Ultrasound-Guided Dextrose Prolotherapy for Coccydynia: A Prospective Study

Coccydynia is a musculoskeletal disorder characterized by localized pain in the coccygeal region, typically exacerbated by sitting and postural changes, and associated with impaired quality of life and functional limitation. Although various conservative and interventional treatment modalities have been described, a subset of patients remains symptomatic despite standard therapies. Considering the potential role of ligamentous dysfunction, repetitive microtrauma, and coccygeal instability in the pathophysiology of coccydynia, regenerative treatment approaches such as prolotherapy may provide clinical benefit.

Prolotherapy is a regenerative injection therapy that involves the administration of an irritant solution, most commonly hypertonic dextrose, to stimulate the body's natural healing response. The proposed mechanism includes induction of a mild, controlled inflammatory response, leading to increased fibroblast proliferation, collagen synthesis, and subsequent strengthening of ligamentous and periarticular structures. In conditions associated with ligamentous laxity or enthesopathy, prolotherapy is thought to enhance tissue repair and restore biomechanical stability. Increasing evidence suggests that prolotherapy may reduce pain and improve function in various chronic musculoskeletal conditions, particularly those with a mechanical or ligamentous component. However, evidence regarding its effectiveness in coccydynia remains limited.

This study is designed as a prospective, single-arm, open-label interventional study to evaluate the effectiveness and safety of dextrose prolotherapy in patients with chronic coccydynia. Adult patients (≥18 years) with mechanical or idiopathic coccydynia persisting for at least 3 months and unresponsive to conservative treatment will be included. Patients with pregnancy, malignancy, active infection, bleeding diathesis, uncontrolled hypertension or diabetes mellitus, or contraindications to prolotherapy will be excluded.

All participants will receive prolotherapy using a 15% dextrose solution prepared under sterile conditions. Injections will be performed under ultrasound (USG) guidance to ensure precise anatomical localization and to enhance procedural safety. During the procedure, the sacral hiatus, sacrococcygeal ligament, and coccygeal bony structures will be visualized, and bone landmarks will be used as references. The fibrous ligamentous attachments in the coccygeal and sacrococcygeal region will be targeted, and injections will be administered to 3-4 periosteal insertion points using a 27G needle, with a maximum of 0.5 mL per site and a total volume not exceeding 2-2.5 mL per session. The procedure will be repeated at 3-week intervals, with a total of 3 to 6 sessions depending on clinical response.

The primary outcome measure will be the change in pain severity assessed by the Visual Analog Scale (VAS). The secondary outcome measure will be the change in functional status evaluated using the Dallas Pain Questionnaire. Outcome assessments will be performed at baseline (pre-treatment) and at 1 month after completion of the treatment protocol.

Sample size was calculated based on a power analysis (α=0.05, power=0.80), which indicated that a minimum of 25 patients would be required. Considering a potential 15% dropout rate, a total of 30 patients will be enrolled.

Safety will be assessed by monitoring and recording any adverse events throughout the study period. All participants will be followed prospectively, and changes in clinical parameters will be analyzed to determine the effectiveness of the intervention.

• Dallas Pain Questionnaire (DPQ) [Time frame: Baseline and 1 month after completion of treatment]