Management of Partial Tears of the Anterior Cruciate Ligament: A Review of the Anatomy, Diagnosis, and Treatment

Mesenchymal stem cell-derived extracellular vesicles in joint diseases: Therapeutic effects and underlying mechanisms

Joint diseases greatly impact the daily lives and occupational functioning of patients globally. However, conventional treatments for joint diseases have several limitations, such as unsatisfatory efficacy and side effects, necessitating the exploration of more efficacious therapeutic strategies. Mesenchymal stem cell (MSC)-derived EVs (MSC-EVs) have demonstrated high therapeutic efficacyin tissue repair and regeneration, with low immunogenicity and tumorigenicity. Recent studies have reported that EVs-based therapy has considerable therapeutic effects against joint diseases, including osteoarthritis, tendon and ligament injuries, femoral head osteonecrosis, and rheumatoid arthritis. Herein, we review the therapeutic potential of various types of MSC-EVs in the aforementioned joint diseases, summarise the mechanisms underlying specific biological effects of MSC-EVs, and discuss future prospects for basic research on MSC-EV-based therapeutic modalities and their clinical translation. In general, this review provides an in-depth understanding of the therapeutic effects of MSC-EVs in joint diseases, as well as the underlying mechanisms, which may be beneficial to the clinical translation of MSC-EV-based treatment. The translational potential of this article: MSC-EV-based cell-free therapy can effectively promote regeneration and tissue repair. When used to treat joint diseases, MSC-EVs have demonstrated desirable therapeutic effects in preclinical research. This review may supplement further research on MSC-EV-based treatment of joint diseases and its clinical translation.

The angle of the lower portion of the posterior cruciate ligament assists in the diagnosis of partial anterior cruciate ligament tears

PURPOSE

To compare the difference of angle of the lower portion of the posterior cruciate ligament (PCL) measured via magnetic resonance imaging (MRI) in patients with and without partial anterior cruciate ligament (ACL) tears and to investigate the effectiveness of the angle of the lower portion of the PCL in diagnosing partial ACL tears.

METHODS

From January 2022 to December 2022, a cohort of consecutive patients presenting with ACL tears who underwent ACL reconstruction and patients with isolated meniscus tears undergoing arthroscopic surgery were enroled for this study. The angle of the inferior portion of the PCL comprises α and β angles, and the posterior offset of the lateral condyle were measured on the MRI and compared between the partial ACL tear and control groups. Receiver operating characteristic curves, the areas under the curve (AUCs) and the 95% confidence intervals (CIs) were calculated to identify cutoff values for diagnosing partial ACL injuries.

RESULTS

Following an assessment of cohort eligibility and matching for age and sex, 100 patients were included in this study. The mean age of the cohort was 46.1 ± 10.3 years. The AUC for the α angle was 0.88 (95% CI, 0.82-0.94), with a sensitivity of 0.74 and specificity of 0.84 for predicting partial ACL ruptures; the α angle cutoff value was 73.6° (diagnostic odds ratio (OR), 14.10; 95% CI, 5.33-37.28). The AUC for the β angle was 0.86 (95% CI, 0.79-0.93), with a sensitivity of 0.64 and a specificity of 0.92 for predicting partial ACL ruptures; the β angle cutoff value was 73.3° (diagnostic OR, 14.54; 95% CI, 5.76-36.68).

CONCLUSIONS

A small α angle and a large β angle were associated with partial ACL tears. The angle of the distal portion of the PCL was simple to measure and reproducible, enhancing the diagnosis of partial ACL tears.

LEVEL OF EVIDENCE

Level III.

Reproducibility of the native ACL mid-substance cross-sectional area in anatomical single bundle ACL reconstruction

Purpose

The purpose of this study was to evaluate the reproducibility of the native anterior cruciate ligament (ACL) mid-substance cross sectional area in anatomic single-bundle ACL reconstruction.

Methods

Fifty-eight subjects who were performed anatomic single-bundle ACL reconstruction were included. Cross section size of the ACL graft was calculated from the graft diameter during surgery. Computed tomography (CT) of the knee was performed pre-operatively. Following Iriuchishima's report, native ACL size was estimated from the axial CT image of intercondylar notch area of femur at the most distal level of Blumensaat's line (In the report, native ACL size was equal to 14% of the intercondylar notch area of femur). The measured ACL graft cross-sectional size and estimated native ACL size were compared and correlation was evaluated.

