Brian S. BealeStephen C. Jones and Selena Tinga Arthroscopic evaluation and treatment of joint disorders has become the gold standard in universities and veterinary specialty hospitals for small animals [1]. Arthroscopy provides a view of the joint under high magnification and illumination. This enhanced view can affect the decision‐making process, not only during surgery but also after. Of particular importance is determining the condition of the cartilage, the severity and type of synovitis, and the integrity of the medial meniscus. Arthroscopic imaging gives the surgeon critical information to decide on the most appropriate intra‐ and postoperative management for each patient to improve long‐term outcome and reduce insidious progression of osteoarthritis. Arthroscopic techniques can be challenging and are associated with a variety of complications and problems. Complications can be acute and obvious in the perioperative period or they may be insidious and take months or years to appear. Complications of arthroscopy are typically not severe but significant morbidity can occur with poor execution. Complications may be self‐limiting or may require intervention and treatment. When performing arthroscopy, the surgeon and their team should consider important factors preoperatively, intraoperatively, and postoperatively to avoid or reduce the occurrence and impact of complications. Important factors to consider prior to surgery include correct patient positioning, adequate limb preparation, limb stabilization, and access to the surgical field. Patient positioning is important for several reasons. Arthroscopic evaluation requires accurate portal placement and the ability to manipulate the limb to certain positions to enhance the view of intraarticular anatomical structures. Technicians and nurses often position, prepare, and drape the patient. The staff should be trained to ensure proper surgical preparation so that portal sites are accessible for the surgeon. A common complication is inadequate clipping or draping of the surgical area. This can lead to compromised positioning of the egress, scope, or instrument portals, which in turn compromises ability to adequately evaluate or treat the joint. The patient should be positioned with a hanging leg preparation so that the entire limb is accessible in an aseptic field (Figure 17.1). Figure 17.1 Recommended positioning for stifle arthroscopy with the patient in dorsal recumbency with the leg hanging off the back of the table. A routine aseptic surgical prep is recommended followed by a final application of iodine povacrylex (3M™ DuraPrep™ Surgical Solution [iodine povacrylex, 0.7% available iodine] and isopropyl alcohol, 74% w/w).The final prep should be allowed to dry completely, a minimum of 3 minutes. The leg is toweled and draped in routine fashion. A final adhesive antimicrobial incise drape is applied to the surgical site (3M Ioban 2™ Incise Drape) (Figure 17.2). This type of drape has been shown to reduce surgical site infections by providing a fluid‐resistant barrier, immobilizing bacteria, and providing continuous antimicrobial activity [2]. The surgeon should consider the likelihood of the need for stifle manipulation and movement throughout the procedure and this should be accounted for in limb preparation and draping. Optimal positioning of the patient for arthroscopy of the stifle has been previously described [3]. Some surgeons prefer a leg holding device [4], but most support the limb with sandbags or a positioning beanbag. The use of a holding device may allow surgeons to perform arthroscopy without an assistant and can be useful to position the leg at the surgeon’s preference. The author does not routinely use a positioning device but prefers to have an assistant who can position the leg as needed to evaluate different areas of the joint. The assistant is particularly helpful to position the stifle appropriately to evaluate the menisci [3]. Figure 17.2 A final adhesive antimicrobial incise drape is applied to the surgical site, providing a waterproof barrier. Surgical preparation of the patient may vary based on the experience and expertise of the surgeon. Novice arthroscopists may be more likely to convert an intended minimally invasive arthroscopic procedure into a traditional open surgical approach. The surgical nurses or assistants should consult with the lead surgeon prior to surgery to ensure adequate clipping of hair to accommodate the arthroscopic portals and the potential for a surgical incision. Complications during surgery include periarticular fluid extravasation, intraarticular hemorrhage, iatrogenic cartilage damage, inability to detect meniscal pathology, accidental trauma to joint structures, and instrument