Four-Year Results From a Randomized Controlled Study of Knee Chondroplasty With Concomitant Medial Meniscectomy: Mechanical Debridement Versus Radiofrequency Chondroplasty

Four-Year Results From a Randomized Controlled Study of Knee Chondroplasty With Concomitant Medial Meniscectomy: Mechanical Debridement Versus Radiofrequency Chondroplasty Gunter Spahn, M.D., Hans Michael Klinger, M.D., Thomas Mückley, M.D., and Gunther O. Hofmann, M.D., Ph.D.

Purpose: This randomized study was undertaken to compare the effectiveness of simple mechanical debridement and 50°C controlled bipolar chondroplasty. Methods: A total of 60 patients who had a grade III articular cartilage defect of the medial femoral condyle were included. After randomization, 30 patients underwent simple debridement of articular cartilage defects, which was performed with a mechanical shaver (mechanical shaver debridement [MSD] group). The remaining patients underwent thermal chondroplasty, which was performed with a temperature-controlled bipolar device with a constant thermo-application of a maximum of 50°C (radiofrequency-based chondroplasty [RFC] group). All patients underwent partial (n ⫽ 41) or subtotal (n ⫽ 19) meniscectomy. Follow-up was undertaken 4 years postoperatively. Results: No significant differences between the preoperative findings for the 2 groups were observed. One patient from the MSD group had died, and one female patient in the RFC group was lost to follow-up. A total of 18 patients had undergone revision operations for persistent knee problems: in the MSD group, there were 8 endoprostheses, 4 osteotomies, and 2 revision arthroscopies, whereas in the RFC group, there was 1 replacement, 2 osteotomies, and 1 revision arthroscopy with subtotal medial meniscectomy. The proportion of revisions was significantly higher in the MSD group (P ⫽ .006). These patients were excluded from the evaluation. The remaining 40 patients from both groups benefited from the operation. The preoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) was 11.3 points in the MSD group and 15.5 points in the RFC group (P ⫽ .279). Patients from the MSD group had a KOOS of 53.2 points at the time of follow-up. In the RFC group the KOOS (71.8 points) was significantly higher (P ⬍ .001). Conclusions: Compared with classical mechanical debridement, bipolar radiofrequency currently appears to be the superior method for achieving a good midterm result. Level of Evidence: Level I, randomized controlled trial.

A

rticular cartilage lesions and meniscus tears are frequently found during arthroscopic knee operations.1-3 Both pathologies contribute to the degener-

From the Center of Trauma and Orthopedic Surgery (G.S.), Eisenach; Orthopedic Clinic, Georg August University (H.M.K.), Göttingen; Department of Trauma, Friedrich Schiller University of Jena (T.M., G.O.H.), Jena; and Trauma Center (G.O.H.), Bergmannstrost Halle, Germany. The authors report no conflict of interest. Received September 20, 2009; accepted February 19, 2010. Address correspondence and reprint requests to Gunter Spahn, M.D., Center of Trauma and Orthopaedic Surgery, Sophienstrasse 16, D-99817 Eisenach, Germany. E-mail: [email protected] © 2010 by the Arthroscopy Association of North America 0749-8063/9551/$36.00 doi:10.1016/j.arthro.2010.02.030

ative process in the knee joint and often are associated with the development of knee osteoarthritis.4 Degenerative meniscal tears usually require partial or subtotal meniscectomy to achieve a stable meniscus remnant to avoid blocking and pain. In degenerative tears reconstruction is seldom successful. There is no consensus about the most effective type of treatment for articular cartilage lesions. Articular cartilage softening or superficial fissures (grade I and II lesions) seldom require any surgical treatment. Complete lesions (grade IV denotes complete defects) can often be treated effectively by bone marrow stimulation (drilling, microfracturing, or abrasion), osteochondral transplantation, or autologous chondral transplantation. Nonetheless, a general consensus about the best kind of treatment

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 26, No 9 (September, Suppl 1), 2010: pp S73-S80

