Epidemiology

Acetabular fracture patterns are determined by the hip position at impact, the local bone quality, and the magnitude of the applied load. As the load is further transmitted, the acetabular fracture displaces, and the femoral head may dislocate from the hip joint. These fractures commonly occur in a bimodal age distribution. Older patients have poor bone quality and sustain them after a fall from standing. Young patients have better bone quality and are also more exposed to high-energy traumatic events such as car and motorcycle crashes.

Osteology

Normal pelvic osteology is complex and confusing, and displaced acetabular fractures are even more challenging to thoroughly comprehend. The acetabulum is a hemisphere-shaped recess located between the ilium, ischium, and pubis. It develops from the triradiate cartilage and matures into the adult acetabulum. The acetabular surface is concave and is mostly covered by hyaline cartilage. The fossa acetabuli is a recessed area in the center of the acetabulum that contains fat and the ligamentum teres. The acetabular labrum is attached to the acetabular wall perimeter and the hip capsule.

The Inverted Y Structural Concept

The structural acetabular concept describes it as being located between the limbs of two boney supports or “columns” shaped as an inverted Y. The anterior column is comprised of the superior pubic ramus, anterior acetabular wall, and the anterior portion of the ilium and quadrilateral surface. The posterior column is comprised of the greater and lesser sciatic notches, posterior acetabular wall, and the posterior half of the quadrilateral surface. The two-column structural model was intended to simplify the acetabular osseous architecture so that clinicians could better understand the injury patterns (Fig. 2).

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Radiology

Acetabular fracture diagnosis and classification schemes are based on the radiographic findings and the two-column acetabular concept (Judet et al. 1964). The normal radiographic markers represent bony cortical surfaces and edges revealed by tangential X-ray beams. These cortical lines include the peripheral edges of both the anterior and posterior walls; the dense line representing the pelvic brim and superior pubic ramus’ posterior cranial edge (iliopectineal line); the dense line representing the pelvic brim and quadrilateral surface (ilioischial line); the dome region’s subchondral arc (sourcil); and the acetabular “teardrop” representing the fossa acetabuli, obturator sulcus, and a portion of the quadrilateral surface. These six radiographic markers help clinicians to better understand and mark the two walls, the two supporting columns, the weight-bearing dome, and the caudal joint. Oblique acetabular imaging is accomplished by rolling the patient 45° toward each side so the fracture is seen in biplanar views. A pelvic computed tomogram (CT) scan uses axial, sagittal, and coronal images to further reveal the osseous and soft tissue details related to the injury. Surface-rendered three-dimensional images are created from the CT information to further identify the specific fracture sites and displacements (Fig. 3). Other imaging modalities may be indicated for certain patients, for example, a hemodynamically unstable patient with fracture involving the greater sciatic notch may benefit from pelvic angiography to assess the superior gluteal artery. These angiographic images can be used for diagnostic means and surgical planning also.

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Classification

Initial Management

Patients with these fractures may present in a variety of manners depending usually on the mechanism of injury. Each patient is resuscitated according to ATLS protocols, and plain pelvic radiographs are obtained once the patient has been stabilized. Fracture-dislocations are reduced urgently once the fracture pattern details are understood. Posteriorly directed dislocations are usually associated with posterior wall, posterior column/posterior wall, and transverse/posterior wall acetabular fracture patterns. Medial dislocations are usually noted with associated both-column, transverse, T-type, anterior column/posterior hemitransverse, and posterior column fracture patterns. Prior to closed reduction, the treating physician should carefully assess the femoral neck area on the X-rays for fracture. Adequate muscle relaxation is mandatory prior to the manipulative reduction attempt and can be achieved using a variety of techniques. The dislocated femoral head is then manipulated so that it can be held beneath the area of the weight-bearing dome. Skeletal traction may be needed to secure this reduction.

Once the patient and the fracture have been stabilized, secondary and tertiary repeat evaluations are indicated to identify other injuries that were initially missed. Pelvic imaging is then obtained so the treatment can be planned.

Some dislocations are obstructed by bone debris in the joint or misplaced soft tissue structures such as the piriformis muscle tendon due to the injury rendering it irreducible via closed manipulation. These rare patients require urgent open reduction (Fig. 4).

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Nonoperative Treatment

For patients with stable and minimally displaced acetabular fractures, nonoperative management is recommended, consisting of protected weight bearing on the injured extremity for 6–12 weeks after injury. Serial weekly plain pelvic radiographs are recommended for 1–3 weeks after injury to assure that further fracture displacement is not occurring and that the hip joint remains congruent when nonoperative management is chosen. Skeletal traction is used when the fracture is unstable but the patient is a poor candidate for surgery and the fracture reduction is sufficient in traction. Usually ten pounds of traction is applied through a distal femoral traction pin and simple pulley system attached to the foot of the bed. When traction is chosen, the head of the patient’s bed should be elevated to decrease the risk of aspiration, especially in elderly patients.

