Meniscal injury: I. Basic science and evaluation

Fully and Weakly Supervised Deep Learning for Meniscal Injury Classification, and Location Based on MRI

Meniscal injury is a common cause of knee joint pain and a precursor to knee osteoarthritis (KOA). The purpose of this study is to develop an automatic pipeline for meniscal injury classification and localization using fully and weakly supervised networks based on MRI images. In this retrospective study, data were from the osteoarthritis initiative (OAI). The MR images were reconstructed using a sagittal intermediate-weighted fat-suppressed turbo spin-echo sequence. (1) We used 130 knees from the OAI to develop the LGSA-UNet model which fuses the features of adjacent slices and adjusts the blocks in Siam to enable the central slice to obtain rich contextual information. (2) One thousand seven hundred and fifty-six knees from the OAI were included to establish segmentation and classification models. The segmentation model achieved a DICE coefficient ranging from 0.84 to 0.93. The AUC values ranged from 0.85 to 0.95 in the binary models. The accuracy for the three types of menisci (normal, tear, and maceration) ranged from 0.60 to 0.88. Furthermore, 206 knees from the orthopedic hospital were used as an external validation data set to evaluate the performance of the model. The segmentation and classification models still performed well on the external validation set. To compare the diagnostic performances between the deep learning (DL) models and radiologists, the external validation sets were sent to two radiologists. The binary classification model outperformed the diagnostic performance of the junior radiologist (0.82-0.87 versus 0.74-0.88). This study highlights the potential of DL in knee meniscus segmentation and injury classification which can help improve diagnostic efficiency.

Emerging biologic augmentation strategies for meniscal repair: a systematic review

BACKGROUND

Meniscal repair should be the gold standard. However, the meniscus is poorly vascularized and even an excellent meniscus repair may not heal. Therefore, numerous studies and systematic reviews have been carried out on platelet-rich plasma (PRP), mesenchymal stem cells (MSCs) and fibrin clots for meniscal augmentation, but the results remain controversial. This systematic review aimed to identify other emerging strategies for meniscal repair augmentation and to assess whether there are different avenues to explore in this field.

METHODS

A systematic literature review was conducted in August 2022. PubMed, Ovid MEDLINE(R) all, Ovid All EBM Reviews, Ovid Embase and ISI Web of Science databases were searched. In Vivo animal and human studies concerning the biological augmentation of meniscal lesions by factors other than PRP, MSCs or fibrin clots were included. Cartilage-only studies, previous systematic reviews and expert opinions were excluded. All data were analyzed by two independent reviewers.

RESULTS

Of 8965 studies only nineteen studies covering 12 different factors met the inclusion criteria. Eight studies investigated the use of growth factors for meniscal biologic augmentation, such as vascular endothelial growth factor or bone morphogenic protein 7. Five studies reported on cell therapy and six studies focused on other factors such as hyaluronic acid, simvastatin or atelocollagen. Most studies (n = 18) were performed on animal models with gross observation and histological evaluation as outcomes. Polymerase chain reaction and immunohistochemistry were also common. Biomechanical testing was the object of only two studies.

CONCLUSIONS

Although several augmentation strategies have been attempted, none has yielded conclusive results, testifying to a lack of understanding with regard to meniscal healing. More research is needed to better understand the pathways that regulate meniscus repair and how to act positively on them.

LEVEL OF EVIDENCE

Systematic review of case-control and animal laboratory studies.

An experimental study of the heterogeneity and anisotropy of porcine meniscal ultimate tensile strength

Characterizing the ultimate tensile strength (UTS) of the meniscus is critical in studying knee damage and pathology. This study aims to determine the UTS of the meniscus with an emphasis on its heterogeneity and anisotropy. We performed tensile tests to failure on the menisci of six month old Yorkshire pigs at a low strain rate. Specimens from the anterior, middle and posterior regions of the meniscus were tested in the radial and circumferential directions. Then the UTS was obtained for each specimen and the data were analyzed statistically, leading to a comprehensive view of the variations in porcine meniscal strength. The middle region has the highest average strength in the circumferential (43.3 ± 4.7 MPa) and radial (12.6 ± 2.2 MPa) directions. This is followed by the anterior and posterior regions, which present similar average values (about 34.0MPa) in circumferential direction. The average strength of each region in the radial direction is approximately one-fourth to one-third of the value in the circumferential direction. This study is novel as it is the first work to focus on the experimental methods to investigate the heterogeneity and anisotropy only for porcine meniscus.