S73

S74

G. SPAHN ET AL.

for deep (grade III) articular cartilage lesions is lacking.5,6 Mechanical debridement (so-called shaving) is one of the measures most frequently performed in arthroscopic operations. The technique aims to produce stable and nearly smooth articular cartilage surfaces, as well as to remove loose flakes and to potentially stimulate articular cartilage regeneration. This improves gliding and reduces crepitus, as well as reducing pain, swelling, and joint synovitis. It has frequently been shown that the application of thermal energy is sufficient to smooth articular cartilage within deep lesions.7 Thermal application is possible through the use of laser devices or through the application of radiofrequency (RF) monopolar or bipolar energy probes. Articular cartilage heating produces a cartilage smelting, and this creates a very smooth articular cartilage surface.8 However, this measure is associated with the temperature-related cell death of chondrocytes and destruction of the articular cartilage matrix. In recent articles it was shown that chondrocytes undergo irreversible death after “shock heating” to temperatures higher than 52°C.9-14 It is generally known that the application of thermal energy can produce tissue smelting, resulting in a smooth cartilage surface. This application can be performed by different laser systems or by monopolar or bipolar RF energy. Monopolar RF devices produce an RF flow from the active electrode (small top of the surgical instrument) to a neutral electrode. This produces high temperatures near the top of the instrument. This thermal application, however, is relatively uncontrolled. Alternatively, in bipolar devices the top of the surgical instruments contains both electrodes. In the presence of an electrolyte solution or tissue between the electrodes, an electrical field is generated. Ohmic resistance causes local heating within these electrical fields. Wienecke and Lobenhoffer8 termed this a “plasma field.” For significant smoothing of cartilage surfaces, a minimal temperature of 45°C is required.15 At temperatures of 50°C to 55°C, however, the chondrocytes undergo irreversible cell death.16 Thus there is a relatively small therapeutic window. Recent experimental studies have investigated the effect of RF treatment on cartilage. Shellock and Shields17 found significantly lower tissue heating under bipolar RF treatment, unlike Lu et al.,9,15 who found significantly less cell death in cartilage after monopolar treatment. Amiel et al.18 found cell death for 100 to 200 ␮m but were unable to determine

whether there was a significant effect on metabolic activity in the area adjacent to the treatment zone. Thus the benefits of RF treatment are currently quite controversial. RF application must be done very carefully to avoid heating, and the generally recommended approach is the noncontact “paintbrush” method.8 The effects of both treatment modalities, mechanical debridement19-23 and thermal chondroplasty,24-26 have been evaluated separately in clinical trials. Recent studies have often evaluated different patient groups. The articular cartilage treatment typically includes the patellar surface, the lateral compartment, and the medial compartment. Other studies included patients with anterior cruciate ligament insufficiency as well as patellar displacements. The purpose of our study was to evaluate the effect of 2 treatment options, mechanical shaver debridement (MSD) and radiofrequency chondroplasty (RFC) (at a maximum of 50°C), in a highly selected group of patients with articular cartilage lesions of grade III isolated to the medial femoral condyle only. We hypothesized that bipolar RFC would produce a better clinical outcome than simple MSD in cases of grade III articular cartilage lesions. METHODS Patients Patients (N ⫽ 60) with knee pain (⬎3 months) and a magnetic resonance imaging (MRI)–visualized grade III articular cartilage lesion of a weight-bearing surface within the medial femoral condyle were considered for participation in the study. After the approval of the regional ethics committee (1026/05/111), patients who had given their informed consent were randomized on the morning of the operative day. All operations were performed by the same author (G.S.) at his institution. Patients were included according to the following criteria: knee pain for 3 months or more, indications for arthroscopy based on positive clinical and MRI meniscus signs, and significant grade III cartilage lesions (full-thickness lesions but no complete defect) in the medial femoral condyle on preoperative MRI (Vallotton grading).27 The exclusion criteria were major knee injury (especially dislocation of the patella, anterior cruciate ligament or posterior cruciate ligament injury, and fractures), significant radiographic knee osteoarthritis (Kellgren-Lawrence grade II or higher), and prior surgery. Before the start of the study, we labeled 30 pieces of paper with either the inscription “MSD” or “RFC.”

