Arthroscopic Knee Synovectomy

Arthroscopic Knee Synovectomy is a safe and effective method, it has major potential advantages over open surgical techniques, including:

1. improved visualization of the knee joint,
2. a more complete synovectomy,
3. less postoperative pain,
4. decreased postoperative knee stiffness/arthrofibrosis,
5. decreased postoperative hemarthrosis,
6. shorter hospitalization, lower surgical site morbidity,
7. the surgery is performed through arthroscopic portals (thus the division of the quadriceps is avoided),
8. better preservation of the menisci,
9. revision surgery, if required, is less complicated.

The major arthroscopic disadvantage for Knee Synovectomy is that it may be a more technically challenging operation to perform, and for some diffuse and malignant conditions, it is contraindicated.

The knee joint has the largest and most extensive synovial membrane compared to any other joint. Thus, pathologic conditions involving the synovium of the knee can be symptomatic and debilitating. Benign and malignant processes can involve the synovial membrane.

Knee Synovectomy Indications

• Plica syndrome
• Pigmented villonodular synovitis (PVNS)
• Synovial chondromatosis/osteochondromatosis
• Synovial hemangioma
• Popliteal (Baker’s) cyst
• Hemophilia
• Seronegative and seropositive arthropathies
• Infection
• Arthrofibrosis

Contraindications/Controversial Indications

Absolute

Intra-articular malignant conditions (eg, synovial sarcoma), treatment for such conditions is often radical excision with chemotherapy and/or radiation.

Relative

Surgeon lack of experience/proficiency: Performing a thorough synovectomy requires excellent technical skills and proficiency in arthroscopy. Inadequate/incomplete performance may lead to local recurrence and/or poor outcomes. Therefore, arthroscopic synovectomy is not recommended if the surgeon does not feel confident in his or her ability to perform a complete and adequate arthroscopic synovectomy. If this is the case, a traditional open approach should be utilized or the patient should be referred to an experienced arthroscopist.

Severe arthritic changes/deformity/contractures: Such conditions may include advanced osteoarthritis, RA, seronegative arthritis, and hemophilia. In such cases, total knee arthroplasty is the definitive treatment of choice.

Physical Examination

• Thorough history and physical exam: Document neurovascular status and discuss risk to posterior neurovascular structures when obtaining informed consent .
• Effusion: Aspiration often performed to obtain synovial fluid analysis for diagnostic purposes, and in some cases provide temporary pain relief.
• Reduced ROM and/or pain with passive ROM.
• Tenderness to palpation, often diffuse in cases of inflammatory arthropathy.
• Mechanical symptoms of clicking, catching, or locking.

Preoperative Imaging

• Standard knee x-rays to evaluate status of joint (eg, periarticular erosions in RA) and overall alignment/presence of any deformity.
• MRI in evaluation of PVNS, synovial chondromatosis, hemangioma, and inflammatory arthropathies to evaluate synovium, extent of disease, and rule out other intra-articular lesions. MRI in PVNS classically demonstrates low T1 and low T2 signal (due to hemosiderin deposits) and is useful in determining extent of intra- and extra-articular disease.
• CT in cases of synovial chondromatosis is only useful when loose, calcific bodies are present.

Equipments

• The use of a well-padded thigh tourniquet may be considered as a more complete synovectomy may result in increased bleeding that can make visibility during arthroscopic synovectomy difficult.
• In most cases, a 30-degree arthroscope is used for the majority of the procedure. Nevertheless, for adequate visualization of the posterior compartment, a 70-degree arthroscope is often necessary and should be available for the entire procedure.
• Initially, the inflow pump should be set at a low setting to reduce knee distention and fluid extravasation intraoperatively. It can be adjusted throughout the procedure accordingly.
• Although choice of shaver depends on the anatomy of the patient and the location of the synovectomy, a variety of shaver sizes should also be available.
• A 5.5-mm full-radius knee synovectomy blade is effective in the anterior compartment. A 3.5-mm full-radius synovectomy blade or a 4.5-mm curved synovial resector can be used in smaller knees or hard to reach areas, such as the posterior compartment and under the menisci.

