Overview — Acetabular Fractures
Acetabular fractures are complex intra-articular injuries requiring highly specialised surgical expertise for management. They occur from high-energy trauma (road traffic accidents, falls from height) — with the femoral head being driven into the acetabulum by the axial force transmitted through the femur. The Judet-Letournel classification, developed by Robert Judet, Jean Judet, and Émile Letournel in their landmark 1964 and 1993 publications, is the universal standard for describing acetabular fractures. Understanding this classification requires a thorough grasp of the two-column concept of the acetabulum — the foundation on which the entire classification is built. Acetabular ORIF is one of the most technically demanding procedures in orthopaedics, requiring understanding of three-dimensional anatomy, specialised approaches, and precise fluoroscopic control.
- The two-column concept: the acetabulum is supported by two bony columns (the anterior and posterior columns), both derived from the ilium and converging on the acetabular socket; (1) Anterior column (iliopubic column): runs from the anterior iliac crest superiorly, through the anterior wall of the acetabulum, and down the superior pubic ramus to the pubic symphysis; the iliopectineal line on the AP pelvis X-ray corresponds to the anterior column; (2) Posterior column (ilioischial column): runs from the greater sciatic notch superiorly through the posterior wall and posterior rim of the acetabulum, down the ischial ramus to the ischial tuberosity; the ilioischial line on the AP pelvis X-ray corresponds to the posterior column; between the two columns lies the `acetabular dome` — the weight-bearing articular surface of the acetabulum (the `roof`); the two columns form an inverted Y shape when viewed from the front
- The five radiological Judet views: for complete assessment of acetabular fractures, three views are standard — (1) AP pelvis (both iliopectineal and ilioischial lines visible); (2) Obturator oblique view (45° rotation toward the injured hip — the obturator foramen is `open`, showing the anterior column and posterior wall en face); (3) Iliac oblique view (45° rotation away from the injured hip — the iliac wing is profiled, showing the posterior column and anterior wall en face); CT with 3D reconstruction is now the gold standard for surgical planning, supplementing the plain films
Judet-Letournel Classification — Elementary & Associated Fractures
The classification divides acetabular fractures into two groups: elementary (simple — involving one part of the acetabulum) and associated (complex — combinations of two or more elementary patterns).
| Fracture Type | Group | Description | AP X-Ray Finding | Key Features |
|---|---|---|---|---|
| Posterior wall | Elementary | A fragment of the posterior acetabular wall is sheared off by the femoral head; the fracture involves the posterior rim of the acetabulum only; the posterior column is intact; the roof (dome) is intact; typically associated with posterior hip dislocation | Ilioischial line INTACT; a posterior wall fragment visible on obturator oblique view; the femoral head may be dislocated posteriorly | The MOST COMMON acetabular fracture; associated with posterior hip dislocation (dashboard injury); if <50% of the posterior wall is involved, conservative management may be appropriate; >50% posterior wall involvement or instability on EUA = ORIF; Kocher-Langenbeck approach; posterior approach preferred |
| Posterior column | Elementary | A fracture through the posterior column (ilioischial column); the fracture exits inferiorly through the ischial tuberosity; the posterior column is separated from the ilium; the entire posterior wall/column complex is displaced | Ilioischial line DISRUPTED; anterior column (iliopectineal line) intact; Kocher-Langenbeck approach | Less common than posterior wall; the inferior portion of the posterior column is displaced medially; the sciatic nerve and superior gluteal neurovascular bundle are at risk during surgical exposure |
| Anterior wall | Elementary | A fragment of the anterior acetabular wall is sheared off; the anterior column is intact; rare in isolation | Iliopectineal line minimally disrupted; anterior wall fragment visible on iliac oblique view | The rarest elementary type; associated with anterior hip dislocation (uncommon mechanism); ilioinguinal approach for fixation |
