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LEGG-CALVÉ-PERTHES DISEASE

LEGG-CALVÉ-PERTHES DISEASE

Legg-Calvé-Perthes disease is defined as idiopathic avascular necrosis of the epiphysis of the femoral head (capital femoral epiphysis) and its associated complications in a growing child. It is a common, but poorly understood hip disorder.

The disease develops more often in boys than girls (4 or 5 : 1). It can occur between 2 and 12 years of age (mean age, 7 years); and when the involvement is bilateral, the changes usually appear in one hip at least 1 year earlier than in the other. If the child is older than 12 years of age at the time of clinical onset, the disorder is not considered true Legg-Calvé-Perthes disease but rather adolescent avascular necrosis, which has a poor prognosis similar to that of the adult form.

 

LEGG-CALVÉ-PERTHES DISEASE: PATHOGENESIS
LEGG-CALVÉ-PERTHES DISEASE: PATHOGENESIS

PREDISPOSING FACTORS

Genetic Aspects

The incidence of Legg-Calvé-Perthes disease is 1% to 20% higher in families of involved children, although there is no consistent pattern of inheritance. Studies in England have indicated that affected children are more likely than normal children to have low birth weight, abnormal birth presentation (breech and transverse presentations), and older parents. The disease is also more prevalent in later-born children (particularly the third to the sixth child).

The disorder occurs more frequently in Asian, Eskimo, and Central European populations, whereas the incidence is decreased in blacks, Australian aborigines, American Indians, and Polynesians.

The English studies have also demonstrated a higher than normal incidence of minor congenital genitourinary anomalies (e.g., renal abnormalities, inguinal hernias, and undescended testes) in affected children as well as in their first-degree relatives.

Abnormal Growth and Development

Legg-Calvé-Perthes disease may be a manifestation of an unknown systemic disorder rather than an isolated abnormality of the hip joint. The bone age of affected children is typically 1 to 3 years lower than their chronologic age. As a consequence, affected children are usually shorter than their peers, and the shortness of stature, although slight, persists into adulthood.

Disproportionate growth, abnormalities in skeletal growth and maturation, and elevated serum levels of somatomedin have been demonstrated. Affected children are typically smaller in all dimensions except head circumference, and their limbs have disproportionately small distal segments. The relationship between growth abnormalities, serum somatomedin, and ischemia of the epiphysis of the femoral head remains obscure. However, these findings support the concept of an underlying systemic disorder.

Environmental Factors

Although the effect of environment on the incidence is not clear, a large number of affected children in England are from lower socioeconomic groups. Whether this reflects dietary or en ironmental influences or a combination is not clear.

 

ETIOLOGY AND PATHOGENESIS

The etiology of Legg-Calvé-Perthes disease is not yet understood, but it is accepted that the avascular necrosis is due to an interruption of the blood supply to the epiphysis of the femoral head, especially the contributions from the superior and inferior retinacular arteries. Current etiologic theories include trauma to the retinacular vessels, vascular occlusion secondary to increased intracapsular pressure from acute transient synovitis, venous obstruction with secondary intra-epiphyseal thrombosis, vascular irregularities (congenital or developmental), and increased blood viscosity resulting in stasis and decreased blood flow.

Although the cause remains unclear, numerous studies have delineated the pathogenesis of Legg-Calvé-Perthes disease. Initially, an ischemic episode of unknown etiology occurs, rendering most, if not all, of the epiphysis avascular (see Plate 2-31). Endochondral ossification in the preosseous epiphyseal cartilage and

growth plate ceases temporarily, while the articular cartilage, which is nourished by synovial fluid, continues to grow. This results in the radiographic appearance of a widened medial cartilage (joint) space and a smaller ossification center in the involved hip. This is the first radiographic manifestation, and it precedes any change in the density of the epiphysis. At this stage, the marrow space of the epiphysis is necrotic.

