The Hip

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Chapter 10 The Hip

The hip is a ball-and-socket joint in which the femoral head articulates deeply into the acetabulum. This deep fit, combined with thick ligamentous and muscular supporting structures, makes the hip extremely stable but relatively inaccessible. Therefore, the diagnosis of disorders of the hip is sometimes difficult.

Anatomy

The proximal portion of the femur consists of a head, neck, and greater and lesser trochanters. The axes of the neck and femoral shaft form an angle in the anteroposterior plane: the neck–shaft angle, or “angle of inclination.” This normally measures 125 to 130 degrees. An increase in this angle is termed coxa valga, and a decrease is termed coxa vara. The neck and shaft also form an angle in the transcondylar plane that is referred to as the angle of femoral torsion (Fig. 10-1). Normal femoral torsion is 40 degrees in children, and this decreases to 15 to 20 degrees in adults. Excessive femoral torsion is termed anteversion or antetorsion and is sometimes responsible for in-toeing. A decrease in the normal femoral torsion is termed retroversion or retrotorsion and may cause an out-toeing gait.

Fig. 10-1 The angle of femoral torsion.

The vascular anatomy of the femoral head is of critical importance in many disorders of the hip. The main sources of blood supply are the retinacular and intramedullary vessels, both of which course from the intertrochanteric region proximally to nourish the femoral head (Fig. 10-2). Diseases or injuries that compromise the circulation may damage the viability of the femoral head and lead to avascular necrosis.

Fig. 10-2 Blood supply to the head of the femur. Fracture through the neck can seriously disrupt the circulation to the head.

Among the nerves that supply the hip joint is the obturator nerve. This nerve also supplies a sensory branch to the medial side of the thigh and motor supply to some of the hip adductors. Irritation of this nerve from hip joint disease may result in referred pain along the inner aspect of the knee and thigh that may cause confusion with disorders of the knee joint. Therefore, complaints of pain in this area in the absence of physical findings in the knee should always draw attention to the hip joint.

Examination

Several bony landmarks are available for orientation on physical examination. The anterior and posterior superior iliac spines and iliac crest are easily palpable because they are not crossed by any muscles (Fig. 10-3). The proximal portion of the iliac crest lies at the level of the fourth lumbar vertebra. The greater trochanter is palpable laterally, and the pubic symphysis is palpable anteriorly. The femoral head lies approximately 2.5 cm distal and lateral to the point where the femoral artery passes beneath the inguinal ligament. This relationship should be recalled when performing venipuncture from the femoral vein. A needle passed through the vein may enter the hip joint and introduce infection into the hip. All femoral venipuncture sites should therefore be meticulously scrubbed and prepared before needle insertion.

Fig. 10-3 Bony landmarks of the hip. A, Anterior superior iliac spine; G, greater trochanter; T, trochanteric bursa; P, posterior superior iliac spine; L, lesser trochanter; I, ischial tuberosity. The upper level of the iliac crest lies at the level of the fourth lumbar vertebra. Adjacent to the posterior superior iliac spine is the sacroiliac joint.

Roentgenographic Anatomy

The roentgenographic study of the hip joint should include views in the anteroposterior and lateral planes (Fig. 10-4). The lateral view maybe either a “true” lateral or a “frog leg” exposure that is taken with the hips in maximum external rotation.

Fig. 10-4 Anteroposterior roentgenogram of the normal hip. A, Rim of the acetabulum; H, head of the femur; N, neck of the femur; L, lesser trochanter; G, greater trochanter; I, intertrochanteric region. The angle of inclination is marked.

Developmental Dysplasia of the Hip

Developmental dysplasia of the hip (DDH) is a term used to describe a spectrum of hip abnormalities in the young child. This can range from simple acetabular dysplasia without instability to complete dislocation of the femoral head. Congenital dysplasia of the hip is the most common subset of this disorder. (Other forms of DDH are commonly caused by neurologic or myopathic factors.)

DDH is frequently bilateral, and although the cause is unknown, heredity appears to play a role. Females are affected nine times more often than males, and although the condition may affect both hips, the left is three times more often involved. Firstborn children or children born by breech deliveries also have a higher incidence of the disorder. It is occasionally present in association with clubfoot and congenital muscular torticollis deformities.

The hip may be frankly dislocated at birth, or the child may simply be born with isolated hip dysplasia without instability (in which case the diagnosis may only be discovered incidentally on radiographic examination at some later date). In between is the minimally subluxable hip with inadequate coverage by the acetabulum, which will usually develop osteoarthritis in adulthood, commonly by the third or fourth decade.

Pathologically, abnormalities are seen in both the acetabulum and femoral head. The acetabulum may be shallower in contour and more vertically inclined than normal and result in insufficient coverage and inadequate containment of the femoral head. The femur is often excessively anteverted, and the hip joint capsule may also be lax. The major abnormalities are acetabular, however.

