Acetabular Reconstruction Fixation Methods in Simple Fracture Patterns

Bruce H. Ziran

Department of Orthopaedic Trauma, St. Elizabeth Health Center and Department of Orthopaedic Surgery, Northeastern Ohio Universities College of Medicine, Youngstown, Ohio, U.S.A.

Daniel R. Schlatterer and Robert M. Harris

Atlanta Medical Center, Department of Orthopaedic Trauma, Atlanta, Georgia, U.S.A.

INTRODUCTION TO SIMPLE FRACTURE PATTERNS OF THE ACETABULUM

Acetabular surgery is one of the more intensive and complex surgeries performed in orthopaedics. This includes the complexity of the surgical dissection, the significant risk of neurovascular and or visceral injury, and the three-dimensional challenge of reducing and fixing the fracture itself. An important aspect of acetabular fracture surgery should be the establishment of expectations for both the surgeon and the patient. Surgeons should be expected to have dedication to improving their skills and be diligent about analyzing and monitoring their own results, in an effort to learn, and improve, their outcomes. So, prior to embarking on such an endeavor, and during their careers managing acetabular fractures, surgeons should make efforts to learn from their own experiences, as well as those of others. The patient's expectations should also be established. They should be informed that even in the hands of subject-matter experts, the outcomes are not uniformly excellent. Preopera-tive counseling with the patient and family members should include a discussion of expected outcomes. In this section, we review techniques used for obtaining reduction, as well as propose a method of fixation.

PLANNING AND OPERATIVE TACTIC

The simple acetabular fractures, while basic in their pattern, are not always the simplest fractures for treatment. After careful preoperative evaluation and planning, the fixation methods usually employ some type of screw or plate fixation. The amount of fixation required is variable, and there will be many opinions. There is no set rule, except to make sure there is stable fixation of the essential elements of the reduced fracture. Whether this is achieved percutaneously, or with extensile approaches, the goals are an acceptable reduction and a stable fixation until healing. With regard to approaches, we have found that the vast majority of fractures with simple patterns can be fixed through one approach. Recently, adjunctive techniques and new "windows" have been developed that help preclude the necessity for more extensile approaches. Occasionally, a second simultaneous or sequential approach is needed, but rarely are extensile approaches required for simple fracture patterns.

An important aspect of acetabular fracture surgery should be the establishment of expectations for both the surgeon and the patient. Surgeons should be expected to have dedication to improving their skills and be diligent about analyzing and monitoring their own results, in an effort to learn, and improve, their outcomes. Acetabular surgery is one of the more intensive and complex surgeries performed in orthopedics. This includes but is not limited to the complexity of the surgical dissection, the significant risk of neurovascular and or visceral injury, and the three-dimensional challenge of reducing and fixing the fracture itself. So, prior to embarking on such an endeavor, and during their careers managing acetabular fractures, surgeons should make efforts to learn from their own experiences as well as those of others. The patient's expectations should also be established. They should be informed that even in the hands of subject-matter experts, the outcomes are not uniformly excellent. Preoperative counseling with the patient and family members should include a discussion of expected outcomes. The avascular structure of cartilage limits its reparative potential. Thus, the combination of articular damage, slightly imperfect reductions, extensive surgical exposures, and load requirements of the hip joint will frequently result in some dysfunction. This may lead to early and rapid post-traumatic arthritis requiring secondary intervention. Thus, the goals of the surgeon and patient should be set at reasonable levels for each patient and fracture. For example, in the elderly, a lengthy operation and exposure to achieve perfection may be at too great a cost because of the associated and increased morbidity in this population. Some acetabular surgeons argue that restoration of the bony architecture and a "good enough" reduction may be all that is necessary, in anticipation of arthroplasty. Even so, many of the elderly are very resilient and may not require arthroplasty even in the face of significant post-traumatic arthritis.

