323 Dysplasia epiphysealis hemimelica is a rare osteocarilagi- nous overgrowth involving one or multiple epiphyses or ossifi- cation centers, usually in the lower extremity on one side of the body. In 1926, Mouchet and Belot described a condition called tarsomegaly, which Trevor, later in 1950, called tarso-epiphyseal aclasis. As the tarsal bones are not the only bones involved, Fairbank used the term dysplasia epiphysealis hemimelica.
GENETICS/BASIC DEFECTS
1. Inheritance:
a. No known hereditary factor, except a report of a single family with seven members affected by different com- binations of dysplasia epiphysealis hemimelica, intra- capsular chondroma, extraskeletal osteochondroma, and typical osteochondroma
b. Male to female ratio: 3:1 2. Etiology and pathogenesis
a. Etiology unknown
b. A congenital disorder becoming clinically evident in the course of the development of the epiphyses c. Basic pathologic process: an abnormal proliferation of
cartilage in an epiphysis, similar to osteochondroma
CLINICAL FEATURES
1. Most frequent presentation: ages 2–14 years (birth to 63 years of age)
2. Chief clinical signs
a. Unilateral asymmetric bony hard swelling on the extremities
b. Usually on the inner or outer aspect of the knee and/or ankle
c. With or without pain
d. With or without restriction of motion e. Slow progression
3. Apparent deformity
a. Varus or valgus deformity depending on the site of involvement
b. Genu valgum or varum depending on the site of involvement
c. Flexion contracture d. Pes planus
e. Pes equinus 4. Sites of involvement
a. Lower extremities, more commonly affected than the upper extremities
i. Talus (most common) ii. Distal femoral epiphysis iii. Distal tibial epiphysis
iv. Proximal tibial epiphysis v. Distal fibula epiphysis vi. Tarsal navicular vii. First cuneiform
viii. Calcaneus
ix. Middle and lateral cuneiforms x. Metatarsals
xi. Phalanges b. Upper extremities
i. Carpal bones a) Scaphoid b) Lunate c) Capitate d) Hamate e) Trapezium
f) Trapezoid ii. Metacarpals iii. Phalanges
iv. Proximal radius
v. Proximal and distal ulna vi. Proximal and distal humerus vii. Glenoid cavity
viii. Coracoid process of the scapula c. Pelvis
i. Acetabulum ii. Pubic bone iii. Iliac bone 5. Affected limb
a. May be longer than the unaffected one due to:
i. The enlargement of several ossification centers ii. Increased diaphyseal length
b. May be shorter due to focal early closure of the epi- physeal plate
6. Quiescent following epiphyseal plate fusion 7. Prognosis
a. Relatively benign condition
b. Malignant degeneration has not been reported 8. Classification based on degrees of involvement (Azouz et
al., 1985)
a. Localized form
i. Usually affecting the bones of the hindfoot or ankle
ii. Also may affect an epiphysis b. Classical form
i. Characteristic hemimelic distribution seen in more than one area in a single lower extremity (2/3rd of the reported cases), particularly:
a) Talus
b) Distal femoral epiphyses c) Distal tibial epiphyses
ii. Lesion localized to the ankle and foot, called Mouchet and Belot type
c. Generalized or severe form
i. Involving a whole lower extremity from the pelvis to the foot or ankle
ii. Involving femoral head, symphysis pubis or tri- radiate cartilage of the acetabulum
Dysplasia Epiphysealis Hemimelica
324 DYSPLASIA EPIPHYSEALIS HEMIMELICA
DIAGNOSTIC INVESTIGATIONS
1. Radiography
a. Skeletal survey to look for sites of involvement b. Earliest radiographic sign
i. Appearance of secondary centers of ossification adjacent to an epiphysis
ii. Slow enlargement of these centers eventually merging with each other and then with the epiphysis
c. Asymmetric hemimelic distribution of overgrowth of one side of epiphysis with irregular contour and ossification
i. Generally only half or part (either the medial or lateral half) of an epiphysis or ossification center affected
ii. Rarely involving the entire epiphysis d. Overgrowth of adjacent bones
e. Adjacent (probably secondary) metaphyseal and growth plate involvement
i. Exhibiting widening and streak-like metaphysis (as in Ollier disease)
ii. Spur formation (as in osteochondroma)
f. Mature lesions showing enlargement of one side of an epiphysis, simulating as osteochondromatous mass or enlargement of one side of an ossification center g. Epiphysis irregularly calcified and ossified h. Joints usually deformed
i. Advanced bone age in unaffected epiphyses j. Less common findings
i. Loose bodies in affected joints ii. Osteochondral fractures k. Bilateral involvement extremely rare 2. CT of the lesions
a. Improving diagnostic accuracy in the growing skeleton b. Demonstration of the anatomic relationship of the
involved structures
c. Visualization of the soft tissues, bones, and tumorous mass
d. Evaluation of the condition of the articular surfaces 3. MRI imaging
a. To identify a definite plane of separation between the pathologic osteochondromatous mass and the normal epiphysis
b. To accurately identify bony and cartilaginous struc- tural abnormalities in multiple planes noninvasively without ionizing radiation
c. To identify secondary changes in menisci, tendons, ligaments, and muscles
4. Histopathology
a. Osteocartilaginous exostosis (with cartilaginous cap) arising from an epiphysis, apophysis, or round bone (Oates)
b. Nests of cartilage cells showing active proliferation during growth of the lesions
c. Diminishing amount and activity of the cartilage as the lesions mature
d. Increased size of lesions in adults showing areas of actively proliferating cartilage
e. Infrequently with an area of necrosis, presumably caused by inadequate nutrition
GENETIC COUNSELING
1. Recurrence risk
a. Patient’s sib: not increased b. Patient’s offspring: not increased 2. Prenatal diagnosis: not been reported 3. Management
a. Observation
b. Surgical excision of the mass or corrective osteotomy generally recommended for the following lesions:
i. Causing disabling pain ii. Interfering function
iii. Increasing deformity of the involved joint c. Simple excision indicated if the cartilaginous over-
growth is not in the weight-bearing articular surface d. Extraarticular osteotomy indicated for correction of
varus/valgus deformities if the arthrogram shows the smooth joint surface
e. Anticipate recurrence of the angular deformity after the corrective osteotomy if the growth plate at the affected joint is open and active
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DYSPLASIA EPIPHYSEALIS HEMIMELICA 325
Fig. 1. A 9-year-old boy with dysplasia epiphysealis hemimelica showing hard swellings on the inner sides of the knees and the ankle of the right lower extremities. The knee radiographs at 9 years of age show the secondary ossification center merged with the medial side of the epiphyses of the distal femur and that of the proximal tibia. The radiographs of ankles at 4, 5, and 9 years of age show irregularly cal- cified mass extending from medial malleolus of the distal tibia and involvement of the talus. The patient had bony protuberance of the right knee and right ankle without pain or restriction of motion. The age of onset was about 2 years of age.
