The basic science of human knee menisci: structure, composition, and function

Age and anatomical region-related differences in vascularization of the porcine meniscus using microcomputed tomography imaging

Meniscal lesions in vascularized regions are known to regenerate while lack of vascular supply leads to poor healing. Here, we developed and validated a novel methodology for three-dimensional structural analysis of meniscal vascular structures with high-resolution microcomputed tomography (µCT). We collected porcine medial menisci from 10 neonatal (not-developed meniscus, n-) and 10 adults (fully developed meniscus, a-). The menisci were cut into anatomical regions (anterior horn (n-AH and a-AH), central body (n-CB and a-CB), and posterior horn (n-PH and a-PH). Specimens were cut in half, fixed, and one specimen underwent critical point drying and µCT imaging, while other specimen underwent immunohistochemistry and vascularity biomarker CD31 staining for validation of µCT. Parameters describing vascular structures were calculated from µCT. The vascular network in neonatal spread throughout meniscus, while in adult was limited to a few vessels in outer region, mostly on femoral side. n-AH, n-CB, and n-PH had 20, 17, and 11 times greater vascular volume fraction than adult, respectively. Moreover, thickness of blood vessels, in three regions, was six times higher in adults than in neonatal. a-PH appeared to have higher vascular fraction, longer and thicker blood vessels than both a-AH and a-CB. Overall, neonatal regions had a higher number of blood vessels, more branching, and higher tortuosity compared to adult regions. For the first time, critical point drying-based µCT imaging allowed detailed three-dimensional visualization and quantitative analysis of vascularized meniscal structures. We showed more vascularity in neonatal menisci, while adult menisci had fewer and thicker vascularity especially limited to the femoral surface.

Meniscus Injuries in Soccer

Soccer is considered the most popular sport in the world. The game involves frequent agile maneuvers, such as rapid accelerations/decelerations and pivoting, and carries an inherent risk of high-speed collisions, which can lead to lower extremity injury. Knee and meniscus injuries can cause significant pain and disability, precluding participation in the sport. Understanding the diagnosis and management of meniscal injuries in soccer players is essential to the care of these athletes. This paper reviews meniscal anatomy, biomechanics, and mechanisms of injury; discusses the work-up, diagnosis, and management of meniscus injuries; and reports on rehabilitation, return to sport, and outcomes after meniscal injuries in soccer players.

Does concomitant meniscus repair and meniscectomy show different efficacy in anterior cruciate ligament reconstruction? A systematic review and meta-analysis

Aims

Currently, it is advised to perform meniscal repair instead of meniscectomy in certain cases of primary anterior cruciate ligament reconstruction (ACLR). However, the level of evidence is low. Therefore, this study aimed to compare the effectiveness of meniscectomy and meniscus repair in addition to ACLR.

Methods

The systematic search was conducted in three online databases (EMBASE, MEDLINE, and Cochrane) from inception until October 2021 for the literature on primary ACLR and concomitant meniscal surgery. Eligible studies compared the following outcomes between meniscal repair and meniscectomy groups: the Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm score, International Knee Documentation Committee (IKDC) score, and KT-arthrometer examinations. Lastly, we calculated pooled mean differences (MDs) with 95 % confidence intervals (CIs) from the change between pre- and post-intervention values.

Results

Of 10,565 studies, 22 met the inclusion criteria, with a follow-up between 6 and 43 months. We found no difference when comparing the KOOS subscale changes-only in the KOOS pain subscale (MD = -1.6; CI: -2.48, -0.72). However, these results were not clinically significant. We analyzed the lateral and media meniscal injuries separately and concluded the same results regarding KOOS changes. We found no significant differences in the Lysholm score change (MD = -2.61; CI: -5.51, 0.29), changes in IKDC score (MD = 1.08; CI: -4.05, 6.21) or the change for the KT-arthrometer side-to-side difference (MD = -0.50; CI: -1.06, 0.06).

Conclusion

Based on our result, we did not find a clinically significant difference between meniscus repair and meniscectomy during primary ACLR regarding patient-reported outcomes in a short-term follow-up.

Translational potential

Our research supports the prompt integration of findings into clinical practice for treating meniscus injuries during ACL reconstruction. We recommend considering both meniscus repair and meniscectomy, as the available data indicate their effectiveness. Further studies are necessary to assess the long-term impacts, particularly on osteoarthritis, and to identify patient subgroups that may benefit most from each technique.

Treatment of chronic and complex meniscal tears with arthroscopic meniscus repair augmented with collagen matrix wrapping: failure rate and functional outcomes

PURPOSE

Meniscal wrapping is a fully arthroscopic technique that involves enhanced meniscal repair with a tissue-engineered collagen matrix wrapping. This study aims to investigate the feasibility of using the meniscal wrapping technique for the treatment of chronic or complex meniscal tears. The primary objective is to assess its failure rate. The secondary objectives are to analyse complication rate, functional outcomes and overall patient satisfaction.

METHODS

This retrospective case series study included patients who sustained chronic and complex tears undergoing meniscal wrapping with autologous liquid bone marrow injection. Failure rate was considered if the patient underwent partial or complete meniscectomy or knee replacement during the follow-up, while other unexpected knee reoperations were considered as complications. Clinical outcomes were evaluated through the IKDC score, Tegner Activity Score and Short Assessment of Patient Satisfaction.

RESULTS

Twenty-one patients were included (15 non-acute bucket-handle tears, three non-acute horizontal tears and three non-acute complex injuries). The failure rate was 9.5% at 33 months. The rate of other unplanned reoperations was 14.3%, but none of these complications were apparently directly related to the wrapping technique. The average postoperative IKDC was 73.3/100. No statistically significant difference was encountered between preinjury and postoperative Tegner Activity Score. The mean overall patient satisfaction was 88.3/100.

CONCLUSIONS

Meniscal wrapping can be safely used as an adjunctive technique to meniscal repair in such difficult-to-treat cases to preserve the meniscus. The technique achieves a low failure rate and promising results of knee function, and patient satisfaction.

Viable Vitreous Grafts of Whole Porcine Menisci for Transplant in the Knee and Temporomandibular Joints

The shortage of suitable donor meniscus grafts from the knee and temporomandibular joint (TMJ) impedes treatments for millions of patients. Vitrification offers a promising solution by transitioning these tissues into a vitreous state at cryogenic temperatures, protecting them from ice crystal damage using high concentrations of cryoprotectant agents (CPAs). However, vitrification's success is hindered for larger tissues (>3 mL) due to challenges in CPA penetration. Dense avascular meniscus tissues require extended CPA exposure for adequate penetration; however, prolonged exposure becomes cytotoxic. Balancing penetration and reducing cell toxicity is required. To overcome this hurdle, a simulation-based optimization approach is developed by combining computational modeling with microcomputed tomography (µCT) imaging to predict 3D CPA distributions within tissues over time accurately. This approach minimizes CPA exposure time, resulting in 85% viability in 4-mL meniscal specimens, 70% in 10-mL whole knee menisci, and 85% in 15-mL whole TMJ menisci (i.e., TMJ disc) post-vitrification, outperforming slow-freezing methods (20%-40%), in a pig model. The extracellular matrix (ECM) structure and biomechanical strength of vitreous tissues remain largely intact. Vitreous meniscus grafts demonstrate clinical-level viability (≥70%), closely resembling the material properties of native tissues, with long-term availability for transplantation. The enhanced vitrification technology opens new possibilities for other avascular grafts.

Radiomic features of the medial meniscus predicts incident destabilizing meniscal tears: Data from the osteoarthritis initiative

The objective of this study was to determine the optimal meniscal radiomic features to classify people who will develop an incident destabilizing medial meniscal tear. We used magnetic resonance (MR) images from an existing case-control study that includes images from the first 4 years of the Osteoarthritis Initiative (OAI). For this exploratory analysis (n = 215), we limited our study sample to people with (1) intact menisci at the OAI baseline visit, (2) 4-year meniscal status data, and (3) complete meniscal data from each region of interest. Incident destabilizing meniscal tear was defined as progressing from an intact meniscus to a destabilizing tear by the 48-month visit using intermediate-weighted fat-suppressed MR images. One reader manually segmented each participant's anterior and posterior horn of the medial menisci at the OAI baseline visit. Next, 61 different radiomic features were extracted from each medial meniscus horn. We performed a classification and regression tree (CART) analysis to determine the classification rules and important variables that predict incident destabilizing meniscal tear. The CART correctly classified 24 of the 34 cases and 172 out of 181 controls with a sensitivity of 70.6% and a specificity of 95.0%. The CART identified large zone high gray level emphasis (i.e., more coarse texture) from the posterior horn as the most important variable to classify who would develop an incident destabilizing medial meniscal tear. The use of radiomic features provides sensitive and quantitative measures of meniscal alterations, allowing us to intervene and prevent destabilizing meniscal tears.

Differences in Graft Tear Configurations in Medial and Lateral Meniscal Allograft Transplantation: Objective Evaluations Using Magnetic Resonance Imaging

BACKGROUND

Few studies have compared the characteristics of meniscal allograft tears between medial and lateral meniscal allograft transplantation (MAT) using bone fixation.

PURPOSE

To investigate the prevalence, location, and patterns of allograft tears after MAT with the bone fixation technique and compare tear patterns between medial and lateral compartments according to the time elapsed after surgery.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The charts of consecutive patients who underwent primary medial or lateral MAT between December 1996 and June 2019 were retrospectively reviewed. The location, pattern, and postoperative periods during which allograft tears occurred were evaluated by reviewing all series of follow-up magnetic resonance imaging (MRI) scans, which were performed at 6 weeks, 3 months, 6 months, and 1 year postoperatively and every 2 years thereafter with the patient's agreement. Postoperative periods for allograft tears were defined as the time between surgery and the follow-up MRI scan in which the meniscal tear was first confirmed. Allograft tears were compared between the medial and lateral MAT groups.

