Simon C. Mears
Trauma to the hip can lead to long-term dysfunction from posttraumatic arthritis, osteonecrosis, malunion, and nonunion. End-stage arthritis may develop quickly after the injury or it may develop years later. In many patients, treatment involves removal of the current hardware and conversion to total hip arthroplasty. Osteoporosis, bone loss, and heterotopic bone formation complicate total hip arthroplasty. Hip salvage via other procedures such as refixation of the fracture, valgus osteotomy, or femoral head reshaping may be considered for patients with a viable femoral head.
Pathogenesis
Etiology
All hip fractures may lead to posttraumatic conditions (Table 6-1). Hip dislocations may damage the blood supply to the femoral head, leading to late osteonecrosis, a risk increased in direct proportion to the length of time the hip remains dislocated. Cartilage damage from the initial injury predisposes patients to later arthritis. Surgical treatment of acetabular fractures may lead to iatrogenic arthritis from intra-articular hardware or malreduction. Elderly patients are at risk for osteoporotic fracture patterns that are difficult to reduce and stabilize effectively.
Femoral neck fractures can lead to osteonecrosis of the femoral head, malunion, nonunion, and severe arthritis. In the older patient, these conditions are treated with hip replacement, whereas in the younger patient hip salvage may be possible. Hip salvage may be achieved by revision fixation, bone grafting, or femoral head reshaping. Intertrochanteric fractures typically are treated with a hip screw and side plate or an intramedullary hip screw. In the young patient, nonunion can occur, and revision internal fixation with bone grafting may be indicated. In the elderly patient, a nonunion or malunion is best treated with arthroplasty.
Epidemiology
Posttraumatic arthritis of the hip can result from trauma to the acetabulum or proximal femur. Acetabular fractures are thought to occur at a rate of 3 per 100,000 population per year. The rate of posttraumatic arthritis for all acetabular fractures is 20% to 30%. Posterior wall fractures represent about 25% of all fractures and are at high risk for late arthritis. The elderly patient and those with more comminuted fractures have worse results from initial reduction and fixation than younger patients with simple fracture patterns. Almost 10% of fractures have severe initial damage to the femoral head or acetabulum, which is best treated with acute arthroplasty.
Of the approximately 250,000 hip fractures that occur each year in the United States, approximately 40% involve the femoral neck. Femoral neck fractures are especially common in the elderly patient. Of those treated with open reduction and internal fixation, 15% develop osteonecrosis, 30% develop nonunion, and 20% to 35% require revision surgery. Intertrochanteric fractures also are common in the osteoporotic individual, and rates in elderly women are estimated at 63 per 100,000 population. Failure of fixation is related to fracture stability and the amount of comminution. In one study, 43% of fractures were classified as unstable and up to 50% of unstable intertrochanteric fractures may develop nonunion after internal fixation.
Pathophysiology
Damage to the cartilage of the femoral head and/or acetabulum resulting from an acetabular fracture or a hip dislocation can lead to arthritic changes in the hip. Cartilage damage occurs to the area of the joint next to the fracture and is termed marginal impaction. Impacted cartilage must be elevated and supported with bone graft during fixation. Postfracture damage to the femoral head also can occur secondary to nonconcentric reduction or intra-articular bodies while the patient awaits surgical fixation. Damage to 40% or more of the weight-bearing articular cartilage, the femoral head, or acetabular surface is an indication for acute total hip replacement.
Osteonecrosis of the femoral head occurs by disruption of the blood supply to the femoral head. Disruption can occur by traumatic dislocation of the femoral head, by traumatic injury from hip fracture displacement, from elevated
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intracapsular pressure, or by surgical injury to the blood supply. The lateral epiphyseal artery (the end branch of the medial circumflex artery), which supplies the femoral head, enters the femoral head through the obturator externus muscle on the posterior aspect of the femoral neck. The risk of femoral head osteonecrosis is directly proportional to both the length of time that a hip is dislocated and the amount of displacement of a femoral neck fracture. Increased pressure in the hip joint by bleeding from an intracapsular femoral neck fracture tamponades the blood supply to the femoral head and also may contribute to the development of osteonecrosis.