Revascularization of the structurally intact but avascular epiphysis occurs from the periphery as new capillaries recanalize the previous vascular channels. Resumption of endochondral ossification within the epiphysis begins peripherally and progresses centrally. With the ingrowth of capillaries, osteoclasts and osteoblasts cover the surface of the avascular subchondral cortical bone and the central trabecular bone. New bone is deposited on the avascular bone, producing a net increase in bone mass per unit area; this accounts for the increased density of the epiphysis that is apparent on radiographs taken in early stages of the disease. The deposition of new trabecular bone and resorption of avascular bone occur simultaneously. In the subchondral area, bone resorption exceeds new bone formation. A critical point is reached during resorption when the subchondral area becomes biomechanically weak and therefore susceptible to a pathologic fracture. Up to this point, the disease process is clinically silent and asymptomatic. The continuation of this “potential” form of Legg-Calvé-Perthes disease or the development of the “true” form depends on whether a sub-chondral fracture occurs.

In the potential form of the disease, a subchondral fracture does not occur because the stresses and shearing forces acting on the revascularized epiphysis of the femoral head do not exceed the strength of the weakened subchondral area. The reossification process continues uninterrupted, with ultimate resumption of normal growth and development. Thus, there is no epiphyseal resorption, no extrusion or subluxation of the femoral head, and no potential for deformity. The child remains asymptomatic and retains a good range of motion in the hip joint. The subchondral area eventually regains its normal strength and stability, and a “head-within-a-head” is visible on radiographs. The head-within-a-head represents a growth arrest line that outlines the ossification center at the time of the initial infarction.

In the true form of the disease, the strength of the weakened subchondral area is exceeded and a pathologic subchondral fracture occurs (see Plate 2-31). The magnitude of stress or trauma necessary to produce such a fracture is difficult to quantitate and appears to vary both with the degree of preexisting weakness and the applied shearing forces. In most cases, the fracture seems to result from normal vigorous activity rather than from a specific injury. The painful subchondral fracture heralds the clinical onset of true Legg-Calvé- Perthes disease, and only the true form produces the typical clinical and radiographic features and requires 2 to 4 years, or even longer, for complete healing to occur.

LEGG-CALVÉ-PERTHES DISEASE: PHYSICAL EXAMINATION
LEGG-CALVÉ-PERTHES DISEASE: PHYSICAL EXAMINATION


Changes in Epiphysis

The subchondral fracture characteristically begins in the anterolateral aspect of the epiphysis near the growth plate, because this area receives the greatest concentration of stress during weight bearing. The pathologic fracture extends superiorly and posteriorly until it reaches areas where the strength of the remaining sub- chondral bone exceeds the shearing forces acting on the femoral head. There is minimal, if any, extension of the subchondral fracture after the initial fracture. The reasons for this are not clear, but presumably the resulting pain causes the child to be less active, thereby reducing the stress on the femoral head.

The revascularized trabecular bone beneath the sub-chondral fracture undergoes a second episode of local ischemia secondary to trabecular collapse and occlusion of the ingrowing capillaries. This second ischemic episode, mechanical in origin, involves either part or all of the epiphysis, depending on the extent of the sub-chondral fracture. The structural stability of the epiphysis is lost; the ingrowth of new capillaries is impeded by the obliteration of the vascular channels and the presence of fractured bone (both cortical and trabecular) and marrow debris. Consequently, the entire area is slowly revascularized, with resorption of the fibro- osseous tissue, by a process termed creeping substitution. In this reparative process, the avascular bone is slowly resorbed from the periphery of the area of the second infarction and replaced by vascular fibrous tissue that, in turn, is eventually replaced by primary trabecular bone.

During the process of creeping substitution, the femoral head, while not soft in the physical sense, can be molded into a round or flat shape by the forces acting on it. This remodeling property, or biologic plasticity, lasts until subchondral reossification begins. Potential deformities may be caused by the different rates of growth within the femoral head—areas not undergoing resorption grow faster than the involved area. The combined factors of pressure and asymmetric growth result in a potential for extrusion and subluxation of the femoral head and eventual deformity. Thus, true Legg-Calvé-Perthes disease is actually a complication of avascular necrosis.

Secondary alterations in the growth plate and metaphysis also occur and can lead to further disturbances in endochondral ossification and growth in the proximal femur.

Changes in Growth Plate

Because the blood supply to the growth plate comes from the epiphyseal side, the two ischemic episodes also produce ischemic changes in the growth plate. The chondrocyte columns become distorted with some loss of their cellular components; they do not undergo normal ossification, which results in an excess of calcified cartilage in the primary trabecular bone.

