Suture selection is dependent on the anatomic site, surgeon’s preference, and the required suture characteristics. No standardized sizing system or nomenclature is available for needles or needle holders; the main consideration in needle selection is to minimize trauma. The length, diameter, and curvature of the needle influence the surgeon’s ability to place a suture.
â€¢ Cutting (conventional, reverse, or side [spatula])
â€¢ Taper-point (round)
â€¢ Beveled, conventional cutting edge
â€¢ Blunt point
â€¢ Half-curved ski
â€¢ Compound curved
Characteristics of the ideal surgical needle and needle performance are reviewed in this section.
Ideal surgical needle characteristics
The ideal surgical needle has the following characteristics:
â€¢ High-quality stainless steel
â€¢ Smallest diameter possible
â€¢ Stable in the grasp of the needle holder (see the following image)
Interaction between the needle holder and suture needle. A: A needle holder of appropriate size for the needle; B: a needle holder that is too large for the needleâ€”pressure applied by the needle holder leads to inadvertent straightening of the suture needle; C: a needle holder that is too small for the needleâ€”the needle rotates around the long axis of the needle holder.
â€¢ Capable of implanting suture material through tissue with minimal trauma
â€¢ Sharp enough to penetrate tissue with minimal resistance
â€¢ Sterile and corrosion-resistant to prevent introduction of microorganisms or foreign materials into the wound
Needle performance characteristics and definitions
The following terms describe various characteristics related to needle performance:
â€¢ Strength – Resistance to deformation during repeated passes through tissue (ie, increased needle strength results in decreased tissue trauma); ultimate moment is the measure of maximum strength determined by bending the needle to 90Â°, and surgical-yield moment is the amount of angular deformation that can occur before permanent needle deformation occurs
â€¢ Ductility – Resistance (of a needle) to breakage under a given amount of deformation/bending
â€¢ Sharpness – Measure of the ability of the needle to penetrate tissue; factors affecting sharpness include the angle of the point and the taper ratio (ie, ratio of taper length to needle diameter)
â€¢ Clamping moment – Stability of a needle in a needle holder, determined by measuring the interaction of the needle body with the jaws of the needle holder
Anatomy of a needle
The anatomy of a needle includes the point, body, and swage (see the following image).
The point portion of the needle extends from the tip to the maximum cross-section of the body. Point types include the following (see the image below):
â€¢ Cutting needles (conventional, reverse, or side [spatula])
â€¢ Taper-point (round) needles
â€¢ Beveled, conventional cutting edge needles
â€¢ Blunt-point needles
Commonly used suture needles, with cross-sections of the needles shown at the point, body, and swage. A: A taper needle; B: a conventional cutting needle; C: a reverse cutting needle.
The cutting needle has at least 2 opposing cutting edges (the point is usually triangular). This type is designed for penetration through dense, irregular, and relatively thick tissues. The point cuts a pathway through tissue and is ideal for skin sutures. Sharpness is due to the cutting edges.
Conventional cutting needles have 3 cutting edges (triangular cross-section that changes to a flattened body). The third cutting edge is on the inner, concave curvature (surface-seeking).
In reverse-cutting needles, the third cutting edge is on the outer convex curvature of the needle (depth-seeking). These needles are stronger than conventional cutting needles and have a reduced risk of cutting out tissue. The needles are designed for tissue that is tough to penetrate (eg, skin, tendon sheaths, oral mucosa). Reverse-cutting needles are also beneficial in cosmetic and ophthalmic surgery, causing minimal trauma.
Side-cutting (spatula) needles are flat on the top and bottom surfaces to reduce tissue injury. These needles allow maximum ease of penetration and control as they pass between and through tissue layers. Side-cutting needles were designed initially for ophthalmic procedures.
Taper-point (round) needles penetrate and pass through tissues by stretching without cutting. A sharp tip at the point flattens to an oval/rectangular shape. The sharpness is determined by taper ratio (8-12:1) and tip angle (20-35Â°). The needle is sharper if it has a higher taper ratio and lower tip angle. The taper-point needle is used for easily penetrated tissues (eg, subcutaneous layers, dura, peritoneum, abdominal viscera) and minimizes the potential tearing of fascia.
Beveled, conventional cutting edge needles
A beveled, conventional cutting edge needle was developed with superior performance characteristics over those of other conventional cutting edge needles. It is composed of a unique stainless steel, ASTM 45500, that has been heat-treated after the curving process to enhance the resistance to bending. The angle of presentation of its cutting edge has been decreased to enhance needle sharpness. On the basis of the results of experimental and clinical studies done by Kaulbach et al, this needle is recommended for closure of lacerations.
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