Arthroscopic Evaluation of Radiofrequency Chondroplasty of the Knee

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1 Arthroscopic Evaluation of Radiofrequency Chondroplasty of the Knee Ilya Voloshin,* MD, Kenneth R. Morse, MD, C. Dain Allred, MD, Scott A. Bissell, MD, Michael D. Maloney, MD, and Kenneth E. DeHaven, MD From the Department of Orthopaedics, University of Rochester Medical Center, Rochester, New York, Department of Orthopaedics, Massachusetts General Hospital, Boston, Massachusetts, and SportsMedicine Partners, Orthopedics & Rehabilitation Therapy, South Windsor, Connecticut Background: Considerable debate exists over the use of radiofrequency-based chondroplasty to treat partial-thickness chondral defects of the knee. This study used second-look arthroscopy to evaluate cartilage defects previously treated with bipolar radiofrequency based chondroplasty. Hypothesis: Partial-thickness articular cartilage lesions treated with bipolar radiofrequency based chondroplasty will show no progressive deterioration. Study Design: Case series; Level of evidence, 4. Methods: One hundred ninety-three consecutive patients underwent bipolar radiofrequency based chondroplasty over 38 months; 15 (25 defects treated with bipolar radiofrequency based chondroplasty) underwent repeat arthroscopy for recurrent or new injuries. Time from the initial to repeat arthroscopy ranged from 0.7 to 32.7 months. At both procedures, the location, size, grade, and stability of lesions were evaluated, recorded, and photographed arthroscopically. Results: At the initial procedure, 25 lesions treated using bipolar radiofrequency based chondroplasty ranged from 9 to 625 mm 2 (mean, ± mm 2 ; median, 120 mm 2 ); at second look, lesion size was 9 to 300 mm 2 (mean, ± mm 2 ; median, 100 mm 2 ). At second look, 3 (12%) demonstrated unstable borders with damage in the surrounding cartilage that appeared to be progressive. Eight (32%) lesions were unchanged in size. Eight (32%) demonstrated partial filling with stable repair tissue, and 6 (24%) demonstrated complete filling with stable repair tissue. Lesions in the tibiofemoral compartments showed better response to radiofrequency chondroplasty than did those within the patellofemoral joint (P <.05). Conclusion: Only 3 of 25 lesions demonstrated progression. More than 50% showed partial or complete filling of the defect. Bipolar radiofrequency chondroplasty is an effective way to treat partial-thickness cartilage lesions; however, long-term effects of this treatment on cartilage remain unknown. Keywords: radiofrequency; chondroplasty; arthroscopy; osteonecrosis Articular cartilage has little ability to repair partial-thickness injuries, and if any repair response does occur, it is often disorganized and inadequate. 28 This poor healing response may predispose the surrounding cartilage to progressive damage, leading to enlargement of the defect and release of intra-articular debris, which may result in mechanical or inflammatory symptoms. Traditionally, unstable partialthickness cartilage lesions have been treated arthroscopically using mechanical instrumentation such as rotary *Address correspondence to Ilya Voloshin, MD, Department of Orthopaedics, University of Rochester Medical Center, 601 Elmwood Ave, Rochester, NY ( Ilya_voloshin@urmc.rochester.edu). No potential conflict of interest declared. The American Journal of Sports Medicine, Vol. 35, No. 10 DOI: / American Orthopaedic Society for Sports Medicine shavers. 7,18,20,25 However, with these techniques, it is difficult to smooth the articular surface, and viable cartilage may be inadvertently removed along with the unstable tissue. 16,21 In the past few years, the use of radiofrequency (RF)-generating energy devices in arthroscopic surgery has gained popularity for applications such as chondroplasty. 4,10,11,19 Radiofrequency-based devices can remove damaged tissue and produce a smooth articular surface. Despite the successful clinical use of these RF devices, chondrocytes are known to be heat sensitive, and the safety of performing chondroplasty using bipolar RF (brf) based methods has been debated. 21 Laboratory investigations evaluating the effect of brf on articular cartilage have reached conflicting conclusions, 4,6,8-11,13-16,19,26 but information describing the clinical results of brf-based chondroplasty is limited. 19 The aim of this study was to evaluate the progression of partial-thickness cartilage defects 1702

