12 Current Management of Posterior Wall Fractures of the Acetabulum Berton R. Moed, MD Philip J. Kregor, MD Mark C. Reilly, MD Michael D. Stover, MD Mark S. Vrahas, MD Abstract regardless of the treatment, the results The general goals for treating an acetabular fracture are to restore congruity and stability after a hip injury would be poor if there of the hip joint. These goals are no different from those for the subset of fractures of the was residual joint instability or incon- posterior wall. Nevertheless, posterior wall fractures present unique problems compared gruity between the femoral head and with other types of acetabular fractures. Successful treatment of these fractures depends on the weight-bearing area of the acetab- a multitude of factors. The physician must understand their distinctive radiologic features, ulum.1-4 In subsequent decades, evalu- in conjunction with patient factors, to determine the appropriate treatment. By knowing ation and treatment protocols, which the important points of posterior surgical approaches to the hip, particularly the posterior are still considered optimal, were de- wall, specifi c techniques can be used for fracture reduction and fi xation in these often veloped and refi ned by Letournel and challenging fractures. In addition, it is important to develop a complete grasp of potential Judet5 and published in their defi nitive complications and their treatment. The evaluation and treatment protocols initially devel- 1993 text. New information and emerg- oped by Letournel and Judet continue to be important; however, the surgeon also should ing trends have appeared in other book be aware of new information published and presented in the past decade. and journal articles, including Instruc- Instr Course Lect 2015;64:139–159. tional Course Lectures.6,7 However, these publications have focused primarily on An acetabular fracture routinely re- confl icting recommendations for both the entire spectrum of acetabular frac- quires surgical intervention. The liter- nonsurgical and surgical treatment reg- tures, with limited discussion of poste- ature from the 1950s and 1960s offered imens.1,2 It was agreed, however, that rior wall fracture treatment. Posterior wall fractures are the most common type, accounting for approximately 25% Dr. Moed or an immediate family member has received royalties from Biomet and serves as a board member, owner, offi cer, or committee member of AO North America and the AO Foundation. Dr. Kregor or an immediate family member is a of all acetabular fractures, and are often member of a speakers’ bureau or has made paid presentations on behalf of Medtronic. Dr. Reilly or an immediate family treated at community medical facilities.5 member is a member of a speakers’ bureau or has made paid presentations on behalf of Stryker. Dr. Vrahas or an immediate With these facts in mind, it is import- family member serves as a board member, owner, offi cer, or committee member of the AO Foundation. Neither Dr. Stover nor any immediate family member has received anything of value from or has stock or stock options held in a commercial ant to refocus on this common—but company or institution related directly or indirectly to the subject of this chapter. potentially debilitating—injury by © 2015 AAOS Instructional Course Lectures, Volume 64 139 Trauma Figure 3 Schematic diagram showing the posterior border of the innominate bone (1) and anterior Figure 1 Schematic diagram rim of the acetabulum (2) as seen showing the six acetabular land- Figure 2 Schematic diagram on an iliac oblique radiograph. The marks seen on an AP radiograph: showing the iliopectineal line (1) iliac wing is seen en face. The ante- (1) iliopectineal line, (2) ilioischial and the posterior rim (2) as seen rior rim of the acetabulum can best line, (3) U or teardrop, (4) roof, (5) on an obturator oblique radiograph. be seen with this view. The proper anterior rim, and (6) posterior rim. The obturator ring is seen en face. amount of rotation for the iliac (Reproduced from Templeman D, The proper amount of rotation for oblique view (inset) is present when Olson S, Moed BR, Duwelius P, the obturator oblique view (inset) is the tip of the coccyx lies just above Matta JM: Surgical treatment of present when the tip of the coccyx the center of the contralateral femo- acetabular fractures. Instr Course lies just above the center of the ral head. (Adapted from Templeman Lect 1999;48:481-496.) ipsilateral femoral head. (Adapted D, Olson S, Moed BR, Duwelius from Templeman D, Olson S, Moed P, Matta JM: Surgical treatment of acetabular fractures. Instr Course reviewing the unique fracture radiolo- BR, Duwelius P, Matta JM: Surgical treatment of acetabular fractures. Lect 1999;48:481-496.) gy, surgical indications and techniques, Instr Course Lect 1999;48:481- pitfalls, and complications of posterior 496.) wall fractures. classifi cation of posterior wall frac- Radiology of the Acetabulum