Residency · Residency · Orthopedic Surgery

Acetabular Fractures: Classification and Surgical Approaches

Anatomy

Bony Architecture

The acetabulum is formed by the convergence of the ilium, ischium, and pubis. Letournel's two-column concept provides the anatomic foundation for understanding acetabular fractures. The anterior column extends from the iliac crest to the pubic symphysis and includes the anterior wall. The posterior column extends from the superior gluteal notch to the ischial tuberosity and includes the posterior wall. Viewed laterally, these columns form an inverted Y configuration with the articular dome at their intersection. The articular dome represents the weight-bearing surface, encompassing the superior 40-60 degrees of the acetabular arc. The cotyloid fossa is the non-articular central portion containing the ligamentum teres and fat pad. The quadrilateral plate is the thin medial wall of the acetabulum, an important landmark for medial displacement of fracture fragments.

Radiographic Landmarks (AP Pelvis)

Six key landmarks must be identified on the AP pelvis radiograph. The iliopectineal line represents the anterior column. The ilioischial line represents the posterior column. The anterior wall appears as the medial border of the anterior acetabulum. The posterior wall appears as the lateral border of the posterior acetabulum. The teardrop (U-figure) represents the medial wall of the acetabulum and the cotyloid fossa floor. The acetabular dome (roof) is the superior weight-bearing surface.

Judet Oblique Views

The obturator oblique view (pelvis rotated 45 degrees toward the affected side) demonstrates the anterior column and posterior wall. The iliac oblique view (pelvis rotated 45 degrees away from the affected side) shows the posterior column and anterior wall. These views remain essential for fracture classification, though CT has supplemented them for surgical planning.

Judet-Letournel Classification

Elementary Fracture Types (5)

Posterior Wall

Posterior wall fractures are the most common acetabular fracture type, accounting for 25-30% of cases. One or more posterior wall fragments are separated from the otherwise intact column structure. These fractures are frequently associated with posterior hip dislocation. The key assessment involves determining the size of the posterior wall fragment and identifying any marginal impaction of the articular surface. CT is essential for evaluating fragment size and comminution.

Posterior Column

A posterior column fracture exits through the ischium (obturator foramen) inferiorly and disrupts the ilioischial line on the AP pelvis radiograph. It is relatively uncommon as an isolated pattern.

Anterior Wall

The anterior wall fracture is the least common elementary type. The fracture passes through the anterior acetabular wall and disrupts the anterior wall line on the AP pelvis.

Anterior Column

An anterior column fracture runs from the iliac wing to the pubic ramus, disrupting the iliopectineal line on the AP pelvis. It may extend high (involving the iliac crest) or low (through the ischiopubic ramus).

Transverse

A transverse fracture divides the acetabulum into a superior (iliac) and inferior (ischiopubic) segment. Both columns are disrupted, but the acetabulum remains connected to the axial skeleton through the intact ilium above. Three subtypes are defined by the level of the transverse line relative to the dome: transtectal (through the weight-bearing dome, carrying the worst prognosis), juxtatectal (at the dome margin), and infratectal (below the dome).

Associated Fracture Types (5)

T-Type

The T-type combines a transverse fracture with a vertical fracture through the cotyloid fossa that splits the inferior ischiopubic fragment into anterior and posterior components, creating a T-shaped pattern.

Posterior Column + Posterior Wall

This pattern combines two elementary types: a posterior column fracture line with a separate posterior wall fragment.

Transverse + Posterior Wall

A transverse fracture with an associated posterior wall fragment is the second most common acetabular fracture pattern overall. It is frequently associated with posterior hip dislocation.

Anterior Column/Wall + Posterior Hemitransverse

This complex pattern involves an anterior column or anterior wall fracture combined with a transverse component through the posterior column. It often requires dual surgical approaches for adequate treatment.

Both-Column

In a both-column fracture, all articular surface is separated from the axial skeleton (the ilium). The pathognomonic radiographic finding is the "spur sign" visible on the obturator oblique view, representing the intact iliac fragment seen superior and posterior to the displaced acetabulum. Paradoxically, the femoral head may remain concentrically located within the displaced acetabulum (secondary congruence) despite complete fracture separation. This is the most complex acetabular fracture pattern and requires careful surgical planning.

Imaging

Radiographic Evaluation

Complete radiographic evaluation includes an AP pelvis with assessment of all six landmarks plus Judet views (obturator oblique and iliac oblique). The surgeon must evaluate fracture lines, displacement, femoral head subluxation, and dome involvement.

CT with 3D Reconstruction

CT is essential for surgical planning and evaluates articular surface comminution and impaction (particularly marginal impaction), fragment size (especially posterior wall fragments, which determines whether fixation is feasible), femoral head integrity (impaction fractures and chondral injury), intra-articular loose bodies, and quadrilateral plate involvement. Three-dimensional reconstructions with digital subtraction of the femoral head significantly enhance fracture pattern visualization.