CLINICAL FEATURES

There are no symptoms in the newborn, but most cases are detectable at birth. The clinical picture of the unstable hip will range from minimal findings to obvious frank dislocation, depending on the age of the child. In the newborn, provocative maneuvers, such as Barlow’s and Ortolani’s tests, are commonly used to detect instability. The tests are similar. The Ortolani test refers to the gentle reduction of the dislocated hip by abduction of the flexed hip (Fig. 10-5). This is often accompanied by a soft “clunk,” sometimes called the click of entry. In Barlow’s test, the hip is purposely dislocated by gentle downward pressure of the flexed, adducted hip. With posterior pressure, the femoral head will be displaced out of the acetabulum if the hip is unstable, sometimes called the click of exit. The head is then reduced by gentle abduction of the flexed hip by performing Ortolani’s maneuver. Barlow’s test should not be performed excessively, because it could make the problem worse. Occasionally, this maneuver may result only in a sensation of excessive gliding without an obvious dislocation. This may be an indicator that the hip is subluxable and therefore unstable. Soft clicks sometimes felt during abduction–adduction movements are not considered pathologic unless other findings are present.

Fig. 10-5 Ortolani’s sign for congenital dislocation of the hip. A “click” is palpable or audible as the hip is reduced by abduction. If the test is negative, the examination should always be repeated in 2 to 4 months.

If the diagnosis is made late, the hip is less flexible, and the ability to reduce the dislocated hip by the provocative maneuvers is lessened. At this time, the physical findings may include asymmetry of the skin folds and limited abduction (Fig. 10-6). If the hip is dislocated, it may not be reducible, and other signs may be present, such as shortening of the extremity (Fig. 10-7).

Fig. 10-6 Restricted abduction of the right hip.

Fig. 10-7 Galeazzi’s or Allis’ sign. The child is placed on a firm surface with the hips and knees flexed. The knee will appear lower on the dislocated side.

If weight bearing has begun, a painless limp is often the initial symptom of dislocation. Hip motion, especially abduction, is limited, and abnormal piston mobility or “telescoping” may be present. The Trendelenburg test is usually positive. This test takes advantage of the fact that normally, when standing on one leg, contraction of the abductor muscles on the side bearing weight will cause the opposite side of the pelvis to be elevated. If the hip is dislocated, these muscles no longer work effectively, and when the child stands on the affected leg, the opposite side of the pelvis drops downward instead. This causes the typical waddling gait caused by abductor weakness.

The roentgenographic examination is usually not very helpful when the patient is younger than 3 months of age unless a complete dislocation is present. After this age, a delay in the ossification of the femoral head is frequently noted (Fig. 10-8). The acetabulum may be more inclined vertically, and the acetabular index is often increased. If subluxation or dislocation has occurred, upward and outward displacement of the femoral head will be seen.

Fig. 10-8 Roentgenogram of the pelvis. P, Perkin’s vertical line; H, Hilgenreiner’s horizontal line; AI, acetabular index. The ossification center of the capital femoral epiphysis should lie in the inferior medial quadrant formed by Perkin’s and Hilgenreiner’s lines. The AI normally measures less than 30 degrees. Here, ossification of the capital epiphysis on the dysplastic hip (arrow) has been delayed as compared with the left.

Ultrasonography is useful in congenital hip dysplasia, especially in high-risk infants (such as those who are breech delivered or who have a positive family history) or those with uncertain clinical findings. Among its benefits is the elimination of exposure to radiation. Magnetic resonance imaging (MRI) may eventually be helpful, but the diagnosis can usually be established by other means.

TREATMENT

Referral is indicated if there is any suggestion of instability in the hip of the newborn. Treatment is initiated as soon as possible and varies with the age of the patient and the degree of dysplasia. Early detection is of utmost importance, because conservative treatment is more likely to succeed in the infant. The more the child’s age exceeds the weight-bearing age, the more likely it is that surgery will be necessary, and the less likely that a normal functional result will ensue. Whenever any doubt exists, treatment and follow-up are indicated.

The objective of treatment is to reduce the femoral head into the acetabulum and maintain that reduction. By maintaining the hip in the reduced position, normal development of the hip joint structures and deepening of the acetabulum are encouraged. A variety of external devices are available for the treatment of hip dysplasia or dislocation, the most functional of which is the Pavlik harness (Fig. 10-9). The brace is usually worn for several weeks until the hip is stable.

Fig. 10-9 The Pavlik harness.

Failure to obtain or maintain a stable reduction necessitates surgical intervention. The objective is to reduce the hip by either closed or open methods and maintain the reduction by casting or osteotomy.

Comments

Children should have an examination of the hips at all well-baby visits up to the age of 18 months. Although most cases of DDH are detectable at birth, normal physical findings do not rule out the disorder, and there are many documented cases that have developed late instability despite a normal examination at birth. High-risk groups for later dislocation are those (1) with minor instabilities at birth, (2) those in the neonatal intensive care unit for extended periods who may not be able to be examined as closely, and (3) those born by cesarean section.

Legg–Calvé–Perthes Disease

Perthes’ disease, or coxa plana, is a self-limited disorder of the hip in which a portion of the ossific nucleus of the femoral head undergoes avascular necrosis. Eventually, the infarcted, necrotic bone is absorbed and replaced by normal bone. The etiology is unknown. The disorder usually occurs between the ages of 4 and 10 years but may affect children as young as 2 or as old as 12. Males are four times more commonly affected than females. Fifteen percent of cases are bilateral, and the condition is rare in African Americans.

