Arthroscopic treatment of meniscal cysts

ARTHROSCOPIC TREATMENT OF MENISCAL CYSTS JESS H. LONNER, MD, and J. SERGE PARISIEN, MD, FACS

Meniscal cysts occur most commonly in the lateral compartment of the knee, rarely involving the medial meniscus. In patients who are symptomatic and require treatment, an associated tear of the meniscus can commonly be found. Although the etiology of meniscal cysts remains controversial, it seems likely that influx of synovial fluid through microscopic and macroscopic tears in the meniscus plays a central role in their development. This observation, coupled with the reality of high recurrence rates with various treatments, led to an era in which complete meniscectomy was espoused. With the advent of arthroscopy, en-bloc excision of the cyst and meniscus, a technique advocated for many years, is no longer honored. A new concept combining arthroscopic excision of the tear with cyst decompression has evolved and has been used with great success over the past few years. KEY WORDS: cyst tract, cystectomy, partial meniscectomy, cyst decompression

The reported incidence of meniscal cysts has varied from less than 1% to 22%, 1-5 and these are associated with meniscal tears in 18% to 100% of cases. 2'4-22 Most tears are horizontal, although radial and complex tears may also be found. The overwhelming majority of cysts tend to occur in the lateral meniscus, anywhere from 3 to 10 times more frequently than those of the medial meniscus. 14'18"19"22"26 It is unclear w h y cysts rarely affect the medial compartment despite a higher incidence of meniscal tears on that side. Controversy has existed regarding the etiology, and therefore the optimal treatment, of meniscal cysts since the earliest reports by Nicaise in 188327 and later by Ebner in 1904. 28 Several theories have been proposed. Earlier, some investigators suggested a traumatic origin that may have resulted in contusion and hemorrhage within the substance of the meniscus, and subsequent mucoid degeneration. Other investigators have e s p o u s e d a purely degenerative cause, a function of aging, with a common end point in local necrosis and mucoid degeneration into a cyst. 5"26"29-32 Still other investigators have theorized that there is a developmental inclusion of synovial cells within the substance of the meniscus, or perhaps a metaplastic event, and like ganglia, these cells secrete mucin, which results in cyst formation. 33-3s Using light and electron microscopy techniques, Hernandez 33 identified synovial cells lining the cystic spaces. He suggested that these synovial cells were first displaced into the substance of the meniscus through microscopic tears in the fibrocartilage, and that these in turn

From the Department of Orthopaedic Surgery, Hospital for Joint Diseases Orthopaedic Institute, New York, NY. Address reprint requests to J. Serge Parisien, MD, 1070 Park Ave, New York, NY 10128. Copyright © 1995 by W. B. Saunders Company 1048-6666/95/0501-0010505.00/0

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were actively involved in the secretion of acid mucopolysaccharides to form the contents of meniscal cysts. More recently, Barrie 6 has postulated that formation of meniscal cysts is related to the influx of synovial fluid through microscopic and macroscopic tears in the substance of the meniscus. He analyzed 1,571 menisci, 112 of which contained cysts. Each of these had an associated horizontal tear or bucket-handle tear with a peripheral horizontal component. Tear and cyst were consistently linked by a tract that served as a conduit for the exchange of synovial fluid between joint and cyst. Furthermore, these cysts were composed of multilocular pseudocapsules lined with synovial epithelial tissue arising from the edge of the meniscus. Biochemical analysis of the cystic fluid has shown that the contents resemble synovial fluid. 6 His findings were corroborated by Ferrer-Roca and Vilalta. 36 Barrie's detailed histopathological studies effectively refuted the earlier theories of cyst etiology. Additionally, if meniscal cysts developed on the basis of degeneration, one would expect the incidence to increase with age. However, epidemiological studies have shown the peak incidence to be among young men in their 20s and 30S.2,5,22,24,26

