Abstract:
An apparatus for performing endoscopic surgical procedures within an internal body cavity. The apparatus includes an imaging unit for viewing the internal body cavity. In addition, the apparatus includes an intra-articular unit for providing a flow of fluid into the internal body cavity as well as for controllably withdrawing fluid from the internal body cavity. The apparatus further includes a cart which allows electrical intercommunication between the imaging unit and the intra-articular unit whereby the operation of the imaging unit and the intra-articular unit are interdependent.

Description:
This is a continuation of U.S. patent application Ser. No. 07/963,448, filed Oct. 19, 1992, which has been expressly abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for use in surgical procedures, and more particularly to a method and apparatus for use in endoscopic surgical procedures. 
     BACKGROUND OF THE INVENTION 
     Endoscopic surgery is a minimally invasive therapeutic and/or diagnostic procedure during which relatively small visualization and surgical tools are introduced into a portion of the human body such as a knee joint through relatively small incisions. Typically, at least three incisions are employed for a therapeutic procedure and at least two are employed for a diagnostic procedure. During endoscopic surgery, physiological fluid such as a sterile saline solution is allowed to flow through the joint so as to distend the joint to facilitate access to the joint. In addition, the flow of physiological fluid through the joint enhances the clarity of the field of view by removing debris from the surgical site. 
     The flow of fluid into the joint during endoscopic surgery is regulated by two independent but yet related functions. These two functions are the pressure of fluid within the joint and the volume of fluid flowing through the joint. The pressure of fluid within the joint determines the extent to which the joint is distended. For example, a surgeon may want to increase the pressure of fluid within the joint when the surgeon needs to view or access the end of the joint opposite to the point of insertion of the probe. In contrast, if there is bleeding or debris in the cavity, an increase in the flow rate of fluid is needed to clear the field of view. In addition, when an instrument such as a shaver with a suction tube is used, a greater flow of fluid into the cavity is required to prevent the cavity from collapsing. 
     Various methods are known to control the pressure and flow rate of fluid during endoscopic surgery. These methods range from certain manual methods, such as manually adjusting the height of fluid supply bags to increase pressure while maintaining flow rates using variable clamps on the tubing leading to and away from the patient, to automatic fluid control systems. Some of these automatic fluid control systems regulate flow rate in response to the sensed pressure corresponding to the pressure within the cavity. Other automatic fluid control systems attempt to maintain a constant volume of fluid flowing into the cavity and therefore a constant pressure within the joint by balancing the inflow and outflow of the physiological fluid into the cavity. Still other of these automatic fluid control systems allow for independent control of the flow rate and the pressure, allowing the system to operate at a specified number of fixed flow rates and fixed pressures. 
     The equipment used for endoscopic surgery in the past been relatively difficult to use. For example, a nurse generally has to connect individual tubes to various cannulas and pumps associated with the system as well as to thread tubes through peristaltic pumps. This is a relatively time consuming activity. In addition, the surgeon often has to adjust the pump speed each time the shaver is used. This is because the shaver will draw fluid from the cavity thereby requiring the surgeon to increase the flow rate of fluid into the cavity. In addition, the light source for illuminating the cavity is functionally independent of the camera used to record the image inside the cavity. Accordingly, the surgeon has to white balance the camera in order to provide a relatively clear image. In addition, because the endoscopy system is typically shared between different surgeons, the various parameters such as flow rate, cavity pressure, shaver speed and so forth have to be readjusted virtually every time a doctor begins using the equipment after another doctor has finished using the equipment. 
     In addition to the foregoing, the equipment used for performing surgery often uses a shaver handpiece which is subject to certain disadvantages. For example, the shaver handpiece is often driven by a motor which is connected by a gear box to the shaver blade. Not only does the presence of the gear box complicate the construction of the shaver, the gears within the gear box could fail upon receipt of excess torque also tended to cause premature failure of the shaver handpiece. In addition, because the flow of debris through the shaver handpiece does not often follow a straight path, the debris will often plug the shaver handpiece making the handpiece inoperable. 
     SUMMARY OF THE INVENTION 
     Accordingly, an advantage of the present invention is to provide an apparatus for endoscopic surgery which is relatively simple to use. In this regard, a related advantage of the present invention is to provide an apparatus for endoscopic surgery which minimizes the time required for surgeons and nurses to set up and operate. 
     A further advantage of the present invention is to provide an apparatus for endoscopic surgery in Which the pressure within the cavity can be accurately controlled. In this regard, a related advantage of the present invention is to provide an apparatus for endoscopic surgery in which the irrigation pump controls the flow rate of fluid into the cavity while the aspiration pump is used to control the pressure of fluid within the cavity. 
     An additional object of the present invention is to provide an apparatus for endoscopic surgery in which various parameters associated with operating the apparatus can be stored and retrieved with relative ease. A related advantage of the present invention is to provide an apparatus for endoscopic surgery which is menu driven. 
     Another advantage of the present invention is to provide an apparatus for endoscopic surgery in which debris from the cavity passes through the shaver handpiece in a relatively straight direction. 
     Another advantage of the present invention is to provide an apparatus for endoscopic surgery which uses gear pumps to control the flow of fluid into and out of the cavity without the use of peristaltic pumps. 
     The present invention provides for an apparatus for endoscopic surgery which utilizes a gear pump for both the irrigation and aspiration of the fluid from the cavity. The speed of the irrigation pump is held generally constant while the speed of the aspiration pump is varied in response to the pressure within the joint. Both the irrigation pump and the aspiration pump are contained in a disposable cassette which is simply inserted into a pump drive unit. Once a flow rate for the irrigation pump is selected, the flow rate of the irrigation pump remains constant. While the input flow rate can be set at various fixed levels during examination, the irrigation pump will automatically be switched to a predetermined input flow rate when a resection tool is used. The present invention further includes a pressure sensor which senses the pressure of the fluid in the conduit connecting the irrigation pump to the cavity. The output of the pressure sensor is used for controlling and varying the speed and therefore the suction rate of the aspiration pump. As a result, the pressure in the cavity is maintained at a desired level. 
