Coccydynia is a musculoskeletal condition characterized by pain in the coccygeal region, particularly exacerbated by sitting, and is associated with impaired quality of life and functional limitation. Although various conservative and interventional treatment options are available, there remains a need for effective and safe alternative therapies, especially in treatment-resistant cases.

Prolotherapy is a regenerative treatment modality that aims to reduce pain and improve function by stimulating tissue repair, particularly in ligamentous structures. While there is increasing evidence supporting its effectiveness in mechanical musculoskeletal pain conditions, the literature regarding its use in coccydynia is limited.

The aim of this study is to evaluate the effect of dextrose prolotherapy on pain severity and functional status in patients diagnosed with coccydynia. This study is designed as a prospective, single-arm, open-label interventional study. Patients will receive 15% dextrose prolotherapy according to a standardized protocol. Pain severity will be assessed using the Visual Analog Scale (VAS), and functional status will be evaluated using the Dallas Pain Questionnaire before treatment and at 1 month after completion of the treatment.

This study aims to provide more comprehensive data on the effectiveness and safety of prolotherapy in coccydynia and to contribute to the currently limited evidence in the literature.

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.

Inclusion Criteria:

• Age between 18 and 75 years
• Pain persisting for ≥3 months and refractory to conservative treatment
• Coccydynia of mechanical or idiopathic origin

Exclusion Criteria:

• Age <18 years or >75 years
• Pregnancy
• Allergy to the proliferant solution
• Active infection
• Use of anticoagulant medications
• Presence of malignancy
• Local abscess
• Hemorrhagic diathesis
• Certain types of septic arthritis
• Parafunctional habits

Individual participant data will not be shared due to institutional data protection policies and the absence of participant consent for data sharing beyond the scope of the current study.