Popliteal cysts (or Baker s cysts) occasionally

Transcription

1 Original Article With Video Illustration Arthroscopic Treatment of Popliteal Cysts: Clinical and Magnetic Resonance Imaging Results Jin Hwan Ahn, M.D., Sang Hak Lee, M.D., Jae Chul Yoo, M.D., Moon Jong Chang, M.D., and Yong Serk Park, M.D. Purpose: This study examined the functional and magnetic resonance imaging (MRI) outcomes of popliteal cysts with combined intra-articular pathologies that were treated arthroscopically by decompression and a cystectomy through an additional posteromedial cystic portal. Methods: From January 2003 to March 2008, 31 patients were treated with a modified arthroscopic technique to decompress a popliteal cyst. The connecting valvular mechanism was found in all cases at the posteromedial compartment through the anterolateral viewing portal, and it was corrected by resecting the capsular fold through the posteromedial working portal. For cysts with multiple fibrous septa, an additional portal, the so-called posteromedial cystic portal, was used for complete cyst removal. The functional outcome was evaluated by use of the Rauschning and Lindgren knee score. All patients were evaluated by MRI, which documented the popliteal cyst and associated intra-articular lesions preoperatively and at follow-up. Results: All patients could return to their previous daily activities with few or no limitations, and no additional surgery was required after a mean follow-up of 36.1 months (range, 12 to 72 months). The Rauschning and Lindgren knee score showed improved clinical features at the final follow-up in 94% of patients. The follow-up MRI study showed that the cyst had disappeared in 17 knees (55%) and had reduced in size in 14 knees (45%) in the 31 patients. The mean cyst size was reduced significantly from 6.8 to 0.8 cm (P.0001). Conclusions: The described arthroscopic technique with or without an additional posteromedial cystic portal is effective for treating popliteal cysts with combined intra-articular lesions. More importantly, follow-up MRI showed that the cyst size was reduced or it had disappeared in all cases, although there was no association between the cyst s disappearance and the follow-up clinical score. Level of Evidence: Level IV, therapeutic case series. From the Department of Orthopaedic Surgery, Sungkyunkwan University School of Medicine, Samsung Medical Center (J.H.A., J.C.Y., M.J.C., Y.S.P.), and Department of Orthopaedic Surgery, School of Medicine, Chung-Ang University (S.H.L.), Seoul, South Korea. The authors report no conflict of interest. Received July 3, 2009; accepted February 10, Address correspondence and reprint requests to Sang Hak Lee, M.D., Department of Orthopaedic Surgery, School of Medicine, Chung-Ang University, 224-1, Heukseok-dong, Dongjak-ku, Seoul, , South Korea. sangdory@hanmail.net 2010 by the Arthroscopy Association of North America /9409/$36.00 doi: /j.arthro Note: To access the video accompanying this report, visit the October issue of Arthroscopy at Popliteal cysts (or Baker s cysts) occasionally cause disabling symptoms and are often associated with other disorders of the knee. 1,2 Although the associated intra-articular pathology is important for understanding the pathogenesis of the cysts, as well as in planning the appropriate treatment, it is often underestimated. Preferred treatments for popliteal cyst have included conservative approaches or open resection. 3-5 However, a recurrence rate as high as 42% to 63% has been reported after simple open resection of the cyst. 6,7 Several studies have reported frequently associated intra-articular pathologies with the cysts and warned of a high recurrence rate if the intraarticular pathologic condition is not addressed Lindgren 2 reported on the valvular mechanism of the capsular fold on the posteromedial capsule and continuous unidirectional flow between the posterior joint 1340 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 10 (October), 2010: pp

