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A new technique of single-portal arthroscopy using new instrumentation for arthroscopic knee surgery is reported. The procedure is intended for “targeted” surgery to address limited pathology. The arthroscope, cutters, and biters are all introduced into the joint through 1 portal. The technique is generally applicable to knee arthroscopy for isolated conditions and potentially useful in treating other joints. A 2.9-mm-diameter, light-sensitive, high-definition, 20-cm-long arthroscope is inserted through a 4.6-mm cannula. This arthroscope-cannula combination yields fluid flow mechanics similar to a standard 4-mm arthroscope in a 5.8-mm cannula. A Parallel Portal Cannula (PPC) (Stryker Endoscopy) is applied to the arthroscope cannula, producing a “double-barrel” system for entry into the joint. The PPC allows for sliding and rotational freedom along the axis of the arthroscope cannula but also locks in place once a desired position is achieved. PPC devices are available in zero-length, short (25-mm), and long (55-mm) sizes. Cutters that are bent in the mid shaft are available in 3.5- and 4-mm diameters. The instrumentation system allows both viewing with the arthroscope and passage of working cutters and biters through a single 9- to 10-mm portal. Potential advantages of single-portal arthroscopy include decreased patient morbidity and recovery time while still allowing for adequate treatment of limited knee pathology.
See video under supplementary data.
Decades ago, the introduction of the arthroscope in the treatment of knee disorders revolutionized the surgical approach for many patients. However, many aspects of the initial instrumentation have remained unchanged. The need for adequate fluid inflow and outflow and the need for visualization with an arthroscope, as well as the need for triangulation of working instruments through 2 or more portals, have remained constants of this surgical procedure.
New designs in optics, digital image transmission, high-definition monitors, and fluid inflow pumps have all improved the efficiency and visualization during arthroscopic surgery. Yet many basic aspects of knee arthroscopy have remained unchanged since 1972, including the need for triangulation and intra-articular convergence of instruments through at least 2 portals. In 1977, O'Connor
reported on the use of an “operating arthroscope” designed to allow passage of a working instrument through the same portal as the arthroscope. This was similar to cystoscopy instrumentation and not designed for the purpose of performing a single-portal technique.
Our hypothesis in design was that we could achieve the same surgical result by implementing a technique that uses 1 portal to pass both arthroscope and working instrument alike. Triangulation occurs outside the joint, with the instruments in parallel entry into the joint yet allowing enough independent instrument manipulation within the joint to effectively treat pathology.
Surgical Instruments and Technique
Single-portal arthroscopy can be accomplished efficiently with a new instrument system that downsizes both the arthroscope sheath and the working cutters and biters. By decreasing the diameters of these instruments, it is possible to pass both the arthroscope sheath and the biter or cutter alongside each other through 1 portal measuring less than 10 mm.
Critical to any arthroscopic technique is the need for fluid flow and visualization. The SPA arthroscope (Stryker Endoscopy, San Jose, CA) is a new 2.9-mm, very light-sensitive arthroscope capable of light transmission and optics that are equivalent to current modern 4-mm arthroscopes that are available in the marketplace. Used within the 4.6-mm sheath, the 2.9-mm SPA arthroscope allows a volume of fluid flow similar to that obtained with the 4-mm arthroscope and 5.8-mm cannula used in traditional arthroscopic techniques. In addition, the arthroscope is slightly longer than a traditional arthroscope (20 cm v 16 cm), and this allows for working instrument passage alongside and in line with the arthroscope sheath.
The SPA arthroscope is a new 2.9-mm-diameter, 20-cm-long, 30° arthroscope with C-mount or eyepiece designs available (Fig 1). There is an improved focus mechanism and closer light post for 1-handed control of tip orientation on the C-mount design compared with previously available arthroscopes. A tight-tolerance speed-lock mechanism attaches to a 4.6-mm-outside diameter cannula with an 18-cm working length. This system achieves excellent fluid flow comparable to the current 4-mm arthroscope and 5.8-mm cannula systems. The added working length allows for curved instrument passage into the joint through the same portal in line with the arthroscope cannula. Multiple stopclock configurations are available including single, double 95°, and double 180° in rotating or fixed positions. There is a speed-lock obturator for introduction into the joint.
Parallel Portal Cannula
A 4.4-mm working channel or Parallel Portal Cannula (PPC) (Stryker Endoscopy) attaches to the arthroscope cannula (Fig 2). This is necessary because the passage of working instruments alongside the arthroscope sheath, yet through the same portal, requires a certain degree of control to prevent instrument crossover or stretching of the skin at the portal site. The SPA system includes the PPC in varied lengths that provide this control.