KNEE CHONDROPLASTY AND MEDIAL MENISCECTOMY These were stored in sealed envelopes in the operating room. After the arthroscopy had confirmed the inclusion criteria for the study, a nurse opened an envelope and instructed the surgeon to carry out an MSD or RFC. The patients were blinded to their groups over the follow-up period. Furthermore, the investigator (H.M.K.) who evaluated the radiographs was blinded. During arthroscopy, a total of 30 patients underwent treatment of the articular cartilage lesions within the medial femoral condyle by mechanical debridement (“shaving”) (MSD group). In the other group the articular cartilage lesions were treated by thermal chondroplasty (RFC group). All patients had undergone medial meniscectomy. Operative Procedure General arthroscopy was performed with the patient under general anesthesia, and the leg was fixed within a leg-holder inclusive tourniquet. After joint assessment for confirmation of the inclusion and exclusion criteria, all operations were performed through the infrapatellar lateral (arthroscope) and medial (instrumentation) approach. The classification of meniscus tears was radial tear, flap tear, buckle-handle tear, horizontal tear (fish mouth), or complex tear. The loose meniscus flaps were resected with a punch, and the flakes were removed with a shaver by use of an oscillating method. Finally, the residual margin of the meniscus was smoothed with the shaver. The stability of the residual meniscus was carefully tested with a hook. The extent of meniscectomy was classified as “partial,” requiring about one-third resection, or “subtotal,” requiring about two-thirds resection. Mechanical debridement in the MSD group was performed with a full-radius resector (Arthrex, Naples, FL). The instrument was moved over the lesions 3 times by permanent suction (about 5 seconds), and the top of the instrument made only mild contact with the surface. No significant manual pressure was applied to avoid a deep abrasion. For RF application, we used the Paragon T2 device (Arthrocare, Austin, TX). This instrument contains a temperature indicator to signal heating over 50°C (the critical temperature for articular cartilage damage). A temperature violation was never observed. This probe also made only mild contact with the surface, and no significant manual pressure was applied by the surgeon (setting, 40 W). In all knees a Redon drain (Drainobag, Braun Melsungen, Germany) was positioned for 24 hours. All patients took ibuprofen in varying dosages, depending

S75

on their level of pain and the amount of swelling. All patients completed a physical exercise program for 6 weeks. Assessment and Statistics For validation of the study, sample size calculations were performed a priori (G Power, version 3.1; Heinrich-Heine-University, Düsseldorf, Germany) based on a significance level of 0.05 and a power of 0.80. This calculation estimated that 25 patients were needed for each group. The patients were evaluated by the Knee Injury and Osteoarthritis Outcome Score (KOOS) preoperatively and at the time of follow-up.28 The activity level of each patient was measured by the Tegner score (activity level before onset of symptoms and at time of follow-up).29 The patients had to estimate their physical activity level from memory. Radiologic evaluation of the medial joint space and determination of the varus angle (anatomic axis) were made by use of standard weight-bearing radiographs in a position of 30° of flexion. Articular cartilage lesions were classified according to the International Cartilage Repair Society score.30 In all patients the MRI finding of a grade III articular cartilage lesion correlated with the arthroscopic finding of a grade III articular cartilage lesion. All statistical analyses were performed with SPSS software (version 13.0; SPSS, Chicago, IL). Continuous data were tested by analysis of variance, and frequencies were tested by the ␹2 test. Significance was considered for P ⬍ .05. RESULTS All 60 patients underwent medial meniscectomy. There were 9 radial tears, 19 flap tears, 21 horizontal tears, 4 buckle-handle tears, and 7 complex tears. Of these tears, 41 required a partial meniscectomy and 19 required a subtotal meniscectomy. The frequency of partial or subtotal meniscectomy was not significantly different between the MSD and RFC groups (P ⫽ .432). The extent of meniscus surgery did not influence the rate of reoperation (P ⫽ .290) or the clinical outcome in terms of KOOS (P ⫽ .159). One patient from the MSD group had died, and one female patient in the RFC group was lost to follow-up. A total of 18 patients had undergone revision operations for persistent knee problems: in the MSD group, there were 8 replacements, 4 osteotomies, and 2 revision arthroscopies; whereas in the RFC group,