2 Vol. 35, No. 10, 2007 Radiofrequency Chondroplasty of the Knee 1703 treated using brf-based methods by second-look arthroscopy in patients who required subsequent surgery for recurrent symptoms or new injury. We previously reported second-look arthroscopy findings in 4 patients who had been treated using brf-based chondroplasty for symptomatic chondral defects 2 to 26 months before presenting for a subsequent surgery for new injury. 29 We observed that the previously brf-treated chondral defects exhibited stable repair tissue, which appeared to be fibrocartilage like in texture and appearance. Greenleaf (unpublished data, 2002) had previously reported similar clinical findings after second-look arthroscopy in a series of 20 patients who had received a brf-based chondroplasty procedure. Histologic cross sections collected from 5 of these patients who underwent subsequent arthroplasty or autologous chondrocytes implantation procedures indicated that the healing response of brf-treated chondral tissue consisted of a stable and smooth surface, and viability staining showed similar concentration of viable chondrocytes in both brftreated and control specimens. 31 On the basis of our previous clinical observations and the reports of others, we thought it would be beneficial to retrospectively examine a larger series of returning patients to evaluate the healing response in brf-treated articular cartilage defects. We hypothesized that partial-thickness articular cartilage lesions treated with brf chondroplasty would show no evidence of progressive deterioration in a series of patients returning for further care and repeat arthroscopy. METHODS Patients One hundred ninety-three consecutive patients underwent brf chondroplasty as performed by the senior author (K.E.D.) to treat partial-thickness cartilage defects in the knee between June 1, 1999, and July 1, The final cohort of patients included in the study consisted of those patients who had previous RF chondroplasty and subsequently underwent repeat arthroscopy secondary to new injury or continued discomfort. The primary indication for surgery in most of these patients was another symptomatic lesion in the knee in addition to a partial-thickness defect, and the indication for treatment of a partial-thickness cartilage defect was the presence of an unstable border and/or cartilage flaps thought either to cause mechanical symptoms or to render the edge vulnerable to propagation of the defect. The size of these lesions had to be visible through the arthroscope and noniatrogenic in nature. Surgical Procedure Standard knee arthroscopy techniques were used. 3 A 30 arthroscope was inserted through the anterolateral portal. A suprapatellar outflow portal was created, and diagnostic arthroscopy was performed. An anteromedial portal was created in all cases as a working portal. After addressing concurrent injuries arthroscopically, partial-thickness cartilage defects were addressed. A calibrated probe was used to assess the stability of the cartilage borders of the defect and to measure the size of the defects. If the border was found to be unstable or the defect contained prominent flaps threatening further propagation, the lesion was treated with brf chondroplasty as described below. The first step in the treatment of the lesion was to determine the size of the defect by measuring the diameter of the lesion if it was round or by measuring the length of the 2 borders of the lesion if it was rectangular in shape. A motorized shaver or a small straight biter was then used to remove loose fragments of cartilage. No marrow-stimulating procedures (abrasion or microfracture) were performed. None of the lesions were debrided down to bone. An electrosurgical generator (ArthroCare 2000 brfe System, ArthroCare, Sunnyvale, Calif) connected to a bipolar wand (60 Bevel ArthroWand, ArthroCare) was used at setting 3 (out of 8) to smooth the base of the defect to create a stable rim. Care was taken to avoid direct contact of the bipolar wand with the articular cartilage surface and to keep the wand moving across the tissue surface while it was activated. Postoperatively, all patients underwent an individualized, supervised rehabilitation program depending on the type of surgery they received. The program consisted of progressing to full weightbearing as tolerated, active and passive range of motion, and progressive resistive exercises with quadriceps techniques modified as necessary to avoid knee pain and stressing the treated areas. At the time of the second procedure, the same arthroscopic technique was used. The area of the previously treated cartilage defect was identified, and its characteristics and measurements were recorded in similar fashion to those collected during the initial procedure. A single surgeon performed all procedures at both time points. Data Collection and Grading of Results The location, size, grade, and stability of lesions were recorded, and arthroscopic photographs were collected. The lesions were characterized as stable or unstable based on arthroscopic probing and graded from 1 to 4 using the Outerbridge classification scheme. 2 The area of each defect was determined based on arthroscopic measurements with the arthroscopic calibrated ruler. The size of the defect was calculated as described above. During follow-up examination, lesions could be classified as completely healed (area had been completely filled), partially healed (partial filling of the defect with stable borders), unchanged (no change in size), or progressive (increase in size with unstable periphery). Statistical Methods SAS statistical software was used to create a linear regression model to predict the mean change in lesion size per subject. This was dependent on mean initial lesion size, time interval between procedures, and the presence of multiple lesions. In addition, linear mixed models were created to predict the change in lesion size for each lesion. This was used to analyze the correlation between change in lesion size and location of the lesion within the

