In order to understanding the acetabular fractures it should be first known the anatomy of the acetabulum
Anatomy of the acetabulum
The acetabulum may be considered as an anterior column and wall and a posterior column and wall. The anterior column comprises the anterior part of the iliac wing extending down to include the anterior half of the acetabulum and anterior wall and around to the superior pubic ramus and pubic tubercle .the posterior column comprises the posterior half of the acetabulum the bone running back to the greater and lesser sciatic notch, and the bone running down to the ischium and the ischial tuberosity. The posterior wall abuts the centre of the posteriors column. these columns come together in an inverted Y with the dome of the acetabulum at the apex The classification of fractures is based on the extent involvement of the two columns and walls.
Causes and Clinical evaluation
Acetabular fractures are usually the result of motor vehicle accidents or high falls. They result from indirectly applied forces transmitted via the foot, knee or greater trochanter. Hip and knee position will further define the fracture created. A blow to the flexed knee with the hip also flexed at 90 degree (as in a dashboard type injury) tends to cause a posterior wall fracture. If the femur abducted, a transverse fracture will result. most of the patients have multiple injuries. the fracture are commonly displaced
A history of the mechanism of injury and site of pain should alert the surgeon to the diagnosis. Bruising and abrasions on the thigh or buttock regions are common, and there may be consider able degloving of skin from underlying tissue (Morel-Lavale lesion). Surgical approaches through this damaged skin have a high rate of wound complications. Leg length discrepancy may present. and a short, flexed. adducted leg with internal rotataed suggests posterior dislocation of the hip. This is common associated with an acetabular fracture involving the posterior column and wall. Weakness of dorsiflexion and numbness on the dorsum of the foot suggest a sciatic nerve palsy, the most common associated neurological lesion.
Radiology and classification
Despite the widespread availability of CT and MRI scanning
high-quality plain radiographs remain essential in the assessment of these fractures. Four radiographs are required: Anteroposterior (AP) of the pelvis view, AP of the injured hip iliac oblique view , and obturator oblique view . The last two views (Judet views) are oblique views to augment the information obtained from the plain AP views ). Six radiographic landmarks arc used to aid diagnosis of the fracture: anterior wall, posterior wall, anatomical teardrop, acetabular roof and ilioischial and iliopectineal lines. Based on the anatomy and radiology, Letournel described 10 types of fracture. There are five elementary types and five associated types the two common patterns observed are by coincidence the simplest and most complex, namely the posterior wall fracture and both columns fracutres
CT scan confirm the plain radiological diagnosis
but is most useful to demonstrate the presence of loose intraarticular fragments and impaction of the articular surface which may need to be addressed at the time of surgery
Three-dimensional CT reconstruction can produce very sophisticated images of the fracture. but is not necessary for either diagnosis or surgical planning.
What areThe role of plain radiographs for evaluation of acetabular fractures and the information that can be derived from each view
AP pelvis view showing
The overall bony integrity of the pelvic ring
Dislocation of the sacroiliac joints or symphsis
Rare bilateral actetabular fractures
AP hip view showing
Pelvic inlet ,ilioischial line ,iliopetineal line
Teardrop medial actetabular wall
Obturator oblique view showing
Obturator foramen seen straight on iliac wing side on
Iliac ohlique view view (roll under uninjured hip,obtutator foramen not seen) showing
Posterior column ilioischial line
Iliac wing broad flat surface
What are the classification of acetabular fractures? divided into
elementary fractures and associated fractures as follow
Posterior column Anterior wall Anterior column Transvrse
Posterior column and posterior wall Transvrse fracture and posterior wall T-shaped fractures
Anterior column posterior hemitransvrse fractures
Both column fractures
Stable undisplaced fractures can be treated non-operatively. Patients can be mobilised partially weight-bearing on crutches, progressing to full weight-bearing at 6 weeks.Serial radiographsat 1, 3 and 6 weeks should be taken to ensure healing without displacement occurs.
There are two main indications for internal fixation
incongruent hip joint and instability of the hip joint
Some displaced fractures are suitable for non-operative treatment:
low transverse fractures and low anterior column fractures that do not involve the major weight-bearing dome of the acetabulum both-column fractures in which the articular components cluster round the femoral head in a reasonably anatomic pattern. which is termed secondary congruence.
