Pathophysiology of Hip Disorders in Patients with Mucopolysaccharidosis IVA

Total hip arthroplasty in patients with common pediatric hip orthopedic pathology

Purpose

Literature regarding total hip arthroplasty for pediatric hip diseases is scarce. This review aims to portray the various orthopedic conditions of childhood that can lead to significant impairment of the hip joint and, ultimately, to total hip arthroplasty in adolescence and adulthood.

Methods

In total, 61 out of 3666 articles were selected according to (1) the diagnosis of one of the 12 pediatric hip pathologies (Legg-Perthes-Calvé disease, developmental dysplasia of the hip, slipped capital femoral epiphysis, neuromuscular hip dysplasia, post-traumatic avascular necrosis of the proximal femur, juvenile rheumatoid arthritis, achondroplasia, spondyloepiphyseal dysplasia, mucopolysaccharidosis, mucolipidosis, hip infections, and tumors) that required total hip arthroplasty; (2) minimum follow-up of 16 months; (3) assessed outcome with a clinical or radiologic score; (4) Methodological Items for Non-Randomized Studies quality score of 9 or higher. The following information for each pathology was retrieved: mean age at total hip arthroplasty, reason for total hip arthroplasty, type of total hip arthroplasty, surgical technique, mean follow-up, and outcomes.

Results

Overall, the mean age at total hip arthroplasty for pediatric hip disease is in the sixth and seventh decade, except for tumors and skeletal dysplasias. The reason for performing total hip arthroplasty is often osteoarthrosis and abnormal anatomy. Prosthesis types change based on patient's conditions and technological advances; custom-made implants are used for tumors, juvenile rheumatoid arthritis, and skeletal dysplasias; for other diseases, the most frequent are modular cementless implants. Outcomes are generally good, and all studies portray functional and pain improvements.

Conclusion

Total hip arthroplasty is performed more frequently than in the past in patients with pediatric hip pathologies; it enhances patients' quality of life by reducing pain and improving function. However, revision rate in these patients is not negligible.

A pictorial review of the radiographic skeletal findings in Morquio syndrome (mucopolysaccharidosis type IV)

Morquio syndrome, also known as Morquio-Brailsford syndrome or mucopolysaccharidosis type IV (MPS IV), is a subgroup of mucopolysaccharidosis. It is an autosomal recessive lysosomal storage disorder. Two subtypes of Morquio syndrome have been identified. In MPS IVA, a deficiency in N-acetylgalactosamine-6-sulfate sulfatase interrupts the normal metabolic pathway of degrading glycosaminoglycans. Accumulated undigested glycosaminoglycans in the tissue and bones result in complications leading to severe skeletal deformity. In MPS IVB, a deficiency in beta-galactosidase results in a milder phenotype than in MPS IVA. Morquio syndrome presents a variety of clinical manifestations in a spectrum of mild to severe. It classically has been considered a skeletal dysplasia with significant skeletal involvement. However, the extraskeletal features can also provide valuable information to guide further work-up to assess the possibility of the disorder. Although the disease involves almost all parts of the body, it most commonly affects the axial skeleton, specifically the vertebrae. The characteristic radiologic findings in MPS IV, such as paddle-shaped ribs, odontoid hypoplasia, vertebral deformity, metaphyseal and epiphyseal bone dysplasia, and steep acetabula, are encompassed in the term "dysostosis multiplex," which is a common feature among other types of MPS and storage disorders. Myelopathy due to spinal cord compression and respiratory airway obstruction are the most critical complications related to mortality and morbidity. The variety of clinical features, as well as overlapping of radiological findings with other disorders, make diagnosis challenging, and delays in diagnosis and treatment may lead to critical complications. Timely imaging and radiologic expertise are important components for diagnosis. Gene therapies may provide robust treatment, particularly if genetic variations can be screened in utero.

Hip pathologies in mucopolysaccharidosis type III

Background

Mucopolysaccharidosis type III (MPS III) comprises a group of rare lysosomal storage diseases. Although musculoskeletal symptoms are less pronounced than in other MPS subtypes, pathologies of hip and spine have been reported in MPS III patients. The purpose of this study was to describe hip pathologies and influencing parameters in MPS III patients.

Methods

A retrospective chart review was performed for 101 MPS III patients. Thirty-two patients met the inclusion criteria of enzymatically or genetically confirmed diagnosis and anteroposterior radiograph of the hips. Modified Ficat classification, Wiberg’s center-edge angle, and Reimer’s migration percentage were measured.

Results

The mean age at data assessment was 11.0 years (SD 5.7). Osteonecrosis of the femoral head was observed in 17/32 patients. No statistically significant association was found between these changes and age, sex, or MPS III subtype. Patients with a severe phenotype showed significantly higher rates of osteonecrosis (14/17) than patients with an intermediate phenotype. Hip dysplasia was present in 9/32 patients and was significantly associated with osteonecrosis of the femoral head (p = 0.04).

Conclusions

The present study demonstrates a high rate of hip pathologies in MPS III patients. Hip dysplasia and severe phenotype were significantly correlated with osteonecrosis of the femoral head. Therefore, radiographs of the hips are highly recommended in baseline and follow-up assessments of MPS III patients.

Trial registration

Retrospectively registered.