The implants used for fixation will most frequently be some type of bendable reconstruction plate. The authors typically have a pelvic reconstruction set and a small fragment set open and available during the surgery. Recently, newer versions of reconstruction plates were introduced that allow the use of locked screws. While rarely needed, there are certain situations where locked screws may be beneficial, such as with osteoporotic bone and, for example, with long posterior column screws. The one instance where the authors have found locking plates to be very helpful has been for combined approaches (for example, a posterior approach followed by an ilioinguinal approach). This is because shorter screws can be used in the locking mode. Shorter locked screws in the posterior column have less of a chance of interfering with hardware placement in the ensuing anterior approach. Keep in mind that bending locking plates can alter the locking mechanism, and it is easier to redirect a nonlocking screw into good bone. Also, acetabular exposures are often confined spaces and the locking guides can be challenging to thread into the locking plate. Finally, despite the theoretical advantages of locking plates, clinical outcome studies are lacking. There are specialized pelvis /acetabular systems available that provide appropriate instrumentation including long screws, long drill bits, and plates. The workhorse plates are the 3.5 mm reconstruction plates, both straight and curved. The curvature has been determined from previous cadaveric work and approximates that of most pelvic brims. Other instruments include an assembly of appropriate reduction clamps, from standard bone forceps to the specialized pelvis and acetabular versions. The ball spike pusher is an invaluable tool, and we recommend two: one with a standard point, and the other with a spiked washer, which will help prevent iatrogenic fractures by distributing the reduction force. The authors recommend putting a saw bone pelvic model into a clear plastic sterile bag for intraoperative referencing. The model can be used for plate contouring and as a reference for safe screw placement.

Regarding the operative table and positioning, it is important to ensure adequate visualization of the entire fracture and the ability to have visual or digital palpation of the fracture reduction. Some of the specialized fracture tables are impractical and costly to obtain, but a radiolucent table is an essential element of this type of surgery. We have found that the radiolucent Jackson flat top table (OSI, Union City, California, U.S.A) is an excellent choice and can also be utilized for most other orthopedic fracture cases, which makes it cost-effective as well. It can be supplemented with various traction setups in order to achieve both longitudinal and lateral traction. We have been able to obtain longitudinal and lateral traction in supine, lateral, and prone positions with this system.

Surgical tactic has many variables, not the least of which is the number and experience of the assistants. A surgeon at a training program may have two to three extra pairs of hands and essentially an endless supply of "traction." Others practicing in a community setting must be more mindful of ergonomic factors. In either case, the surgeon must understand that traction for long periods of time has well-described complications. With regard to positioning of the patient, the ilioinguinal approach will necessitate a supine position. If exposure of the outer aspect of the ilium or placement of an ipsilateral iliosacral screw is required, the patient should be positioned closer to the edge of the table. Bean bag use is minimized as it can interfere with fluoroscopy. An appropriate "mini" bowel prep with a lower abdominal radiograph (KUB) before surgery is also recommended to ensure adequate visualization of the sacrum if percutaneous fixation is a possibility. If traction is used and the pelvis and limbs become somewhat "statically" positioned (as compared to free), then we recommend distal femoral traction and some pads under the thigh to allow hip flexion. Flexing the hip will help relax the iliopsoas muscles and greatly facilitates exposure (Fig. 1). Use of manual traction is performed by pulling on the leg or with use of a temporary 5-mm Schantz pin at the level of the lesser trochanter. Use of a radiolucent triangle is used for hip flexion

Figure 1 Supine positioning for ilioinguinal approach. Distal femoral traction can be employed. Alternatively, flexion of the hip (supported by a radiolucent triangle) will relax the iliopsoas muscle to facilitate exposure during reduction and fixation.

(thus relaxing the iliopsoas muscles). If an extensile approach such as the triradiate or the extended iliofemoral is used, the lateral position is most suitable. This will provide access to all aspects of the ilium and joint, but this approach is rarely done.

