High-yield overview
Glenoid fossa fracture classification by fracture-line exit direction through the scapula
6 typesIa, Ib, II, III, IV, V, VI — glenoid fossa fracture patterns
High-energytypically blunt trauma; strong association with ipsilateral chest injury
Operative if displacedarticular step-off greater than 2 mm, glenohumeral instability, or significant rim fragment
CT essentialplain films underestimate glenoid involvement; CT with 3D reconstruction is mandatory
Critical Must-Knows
- The Ideberg classification describes six patterns of glenoid fossa fracture based on the fracture line exit through the scapula, originally described by Ideberg in 1984 and refined in 1995. It is the most widely used system for intra-articular scapular fractures.
- Type I is a glenoid rim fracture (Ia anterior, Ib posterior) — essentially a bony Bankart or reverse bony Bankart variant. Types II through IV exit through the scapular body laterally, superiorly, or medially. Type V combines patterns, and Type VI is severe comminution.
- Operative fixation is indicated for displaced intra-articular fractures with greater than 2 mm articular step-off, glenohumeral instability, or a large rim fragment (typically greater than 20 percent of the glenoid arc). Non-operative management suits minimally displaced, stable patterns.
- These are high-energy injuries: up to 80 to 90 percent of patients have associated injuries — ribs, lung, clavicle, brachial plexus. Always complete a full trauma survey and do not be distracted by the scapular fracture from life-threatening thoraco-abdominal pathology.
Clinical Pearls
- “Greater than 2 mm articular displacement or instability means operate
- “Type Ia/Ib: rim fractures — fix if greater than 20-25 percent of glenoid arc
- “Type IV exits medially (through scapular body) — posterior Judet approach
- “Always complete ATLS survey first — 80 to 90 percent have associated injuries
The threshold examiners want
An intra-articular glenoid fracture with greater than 2 mm of articular displacement or glenohumeral instability is generally an indication for operative fixation. Type I rim fractures associated with shoulder dislocation need fixation if the fragment involves greater than 20 to 25 percent of the glenoid arc (risk of recurrent instability). For Types II through V, the goal is anatomic restoration of the joint surface with stable internal fixation to allow early mobilisation. Type VI (comminuted) may require arthroplasty if reconstruction is impossible.
The Ideberg Classification
The Ideberg classification categorises glenoid fossa fractures by the direction the fracture line exits the scapula. The mechanism differs by type and this drives both the fracture pattern and the associated soft-tissue injuries.
| Type | Fracture Pattern | Mechanism | Key Feature |
|---|---|---|---|
| Ia | Anterior glenoid rim | Shoulder dislocation (anterior) | Bony Bankart equivalent — anterior inferior glenoid rim avulsed with labrum and capsule |
| Ib | Posterior glenoid rim | Shoulder dislocation (posterior) or direct posterior force | Reverse bony Bankart — posterior rim fragment with posterior capsulolabral complex |
| II | Transverse fracture through glenoid fossa exiting laterally through the lateral scapular border | Axial load through humeral head (fall on outstretched hand or direct lateral shoulder impact) | Inferior glenoid fragment displaced laterally with humeral head |
| III | Transverse fracture through glenoid fossa exiting superiorly through the superior scapular angle | Axial load with superior shear component | Superior fragment may include coracoid; associated with acromioclavicular and coracoclavicular ligament disruption |
| IV | Transverse fracture through glenoid fossa exiting medially through the scapular body (spine of scapula) | Axial load with strong medial vector | Fracture crosses the scapular spine; medial displacement of the glenoid fragment; often high-energy |
| Va | Combination of II and IV | Severe axial load with lateral and medial components | Lateral and medial exits — inferior and medial fragments |
| Vb | Combination of III and IV | Severe axial load with superior and medial components | Superior and medial exits — superior and medial fragments |
| Vc | Combination of II, III, and IV | Extreme violence | Three exits — inferior, superior, and medial fragments; very unstable |
| VI | Severe comminution of the glenoid fossa | Extreme high-energy crush or blast | No single identifiable fracture line; articular surface shattered — worst prognosis |
Mnemonic
Rim — Lateral — Superior — Medial — Combo — CrushThe six Ideberg types in order
R
Rim — Type I (anterior Ia or posterior Ib glenoid rim)
L
Lateral — Type II (exits laterally through lateral scapular border)
S
Superior — Type III (exits superiorly through superior scapular angle)
M
Medial — Type IV (exits medially through scapular body)
C
Combo — Type V (Va = II+IV, Vb = III+IV, Vc = II+III+IV)
C
Crush — Type VI (severe comminution, unreconstructible)
Hook:RLSMCC: Rim Lateral Superior Medial Combo Crush — exit direction from simple to devastating
Clinical Pearl
The key to remembering the Ideberg classification is the exit direction of the fracture line. Type II exits laterally (inferior fragment goes lateral). Type III exits superiorly (superior fragment includes coracoid region). Type IV exits medially (through the scapular body and spine). Type V combines these exit points. Type VI is comminuted beyond classification.
