Fractures of the acetabulum occur when the head of the femur is driven into the pelvis. This injury is caused by a blow to either the side or front of the knee and often occurs as a dashboard injury accompanied by a fracture of the femur. The acetabulum is a cavity situated on the outer surface of the hip bone, also called the coxal bone or innominate bone. It is made up of three bones, the ilium, ischium, and pubis. Together, the acetabulum and the head of the femur form the hip joint. Fractures of the acetabulum in young individuals usually result from a high energy injury like vehicular accident or feet first fall. In older individuals or those with osteoporosis, a trivial fall may result in acetabular fracture. In 1964, French surgeons Robertt Judet, Jean Judet, and Emile Letournel first described the mechanism, classification, and treatment of acetabular fracture. They classified these fractures into elementary (simple two part) and associated (complex three or more part) fractures. Judet-Letournel classification Presentation Associated injuries and complications The broken bone pieces or the dislocated head of the femur may injure the sciatic nerve, causing paralysis of the foot; the patient may or may not recover sensation in the foot, depending on the extent of injury to the nerve. The posterior wall fragment may be one large piece, or multiple pieces, and may be associated with impaction of the bone. Sciatic nerve injury and stoppage of blood supply to the femoral head at the time of accident or during surgery to treat the injury may occur. Deep vein thrombosis and pulmonary embolism are other complications that may occur in any type of injury to the acetabulum. A common postoperative complication is heterotopic ossification around the injured hip joint. Anatomy To understand the fracture pattern of a fractured acetabulum, it is essential to have minimum three x-ray views, though use of CT scan with 3-D reconstruction of images has made understanding of these fractures easier. Pelvis with both hips antero posterior view. This view shows six important landmarks of the acetabulum, specifically: Pelvic brim Ilio ischial line Tear drop Anterior wall Posterior wall Weight bearing dome Iliac oblique view. This view shows the whole of the ilium, the posterior column, and the anterior wall Obturator oblique view. Shows the anterior column and the posterior wall. Patterns of fracture Tile's classification of acetabular fracture: I -