     The present system monitors the fluid pressure in the input conduit by using a pressure dome located in the disposable cassette. The pressure dome rises and falls with increases and decreases of fluid pressure within the cavity respectively. The pump drive unit utilizes a proximity sensor for sensing the height of the pressure dome which is then determinative of the fluid pressure. Prior art systems utilize an air column for indicating pressure which is a more complex and fragile system using an orifice which has a tendency to plug during the operation. This sensed pressure of the input conduit is corrected to accurately determine the actual pressure within the cavity. Typical endoscopy systems have a relatively long input conduit. At the same time, the inside diameter of the input conduit is relatively small so as to maintain flexibility. When fluid under pressure flows through the input conduit, a pressure drop occurs through the input conduit. This pressure drop through the input conduit, which may be a relatively large percentage of the pressure within the cavity, will be influenced by the diameter of the input conduit and also by the rate of flow through the input conduit. Accordingly, as the flow rate through the input conduit is varied, the pressure drop through the input conduit will vary correspondingly. For this reason, sensing the pressure in the input conduit alone will not accurately measure the pressure within the cavity because of the pressure drop through the input conduit. It is therefore desirable to be able to reliably determine the pressure drop through the input conduit in order to more accurately provide an indication of (and ultimately control) the pressure within the cavity based upon a pressure measurement taken at the input conduit. 
     Because the irrigation pump of the present invention is used to provide a fixed, selected flow rate of fluid into the cavity while the aspiration pump, through variable speed, controls pressure, the present system has several important advantages. First, the present system is able to estimate the pressure in the cavity with greater accuracy by compensating for the pressure drop which occurs through the portion of the input conduit between the pressure sensor and the cavity. This is because the pressure drop through the input conduit is a function of the flow rate through the input conduit which can be easily determined because the irrigation pump establishes the flow rate at a preselected fixed magnitude. With a fixed input flow rate, the pressure drop through the input conduit can be accurately determined and therefore the output from the pressure sensor located at the outlet of the irrigation pump can more precisely indicate the actual pressure of fluid in the cavity. With a more accurate indication of the actual pressure in the cavity, the present system can provide a more accurate way for controlling the pressure in that cavity. 
     In other endoscopy systems where the irrigation pump is used to control pressure, the flow rate through the input conduit (1) would vary as the speed of the input pump continuously changed to maintain the desired pressure within the cavity and (2) would be more difficult to accurately determine because of the continuous variation in flow. Because the flow rate through the input conduit would vary and be difficult to determine, the pressure drop through the input conduit would also vary and be difficult to determine. The output of the pressure sensor would therefore not provide such an accurate estimate of the pressure within the cavity. Accordingly, the fact that the irrigation pump of the present system is used to control the flow at a constant rate while the aspiration pump is used to control pressure allows a more accurate determination of both the magnitude of pressure within the cavity and the volume of flow of fluid into the cavity. 
     Second, another important advantage of the present system which is obtained by having the irrigation pump provide a preselected fixed flow rate while the speed of the aspiration pump is varied to control pressure involves the performance of the present system when leakage of fluid occurs from the cavity, which is quite common during endoscopic procedures. When such leakage occurs, the pressure drop sensed by the present system automatically reduces the speed of the aspiration pump in order to maintain the pressure so that less fluid flows through the output conduit. At the same time, the flow of fluid delivered by the input conduit remains unchanged. The present system is therefore able to maintain the pressure in the joint while accommodating for substantial variations in leakage without a change in the input flow rate. 
     In other endoscopy systems where the aspiration pump is used to provide a preselected fixed flow rate, the irrigation pump would have to supply a sufficient amount of fluid to maintain the pressure in the cavity as well as to compensate for fluid leaving the cavity (1) by leakage and (2) through the aspiration pump. When such leakage becomes large, the capacity of the irrigation pump could be exceeded as the irrigation pump attempts to increase the input flow rate to maintain the desired pressure within the cavity while also attempting to compensate for both the leakage out from the cavity as well as the fluid drawn out of the cavity by the aspiration pump. In addition, if the aspiration pump were used to provide a fixed flow rate, the amount of fluid flowing into the cavity would also not be as accurately determined because of leakage of fluid from the cavity, the amount of which could vary substantially between different operations. 
     There are several other important features of the present system. For example, the aspiration pump of the present system is a two-directional gear pump which allows fluid to flow through a first output conduit when the aspiration pump is driven in one direction and allows fluid to flow through a second output conduit when the aspiration pump is driven in a second direction. The flow of fluid through the second output conduit occurs when a resection tool is used. This switching of output conduits is accomplished by a series of check valves which automatically switch the conduits when the direction of the motor is reversed eliminating the need to manually adjust valves or tubing to accommodate the different flow rates coming from the separate conduits. 
     An additional feature of the present invention is that both the irrigation pump and the aspiration pump are gear pumps and are contained in the disposable cassette. The use of the disposable cassette significantly simplifies the process for getting ready for surgery by providing a one step system of inserting the cassette for engaging the two pumps. The use of gear pumps instead of prior art peristaltic pumps provides a system which requires less energy and is more efficient. A peristaltic pump requires the tubing to be threaded through the pump in order for the pump to function. Once assembled, most of the energy required for the pump to operate is used to compress the plastic tube and not to pump the liquid. Because the cassette system is disposable, the fluid medium can be introduced into the pump and the cassette then can be simply inserted into the pump drive unit. This one step operation significantly simplifies the steps necessary to get ready for the operation. 
     Moreover, the present system does not have a tachometer per se which measures the speed of the motors that drive the irrigation and aspiration pumps. Rather, the present system measures the frequency of electrical pulses generated in part by the movement of magnets within each of the motors. The frequencies of the electrical pulses are indicative of the speed of their respective motors. These electrical pulses are delivered to a microprocessor which monitors the changing frequencies of the pulses to control the speed of the irrigation and aspiration pump motors. 