2 ARTHROSCOPIC TREATMENT OF POPLITEAL CYSTS 1341 capsule and gastrocnemius semimembranosus bursa. If the valvular mechanism is not corrected during surgery, the continuous flow of joint fluid will occur, which will lead to a postoperative recurrence. Recent advances in arthroscopic techniques have been made to effectively address the intra-articular pathology, particularly the orifice of the cyst, which has a valvular mechanism. 1,10,12-15 We have been decompressing the popliteal cyst arthroscopically since 2000, and an additional portal, the so-called posteromedial cystic portal, which is located directly above the popliteal cyst, has been used for a complete cystectomy in patients with a fibrous membrane within the cyst. 13 This portal is designed to effectively assess a popliteal cyst with a fibrous membrane, nodule, or septum within it. The purpose of this study was to examine the functional and magnetic resonance imaging (MRI) outcomes of popliteal cysts combined with intra-articular pathologies that were treated arthroscopically by decompression and a cystectomy by use of an additional posteromedial cystic portal. We hypothesized that arthroscopic treatment for popliteal cyst would yield satisfactory clinical and MRI outcomes without serious complications. Patient Demographics METHODS From January 2003 to March 2008, 38 consecutive patients were treated by a modified arthroscopic technique to decompress a popliteal cyst. All procedures were performed by the senior author (J.H.A.). The indications for surgery were (1) patients who reported symptomatic knee joint pain with cysts and a combined intra-articular lesion and (2) any cyst larger than 5 cm that failed to decrease in size after 3 or more aspirations. Conservative treatments for more than 6 months had failed in all patients. The exclusion criteria were (1) any prior surgery to the cyst either in an open manner or arthroscopically and (2) any combined intraarticular ligament surgery. All popliteal cysts with indications were treated by the same arthroscopic technique without an open procedure. One patient who had a popliteal cyst excised by an open technique was excluded because of associated pigmented villonodular synovitis in the extra-articular compartment. Also excluded from our study were 4 patients who refused to undergo MRI because of economic issues or lack of time. Two patients were lost during a follow-up period of less than 12 months. Overall, the study group consisted of 31 patients who were followed up for a mean period of 36.1 months (range, 12 to 72 months) after surgery. There were 14 men and 17 women with a mean age of 47.7 years (range, 23 to 65 years). The popliteal cysts were located in the right knee in 16 cases and left knee in 15 cases. Surgical Technique Arthroscopically assisted popliteal cyst decompression was performed as previously described. 13 The most important step in this procedure was to locate the opening connection between the joint cavity and popliteal cyst at the posteromedial compartment (Video 1, available at By use of a probe through a standard posteromedial portal, the opening of the cyst was identified by inferiorly displacing the overlying capsular fold located at the posteromedial side of the medial head of the gastrocnemius (Fig 1). It is helpful to rotate the bevel of the arthroscope upward to the 11-, 12-, and 1-o clock positions for most effective visualization of the capsular fold. All procedures were performed in an allarthroscopic manner with a standard 30 arthroscope. With a close examination with probing under a 30 arthroscope, the entrance or orifice was located behind the capsular fold in most cases. Once the opening connection of the cyst had been identified, the capsular fold was resected partially by inserting a set of basket forceps through the posteromedial portal (Fig 2A). If the orifice was covered by thin membrane over the capsular fold, both thin membrane and capsular fold were removed by basket forceps to verify the connection into the cyst. When the cyst at the posteromedial part of the skin was compressed by hand, a yellowish fluid was observed gushing into the posteromedial compartment through the opening (Fig 2B). The valvular opening of the posterior capsule was enlarged with a shaver and basket forceps to resect the capsular fold completely. The arthroscope could be used to observe the posteromedial compartment after switching the arthroscope to the standard posteromedial portal through a switching stick. The arthroscope was then advanced into the popliteal cyst through the opening, which was posteromedial to the medial head of the gastrocnemius (Fig 3). Excisional debridement of the popliteal cyst is not required if the fibrous membrane, nodules, and septa are not observed within the cystic hole. Otherwise, popliteal cyst excisional debridement should be performed through an additional portal, the so-called posteromedial cystic portal (Fig 4). The surgeon created a posteromedial cystic portal on the medial side of the skin overlying

