Proximal Hamstring Repair Strength: A Biomechanical Analysis at 3 Hip Flexion Angles

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Rehabilitation science

Background:

• Proximal hamstring repair is common for complete ruptures, but rehabilitation protocols lack consensus.
• Existing literature lacks biomechanical studies on proximal hamstring repairs and the effect of hip flexion angles.

Purpose of the Study:

• To biomechanically evaluate the effect of varying hip flexion angles on proximal hamstring repairs under cyclical loading.
• To determine the optimal postoperative hip flexion angle to minimize gap formation and ensure repair integrity.

Main Methods:

• Controlled laboratory study involving 24 cadaveric proximal hamstring insertions repaired with suture anchors.
• Cyclical loading (10-125 N at 1 Hz for 1500 cycles) was applied at 0°, 45°, and 90° of hip flexion.
• Comparison of gap formation, stiffness, yield load, and ultimate load between different hip flexion angles.

Main Results:

• Gap formation increased significantly with hip flexion, from 2.39 mm at 0° to 4.19 mm at 90°.
• No significant difference in ultimate load was observed across hip flexion angles (0°, 45°, 90°).
• Knot or suture failure was the most frequent mode of failure (n=17).

Conclusions:

• Increasing hip flexion from 0° to 90° leads to greater displacement across proximal hamstring repairs.
• Postoperative bracing to limit hip flexion is advisable to prevent repair compromise.
• Repetitive hip flexion post-surgery may compromise the repair integrity.