CHAPTER SYNOPSIS
The specialized problems associated with a total hip arthroplasty after an acetabular fracture are characterized by the initial conservative or operative treatment. In general, poorer clinical results follow arthroplasties performed after initial operative management, especially when an extensile surgical approach is used. The technical problems associated with arthroplastic replacement are categorized by the timing of the procedure: within less than 3 weeks after the acute injury, between 3 and 12 weeks, or at a later period. This chapter presents the operative planning, surgical techniques, clinical results, and complications.
IMPORTANT POINTS
- 1
Overall, a total hip replacement after an acetabular fracture managed acutely with an open reduction presents more surgical complexities and a poorer prognosis than one initially managed conservatively.
- 2
After an acetabular fracture, a total hip arthroplasty may be performed within 3 weeks, between 3 and 12 weeks, or later. Each period presents unique technical considerations.
- 3
The surgical strategy must account for special problems, including retained hardware, heterotopic bone, fracture defects, and pelvic deformity.
- 4
The surgical technique includes an understanding of acute internal fixation of acetabular fractures and revision arthroplasty.
- 5
Femoral preparation and stem selection are similar to a conventional total hip arthroplasty.
CLINICAL/SURGICAL PEARLS
- 1
For a conventional total hip arthroplasty after an acetabular fracture with minimal acetabular deformity, heterotopic bone, and retained hardware, a conventional surgical approach suffices.
- 2
When extensive posterior column hardware is documented, a two-incision anterior approach with hardware retention minimizes risk of injury to the sciatic nerve. Isolated partial screw removal may be needed.
- 3
To manage an acetabular defect, the established revision arthroplasty techniques are used, including impaction bone graft, as well as special hardware including rings, cages, and augment blocks.
CLINICAL/SURGICAL PITFALLS
- 1
Hardware removal through a posterior approach provides a particular risk for injury of the sciatic nerve. Consider an anterior approach and retention of hardware or limited anterior screw removal.
- 2
When extensive heterotopic bone removal is needed as part of the arthroplasty, a more extended surgical approach may be required. An occult infection may be masked within the hip joint.
- 3
For an acute acetabular fracture with marked comminution and osteopenia, a total hip arthroplasty is deferred until union of the fracture and an unfavorable clinical picture have been confirmed.
INTRODUCTION
Regardless of the initial method of treatment, a patient who sustains an acetabular fracture may develop features of a poor clinical outcome, including the onset of incapacitating hip pain caused by posttraumatic arthrosis or avascular necrosis of the hip. Subsequently, the principal therapeutic option is a total hip arthroplasty (THA). Arthrodesis of the hip may be feasible in selected cases, but such a fusion can be exceedingly challenging in the presence of displaced, osteopenic, or avascular bone. In the United States, even when such a procedure is a viable option, many patients are reluctant to consider it. THA after an acetabular fracture has been recognized for many years as a potentially difficult procedure. In the presence of an acetabular fracture with little displacement and limited extraarticular hardware, an uncomplicated THA generally can be performed with diverse surgical approaches in a way similar to a procedure performed for degenerative arthritis. Whether or not initial nonoperative or operative treatment was used to manage an acute and highly displaced acetabular fracture, formidable problems such as a nonunion, a bone defect, the presence of interposed hardware, and heterotopic bone may complicate the arthroplasty. One question is whether such a secondary arthroplasty would be technically easier to perform and potentially more durable if an open reduction of a displaced acetabular fracture initially was undertaken. Letournel and Judet argued that an open reduction and internal fixation (ORIF) provided the optimal potential for a favorable clinical outcome and the best potential for late arthroplastic reconstruction if posttraumatic arthrosis or avascular necrosis ensued. These authors suggested that an unreduced acetabular fracture that followed a nonoperative course of treatment was vulnerable to the presence of a nonunion, the presence of a large acetabular defect, or a pelvic malunion. Any of these late problems could jeopardize the outlook for a secondary THA.
