Veterinary Teaching Hospital, Colorado State University, Fort Collins, CO, USA
Arthroscopy is an exciting field of minimally invasive orthopaedic surgery. For the surgeon, it requires the development of a new skill set using expensive and often delicate instrumentation. Because the arthroscopic surgeon must control the instrumentation in each hand while keeping his/her eyes upon the image monitor, having a knowledgeable and engaged support team is vital to the success of the procedure.
An arthroscopic system is nothing more than a method to attach a camera and fiberoptic light cable to the end of the scope and project an illuminated and magnified image to a monitor (Fig 1).1 Each of the above components (camera head, fiberoptic light cable, arthroscope) as well as many arthroscopic hand instruments (grasping forceps, etc.) are delicate and must be handled with care during cleaning and packing. For example, mishandling of the light cable may cause accidental damage to the delicate fiberoptic cables within which may prevent proper joint illumination.
First, one must understand the importance of camera orientation upon one's ability to maintain a point of reference within the joint. Just as with any video camera, if the camera is properly oriented ("right side up"), the individuals in the room will accurately appear to be standing on the floor and one's ability to systematically evaluate the room with the camera is quite simple. If, however, the camera is turned sideways, the persons in the room will appear to be standing on the wall and one's ability to systematically move about the room with the video image is seriously compromised. Typically, an arthroscopic camera head is properly oriented when the buttons are on top and the camera head is maintained in this orientation.
Next, one must understand that the end of the typical arthroscope is not flat, but is beveled 30° (Fig 2). This bevel means that the image visualized from the tip of scope is not as though one is looking through a pipe; rather it is as though one is looking through the periscope of a submarine. One can rotate the arthroscope to look around the joint. The bevel is typically directed opposite to the light post attachment to the scope. Thus, the light post becomes an important reference point for directing the field of view. It is often helpful to think of the light post & light cable as a "pony tail" style hairdo and the scope as "eyes"; pulling the pony tail gently in one direction will direct the eyes in the opposite direction. If one wishes to direct the field of view to the left, the light post is pivoted to the right and vice-versa.
Next, one must appreciate the importance of depth of field when performing arthroscopic surgery. To understand this concept, imagine that I am looking at a friend across the room, I immediately recognize her. As I move ever closer, a pimple on her ear lobe comes into view. As I get closer still, I can see amazing detail of the pimple and her ear lobe, but I can no longer tell to whom this pimple-covered ear belongs. As I get closer still, I can see the white dome of the pimple, but I have no context that it is attached to an ear or even that it represents a pimple because all I see is white. The ideal arthroscopic depth of field is close enough to visualize the lesion and far enough to have appropriate context and orientation.
Finally, arthroscopic surgery requires proper fluid flow into and out of a joint. Ideally, the flow rate into and out of a joint allows distension of the joint and lavage to maintain a clear visual field. Too little flow and the joint is not adequately distended or lavaged to allow visualization. If the fluid flow into the joint drastically exceeds the flow out of the joint, fluid will extravasate into the surrounding tissues and, ultimately, collapse the joint.
To perform diagnostic arthroscopy, one's arthroscopic system should include the following: an arthroscopic camera with quality color monitor, a 1.9, 2.4 or 2.7 mm (depending upon the joint of interest and size of patient), 30°, short arthroscope with compatible cannula/blunt trocar and light source, lactated Ringer's bags and sterile administration tubing, and photo documentation system (Fig 3). With gravity flow or pressure sleeve administration of fluid, the fluid flow will decrease as the pressure inside the joint approaches that of fluid administration system. Gravity flow has the disadvantage of not always being able to distend the joint or lavage the joint as well as one would like (can be a problem in smaller joints like the elbow), but the risk of extravasation of large volumes of fluids is reduced. Optional equipment for diagnostic arthroscopy includes a fluid pump for controlled inflow of fluid. Fluid pumps may be volume-controlled or pressure-controlled. Volume-controlled pumps deliver a set volume of fluid/minute regardless of the amount of pressure that develops within the joint and there is risk of extravasation. Pressure-controlled pumps are set to not exceed a specified pressure and reduce the risk of fluid extravasation (Fig 4).
It is "Go Time" In the Operating Room
It is helpful to have at least one knowledgeable assistant scrubbed into the surgical procedure ("scrub nurse") and one knowledgeable non-scrubbed assistant in the operating room ("OR nurse") to help with tower set up and troubleshooting intraoperatively. The scrub nurse can be sure to hand the proper ends of light cables, camera cables, ingress tubing, etc. to the OR nurse after appropriate patient draping. The OR nurse must be knowledgeable about the proper "startup" sequence for arthroscopic tower and how to correctly connect cables to the appropriate camera box, light box, etc. Often a thin film may form on the glass face of the camera head and/or arthroscope, so the scrub nurse can delicately cleanse these glass surfaces with a sterile moistened soft cotton wipe or manufacturer supplied cleansing wipes in preparation for surgery. Once surgery has started, the surgeon will be focused upon the patient and the procedure so it is helpful to run through a checklist of necessary instrumentation and supplies. It is also wise to make sure the trocar, cannula and arthroscope are all of the proper corresponding sizes prior to attempting to instrument the patient's joint. While there may be a lesser trained assistant holding the patient's limb in proper position, the scrub nurse is helpful by anticipating the surgeon's needs and passing surgical instruments as needed.
1. Beale BS, Hulse DA, Schulz K, Whitney WO, eds. Small Animal Arthroscopy. Philadelphia, PA: WB Saunders; 2003.
VIN editor: No figures were provided at time of publication.