LEGG-CALVÉ-PERTHES DISEASE: PHYSICAL EXAMINATION (CONTINUED)
LEGG-CALVÉ-PERTHES DISEASE: PHYSICAL EXAMINATION (CONTINUED)


Changes in Metaphysis

Four types of metaphyseal changes have been noted: presence of adipose tissue, osteolytic lesions (well-circumscribed areas of fibrocartilage), disorganized ossification, and extrusion of the growth plate. Whereas only adipose tissue changes are detected early in the disease, osteolytic lesions are seen in the later stages. When these fibrocartilaginous lesions are in contact with the growth plate, the normal architecture of the growth plate is lost and the lesions appear on radiographs as cysts. In the areas without osteolytic lesions, ossification is disorganized and bars, or columns, of unossified cartilage appear to “stream” or “flow” down into the metaphysis. Necrosis of bone is not seen in the metaphysis. In some severely deformed femoral heads, the growth plate extrudes down the sides of the femoral neck.

The changes in the growth plate and metaphysis ultimately alter the growth in length of the proximal femur and produce the short, thick femoral neck (coxa vara) and enlarged femoral head (coxa magna) typically seen in Legg-Calvé-Perthes disease. The greater trochanter, being uninvolved, continues to grow and may eventually rise above the level of the femoral head. The combination of a short femoral neck and a high greater trochanter is considered “functional” coxa vara. The performance of the hip abductor (gluteus medius) muscles is disturbed, with a resultant limp or Trendelenburg gait and a positive Trendelenburg test (see Plate 2-32). The short femoral neck also produces a lower limb-length discrepancy of 1 to 2 cm.

 

CLINICAL MANIFESTATIONS

The pertinent early findings include antalgic gait, muscle spasm and restricted hip motion, atrophy of the proximal thigh, and short stature. A small percentage of children have a history of trauma that is usually mild. Nevertheless, such trauma may be sufficient to produce the pathologic subchondral fracture.

Initial symptoms are mild and intermittent pain in the anterior thigh or a limp, or both. Although many children do not complain of pain, on close questioning most admit to mild pain either in the anterior thigh or the knee. The onset of pain may be acute or insidious. Referred pain from the hip to the anterior thigh or knee must be considered. Because the child’s initial symptoms are typically mild, parents frequently do not seek medical attention for several weeks after clinical onset, or longer.

Antalgic gait is noted when the patient shortens the time of weight bearing on the involved limb during walking to reduce discomfort. Pain from the irritable hip can also cause reflex inhibition of the hip abductor muscles with a resultant positive Trendelenburg test, a common early sign (see Plate 2-32).

Muscle spasm is best detected by the “roll” test, a painless test that reveals any guarding or muscle spasm (secondary to irritability of the hip joint), especially when the involved limb is rolled inward (see Plate 2-32). Once the child’s confidence is gained, the hip can usually be examined more thoroughly to determine the complete range of motion. Mild limitation of motion, particularly abduction and internal rotation, is the typical finding. This may be best elucidated by noting asymmetry in both abduction and internal rotation. There may also be limitation of extension, as evidenced by a mild hip flexion contracture (Thomas sign), as well as deep tenderness over the anterior aspect of the hip. Disuse atrophy of the proximal thigh muscles is a consequence of prolonged hip irritability and the resultant limitation of motion. The atrophic thigh is usually 2 to 3 cm smaller, especially during the early symptomatic phases. As the symptoms subside, the atrophy resolves. Short stature due to delayed bone age is another typical finding in affected children. The patient’s bone age can be determined with the Greulich and Pyle atlas. Results of laboratory tests are normal, except for an occasionally abnormal erythrocyte sedimentation rate, which may be slightly elevated (30 to 40 mm/hr).

 

STAGES OF LEGG-CALVÉ-PERTHES DISEASE
STAGES OF LEGG-CALVÉ-PERTHES DISEASE

RADIOGRAPHIC EVALUATION

Routine radiographic assessment is essential for diagnosis and for determining progression of the disease, sphericity of the femoral head, possibility of epiphyseal extrusion or collapse, and response to treatment. Arthrography is a useful adjunct, especially in the setting of the operating room to best define the true sphericity, or lack thereof, of the femoral head. Magnetic resonance imaging (MRI) can also be helpful in rare cases, and radionuclide bone scanning currently plays a very limited role.

