Does the Latissimus dorsi insert on the iliac crest in man? Anatomic and ontogenic study

Fetal development of the thoracolumbar fascia with special reference to the fascial connection with the transversus abdominis, latissimus dorsi, and serratus posterior inferior muscles

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.

Posterior Iliac Crest Bone Graft: How Much Is Enough?

Autogenous bone grafting is the gold standard for reconstructing craniofacial defects. Mandibular defects are reliably reconstructed with free nonvascularized bone, such as from the posterior iliac crest (PIC). In light of improved imaging, including 3-dimensional computed tomography scanning, a more accurate defect estimation is possible. A strong understanding of bone graft available is necessary. The purpose of this study was an updated review of the dissection and quantification of the amount of bone that can be safely harvested. Bilateral bicortical osteotomy was performed on 55 cadavers to obtain 110 PIC bone grafts. Demographic factors and bicortical osteotomy measurements were recorded. Average osteotomy lengths, widths, and depths were 7.4, 5.5, and 1 cm, respectively. The average bicortical osteotomy volume was 40.6 cm. During the dissection, the authors identified 2 anatomical variants with respect to muscle insertion into the PIC. In variation 1, which occurred in 62% of dissections, the latissimus dorsi and thoracolumbar fascia did not originate from the PIC. When this occurred, the quadratus lumborum attached to the PIC. In variation 2, which occurred in 38% of dissections, the latissimus dorsi and thoracolumbar fascia originate from the PIC. By identifying the maximal bone volume obtainable from a PIC graft and noting 2 anatomical variants, this study allows for more accurate surgical planning and management.

Hitherto unknown detailed muscle anatomy in an 8-week-old embryo

Congenital muscle diseases, such as myopathies or dystrophies, occur relatively frequently, with estimated incidences of up to 4.7 per 100 000 newborns. To diagnose congenital diseases in the early stages of pregnancy, and to interpret the results of increasingly advanced in utero imaging techniques, a profound knowledge of normal human morphological development of the locomotor system and the nervous system is necessary. Muscular development, however, is an often neglected topic or is only described in a general way in embryology textbooks and papers. To provide the required detailed and updated comprehensive picture of embryologic muscular anatomy, three‐dimensional (3D) reconstructions were created based on serial histological sections of a human embryo at Carnegie stage 23 (8 weeks of development, crown–rump length of 23.8 mm), using amira reconstruction software. Reconstructed muscles, tendons, bones and nerves were exported in a 3D‐PDF file to permit interactive viewing. Almost all adult skeletal muscles of the trunk and limbs could be individually identified in their relative adult position. The pectoralis major muscle was divided in three separate muscle heads. The reconstructions showed remarkable highly developed extraocular, infrahyoid and suprahyoid muscles at this age but surprisingly also absence of the facial muscles that have been described to be present at this stage of development. The overall stage of muscle development suggests heterochrony of skeletal muscle development. Several individual muscle groups were found to be developed earlier and in more detail than described in current literature.

The Decussating Fibers of the Lumbar Thoracolumbar Fascia: A Landmark for Identifying the L5 Spinous Process?

BACKGROUND

The thoracolumbar fascia (TLF) has been well studied and is known to have crisscrossing fibers. Based on surgical experience, we hypothesized that the decussating fibers of the TLF may indicate a specific vertebral level and performed an anatomic study.

METHODS

Twenty adult fresh frozen cadavers aged 72-84 years at death were placed in the prone position, and the skin of the lumbar and upper sacrum was removed. Careful attention was given to the TLF and any fibers of it that grossly crossed the midline to interdigitate with its contralateral counterpart. Once such decussations were identified, a metal wire was laid on them at their center, and fluoroscopy was performed to verify the vertebral level.

RESULTS

Decussating fibers of the TLF were found on all but 1 specimen (95%). The central part of the decussation on the midline corresponded to the spinous process of L5 in 17/19 (89%) of specimens and the lower edge (L4-L5 interspace) of the spinous process of L4 in the remaining 2 specimens (11%). No specimens were found to have previous surgery in the area dissected or congenital anomalies of the spine.