S76

G. SPAHN ET AL.

FIGURE 1. Required revision surgery. The proportion of revisions within 4 years postoperatively was significantly higher in the MSD group (P ⫽ .006). These patients were excluded from the evaluation. (MSD, mechanical shaver debridement; RFC, radiofrequency chondroplasty.)

there was 1 replacement, 2 osteotomies, and 1 revision arthroscopy with subtotal medial meniscectomy. The proportion of revisions was significantly higher in the MSD group (P ⫽ .006). These patients were excluded from the evaluation (Fig 1). The remaining patients (n ⫽ 40 [15 in MSD group and 25 in RFC group]) are included in this evaluation. There were no significant differences between the groups (Tables 1 and 2). TABLE 1. Baseline Data (Demographics, Self-Reported Assessment Scores, and Findings) of Patients Who Underwent 4-Year Follow-Up (n ⫽ 40) MSD No. of patients Sex (male/female) Side (right/left) Age (yr) History of disease (mo) Medial joint space width (mm) Varus angle (°) KOOS (%) Preinjury physical activity (Tegner score) (points) Preoperative physical activity (Tegner score) (points) Extent of meniscectomy (partial/subtotal) Diameter of medial femoral condyle defect (mm2)

RFC

P Value

15 6/9 11/4 47.0 ⫾ 8.1 10.6 ⫾ 4.1

25 11/14 14/11 43.5 ⫾ 10.7 9.9 ⫾ 4.7

— .534 .225 .284 .058

4.4 ⫾ 1.8 1.5 ⫾ 1.1 11.3 ⫾ 8.8

4.8 ⫾ 1.6 1.6 ⫾ 0.6 15.5 ⫾ 12.7

.406 .721 .279

5.2 ⫾ 1.0

5.3 ⫾ 1.1

.754

1.9 ⫾ 0.7

2.4 ⫾ 1.0

.630

10/5

19/6

.387

20.9 ⫾ 4.7

20.2 ⫾ 3.7

.583

NOTE. Data presented as mean ⫾ SD unless otherwise indicated.

Self-Reported Assessments Both groups benefited from the operation. The preoperative KOOS was 11.3 points in the MSD group and 15.5 points in the RFC group (P ⫽ .279). Patients from the MSD group had a KOOS of 53.2 points at follow-up. In the RFC group the KOOS (71.8 points) was significantly better (P ⬍ .001) (Table 3). Patients were asked to describe their level of physical activity (Fig 2) 1 year before the onset of their TABLE 2. Baseline Data (Demographics, Self-Reported Assessment Scores, and Findings) of Patients Who Were Lost to Follow-Up (n ⫽ 20)

No. of patients Sex (male/female) Age (yr) History of disease (mo) Medial joint space width (mm) Varus angle (°) KOOS (%) Preinjury physical activity (Tegner score) (points) Preoperative physical activity (Tegner score) (points) Extent of meniscectomy (partial/subtotal) Diameter of medial femoral condyle defect (mm2)

MSD

RFC

P Value

15 9/6 40.5 ⫾ 9.1 7.4 ⫾ 3.2

5 2/3 39.8 ⫾ 9.2 9.8 ⫾ 5.2

— .396 .879 .229

4.1 ⫾ 2.4 1.8 ⫾ 1.6 17.6 ⫾ 15.1

4.2 ⫾ 1.7 2.2 ⫾ 1.1 11.4 ⫾ 8.6

.913 .829 .510

5.3 ⫾ 1.1

4.2 ⫾ 0.6

.063

1.8 ⫾ 0.8

1.4 ⫾ 0.9

.385

9/6

3/2

.704

21.7 ⫾ 3.8

20.8 ⫾ 5.6

.670

NOTE. Data presented as mean ⫾ SD unless otherwise indicated.