Results

Measured ACL graft cross-sectional size was 49 ± 14 mm2. Measured intercondylar notch area of femur at the most distal level of Blumensaat's line was 372 ± 91.6 mm2, and estimated native ACL size was 53 ± 12.5 mm2. Measured ACL graft cross-section and estimated native ACL showed no significant size difference. Measured ACL graft cross-section and estimated native ACL had no significant size correlation.

Conclusion

Native ACL cross-sectional size was reproduced in anatomic single-bundle ACL reconstruction. However, as measured ACL graft and estimated native ACL showed no size correlation, it is possible that size of native ACL might not be reproduced. Such cases would be susceptible to the risk of graft impingement or knee instability.

Principles of musculoskeletal sport injuries for epidemiologists: a review

BACKGROUND

Musculoskeletal injuries are a common occurrence in sport. The goal of sport injury epidemiology is to study these injuries at a population level to inform their prevention and treatment.

MAIN BODY

This review provides an overview of musculoskeletal sport injuries and the musculoskeletal system from a biological and epidemiologic perspective, including injury mechanism, categorizations and types of sport injuries, healing, and subsequent injuries. It is meant to provide a concise introductory substantive background of musculoskeletal sport injuries for epidemiologists who may not have formal training in the underlying anatomy and pathophysiology.

CONCLUSION

An understanding of sport injuries is important for researchers in sport injury epidemiology when determining how to best define and assess their research questions and measures.

The potential of posterior cruciate ligament buckling phenomenon as a sign for partial anterior cruciate ligament tears

INTRODUCTION

Diagnosis of a partial tear of the anterior cruciate ligament (ACL) can be challenging with physical examination and imaging techniques. Although magnetic resonance imaging (MRI) has high sensitivity and specificity for diagnosing complete ACL tears, its effectiveness may be limited when it is used to diagnose for partial tears. The hypothesis of the present study is that the posterior cruciate ligament (PCL) buckling phenomenon, which is a secondary sign of complete ACL tears on MRI, may be a useful method for diagnosing partial ACL tears.

MATERIALS AND METHODS

The data of 239 patients who underwent knee arthroscopy in a single institution between 2016 and 2022 were analyzed retrospectively. Patients were divided into three groups based on the condition of their ligaments: partial tears, complete tears and intact ligaments. To evaluate the buckling phenomenon on sagittal T2-weighted MRI, measurements of the posterior cruciate ligament angle (PCLA) and the posterior cruciate ligament-posterior cortex angle (PCL-PCA) were conducted in each group. Subsequently, the ability of these two measurement methods to distinguish partial tears from the other groups was assessed.

RESULTS

Both methods provided significantly different results in all three groups. Partial tears could be distinguished from intact ligaments with 86.8% sensitivity, 89.9% specificity when PCLA < 123.13° and 94.5% sensitivity, 93.2% specificity when PCL-PCA < 23.77°. Partial tears could be distinguished from complete tears with 79.5% sensitivity, 78.4% specificity when PCLA > 113.88° and with 86.1% sensitivity, 85.3% specificity when PCL-PCA > 16.39°.

CONCLUSION

The main finding of the present study is that the PCLA and PCL-PCA methods are useful on MRI for diagnosing partial ACL tears. PCLA value between 113°-123° and PCL-PCA value between 16°-24° could indicate a partial ACL tear. With these methods, it is possible to distinguish partial tears from healthy knees and reduce missed diagnoses. In addition, the differentiation of partial and complete tears by these methods may prevent unnecessary surgical interventions.

LEVEL OF EVIDENCE

Level III.

Medial meniscal lesions increase antero-posterior laxity in knees with anterior cruciate ligament injury

PURPOSE

The aim of this study was to quantify the impact of concomitant meniscal lesions on knee laxity using a triaxial accelerometer in a large population of patients affected by anterior cruciate ligament (ACL) injury.