Operative Treatment

Displaced and unstable acetabular fractures are treated operatively (Letournel 1993; Helfet et al. 1992). Open anatomical reduction with stable internal fixation (ORIF) is recommended for the majority of patients with these articular injuries. Anatomical reduction restores the articular surfaces and lowers the risk of post-traumatic arthritis formation. Access to the fracture fragments allows the surgeon to directly clean the fracture surfaces of organized hematoma and small bone fragments that can obstruct the reduction and physically manipulate the fracture fragments into a reduced position. Clamps, wires, lag screws, and other devices are routinely used to temporarily maintain the reduction while the definitive fixation is applied to the bone. The Kocher-Langenbeck surgical exposure is used for posterior acetabular injuries, and the ilioinguinal surgical exposure provides access to anterior acetabular fractures. For patients with more complex fracture patterns, the two exposures can be used in sequence either at the same anesthesia or at a subsequent anesthesia. Some recommend using the two exposures simultaneously (Routt and Swiontkowski 1990). The extended iliofemoral and several other more extensive surgical exposures have also been advocated for difficult fracture patterns (Siebenrock et al. 2002). Each surgical exposure and patient positioning for surgery has associated risks. When the lateral patient position is chosen, the patient must be securely positioned on the operating table, usually using a vacuum beanbag and obstructing posts. In the lateral decubitus position, the uninjured side is at risk to pressure points particularly at the axilla, hip, and knee. Medially displaced fracture fragments and instability are much more difficult to accurately correct in the lateral position. Prone patient positioning risks blindness if hypotensive anesthesia is used and the eye regions are not relieved of pressure. The airway access, upper extremities, and male genitalia are also at risk while the patient is prone. When positioned prone, supporting chest rolls suspend the abdomen to facilitate mechanical ventilation during surgery.

The foundation for stable fixation is a well-reduced fracture. In surgery, bone clamps are initially positioned to hold the reduced fracture fragments, and then lag screws and plates link and stabilize the acetabular fracture fragments together. Malleable plates are contoured precisely to match the cortical surfaces so the implant functions best (Qureshi et al. 2004). Long-length medullary screws are often used in both the anterior and posterior columns to stabilize the fractures (Fig. 5).

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Manipulative reduction of the fracture fragments with percutaneous fixation is another operative treatment method. These techniques usually are reserved for patients who are unable to withstand a routine open reduction due to their overall clinical condition and those fractures that are minimally or essentially non-displaced and do not involve the acetabular dome. In these patients, simple traction maneuvers realign the major fracture fragments so that medullary columnar screws are inserted to stabilize the fracture. This technique may also be useful for morbidly obese patients or those with soft tissue injuries that preclude open procedures.

Arthroplasty has been used sparingly as a primary treatment for certain patients with acetabular fractures (Herscovici et al. 2010). Usually this technique is reserved for older patients with preexisting arthritis and extensive articular damage such that the fracture cannot be reduced accurately. Reduction and stable fixation of the displaced column and wall components of the fracture are still required initially so the replacement cup can be securely placed into stabilized acetabular fracture fragments. Patients with acute acetabular fractures are not as medically optimized as those with degenerative conditions scheduled for elective total hip replacement. A patient with acute acetabular fractures may have other injuries or complications due to their overall condition after trauma that threatens the hip arthroplasty success.

Rehabilitation

Rehabilitation after acetabular fracture repair consists of protected weight bearing on the injured side using crutches or a walker for 12 weeks after surgery. During the initial 6 weeks, the amount of pressure applied to the injured side is limited to the weight of the extremity. Isometric muscle exercises and active range of motion activities are allowed. During the second 6-week time period, muscle strengthening exercises are instituted along with gradual progression of load applied to the injured limb. The goal of independent ambulation at week 13 is achieved for most patients.

Complications

Deep venous thrombosis (DVT), infection, and symptomatic ectopic bone formation are several of the complications associated with acetabular fractures (Russell et al. 2001). A variety of techniques such as early surgery, anticoagulation, and sequential compression devices have been advocated for DVT prophylaxis. Deep wound infections are unusual but demand early and aggressive surgical debridement along with appropriate intravenous antibiotics. Indomethacin, targeted low dose irradiation, and muscle debridement have been recommended to decrease the incidence and extent of heterotopic ossification (Rath et al. 2002; Moore et al. 1998).