3 1342 J. H. AHN ET AL. treated arthroscopically. The meniscus tears were treated with a partial meniscectomy. The chondral lesions were treated with arthroscopic debridement (grade II and III) or microfracture technique (grade IV) depending on the Outerbridge grade. A radical synovectomy was performed on patients with chronic synovitis. A suction drain was inserted, and a compressive dressing was used. Full weight bearing and active-passive motion were permitted from 1 week after surgery in patients who had not been treated by microfracture technique. However, partial weight bearing and passive motion were recommended for 6 FIGURE 1. (A) Schematic cross-section image of the knee with the opening of the connection. The image shows the location of the posteromedial portal and the anterolateral viewing portal. (P, popliteal cyst.) (B) Arthroscopic finding from the anterolateral portal of the right knee shows a connecting hole (curved arrow) at the posteromedial compartment that verifies the retraction of the capsular fold (C) by probing (straight arrow). (M, medial femoral condyle.) the cyst, avoiding the underlying veins, using the outside-in technique (Fig 5A). This portal was usually located in the posterior or inferior direction from the posteromedial portal, although it depends on the location of the popliteal cyst. A complete arthroscopic cystectomy was performed by shaving the inner wall of the popliteal cyst (Figs 5B and 5C). Any associated intra-articular pathologies, such as tears of the medial meniscus, chondral lesions, and synovitis, were then FIGURE 2. (A) Arthroscopic finding from the anterolateral portal of the right knee shows that the capsular fold (C) was resected by basket forceps (arrow) inserted from the posteromedial portal. (B) Arthroscopic finding from the anterolateral portal of the right knee shows a yellowish cystic fluid that gushes out to the posteromedial compartment by compressing the posteromedial part skin of the ballooned cyst. (M, medial femoral condyle.)

4 ARTHROSCOPIC TREATMENT OF POPLITEAL CYSTS 1343 All patients were evaluated by MRI documenting the popliteal cyst and associated intra-articular lesions preoperatively and postoperatively. The MRI studies were carried out by use of the same MRI parameters to reduce bias. The magnetic resonance (MR) examinations were performed with a 1.5-T MR imager (Signa; GE Medical Systems, Milwaukee, WI) with a quadrature knee coil according to the following MRI protocol: sagittal and coronal T2-weighted and proton density weighted fast spin echo images and axial fatsaturated proton density weighted fast spin echo images. The knee imaging parameters were as follows: repetition time/echo time of 2,000/20 for proton density-weighted image and 2,000/80 for T2-weighted image, echo train length of 8 to 12, 3-mm slice thickness, 1-mm interval, matrix, scan time of 2 minutes 34 seconds to 3 minutes 28 seconds, and 14-cm field of view. Two experienced musculoskeletal radiologists, who were unaware of the arthroscopic findings, clinical history, and initial MRI interpretations, reviewed the MRI studies by consensus. One reviewer was a musculoskeletal radiologist with 10 years of MRI interpretation experience, and the other FIGURE 3. Arthroscopic finding of the anterolateral portal of the right knee shows an opening (curved arrow). The opening is shown at the posteromedial side of the medial head of the gastrocnemius (G) after the capsular fold was completely resected with a shaver (straight arrow) and basket forceps. (M, medial femoral condyle.) weeks when the patients underwent surgery with microfracture technique. Clinical Evaluation The functional outcome was evaluated with the Rauschning and Lindgren 7 knee score preoperatively and at final follow-up. The parameters considered for the evaluations were the subjective symptoms related to the presence of a popliteal cyst, such as pain and sense of tension in the popliteal fossa, posterior swelling, and limitations in range of motion (ROM). All patients were graded according to the following scale 10 : grade 0, absence of pain and swelling, with no limitation in ROM; grade 1, light swelling or a sense of posterior tension after intense activity, with minimal ROM limitation; grade 2, swelling and pain after normal activity, with ROM limitation of less than 20 ; and grade 3, swelling and pain even when resting, with ROM limitation of greater than 20. MRI Evaluations FIGURE 4. (A) Schematic cross-sectional image of the knee with the opening of the connection. The image shows the location of the posteromedial viewing portal (b). (P, popliteal cyst.) (B) Arthroscopic finding from the posteromedial portal of the right knee shows septation and loose fragments of the inside of the popliteal cyst.