The entire disease process can usually be assessed from plain anteroposterior and Lauenstein frog-leg radiographs of the pelvis (both hips). Extrusion and subluxation of the femoral head can be measured on these radiographs using the Wiberg center-edge angle. An extrusion index developed by Green and associates has been demonstrated to be prognostically significant. Sphericity of the femoral head in the reossification and healed stages is currently best determined by the Mose circle criteria. In this technique, a transparent template with concentric circles at 2-mm intervals, placed on both anteroposterior and frog-leg radiographs, is centered over the femoral head to measure both the sphericity and diameter of the femoral head. If the sphericity is equal in both projections, the hip is rated “good.” A variance of up to 2 mm is rated “fair,” whereas a variance of 3 mm or more is rated “poor.” The good and fair ratings are considered satisfactory results, whereas poor ratings are unsatisfactory. Sphericity may improve with growth and development if the healed femoral head remains well contained in the acetabulum.

Computerized methods are being investigated to allow better objective quantification of hip joint architecture and for plotting changes in configuration that occur with time.

Early in the resorption stage, arthrography may be required to assess the sphericity of the articular surface of the femoral head. The contour of the partially resorbed ossification center of the epiphysis may not reflect the contour of the articular surface, and range of motion in the hip is usually the best indicator of potential femoral head deformity. Only “questionable” hips require arthrography.

Bone scans have largely been replaced by MRI. MRI is helpful in defining epiphyseal infarction and the contours of the femoral head, both of which are prognostically significant. Like radionuclide bone scans, MRI does not correlate with the extent of epiphyseal involvement.

 

LEGG-CALVÉ-PERTHES DISEASE: LATERAL PILLAR CLASSIFICATION
LEGG-CALVÉ-PERTHES DISEASE: LATERAL PILLAR CLASSIFICATION

STAGES OF DISEASE

Radiographic evaluation has determined five distinct stages of Legg-Calvé-Perthes disease, which represent a continuum of the disease process.

Growth Arrest

This stage occurs immediately after the initial ischemic episode in the femoral head, when endochondral ossification of the preosseous cartilage ceases. During this avascular phase, which may last 6 to 12 months, there is a slight but progressive difference in the size (height and width) of the involved epiphysis and that of the opposite normal hip. The joint space also appears to be wider because of the continued growth of the articular cartilage. These relatively small differences (1 to 3 mm) are visible and measurable on an anteroposterior radio- graph of the pelvis. Toward the end of this stage, epiphyseal density increases. During this stage, which is only potential Legg-Calvé-Perthes disease, the disease is clinically silent and asymptomatic.

Subchondral Fracture

The subchondral fracture initiates true Legg-Calvé- Perthes disease. Radiographic visibility of the fracture varies with the age of the patient at clinical onset and the extent of epiphyseal involvement. The duration varies from an average of 3 months in children 4 years of age or younger to 812 months in children 10 years or older.

Resorption

In this stage, also called fragmentation or necrosis, the necrotic bone beneath the subchondral fracture is gradually and irregularly resorbed. This process produces the radiographic appearance of fragmentation because the bone is resorbed and replaced by vascular fibrous tissue (creeping substitution) and later by primary bone. The resorption phase lasts 6 to 12 months and is longest when there is extensive epiphyseal involvement or when the child is 10 years of age or older at clinical onset. This phase is usually complete 12 to 17 months after clinical onset.

Reossification

During the healing, or reossification, stage, ossification of the primary bone begins irregularly in the subchondral area and progresses centrally. Eventually, the newly formed areas of bone coalesce and the epiphysis progressively regains its normal strength. Reossification takes 6 to 24 months.

Healed Stage

The healed, or residual, stage signals the complete ossification of the epiphysis of the femoral head, with or without residual deformity.

 

CLASSIFICATION

There have been many classification systems developed to describe the disease process. Most such as the Catterall and Salter-Thompson classification systems are helpful retrospectively but have had little prognostic value. The lateral pillar classification system is currently the most widely used and valuable classification system because it has been shown to have some prognostic significance.