3 1704 Voloshin et al The American Journal of Sports Medicine TABLE 1 Patients and Procedures Performed a Patient No. Age, y Gender Side Initial Procedure(s) Second-Look Procedure 1 31 M R PMM, PLM, ORIF OCD, chondroplasty Hardware removal, synovectomy 2 49 M R PMM, PLM, chondroplasty PLM 3 30 M R ACLR, PLM, chondroplasty Hardware removal, synovectomy 4 46 M L ACLR, LMR, chondroplasty Synovectomy 5 31 M R PMM, debridement, chondroplasty PMM, collagen medial meniscal implant 6 27 F R Chondroplasty Synovectomy, chondroplasty 7 37 M L PMM, synovectomy, chondroplasty ACLR 8 43 M L MMR, removal hardware, chondroplasty Synovectomy 9 52 F R PMM, chondroplasty Synovectomy F R ACLR, PLM, chondroplasty Synovectomy F L PLM, chondroplasty Chondroplasty M L ACLR, chondroplasty ACLR, microfracture F R Debridement, removal of hardware, chondroplasty Revision ACLR, PLM M L Synovectomy, PLM, removal of loose bodies, chondroplasty Removal of loose bodies F L Chondroplasty Synovectomy a PMM, partial medial meniscectomy; PLM, partial lateral meniscectomy; ORIF OCD, open reduction and internal fixation of an osteochondral defect; ACLR, anterior cruciate ligament reconstruction; LMR, lateral meniscal repair; MMR, medial meniscal repair; M, male; F, female; L, left; R, right. tibiofemoral or patellofemoral joint. In this model, each subject contributed 1, 2, or 3 observations based on the number of lesions present, and a subject-specific random effect was assumed. Probability values of less than.05 were considered statistically significant. RESULTS Of the 193 patients treated using brf-based chondroplasty through July 1, 2002, 15 patients underwent repeat arthroscopy and were therefore included in the analysis. Several patients were treated for multiple lesions, and a total of 25 cartilage lesions were treated and followed. The age of the patients at the initial procedure ranged from 27 to 52 years with a mean of 38.5 ± 7.2 years. There were 9 male and 6 female patients treated, and surgery was performed on 8 right knees and 7 left knees. The initial surgical procedures included partial meniscectomy, ACL reconstruction, synovectomy, debridement, open reduction and fixation of an osteochondral defect, and chondroplasty. At the time of second surgery, procedures performed included removal of hardware, synovectomy, partial meniscectomy, ACL reconstruction, microfracture, and chondroplasty (Table 1). Of the 25 lesions, 11 were located in the patellofemoral joint, and the remaining 14 were located in the tibiofemoral joint. Most of the lesions consisted of grade III changes (23/25), and all were unstable at initial arthroscopy. At the time of the initial procedure, the size of the untreated chondral defect ranged from 9 to 625 mm 2 with a mean of ± mm 2 and a median of 120 mm 2. The interval time between arthroscopic surgeries ranged from 0.7 to 32.7 months with a mean of 10.4 ± 9.6 months and a median of 6.53 months. At the time of second look and the follow-up surgery, the size of the brf-treated defects ranged from not detectable (0 mm 2 ) to 300 mm 2 (107.7 ± mm 2 ), with a median of 100 mm 2. The change in lesion size ranged from 100% (complete healing) to a 212.5% growth in size ( 30.4 ± 70.7) (Table 2). At follow-up arthroscopy, 3 lesions (12%) demonstrated unstable borders and progressive damage to surrounding cartilage based on either grade or follow-up size. These lesions did not demonstrate massive gross cartilage loss around the original defects, but they had continued progression of cartilage damage around the unstable borders. Eight lesions (32%) were noted to have no progressive damage to the articular surface. Eight lesions (32%) demonstrated partial filling with stable repair tissue (partial healing), and 6 lesions (24%) demonstrated complete filling with stable repair tissue (complete healing) covering previous defects (Table 3). The newly formed repair tissue was distinguishable from surrounding native cartilage based on texture and color (Figure 1). The repair tissue generally exhibited more white color and felt firmer to probing. The gross appearance of this cartilage was similar to the fibrocartilage found after microfracture treatment. Five of the lesions within the tibiofemoral joint were classified as partially healed (36%), an additional 5 lesions were classified as healed, whereas the remaining 4 lesions stayed the same. The mean change in size of these lesions within the tibiofemoral joint was a decrease in size of 58.0% ± 42.6%. Those within the patellofemoral joint were classified as partially healed in 3 of 11 lesions, healed in 1 of 11 lesions, progressive in 3 of 11 lesions, whereas the remaining 4 stayed the same. The mean change in size was an increase in size of 4.7% ± 85.0%. Using the data analysis methods as described previously, the contributions of initial lesion size, time interval between procedures, presence of multiple lesions, and the location of the lesions were analyzed in reference to change in lesion size. With the linear regression model, the variables of initial lesion size, time interval, and the presence of multiple lesions were not found to be significant predictors of change in lesion size. However, with the linear mixed model unadjusted for other covariants, lesion site was

