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Direct Radiological Visualization of the Effect of Loading on Four Suture Configurations Used in Flexor Tendon Repair
Xiaoke Dong, MRCS, (Edinburgh)1; Min He1; Christopher Fang2; Sandeep Jacob Sebastin1
1National University Hospital, Singapore; 2Yong Loo Lin School of Medicine, Singapore

Introduction: To determine the pattern of deformation of four suture designs used in flexor tendon repair.
Materials and Methods: Forty flexor tendons from the 1st ray of fresh frozen porcine limbs were harvested. They were divided into 4 groups of ten tendons. Each group underwent one of the following four suture designs (Figure).

Group 1 - Arc design: Transverse suture component passed below longitudinal suture component
Group 2 - Simple loop design: Transverse suture component passed above longitudinal component with a single pass
Group 3 - Complex loop design: Transverse suture component passed above longitudinal suture component with a double pass
Group 4 - Knot design: There is no transverse component. The longitudinal components are secured using a knot.
0.5mm stainless steel wire was used as suture material. Only one half of a tendon repair was simulated. The transverse components (or knot) were placed 1 cm from the cut end of the tendon. The free ends of the sutures and the tendon were anchored to a jig secured to an Intron machine. A radiopaque ruler was fixed parallel to the tendon. The tendon was loaded using the Instron machine at 50mm/min until failure (suture rupture or pull out). The deformation of the suture was observed directly using an image intensifier. Additionally data with regards to the ultimate force prior to rupture/ pullout was obtained.
Results: All repairs failed by suture pull-out. In the arc design, the loop unravels and then the transverse suture component flips over the longitudinal component before pulling out. In the simple loop design, there is an initial constricting effect that is followed by behavior similar to the arc design. In the complex loop design, there is a progressive constricting effect before gradual pullout of the suture. In the knot design, some constriction of the knot is seen before it pulls out of the tendon.
Summary: Most flexor tendon suture techniques use one of the four suture designs illustrated in this study. Our study has shown that the deformation pattern is different between the four suture designs. The arc and simple loop design deform by unraveling of the loop, whereas the complex loop constricts before pulling out. The tendon grasping ability of the complex loop design was also the strongest.

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