Purpose
To report the percentages of full-thickness meniscal tears per anterior cruciate ligament reconstruction (ACLR) at the time of primary ACLR and the contributions of individual tear patterns, specifically ramp lesions and root tears, to the overall prevalence of tears.
Methods
This retrospective cross-sectional study included patients from 2007 to 2021. The inclusion criteria were patients who underwent primary ACLR. Patients were excluded if they had suffered from multiligamentous injuries, were skeletally immature, or had missing information regarding the outcomes. The outcomes included the presence of full-thickness meniscal tears detected during arthroscopy, the tear pattern according to the International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine classification, and the time between injury and ACLR. Follow-up data were not collected.
Results
Among 731 patients, 606 were male, and 125 were female. The mean age was 28 ± 8 years, with an average time between injury and surgery of 539 ± 988 days. The primary causes of injury were soccer (38%) and basketball (32%). Medial meniscal (MM) tears occurred in 43.7% knees, while lateral meniscal (LM) tears occurred in 47.5% of patients. Ramp lesions accounted for 46.9% of all MM tears, and root tears accounted for 15.8% of all LM tears. As the time from injury to ACLR increased, MM tears significantly increased ( P <.001). However, the time between injury and ACLR was not able to discriminate between the presence or absence of lateral meniscus tears ( P = 0.84), ramp lesions ( P =.06), or root tears ( P =.16).
Conclusions
Aside from the initial 3 months postinjury, the percentage of medial meniscal tears per ACLR steadily increases with increasing time elapsed from injury to surgery, whereas the percentage of lateral meniscal tears per ACLR remains unchanged. Increased surgical delay is not associated with a higher chance of ramp lesions or lateral meniscus root tears observed at the time of primary ACLR.
Level of Evidence
Level III: Retrospective cross-sectional study.
There has been a rapid increase in the number of publications about meniscal tears at the time of anterior cruciate ligament reconstruction (ACLR) over the past 10 to 15 years, particularly those concerning ramp lesions of the medial meniscus ,,,,,,,, and root tears of the lateral meniscus. ,,,,,,,,, Ramp lesions are commonly defined as longitudinal tears of the red–red zone of the posterior horn of the medial meniscus and may involve disruption of the meniscocapsular junction or meniscotibial ligament. This disruption may be associated with a loss of the stabilizing function of the medial meniscus against anterior translation, especially in the scenario of ACL deficiency, , which may potentially increase the chance of graft rupture in patients who undergo ACLR. On the other hand, root tears are meniscal tears that occur at the root of the meniscus or within 9 mm of the root. Over 85% of the root tears are complete radial tears of the lateral meniscus. A complete root tear is believed to result in a loss of hoop stress within the meniscus and subsequent meniscus extrusion, leading to a higher chance of early osteoarthritis. , The reported rate of meniscal tears found at the time of primary ACLR ranged from 9% to 41.7% for medial meniscal ramp lesions ,, and 5.1% to 33.8% for lateral meniscal root tears. ,
Longitudinal tears are the most common tear pattern of meniscal tears found at the time of ACLR, regardless of whether it is the medial meniscus or the lateral meniscus. ,, The reported rate of longitudinal tears ranges from 11.7% to 41.2%. ,,,,, On the other hand, radial tears of the lateral meniscus have been historically considered uncommon, with a reported prevalence of less than 2%. While ramp lesions are a type of longitudinal tear, and most root tears are radial tears, given that the average pooled reported rates of ramp lesions and root tears in systematic reviews can be as high as 21.9% and 9.6%, respectively, it is possible that some of the previous literature ,,,,, has under-reported the rate of medial and lateral meniscal tears due to the omission of the ramp and root lesions.
In addition, despite the large number of publications relating to ramp lesions ,,, or root tears, ,,,,, few studies have quantified the contribution of these specific tear patterns to the overall prevalence of medial and lateral meniscal tears found at primary ACLR. ,,, There is a need to update the current literature by providing a detailed report of the relative contributions of individual tear patterns to the overall prevalence of meniscal tears observed at the time of ACLR.