failure. A common intraoperative complication during arthroscopy is extravasation, which is the accumulation of arthroscopic fluid in the subcutaneous tissues (Figure 17.3). As fluid accumulates, edema and increased interstitial tissue pressure occur [5]. This increased pressure causes the joint capsule to collapse (Figure 17.4), compromising the ability to view the joint and complete the arthroscopic procedure. In addition, the tissue planes around the portals can shift in position and may close, making it difficult to insert instruments and manipulate the scope to obtain the desired arthroscopic view (Figure 17.5). Collapse of the joint capsule and/or loss of portal access are common causes for surgeons to convert to a miniarthrotomy or an open surgical approach to complete the procedure [6]. Extravasation is a common issue in stifle arthroscopy, particularly when the procedure is prolonged. Extravasation occurs due to high intraarticular pressures and inability for fluids to exit adequately [5]. The surgeon should be cautious when performing arthroscopy to ensure adequate egress flow, especially when fluid inflow pressure is high. Egress can be provided by placement of an egress cannula [3], large gauge needle or creation of a large instrument portal. An egress cannula is the preferred method due to the multiple fenestrations in the cannula that help prevent obstruction (Figure 17.6). The surgeon needs to remember to reduce fluid inflow pressure after temporarily increasing it to distend the joint capsule or control hemorrhage. If extravasation occurs, the arthroscopic procedure can be continued in many patients if adequate egress flow can be reestablished. If significant extravasation is noted, it is important to make a conscious effort to maintain the scope in the joint while egress is reestablished. Loss of scope access in the face of extravasation and subsequent joint capsule collapse can make reentering the joint extremely difficult and often necessitates conversion to an arthrotomy. Figure 17.3 Extravasation is the accumulation of arthroscopic fluid in the lateral subcutaneous tissues adjacent to the scope portal (white arrows). In addition to reestablishing fluid egress, massage of the leg in the area of extravasation can force fluid out of the portals, decreasing tissue swelling and pressure and, causing the joint capsule to collapse. Figure 17.4 At the start of arthroscopy, the joint capsule is distended, enhancing the view of joint structures (a). Subcutaneous fluid extravastion leads to increased pressure, causing the joint capsule to collapse and compromising the ability to view the joint and complete the arthroscopic procedure (b). Figure 17.5 The scope and instrument portals can shift in position and may close, making it difficult to insert instruments and manipulate the scope to obtain the desired arthroscopic view. Figure 17.6 An egress cannula is the preferred method of egress due to the multiple fenestrations in the cannula that help prevent obstruction. Intraoperative hemorrhage is a common problem that obscures the image, making diagnosis and treatment very difficult (Figure 17.7). A clear image is needed for accurate assessment of intraarticular anatomy and precise treatment. Chronic injuries and conditions that have severe synovitis are more likely to have excessive intraarticular bleeding. The surgeon should be meticulous with portal placement and motorized shaving to lessen the chance of bleeding. Figure 17.7 Intraoperative hemorrhage obscures the image, making diagnosis and treatment very difficult (a). Debridement of synovium should be limited to that required to obtain the necessary view to decrease the risk of hemorrhage. Bleeding can also result in thrombi that adhere to the joint structures, obscuring the surgeon’s view (b). Fluid flow should be maintained in the joint to prevent thrombi formation. Excessive shaving disrupts more of the highly vascularized synovium, leading to bleeding. Shaving should be limited to that needed to provide an adequate view for diagnosis and treatment of the area of interest. One of the most frequent sources of hemorrhage in the stifle is a branch of the descending genicular artery that can be damaged when shaving or manipulating the infrapatellar fat pad. The surgeon is recommended to shave only that portion of the fat pad that obscures the field of interest. The inexperienced arthroscopist can spend much time and effort shaving and removing all visible fat pad. Not only does this increase surgery/anesthesia time and the potential for other complications, it also increases the risk of significant intraarticular hemorrhage. Portal placement can also help in reducing the need for fat pad shaving. The more proximal