Essentials of Orthopedic Surgery, third edition / 11-The Hip and Femur

426 B.G. Evans

A

B

C

FIGURE 11-8. A 34-year-old man with a history of 4 months of increasing bilateral hip pain. (A) Anteroposterior (AP) pelvic radiograph is essentially normal. (B) T1-weighted magnetic resonance image (MRI) of the pelvis and hips demonstrates a line of decreased signal intensity across the superior one-third of the femoral head, which represents the new bone laid down at the periphery of the lesion that serves to wall off the lesion. (C) T2-weighted image demonstrates the same line of decreased signal intensity across the femoral head. However, this image also demonstrates a zone of increased signal intensity, consistent with the fibrovascular response to the necrotic bone.

A

B

FIGURE 11-9. This 84-year-old woman presented with severe hip pain after a car ride. The patient had bilateral hip replacement approximately 15 years before presentation. (A) AP pelvic radiograph demonstrates a patient with significant diffuse osteopenia and two hip replacements. Both hips appear to have some loosening of the acetabular components but demonstrate no acute changes. (B) Delayed image from a Tc 99-MDP bone scan demonstrates significant uptake in the left acetabulum. However, there is diffuse marked increase uptake throughout the sacrum. This pattern of uptake is consistent with a sacral insufficiency fracture.

428 B.G. Evans

The inlet and outlet views are useful for patients with pelvic trauma to demonstrate translation of the involved hemipelvis (Fig. 11-10). The inlet view is taken with the beam oriented from cephalad to caudad 45 degrees to demonstrate the anterior or posterior translation of the involved hemipelvis. The outlet view is taken with the beam oriented 45 degrees from

A

B

FIGURE 11-10. A 37-year-old woman with 1 year of increasing right hip pain. (A) Initial AP radiograph demonstrates a large femoral head with a shortened femoral neck, most likely the late result of Perthe’s disease of the hip. (B) The patient underwent an osteotomy of the proximal femur to address her hip pain.

caudad to cephalad, providing a true AP view of the sacrum. Also, this view can clearly demonstrate any superior or inferior translation of the hemipelvis.

Computerized tomography (CT) of the pelvis is most helpful in evaluating trauma. In some centers this modality has replaced and certainly augments the use of oblique pelvic radiography. CT imaging is particularly helpful in demonstrating fractures in the posterior pelvis and sacrum, which may be poorly visualized in routine radiography. Fractures to the acetabulum are well visualized on CT scan images. CT images can clearly delineate the extent of the fracture as well as demonstrate any intraarticular fragments that may be present. The CT can also be converted into a three-dimensional image to more clearly demonstrate the fracture pattern. CT imaging can also be utilized to demonstrate other nontraumatic pathology. For example, anterior osteoarthritis, which may be subtle on the plain radiographs, can readily be appreciated on CT images. Avascular necrosis may also be evaluated with this technique. CT images can augment plain radiography in demonstrating early collapse, which may affect the treatment options available to the patient.

Magnetic resonance imaging (MRI) of the hips is indicated in patients in whom a periarticular lesion is suspected or to evaluate for the presence of avascular necrosis of the femoral heads (see Fig. 11-8). MRI is a very sensitive and specific tool for the evaluation of AVN as it can readily demonstrate the avascular segment before changes are seen on the plain radiographs. MRI can also be helpful in demonstrating a tear in the acetabular labrum, which is best demonstrated by the use of MR arthrography. MR contrast material is injected intraarticularly and an MR of the hip is obtained; the contrast outlines the labrum and any defect in labrum can be identified.

The Tc 99-MDP bone scan can be helpful in evaluating pelvic pathology. The bone scan can be used as a sensitive indicator of osseous pathology in the pelvis. Metastatic disease, occult fractures, infection, or osteomyelitis can be identified (see Fig. 11-9). The bone scan is most helpful as a general skeletal screening tool for metastatic disease. The bone scan is very sensitive but is not specific. Therefore, other studies such as MR or CT may be necessary to fully evaluate the nature and extent of any identified pathology.