Clinical Presentation and Diagnosis
- Mechanism: These are overwhelmingly high-energy injuries — motor vehicle collisions, falls from height, pedestrian versus vehicle. A low-energy mechanism should prompt suspicion of a glenoid rim fracture (Type I) in the context of a shoulder dislocation rather than a true glenoid fossa fracture.
- Associated injuries are the rule, not the exception: ipsilateral rib fractures, pneumothorax or haemothorax, pulmonary contusion, clavicle fracture, brachial plexus injury, vascular injury (subclavian/axillary artery), and head injury are all common. Up to 80 to 90 percent of patients with a glenoid fossa fracture have at least one associated injury.
- Examination: localised posterior or lateral shoulder pain, swelling, and ecchymosis. The arm is typically held adducted and internally rotated. Palpate the entire shoulder girdle, clavicle, and chest wall. Perform a thorough neurovascular examination — particularly assess the axillary, suprascapular, musculocutaneous, and brachial plexus distributions.
- Imaging cascade:
- AP and axillary radiographs of the shoulder are the initial study but frequently underestimate the fracture. The axillary view is essential to assess glenohumeral alignment and anterior/posterior rim involvement.
- CT with 3D reconstruction is mandatory for all glenoid fossa fractures. It delineates the fracture pattern, degree of articular displacement, fragment size, and comminution. It is the study that determines the Ideberg type.
- MRI is useful for associated soft-tissue injuries (labral tears, rotator cuff, ligamentous disruption) but is not the primary classification tool.
Mnemonic
AP — Axillary — CT 3D — Full Trauma SurveyEssential imaging work-up
A
AP radiograph of the shoulder — initial screen
A
Axillary view — essential for glenohumeral alignment and rim assessment
C
CT with 3D reconstruction — mandatory for Ideberg classification and surgical planning
T
Trauma survey — chest imaging for associated rib, lung, and clavicle injuries
Hook:AACT: AP Axillary CT Trauma-survey — never skip the CT for glenoid fractures
Management: Operative versus Non-operative
| Type | Non-operative Criteria | Operative Indications | Typical Approach |
|---|---|---|---|
| Ia/Ib | Fragment less than 20 percent of glenoid arc, no instability, no dislocation | Greater than 20 to 25 percent of glenoid arc, glenohumeral instability, recurrent dislocation | Arthroscopic or open reduction and internal fixation with suture anchors or mini-fragment screws; address labrum and capsule |
| II | Less than 2 mm displacement, stable glenohumeral joint, intact lateral column | Greater than 2 mm articular step-off, glenohumeral subluxation, displaced inferior fragment | Open reduction via deltopectoral or posterior approach; plate and screw fixation of the inferior glenoid fragment |
| III | Minimally displaced, coracoid and AC joint stable | Displaced superior fragment, coracoid displacement, AC joint disruption | Superior approach (supraspinatus split or deltoid-split); lag screw or plate fixation; address AC/coracoclavicular instability |
| IV | Non-displaced transverse fracture, intact scapular body | Medial displacement of glenoid fragment, articular incongruity, scapular spine disruption | Posterior approach (Judet or modified Judet); plate fixation of glenoid to scapular body; may need dual approach |
| V (a/b/c) | Rarely non-operative — most are displaced and unstable | Almost always operative due to multi-fragment instability and articular incongruity | Combined anterior and posterior approaches; plate and screw reconstruction; strategies tailored to the specific sub-type |
| VI | Not reconstructible (definition) | Attempted ORIF if any large articular fragments salvagable; otherwise consider arthroplasty | Individualised — may require total shoulder arthroplasty or reverse total shoulder arthroplasty if the glenoid is beyond reconstruction |
Caution
Do not be distracted by the scapular fracture. These patients are multiply injured. Complete ATLS primary and secondary surveys. Life-threatening thoraco-abdominal injuries take precedence. The scapular fracture is often a marker of significant energy transfer and should prompt a thorough search for occult chest, abdominal, and neurovascular injuries.
