Letournel-Judet Classification of Acetabular Fractures

The acetabulum is not a single bone but a complex articular surface formed where the ilium, ischium and pubis fuse at the triradiate cartilage. The Letournel system simplifies this into a two-column model.

Walls are the articular extensions of the columns that form the cup around the femoral head:

• The posterior wall is the articular rim attached to the posterior column; it restrains posterior femoral head subluxation and is disrupted in posterior wall fractures and posterior fracture-dislocations.
• The anterior wall is the smaller articular extension of the anterior column; isolated anterior wall fractures are uncommon.

Elementary fractures involve a single structural element: one wall, one column, or the transverse plane.

Associated fractures combine two or more elementary patterns and are more complex to reduce and fix.

Examiners may ask for the AO/OTA classification, the alphanumeric system that runs in parallel with Letournel (the acetabulum is bone segment 62). It groups fractures by how much of the articular surface remains attached to the intact ilium.

The conceptual divide is the same one the spur sign signals: in 62-A and 62-B some articular surface stays in continuity with the axial skeleton, whereas in 62-C none does.

Accurate classification requires three specific radiographic views plus CT.

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CT assessment is mandatory for every acetabular fracture and adds critical information:

• Axial cuts: identify fracture planes, marginal impaction, intra-articular fragments (loose bodies), femoral head lesions, and the degree of posterior wall comminution.
• 2D reformats (coronal and sagittal): clarify the orientation of fracture lines and assess the weight-bearing dome.
• 3D surface rendering: invaluable for visualising the overall pattern and communicating with the team. Subtract the femoral head to see the articular surface from inside the acetabulum.
• Posterior wall fragment size: CT quantifies the percentage of the posterior wall involved. Fragments involving greater than 40 to 50 percent of the posterior wall in sagittal reconstruction are generally considered unstable and require fixation, though clinical assessment of hip stability under fluoroscopy remains the gold standard for borderline cases.

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The Letournel-Judet classification directly determines the surgical approach because each pattern has a predictable displacement direction and a specific reduction strategy.

A both-column fracture has a unique escape route from surgery: secondary congruence (Letournel's original term was "apparent congruence"). Because the detached articular fragments stay tethered to the femoral head by intact capsule and labrum, the displaced columns can rotate around the head and settle into a congruent - though medially displaced - relationship with it, even though every articular fragment is separated from the ilium.

• Why it matters: if the femoral head sits congruently within the secondarily-congruent acetabulum and the patient is elderly or low-demand, a both-column fracture may be managed non-operatively with protected weight-bearing, accepting some medialisation, rather than undergoing major reconstruction.
• The caveat: congruence must be present on all three Judet views - congruence on one view but not the others is not acceptable and mandates surgery. The roof fragments must not leave an incongruent, subluxating joint, and a young, high-demand patient is still better served by anatomic open reduction.

• Inter-observer reliability is moderate, not perfect. Studies show that experienced pelvic surgeons agree on the Letournel classification in about 70 to 80 percent of cases. Disagreement is greatest for the associated patterns, particularly distinguishing anterior column plus posterior hemitransverse from both-column. CT and 3D reconstruction improve agreement significantly over plain films alone.
• The classification does not account for marginal impaction, femoral head injury, or cartilage damage, all of which influence prognosis independently. A perfectly reduced both-column fracture with a femoral head impaction may still do poorly.
• Roof-arc angle measurements (medial, anterior, posterior roof-arc angles on the three views) supplement the classification by quantifying how much of the weight-bearing dome remains intact, guiding non-operative versus operative management for minimally displaced patterns. A roof-arc angle greater than 45 degrees on all three views suggests sufficient dome integrity for non-operative treatment if the femoral head is congruent.
• Modern trends favour anterior approaches (ilioinguinal, modified Stoppa) over extensile posterior approaches because of lower morbidity. The ilioinguinal approach is now the workhorse for most anterior and both-column patterns. Percutaneous screw fixation (column screws) is increasingly used for minimally displaced patterns or as adjunct fixation, but demands intra-operative CT or stereotactic navigation.
• Time to surgery matters. Open anatomic reduction is technically easier within the first 10 to 14 days. After three weeks, the fracture begins to consolidate and reduction becomes substantially harder, often requiring more extensile approaches and osteotomies.