Hip aspiration and arthrography can be helpful in the evaluation of pathology. Aspiration can be helpful in evaluating hip sepsis in both a native hip as well as after hip arthroplasty. Aspiration is best performed under fluoroscopic guidance. An arthrogram can then be utilized to confirm the intraarticular position of the needle. Arthrography can also be utilized to assess loosening of a hip prosthesis. The contrast material can be noted flowing around the loosened implant, demonstrating the separation of the implant, cement, and bone. Not infrequently patients present with a history of both hip and spine pathology. Injection of local

430 B.G. Evans

anesthetic with or without a corticosteroid medication into the hip under fluoroscopic guidance can be helpful in differentiating the pain coming from the hip with that coming from the spine. If the intraarticular local anesthetic results in significant relief of pain, the pain is most likely intraarticular in origin. If the local anesthetic agent does not alter the pain, extraarticular pathology or spine disease should be investigated. Aspiration of the hip should be performed under fluoroscopic guidance.

The patient’s history and physical examination direct the use of these radiographic techniques. The appropriate use of these diagnostic tests can result in cost-effective and accurate diagnosis and properly directed treatment.

Hip Pathology

A variety of soft tissue conditions can affect the hip. Although these conditions are not uniformly associated with trauma or injury, an injury can be the inciting event. Trochanteric bursitis is a common condition of the hip. The pain results from inflammation within the trochanteric bursa, which is located over the lateral aspect of the greater trochanter under the fascia lata. It is associated with pain over the lateral aspect of the hip in the region of the greater trochanter. The pain is a deep ache centered over the greater trochanter with radiation both proximally to the pelvic brim and distally occasionally all the way to the knee. The pain is exacerbated by adduction of the hip with the knee extended. No pathologic changes are noted on either plain radiographs or MRI. The treatment consists of stretching the fascia lata and iliotibial band and the use of nonsteroidal antiinflammatory medications. If these conservative measures are unsuccessful, the patient may benefit from physical therapy with the use of local modalities such as ultrasound and iontophoresis. These modalities can be augmented with a corticosteroid injection into the bursa. If these nonoperative modalities fail to relieve the pain, the bursa can be surgically excised. However, this option is rarely required.

The iliotibial band and the trochanteric bursa can also be involved in the snapping hip. The iliotibial band snapping over the trochanteric bursa and the greater trochanter causes this condition, which is not always painful. The treatment is similar to that for trochanteric bursitis. Snapping in the hip can also occur anteriorly. The iliopsoas tendon can snap over the anterior aspect of the hip where the tendon exits the pelvis over the anterior pelvic brim, resulting in an anterior snap with flexion and extension. The amount of pain associated with the snap is variable. Treatment is directed toward alleviation of the pain. Nonsteroidal antiinflammatory medications can be helpful in alleviating the pain. Stretching of the iliopsoas with hip extension can also help to reduce the symptoms.

Another cause of a snapping hip is a tear in the acetabular labrum. The acetabular labrum is a dense fibrocartilaginous structure that is attached

to the acetabular rim which can be injured similarly to a meniscal injury in the knee. The labrum is more prone to injury in patients with acetabular dysplasia. In this condition, the acetabulum is shallow and the labrum hypertrophies and is weight-bearing. A tear in the acetabular labrum presents clinically with pain in the hip anteriorly, particularly with internal rotation; this is also commonly associated with a click noted when the hip is flexed and extended. The diagnosis can be confirmed with an MRI obtained after the injection of intraarticular contrast dye. The accuracy of this assessment is approximately 85%; without the intraarticular contrast, the accuracy is only 50% to 60%. When a tear is identified, no treatment is necessary if the pain is mild. If, however, the patient has pain or the click is activity limiting, then the tear should be excised or repaired; this can be done either arthroscopically or with an open hip arthrotomy.

