Dynamic properties of self-retaining retractors under load.

Abstract

Dynamic properties of seven kinds of self-retaining retractors were examined by analyzing the stress-strain curve of the flexible arm under load. The stress that generated a remaining strain of 1 mm was about 80% of the maximum stress of the fixed flexible arm, and was a suitable indicator of the ability of a retractor under load. It had good correlation with the fixing torque of the flexible arm and was also influenced by the diameter of the arch of the fixed flexible arm. For all three commercially available retractors, the strongest resistance was obtained when the flexible arm was arranged in a semicircular shape with a diameter of 20 cm, regardless of the length of the arm. The retractor made of titanium alloy was superior to the retractor of the same shape made of stainless steel for vertical load, regardless of different arm-fixing torques. The tapered flexible arm of the Mizuho titanium retractor showed greater resistance to loading than a nontapered one at stronger arm-fixing torques. The Aesculap Leyla retractor had different dynamic properties from the Mizuho stainless retractors, despite their similarity in shape. The Leyla retractor was weaker than the Mizuho stainless retractors for vertical loading but stronger for horizontal loading. These experimental observations may be helpful when applying a self-retaining retractor during surgery.