Protrusio acetabuli is an uncommon defect of the acetabulum

Acetabulum

The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...

. The acetabulum is the socket that receives the femoral head to make the hip joint. The hip bone

Hip bone

The hip bone, innominate bone or coxal bone is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below...

 of the pelvic bone/girdle is composed of three bone

Bone

Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

s, the ilium

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

, the ischium and the pubis

Pubis (bone)

In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....

. The socket is too deep and may protrude into the pelvis

Pelvis

In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...

.

Primary protrusio acetabuli

• Characterized by progressive protrusio in middle aged women
• May be associated with OA
• May be familial

Secondary protrusio acetabuli

Causes include:

• Femoral head prosthesis
  Prosthesis
  In medicine, a prosthesis, prosthetic, or prosthetic limb is an artificial device extension that replaces a missing body part. It is part of the field of biomechatronics, the science of using mechanical devices with human muscle, skeleton, and nervous systems to assist or enhance motor control...
  
  
• Cup arthroplasty
  Arthroplasty
  Arthroplasty is an operative procedure of orthopedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure.-Background:Previously, a popular form of arthroplasty was...
  
  
• Septic arthritis
  Septic arthritis
  Septic arthritis is the purulent invasion of a joint by an infectious agent which produces arthritis. People with artificial joints are more at risk than the general population but have slightly different symptoms, are infected with different organisms and require different treatment. Septic...
  
  
• Central fracture dislocation
• Total hip replacement surgery
  Surgery
  Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
  
  

In addition, protrusio acetabuli may be present bilaterally in Paget's disease

Paget's disease

Sir James Paget, a surgeon and pathologist, described several diseases, including:* Paget's disease of bone * Paget's disease of the breast* Paget-Schroetter disease* Extramammary Paget's disease...

, Marfan syndrome

Marfan syndrome

Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers....

, rheumatoid arthritis, ankylosing spondylitis, and osteomalacia

Osteomalacia

Osteomalacia is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available phosphorus and calcium, or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism...

;

Signs and Symptoms

• May be asymptomatic
  Asymptomatic
  In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
  
  
• Limitation of joint range of movement is the earliest sign
• Pain

Treatment

Arthroscopic surgery (or open joint surgery) is an effective treatment. Joint replacement surgery may be necessary in the case of severe pain or substantial joint restriction.
Prominent trabeculae. * Normal sacro-iliac joints and symphysis pubis.