Limb development in skeletally-immature large-sized dogs: A radiographic study

Despite the extreme morphological variability of the canine species, data on limb development are limited and the time windows for the appearance of the limb ossification centres (OCs) reported in veterinary textbooks, considered universally valid for all dogs, are based on dated studies. The aim of this study was to acquire up-to-date information regarding the arm, forearm and leg bone development in skeletally-immature large-sized dogs from 6 weeks to 16 weeks of age. Nine litters of 5 large-sized breeds (Boxer, German Shepherd, Labrador Retriever, Saarloos Wolfdog, White Swiss Shepherd Dog) were included, for a total of 54 dogs, which were subject to radiographic examination on a bi-weekly basis. The appearance of 18 limb OCs was recorded and 14 radiographic measurements were performed; their relationship with age and body weight was investigated and any breed differences were analysed using different statistical non-parametric tests. The number of OCs present was significantly different at 6 and 8 weeks of age between the investigated breeds. The appearance of the OCs occurred earlier in the Saarloos Wolfdog, while the Labrador Retriever was the later breed. In Boxers and Labrador Retrievers, various OCs showed a delayed appearance compared to the data reported in the literature. The number of OCs was strongly and positively correlated to body weight. Breed differences were also observed in the relative increase of the measured OCs and were not limited to dogs of different morphotypes. Statistically significant differences were most frequently observed between Saarloos Wolfdogs and the other breeds. The OCs that showed a greater variability in their development were the olecranon tuber, the patella and the tibial tuberosity. Their increase was more strongly correlated with the dog’s age and body weight. Our data strongly suggest that differences in limb development exist in dog breeds of similar size and morphotype.

Three dimensional ultrastructure of transverse (Harris) lines in the long bone

To investigate the occurrence of transverse lines in long bones of adults, we studied 27 cadavers (14 males and 13 females). After confirming the presence of a transverse line, a cross-sectional sample was examined macroscopically, and by soft X-ray and scanning electron microscopy. The following results were obtained: 1. According to roentgenograms, transverse (Harris') lines were observed in 40.7% of the distal half of the femur and in 29.6% of the proximal half of the tibia. 2. Macroscopic examination of the bone cross-sections at the level of the transverse line showed various membranous structures. 3. In scanning electron micrographs, no marked difference in structure was observed between the transverse line trabeculae and the compact bone.

Patterns of premature physeal arrest: MR imaging of 111 children

OBJECTIVE

The purpose of this study was to use MR imaging, especially fat-suppressed three-dimensional (3D) spoiled gradient-recalled echo sequences, to identify patterns of growth arrest after physeal insult in children.

MATERIALS AND METHODS

We evaluated 111 children with physeal bone bridges (median age, 11.4 years) using MR imaging to analyze bridge size, location in physis, signal intensity, growth recovery lines, avascular necrosis, and metaphyseal cartilage tongues. Fifty-eight patients underwent fat-suppressed 3D spoiled gradient-recalled echo imaging with physeal mapping. The cause, bone involved, radiographic appearance, and surgical interventions (60/111) were also correlated. Data were analyzed with the two-tailed Fisher's exact test.

RESULTS

Posttraumatic bridges, accounting for 70% (78/111) of patients, were most often distal, especially of the tibia (n = 43) and femur (n = 14), whereas those due to the other miscellaneous causes were more frequently proximal (p < 0.0001). The position of the bridge in the physis was related to the bone involved (p < 0.0001). Sixty-five percent of distal tibial bridges involved the anteromedial physis, whereas 60% of the distal femoral arrests were central. Larger bridges had higher T1 signal intensity (p < 0.008). Oblique growth recovery lines were seen exclusively with bridges involving the peripheral physis (p = 0.002) and smaller, more potentially resectable bridges. Metaphyseal cartilaginous tongues were seen with all causes, but avascular necrosis was exclusively posttraumatic (p = 0.03). Signal characteristics and bridge size did not vary with the cause.

CONCLUSION

Premature physeal bony bridging in children is most often posttraumatic and disproportionately involves the distal tibia and femur where bridges tend to develop at the sites of earliest physiologic closure, namely anteromedially and centrally, respectively. MR imaging, especially with the use of fat-suppressed 3D spoiled gradient-recalled echo imaging, exquisitely shows the growth disturbance and associated abnormalities that may follow physeal injury and guides surgical management.

Heterogeneity in the growth of the axial and appendicular skeleton in boys: implications for the pathogenesis of bone fragility in men

Men with spine fractures have reduced vertebral body (VB) volume and volumetric bone mineral density (vBMD). Men with hip fractures have reduced femoral neck (FN) volume and vBMD, site-specific deficits that may have their origins in growth. To describe the tempo of growth in regional bone size, bone mineral content (BMC), and vBMD, we measured bone length, periosteal and endocortical diameters, BMC, and vBMD using dual-energy X-ray absorptiometry in 184 boys aged between 7 and 17 years. Before puberty, growth was more rapid in the legs than in the trunk. During puberty, leg growth slowed while trunk length accelerated. Bone size was more advanced than BMC in all regions, being approximately 70% and approximately 35% of their predicted peaks at 7 years of age, respectively. At 16 years of age, bone size had reached its adult peak while BMC was still 10% below its predicted peak. The legs accounted for 48%, whereas the spine accounted for 10%, of the 1878 g BMC accrued between 7 and 17 years. Peripubertal growth contributed (i) 55 % of the increase in leg length but 78% of the mineral accrued and (ii) 69% of the increase in spine length but 87% of the mineral accrued. Increased metacarpal and midfemoral cortical thickness was caused by respective periosteal expansion with minimal change in the endocortical diameter. Total femur and VB vBMD increased by 30-40% while size and BMC increased by 200-300%. Thus, growth builds a bigger but only slightly denser skeleton. We speculate that effect of disease or a risk factor during growth depends on the regions maturational stage at the time of exposure. The earlier growth of a regions size than mass, and the differing growth patterns from region to region, predispose to site-specific deficits in bone size, vBMD, or both. Regions further from their peak may be more severely affected by illness than those nearer completion of growth. Bone fragility in old age is likely to have its foundations partly established during growth.