The PPC is a second cannulated device that is assembled over the arthroscope sheath. Its design allows for it to slide along and rotate around the arthroscope sheath but also provides a locking lever to secure it in place once the desired position is obtained. The 25- and 55-mm versions of the PPC include a plastic locking lever and a rubber dam diaphragm that prevent fluid egress through the working lumen. This PPC comes in 3 types, based on the length of the 4.4-mm-diameter tubular component, that allow instrument passage.
The zero-length version has the locking lever but has no tubular extension. The short PPC has a 25-mm tubular extension, and the long PPC has a 55-mm tubular extension. With increased length, more control is provided at the expense of more constrained maneuverability. The zero-length version allows for quite a bit of instrument maneuverability within the joint. In addition, the zero-length version allows for double-curved cutter passage as compared with single-curved cutter passage with the short or long PPC (Fig 3A). The 55-mm PPC allows passage of instruments that are straight at the tip. Both the zero-length version and the 25-mm version will allow for passage of some curved instruments, but the 25-mm PPC will allow passage of instruments that are curved no more than 9° near the tip.
A variety of Stryker manual instruments are available for performance of surgical procedures in the knee (Fig 4). Redesigned handles with improved ergonomics for both palming and finger-loop use are standard. Punch styles include round Bird Beak (Stryker Endoscopy), square big bite, and up tip square big bite versions in sizes that allow passage through the PPC.
The Stryker SPA shaver design is different from standard arthroscopic shavers in that there is a 30° proximal bend for ideal ergonomics (Fig 4). This essentially allows for moving the triangulation point of the technique outside the knee joint with the arthroscope and instruments in parallel entry into the joint, thus easing the traditionally difficult aspect of arthroscopic triangulation. The shavers have a new inner tube laser-cut design that allows for multipoint flexibility yet smooth turning, with minimal friction yet excellent cutting torque. Shavers are available in 3.5- and 4-mm diameters and Aggressive Plus, Resector, and Tomcat window styles. There is also a model with an additional distal bend near the tip for more deviation inside the joint space.
The SPA technique is dependent on placement of a transverse 9- to 10-mm medial infrapatellar portal site at a level approximately 5 mm distal to the inferior pole of the patella. For most procedures in the medial or lateral compartment, the medial portal will be used. Certain patellofemoral procedures may be better performed with a single suprapatellar or patellofemoral portal, when imaging of the other compartments has confirmed that they are normal and a full diagnostic tour is not necessary.
Patient positioning for the SPA technique is similar to that of 2- or 3-portal knee arthroscopy, that is, the supine position with a thigh holder or post. Depending on surgeon preference, the end of the table may be flexed or out straight. The SPA technique requires a somewhat different ergonomic setup than 2-portal arthroscopy. In general, it is recommended that the leg be in a thigh holder and the end of the table flexed to improve ergonomics and leg positioning during surgery. The medial portal is used for visualization and instrument passage, regardless of whether the pathology is in the medial or lateral compartment. Positioning for lateral compartment procedures should be in the figure-of-4 position with varus stress.
Medial compartment procedures are likewise performed through the medial portal but with 30° to 40° of flexion and valgus stress applied. The procedure is greatly facilitated by use of a surgical assistant to apply stress while the surgeon stands in line with the medial portal to improve the ergonomics of the procedure.
Once positioning is complete and after antibiotic administration, surgical preparation, and time out, a transverse 9- to 10-mm medial infrapatellar portal is made with a No. 11 blade. Care is taken to incise the capsule also, and a hemostat or Kelly clamp is passed into the joint and used to spread the fat pad and capsule.
The PPC is assembled on the arthroscope cannula through the locking hole in the PPC. It is slid back to the coupler end of the arthroscope cannula, which is then introduced into the joint through the single portal. Fluid flow is established, the knee is lavaged to improve visualization, and a diagnostic evaluation is performed. Fluid flush may be obtained either by removing the arthroscope from the 4.6-mm cannula or by introducing the PPC into the joint as a second lumen. Structures may be probed by use of a mid-shaft curved probe through the PPC.
Once the diagnostic tour is completed, the knee is positioned appropriately for operative procedures in the desired compartment. The PPC is advanced into the knee along the arthroscope cannula until it reaches a desired depth of penetration, as indicated by laser lines on the arthroscope cannula. The surgeon may at times prefer that the PPC remain within the fat pad or prefer that it be fully introduced into the joint. To avoid iatrogenic chondral injury, the PPC working tube should not be advanced past the tip of the arthroscope. The PPC is now rotated to whichever position of rotation that allows for the best working trajectory. The PPC has 360° of rotational freedom. Once the PPC is in the desired position, it is locked by use of the locking lever. At any time during the procedure, the lever may be unlocked, the PPC longitudinal or rotational position adjusted, and then the lever relocked to secure the new position.