5 1344 J. H. AHN ET AL. was a musculoskeletal radiologist with 2 years of fellowship experience. The cyst size was measured at its longest dimension in the superior-inferior length of the sagittal plane. The cyst size was analyzed both preoperatively and at follow-up. A qualitative comparison was made to determine whether the cyst had reduced in size. Statistical Analysis Statistical analysis of the clinical results in scoring was performed with the generalized estimating equation method with a Bonferroni correction. All such analyses were carried out with SAS software, version 9.13 (SAS Institute, Cary, NC). Comparisons between preoperative and follow-up MR images for the dimensions of the cysts were made by use of a Wilcoxon signed-rank test. A 1-sided Cochran-Armitage trend test was used to determine the association between the follow-up knee scores and cyst disappearance/reduction on the MR images. P.05 was considered significant. RESULTS FIGURE 5. (A) Schematic cross-sectional image of the knee with the opening of the connection. The image shows the location of the posteromedial viewing portal (b) and the posteromedial cystic portal (c). (P, popliteal cyst.) (B) Gross view of the right knee joint that was positioned for arthroscopic surgery for a popliteal cyst. The arthroscope was inserted through the posteromedial portal, and a motorized shaver was introduced from the posteromedial cystic portal. (C) Arthroscopic finding from the posteromedial portal of the right knee shows that a motorized shaver (S) was inserted to the inside of the popliteal cyst through the posteromedial portal. The cyst wall (W) was resected with the shaver. In all cases the associated intra-articular lesion was treated, and the capsular fold that overlaid the opening of the valvular mechanism in the posteromedial compartment was found and corrected arthroscopically. Twenty-four patients with a fibrous membrane, nodule, or septum within the cysts underwent a direct excisional cystectomy through the posteromedial cystic portal. Seven patients without fibrous structures underwent decompression of the popliteal cyst only without a cystectomy. The associated findings were medial meniscus tears in 21 cases (68%), degenerative cartilage damage in 12 (39%), lateral meniscal tears in 9 (29%), and synovitis in 2 (6%). At the same time, all the associated intra-articular pathologies were treated by arthroscopic procedures. All meniscal tears were treated with partial or subtotal meniscectomy. Three patients with grade II chondral lesions were treated with debridement, and nine patients with grade III and IV chondral lesions were treated with microfracture technique by use of awls. In case of chronic synovitis, a total synovectomy was performed. The Rauschning and Lindgren knee score was improved significantly from grades 1, 2, and 3 preoperatively in 6 cases (19%), 19 cases (61%), and 6 cases (19%), respectively, to grades 0, 1, and 2 in 25 cases (81%), 5 cases (16%), and 1 case (3%) at final follow-

6 ARTHROSCOPIC TREATMENT OF POPLITEAL CYSTS 1345 TABLE 1. Criteria Clinical Grading According to Modified Criteria of Rauschning and Lindgren 7 and Follow-Up MRI Results Before Surgery (No. of Cases) Last Follow-up (No. of Cases) Follow-up MRI (No. of Cases) Grade D, 15; R, 10 Grade D, 2; R, 3 Grade R, 1 Grade Abbreviations: D, disappeared; R, reduced. up, respectively (Table 1) (P.0001). Of the knees, 29 (94%) showed clinical improvement. All patients underwent follow-up MRI. They were assessed for any postoperative recurrence, and the size of the remaining cysts was measured (Table 1). The mean time from the arthroscopic operation to the MRI examination was 8.6 months (range, 6 to 14 months). The follow-up MRI study showed that the cyst had disappeared or reduced in size in all cases; it had disappeared in 17 knees (55%) and had reduced in size in 14 knees (45%) (Fig 6). The cyst size was reduced significantly, from 6.8 cm (range, 5.2 to 10.3 cm) to 0.8 cm (range, 0 to 2.8 cm) (P.0001). However, cyst disappearance/reduction at the follow-up MRI study was not significantly associated with the follow-up knee scores (P.0875). The 1 patient who scored grade 2 at 20 months follow-up had mild knee joint pain and swelling because of degenerative arthritis in the medial compartment. However, the patient improved clinically from grade 3 to grade 2, and the cyst size showed a decrease from 8.2 to 1.2 cm. have several benefits. They are relatively