Intrameniscal Cyst—Arthroscopic Open- and Closed-Door Repair Technique

Abstract

Meniscal cyst is rare and usually is associated with degenerative horizontal meniscus tears. These cysts are parameniscal in nature, as synovial fluid collects due to a check-valve mechanism. Most often, they are located on at the posteromedial aspect of the knee. Various repair techniques had been established in the literature to decompress and repair them. We describe an isolated intrameniscal cyst with an intact meniscus managed by arthroscopic open- and closed-door repair technique.

Meniscal cyst frequently is seen in clinical practice, with incidence rate of 1% to 22%.¹ It usually is accompanied by meniscal tear, which may be an isolated or a complex horizontal meniscal lesion, with rates varying from 64% to 74% to 90% to 100%, respectively.² Meniscal cyst is classified as intrameniscal cyst or parameniscal cyst depending on the cystic fluid collection. Medial meniscus cyst is more common than lateral meniscus cyst, with a ratio of 2:1 to 4:1, where posterior horn of the medial meniscus is most common site.² Meniscal cyst often is diagnosed on magnetic resonance imaging, where 5% of the meniscal cyst are intrameniscal and 95% are parameniscal. Parameniscal cyst formation is based on the concept of an influx of synovial fluid through a check valve mechanism by meniscal tear.³ Isolated intrameniscal cyst with meniscus tear is not yet reported in the literature, and only one case has been reported by Kim et al.⁴ in which the patient had an intrameniscal cyst located at the posteromedial corner of the medial meniscus with small-sized meniscus tear, which was treated by combined open debridement and arthroscopic repair. We describe an isolated intrameniscal cyst with intact meniscus managed by an arthroscopic open- and closed-door repair technique.

Surgical Technique (With Video Illustration)

Positioning

The patient is placed in a supine, leg-dangling position after spinal anesthesia. The operated knee is prepared and draped. A tourniquet is applied at the proximal aspect of the thigh and elevated up to 300 mm.

Surgical Steps

Standard anterolateral (AL) and anteromedial (AM) portals are created. The AL is the viewing portal during the surgery and AM is the working portal. Viewing from the AL portal and probing from the AM portal shows an intact but bulky posterior horn of medial meniscus (Fig 1). A meniscus upbiter punch (ACUFEX; Smith & Nephew, Andover, MA) is used through the AM portal to trim the innermost layer of the posterior horn of medial meniscus (Fig 2). An arthroscopy probe is then introduced in the meniscus tissue between the superior and inferior layer, and it enters smoothly in the meniscal tissue as if opening the door (Fig 3), indicating intrameniscal cyst. Same meniscal upbiter punch is used in horizontal manner to open the intrameniscal cyst through its full length until the posterior aspect as shown (Fig 4). Then, viewing from the AL portal shaver blade is inserted from AM portal between superior and inferior meniscal layer, on nonsuction mode to debride the degenerative intrameniscal tissue (Fig 5). After debridement, viewing from AL portal clearly shows that it is a horizontal cleavage tear, like open door, after debridement (Fig 6). A meniscus rasp (ACUFEX; Smith & Nephew) is then introduced into the joint through the AM portal to debride intrameniscal degenerative tissue to enhance the healing potential of the meniscus (Fig 7). Then, an 18-G spinal needle from the AM portal is used to make multiple vascular rents in the posterior capsule to enhance meniscal healing as viewed from AL portal (Fig 8). Fibrin clot, which is prepared on back table, is then used to fill the gap in the intrameniscal tissue like a sandwich technique (Fig 9). Then, an all-inside meniscus repair device, the Knee Scorpion (Arthrex, Naples, FL), is introduced from the AL portal and the arthroscope from the AM portal to take a bite from inferior-to-superior aspect of meniscus using a 2.0 FiberWire (Arthrex), as shown in Fig 10. Three such stitches are taken to close the mouth of the meniscus, like the closed-door technique (Fig 11).

Fig 1.

Arthroscope in the AL portal and probing from the AM portal showing intact but bulky posterior horn medial meniscus as marked by blue arrow. (AL, anterolateral; AM, anteromedial.)

Fig 2.