For the posterior approach, there are two alternatives for patient positioning, both with strong proponents. The traditional position for the Kocher-Langenbach approach has been prone with flexed knee traction. Proponents of this tactic cite a better access to the sciatic notch and a better ability to work through the notch for the "felt but not seen" portion of the pelvis. Also, the fact that the weight of the leg is not a force vector into the acetabulum medially or posteriorly (e.g., the femoral head is not opposing the reduction) is cited as an advantage. Placement of an anterior column screw or a sacroiliac screw is also permissible with prone positioning. However, access to more anterior structures is significantly limited as is the ability to perform an extended trochanteric osteotomy. Proponents of the lateral position cite ease of set up and access to the anterior structures. Those who are comfortable with a floppy lateral may also propose that it allows for simultaneous posterior and anterior approaches. A detriment to this tactic is the need for an extra assistant to neutralize the weight of the femoral head into the acetabulum. One of us (B.Z.) feels that the lateral position, when used with fixed (but adjustable) traction, provides the best of both methods. The perineal post and longitudinal femoral traction both neutralize the weight of the femur, and allow for subluxation of the joint. Note that the Jackson apparatus has an attachable arc that allows for traction and extension of the hip and a leg holder to allow flexion of the knee. These tactics allow for relaxation of the sciatic nerve (Fig. 2). Alternatively, others (D.S.) utilize a five to six-inch stack of folded towels placed deep into the groin between the legs. Gentle downward pressure at the flexed knee reduces the weight of the femoral head on the acetabulum. The stack of towels combined with longitudinal and lateral traction via the trochanteric Schantz pin results in very good joint exposure for many posterior fractures (Fig. 3). The lateral position also allows "neutralization" of the weight of the gluteal musculature and does not require an assistant for retraction. While proponents of the prone approach state that access to the notch and inner pelvis is difficult with the lateral approach, we have not found this to be the case. Also, if the need for an extended trochanteric flip osteotomy is needed, it can be done easily, and the spectrum of treatable fractures with this tactic is extended. Finally, if needed, the traction can easily be relaxed to allow minor positional changes.

We are not proponents of simultaneous front and back approaches because there is a distinct loss of visualization and access when the patient cannot be fully supine and fixed traction cannot be used (thus losing a major advantage of each approach). So, if front and back access is needed, we recommend sequential (do one, close, and flip over), and not simultaneous approaches. While these issues have been covered elsewhere, we believe it is salient to the discussions in this chapter and the next chapter,

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Figure 2 (A) The flat top Jackson table with longitudinal traction and perineal post. The perineal post can move vertically and thus provide a "lateral" vector to overcome the weight of the leg. Setup shown without patient. (Continued)
Leg Traction Setup

Figure 2 (Continued) (B and C) The patient in lateral position with longitudinal traction via femoral traction. The perineal post is set under the femur and padded in the perineum to counter the longitudinal force of the femoral traction, as well as provide a vertical lift. It can actually distract the joint laterally and lift the patient. For this reason, the patient has to be bound down to the table via taping and strapping.

Figure 3 The patient in the lateral position with no fixed traction. A stack of towels tucked under the thigh acts as a fulcrum to assist with hip subluxation. Longitudinal traction is provided manually via the Schanz pin placed into the femur at the level of the trochanters. The extremity and hip are free for repositioning as needed.

Figure 3 The patient in the lateral position with no fixed traction. A stack of towels tucked under the thigh acts as a fulcrum to assist with hip subluxation. Longitudinal traction is provided manually via the Schanz pin placed into the femur at the level of the trochanters. The extremity and hip are free for repositioning as needed.

and have included our personal views to facilitate discussion. As in many fractures, there are very strong opinions on indications, approach, and tactic, and the reader is referred to the literature for a more comprehensive view for each school of thought.

ANTERIOR WALL ACETABULAR FRACTURES

Isolated anterior wall fractures are relatively rare, and these fractures are usually a part of a more complex pattern. Normally, the ilioinguinal approach will be used to operate on anterior wall fractures with the patient in supine position on a radiolucent table. Unlike the posterior wall, access and fixation of the anterior wall may be a bit more difficult. In 2002, Kloen et al. reported their favorable experience in treating 15 patients with a modified ilioinguinal approach, which was combined with a Smith-Petersen anterior approach. An anterior superior iliac spine (ASIS) osteotomy is a component of this modified approach, and it greatly enhances access to the anterior wall (Fig. 4). In some cases of femoral head lesions with anterior or superior wall lesions, this approach can be very useful (Fig. 5).