Displaced fractures which are judged suitable for non-operative management are often treated for a period of 3-4 weeks by skeletal traction. followed by mobilisationon crutches.
In general. displaced fractures do poorly if treated non operatively. with a high rate of post-traumatic osteoarthrosis. The aim of operative treatment is anatomical reduction. with rigid internal fixation to allow early mobilisation in order to minimise this complication. Accurate preoperative diagnosis of fracture type is necessary to determine the correct surgical approach.
Three types of surgical approach are in common use:
The posterior Kocher-Langenbeck approach is an extended posterior approach to the hip joint that allows access to the posterior wall and column. The anterior ilioinguinal approach allows access to the antenor wall and anterior
Extensile exposures have been developed to enable access to both columns simultaneously.The most commonly used is the extended iliofemoral approach.
Posterior wall, posterior column. transverse and combinations of these types account for 66% of displaced fractures, and may be accessed using the posterior Kocher-Langenbeck approach to the hip. Anterior wall. anterior column and more complex fractures mainly involvingthe anterior aspect of the acetabulum require the anterior ilioinguinal approach. Some fractures. such as the T-shaped or exposure. Combined ilioinguinal and Kocher-Langenbeck exposures are an alternative for a single extensile exposure. Antibiotic prophylaxis is routine, and deep vein thrombosis prophylaxis in patients without a coagulopathy is recommended. Following surgerythe patient can be mobilisednon non weight-bearing on crutches for 6-8 weeks. Radiographs are taken at 1, 3 and 6 weeks to ensure no loss of fixation. Patients should be followed for a further 2 years with radiographs to detect late complications.
Sciatic nerve palsy occurs preoperatively in 10-15% of cases and is associated with acetabular fractures with posterior dislocanon of the hip or marked displacement of the sciatic notch. Complete recovery occurs in 50% of cases, partial
recovery in 40% and no recovery in 10%. The peroneal component is most commonly
involve More extensive nerve involvement and dense motor paralysis are associated with a poorer prognosis for recovery
Nerve palsy is also seen as an iatrogenic complication in 3-5%. Intraoperative nerve monitoring has been suggested to reduce this problem.
other intraoperative complications include intra-articular
screw placement and injury to the superior gluteal artery or nerve. Gluteal nerve injury may result in a Trendelenburg limp post operatively. Superior gluteal artery injury can result in muscle necrosis and in extensile exposures may compromise the overlying skin also due to loss of collateral circulation associated with the approach. Postoperative wound infection complicates up to 5% of cases and may result in septic arthritis, which is inevitably associated with a poor outcome. Heterotopic ossification is a significant problem. particularly with posterior or extensile exposures , although the ossification is not always clinically significant. It can be reduced to 10% by postoperative administration of Indomethacin (25 mg r.d.s. for 6 weeks) or post operanve irradiation
Summary of complications of acetabular fractures and the surgery to repair them
• Sciatic nerve palsy
• Traumatic arthritis of the hip
• Avascular necrosis of the hip
• Unstable hip joint
• Gluteal palsy
Avascular necrosis is a particular risk in fractures associated with posterior dislocation, occurring in 20-25% of cases. Post traumatic osteoarthritis is the major late complication. The rate depends on the age of the patient, the type of fracture and the quality of reduction. Advancing age. posterior dislocation,
marginal impaction of the acetabulum or impaction fractures of the femoral head are all poor prognostic features. Post-traumatic osteoarthritis may be treated with total hip replacement in older patients. In young patients, the treatment is more difficult and consideration may have to be given to hip fusion
Acetabular fractures are rare and usually the result of high energy trauma.
Plain radiographs, Judet views and CT scans are required to
evaluate the Injury.
There are 10 principal varieties of injury, five simple types and five more complex injury patterns.
The indication for internal fixation is the presence of instability or incongruity of the hip joint.
Defining the type of fracture is of key importance to determine which surgical approach to use.
The acetabulum can be approached from anterior, posterior or extensile exposures • Satisfactory reductions are associated with good long-term results