More recent studies have evaluated the techniques for THA after an acetabular fracture initially managed by a nonoperative or operative course. Various reconstructive strategies have been assessed in an attempt to devise improvements in the surgical protocol. A secondary objective has been to determine whether an initial nonoperative or operative course of management for an acute acetabular fracture provides a superior environment for a secondary THA in terms of technical ease and reproducibility of a favorable and durable clinical outcome. Such an evaluation was intended to address the second contention of Letournel and Judet that an initial operative treatment of an acetabular fracture provided the optimal environment for a successful late reconstruction. An additional question pertains to the presence of an acute acetabular fracture, which might possess identifiable complicating features that virtually ensure an abysmal outcome regardless of whether nonoperative treatment or an open reduction was performed. In this situation the potential therapeutic options might include a method of an acute THA. This chapter evaluates the indications for a THA after an acetabular fracture, the timing of the procedure, and the technical considerations along with the appropriate clinical protocol and potential complications.
TIMING FOR TOTAL HIP ARTHROPLASTY AFTER ACETABULAR FRACTURE
Mears and Velyvis have previously identified three distinct time periods after an acute acetabular fracture when a total hip replacement merits consideration: acutely within 3 weeks of the injury, between 3 weeks and 3 months, and at 3 months or later.
Three Months or More after Injury
By 3 months after the procedure the fracture typically has united, with or without a residual deformity. The principal indications for the procedure are posttraumatic arthritis and avascular necrosis. Associated considerations include the presence of an acetabular nonunion and/or a potential acetabular deformity, which occasionally is accompanied by a deformity of the ipsilateral or contralateral pelvic ring. If an ORIF of the acetabulum is performed acutely, supplementary problems may include the presence of interposed hardware, heterotopic bone, dense scar tissue, frank or occult infection, a sciatic nerve palsy, or entrapment of the sciatic nerve in scar tissue or heterotopic bone. Special preoperative diagnostic tests may be indicated in an attempt to identify and characterize these problematic factors.
Between 3 and 12 Weeks after Injury
In some instances, after an apparently uneventful acute presentation and course of management, some complicating factor arises or becomes clinically or radiographically apparent. After an initial conservative treatment, the fracture may undergo a belated displacement, which secondarily provokes a mechanical erosion of the femoral head. Susceptible fracture patterns include transverse, T-type, and posterior fracture dislocations. After an acute ORIF, failure to achieve an accurate reduction or a loss of fixation with a secondary displacement may culminate in a precipitous onset of erosive damage to the femoral head. Once incapacitating pain is accompanied by radiographic features of extensive erosion of the femoral head and an incongruent hip joint, the likelihood for a successful clinical outcome becomes a remote possibility. A THA merits consideration as the principal realistic way for the patient to achieve relief of pain and a functional clinical outcome.
Less than 3 Weeks after Injury
The most controversial situation is an acute presentation of an acetabular fracture that possesses an intrinsically abysmal outcome. Provocative factors include marked impaction or erosion of the femoral head and/or acetabulum, an associated displaced subcapital femoral neck fracture and, occasionally, extensive comminution. For an elderly, osteoporotic woman who sustains a posterior wall fracture, extensive impaction of the femoral head and the acetabulum is likely to culminate in a rapid destruction of the hip joint. In contrast, for a young, active adult with a potentially long life expectancy, somewhat greater effort may be indicated in an attempt to defer THA. In some situations, however, the extensive damage and deformity of the hip preclude the realization of a painless and functional hip joint after closed or operative management unless a THA is undertaken. In the presence of the isolated posterior wall fracture, the technical difficulty associated with an acute THA is not materially greater than that for a conventional primary procedure performed for degenerative arthritis. In contrast, for a highly comminuted acetabular fracture with marked displacement, bony impaction, and the presence of osteopenic bone in which an acute open reduction has a poor prognosis, an acute THA may not be a realistic procedure to achieve a stable cup in the disrupted acetabulum. If the likely outcome after an acute ORIF is extremely poor, an initial course of conservative treatment merits consideration. Although some residual acetabular deformity may ensue, the technical difficulty of a THA generally is not materially altered by such a deformity. Admittedly, a marked deformity may pose a considerable technical challenge, although that is an unusual presentation ( Fig. 18-1 ). Although Letournel and Judet and others recommended that an acute ORIF be performed, even when the prognosis for the procedure was predictably poor, a more recent appraisal of this situation has favored an initially conservative approach with a late THA after a bony union has ensued. Inevitably, the acute ORIF is accompanied by some degree of scar tissue formation, muscular injury, potentially heterotopic bone formation and, conceivably, infection (see Fig. 18-1 ). A more extensive initial surgical exposure amplifies the potential for these complications, all of which may hamper the completion of a subsequent THA and further jeopardize the late clinical outcome.
