Airways and craniofacial assessment in children affected by achondroplasia with and without sleep-disordered breathing: quantitative magnetic resonance study.

PURPOSE: To identify MRI-based quantitative craniofacial variables linked to airways narrowing and obstructive sleep apnea (OSA) development in children with achondroplasia. METHODS: We evaluated skull base and midface MRI in two cohorts of children affected by achondroplasia, with (group 1) or without OSA (group 2). 3DFSPGR-T1weighted images were used to assess airways volume (nasopharynx, oropharynx, and laryngopharynx), jugular foramina (JF) and hypoglossal foramina (HF) areas, foramen magnum area, cervical cord area, and maxillary retrusion (SNA angle). RESULTS: Nineteen out of 27 children with achondroplasia exhibited different degrees of obstructive respiratory impairment (n.4 mild, n.8 moderate, n.7 severe), while 8 children did not show OSA. Each group was compared with age-matched controls without neuroimaging abnormalities. Both groups showed reduced nasopharynx volume, JF areas, and SNA angle, while group 1 showed also reduced oropharynx volume, ratio of FM/cervical cord areas, and HF areas (p < 0.05). A positive correlation between nasopharynx volume and SNA angle was found in both groups, while a positive correlation among upper airways volume, JF and HF areas was found only in group 1. No correlation between upper airways volume and OSA severity was found. CONCLUSION: In children with achondroplasia, multifaced craniofacial abnormalities contribute to airways volume reduction predisposing to sleep disordered breathing. MRI-based quantitative assessment allows the appraisal of craniofacial variables linked to the development of sleep-disordered breathing such as FM stenosis, jugular and hypoglossal foramina stenosis, and retruded maxillary position and may be a valuable tool for clinical surveillance.

Skeletal Dysplasias: What Every Bone Health Clinician Needs to Know.

PURPOSE OF REVIEW: This review highlights how skeletal dysplasias are diagnosed and how our understanding of some of these conditions has now translated to treatment options. RECENT FINDINGS: The use of multigene panels, using next-generation sequence technology, has improved our ability to quickly identify the genetic etiology, which can impact management. There are successes with the use of growth hormone in individuals with SHOX deficiencies, asfotase alfa in hypophosphatasia, and some promising data for c-type natriuretic peptide for those with achondroplasia. One needs to consider that a patient with short stature has a skeletal dysplasia as options for management may be available.

Growth disturbance after lengthening of the lower limb and quantitative assessment of physeal closure in skeletally immature patients with achondroplasia.

This study evaluated the effect of limb lengthening on longitudinal growth in patients with achondroplasia. Growth of the lower extremity was assessed retrospectively by serial radiographs in 35 skeletally immature patients with achondroplasia who underwent bilateral limb lengthening (Group 1), and in 12 skeletally immature patients with achondroplasia who did not (Group 2). In Group 1, 23 patients underwent only tibial lengthening (Group 1a) and 12 patients underwent tibial and femoral lengthening sequentially (Group 1b). The mean lengthening in the tibia was 9.2 cm (59.5%) in Group 1a, and 9.0 cm (58.2%) in the tibia and 10.2 cm (54.3%) in the femur in Group 1b. The mean follow-up was 9.3 years (8.6 to 10.3). The final mean total length of lower extremity in Group 1a was 526.6 mm (501.3 to 552.9) at the time of skeletal maturity and 610.1 mm (577.6 to 638.6) in Group 1b, compared with 457.0 mm (411.7 to 502.3) in Group 2. However, the mean actual length, representing the length solely grown from the physis without the length of distraction, showed that there was a significant disturbance of growth after limb lengthening. In Group 1a, a mean decrease of 22.4 mm (21.3 to 23.1) (4.9%) was observed in the actual limb length when compared with Group 2, and a greater mean decrease of 38.9 mm (37.2 to 40.8) (8.5%) was observed in Group 1b when compared with Group 2 at skeletal maturity. In Group 1, the mean actual limb length was 16.5 mm (15.8 to 17.2) (3.6%) shorter in Group 1b when compared with Group 1a at the time of skeletal maturity. Premature physeal closure was seen mostly in the proximal tibia and the distal femur with relative preservation of proximal femur and distal tibia. We suggest that significant disturbance of growth can occur after extensive limb lengthening in patients with achondroplasia, and therefore, this should be included in pre-operative counselling of these patients and their parents.

Analysis of callus pattern of tibia lengthening in achondroplasia and a novel method of regeneration assessment using pixel values.

OBJECTIVE: To relate morphology of new bone formation to outcome after tibial lengthening performed in patients with achondroplasia. MATERIAL AND METHODS: A retrospective analysis of 60 tibial segments in 30 achondroplasia patients was performed. There were 22 female patients and eight male patients, with a mean age of 9.8 years. New bone formation was classified by shape, homogeneity and density. Pixel values in relation to original bone were measured using a picture-archiving communication system (PACS). Clinical outcome was described by the external fixator and maturation indices. RESULTS: Mean lengthening was 9.2 cm (range 3-12.7 cm). The mean external fixator index was 23.4 (range 15.1-50). The mean maturation index was 12.3 days/cm (range 6-40 days/cm). Homogeneous pathways were associated with the best clinical results (fixator index 20.4, maturation index 10.8), followed by heterogeneous pathway (external fixator index 26.5, maturation index 16.8) and radiolucent pathway (fixator index 31.2, maturation index 21.4). Both cylindrical (external fixator index 25.2, maturation index 14.5) and concave (external fixator index 26.6, maturation index 16.3) callus shapes were favourable. Mineralization of new bone became equal to that of normal bone within 16 weeks (mean) for homogeneous pathway, 12 weeks for heterogeneous pathway and 32 weeks for lucent pathway. CONCLUSION: The type of new bone formation seen on radiographs is related to clinical outcome, with homogeneous pathways being the most favourable ones.