critical" bone defects (up to 89%).
Open Bankart Repair (OBR)¶
While less common now, OBR remains a robust alternative for specific populations.
• Mechanism: It allows for a more robust capsulolabral repair and precise tensioning of the capsule but requires the detachment or splitting of the subscapularis.
• Comparison to ABR: OBR is often preferred for young collision athletes or revision cases as it may offer lower recurrence rates (approx. 3% vs 54% for non-op) in high-risk groups.
• Downsides: It is associated with longer recovery times and a higher risk of postoperative stiffness, particularly a loss of external rotation.
Arthroscopic Remplissage¶
This is an adjunctive procedure performed alongside a Bankart repair.
• Mechanism: It involves capsulotenodesis of the infraspinatus into a humeral Hill-Sachs defect, effectively converting it into an extra-articular lesion to prevent it from engaging the glenoid rim.
• Indications: It is indicated for "off-track" or engaging Hill-Sachs lesions when glenoid bone loss is subcritical (\<20--25%).
• Outcomes: Adding remplissage to ABR reduces recurrence risk by 4-fold compared to isolated ABR.
• Controversy: It is often contraindicated in elite overhead athletes (e.g. pitchers) due to the risk of restricted external rotation, which can impair performance.
Latarjet Procedure¶
The Latarjet is the "gold standard" for patients with significant bone loss.
• Mechanism: It provides a "triple effect": (1) the bone block effect (coracoid transfer) increases glenoid surface area; (2) the sling effect (conjoined tendon) provides dynamic stability in abduction; and (3) a ligament effect through capsular repair to the coracoacromial stump.
• Indications: Indicated for critical glenoid bone loss (>15--25%), off-track lesions, or high-risk collision athletes (e.g. rugby, MMA).
• Outcomes: It significantly outperforms ABR in collision athletes; in one study of MMA athletes, Latarjet recurrence was 6% compared to 25% for ABR.
• Risks: It is technically demanding with a complication rate up to 30%, including neurovascular injury (axillary/musculocutaneous nerves) and graft nonunion.
Glenoid Bone Grafting (Non-Latarjet)¶
These procedures use free grafts such as iliac crest autograft (Eden-Hybinette) or distal tibia allograft (DTA).
• Mechanism: They restore the glenoid arc without the "sling effect" of the Latarjet.
• Advantages: DTA offers a cartilaginous surface and matches glenoid curvature well. Eden-Hybinette is often used as a salvage procedure for failed Latarjet or in patients with epilepsy to reduce convulsion-related graft failure.
• Anatomy: A key advantage of the all-arthroscopic Eden-Hybinette is that it preserves normal shoulder anatomy (no coracoid transfer) and leaves the subscapularis untouched.
Comparison Summary Table
Feature Bankart **Remplissage **Latarjet Bone (ABR/OBR) (+Bankart)** Grafting**
Primary Goal Soft tissue repair Humeral head Bony & dynamic Bony augmentation stabilization reconstruction
Glenoid Loss \<13.5% \<20% >15--25% >25% or salvage
Hill-Sachs On-track Off-track Off-track Any
Main Anatomic/Minimally Addresses Highest Can use larger Advantage invasive bipolar loss stability for grafts; with low contact sports cartliage morbidity restoration
Main Risk High recurrence if Loss of Neurovascular Donor site bone loss present external injury; morbidity rotation non-anatomic (autograft); no sling effect
Finally, Dynamic Anterior Stabilization (DAS) is an emerging arthroscopic technique that mimics the Latarjet\'s sling effect by transferring the long head of the biceps or conjoined tendon through a subscapularis split without requiring bony fixation, showing over 86% RTS in early studies.
Patient explanation for "On track/off track"¶
The "on-track" and "off-track" concepts describe the interaction between bone damage on both sides of the shoulder joint---the ball (humerus) and the socket (glenoid)---which is known as bipolar bone loss. This system helps surgeons predict whether a dent in the humeral head, called a Hill-Sachs lesion, will catch on the edge of the socket and cause the shoulder to dislocate again.
The Glenoid Track
The glenoid track is the specific area of the ball that stays in constant contact with the socket when the arm is raised and rotated outwards, a position common in many sports. In a healthy shoulder, this track covers approximately 83% of the socket\'s width. If the socket has suffered bone loss due to previous dislocations, the track becomes narrower, making the joint inherently less stable.
On-Track vs Off-Track Lesions
• On-Track: A Hill-Sachs lesion is considered "on-track" if the dent is small enough to stay within the contact zone during movement. These lesions are generally non-engaging, meaning there is enough healthy bone remaining to support the ball and prevent it from catching on the socket\'s rim.
• Off-Track: A lesion is "off-track" if it is large enough, or if the socket is narrow enough, that the dent extends medially past the glenoid track. These are known as engaging lesions. They are at a very high risk of catching on the anterior edge of the socket during motion, which acts as a pivot point that levers the ball out of the joint.
Clinical Importance and Surgery
Classifying a lesion as on-track or off-track is critical for deciding the most effective surgical treatment.
• On-track lesions with minimal bone loss are typically successfully treated with a standard arthroscopic Bankart repair, which fixes the soft tissues around the socket.
• Off-track lesions have a significantly higher failure rate (up to 75% in some studies) if only a standard Bankart repair is performed. These high-risk cases usually require more aggressive interventions, such as Remplissage (filling the humeral dent with nearby tendon and capsule) or a Latarjet procedure (transferring bone to the socket to widen the track and create a "sling" of stability)