Aim: To describe the sonoanatomy of the long posterior sacroiliac ligament (LPSL) in healthy volunteers and to assess by ultrasound the LPSL in patients with noninflammatory sacroiliac joint pain (SIP).Material and methods: We assessed 64 LPSLs of 32 healthy controls and 40 LPSLs of 40 patients with unilateral noninflammatory SIP and a positive Fortin finger test. LPSLs in both groups were assessed for the presence of alterations in their structure, continuity and echogenicity and their thickness was measured in three predefined points. All patients were examined in prone position following a strict scanning protocol.Results: Detailed sonoanatomy description and measurement of the LPSL in healthy volunteers are provided (length: 31.32±4.79 mm, width: 8.14±1.28 mm, thickness: 2.05±0.55 mm; 1.64±0.41 mm and 1.51±0.42 mm at the iliac and sacral entheses and in its middle part, respectively). The LPSLs were found to be significantly thicker in the SIP group, with an optimum criterion value of >2.0 mm in its middle part to identify pathologically thickened ligaments. In addition, LPSLs inthe SIP group presented significantly more often hypoechogenicity/altered fibrillar structure (57.5% vs.16%) and/or periligamentous edema (72.8% vs 28%). The combination of either altered structure or periligamentous edema, with thickening of theligament’s body showed the best diagnostic accuracy (sensitivity and specificity 83.9% and 94.7% for the first combination and 100% and 84.6% for the second combination) to identify LPSL pathology in noninflammatory SIP.Conclusions: LPSL could be assessed by ultrasound and sonopathological lesions could be identified in patients with SIP.

Low back pain (LBP) is an extremely common symptom in populations of all ages with significant economic and social burden worldwide. As such it should be among the priorities for trying to find more efficient methods for prevention and treatment. Currently the exact cause for the complaints can be found in most of the cases following thorough clinical examination, adequate diagnostic tests and modern image diagnosis. Most often the complaints are cause by degenerative processes affecting certain structures in the lumbosacral area – the intervertebral discs, the tendons/entheses along the iliac crest, the sacroiliac and lumbar facet joints. Platelet rich plasma (PRP) is a widely used therapeutic method aimed at recovering (both anatomical and functional) degenerative or traumatic damaged collagen tissues by injecting/applying autologous blood concentrate, rich in growth factors and other biologically active molecules. PRP demonstrates huge potential in stimulating cell proliferation and metabolic activity in vitro. Trials with animals show/prove the full recovery of the structural changes and the matrix integrity of the damaged tissue. In recent years some prospective clinical studies and published case series report that PRP could be a safe and efficient therapy for patients with chronic low back pain that do not yield to traditional/standard treatment options. Data though limited/scarce for the time being includes/covers the most common cause for this complaint, namely pathology of the intervertebral discs, facet and sacroiliac joints, as well as paraspinal soft tissues. The possibility for precise intralesional application of this regeneration autologous product in the damaged tissue gives it a huge advantage over the common algorithms currently used in the clinical practice to treat patients with such complaints. Future bigger studies including image methods to evaluate the structural recovery of the degenerative changed tissue responsible/blamed for the pain and functional deficit would bring light to the place PRP therapy should take in the treatment of low back pain.