TABLE 1, Differential Diagnosis of Cysts of the Meniscus Nonmeniscal ganglion cysts Torn menisci with pedunculated flaps Pes or lateral collateral ligament bursitis Popliteal cysts Semimembranosis bursitis Iliotibial band bursitis Lipomata Neu rofibromata Sebaceous cysts Exostoses/Ioose bodies Synovial sarcoma Popliteus tendinitis

Operative Techniques in Orthopaedics, Vol 5, No 1 (January), 1995: pp 72-77

Fig 1. (A) MRI of a cyst of the lateral meniscus of a right knee with an associated horizontal tear. (B) MRI of a cyst of the medial meniscus of a right knee associated with a meniscal tear.

CLINICAL PRESENTATION Characteristically, patients with meniscal cysts complain of the insidious onset of a dull ache over the joint space, with intermittent swelling. Approximately 35% to 50% of patients report preceding trauma, and locking of the knee is r a r e .2' 1 4 1.6. 1. 8. 1 9 2 2 Swelling associated with the cyst is variable. While Pisani 37 asserted that it is pathognomonic for meniscal cysts to disappear or decrease in size with knee flexion and increase with extension, other investigators have shown the opposite may sometimes be true. 23 Cysts of the lateral meniscus tend to be smaller, their borders confined by lateral soft tissue structures. This contrasts to the larger medial meniscal cysts that

Fig 2. Arthroscopic visualization of a radial tear of the lateral meniscus with an associated meniscal cyst (right knee), TREATMENT OF MENISCAL CYSTS

may dissect freely through the less-restrictive medial capsule. The differential diagnosis of masses around the knee joint is extensive, 2"5"7"14'16A9'22 and appropriate management begins with the exclusion of other processes (Table 1). Magnetic resonance imaging (MRI) is a helpful tool in confirming the diagnosis. 7"22 Additionally MRI has a well-recognized role in identifying the presence of associated meniscal tears (Fig 1).

Fig 3. Arthroscopic view of a radial tear, lateral meniscus. Spinal needle is through the cyst tract (right knee). 73

Fig 4. Arthroscopic view of an oblique tear of the lateral meniscus with an associated meniscal cyst (right knee).

Fig 5. Peripheral tear of the lateral meniscus with an associated cyst (left knee),

Fig 6. Cleavage tear of the lateral meniscus before and after arthroscopic partial meniscectomy and internal cyst decompression (left knee).

Fig 7. Radial tear with cleavage component of a torn lateral meniscus of a left knee with an associated cyst before and after arthroscopic debridement and decompression. The last two pictures show the cyst track,

TREATMENT

ARTHROSCOPIC TECHNIQUE

Historically, nonoperative measures such as aspiration of cystic contents and injection of corticosteroids have been marked by poor results. 38 The surgical management of this lesion evolved from local cyst excision to total meniscectomy with open cystectomy because cyst excision alone was associated with high r e c u r r e n c e r a t e s . 24"26'38"40 Flynn and Kelly9 reported 12 cases treated by local cyst excision without recurrence at an average of 7.5 years. However, these were not associated with torn menisci, and some of them may have represented a different entity. Reagan et a116later recommended partial meniscectomy to a stable peripheral rim followed by open cystectomy in cases associated with meniscal tears. They added that cystectomy alone should be performed w h e n no meniscal tear is found. Our preferred treatment of symptomatic meniscal cysts has been shaped by a better understanding of the pathophysiology and etiology of these lesions, as well as by advances made in the field of arthroscopic surgery. Additionally, the new approach has developed in response to our appreciation of the dual role of the meniscus in both protecting the knee from degeneration and conferring joint stability. When the meniscus is torn, partial arthroscopic meniscectomy coupled with arthroscopic cyst decompression is the treatment of choice. It is advocated by many investigators and has proven to be an effective alternative to the other methods used in the past. 8J°-15"17AS'21'41-45