The purpose of this study was to report the percentages of full-thickness meniscal tears per ACLR at the time of primary anterior cruciate ligament reconstruction and the contributions of individual tear patterns, specifically ramp lesions and root tears, to the overall prevalence of tears. The hypotheses are (1) there is no difference in the proportion of specific meniscal tear patterns between the medial and lateral meniscus; and (2) there is no association between the presence of a meniscal tear, including ramp lesions and root tears, and the time between injury and ACLR.
Methods
This is an Institutional Review Board (IRB)-approved retrospective cohort study based on prospectively collected data for patients who underwent ACLR at a single institute from July 1, 2007, to December 31, 2021. The current study was approved by the local ethic committees: IRB of the University of Hong Kong/ Hospital Authority Hong Kong and West Cluster (HKU/HA HKW IRB; approval document number: UW 25-192). The data were prospectively documented using a standard research documentation form, designed for the use in other studies conducted at the author’s institute. The need to obtain informed consent from the participants was waived by the local ethics committee. Patients were included in the study if they underwent primary ACLR. Patients were excluded if (1) they suffered from multiligamentous knee injuries; (2) they were skeletally immature at the time of ACLR; (3) there was missing information regarding the time between injury and surgery; or (4) there was missing information regarding the pattern of meniscal tears.
Preoperative Assessment
Patients were assessed in a preoperative assessment clinic 1 week prior to their scheduled surgery. Demographic data, including age, sex, as well as information such as the preinjury Tegner Activity Scale (TAS), the type of sport or activity that led to the injury, and the time between injury and ACLR. Activity leading to injury was classified according to the IKDC classification into very strenuous, strenuous, moderate, and light.
Surgical Procedure
The surgeries were performed by one of the two sports medicine surgeons, including the author (W.P.Y.). Patients were placed under general anaesthesia in a supine position. A pneumatic tourniquet was applied to the proximal thigh and inflated to a pressure of 250 mm Hg. Standard anterolateral and anteromedial portals were created. Diagnostic arthroscopy was then performed with a 30° arthroscope. The site and pattern of the full-thickness tear of the meniscus were documented by the surgeon, according to the International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine (ISAKOS) classification. Treatment of the meniscal tears was then performed before ACLR.
Study Outcomes
The primary outcome of this study was the presence of full-thickness medial and lateral meniscal tears at the time of diagnostic arthroscopy. Knees were classified as having a medial or lateral meniscal tear based on the presence of a tear in the respective area, regardless of any tear in the opposite meniscus. Knees with meniscal tears were defined as knees having a full-thickness meniscal tear in either the medial, lateral, or both menisci. The secondary outcomes were (1) the site of tear, (2) the pattern of tear, and (3) the time between injury and ACLR. The site of the tear was recorded according to whether it was in the anterior horn, body, posterior horn, or a combination of the aforementioned. Tear patterns were categorized according to a modification of the ISAKOS classification, into longitudinal tears (including bucket-handle tears but excluding ramp lesions), horizontal tears, radial tears (excluding root tears), ramp lesions (if it was the medial meniscus), root tears, and other tears, which are generally irreparable (complex tears, beak tears, flap tears, degenerative tears, and meniscal tears with tissue loss). Ramp lesions were defined as longitudinal lesions occurring at the red–red zone of the posterior horn of the medial meniscus. Root tears were defined as tears located at the root of the meniscus or within 9 mm from the root, involving either the anterior or posterior horns of the meniscus. All this information was prospectively documented at the time of surgery using a standardized research documentation form completed by the surgeons. In addition, the number of ramp lesions and root tears were reported according to the Sonnery-Cottet and LaPrade classification systems, respectively. For cases performed before the publication of these studies (i.e., before 2016), the subtypes of ramp lesions and root tears were retrospectively classified by reviewing operative videos and medical records. Starting from 2016, data regarding the subtypes were prospectively documented alongside other information during the procedures. Time between injury and ACLR was recorded in days and was subsequently grouped into the following intervals: 0 to 3 months, 4 to 6 months, 7 to 12 months, 13 to 24 months, 25 to 60 months and >60 months. ,,
Data Analysis
