General principles and aims of treatment
Acetabular fracture surgery is one of the most complex and challenging aspects of orthopaedic surgery. In addition to the complexity involved in the treatment of acetabular fractures, these patients often present with other injuries. First, life-threatening injuries must be ruled out, and, if found, treated expeditiously.
The secondary survey will identify associated musculoskeletal injuries. Special attention should be given to examination of the ipsilateral knee and thigh when an acetabular fracture is present, especially in cases of high-energy motor vehicle collisions (“dashboard injury”). When all musculoskeletal injuries have been identified, the orthopaedic surgeon must decide when and how to treat each injury.
Minimally invasive fracture surgery is an evolving branch of orthopaedic trauma surgery, especially as it pertains to techniques and indications in acetabular fixation. The potential of achieving satisfactory articular reductions with mechanical stability with a decreased risk of soft-tissue complications make percutaneous techniques particularly appealing [ 1]. Percutaneous techniques are biologically friendly because of preservation of the fracture hematoma and the soft-tissue envelope. The primary goals of percutaneous acetabular treatment are to reduce and stabilize displaced fractures with minimal local or systemic morbidity. A secondary and more controversial goal is to provide stability for minimally displaced fractures to allow early mobilization and weight bearing. Fixation is provided without the morbidity associated with an open approach or the need for external fixation. In some cases, the risk of surgery may be lessened to a point where the benefits of early ambulation, particularly in the multiple-injured or geriatric patient, dictate more aggressive surgical intervention.
This chapter discusses the risks, benefits, indications, techniques, and specific tips and tricks of minimally invasive osteosynthesis (MIO) for fractures of the acetabulum.
Indications and contraindications for MIO
Generally, acetabular fractures with displacement of the weight-bearing surface of more than 2 mm meet criteria for operative fixation. Fractures outside the weight-bearing dome as measured by roof arcs (> 45°) and/or by evaluation of the weight-bearing dome on CT scan may be amenable to nonoperative treatment despite displacement of more than 3 mm [ 2, 3]. Joint subluxation on films out of traction or during stress views may be another indication for operative treatment in the case of acetabular fractures. Medical comorbidities, activity level, and other patient-related factors must also be considered before recommending operative treatment for acetabular fractures.
At present, there are limitations for purely percutaneous treatment of displaced acetabular fractures performed for the need for anatomical reduction. This is particularly true in young patients with complex fracture patterns when closed manipulation may not be enough to obtain the anatomical reduction necessary for a good outcome. Elderly patients, however, may have broader indications for percutaneous fixation when the morbidity associated with an open approach is greater than the benefits provided by an anatomical reduction. Additionally, there is evidence that elderly patients will tolerate imperfect reduction better than young patients [ 4]. Incongruent joint reduction in the elderly patient may be treated in a delayed fashion with total hip arthroplasty, as long as there is adequate bone stock.
In nondisplaced and minimally displaced acetabular fractures, minimally invasive techniques can facilitate early mobility and pain control. This can allow for improved aftercare without the risk of secondary displacement of the fracture. With maintenance of alignment and minimal incisions, resulting posttraumatic arthritis can be treated with a primary arthroplasty without the increased risks of operating through scarred, contracted tissues.
Certain fracture patterns are more amenable than others to MIO. Isolated anterior column, juxtatectal transverse, anterior column, posterior hemitransverse, and some both-column fractures can be manipulated with closed or minimally invasive reduction maneuvers and successful percu taneous screw placement. However, displaced posterior wall, posterior column, and T-type fractures are difficult to reduce and fix with current minimally invasive techniques. Marginal impaction fractures cannot be treated with a pure MIO approach but can be indirectly treated via limited anterior approaches, using bone windows above the quadrilateral plate. To some degree, current limitations in reduction and fixation techniques are due to lack of specific instrumentation to safely access and manipulate fracture fragments. Proponents of acetabular MIO have described various modifications of existing equipment to facilitate the operative technique . The spectrum of MIO in the acetabulum encompasses pure percutaneous fixation, percutaneous fixation with small assistive incisions, fixation of complex fractures with the Stoppa approach, and combinations of conventional approaches with percutaneous screw fixation.
Special aspects for acetabulum
To begin using MIO techniques the anatomy of the pelvis and acetabulum must be appreciated in three dimensions. The acetabulum is formed by the confluence of three bones: the ilium, ischium, and pubis. Contributing a little more than two-fifths of the structure is the ischium, which provides lower and side boundaries to the acetabulum. The ilium forms the upper boundary, providing a little less than two-fifths of the structure of the acetabulum. The rest is formed by the pubis, near the midline. Named after the Latin word for “a little Roman dipping saucer,” the acetabulum is a cup-shaped anatomical structure, facing slightly anterior and caudal.
