Hiroshi Abe1, Shogo Hayashi2, Ji Hyun Kim3, Gen Murakami4, José Francisco Rodríguez-Vázquez5, Zhe Wu Jin6. 1. Department of Anatomy, Akita University Graduate School of Medicine and Faculty of Medicine, Akita, Japan. 2. Department of Anatomy, Division of Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara-shi, Kanagawa, 259-1193, Japan. sho5-884@umin.ac.jp. 3. Department of Anatomy, Jeonbuk National University Medical School, Jeonju, Republic of Korea. 4. Division of Internal Medicine, Cupid Clinic, Iwamizawa, Hokkaido, Japan. 5. Department of Human Anatomy and Embryology, School of Medicine, Complutense University, Madrid, Spain. 6. Department of Anatomy, Wuxi Medical School, Jiangnan University, Wuxi, Jiangsu Province, China.
Abstract
PURPOSE: The three-layered thoracolumbar fascia (TLF) encapsulates the erector spinae and the quadratus lumborum and has been a major concern for physical therapists. However, knowledge of its prenatal development and growth is limited. METHODS: Histological examination of 25 embryos and fetuses at 6-37 weeks (CRLs, 15-310 mm). RESULTS: At the posterior end, the abdominal muscles continued toward an initial posterior layer of the TLF (pTLF) at 6 weeks, but the connection became narrow and limited to the obliquus externus aponeurosis until near term. The middle layer of the TLF (mTLF) appeared as a posterior continuation of the transversalis fascia at 9 weeks and, depending on a mechanical demand for the vertebral column extension near term, it grew as a thick intermuscular septum between the iliocostalis and quadratus lumborum. Thus, the mTLF lateral end changed from the abdominal wall to the back or pTLF. The serratus posterior inferior originated from the pTLF after 9 weeks, but a connection of the latissimus dorsi with the fascia was established much later. Near term, the gluteus maximus was attached to an aponeurosis covering the multifidus behind the sacrum. Therefore, the pTLF extended to cover the gluteal muscles. CONCLUSION: We rejected the hypothesis that the mTLF develops as a marginal tissue between the primitive epaxial and hypaxial muscles. This study seemed to be the first report showing a fact that, within prenatal life, a drastic change is likely to occur in interfascial connections and their topographical relation to muscles; the TLF might be the best sample.
PURPOSE: The three-layered thoracolumbar fascia (TLF) encapsulates the erector spinae and the quadratus lumborum and has been a major concern for physical therapists. However, knowledge of its prenatal development and growth is limited. METHODS: Histological examination of 25 embryos and fetuses at 6-37 weeks (CRLs, 15-310 mm). RESULTS: At the posterior end, the abdominal muscles continued toward an initial posterior layer of the TLF (pTLF) at 6 weeks, but the connection became narrow and limited to the obliquus externus aponeurosis until near term. The middle layer of the TLF (mTLF) appeared as a posterior continuation of the transversalis fascia at 9 weeks and, depending on a mechanical demand for the vertebral column extension near term, it grew as a thick intermuscular septum between the iliocostalis and quadratus lumborum. Thus, the mTLF lateral end changed from the abdominal wall to the back or pTLF. The serratus posterior inferior originated from the pTLF after 9 weeks, but a connection of the latissimus dorsi with the fascia was established much later. Near term, the gluteus maximus was attached to an aponeurosis covering the multifidus behind the sacrum. Therefore, the pTLF extended to cover the gluteal muscles. CONCLUSION: We rejected the hypothesis that the mTLF develops as a marginal tissue between the primitive epaxial and hypaxial muscles. This study seemed to be the first report showing a fact that, within prenatal life, a drastic change is likely to occur in interfascial connections and their topographical relation to muscles; the TLF might be the best sample.