Schmid's Type of Metaphyseal Chondrodysplasia: Diagnosis and Management

Abstract

Objectives: There are several types of metaphyseal chondrodysplasia and various clinical types have been differentiated. The Schmid type of metaphyseal chondrodysplasia is the most common. Diffuse metaphyseal flaring, irregularity, and growth plate widening, which are most severe in the knees, are the most striking radiological features of this disease. The Schmid type of metaphyseal dysostosis is characterized by failure of normal mineralization of the zone of provisional calcification, leading to widened physes and enlarged knobby metaphyses, effectively causing shortening of the tubular bones, splaying of the metaphyses, coxa vara, and bow legs. Orthopaedic interventions were primarily performed on the lower extremities.

Methods: Twelve children (seven girls and five boys) aged 7-10 years were enrolled in this study. Moderate short stature was a uniform feature associated with predominant involvement of the proximal femora and bow legs resulted in the development of angular deformities. A waddling gait was a consequence of coxa vara in eight children. Valgus osteotomy of the proximal femur was planned after physeal closure for the group of children with coxa vara. Hemiepiphysiodesis was performed to re-align the genu varum in three children.

Results: Other forms of metaphyseal dysostosis were ruled based on full clinical and radiographic phenotypes, with confirmation through molecular pathology. Mutations in the COL10A1 gene located on chromosome 6q21-q22.3 were confirmed. Re-alignment was accomplished in our group of patients.

Conclusion: The most striking clinical features of Schmid metaphyseal chondrodysplasia which appear within the first 2-3 years of life are: moderate short limbs and short stature, a waddling gait, and increasing shortness of stature with age. The Schmid type of metaphyseal chondrodysplasia is a disorder that arises from defective type X collagen, which is typically found in the hypertrophic zone of the physes. Moderate short stature and a waddling gait associated with pain are the most common clinical presentations. Osteotomies to correct bow legs are sometimes combined with lengthening procedures. Recurrence of the deformities with growth is not uncommon; therefore, hemiepiphysiodesis or stapling might be indicated in some cases.

Keywords: Bowed legs; Metaphyseal dysostosis Schmid type; Mutations in the COL10A1; Surgical corrections.

Figure 1

(A) Genu varum in a 5‐year‐old boy with Schmid's metaphyseal chondrodysdplasia presented with bowing of the legs; (B) genu varum in a 7‐year‐old girl with Schmid's metaphyseal chondrodysplasia; and (C) less pronounced genu varum in a 9‐year‐old girl with Schmid's metaphyseal dysostosis. All children showed widening of the physes associated with metaphyseal cupping that resembles rickets.

Figure 2

(A, B) Coxa vara were dealt with by bilateral proximal osteotomy. Radiographic appearance after bilateral valgisation osteotomy fixed with locking plate.

Figure 3

(A, B) AP radiographs show that valgus knees (both sides) were corrected by means of guided growth technique with hemiepiphyseodesis. The plates were applied asymmetrically. On the right side, two plates (on the medial sides of distal femoral and proximal tibial physes), and on the left side one plate (medial side of distal femoral physis) have been applied. (C) Clinical appearance of the lower extremities postoperatively and at the end of correction after “guided growth” using 8‐plates in a 10‐year‐old girl.