Differences in pathways contributing to thyroid hormone effects on postnatal cartilage calcification versus secondary ossification center development

The proximal and distal femur epiphysis of mice are both weight bearing structures derived from chondrocytes but differ in development. Mineralization at the distal epiphysis occurs in an osteoblast rich secondary ossification center (SOC), while the chondrocytes of the proximal femur head (FH) in particular, are directly mineralized. Thyroid hormone (TH) plays important roles in distal knee SOC formation, but whether TH also affects proximal FH development remains unexplored. Here, we found that TH controls chondrocyte maturation and mineralization at the FH in vivo through studies in Thyroid stimulating hormone receptor (Tshr -/-) hypothyroid mice by X-ray, histology, transcriptional profiling, and immunofluorescence staining. Both in vivo, and in vitro studies conducted in ATDC5 chondrocyte progenitors concur that TH regulates expression of genes that modulate mineralization (Bsp, Ocn, Dmp1, Opn, and Alp). Our work also delineates differences in prominent transcription factor regulation of genes involved in the different mechanisms leading to proximal FH cartilage calcification and endochondral ossification at the distal femur. The information on the molecular pathways contributing to postnatal cartilage calcification can provide insights on therapeutic strategies to treat pathological calcification that occurs in soft tissues such as aorta, kidney, and articular cartilage.

Radiological study of Os trigonum and its clinical significance

Background: Os trigonum (OST) is commonly located on the posterior aspect of the talus. It occurs as a result of secondary ossification center failing to fuse with the lateral tubercle of the posterior process of the talus; its incidence varies between 2 and 25%, and is more often bilateral. It occurs as an intra-articular Os, which is most often securely rooted to the lateral tubercle of the talus by a fibrocartilaginous synchondrosis. Aims and Objective: To determine the incidence, morphology, and distribution of Os Trigonum (OST). Materials and Methods: Retrospective 500 lateral foot radiographs view were studied to determine the incidence, morphology, and distribution of OST. Results: Incidence of OST in the present study was 6.6%, with predominantly round or ovoid in shape. OST was located on the posterolateral aspect of the talus. Conclusion: OST can be one of the causative factor responsible for Flexor hallucis longus tendonitis, OST syndrome, which occur in plantarflexion of the ankle, leading to compression of the OST between the distal tibia and the calcaneus. Hence, knowledge regarding the incidence, morphology, and distribution of OST is important for the radiologist, orthopedic surgeons to arrive at a correct diagnosis, which aids in the management of cases presenting with complaints of posterior ankle pain.

Clinical, Genetic and Orthopedic Characteristics of Desbuquois Dysplasia

Introduction. Desbuquois dysplasia is a rare skeletal dysplasia with an autosomal recessive inheritance, resembling to the group of multiple joint dislocations. The disease is caused by mutations in the CANT1 and XYLT1 genes, the protein products of which are involved in the degradation of proteoglycans, which play an important role in endochondral ossification. The polymorphism of clinical and radiological characteristics and the genetic heterogeneity of Desbuquois dysplasia necessitate the description of the phenotypic characteristics of patients with various types of mutations, which optimize diagnosis. Objective description of the clinical and radiological characteristics of three Russian patients with Desbuquois dysplasia of types 1 and 2 with remarkable orthopedic manifestation, caused by mutations in the CANT1 and XYLT1 genes. Materials and Methods. Genealogical, clinical, radiographic and genetic data of three unrelated Russian patients aged 2 to 8 years was carried out. Genetic testing was carried out using clinical exome sequencing and methyl-sensitive PCR. Results. Two patients were diagnosed with type 1 disease due to a previously described homozygous mutation in the CANT1 gene: c.898CT (p.Arg300Cys), and one type 2 due to heterozygous mutations in the XYLT1 gene. One mutation: c.1651CT (p.Arg551Cys) was detected during exome sequencing, and the second mutation: expansion of GGC repeats in the promoter region of the gene, revealed by methyl-sensitive PCR of the first exon of the gene. The main clinical signs of the disease were micromelic dwarfism, hypermobility in the joints and specific facial dysmorphisms, radiographic analysis revealed characteristic monkey wrench appearance of the proximal femur in all 3 patients, additional ossification center of the second metacarpal, advanced bone age and multiple dislocations in the joints. The patients also had extra-skeletal manifestations (congenital glaucoma, obstructive bronchitis, renal hypoplasia and congenital heart malformations). Conclusion. Genetic heterogeneity and the presence of polymorphism of clinical manifestations make it possible to consider sequencing of the clinical exome as the optimal method for diagnosing Desbuquois dysplasia types 1 and 2. Analysis of the literature and the results of our molecular genetic data indicate the possibility of expansion of the GGC repeat in the XYLT1 gene in patients with clinical manifestations of type 2 Desbuquois dysplasia.

Trochlear Development in Children From 1 Month to 10 Years of Age: A Descriptive Study Utilizing Analysis by Magnetic Resonance Imaging

