Cartilage-bone interactions are structurally and functionally complex. Understanding this complexity is crucial with regard to non-invasive diagnosis and characterization of disease, as well as for development of treatment methods.
Target Audience:
Clinical radiologists, radiology trainees (residents/ fellows), researchers at
all levels of training, MR technologists
Outcome/ Objectives:
The primary objectives of this talk are to: 1) review various anatomic
cartilage-bone interfaces in the human musculoskeletal system, 2) briefly
explain the biomechanical rationale for this structural interface, and 3)
illustrate the clinical implications of an altered cartilage-bone interface
through examples of commonly encountered pathology.
Discussion: While cartilage-bone interactions are most commonly described at articular surfaces in synovial joints (calcified layer cartilage between hyaline cartilage and bone), they exist elsewhere in the musculoskeletal system. Fibrous joints, such as the intervertebral disc, have the calcified and uncalcified cartilaginous endplate that abut the vertebral body. Fibrocartilaginous entheses have been well-described in the imaging and pathology literature, and have been broadly described in the setting of the synovial-entheseal complex.
In a very general sense, these tissue transitions serve as a means to mitigate severe material property differences between soft tissue structures (hyaline articular cartilage, intervertebral disc, tendon) and bone. This provides a biomechanical advantage to decrease failure at an abrupt material property difference.
From a clinical standpoint, transition tissues (calcified layer cartilage, calcified and uncalciifed cartilaginous endplate and fibrocartilaginous nodules/ sesamoids) are short T2 tissues and not readily visible on standard MR pulse sequences. In current clinical practice, failure at the cartilage-bone interfaces are expressed as changes in bone versus soft tissue.
We will emphasize the MR characterization of commonly encountered cartilage-bone interfaces, including the intervertebral disc, the Achilles tendon, and the articular surfaces of the knee. Further, we will discuss commonly encountered pathology, and the need for a balanced structural and biomechanical construct to maintain structural and functional integrity.
Conclusion: Cartilage-bone interactions are structurally and functionally complex. Understanding this complexity is crucial with regard to non-invasive diagnosis and characterization of disease, as well as for development of treatment methods.
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Bae, et al., Morphology of the cartilaginous endplate in human intervertebral discs with ultrashort echo time MR imaging. Radiology 2013; 266(2): 564-74.