7T MRI of distal radius trabecular bone microarchitecture: How trabecular bone quality varies depending on distance from end-of-bone.

PURPOSE: To use 7T magnetic resonance imaging (MRI) to determine how trabecular bone microarchitecture varies at the epiphysis, metaphysis, and diaphysis of the distal radius. MATERIALS AND METHODS: The distal radius of 24 females (mean age = 56 years, range = 24-78 years) was scanned on a 7T MRI using a 3D fast low-angle shot sequence (0.169 × 0.169 × 1 mm). Digital topological analysis was applied at the epiphysis, metaphysis, and diaphysis to compute: total trabecular bone volume; trabecular thickness, number, connectivity, and erosion index (a measure of network resorption). Differences and correlations were assessed using standard statistical methods. RESULTS: The metaphysis and epiphysis had 83-123% greater total bone volume and 14-16% greater trabecular number than the diaphysis (both P < 0.0001). The erosion index was significantly higher at the diaphysis than the metaphysis and epiphysis (both P < 0.01). The most elderly volunteers had lower trabecular number (<66 years mean 0.29 ± 0.01; ≥66 years, 0.27 ± 0.02, P < 0.05) and higher erosion index (<66 years mean 1.18 ± 0.17; age ≥66 years, mean 1.42 ± 0.46, P < 0.05) at the epiphysis; differences not detected by total trabecular bone volume. CONCLUSION: 7T MRI reveals trabecular bone microarchitecture varies depending on scan location at the end-of-bone, being of overall higher quality distally (epiphysis) than proximally (diaphysis). Age-related differences in trabecular microarchitecture can be detected by 7T MRI. The results highlight the potential sensitivity of 7T MRI to microarchitectural differences and the potential importance of standardizing scan location for future clinical studies of fracture risk or treatment response. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:872-878.

Histologic structure of the articular disk of the human distal radioulnar joint.

A histologic study of the structure of the articular disk of the distal radioulnar joint in humans was performed on 57 disks from 37 fresh cadavers that included fetuses and individuals up to age 65 years. The specimens were stained with hematoxylin and eosin, orcein, and Mallory and Mann-Dominici's methods, and studied with the light microscopy. It was found that the disks of adults were basically formed of the so-called fibrocartilagenous tissue composed of an intercellular substance in which there were interwoven wavelike collagen fiber bundles and between them three specific types of cells: (1) rather sparse fibrocytes mostly situated in dorsal and palmar margins, (2) predominant and constant chondroid cells dispersed throughout the disk, and (3) less-frequent real chondocytes distributed mostly in the central parts. This basic tissue is modified according to the age of the subjects and functional requirements. In fetuses and newborns, it is almost completely fibrous and very cellular, while in adults, it is more cartilaginous with significantly reduced cellularity. The structure of various parts of disks is adapted to the functional stresses exerted on them. In central parts exposed to pressure, the tissue is more cartilaginous, while peripheral, massive margins, subjected mostly to traction, are built in a ligamentlike pattern. The ulnar and carpal surfaces are adapted to the gliding movements of the ulna and carpus. It is concluded that the articular disk in humans, which is basically of fibrocartilagineous nature, is a dynamic structure biomechanically, predetermined and changing with aging.