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TABLE 6-1 Conditions After HIP Trauma |
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Figure 6-1 Patient with malunion of the femoral neck after pinning of a slipped capital femoral epiphysis. A: Anteroposterior radiograph showing the development of severe arthritis from femoroacetabular impingement. B: An oblique view gives a “true” view of the femoral neck and osteophytes and is helpful for preoperative templating. |
The acetabulum is supplied by multiple arteries, including the superior and inferior gluteal, medial femoral circumflex, obturator, fourth lumbar, and iliolumbar arteries. Disruption of the entire blood supply requires stripping of the soft tissues from the inner and outer tables of the acetabulum. Avoidance of excessive stripping during extensile approaches is critical when stabilizing complex acetabular fractures.
Malunion can lead to several posttraumatic conditions, including posttraumatic arthritis, femoroacetabular impingement, and limb-length discrepancy. Malreduction of an acetabular fracture causes joint incongruity. Residual fracture step-off increases contact pressure in the hip and leads to cartilage wear, arthritis, and poor clinical outcomes. Malunion of a femoral neck or intertrochanteric fracture leads to shortening of the hip with resultant limb-length discrepancy and Trendelenburg gait. Shortening can occur when a fracture is treated with parallel screw or sliding hip screw fixation. Malunion of a femoral neck fracture results in an abnormal head/neck angle, with retroversion and varus deformity of the femoral neck. The abnormal neck/shaft angle causes the anterior aspect of the neck to impinge on the acetabulum and is termed femoroacetabular impingement. Impingement damages the superior anterior
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acetabular labrum and leads to osteophyte formation and arthritis through a cam mechanism (Fig. 6-1).
Femoral neck and intertrochanteric fracture nonunions are more common after unstable fractures. Factors related to the nonunion include the stability and comminution of the initial fracture and the quality of the reduction and fixation of the fracture. Technical problems of initial fixation such as malreduction and incorrect hardware selection or placement can lead to nonunion. The role of bone mineral density is controversial.
Classification
There are no classification systems specific to posttraumatic conditions of the hip. Osteoarthritis is graded radiographically by an evaluation of the minimal joint space or by the system of Kellgren and Lawrence. Osteonecrosis is graded according to the modified system of Ficat by its appearance on scans and plain radiographs ranging from grade 1 (a lesion seen only on magnetic resonance imaging) to grade 4 (severe degenerative joint disease on radiographs). Nonunions are graded as atrophic or hypertrophic. Individual fracture patterns can be classified using the Arbeitsgemeinschaft fur Osteosyntheses/Orthopaedic Trauma Association (AO/OTA) classification system, which numerically lists fractures by site and pattern. Acetabular fractures are classified using the system of Letournel and Judet into elementary and associated fracture patterns. Femoral neck fractures are classified as stable or unstable based on the amount of fracture displacement. Intertrochanteric fractures are classified as stable or unstable depending on the number of fracture fragments, the presence of an intact medial or lateral buttress, and the direction of the fracture. Many fracture classification systems lack interobserver and intraobserver reliability.
Diagnosis
Physical Examination and History
Clinical Features
It is important for the clinician to understand the specifics about the energy (high or low) that caused the fracture, patient age, comorbidities, and a determination of the presence of osteoporosis. Any patient who fractured a bone after the age of 50 years is at high risk for osteoporosis and should be considered for assessment with bone densitometry. Other evaluations should include the patient's gait to determine if a limp is present, measurement of limb lengths for discrepancy, measurement of hip motion, and examination of the patient and signs of infection. Patients should be questioned carefully about severity and pattern of pain, the level of hip dysfunction, and infection issues, including previous wound healing problems.
Imaging Studies
If possible, existing radiographs should be reviewed to evaluate the initial injury and to assess serial changes in the hip over time. Up-to-date anteroposterior and lateral views of the hip and an anteroposterior view of the pelvis are required. If substantial rotational contracture of the hip exists, oblique views can be helpful (Fig. 6-1). In the case of an acetabular fracture, Judet views of the pelvis can help assess the columns and walls of the acetabulum. A computed tomography scan is used to assess for nonunion of the acetabulum or hip, bone defects of the acetabulum, and heterotopic ossification. In particular, a transverse nonunion of the acetabulum, termed a pelvic discontinuity, requires refixation of the pelvis and must be evaluated on the Judet views and computed tomography scan.
