Orthopedic management of the extremities in patients with Morquio A syndrome

Abstract

Background: Musculoskeletal involvement in Morquio A syndrome (mucopolysaccharidosis IVA; MPS IVA) contributes significantly to morbidity and mortality. While the spinal manifestations of the disorder have received considerable attention in the literature, there have been few reported studies to date to guide the management of the orthopedic problems associated with the lower and upper extremities.

Purpose: The objective was to develop recommendations for the management of the extremities in patients with Morquio A syndrome.

Methods: A group of specialists in orthopedics, pediatrics and genetics with experience in the management of Morquio A patients convened to review and discuss current clinical practices and to develop preliminary recommendations. Evidence from the literature was retrieved. Recommendations were further refined until consensus was reached.

Results and conclusions: This present article provides a detailed review and discussion of the lower and upper extremity deformities in Morquio A syndrome and presents recommendations for the assessment and treatment of these complications. Key issues, including the importance of early diagnosis and the implications of medical therapy, are also addressed. The recommendations herein represent an attempt to develop a uniform and practical approach to managing patients with Morquio A syndrome and improving their outcomes.

Fig. 1

Progression of hip deformities in Morquio A syndrome. a 3-year-old female with dysplastic proximal femoral epiphyses and dysplastic acetabulum. Subluxation, as evident by the break in Shenton’s line, is present at this early age. b A similar deformity is found in an untreated 8-year-old with worsening epiphyseal flattening and incongruent acetabulum

Fig. 2

Genu valgum is common in Morquio A syndrome and often requires surgical correction. Guided growth using the tension band plate technique can be effective for genu valgum correction in younger patients with adequate growth potential. A patient who underwent surgical intervention for genu valgum a at age 9 years, b at age 10 years, c at age 12 years (slight over-correction, tension band plates removed) and d at age 16 years (skeletally mature)

Fig. 3

Malalignment of the knee joint alters the biomechanics of gait in patients with Morquio A syndrome. Knee valgus causes the ground reaction force to be shifted laterally, which forces the knee into further valgus. The degree of genu valgum may be estimated by the quadriceps angle, or Q angle (the angle formed by a line drawn from the anterior superior iliac spine through the center of the patella and a line drawn from the center of the patella to the center of the tibial tubercle). Multiple anatomical factors contribute to the magnitude of the Q angle, including hip rotation, tibial torsion and foot position

Fig. 4

Hand and wrist changes in Morquio A syndrome. Carpal ossification delay, short and broad metacarpals, metacarpal rounding, and a short ulna are evident in the radiograph of an 8-1/2-year old female.

Fig. 5

Hypermobility and ulnar deviation of the wrist joint are characteristic features of Morquio A syndrome