Effect of Meniscal Tear Patterns and Preoperative Cartilage Status on Joint Space Width After Medial Opening-Wedge High Tibial Osteotomy

BACKGROUND

Medial opening-wedge high tibial osteotomy (MOWHTO) is performed to treat young adults with medial compartment knee osteoarthritis associated with varus deformity. However, factors influencing joint space width (JSW) vary according to the type of medial meniscal tear and have not yet been completely elucidated.

PURPOSE

To examine changes in JSW according to the type of medial meniscal tear after MOWHTO and analyze the influencing factors.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This study was conducted on 134 patients who underwent MOWHTO for medial osteoarthritis and were followed up for >2 years. The patients were classified into 3 groups based on medial meniscal status: intact, nonroot tear, and root tear. The authors then measured the JSW preoperatively and at 3 months, 6 months, 1 year, and >2 years postoperatively; analyzed whether the change in JSW varied according to meniscal status; and determined the association of these changes with the preoperative cartilage grade of the medial femoral condyle (MFC) and medial tibial plateau (MTP). International Knee Documentation Committee (IKDC) scores were used to evaluate clinical function.

RESULTS

Of the 134 patients, the medial meniscus was intact in 29 patients, a nonroot tear was observed in 58 patients, and a root tear was observed in 47 patients. Postoperatively, JSW increased for all groups, but the timing of the increase varied between the groups (P < .001). JSW increased the most 6 months postoperatively in the intact group and 3 months postoperatively in the nonroot tear and root tear groups (P < .001). Additionally, the increase in JSW was the greatest in the root tear group. Preoperatively, MFC and MTP cartilage status differed among the groups; MTP status did not affect the JSW, but MFC status did (P < .001). The IKDC score increased from the preoperative to postoperative time point in all groups, but there was no significant difference between groups.

CONCLUSION

The authors observed that the amount and timing of increase in JSW were dependent on the pattern of medial meniscal tear observed when MOWHTO was performed. In addition, the cartilage grade of MFC before surgery was associated with changes in JSW. The IKDC score was not significantly different between groups. However, a longer follow-up period is needed to analyze the correlation with the meniscal tear pattern and JSW.

Assessing the role of surface layer and molecular probe size in diffusion within meniscus tissue

Diffusion within extracellular matrix is essential to deliver nutrients and larger metabolites to the avascular region of the meniscus. It is well known that both structure and composition of the meniscus vary across its regions; therefore, it is crucial to fully understand how the heterogenous meniscal architecture affects its diffusive properties. The objective of this study was to investigate the effect of meniscal region (core tissue, femoral, and tibial surface layers) and molecular weight on the diffusivity of several molecules in porcine meniscus. Tissue samples were harvested from the central area of porcine lateral menisci. Diffusivity of fluorescein (MW 332 Da) and three fluorescence-labeled dextrans (MW 3k, 40k, and 150k Da) was measured via fluorescence recovery after photobleaching. Diffusivity was affected by molecular size, decreasing as the Stokes' radius of the solute increased. There was no significant effect of meniscal region on diffusivity for fluorescein, 3k and 40k dextrans (p>0.05). However, region did significantly affect the diffusivity of 150k Dextran, with that in the tibial surface layer being larger than in the core region (p = 0.001). Our findings contribute novel knowledge concerning the transport properties of the meniscus fibrocartilage. This data can be used to advance the understanding of tissue pathophysiology and explore effective approaches for tissue restoration.