Diagnostic Workup Algorithm
A diagnostic workup algorithm is shown in Figure 6-2.
Treatment
Nonoperative
For patients with posttraumatic hip arthritis, nonoperative modalities should be the first line of treatment. Interventions include activity modification, weight reduction if the patient is obese, ambulatory assistance devices (walker, wheelchair, or motorized scooter, especially if the patient is elderly and infirm), pain medications (such as acetaminophen, nonsteroidal anti-inflammatory medications, and narcotic agents), and shoe lifts for limb-length discrepancy. Patients with healing fractures require careful radiographic follow-up until fracture union. In the event of a malunion or nonunion, the younger patient may be at risk for early posttraumatic arthritis and the older patient may be at risk for substantial bone loss from screw cutout. In either case, earlier surgery may lead to a better outcome.
Surgical
Preoperative Considerations
All patients who have had previous surgery to the hip should be assessed for infection. Infection may have caused the failure of previous treatment, and if present, it will affect the management of the patient. Erythrocyte sedimentation rate and C-reactive protein serve as screening tools. Any patient with elevation of these values should undergo hip aspiration under fluoroscopy. White blood cell–tagged bone scans also may be used to evaluate for infection. In all cases, intraoperative frozen sections should be sent to assess for infection, and intraoperative cultures should be taken.
Surgery on the previously traumatized hip is not routine, and the treatment plan should be made well in advance of the surgical date. Templating should be performed on the preoperative radiographs ahead of time to help determine what implant systems will be required. Operative reports from previous surgeries facilitate ordering the correct tools for hardware removal. A broken-screw removal set and a high-speed metal cutting burr should be available in case screw heads are stripped.
Elderly patients with failed fracture repair are frail and usually have been in poor health since their initial injury. Contractures or bed sores may have developed from lack of activity. The patient should be evaluated for systemic problems, may require preoperative evaluation by a cardiologist, and may need an intensive care unit bed postoperatively. It is
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helpful to plan for a geriatrician or hospitalist to follow the patient in the postoperative period because postoperative medical complications such as delirium are common. The patient and family should be prepared for a lengthy recovery and the possibility of complications, including death.
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Figure 6-2 Diagnostic workup algorithm. |
Goals/Approaches
Joint arthrosis may be the end result of osteonecrosis of the femoral head, malunion, or cartilage damage. Because total hip replacement has been so successful, it is now the most commonly used treatment option. Alternate options include hip resection or fusion, but both lead to substantial leg-length discrepancy and hip dysfunction and are not well accepted by patients.
Acetabular Fracture.
Hip arthroplasty after acetabular fracture is difficult, and an uncemented acetabular component with additional screw fixation should be used. Existing hardware from the previous fixation, including posterior wall plates or column screws, should be removed only if they impede reaming or cup insertion. The sciatic nerve is at great risk when a posterior column plate is removed, and care must be taken with retractor placement. Bone defects must be expected, depending on the initial fracture pattern: The most common defects occur posteriorly after posterior wall fractures or anteriorly and medially after osteoporotic acetabular fractures. Bone graft from the arthritic femoral head should be used first, and then cancellous allograft chips as needed. Each patient should be examined intraoperatively for pelvic dissociation; if present, the posterior
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column must be stabilized with a contoured reconstruction plate. The defect then is packed with bone graft, and an uncemented cup is inserted with multiple screws. For very large defects, an acetabular autograft (protected by a cage) may be required.
Femoral Neck Fracture.
Femoral neck fracture complications, such as arthritis, nonunion, or malunion, generally are treated with hip arthroplasty. Arthroplasty requires removal of the existing screws, but a standard femoral stem usually can be inserted. Pain after hip fracture repair may occur directly over hardware such as a sliding hip screw or cannulated screw or it may be secondary to screws having backed out substantially. However, before considering hardware removal, fracture nonunion should be excluded by computed tomography scan.