CLINICAL AND RADIOGRAPHIC ASSESSMENT
An acetabular fracture may follow a major traumatic event, such as a motor vehicular accident, a fall from a height, or an industrial mishap. At present, in the rapidly expanding elderly population, the majority of acetabular fractures follow minor trauma, such as a fall from a standing position, in which moderately or markedly osteopenic bone is a major contributor to the injury. In the presence of osteopenic bone, the injury is vulnerable to a marked impaction of the femoral head or the acetabulum, and thereby a poor prognosis regardless of whether an open reduction is performed. A history of symptomatic degenerative or inflammatory arthritis of the hip or avascular necrosis occasionally is documented as another indicator of a compromised prognosis after the acute acetabular fracture management. After a major traumatic event, a patient is vulnerable to complicating features such as a sciatic nerve palsy. Even if a minor degree of posttraumatic neurologic deficit is documented, at the time of an open reduction or belated THA, the patient is vulnerable to an exacerbation of the nerve deficit, which may become a permanent source of dysesthesia, motor weakness, or sensory impairment. These complications are most likely to arise in the susceptible patient who undergoes a posterior approach to the hip and acetabulum in which the sciatic nerve is manipulated even to a minor degree. This concern influences the preoperative planning for a THA, including the optimal surgical approach.
For the preoperative planning of a THA after a prior acetabular fracture, other relevant features of the history include an evaluation for drug and alcohol abuse and the nature of vocational activities or hobbies that may provide a high likelihood for falls, major accidents, heavy lifting, or other abuse of the hip. For an elderly individual, the presence of posturing of the hip, marked weakness of the hip abductor muscles, or a comorbidity that culminates in recurring falls merit consideration as contraindications to an acute arthroplasty.
In addition to a general evaluation of the patient, the clinical examination includes an examination of the relevant hip and the pelvis for features of deformity and traumatic or surgical scars. A potential hip deformity or limb-length discrepancy is documented along with the range of motion of the hip. The examination attempts to identify any clinical features of a sciatic or femoral nerve palsy, even of a subtle degree. If a previous open reduction was performed, the hip is evaluated for features of possible occult infection and heterotopic bone.
A radiographic evaluation of the hip and pelvis includes the standard anteroposterior, iliac, and obturator oblique views along with a computed tomographic (CT) scan ( Figs. 18-2 and 18-3 ). The images are carefully assessed for the presence of impaction that is optimally visualized in sagittal and coronal reconstructions. On the standard CT transaxial images, even a large area of impaction involving 30% of the femoral head or the acetabular dome may be difficult to appreciate. In an osteoporotic individual who sustains a fracture after a simple fall, despite minimal preoperative radiographic evidence an extraordinarily large area of impaction or abrasive damage to the joint may be encountered at the open reduction ( Fig. 18-4 ). A three-dimensional CT with supplementary disarticulated images of the acetabulum and the femoral head (see Fig. 18-4 ) provides the optimal means to accurately characterize a complex deformity of the hemipelvis and potentially the entire pelvic ring where it is involved in the deformity.
