This prospective randomized controlled trial aims to evaluate the efficacy and safety of ultrasound-guided repeated normal saline injections for the prevention and treatment of tendon adhesion following flexor tendon repair. Tendon adhesion is a common complication after tendon injury, leading to pain, stiffness, and impaired hand function. Conventional anti-adhesion strategies, such as physical barrier membranes, may induce local inflammation or have limited effectiveness.

In this study, patients undergoing tendon repair will be randomly assigned to receive either ultrasound-guided peritendinous saline injections at 7, 14, and 21 days after surgery (intervention group) or no injection (control group). The primary outcome is total active motion (TAM-%) at 3 months after surgery. Secondary outcomes include TAM-% at 6 weeks, pain scores (VAS), Michigan Hand Questionnaire (MHQ) scores, infection rate, and tendon rupture rate. A total of 136 patients will be enrolled (68 in each group).

The findings of this trial will help to establish whether repeated saline injections under ultrasound guidance can effectively prevent tendon adhesion, improve pain and functional outcomes, and ensure tendon healing with minimal complications.

Tendon adhesion is one of the most common complications following flexor tendon repair, with an incidence of up to 60%. Adhesion significantly impairs hand function, often leading to a cycle of adhesion formation, surgical release, and recurrent adhesion, which causes long-term disability and high healthcare costs. Current preventive measures mainly rely on physical barrier materials, such as membranes or gels, but these approaches may induce aseptic inflammation and pain, and their long-term effectiveness remains limited.

Our previous research suggested that early peritendinous injection therapy may be more effective than intraoperative application in preventing tendon adhesion. Using dynamic ultrasound, we successfully localized tendon adhesion sites and demonstrated the feasibility of delivering precise peritendinous injections under ultrasound guidance. Based on these findings, we hypothesize that repeated ultrasound-guided saline injections at early postoperative stages can reduce adhesion formation while minimizing the impact on tendon healing.

This is a prospective, single-center, randomized controlled clinical trial enrolling 136 patients (68 per group) after flexor tendon repair. Patients in the intervention group will undergo ultrasound-guided peritendinous injections of 1 mL normal saline on postoperative days 7, 14, and 21. The control group will receive standard care without injections. Patients will be followed up at 6 weeks and 3 months after surgery. The primary endpoint is total active motion (TAM-%) at 3 months. Secondary endpoints include TAM-% at 6 weeks, visual analog scale (VAS) pain scores, Michigan Hand Questionnaire (MHQ) scores, infection rate, tendon rupture rate, and wound healing time.

Safety will be assessed through physical examinations, laboratory tests (blood count, C-reactive protein, erythrocyte sedimentation rate), and adverse event monitoring. Statistical analysis will be performed using appropriate parametric or non-parametric methods, with significance set at P < 0.05.

The successful completion of this study is expected to provide clinical evidence supporting ultrasound-guided saline injections as a safe, effective, and low-cost strategy for preventing tendon adhesion, improving hand function, and reducing complications.

Inclusion Criteria:

Age between 18 and 60 years. Diagnosed with flexor tendon rupture. Scheduled for surgical tendon repair.

Exclusion Criteria:

Associated vascular or nerve injury. History of diabetes mellitus. History of non-steroidal anti-inflammatory drug (NSAID) treatment. History of cardiac insufficiency. History of hematologic diseases. History of hepatic or renal dysfunction. History of rheumatologic or autoimmune diseases. History of radiotherapy or chemotherapy. History of corticosteroid treatment. Pregnancy. Currently participating in another clinical trial.

Individual participant data will not be shared due to concerns regarding patient privacy and institutional regulations.

This is an open-label study; no masking will be applied.