KNEE CHONDROPLASTY AND MEDIAL MENISCECTOMY TABLE 3.

Results of Patient Self-Reported Assessments Preoperative

MSD

Symptoms Pain Function in activities of daily living Function in sports/recreation Knee-related quality of life KOOS

S77

Follow-Up (4 yr)

RFC

MSD

Mean

SD

Mean

SD

P Value

11.4 12.1 11.4 11.3 9.5 11.3

11.5 13.7 9.9 8.7 7.0 8.8

17.5 14.7 15.1 16.0 14.5 15.5

16.4 15.2 13.9 13.8 11.1 12.7

.212 .588 .375 .250 .132 .279

RFC

Mean

SD

Mean

SD

P Value

53.1 55.7 50.9 56.7 52.9 53.2

19.6 20.1 17.9 18.6 20.6 17.5

72.7 75.1 69.9 75.0 67.0 71.8

9.9 9.3 10.8 8.4 15.0 9.1

⬍ .001 ⬍ .001 ⬍ .001 ⬍ .001 .017 ⬍ .001

complaints, their activity level at the time of the operation, and the outcome (Fig 3). Before their illness, the patients had a Tegner score of 5.2 ⫾ 1.0 (P ⫽ .745). The disease-related score decreased to 2.2 ⫾ 0.9 at the time of the operation (P ⫽ .063). At follow-up, patients in the RFC group had a significantly higher level of physical activity (P ⫽ .005).

In both groups the varus angle increased significantly (MSD, P ⬍ .001; RFC, P ⫽ .001). The varus angle at follow-up was significantly higher in MSD patients (P ⬍ .001) (Fig 4).

Results of Radiologic Investigation

We confirm our hypothesis that arthroscopic RFC produces better clinical outcomes in the treatment of grade III articular cartilage lesions. In the pathophysiology of osteoarthritis, the progression of articular cartilage lesions is crucial. The function of the diarthrodial joint strongly depends on the integrity of the hyaline articular cartilage layer. Articular cartilage facilitates nearly friction-free movement and shock absorption between the corresponding joint surfaces. The hyaline layer comprises complex tissue with poor restoration ability. It is generally accepted that the fre-

The medial joint space measurement was used for evaluation of osteoarthritic progression. In MSD patients we observed a significant progression of joint space narrowing from the preoperative evaluation to the third postoperative year (P ⬍ .001). Patients in the MSD group tended (P ⫽ .024) to have a smaller medial joint space than RFC patients (Fig 3). The preoperative joint space widths did not differ between the groups (Table 4).

FIGURE 2. Physical activity level (Tegner score). Before their illness (last year before onset of complaints), the patients had no differences in Tegner scores (P ⫽ .745). The disease-related score decreased at the time of the operation in both groups (P ⫽ .063). At follow-up, patients in the RFC group had a significant higher level of physical activity (P ⫽ .005).

DISCUSSION

S78

G. SPAHN ET AL.

FIGURE 3. Width of medial joint space on standard standing radiographs. In MSD patients we observed a significant progression of joint space narrowing from the preoperative evaluation to the third postoperative year (P ⬍ .001). Patients in the MSD group tended (P ⫽ .024) to have a smaller medial joint space than RFC patients.

quency of articular cartilage lesions increases with age and that such lesions are more frequent in obese patients, women, or patients with a high level of physical activity (professional or sports). Injuries (loss of meniscus, instability, or fractures) can also promote articular cartilage lesions. The initial articular cartilage lesion often produces minimal complaints or no complaints at all. In the late stage of disease, the subchondral bone is involved in the damage; loose bodies provoke joint blockade or synovitis, and the roughness provokes painful crepitus. TABLE 4. Baseline Data (Demographics, Self-Reported Assessment Scores, and Findings) of All Patients (n ⫽ 20) MSD