tures, as with all acetabulum fractures, and Posterior Wall continues to be determined primarily Fracture Classification by analyzing the aforementioned plain The plane of the ilium is approximately radiographic projections and two- 90° to the plane of the obturator fora- dimensional CT scans (Figures 1, 2, men, and both structures are oriented 3, and 4). approximately 45° to the frontal plane. On the AP view, the rim of the pos- On this basis, Judet et al8 proposed that terior wall approximates a straight line the AP view and two 45° oblique views and is more vertical than the anterior of the pelvis can be used to study the wall (Figure 5). Any break or defi cit in radiographic anatomy of the acetabu- this line indicates fracture or displace- Figure 4 Axial CT scan showing lum. Thus, the fi rst systematic classi- ment of the posterior rim of the ace- a section through the acetabulum in which the posterior wall is frac- fi cation of acetabular fractures based tabulum. The signs of hip dislocation tured (black arrows) with marginal on the anatomic pattern was derived, on the AP view include a break in the impaction (white arrowhead). An which later incorporated the analysis of Shenton line, proximal migration of the intra-articular loose body appears between the femoral head and the 5 two-dimensional CT scans. Although lesser trochanter, relatively smaller size acetabulum (white arrow). (Copy- three-dimensional CT technology of the affected femoral head (closest to right Berton R. Moed, MD, St. has progressed, the diagnosis and the the x-ray cassette), and a bony double Louis, MO.) 140 © 2015 AAOS Instructional Course Lectures, Volume 64 Current Management of Posterior Wall Fractures of the Acetabulum Chapter 12 Table 1 Additional Information Provided by a CT Scan Intra-articular bony fragments Intra-articular osteochondral fragments Size of the posterior wall fracture Location of the posterior wall fracture Number of posterior wall fragments Figure 5 AP radiograph showing Rotation of the fracture fragments a dislocated right hip and a poste- Figure 6 Two-dimensional CT Marginal impaction of the articular rior wall fracture. (Copyright Berton section of the hip of the patient surface R. Moed, MD, St. Louis, MO.) in Figure 5. (Copyright Berton R. Moed, MD, St. Louis, MO.) Fractures of the femoral head density above the femoral head. The Table 2 double density (Figure 5) is the poste- Letournel and Judet Classifi cation of Acetabular Fractures rior wall fragment. It often sits atop the dislocated femoral head and can give Elementary Fracture Types Associated Fracture Types the appearance of normal joint space, Posterior wall Posterior column and posterior wall potentially resulting in a misdiagnosis. Posterior column Transverse and posterior wall The obturator oblique view is espe- Anterior wall T-shaped cially helpful in diagnosing a posterior Anterior column Anterior column and posterior hemitransverse wall fracture because it places the pos- Transverse Both-column terior wall almost perpendicular to the x-ray beam and minimizes overlay of the anterior wall (Figure 2, inset). A into a system consisting of 10 fracture fracture line (type 62-A1.3, the so-called dislocated hip will become more ob- types: 5 elementary types and 5 associ- marginal impaction; Figure 7). These vious on the obturator oblique view.9 ated (or combined) types5,8 (Table 2). subgroups are then further categorized The iliac oblique view does not provide The Orthopaedic Trauma Association (Table 3). additional information specifi c to the (OTA) comprehensive fracture classifi - A potential point of confusion in posterior wall—other than showing cation system uses a basic alphanumeric the OTA classifi cation is the use of the posterior border of the innominate coding of the acetabular fracture clas- “fracture-dislocation” in the subgroup bone (greater and lesser sciatic notch), sifi cation developed by Letournel and descriptions. It is well known that frac- which may be involved in an extended Judet and offers no clinical advantage. tures of the posterior wall can occur fracture. The CT scan provides addi- However, the OTA system is often used without any history of dislocation of tional information specifi c to posterior to allow computerized categorization the hip joint.11 Acetabular fractures en- wall fractures that is not readily appar- and subclassifi cation of the fracture compass a broad spectrum of injuries ent on plain radiographs (Table 1). types.10 The posterior wall fracture is that are artifi cially separated by the clas- The contiguous sections should have a codifi ed in the OTA system as type 62- sifi cation systems into specifi c types. slice thickness of no more than 3 mm A1 and is separated into three basic sub- As such, there are many transitional to provide satisfactory evaluation of the groups: fractures with a single posterior types. For example, the type originally posterior wall (Figures 4 and 6).