Acetabulum

The acetabulum is a critical component of the pelvic bone, forming the socket portion of the ball-and-socket hip joint. Its primary role is to house the head of the femur, enabling a wide range of hip movements and providing stability to the lower body. The acetabulum is essential for activities such as walking, running, and bearing the body's weight.

1.0Structure

• The acetabulum is a deep, cup-shaped cavity formed by the fusion of three pelvic bones: the ilium, ischium, and pubis. 
• These bones converge during development to create the acetabulum, which has a horseshoe-shaped articular surface known as the lunate surface. 
• This surface is covered with hyaline cartilage, providing a smooth interface for the femoral head and reducing friction during movement. 
• The acetabular notch, a gap in the inferior part of the lunate surface, is bridged by the transverse acetabular ligament.

2.0Articulation With Other Bones

• The acetabulum articulates with the head of the femur, forming the hip joint. 
• This articulation is crucial for the mobility and stability of the hip, allowing for flexion, extension, abduction, adduction, and rotational movements. 
• The depth and orientation of the acetabulum are essential for maintaining joint congruency and distributing the load across the joint.

3.0Attached Muscles

Several muscles attach around the acetabulum, contributing to the stability and movement of the hip joint. These include:

• Gluteus Medius and Gluteus Minimus: These muscles originate from the ilium near the acetabulum and are responsible for hip abduction and internal rotation.
• Rectus Femoris: Part of the quadriceps group, this muscle attaches to the anterior inferior iliac spine near the acetabulum and aids in hip flexion.
• Obturator Internus and Obturator Externus: These muscles attach near the acetabulum and are involved in hip external rotation.

4.0Acetabulum in Os Innominatum Bone

• The acetabulum is a key feature of the os innominatum (hip bone), which is formed by the fusion of the ilium, ischium, and pubis. 
• The os innominatum on each side of the body joins with the sacrum at the sacroiliac joint, forming the pelvis. The acetabulum's position at the junction of these three bones is vital for the integrity and function of the hip joint.

5.0Left & Right Coxal Bone

• The pelvis consists of two coxal bones (hip bones), each with its own acetabulum. 
• The left and right acetabula are symmetrical structures that articulate with the corresponding femoral heads to form the left and right hip joints. 
• These joints work together to provide stability and mobility to the lower body, ensuring efficient movement and weight distribution.

6.0Function of the Acetabulum

• The acetabulum's primary function is to serve as the socket for the femoral head, enabling the hip joint's wide range of motion while providing stability. 
• The depth and orientation of the acetabulum are crucial for maintaining joint congruency, distributing mechanical load, and preventing dislocation. 
• It also plays a role in absorbing and dissipating forces transmitted through the lower limbs.

7.0Femur and Acetabulum Articulation

• The articulation between the femur and acetabulum is a ball-and-socket joint, one of the body's most mobile joints. 
• The femoral head fits snugly into the acetabulum, allowing the leg to move in multiple directions. 
• The acetabular labrum, a ring of fibrocartilage surrounding the acetabulum, deepens the socket and enhances joint stability by sealing the joint and maintaining a vacuum effect.

1. Broken/Fractured Acetabulum

• Acetabular fractures are serious injuries typically resulting from high-energy trauma, such as car accidents or falls from significant heights. 
• These fractures can range from simple, involving a single part of the acetabulum, to complex, involving multiple parts and extending into the surrounding pelvic bones. Symptoms include severe pain, swelling, and difficulty bearing weight on the affected leg. 
• Treatment may involve conservative management, such as rest and physical therapy, or surgical intervention to realign and stabilize the fractured bone.

2. Anteverted Acetabulum

• An anteverted acetabulum refers to the forward orientation of the acetabular opening. 
• This orientation allows greater hip flexion but can also increase the risk of hip instability and dislocation, particularly during activities involving external rotation of the leg. 
• Anteversion is a normal variation, but excessive anteversion may require surgical correction to prevent recurrent dislocations or other complications.

3. Retroverted Acetabulum

• Retroversion of the acetabulum refers to a backward tilt of the acetabular opening. 
• This can limit the range of motion, particularly in hip flexion and internal rotation, and may lead to hip impingement, where the femoral head abnormally contacts the acetabular rim. 
• This condition can cause pain and restrict movement, often requiring surgical intervention to correct the orientation of the acetabulum.

4. Shallow Acetabulum

• A shallow acetabulum, often associated with developmental dysplasia of the hip (DDH), lacks sufficient depth to fully accommodate the femoral head. 
• This can lead to joint instability and an increased risk of dislocation. 
• In some cases, a shallow acetabulum can result in premature wear and tear of the joint, leading to osteoarthritis. 
• Treatment options may include bracing in infants or surgical procedures, such as a periacetabular osteotomy, to deepen the acetabulum.

5. Spring Plate Acetabulum

• The term "spring plate acetabulum" refers to the concept of using a spring plate in the surgical treatment of acetabular fractures. 
• This technique involves placing a thin metal plate over the fracture site, allowing for some flexibility and minimizing the risk of impinging on the joint. 
• The spring plate helps maintain the reduction of the fracture while allowing for slight movement, which can aid in the healing process. 
• This technique is particularly useful in cases where the bone is fragmented or the fracture involves the weight-bearing dome of the acetabulum.