Meniscus Surgery Criteria Called Into Question

Laird Harrison

February 11, 2016

Surgeons should not necessarily operate on patients with degenerative meniscus tears whose knees catch and lock, researchers say.

In a secondary analysis of data from a randomized controlled trial, such patients fared equally well whether they had sham surgery or arthroscopic partial meniscectomies.

"Taken together, our findings support the evolving concept that degenerative meniscal tears represent an early sign of knee osteoarthritis, rather than a clinically important entity in their own right," write Raine Sihvonen, MD, PhD, from Hatanpää Hospital, Tampere, Finland, and colleagues in an article published online February 9 in the Annals of Internal Medicine.

Surgeons often turn to arthroscopic surgery to treat knee pain attributed to degenerative meniscus tears, performing an estimated 700,000 such procedures each year in the United States, the researchers report.

Previous research has not shown better results for this approach than sham surgery or physical therapy, the researchers write. But they point out that some experts have argued that a subgroup of patients who report locking or catching benefit from the procedure.

In theory, the tear in the meniscus mechanically blocks the knee, and trimming the meniscus can restore the knee's function.

On the basis of this thinking, some official guidelines, including those of the National Institute for Health and Care Excellence ( BMJ. 2008;336:502-503) in the United Kingdom, identify mechanical locking as an indication for surgery.

Yet Dr Sihoven and colleagues could find no studies that assessed the success of surgery in patients with these symptoms. So they analyzed data from their previously published sham-controlled trial, which included such patients.

In the initial eligibility screening for the trial, an orthopedic surgeon excluded the patients who could not fully straighten the knee, a condition they describe as "true locked knee." A true locked knee is usually caused by a traumatic (as opposed to degenerative) "bucket handle" type of meniscus tear, the researchers write, and can be cured by removing or repairing the lesion arthroscopically.

The researchers also excluded those who declined to participate, did not meet anesthesiologic outpatient criteria, or became asymptomatic while waiting for a procedure.

The researchers performed diagnostic knee arthroscopy on all patients, using anterolateral and anteromedial portals and a standard 4-mm arthroscope under spinal or general anesthesia.

They excluded patients who did not have a tear in the medial meniscus and those who had an additional tear in the lateral meniscus, a major chondral flap, a meniscal repair, or an osteochondral microfracture. That left 146 patients aged 35 to 65 years who had knee pain for more than 3 months that was unresponsive to conventional conservative treatment. The researchers then randomly assigned 70 patients to arthroscopic partial meniscectomy and 76 to sham surgery.

The researchers asked all the patients to choose from the following descriptions of their knee: "no locking or catching," "catching but no locking," "occasional locking," "frequent locking," and "locked at present."

To test the reliability of the patients' responses, the researchers asked 40 of the patients to answer the same question 2 weeks later. Thirty-three gave the same responses.

Thirty-two patients in the meniscectomy group and 37 in the sham surgery group reported mechanical symptoms. These two subgroups were similar in age, sex, body mass index, and severity of preoperative mechanical symptoms.

In the meniscectomy group, surgeons used a mechanized shaver and meniscal punches to remove the damaged and loose parts of the meniscus. In the sham group, the surgeons simulated the same procedure, asking for all instruments, manipulating the knee, and pushing a mechanized shaver without its blade against the patella outside the knee. They also used suction.

The two groups did not differ much in outcomes. Of the 146 patients, 34 (49%) in the meniscectomy group and 33 (43%) in the sham surgery group said they had mechanical problems at least once during the 12 months after their procedures. The relative risk was 1.06 (confidence interval [CI], 0.75 - 1.59). The two groups also had similar severity and frequency of mechanical symptoms.

Likewise, meniscectomy seemed to have a similar effect as sham surgery on those patients with preoperative mechanical symptoms. In this subgroup, 23 (72%) who got partial meniscectomies and 22 (59%) who got sham surgery reported mechanical symptoms (relative risk, 1.12; CI, 0.73 - 1.65).

"Our findings should prompt caution in using patients' self-report of mechanical symptoms as an indication for performing [arthroscopic partial meniscectomy]," the authors conclude.

Given these findings, how should clinicians proceed? An accompanying editorial addresses that question.

Jeffrey N. Kattz, MD, from Brigham and Women's Hospital in Boston, Massachusetts, and Morgan H. Jones, MD, MPH, from the Cleveland Clinic in Ohio, point out that clicking and catching may arise from intra-articular debris associated with osteoarthritis, or from the absence of functional meniscal tissue.

A large percentage of middle-aged and older people have musculoskeletal abnormalities. In light of this new research by Dr Sihvonen and colleagues, clinicians should be cautious about attributing musculoskeletal pain to these abnormalities, they write.

But since at least one other trial has shown a benefit of surgery over physical therapy, they argue, clinicians should start by recommending physical therapy and then offer surgery as a second-line treatment, even though the benefits may not be greater than the benefits of a sham procedure.

Dr. Sihvonen reports receiving grants from the Competitive Research Fund of Pirkanmaa Hospital District, the Maire Lisko Foundation and Duodecim/Finnish Medical Foundation, Merck Sharp & Dohme Finland and DePuy Synthes Finland. Other researchers report receiving grants from the Swedish Research Council, Swedish Rheumatism Association, Governmental Funding of Clinical Research within the National Health Service, Lund University, the Jane and Aatos Erkko Foundation, Sigrid Juselius Foundation, Competitive Research Fund of Pirkanmaa Hospital District, and Academy of Finland and personal fees from Amgen. Dr Jones reports receiving grants from the National Institutes of Health. Dr Katz has disclosed no relevant financial relationships.

Ann Intern Med. Published online February 9, 2016. Article abstract, Editorial extract

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