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Figure 6-3 Young patient with femoral neck nonunion treated with valgus osteotomy and blade plate fixation. A: Anteroposterior view of the hip showing the blade plate. B: Lateral view of the hip reveals that the femoral head has collapsed from osteonecrosis. C:Anteroposterior view of the hip showing the uncemented total hip arthroplasty after blade plate removal. |
Young patients with a viable concentric femoral head should be considered for hip salvage surgery. For the young patient with femoral neck nonunion, an intertrochanteric valgus producing osteotomy converts shear forces into compression forces, allowing for fracture healing (Fig. 6-3). The osteotomy is performed on a fracture table with fluoroscopy, and a 95-degree blade plate is used for fixation.
Femoral neck malunion may result in femoroacetabular impingement. A femoral reshaping procedure can remove impinging osteophytes to prevent additional arthritic
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changes. A trochanteric slide osteotomy approach to the hip avoids damage to the femoral head's blood supply. A burr is used to remove the impinging osteophytes.
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TABLE 6-2 Tips for Total HIP Replacement After Failed Treatment for Intertrochanteric Fracture |
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Intertrochanteric Hip Fracture.
In the elderly patient, intertrochanteric nonunion and malunions should be treated with prosthetic replacement. Hemiarthroplasty may be used in the elderly patient with intact acetabular cartilage. Some technical difficulties of total hip replacement should be recognized and are summarized in Table 6-2. The previous scar from internal fixation may be too far anterior, requiring a second incision. Care must be taken during exposure because a hip contracture is usually present, making exposure difficult. Fracture of the femur or ankle may occur by overzealous retraction. The greater trochanter usually is widened and partially healed with callus and heterotopic ossification. A modified direct lateral or posterior approach can be used per surgeon preference. In some cases, the trochanteric fragment has not healed to the femur, and a trochanteric slide approach can be used. The hip should be exposed and dislocated before hardware removal.
Often, the hip screw has cut out through the femoral head, producing cartilage damage and a bony defect in the acetabulum. In such a case, the remains of the femoral head should be used to graft the defect, and an uncemented cup should be inserted. A bony defect of the medial proximal femur often is present, leading to the need for a calcar-replacing femoral prosthesis. A cemented or uncemented prosthesis can be used, but the stem should extend past the final screw hole to avoid a stress riser (Fig. 6-4). Previous screw holes should be plugged to prevent cement extravasation. Careful trial reduction and intraoperative radiographs are recommended to help ascertain whether the appropriately sized calcar buildup has been used. If the calcar buildup is too small, the hip will remain short and instability may result. Because instability is a larger concern than wear in these elderly patients, a large femoral head should be used. During closure, care should be taken with the greater trochanter. If unstable fracture lines remain, the trochanter can be stabilized with a claw and cables or wires.
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Figure 6-4 Elderly man with intertrochanteric fracture nonunion and sliding hip screw cutout. A: Anteroposterior view of the hip shows nonunion of the fracture and collapse. B: Anteroposterior view of the hip showing a long-stemmed uncemented prosthesis used to bypass screw holes with calcar buildup for leg-length restoration. |
In the young patient with an intact femoral head and acetabulum, revision fixation with bone grafting is an option. A 95-degree fixed-angle blade-plate device can be inserted using the intact inferior portion of the femoral head for fixation.
Results and Outcome
Most reports of the results and outcomes of treatment of posttraumatic hip problems are case series. Little is known about outcome measures in these patient groups, and no studies in the literature are randomized or controlled. This lack of large, investigative studies may reflect the fact that the numbers of patients with these posttraumatic problems is small and that the spectrum of failure mechanisms is wide.
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Conditions after Acetabular Fracture.