The disease is frequently divided into three stages. The early stage of the disease is characterized by synovitis of the hip joint and early ischemic changes in the ossific nucleus of the femoral head. Roentgenograms taken at this stage reveal joint swelling that may result in lateral displacement of the femoral head. An increase in the opacity of the ossific nucleus is usually present (Fig. 10-10).

Fig. 10-10 Roentgenographic changes in Legg–Calvé–Perthes disease. A, In the early stages, the joint space is widened, and the head is dense. B, The head is fragmented, and the metaphysis is widened. C, End result after treatment. Normal function was restored.

In the second, regenerative stage, or fragmentation stage, the necrotic area begins to be replaced by viable bone. This phase lasts from 1 to 2 years. The roentgenographic appearance during this stage is one of fragmentation and compression of the femoral head with secondary widening of the femoral neck.

Reossification and healing occur in the third stage, which varies in duration beyond 1 year. The roentgenogram in this stage shows a disappearance of the rarefaction while normal bone continues to reform. The final roentgenographic appearance depends on several factors, including the age of the patient and the degree of involvement. The femoral head may end up normal in shape or irregular and flat (coxa plana) because of the collapse of the osteonecrotic bone and overlying cartilage. The end result may be osteoarthritis if coxa plana develops.

CLINICAL FEATURES

The onset is gradual, and the initial complaint is usually a mildly painful limp. The pain is often referred down the inner aspect of the thigh to the knee (via the obturator nerve). The discomfort is frequently relieved by rest and aggravated by weight bearing. Examination reveals moderate restriction of motion secondary to the synovitis. Abduction and internal rotation are especially limited. Pain is present at the extremes of motion, and tenderness is usually noted over the anterior hip joint.

Plain roentgenograms are usually abnormal, but MRI or bone scanning may be helpful in equivocal cases.

TREATMENT AND PROGNOSIS

Referral is indicated whenever the diagnosis is suspected. Treatment recommendations continue to evolve. The ultimate goal of treatment is to prevent deformity of the femoral head while healing is progressing. If a deformity can be prevented, the chances of degenerative joint disease developing at a later date are lessened. The initial goals of treatment are the relief of pain and maintenance of joint motion, which are accomplished by rest to control synovitis. Many children younger than 6 years of age with minimal involvement have a good prognosis and require only symptomatic care. The older child who is at risk for having a poor outcome may require treatment. In these children, treatment is aimed at keeping the femoral head centered in the acetabulum. If the head is contained in the acetabulum while it is re-forming, the acetabulum will “mold” the head and prevent significant deformity from occurring. These goals of treatment are usually accomplished by the use of an abduction brace that allows motion but contains the head in the acetabulum (Fig. 10-11). The brace must be worn continuously for up to 2 years, although the results of specific forms of treatment remain inconclusive, and some investigators advocate only nighttime bracing. Surgery may be necessary in select cases.

Fig. 10-11 Abduction brace for Perthes’ disease.

The prognosis depends on the age of the patient, the degree of involvement, and the adequacy of treatment. Young patients with minimal involvement who are treated early do very well with few sequelae. Patients over 8 years of age frequently have some permanent restriction of motion, a slight limp, and a more irregular or flattened femoral head. A few patients will later develop degenerative arthritis.

Slipped Capital Femoral Epiphysis

Slipped capital femoral epiphysis is a disorder of unknown cause in which weakening of the epiphyseal plate of the upper femur occurs and results in upward and anterior displacement of the femoral neck. The actual amount of displacement varies. In most cases, the slippage is gradual, and some elements of healing are usually present. The condition is seen most commonly in boys between the ages of 11 and 16 years during their rapid growth spurt. The disorder is bilateral in 25% of cases and frequently occurs in two distinct body types. The first is the slender, tall, rapidly growing boy, and the second is the large, obese boy with underdeveloped sexual characteristics. The presence of the disorder in these two body types suggests a hormonal cause, but none has been proved.

CLINICAL FEATURES

The onset is generally gradual, and symptoms usually occur even when little displacement is present. Mild discomfort in the hip, groin, and knee and a painful limp with activity are the most common initial complaints. Symptoms have often been present for several weeks. Examination reveals tenderness over the hip joint capsule. An external rotation (toeing-out) deformity of the lower extremity may be present, and internal rotation, abduction, and flexion are usually restricted. Pain is present at the extremes of motion, and the hip tends to rotate externally and abduct as it is flexed (Whitman’s sign).

In the early “preslipping” stage, the roentgenogram characteristically reveals irregular widening of the epiphyseal plate and joint swelling (Fig. 10-12). As displacement occurs, a line drawn along the superior or anterior neck of the femur will transect less of the femoral head than normal. This may be more readily seen on the lateral view. More severe degrees of slippage are usually easily diagnosed.

Fig. 10-12 Slipped capital femoral epiphysis. A, Widening of the epiphyseal plate on the right side (arrow) and B, displacement of the femoral head are present. Displacement is best seen on the lateral view.