simple procedures, allow early rehabilitation, require minimal incision, and effectively address any concomitant intraarticular pathologies, and most importantly, they can remove the opening of the cyst. Some authors have stressed the importance of addressing the associated intra-articular pathology to reduce the recurrence rate. 8,10,16 Fielding et al. 17 reported an 82% incidence of posterior horn medial meniscus tears in patients with documented popliteal cysts. Johnson et al. 18 described a medial meniscus tear in 68% of cases, osteoarthritis in 81%, a loose body in 38%, edema in 35%, and cartilage injury to the patellofemoral joint in 30%. In this study a medial DISCUSSION The clinical results of this study were promising, particularly in terms of the recurrence rate. Of the patients, 29 (94%) improved by at least 1 grade on the Rauschning and Lindgren scale. In addition, follow-up MRI studies were evaluated in all patients; the results showed that the cyst was significantly reduced in size, with all patients showing either disappearance or a marked reduction of the cyst. The popliteal cyst is almost never an isolated pathology in an adult knee. An open surgical excision cannot be considered a definitive solution in most patients. We believe that addressing the opening or rather the connection between the joint cavity and cyst is a key procedure for completely excising the cyst. Arthroscopic procedures FIGURE 6. (A) A preoperative MR image (axial view) shows a huge popliteal cyst with multiple septation. (B) A follow-up (postoperative 9 months) MR image (axial view) shows that the popliteal cyst has disappeared.

7 1346 J. H. AHN ET AL. meniscal tear was the most frequent injury (21 cases [68%]). We believe that the intra-articular pathologies can cause joint effusion, leading to a secondary popliteal cyst through the communication between the cyst and the joint. So, the first step in treating a symptomatic popliteal cyst is performing arthroscopic treatment of combined intra-articular lesions causing chronic synovitis. However, Chatzopoulos et al. 3 reported that Baker s cysts are significantly more frequent ultrasonographic findings in knees with chronic osteoarthritis (89 of 329 knees [27%]) than in those without osteoarthritis (1 of 54 [2%]). In osteoarthritic knees recurrent effusions can occur, and the cyst may recur, because all combined lesions may not be definitively treated. The arthroscopic approach to a popliteal cyst would provide an effective solution for managing not only the cyst by arthroscopic decompression but also the associated intra-articular pathology. Anatomic studies have shown a communication or an opening between popliteal cysts and the joint cavity. 2,19 This connection is usually formed between the joint and semimembranosus bursa. The septum dividing the 2 structures becomes thinner and more fragile, ultimately forming a communication. Rauschning and Lindgren 7 reported the significance of the valvular connection mechanism behind the capsular fold. In most cases (all cases in our series), a close examination behind the capsular fold in the posteromedial compartment will identify this connecting hole. The unidirectional flow can be converted to bidirectional flow by enlarging this posteromedial connecting hole. There are several reports on arthroscopic decompression for popliteal cysts. 20 Sansone and De Ponti 10 described the arthroscopic approach with an anteromedial portal to treat an associated intra-articular pathology and correct the valvular mechanism by opening the connection after removing the posterior horn of the medial meniscus. However, they did not remove the capsular fold in the posterior wall of the capsule but enlarged the opening between the meniscal body and articular capsule. Their procedure may not be biomechanically ideal in that it results in the complete removal of the posterior horn of the medial meniscus. In our experience, opening the cyst connection at the posteromedial compartment can be managed effectively without removing the entire posterior horn of the medial meniscus. Takahashi and Nagano 12 reported a similar arthroscopic technique to that described in this report. They performed a correction of the valvular mechanism to remove a slit structure at the communication through the posterior portal between the joint and popliteal cyst. They also reported that some cysts have no communication with the joint and require open surgery. However, a