The lateral pillar classification system developed by Hering and colleagues separates diseased hips into three groups (A, B, and C) on the basis of the remaining height of the lateral third of the femoral head. Group A hips have maintenance of 100% of the lateral pillar height. These have the best prognosis long term and are least likely to extrude. Group B hips have decreased lateral pillar height but have at least 50% of the lateral pillar height remaining. Group C hips have less than 50% of the lateral pillar height remaining and have an almost uniformly poor prognosis.

 

LEGG-CALVÉ-PERTHES DISEASE: CONSERVATIVE MANAGEMENT
LEGG-CALVÉ-PERTHES DISEASE: CONSERVATIVE MANAGEMENT

PROGNOSIS

The short-term prognosis for patients with Legg-Calvé-Perthes disease focuses on femoral head deformity at the completion of the healing stage. The long-term prognosis involves the potential for secondary osteoarthritis of the hip in adulthood.

Deformity of Femoral Head

The ultimate goal of treatment is a spherical femoral head at the completion of growth. Six factors determine the potential for femoral head deformity.

1.   Sex of patient. In general, the outcome is less favorable in girls than in boys. Involvement of the femoral head is often more extensive in girls; and because they mature earlier than boys, there is less remaining skeletal growth from the time of clinical onset and consequently less opportunity for epiphyseal remodeling.

2.  Age at clinical onset. The older the child at clinical onset, the less favorable the prognosis, particularly in children 10 years of age and older. This may also be related to the reduced remaining skeletal growth and potential for femoral head remodeling in older children.

3. Extent of epiphyseal involvement. More extensive involvement is correlated with a poorer prognosis.

4. Containment of femoral head. Extrusion, subluxation, or asymmetric growth of the femoral head increases the stress concentrated on it during weight bearing. The ability to maintain the femoral head well within the acetabulum with appropriate treatment is a significant factor for a favorable prognosis.

5.  Persistent loss of motion. This is usually due to either muscle spasm (adductors or iliopsoas muscle), muscle contractures, anterolateral extrusion or subluxation of the femoral head, or a com- bination thereof. The loss of motion prevents adequate remodeling of the femoral head by the acetabulum.

6.  growth plate. When involvement of the epiphysis is extensive (lateral pillar group C), the growth plate may be sufficiently damaged to cause premature closure. This can result in asymmetric growth and inadequate remodeling that contributes to femoral head deformity, greater trochanteric overgrowth (functional coxa vara), and a lower limb-length discrepancy.

Late Degenerative Osteoarthritis

The incidence of late degenerative osteoarthritis depends on residual deformity of the femoral head and the patient’s age at clinical onset. The risk is directly correlated with the extent of residual deformity. Three types of congruency between the femoral head and the acetabulum have been classified: spherical congruency, aspherical congruency, and aspherical incongruency. Spherical congruency is not associated with osteoarthritis, whereas aspherical congruency predisposes to mild-to-moderate osteoarthritis in late adult-hood. Patients with aspherical incongruency usually develop degenerative osteoarthritis before age 50.

Studies also show that the incidence of osteoarthritis of the hip in adults with deformed femoral heads is negligible in patients 5 years of age or younger at the time of clinical onset, 38% in patients 6 to 9 years of age, and 100% in patients 10 years of age or older. Aspherical incongruency, a predisposing factor for osteoarthritis, is also more likely to develop in children who are older at the time of clinical onset.

Thus, of the two significant factors in the longterm prognosis, only femoral head deformity may be preventable, or at least altered, by appropriate treatment.

 

FEMORAL VARUS DEROTATIONAL OSTEOTOMY
FEMORAL VARUS DEROTATIONAL OSTEOTOMY

TREATMENT

The only justification for treatment is prevention of femoral head deformity and secondary osteoarthritis. When indicated, treatment should interfere as little as possible with the child’s psychological and physical development.

The four basic goals of treatment are to eliminate hip irritability, restore and maintain a good range of hip motion, prevent femoral head extrusion and sub-luxation, and attain a spherical femoral head on healing.

Elimination of Hip Irritability

After the subchondral fracture, the synovium becomes inflamed and the hip irritable. The associated pain and muscle spasm lead to the restriction of motion followed by muscle contractures, especially of the adductor and iliopsoas muscles, and possible anterolateral extrusion or subluxation of the femoral head. Elimination of this irritability is always the first objective and is usually accomplished by rest and scheduled anti-inflammatory medications. Non–weight bearing for brief periods may also help the symptoms of irritability, and crutches or other aids can be helpful if the child is able to use them.