Patient Position

The patient is placed supine on the operative table. It’s preferred that the operative leg be placed into a thigh-holding device 4 finger-breadths above the superior patella such that when the foot of the bed is lowered, the leg is allowed to hang free off the end of the table. This allows for deep flexion and varus/valgus stress of the knee without compromise of portal position. The well leg is placed into a well-leg holder.

Alternatively, the arthroscopic synovectomy procedure can be performed supine with knee flexed over the side of the table against a lateral post with the well leg placed supine on the flattened operative table. The operative extremity is then prepped and draped in the usual sterile technique.

Arthroscopic Synovectomy Portal

Proper portal placement is critical for any arthroscopic procedure. Improper portal placement can lead to iatrogenic injury to the knee as well as inadequate synovectomy due to the difficulty of the procedure. It is often helpful to draw out the anatomy prior to obtaining the portals.

A complete arthroscopic synovectomy of the knee can be performed through the use of a combination of 6 portals: anterolateral, anteromedial, lateral suprapatellar, medial suprapatellar, posterolateral, and posteromedial.

Arthroscopic Synovectomy Procedure

• Supine position, well-padded thigh tourniquet, thigh-holding device 4-finger breadths above the superior patella, well leg placed in well-leg holder
• Operative leg prepped and draped in usual sterile fashion
• Mark out bony landmarks for eventual portal placement
• Inflate tourniquet
• Establish anterolateral and anteromedial portals in routine fashion
• Perform standard diagnostic arthroscopy
• With camera in suprapatellar pouch, establish lateral suprapatellar and medial suprapatellar portals
• Perform synovectomy as indicated, utilizing triangulation to gain access to the gutters, anterior compartment, and intercondylar notch
• Visualize the posterior compartments with the knee flexed 70 to 90 degrees
• Establish posteromedial and posterolateral portals under direct visualization
• Utilize 70-degree arthroscope to perform synovectomies of the posteromedial and posterolateral compartments in systematic fashion.

After the anterolateral and anteromedial portals are established, a standard diagnostic arthroscopy is performed, visualizing and probing the suprapatellar pouch, medial and lateral gutters, trochlear groove, undersurface of the patella, medial and lateral compartments, including the mensci, intercondylar notch, and cruciate ligaments. Any concurrent intra-articular pathology seen during diagnostic arthroscopy, such as meniscal or chondral injury, can be addressed throughout the procedure. In cases in which a pathologic specimen is required, an arthroscopic biter may then be used through the anteromedial portal to obtain a synovial tissue sample from an area of significant pathology. Alternatively, an arthroscopic trap may be placed in the suction tubing of the shaver to obtain significant quantities of resected synovium.

With the camera looking into the suprapatellar pouch, the lateral suprapatellar and medial suprapatellar portals are established under direct visualization approximately 1 cm above and 1 cm lateral (for lateral suprapatellar) or medial (for medial suprapatellar) to the corner of the patella. The 5.5- or 4.5-mm full-radius synovectomy blade can be used through these portals to resect the synovium in the suprapatellar pouch and the upper lateral and medial gutters and to access any portion of a hypertrophic anterior fat pad. Synovial resection is adequate when the shiny capsular layer that lies directly beneath is seen. The lower portions of the lateral and medial gutters can be accessed for resection by alternating the camera through the lateral and medial suprapatellar portals and using the shavers through the anterolateral and anteromedial portals. Next, synovectomy in the anterior compartment and intercondylar notch can be achieved by triangulation of the arthroscope and shaver through the anteromedial and anterolateral portals. The lower lateral and medial gutters can also be visualized and resected through these 2 portals.