A condition similar to slipped capital femoral epiphysis is termed acute traumatic separation of the upper femoral epiphysis (Fig. 10-13). This is actually an epiphyseal fracture and has a much poorer prognosis than the gradual slippage that occurs in slipped capital femoral epiphysis.

Fig. 10-13 Acute traumatic separation of the upper femoral epiphysis.

TREATMENT

As soon as the diagnosis is made, a referral for surgery is indicated. The patient is immediately placed on crutches, and weight bearing is prohibited. Traction in the hospital may be necessary to reduce the acute component of the slippage. To prevent further slippage from occurring, the femoral head is fixed to the neck, generally by using small pins (Fig. 10-14). Weight bearing is prohibited for several months until the epiphyseal plate closes. Severe deformities may also require osteotomy of the femur.

Fig. 10-14 Postoperative roentgenogram following pinning for slipped capital femoral epiphysis.

The prognosis is usually good, except in those cases with acute traumatic separation. The chronic form may result in slight shortening of less than 1.25 cm along with a mild external rotation deformity. In cases with acute traumatic separation, avascular necrosis of the femoral head is a common complication, and this usually results in severe traumatic arthritis of the hip (Fig. 10-15). The more common chronic slippage does not usually cause avascular necrosis.

Fig. 10-15 Avascular necrosis and osteoarthritis following acute traumatic slipped capital femoral epiphysis. Reconstructive surgery was eventually required.

ACUTE CARTILAGE NECROSIS (CHONDROLYSIS)

An occasional complication of slipped capital femoral epiphysis is acute necrosis or lysis of the articular cartilage of the hip joint. The articular surfaces of both the acetabulum and femoral head may be involved up to 1 year after the slippage. This condition appears to be directly related to the severity of the slippage. The cause of this process is unknown, but destruction and degeneration of the hyaline cartilage occur. A painful fibrous ankylosis of the hip joint is frequently the end result.

Transient Synovitis (Irritable Hip)

Transient synovitis is a self-limited, nonspecific inflammation of the synovium of the hip joint that occurs in children. It is the most common cause of pain in the hip in children younger than 10 years of age. The cause is unknown, but a viral infection is suspected. Its importance lies in its similarity to other hip joint disorders, especially septic arthritis. The diagnosis is one of exclusion.

CLINICAL FEATURES

The onset is frequently acute and may follow a traumatic event or a recent upper respiratory tract infection. A painful limp is characteristic, and the pain is frequently referred to the inner aspect of the thigh and knee joint. A few patients have night pain. The hip is typically held in a position of slight flexion, abduction, and external rotation so that the hip joint capsule is under the least amount of tension. Pressure and discomfort are thereby reduced. Passive motions, especially internal rotation and abduction, are restricted. Temperatures of 37.3°C to 38.3°C may be present.

The roentgenograms may reveal swelling of the capsule and adjacent soft tissue but are usually normal. Slight widening of the joint space may be present, but there are no changes in bone texture. Ultrasonography may help determine the presence of excessive joint fluid.

Laboratory findings are usually minimal, although there may be a slight increase in the white blood cell count. Aspiration and culture of the hip joint fluid are negative, although fluid examination is required only if septic arthritis is suspected.

TREATMENT

Bed rest, gentle skin traction, and the elimination of weight bearing are indicated. Equivocal cases may need hospitalization. The relief of pain and discomfort is usually rapid, and motion is restored in 2 to 4 days. Crutches are used for 2 to 4 weeks, and the patient is observed closely for up to 2 years, because Perthes’ disease may develop in some cases, but the exact relationship is uncertain. Antibiotics are used only when the disorder is associated with an infection elsewhere. Recurrences are possible.

NOTE: It is often difficult to differentiate transient synovitis from pyogenic (septic) arthritis. In an attempt to minimize the need for painful diagnostic interventions, such as arthrocentesis, several diagnostic criteria have been evaluated to determine their usefulness in predicting infection. These include (1) history of fever; (2) non–weight-bearing status; (3) previous recent health care visit; (4) serum white blood cell count in excess of 12,000; and (5) elevated C-reactive protein or erythrocyte sedimentation rate. Although these criteria have value, they should be used cautiously in determining which patient needs aspiration.

Septic Arthritis in Childhood

Pyogenic infection of the hip may result from an osteomyelitis of the femoral neck or a bacteremia. It may even develop from contamination by a faulty femoral venipuncture. If improperly treated, complete destruction of the hip joint may occur.