careful examination showed that in all of our consecutive 31 patients with popliteal cysts, a connection to the posteromedial joint compartment was present. Furthermore, without dye injection, a yellowish fluid within the cysts was observed by compressing the skin after the capsular fold had been partially removed. Few reports performed follow-up with MRI study after arthroscopic treatment of the popliteal cyst. Calvisi et al. 14 reported an arthroscopic all-inside suture for a symptomatic Baker s cyst. They reported on an arthroscopic suture technique in which the 1-way valve mechanism is sutured to the Baker s cyst at the posteromedial compartment. Of the 22 patients, 21 (96%) showed improvement on the Rauschning and Lindgren scale, and the MRI analysis showed disappearance or reduction of the cyst at 2 years follow-up in 20 of 22 patients (91%). However, the all-inside suture technique is a technically demanding procedure, and it is possible to incompletely close the 1-way pathway. In addition, our technique, where the cystic fluid is evacuated by needle aspiration, can result in the incomplete evacuation of the cystic fluid if the cyst has multiple septation or is placed in an unusual location. So, the follow-up MRI study showed that the cyst had disappeared or reduced in size in all cases. All previous arthroscopic studies reported removing the valvular opening of the cyst. However, only 1 study reported an intracystic fibrous or septal membrane. Kanekasu et al. 21 presented good results with a shaving cystectomy and intra-articular synovectomy in popliteal cysts associated with rheumatoid arthritis. It was agreed that the fibrous membrane, nodule, and septum within the cysts may be factors associated with a postoperative recurrence after arthroscopic cystectomy. Therefore direct excisional debridement of the cysts was performed through the posteromedial cystic portal in 24 cases with fibrous structures within the cyst. When the cyst is debrided by use of a shaver, forceful manipulation and suctioning of the motorized shaver should be avoided to prevent damage to the neighboring popliteal neurovascular structures, especially if the cyst has extended into the posterolateral side. One of the critical issues of concern regarding the posterior medial aspect is avoiding the saphenous nerve. There were no neural complications encountered, particularly injury to the saphenous nerve, during this procedure. The reasons for this are as follows: (1) The saphenous vein was identified by the transil-

8 ARTHROSCOPIC TREATMENT OF POPLITEAL CYSTS 1347 lumination technique, and injury to it was avoided. This in turn prevented injury to the saphenous nerve because it usually lies immediately posterior to the vein. 22 (2) With the knee flexed 80 to 90, the sartorial branch of the saphenous nerve and vein becomes more distal to the posteromedial portal. (3) Only the skin and the subcutaneous tissue were incised, and the capsule was spread open with a hemostat to create a posteromedial and posteromedial cystic portal. This study has a few limitations. First, there was no comparison with a control group given conservative treatment: only arthroscopic treatment of intra-articular pathologies or an arthroscopic 1-way valve opening procedure without a cystectomy was studied. So we cannot describe the exact reason why our results were improved subsequently. Furthermore, the possible cause of the cyst could not be correlated with the intra-articular pathology. However, this study was retrospective and not a randomized controlled trial. Further controlled or prospective studies are needed to define the cause of improvement precisely. Third, although our study included MRI studies for all enrolled patients, follow-up is short term. In addition, there was a different follow-up period between MRI and clinical study. CONCLUSIONS The described arthroscopic technique with or without an additional posteromedial cystic portal is effective for treating popliteal cysts with combined intraarticular lesions. More importantly, follow-up MRI showed that the cyst s dimensions were reduced or the cyst had disappeared in all cases, although there was no association between the cyst s disappearance and the follow-up clinical score. REFERENCES 1. Burger C, Monig SP, Prokop A, Rehm KE. Baker s cyst Current surgical status. Overview and personal results. Chirurg 1998;69: (in German). 2. Lindgren PG. 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