RESULTS

A total of 327 consecutive patients who underwent MAT (55 medial, 272 lateral) with a minimum 2-year follow-up were retrospectively reviewed. The incidences of allograft tears after medial and lateral MATs were 32.7% and 30.9%, respectively. The mean times for tears were 80.1 ± 81.1 months and 48.9 ± 46.3 months in the medial and lateral MAT groups, respectively (P = .130). In both the medial and lateral MAT groups, allograft tears were observed mainly in the posterior horn, with complex tears being the most commonly identified tear type. In medial MATs, root tears were the second most common at 27.8%, with a significantly higher proportion than the lateral MATs (P = .014). On the other hand, in lateral MATs, meniscocapsular separation and radial tears were the second most common at 15.5% each, albeit not significantly more common than in medial MATs (P = .123 and P = .454, respectively). All root tears in medial MATs and meniscocapsular separations in lateral MATs were observed within 1 year postoperatively.

CONCLUSION

Significant differences in allograft tear patterns were identified between the medial and lateral MAT groups. The proportion of root tears in medial MATs was higher than that in lateral MATs; conversely, the proportion of meniscocapsular separation was more common in lateral MATs. Such tear patterns, which may require surgical repair or graft resection, were observed only within 1 year of surgery. Therefore, close observation and regular follow-up in the earlier postoperative period are necessary after medial or lateral MATs.

Decreasing Incidence of Partial Meniscectomy and Increasing Incidence of Meniscus Preservation Surgery From 2010 to 2020 in the United States

PURPOSE

To characterize the incidence of meniscus surgery from 2010 to 2020 in the United States, using the metrics of age, sex, type of meniscus surgery, and Charlson Comorbidity Index (CCI).

METHODS

A retrospective analysis was performed using the PearlDiver national insurance claims database from 2010 to 2020. Meniscus surgeries were identified using Current Procedural Terminology codes. Patients were stratified by procedure type, age, biological sex, and CCI scores. Compound annual growth rate analysis and analysis of variance were performed to analyze the trends and demographic variables between cohorts.

RESULTS

Of 2,053,884 meniscus surgeries, 94.7% were meniscectomies, 0.3% were open repairs, 4.9% were arthroscopic repairs, and 0.1% were meniscal transplantations. Compound annual growth rate analysis displayed a 4.0% decrease per year in total meniscus surgery. For individual procedure types, the largest decrease was in meniscectomy, and the largest increase was in open repair. Patients undergoing meniscal transplantation were youngest, with the lowest CCI. Meniscectomy patients were oldest, and open repair patients had the highest average CCI. Most procedures were performed on female patients (52.4%) and patients in the 50- to 59-year age group (30.4%).

CONCLUSIONS

There was a sustained decrease in the incidence of total meniscus surgeries from 2010 to 2020. Meniscectomy was the procedure with the highest incidence, but it showed the most significant decline in usage over the study period. Conversely, meniscal repair and transplantation procedures increased during the study period.

LEVEL OF EVIDENCE

Level IV, epidemiologic study.

Incomplete histologic healing and diminished biomechanical strength of meniscus-bone interface after medial meniscus posterior root transosseous repair in a goat model

PURPOSE

To enhance the understanding of histological healing after repairing medial meniscal posterior root tear (MMPRT) at an early stage, utilizing a goat model.

METHODS

Eighteen adult goats, totaling thirty-six knee joints, were allocated into three groups (n = 12): Sham group (Sham), Root Tear group (RT), and Root Tear with Transosseous Suture group (RTS). At 12- and 24-week intervals post-surgery, all the knees were harvested for imaging, macroscopic, histological, and biomechanical assessments.

RESULTS

The intact root served as a meniscus-bone interface which connected the tibial and the circular fibers of the meniscus, with a bony insertion and a root-meniscus transition. A direct-fibrous-connection displayed at the bony insertion proximal to the synovium in the RTS group, while the remaining regions of the root displayed indirect-fibrous healing. The healing in the RT group was disjointed and reminiscent of scar tissue. The RTS group exhibited a more pronounced coronal extrusion compared to the Sham group (0.42 ± 0.09 vs. 0.19 ± 0.02, P = 0.0012) but was improved relative to that of the RT group (0.49 ± 0.02, P = 0.0028). The failure load and stiffness of the RTS group were notably higher than those of the RT group, with a strength of 42.67% and a stiffness of 83.75% of the intact root. All the samples ruptured at the root-meniscus transitions.

CONCLUSION

The incomplete healing may be attributed to the histological factors underlying the low healing rate and persistent MME. Notably, the region attached to the posterior-cruciate-ligament exhibited superior healing compared to other regions of the bony insertion in the repaired group. Conversely, the root-meniscus transition displayed discontinuity, representing a mechanical weakness in the healing process.

CLINICAL RELEVANCE

Modifications of bone tunnel positioning and suture placement could be undertaken in subsequent studies to particularly enhance the healing of the root-meniscus transition.

Corneal aberrations are associated with low-energy meniscus injuries

BACKGROUND

Visual impairment can cause balance problems. Therefore, visual impairment caused by an increase in corneal deviations can lead to sudden and unstable loads in the lower extremities. We aimed to investigate the possible relationship between low-energy meniscal injuries and corneal structural measures.

METHODS

This prospective, observational study included individuals aged between 18-40 years with a normal body-mass index. The study group consisted of 54 patients with grade 2 or 3 meniscus injuries after low-energy activity. The control group consisted of 54 healthy individuals without any complaints in the knee joint. The corneal parameters of all participants were evaluated with a Scheimpflug corneal topography and specular microscopy device. Simulated keratometry (SimK), minimum central corneal thickness (MCCT), cylindrical diopter (ClyD), corneal volume (CVol) spheric aberrations (SphAbb), high-order aberration (HOA), coma values, and endothelial parameters were recorded.

RESULTS

The research and control groups were similar in terms of age, body mass index, and gender distribution. There was no significant difference between the groups in the corneal SimK and CylD, parameters. However, HOA, Coma, SphAbb, and cell variability (Cv) values were significantly higher in the study group, and contrarily MCCT, CVol, and endothelial count (Cd) values were significantly lower.

CONCLUSIONS

Our findings suggest that individuals with relatively lower MCCT values tend to develop meniscal damage after low-energy activity. Hence, the loss of corneal strength in these patients may be a sign of possible weakness in the meniscus. The HOA value above 0.26, the coma value above 0.16, and the SphAbb value above 0.1 may significantly increase the possible meniscus injury.

The Relationship Between Medial Meniscal Extrusion and Outcome Measures for Knee Osteoarthritis: A Systematic Review

Background

Medial meniscal extrusion (MME) has been associated with knee osteoarthritis (OA). However, there is no standardized method to measure MME.

Purpose/Hypothesis

The purpose of this study was to investigate the relationship between MME and outcome measures related to knee OA and discuss different magnetic resonance imaging (MRI) methods of measuring MME. It was hypothesized that MME would be associated with outcome measures of OA and that the distance extruded over the tibial plateau would be the most common MRI method to measure MME.

Study Design

Systematic review; Level of evidence, 3.

Methods

The MEDLINE, Embase, Cochrane Library, Scopus, Web of Science Core Collection, Global Index Medicus, and ClinicalTrials.gov databases were systematically searched. The inclusion criteria were studies that (1) measured MME on nonoperated knees using MRI; (2) evaluated knee OA with at least 1 knee OA grading scale, outcome measure, or direct characterization of cartilage or bone; (3) statistically evaluated the association between MME and knee OA outcome measure; (4) were randomized controlled trials, nonrandomized controlled trials, cohort studies, or case series; and (5) reported original results.

Results

A total of 19 studies were included, of which 14 reported MME as the distance extruded over the tibial plateau, 7 reported MME as the volume extruded over the tibial plateau, and 1 reported MME as the percentage of the tibial plateau covered by the meniscus. All studies reported that MME was significantly associated with at least 1 OA outcome measure-including increased Kellgren-Lawrence grade, osteophytes, cartilage damage, varus alignment, knee pain, bone marrow lesions, and progression to arthroplasty. Eight studies found that MME was associated with worse OA outcomes over time (range, 2-10 years).

Conclusion

All 19 reviewed studies reported that MME was associated with at least 1 knee OA outcome measure reflective of worsening arthritis, suggesting a strong association between OA and MME. Future research is needed to investigate this relationship and standardize the methods of measuring MME.

Rapid Volumetric Bioprinting of Decellularized Extracellular Matrix Bioinks

Decellularized extracellular matrix (dECM)-based hydrogels are widely applied to additive biomanufacturing strategies for relevant applications. The extracellular matrix components and growth factors of dECM play crucial roles in cell adhesion, growth, and differentiation. However, the generally poor mechanical properties and printability have remained as major limitations for dECM-based materials. In this study, heart-derived dECM (h-dECM) and meniscus-derived dECM (Ms-dECM) bioinks in their pristine, unmodified state supplemented with the photoinitiator system of tris(2,2-bipyridyl) dichlororuthenium(II) hexahydrate and sodium persulfate, demonstrate cytocompatibility with volumetric bioprinting processes. This recently developed bioprinting modality illuminates a dynamically evolving light pattern into a rotating volume of the bioink, and thus decouples the requirement of mechanical strengths of bioprinted hydrogel constructs with printability, allowing for the fabrication of sophisticated shapes and architectures with low-concentration dECM materials that set within tens of seconds. As exemplary applications, cardiac tissues are volumetrically bioprinted using the cardiomyocyte-laden h-dECM bioink showing favorable cell proliferation, expansion, spreading, biomarker expressions, and synchronized contractions; whereas the volumetrically bioprinted Ms-dECM meniscus structures embedded with human mesenchymal stem cells present appropriate chondrogenic differentiation outcomes. This study supplies expanded bioink libraries for volumetric bioprinting and broadens utilities of dECM toward tissue engineering and regenerative medicine.

