Synovial chondromatosis (SC) is a proliferative metaplastic process of joint synovial cells that can result in the formation of loose cartilaginous bodies in the articular space, commonly involving large joints such as hip, shoulder and knee.1 The surgical procedure involves removal of the loose bodies by arthroscopy or open surgery, with or without synovectomy. Arthroscopy is considered the standard technique for loose bodies removal in the knee. In the knee, where the loose bodies typically arise in the anterior compartment2 the anteromedial (AM) and anterolateral (AL) portals are sufficient to perform the procedure. However, SC rarely involves the posterior compartment and the posterior portals become crucial. Removing loose bodies in the posterior compartment is highly technically demanding and potentially dangerous given the proximity of the vessels to the posterior capsule. We report our arthroscopic technique to treat the SC of the posterior knee, with the objective to describe a procedure that allows to explore the posterior knee compartment performing a posteromedial (PM) portal without other accessory posterior portals, in order to minimize the complications and result in a complete removal of the loose bodies and synovectomy.

SURGICAL TECHNIQUE Preoperative Planning

Preoperative radiographs and computer tomography (CT) are essential to identify radiopaque loose bodies and signs of osteoarthritis (Figs. 1A, B). A simple radiograph can show multiple oval calcified lesions in the popliteal area and arthritic changes. Magnetic resonance imaging on the other hand, allows to evaluate joint effusions, synovial thickening and to localize the loose bodies and osteophytes (Figs. 1C–E). A CT scan is crucial to investigate the bony structures, calcification and bone erosion, the morphology of the intercondylar notch and the presence of osteophytes localized on the medial and lateral femoral condyles. The CT scan allows to plan the transnotch passage in order to reach the posterior compartment (Fig. 1F).

FIGURE 1:

A–B, Anteroposterior and later views of preoperative radiograph. C, Computed tomography axial view: posterior loose bodies and multiple intercondylar notch osteophyte. D, MRI sagittal view: multiple loose bodies in posterior compartment. E, Magnetic resonance imaging coronal view: posterior compartment of the knee, multiple loose bodies and edema. F, Magnetic resonance imaging axial view posterior loose bodies and intercondylar notch osteophyte.

Patient Positioning

The patient is placed supine on the operating table with the operative leg at 90 degrees of flexion. A lateral post is placed proximal to the knee at the level of the tourniquet, and a foot roll to prevent the hip from externally rotating and to maintain 90 degrees of knee flexion. This allows the knee to be moved freely through its full range of motion (ROM) and can be accessed 270 degrees mediolaterally. The operative side is prepared with an aseptic sterile technique, the lower limb is exsanguinated, and the tourniquet is inflated. Knowledge of local neurovascular structures is crucial, especially for the posterior portals. The patella, patellar tendon, medial and lateral tibial joint lines, and medial and lateral femoral condyles are marked. In addition to standard AL and AL portals and the PM are identified and marked.

SURGICAL STEPS Standard Portal Placement

The AL portal is the first to be created. An incision is made on the inferolateral edge of the patella, 1 cm superior to the tibial joint line. The AM portal is then made under direct visualization, 1 cm distal to the patella’s inferomedial margin, just medial to the patellar tendon at 1 cm proximal to the medial tibial plateau. This portal is localized with an 18-gauge spinal needle and then an incision is made by a No. 11 scalpel blade.

Diagnostic Knee Arthroscopy

The integrity of the anterior and posterior cruciate ligament (PCL) is checked a 90 degrees of knee flexion. The medial meniscus is explored and probed with the knee stressed in valgus and external rotation. The lateral meniscus is visualized and probed with the knee in the figure-of-4 position and the foot internally rotated. The intercondylar notch is explored. Multiple osteophytes localized on the lateral surface of medial femoral condyle, that interfered with the transnotch passage of the arthroscope through the space between the PCL and medial femoral, are visualized.