Restoration and Maintenance of Motion Generally, satisfactory range of motion in the hip returns as the hip irritability is eliminated, although residual stiffness may persist in some children. Physical therapy with passive and active range-of-motion exercises helps to restore motion, but gentle progressive-abduction traction, especially at night, is occasionally required. To maintain hip motion, a program consisting of abduction and internal rotation stretching exercises may be helpful.

Regardless of the sphericity of the femoral head, almost all children with lateral pillar group C involvement show a slight but persistent loss of abduction and internal rotation due to mild coxa magna.

Prevention of Femoral Head Collapse Extrusion or subluxation of the femoral head increases the risk of epiphyseal collapse and subsequent deformity. Radiographic evidence of extrusion is therefore a prognostic factor and an indication for treatment.

Attainment of Spherical Femoral Head

This goal requires a full understanding of the pathogenesis and prognostic factors associated with deformity of the femoral head as well as the appropriate management techniques.

 

CONCEPTS OF CONTAINMENT

Until the 1960s, treatment for Legg-Calvé-Perthes disease was complete and prolonged bed rest—with or without traction or abduction of the involved limb—and the use of so-called weight-relieving devices. All children were treated, and treatment often lasted 2 to 4 years. Containment techniques have been devised to permit weight bearing while redirecting the compressive forces on the femoral head to assist in the healing and remodeling process. The currently accepted forms of management range from observation to surgery.

Observation

Appropriate treatment of all children who are younger than 6 years of age at clinical onset regardless of the extent of epiphyseal involvement is by observation only, provided there is no limitation of hip motion and no subluxation. Observation is also appropriate for children 6 years of age or older with lateral pillar A and some lateral pillar B involvement who have a good range of hip motion and no radiographic evidence of femoral head extrusion or collapse.

Intermittent Symptomatic Treatment

Temporary or periodic bed rest and abduction stretching exercises can be used in conjunction with observation. Hip irritability with a temporary decrease in motion often recurs during the subchondral fracture and resorption phases. If these symptoms persist and there is no radiographic evidence of femoral head extrusion, rest and protected weight bearing for 1 to 2 weeks sometimes may be necessary. Two or three recurrent episodes of irritability may indicate the need for a short period (1 to 2 months) of nonsurgical containment to decrease the risk of extrusion. Radiographs should be taken at 2- to 4-month intervals to ensure that the irritability is not due to early deformity of the femoral head.

INNOMINATE OSTEOTOMY
INNOMINATE OSTEOTOMY


Definitive Early Treatment

Nonsurgical or surgical containment of the femoral head early in the disease is indicated in children 6 years of age or older at clinical onset—possibly in girls 5 years of age or older—who have lateral pillar group B or B/C border involvement or when femoral head extrusion is seen on the weight-bearing anteroposterior radiograph.

Use of containment techniques requires a good-to-full range of hip motion (especially abduction), no residual irritability, and a round or almost round femoral head. Containment methods, whether nonsurgical or surgical, appear to increase satisfactory results (most good and fair) by 16% to 20% compared with no treatment or natural history.

Nonsurgical containment refers to the use of abduction casts (Petrie) or occasionally an orthosis to abduct the involved limb and redirect the femoral head within the acetabulum (see Plate 2-36). The Petrie cast fixes the lower limbs in 30 to 40 degrees of abduction with an approximate 5-degree internal rotation. The cast provides continuous containment because it cannot be removed by either the child or the parents. Disadvantages include stiffness of the knee and ankle joints with adaptive articular changes, significant restriction in ambulation, frequent need for change and repair, and excessive weight. Petrie casts are now reserved for management after surgical adductor lengthening to improve and maintain motion in abduction, therefore “containing” the joint.

Abduction braces are lighter and less cumbersome than casts, but they are quite expensive. Also, because they are removable, compliance may not be consistent. Their use is now largely historical. The Atlanta Scottish Rite Children’s Hospital brace and Salter stirrup provided temporary nonsurgical containment.

