Osteochondroses

7.1 Anatomy, Etiology, and Pathogenesis

Anatomy. See Chapter 7.1 for anatomy ( Fig. W7.1).

“Osteochondrosis” is a very general term which, strictly speaking, means nothing other than “disorder of cartilage and bone” (Greek -osis = process or condition). The decisive feature is involvement of bone and cartilage in the epiphysis, apophysis, and growth plate of the growing skeleton. It is considered probable that a failure of blood supply sets off a disturbance of enchondral ossification. Osteochondrosis has nothing to do with acute injury to the growth cartilage.

7.1.1 What Do the Different Forms of Osteochondrosis Have in Common?

They develop primarily in children and adolescents during the growth phase. Risk factors play an important role in osteochondrosis:

• Inheritance: This is supported by the presence of osteochondroses in members of one family or in twins.

• “Metabolic” and “hormonal” changes: Although difficult to define, these alterations must also play a role. Thus, osteochondrosis develops in particular in growth-delayed children (especially boys) or in children with congenital skeletal dysplasias. Osteochondrosis is also seen particularly during strong growth spurts.

• Anatomy: This appears to play a role. Certain bones and joints may be affected because of some incongruence of the joint surfaces leading to abnormal forces at those sites. Children with a congenitally abnormal discoid meniscus are more commonly affected with osteochondritis dissecans than other children. Similarly, osteochondrosis of the elbow develops much more commonly in the capitulum than in the trochlea.

Osteochondrosis is a disease and not a normal variant of ossification, but it is striking that the sites of predilection for variants coincide with locations of osteochondrosis.

Osteochondrosis appears in many epiphyses and apophyses as well as in the region of the growth plate. There are currently approximately 75 known entities and most are named after those who first reported them. For good reasons, osteochondritis dissecans is assigned to the articular osteochondroses in this book. Table 7.1 intentionally specifies only the most important disorders; for other disorders see References for Chapter 7.1.

Table 7.1 Classification of the osteochondroses based on Siffert

Description		Location
Articular (epiphyseal) osteochondroses	Legg–Calvé–Perthes’ disease	Femoral head
	Freiberg’s disease (Köhler’s disease Type II)	Metatarsal heads II–IV
	Köhler’s disease Type I	Navicular bone
	Panner’s disease	Humeral capitellum
	Osteochondritis dissecans	Any joint, especially knee, talus, and elbow
Nonarticular (apophyseal) osteochondroses	Osgood–Schlatter disease	Tibial tuberosity
	Sinding–Larsen–Johansson disease	Inferior patellar pole
	Sever’s disease	Calcaneal apophysis
Osteochondroses of the growth plate	Scheuermann’s disease	Hyaline cartilage end plate, and subchondral superior end plate of the spine
Osteochondroses of the growth plate	Blount’s disease	Medial part of the proximal tibial epiphysis

7.1.2 To Which Disorders is the Term “Osteochondrosis” Not Applicable?

Of course, the cartilage and subchondral bone may also be affected in adults, but there is usually a history of some form of injury. For this reason, the following common cases are not assigned to the osteochondroses:

• Posttraumatic osteoarthritis.

• Posttraumatic osteonecrosis (e.g., of the talar dome).

These are usually secondary to a fracture involving the articular surfaces (e.g., intra-articular radial fracture or osteochondral fracture).

7.2 Articular Osteochondroses

7.2.1 Perthes’ Disease

Perthes’ disease (synonym: Legg–Calvé–Perthes’ disease) is an osteochondrosis of the femoral head. Its etiology remains unclear; its pathogenesis is slowly becoming understood. Perthes’ disease has a self-limiting clinical course that proceeds in stages and carries a risk of incomplete recovery.

Pathology. It is not known why the vessels supplying the femoral head fail. It also remains unclear whether one or several ischemic attacks are required to initiate the disease. The concept of “osteonecrosis” does not go far enough; in this condition, the epiphyseal cartilage, the ossification center of the epiphysis, the growth plate, and even the metaphysis are all affected. The necrotic ossification center is extremely vulnerable to mechanical loading and there is an imbalance between bone degradation and regeneration. The disorder is self-limiting; spontaneous revascularization occurs.

There are four characteristic stages:

• Early stage: Cell death in the bony epiphysis, resulting in the development of microfractures. The deep layer of the epiphyseal cartilage becomes necrotic and enchondral ossification ceases.

• Condensation stage: Condensation and narrowing of the ossified epiphysis. The cartilage undergoes early revascularization and becomes hypertrophic.

• Fragmentation stage: Fibrotic bony remodeling and trabecular absorption result in an unstable structure with fragmentation and further reduction in size of the bony epiphysis. Epiphyseal contour deformity and exuberant growth of the epiphyseal cartilage lead to decentralization of the femoral head and thus to lateral subluxation. Concomitant involvement of the metaphysis leads to widening and shortening of the femoral neck.