General or regional anesthesia is used; local anesthesia should be avoided. Standard arthroscopy portals are used, establishing inflow via a superomedial parapatellar portal. Inferomedial and inferolateral portals are then used alternatively to perform the surgical procedure. Careful probing of the meniscus must be performed to clearly identify the extent of the meniscal tear (Figs 2 to 5). Radial tears are excised to a stable peripheral rim. We resect only the inferior leaf of a stable horizontal tear after gentle trimming of the superior leaf. A spinal needle introduced percutaneously through the cystic mass may help to locate the tract between cyst and meniscus. Punch forceps may be passed through the tear and tract into the cyst. This maneuver alone may be effective at widening the tract so that the contents of the cyst can be evacuated into the joint. Additionally, a small motorizedshaver may be introduced into the cyst to break up loculations, assist in cystic decompression, and stimulate inflammation and scarring of the cyst and its tract (Figs 6 to 9). Although some investigators advocate suturing the remnants of a discrete tract within the meniscus after partial meniscectomy,21 we have not found a need for this. Alternatively, if a peripheral margin of meniscus is left that appears unstable, an arthroscopically assisted repair of meniscus to joint capsule may be performed in certain cases. The knees are then flushed out, and arthroscopy portals are sutured. Postoperatively, patients are instructed to perform early isometric quadriceps ex-

TREATMENT OF MI:'NISCAL CYSTS

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ercises and are allowed immediate full weight-bearing, with a cane if needed.

RESULTS OF ARTHROSCOPIC

TREATMENT

Critical analysis of the literature reviewing the role of arthroscopy for the treatment of meniscal cysts and their associated meniscal pathology suggests that the technique outlined above is highly successful and should be considered the mainstay of treatment for this pathological entity. It also supports our recommendation that open cystectomy is unnecessary in most cases. Ferriter and Nisonson 8 reported on 18 patients with follow-up ranging from 8 months to 3 years. All patients had relief of their knee pain and disappearance of the cysts. Seger and Woods TM had no cyst recurrences at an average of 28 months in six cases treated by partial lateral meniscectomy and manipulation of the contents of the cyst into the knee joint. Parisien 14 evaluated his results of 25 cases treated by the technique described. At an average follow-up of 33.5 months, there were no cyst recurrences, and preoperative symptoms were alleviated in all but one patient. Matthews and Dennis 41 reported their results in four patients who underwent partial arthroscopic meniscectomy and internal debridement of the cyst. They had no cystic recurrences after a minimal follow-up of 6 months. Calvisi et a142 reported good results in 12 patients, with disappearance of pain and no cyst recurrence after an average follow-up of 12 months. Partial lateral meniscectomy was performed in all patients; percutaneous cyst decompression was performed in 10 of these patients, and cyst debridement with a 3.2-mm cutter was performed in two others. Lopez 12 reported his experience with the arthroscopic management of 17 meniscal cysts, with only one recurrence after an average follow-up of 22 months. Tesner et al2] reported no recurrences after partial meniscectomy followed by arthroscopic evaluation of the cyst and either

A

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Fig 8. Illustration of steps involved in excision of tears associated with meniscal cysts. (Reprinted with permission. "a) 76

Fig 9. Illustration of cyst decompression using basketpunch forceps. (Reprinted from Warren RF, Hanley S, Bach BR: Chronic anterior ligament injury, in Parisien JS (ed): Arthroscopic Surgery, 1988, with permission from McGraw-Hill, Inc. aS)

