The Proximal Origin of the Gluteus Maximus: A Cadaveric Study

Objectives: Many anatomy textbooks describe the origin of the gluteus maximus indistinctly as the gluteal surface of the ilium, lumbar fascia, sacrum, and sacrotuberous ligament and depict it laterally along the sacral margin. Our observation is that the origin of the gluteus maximus occurs much more medial and just off midline than what is typically depicted in standard anatomy textbooks. The purpose of the present study was to define the anatomy of the proximal origin of the gluteus maximus through anatomical dissections of donated human fresh tissue and compare the findings with multiple anatomy drawings, textbook figures, and MRI depictions of the gluteus maximus. Methods: Six donated human torso cadaveric specimens, for a total of 12 gluteus maximus specimens, were dissected in the prone position. The proximal origin of the gluteus maximus and its relationship to the surrounding structures were documented and measured with the use of digital calipers. Photographs were obtained of the dissections, which were compared with 30 illustrative depictions of the origins of the gluteus maximus. These were compared with MRI scans of 12 patients. Results: The gluteus maximus originates on the gluteal surface of the ilium, lumbar fascia, sacrum, sacrotuberous ligament, and laterally along the sacral margin. A number of measurements were obtained. In the cadavers and MRI samples a larger percentage of the gluteus maximus was medial to the posterior superior iliac spine (PSIS). In the cadaver specimens, the gluteus maximus was on average 29 ± 6% medial to the PSIS. In the MRI scans, the gluteus maximus was on average 21 ± 6% medial to the PSIS. In the illustrative depictions, the gluteus maximus was on average 15 ± 20% medial to the PSIS. A larger percentage of the space between the midline and the PSIS was occupied by gluteus maximus in the MRI depictions and cadaver specimens. In the cadaver specimens, 82 ± 11% of the area between the midline and the PSIS was occupied by the gluteus maximus. In the MRI scans, 80 ± 12% of the area between the midline and the PSIS was occupied by the gluteus maximus. In the illustrative depictions, 28 ± 37% of the area between the midline and the PSIS was occupied by the gluteus maximus. The gluteus maximus origins in both the fresh-tissue dissections and the MRI scans were much more midline than what was depicted in the textbooks and anatomy drawings. Conclusions: Many anatomy textbooks incorrectly depict the origin of the gluteus maximus. Care must be taken to preserve the medial fibres of the gluteus maximus origin when a posterior approach to the sacroiliac joint is undertaken. Because of the mid-maximus vascular pedicle, incision through a standard approach based on text figures will amputate the medially based fibres. This leads to devitalized muscle in the surgical field with increased risk for wound complications.