METHODS

A total of 326 consecutive patients (261 men and 65 women, mean age 31.3 ± 11.3) undergoing primary ACL reconstruction, were preoperatively evaluated through Lachman and pivot shift tests using a triaxial accelerometer to quantify knee laxity. An analysis based on the presence of meniscal tears assessed during surgery was performed to evaluate the impact of meniscal lesions on knee laxity.

RESULTS

The anterior tibial translation (Lachman test) presented significantly higher values in patients with medial meniscal lesions (7.3 ± 1.7 mm, p = 0.049) and both medial and lateral meniscal lesions (7.7 ± 1.6 mm, p = 0.001) compared to patients without concomitant meniscal lesions (6.7 ± 1.3 mm). Moreover, patients with both medial and lateral meniscal lesions presented significantly higher values of anterior tibial translation compared to patients with lateral meniscal lesions (p = 0.049). No statistically significant differences were found between the groups in terms of tibial acceleration (pivot shift test).

CONCLUSION

This study demonstrated that the contribution of concomitant meniscal lesions to knee laxity can be objectively quantified using a triaxial accelerometer in ACL-injured knees. In particular, medial meniscus lesions, alone or in association with lateral meniscus lesions, determine a significant increase of the anterior tibial translation compared to knees without meniscus tears.

LEVEL OF EVIDENCE

Level IV.

Risk factors for secondary meniscus tears can be accurately predicted through machine learning, creating a resource for patient education and intervention

PURPOSE

This study sought to develop and internally validate a machine learning model to identify risk factors and quantify overall risk of secondary meniscus injury in a longitudinal cohort after primary ACL reconstruction (ACLR).

METHODS

Patients with new ACL injury between 1990 and 2016 with minimum 2-year follow-up were identified. Records were extensively reviewed to extract demographic, treatment, and diagnosis of new meniscus injury following ACLR. Four candidate machine learning algorithms were evaluated to predict secondary meniscus tears. Performance was assessed through discrimination using area under the receiver operating characteristics curve (AUROC), calibration, and decision curve analysis; interpretability was enhanced utilizing global variable importance plots and partial dependence curves.

RESULTS

A total of 1187 patients underwent ACLR; 139 (11.7%) experienced a secondary meniscus tear at a mean time of 65 months post-op. The best performing model for predicting secondary meniscus tear was the random forest (AUROC = 0.790, 95% CI: 0.785-0.795; calibration intercept = 0.006, 95% CI: 0.005-0.007, calibration slope = 0.961 95% CI: 0.956-0.965, Brier's score = 0.10 95% CI: 0.09-0.12), and all four machine learning algorithms outperformed traditional logistic regression. The following risk factors were identified: shorter time to return to sport (RTS), lower VAS at injury, increased time from injury to surgery, older age at injury, and proximal ACL tear.

CONCLUSION

Machine learning models outperformed traditional prediction models and identified multiple risk factors for secondary meniscus tears after ACLR. Following careful external validation, these models can be deployed to provide real-time quantifiable risk for counseling and timely intervention to help guide patient expectations and possibly improve clinical outcomes.

LEVEL OF EVIDENCE

III.

Is augmentation the best solution in partial anterior cruciate ligament tears? A literature systematic review and meta-analysis

Purpose

The appropriate management of partial anterior cruciate ligament (ACL) tears is still debated. There is a tendency in orthopedic clinical practice to prefer complete ACL reconstruction, while few surgeons perform ACL augmentation. The purpose of the present study is to evaluate the current evidence on the effectiveness of ACL augmentation compared with standard ACL reconstruction to assess whether ACL augmentation may be the treatment of choice in partial ACL injury.

Methods

According to PRISMA guidelines, literature research was performed in PubMed/Medline, Cochrane Library, Embase, Scopus, and Web of Science databases. A PICOS model was used, and a preliminary search resulted in 1101 articles. The methodological quality was assessed through ROBINS-I. A meta-analysis was conducted on postoperative Tegner, Lysholm scores and KT-1000 values between ACL augmentation and ACL reconstruction, and a p < 0.05 has been assumed as statistically significant. PROSPERO, ID: CRD42022343502.

