Ideberg Classification of Glenoid Fractures

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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.

• 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.

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Goss described the superior shoulder suspensory complex (SSSC) — a bone–soft-tissue ring suspending the upper limb from the axial skeleton. It is the conceptual key to shoulder-girdle injury patterns and explains why some scapular fractures are stable and others (such as the floating shoulder) are not.

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• The ring: the glenoid process, the coracoid process, the coracoclavicular ligaments, the distal clavicle, the acromioclavicular joint, and the acromion.
• The two struts (links to the trunk): a superior strut — the middle third of the clavicle — and an inferior strut — the lateral border of the scapular body and the scapular spine.
• Single versus double disruption: a single break in the ring is usually stable and treated non-operatively. A double disruption (two breaks in the ring or its struts) destabilises the complex, allows the glenoid segment to displace under muscle pull and arm weight, and is a relative indication to stabilise at least one — often both — of the disruptions to restore the suspensory mechanism.
• The floating shoulder is the classic double disruption: an ipsilateral mid-clavicle fracture (superior strut) plus a scapular neck or glenoid fracture (the ring/inferior strut). Restoring the clavicle alone often realigns the glenoid by ligamentotaxis; some patterns need both fixed.
• Relevance to Ideberg: Type III fractures can disrupt the coracoid and the AC/coracoclavicular ligaments — several SSSC components in one injury; Types IV and V combined with a clavicle fracture create a floating shoulder. Recognising the double disruption converts an apparently isolated scapular fracture into an unstable girdle injury that may need fixation.

The surgical approach is dictated by the Ideberg type and the location of the fracture 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.

• 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.

• 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.

• 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.