     Further, while the present system terminates the operation of the irrigation and aspiration pumps when the pressure in the cavity becomes excessive, the present system does not immediately terminate the flow of fluid into the cavity when the pressure in the cavity falls below a predetermined limit. Rather, the aspiration pump progressively reduces its speed in an attempt to maintain the pressure within the cavity at the desired magnitude. This reduction in speed continues up to the point where the operation of the aspiration pump terminates. When this occurs, while flow of fluid into the cavity continues, there is no flow of fluid drawn from the cavity through the aspiration pump and therefore the only flow of fluid out from the cavity is by virtue of leakage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various advantages of the present invention will become apparent to one skilled in the art upon reading the following specification and by reference to the following drawings in which: 
     FIG. 1 is a front view of the apparatus for performing endoscopic surgical procedures according to the preferred embodiment of the present invention; 
     FIG. 2 is a rear view of the apparatus for performing endoscopic surgical procedures according to the preferred embodiment of the present invention; 
     FIG. 3 is an enlarged front view of the imaging unit of the apparatus for performing endoscopic surgical procedures shown in FIG. 1 according to the preferred embodiment of the present invention; 
     FIG. 4 is an enlarged front view of the intra-articular unit of the apparatus for performing endoscopic surgical procedures shown in FIG. 1 according to the preferred embodiment of the present invention; 
     FIG. 5 is a block diagram showing the components of the apparatus for performing endoscopic surgical procedures shown in FIG. 1 according to the preferred embodiment of the present invention; 
     FIG. 6 is a block diagram showing the components of the imaging unit of the apparatus for performing endoscopic surgical procedures shown in FIG. 1 according to the preferred embodiment of the present invention; 
     FIG. 7 is a block diagram showing the components of the intra-articular unit of the apparatus for performing endoscopic surgical procedures shown in FIG. 1 according to the preferred embodiment of the present invention; 
     FIG. 8 is a perspective view of the pump cassette which is used with the intra-articular unit shown in FIG. 4 according to the preferred embodiment of the present invention; 
     FIG. 9 is a plan view showing the internal components of the pump cassette shown in FIG. 8 according to the preferred embodiment of the present invention; 
     FIG. 10 is a plan view partially in cross-section of the internal components of the pump cassette shown in FIG. 8 according to the preferred embodiment of the present invention; 
     FIG. 11 is a longitudinal cross sectional view partially in cross-section of the shaver handpiece unit shown in FIG. 1 according to the preferred embodiment of the present invention; and 
     FIGS. 12-14 show a flowchart illustrating the various user-driven menus which are generated by the apparatus for performing endoscopic surgical procedures shown in FIG. 1 according to the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment of the present invention is merely exemplary in nature and is in no way intended to limit the invention or its application or uses. 
     The apparatus for performing endoscopic examination and resection apparatus of the present invention is shown in FIGS. 1 and 2 and is generally designated by the numeral 10. The apparatus 10 comprises an imaging unit 12, an intra-articular unit 14, a keyboard 16, an autoclavable remote control unit 18, a video monitor 20, a video cassette recorder 22, a video printer 24 and a cart 26. Each of these components of the apparatus 10 will be individually discussed below. 
     The cart 26 houses the majority of the components of the apparatus 10. The cart 26 is pre-wired for easy installation of the imaging unit 12, the intra-articular unit 14, the video cassette recorder 22 and the video printer 24. In this regard, most of the electrical conductors connecting the various components of the apparatus 10 are contained internally within the cart 26 and are connected to various electrical connectors mounted on the cart 26. By simply inserting the imaging unit 12 or the intra-articular unit 14 into the cart 26, all the necessary inter-related connections are automatically made thereby reducing the time required to set-up of the system. As will be more fully described below, the electrical conductors within the cart 26 allow the imaging unit 12 to intercommunicate with the intra-articular unit 14 so as to allow the imaging unit 12 to operate interdependently with the intra-articular unit 14. For example, the remote control unit 18 may be connected to either the imaging unit 12 or the intra-articular unit 14 and can control both. In addition, the imaging unit 12 may be used when the operation of the intra-articular unit 14 is being programmed. Other ways in which the imaging unit 12 and the intra-articular unit 14 operate interdependently are described below. 
     The cart 26 provides ample storage racks 58 for storage trays, the video cassette recorder 22 and the video printer 24. The cart 26 is also equipped with an isolation transformer located in the base 60 of the cart 26 which provides for electrical leakage containment of the components within the cart 26. The cart 26 can be easily maneuvered on its swivel locking caster wheels 62. 
     The imaging unit 12 of the apparatus 10 as shown in FIG. 3 comprises an RGB monitor 30, a high output xenon light source 32 and a camera 34 all contained in a chassis 36. The RGB monitor 30 can be used as a programming screen with menu driven control for individual system preferences such as light illumination and picture color as more fully described below. Alternatively, the monitor 30 can be used as a secondary monitor for viewing the surgical procedure. System programming of the imaging unit 12 is accomplished by utilizing the keyboard 16 as well as by the remote control unit 18 as will also be more fully described below. The camera 34 has an auto iris which provides instant illumination adjustments to reduce glare while an auto white balance eliminates time consuming camera set-ups. The camera 34 receives optical signals from a camera head 38 which is connected to the chassis 36 by both a fiber optic cable 39 and an electrical cord 40. Operation of the various functions of the imaging unit 12 can be accomplished by controls on the front panel of the imaging unit 12 or by the remote control unit 18 as described below. 
     The intra-articular unit 14 of the apparatus 10 as shown in FIG. 4 comprises an RGB monitor 42, a shaver power unit 44 and a pumping unit 48, all of which are contained in a chassis 64. The RGB monitor 42 provides display of current running information (e.g., the speed of the shaver, fluid flow rate and cavity pressure) and can be utilized for information on operating the apparatus 10. Inflow of fluid from the pumping unit 48 to the cavity can be accomplished through the camera head 38 or by a separate cannula, both utilizing built-in pressure protection. The shaver power unit 48 is used to drive shaver handpiece 52 (see FIG. 1) which is connected to the chassis 64 by the electrical cord 54. Operation of the various functions can be accomplished by controls on the front panel of the intra-articular unit 14 or also by means of the remote control unit 18 as described below. 