Surgical Approaches and Fixation Principles
The surgical approach is dictated by the Ideberg type and the location of the fracture fragments.
| Approach | Access | Ideal For | Key Risks |
|---|---|---|---|
| Deltopectoral (anterior) | Anterior glenoid, coracoid, superior glenoid | Type Ia, Type III | Cephalic vein, musculocutaneous nerve, axillary nerve (retraction) |
| Posterior (Judet / modified Judet) | Posterior glenoid, scapular body, scapular spine | Type Ib, Type IV, Type V | Axillary nerve, suprascapular nerve and artery, circumflex scapular artery |
| Combined anterior and posterior | Full access to glenoid circumference and scapular body | Type V (complex), selected Type VI | Positioning challenges; prolonged operative time; increased blood loss |
| Arthroscopic | Anterior and posterior rim, labrum, articular surface visualisation | Type Ia/Ib (rim fractures), assessment of articular reduction | Learning curve; limited ability to address comminuted or medially displaced fragments |
Fixation principles:
- Anatomic reduction of the articular surface is paramount — any residual step-off greater than 2 mm increases the risk of post-traumatic glenohumeral arthritis.
- Use lag screws for simple fracture patterns and neutralisation or buttress plates for comminuted or vertically oriented fracture lines.
- For Type IV fractures with medial exit, restore the relationship between the glenoid fragment and the scapular body — this re-establishes the glenoid version and the medial-lateral column.
- In Type V variants, stabilise each exit point individually before linking them with a reconstructive plate across the scapular body.
- Type VI may not be reconstructible. If ORIF is attempted, the goal is containment of articular fragments. Definitive treatment may be delayed arthroplasty once the soft tissues have healed.
Mnemonic
Lateral exit — Anterior. Superior exit — Anterior or Superior split. Medial exit — Posterior (Judet). Combined exits — Combined approaches.Approach selection by exit direction
L
Lateral exit (Type II) — Anterior (deltopectoral) approach
A
Anterior approach also for Superior exit (Type III) or deltoid split
S
Superior split access for Type III fractures involving the coracoid
M
Medial exit (Type IV, V) — Posterior (Judet) approach
Hook:LASM: Lateral=Anterior, Superior=Anterior/Split, Medial=Posterior — match approach to exit direction
Outcome and Complications
- Post-traumatic glenohumeral arthritis is the most significant long-term complication, particularly when articular reduction is imperfect. Studies report degenerative changes in a substantial proportion of patients followed beyond five years.
- Shoulder stiffness and loss of motion — prolonged immobilisation worsens this; stable internal fixation should allow early passive range of motion within the limits of the construct.
- Neurovascular injury — the suprascapular nerve is at risk during posterior approaches as it traverses the spinoglenoid notch. The axillary nerve is vulnerable during both anterior and posterior dissection. Pre-operative neurovascular assessment and intra-operative identification are essential.
- Non-union is uncommon but reported, particularly in Type IV and V fractures where the medial fragment loses its soft-tissue attachments. Rigid fixation and bone grafting of gaps may be required.
- Heterotopic ossification can occur after extensile approaches (Judet). Prophylaxis with indometacin or single-dose radiation is used in some centres for high-risk patients.
- Associated injuries dominate the early outcome — the scapular fracture itself may not be the limiting factor for functional recovery; concomitant brachial plexus injury, chest trauma, or head injury often determine the final result.
Limitations and Modern Context
- The Ideberg classification is anatomically descriptive but does not directly dictate treatment. The decision to operate rests on articular displacement, glenohumeral stability, fragment size, and patient factors — not the Ideberg type alone.
- Inter-observer reliability is moderate. Studies show better agreement for Type I (rim) and Type VI (comminuted) than for the intermediate types, particularly distinguishing Type II from Type IV and subtyping Type V. CT with 3D reconstruction improves agreement.