Disorder	Symptoms/History	Findings
Congenital dislocated hip	Painless. Usually noticed when child first begins to walk (12–18 mo). May be bilateral	Trendelenburg sign positive. Leg shortened if unilateral. “Telescoping” of leg at hip. Abnormal roentgenogram
Perthes’ disease (or other AVN)	Minimal pain (groin, anteromedial thigh) Age 4–8 yr. Family history positive if due to rare sickle cell or other hereditary anemia. No fever	Decreased hip ROM, especially abduction, and IR. Roentgenogram may show early joint widening. Later (2–4 wk) bony changes. Lab values normal (except if due to blood disorder)
Transient synovitis	Irritable. Slight fever, groin and anteromedial thigh pain. Age 4–8 yr	Diminished hip movement. Slightly painful with motion. Roentgenogram may show slight joint space widening, fluid. Slight increase in ESR, WBC. Hip aspirate shows increased WBC, no bacteria
Septic hip	Painful! Septic, febrile, unable to ambulate. Groin pain (may be difficult to localize findings in young child)	Pain on slightest hip movement. Roentgenogram shows hip joint swelling. Hip aspirate positive for bacteria. Lab reflects infection
Slipped upper femoral epiphysis	Age 10–14 yr. Mild ache in groin, thigh. Leg often externally rotated	Limited IR. Roentgenogram shows slippage
“Low-grade” osteomyelitis, lower limb.	Fever, irritable. Moderate pain with weight bearing (may be difficult to localize findings in young child)	Local bony tenderness and soft tissue swelling. Protected motion. Early plain roentgenogram normal. Bone scan abnormal
Inflammatory joint disease	Single or multiple joints. May be mildly febrile	Joint swelling, heat. Some limitation of motion. Serum studies sometimes abnormal. Often diagnosis of exclusion
Neurologic disorders (CP, etc.)	Often bilateral. No pain. Gait may be wide based. Delay in motor development. History of perinatal problems	Abnormal neurologic findings

AVN, Avascular necrosis; CP, cerebral palsy; ESR, erythrocyte sedimentation rate; IR, internal rotation; ROM, range of motion; WBC, white blood cell count.

* NOTES: Always consider (1) battered child (especially if history of previous injuries, such as burns), (2) tumor, and (3) occult fractures. When knee pain occurs in children, always evaluate the hips.

Coxa Vara

Coxa vara is an abnormality of the upper portion of the femur that consists of a decrease in the normal angle of inclination below 110 to 125 degrees (Fig. 10-16). This may result from a wide variety of acquired and congenital conditions and usually results in a shortened extremity.

Fig. 10-16 A, The normal neck–shaft angle. B, Coxa vara. C, Proximal focal femoral deficiency.

ACQUIRED FORMS

Acquired forms are the most common types of coxa vara. Included in this category are Perthes’ disease, slipped capital femoral epiphysis, rickets, osteomalacia, and various injuries to the upper part of the femur. Each disease has its own clinical and roentgenographic features.

CONGENITAL FORMS

Congenital local disturbances in the growth of the proximal aspect of the femur may also lead to shortening and a significant coxa vara deformity. These disorders usually fall into three distinct classifications: congenital coxa vara, congenital bowed femur with coxa vara, and congenital short femur with coxa vara.

CONGENITAL COXA VARA (INFANTILE, CERVICAL, OR DEVELOPMENTAL)

This disorder is the result of faulty development of the femoral neck, which leads to the varus deformity. The cause is unknown. The disorder is frequently bilateral and becomes manifested after weight bearing has begun. The child usually presents with a painless limp. If the disorder is bilateral, a “duck-waddle” gait may be present. In this gait pattern, the body sways from side to side. Abduction and internal rotation of the affected extremity are usually restricted, and the leg may be from 2.5 to 5 cm shorter than normal. The lumbar lordosis is usually exaggerated, and with continued weight bearing the varus deformity may progress.

Roentgenographic examination usually reveals a decrease in the neck shaft angle. In addition, a triangular defect in the inferior aspect of the femoral neck may be present.

The treatment of mild deformities in which the neck shaft angle is greater than 100 degrees consists of a shoe lift, exercises to release contractures, and periodic reexamination. A brace that prohibits weight bearing may be necessary. More severe deformities require an osteotomy of the upper portion of the femur to correct the angulation.

CONGENITAL BOWED FEMUR WITH COXA VARA

This type of coxa vara is characterized by lateral bowing of the femur. The coxa vara is usually not as severe as that found with congenital coxa vara, but the shortening of the extremity may reach 10 to 15 cm. Treatment consists of equalizing the extremities by shoe lifts. Leg lengthening procedures may be considered.

CONGENITAL SHORT FEMUR WITH COXA VARA

This uncommon disorder is also known as proximal focal femoral deficiency. Portions of the proximal aspect of the femur are either completely absent or severely underdeveloped, and shortening of the limb may reach 25 to 37.5 cm by adulthood. Bracing is necessary in the young child, and amputation or rotation of the lower part of the leg, followed by prosthetic fitting to equalize the leg lengths, is usually the definitive treatment.

Degenerative Arthritis (Osteoarthritis)

Degenerative arthritis confined to the hip joint is a common affliction in the middle and later years of adult life. The cause is not completely understood, but trauma, congenital hip dysplasia, avascular necrosis of the femoral head, and slipped capital femoral epiphysis can be factors in its onset. Most cases are primary (idiopathic) and not secondary to another disorder. Pathologically, the articular cartilage becomes progressively thinned and worn away. New bone proliferation around the femoral head and acetabulum occurs, and the synovium becomes chronically thickened and congested.