Descriptive data regarding the demographic data, the cumulative total of ACLRs, the number of meniscal tears, including the site and pattern of the tears, and the time between injury and ACLR were reported. The percentage of meniscal tears per ACLRs were provided. TAS and the most common sport activities leading to the injury were presented. The contribution of ramp lesions to the medial meniscal tears is calculated as the proportion of the number of ramp lesions in relation to the number of medial meniscal tears (%). The same method is applied for root tears and lateral meniscal tears. The percentage of medial and lateral meniscal tears per ACLR were compared using the χ 2-test. Subsequently, the percentage of specific tear patterns per ACLR were compared between the medial and lateral meniscus using the χ 2-test. The relationship between the rate of meniscal tears and the time between injury and ACLR (in days) was examined using Pearson correlation. The strength of correlation is considered weak when the r value is between 0.1 and 0.3, moderate between 0.3 and 0.5, strong between 0.5 and 0.7, and very strong between 0.7 and 1. Logarithmic transformation was applied to the time between injury and ACLR. The relationship between the percentage of meniscal tears per ACLRs and time was visualized using scatterplots. If a significant association was identified using Pearson correlation, receiver operating characteristic analysis was conducted to evaluate the ability of the time (in days) to discriminate between the presence and absence of a meniscal tear. Linear regression analysis was performed to examine the change in the percentage of meniscal tears per ACLR over time, and R 2 was reported to represent the proportion of variance in the dependent variable explained by time in the regression model. Standardized β was reported. Additionally, time was also categorized into discrete intervals: 0–3 months, 4–6 months, 7–9 months, 10–12 months, 13–24 months, 25–60 months, and >60 months. The acute, subacute, and chronic settings were defined as 0-3 months, 4-12 months, and >12 months, respectively. The relationship between the percentage of meniscal tears per ACLR and the aforementioned time periods was assessed using the χ 2 test. The difference in the time from injury to ACLR between patients with medial and lateral meniscal tears was analyzed using Kaplan–Meier survival analysis, with the log-rank, Breslow, and Tarone-Ware tests to assess statistical significance. The relationship between the proportion of ramp lesions among medial meniscal tear and time was examined using scatterplots. The same approach was applied to analyze the proportion of root tears among lateral meniscal tears. P <.05 was defined as statistically significant. Finally, the data were disaggregated by sex and reported.
Power Analysis
Erard et al. reported on meniscal tears, according to the ISAKOS classification, which does not specifically include ramp lesions. The reported percentage of longitudinal tears per ACLR, including bucket-handle tears, in the medial meniscus was 21.6%. Giurazza et al. reported the percentage of medial meniscal tears per ACLR classified as vertical lesions, bucket-handle lesions, ramp lesions, flap lesions, and complex lesions. The combined percentage for vertical lesions, bucket-handle lesions, and ramp lesions per ACLR, as reported by Giurazza et al., was 32.5%. To detect a clinically important increase of 10.9% by including the ramp lesions in the classification of meniscal tears, with a power of 80% and an α of 0.05, a minimum of 520 knees were required.
Results
731 patients were included in the analysis ( Fig 1 ). 606 (83%) were male and 125 (17%) were female, with an average age of 28 ± 8 years. The time between injury and ACLR was 539 ± 988 days, with a median of 204 days and an interquartile range from 109 to 492 days. The preinjury Tegner activity scale was 6.5 ± 1.3. Ninety-one percent of patients were injured while participating in a pivoting sport. The most common activity leading to the injury was soccer (38%), followed by basketball (32%).
Enrolment of subjects. ACLR, anterior cruciate ligament reconstruction; n, number.
Site of Meniscal Tear
Meniscal tears were found in 508 knees, accounting for 69.4% of primary ACLR. Of the 731 knees, 320 (43.7%) had medial and 348 (47.5%) had lateral meniscal tears; these percentages did not differ significantly ( P =.208). Regarding the tear site, tears most commonly occurred at the posterior horn in isolation ( P <.001), followed by the body and the posterior horn ( P <.001) ( Table 1 ).
Table 1
Sites of Meniscal Tears
| Site of Tear | Medial Meniscus | Lateral Meniscus |
|---|---|---|
| Anterior horn | 3 | 5 |
| 0.4% | 0.7% | |
| Body | 8 | 26 |
| 1.1% | 3.5% | |
| Posterior horn | 201 | 247 |
| 27.5% | 33.8% | |
| Body + posterior horn | 96 | 59 |
| 13.1% | 8% | |
| Anterior horn + body + posterior horn | 8 | 7 |
| 1.1% | 1% | |
| Anterior horn + body | 1 | 1 |
| 0.1% | 0.1% | |
| Anterior horn + posterior horn | 3 | 3 |
| 0.4% | 0.4% |
% refers to the percentage in relation to the total number of anterior cruciate ligament reconstructions.