If a prior open reduction of an acetabular fracture was performed, the hardware, possibly including trochanteric screws, is studied for its location in the anteroposterior and the oblique radiographs (see Fig. 18-3 ). An obturator oblique view highlights the position of an anterior column screw, which may interfere with the reaming of the acetabulum and insertion of the cup. The iliac oblique view indicates the position of hardware attached to the posterior column and wall. The images are assessed for features of a residual acetabular or pelvic ring deformity, including the magnitude and vector of the displacement. Subsequently, a postoperative evaluation of comparable post-THA images and a comparison with the preoperative images enable the surgeon to assess the adequacy of the preoperative plan (see Figs. 18-2 and 18-3 ).
PREOPERATIVE PLANNING AND FORMATION OF A SURGICAL STRATEGY
The degree of appropriate preoperative planning correlates with the nature of the complicating features of the injury and the type of initial management. On the one hand, a THA for posttraumatic degenerative arthritis or avascular necrosis in which the initial fracture possessed minimal displacement and received conservative management may be identical to a standard THA. In this situation, the prior operative experience of the surgeon will dictate the type of surgical exposure, bony preparation, and the types of cementless or hybrid implants used. The presence of one or more complicating features may favor a modification of the surgical procedure in diverse ways.
Prior Posterior Surgical Approach and/or Sciatic Nerve Palsy
To minimize the risk of iatrogenic sciatic nerve palsy or a recurrence of neurologic deficit, a THA is optimally performed by an anterolateral or anterior approach. In this way a manipulation of the sciatic nerve or a dissection of the nerve from adjacent scar tissue is avoided. If a posterior or a posterolateral approach is required, possibly to remove an errant intraarticular screw, the use of intraoperative neurologic monitoring with continuous electromyelographic monitoring, nerve conduction velocities, and somatosensory evoked potentials is recommended. In this way a potentially deleterious manipulation of the nerve may be avoided by early detection.
Presence of Periacetabular Hardware
The hardware may have followed a standard posterior (i.e., Kocher-Langenbeck) approach, an ilioinguinal approach, or an extended lateral (i.e., extended iliofemoral or a triradiate ) exposure. The initial exposure dictates the sites and orientations of fixation screws and considerations for screw removal. The preoperative obturator and iliac oblique radiographs permit a general assessment of the regions of the screws and the likelihood for a screw to occupy a site needed for the acetabular cup (see Fig. 18-4 ). An errant screw may be managed in one of several ways. If the screw head is readily exposed, especially by the incision used for the arthroplasty, the screw may be removed. A screw occasionally may be removed by a limited percutaneous approach along with the use of intraoperative fluoroscopy. If the screw was inserted by an ilioinguinal approach or an alternative exposure, direct visualization of the screw head may be impractical unless a large dissection is performed. As an alternative strategy, the segment of the screw that traverses the region of the acetabulum to be occupied by the cup can be removed within the acetabular recess under direct exposure with a diamond burr or wheel.
A fixation plate previously inserted to buttress the posterior wall may impinge on the femoral head. This situation may arise as the result of an errant placement of the plate or in the aftermath of an erosive or avascularity loss of the articular portion of the wall. To address the situation, either the plate can be removed by a direct exposure of the posterior column or the exposed undersurface of the plate can be covered by resort to an impaction grafting technique within the acetabulum. After a debridement of membrane and scar tissue within the acetabulum, morselized cancellous allograft is placed in the acetabular recess to cover the exposed hardware. Then reverse reaming is performed to pack the graft material before insertion of the cup.