Results

Seven papers were included. A total of 472 knees underwent ACL reconstruction, and 311 underwent ACL augmentation. A statistically significant discrepancy was found in the postoperative Tegner score in favor of ACL augmentation compared with ACL reconstruction (p < 0.05). Regarding the postoperative Lysholm score and KT-1000 measurement, no statistically significant difference was shown between ACL reconstruction and ACL augmentation (p > 0.05).

Conclusions

ACL augmentation has proved to be an effective and safe procedure and should be preferred to ACL reconstruction in partial ACL tears for the tendency to achieve better functional outcomes.

Selective bundle versus complete anterior-cruciate ligament reconstruction: A systematic review and meta-analysis

Purpose

Selective bundle reconstruction (SLB) refers to preservation of the intact bundle and reconstruction of the ruptured bundle in a partial tear while complete ACL reconstruction involves the removal of all remnant tissue and reconstruction of one or both bundles. As the evidence for SLB versus complete ACL reconstruction remains unclear, this study aimed to compare the two techniques. This study's hypothesis was that SLB reconstruction allows better function and stability compared to complete ACL reconstruction.

Methods

A systematic search of PubMed, EMBASE, Scopus and Cochrane Library was conducted, identifying studies that compared SLB ('selective' group) versus complete ('complete' group) ACL reconstruction. Meta-analysis was conducted for post-operative functional scores, stability outcomes and complications as well as pre-operative to post-operative change.

Results

Eleven studies were included in the meta-analysis, with 1107 patients and a pooled mean follow-up of 29.5 months. Post-operatively, the Selective group had significantly reduced anterior laxity, shown by a lower mean arthrometry side-to-side difference (p<0.01). Analysis of change results showed that the Selective group had a lower mean improvement in arthrometry side-to-side difference as well (p<0.01). No significant difference was shown for all other post-operative outcomes.

Conclusion

This study provides valuable insight to the management of partial tears. It has demonstrated that the preservation of the intact bundle offers stability and function that is as good as complete reconstruction and that SLB is a potentially viable option in the management of partial tears.

Level of evidence

Meta-analysis; Level of evidence, 4.

The posterior cruciate ligament inclination angle is higher in anterior cruciate ligament insufficiency

PURPOSE

Magnetic resonance imaging (MRI) is the gold standard image examination for anterior cruciate ligament (ACL) lesion diagnosis. Our hypothesis was that measuring the posterior cruciate ligament inclination angle (PCLIA) using MRI images may be an auxiliary tool to aid the recognition of ACL insufficiency. The purpose of this study was to compare the PCLIA measurement in MRIs of individuals with and without ACL injury.

METHODS

The PCLIA was measured by two radiologists in 65 knee MRIs of patients with intact ACL (control group) and in 65 knee MRIs of people with ACL injury (study group). In both groups, the posterior cruciate ligament was intact. The control group was included 35 men (53.8%) and 30 women (46.1%). The patients' average age was 38.7 years (range 15-75; SD ± 14.8 years). In this group, 31 (47.6%) MRIs were from right knees and 34 (52.3%) were from left knees. The study group consisted of 45 men (69.2%) and 20 women (30.7%). The patients' average age was 36.8 years (range 14-55; SD ± 10.3 years). In this group, 33 (50.7%) were right knees and 32 (49.2%) were left knees. PCLIA was formed by the intersection of two lines drawn in MRI sagittal images. The first passed tangentially to the articular surface of the tibial condyle and the second was drawn over the fraction of the ligament that originated where the first crossed the PCL, outlined proximally.

RESULTS

The average PCLIA was 44.2 ± 3.8° in the control group and 78.9 ± 8.6° in the study group. Statistical analyses showed that the PCLIA was higher in the group with ACL injury (p < 0.05). Conclusion The PCLIA was significantly higher in individuals with ACL injuries. The measurement of this angle using MRI images may allow for detection of ACL insufficiency and thus assist in an individualized and precise approach to the treatment of injuries to the ACL.

CLINICAL RELEVANCE

PCLIA may be a way to detect ACL insufficiency and thus help surgeons to decide which patient might need ACL reconstruction.

LEVEL OF EVIDENCE

III.