Age-dependent changes in collagen crosslinks reduce the mechanical toughness of human meniscus

The mechanical resilience of the knee meniscus is provided by a group of structural proteins in the extracellular matrix. Aging can alter the quantity and molecular structure of these proteins making the meniscus more susceptible to debilitating tears. In this study, we determined the effect of aging on the quantity of structural proteins and collagen crosslinks in human lateral meniscus, and examined whether the quantity of these molecules was predictive of tensile toughness (area under the stress-strain curve). Two age groups were tested: a young group under 40 and an older group over 65 years old. Using mass spectrometry, we quantified the abundance of proteins and collagen crosslinks in meniscal tissue that was adjacent to the dumbbell-shaped specimens used to measure uniaxial tensile toughness parallel or perpendicular to the circumferential fiber orientation. We found that the enzymatic collagen crosslink deoxypyridinoline had a significant positive correlation with toughness, and reductions in the quantity of this crosslink with aging were associated with a loss of toughness in the ground substance and fibers. The non-enzymatic collagen crosslink carboxymethyl-lysine increased in quantity with aging, and these increases corresponded to reductions in ground substance toughness. For the collagenous (Types I, II, IV, VI, VIII) and non-collagenous structural proteins (elastin, decorin, biglycan, prolargin) analyzed in this study, only the quantity of collagen VIII was predictive of toughness. This study provides valuable insights on the structure-function relationships of the human meniscus, and how aging causes structural adaptations that weaken the tissue's mechanical integrity.

Epigenetic Dynamics in Meniscus Cell Migration and its Zonal Dependency in Response to Inflammatory Conditions: Implications for Regeneration Strategies

Meniscus injuries pose significant challenges in clinical settings, primarily due to the intrinsic heterogeneity of the tissue and the limited efficacy of current treatments. Endogenous cell migration is crucial for the healing process, yet the regulatory mechanisms of meniscus cell migration and its zonal dependency within the meniscus are not fully understood. Thus, this study investigates the role of epigenetic mechanisms in governing meniscus cell migration under inflammatory conditions, with a focus on their implications for injury healing and regeneration. Here, we discovered that a proinflammatory cytokine, TNF-α treatment significantly impedes the migration speed of inner meniscus cells, while outer meniscus cells are unaffected, underscoring a zonal-dependent response within the meniscus. Our analysis identified distinct histone modification patterns and chromatin dynamics between inner and outer meniscus cells during migration, highlighting the necessity to consider these zonal-dependent properties in devising repair strategies. Specifically, we found that TNF-α differentially influences histone modifications, particularly H3K27me3, between the two cell types. Transcriptome analysis further revealed that TNF-α treatment induces substantial gene expression changes, with inner meniscus cells exhibiting more pronounced alterations than outer cells. Gene cluster analysis pointed to distinct responses in chromatin remodeling, extracellular matrix assembly, and wound healing processes between the zonal cell populations. Moreover, we identified potential therapeutic targets by employing existing epigenetic drugs, GSKJ4 (a histone demethylase inhibitor) and C646 (a histone acetyltransferase inhibitor), to successfully restore the migration speed of inner meniscus cells under inflammatory conditions. This highlights their potential utility in treating meniscus tear injuries. Overall, our findings elucidate the intricate interplay between epigenetic mechanisms and meniscus cell migration, along with its meniscus zonal dependency. This study provides insights into potential targets for enhancing meniscus repair and regeneration, which may lead to improved clinical outcomes for patients with meniscus injuries and osteoarthritis.

IPACK Block Efficacy for Acute Pain Management after Total Knee Replacement: A Review

PURPOSE OF REVIEW

Patients often experience a significant degree of knee pain following total knee replacement (TKR). To alleviate this pain, nerve blocks may be performed such as the adductor canal block (ACB). However, ACBs are unable to relieve pain originating from the posterior region of the knee. A new type of nerve block known as the IPACK block may be used in conjunction with ACBs as it is designed to inhibit nerve branches innervating this area. In this article, we examine the rationale behind the IPACK procedure, how it is performed, and clinical trials examining its efficacy.

RECENT FINDINGS

5 of the 7 clinical trials examined in this article showed the IPACK + ACB block to show superior efficacy in treating pain following TKR compared to other blocks. These blocks included PMDI+ACB, SPANK+ACB, PAI+ACB, ACB alone, and SCAB. 2 of the 7 clinical trials showed the IPACK + ACB to be less effective in managing patients pain following TKR compared to other blocks which included the CACB and 4 in 1 block. In most instances, the IPACK + ACB showed superior efficacy in managing patients' pain following TKR when compared to other types of nerve blocks. This was determined by measuring usage of opioids, reported postoperative pain, and length of hospital stays following TKR. Thus, we suppose the IPACK block may be used in conjunction with the ACB to effectively reduce patient's pain following TKR.

Novel Meniscus Transfer Technique: A Case Report

The meniscus is an essential component of the knee joint, acting as a shock absorber as well as assisting in the transmission of forces. Due to the meniscus importance of the knee, much of the current literature focuses on treatment techniques that can spare and repair the meniscus when it is torn. The unique vasculature of the meniscus often makes repair difficult or, in many cases, impossible. A current focus within orthopedics has been on meniscal allograft transplantation to fill this gap. The lack of a universal surgical technique for graft fixation, along with the current failure rates, demonstrates the need for further improvements. The senior author proposes a novel technique for meniscal allograft transplantation that has shown decreased blood loss and surgical time, while also reducing intra-operative trauma to the knee. This case reports a 16-year-old patient who underwent a right lateral meniscal allograft transplant following a large segmental defect tear of the lateral meniscus. The patient initially underwent arthroscopy and meniscectomy with screw fixation of the lateral femoral condyle lesion. After physical therapy, the patient experienced increased pain and swelling, with magnetic resonance imaging (MRI) demonstrating a meniscal defect unamenable to repair. The patient met indications for meniscal allograft transplantation given the failed meniscectomy, absence of cartilage loss and significant osteoarthritis, and the patient's age of less than 50 years old.

Identifying autophagy-related mRNAs and potential ceRNA networks in meniscus degeneration based on RNA sequencing and experimental validation

Purpose

The intimate connection between long noncoding RNA (lncRNA) and autophagy has been established in cartilage degeneration. However, their roles in meniscal degeneration remain ambiguous. This study aimed to identify the key autophagy-related lncRNA and its associated regulatory network in meniscal degeneration in the context of osteoarthritis (OA).

Methods

RNA sequencing was performed to identify differentially expressed lncRNAs (DELs) and mRNAs (DEMs), which were then conducted to enrichment analyses using the DAVID database and Metascape. Autophagy-related DEMs were identified by combining DEMs with data from the Human Autophagy Database. Three databases were used to predict miRNA, and the DIANA LncBase Predicted database was utilized to predict miRNA-lncRNA interactions. Based on these predictions, comprehensive competitive endogenous RNA (ceRNA) network were constructed. The expression levels of the classical autophagy markers and autophagy-related ceRNA network were validated. Additionally, Gene Set Enrichment Analysis (GSEA) was performed using autophagy-related DEMs.

Results

310 DELs and 320 DEMs were identified, with five upregulated and one downregulated autophagy-related DEMs. Through reverse prediction of miRNA, paired miRNA-lncRNA interactions, and verification using RT-qPCR, two lncRNAs (PCAT19, CLIP1-AS1), two miRNA (has-miR-3680-3p and has-miR-4795-3p) and two mRNAs (BAG3 and HSP90AB1) were included in the constructed ceRNA regulatory networks. GSEA indicated that the increased expression of autophagy-related mRNAs inhibited glycosaminoglycan biosynthesis in the degenerative meniscus.

Conclusion

This study presented the first construction of regulatory ceRNA network involving autophagy-related lncRNA-miRNA-mRNA interactions in OA meniscus. These findings offered valuable insights into the mechanisms underlying meniscal degeneration and provided potential targets for therapeutic intervention.

Nonanatomic femoral tunnel placement increases the risk of subsequent meniscal surgery after ACLR: Part II-Patients without recurrent ACL injury

PURPOSE

The purpose of this study was to identify risk factors for subsequent meniscal surgery following anterior cruciate ligament (ACL) reconstruction (ACLR) in patients without recurrent ACL injury.

METHODS

Patients aged ≥14 years who underwent primary ACLR with minimum 1-year follow-up and without recurrent ACL injury were retrospectively reviewed. Patient demographics and surgical data at the time of ACLR were collected. Postoperative radiographs were used to measure femoral and tibial tunnel position, and posterior tibial slope. Univariate and multivariate analyses were performed to identify risk factors for subsequent meniscal surgery.

RESULTS

Of 629 ACLRs that fulfilled the inclusion criteria, subsequent meniscal surgery was performed in 65 [10.3%] patients. Multivariate analysis revealed that medial meniscal repair at the time of ACLR, younger age, anterior femoral tunnel position and distal femoral tunnel position were significantly associated with subsequent meniscal surgery (p < 0.001, p = 0.016, p = 0.015, p = 0.035, respectively). The frequency of femoral tunnel placement >10% outside of the literature-established anatomic position was significantly higher in those who underwent subsequent meniscal surgery compared to those who did not (38.3% vs. 20.3%, p = 0.006). Posterior tibial slope and ACL graft type were not significantly associated with subsequent meniscal surgery.

CONCLUSION

Medial meniscal repair at the time of ACLR, younger age and nonanatomic femoral tunnel placement were risk factors for subsequent meniscal surgery in patients without recurrent ACL injury. Femoral tunnel placement <10% outside of the native anatomic position is important to reduce the risk of subsequent meniscal surgery.

LEVEL OF EVIDENCE

Level IV.

Lateral Unicompartmental Knee Arthroplasty for Osteoarthritis Secondary to Lateral Meniscectomy: High Functional Results and Survivorship and Low Osteoarthritis Progression at a Mean 10 Years of Follow-up

BACKGROUND

Meniscectomy, whether partial or total, is a common knee surgery, but it considerably increases the risk of knee osteoarthritis (OA). Lateral meniscectomy has more severe consequences than medial meniscectomy, leading to faster OA progression and worse clinical outcomes. Unicompartmental knee arthroplasty (UKA) is a suitable treatment option for lateral OA and has demonstrated better outcomes than total knee arthroplasty (TKA). The aims of this study were to evaluate the clinical and functional results, OA progression in the medial compartment, and implant survivorship following lateral UKA in patients with OA secondary to lateral meniscectomy and to compare these outcomes with those of patients who underwent lateral UKA for primary lateral OA.