Surgical containment has three major advantages: (1) the period of restriction is less than 2 months, after which the child may gradually return to full activity; (2) the femoral head containment is permanent; and (3) the permanent improvement in containment continues to enhance remodeling of the healed femoral head long after the active phase of disease is over. Surgery does not alter the length of the disease process or provide a cure, but it does provide satisfactory results in the great majority of patients.

Treatment with femoral varus derotational osteotomy usually involves a varus angulation of the proximal femur, with or without rotation, to redirect the femoral head into the acetabulum (see Plate 2-37). The varus angulation should be no greater than 110 degrees but should allow containment of the epiphysis of the femoral head within a vertical (Perkin’s) line drawn on the radiograph at the lateral margin of the acetabulum; some surgeons also recommend 10 to 15 degrees of internal rotation of the proximal segment. The osteotomy is usually held securely with threaded screws and a side plate or blade plate. Femoral osteotomy, while a technically less demanding procedure than innominate osteotomy, produces some inherent problems, mainly the increase in lower limb-length discrepancy, potential coxa vara, and Trendelenburg gait. In addition, the metal fixation device should be removed and there is a small risk of fracture of the proximal femur through the screw holes. The limb shortening associated with femoral osteotomy usually resolves in younger children and in patients who achieve satisfactory results.

In 1962, Salter began to treat older children with more severe forms of the disease with innominate osteotomy (see Plate 2-38), which is a technically more difficult procedure than femoral osteotomy. However, its advantages include better anterior and lateral coverage of the femoral head, no further shortening of the femoral neck (coxa breva), no increase in limb-length discrepancy (it actually lengthens the lower limb by about 1 cm), and improvement of the Trendelenburg gait. Also, removal of fixation devices is easier and there is no risk of fracture of the proximal femur. The triple innominate osteotomy has also been utilized for containment. The Salter innominate osteotomy can be combined with a proximal femoral osteotomy for additional containment. Although even more technically demanding than the Salter innominate osteotomy, the triple innominate osteotomy provides significantly more containment when needed, without the disadvantages of the proximal femoral procedure (varus, limp, and Trendelenburg gait and implant removal).

INNOMINATE OSTEOTOMY (CONTINUED)
INNOMINATE OSTEOTOMY (CONTINUED)


Late Surgical Management for Deformity

If a significant deformity prevents reduction of the femoral head into the acetabulum or remodeling after treatment with standard containment methods, an alternative must be considered. Several surgical procedures at least partially correct the various existing deformities, thereby alleviating the associated symptoms. These are salvage procedures that can alleviate symptoms but do not favorably alter the natural history of the disease.

Proximal femoral valgus osteotomy is employed when the radiograph demonstrates that hip joint congruency is better when the extended hip is adducted. The biomechanics of the hip joint are improved by this procedure in which the greater trochanter is moved distally as well as laterally, thus enhancing the strength of the abductor muscles as well as increasing the range of abduction of the lower limb.

Premature closure of the epiphysis of the femoral head can occur in advanced forms of the disease, resulting in shortening of the femoral neck and progressive overgrowth of the greater trochanter. Advancing the greater trochanter distally and laterally relieves muscle pain and decreases or eliminates the characteristic Trendelenburg gait. Lateral displacement of the greater trochanter can also decrease the pressure between the femoral head and the acetabulum and may minimize the risk of late degenerative osteoarthritis.

In addition to the proximal femoral valgus osteotomy, a Chiari osteotomy or shelf osteotomy may produce improved coverage of the femoral head and reduction of symptoms. These procedures are, again, salvage procedures that are designed to reduce the short-term symptoms, but unfortunately do not seem to alter the natural history of severe Legg-Calvé-Perthes disease, which is ultimately early arthrosis of the joint.

Late Surgical Management for

Degenerative Osteoarthritis

Significant degenerative osteoarthritis in adults is usually managed by total hip replacement.

The prognosis for children with Legg-Calvé-Perthes disease is much better now than in the past. Active treatment is not always required, and many patients need only careful observation or intermittent symptomatic treatment. A variety of nonsurgical and surgical containment techniques are available that produce equally good long-term results. When surgical treatment is required, it restricts the child for relatively short period of time, thus reducing the potential for psycho- logical problems.

Further studies will concentrate more on the etiology of Legg-Calvé-Perthes disease than on better treatment. Only greater understanding of the disease can provide the means for eliminating it or significantly altering its course.