View from the AL portal, meniscus punch used from the AM portal to trim innermost layer of medial meniscus as marked by blue arrow. (AL, anterolateral; AM, anteromedial.)

Fig 3.

Probe from the AM portal entering the substance of medial meniscus like opening the door as marked by blue arrow while viewing from the AL portal. (AL, anterolateral; AM, anteromedial.)

Fig 4.

View from the AL portal, small-sized meniscal punch from the AM portal is used to further open the meniscal cyst as marked by blue arrow. (AL, anterolateral; AM, anteromedial.)

Fig 5.

Shaver blade with no suction mode as marked by blue arrow, is used from the AM portal to debride degenerative intrameniscal tissue while viewed from the AL portal. (AL, anterolateral; AM, anteromedial.)

Fig 6.

View from the AL portal showing horizontal cleavage like open door tear after debridement as marked by blue arrow. (AL, anterolateral.)

Fig 7.

Meniscus rasp as marked by blue arrow is used from the AM portal to enhance meniscal healing potential while viewing from the AL portal. (AL, anterolateral; AM, anteromedial.)

Fig 8.

View from the AL portal, 18-G spinal needle is inserted from the AM portal to puncture posterior medial capsule through meniscus tear to increase healing potential as marked by blue arrow. (AL, anterolateral; AM, anteromedial.)

Fig 9.

Fibrin clot is packed between superior and inferior meniscus tissue as marked by blue arrow, through the AM portal with help of probe as viewed from the AL portal. (AL, anterolateral; AM, anteromedial.)

Fig 10.

View from the AM portal, all-inside meniscus repair Knee Scorpion is used to close the tear from the AL portal as marked by blue arrow. (AL, anterolateral; AM, anteromedial.)

Fig 11.

View from the AL portal showing final repair using three 2-0 FiberWires, a like closed-door technique, as marked by blue arrow. (AL, anterolateral.)

Discussion

Meniscal cyst is seen in 1% to 22% of our clinical practice.¹ Very often, meniscal cyst is associated with a meniscal tear or complex horizontal meniscal lesion, with rates varying from 64% to 74% to 90% to 100%, respectively.² The ratio of meniscal cyst in the medial and lateral meniscus is 2:1 to 4:1, where posterior horn of medial meniscus is the most common site.² Meniscal cyst is classified as an intrameniscal cyst or parameniscal cyst depending on the cystic fluid collection, where only 5% are intrameniscal cyst and 95% are parameniscal cyst, which are diagnosed on magnetic resonance imaging and all are seen with some type of meniscal tear.³

Formation of this cyst is based on the influx of synovial fluid through a check-valve mechanism associated within the meniscal tear.³ Fluid accumulates in the meniscal parenchyma, where it may form focal enlargement of the meniscus because it usually forms a cystic pouch in capsule through meniscal tear, resulting in a parameniscal cyst. In the literature, only a single case has been reported by Kim et al.⁴ on an intrameniscal cyst, which was located at the posteromedial corner of the medial meniscus and associated with meniscal tear.

For this, they performed open debridement and combined arthroscopic and open repair. They created a vertical skin incision over subcutaneous tissue of posteromedial corner and medial joint line of knee joint to expose posteromedial capsule. An additional skin incision was taken over the meniscocapsular junction and meniscal cyst was exposed. Debridement of the cyst was performed by rasp and curette. Open meniscal repair was done by to close the mouth of surgically open intrameniscal cyst with the help of 2.0 FiberWire horizontal sutures were taken by inside out technique and meniscus repair was done.

Being completely intrameniscal, we have used the open- and closed-door technique to debride and repair the meniscus. The advantage of this technique is it's all arthroscopic, minimally invasive, less morbid, and has a fast recovery for the patient. A disadvantage is the need to have a specialized all-inside meniscus repair instrument like the Knee Scorpion (Table 1).

Table 1.

Advantages and Disadvantages

Advantages	Disadvantages
Minimally invasive—all arthroscopic	Needs special instrument—Knee Scorpion
Less pain
Fast recovery
Cheap; only 2-0 FiberWire needed

Supplementary Data

Video 1

Detail surgical steps of the technique with voiceover.