METHODS

Between 2001 and 2017, 214 lateral UKAs were performed. Of these, 42 were performed for OA secondary to lateral meniscectomy. The control group was composed of patients who underwent lateral UKA for primary lateral OA and was formed through a 1:1 case-control matching process based on sex, age, body mass index, and operation date. The outcomes that were studied included range of motion, Knee Society Score, University of California Los Angeles (UCLA) Activity Score, Tegner Activity Scale, Forgotten Joint Score, visual analog scale for pain, OA progression in the medial compartment, and implant survivorship.

RESULTS

At a mean follow-up of 10.2 years, both groups demonstrated significant improvements (p < 0.01) after lateral UKA in all clinical and functional scores except the UCLA Activity Score and Tegner Activity Scale. No significant differences in clinical and functional scores were found between the groups. However, patients with OA secondary to meniscectomy exhibited significantly less OA progression in the medial compartment (p = 0.035) and higher 10-year implant survival (97.6% versus 83.3%).

CONCLUSIONS

Lateral UKA is an effective treatment option for OA secondary to lateral meniscectomy, providing excellent functional outcomes and survivorship. Patients with post-meniscectomy OA exhibited less OA progression in the medial compartment than patients with primary OA and, consequently, had better 10-year implant survivorship.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

The cumulative incidence and risk factors associated with 5-year conversion to knee arthroplasty following primary meniscus repair or primary meniscectomy

Background

This study aimed to observe the 5-year knee arthroplasty conversion incidence rate and associated risk factors in patients who underwent meniscus procedures.

Methods

Using a national database, we analyzed patients who had undergone primary meniscus repair or meniscectomy without prior knee surgeries. The cumulative knee arthroplasty conversion incidence was determined via Kaplan Meier analysis. Risk factors for conversion within 5 years were assessed using a Cox proportional hazard ratio model, with results as hazard ratios (HR).

Results

8125 patients had meniscus repair, while 240,209 had meniscectomy. 5-year conversion rates: repair 1.7%, meniscectomy 8.4%. Arthroplasty likelihood decreased as age decreased for repair (70+ [HR: 162.20]; 60-69 [HR: 81.64]; 50-59 [HR: 49.85]; 40-49 [HR: 17.79]; p < 0.001 all). Additional risk factors included male sex (HR: 0.35; p < 0.001) and higher Charlson Comorbidity Index (CCI) (CCI1 [HR: 1.28; p = 0.012]). For meniscectomy, arthroplasty likelihood also decreased with age (70+ [HR: 99.41]; 60-69 [HR: 84.57]; 50-59 [HR: 66.60]; 40-49 [HR: 36.15]; 30-39 [HR: 10.18]; p < 0.001 all). Additional risk factors included male sex (HR: 0.68; p < 0.001), obesity (HR: 1.18; p < 0.001), smoking (HR: 0.1.12; p = 0.010), and higher CCI (CCI1 [HR: 1.25]; CCI2 [HR 1.39]; CCI3+ [HR 1.46]; p < 0.001 all).

Conclusion

This study revealed the national 5-year conversion incidence following primary meniscus repair (1.7%) and meniscectomy (8.4%). It also enhanced understanding of age, sex, obesity, smoking, comorbidities (CCI), and knee arthroplasty likelihood after meniscus procedures.

Injectable ChitHCl-DDA tissue adhesive with high adhesive strength and biocompatibility for torn meniscus repair and regeneration

Suture pull-through is a clinical problem in meniscus repair surgery due to the sharp leading edge of sutures. Several tissue adhesives have been developed as an alternative to traditional suturing; however, there is still no suitable tissue adhesive specific for meniscus repair treatment due to unsatisfactory biosafety, biodegradable, sterilizable, and tissue-bonding characteristics. In this study, we used a tissue adhesive composed of chitosan hydrochloride reacted with oxidative periodate-oxidized dextran (ChitHCl-DDA) combined with a chitosan-based hydrogel and oxidative dextran to attach to the meniscus. We conducted viscoelastic tests, viscosity tests, lap shear stress tests, Fourier transform infrared (FTIR) spectroscopy, swelling ratio tests, and degradation behavior tests to characterize these materials. An MTT assay, alcian blue staining, migration assay, cell behavior observations, and protein expression tests were used to understand cell viability and responses. Moreover, ex vivo and in vivo tests were used to analyze tissue regeneration and biocompatibility of the ChitHCl-DDA tissue adhesive. Our results revealed that the ChitHCl-DDA tissue adhesive provided excellent tissue adhesive strength, cell viability, and cell responses. This tissue adhesive has great potential for torn meniscus tissue repair and regeneration.

The Effect of Lower Limb Alignment on Tibiofemoral Joint Contact Biomechanics after Medial Meniscus Posterior Root Repair: A Finite-Element Analysis

INTRODUCTION

The purpose of this study was to determine how variations in lower limb alignment affect tibiofemoral joint contact biomechanics in the setting of medial meniscus posterior root tear (MMPRT) and associated root repair.

METHODS

A finite-element model of an intact knee joint was developed. Limb alignments ranging from 4° valgus to 8° varus were simulated under a 1,000 N compression load applied to the femoral head. For the intact, MMPRT, and root repair conditions, the peak contact pressure (PCP), total contact area, mean and maximum local contact pressure (LCP) elevation, and total area of LCP elevation of the medial tibiofemoral compartment were quantified.

RESULTS

The PCP and total contact area of the medial compartment in the intact knee increased from 2.43 MPa and 361 mm 2 at 4° valgus to 9.09 MPa and 508 mm 2 at 8° of varus. Compared with the intact state, in the MMPRT condition, medial compartment PCP was greater and the total contact area smaller for all alignment conditions. Root repair roughly restored PCPs in the medial compartment; however, this ability was compromised in knees with increasing varus alignment. Specifically, elevations in PCP relative to the intact state increased with increasing varus, as did the total contact area with LCP elevation. After root repair, medial compartment PCP remained elevated above the intact state at all degrees tested, ranging from 0.05 MPa at 4° valgus to 0.27 MPa at 8° of varus, with overall PCP values increasing from 2.48 to 9.09 MPa. For varus alignment greater than 4°, root repair failed to reduce the total contact area with LCP elevation relative to the MMPRT state.

DISCUSSION

Greater PCPs and areas of LCP elevation in varus knees may reduce the clinical effectiveness of root repair in delaying or preventing the development of tibiofemoral osteoarthritis.

Kinesio Taping Increases Peak Torque of Quadriceps Muscle After Arthroscopic Meniscectomy, Double-Blinded RCT

Purpose

This study was conducted to release the debate and examine the short-term impact of KT on the quadriceps muscle following arthroscopic surgery for partial meniscectomy.

Patients and Methods

As part of a double-blind, randomized controlled trial, 40 people who had an arthroscopic partial meniscectomy (APM) were randomly put into two groups, A and B. Group A received Kinesio tape (KT) for the superficial heads of the quadriceps muscle, while group B received placebo KTk. After 10 minutes of KT application, the peak torque of both groups was measured using a Biodex isokinetic dynamometer.

Results

Peak torque showed a significant increase in group A in comparison with group B during angular velocity 60◦/Sec. (F (1, 130) = 58.9, p <0.001, ƞ2 =0.31) and during angular velocity 180◦/Sec. (F (1, 38) = 25.0, p <0.001, ƞ2 =0.40).

Conclusion

After APM, individuals experienced an immediate and significant improvement in the quadriceps' peak torque following KT application to the Rectus femoris, Vastus medialis, and Vastus lateralis muscles from origin to insertion.

Three Morphological Risk Factors for Predicting Isolated Meniscal Bucket-handle Tear

Purpose

The study aimed to investigate whether morphometric variables of the knee can predict isolated meniscal bucket-handle tears and identify the risk factors.

Methods

The study included 146 participants with a mean age of 36.547 ± 12.279 years. They included two groups of 73 patients each: one group with isolated meniscal bucket-handle tears and another with no knee injury (control group). Magnetic resonance imaging findings of the participants were retrospectively assessed. A few morphometric variables associated with distal femur, proximal tibia, and cruciate ligaments were measured.

Results

Cruciate ligament tensity (CLT), medial femoral condylar height (MFCH), and lateral meniscal bone angle (LMBA) were found to be 12.7 ± 0.3, 30.1 ± 2.5 mm, and 21.2° ± 3.4°, respectively, in patients with meniscal bucket-handle tear, compared with 11.9 ± 0.2, 28.3 ± 2.7 mm, and 26.5° ± 3.7° in the control group, respectively. Based on multivariate Firth's logistic regression analysis, CLT (Odds ratio [OR]: 456.533; 95% confidence interval [CI]: 27.582 to > 999.999), MFCH (OR: 1.603; 95% CI: 1.023-2.513), and LMBA (OR: 0.780; 95% CI: 0.624-0.975) could distinguish between meniscal bucket-handle tears and knees without meniscus tears (p < 0.05). Based on the multicategorical multinominal regression model, CLT (OR: > 999.999; 95% CI: 49.937 to > 999.999) and MFCH (OR: 1.903; 95% CI: 1.005-3.606) were the determinant variables in differentiating medial meniscal bucket-handle tears from knees without meniscus tears (p < 0.05).

Conclusion

Large CLT, high medial condyle, and small LMBA were revealed as the morphometric risk factors for meniscal bucket-handle tear.

Photo-Polymerizable Autologous Growth-Factor Loaded Silk-Based Biomaterial-Inks toward 3D Printing-Based Regeneration of Meniscus Tears

Meniscus tears in the avascular region undergoing partial or full meniscectomy lead to knee osteoarthritis and concurrent lifestyle hindrances in the young and aged alike. Here they reported ingenious photo-polymerizable autologous growth factor loaded 3D printed scaffolds to potentially treat meniscal defects . A shear-thinning photo-crosslinkable silk fibroin methacrylate-gelatin methacrylate-polyethylene glycol dimethacrylate biomaterial-ink is formulated and loaded with freeze-dried growth factor rich plasma (GFRP) . The biomaterial-ink exhibits optimal rheological properties and shape fidelity for 3D printing. Initial evaluation revealed that the 3D printed scaffolds mimic mechanical characteristics of meniscus, possess favourable porosity and swelling characteristics, and demonstrate sustained GFRP release. GFRP laden 3D scaffolds are screened with human neo-natal stem cells in vitro and biomaterial-ink comprising of 25 mg mL-1 of GFRP (GFRP25) is found to be amicable for meniscus tissue engineering. GFRP25 ink demonstrated rigorous rheological compliance, and printed constructs demonstrated long term degradability (>6 weeks), GFRP release (>5 weeks), and mechanical durability (3 weeks). GFRP25 scaffolds aided in proliferation of seeded human neo-natal stem cellsand their meniscus-specific fibrochondrogenic differentiation . GFRP25 constructs show amenable inflammatory response in vitro and in vivo. GFRP25 biomaterial-ink and printed GFRP25 scaffolds could be potential patient-specific treatment modalities for meniscal defects.