     Referring now to FIG. 5, an upper level block diagram of the apparatus 10 is shown depicting the imaging unit 12, the intra-articular unit 14, the video cassette recorder 22, the video printer 24, the video monitor 20, the keyboard 16, an optional bar code wand 72 and the cart 26. The components of the imaging unit 12 and the intra-articular unit 14 will be more fully discussed below. The video monitor 20, normally located on the top of the cart 26, receives the output of the imaging unit 12 and provides a color picture of the endoscopic procedure from the output of the camera head 38. Various connections are made from the video monitor 20 to the cart 26 to provide video output for the imaging unit 12 as well as receiving output from the video cassette recorder 22. These connections are made through the bus 134 and include RGB video, y/c video input and audio input. 
     The video cassette recorder 22 is provided to enable the surgeon to make a taped record of the endoscopic examination or procedure. The video cassette recorder 22 is located in the rear of the cart 26 normally located on one of the storage racks 58. Various connections are made to the cart 26 for recording and playback of the pictures created by the imaging unit 12. These connections are made through the bus 118 and include composite VCR out, audio in, video cassette recorder control, y/c video, audio out and y/c video out. 
     The video printer 24 is provided in order to allow the surgeon to have a permanent copy of any picture displayed on the video monitor 20. The video printer 24 is also located at the rear of the cart 26 on one of the storage racks 58. Various connections are made through the cart 26 for allowing the video printer 24 to interface with the other components of the imaging unit 12. These connections are made through the bus 128 and include freeze RGB, RGB video in and RS232. 
     The bar code wand 72 connected to the cart 26 through the wand bus 136. The bar code wand 72 is used to allow easy and relatively quick readouts of operating room charges, patient charges or other standard information. The keyboard 16 is also an optional device and is connected to the cart 26 by the keyboard bus 138. 
     The remote control unit 18 may be connected to either the imaging unit 12 or the intra-articular unit 14. The operation of the remote control unit 18 is identical regardless of where the connection is made. The remote control unit 18 includes a plurality of push-button switches which control the following operational characteristics of the apparatus 10: 
     increase fluid flow rate 
     decrease fluid flow rate 
     increase cavity pressure 
     decrease cavity pressure 
     on/off 
     lavage mode 
     shaver stop/start 
     increase shaver speed 
     decrease shaver speed 
     shaver mode change (i.e., forward, reverse, oscillate) 
     print image 
     start/stop video cassette recorder 
     start/stop timer 
     increase iris contrast 
     auto/manual iris 
     decrease iris contrast 
     scroll up menu 
     enter selection on menu 
     scroll down menu 
     Because the remote control unit 18 is autoclavable and therefore used in the sterile field proximate to the surgical site, the surgeon is able to control the apparatus 10 from the sterile field by using the remote control unit 18. 
     Referring now to FIG. 6, a block diagram of the imaging unit 12 is shown. The imaging unit 12 comprises a camera front panel 142, a light source front panel 144, the light source 32, the RGB monitor 30, a camera MPU 146, and the camera 34. All necessary connections to the other components within the apparatus 10 are located on the rear of the imaging unit 12 and inserting the imaging unit 12 into the cart 26 makes the connections through the use of Hypertronic™ zero insertion connectors. In this regard, the insertion of the imaging unit 12 makes the following connections through the bus 88 to the cart 26: audio, video cassette recorder control, y/c video, composite video, freeze RGB video, RGB video, RS 232-to-print, remote control unit bus, serial bus (unit-to-unit), wand bus, keyboard bus, serial image unit bus and unit-to-unit enable. The camera front panel 142 provides an electrical connection to electrically couple the imaging unit 12 to the microphone 74 through the bus 80, the camera head 38 through the bus 116, the polaroid camera 76 through the bus 84 and the remote control unit 18 through the bus 82. The camera front panel 142 is also electrically coupled to the camera 34 through the bus 120, the camera MPU 146 through the bus 122 and the input power 150. 
     All five RS-232 serial ports of the imaging unit 12 use a plurality UARTS controlled by the camera MPU 146, each having their own baud rate generator. The S-bus output is a serial data bus with a standard protocol data system generated by the camera MPU 146 using an internal timer. All ports are double buffered allowing the camera MPU 146 to write or read characters irrespective of the peripheral timing. The camera MPU 146 itself contains multiple pulse modulators which when attached to a low pass filter produce controllable analog voltages. These voltages preferably control the adjustment of a camera iris for the camera 34 as well as the beeper volume. Multiple digital input/output lines of the camera MPU 146 are used for switch status input, remote scanning, S-bus generation, SIO control, camera control and video multiplexer control. 
     The RGB monitor 30 of the imaging unit 12 is preferably a 9-inch monitor which displays various menus enabling the surgeon to quickly set or change various operating parameters by using the remote control unit 18. Each menu is generated in accordance with a software program 298 (which is described in connection with FIGS. 12 and 13) by the camera MPU 146 and written to the external RAM memory at VIDSTORE, as listed in the Appendix. This data is then downloaded to a video RAM in the MPU 146 during the vertical retrace. The various menus displayed on the RGB monitor 30 will be more fully described below. 
     The video signal generated by the camera MPU 146 represents three identical channels of RGB information. The video signal from the camera MPU 146 is delivered to the video monitor 20, the RGB monitor 30, the video printer 24 and the video cassette recorder 22. In this regard, a composite video signal is delivered to the video cassette recorder 22, with all other peripherals receiving either composite or RGB video. 
     The RGB monitor 30 preferably displays the video signal from the camera MPU 146 with a computer generated overlay or with freeze images. The video printer 24 and the video cassette recorder 22 preferably receive a camera image with an overlay generated thereon. The overlays may represent patient ID or other helpful information relating to the surgical procedure. Selection of the source/destination video and sync is performed by a multiplexer in the video section operating under CPU control. 