Post-traumatic and OA-related lesions in the knee at baseline and 2 years after traumatic meniscal injury: Secondary analysis of a randomized controlled trial

OBJECTIVE

To assess the presence of early degenerative changes on Magnetic Resonance Imaging (MRI) 24 months after a traumatic meniscal tear and to compare these changes in patients treated with arthroscopic partial meniscectomy or physical therapy plus optional delayed arthroscopic partial meniscectomy.

DESIGN

We included patients aged 18-45 years with a recent onset, traumatic, MRI verified, isolated meniscal tear without radiographic osteoarthritis. Patients were randomized to arthroscopic partial meniscectomy or standardized physical therapy with optional delayed arthroscopic partial meniscectomy. MRIs at baseline and 24 months were scored using the MRI Osteoarthritis Knee Score (MOAKS). We compared baseline MRIs to healthy controls aged 18-40 years. The outcome was the progression of bone marrow lesions (BMLs), cartilage defects and osteophytes after 24 months in patients.

RESULTS

We included 99 patients and 50 controls. At baseline, grade 2 and 3 BMLs were present in 26% of the patients (n = 26), compared to 2% of the controls (n = 1) (between group difference 24% (95% CI 15% to 34%)). In patients, 35% (n = 35) had one or more cartilage defects grade 1 or higher, compared to 2% of controls (n = 1) (between group difference 33% (95% CI 23% to 44%)). At 24 months MRI was available for 40 patients randomized to arthroscopic partial meniscectomy and 41 patients randomized to physical therapy. At 24 months 30% (n = 12) of the patients randomized to arthroscopic partial meniscectomy showed BML worsening, compared to 22% (n = 9) of the patients randomized to physical therapy (between group difference 8% (95% CI -11% to 27%)). Worsening of cartilage defects was present in 40% (n = 16) of the arthroscopic partial meniscectomy group, compared to 22% (n = 9) of the physical therapy group (between group difference 18% (95% CI -2% to 38%)). Of the patients who had no cartilage defect at baseline, 33% of the arthroscopic partial meniscectomy group had a new cartilage defect at follow-up compared to 14% of the physical therapy group. Osteophyte worsening was present in 18% (n = 7) of the arthroscopic partial meniscectomy group and 15% (n = 6) of the physical therapy group (between group difference 3% (95% CI -13% to 19%)).

CONCLUSIONS

Our results might suggest more worsening of BMLs and cartilage defects with arthroscopic partial meniscectomy compared to physical therapy with optional delayed arthroscopic partial meniscectomy at 24-month follow-up in young patients with isolated traumatic meniscal tears without radiographic OA.

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.

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.

The biomechanical properties of human menisci: A systematic review

Biomechanical characterization of meniscal tissue ex vivo remains a critical need, particularly for the development of suitable meniscus replacements or therapeutic strategies that target the native mechanical properties of the meniscus. To date, a huge variety of test configurations and protocols have been reported, making it extremely difficult to compare the respective outcome parameters, thereby leading to misinterpretation. Therefore, the purpose of this systematic review was to identify test-specific parameters that contribute to uncertainties in the determination of mechanical properties of the human meniscus and its attachments, which derived from common quasi-static and dynamic tests in tension, compression, and shear. Strong evidence was found that the determined biomechanical properties vary significantly depending on the specific test parameters, as indicated by up to tenfold differences in both tensile and compressive properties. Test mode (stress relaxation, creep, cyclic) and configuration (unconfined, confined, in-situ), specimen shape and dimensions, preconditioning regimes, loading rates, post-processing of experimental data, and specimen age and degeneration were identified as the most critical parameters influencing the outcome measures. In conclusion, this work highlights an unmet need for standardization and reporting guidelines to facilitate comparability and may prove beneficial for evaluating the mechanical properties of novel meniscus constructs. STATEMENT OF SIGNIFICANCE: The biomechanical properties of the human meniscus have been studied extensively over the past decades. However, it remains unclear to what extent both test protocol and specimen-related differences are responsible for the enormous variability in material properties. Therefore, this systematic review analyzes the biomechanical properties of the human meniscus in the context of the underlying testing protocol. The most sensitive parameters affecting the determination of mechanical properties were identified and critically discussed. Currently, it is of utmost importance for scientists evaluating potential meniscal scaffolds and biomaterials to have a control group rather than a direct comparison to the literature. Standardization of both test procedures and reporting requirements is needed to improve and accelerate the development of meniscal replacement constructs.