Background: Understanding the morphology of cartilage/bony maturation in preadolescents may help explain adult trochlear variation. Purpose: To study trochlear morphology during maturation in children and infants using magnetic resonance imaging (MRI). Study Design: Descriptive laboratory study. Methods: Twenty-four pediatric cadaveric knees (10 male and 14 female knees; age, 1 month to 10 years) were included. High-resolution imaging of the distal femoral secondary ossification center was performed using 7-T or 9.4-T MRI scanners. Three-dimensional MRI scans were produced, and images were reformatted; 3 slices in the axial, sagittal, and coronal planes images were analyzed, with coronal and sagittal imaging used for image orientation. Biometric analysis included lateral and medial trochlear height (TH); cartilaginous sulcus angle (CSA); osseous sulcus angle (OSA); trochlear depth; and trochlear facet (TF) length symmetry. Sex comparisons were considered when ≥1 specimen from both sexes of the same age was available; these included 11 knees spanning 4 age groups (ages 1, 3, 4, and 7 years). Results: The analysis of trochlear morphology showed a lateral TH greater than the medial TH at all ages. The thickest cartilage was found on the lateral TF in the younger specimens. Regarding the development of osseous and cartilaginous trochlear contour, a cartilaginous sulcus was present in the 3-month-old specimen and continued to deepen up to the age of 4 years. The shape of the osseous center evolved from round (1 month) to oval (9 months) to rectangular (2 years); no distinct bony trochlear sulcus was present, although a well-formed cartilaginous sulcus was present. The first evidence of formation of a bony sulcus was at 4 years. By the age of 7 to 8 years, the bony contour of the adult distal femur resembled its cartilaginous contour. Female samples had a shallower CSA and OSA than did the male ones in all samples that had a defined OSA. Conclusion: Female trochlear grooves tended to be shallower (flatter). The lateral trochlea was higher (TH) and wider (TF length) during growth than was the medial trochlea in both sexes; furthermore, the development of the osseous sulcus shape lagged behind the development of the cartilaginous sulcus shape in the authors’ study population. Clinical Relevance: Bony anatomy of the trochlear groove did not match the cartilaginous anatomy in preadolescent children, suggesting that caution should be used when interpreting bony anatomy in this age group.

Correlated Imaging of the Equine Hyoid Apparatus Using CT, Micro-CT, and Histology

Background: Detailed radiological evaluation of the normal hyoid apparatus by computed tomography (CT) has not yet been conducted. Thus, it is unclear what type of junction connects the different parts of the equine hyoid apparatus.Objectives: To describe the normal CT anatomy of the equine hyoid apparatus, and to determine the junction type that connects the different parts of the hyoid apparatus.Study Design: Combination of retrospective study and prospective cadaver study.Methods: The medical records of horses that underwent head CT scans from 2009 to 2018 were retrieved. Inclusion criteria for the CT scans were visibility of at least two of the four junctions of the hyoid apparatus. CT images were analyzed in three different planes. Additionally, 10 cadaver heads were processed using CT, micro-CT of selected joints, and histology of all joints.Results: CT scans of 200 horses fulfilled the inclusion criteria. The tympanohyoid cartilage consisted of hyaline cartilage. Areas of mineralization within the cartilage were visible on CT scans as early as 2 years of age. The epihyoid was not fused with the stylohyoid in one-third of the horses. All horses younger than 2.5 years showed three ossification centers of the basihyoid, and all horses younger than 1.5 years had a non-fullydeveloped lingual process. In total, 10 of 11 horses between 1.5 and 3 years had separate ossification centers of the lingual process. We found a synchondrosis between the styloid process and the stylohyoid bone. The basihyoid and thyrohyoid, as well as the stylohyoid and epiyhoid were connected by a synostosis in two-thirds of the horses. The remaining parts were connected to one another by synovial joints.Main limitations: The junctions studied by histologic examination were from older horses, therefore growing patterns of different bones could not be totally clarified.Conclusion: The temporohyoid joint is a synchondrosis. The epihyoid is an ossification center of the stylohyoid and fuses with the stylohyoid in two-thirds of horses. The lingual process has a separate ossification center.

Osteochondrosis of Primary Center of Patella: A Case Report

Introduction: Osteochondrosis of the primary ossification center of the patella (Kohler’s Disease) is a rare and self-limiting condition of unknown etiology. Sometimes it may be found as normal variant. Case Report: A 7-year-old boy presented with anterior right knee pain. On radiological examination, there was increased density, irregularity, and fragmentation of the patellar primary ossification center. Activity modification and exercise led to marked symptomatic improvement after 1 year. Conclusion: It was concluded that the disease either physiological or pathological, diagnosis is usually difficult. However, the treatment is simple. There was improvement functionally as well as radiologically with activity modification. Keywords: Osteochondrosis, primary center, patella.

Short-term Outcomes of Herbert Screw Fixation for Isolated Olecranon Fractures in Children: a Single-institution Retrospective Study

Background: Although various fixation methods can be used for the treatment of displaced olecranon fractures, there are no clear indications in the current literature regarding which surgical technique should be adopted. In this study, we evaluated the clinical and radiological outcomes of closed reduction with percutaneous Herbert screw fixation in children with isolated olecranon fractures.Methods: We retrospectively reviewed the records of children treated at our center for isolated olecranon fractures (Mayo type IIA) with closed reduction and percutaneous Herbert screw fixation between January 2016 and December 2018. Radiographic assessment of fracture healing was performed 6–8 months postoperatively and included assessment for loss of reduction and maximum length of the ulna. Clinical outcomes included elbow flexion and extension, forearm pronation and supination, short version of the Disabilities of the Arm, Shoulder, and Hand (QuickDASH) score, and complications. The Herbert screws were removed by a second operation.Results: A total of 14 patients with an average age at the time of injury of 11.36 (range, 10–14) years were included. All patients had good radiological and clinical outcomes at 6–8 months postoperatively; all had normal elbow ranges of motion and showed complete bone healing on radiographs. There were no cases of foreign body irritation, implant migration, or osteoarthritis. Premature epiphyseal closure was noted in six patients. The average QuickDASH score was 1.58. Conclusions: Fixation of olecranon fractures with Herbert screws is a safe and easy fixation method in young patients, leading to good functional and radiological results. Nonetheless, determination of the effects of this treatment method on the olecranon ossification center requires long-term follow-up.