RFC

No. of patients 30 30 Sex (male/female) 15/15 13/17 Age (yr) 43.8 ⫾ 9.0 42.9 ⫾ 10.4 History of disease (mo) 9.0 ⫾ 3.9 7.4 ⫾ 4.8 Medial joint space width (mm) 4.2 ⫾ 2.1 4.7 ⫾ 1.6 Varus angle (°) 1.8 ⫾ 3.5 1.8 ⫾ 1.8 KOOS (%) 18.3 ⫾ 15.1 23.5 ⫾ 21.9 Preinjury physical activity (Tegner score) (points) 5.3 ⫾ 5.1 5.1 ⫾ 4.1 Preoperative physical activity (Tegner score) (points) 1.8 ⫾ 0.7 2.2 ⫾ 1.1 Extent of meniscectomy (partial/subtotal) 19/11 22/8 Diameter of medial femoral 21.0 ⫾ 4.2 20.3 ⫾ 4.0 condyle defect (mm2)

P Value — .980 .732 .175 .290 .964 .291 .648 .076 .209 .329

NOTE. Data presented as mean ⫾ SD unless otherwise indicated.

The menisci are also involved in this degenerative process. Normally, the menisci are mechanical shock absorbers, which stabilize and moisten the articular cartilage with synovial fluid. Meniscus degeneration leads to a reduction of the resistance against shear stress, increased pressure, and consequent tearing. The unstable meniscus flaps disrupt harmonic joint movement. This is associated with painful loss of movement. Degenerative meniscus tears are often the first symptom of joint degeneration. A 60% to 90% association of degenerative meniscus tears with articular cartilage lesions has been noted in large arthroscopic series.1-3 Degenerative meniscus tears typically require a partial or subtotal meniscectomy. These approaches aim to produce a stable residual meniscus to prevent unstable flaps. The outcome after meniscectomy depends on the extent of resection. The most effective type of chondroplasty for deep articular cartilage lesions in the treatment of lowgrade knee osteoarthritis remains to be determined. Surely, the development of excellent techniques for chondrocyte implementation, osteotomies, and replacements presents enormous advantages in the context of knee surgery. However, all these methods have disadvantages: a high degree of invasiveness, long period for rehabilitation, high costs, and relatively high rates of complications. Notably, the replacement is an irreversible step for patients and surgeons.31 The ability to alleviate pain and functional loss by minimally invasive arthroscopy is therefore highly desirable. However, descriptions of the outcome after arthro-

KNEE CHONDROPLASTY AND MEDIAL MENISCECTOMY

S79

FIGURE 4. Varus angle on standard standing radiographs. The preoperative joint space widths did not differ between the groups (Table 4). In both groups the varus angle increased significantly (MSD, P ⬍ .001; RFC, P ⫽ .001). The varus angle at follow-up was significantly higher in MSD patients (P ⬍ .001).

scopic therapy are not uniform. Some authors have stated that no debridement is advantageous. For example, Moseley et al.32 found in a prospective placebo-controlled study that arthroscopic debridement or simple lavage had no effect on the midterm outcome, as compared with a sham-operated placebo group. However, other investigators found a dependence of outcome after arthroscopic treatment on different factors, for example, the necessity for extended meniscectomy.4 It appears that arthroscopic debridement represents a symptom-reducing therapy but in no way treats the underlying pathology of the degenerative process. However, the approach succeeds in delaying definitive replacement in 50% to 70% of patients, as observed in our study. Therefore the strategy outlined previously represents a promising treatment.19 The situation is similar with regard to studies about the effect of thermal (RF) chondroplasty. There are protagonists for these treatment modalities. Above all, the use of bipolar RF appears to yield superior results compared with monopolar RF. The major limitation of most studies is an inhomogeneous patient population. We avoided this effect in our study. This study was undertaken to compare the effect of 2 generally accepted arthroscopic treatment modalities: classical mechanical debridement (MSD) versus bipolar temperature-controlled RFC. Before randomization, both groups were comparable, but the patient population was highly selected. Only patients with a medial meniscus tear and grade III articular cartilage lesion of the medial femoral condyle were included. This distinguishes our study from other re-

