Original Article Anatomical analysis of the relation between human ligamentum flavum and posterior spinal bony prominence * Javid Akhgar, Hidetomi Terai * , Mohammad Suhrab Rahmani, Koji Tamai, Akinobu Suzuki, Hiromitsu Toyoda, Masatoshi Hoshino, Mitsuhiko Ikebuchi, Sayed Abdullah Ahmadi, Kazunori Hayashi, Hiroaki Nakamura Department of Orthopedic Surgery, Osaka City University Graduate School of Medicine, Japan article info Article history: Received 22 September 2016 Received in revised form 28 November 2016 Accepted 1 December 2016 Available online xxx abstract Background: Posterior spinal bony prominences are commonly used as landmarks during posterior spinal surgery; however, the exact relationship of these structures with ligamentum flavum (LF) borders and attachments has not been clarified. Materials and methods: Whole spines were removed en bloc from 20 embalmed human cadavers. Plain radiographs and computed tomography (CT) scans of each whole spine were taken, and then the spine was divided in two parts along the pedicle bases. The LFs were painted with contrast dye, and second radiographs and CT scans were taken again. Radiographic data were analyzed using CT image analyzer. Results: The craniolateral border of LF at four upper lumbar levels (from L1/2 to L4/5) located cranial to isthmus in both sides (3.5 mm), meanwhile, it located at or below isthmus in both sides at L5eS1 level (0.5 mm). In the midline, LF attached below the isthmus levels at four upper lumbar levels (4 mm), though it located in the same level of isthmus at L5eS1 (1 mm). The mean distance between medial border of pedicles and lateral border of LF increased from upper to the lower lumbar levels (6.5 mm at L1/ 2 e 11.4 mm at L5eS1). Distance between interlaminar space and cranial border of LF at the midline gradually increased from 8.2 mm at L1 toward 11.1 mm at L4, it was 9.3 mm in L5. Conclusions: From the data of new analytical method using contrasted LF and reconstructed CT, the detailed relations between bony prominence and the border of LF were uncovered. Based on these findings and reconstructed LF images superimposed on lamina, surgeons would design safe and adequate lumbar spinal decompression with imagination of overall pictures of the LF from the dorsal side. © 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved. 1. Introduction Ligamentum flavum (LF) plays an important role in the control of intervertebral movement, the provision of intrinsic spinal sta- bility in sitting and standing postures, and the maintenance of a smooth surface on the posterior wall of the spinal canal and neural foramina [1e3]. In patients with hypertrophied LF, lumbar spinal decompression surgery is done to remove the LF; the aim of this is to release compression and prepare enough space for the neural elements without causing iatrogenic instability. The overall shape of the LF cannot be seen from the dorsal side of the vertebrae. Therefore, information about the relationship of the LFs attach- ments with bony prominences is mandatory for determining safe penetration depths and sufficient resection of the LF during decompression surgery and to prevent iatrogenic instability due to bone over-resection [4,5]. A pioneer clinical and anatomical study of intervertebral disc lesions and the LF published in 1938 provided a clear visualization of the ligaments of the lumbar spine in different section planes [6]; further descriptions of LF have been added over the past seven decades [1e4,7e25]. There is little difference between the initial anatomical description of LF described in 1938 and the current one, especially regarding the cranial and caudal attachments; however, from a surgical point of view, much practical and useful knowledge has been gained. We now know that the LF is composed of deep and * The submitted manuscript does not contain any information about medical drugs. * Corresponding author. Department of Orthopedic Surgery, Osaka City Univer- sity Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan. Fax: þ81 6 6645 6260. E-mail address: hterai@med.osaka-cu.ac.jp (H. Terai). Contents lists available at ScienceDirect Journal of Orthopaedic Science journal homepage: http://www.elsevier.com/locate/jos http://dx.doi.org/10.1016/j.jos.2016.11.020 0949-2658/© 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved. Journal of Orthopaedic Science xxx (2016) 1e6 Please cite this article in press as: Akhgar J, et al., Anatomical analysis of the relation between human ligamentum flavum and posterior spinal bony prominence, Journal of Orthopaedic Science (2016), http://dx.doi.org/10.1016/j.jos.2016.11.020