Examining the Evidence Regarding Smoking and Patient Outcomes for Isolated Meniscus Pathology: A Comprehensive Systematic Review and Meta-Analysis

Smoking is a well-known cause of impairment in wound healing and postoperative outcomes; however, its effects on treating meniscus issues remain unclear. This study assesses the relationship between smoking and meniscus treatment outcomes. PubMed, Scopus, Cochrane, and CINAHL were searched from inception to 24 December 2023. Inclusion criteria encompassed studies examining smoking's impact on patient outcomes regarding meniscus pathology. A secondary PubMed search targeted randomized controlled trials (RCTs) in the top ten orthopedic journals focusing on meniscus pathology and smoking as a demographic variable. Meta-analysis of six studies (n = 528) assessed meniscus failure rate based on smoking status. Eighteen observational studies (n = 8353 patients; 53.25% male; mean age: 51.35 ± 11.53 years; follow-up: 184.11 ± 117.34 months) were analyzed, covering meniscus repair, meniscectomy, allograft transplant, conservative care, and arthroscopy. Results showed four studies (36.36%) linked smoking with worse meniscus repair outcomes, while seven studies (63.64%) did not find significant associations. Meta-analysis from six studies showed no significant impact of smoking on repair failure (p = 0.118). Regarding meniscectomy, one study (33.33%) identified a significant association with smoking, but two did not. Only one (3.8%) of the RCTs in leading orthopedic journals included smoking as a factor. The evidence on smoking's effect on meniscus treatment is mixed, necessitating further investigation.

Comparison of Functional Outcomes after Anterior Cruciate Ligament Reconstruction with Meniscal Repair for Unstable versus Stable Meniscal Tears

This study aimed to compare functional outcomes including knee muscle strength in the quadriceps and hamstrings, and proprioception, assessed through dynamic postural stability (overall stability index [OSI]) and self-reported outcomes in the operated and non-operated knees between anterior cruciate ligament reconstruction (ACLR) with meniscal repair for unstable (root and radial tears) and stable (longitudinal, horizontal, and bucket handle tears) meniscal tears. A total of 76 patients were randomly selected (41 with ACLR with meniscal repair for unstable meniscal tears and 35 with ACLR with meniscal repair for stable meniscal tears) at three different time points (preoperative, 6 months, and 12 months). Repeated measures analysis of variance was used to investigate the differences in outcomes for between-subject and within-subject factors. In the operated knees, there were no significant differences for functional outcomes between the two groups (all p > 0.05). In the non-operated knees, a significant difference was observed for the OSI between the two groups, which was significantly higher in ACLR with meniscal repair for unstable meniscal tears than for stable meniscal tears at 6 months (p < 0.001). Multiple linear regression analysis showed that age (p = 0.027), preoperative OSI in the operated knees (p = 0.005), and postoperative OSI in the operated knees at 6 months (p = 0.002) were significant and independent predictors for OSI in the non-operated knees at 6 months postoperatively. Therefore, while no differences were observed in functional outcomes between the two groups in the operated knees, dynamic postural stability was poorer at 6 months postoperatively in the non-operated knees of patients with ACLR with meniscal repair for unstable meniscal tears. Furthermore, a significant correlation was observed between preoperative/postoperative dynamic postural stability in the operated knees and postoperative dynamic postural stability in the non-operated knees. Hence, we recommend incorporating balance exercises for both knees in post-surgical rehabilitation, particularly for patients with unstable meniscal tears.

Differences Between Traumatic and Degenerative Medial Meniscus Posterior Root Tears: A Systematic Review

BACKGROUND

Intact meniscus roots are a prerequisite for normal meniscal function, including even distribution of compressive forces across the knee joint. An injury to the root disrupts the hoop strength of the meniscus and may lead to its extrusion and the development of osteoarthritis. A medial meniscus posterior root tear (MMPRT) is often thought to have a primary degenerative pathogenesis. However, there is mention of some cases of MMPRTs where the patients have a solely traumatic injury to a previously healthy meniscus.

PURPOSE

To describe a subpopulation of patients with traumatic MMPRT.

STUDY DESIGN

Systematic review; Level of evidence, 5.

METHODS

The Web of Science database (www.webofscience.com) was queried using the Medical Subject Headings term "medial root tear." Articles were reviewed, and those evaluated for MMPRTs in a degenerative meniscus were excluded. A total of 25 articles describing cases of acute traumatic causes were included in this study. For these articles, the patient characteristics, injury mechanisms, and concomitant injuries evaluated were recorded and pooled.

RESULTS

The search revealed 660 articles, and 25 were selected for inclusion. A total of 113 patients with a traumatic MMPRT were identified and included in this review. The study population had a mean age of 27.1 years and a high share of men (64%). Also, this review displays how most patients with traumatic MMPRTs also suffer concomitant injuries (68%).

CONCLUSION

The findings in this review support our hypothesis that there is a unique subgroup with acute traumatic MMPRTs that have unique patient characteristics, injury mechanisms, and combined injuries, compared with previously published reviews on MMPRTs.

Meniscus root tears: state of the art

BACKGROUND

Meniscus root tears represent significant pathology that, historically, has been underdiagnosed and undertreated. However, the recognition of their clinical and functional significance has recently surged, mainly due to their frequent association with anterior cruciate ligament injuries.

AIM

This comprehensive review discusses various aspects of meniscal root tears, including their epidemiology, biomechanics, etiology, clinical and radiological findings, classification, management and surgical techniques.

Osteoarthritis Development Following Meniscectomy vs. Meniscal Repair for Posterior Medial Meniscus Injuries: A Systematic Review

This systematic review aims to evaluate critically and synthesize the existing literature on the outcomes of meniscectomy versus meniscal repair for posterior medial meniscus injuries, with a focus on osteoarthritis (OA) development. We sought to assess the incidence of OA following both treatment modalities, compare functional outcomes post-treatment, and identify factors influencing treatment choice, providing evidence-based recommendations for clinical decision-making. A comprehensive search strategy was employed across PubMed, Scopus, and Embase up until December 2023, adhering to PRISMA guidelines. The primary outcomes included OA development, functional knee outcomes, and quality of life measures. Six studies met the inclusion criteria, encompassing 298 patients. The systematic review revealed a significant association between meniscal repair and decreased progression of OA compared to meniscectomy. Meniscectomy patients demonstrated a 51.42% progression rate towards OA, significantly higher than the 21.28% observed in meniscal repair patients. Functional outcomes, as measured by the International Knee Documentation Committee (IKDC) and Lysholm scores, were notably better in the repair group, with average scores of 74.68 (IKDC) and 83.78 (Lysholm) compared to 67.55 (IKDC) and 74.56 (Lysholm) in the meniscectomy group. Furthermore, the rate of complete healing in the repair group was reported at 71.4%, as one study reported, indicating a favorable prognosis for meniscal preservation. However, these pooled data should be interpreted with consideration to the heterogeneity of the analyzed studies. Meniscal repair for posterior medial meniscus injuries is superior to meniscectomy in preventing OA development and achieving better functional outcomes and quality of life post-treatment. These findings strongly suggest the adoption of meniscal repair as the preferred treatment modality for such injuries, emphasizing the need for a paradigm shift in clinical practice towards preserving meniscal integrity to optimize patient outcomes.

Extrusion After Meniscal Allograft Transplantation Is Lower or Equal With Bony Compared With Soft-Tissue Root Fixation: A Systematic Review

PURPOSE

To provide an update on the incidence and extent of graft extrusion after meniscal allograft transplantation (MAT) and to systematically review the literature to identify whether the type of root fixation or additional surgical techniques may reduce the risk of graft extrusion development.

METHODS

A systematic search, in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines, was conducted using the MEDLINE database, EMBASE database, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials (CENTRAL) database. Patients undergoing medial meniscal allograft transplantation (MMAT) or lateral meniscal allograft transplantation (LMAT) were included. The primary outcome measure was meniscal extrusion measured on postoperative magnetic resonance imaging scans taken more than 6 weeks after MAT. The following extrusion outcomes were investigated: absolute extrusion (AE), relative percentage of extrusion (RPE), and proportion of major extrusion (PME). Additional surgical techniques that reduced the risk of graft extrusion development in the included comparative studies were identified.

RESULTS

For MMAT, the pooled mean extrusion outcomes for soft-tissue versus bony fixation were as follows: AE of 3.2 mm versus 3.36 mm and RPE of 44.43% versus 33.18%. The pooled mean PME for MMAT with soft-tissue fixation was 51.62%. For LMAT, the pooled mean extrusion outcomes for soft-tissue versus bony fixation were as follows: AE of 3.72 mm versus 2.78 mm, RPE of 31.89% versus 29.47%, and PME of 64.37% versus 35.80%. Additional capsulodesis was identified as a technique to reduce LMAT extrusion.

CONCLUSIONS

This study highlights that graft extrusion is a common finding after MMAT and LMAT, independent of the root fixation technique. However, MAT extrusion with bony fixation was, depending on the outcome measurement, lower than or equal to that with soft-tissue fixation.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I, III, and IV studies.

