Arthroscopic sheath design and technical evaluation

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 (Ø4.5 mm) used with a smaller diameter arthroscope (Ø2.7 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.