Intercondylar Notch Tunneling

Because of the impossibility to insert the arthroscope through the intercondylar femoral notch, a meticulous debridement and tunneling of the osteophytes, that obstructed the transnotch passage, and the removal of the loose bodies of the anterior compartment are necessary. With the 30 degrees arthroscope in the AL viewing portal, a round arthroscopic burr is inserted in the anterior compartment of the knee through the working AM portal. Multiple osteophytes on the lateral surface of the medial femoral condyle are removed, from anterior to posterior. The PCL, meniscus and articular cartilage are protected during this procedure. The viewing and working portals may be changed to facilitate a more advantageous angle for osteophytes resection. After adequate resection and shaping of the notch using the burr, the arthroscopic shaver is introduced into the notch to clear remaining debris. With this regard the transnotch tunnel has been created and the arthroscope can access the posterior compartment (Figs. 2A, B).

FIGURE 2:

A, Intercondylar notch tunneling before with burr and 10 using the 5.0 shaver. B, Intercondylar notch tunnel. C, Pass of the trocar with the arthroscope sleeve from the anterolateral portal through the tunnel previously performed. D, The trocar replaced by the arthroscope.

Posteromedial Portal

We performed the Modified Gillquist maneuver3 to reach the posterior knee compartment. Because of the nonoptimal transnotch passage, we preferred to pass a trocar with the arthroscope sleeve from the AL portal through the intercondylar tunnel, we performed in the previous phase, between the lateral border of the medial femoral condyle and the medial border of the PCL, with the knee in 90 degrees of flexion (Fig. 2C) Once the trocar has gently passed the intercondylar notch and reached the posterior compartment, was replaced by the arthroscope (Fig. 2D). We performed this procedure to traverse the transcondylar notch because of the resulting minimal trauma and to prevent breakage or bending of the camera. Skin marking had been performed to identify the medial epicondyle and the entry point for the PM portal, defined as roughly 2.5 cm inferior and 2.5 cm posterior to the medial epicondyle with the knee in 90 degrees of flexion. The PM portal was made under the guidance of transillumination created by the arthroscopic light source introduced into the PM compartment, with the regards to prevent injury to the neurovascular structures. Care must be taken to ensure that the portal was not positioned too posteriorly to minimize risk to the saphenous nerve and vein. An 18-gauge spinal needle assured the correct location (Fig. 3A). A No. 11 blade was used to cut skin only, and a straight hemostat was used to follow the spinal needle trajectory and bluntly dissect into the PM compartment.

FIGURE 3:

A, The posteromedial portal was made under the guidance of transillumination, created by the arthroscopic light source introduced into the posterior compartment through transnotch passage. An 18-gauge spinal needle assured the correct location. B, Removal of loose bodies with 30 degrees arthroscope. C, Removal of loose bodies with 70 degrees arthroscope. D, Localized synovectomy. E, Removed loose bodies.

Loose Bodies Removal and Synovectomy

With the arthroscope in the AL portal, the forceps were introduced through the PM portal and the loose bodies were removed. To avoid additional accessory PL and posterior trans-septal portals, most commonly reported for approaching the posterior SC,4 we used a 70 degrees arthroscope to better explore the posterior knee compartment and visualize the synovitis and loose bodies. Furthermore, alternating between 30 and 70 degrees arthroscopes (Figs. 3B, C) and using both AL and PM portals to place the arthroscope, we successfully performed complete removal of loose bodies. A surgical assistant could adjust the knee flexion angle to allow for instruments to reach challenging areas of the PM compartment. Finally, using a combination of shaver and hemostat a meticulous synovectomy was performed for the adjacent synovitis (Fig. 3D). A final radiographic control documented the result of the procedure (Fig. 3E).

