The meniscus is vulnerable to degenerative change and injuries, and degenerative meniscal tear (DMT) is the most common type of knee injury in middle-aged and older patients with osteoarthritic knee.1,2 Arthroscopic partial meniscectomy (APM) is one of the most commonly performed procedures in orthopedics but is generally not recommended as initial treatment for symptomatic DMT in the osteoarthritic knee.3,4 It is sometimes preferred in patients with mechanical symptoms in an osteoarthritic knee but is still controversial because some studies could not justify performing APM for a DMT with mechanical symptoms.5–7 In addition, both meniscal injury and a meniscectomy are paradoxically associated with the development of knee osteoarthritis.8–10 Therefore, many patients are being exposed to potential risks associated with a treatment that may or may not offer specific benefits.11
Recently, 3 meta-analyses were published on the outcome after APM for DMT.2,12,13 All 3 meta-analyses included studies that enrolled patients with DMT in knees with moderate to advanced osteoarthritis. Another recent systematic review of the role of APM in knees with degenerative change reported that patients with symptomatic DMT can benefit from APM, particularly if the osteoarthritis is mild.14 It corresponds with the consensus that the presence or absence of osteoarthritis and the degree of arthritis may allow or obviate APM.7 Therefore, it would be logical to analyze the efficacy of the APM according to the degree of arthritis.
Several studies reported that APM has no evidence of benefit in younger people with mild or no osteoarthritic change.3,4 On the contrary, some high-quality studies have examined the benefit of APM in relatively young patients with mild or no knee osteoarthritis.8,15 The purpose of this systematic review and meta-analysis was to evaluate the efficacy of APM for symptomatic DMT in knees with mild or no osteoarthritis. We hypothesized that APM would provide greater improvement in functional activity and pain reduction than conservative treatment or sham operation in knees with mild or no osteoarthritis.
MATERIALS AND METHODS
To test the hypotheses, a rigorous and systematic approach in accordance with the preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines was used.16 In phase 1 of the PRISMA search process, the MEDLINE, EMBASE, and Cochrane database were systematically searched in October 2016. Using a Boolean strategy, all field search terms included the following: Search [(meniscal lesion) OR (meniscal tear) AND (arthroscopy) OR (partial meniscectomy) OR (meniscectomy) NOT (meniscal repair) NOT (meniscal transplantation)]. In phase 2, abstracts and titles were screened for their relevance. In phase 3, the full text of the selected studies was reviewed to assess the inclusion criteria and methodological appropriateness with a predetermined question. The citations in the included studies were screened, and articles not identified in the search were also manually checked. The bibliographies of the relevant articles were subsequently cross-checked for articles not identified in the search. In phase 4, the studies underwent a systematic review process and meta-analysis, if appropriate.
The inclusion criteria were as follows: (1) English language; (2) randomized controlled trial (RCT); (3) comparison between APM and other treatment modalities as a primary objective; and (4) complete DMT in knees with mild or no osteoarthritis (Figure 1). Mild or no osteoarthritis was defined as Kellgren–Lawrence grade 0 to 2 or Ahlbäck 0 to 1 on radiography.8
The following data were extracted: study type, level of evidence, inclusion criteria, exclusion criteria, number of cases, age, sex, clinical score, follow-up, and other relevant findings. The interreviewer agreement was assessed by the calculation of a weighted κ (kappa) for each phase of the abstract and full-text screening, and quality assessment agreement was also evaluated using an intraclass correlation coefficient (ICC).17 The following interpretation of the κ values was selected a priori: a κ value of 0.75 or greater indicates excellent agreement; κ of 0.40 to 0.75, intermediate to good agreement; and κ of 0.40 or lower, poor agreement.
Each of the selected studies was evaluated by 2 independent authors for methodological quality. The methodological quality of the RCT was assessed using risk of bias (ROB), based on the Cochrane handbook, with the following 9 standard criteria: allocation sequence generation, allocation concealment, baseline outcome measurement, baseline characteristics, incomplete outcome data, knowledge of the allocated interventions, protection against contamination, selective outcome reporting, and other ROB. Each criterion was scored as “Yes (low ROB),” “No (high ROB),” or “Unclear.”