CLINICAL FEATURES

The clinical course is gradual, and both hips may be affected. The onset of symptoms may be precipitated by a relatively minor injury. Pain after activity and stiffness after rest are characteristic. The stiffness frequently subsides with activity, and the pain frequently subsides with rest. The pain is often referred to the knee joint region. With the passage of time, the pain increases, sometimes even occurring at rest. Crepitus and grating in the hip may develop, and a painful limp is common. Patients often complain that they cannot flex and externally rotate the hip in order to put on their stockings and shoes.

Examination reveals tenderness over the anterior and posterior hip joint and restriction of motion, especially rotation and abduction. Pain is usually present at the extremes of motion. A flexion contracture frequently develops. This can be measured by the Thomas test. In this test, the patient is placed in a supine position, and the opposite thigh is flexed up to the chest to eliminate motion at the pelvis and lumbar spine. The angle formed between the affected thigh and the examining table is the amount of flexion contracture of the hip. These patients also have difficulty flattening the knee down onto the examination table because of the hip tightness.

The roentgenographic findings are characteristic (Fig. 10-17). Irregular sclerosis, joint space narrowing, and osteophyte formation are prominent features.

Fig. 10-17 Degenerative arthritis of the hip. The joint space is narrowed, and there is subchondral sclerosis.

TREATMENT

Conservative treatment frequently relieves symptoms and improves motion. The regimen requires a cooperative patient. Nonsteroidal anti-inflammatory drugs (NSAIDs) and acetaminophen are often helpful, and the joint is unloaded. Weight reduction is recommended when indicated, and the use of a cane is encouraged. The cane is usually used in the hand opposite the affected extremity (although it may be used in the ipsilateral hand), and pressure is applied to the cane at the same time that weight is being borne on the painful hip (see Chapter 18). Moist heat is sometimes helpful. Gentle range-of-motion exercise, such as swimming, will often overcome contractures and restore motion. The treatment plan may have to be repeated at intervals. Intraarticular hip joint injection with steroid is rarely performed because of the relative inaccessibility of the joint.

A variety of surgical options are available for patients who fail to respond to conservative treatment. Osteotomy or arthrodesis may be considered, but the most popular is total hip arthroplasty. The goal is the elimination of pain. In addition, joint replacement will usually improve hip joint motion. The indications for each procedure vary according to the age and occupation of the patient.

Avascular Necrosis (Osteonecrosis)

Avascular or aseptic necrosis of the femoral head is an uncommon condition that occurs in the third to fifth decade of life. It is characterized by the development of an area of bone necrosis in the anterosuperior weight-bearing portion of the femoral head. The cause is unknown in most cases (“idiopathic”), but the condition is frequently bilateral and is more common in men. It may be seen in association with gouty arthritis, chronic alcoholism, and chronic renal disease; in divers and workers who use compressed air (caisson disease, dysbarism); and in those patients who have undergone long-term steroid therapy. It can develop following dislocation of the hip. It probably occurs secondary to a circulatory disturbance to the femoral head. Following the initial infarction, collapse and fragmentation may occur, which lead to deformity of the femoral head and secondary degenerative arthritis.

CLINICAL FEATURES

The onset is gradual, with pain and a slight limp being common. A history of trauma is usually absent in the usual idiopathic type. Joint motion becomes progressively restricted, mainly caused by chronic synovitis. The roentgenogram reveals an increase in the density of the superior portion of the femur (Fig. 10-18). A radiolucent zone is frequently present between the avascular segment and the surrounding bone. The joint space is usually well preserved until late in the disease, when collapse of the head occurs, which can cause irregularity and later degenerative arthritis. Avascular necrosis is one of the main indications for MRI, which usually reveals the lesion quite clearly (Fig. 10-19).

Fig. 10-18 Avascular necrosis of the femoral head. Collapse of the head has not yet occurred, and the joint space is intact.

Fig. 10-19 MRI showing bilateral avascular necrosis.

TREATMENT

The goal of treatment is to prevent collapse of the femoral head and encourage repair of the necrotic area. With minimal involvement, prolonged abstinence from weight bearing by the use of crutches may allow regen eration of the avascular segment, although considerable time is required. Later in the disease, when collapse has occurred, prosthetic replacement is indicated.

Bursitis

Several bursae are present about the hip joint. The one most commonly subjected to irritation and pain is the trochanteric bursa. This sac lies between the greater trochanter and the overlying tendinous portion of the gluteus maximus muscle. Inflammation of the sac is common in the adult patient and is characterized by local pain over the trochanter that frequently radiates down the iliotibial band to the lateral aspect of the thigh and knee. This pain pattern may cause confusion with radicular pain from lumbar disc disease. Local point tenderness is usually present, and hip motion, especially internal rotation and abduction, may be painful. It is difficult for the patient to lie or sleep on the affected side. Roentgenograms are usually normal, although irregularity and calcification over the trochanter have been observed.

Treatment consists of moist heat, rest, and anti-inflammatory agents. Ultrasound to the affected area may be beneficial, and a local injection of a steroid/lidocaine mixture into the area of maximum tenderness is frequently curative (Fig. 10-20). Surgery is not helpful.