There is a 15- to 28-mm safe zone between the posterior cruciate ligament and the popliteal neurovascular bundle for safe arthroscopy of the posterior knee. By holding the knee flexed at 70 to 90 degrees, one can gain better access to the posterior compartment as the intercondylar notch is widened and the neurovascular bundle falls more posteriorly. A 70-degree arthroscope is then used for visualization of the posterior compartment. Furthermore, this allows the posterior neurovascular bundle to fall posteriorly.

A modified Gillquist maneuver is performed with the arthroscope through the anterolateral portal and advanced under the posterior cruciate ligament in order to establish a posteromedial portal under direct visualization. Palpation of the posteromedial knee is performed under visualization to better localize portal placement. At this time, a spinal needle is introduced into the posteromedial corner of the knee joint aiming anteriorly. Dimming of the overhead and room lights and transillumination using the arthroscopy may also aid in introduction of the spinal needle.

The posteromedial portal is the then established, and a blunt cannula is introduced via this portal. The cannula is best introduced over a switching stick to allow for easier and more accurate cannula placement. Caution must be exercised when introducing any instrument into the joint in this location with an emphasis on aiming slightly anteriorly to avoid iatrogenic injury to the posterior neurovascular bundle. The posteromedial portal is typically placed 16 to 35 mm from the saphenous vein.

Arthroscopic Synovectomy of the posteromedial knee is then performed through this portal with a 4.5-mm shaver systematically from the periphery to the center. One must be mindful of the suction during this part of the procedure to avoid drawing the posterior capsule into the shaver, thereby risking accidental iatrogenic injury to vital posterior structures.

Lastly, the lateral portion of the posterior compartment is then accessed similarly by switching the arthroscope to the anteromedial portal. Holding the knee flexed at 90 degrees will allow the common peroneal nerve to fall further posteriorly behind the biceps femoris tendon. A spinal needle is introduced anterior to the biceps femoris tendon, 1 cm above the joint line and 1 cm posterior to the femoral condyle. The posterolateral portal is established and then cannulated like the posteromedial portal. The posterolateral portal is typically placed 40 to 52 mm from the peroneal nerve. Synovectomy of the posterolateral knee is then performed similar to the posteromedial side in a systematic fashion.

Postoperative Protocols

Depending on the extent of arthroscopic synovectomy performed, a drain may be placed and monitored for at least 1 day prior to removal to reduce postoperative hemarthrosis. Nevertheless, this may not be needed if the bleeding is not significant at the conclusion of the case. A compressive dressing is applied to the knee. Patients can be made partial weightbearing with crutches for assistance and are typically discharged the same day or on the first postoperative day.

Cryotherapy with ice packs can aid in postoperative reduction in pain and swelling. Oral pain medication should be prescribed, and physical therapy should start early to ensure rapid restoration of normal gait, ROM, and strength.

Patients should be provided with written home instructions to begin immediate postoperative home therapy with a focus on active ROM and quadriceps strengthening. Although not critical, the use of a continuous passive motion machine to facilitate early motion is reasonable. The majority of patients approach near normal activity level by the fourth postoperative week.

Arthroscopic Synovectomy Complications

Complications resulting from arthroscopic synovectomy are similar to those of any arthroscopic procedure, including anesthesia concerns, infection, bleeding, deep venous thrombosis, arthrofibrosis, and iatrogenic injury to articular cartilage or neurovascular structures.

Caution must be taken during the procedure to maneuver the arthroscope or instruments to avoid excessive pressure on the articular cartilage and to direct instruments away from vulnerable posterior structures when using the posterolateral and posteromedial portals, namely the neurovascular bundle, saphenous vein and nerve, and the common peroneal nerve.

Other complications specific to arthroscopic synovectomy include hemarthrosis resulting in pain and stiffness, postoperative arthrofibrosis requiring a manipulation or arthroscopic lysis of adhesions, reflex sympathetic dystrophy, or incomplete resection resulting in recurrence or persistence of the synovial pathology, thereby requiring additional surgery.

References

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