4 Vol. 35, No. 10, 2007 Radiofrequency Chondroplasty of the Knee 1705 TABLE 2 Lesion Demographics a No. of Lesions Demographic Initial Procedure Second Procedure Total 25 Location MFC 10 Troch 5 MPF 3 CP 3 LFC 3 LTP 1 Outerbridge grade 0 6 II 1 2 III IV 1 Stability Stable 0 19 Unstable 25 6 Size, mm Mean ± ± Median Time interval between procedures, mo Mean 10.4 ± 9.6 Median 6.53 Percentage change 100 to Mean 30.4 ± 70.7 a MFC, medial femoral condyle; Troch, trochlea; MPF, medial patella facet; CP, central patella; LFC, lateral femoral condyle; LTP, lateral tibial plateau. a significant predictor of change in lesion size, with those within the tibiofemoral joint more predictive of healing than were those within the patellofemoral joint (P <.05). DISCUSSION Devices using RF-generated energy to perform arthroscopic chondroplasty have been gaining popularity. This technology is attractive for several reasons: (1) RF energy is a relatively inexpensive surgical tool, (2) a variety of probes exist to deliver the RF energy arthroscopically, and (3) precise delivery of RF energy is possible, allowing for accurate debridement and smoothing of unstable cartilage on a macroscopic level. The brf system we used ablates biological tissues by creating a plasma field at the tip of the active electrodes. 23,30 A high voltage ( V) is applied across the active and return electrodes of the brf wand. This voltage creates an ionized vapor layer, or plasma, within the gap between the electrodes in an electrically conductive fluid (usually isotonic saline). 23 The charged particles in this ionized vapor layer carry enough energy to cause molecular dissociation in biological tissues, creating an ablative path while resulting in minimal thermal penetration into surrounding tissue. It is difficult, however, to determine the exact energy delivered to the chondral tissue. Although a setting of 3 supplies 150 V to the electrodes, the exact energy absorbed by the tissue Figure 1. A, partial-thickness chondral defect of the medial femoral condyle before bipolar radiofrequency based chondroplasty. B, after radiofrequency chondroplasty, the borders of the lesion are smooth and stable. C, fibrocartilage-like tissue filling the previously treated lesion is observed on second-look arthroscopy. depends on the device setting, the electrode used, the irrigation solution used, and the distance from the electrode. 30 Currently, there are limited data in the literature regarding the effects of RF energy on articular cartilage. The few studies that have been reported offer contradictory results. 8,13,14,17,26 Kaplan and Uribe 8 and Turner et al 26 used light microscopy to evaluate articular cartilage. They concluded that RF energy showed no harmful effects on cartilage as observed by this method. Lu et al 14 compared light microscopy and confocal laser microscopy in the evaluation of articular cartilage treated with brf energy. Observations with confocal laser microscopy demonstrated extensive chondrocyte death in the areas adjacent to the articular defects treated with RF ablation They concluded that light microscopy was much less sensitive than was confocal laser microscopy in demonstrating damage in healthy cartilage. Clinically, Owens et al 19 reported 2-year outcomes of a prospective, randomized study of patients treated using brf-based methods for

5 1706 Voloshin et al The American Journal of Sports Medicine TABLE 3 Results of Bipolar Radiofrequency Chondroplasty a Initial Second-Look Lesion Time Percentage Patient No. Location Grade Stability Size, mm 2 Interval, mo Grade Stability Size, mm 2 Change Healing 1 LFC 3 Unstable Stable 9 0 Same 2 MFC 3 Unstable Stable Partial 3 MFC 4 Unstable Stable Healed 4 MFC 3 Unstable Stable Partial 5 LFC 3 Unstable Stable Same 6 MP 3 Unstable Stable Same 7 Troch 3 Unstable Unstable Progression 8 Troch 3 Unstable Stable Healed 9 MFC 3 Unstable Stable Healed MP 3 Unstable 64 3 Unstable Partial 10 MFC 3 Unstable Stable Healed MP 3 Unstable Stable Same 11 MFC 3 Unstable Stable Healed Troch 3 Unstable Stable Partial 12 MFC 3 Unstable Stable Partial Troch 3 Unstable 75 3 Unstable Progression 13 Pat 3 Unstable Stable Partial MFC 3 Unstable Stable Same LTP 2 Unstable Stable Partial 14 Pat 3 Unstable Stable Same LFC 3 Unstable Stable Healed MFC 3 Unstable Stable Partial 15 Pat 3 Stable Unstable Same MFC 3 Stable Unstable Same Troch 3 Unstable 96 3 Unstable Progression a MFC, medial femoral condyle; Troch, trochlea; MP, medial patella; CP, central patella; LFC, lateral femoral condyle; LTP, lateral tibial plateau; same, no change in lesion