CONCLUSIONS

In our cadaveric study, the decussating fibers of the TLF in the lumbar region helped predict the L5 spinous process in 89% of specimens and the L4 spinous process in 11% of specimens. This anatomic landmark might be used as an adjunct to palpation and intraoperative imaging during surgical exploration of the lower lumbar region.

[Comparison of the Latissimus dorsi insertions on the iliac crest in chimpanzee (Pan troglodytes) and in man]

INTRODUCTION

Comparing to other primates, one of the most important specificities of the human anatomy are consequences of bipedalism. Although bone consequences are well known (lumbar lordosis, horizontal position of the foramen magnum, lengthening of the lower limbs, reduction of the pelvis, specialization of the foot), consequences of our locomotion on the Latissimus dorsi are still unclear.

MATERIALS AND METHODS

One dissection of a chimpanzee Latissimus dorsi (Pan troglodytes) has been performed and compared to 30 human Latissimus dorsi dissections (10 fresh cadavers and 20 formoled cadavers). In each dissection, the existence of direct muscular insertions on the iliac crest has been investigated and the constitution of the thoracolumbar fascia has been described.

RESULTS

In chimpanzee dissection, a muscular direct insertion of the Latissimus dorsi was present on the iliac crest of 9 cm long. The TLF was made of the superficial and the deep fascias of the Latissimus dorsi and the superficial fascia of the erector spinae muscles which was deeper. In man, there was no direct muscular insertion of the Latissimus dorsi in 90 % of cases, the TLF was constituted the same way.

CONCLUSION

This study suggests that the Latissimus dorsi has been separated from the iliac crest in man during the evolution because of the permanent bipedalism and that it stayed inserted on the iliac crest in chimpanzee because of the brachiation.

The thoracolumbar fascia: anatomy, function and clinical considerations

In this overview, new and existent material on the organization and composition of the thoracolumbar fascia (TLF) will be evaluated in respect to its anatomy, innervation biomechanics and clinical relevance. The integration of the passive connective tissues of the TLF and active muscular structures surrounding this structure are discussed, and the relevance of their mutual interactions in relation to low back and pelvic pain reviewed. The TLF is a girdling structure consisting of several aponeurotic and fascial layers that separates the paraspinal muscles from the muscles of the posterior abdominal wall. The superficial lamina of the posterior layer of the TLF (PLF) is dominated by the aponeuroses of the latissimus dorsi and the serratus posterior inferior. The deeper lamina of the PLF forms an encapsulating retinacular sheath around the paraspinal muscles. The middle layer of the TLF (MLF) appears to derive from an intermuscular septum that developmentally separates the epaxial from the hypaxial musculature. This septum forms during the fifth and sixth weeks of gestation. The paraspinal retinacular sheath (PRS) is in a key position to act as a 'hydraulic amplifier', assisting the paraspinal muscles in supporting the lumbosacral spine. This sheath forms a lumbar interfascial triangle (LIFT) with the MLF and PLF. Along the lateral border of the PRS, a raphe forms where the sheath meets the aponeurosis of the transversus abdominis. This lateral raphe is a thickened complex of dense connective tissue marked by the presence of the LIFT, and represents the junction of the hypaxial myofascial compartment (the abdominal muscles) with the paraspinal sheath of the epaxial muscles. The lateral raphe is in a position to distribute tension from the surrounding hypaxial and extremity muscles into the layers of the TLF. At the base of the lumbar spine all of the layers of the TLF fuse together into a thick composite that attaches firmly to the posterior superior iliac spine and the sacrotuberous ligament. This thoracolumbar composite (TLC) is in a position to assist in maintaining the integrity of the lower lumbar spine and the sacroiliac joint. The three-dimensional structure of the TLF and its caudally positioned composite will be analyzed in light of recent studies concerning the cellular organization of fascia, as well as its innervation. Finally, the concept of a TLC will be used to reassess biomechanical models of lumbopelvic stability, static posture and movement.