It is common for more than 1 PPC position to be used to accomplish a surgical procedure. For example, the anterior horn of the lateral meniscus is best treated with the PPC on the lateral side of the arthroscope cannula, and the posterior horn of the lateral meniscus is best treated with the PPC on the medial side of the arthroscope cannula. The angled tip of the arthroscope should generally be rotated to look toward the PPC. In this desired position of rotation, the locking lever will be on the same side of the arthroscope cannula as the light post. Once the arthroscope cannula and PPC are in a desired position, the shaver and manual instruments are passed to complete the procedure.
After completion of the procedure, the arthroscope and PPC are removed from the knee. The portal may be closed according to surgeon preference. Generally, a subcutaneous suture and Dermabond (Ethicon; Somerville, NJ) or Steri-Strip (3M Nexcare; St. Paul, MN) application is adequate. A sterile dressing is applied. Knee hyperflexion should be avoided for 2 weeks to avoid drainage and allow complete healing of the skin portal.
The early-generation operating arthroscope was an awkward and bulky method of passing instruments alongside the arthroscope cannula into the same portal. Acceptance was poor because of the right-angle bend for a side eyepiece, the rigidity of the working cannula, and primitive gravity fluid flow and optics that mandated bulkier dimensions. Single-portal arthroscopy with new instrumentation is a new technique in arthroscopic knee surgery performed with an all-new system of instruments from Stryker. By moving the triangulation point outside the knee, we have found that the technique facilitates easy instrument passage into the desired compartment of the knee and may minimize the potential for iatrogenic chondral damage during arthroscopy. The independent design of the PPC allows for free rotation around and sliding along the axis of the arthroscope cannula, giving the surgeon much more flexibility in delivering surgical instruments to the desired working zone without requiring much movement of the arthroscope. In addition, the locking lever maintains the desired position and control while working and prevents portal stretching that would otherwise occur because of divergence of the instruments at skin level.
There is potential advantage by minimizing invasiveness and morbidity. Each portal does have the potential for drainage, stitch abscess, and/or fibrosis that can contribute to postoperative morbidity.
If this technique does, in fact, offer a similar reduction of morbidity and improved recovery times, then there is tremendous potential in sports medicine and arthroscopy to offer this procedure as a less invasive option compared with standard techniques. This would be an advantage to the average patient but particularly desirable for athletes who must have in-season surgery if a more rapid return-to-play interval is accomplished.
Preoperative workup for patients should include standing radiographs, high-field strength magnetic resonance imaging, and clinical examination to confirm the limited areas of pathology. This evaluation makes complete operative access to all compartments less than mandatory and allows for a more targeted surgical approach. In addition, the technique is easily converted to a 2- or 3-portal technique should the surgeon determine that is appropriate.
Positioning issues in single-portal arthroscopy may be different from the traditional 2- or 3-portal techniques, and the surgeon must carefully assess these issues when considering this technique (Video 1). The ergonomic setup is somewhat different and is similar to other advanced arthroscopic procedures. Moreover, there is a learning curve, and the technique is best performed in a dry or wet laboratory environment before use on patients in the operating room.
Like the operating arthroscope, the PPC can give the surgeon the ability to access regions with instruments in areas that are easily visualized but difficult to reach through other established portals. Unlike the operating arthroscope, the PPC is small in diameter and has 2 df in positioning, which facilitates instrument passage and working trajectory. This application may offer benefit in more complex multiportal surgical techniques, by allowing direct instrument passage to the area seen and not requiring triangulation for delivery. The PPC may also provide benefit in suture management in a variety of arthroscopic suture anchor repair procedures by decreasing the need for a separate portal just for suture retrieval.
Single-portal arthroscopy may prove useful in treating numerous conditions, offering less invasiveness and morbidity and potentially speeding up postoperative recovery. Pathology that may be well suited for treatment with single-portal arthroscopy includes meniscus tears, chondral lesions, loose bodies, synovial plica, and proliferative lesions. In general, the SPA technique is not designed for major operative arthroscopy such as reconstructive techniques. Rather, it is a focused targeted procedure that is intended to be used for limited lesions in a knee without arthritis and that has undergone a complete preoperative evaluation. A clinical study is under way to study the relative short-term morbidity of the procedure and its long-term outcomes compared with traditional arthroscopic techniques.
Reviews Stryker Parallel Portal System instrumentation, ideal candidates for single-portal arthroscopy, patient positioning, and surgical technique for targeted arthroscopy that treats limited pathology.
The authors report the following potential conflict of interest or source of funding in relation to this article: Stryker Endoscopy. D.E.C. is a Consultant to Stryker Endoscopy, and his design laboratory travel expenses are reimbursed; B.F. is a full-time engineer employed by Stryker Endoscopy, and he is the lead designer for the development of the single-portal arthroscopy system.