Intraarticular loose bodies can occur either as a result of trauma or as a result of synovial chondromatosis. In synovial chondromatosis, the synovium develops osteochondral loose bodies that are free in the articular space. In the knee, these loose bodies cause a great deal of mechanical symptoms such as locking. In the hip, there is not enough free space for the loose body to cause locking. However, these loose bodies can restrict motion and cause pain. Synovial chondromatosis can be difficult to diagnose. The plain radiographs are usually normal or demonstrate the very subtle stippled calcifications of the osteochondral fragments. The MRI or CT scan can be helpful in demonstrating the loose bodies and the expansion of the synovial space and effusion. The treatment is surgical: an arthrotomy is performed and the fragments removed. Synovectomy can be performed, although care should be taken to preserve the vascularity of the femoral head.

Avascular necrosis (AVN) is a condition that most commonly affects the femoral head. However, this condition can also affect the proximal humerus, knee, and talus. The specific mechanism causing AVN is unclear. Several factors have been associated with increased risk of developing this condition. The most common factors are trauma to the femoral head or neck, systemic corticosteroid administration, and excessive alcohol intake. In addition to these factors there is a long list of other less common factors such as hemoglobinopathies, metabolic conditions, and inflammatory conditions that can cause AVN. However, in as many as one-third of patients with nontraumatic AVN no specific etiology can be identified, and thus these cases are identified as idiopathic AVN.

In all cases of AVN there is compromise of the blood supply of the femoral head, which most commonly occurs in the anterosuperior portion of the femoral head, leading to necrosis of a portion of the subchondral bone. If the avascular segment is large and in a weight-bearing area, the stability of the subchondral bone will be compromised as the necrotic trabeculae weaken. This process occurs over 6 to 24 months. Although a Tc 99-MDP bone scan can demonstrate the lesion early, plain radiographs are

432 B.G. Evans

frequently normal after the segment becomes avascular. Over time the round femoral head weakens and then develops an area of collapse. At this point the joint is no longer round and congruent, and without intervention the condition frequently progresses to degenerative arthritis.

The lesion of AVN has a very typical pathologic and radiographic pattern. The lesion is most commonly in the anterior and superior subchondral bone of the femoral head and has several distinct zones to the lesion. The outer zone is an area of increased vascularity and inflammation that develops in response to the necrotic segment. The next layer is a dense area of sclerotic bone, which is laid down around the necrotic segment in an attempt to heal the lesion. However, this response simply serves to wall off the lesion and prevents vascular invasion and healing of the lesion. Inside the sclerotic bone is the necrotic bone with the trabecular structure relatively intact. Histologically, the necrosis of the bone is demonstrated by trabecular bone with empty lacunae. Closer to the subchondral bone is the area of collapse of the trabecular bone. The outer layer is composed of the subchondral bone and articular cartilage. Radiographically, a subchondral radiolucent line that is referred to as a crescent sign demonstrates this region. Frequently, after collapse of the subchondral bone there is a defect through the cartilage and the subchondral bone that allows articular fluid to enter the necrotic area; this will further impair healing of the lesion.

In early cases, before collapse of the femoral head, attempts can be made to save the femoral head and restore viability to the necrotic bone. These techniques are surgical. There are several variations; however, all involve drilling a core tract into the avascular portion of the femoral head in an attempt to restore vascularity to the necrotic bone and possibly heal the lesion. Several techniques have been described to augment this procedure: autologous cancellous bone grafting, bone graft substitutes, allograft cortical or cancellous bone, or using one of the patient’s fibulae on a vascular pedicle to place vascularized bone into the lesion.

Of patients who have documented AVN that is untreated, 70% will require a total hip replacement with in 5 years. Patients who have had a core decompression-type procedure will require a total hip replacement in 30% to 35% of cases by 5 years. The results are an improvement compared to the natural history; however, the success rate is less than we would prefer. Vascularized fibular grafting has demonstrated an improvement in the survivorship of the involved hip. However, there can be significant weakness in foot and ankle function on the involved side after harvesting the fibula.