Indications for Surgery

Operative Indications

Surgery is indicated for displacement greater than 2 mm in the weight-bearing dome, femoral head subluxation or incongruity on any radiographic view, posterior wall fractures involving more than 40% of the wall, associated femoral head fractures (Pipkin classification), intra-articular loose bodies, and inability to maintain a concentric reduction.

Roof Arc Measurements

Matta's roof arc angles are measured on the AP, obturator oblique, and iliac oblique views. If all three arcs exceed 45 degrees from the dome to the nearest fracture line, the weight-bearing surface is intact and nonoperative management may be considered. On CT, if both 10 mm subchondral cuts are intact (no fracture in the subchondral bone), nonoperative treatment may be acceptable.

Nonoperative Management

Nonoperative treatment is appropriate for minimally displaced fractures (less than 2 mm) with a congruent joint, both-column fractures demonstrating secondary congruence with maintained head coverage, and patients with medical contraindications to surgery. Treatment involves traction for 6-8 weeks with serial radiographs to ensure the reduction is maintained.

Surgical Approaches

Kocher-Langenbeck (Posterior)

The Kocher-Langenbeck approach is indicated for posterior wall, posterior column, transverse, T-type, and transverse with posterior wall fractures. The patient is positioned in lateral decubitus or prone. The internervous plane lies between the gluteus medius (superior gluteal nerve) and the short external rotators. The incision runs from the PSIS toward the greater trochanter and then along the femoral shaft. The gluteus maximus is split in line with its fibers. The short external rotators (piriformis, obturator internus, gemelli) are tagged and released. The sciatic nerve lies deep to the short external rotators and must be identified and protected throughout the case. Keeping the hip extended and knee flexed relaxes the sciatic nerve. Risks include sciatic nerve injury (10-15% transient, 2-3% permanent), heterotopic ossification, and AVN of the femoral head. The trochanteric flip osteotomy provides additional exposure of the dome when needed.

Ilioinguinal Approach (Anterior)

The ilioinguinal approach is indicated for anterior wall, anterior column, both-column, and some associated fracture patterns. The patient is supine. The approach utilizes three windows: the lateral window between the iliacus and iliopsoas (exposing the internal iliac fossa), the middle window between the iliopsoas and femoral vessels (exposing the quadrilateral plate and pelvic brim), and the medial window between the femoral vessels and the rectus/spermatic cord (exposing the pubic symphysis and superior ramus). Risks include injury to the femoral nerve, femoral vessels, lateral femoral cutaneous nerve, lymphatic structures (lymphocele), and corona mortis hemorrhage. A significant limitation is that it does not allow direct visualization of the articular surface.

Modified Stoppa Approach (Anterior Intrapelvic)

The modified Stoppa approach is indicated for anterior column fractures, quadrilateral plate fractures, and both-column fractures. The patient is supine. A midline or Pfannenstiel incision provides access to the intrapelvic space deep to the rectus abdominis. This approach offers direct access to the quadrilateral plate and pelvic brim and can be combined with a lateral window of the ilioinguinal for extended exposure. Its advantage over the full ilioinguinal is improved visualization of the quadrilateral plate and easier medial plate application. Risks include obturator nerve and vessel injury, corona mortis hemorrhage, and bladder injury.

Combined Approaches

Complex associated fracture patterns (both-column, anterior column with posterior hemitransverse) may require combined anterior and posterior approaches, performed simultaneously or in staged fashion. The extended iliofemoral approach is rarely used today due to its high complication rate including heterotopic ossification and wound problems.

Fixation Principles

Goals

The goals of acetabular fracture fixation are anatomic reduction of the articular surface (less than 1 mm residual displacement), stable fixation permitting early mobilization, and restoration of column integrity and dome congruence.

Techniques

Reconstruction plates (3.5 mm) are contoured to the pelvic brim, posterior column, or around the acetabular rim. Lag screws provide interfragmentary compression of large fragments. Spring plates secure small posterior wall fragments that are too small for standard screw fixation. Quadrilateral plate buttress plates are applied medially to prevent medialization of the femoral head. Percutaneous column screws (anterior and posterior) represent an advanced technique performed under fluoroscopic guidance for select fracture patterns.

Intraoperative Assessment

Reduction quality is assessed by evaluating femoral head congruence within the acetabulum, fluoroscopic Judet views confirming restoration of all radiographic landmarks, and postoperative CT scan to confirm articular reduction.

Acute Total Hip Arthroplasty

Indications in Acetabular Fractures

Acute THA is increasingly considered for elderly patients (over 60-70 years) with associated femoral neck fractures, pre-existing hip arthritis, severe articular comminution or impaction precluding reconstruction, femoral head damage, or poor bone quality that precludes stable internal fixation. Growing evidence supports this approach in select elderly patients as it avoids the prolonged recovery and high failure rates of ORIF in osteoporotic bone.