| Anterior column | Elementary | A fracture through the anterior column (iliopubic column); the fracture line runs from the iliac wing through the anterior wall and down the superior pubic ramus; the entire anterior column (including the iliopectineal eminence) is displaced medially | Iliopectineal line DISRUPTED; ilioischial line intact; superior pubic ramus fracture visible; ilioinguinal approach for fixation | Less common than posterior fractures; typical mechanism is an anteriorly directed force on the flexed hip; the ilioinguinal approach (Smith-Petersen interval) allows anterior column fixation; the lateral femoral cutaneous nerve is at risk |
| Transverse | Elementary | A horizontal fracture that transects the acetabulum in a single plane — dividing it into a superior portion (attached to the ilium and the dome) and an inferior portion (attached to the ischium + pubis); BOTH the iliopectineal AND ilioischial lines are disrupted; the entire inferior acetabulum is displaced medially (central acetabular fracture-dislocation) | BOTH iliopectineal AND ilioischial lines DISRUPTED; the horizontal fracture line passes through the acetabular fossa; medial displacement of the inferior fragment (the femoral head may migrate medially — `central dislocation`) | The only elementary type that disrupts BOTH columns; however, the roof is typically preserved (the transverse fracture passes below the dome); if the roof is intact and the femoral head is concentrically reduced → non-operative management may be appropriate; if roof involvement or incongruency → ORIF; approach depends on fracture level (high transverse = ilioinguinal; low transverse = Kocher-Langenbeck) |
| Associated Type | Components | AP X-Ray | Clinical Significance |
|---|---|---|---|
| T-shaped fracture | Transverse + vertical component through the ischiopubic ramus; the vertical limb of the `T` runs through the obturator foramen and the inferior portion of the acetabulum | BOTH lines disrupted; vertical limb through the obturator foramen creates the T-shape; the most complex of the associated types | Very complex; requires either a combined approach or an extensile approach; the T-fracture is particularly difficult to reduce and fix because the two components (horizontal + vertical) are independent; modified Gibson approach or ilioinguinal approach depending on fragment positions |
| Posterior column + posterior wall | Posterior column fracture + posterior wall fracture; both posterior structures are disrupted; the posterior column fragment carries the posterior wall with it | Ilioischial line disrupted; posterior wall fragment visible on obturator oblique | Kocher-Langenbeck approach; the posterior wall fragment requires additional fixation beyond the column plate; comprehensive posterior approach gives access to both components |
| Transverse + posterior wall | Transverse fracture + separate posterior wall fracture — the most common associated type; the femoral head is typically displaced centrally AND posteriorly | BOTH lines disrupted (transverse component) + posterior wall fragment (obturator oblique) | Most commonly approached via Kocher-Langenbeck; combined approach (ilioinguinal + K-L) for complex cases; the posterior wall reduction must be anatomical to prevent re-dislocation |
| Anterior column + posterior hemitransverse (ACPHT) | Anterior column fracture + posterior hemitransverse fracture (a partial transverse involving only the posterior column); the anterior column is fully fractured, the posterior has a partial horizontal fracture; the dome is typically intact | Iliopectineal disrupted (anterior column); partial disruption of ilioischial (posterior hemitransverse component) | Common in elderly patients (more common than other complex types in osteoporotic patients); ilioinguinal approach allows fixation of both components; the ACPHT is important to recognise as it may be misclassified as a transverse fracture |
| Both-column fracture | Complete separation of the entire articular surface from the stable ilium; BOTH the anterior AND posterior columns are fractured; the articular surface (roof) is disconnected from the stable ilium; the `spur sign` (the intact posterior portion of the iliac wing, visible as a spike on the obturator oblique view, without any articular cartilage attached) is pathognomonic of a both-column fracture | BOTH lines disrupted; the `spur sign` on the obturator oblique view is pathognomonic; all articular bone is separated from the stable ilium | The most complex acetabular fracture pattern; despite the complete articular disruption, many both-column fractures demonstrate `secondary congruence` — the displaced articular fragments reorient around the femoral head to create a congruent (though medialized) joint; secondary congruence = non-operative management may be appropriate in elderly patients with poor bone stock; younger patients with displacement require ORIF; combined approaches (ilioinguinal + K-L); high technical complexity |
