No identifiable group of patients benefits much more from arthroscopic partial meniscectomy than any other group, researchers say.
Analyzing the data on 641 Danish patients, Kenneth Pihl, PhD, at the University of Southern Denmark in Odense, and colleagues found that even patients with traumatic meniscal tears or locked knees were not significantly more likely to benefit from the surgery.
“This essentially quashes the existence of ‘subgroups’ with certain characteristics having a particularly favourable outcome after meniscal surgery,” they write in an article published online December 12 in the British Journal of Sports Medicine.
In randomized clinical trials, middle-aged and older patients who underwent arthroscopic partial meniscectomy fared no better than patients who received sham surgery or who simply performed exercises to improve their knee symptoms.
At the same time, the procedure poses risks of worsening cartilage damage and other adverse events.
Critics of these studies have argued that they don’t include the full range of patients who might be good candidates, such as younger patients with traumatic meniscal tears or locked knees. Even when important groups are included, the number of such patients is often not sufficient to draw statistically significant conclusions, these critics point out.
To see whether certain groups of patients are more likely to benefit, Pihl and colleagues created a statistical model to analyze the relationship between improvement in knee symptoms after the surgery and various prognostic factors.
They used data from the Knee Arthroscopy Cohort Southern Denmark, a prospective cohort that follows patients who undergo knee arthroscopy for a meniscal tear.
The patients, who were aged 18 years and older, were assigned to undergo knee arthroscopy by an orthopedic surgeon on suspicion of a meniscal tear. They were excluded if they did not have a meniscal tear at surgery, had undergone or planned to undergo reconstruction of the anterior or posterior cruciate ligament, or had experienced fracture of lower extremities within the past 6 months.
Using the Knee Injury and Osteoarthritis Outcome Score (KOOS), the researchers evaluated the patients’ symptoms before and a year after the surgery. The KOOS includes subscales with scores from 0 to 100, with 0 representing extreme problems and 100 representing no knee problems.
Pihl and colleagues aggregated the subscales for pain, symptoms, sports and recreational activities, and knee-related quality of life. They omitted the subscale for activities of daily living because of a documented ceiling effect in this subscale. They then compared improvement in KOOS scores on 18 prognostic factors.
The researchers measured the correlation between the prognostic factors and the change in KOOS scores using linear regression, a statistical method in which the changes in one variable are plotted against the changes in another variable.
In this system, r 2 measures the strength of the correlation, such that r 2 = 1.0 is a perfect correlation, with all the data from both variables coinciding on the same line on a graph.
The patients improved an average of 18.6 points on the KOOS (standard deviation, 19.7; range, –38.0 to 87.8).
The apparent r 2 ranged from 0.13 to 0.42. After the model was adjusted to account for the small number of data points for some of the prognostic factors, r 2 ranged from 0.04 to 0.10.
The most significant prognostic factors were previous meniscal surgery, level of education, and knee-related symptoms, such as difficulty twisting/pivoting and inability to straighten the knee fully.
Statistical models that included only patients younger than 41 years showed a greater correlation between the prognostic factors and the change in KOOS scores than models with older patients.
Older patients typically have degenerative meniscal tears, often in combination with other degenerative changes, such as knee osteoarthritis, the researchers point out.
Younger patients are more likely to experience a traumatic meniscal tear, such as through a sports injury, in an otherwise normal joint. As a result, symptoms are more likely to originate from the meniscal tear, resulting in a loss of meniscus function, the researchers say.
The study was supported by the Danish Council for Independent Research.
Br J Sports Med. Published online December 12, 2019. Abstract