Limited information is available about the acute treatment of acetabular fractures with total hip arthroplasty. In one case series, 80% of patients had good or excellent results at intermediate follow-up. Excessive medialization of the acetabular component occurred in 10% of patients, and the difficulty of acute arthroplasty was stressed. Several authors have reported the results of late total hip arthroplasty for acetabular fractures: With modern implants, 90% have good to excellent results at intermediate follow-up. The procedures were noted to be more difficult with more blood loss than with primary hip arthroplasty. Extended liners and additional bone grafts often were required. Some reports have shown increased evidence of component loosening that is thought to be related to the young age and activity of patients at the time of hip replacement.
Conditions after Femoral Neck Fracture.
Excellent results have been reported for the treatment of femoral neck nonunion or osteonecrosis with total hip replacement. Results are slightly inferior to those of primary total hip arthroplasty, with higher rates of dislocation and trochanteric complications. Valgus-producing osteotomies have been reported as leading to healing of femoral neck nonunions in 80% of cases. However, patients often continue to have a limp from abductor weakness. Osteonecrosis may occur later after osteotomy, requiring subsequent hip replacement. The results of femoral reshaping procedures for femoroacetabular impingement from malunion of the femoral neck are preliminary: One case series of the use of a trochanteric flip osteotomy and femoral head reshaping showed excellent pain relief. Long-term follow-up is needed to determine whether arthrosis is prevented.
Conditions after Intertrochanteric Fracture.
The results of treating failed intertrochanteric fractures with bone grafting and revision fixation are limited, but available reports show 80% to 95% healing rate after the use of a fixed-angle 95-degree blade-plate device in selected patients. Arthroplasty for failed intertrochanteric fractures has been reported to have 90% good to excellent results at intermediate follow-up. These cases were technically difficult, and long-stemmed and calcar-replacing implants commonly were used.
Postoperative Management
Total Hip Replacement.
After hip replacement, intraoperative cultures should be followed for 5 days. Postoperative radiographs should be scrutinized carefully for iatrogenic fractures. Hip dislocation precautions relative to the specific operative approach should be followed. Weight-bearing restrictions depend on the stability of the components achieved intraoperatively. If at all possible, weight bearing should be allowed as tolerated because elderly patients often have difficulty following weight-bearing restrictions. Radiographs should be obtained and assessed during the postoperative year to document component stability and bone in-growth.
Osteotomy.
After valgus osteotomy of the hip, weight bearing is restricted for 6 weeks after surgery and then may be advanced per the patient's tolerance. Radiographs must be assessed carefully to monitor healing of the femoral neck and osteotomy and to monitor for the development of osteonecrosis of the femoral head. If the fracture does not heal or if substantial osteonecrosis develops, the patient is best treated with hip replacement.
Femoral Reshaping.
After femoral head reshaping, partial weight bearing may be started immediately. Active hip abduction exercises should be restricted, and hip flexion >90 degrees should be restricted for 6 weeks to allow for osteotomy healing. Strengthening, stretching, and full weight bearing begin thereafter. The hip should be followed radiographically for trochanteric healing, osteonecrosis, and arthritic changes.
Suggested Readings
Bachiller FG, Caballer AP, Portal LF. Avascular necrosis of the femoral head after femoral neck fracture. Clin Orthop Relat Res. 2002;399:87–109.
Bellabarba C, Berger RA, Bentley CD, et al. Cementless acetabular reconstruction after acetabular fracture. J Bone Joint Surg. 2001;83A:868–876.
Eijer H, Myers SR, Ganz R. Anterior femoroacetabular impingement after femoral neck fractures. J Orthop Trauma. 2001;15:475–481.
Haidukewych GJ, Berry DJ. Hip arthroplasty for salvage of failed treatment of intertrochanteric hip fractures. J Bone Joint Surg. 2003;85A:899–904.
Mabry TM, Prpa B, Haidukewych GJ, et al. Long-term results of total hip arthroplasty for femoral neck fracture nonunion. J Bone Joint Surg. 2004;86A:2263–2267.
Mathews V, Cabanela ME. Femoral neck nonunion treatment. Clin Orthop Relat Res. 2004;419:57–64.
Mears DC, Velyvis JH. Acute total hip arthroplasty for selected displaced acetabular fractures: two to twelve-year results. J Bone Joint Surg. 2002;84A:1–9.