Displacement of Acetabular Wall
In the presence or absence of internal fixation, a portion of the acetabular wall may be displaced by a few millimeters or more. After a cup is inserted, the acetabular deformity compromises the anticipated bony support of the implant. As part of the THA, the wall fragment can be reduced through an open exposure (see Fig. 18-4 ). In the late setting the reduction is hampered by the presence of proliferative scar tissue. Unlike an acute open reduction of a displaced wall fragment, the late reduction may denude the bone, eliminate its blood supply, and predispose to avascular necrosis. As an alternative strategy, an impaction grafting of the acetabular recess may be preferred. In this scenario the fracture lines at sites of displacement are debrided. Morselized cancellous allograft is placed into the acetabulum for impaction and thereby the restoration of a hemispherical recess suitable for a cup (see Fig. 18-4, A ).
Displacement of an Acetabular Column or Transverse Fracture
An anterior or posterior column may be displaced by various degrees as a linear, rotational, or combined deformity. The magnitude of the deformity may vary from small (less than 1 cm) to medium (1 to 2 cm) to large (more than 2 cm). To address a small deformity, a large cup can be used or impaction bone grafting can be undertaken ( Fig. 18-5 ). For a medium to large deformity, a partial or complete correction of the deformed column or transverse fracture merits consideration ( Fig. 18-6 ). As the magnitude of the deformity increases, the surgical procedure becomes progressively more involved. The wall segment typically is scarified, possibly with callous formation. To mobilize the fragment, a sufficient release of the scar and callous is needed so that a correction of the deformity is feasible. In general, the fragment does not precisely fit in the site of the defect, so stabilization of the bone with screws, plates, or screws anchored to the cup is impaired (see Fig. 18-4, B ).
Multicolumn Deformity
After a column fracture and other associated injury patterns, a complex displacement of multiple acetabular segments may ensue in which the segments can be directly united, indirectly united with callus, or ununited. If a limited displacement of the segments (less than 1 cm) is documented, the application of a jumbo cup or impaction bone grafting may suffice. In the presence of a large displacement (more than 2 cm) as part of the THA, a correction of the deformity is necessary. Although the acetabular reconstruction could be undertaken as a preliminary procedure before the THA, the completion of both stages under a single anesthetic is preferred to take full advantage of the extensive surgical exposure. When the stages are separated, scar tissue and potential heterotopic bone formation after the first procedure hamper the second exposure and increase the risk for an iatrogenic neurovascular injury.
Heterotopic Bone Formation
After an acetabular fracture, heterotopic bone (HO) may spontaneously form. Most instances follow a subsequent ORIF of the fracture. Well-recognized predisposing factors include a concomitant closed-head injury and obese, middle-aged, male patients. The extent of HO formation varies widely, from limited areas of capsule or hip muscle to a circumferential mass of bone that completely surrounds the hip joint. The potential functional implications include stiffness of the hip and pain. The HO may arise in an otherwise functional hip joint or one with varying degrees of posttraumatic arthritis. In terms of management, this distinction is crucial. If the hip joint with symptomatic HO is substantially arthritic, then an effective attempt to remove the HO necessitates a THA. When a THA is planned, the surgical strategy involves a plan to expose and remove the HO. From the preoperative radiographs and CT images, the extent and location of the HO is identified (see Fig. 18-1, C ). A suitable surgical approach is identified. Intraoperative fluoroscopy merits consideration so that the HO can be radiographically distinguished from the intact acetabular and proximal femoral bone. When the HO infiltrates the adjacent hip muscles, the principal muscle mass is preserved. The ossified hip capsule typically is a discrete layer, so the more peripheral muscles can be distinguished. In a patient with Brooker grade 3 or 4 HO, despite an extensive resection the restoration of effective motion of the hip may be limited by the combination of scarring and stiffness of the adjacent muscles and the recurrence of HO within the hip ( Fig. 18-7 ).
Related posts:
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Total Hip Arthroplasty in Developmental Dysplasia of the Hip
Proximal Femur Fracture: The Challenging Primary Total Hip Arthroplasty
The Minimally Invasive Total Hip Arthroplasty with Two Incisions
Component Removal: Tricks of the Trade
Impaction Grafting of the Femur
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