The METEOR trial: No rush to repair a torn meniscus
ABSTRACTIt is uncertain whether arthroscopic partial meniscectomy is better than physical therapy in patients who have a symptomatic torn meniscus on top of osteoarthritis of the knee. The Meniscal Repair in Osteoarthritis Research (METEOR) trial concluded that physical therapy is acceptable at first, and that surgery is not routinely needed. In patients assigned to physical therapy who eventually needed surgery, the delay resulting from a trial of conservative management did not impair outcomes at 12 months from the initial presentation. Here, we analyze the background, design, findings, and clinical implications of the METEOR trial.
KEY POINTS
- METEOR trial was a randomized controlled trial comparing the short-term and long-term efficacy of arthroscopic partial meniscectomy vs physical therapy in patients with a symptomatic meniscal tear and knee osteoarthritis.
- Both treatment groups in the METEOR trial received physical therapy in order to determine the incremental benefit of surgery and physical therapy compared with physical therapy alone.
- The trial investigators used specific definitions of osteoarthritis and symptoms of meniscal tear.
- Meniscectomy is often performed for patients with symptoms consistent with a meniscal tear and evidence of a meniscal tear on magnetic resonance imaging, but the benefits of this procedure are unclear.
TRANSLATING THE METEOR RESULTS TO EVERYDAY PRACTICE
There are many challenges in designing surgical trials. Indeed, by one estimate,22 only about 40% of treatment questions involving surgical procedures can be evaluated by a randomized controlled trial.
Although the METEOR trial was not blinded, it was the first large, multicenter, randomized controlled trial to compare arthroscopic partial meniscectomy vs standardized physical therapy by using high-quality methodology such as careful sample-size calculation, balancing the groups according to known prognostic factors with block randomization, and intention-to-treat analysis. Moreover, the outcome measures were obtained from validated self-reporting questionnaires (WOMAC for function and KOOS for pain), reducing the possibility of observer bias.19 In addition, analyses were performed with the analysts blinded to the randomization assignment.
Limitations of the trial
A few limitations of the study are worth noting.
Patients age 45 or older with both symptomatic meniscal tear and osteoarthritis were the target population of this study. However, it is important to distinguish between the study population and the target population in a physician’s practice.
The investigators adopted broad definitions of osteoarthritis and symptoms of meniscal tear. Twenty-one percent of participants had normal findings on plain radiography, with cartilage defects visible only on MRI. Further, episodic pain or acute pain localized to a joint line was regarded as a symptom consistent with a torn meniscus.
In practice, arthroscopic partial meniscectomy is usually considered when a patient with a long history of tolerable osteoarthritis presents with a sudden onset of intolerable pain after a squatting or twisting injury.
In addition, the study population was predominantly white (85%), and the study was performed in tertiary referral academic medical centers. Therefore, the outcomes achieved with surgery or physical therapy may not translate to the community setting. Clinicians must be careful to account for these types of differences in extrapolating to patients in their own practice.
Potential enrollment bias
Although randomization is a rigorous method that eliminates selection bias in assigning individuals to study and control groups, selective enrollment could have created bias.1 As the authors mentioned, only 26% of eligible patients were enrolled, possibly reflecting patients’ or surgeons’ strong preferences for one treatment or the other. Because the study and control groups were hardly random samples of eligible populations, we must be careful in generalizing the efficacy of physical therapy.1
Crossover may have obscured the benefit of surgery
During the first 6 months, 30% of patients crossed over from physical therapy to surgery. High crossover rates in surgical trials are common, especially when comparing surgery with medical therapy.23 Given that most of the patients assigned to only physical therapy who crossed over to surgery did not have substantial improvement in functional status, it seems that crossover occurred by nonrandom factors, potentially biasing the study results. With the high degree of crossover from the nonoperative group to the surgical group, intention-to-treat analysis may have given an inflated estimate of the effect of physical therapy.
To account for crossovers, researchers defined a binary outcome a priori: patients were considered to have had a successful treatment response if they improved by at least 8 points on the WOMAC scale (a clinically important difference) and did not cross over from their assigned treatment. At 6 months, 67.1% of patients assigned to surgery showed a successful treatment response, compared with 43.8% of patients assigned to physical therapy alone (P = .001).1
In patients who crossed over, the last scores before crossover were carried over, and primary analysis of the WOMAC score at 6 months was repeated to estimate the effect of crossovers from the nonoperative to the surgery group. This exploratory analysis showed a 13.0-point improvement in WOMAC score at 6 months with physical therapy alone vs a 20.9-point improvement with surgery, suggesting that the similarity in outcomes between the two groups may be explained in part by additional improvements from surgery for those who crossed over from physical therapy alone.1
Implications for functional improvement
Lacking a comparison group that underwent a sham surgical procedure, one cannot conclude that surgery after crossover improved functional status in those patients. However, there was no significant difference in WOMAC physical function scores at 12 months between the 30% of patients in the physical therapy group who crossed over and underwent surgery during the first 6 months and patients initially assigned to surgery. This finding suggests that physical therapy can be recommended as a first-line therapy, although we must be cautious, given that the physical therapy group required more background therapy (eg, intra-articular glucocorticoid injections), and that this study was not powered to detect such differences at 12 months.
Also, a patient may need to get better quickly, to get back to work, for example. Although the data were not definitive, at 3 months the patients in the surgery group seemed to have better pain control and function than those in the physical therapy group. A cost-benefit analysis of physical therapy compared with surgery for short-term outcomes may be helpful before generalizing these findings.
SURGERY VS SHAM PROCEDURE: THE FIDELITY GROUP RESULTS
In a later publication from the Finnish Degenerative Meniscal Lesion Study (FIDELITY) Group,24 146 patients with symptoms consistent with degenerative meniscal tear but no knee osteoarthritis were randomized to undergo arthroscopic partial meniscectomy or a sham procedure. At 12 months, no differences were noted between the groups in terms of change of symptoms from baseline to 12 months.
The authors concluded that the outcomes with meniscectomy were no better than with a sham procedure.24
SURGERY FIRST, OR PHYSICAL THERAPY FIRST?
The use of knee arthroscopy has increased sharply in middle-aged patients in recent years. Indeed, this demographic group accounts for nearly half of the knee arthroscopic procedures performed for meniscal tears, although the increase may be due in part to issues with surgeons’ coding and insurance authorization.16
The METEOR trial showed that a structured physical therapy program can be as effective as surgery as a first-line therapy in many patients with symptomatic meniscal tears and mild to moderate osteoarthritis. These results should inform clinical practice in that most such patients need not be immediately referred for surgical intervention.
However, a subset of these patients may benefit from surgery rather than nonoperative therapy. Given the potential risks and public health implications of arthroscopic surgery for meniscal tears, further study is needed to better characterize these patients. A randomized sham-controlled trial is under way25 with the goal of assessing the efficacy of arthroscopic partial meniscectomy for medial meniscus tears in patients with or without knee osteoarthritis, and it is hoped this study will shed further light on this issue.
Based on the results of the METEOR trial, the physical therapy regimen that was used may be reasonable before referring patients with knee osteoarthritis and symptomatic meniscal tears for surgery.