Figure 4 Schematic illustration of modified anterior approach for treatment of anterior wall fractures. Note anterior superior iliac spine osteotomy and release of rectus femoris insertion.

Figure 5 Use of an anterior approach for a superior wall fracture with femoral head fracture. Exposure of the external aspect of the iliac wing provides additional access to the superior anterior wall. (A, B) Radiograph and axial CT scan of the lesion. (C) Demonstrates repair of head and use of buttress plate using distal radial T plate to distribute force on small wall fragment.

Figure 5 Use of an anterior approach for a superior wall fracture with femoral head fracture. Exposure of the external aspect of the iliac wing provides additional access to the superior anterior wall. (A, B) Radiograph and axial CT scan of the lesion. (C) Demonstrates repair of head and use of buttress plate using distal radial T plate to distribute force on small wall fragment.

If the wall is comminuted or with impaction, smaller implants (hand and foot) may be necessary for stabilization. In cases where the wall involves a portion of the quadrilateral surface there is more bone to consider, and adjunct screws along the corner of the brim or plates can be used. Use of a ball-spike pusher and clamps will generally be enough to reduce and hold the fragment. Kirschner wires can then be placed for provisional fixation, which permits removal of the clamps and facilitates plate positioning. A standard curved plate placed along the pelvic brim will frequently be enough to hold the wall in place. Similar to the posterior wall, the plate provides a buttressing effect. Screws are placed at the ends of the plate, and the mid-portion of the plate is the buttress with unused screw holes. Unlike the posterior wall, fixation directly into the wall fragment is problematic. Usually, screws have to be angled into the pelvis and catch the corner of the pelvic brim. These screws actually course behind the articular surface of the acetabulum. In the area of the pectineal eminence, usually only a short screw (approximately 12-18 mm long) can be placed to avoid entering the joint (Fig. 6). After fixation, the reduction can be checked using an image intensifier, which additionally confirms that screws are clear of the joint. The provisional Kirschner wires (K-wires) can give invaluable clues as to the safe position and direction of screws. When checking the reduction on fluoroscopy and prior to definitive fixation, use the K-wires as references to identify safe zones for hardware placement.

ANTERIOR COLUMN ACETABULAR FRACTURES

The anterior column is more common than the anterior wall and will frequently be accompanied by an incomplete hemitransverse component. Some anterior column fractures can be rather extensive and comminuted and can be as challenging as more complex associated patterns. In general, the approach will be some anterior exposure, followed by systematic reduction and fixation. With more extensive patterns, the fixation usually progresses from posterior (intact component) to anterior (fracture component). For the crest, both large and small tenaculums can be used to effect a reduction of the crest. Kirchner wires can then provide provisional fixation that permits clamp removal and plate or screw placement. If needed, the exposure can be extended over the ASIS to allow placement and use of the Farabeuf clamp, which can help control rotation of the wing. The ball spike pusher is a very effective reduction tool but care is necessary to prevent iatrogenic fracture propagation in thin areas (Fig. 7). Once reduced, 3.5 mm reconstruction plates or judiciously placed screws will suffice to provide stabilization.

The low anterior column fractures will frequently have a portion of the quadrilateral surface attached. In these cases, it is important to recognize if there is any instability from the central component of this fracture, especially in osteoporotic bone. If so, fixation of the anterior column alone may leave the central portions unstable, and can potentially allow a protrusion of the femoral head. In these cases, a standard plate can be placed along the pelvic brim, but attention to the quadrilateral surface is needed. While standard spring plates can be used, they can be difficult to contour and, due to the thin plate profile, may be overcome by the high forces in the hip. We have used an alternate method of fixation that has the plate along the quadrilateral surface in the inner portion of the brim. The plates and screws are oriented about 90° to normal. In

Figure 6 (A, B) Anterior wall fracture radiograph and axial CT scan. (C) The buttress plate spans the fracture, but also uses screws directed behind the joint (gray arrow) into the quadrilateral surface bone outside of the joint.
Figure 7 (A, B) Various retractors and equipment useful during surgery of the acetabulum. (C) Illustration on a sawbone model showing the various clamps and assistive devices that can be used to help effect a reduction.

order to accomplish this, we have used the subinguinal window for visualization and access. We began using this modification in the late 1990s and it was described formally by others. The approach involves the surgeon moving to the opposite side of the table and working through the medial window of the ilioinguinal approach but under the vessel and muscle sheath. Once the bladder is moved, there is direct access to the quadrilateral surface, posterior column, and anterior ramus (Figs. 8 and 9).