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.

High tibial osteotomy is equally effective for varus malaligned knees with either virgin or wrecked medial meniscus: An age and gender-matched secondary analysis of a Francophone Arthroscopy Society Symposium

INTRODUCTION

Despite the growing concept of meniscal preservation, partial meniscectomy could be the definitive procedure in specific scenarios. And total meniscectomy was once before a frequent procedure, with current sequelae of degenerate knees. High tibial osteotomy (HTO) is an effective treatment for patients suffering from unicompartmental degenerative changes, and substantial deformities. However, it is yet to be answered, whether HTO is similarly effective in both post-meniscectomy knees and knees with not previously operated meniscus.

HYPOTHESIS

Outcomes of HTO is similar with or without previous history of total or subtotal meniscectomy.

METHODS

This study compared the clinical and radiological outcomes of 41 patients who received HTO and had no previous history of surgery in the ipsilateral knee (group I), and 41 age, and gender-matched patients who had meniscectomy surgery in the ipsilateral knee (group II). Preoperatively and postoperatively, all patients were clinically evaluated; the visual analogue scale scores, Tegner activity score, and the Western Ontario and Macmaster University scores were reported. Radiographically, osteoarthritis grade and pre- and postoperative parameters were reported, including hip-knee-ankle angle, femoral mechanical angle, medial proximal tibial angle, joint line convergence angle, proximal posterior tibial angle, and limb length discrepancy. Perioperative details and complications were reported.

RESULTS

A total of 82 patients were included; group I (n=41) and group II (n=41). The mean age was 51.18±8.64 (27-68) and 90.24% were male. The duration since the onset of symptoms was longer in group II vs. group I, 43.34±41.03 versus 38.07±36.11months respectively. No significant differences in the clinical evaluation between the two groups with a greater proportion of patients demonstrating moderate degenerative changes. Similar preoperative and postoperative radiographic parameters were reported, in group I, Δ HKA was 7.19±4.14 versus 7.65±3.16 in group II. Preoperative pain VAS scores were slightly higher in group II vs. group I, 79.23±26.35 vs. 76.31±24.45, respectively. However, postoperatively, the pain scores significantly improved in group I vs. group II, 22.84±3.65 vs. 41.69±17.33, respectively. Tegner activity scores and WOMAC scores were comparable between both groups preoperatively and postoperatively. Only the WOMAC function scores were better in group I when compared to group II, 26.13±25.84 versus 20.01±17.98. All patients returned to work at an average of 0.82±0.38months.

CONCLUSION

Knee preservation with high tibial osteotomy is equally effective in managing unicompartmental degenerative changes in varus malaligned knees with either no previous history of meniscal surgeries or where a meniscal sacrifice was inevitable, either with subtotal or total meniscectomy.

LEVEL OF EVIDENCE

III, retrospective case-control study.

Meniscectomy is associated with a higher rate of osteoarthritis compared to meniscal repair following acute tears: a meta-analysis

PURPOSE

Meniscal tears are common and may impair knee function and biomechanics. This meta-analysis compared meniscal repair versus resection in patients with symptomatic meniscal tears in terms of patient-reported outcomes measures (PROMs), joint width, surgical failure, and rate of progression to osteoarthritis (OA) at conventional radiography.

METHODS

This study was conducted according to the 2020 PRISMA statement. In August 2023, the following databases were accessed: PubMed, Web of Science, Google Scholar, and Embase. Two reviewers independently performed the analysis and a methodological quality assessment of the included studies. All the clinical investigations which compared repair versus resection of meniscal tears were accessed.