- The OTA/AO classification (14-F) and the Mayo classification are alternatives that some surgeons prefer for operative planning, but the Ideberg system remains the most frequently tested in fellowship examinations.
- Modern trends favour arthroscopic-assisted reduction for rim fractures (Type I), minimally invasive plate osteosynthesis for selected Type II and IV patterns, and reverse total shoulder arthroplasty for unreconstructible Type VI fractures in older patients.
- 3D printing and patient-specific instrumentation are increasingly used for pre-operative planning in complex Type V patterns, allowing surgeons to rehearse reduction strategies before entering the theatre.
Evidence Base
Evidence
Epidemiology of scapular fractures: incidence and classification of 338 fractures
Ideberg R, Grevsten S, Larsson S • Acta Orthop Scand (1995)
Key Findings:
- Classification of 338 scapular fractures into five types (later extended to six with Type VI added), based on fracture exit direction through the scapula
- Demonstrated that operative treatment of displaced fractures yielded better outcomes than non-operative management
- Established the anatomic basis for the classification: fracture exit direction through the scapula determines the type
Clinical implication: Established the classification system and provided the foundational evidence for operative management of displaced glenoid fossa fractures.
Limitation: Retrospective case series; no control group; heterogenous fixation methods.
Source: Acta Orthop Scand 1995;66(5):395-7
Guidelines, Registries and Global Practice
- No single international guideline exists specifically for glenoid fossa fractures. Management is guided by expert consensus, institutional protocols, and the principles outlined above.
- AO Foundation principles emphasise anatomic articular reduction, stable fixation, and early mobilisation — these apply directly to Ideberg Type II through V fractures. The AO Trauma community provides online decision-making tools and surgical planning resources.
- Boehler's principle of restoring the articular surface underpins the operative threshold: greater than 2 mm displacement is the most widely cited cut-off, used across North American, European, and Australasian trauma centres.
- Registry data on scapular fractures specifically are sparse because these injuries are uncommon and captured within broader polytrauma registries. The German TraumaRegistry DGU and the NTDB (National Trauma Data Bank, US) record scapular fractures as part of polytrauma datasets, and their data consistently confirm the high-energy mechanism and high rate of associated injuries.
- Global practice variation: Some centres in Europe and North America favour more aggressive operative management of all displaced glenoid fractures, while some Asian and Australasian centres are more selective, operating only when instability or significant articular incongruity is demonstrated. Arthroscopic expertise is a key determinant — centres with established shoulder arthroscopy programmes treat more Type I fractures arthroscopically. Access to 3D CT reconstruction and modern mini-fragment fixation systems also influences operative rates.
- Reverse total shoulder arthroplasty for unreconstructible Type VI fractures is increasingly reported, particularly in older patients, following the same principles used for comminuted proximal humerus fractures where ORIF is not feasible.
Exam Viva
Practise clinical reasoning and management decisions out loud
Viva scenarioStandard
Clinical prompt
“A 34-year-old man is involved in a high-speed motorcycle collision. He has a right pneumothorax (already drained), a clavicle fracture, and CT demonstrates a fracture line through the glenoid fossa exiting medially through the scapular body with approximately 4 mm of displacement of the glenoid fragment. Classify this fracture and outline your management plan.”
Practical approach
This is an Ideberg Type IV glenoid fossa fracture — a transverse fracture through the glenoid with the fracture line exiting medially through the scapular body. With 4 mm of articular displacement, this exceeds the widely accepted 2 mm threshold for operative fixation. My management plan would be: first, complete the trauma survey and manage life-threatening injuries first (the pneumothorax has been drained, but I would re-assess respiratory status and exclude other chest, abdominal, and head injuries). Once the patient is stable and the soft tissues allow, I would plan operative fixation — typically via a posterior Judet or modified Judet approach to access the glenoid and scapular body. The goal is anatomic reduction of the articular surface with plate-and-screw fixation restoring the medial-lateral column of the scapula. I would also address the clavicle fracture (ORIF) as the ipsilateral clavicle and scapular neck fracture combination constitutes a floating shoulder, and stabilising both may improve outcomes. Post-operatively, I would begin protected passive range of motion early, progressing to active motion as fixation allows, with serial radiographs to confirm maintenance of reduction.
