Background: Forces applied to knots used for interrupted vs. continuous closures are very different. We studied the knot strength and knot security of three knots when simulating a continuous wound closure: the square...Background: Forces applied to knots used for interrupted vs. continuous closures are very different. We studied the knot strength and knot security of three knots when simulating a continuous wound closure: the square, the sliding, and a hybrid constructed using a surgeon’s square knot followed by a sliding knot. Mate-rials and Methods: Knot holding capacity (KHC) of single-strand 1-0 polypropylene was determined by slow distraction on a horizontal testing sled of the strand that would be used to complete a continuous (“running”) closure following placement of an anchoring knot with six throws. Distraction continued until failure of the knot defined as breakage or slippage of the knot. Results: The mean and standard deviation of KHC meas-ured in pounds was determined (n = 30 for each knot): standard square 8.94 +/– 1.04;sliding 10.72 +/– 1.35;and hybrid 10.95 +/– 1.10. For each knot the relative knot security [(KHC of the knot/Tensile strength of untied strand) x 100] was calculated: standard square 69.5%;sliding 83.4%;hybrid 85.2%. Significant dif-ferences (p < 0.0001) in KHC exist between square and sliding knots (favoring sliding knots) and between square and hybrid knots (favoring hybrid knots). Hybrid and sliding knots were not statistically different. Conclusion: Sliding knots and hybrid knots are superior to square knots as anchoring knots for single-strand continuous wound closure.展开更多
Sternum closure after open heart surgery is typically done with steel wires. Final approximation of sternal parts and connection is achieved by twisting the ends of the wire and bending the twisted assembly towards th...Sternum closure after open heart surgery is typically done with steel wires. Final approximation of sternal parts and connection is achieved by twisting the ends of the wire and bending the twisted assembly towards the sternum in order to minimize outward protrusion. Though this routine procedure is highly effective, some failures do occur, e.g. due to wire fracture. Fatigue fracture of the wires, e.g. due to coughing implies a failure risk. An alternative development is to make cables from gel spun Ultra High Molecular Weight Poly Ethylene (UHMWPE) fibres, such fibres are extremely strong, yet flexible, and if made as a very pure grade, they are highly bio compatible. The optimal connection technique will be different from that of steel. Connection will rather be with knotting than twisting. A new sternum closure and fixation technique has been developed for the sternum. Additionally, a testing technique was developed, for a connection of simulated sternum parts, using different materials according to their respective optimal connection method and subsequently testing the mechanical properties of the connection. Substantial differences were observed. The mechanical behaviour of twisted steel wire connection showed more scatter than the knotted UHMWPE cables and some initial slack was sometimes present in the twisted cables. The maximum attainable force in the steel wires was determined by “untwisting” due to the external load. The maximum force in the UHMWPE cables was determined by the knot strength, either slipping for small knots, or breaking of the cables at the knots for slip-improved knots. The maximum force on the knotted UHMWPE cables was substantially larger than the maximum force on the twisted steel wires. Fatigue tests were performed on both the steel solution and the UHMWPE cables solution. The performance was about similar, although the simulated sternum opening was smaller for the UHMWPE cables at higher load levels. Summarizing, the UHMWPE cables show two advantages namely higher maximum load and more reproducible mechanical behaviour due to less scatter in the mechanical behaviour. On the other hand, the connection by knotting UHMWPE cables is somewhat more elaborate than the simple twisting connection of steel wires.展开更多
文摘Background: Forces applied to knots used for interrupted vs. continuous closures are very different. We studied the knot strength and knot security of three knots when simulating a continuous wound closure: the square, the sliding, and a hybrid constructed using a surgeon’s square knot followed by a sliding knot. Mate-rials and Methods: Knot holding capacity (KHC) of single-strand 1-0 polypropylene was determined by slow distraction on a horizontal testing sled of the strand that would be used to complete a continuous (“running”) closure following placement of an anchoring knot with six throws. Distraction continued until failure of the knot defined as breakage or slippage of the knot. Results: The mean and standard deviation of KHC meas-ured in pounds was determined (n = 30 for each knot): standard square 8.94 +/– 1.04;sliding 10.72 +/– 1.35;and hybrid 10.95 +/– 1.10. For each knot the relative knot security [(KHC of the knot/Tensile strength of untied strand) x 100] was calculated: standard square 69.5%;sliding 83.4%;hybrid 85.2%. Significant dif-ferences (p < 0.0001) in KHC exist between square and sliding knots (favoring sliding knots) and between square and hybrid knots (favoring hybrid knots). Hybrid and sliding knots were not statistically different. Conclusion: Sliding knots and hybrid knots are superior to square knots as anchoring knots for single-strand continuous wound closure.
文摘Sternum closure after open heart surgery is typically done with steel wires. Final approximation of sternal parts and connection is achieved by twisting the ends of the wire and bending the twisted assembly towards the sternum in order to minimize outward protrusion. Though this routine procedure is highly effective, some failures do occur, e.g. due to wire fracture. Fatigue fracture of the wires, e.g. due to coughing implies a failure risk. An alternative development is to make cables from gel spun Ultra High Molecular Weight Poly Ethylene (UHMWPE) fibres, such fibres are extremely strong, yet flexible, and if made as a very pure grade, they are highly bio compatible. The optimal connection technique will be different from that of steel. Connection will rather be with knotting than twisting. A new sternum closure and fixation technique has been developed for the sternum. Additionally, a testing technique was developed, for a connection of simulated sternum parts, using different materials according to their respective optimal connection method and subsequently testing the mechanical properties of the connection. Substantial differences were observed. The mechanical behaviour of twisted steel wire connection showed more scatter than the knotted UHMWPE cables and some initial slack was sometimes present in the twisted cables. The maximum attainable force in the steel wires was determined by “untwisting” due to the external load. The maximum force in the UHMWPE cables was determined by the knot strength, either slipping for small knots, or breaking of the cables at the knots for slip-improved knots. The maximum force on the knotted UHMWPE cables was substantially larger than the maximum force on the twisted steel wires. Fatigue tests were performed on both the steel solution and the UHMWPE cables solution. The performance was about similar, although the simulated sternum opening was smaller for the UHMWPE cables at higher load levels. Summarizing, the UHMWPE cables show two advantages namely higher maximum load and more reproducible mechanical behaviour due to less scatter in the mechanical behaviour. On the other hand, the connection by knotting UHMWPE cables is somewhat more elaborate than the simple twisting connection of steel wires.