Grading of the Quality of the Evidence
In addition to describing the methodological quality of the included studies, evidence was examined using the guidelines of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) working group.18 The GRADE system uses a sequential assessment of evidence quality, followed by an assessment of the risk–benefit balance and a subsequent judgment on the strength of the recommendations. The evidence grades are divided into the following categories: (1) high, which indicates that further research is unlikely to alter confidence in the effect estimate; (2) moderate, which indicates that further research is likely to significantly alter confidence in the effect estimate and may change the estimate; (3) low, which indicates that further research is likely to significantly alter confidence in the effect estimate and may change the estimate; and (4) very low, which indicates that any effect estimate is uncertain. The strengths of the recommendations were based on the quality of the evidence.19
Statistical analysis of the functional activity and pain improvement after APM and conservative treatment or sham operation was performed using R version 3.3.1 (The R Foundation for Statistical Computing). To estimate the standardized mean difference (SMD), the mean and standard deviation values of each group or the P values were used. All results were presented as forest plots. The 95% confidence interval (CI) was calculated for each effect size. The I2 statistic was calculated to determine the percentage of total variation attributable to the heterogeneity among studies, and values of <25%, 50%, and >75% were interpreted as small, moderate, and high levels of heterogeneity, respectively. The random effects model rather than the fixed effects model was used to calculate the effect size because it was assumed that studies within each subgroup did not share a common effect size.
Five articles were included in the final analysis. All were level I studies.15,20–23 Four studies15,20,21,23 compared clinical results of APM and physical therapy, and one study22 compared APM and sham operation. All cases were allocated into either the APM group with 296 cases or the conservative treatment or sham operation group with 284 cases. The follow-up period ranged from 6 months to 5 years. The mean age was 52 to 55 years (weighted mean, 54) for the APM group and 54 to 58 years (weighted mean, 55) for the conservative treatment or sham operation group. Further detailed demographics are presented in Table 1. Studies of knees with only mild or no arthritis (Kellgren–Lawrence grade 0-2 or Ahlbäck < 2) were included, and detailed inclusion and exclusion criteria for each study are presented in Table 2. The reviewers showed substantial agreement in selecting articles for inclusion at the abstract phase, with κ = 0.85 (95% CI, 0.84-0.93), and at the full-text screening phase, with = 1.0.
The details of the quality assessment are presented in Table 3. For 5 (100%) studies, criteria 1, 2, 3, 5, 8, and 9 were scored as “Yes”. Baseline characteristics (criteria 4) were scored as “Yes” in 2 (40%) and “No” in 3 (60%) studies. Allocated intervention (criteria 6) was scored as “Yes” in 3 (60%) and “Unclear” in 2 (40%) studies. Protection against contamination (criteria 7) was scored as “Yes” in 4 (80%) studies and “Unclear” in 1 (20%) study. All articles included in this study showed high quality enough to be scored as “Yes” in most of the assessment. It's probably because all of them were high-quality RCTs.
GRADE Evidence Quality of Each Outcome
GRADE evidence quality of each outcome is shown in Table 4. Two outcomes were evaluated and showed moderate to high-quality evidence.
The clinical results are presented in Table 5. All 5 studies reported clinical results, and all stated that APM does not improve functional activity better than conservative treatment. Functional activities were reported as follows: Lysholm score in 4 studies20–23 and Knee Injury and Osteoarthritis Outcome Score (KOOS) Activity of Daily Living (ADL) in 1 study.15 Pooled analysis was performed by using the follow-up Lysholm scores and KOOS (ADL) in 5 studies. Two different scales were used in pooled analysis, and the SMD was determined. Lysholm score was used when the study contained both Lysholm and KOOS (ADL) data. After pooling of the data, the SMD was 0.01 (95% CI, −0.10 to 0.11); the functional activity did not show statistically significant differences between case and control groups (I2: 0%, small level of heterogeneity) (Figure 2). The study by Gauffin et al15 reported baseline and final results of treatment differently. When the final results were compared, there was no significant difference between APM and the conservative treatment or sham operation group (P = 0.091), although there was a significant different baseline KOOS (ADL) in the 2 groups (P = 0.036).
Pain outcomes are presented in Table 5. Five studies reported pain outcomes, and 4 studies reported that APM does not improve pain better than conservative treatment. Pain was reported using a visual analogue scale (VAS)15,20–23 and KOOS (pain).15,20 KOOS (pain) was used when the study contained both VAS and KOOS (pain) data. Pooled analysis was performed by using the follow-up VAS and KOOS (pain) in 6 studies. After pooling of the data, the SMD was −0.09 (95% CI, −0.23 to 0.06); VAS and KOOS (pain) did not show statistically significant difference between case and control groups (I2: 0∼90%, high level of heterogeneity) (Figure 3).
The study by Gauffin et al15 reported the baseline and final results of treatment differently. When the final results were compared, there were statistically significant differences between the APM and conservative treatment groups (P = 0.009). APM reduced pain better than conservative treatment, as shown by KOOS (pain) (P < 0.001), in a comparison of baseline and final results. However, no statistically significant differences were observed between VAS and KOOS (pain) for all other comparisons.