size/grade; partial, reduction in lesion size and/or grade; healed, complete filling of defect; progression, increase in lesion size with instability; Pat, patella. symptomatic grade 2 and 3 chondral lesions of the patella. Patients treated using brf chondroplasty were suggested to have better outcomes than did those treated with mechanical debridement. Uribe 27 also showed favorable outcomes in patients treated with brf for lesions in the trochlea compared with mechanical debridement. The disparity between these encouraging clinical outcome data and the less favorable short-term histologic studies that used confocal laser microscopy raises the question of the clinical applicability of the histologic studies. To date, there are no human long-term histologic reports in the peer-reviewed literature. A recently presented study by Gambardella et al (unpublished data, 2004) histologically compared the articular cartilage of sheep after treatment with brf, microfracture, and mechanical shaving. The histologic appearance of the tissue that filled the defects in the brf group and the microfracture group resembled fibrocartilage, and the cartilage surrounding the treated areas was similar in all 3 groups. This fibrocartilage repair tissue has also been reported to fill the articular surface after a variety of surgical techniques that involve therapeutically induced bleeding from the subchondral bone spaces and subsequent clot formation. 12,22,24 Steadman et al 24 used a microfracture technique to treat full-thickness traumatic chondral injuries. In a series of more than 200 treated patients, the authors found that 75% had an improvement in pain at a minimum follow-up interval of 7 years. The resultant fibrocartilage repair tissue after marrow-stimulating techniques is heterogeneous and has been shown to be mechanically inferior to that of the hyaline cartilage. 1,5 It remains unclear how to account for the production of a stable, smooth repair tissue in the defects treated in this study. Although no marrow-stimulating procedures (abrasion or microfracture) were performed in any of the patients in this study, only 12% of the defects showed progressive deterioration of articular lesions, and several showed complete healing with fibrocartilage tissue. Additionally, one of the progressive lesions was visualized at 0.7 months at anterior cruciate ligament reconstruction, which may be too early to appreciate any reparative process. The potential sources for cell migration into the defects that filled in with tissue are speculative and not supported by data in this study but may include stimulation of the subchondral bone by brf energy and subsequent production of the reparative tissue. This study has several limitations. The only patients included in this study had symptoms sufficient to warrant repeat arthroscopy. Thus, this study group cannot truly represent the incidence of cartilage lesion progression in the original group of 193 patients because of the obvious selection bias. However, the purpose of the study was to evaluate the appearance of brf-treated lesions over time; for this purpose, looking only at the symptomatic group would likely lead to finding

6 Vol. 35, No. 10, 2007 Radiofrequency Chondroplasty of the Knee 1707 a higher percentage of progressive lesions than in the overall group. Another limitation is that the authors of the article performed the grading and size measurements of the lesions at the time of surgery. However, all of the lesions were documented on arthroscopic photographs, which permitted independent verification of the surgical observations. This method of verification was not incorporated into the study s methods as it is difficult to establish grade and size of the lesion from the photograph without the physical feedback obtained during arthroscopy. Unfortunately, no biopsies of the repair tissue that filled the defects were performed, and we can only speculate about its histologic nature. It is therefore difficult to determine if the RF treatment induced a reparative process or if necrosis occurred followed by generation of repair tissue. In addition, as mentioned earlier, the energy delivered depends on several factors. Therefore, it is difficult to apply the authors power settings when using a different model, power supply, or probe. Finally, our data did not include functional outcomes of the patients in the study group, and variable associated injuries in our patients might have affected our second-look observations. Consistent with our hypothesis, only 3 of the 25 lesions in this study demonstrated further deterioration of the cartilage defects after treatment with brf chondroplasty. Surprisingly, partial or complete filling was found in more than 50% of the treated lesions. In addition, lesions within the tibiofemoral joint were more predictive of a positive response to brf chondroplasty than were those within the patellofemoral joint. We conclude that this type of RF chondroplasty offers a good chance of stabilizing and potentially filling partial cartilage lesions. 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