This single-blind randomized controlled trial will aim to determine the effectiveness of a connective tissue dry needling (CTDN) technique, in reducing pain and improving function in individuals with chronic mechanical low back pain associated with pain and tenderness at the posterior superior iliac spine (PSIS). Forty participants with local PSIS-related low back pain will be recruited and randomly assigned into two groups using the block balanced randomization method. The treatment group will receive CTDN targeting connective tissue trigger points around the PSIS in addition to a sacroiliac joint stabilization exercise program, while the control group will perform the same exercise program alone under the supervision of a physiotherapist. The intervention protocol will span two weeks, during which participants will attend three treatment sessions per week, for a total of six sessions. The primary outcome measurement will use the Visual Analog Scale (VAS) to assess pain intensity. The study will measure secondary outcomes through lumbar range of motion (ROM) in flexion and extension and pressure pain threshold (PPT), and Roland-Morris Disability Questionnaire (RMDQ) functional disability and Short Form-36 (SF-36) health-related quality of life. The researchers will assess all outcomes at three time points: baseline and after the first session, and the sixth session, while VAS will receive an additional assessment at the 3-month follow-up. The findings of this study are expected to provide evidence supporting CTDN as a safe, effective, and cost-efficient treatment option for PSIS-related mechanical low back pain.

Low back pain (LBP) is one of the most widespread musculoskeletal disorders, which creates substantial disability and healthcare expenses throughout both developed and developing nations (1,2). The medical field categorizes LBP into two distinct types: specific and non-specific. The medical field identifies specific LBP through detectable causes, including infections and trauma and structural problems but non-specific LBP lacks identifiable spinal pathology and represents most cases (3,4). Research shows that LBP originates from multiple sources including intervertebral discs and facet joints and sacroiliac joints (SIJ) and their associated ligaments and muscles (5-8).

Research indicates that the SIJ acts as a primary pain source for 15-25% of patients who experience chronic LBP (9). The SIJ plays a vital biomechanical role by connecting the spine to the lower extremities through its complex network of ligaments and fascia which distributes both axial and rotational forces (10). The Posterior Superior Iliac Spine (PSIS) represents a significant anatomical reference point near the SIJ where multiple essential soft tissue structures including the long posterior sacroiliac ligament and thoracolumbar fascia and gluteus maximus converge (10,11). Studies based on clinical and anatomical evidence show that tissue dysfunction or irritation in this area leads to pain development in the PSIS region (12).

The Fascial Distortion Model (FDM) among other recent models demonstrates how fascia-bone junctions produce musculoskeletal pain through their mechanical interactions. The model indicates that extended periods of inactivity together with abnormal mechanical forces disrupt cellular communication and mineral transport at these junctions which leads to fascial adhesions and persistent pain (13,14). The complex anatomy and high sensitivity of the PSIS area has led to increased research about treatments that focus on the surrounding connective tissue structures.

The minimally invasive technique of dry needling fascial structures known as fascia dry needling (FDN) aims to create mechanical and cellular changes in the extracellular matrix of connective tissues. Research shows that dry needling procedures in connective tissue areas lead to increased fibroblast activity and cytoskeletal rearrangement which may create better matrix organization and decrease pain signals (15,17-19). Research through imaging and mechanobiological studies has proven that needle rotation in both directions leads to substantial tissue movement and increased gene expression for tissue repair without inflicting any structural harm (20-25).

Research conducted with animal subjects has validated these mechanistic results through observations of tendon recovery and tissue reorganization following needling procedures (22-25). The clinical application of dry needling has produced beneficial results for patients with lateral epicondylosis and Achilles tendinopathy and thoracic pain syndromes by improving their pain levels and mobility and functional abilities (26,29,30).

The medical field lacks any randomized controlled trial that investigates how fascia dry needling affects the PSIS region despite rising evidence about dry needling effects on different musculoskeletal conditions. The current clinical guidelines recommend periarticular or intra-articular injections for PSIS or SIJ-related pain but these procedures come with high costs and complex procedures and potential adverse effects for patients (31). The non-invasive nature of FDN makes it an attractive treatment option which needs thorough clinical assessment.

The research study aims to evaluate PSIS area fascia dry needling as an additional treatment for standard physiotherapy represents a critical knowledge gap in current medical literature. The confirmation of safety and effectiveness of this treatment method would lead to updated clinical guidelines and help decrease reliance on invasive procedures while giving healthcare providers an effective new treatment option for patients with PSIS-related mechanical low back pain.

Hypotheses:

Null Hypothesis (H₀): The fascia dry needling technique (Mahshid method) has no significant effect on pain intensity, lumbar range of motion, pain pressure threshold, functional disability, or quality of life in patients with chronic mechanical low back pain and point tenderness at the posterior superior iliac spine.

Alternative Hypothesis (H₁): The fascia dry needling technique (Mahshid method) has a significant positive effect on pain intensity, lumbar range of motion, pain pressure threshold, functional disability, and quality of life in patients with chronic mechanical low back pain and point tenderness at the posterior superior iliac spine.

Inclusion criteria:

1. Adults aged 18 to 75 years.
2. Diagnosed with chronic mechanical low back pain localized at the posterior superior iliac spine region.
3. Presence of point tenderness reproducible by palpation at the posterior superior iliac spine area.
4. Pain duration of at least two weeks, indicating the non-acute stage of low back pain.
5. Negative results in at least three out of five sacroiliac pain provocation tests (Distraction, Compression, Thigh Thrust, Sacral Thrust, Gaenslen).
6. Pain intensity ≥ 3 on the Numeric Rating Scale at baseline.
7. Ability to communicate and cooperate with the research team during intervention and follow-up.
8. Access to WhatsApp or equivalent communication application for follow-up pain reporting at the 3-month stage.

Non-inclusion criteria:

1. Presence of lumbar radicular pain or referred pain to the lower limbs.
2. History of lumbar spine trauma within the previous three months.
3. Fear or intolerance of needling procedures.
4. Current use of anticoagulant medication.
5. Known lymphatic disorders, immunosuppressive diseases, or neurological conditions such as epilepsy or seizure disorders.
6. Pregnancy or suspected pregnancy.

Exclusion criteria:

1. Voluntary withdrawal of consent at any time during the study.
2. Inability to tolerate the intervention or adverse reaction during treatment sessions.
3. Occurrence of serious adverse events or complications (e.g., infection, bleeding).
4. Non-compliance with treatment protocol or missing more than two sessions.
5. Any intercurrent illness or therapy that could interfere with the study outcomes or safety assessment

We have not decided yet, but at this moment, we have decided to share brief data with future researchers after requesting and submitting ethical committee permission.