the scope and instrument portals are placed, the less likely the fat pad will impede visualization and require debridement. In general, placement of these portals halfway between the patellar apex and the tibial tuberosity permits good visualization of the caudal poles of the menisci with minimal fat pad obstruction (Figure 17.8). The scope should be positioned to view the top of the intercondylar notch while the stifle is positioned in flexion. The shaver should be inserted just proximal to the fat pad into the roof of the intercondylar notch (Figure 17.9). Shaving of the fat pad from proximal to distal is performed until the cruciate ligaments and menisci are visible (Figure 17.10). Temporarily closing the egress cannula can improve visualization of the notch by increasing intraarticular pressure, thus compressing the fat pad. Fat pad shaving if performed as described above requires 3–5 minutes. Some surgeons perform arthroscopy without shaving, but the authors would recommend shaving a small portion of the fat pad as described to enhance visualization, improve accuracy, and shorten arthroscopic time.Bleeding can be controlled using intraarticular cautery. Insulated cautery probes are available that function in a fluid environment to provide effective control of bleeding vessels. The surgeon can view the bleeding vessel arthroscopically while cauterizing the vessel under visualization (Figure 17.11). Caution most be exercised to prevent inadvertent thermal injury to the articular cartilage in proximity to the bleeding vessel. Hemorrhage can also be controlled by increasing intraarticular pressure by increasing the pressure of the fluid inflow and decreasing the egress flow. The increased pressure will collapse small bleeding vessels, reducing hemorrhage. Figure 17.8(a) Appropriate placement of the arthroscope, and egress cannula. A #11 blade is used for creation of the instrument portal. (b) The scope portal (orange arrow) is located lateral to the midpoint of the patellar tendon (green lines) which runs from the patella (yellow) to the tibial tuberosity (blue). The instrument portal (white arrow) is located medial to the patellar tendon at the same level as the scope portal. Figure 17.9 The scope should be positioned to view the top of the intercondylar notch while the stifle is positioned in flexion. The shaver should be inserted just proximal to the fat pad into the roof of the intercondylar notch. Minimal shaving is needed if the shaver is inserted in this position. MFC, medial femoral condyle; CdCL, caudal cruciate ligament; FP, fat pad The surgeon needs to be cautious of increasing intraarticular pressure too high or for too long because of the risk of fluid extravasation into the periarticular tissues. The inflow irrigation fluid pressure varies depending on the make of fluid pump, the elasticity of the joint capsule, and the extracapsular interstitial tissue pressure. The pump is often set to 30–35 mmHg when starting arthroscopy, but this setting may need to be adjusted higher to control bleeding and distend the joint capsule. It is not uncommon to raise the pressure up to 60 mmHg and occasionally a fluid pressure of over 100 mmHg may be used briefly to complete a procedure. Another common intraoperative complication is iatrogenic cartilage damage [7]. Placement of the egress cannula is a common cause of this damage [8]. The egress cannula was first described to be placed using the scope portal under the patella in the trochlear notch due to ease of insertion [3]. The cannula should be inserted with the stifle positioned in relative extension to relax the tension on the patellar mechanism, thus creating more space to insert the obturator for the egress cannula (Figure 17.12). Direct placement into the medial compartment of the stifle in an effort to reduce the chance of iatrogenic cartilage damage has also been described but may be technically more challenging [8]. Flexible egress cannulas can also be used to reduce iatrogenic cartilage abrasion (Figure 17.13). Figure 17.10 Shaving of the fat pad from proximal to distal is performed until the cruciate ligaments (a) and menisci (b) are visible. CrCL, cranial cruciate ligament; CdCL, caudal cruciate ligament; MFC, medial femoral condyle; MM, medial meniscus. Figure 17.11 Cautery of bleeding vessels in the joint can be performed using a monopolar insulated electrode.
17
Complications Associated with Arthroscopic Evaluation of the Stifle and Decision Making
17.1 Introduction
17.2 Preoperative Considerations and Complications
17.3 Intraoperative Considerations and Complications
17.3.1 Extravasation of Fluid
17.3.2 Intraarticular Hemorrhage
17.3.3 Iatrogenic Cartilage Damage
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