MMP2 and lumbar disc herniation: Abbreviations: USA- United States of America, VNTR- variable number of tandem repeats, DDD- degenerative disc disease, OR- odds ratio, CI- confidence interval, p- p-value, SNP- single nucleotide polymorphism, LDH- lumbar disc herniation, IL-1⍺- interleukin 1 alpha, IDD- intervertebral disc degeneration, MMP- matrix metalloproteinase, ECM- extracellular matrix, MMP2- matrix metallopeptidase 2, a- systematic review and meta-analysis