     The front panel 142 of the camera 34 offers various controls for operating the apparatus 10. A power switch is electrically coupled to the input power 150 through the fuse block 154. The power switch is also electrically coupled to the various power supplies of the imaging unit 12 through an EMI filter 156 and an isolation transformer 158. In addition to the power switch, the front panel 142 of the camera 34 provides an auto iris on/off switch, a print switch, a scroll up switch, a scroll down switch and an enter switch. All of the above mentioned switches are electrically coupled to the camera MPU 146 through the bus 122. 
     The camera MPU 146 is preferably a Zilog Z86C97 CMOS digital TV controller containing a Z8 CPU core, on screen display generator, multiple pulse width modulator and parallel input/output ports. Documentation on this microprocessor is available from the manufacturer in the form of the Z86C27/C97 Manual and the Z8 Family Design Handbook, both documents of which are hereby incorporated by reference. 
     The imaging unit 12 further contains both internal and external random-access memory and an external EPROM program memory. A memory mapping may be found in module EQ, also listed in the Appendix B. 
     The imaging unit 12 further includes a front panel 144 of the light source 32 which provides a port 170 for connection of the optical fiber cable 39, as well as a lamp-on switch and a lamp-off switch. The lamp-on and lamp-off switches control the xenon light source 32 which delivers light to the camera head 38 through the optical fiber cable 39. 
     The components of the intra-articular unit 14 will now be described in greater detail with reference to FIG. 7. The intra-articular unit 14 comprises the shaver power console 46, the pump console 50, the shaver power unit 44, the pumping unit 48, the RGB monitor 42, and a shaver/pump MPU 182. All necessary connections to the other components within the apparatus are located on the rear of the intra-articular unit 14 and inserting the intra-articular unit 14 into the cart 26 makes the connections through the use of Hypertronic™ zero insertion connectors 184. In this regard, the insertion of the intra-articular unit 14 into the cart 26 makes the following connections through the bus 108 to the cart 26: serial intra-articular unit bus, data bus (unit-to-unit), remote control unit bus and unit-to-unit enable. 
     The shaver power console 46 provides electrical connections to electrically couple to the intra-articular unit 14 the shaver handpiece 52 through the bus 104, the foot switch 56 through the bus 106, and the remote control unit 18 through the bus 110. The shaver power console 46 is also electrically coupled to the shaver motor drive electronics 44 through the bus 90, the shaver/pump MPU 182 through the bus 92 and the input power 186. The shaver power console 46 includes a power switch which is electrically coupled to the input power 186 through a fuse block 190. The power switch is also electrically coupled to the various power supplies of the intra-articular unit 14 through an EMI filter 192 and an isolation transformer 194. 
     The RGB monitor 42 preferably comprises a 9 inch VGA color monitor which displays real-time system variables in a variety of bar, numeric and message formats. For example, the RGB monitor 42 may simultaneously display a bar graph of the speed of the shaver handpiece 52, an indication of the mode of operation of the shaver handpiece 52 (forward, reverse or oscillate), as well as an indication of whether the shaver handpiece 52 in on or off. Alternatively or simultaneously displayed on a split screen, the RGB monitor 42 may generate a display showing a bar graph of the flow rate of fluid into the cavity as well as the pressure of fluid in the cavity. The VGA interface for the RGB monitor 42 preferably comprises an industry standard VGA card which is mounted as a daughter board within the intra-articular unit 14. 
     The RGB monitor 42 provides a high resolution (640×480) pixel VGA map. Due to this high resolution, the intra-articular unit 14 hardware is designed to maximize transfer rate between the shaver/pump MPU 182 and the VGA card in communication with the RGB monitor 42. Maximum data transfer is accomplished by the use of several techniques. First, a memory address-auto increment capability is used to allow CPU-VGA memory transfers without having to load each address prior to each data transfer. In addition, a function decode produces input/output write, input/output read, memory write and memory read pulses with a single input/output instruction. Furthermore, a strobe pulse is generated on either the rise or fall of a generated command. This eliminates the necessity to use two instructions to produce a strobe pulse. In addition, the VGA transfer is synchronized by an automatic weight pulse stretcher. This eliminates the requirement of the CPU to test for VGA ready status. 
     Furthermore, the VGA screen is normally mapped as four planes to produce one out of 16 color codes and normally requires writing data four times to the same address to produce color pixels. By eliminating the allowable number of colors to 6 and restricting which colors can over-write others, the intra articular unit 14 can write a color pixel in one operation. In addition, by using a memory mapping technique, the high order bits of the VGA memory map can be set to allow a mirror image of a ROM memory, containing, for example, high resolution logo pictures. When used in conjunction with the auto increment address capability, bytes can be transferred directly from the ROM to the VGA card with one instruction. Finally, incorporating a hardware pixel rotator allows read-modify-write shifting of pixel row data with only two instructions. The combination of the above techniques increases the CPU to VGA data throughput to a peak rate of approximately 682K pixels/second. Reference information relating to VGA programming is available from the &#34;Programmers Guide to the EGA and VGA Cards&#34;, by Ferraro and Addison-Wesley, and &#34;Cirrus CL-GD5320 Technical Reference Manual&#34; by Cirrus Logic, Inc., both documents of which are hereby incorporated by reference. 
     As shown in FIG. 7, the front panel 50 of the pumping unit 48 of the intra-articular unit 14 provides an access door 196 to install a pump cassette 198, a pressure-up switch, a pressure-down switch, a flow-up switch, a flow-down switch and a pump prime switch. All of the above mentioned switches are electrically coupled to the shaver/pump MPU 182 through the bus 208. 
     The pumping unit 48 of the intra-articular unit 14 is electrically coupled to the shaver/pump MPU 182 and comprises an irrigation pump motor drive 210 with an associated tachometer 212, an aspiration pump motor drive 214 with an associated tachometer 216 and a pressure sensor 218. Including both the irrigation and aspiration pumps 222 and 224 within the pump cassette 198 enables both of the pumps 222 and 224 to be driven when the pump cassette 198 is inserted through the access door 196. The pressure sensor 218 monitors the system pressure as will be described later herein. The separate pumps for irrigation and aspiration have capabilities of 0-1000 ml/min and a pressure range of 0-150 mm Hg. 