RESULTS

Data from 20 studies (31,783 patients) were collected. The mean BMI was 28.28 ± 3.2 kg/m2, and the mean age was 37.6 ± 14.0 years. The mean time elapsed from injury to surgery was 12.1 ± 10.2 months and the mean medial joint width was 4.9 ± 0.8 mm. Between studies comparability at baseline was found in age, women, BMI, time from injury to surgery and length of the follow-up, PROMs, medial joint width, and stage of OA. The resection group demonstrated a greater Lysholm score (P = 0.02). No difference was found in the International Knee Documentation Committee (P = 0.2). Nine studies reported data on the rate of failures at a mean of 63.00 ± 24.7 months. No difference was found between the two groups in terms of persistent meniscal symptoms (P = 0.8). Six studies reported data on the rate of progression to total knee arthroplasty at a mean of 48.0 ± 14.7 months follow-up. The repair group evidenced a lower rate of progression to knee arthroplasty (P = 0.0001). Six studies reported data on the rate of advanced knee OA at a mean of 48.0 ± 14.7 months of follow-up. The repair group evidenced a lower rate of advanced knee OA (P = 0.0001). No difference was found in the mean joint space width (P = 0.09).

CONCLUSION

Meniscal repair is associated with a lower progression to knee osteoarthritis at approximately six years of follow-up compared to partial meniscectomy. No difference in PROMs, medial joint width, and failures were evidenced.

LEVEL OF EVIDENCE

Level III, meta-analysis.

Short-term transplantation effect of a tissue-engineered meniscus constructed using drilled allogeneic acellular meniscus and BMSCs

During the construction of tissue-engineered meniscus, the low porosity of extracellular matrix restricts the flow of nutrient solution and the migration and proliferation of cells, thus affecting the tissue remodeling after transplantation. In this study, the canine allogeneic meniscus was drilled first and then decellularized. The drilled tissue-engineered menisci (Drilled Allogeneic Acellular Meniscus + Bone Marrow Mesenchymal Stem Cells, BMSCs) were transplanted into the knee joints of model dogs. On the basis of ensuring the mechanical properties, the number of the porosity and the cells implanted in allogeneic acellular meniscus was significantly increased. The expression levels of glycosaminoglycans and type II collagen in the drilled tissue-engineered meniscus were also improved. It was determined that the animals in the experimental group recovered well-compared with those in the control group. The graft surface was covered with new cartilage, the retraction degree was small, and the tissue remodeling was good. The surface wear of the femoral condyle and tibial plateau cartilage was light. The results of this study showed that increasing the porosity of allogeneic meniscus by drilling could not only maintain the mechanical properties of the meniscus and increase the number of implanted cells but also promote cell proliferation and differentiation. After transplantation, the drilled tissue-engineered meniscus provided a good remodeling effect in vivo and played a positive role in repairing meniscal injury, protecting articular cartilage and restoring knee joint function.

Surgical Management of Failed Articular Cartilage Surgery in the Knee

Failure rates of cartilage restoration surgery range from 14% to 43%. When failure of prior cartilage restoration surgery is suspected, a thorough clinical workup should be performed to assess the timing and duration of symptoms. Attention should be paid to patient risk factors such as age, body mass index, and smoking status. Concomitant pathology such as malalignment, ligament insufficiency, and meniscus status must be evaluated before revision surgery. As outlined in our treatment algorithm, the size/location of the lesion and the type of primary procedure will guide planning for revision procedures. [Orthopedics. 2023;46(5):262-272.].

Impact of Biologic Augmentation on Revision Surgery Rates After Meniscus Repair: A Matched-Cohort Analysis of 3420 Patients

Background

Platelet-rich plasma (PRP) and bone marrow aspirate concentrate (BMAC) have gained popularity in recent years as biologic approaches to potentially augment healing after meniscus repair. There have been few studies comparing outcomes in patients undergoing meniscus repair with versus without biologic augmentation and, furthermore, little clarity on the role of biologic augmentation for meniscus repairs performed with concomitant anterior cruciate ligament reconstruction (ACLR).