Fig. 10-20 Injection for trochanteric bursitis. The point of maximal tenderness is injected with 1 mL of steroid and 5mL of lodocaine. A spinal needle may be required in the obese patient. The needle tip should encounter bone, and the area should be widely infiltrated.

The iliopsoas bursa can also become irritated and cause anterior hip and thigh pain. A snapping sensation may occasionally be felt with certain hip motions, and pain may be increased with hip extension. The diagnosis is difficult to establish, and MRI may be required. Treatment is symptomatic. A local injection may be tried but usually requires fluoroscopic guidance.

The Snapping Hip

This is a condition in which a palpable snapping sensation occurs with hip motion, usually during rotation in adduction. The snap may even be audible and visible. The most common cause is a tightness of a portion of the iliotibial band, which catches on the prominent greater trochanter during movement. The condition may be associated with trochanteric bursitis. Rare causes include snapping of the iliopoas tendon over the head of the femur or intraarticular hip joint pathology, such as a loose body. The sensation often can be reproduced by the patient. Usually, there is little discomfort.

Treatment is generally symptomatic for the common trochanteric bursitis. Heat, local cortisone injections, reassurance, and modification of activities are usually curative.

Meralgia Paresthetica

Meralgia paresthetica is a common disorder characterized by pain and paresthesias occurring along the course of the lateral femoral cutaneous nerve of the thigh. This nerve enters the leg beneath the inguinal ligament 1 cm?medial to the anterior superior iliac spine and supplies sensation to the anterolateral aspect of the thigh (Fig. 10-21). Painful involvement of the nerve may be confused with hip and low back disorders. The cause of this condition is unknown, but direct pressure or constriction of the nerve at its point of exit into the thigh is thought to play a role. The condition is more common in joggers and gymnasts (possibly as a result of repeated excessive hip extension exercises). Rarely, the disorder can be traced to an intraabdominal or pelvic mass (because of the retroperitoneal course of the nerve). The condition may also be confused with an L3–L4 disc problem.

Fig. 10-21 Sensory area of the anterolateral thigh affected in meralgia paresthetica.

CLINICAL FEATURES

The disorder is sometimes seen in obese patients or those who wear tight corsets or undergarments. Hypersensitivity, burning, tingling, and pain that occurs with activity or direct pressure over the nerve are characteristic. The symptoms are often relieved by rest and hip flexion.

The pain may be aggravated by passive extension of the hip. A slight decrease in sensation over the anterolateral aspect of the thigh is sometimes noted, and pain may be reproduced with pressure on the nerve medial to the anterior superior iliac spine. A good pelvic and abdominal examination should be performed. Electrodiagnostic studies are not helpful, except to rule out other causes. If there are gastrointestinal or genitourinary symptoms, pelvic or abdominal disease should be considered.

TREATMENT

Painful symptoms often subside spontaneously over a variable length of time, but numbness may be permanent. Weight loss and the avoidance of constricting garments are advised. Injection of the nerve distal to the inguinal ligament 1.25 cm medial and 2.5 cm below the anterosuperior iliac spine with a local anesthetic may relieve symptoms. Surgical release or even removal of the nerve may occasionally be necessary for intractable cases, but the surgical results are only fair.

Protrusio Acetabuli (Otto Pelvis)

Abnormal intrapelvic protrusion of the acetabulum is a relatively uncommon disorder that may be present on a primary basis or develop secondary to trauma or arthritis. The primary (idiopathic) form is rare. Secondary causes include osteomalacia, Paget’s disease, and neoplasia. It is characterized by abnormal deepening of the acetabulum, which allows the femoral head to be displaced further into the pelvis.

CLINICAL FEATURES

The onset is usually gradual, with progressive restriction of hip motion occurring over several years. Eventually, pain becomes a prominent symptom. Complete ankylosis of the joint frequently occurs. The roentgenogram reveals abnormal protrusion of the medial wall of the acetabulum with thinning and degenerative changes (Fig. 10-22). The underlying disorder may also be noted.

Fig. 10-22 Protrusio acetabuli. The medial acetabular wall protrudes, and the femoral head has migrated medially.

TREATMENT

If the condition is secondary, correction of the underlying disorder may be helpful. Once protrusio develops, treatment is the same as that for osteoarthritis. Surgery is usually required for disabling pain.

Dislocations of the Hip

Dislocations of the hip are the result of severe trauma and are usually posterior in direction (Fig. 10-23). They commonly result from the knee being struck while the hip and the knee are in a flexed position. This force drives the femoral head out of the joint posteriorly. These injuries are frequently associated with fractures of the posterior acetabular wall. Anterior dislocations are less common and usually result from a force on the knee with the thigh abducted. The neck of the femur impinges on the posterior rim of the acetabulum, and the head is levered out the front.

Fig. 10-23 Posterior dislocation of the hip (with fracture of acetabulum).

CLINICAL FEATURES

With posterior dislocation, the hip is characteristically held in a position of flexion and internal rotation (Fig. 10-24). All motions are painful. There may be an associated injury of the ipsilateral knee. In anterior dislocations the leg usually rests in external rotation.

Fig. 10-24 Appearance of hip dislocations. A, Anterior (hip is externally rotated). B, Posterior (hip is internally rotated).

