Anatomical and Radiological Study of Adult Human Sacrotuberous Ligament and Its Relation to the Sacroiliac Joint

Low back pain (LBP) is an important problem that increased nowadays and affects quality of life. Sacroiliac joint (SIJ) is one of the important causes of LBP in about 15%_25% of the cases. Sacrotuberous ligament (STL) is a part of the fibromuscular network of the joint that may alter its biomechanics and become a diagnostic or management tool in dealing with LBP patients and sacroiliitis.
Aim of the Work: The study aimed to give an anatomical and radiological review of the STL and correlate it with LBP and sacroiliitis.
Materials and methods: Cadaveric study: 20 formalin fixed and 20 fresh frozen specimens of adult male human hip, gluteal and upper thigh were dissected exposing the STL and surrounding communications, also the pelvic cavity was dissected. The length and width of the ligament were measured and calculated as Mean ±SD.
Radiological study: In a retrospective study, 35 pelvic reconstructed CT scans were collected from adult human male ranging from 20-40 years old and divided into three groups: 2 control groups, group (A): no LBP nor sacroiliitis, group (B): LBP but no sacroiliitis and group (C): LBP and sacroiliitis and this group was further subdivided into: group (C-): Normal STL and group (C+): Redundant free limb of the STL. Shape and length of STL in each group and measurements were statistically analyzed.
Results: In cadaveric study: STL was divided to three limbs: two attached, one extending from posterior superior iliac spine to back of S3 and its length ranged from 20mm-35mm in formalin fixed specimens and from 32.9mm-44mm in fresh frozen specimens, and the other one extending from back of S3 to back of S5 and back of the coccyx and measured 28.1mm-38.4mm in formalin fixed specimens and from 35.2mm-45mm in fresh frozen specimens. The third limb (free limb) extending from the previous point to midpoint of medial surface of ischial tuberosity and its mean length was 45.21± 6.04mm in formalin fixed specimens and 52.17± 8.39mm in fresh frozen specimens.
In radiological study: Redundancy of free limb of the STL was found in 10 out of 16 of CT scans with sacroiliitis with increased mean length up to 69.38 mm.
Conclusion: Wide attachment of STL to the surrounding was observed and may affect SIJ biomechanics and increases probability of LBP. We recommend in further studies to consider STL in diagnosis and treatment of LBP patients and clinically evaluate the intensity of the condition and correlate it with the degree of the laxity of the ligament in CT scans.