• Regeneration phase: Revascularization of the femoral head occurs with new bone formation, usually associated with incomplete recovery, though rarely with complete restoration.

Clinical presentation. The disorder presents between the ages of 3 and 12 years, with a peak between the ages of 5 and 6 years. The cardinal symptom is a limp. The signs and symptoms in the early stage are indistinguishable from transient synovitis. The prognosis of Perthes’ disease depends on early detection.

Fig. 7.1 Perthes disease. Initial stage. (a) Very subtle alterations on the AP image. (b) Typical subchondral fracture on the frog lateral view.

Fig. 7.3 Perthes’ disease. Fragmentation stage. As well as the fragmentation, flattening of the epiphysis is typical for this stage.

Fig. 7.2 Radiological course of Perthes’ disease. (a) Condensation stage. (b) Healthy contralateral side for comparison. (c) Fragmentation stage. (d) Final stage with remodeling, flattening, and lateralization of the femoral head.

Radiography/CT. Radiographic diagnostic examinations are inadequate during the early stage. However, over the course of the disease, AP and frog-leg lateral views are helpful for establishing the diagnosis and determining prognosis. Classification of the radiographic abnormalities is based on the disease course outlined above. The use of 3D-reconstruction CT is primarily reserved for operative planning.

• Initial stage: Minimal radiographic signs:

Joint-space widening.

Periarticular soft-tissue swelling.

Subtle irregularity of structure and contour of the epiphysis ( Fig. 7.1).

• Condensation stage: Increased density and decreased size of the bony epiphysis ( Figs. 7.2a and 7.2b).

• Fragmentation stage: Decreased size and fragmentation of the epiphysis ( Figs. 7.2c–7.5 and W7.2).

• Regeneration stage ( Figs. 7.6, 7.7, and W7.3):

Fusion of the ossification centers with a tendency for remodeling of the bone.

Irregular widening of the physeal plate; later premature physeal closure as a result of epiphyseal–metaphyseal bridging.

Metaphyseal involvement with radiolucent bands, densities, and cystic lesions.

• Final stage ( Figs. 7.2d and 7.8):

Complete restoration or

Widening, flattening, and subluxation of the femoral head (mushroom deformity, “coxa plana”) with secondary acetabular hypoplasia (predisposition for degenerative osteoarthritis, see Fig. 7.8).

Widening of the metaphysis and shortening of the femoral neck.

Fig. 7.4 Perthes’ disease. Fragmentation stage. (a) Fragmentation and flattening of the epiphysis. (b) The fragmentation does not involve the entire epiphysis.

Fig. 7.5 Perthes’ disease. Fragmentation stage ( see also Fig. W7.2).

Fig. 7.6 Perthes’ disease. Regeneration stage. Lateral calcification of the epiphyseal plate and the metaphyseal cysts are regarded as head-at-risk signs and suggest a poor prognosis.

Fig. 7.7 Perthes’ disease. Regeneration stage ( see also Fig. W7.3).

Fig. 7.8 Perthes’ disease. Final stage. As well as the mushroom deformity of the femoral head (pre-osteoarthritis), this example also demonstrates a large defect in the femoral head.

The Catterall Classification ( Fig. 7.9) provides prognostic information for possible surgical intervention. Stages III and IV represent severe forms in which more than one-half of the femoral head is involved. In addition, these prognostically unfavorable radiological signs (head-at-risk signs) should also be reported:

• Decentralization of the femoral head in a lateral direction ( Fig. 7.4a).

• Lateral calcification of the physeal plate ( Figs. 7.5 and 7.6).

• Metaphyseal involvement ( Figs. 7.5 and 7.6).

• Horizontalization of the physeal plate.

The final stage may be further classified according to Stulberg and co-workers ( see References for Chapter 7.2.1).

US. Ultrasound provides confirmation of a joint effusion.

MRI. In the initial stage, MRI allows an early diagnosis with evidence of bone marrow edema in the ossification center of the epiphysis while the radiograph is still unremarkable ( Fig. 7.10a, b). Coronal fat-suppressed, fluid-sensitive, and coronal and sagittal T1W sequences are useful for diagnosis. In the presence of bone marrow edema, an additional fat-suppressed, contrast-enhanced T1W sequence, or even better a dynamic contrast MRI, is helpful for determining the stage (early stage, revascularization stage) and for early detection of compromised perfusion ( Fig. 7.11).

Serial MRI examinations reveal development of the necrotic area and hypertrophy of the epiphyseal cartilage and, thus, the decentralization of the epiphysis within the acetabulum. The final stage shows fat-equivalent signal ( Fig. 7.10c) or—depending on the severity of the course—increased sclerosis with loss of signal.

Functional MRI (neutral position, abduction and internal rotation) is helpful for preoperative planning in the incomplete recovery phase in order to document the degree of incongruence and risk of impingement between acetabulum and deformed femoral head.