Other Relevant Findings
Two studies21,23 reported arthritic change after treatment. Herrlin et al21 evaluated arthritic change using Ahlbäck grades. Two of 43 patients in the APM group and 2 of 45 patients in the conservative treatment group had slight progression of osteoarthritis after 5 years. Yim et al23 also reported osteoarthritic progression in 2 of 50 patients in the APM group and 1 of 52 patients in the conservative treatment group by more than one Kellgren–Lawrence grade over a 2-year period.
Two studies21,22 reported that some patients had persistent pain and underwent additional surgery. Herrlin et al21 evaluated 13 patients who underwent APM after conservative treatment. In a comparison of the APM after conservative treatment group with the continued conservative treatment group, the APM group was superior in terms of functional activity and pain reduction. Sihvonen et al22 reported that 2 patients in the APM group and 5 in the conservative treatment group still had pain and underwent additional surgery, but further information on the additional surgery group was not available.
This systematic review and meta-analysis was performed to determine the benefit of APM in relatively young patients with mild or no knee osteoarthritis. The principal findings were as follows: (1) functional activity was not different between the groups; and (2) the pain score was not different between both groups. By using 2 important parameters in the pooled analysis, our hypotheses were denied. Although it is generally accepted that APM is not superior to the conservative treatment for DMT, especially in an osteoarthritic knee, the efficacy in knee with mild or no osteoarthritis remained unclear. Therefore, it was initially hypothesized that APM would be effective in knees with mild or no osteoarthritis because APM has been effectively used in traumatic meniscal tears and DMT of similarly affected knees.
It is generally believed that APM in patients with mild to moderate osteoarthritis results in better outcomes than in patients with severe osteoarthritis.24 El Ghazaly et al7 reported that 70 patients (Kellgren–Lawrence grade 0-2) who had persistent pain and decreased functional activity after conservative treatment achieved significant pain reduction and increased functional activity after APM. Gauffin et al15 also reported that APM reduced pain better than conservative treatment in middle-aged patients with meniscal symptoms. However, this was contradicted by the subgroup analyses of 2 studies included in a meta-analysis by van de Graaf et al,2 in which the severity of osteoarthritis did not influence the outcome. Our results also showed that there was little benefit of APM for DMT, even in knees with mild or no osteoarthritis. However, APM could be a useful treatment option in patients with persistent pain despite conservative treatment. Herrlin et al21 reported that APM had effects on the improvement of the functional activity and reduction of pain in the patients who did not respond to the conservative treatment for 2 months.
Three meta-analyses2,12,13 compared APM and conservative treatment for DMT. However, these 3 meta-analyses included some knees with advanced osteoarthritis. All reported that APM was not superior to conservative treatment in all subscales, but each included knees with advanced osteoarthritis. Khan et al12 performed meta-analysis using 7 RCTs; among the RCTs, the study by Katz et al3 included advanced osteoarthritis (Kellgren–Lawrence grade 0-3), and the study by Vermesan et al25 included grade 3 and 4 patients, despite stating that only grade 0 and 1 were included. In the meta-analysis of Thorlund et al,13 Moseley et al26 included all grades of osteoarthritis, and Kirkley et al4 studied advanced osteoarthritis (Kellgren–Lawrence grade 2-4). The study by Katz et al3 was also included in this meta-analysis. The meta-analysis by Victor et al2 evaluated 6 RCTs, including the study by Katz's et al.3 Accordingly, we performed a meta-analysis using knees with only mild or no osteoarthritis to determine the effect of APM. An additional reason for this meta-analysis was that more recent studies on APM might change the results of a previous meta-analysis.15
This article has some strengths. First, this systematic review and meta-analysis included only level I and RCT studies, and most of the results were consistent. Second, our study included the result of knees with only mild or no osteoarthritis. Limitations should also be considered. First, each study used various scales to assess functional activity and pain. In addition, some results did not report standard deviations. Therefore, a comparative meta-analysis was impossible, as this was a source of bias. Second, each study had a different follow-up period, making comparison of the results at specific time points impossible. Third, we analyzed 5 studies, but 2 of them20,21 were published by the same study group using different follow-up periods, so the results were similar. Fourth, some studies13,21 changed their treatment methods because of patient dissatisfaction, but further information on additional surgery was unavailable. Fifth, conservative treatment such as physical therapy and medication after the APM surgery could also be performed in the APM group. Although physiotherapy and medication are followed by the APM, they are not the main treatments to determine the outcomes of the patients who received surgeries. In the APM group, physiotherapy and medication are usually intended for the postoperative recovery. However, in the conservative treatment or sham operation group, physiotherapy and medication are applied to patients as a definitive treatment for DMT.
This systematic review and meta-analysis of high-quality literature provides relatively strong evidence that APM did not improve functional activity or reduce pain compared with the results with conservative treatment or sham operation in knees with mild or no osteoarthritis.
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