Pattern of Meniscal Tears
The distribution of tear patterns relative to the medial or lateral meniscus is shown in Fig 2 . The percentage of different tear patterns per ACLR was comparable between the medial and lateral menisci ( Fig 2 ). Out of 731 knees, 122 were found to have longitudinal tears (excluding ramp lesions) (16.7%), and 150 had ramp lesions (20.5%) in the medial meniscus. With regard to the lateral meniscus, 161 longitudinal tears (22%), 55 root tears (7.5%) and 26 radial tears (3.6%) were found.
Comparison of tear patterns between medial and lateral menisci. Radial tears do not include root tears, while other tears include beak tears, flap tears, complex tears, degenerative tears, and tears with loss of meniscus tissue. % refers to the percentage rates of meniscal tear in relation to all anterior cruciate ligament reconstructions. P is the value of the statistical comparison of the corresponding tear pattern between medial and lateral meniscus.
Among the 150 ramp lesions, according to the Sonnery-Cottet classification, 15% were type 1, 5% were type 2, 3% were type 3, 69% were type 4, and 8% were type 5. Regarding the 55 root lesions of the lateral meniscus, 2 were anterior horn root tears and 53 were posterior horn root tears. According to the LaPrade classification, 30.9% were type I, 25.5% were type II, 9.1% were type III, 32.7% were type IV, and 1.8% were type V.
Relationship Between Meniscal Tears and Time Between Injury and Surgery
Figure 3 depicts the relationship between the percentage of meniscal tears per ACLR and the time elapsed between injury and ACLR, as well as the comparison of the rates of medial and lateral meniscal tears over time as a continuous variable. The relationship between meniscal tears and the time elapsed from injury to ACLR in days is reported in Table 2 . There was a moderate to strong positive correlation between the percentage of medial meniscal tears per ACLR and the time elapsed from injury to ACLR. Weak correlations were observed between time and the percentages of lateral meniscal tears, ramp lesions, and root tears per ACLR. When treating time as a continuous variable, it was able to distinguish the presence or absence of medial meniscal tears, but not for the other lesion types. The percentage of medial meniscal tear per ACLR increased with time ( p <.001), accounting for 33% of the variance ( Table 2 ). In contrast, the percentage of lateral meniscal tear per ACLR was high initially. It began to decrease around 100 days after the initial injury leading to the ACL tear. Subsequently, the tear percentage remained stable despite further increases in the time between injury and ACL reconstruction ( Fig 3 ). A significant difference was observed between the percentages of medial and lateral meniscal tears per ACLR (Breslow test, P =.006; Tarone-Ware test, P =.029) ( Fig 3 ).
Comparison of the percentages of medial and lateral meniscal tears per anterior cruciate ligament reconstruction (ACLR) in relation to time between injury and ACLR.
Table 2
The relationship between meniscal tears and the time between injury and ACLR (in days).
| Medial Meniscal Tears | Lateral Meniscal Tears | Medial Meniscus Ramp Lesions | Lateral Meniscus Root Tears | |
|---|---|---|---|---|
| Pearson correlation | r = 0.57 (P <.001∗) | r = −0.24 (P <.001∗) | r = 0.33 (P <.001∗) | r = −0.13 (P <.001∗) |
| ROC analysis | AUC = 0.64 (P <.001∗) | AUC = 0.50 (P =.84) | AUC = 0.55 (P =.06) | AUC = 0.56 (P =.16) |
| Regression analysis | R 2 = 0.33 | R 2 = 0.06 | R 2 = 0.11 | R 2 = 0.13 |
| standardized beta = 0.57∗ | − | − | − |
AUC, area under curve; r, correlation coefficient; ROC, receiver operating characteristics analysis; R 2, proportion of variance in the dependent variable explained by the regression model. An asterisk denotes statistical significance.– indicates not performed.
Figure 4 depicts the relation between ramp lesions and medial meniscal tears in relation to the time between injury and ACLR.