EXPECTED OUTCOME

SC is a rare benign metaplastic process of the synovial joints. A prompt diagnosis and treatment are crucial because of the potential malignant transformation, the invalidating symptoms and the occurrence of secondary osteoarthritis. The surgical removal of loose bodies is the optimal treatment, but controversy remains over the best surgical options.5 Open surgery decreases the risk of recurrence because all the joint compartments could be easily explored, but it is more invasive. The arthroscopic procedure resulted in lower morbidity and decreased postoperative pain, offering better cosmetic results, earlier recovery of ROM, a shorter rehabilitation course and an earlier return to function.2 The posterior knee compartment is an uncommon location for SC and only few cases successfully treated using different arthroscopic posterior approaches are reported.2 The localization of the bodies in the posterior compartment affects decision making regarding the surgical treatment. The highly technically demanding and potentially dangerous access through posterior portals could drive surgeons to convert the procedure to an open approach. Different techniques for arthroscopic treatment of posterior knee disease are reported.4 The use of accessory posterior portals has been described to provide adequate surgical access and to perform a meticulous debridement and loose bodies excision, protecting the popliteal neurovascular bundle.4 Performing an appropriate tunneling of the intercondylar notch through osteophytes in the space between the PCL and medial femoral condyle is crucial to insert the arthroscope through the transnotch passage and visualize the PM compartment of the knee. Moreover, the use of a 70 degrees arthroscope helped us to explore the posterior compartment well. The effectiveness of synovectomy for preventing recurrence of primary SC is still debated. Some studies reported that the removal of loose bodies alone was preferred to synovectomy and the total synovectomy was not indicated because of the risk of stiffness.5 Mainly, the traditional open synovectomy requires an extensive posterior approach that could lead to persistent joint stiffness and prolonged rehabilitation.6 According to Authors that recommended the loose body removal combined with the synovectomy to decrease the recurrence rate,7 we performed the excision of the bodies combined with localized synovectomy to completely eliminate abnormal synovial tissue and prevent recurrence. An all-arthroscopic approach to treat the SC of the posterior knee is technically demanding and the surgical pearls and pitfalls described in this article may help to facilitate the procedure (Table 1). The all-arthroscopic approach using a single PM portal, compared with an open approach or an arthroscopic procedure with more posterior portals, results in a good recovery of the knee function, allowing shorter rehabilitation courses and an earlier return to return to basic activities of daily living and sport.

TABLE 1 - Surgical Technique Pearls and Pitfalls Pearls  The CT scan is crucial to investigate the bony structures, calcification, bone erosion, and of the intercondylar notch morphology. It allows to plan how to reach the posterior compartment of the knee through a transnotch passage  Performing the posteromedial portal is required, to explore the posterior compartment  The knee leg at 90 degrees of flexion with a lateral post proximal at the level of the tourniquet and a foot roll to prevent the hip from externally rotating, allows the knee to be moved freely through its full ROM and can be accessed 270 degrees mediolaterally  Debridement and removal bodies of the anterior compartment and tunneling of the osteophytes, that obstructed the transnotch passage, is crucial to perform posteromedial portal transnotch  Gently passing the trocar with the arthroscope sleeve from the AL portal through the tunnel and then replacing the trocar by the arthroscope is preferred because reduce the trauma and to prevent breakage or bending of the camera  Cycling between 30 and 70 degrees arthroscope and using both AL and PM portals to place the arthroscope, we performed the complete removal of loose bodies, without performing accessory portals  A surgical assistant could adjust the knee flexion angle to allow for instruments to reach challenging areas of the posterior compartment  The use of Kelly forceps or Kocher graspers is a more robust option for removal larger loose bodies in comparison to standard arthroscopic graspers Pitfalls  Improper leg positioning or tourniquet placement can limit the movement of the knee and the proper visualization throughout the arthroscopic procedure  Inadequate debridement and removal of the bodies of the anterior compartment result in a difficult visualization and tunneling of the transnotch passage  Using a single shaver for resection is inadequate. The shaver can become blocked, which impacts surgical efficiency if the burr is not used  A not correct positioning of PM portal can limit the proper visualization of the compartment and the loose bodies removal procedure  The use of a single 30 degrees arthroscope limits the visualization and drive surgeons to perform others posterior portals or convert to an open approach in order to excise loose of the posterior compartment  Not performing the synovectomy increases the recurrence rate

AL indicates anterolateral; CT, computed tomography; PM, posteromedial; ROM, range of motion.

COMPLICATIONS

Arthroscopy is minimally invasive and allows the surgeon to manage all the compartments of the knee. The arthroscopic tunneling of the intercondylar notch through osteophytes in the space between the PCL and medial femoral condyle, to reach the posterior compartment transnotch, combined with the cycling between 30 and 70 degrees arthroscopes helped us to explore the posterior compartment. The combination of these 2 techniques to remove loose bodies and the synovectomy without other accessory posterior portals decreases the risk of neurovascular complications related to accessory posterolateral portals. An all-arthroscopic approach minimizes complications reported in open surgery such as stiffness, popliteal neurovascular injury, wound morbidity, and postoperative local pain. Furthermore, in case of general anesthesia having the patient in a prone position may be problematic if he has anesthetic complications.

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