The acetabulum is bounded by a prominent uneven rim that is thick and strong above, and serves for the attachment of the acetabular labrum which reduces its opening and deepens the surface for formation of the hip joint. At the lower part of the acetabulum is the acetabular notch which is continuous with a circular depression, the acetabular fossa, at the bottom of the cavity of the acetabulum. The rest of the acetabulum is formed by a curved, crescent moon-shaped surface, the lunate surface, where the joint is made with the head of the femur. Its counterpart in the pectoral girdle is the glenoid fossa ( Fig 15.1-1 ).
Fracture and soft-tissue assessment
All acetabular fractures should be assessed in accordance with advanced trauma life support (ATLS) protocols. Initial assessment includes a careful physical examination and review of relevant x-rays. Percutaneous fixation offers several advantages over open reduction of acetabular fractures. It virtually eliminates soft-tissue disruption with the potential for devascularization or denervation. A physical examination focusing on the acetabular injury should include complete neurological assessment of the pelvis and lower extremity, and evaluation of the soft tissues in the trochanteric and gluteal regions. Because the sciatic nerve is damaged in as many as 20% of acetabular fractures affecting the posterior wall or column, the motor and sensory functions of the extremity must be carefully documented [ 5].
Closed soft-tissue injuries, including local wounds, abrasions, and closed degloving injury may occur around the hip region, especially over the trochanter. A closed degloving injury is referred to as a “Morel-Lavallee lesion” [ 6]. The serosanguineous fluid collections that develop in these cavities should be cultured to rule out infection. If a closed degloving injury is discovered, irrigation and debridement of these areas should be performed, and internal fixation should be delayed until the area is clean.
Type of x-rays and CT scans
The x-ray assessment of acetabular fractures is well described using the AP and Judet views (iliac oblique and obturator oblique). Each view allows an optimum visualization of different aspects of the anatomy relevant to acetabular fractures. On the AP view the iliopectineal and ilioischial lines represent outlines of the anterior and posterior columns respectively ( Fig 15.1-2 ). The obturator oblique demonstrates the obturator ring, posterior wall, and lower portion of the anterior column which can be obtained when the patient is positioned supine and the injured side of the pelvis is rotated anteriorly 45° with the x-ray tube and film vertically aligned. The iliac oblique demonstrates the iliac wing, greater sciatic notch, posterior column, and edge of the anterior wall which can be obtained when the patient is positioned supine with the uninjured side of the pelvis rotated anteriorly 45°, the x-ray tube and film positioned vertically toward the affected hip ( Fig 15.1-3 ). If associated with pelvis ring disruption, the inlet and outlet views are necessary.
A CT scan with sections of 1.5 or 2 mm through the affected area of the acetabulum provides the most detail and most valuable information about the fracture pattern with regard to comminution, marginal impaction (wall fractures), and intraarticular fragments. The fracture pattern can be determined by the direction of the fracture lines on the CT scan ( Fig 15.1-4 ). On the axial views, splits in the coronal plane often represent column fractures. Sagittal splits in the roof of the acetabulum are commonly seen with transverse or T-shaped fractures. Oblique fractures that do not extend into the quadrilateral plate are seen with wall fractures .
Two-dimensional and three-dimensional (3-D) reconstructions of the fracture often help in understanding the rotational deformities of the displaced fractures but are not necessary for traditional decision making or operative planning, except to delineate the extent of marginal impaction. Three-dimensional CT reconstructions can greatly aid in the preoperative planning in delineating fracture patterns and the direction of reduction tools for acetabular MIO (Fig 15-5). The 3-D views better correspond to the spatial conception required of the surgeon in planning reductions and placing fixation.
Timing of surgery
Several studies have shown that the timing of operative intervention is important [2–4, 7]. With hemodynamically stable patients MIO is initiated as soon as possible with most operations performed 2–5 days postinjury. With progressive delays reduction becomes harder to achieve due to consolidating fracture hematoma. Delay is also associated with an increase in deep vein thrombosis and skin problems. If the reduction is performed partially percutaneously, as in the Stoppa approach, early fixation is helpful but less necessary.
As for all trauma surgery, every attempt should be made to optimize the patient physiologically. Surgical preparation is also necessary as MIO is technically demanding and requires appropriate equipment and manpower. A preoperative plan using all available imaging will enable anticipation of most problems and lead to the correct equipment being available. Experienced assistance is vital. The main points to consider at the preoperative planning stage are:
Administration of prophylactic antibiotics before surgery
Patient positioning: supine, prone, or lateral decubitus?
Radiolucent operating table
Appropriate pelvic instrumentation, including specialized reduction tools
The reduction technique (some fractures will benefit from intraoperative traction either using the table attachments or a femoral distractor. Intraoperative nerve monitoring has been described but is not routinely used in most centers.)
Insertion of the guide wire
Insertion of the appropriate implant
Administration of postoperative thromboembolism prophylaxis