cent studies. Both groups (MSD and RFC) were comparable at baseline. The midterm outcome after mechanical debridement (meniscectomy and MSD) was comparatively worse. About half of the patients benefited only in the short term and required reoperations within the observation interval. The remaining patients had a good to moderate outcome, although the results were worse than in the RFC group. The intention of MSD is to remove instable flakes to improve gliding and reduce the development of loose bodies.33 Restoration of the articular cartilage layer is difficult. It is impossible to produce nearly smooth surfaces by conventional shaving. Therefore this procedure must be carried out very carefully to avoid altering the still intact or nearly intact articular cartilage layer. Our results suggest that RFC treatment of grade III articular cartilage lesions produces an acceptable midterm outcome. Significantly fewer patients required revision operations within the observation interval. On the one hand, this may result from the use of a less invasive articular cartilage ablation technique (avoiding additional damage within residual articular cartilage). On the other hand, RFC treatments may stimulate the remaining articular cartilage to a certain level of restoration (“neo-surface”). In both groups the degenerative processes could not be stopped completely. Nonetheless, joint space narrowing and the varus progression were slower in the RFC group. These radiologic symptoms are indirect signs of articular cartilage layer quality as well as of osteoarthritis progression. This may offer the possi-

S80

G. SPAHN ET AL.

bility for real articular cartilage restoration in the future, although our results reaffirm the difficulty of achieving this goal. Although our study was a randomized, moderately powered study, it had some limitations. We only studied patients with grade III articular cartilage lesions and concomitant medial meniscus tears. Furthermore, we only studied the differences between mechanical shaving and RF treatment and had no real control group. Finally, 30% of the patients were lost to follow-up or required a second attempt at surgery. Although our results suggest that RF treatment produces a better midterm clinical outcome, it is not possible to make a definitive statement regarding this method based on our results. Further investigations with long-term follow-up are required. CONCLUSIONS Compared with classical mechanical debridement, bipolar RF currently appears to be the superior method for achieving a good midterm result. REFERENCES 1. Aroen A, Loken S, Heir S, et al. Articular cartilage lesions in 993 consecutive knee arthroscopies. Am J Sports Med 2004; 32:211-215. 2. Curl WW, Krome J, Gordon ES, Rushing J, Smith BP, Poehling GG. Cartilage injuries: A review of 31,516 knee arthroscopies. Arthroscopy 1997;13:456-460. 3. Hjelle K, Solheim E, Strand T, Muri R, Brittberg M. Articular cartilage defects in 1,000 knee arthroscopies. Arthroscopy 2002;18:730-734. 4. Christoforakis J, Pradhan R, Sanchez-Ballester J, Hunt N, Strachan RK. Is there an association between articular cartilage changes and degenerative meniscus tears? Arthroscopy 2005;21:1366-1369. 5. Hunziker EB. Articular cartilage repair: Basic science and clinical progress. A review of the current status and prospects. Osteoarthritis Cartilage 2001;10:432-463. 6. Sellards RA, Nho SJ, Cole BJ. Chondral injuries. Curr Opin Rheumatol 2002;14:134-141. 7. Barber FA, Uribe JW, Weber SC. Current applications for arthroscopic thermal surgery. Arthroscopy 2002;18:40-50 (Suppl 1). 8. Wienecke H, Lobenhoffer P. Basic principles of radiosurgical systems and their applications in arthroscopy. Unfallchirurg 2003;106:2-12 (in German). 9. Lu Y, Markel MD. Radiofrequency energy for cartilage treatment. In: Cole BJ, Malek MM, eds. Articular cartilage lesions. A practical guide to assessment and treatment. New York: Springer, 2004;47-56. 10. Kaplan LD, Ernsthausen JM, Bradley JP, Fu FH, Farkas DL. The thermal field of radiofrequency probes at chondroplasty settings. Arthroscopy 2003;19:632-640. 11. Kaplan LD, Chu CR, Bradley JP, Fu FH, Studer RK. Recovery of chondrocyte metabolic activity after thermal exposure. Am J Sports Med 2003;31:392-398. 12. Kaplan LD. The analysis of articular cartilage after thermal exposure: “Is red really dead?” Arthroscopy 2003;19:310-313.