Utility of Platelet-Rich Plasma Therapy in the Management of Meniscus Injuries: A narrative review

Menisci are crucial for knee joint functions and meniscal tears are common injuries, especially in sports activities. Platelet-rich plasma (PRP), which enhances healing, has emerged as a promising additive treatment for meniscus injuries, utilizing the regenerative properties of platelets and growth factors for improved clinical outcomes. In studies with a follow-up period of less than one year, the use of platelet-rich plasma (PRP) therapy for meniscus injuries showed significant improvements in knee symptoms and daily activity. Patients experienced enhanced outcomes in terms of pain reduction and increased sports activity, with MRI scans indicating stable meniscus conditions after six months. Studies with a follow-up of more than one year, however, did not find significant differences between groups treated with PRP and groups not treated with PRP in terms of various outcome measures, including pain and knee function. The vascularization of the menisci is vital for their proper function, and insufficient blood supply can affect healing of meniscal injuries. PRP therapy is used to enhance meniscal healing by introducing growth factors and anti-inflammatory agents. PRP therapy may enable athletes with meniscal tears to return to sports more quickly and has less rehabilitation duration. While PRP seems promising as an alternative to failed treatment or as an adjunct to treatment in the short term, its long-term effectiveness remains inconclusive. Patient preferences, commitment to therapy rehabilitation, and cost should all be considered on an individual basis.

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Changes in Functional Meniscal Morphology During Skeletal Growth and Maturation

Background

Little is known on how meniscal morphology develops during skeletal growth and maturation and its subsequent relationship with the corresponding bony anatomy.

Hypotheses

(1) Meniscal dimensions and morphology would change by age during skeletal growth and maturation in different ways in boys compared with girls. (2) Morphological features of the medial and lateral menisci would correlate to medial and lateral femoral condyle curvatures.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Anatomic features of the medial and lateral menisci were measured on magnetic resonance imaging scans from 269 unique knees (age, 3-18 years; 51% female) with no prior history of injury, congenital or growth-related skeletal disorders, or bony deformities. Morphological shape-based measurements were normalized to tibial plateau width or determined as ratios of meniscal dimensions. The association between age and anatomy was analyzed with linear regression. Two-way analysis of variance with the Holm-Šídák post hoc method was used to compare anatomy between sexes in different age groups. Linear regression was used to evaluate the relationship between femoral condyle curvature radius and meniscal morphology in each compartment after adjusting for age and sex.

Results

Meniscal length, width, horn distance, mean cross-sectional area (CSA), and mean height increased with age in both sexes (R2 > 0.1; P < .001). Age-related changes in meniscal morphology were seen in normalized length, width, horn distance, and mean height; width-to-length ratio; horn distance-to-length ratio (lateral meniscus only); normalized mean CSA (except lateral meniscus in girls); and mean tip angle (R2 > 0.04; P < .02). Sex-based differences were also found, with some morphological differences (normalized length and height) throughout development (P < .03) and size differences (length, width, and mean CSA) in later development (P < .01). After adjusting for age and sex, there were significant correlations between medial condyle curvature radius and normalized width, width-to-length ratio, horn distance, horn distance-to-length ratio, mean CSA, and mean height of the medial meniscus (P≤ .041) and between lateral condyle curvature radius and normalized length, mean height, and mean tip angle of the lateral meniscus (P≤ .004).

Conclusion

Age-related changes in meniscal dimensions and morphology, most notably a nonuniform growth pattern in meniscal geometry, occurred during skeletal growth and maturation, with different trends in boys than in girls.

The role of inflammatory mediators and matrix metalloproteinases (MMPs) in the progression of osteoarthritis

Osteoarthritis (OA) is a chronic musculoskeletal disorder characterized by an imbalance between (synthesis) and catabolism (degradation) in altered homeostasis of articular cartilage mediated primarily by the innate immune system. OA degenerates the joints resulting in synovial hyperplasia, degradation of articular cartilage with damage of the structural and functional integrity of the cartilage extracellular matrix, subchondral sclerosis, osteophyte formation, and is characterized by chronic pain, stiffness, and loss of function. Inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. In OA apart from catabolic effects, anti-inflammatory anabolic processes also occur continually. There is also an underlying chronic inflammation present, not only in cartilage tissue but also within the synovium, which perpetuates tissue destruction of the OA joint. The consideration of inflammation in OA considers synovitis and/or other cellular and molecular events in the synovium during the progression of OA. In this review, we have presented the progression of joint degradation that results in OA. The critical role of inflammation in the pathogenesis of OA is discussed in detail along with the dysregulation within the cytokine networks composed of inflammatory and anti-inflammatory cytokines that drive catabolic pathways, inhibit matrix synthesis, and promote cellular apoptosis. OA pathogenesis, fluctuation of synovitis, and its clinical impact on disease progression are presented here along with the role of synovial macrophages in promoting inflammatory and destructive responses in OA. The role of interplay between different cytokines, structure, and function of their receptors in the inter-cellular signaling pathway is further explored. The effect of cytokines in the increased synthesis and release of matrix-decomposing proteolytic enzymes, such as matrix metalloproteinase (MMPs) and a disintegrin-like and metalloproteinase with thrombospondin motif (ADAMTS), is elaborated emphasizing the potential impact of MMPs on the chondrocytes, synovial cells, articular and periarticular tissues, and other immune system cells migrating to the site of inflammation. We also shed light on the pathogenesis of OA via oxidative damage particularly due to nitric oxide (NO) via its angiogenic response to inflammation. We concluded by presenting the current knowledge about the tissue inhibitors of metalloproteinases (TIMPs). Synthetic MMP inhibitors include zinc binding group (ZBG), non-ZBG, and mechanism-based inhibitors, all of which have the potential to be therapeutically beneficial in the treatment of osteoarthritis. Improving our understanding of the signaling pathways and molecular mechanisms that regulate the MMP gene expression, may open up new avenues for the creation of therapies that can stop the joint damage associated with OA.

The Association between the Extent of the Osteoarthritic Meniscus Degeneration and Cigarette Smoking-A Pilot Study

Background and Objectives: The negative effects of smoking on the musculoskeletal system were presented by many authors, although the relationship between smoking and osteoarthritis remains unclear. The aim of this paper was to investigate the negative effects of smoking on meniscal tissue in osteoarthritic knees by microscopic examination, by adapting the Bonar scoring system and its modifications. Materials and Methods: The study involved 34 patients with varus knees, from whom 65 samples of knee menisci were obtained. The mean age in the studied group was 65.385 years. The smoking status of the patients concluded that there were 13 smokers and 21 nonsmokers. Results: Among smokers, the mean classical Bonar score was 8.42 and the mean modified Bonar score was 6.65, while nonsmokers were characterized by scores of 8.51 and 7.35, respectively. There was a statistically significant negative correlation between the number of cigarettes and the collagen in the medial meniscus (p = 0.0197). Moreover, in the medial meniscus, the modified Bonar score correlated negatively with the number of cigarettes (p = 0.0180). Similarly, such a correlation was observed between the number of cigarettes and the modified Bonar score in the lateral meniscus (p = 0.04571). Furthermore, no correlation was identified between the number of cigarettes and the classical Bonar score in the lateral meniscus. There was a statistically significant difference in the collagen variable value between the smokers and nonsmokers groups (p = 0.04525). Conclusions: The microscopic investigation showed no differences in the menisci of smokers and nonsmokers, except for the collagen, which was more organized in smokers. Moreover, the modified Bonar score was correlated negatively with the number of cigarettes, which supports the role of neovascularization in meniscus pathology under the influence of tobacco smoking.

On the characteristics of natural hydraulic dampers: An image-based approach to study the fluid flow behaviour inside the human meniscal tissue

The meniscal tissue is a layered material with varying properties influenced by collagen content and arrangement. Understanding the relationship between structure and properties is crucial for disease management, treatment development, and biomaterial design. The internal layer of the meniscus is softer and more deformable than the outer layers, thanks to interconnected collagen channels that guide fluid flow. To investigate these relationships, we propose an integrated approach that combines Computational Fluid Dynamics (CFD) with Image Analysis (CFD-IA). We analyze fluid flow in the internal architecture of the human meniscus across a range of inlet velocities (0.1 mm/s to 1.6 m/s) using high-resolution 3D micro-computed tomography scans. Statistical correlations are observed between architectural parameters (tortuosity, connectivity, porosity, pore size) and fluid flow parameters (Re number distribution, permeability). Some channels exhibit Re values of 1400 at an inlet velocity of 1.6 m/s, and a transition from Darcy's regime to a non-Darcian regime occurs around an inlet velocity of 0.02 m/s. Location-dependent permeability ranges from 20-32 Darcy. Regression modelling reveals a strong correlation between fluid velocity and tortuosity at high inlet velocities, as well as with channel diameter at low inlet velocities. At higher inlet velocities, flow paths deviate more from the preferential direction, resulting in a decrease in the concentration parameter by an average of 0.4. This research provides valuable insights into the fluid flow behaviour within the meniscus and its structural influences. 3D models and image stack are available to download at https://doi.org/10.5281/zenodo.10401592. STATEMENT OF SIGNIFICANCE: The meniscus is a highly porous soft tissue with remarkable properties of load transfer and energy absorption. We give insight on the mechanism of energy absorption from high resolution uCT scans, never presented before, and a new method which combine CFD and image. The structure is similar to a sandwich structure with a stiff outside layer and a soft internal layer made of collagen channels oriented in a preferential direction guiding the fluid flow, enabling it to accommodate deformation and dissipate energy, making it a potentially optimized damping system. We investigate architectural/ fluid flow parameters- fluid regimes relationship, which is of interest of the readers working on designing suitable biomimetic systems that can be adopted for replacement.

Evaluation of meniscal elasticity using shear wave elastography in obese children and adolescents: a preliminary cross-sectional study

BACKGROUND

Musculoskeletal problems such as pain, joint pathology, increased risk of fracture, and the development of structural deformities are common in childhood obesity. Increased mechanical stress on the knee joint leads to degenerative changes in the cartilage and meniscus. Meniscal elasticity values increase in meniscal degeneration. Shear wave elastography (SWE) is an ultrasound-based imaging technique based on the principle of measuring tissue elasticity.

OBJECTIVE

We aimed to investigate the changes in meniscal stiffness and thickness that can be caused by obesity in children and adolescents using SWE.

MATERIALS AND METHODS

In this prospective cross-sectional study, the menisci of obese (n=44) and age- and sex-matched healthy weight (n=44) children and adolescents were assessed by SWE. Meniscal elasticity was measured in kPa on the coronal plane. Independent samples t-test was used to compare meniscal elasticity values between groups. Additionally, Pearson's correlation test was used to examine the relationships between elasticity values and age, height, weight, and body mass index (BMI).