Technique Considerations

The fracture is first stabilized with plates and screws to create a stable acetabular construct for cup fixation. Acetabular component fixation may use cement or cementless techniques with or without augments. Cup-cage constructs address severe bone deficiency. Dual-mobility bearings reduce the dislocation risk inherent in the acute fracture setting.

Complications

Sciatic Nerve Injury

Sciatic nerve injury most commonly involves the peroneal division, producing foot drop. Risk is highest with posterior approaches, posterior fracture-dislocations, and prolonged hip dislocation. Intraoperative neuromonitoring may reduce risk, and keeping the hip extended with the knee flexed reduces tension on the nerve during posterior dissection.

Heterotopic Ossification (HO)

HO is graded by the Brooker classification from Grade I (small islands of bone) to Grade IV (complete ankylosis). Risk factors include extensile surgical approaches, associated traumatic brain injury, and delay to surgery. Prophylaxis options include indomethacin (75 mg/day for 6 weeks) or single-dose radiation (700-800 cGy within 72 hours of surgery). Indomethacin may impair fracture healing, requiring the surgeon to weigh the competing risks.

Post-Traumatic Arthritis

Post-traumatic arthritis is the most common long-term complication, occurring in 20-40% of cases. Risk factors include articular comminution, residual displacement greater than 2 mm, marginal impaction, and dome involvement. Many patients ultimately require THA years after the initial injury.

Avascular Necrosis of the Femoral Head

The risk of AVN is highest with posterior fracture-dislocations and when reduction of the dislocated hip is delayed beyond 6 hours. Urgent reduction of a dislocated hip is therefore critical. AVN may not become evident for years after the initial injury.

<image>An illustration of the Judet-Letournel two-column concept of the acetabulum. Show a lateral view of the hemipelvis with the anterior column highlighted in one color (from iliac crest to pubic symphysis) and the posterior column in another (from greater sciatic notch to ischial tuberosity), forming an inverted Y configuration. Include the acetabular dome at the intersection and label the key bony landmarks: iliac wing, pubic ramus, ischial tuberosity, quadrilateral plate.</image>

<image>A diagram showing the three windows of the ilioinguinal approach for acetabular fracture surgery. Display a supine patient view of the anterior pelvis with three labeled surgical windows: the lateral window (between iliacus and iliopsoas exposing the inner iliac fossa), the middle window (between iliopsoas and femoral vessels exposing the quadrilateral plate), and the medial window (between femoral vessels and spermatic cord/rectus exposing the symphysis). Include the inguinal ligament, femoral nerve, artery, vein, and spermatic cord.</image>

<image>AP pelvis radiograph diagram showing the six radiographic landmarks of the normal acetabulum. Label and trace: (1) iliopectineal line (anterior column), (2) ilioischial line (posterior column), (3) anterior wall, (4) posterior wall, (5) teardrop figure, and (6) acetabular dome/roof. Use different colors or line styles for each landmark to clearly distinguish them.</image>

Clinical Pearls

The posterior wall is the most common acetabular fracture, and CT is always required to evaluate fragment size, comminution, and marginal impaction before making treatment decisions. A dislocated hip associated with an acetabular fracture must be reduced emergently because delay beyond 6 hours significantly increases AVN risk. The "spur sign" on the obturator oblique view is pathognomonic for a both-column fracture. Roof arc angles greater than 45 degrees on all three views suggest the weight-bearing dome is intact and nonoperative management may be appropriate. The sciatic nerve is at greatest risk during the Kocher-Langenbeck approach, and keeping the hip extended and knee flexed reduces tension on it. The corona mortis must be identified and ligated during anterior approaches to prevent potentially significant hemorrhage. Marginal impaction is often underappreciated on plain radiographs but clearly visible on CT; failure to elevate and bone-graft impacted articular fragments leads to malreduction. Acute THA is an increasingly accepted option for elderly patients with displaced acetabular fractures and pre-existing arthritis or femoral head damage.

References

• Letournel E, Judet R. Fractures of the Acetabulum. 2nd ed. Springer-Verlag; 1993.
• Matta JM. Fractures of the acetabulum: accuracy of reduction and clinical results in patients managed operatively within three weeks after the injury. J Bone Joint Surg Am. 1996;78(11):1632-1645.
• Giannoudis PV, et al. Operative treatment of displaced fractures of the acetabulum: a meta-analysis. J Bone Joint Surg Br. 2005;87(1):2-9.
• Stannard JP, et al. Modified Stoppa approach for acetabular fracture surgery. J Orthop Trauma. 2020;34 Suppl 2:S26-S30.
• Daurka JS, et al. Acute total hip arthroplasty for displaced acetabular fractures in the elderly. Bone Joint J. 2014;96-B(11):1443-1449.

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