Surgical Indications & Approaches
- Indications for ORIF: (1) fracture with articular displacement >2–3 mm, particularly involving the weight-bearing dome (`roof arc angles` — Matta`s criteria: if the medial roof arc angle, anterior roof arc angle, and posterior roof arc angle all exceed 45°, the weight-bearing dome is intact and non-operative management may be appropriate); (2) hip joint instability (the femoral head is not concentrically reduced and maintained with a reasonable range of motion); (3) incarcerated intra-articular fragment; (4) the femoral head cannot be maintained in a reduced position; (5) neurological deficit requiring decompression; (6) open fractures
- Matta`s roof arc angles: the three roof arc measurements (medial, anterior, and posterior) define the amount of intact acetabular dome; if ALL three angles are >45° → the weight-bearing roof is intact → non-operative management may suffice; if ANY angle is <45° → the dome is involved → ORIF typically indicated; the roof arc angles are measured on the three standard views (AP, obturator oblique, iliac oblique)
- Surgical approaches: (1) Kocher-Langenbeck (K-L) approach: posterior approach between gluteus maximus and piriformis/external rotators; provides access to the posterior column, posterior wall, and iliac fossa; the gold standard for posterior wall and column fractures; sciatic nerve at risk; (2) Ilioinguinal (Smith-Petersen) approach: anterior approach through three windows (lateral, middle, obturator) between the external iliac vessels, iliopsoas, and obturator neurovascular bundle; provides access to the anterior column, quadrilateral surface, and superior pubic ramus; (3) Combined approaches: for complex fractures involving both columns; some centres use the `modified Stoppa approach` (direct medial approach through the space of Retzius — provides excellent access to the quadrilateral surface and anterior column with less neurovascular risk than the full ilioinguinal); (4) `Pararectus` approach and other minimal-access approaches: increasingly used for percutaneous screw fixation and minimally invasive techniques
Exam Pearls
- Two-column concept: anterior column (iliopubic — iliopectineal line on AP X-ray); posterior column (ilioischial — ilioischial line on AP X-ray); both lines disrupted = transverse or both-column fracture; only one line disrupted = single column fracture; dome (roof) integrity = most important for prognosis
- 5 elementary types: posterior wall (most common), posterior column, anterior wall (rarest), anterior column, transverse (only one that disrupts BOTH lines); 5 associated types: T-shaped, posterior column + wall, transverse + posterior wall, ACPHT, both-column
- Both-column fracture: spur sign (pathognomonic on obturator oblique view — the intact posterior iliac wing spike without articular attachment); secondary congruence — the articular fragments reorient around the femoral head creating a congruent medialized joint → non-operative in elderly; ORIF in young patients
- Posterior wall: most common; associated with posterior hip dislocation (dashboard mechanism); >50% wall involvement or instability on EUA = ORIF; Kocher-Langenbeck approach
- Roof arc angles (Matta): medial + anterior + posterior roof arc all >45° = dome intact = non-operative may be appropriate; ANY angle <45° = dome involvement = ORIF typically indicated; measured on AP, obturator oblique, and iliac oblique views
- Obturator oblique view: anterior column + POSTERIOR WALL en face (the obturator foramen is `open`; the posterior wall is best seen); remember: `obturator = anterior column visible`
- Iliac oblique view: POSTERIOR column + anterior wall en face (the iliac wing is profiled); remember: `iliac = posterior column visible`; the two oblique views show opposite structures
- Timing: acetabular ORIF ideally performed at day 3–10 (after physiological stabilisation in polytrauma; before callus makes reduction impossible; within 14 days for best results); emergent reduction for unreduced hip dislocation (<6 hours to prevent AVN)