For patients with small lesions that have already undergone subchondral collapse, an osteotomy may be done to rotate the necrotic collapsed segment out from under the weight-bearing area of the hip. However, commonly the lesion is extensive and not enough viable bone remains to allow the necrotic segment to be rotated away from the weight-bearing area of the hip. As the AVN progresses and the hip becomes severely degenerated,

hip replacement offers the most reliable means of restoring function and relieving pain. Many of the patients are relatively young to receive a total hip replacement. The average age of patients with AVN is approximately 35 to 45 years. The results of cemented arthroplasty in this population have not been as successful as in patients with osteoarthritis. Noncemented fixation does appear to have less loosening compared to cemented fixation in this population. However, the rate of other complications such as dislocation, infection, and hematoma are increased in this population regardless of the method of fixation of the components.

Hip Arthritis

A wide variety of arthritic conditions can affect the hip joint. While the medical therapy can vary based upon the specific diagnosis, the operative treatments fall into several broad categories and are discussed as such. Arthritis is defined as any condition that results in articular cartilage damage with resulting pain and limitation of the motion of a joint. Hip arthritis can be divided into several broad categories (Table 11-1).

The clinical presentation of hip arthritis is a gradual increase in pain and limitation of motion. Frequently patients complain of a reduction in their ability to walk for distances. Patients also notice a marked stiffness in the joint when they have been sitting for a period of time and then stand. The joint feels out of place or stiff, although this symptom usually resolves after a few steps. As the arthritis progresses and the joint begins to lose motion, patients will also notice a reduction in their ability to care for their own toenails and difficulty with activities such as putting on socks or stockings and tying their shoes. A limp also commonly occurs in patients with hip arthritis, particularly after long walks or at the end of the day.

TABLE 11-1. Classification of hip arthritis.

434 B.G. Evans

Radiographic and etiologic criteria can assist in dividing the patients into two broad categories, osteoarthritis and inflammatory arthritis, based upon the history and the radiographic appearance of the hip joints. Osteoarthritis has four classic features on plain radiography: localized joint space narrowing, subchondral sclerosis, osteophyte formation, and subchondral cysts. In rheumatoid arthritis, as a classic example of an inflammatory arthritis, the radiographic features are periarticular osteopenia, diffuse or global joint space narrowing, and occasionally subchondral cysts. In inflammatory arthritis of the hip, protrusio deformity of the femoral head beyond the ilioischial line can be noted as well. In most cases of arthritic disease in the hip no additional studies other than plain radiography are necessary for the evaluation.

The nonoperative treatment varies based upon the specific diagnosis. Osteoarthritis, whether primary or secondary, is treated in a similar fashion. The treatment for the majority of patients with osteoarthritis is nonoperative. There are five primary interventions in the nonoperative management of the patient with osteoarthritis (Table 11-2).

These five interventions can be used in isolation or in combination based upon the specific clinical situation in which the patient presents. Nonsteroidal antiinflammatory drugs (NSAIDs) can be very effective in reducing the pain and improving function. However, there is a large individual variation in the efficacy and side effects with each of these agents. Therefore, patients should be tried on several NSAIDs from different chemical classes before abandoning this limb of therapy. The principal side effect of NSAIDs is gastrointestinal (GI) intolerance with the possibility of ulcer formation. NSAIDs can also affect renal and hepatic function, and in the long-term, use of these agents renal and hepatic function should be followed. In addition, these medications can affect platelet function and may have an adverse effect on bleeding times. These medicines should not be used in patients requiring anticoagulation therapy or within 5 to 7 days preceding any surgical intervention.

The cyclooxygenase 2 (COX-2) inhibitors may offer lesser side effects compared to the nonspecific cyclooxygenase inhibitors that represent the majority of the NSAIDs on the market; however, this benefit needs to be demonstrated in large clinical trials. The COX-2 inhibitors also have less effect on platelet function and may be safe to use for patients on anticoagu-

TABLE 11-2. Primary interventions in the nonoperative management of osteoarthritis.

Nonsteroidal antiinflammatory medications

Physical therapy

Intraarticular injection of corticosteroids

Assistive devices

Modification of activities