Purpose

To determine the association of BMAC or PRP augmentation with revision surgery after both isolated meniscus repair and meniscus repair performed concomitantly with ACLR.

Study Design

Cohort study; Level of evidence, 3.

Methods

The PearlDiver Mariner dataset was queried to identify all patients who underwent primary meniscus repair, both with and without concomitant ACLR, and who received ipsilateral BMAC or PRP at the time of surgery. Patients who underwent similar surgery but without BMAC or PRP augmentation were then identified and matched in a 5:1 ratio according to age, sex, body mass index, and various comorbidities to 3 separate BMAC/PRP augmentation groups: overall cohort (with and without ACLR), repair with concomitant ACLR, and isolated repair. The primary outcome was revision meniscus surgery (meniscectomy or revision meniscus repair).

Results

Overall, 3420 patients (570 with BMAC/PRP augmentation; 2850 matched controls without augmentation) were included. There were no significant differences in the reported demographics or comorbidities between any of the BMAC/PRP groups and their respective matched controls (P > .05 for all comparisons). There was no difference in revision rate between BMAC/PRP-augmented isolated meniscus repairs and matched controls (P = .235). Patients who underwent BMAC/PRP-augmented meniscus repair with concomitant ACLR experienced a significantly lower incidence of revision surgery compared with matched controls without BMAC/PRP augmentation (5.2% vs 7.9% respectively; odds ratio, 0.41; 95% CI, 0.27-0.63; P < .001), but the number of revisions was relatively small.

Conclusion

There was no association between BMAC or PRP augmentation and the incidence of revision surgery after isolated primary meniscus repair. There was a statistically significant decrease in the rate of revision meniscus surgery when BMAC or PRP was used to augment meniscus repairs in the setting of concurrent ACLR; however, the overall revision rates were small.

Heterogeneity of dynamic shear properties of the meniscus: A comparison between tissue core and surface layers

Damage to the meniscus has been associated with excessive shear loads. Aimed at elucidating meniscus pathophysiology, previous studies have investigated the shear properties of the meniscus fibrocartilaginous core. However, the meniscus is structurally inhomogeneous, with an external cartilaginous envelope (tibial and femoral surface layers) wrapping the tissue core. To date, little is known about the shear behavior of the surface layers. The objective of this study was to measure the dynamic shear properties of the surface layers and derive empirical relations with their composition. Specimens were harvested from tibial and femoral surface layers and core of porcine menisci (medial and lateral, n = 10 each). Frequency sweep tests yielded complex shear modulus (G*) and phase shifts (δ). Mechanical behavior of regions was described by a generalized Maxwell model. Correlations between shear moduli with water and glycosaminoglycans content of the tissue regions were investigated. The femoral surface had the lowest shear modulus, when compared to core and tibial regions. A 3-relaxation times Maxwell model satisfactorily interpreted the shear behavior of all tissue regions. Inhomogeneous tissue composition was also observed, with water content in the surface layers being higher when compared with tissue core. Water content negatively correlated with shear properties in all regions. The lower measured shear properties in the femoral layer may explain the higher prevalence of meniscal tears on the superior surface of the tissue. The heterogenous behavior of the tissue in shear provides insight into meniscus pathology and has important implications for efforts to tissue engineer replacement tissues.

Effect of molecular weight and tissue layer on solute partitioning in the knee meniscus

Objective

Knee meniscus tissue is partly vascularized, meaning that nutrients must be transported through the extracellular matrix of the avascular portion to reach resident cells. Similarly, drugs used as therapeutic agents to treat meniscal pathologies rely on transport through the tissue. The driving force of diffusive transport is the gradient of concentration, which depends on molecular solubility. The meniscus is organized into a core region sandwiched between the tibial and femoral superficial layers. Structural differences exist across meniscal regions; therefore, regional differences in solubility are also hypothesized.