13. Li S, Chien S, Branemark PI. Heat shock-induced necrosis and apoptosis in osteoblasts. J Orthop Res 1999;17:891-899. 14. Mitchell ME, Kidd D, Lotto ML, et al. Determination of factors influencing tissue effect of thermal chondroplasty: An ex vivo investigation. Arthroscopy 2006;22:351-355. 15. Lu Y, Edwards RB III, Nho S, Heiner JP, Cole BJ, Markel MD. Thermal chondroplasty with bipolar and monopolar radiofrequency energy: Effect of treatment time on chondrocyte death and surface contouring. Arthroscopy 2002;18:779-788. 16. Benton HP, Cheng TC, MacDonald MH. Use of adverse conditions to stimulate a cellular stress response by equine articular chondrocytes. Am J Vet Res 1996;57:860-865. 17. Shellock FG, Shields CL Jr. Radiofrequency energy-induced heating of bovine articular cartilage using a bipolar radiofrequency electrode. Am J Sports Med 2000;28:720-724. 18. Amiel D, Ball ST, Tasto JP. Chondrocyte viability and metabolic activity after treatment of bovine articular cartilage with bipolar radiofrequency: An in vitro study. Arthroscopy 2004; 20:503-510. 19. Kruger T, Wohlrab D, Birke A, Hein W. Results of arthroscopic joint debridement in different stages of chondromalacia of the knee joint. Arch Orthop Trauma Surg 2000;120:338-342. 20. Jackson RW, Dieterichs C. The results of arthroscopic lavage and debridement of osteoarthritic knees based on the severity of degeneration: A 4- to 6-year symptomatic follow-up. Arthroscopy 2003;19:13-20. 21. Harwin SF. Arthroscopic debridement for osteoarthritis of the knee: Predictors of patient satisfaction. Arthroscopy 1999;15: 142-146. 22. Dervin GF, Stiell IG, Rody K, Grabowski J. Effect of arthroscopic debridement for osteoarthritis of the knee on health-related quality of life. J Bone Joint Surg Am 2003; 85:10-19. 23. Fond J, Rodin D, Ahmad S, Nirschl RP. Arthroscopic debridement for the treatment of osteoarthritis of the knee: 2- and 5-year results. Arthroscopy 2002;18:829-834. 24. Barber FA, Iwasko NG. Treatment of grade III femoral chondral lesions: Mechanical chondroplasty versus monopolar radiofrequency probe. Arthroscopy 2006;22:1312-1317. 25. Owens BD, Stickles BJ, Balikian P, Busconi BD. Prospective analysis of radiofrequency versus mechanical debridement of isolated patellar chondral lesions. Arthroscopy 2002;18: 151-155. 26. Spahn G, Muckley T, Kahl E, Hofmann GO. Factors affecting the outcome of arthroscopy in medial-compartment osteoarthritis of the knee. Arthroscopy 2006;22:1233-1240. 27. Vallotton JA, Meuli RA, Leyvraz PF, Landry M. Comparison between magnetic resonance imaging and arthroscopy in the diagnosis of patellar cartilage lesions: A prospective study. Knee Surg Sports Traumatol Arthrosc 1995;3:157-162. 28. Roos EM, Roos HP, Lohmander LS, Ekdahl C, Beynnon BD. Knee Injury and Osteoarthritis Outcome Score (KOOS)— Development of a self-administered outcome measure. J Orthop Sports Phys Ther 1998;28:88-96. 29. Tegner Y, Lysholm J. Rating systems in the evaluation of knee ligament injuries. Clin Orthop Relat Res 1985:43-49. 30. Brittberg M, Winalski CS. Evaluation of cartilage injuries and repair. J Bone Joint Surg Am 2003;85:58-69 (suppl 2). 31. Bonnin M, Chambat P. Osteoarthritis of the knee. Surgical treatment. New York: Springer, 2008. 32. Moseley JB, O’Malley K, Petersen NJ, et al. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med 2002;347:81-88. 33. Strobel MJ. Manual of arthroscopic surgery. New York: Springer, 2002.