RESULTS

Meniscal elasticity values were significantly higher in the obese group than in the control group (P<0.001). In both groups, there was no significant difference in meniscal stiffness between the boys and girls or between the right and left sides. In the obese group, there were weak and moderate positive correlations between meniscal elasticity values and age, weight, and BMI (P<0.05). There was no significant difference in meniscal thickness between the obese and control groups.

CONCLUSION

Meniscal stiffness is increased in obese children and adolescents.

Incidence of and Risk Factors for Medial Meniscal Lesions at the Time of ACL Reconstruction: An Analysis of 4697 Knees From the SANTI Study Group Database

BACKGROUND

Medial meniscal (MM) lesions (MMLs) are a common finding at the time of anterior cruciate ligament reconstruction (ACLR). It is recognized that evaluation of the posteromedial compartment reduces the rate of missed MML diagnoses.

PURPOSE

To determine the incidence of MMLs in patients undergoing ACLR, when using a standardized arthroscopic approach that included posteromedial compartment evaluation, as well as to determine how the incidence of MMLs changed with increasing time intervals between injury and surgery, and to investigate what risk factors were associated with their presence.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective analysis of prospectively collected data was performed. All patients who underwent primary ACLR between January 2013 and March 2023 were considered for study eligibility. The epidemiology was defined by categorizing and reporting the incidence and categorizing the spectrum of MM tear types. Risk factors associated with MMLs were analyzed using a logistic regression model.

RESULTS

MMLs were identified in 1851 (39.4%) of 4697 consecutive patients undergoing ACLR. The overall incidence of MMLs was 33.1% for the period of 0 to 3 months, 38.7% for the period of 3 to 12 months, and 59.6% for the period of >12 months. The overall incidence of MMLs increased with longer durations of time between injury and surgery, along with significant increases in complex, bucket-handle, ramp, and/or flap lesions. The largest increase in incidence of MMLs was observed for complex MM tear patterns. Risk factors associated with MMLs included time between injury and surgery >3 months (odds ratio [OR], 1.320; 95% CI, 1.155-1.509; P < .0001) and >12 months (OR, 3.052; 95% CI, 2.553-3.649; P < .0001), male sex (OR, 1.501; 95% CI, 1.304-1.729; P < .0001), body mass index (BMI) ≥25 (OR, 1.193; 95% CI, 1.046-1.362; P = .0088), and lateral meniscal lesion (OR, 1.737; 95% CI, 1.519-1.986; P < .0001).

CONCLUSION

Overall, MMLs were identified in 39.4% of 4697 patients undergoing ACLR when posteromedial compartment evaluation was performed in addition to standard anterior viewing. The incidence of MMLs and the complexity of tear types increased significantly with increasing time intervals between the index injury and ACLR. Secondary risk factors associated with an increased incidence of medial meniscal tears include male sex, increased BMI, and lateral meniscal lesions.

A Pilot Study of Decellularized Cartilage for Laryngotracheal Reconstruction in a Neonatal Pig Model

OBJECTIVE

Severe subglottic stenosis develops as a response to intubation in 1% of the >200,000 neonatal intensive care unit infants per year and may require laryngotracheal reconstruction (LTR) with autologous hyaline cartilage. Although effective, LTR is limited by comorbidities, severity of stenosis, and graft integration. In children, there is a significant incidence of restenosis requiring revision surgery. Tissue engineering has been proposed to develop alterative grafting options to improve outcomes and eliminate donor-site morbidity. Our objective is to engineer a decellularized, channel-laden xenogeneic cartilage graft, that we deployed in a proof-of-concept, neonatal porcine LTR model.

METHODS

Meniscal porcine cartilage was freeze-thawed and washed with pepsin/elastase to decellularize and create microchannels. A 6 × 10-mm decellularized cartilage graft was then implanted in 4 infant pigs in an anterior cricoid split. Airway patency and host response were monitored endoscopically until sacrifice at 12 weeks, when the construct phenotype, cricoid expansion, mechanics, and histomorphometry were evaluated.

RESULTS

The selective digestion of meniscal components yielded decellularized cartilage with cell-size channels. After LTR with decellularized meniscus, neonatal pigs were monitored via periodic endoscopy observing re-epithelization, integration, and neocartilage formation. At 12 weeks, the graft appeared integrated and exhibited airway expansion of 4 mm in micro-CT and endoscopy. Micro-CT revealed a larger lumen compared with age-matched controls. Finally, histology showed significant neocartilage formation.

CONCLUSION

Our neonatal porcine LTR model with a decellularized cartilage graft is a novel approach to tissue engineered pediatric LTR. This pilot study sets the stage for "off-the-shelf" graft procurement and future optimization of MEND for LTR.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:807-814, 2024.

Surgical Management of Traumatic Meniscus Injuries

The menisci increase the contact area of load bearing in the knee and thus disperse the mechanical stress via their circumferential tensile fibers. Traumatic meniscus injuries cause mechanical symptoms in the knee, and are more prevalent amongst younger, more active patients, compared to degenerative tears amongst the elderly population. Traumatic meniscus tears typically result from the load-and-shear mechanism in the knee joint. The treatment depends on the size, location, and pattern of the tear. For non-repairable tears, partial or total meniscal resection decreases its tensile stress and increases joint contact stress, thus potentiating the risk of arthritis. A longitudinal vertical tear pattern at the peripheral third red-red zone leads to higher healing potential after repair. The postoperative rehabilitation protocols after repair range from immediate weight-bearing with no range of motion restrictions to non-weight bearing and delayed mobilization for weeks. Pediatric and adolescent patients may require special considerations due to their activity levels, or distinct pathologies such as a discoid meniscus. Further biomechanical and biologic evidence is needed to guide surgical management, postoperative rehabilitation protocols, and future technology applications for traumatic meniscus injuries.

Surgical Repair of Hypermobile Lateral Meniscus Secondary to Popliteomeniscal Fascicle Tears Improves Pain and Mechanical Symptoms

Purpose

To describe the clinical and radiographic features associated with isolated hypermobile lateral meniscus (HLM), and report patient outcomes following surgically repaired isolated HLM.

Methods

All patients diagnosed with HLM from 2000 to 2020 at a single academic institution were identified and reviewed. Patients were excluded if they had concomitant ligament injury or lacked 2-year follow-up. Preoperative and postoperative visual analog scale (VAS) pain scores were determined from clinical notes. Statistical analysis was performed in JMP, and statistical significance was determined with use of a paired t-test.

Results

Eighteen knees in 17 patients met inclusion criteria. Mean patient age was 24.1 (range: 6-61) years. Mean follow-up was 73 months (25-151 months). All 18 knees reported pain at presentation; 94% (17/18) had mechanical symptoms. All 18 knees had preoperative MRIs, but only 1 (5.6%) knee was correctly diagnosed by a musculoskeletal trained radiologist. Most repairs were performed with an all-inside technique (61%, 11/18). VAS score improved significantly from 7.2 ± 2.9 preoperatively to 0.7 ± 1.9 postoperatively, with average improvement of VAS score of 6.5 (P < .001). Only one (5.6%) knee required revision meniscal surgery.

Conclusion

Hypermobile lateral meniscus patients commonly see multiple providers, fail to have their HLM diagnosed on MRI, and undergo various treatments prior to a successful diagnosis. Localized lateral joint line pain, mechanical symptoms, and absence of distinct meniscus tear on MRI are the most frequent clinical presentations. Surgery with meniscus repair is a reliable solution to improve pain and mechanical symptoms.

Level of Evidence

Level IV, therapeutic case series.

Cell Count and Cell Density Decrease as Age Increases in Cadaveric Pediatric Medial Menisci

Purpose

To examine the histologic changes in terms of cellularity, cell density, and nuclear shape in medial meniscal cellularity during skeletal development using pediatric cadaver specimens.

Methods

Medial menisci from 26 pediatric cadavers, 11 female and 15 male (total 36 menisci), were obtained from tissue bank. Mean age of female donors was 34 months (1-108 months) and of male donors was 52 months (1-132 months). Menisci were processed and embedded in paraffin blocks. Each tissue block containing 6 representative areas of meniscus (anterior root, anterior horn, body [n = 2], posterior horn, and posterior root) was sectioned at 4 microns and stained with hematoxylin and eosin for evaluation of chondrocyte nuclei. Each of the 6 representative areas was imaged at 10×; one image on peripheral one-third of section, the second image on central two-thirds of the section. FIJI imaging software was used to measure cell count, cell density, and nuclear morphology (1 = perfect circle). Data analysis included linear mixed models, Type II analysis of variance tests, and pairwise tests with the Tukey correction to assess statistical significance.

Results

Peripheral meniscus was more cellular than central meniscus. The cell count was found to decrease by 14% per year of age. Peripheral cell count decreased at a rate similar to the cell count in the central meniscus. Meniscal cell density was 2× higher peripherally than centrally. Overall average cell density in all locations in the menisci decreased by an average of 14% per year of age.

Conclusions

The results of this study reveal decreases in cell count, cell density, and circularity as age increases in cadaveric pediatric medial menisci.

Clinical Relevance

To better understand the development of pediatric menisci at a cellular level and use this knowledge in the future on how to maintain the menisci in a younger, healthier state.

Assessment of Knee Menisci in Healthy Adults Using Shear Wave Elastography

OBJECTIVES

The aim of this study was to explore the application value of shear wave elastography in healthy adults with knee meniscus.

METHODS

One hundred adult subjects who underwent health checkups at our hospital from December 2022 to February 2023 were selected as research participants. Shear wave elastography was used to evaluate the periphery of the lateral and medial meniscus in both knees. To assess the mean differences in Young's modulus values between male and female groups, a one-way analysis of variance (ANOVA) and independent samples t-test were conducted. In addition, a Pearson correlation coefficient test was used to analyze the correlation between the elastic values of the meniscus and age, height, weight, and body mass index (BMI).

RESULTS

There were no significant differences in elastic values between the lateral meniscus of the left and right sides or between the medial meniscus of the left and right sides within the same gender group (P > .05). Stiffness values of the medial meniscus were higher in each gender group than those of the lateral meniscus (P < .01). Additionally, males demonstrated higher stiffness values than females (P < .01). As age increased, the Young's modulus of the meniscus increased significantly (r > .75, P < .01).