Methods

Samples from the core, tibial and femoral layers were obtained from 5 medial and 5 lateral porcine menisci. The partition coefficient (K) of fluorescein, 3 ​kDa and 40 ​kDa dextrans in the layers of the meniscus was measured using an equilibration experiment. The effect of meniscal compartment, layer, and solute molecular weight on K was analyzed using a three-way ANOVA.

Results

K ranged from a high of ∼2.9 in fluorescein to a low of ∼0.1 in 40 ​kDa dextran and was inversely related to the solute molecular weight across all tissue regions. Tissue layer only had a significant effect on partitioning of 40k Dex solute, which was lower in the tibial surface layer relative to the core (p ​= ​0.032).

Conclusion

This study provides insight into depth-dependent partitioning in the meniscus, indicating the limiting effect of the meniscus superficial layer on solubility increases with solute molecular size. This illustrates how the surface layers could potentially reduce the effectiveness of drug delivery therapies incorporating large molecules (>40 ​kDa).

Suspension bath bioprinting and maturation of anisotropic meniscal constructs

Due to limited intrinsic healing capacity of the meniscus, meniscal injuries pose a significant clinical challenge. The most common method for treatment of damaged meniscal tissues, meniscectomy, leads to improper loading within the knee joint, which can increase the risk of osteoarthritis. Thus, there is a clinical need for the development of constructs for meniscal repair that better replicate meniscal tissue organization to improve load distributions and function over time. Advanced three-dimensional bioprinting technologies such as suspension bath bioprinting provide some key advantages, such as the ability to support the fabrication of complex structures using non-viscous bioinks. In this work, the suspension bath printing process is utilized to print anisotropic constructs with a unique bioink that contains embedded hydrogel fibers that align via shear stresses during printing. Constructs with and without fibers are printed and then cultured for up to 56 din vitroin a custom clamping system. Printed constructs with fibers demonstrate increased cell and collagen alignment, as well as enhanced tensile moduli when compared to constructs printed without fibers. This work advances the use of biofabrication to develop anisotropic constructs that can be utilized for the repair of meniscal tissue.

The Interplay of Biomechanical and Biological Changes Following Meniscus Injury

PURPOSE OF REVIEW

Meniscus injury often leads to joint degeneration and post-traumatic osteoarthritis (PTOA) development. Therefore, the purpose of this review is to outline the current understanding of biomechanical and biological repercussions following meniscus injury and how these changes impact meniscus repair and PTOA development. Moreover, we identify key gaps in knowledge that must be further investigated to improve meniscus healing and prevent PTOA.

RECENT FINDINGS

Following meniscus injury, both biomechanical and biological alterations frequently occur in multiple tissues in the joint. Biomechanically, meniscus tears compromise the ability of the meniscus to transfer load in the joint, making the cartilage more vulnerable to increased strain. Biologically, the post-injury environment is often characterized by an increase in pro-inflammatory cytokines, catabolic enzymes, and immune cells. These multi-faceted changes have a significant interplay and result in an environment that opposes tissue repair and contributes to PTOA development. Additionally, degenerative changes associated with OA may cause a feedback cycle, negatively impacting the healing capacity of the meniscus. Strides have been made towards understanding post-injury biological and biomechanical changes in the joint, their interplay, and how they affect healing and PTOA development. However, in order to improve clinical treatments to promote meniscus healing and prevent PTOA development, there is an urgent need to understand the physiologic changes in the joint following injury. In particular, work is needed on the in vivo characterization of the temporal biomechanical and biological changes that occur in patients following meniscus injury and how these changes contribute to PTOA development.

