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Research Papers

# Arthroscopic Sheath Design and Technical Evaluation

[+] Author and Article Information
Gabriëlle J. M. Tuijthof

Department of Orthopedic Surgery, Orthopedic Research Center Amsterdam, Academic Medical Centre, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, 2628CD Delft, The Netherlandsg.j.tuijthof@amc.uva.nl; g.j.m.tuijthof@tudelft.nl

Leendert Blankevoort

Department of Orthopedic Surgery, Orthopedic Research Center Amsterdam, Academic Medical Centre, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlandsl.blankevoort@amc.uva.nl

Just L. Herder

Department of Biomechanical Engineering, Delft University of Technology, Mekelweg 2, 2628CD Delft, The Netherlandsj.l.herder@tudelft.nl

C. Niek van Dijk

Department of Orthopedic Surgery, Orthopedic Research Center Amsterdam, Academic Medical Centre, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlandsc.n.vandijk@amc.uva.nl

J. Med. Devices 3(2), 021003 (Jun 04, 2009) (7 pages) doi:10.1115/1.3148835 History: Received June 18, 2008; Revised May 11, 2009; Published June 04, 2009

## Abstract

The maintenance of a clear view on the operation area is essential to perform a minimally invasive procedure. In arthroscopy, this is achieved by irrigating the joint with a saline fluid that is pumped through the joint. At present, the arthroscopic sheaths are not designed for optimal irrigation, which causes suboptimal arthroscopic view. The goal of this study is to present new design concepts and their technical evaluation to optimize irrigation. We focused on decreasing the fluid restriction and stimulating turbulent inflow streams. This is achieved by combining analysis of clinical practice, fluid mechanics theory, and experiments. A distinction is made between a three- and a two-portal technique. For a three-portal technique, the design concept consisted of a conventional sheath $(∅4.5 mm)$ used with a smaller diameter arthroscope $(∅2.7 mm)$. This resulted in a decreased fluid restriction. For the two-portal technique, a partition is designed, which separates the inflow and outflow streams in this sheath. Practical embodiments of the concepts are evaluated experimentally, in comparison with conventional sheaths. The setup consisted of a simulated arthroscopic operative setting of a knee joint. The main discriminating measures are the irrigation time, the fluid restriction, the flow, and the pressure in the joint. The results show that the proposed concept for the three-portal technique decreased the irrigation time significantly by 25%, and the concept with the partition for the two-portal technique decreased the irrigation time by 67% (analysis of variance, $p<0.05$). Different sheath tips showed no significant differences, leaving the straight shaft as the preferred embodiment. The simulation environment proved to be a suitable platform to test devices in a conditioned setting. The new sheath is expected to be a valuable improvement in achieving optimal irrigation.

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## Figures

Figure 1

Scheme of an irrigation system used to perform arthroscopic operations. In this example, a knee joint is operated. The saline fluid bags are hung at a height of 0.66 m above the joint, which is equal to a preset pressure of 6.5 kPa (49 mm Hg).

Figure 2

(a) Normal sheath used in combination with a ∅4 mm arthroscope. (b) Practical embodiment of the proposed sheath-scope combination. The partition consists of a tube with two fins, one on each side. (c) The ∅2.7 mm arthroscope and the partition can be placed simultaneously in the sheath. (d) Frontal view of the practical embodiment with in its center the tip of the arthroscope. Around it, the partition with fins is placed. Finally, the pins can be seen at the tip of the sheath used for the inflow stream (upper right part). (e) Apart from an unmodified tip of the sheath, three other sheath tips are tested: tip with two holes (this implies that if the partition is used there is one hole in the inflow and one in the outflow), tip with six pins in the inflow stream, and tip with four holes.

Figure 3

Close up of the experimental setup showing the physical knee phantom (25), a scope-sheath combination placed in the anteromedial portal, a separate outflow cannula placed in the superomedial portal, and a video camera that is positioned in the lower leg to record an overview of the knee phantom form underneath the transparent tibial surface. P1 and P2 indicate the position of the pressure sensors, and Q of the flow sensor. Blue-colored ink is injected in the inflow stream.

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