CONCLUSION

Shear wave elastography can serve as an adjunctive tool to aid in the assessment of knee meniscal elasticity.

Isolated meniscus allograft transplantation with soft-tissue technique effectively reduces knee laxity in the presence of previous meniscectomy: In-vivo navigation of 18 consecutive cases

OBJECTIVES

Although meniscal allograft transplantation (MAT) is a well-established procedure with satisfactory clinical results, limited in vivo kinematic information exists on the effect of medial and lateral MAT performed in the clinical setting. The purpose of the present study was to evaluate the biomechanical effect of arthroscopic isolated medial and lateral MAT with a soft-tissue fixation on pre- and post-operative knee laxity using a surgical navigation system.

METHODS

18 consecutive patients undergoing MAT (8 medial, 10 lateral) were enrolled. A surgical navigation system was used to quantify the anterior-posterior displacement at 30 and 90 degrees of knee flexion (AP30 and AP90), the varus-valgus rotation at 0 and 30 degrees of knee flexion (VV0 and VV30) and the dynamic laxity on the pivot-shift test (PS), which was determined through the anterior displacement of the lateral tibial compartment (APlat) and posterior acceleration of the lateral tibial compartment during tibial reduction (ACC). Data from laxity before and after MAT were compared through paired t-test (p ​< ​0.05).

RESULTS

After medial MAT, there was a significant decrease in tibial translation of 3.1 ​mm (31%; p ​= ​0.001) for AP30 and 2.3 ​mm (27%; p ​= ​0.020) for AP90, a significant difference of 2.5° (50%; p ​= ​0.002) for VV0 and 1.7° (27%; p ​= ​0.012) for VV30. However, medial MAT did not determine any reduction in the PS kinematic data. Lateral MAT determined a significant decrease in the tibial translation of 2.5 ​mm (38%; p ​< ​0.001) for AP30 and 1.9 ​mm (34%; p ​= ​0.004) for AP90 as well as a significant difference of 3.4° (59%; p ​< ​0.001) for VV0 and of 1.7° (23%; p ​= ​0.011) for VV30. There was also a significant reduction of the PS of 4.4 ​mm (22%; p ​= ​0.028) for APlat and 384.8 ​mm/s2 (51%; p ​= ​0.005) for ACC.

CONCLUSION

MAT with soft-tissue fixation results in a significant laxity reduction in an in-vivo setting. Medial MAT improved knee kinematics by determining a significant reduction with particular emphasis on AP translation and VV manoeuvre. Conversely, Lateral MAT determined a massive reduction of the PS and a mild decrease of the AP translation and VV manoeuvre.

STUDY DESIGN

Controlled laboratory study.

Graft failure within 2 years of isolated anterior cruciate ligament reconstruction is associated with increased risk of secondary meniscus tears

PURPOSE

A debilitating complication following anterior cruciate ligament reconstruction is a secondary meniscus tear. Currently, the literature is mixed regarding the risk factors associated with the incidence of secondary meniscus tears. The aim of this study was to investigate risk factors associated with meniscus tears following an isolated primary anterior cruciate ligament reconstruction. ACL graft failure was hypothesized to be the strongest risk factor for secondary meniscal injury occurrence.

METHODS

A retrospective cohort analysis was performed using the PearlDiver Database. Patients with a primary anterior cruciate ligament reconstruction were identified in the database. Patients with concomitant knee ligament injury or meniscus injury present at the time the index procedure were excluded. Patients were grouped to those who had a secondary meniscus tear within 2 years following anterior cruciate ligament reconstruction and those who did not. Univariate analysis and multivariable regression analysis was conducted to identify significant risk factors for a secondary meniscus tear.

RESULTS

There were 25,622 patients meeting criteria for inclusion in this study. Within 2 years from the primary anterior cruciate ligament reconstruction, there were 1,781 patients (7.0%) that experienced a meniscus tear. Graft failure had the highest odds of having a postoperative meniscus tear within 2 years (OR: 4.1; CI 3.5-4.8; p < 0.002). Additional significant risk factors included tobacco use (OR: 2.0; CI 1.0-3.1; p < 0.001), increased Charlson Comorbidity Index (OR: 1.2; CI 1.1-1.4), male gender (OR: 1.1; CI 1.1-1.2; p < 0.001), obesity (OR: 1.1; CI 1.1-1.2; p < 0.001), delayed surgery (OR:1.1; CI 1.1-1.2; p < 0.002), and patients age 30 and older (OR: 1.0; CI 1.0-1.0; p < 0.001).

CONCLUSIONS

This study found that anterior cruciate ligament graft failure is the strongest predictor of post-operative meniscus tears. Other risk factors, including tobacco use, increased CCI, male gender, obesity, delayed surgery, and age 30 and older, were established, with several being modifiable. Therefore, targeted preoperative optimization of modifiable risk factors and postoperative protocols may reduce the risk of secondary meniscus tears.

LEVEL OF EVIDENCE

Level III, prognostic trial.

Basic fibroblast growth factor promotes meniscus regeneration through the cultivation of synovial mesenchymal stem cells via the CXCL6-CXCR2 pathway

OBJECTIVE

To investigate the efficacy of basic fibroblast growth factor (bFGF) in promoting meniscus regeneration by cultivating synovial mesenchymal stem cells (SMSCs) and to validate the underlying mechanisms.

METHODS

Human SMSCs were collected from patients with osteoarthritis. Eight-week-old nude rats underwent hemi-meniscectomy, and SMSCs in pellet form, either with or without bFGF (1.0 × 106 cells per pellet), were implanted at the site of meniscus defects. Rats were divided into the control (no transplantation), FGF (-) (pellet without bFGF), and FGF (+) (pellet with bFGF) groups. Different examinations, including assessment of the regenerated meniscus area, histological scoring of the regenerated meniscus and cartilage, meniscus indentation test, and immunohistochemistry analysis, were performed at 4 and 8 weeks after surgery.

RESULTS

Transplanted SMSCs adhered to the regenerative meniscus. Compared with the control group, the FGF (+) group had larger regenerated meniscus areas, superior histological scores of the meniscus and cartilage, and better meniscus mechanical properties. RNA sequencing of SMSCs revealed that the gene expression of chemokines that bind to CXCR2 was upregulated by bFGF. Furthermore, conditioned medium derived from SMSCs cultivated with bFGF exhibited enhanced cell migration, proliferation, and chondrogenic differentiation, which were specifically inhibited by CXCR2 or CXCL6 inhibitors.

CONCLUSION

SMSCs cultured with bFGF promoted the expression of CXCL6. This mechanism may enhance cell migration, proliferation, and chondrogenic differentiation, thereby resulting in superior meniscus regeneration and cartilage preservation.

Bioprinting of scaled-up meniscal grafts by spatially patterning phenotypically distinct meniscus progenitor cells within melt electrowritten scaffolds

Meniscus injuries are a common problem in orthopedic medicine and are associated with a significantly increased risk of developing osteoarthritis. While developments have been made in the field of meniscus regeneration, the engineering of cell-laden constructs that mimic the complex structure, composition and biomechanics of the native tissue remains a significant challenge. This can be linked to the use of cells that are not phenotypically representative of the different zones of the meniscus, and an inability to direct the spatial organization of engineered meniscal tissues. In this study we investigated the potential of zone-specific meniscus progenitor cells (MPCs) to generate functional meniscal tissue following their deposition into melt electrowritten (MEW) scaffolds. We first confirmed that fibronectin selected MPCs from the inner and outer regions of the meniscus maintain their differentiation capacity with prolonged monolayer expansion, opening their use within advanced biofabrication strategies. By depositing MPCs within MEW scaffolds with elongated pore shapes, which functioned as physical boundaries to direct cell growth and extracellular matrix production, we were able to bioprint anisotropic fibrocartilaginous tissues with preferentially aligned collagen networks. Furthermore, by using MPCs isolated from the inner (iMPCs) and outer (oMPCs) zone of the meniscus, we were able to bioprint phenotypically distinct constructs mimicking aspects of the native tissue. An iterative MEW process was then implemented to print scaffolds with a similar wedged-shaped profile to that of the native meniscus, into which we deposited iMPCs and oMPCs in a spatially controlled manner. This process allowed us to engineer sulfated glycosaminoglycan and collagen rich constructs mimicking the geometry of the meniscus, with MPCs generating a more fibrocartilage-like tissue compared to the mesenchymal stromal/stem cells. Taken together, these results demonstrate how the convergence of emerging biofabrication platforms with tissue-specific progenitor cells can enable the engineering of complex tissues such as the meniscus.

Assessment of the relationship between smoking and meniscal injury

Objective

To determine whether being a smoker and the years of smoking correlate with the presence and degree of meniscal injury.

Materials and Methods

Individuals who underwent magnetic resonance imaging of the knee were divided into two groups: smokers and nonsmokers. For each smoker, the total smoking history was calculated by multiplying the daily consumption (packs/day) by the years of smoking, and the result is expressed as pack-years. In the evaluation of meniscal injury, the grade of injury was recorded. The thickness of the subcutaneous adipose tissue, as an indicator of obesity, was measured at the medial knee on axial plane images. The relationships that smoking and obesity had with meniscal injury were analyzed statistically.

Results

A total of 156 individuals were included in the study. The smoker group consisted of 48 individuals (30.8%), and the nonsmoker group consisted of 108 (69.2%). The meniscus was normal in one (2.1%) of the smokers and in 32 (29.6%) of the nonsmokers (p < 0.0001). The median subcutaneous adipose tissue thickness was 23 mm and 24 mm in the smokers and nonsmokers, respectively (p = 0.900). A moderate but statistically significant correlation was observed between packs/day and injury grade, as well as between pack-years and injury grade (r = 0.462, p = 0.001 and r = 0.523, p = 0.001, respectively). Smoking and age significantly increased the risk of meniscal injury, by 31.221 times (p = 0.001) and 1.076 times (p < 0.001), respectively.

Conclusion

Our findings indicate that current smoking and smoking history correlate significantly with meniscal injury grade.