debridement of the cyst tract or suture closure. Keating et a111 reported one cyst recurrence among 14 cases after follow-up averaging 19 months. Their treatment modality included arthroscopic partial meniscectomy and internal cyst decompression. Ryu and Ting 17 similarly treated 18 patients and had no recurrences after an average of 26 months. All patients returned to their premorbid level of functioning. Glasgow et al 1° reported 89% good-to-excellent results in 72 cases after an average follow-up of 34 months. Passler et a115 had no recurrences in 16 patients, 14 of w h o m underwent arthroscopic cyst decompression. Two patients underwent open cystectomy because no meniscal tear could be identified. Mills and Henderson 13 compared 12 of their early cases in which medial meniscal cysts were treated by open cyst excision coupled with arthroscopic partial meniscectomy, with eight cases in which partial meniscectomy was combined with arthroscopic cyst decompression. At followup averaging 20 months, there were no recurrences, and 19 patients had returned to their preinjury level of functioning. Reagan et a116 reported results on 32 patients, which were less favorable than the aforementioned studies; however, it is apparent that their arthroscopic technique did not involve all the steps that we have outlined. In their retrospective review of lateral meniscal cysts, the investigators report 80% excellent-to-good results in 20 patients managed by arthroscopic partial meniscectomy combined with open cystectomy. This contrasts to 50% excellent-to-good results in 12 patients treated only with arthroscopic partial meniscectomy without either external LONNER AND PARISIEN

c y s t e c t o m y or i n t e r n a l d e c o m p r e s s i o n . A l t h o u g h at the time of t h e r e p o r t t h e i n v e s t i g a t o r s d i d n o t p e r f o r m either n e e d l e d e c o m p r e s s i o n or a r t h r o s c o p i c m e c h a n i c a l d e b r i d e m e n t of t h e cysts, t h e y a c k n o w l e d g e d the b e n e f i t s of d o i n g so, r e f e r r i n g to t w o p a t i e n t s , n o t i n c l u d e d in their report, w h o w e r e t r e a t e d this w a y , a n d w h o w e r e s y m p t o m - f r e e 2 y e a r s after s u r g e r y .

CONCLUSION The t e c h n i q u e p r e s e n t e d h e r e p r o v i d e s the a d v a n t a g e of p r e s e r v i n g a stable r i m of m e n i s c u s a n d m i n i m i z i n g the risk of r e c u r r e n c e of t h e m e n i s c a l cyst. A d d i t i o n a l l y , it obviates the n e e d for p e r f o r m i n g o p e n c y s t e c t o m y ; w h i c h m a y be a s s o c i a t e d w i t h h i g h e r m o r b i d i t y . As c o n t e m p o r a r y t e c h n i q u e s of m e n i s c a l repair are being advanced, the orthopaedic surgeon may wonder w h a t t h e p o t e n t i a l a p p l i c a t i o n is in cases of m e n i s c a l tears associated w i t h cysts. M c L a u g h l i n a n d N o y e s 46 r e c e n t l y recommended open cystectomy followed by open repair of the p e r i p h e r a l r i m of m e n i s c u s a n d a r t h r o s c o p i c r e p a i r of tears e x t e n d i n g m o r e centrally. As t h e y assert, this m a y p r e s e r v e m o r e of t h e s t r u c t u r a l integrity, a n d t h e r e fore f u n c t i o n of the m e n i s c u s , c o m p a r e d w i t h the p u r e l y a r t h r o s c o p i c t e c h n i q u e t h a t w e favor. A l t h o u g h their a p p r o a c h m a y be a c c e p t a b l e for s o m e large multiloculated cysts w i t h or w i t h o u t p e r i p h e r a l tears of t h e m e n i s cus, it m a y n o t be a p p r o p r i a t e w h e n the cyst h a s itself c a u s e d localized t h i n n i n g or d i s t o r t i o n of the m e n i s c u s or in cases a s s o c i a t e d w i t h d e g e n e r a t i v e c o m p l e x tears of the m e n i s c u s . As far as r e p a i r i n g central tears of a cystic m e n i s c u s , m o r e clinical a n d l a b o r a t o r y d a t a are n e e d e d before definite r e c o m m e n d a t i o n s m a y be g i v e n in this regard.

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TREATMENT OF Mi-NISCAL CYSTS

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