For middle and high anterior column fractures, the options are more plentiful. In these fracture patterns, where the required access is high on the ilium, the iliofemoral approach may be considered. We typically prep and drape for a full ilioinguinal approach, though the lateral window is often all that is needed. Working in the lateral window can be very tight quarters, and determining the best direction for screws that are safely out of the joint and in an ideal orientation for secure fixation can be challenging. One can place a finger along the inner iliac table to get proprioceptive feedback during drilling and screw placement. Slowly advance the drill, and leave your fingers of one hand on the inside of the anterior column for feedback on the exit point of the drill. Redirect the drill as necessary to get a screw through the best bone. The use of the obturator-outlet view can also provide an end-on view of the screw pathway between the iliac tables, which will identify the axis for screw placement. Once reduced, a long screw across the anterior column fracture heading towards the sacroiliac joint and above the sciatic notch is usually sufficient for fixation (the so called LCII screw) (Fig. 10). Plating along the superior ramus can be achieved by developing the medial window of the ilioinguinal approach. An alternate method would be to use percutaneous methods, described elsewhere in this book. Keep in mind that the fracture hematoma becomes more mature daily and delayed operative treatment results in a more challenging closed reduction and percutaneous fixation. For the purposes of this chapter, we discuss open fixation techniques.

With all such fractures, the reduction should be verified in two locations: the crest (if the fracture exits the crest in high fractures) and the articular surface (which is the essential element). Methods to effect a reduction include use of tenaculums, pelvic clamps, and direct pressure from a ball spike pusher. With the hip flexed and the iliopsoas muscles relaxed, placement of the longer limb of an offset clamp low on the anterior column or on the medial wall is achievable. The shorter limb of the offset clamp can be placed on the outer table after lateral release of the fascia on the iliac crest (Fig. 11). Occasionally there will be marginally impacted segments or small articular osteocartilagenous fragments. In these cases, the fracture can be "booked" open to gain access to the joint. In cases where there is an extended plate of quadrilateral surface involved, a more invasive approach with an ilioinguinal is needed. Care should be taken when reduction is difficult, so that forceful maneuvers with a pelvic clamp on the quadrilateral surface do not create a fracture, thus destabilizing the area even further. The spiked washer can be used to distribute forces and minimize the risk of fracture comminution. This is where a Schantz pin in the lesser trochanter, with a laterally directed pull, helps to reduce the "protrusio" significantly. Finally, high anterior column fractures that exit the iliac wing require stabilization. Plates along the inner table or individual screws along the iliac crest are advisable. A plate along the iliac crest may utilize longer screws through a plate and achieve

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Figure 8 (A) Iliac oblique and (B) AP view of anterior wall and column involvement of a transverse fracture. The anterior wall component was the predominant characteristic with a protrused quadrilateral surface. It was treated with a retrograde ramus screw and a quadrilateral plate. The plate buttresses the quadrilateral surface directly with excellent inside out screw placement.

Figure 8 (A) Iliac oblique and (B) AP view of anterior wall and column involvement of a transverse fracture. The anterior wall component was the predominant characteristic with a protrused quadrilateral surface. It was treated with a retrograde ramus screw and a quadrilateral plate. The plate buttresses the quadrilateral surface directly with excellent inside out screw placement.

Figure 9 (A) Low anterior column fracture with quadrilateral surface involvement. (B) The "inside-out" screw with a small plate is used to prevent protrusion. (C) Demonstrates clamp placement if necessary.
Figure 10 (A) High anterior column fracture with rotation. (B) highlights the pathway of the screw seen in (E) placed between the inner and outer iliac tables (arrows). (Continued)

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