Biomechanical performance of shock wave interventions on the knot after rotator cuff repair

Background Rotator cuff standard surgery carries retear risks. Early postoperative Extracorporeal Shock Wave Therapy (ESWT) may enhance recovery and tendon healing, but its early-postoperative-use safety on suture knots remains unproven. Methods This study compared radial pressure wave therapy (EPAT) and focused ESWT on suture knots in rotator cuff repairs. EPAT comprised four standard-dose groups delivering 2000 impulses at 6 Hz (G1 Evo Blue 2.5 bar; G2 Evo Blue 4.0 bar; G3 Power + 2.5 bar; G4 Power + 3.8 bar) and a high-energy condition with 10,000 impulses (G4, 3.8 bar). ESWT included four energy groups (G1–G4: 0.08–0.38 mJ/mm 2 ) plus a high-energy G4 at 0.38 mJ/mm 2 with 10,000 impulses. Knots were secured to a 24 mm ringed syringe; loop circumference was measured after stretch. Knot strength was tested by single-load failure or 3 mm slip from a 10 N preload. Cyclic loading used a 10 N preload, 20 mm/min: 100 cycles at 25 N, then 50 N, increasing by 25 N every 100 cycles until failure or 3 mm slip. Findings Under medium energy (ESWT ≤0.28 mJ/mm 2 ; EPAT ≤4.0 bar; EvoBlue, 6 Hz), knot integrity was preserved in both groups under single-cycle and cyclic loading ( P > 0.05). Under high energy (ESWT =0.38 mJ/mm 2 ; EPAT ≤3.8 bar; Power+, 6 Hz), after 10,000 impulses single-cycle loads decreased in both groups ( P < 0.05), while cyclic loading showed no difference (P > 0.05). Interpretation Medium- to low-energy EPAT and focused ESWT did not affect knot integrity or loop dimensions under loading, indicating safety and potential for early postoperative use.