     With reference to FIGS. 7 and 8, the tachometers 212 and 216 are not physically connected to the motors that drive the pumps 222 and 224. Rather, the pumping unit 48 generates electrical pulses by the movement of magnets on rotors of the irrigation and aspiration pumps 222 and 224 as the magnets move rotationally past stationary Hall-effect sensors. The electrical pulses are indicative of the speed of the motors and are delivered to the shaver/pump MPU 182. The shaver/pump MPU 182 uses the changing frequency of the pulses to control the speed of the motor drives 210 and 214. 
     The microprocessor of the shaver/pump MPU 182 is preferably a Hitachi HD647180X CMOS device containing an HD64180 CPU core, multiple timers, dual serial input/output port, a 512 byte internal ram memory and a 16K byte internal OTP program ROM memory and parallel input/output ports. Documentation for these components is available from the manufacturer in the form of HD 647180X 8 bit Microcontroller Hardware Manual and an HD 64180 Series 8 bit Microprocessor Programming Manual, both documents of which are hereby incorporated by reference. Detailed mapping for memory and input/output is defined in the Equate module EQ, as listed in the Appendix D. 
     The shaver motor drive electronics 44, the irrigation pump motor drive 210 and the aspiration pump motor drive 214 each determine speed and direction for each of the motors of the motor drive circuits 210 and 214. More specifically, the speed is controlled by analog voltages produced from three D/A converters. The direction of each of the irrigation and aspiration pump motors is determined by a logic level signal generated by the shaver/pump MPU 182. 
     The intra-articular unit 14 includes several internal monitoring circuits for monitoring motor current, motor drive fault, status and pressure sensed by the pressure sensor 218. The two port serial input/output is provided to allow communication with the imaging unit 12 or an external computer and external host computer interface. The intra-articular unit14 may be controlled by either the front panel switches on the unit 14, the foot switch 56 or the remote control unit 18. An external, non-volatile memory contains calibration constants which control motor control offset and gain. 
     The pump cassette 198 will now be described in greater detail with particular reference to FIGS. 1 and 8 through 10. The pump cassette 198 comprises the housing 220, the irrigation pump 222, the aspiration pump 224, the ball check valves 226, 228, 230 and 232, the pressure dome 234 and the five fluid tubes 236, 238, 240, 242 and 244. 
     The tube 236 connects a fluid supply 246 with the inlet side 222a of the irrigation pump 222. The tube 238 connects the output 222b of the irrigation pump 222 to the cannula 248 being used for introducing fluid into the cavity. The pressure dome 234 reacts to the pressure present in the tube 238 so as to provide an estimate of the fluid pressure within the cavity. The tube 240 connects an outflow cannula 250 with a first input 224a of the aspiration pump 224 through the check valve 226 and the filter 221. The tube 242 connects on output 224b, and on output 224b2 of the aspiration pump 224 with a drain reservoir 252 through both the check valves 228 and 230. The tube 244 connects the outflow from the shaver handpiece 52 with a second input 224c to the aspiration pump 224 through the filter 245. The pump cassette 198 is inserted through the access door 196 (FIG. 7) into the intra-articular unit 14. Once the pump cassette 198 has been inserted into the intra-articular unit 14, the irrigation pump motor drive 210 is automatically coupled to the irrigation pump 222, the aspiration pump motor drive 214 is automatically coupled to the aspiration pump 224, and the pressure sense 218 is positioned proximate to the pressure dome 234. 
     While the pressure at the outlet of the irrigation pump 222 is readily measured by the pressure sensor 218 in conjunction with the pressure dome 234, the pressure sensed by the pressure sensor 218 may not accurately indicate the pressure in the cavity because the pressure drop through the tube 238 can be significant. The advantage of having the irrigation pump 222 control the flow rate into the cavity is that the flow rate through the tube 238 is known. Since the pressure drop through the tube 238 is a function of the flow rate through the tube 238, the pressure drop through the tube 238 can be accurately determined by the apparatus 10 by subtracting the known pressure drop in the tube 238 from the pressure sensed by the pressure sensor 218. 
     Operation of the apparatus 10 begins by insertion of the cannulas 248 and 250 into the internal cavity of the patient as shown in FIG. 1. Depending upon the specific operation being performed, the number of incisions can vary between two and four. If the surgery is exploratory in nature and the inflow of fluid is accomplished through the camera head 38, the only incisions required are for the camera head 38 and the cannula 250 for the outflow from the cavity. If the surgery is exploratory in nature, and the inflow of fluid is accomplished by a separate cannula, three incisions must be made: one for the camera head 38, one for the cannula 248 for inflow of fluid and one for the cannula 250 for outflow of fluid. When the surgery is to include use of the shaver handpiece 52, then an additional incision to those mentioned above must be made. 
     The pump cassette 198, being disposable, allows for the insertion and attachment of all required tubing and surgical instruments prior to insertion into the cavity. Once the patient has been prepared, the pump cassette 198 is inserted through the access door 196 of the intra-articular unit 14 and coupling of the motor drivers 210 and 214 with the gear pumps 222 and 224 respectively is accomplished. In addition, the proximity pressure sensor 218 is positioned proximate to the pressure dome 234. The imaging unit 12 and the intra-articular unit 14 are then switched on and operation of the apparatus 10 begins. 
     The surgeon selects a fixed flow rate for the irrigation pump 222 and a desired pressure to be maintained within the cavity either by front panel controls on the intra-articular unit 14 or by the remote control unit 18. The irrigation pump 222 begins pumping fluid from the fluid supply 246 to the cavity. The pressure within the cavity is monitored by the pressure sensor 218 reacting to the proximity of the pressure dome 234. As the pressure within the cavity increases, the pressure dome 234 expands and moves closer to the pressure sensor 218. The pressure sensor 218, being a proximity sensor, senses the change in location of the pressure dome 234 and converts the position of the pressure dome 234 into a corresponding pressure signal. Once the predetermined pressure set by the surgeon is reached, the aspiration pump 224 begins pumping fluid from the cavity through the tube 240 and the check valve 226, through the output port 224b2, through the check valve 230, and through the tube 242 to the drain reservoir 252. The speed of the aspiration pump 224 is responsive to the pressure sensor 218 and provides for a constant pressure within the cavity regardless of the leakage which may occur. 
