The Intervertebral Disc: Physiology and Pathology of a Brittle Joint.

BACKGROUND: Intervertebral disc (ID) degeneration represents the number one cause for outpatient clinic visits worldwide. Mechanisms are discussed but not yet clearly established. Consequently, back pain management is commonly limited to symptomatic treatment therapies.
OBJECTIVES: The aim of this review is to evaluate major progress and to unravel the biology and pathology of ID discogenic pain.
METHODS: The design of this study is a systematic review. A literature search was conducted using Medline, EMBASE, and Google Scholar databases, with no time constraints to locate relevant literature. Significant articles (literature reviews, therapeutic essays, clinical-human-research studies, animal research, and laboratory research) on the intervertebral disc were identified and reviewed. The exclusion criteria were the following: case reports and clinical studies with <10 patients.
RESULTS: Through a dense review of the literature, the ID is deciphered and described as a fragile anatomic entity. For this systematic review, 132 studies were identified and 79 were retained. The main deterioration and alteration mechanisms that lead to the programmed death of the ID are summarized. In addition, the large variety of biological therapies that override surgical treatment are determined.
CONCLUSIONS: The degeneration mechanisms of the ID are well defined and decrypted. Although therapies have progressed, none has been effective. The regeneration of the ID remains highly challenging because of the complexity of its natural composition, microstructure, and mechanical properties.