NUC MED. Bone scan is sensitive during the early stages by detecting absent or reduced tracer uptake in the anterolateral portion of the femoral head. However, it has been largely replaced by MRI.

DD.

Transient synovitis and synovitis of other etiologies. MRI is helpful to further investigate equivocal radiographic findings and/or laboratory findings and the detection of a joint effusion on ultrasound.

Other origins of osteonecrosis of the femoral head. Simultaneous development of bilateral osteonecrosis of the femoral heads suggests a systemic disease (sickle cell anemia, hypothyroidism, Gaucher’s disease).

Meyer dysplasia. This is associated with delayed, irregular ossification of the femoral head that results in multiple ossification centers. If the clinical and radiological findings are unclear, differentiation can be achieved using MRI.

Fig. 7.9 Classification of Perthes’ disease according to Catterall.

Fig. 7.10 Monitoring of disease progression in a case of left-sided Perthes’ disease. (a) Early stage. (b) Eventually, there is complete loss of signal. (c) Finally, fatty marrow evident in the center and reactive deposition of fatty marrow in the metaphysis. (d) Contrast enhancement in the medial part of the epiphysis as a sign of repair.

Fig. 7.11 Early diagnosis of Perthes’ disease in the initial stage. (Courtesy of M. Anderson, Charlottesville, Virginia, USA.) (a) No definite detection of edema on the T1W image. (b) However, there is evidence of compromise of perfusion of the right femoral head based on absent contrast uptake.

7.2.2 Freiberg’s Disease (Osteochondrosis of the Metatarsal Heads)

The term “Köhler’s disease Type II” is also used for this condition. The cause of osteochondrosis of the metatarsal heads (primarily the second metatarsal) is unclear. The diagnosis is usually made in adolescence (girls are more commonly affected than boys), but is also seen as an incidental finding during adulthood.

Radiography. Depending on when the diagnosis is made, the following radiographic signs are seen:

• Flattening and widening of the head ( Fig. 7.12).

• Fragmentation.

• Possible premature closure of the growth plate.

• Reactive sclerosis.

• The joint space is usually maintained.

• Widening of the opposite base of the proximal phalanx is seen in marked cases.

DD. Overuse-related insufficiency fractures with subsequent collapse of the joint surface may result in a similar appearance of a metatarsal head ( Fig. 7.13).

7.2.3 Köhler’s Disease Type I

Osteochondrosis of the navicular bone can occur from age 2 years onward, being most common during the 4th and 5th years of age. The prognosis of Köhler’s disease Type I is very good. The navicular bone assumes a normal appearance after spontaneous healing (~ 6–18 months after diagnosis). Only rarely does pain persist after skeletal maturity.

Radiography/CT. Conventional radiography demonstrates mixed areas of sclerosis and lucency in the ossification center. In other cases the ossification center is collapsed and sclerotic ( Fig. 7.14), sometimes only sclerotic, and sometimes fragmented.

MRI. MRI is frequently employed even before radiographic examination for a painful foot of unknown origin, so the radiologist may also be confronted with the findings of Köhler’s disease type I on MRI, typically those of sclerosis and bony remodeling ( Fig. 7.15).

DD. Muller–Weiss syndrome. The age of the patient prevents confusion with the rare Muller–Weiss syndrome (osteonecrosis of the tarsal navicular in the adult; Fig. 7.16).

7.2.4 Panner’s Disease and Hegemann’s Disease

Panner’s disease is an osteochondrosis of the humeral capitulum in children up to the age of about 10 years; boys are more commonly affected. The majority of these osteochondroses heal spontaneously. Cases in which collapse of the capitulum results in secondary osteoarthritis are very rare. Radiographic findings include diffuse sclerotic changes of the ossification center of the lateral humeral joint surface—similar to Köhler’s disease although in some cases mixed lytic and sclerotic changes are seen along with irregularity of the joint surface. During spontaneous healing, a lytic lesion without contour irregularity is seen in adolescents just prior to complete fusion of the ossification center ( Figs. 7.17 and W7.4). Patients with Panner’s disease present without a history of significant injury or chronic overuse. It may, however, also be associated with chronic overuse in throwing sports.

The more focal osteochondritis dissecans is also found in the capitulum and the trochlea and must be distinguished from Panner’s disease, although it does tend to affect an older age group: adolescents up to the age of 15 to 16 years (Chapter 7.2.5).

If the trochlea is involved instead of the capitulum (Panner’s disease), this is known as Hegemann’s disease ( Fig. 7.18), which is rare.

Caution

The term “Little Leaguer’s Elbow,” used by many authors globally for all types of overuse injuries of the elbow joint, but should be reserved for chronic traction apophysitis (either as epiphysiolysis and/or as osteochondrosis) of the medial epicondyle (cf. Chapter 2.7.1).

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