The acetabulum, a component of the pelvic bone, forms the cup-shaped socket of the hip joint. It houses the head of the femur, allowing for a wide range of movements and supporting body weight during activities like walking and standing. An acetabular fracture is a break in this hip socket, often resulting from significant force.
These injuries are severe due to the hip joint’s impact on mobility and weight-bearing. Understanding the various types of acetabular fractures is important for healthcare professionals to accurately diagnose and plan appropriate interventions.
Elementary Acetabular Fracture Types
Acetabular fractures are categorized into ten primary types using the Judet and Letournel classification system: five elementary and five associated patterns. Elementary fractures are simpler, typically involving a single, distinct part of the acetabulum.
Posterior Wall Fracture
This fracture involves a break in the back rim of the acetabulum, affecting a portion of the retroacetabular surface and varying amounts of articular cartilage. It is the most common acetabular fracture, often occurring from high-energy events like car accidents.
Posterior Column Fractures
These fractures begin at the greater sciatic notch, extend through the articular surface and the quadrilateral surface, and cross the inferior pubic ramus. This fracture pattern results in the detachment of the entire posterior column of the acetabulum.
Anterior Wall Fracture
This less common type involves a segment of the mid-anterior column, often trapezoidal in shape. The fracture typically begins at the anterior border of the acetabulum, just below the anterior-inferior iliac spine, and extends across the articular surface, detaching the anterior articular facet.
Anterior Column Fracture
A segment of the anterior acetabulum separates from the rest of the innominate bone. The fracture line usually starts from the middle of the ischiopubic ramus and passes through the anterior acetabulum, extending variably into the iliac wing.
Transverse Fracture
This features a single fracture line that horizontally crosses the acetabulum, dividing it into upper and lower portions through both the anterior and posterior columns. This fracture separates the ilium, which includes the acetabular roof, from the ischium and pubis.
Associated Acetabular Fracture Types
Associated acetabular fractures are more complex patterns, often combining elements of the elementary types or involving multiple parts of the acetabulum. These injuries typically result from high-energy trauma.
Both Columns Fracture
This fracture involves both the anterior and posterior columns of the acetabulum and extends through the obturator ring. This type completely disconnects the acetabulum from the axial skeleton, meaning the entire articular surface becomes detached from the rest of the pelvis.
T-type Fracture
This fracture is characterized by a transverse fracture line that divides the acetabulum into upper and lower segments, combined with an additional vertical fracture line. This vertical component typically transects the inferior parts of both the anterior and posterior columns, often extending through the obturator foramen.
Anterior Column with Posterior Hemitransverse Fracture
This involves a break in the anterior column or wall along with a secondary fracture line that partially crosses the posterior aspect of the acetabulum. The primary fracture is located anteriorly, while the secondary line extends through the articular surface to the posterior border.
Posterior Column with Posterior Wall Fracture
This combines the features of a classical posterior column fracture with additional fragments from the posterior wall. In this associated type, the posterior column component is frequently less displaced, with the posterior wall injury being more prominent.
Transverse with Posterior Wall Fracture
This combines a transverse fracture with one or more separate fragments from the posterior wall of the acetabulum. This pattern is a combination of two elementary fracture types, signifying a break that extends across the acetabulum horizontally along with damage to its posterior rim.
Diagnosing and Classifying Fractures
Diagnosing acetabular fractures involves a detailed assessment to identify the specific fracture pattern and its extent. Initial evaluation typically includes X-rays, which provide basic images of the bone structure and can indicate displacement. However, due to the complex three-dimensional anatomy of the pelvis, X-rays alone often do not provide sufficient detail for precise diagnosis and treatment planning.
Computed tomography (CT) scans play a role in visualizing the 3D anatomy of the fracture. CT scans offer detailed cross-sectional images that allow medical professionals to identify the orientation of fracture lines, the number and size of fragments, and the involvement of the articular surface. The Judet and Letournel classification system remains the standard for categorizing these fractures, distinguishing between the five elementary and five associated patterns based on the anatomical structures affected.