     The operation continues with the irrigation pump 222 pumping at a fixed flow rate and the pressure sensor 218 maintaining a specified pressure within the cavity by controlling the speed of the aspiration pump 224. If the surgeon desires a higher pressure with the cavity, the desired selection may be made by either a switch on the front panel 50 or by the remote control unit 18. Similarly, if the surgeon desires a lower pressure, that selection is also made by a switch on the front panel 50 or the remote control unit 18. When a higher pressure is selected, the speed of the aspiration pump 224 is slowed until the higher pressure is reached. When a lower pressure is selected, the speed of the aspiration pump 224 is increased until the lower pressure is reached. In a similar fashion, the surgeon can increase or decrease the flow rate of the irrigation pump 222 by using additional switches located on the front panel 50 or the remote control unit 18. When an increase or decrease in the flow rate is selected, the pressure sensor 218 maintains the desired pressure within the cavity by controlling the speed of the aspiration pump 224. 
     When the surgeon has selected to use the shaver handpiece 52, the fluid within the cavity is also withdrawn through the shaver handpiece 52 in a manner described below so as to cause a change in the flow of fluid leaving the cavity. In addition, the flow rate of fluid may have to be increased to provide for the flushing of debris or blood. This increased inflow rate and the switching of outflow of fluid to go through the shaver handpiece 52 occurs automatically with the activation of the shaver handpiece 52. In this regard, when the shaver handpiece 52 is activated, the direction of the aspiration pump 224 is reversed and the speed of the irrigation pump 222 is set to a predetermined (usually higher) flow rate. The reversing of the aspiration pump 224 changes the input from the tube 240 and the check valve 226 to the tube 244 and the check valve 232. The outflow is changed from the check valve 230 to the check valve 228. As can be seen from FIG. 10, both the check valve 228 and the check valve 230 are in communication with the tube 242, which is in communication with the drain reservoir 252. During the increase in flow rate and switching of inputs to the aspiration pump 224, the pressure sensor 218, working in conjunction with the pressure dome 234, maintains the preselected pressure within the cavity. Upon deactivation of the shaver handpiece 52, the system reverts back to the operation as described above. 
     The shaver handpiece 52 can be controlled by front panel controls on the intra-articular unit 14 or by the remote control unit 18. In either instance, the speed of the shaver handpiece 52 can be adjusted by suitable push button switches to either increase or decrease the shaver speed, and to control start and stop operation of the shaver handpiece. 
     Referring now to FIG. 11, an enlarged longitudinal cross-section of the shaver handpiece 52 is shown. The shaver handpiece 52 comprises a generally hollow cylindrical housing 260. An aspiration port 262 is located toward the rear end of the housing 260 and provides a connecting port for the tube 232. A seal 264 is located between the aspiration port 262 and the housing 260 to seal the internal portion of the housing 260. The aspiration port 262 has a hollow bore 258 to provide for the movement of fluid as will be described later herein. A motor stator 264 is positioned in the housing 260 using an interference fit between the motor stator 264 and the inside diameter of the housing 260. A frame 266 is positioned between the aspiration port 262 and the motor stator 264 within the housing 260. The frame 266 axially locates the motor stator 264 within the housing 260. An end cap 270 is fixedly secured to the end of the housing 260 opposite the aspiration port 262 to enclose the interior portion of the housing 260. A seal 272 located between the housing 260 and the end cap 270 seals the interior portion of the housing 260 from the outside environment. A hollow motor rotor 274 is rotatably positioned within the housing 260 and the motor stator 266 by a pair of bearings 276 and 278. The bearing 276 rotatably mounts the rear end of the motor rotor 274 relative to the frame 266. The bearing 278 rotatably mounts the front end of the motor rotor 274 relative to the end cap 270. The motor rotor 274 has a hollow bore 280 which is in communication with the hollow bore 258 for the movement of fluid. A pair of seals 282 and 284 seal the interior of the housing 260. 
     A chuck 286 is fixedly attached to the open end of the end cap 270 and provides for the quick change of the various shaver blades 288 which are needed during the procedure. The shaver blades 288 can include a full radius shaver of various sizes, a synovial resector, a meniscus cutter, a flat end cutter, a round end cutter, a side cutter, a slotted whisker cutter, a round abrader, a tapered abrader, as well as a wide variety of other shaver blades. The shaver blades 288 have a hollow bore 290 which is in communication with the hollow bore 280 of the motor rotor 274 when the shaver blade 288 is locked into the shaver handpiece 52 by the chuck 286. Locking the shaver blade 288 into the shaver handpiece 52 by the chuck 286 also connects the shaver blade 288 with the motor rotor 274 for rotation therewith. 
     Upon activation of the shaver handpiece 52, the motor rotor 274 rotates the blades 288 to perform the necessary operation on the patient. Activation of the shaver handpiece 52 also switches the outflow of fluid from the cavity from a separate cannula to the shaver handpiece 52 as previously described. Fluid withdrawn from the cavity travels through the hollow bore 290, through the hollow bore 280, through the hollow bore 258 and into the tube 232. During the aspiration of fluid from the cavity, the direction of travel of fluid through the shaver handpiece 52 is in a generally straight line. The design of the shaver handpiece 52 eliminates the need for the fluid to travel around corners which tend to cause clogging of the aspiration path. The generally straight path formed within the shaver handpiece 52 insures a free flow of fluid from the cavity and minimizes the tendency of the aspiration path to clog. 