TREATMENT

Hip dislocation is an emergency. In the dislocated position, great tension is placed on the blood supply to the femoral head, and avascular necrosis may result if the dislocation is not promptly reduced. To prevent this complication, early reduction is indicated. Weight bearing is often prohibited following reduction.

Fractures of the Hip

The femoral head receives its blood supply from vessels that course proximally up the femoral neck. Fractures that occur distal to these vessels (intertrochanteric) do not disturb the blood supply to the femoral head, but fractures that occur proximally (intracapsular) may destroy the blood supply. With disruption of the blood supply, nonunion of the fracture and avascular necrosis of the femoral head are much more common.

Intracapsular and intertrochanteric fractures are both common in the older patient and usually result from a fall on the hip. Both fractures are characterized by shortening and external rotation of the affected leg with pain in the region of the hip joint (Fig. 10-25). Osteoporosis clearly plays a significant role (see Chapter 8). Occasionally, the patient may actually fracture the femoral neck before falling, the fracture representing the completion of an insufficiency injury. Femoral neck fractures may also be occult and show up only with repeated examinations, bone scan, or MRI.

Fig. 10-25 External rotation deformity typical of hip fractures.

TREATMENT

The objective of management is the return to the pre-injury level of function as soon as possible. If external immobilization or prolonged bed rest were required in the treatment of these fractures in this age group, the mortality would be high because of pneumonia, deep vein thrombosis, and urinary tract infections. For this reason, early surgery (within 24–48 hours) is indicated to allow the patient to be out of bed at the earliest possible time. Displaced intracapsular fractures in the elderly are best treated by early prosthetic replacement (Fig. 10-26). This allows early weight bearing and eliminates the possibility of nonunion and avascular necrosis that could necessitate secondary surgical procedures. (If osteoarthritis is present, total hip replacement is often performed.) Undisplaced or impacted fractures are often treated nonoperatively or by simple internal fixation to add stability. These fractures have a much better prognosis regarding healing and avascular necrosis. Patients with fractures from low trauma events (sometimes called fragility fractures) should be evaluated for osteoporosis.

Fig. 10-26 Roentgenogram of the hip showing a displaced femoral neck fracture.

Younger patients are treated by reduction of the fracture (if needed) and internal fixation. It is best to try to preserve the femoral head in this age group if it is possible, because the long-term results are better than with prosthetic replacement in the young active patient.

Intertrochanteric fractures are treated by open reduction and internal fixation (Fig. 10-27). This allows early activity by eliminating the pain at the fracture site. Nonunion in this fracture is much less common than with the intracapsular fracture. Weight bearing is usually restricted for several weeks until union of the fracture has occurred, however.

Fig. 10-27 A, Intertrochanteric fracture of the hip. B, Following open reduction and internal fixation.

Prevention

The mortality rate within 1 year following a hip fracture in the elderly is 15% to 20%, and the incidence of hip fracture is expected to continue to increase. Although it is not possible to prevent all hip fractures, some methods may reduce the rate of these injuries. Among the considerations are (1) elimination of environmental hazards (poor lighting, loose rugs); (2) regular exercise for balance and strength; (3) patient education about fall prevention; (4) medication review to minimize side effects; (5) use of hip protector pads; (6) correction of vision problems; and (7) prevention and treatment of osteoporosis.

Nonsurgical treatment

Intertrochanteric and intracapsular fractures occasionally occur in nonambulatory patients, sometimes as a result of a fall during a transfer. These fractures are often treated nonsurgically. Early bed-to-chair mobilization and vigilant nursing care are important to prevent complications. The fracture usually becomes pain-free in a short time, and even if solid bony healing does not occur, a painless fibrous union develops with a satisfactory end result.

Occasionally, an isolated fracture of either trochanter may occur following a minor injury (Fig. 10-28). Treatment is symptomatic, with crutches and weight-bearing activity as tolerated.

Fig. 10-28 Avulsion fracture of the greater trochanter.

THE OCCULT HIP FRACTURE

Some fractures about the hip are difficult to diagnose. This is especially true of the fatigue (insufficiency) fracture of the femoral neck or pelvis. There may be no history of injury, particularly when the femoral neck is involved. Females with osteoporosis are susceptible. Vague groin pain may be present, and, as with other disorders involving the hip region, the pain may be referred down the medial thigh to the knee. In the absence of displacement, there is no deformity, and there is often full range of motion, although there is usually pain with movement, especially “log rolling” the leg in the supine patient. Weight bearing is painful as well. There may be some local tenderness. The initial roentgenograms may be negative, although a true lateral view occasionally reveals a femoral neck fracture not obvious on other views.

If the diagnosis is suspected, the patient should be admitted to the hospital and placed on non–weight-bearing status to prevent displacement of the fracture in case one is present. Bone scanning is helpful (Fig. 10-29). It may show evidence of the fracture as early as 24 hours but is often not diagnostic until 48 to 72 hours. MRI is also helpful, and although more costly, it can allow more early diagnosis and treatment. Computed tomographic scanning is also helpful. Treatment is usually surgical for femoral neck fractures to prevent displacement that could require a more complicated operation.