WATER JET CUTTING, AN ALTERNATIVE METHOD FOR CARTILAGE SURGERY

Abstract

Introduction: Autologous osteochondral transfer is an option for the treatment of articular defects. However, there are concerns about graft integration and the nature of the tissue forming the cartilage-cartilage interface. Chondrocyte viability at graft and recipient edges is stated to be an important determinant of the success of repair.

As a tool, water jet (WJ) provides a cold cutting process. The cut is performed using water under high pressure (potential energy) by transforming it into water with high velocity (kinetic energy) using a nozzle.

This study evaluates the feasibility of performing selective cutting on the cortical bone and articular cartilage tissue by the use of plain water jetting.

Materials and Methods: Fresh full thickness cartilage explants were obtained from the stifle joints of 5 young calves (6–8 months old). Full thickness cartilage explants were removed from the femoral condyles using a scalpel. A specially designed water jet system was used for the study. The intensifier pump allowed pressure variations between 100–700 bars. The nozzle (Ø=0.2mm) was mounted on a gantry with two degrees of freedom. The cutting experiments were performed in displacement control mode, with cartilage held stationary and the nozzle moving at a traverse speed of 1mm/s. To calculate the energy typically required for consistent material removal, 40 cartilage samples were cut at various pressure levels using the water jet. Depths of the cut were measured by a Vernier caliper.

Multi- and one-way analyses of variance were computed with cutting depth as dependent variable.

In the second part of the study osteochondral cylinders were obtained from the femoral condyles using:

1. 8 mm diameter Arthrex OATS punch,

2. 8 mm diameter diamond coated drill punch and

3. the water jet cutting device.

Plugs were then assessed for cell viability along the cut periphery by performing live-dead cell staining and viewing under the confocal laser scanning microscope.

Results: There was a significant correlation between pressure and kerf depth (p< 0.001). At a relatively high transverse speed of 1mm/s cartilage was cut smoothly and easily. The typical material removal energy for bovine cartilage is 7,38.109 J/m³. Using Equation 1, the resultant kerf depths of multiple jet parameter can be calculated easily.

The margin of superficial zone cell death at the curved edge was significantly greater in the OATS punch group (390±18μm) and in the diamond drill group (440±18μm), when compared to the WJ group (10±4 μm).

Discussion: The dead at the cutting edge was greatly for WJ cut samples, making it a promising technology for cartilage repair. The results of the present study suggest that water jet cutting has the potential to be developed as an alternative means to prepare the cartilage for patients undergoing cartilage transplantation.