Contribution of ramp lesion to medial meniscal tear. (A) Comparison of the percentages of medial meniscal tears and ramp lesions in relation to the time between injury and anterior cruciate ligament reconstruction (ACLR). (B) Proportion of ramp lesions among medial meniscal tears in relation to the time between injury and ACLR.
There were a total of 150 ramp lesions, accounting for 20.5% of the ACLRs ( Table 3 ). The percentage of ramp lesions per ACLR increased to a peak around 100 days and then remained relatively unchanged over time ( Table 3 ). Ramp lesions accounted for 46.9% of the observed total number of medial meniscal tears ( Fig 4 B). The proportion of ramp lesions among medial meniscal tears was highest (73%) during the second and third month after injury. Subsequently, there was a progressive decline in the contribution of ramp lesions to the medial meniscal tears, decreasing to 46.9% over time. Figure 5 depicts the relation between root tears and lateral meniscal tears in relation to the time between injury and ACLR.
Table 3
Distribution of Tear Patterns in Relation to the Medial or Lateral Meniscus and Time Between Injury and ACLR
| Total |
0-3
Months |
4-6
Months |
7-9
Months |
10-12
Months |
13-24
Months |
25-60
Months |
>60
Months |
P Value | |
|---|---|---|---|---|---|---|---|---|---|
| Number of knees | 731 | 140 | 199 | 103 | 59 | 103 | 77 | 50 | |
| Knees with medial meniscal tears | 320 | 40 | 71 | 44 | 24 | 56 | 51 | 34 | P <.001∗ |
| 43.7% | 28.6% | 35.7% | 42.7% | 40.0% | 54.4% | 66.2% | 68.0% | ||
| Longitudinal tears | 122 | 12 | 25 | 22 | 12 | 23 | 16 | 12 | P =.017∗ |
| 16.7% | 8.6% | 12.6% | 21.4% | 20.0% | 22.3% | 20.8% | 24.0% | ||
| Horizontal tears | 2 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | P =.40 |
| 0.3% | 0.0% | 0.0% | 0.0% | 0.0% | 1.0% | 1.3% | 0.0% | ||
| Radial tears | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | — |
| 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | ||
| Ramp lesions | 150 | 24 | 38 | 20 | 9 | 23 | 22 | 14 | P =.33 |
| 20.5% | 17.1% | 19.1% | 19.4% | 15.0% | 22.3% | 28.6% | 28.0% | ||
| Root lesions | 4 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | P =.71 |
| 0.5% | 0.7% | 0.5% | 0.0% | 1.7% | 0.0% | 1.3% | 0.0% | ||
| Other tears | 42 | 3 | 7 | 2 | 2 | 9 | 11 | 8 | P <.001∗ |
| 5.7% | 2.1% | 3.5% | 1.9% | 3.3% | 8.7% | 14.3% | 16.0% | ||
| Knees with lateral meniscal tears | 348 | 75 | 85 | 47 | 21 | 52 | 39 | 29 | P =.086 |
| 47.5% | 53.6% | 42.7% | 45.6% | 35.0% | 50.5% | 50.6% | 58.0% | ||
| Longitudinal tears | 161 | 35 | 39 | 28 | 11 | 22 | 20 | 6 | P =.24 |
| 22.0% | 25.0% | 19.6% | 27.2% | 18.3% | 21.4% | 26.0% | 12.0% | ||
| Horizontal tears | 14 | 0 | 2 | 0 | 3 | 0 | 3 | 6 | P <.001∗ |
| 1.9% | 0.0% | 1.0% | 0.0% | 5.0% | 0.0% | 3.9% | 12.0% | ||
| Radial tears | 26 | 7 | 6 | 1 | 0 | 8 | 1 | 3 | P =.07 |
| 3.6% | 5.0% | 3.0% | 1.0% | 0.0% | 7.8% | 1.3% | 6.0% | ||
| Root lesions | 55 | 14 | 17 | 8 | 2 | 7 | 3 | 4 | P =.54 |
| 7.5% | 10.0% | 8.5% | 7.8% | 3.3% | 6.8% | 3.9% | 8.0% | ||
| Other tears | 92 | 19 | 21 | 10 | 5 | 15 | 12 | 10 | P =.45 |
| 12.6% | 13.6% | 10.6% | 9.7% | 8.3% | 14.6% | 15.6% | 20.0% |
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