Key clinical points
Correctly classify as Ideberg Type IV (medial exit through scapular body)
Recognise the 4 mm displacement exceeds the 2 mm operative threshold
ATLS first: manage life-threatening injuries before the scapular fracture
Plan a posterior approach (Judet) for medial-exit fractures
Address the clavicle: floating shoulder (ipsilateral clavicle plus scapular fracture)
Common pitfalls
Treating the scapular fracture before completing the trauma survey
Classifying this as Type II (lateral exit) instead of Type IV (medial exit)
Forgetting to assess and treat the associated clavicle fracture
Attempting an anterior approach for a medially displaced glenoid fragment
Further questions
“What is a floating shoulder and why does it change your management?”
“How would your management differ if this were an Ideberg Type Ia fracture with an anterior shoulder dislocation?”
“What are the key structures at risk during a Judet posterior approach to the scapula?”
Viva scenarioAdvanced
Clinical prompt
“A 28-year-old woman presents after a seizure with a posterior shoulder dislocation. Reduction is achieved, but the post-reduction CT shows a posterior glenoid rim fracture involving approximately 30 percent of the glenoid arc. How do you classify this injury and what is your management?”
Practical approach
This is an Ideberg Type Ib — a posterior glenoid rim fracture sustained during a posterior shoulder dislocation, likely from a seizure. The key issue is that the fragment involves approximately 30 percent of the glenoid arc, which exceeds the commonly cited 20 to 25 percent threshold for operative fixation. With this amount of posterior bone loss, there is a high risk of recurrent posterior instability if treated non-operatively. I would recommend operative fixation — either arthroscopic or open reduction and internal fixation of the posterior rim fragment with suture anchors or mini-fragment screws, combined with repair of the posterior labrum and capsulolabral complex. I would also investigate and optimise the underlying seizure disorder with the neurology team, as uncontrolled seizures are a significant risk factor for recurrent posterior dislocation. Post-operatively, I would immobilise the arm in neutral to slight external rotation (avoiding the at-risk position of flexion, adduction, and internal rotation) for approximately four to six weeks before commencing rehabilitation.
Key clinical points
Classify as Ideberg Type Ib (posterior glenoid rim fracture)
Recognise that 30 percent of the glenoid arc exceeds the operative threshold
Posterior instability risk is significant with greater than 20 to 25 percent posterior bone loss
Address the underlying seizure disorder in collaboration with neurology
Common pitfalls
Classifying as anterior (Type Ia) — this is a posterior dislocation with a posterior rim fracture
Discharging without recognising that 30 percent involvement mandates fixation
Forgetting to manage the seizure disorder — recurrent dislocation is likely without seizure control
Immobilising in internal rotation (the at-risk position for posterior instability)
Further questions
“What is the reverse Hill-Sachs lesion and how does it influence management?”
“When would you consider a McLaughlin procedure versus simple ORIF of the rim fragment?”
“How does the management differ if the fragment is comminuted and too small for screw fixation?”
Exam day cheat sheet
Ideberg Classification — Exam Cheat Sheet
The six types (by exit direction)
- Type I: Rim fracture — Ia anterior (bony Bankart), Ib posterior (reverse bony Bankart)
- Type II: Transverse glenoid, exits laterally through lateral scapular border
- Type III: Transverse glenoid, exits superiorly through superior scapular angle
- Type IV: Transverse glenoid, exits medially through scapular body (crosses scapular spine)
- Type V: Combination — Va (II plus IV), Vb (III plus IV), Vc (II plus III plus IV)
- Type VI: Severe comminution — unreconstructible; consider arthroplasty
Operative thresholds
- Articular step-off greater than 2 mm: fix (applies to all Types II through V)
- Rim fragment greater than 20 to 25 percent of glenoid arc: fix (Type I)
- Glenohumeral instability: fix regardless of fragment size
- Floating shoulder (clavicle plus scapular fracture): fix both to restore the superior suspensory complex
Approaches and pearls
- Anterior (deltopectoral): Type Ia, Type III
- Posterior (Judet): Type Ib, Type IV, Type V
- Combined: complex Type V patterns
- CT with 3D reconstruction is mandatory for classification and surgical planning
- Always complete ATLS survey first — associated injuries are the rule (80 to 90 percent)