     Referring now to FIGS. 12-14, there is shown a simplified flowchart 298 of the menu-driven software of the apparatus 10 of the present invention. After power up of the apparatus 10, the user may select a main menu 300 having the following nine fields representing options by which the user can adjust or set up the apparatus 10 to suit a variety of particular preferences and/or for a variety of operating parameters: 
     System status 
     Auto setup 
     Patient ID 
     Normalized system 
     VCR controls 
     Auto iris 
     Select Timer 
     System setup 
     Color bar 
     The user selects one of the above nine mentioned options 302-318 by using either the keyboard 16, the remote control unit 18 or the front panel controls of the imaging unit 12. If the system status 302 option is selected, then the RGB monitor 30 of the imaging unit 12 displays the amount of time the bulb of the camera head 38 has been used (in hours), the amount of time the apparatus 10 has been on and the amount of print ribbon remaining in the video printer 24, as indicated at block 320. Accordingly, if the time of use of the bulb indicates that the bulb should be changed, or if the amount of print ribbon left indicates that the print ribbon should be changed, these items can be attended to before beginning the surgical procedure. The system 298 then returns to the main menu 300, as indicated by block 322. 
     If the auto setup 304 option is selected, the user is presented with the choice of either retrieving existing operating parameters as indicated by block 324, stored in the apparatus 10 or storing new operating parameters, as indicated by block 326, for the apparatus 10. If the existing parameters are to be used, then the user merely enters his/her name, as indicated by block 328, and the system 298 returns to the main menu 300, as shown by block 330. If the user desires to store new operating parameters, then the user selects and stores the new parameter(s), as indicated by the block 326, enters his/her name, as indicated by the block 332, then selects new parameters, as indicated by the block 334. This associates the new parameters with the entered user&#39;s name and may be recalled at future times by merely entering the user&#39;s name. The system 298 then returns to the main menu 300 as indicated by the block 330. 
     If the user selects the select patient ID field 306, then a menu showing the existing patient&#39;s name is displayed, as indicated at the block 336, and the system 298 returns to the main menu 300 as indicated by the block 338. If the user desires to enter a new patient name, then this option is provided, as indicated by the block 340, whereby the system 298 will store the new patient name entered before returning to the main menu 300, as indicated by the block 338. 
     If the normalized system option 308 is selected, then the system 298 automatically resets all of the operating parameters previously stored to default selections, as indicated at the block 342, before returning to the main menu 300, as indicated by block 344. 
     If the select VCR controls option 310 is selected by the user, a menu displaying options to select either VCR stop 346 to stop recording or playback operation of the video cassette recorder 22, enabling VCR recording 348, initiating VCR playback 350, initiating rewind 352, and initiating VCR fast forward operation 354 are provided. After the user selects the desired option the system 298 returns to the main menu 300 as shown by block 356. 
     If the user selects the auto iris option 312 from the main menu 300, the user will be presented with a menu displaying the option of having the iris adjustment performed automatically, as indicated by the block 358, or the option of manually adjusting the iris, as indicated by the block 360. If the manual iris adjustment option 360 is selected, the user is allowed to manually adjust the iris, as indicated by the block 362, before the system 298 returns to the main menu 300, as indicated by the block 364. If the auto iris option 358 is selected, the system 298 automatically adjusts the iris before returning to the main menu, as indicated by the block 364. 
     If the select timer option 314 is selected, then a menu is displayed which provides the user with the option of starting or stopping a timer for timing the surgical procedure, as indicated by the block 366, or displaying the elapsed time of the timer on the RGB monitor 30, as indicated by the block 368, before the system returns to the main menu 300, as shown by the block 370. 
     If the select system setup option 316 is selected, then the user is presented with a variety of options for setting up the various peripherals of the system 10, as will be described momentarily in connection with FIG. 14. Finally, if the color bar option 318 is selected by the user, a color bar is displayed on the RGB monitor 30 which can then be manually adjusted, as indicated by the block 372, before proceeding with the surgical procedure, before returning to the main menu 300, as indicated by the block 374. 
     Referring now to FIGS. 13 and 14, the options presented to the user if the system setup 316 option is selected from the main menu 300 are shown. When the system setup 316 option is selected, the user is presented with another menu having a camera setup 376 option, a beeper setup 378 option, a printer setup 380 option, and a monitor setup 382 option. If the camera setup 376 option is selected, then the user is presented with another menu which displays the choice of adjusting the auto gain of the camera head 38, as indicated by the block 384, or adjusting the white balance of the camera head 38, as indicated by the block 386, before returning to the main menu, as shown by the block 388. If the auto gain adjustment is selected, as indicated by the block 384, then the user is presented with yet another menu displaying the options of increasing the auto gain setting, as indicated by the block 390, or decreasing the auto gain setting, as indicated by the block 392, before the system 298 returns to the main menu 300. 
     If the user selects the beeper setup 378 option, then the user is presented with another menu displaying the option of increasing the beeper volume, as indicated by the block 394, or decreasing the beeper volume, as indicated by the block 396, before the system 298 returns to the main menu 300. 
     If the user has selected the printer setup 380 option, then another menu is displayed showing the option of exiting the current menu, as shown by the block 398, the option of setting the color/contrast of the printer 24 as shown by the block 400, the option of setting the sharpness of the printer 24, as shown by the block 402 and the option of selecting either a full or split printout, as indicated by the block 404 are provided. After selecting one of the four above mentioned options, the system 298 returns to the main menu 300, as shown by the block 388. 
     If the user has selected the monitor setup 382 option, then the system 298 displays a menu having four options. The first option is a monitor volume option, indicated by the block 406, which enables the volume of the RGB monitor 30 to be adjusted before returning to the main menu 300. An RGB or composite video option, as indicated by the block 408, if selected, causes another menu to be generated from which either RGB or composite video may be selected, as indicated by the blocks 410 and 412, respectively, before the system 298 returns to the main menu 300. A small monitor video option, indicated by the block 414, if selected, enables video display of the surgical procedure on the RGB monitor 30, as indicated by the block 416 or allows the RGB monitor 30 to be turned off, as indicated by the block 418, before returning to the main menu 300. 
     Accordingly, the above-described, menu-driven software system provides a means by which the various operating parameters and peripherals may be adjusted and/or selected quickly and easily by the user either before the surgical procedure is under way or during the procedure. The various menus of the system 298 enable a wide variety of operational parameters to be changed quickly and also without interrupting the surgical procedure once started. 
     While the above detailed description describes the preferred embodiment of the present invention, it should be understood that the present invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims. ##SPC1##