The midline interlaminar ligament of the spine: An anatomical study

Abstract

AbstractIntroductionDuring routine cadaveric dissection, Simonds et al. in 2019 found a previously undocumented ligament, which they termed the midline interlaminar ligament (MIL), in 24 out of 36 (76.5%) lumbar spinal levels. The MIL is an unpaired ligament located between and distinctly separate from the right and left ligamenta flava (LF). The purpose of this study was to identify the presence or absence of the MIL in the cervical, thoracic, and lumbar spinal regions and obtain detailed measurements of the ligaments' toughness (R) and elastic modulus (E).Materials and MethodsIntact preserved cadaveric vertebrae from C2 to the upper sacral region were dissected. Presence or absence of the MIL was documented, and length and width of each MIL were measured in situ. The R and E of the LFs from corresponding spinal segments were found for comparison.ResultsAt least one MIL was observed in 90.3% (28) of specimens. Eighty‐eight MIL's were observed out of 186 cervical intervertebral levels (0.5%), 371 thoracic intervertebral levels (5.9%), and 101 lumbar intervertebral levels (63.4%). The mean width and length of the MIL were 1.21 ± 0.36 and 16.37 ± 2.17 mm, respectively. The mean R of the MIL and the LF were 1390.27 and 2068.04 J m−2, respectively. The mean E of the MILs and LFs was 46.78 ± 16.65 and 51.15 ± 21.68 MPa, respectively.ConclusionsBased on our findings, the MIL was present in the majority of vertebrae in our cadaveric population with a predominance for the lumbar region.