Biomechanical properties of porcine meniscus as determined via AFM: Effect of region, compartment and anisotropy

The meniscus is a fibrocartilaginous tissue that plays an essential role in load transmission, lubrication, and stabilization of the knee. Loss of meniscus function, through degeneration or trauma, can lead to osteoarthritis in the underlying articular cartilage. To perform its crucial function, the meniscus extracellular matrix has a particular organization, including collagen fiber bundles running circumferentially, allowing the tissue to withstand tensile hoop stresses developed during axial loading. Given its critical role in preserving the health of the knee, better understanding structure-function relations of the biomechanical properties of the meniscus is critical. The main objective of this study was to measure the compressive modulus of porcine meniscus using Atomic Force Microscopy (AFM); the effects of three key factors were investigated: direction (axial, circumferential), compartment (medial, lateral) and region (inner, outer). Porcine menisci were prepared in 8 groups (= 2 directions x 2 compartments x 2 regions) with n = 9 per group. A custom AFM was used to obtain force-indentation curves, which were then curve-fit with the Hertz model to determine the tissue's compressive modulus. The compressive modulus ranged from 0.75 to 4.00 MPa across the 8 groups, with an averaged value of 2.04±0.86MPa. Only direction had a significant effect on meniscus compressive modulus (circumferential > axial, p = 0.024), in agreement with earlier studies demonstrating that mechanical properties in the tissue are anisotropic. This behavior is likely the result of the particular collagen fiber arrangement in the tissue and plays a key role in load transmission capability. This study provides important information on the micromechanical properties of the meniscus, which is crucial for understanding tissue pathophysiology, as well as for developing novel treatments for tissue repair.

Meniscal procedures are not increased with delayed ACL reconstruction and rehabilitation: results from a randomised controlled trial

OBJECTIVE

To assess whether initial non-operative treatment of anterior cruciate ligament (ACL) ruptures with optional delayed ACL reconstruction leads to more meniscal procedures compared with early ACL reconstruction during the 2-year follow-up.

METHODS

We compared the number of meniscal procedures of 167 patients with an ACL rupture, who either received early ACL reconstruction (n=85) or rehabilitation therapy plus optional delayed ACL reconstruction (n=82), participating in the Conservative vs Operative Methods for Patients with ACL Rupture Evaluation trial. Patients were aged 18 to 65 years (mean 31.3, SD 10.5), 60% male sex (n=100). We evaluated the presence and location of meniscal tears by baseline MRI. We analysed and compared how many patients per randomisation group had a meniscal procedure during follow-up in the ACL injured knee, adjusted for sex, body mass index, age group and orthopaedic surgeon.

RESULTS

At baseline, 41% of the entire study population (69/167 patients) had a meniscal tear on MRI. During the 2-year follow-up, 25 patients randomised to early ACL reconstruction (29%, 25/85 patients) had a meniscal procedure, compared with 17 patients randomised to rehabilitation plus optional delayed reconstruction (21%, 17/82 patients) (risk ratio 0.67 with 95% CI 0.40 to 1.12, p=0.12). Of these patients who received early ACL reconstruction (n=82) and patients that received delayed ACL reconstruction (n=41), 5% of the patients had an additional isolated meniscal procedure after ACL reconstruction. In patients who received no ACL reconstruction (n=41), 10% (n=4) had an isolated surgical procedure for a meniscal tear during the 2-year follow-up period.

CONCLUSION

Initial non-surgical treatment of ACL ruptures followed by optional delayed ACL reconstruction does not lead to a higher number of meniscal procedures compared with early ACL reconstruction over a 2-year follow-up period.

TRIAL REGISTRATION NUMBER

NL 2618.

Attachment Type, Thickness, and Volume of the Posterior Meniscofemoral Ligament and Meniscal Pathology

Several studies have investigated the relationship between the thickness of the posterior meniscofemoral ligament (pMFL) and the presence of a discoid meniscus. We investigated the correlation between meniscal pathology and anatomic features of pMFL such as attachment type, thickness, and volume. We retrospectively evaluated 191 patients who underwent knee MRI. MR images were reviewed to assess the attachment type of the pMFL on the medial femoral condyle (high vs. low), the thickness of the pMFL, and the presence of a meniscal tear or a discoid meniscus. The pMFL volume was quantified by using three-dimensional (3D) segmentation software. The relationship between the frequency of medial or lateral meniscal tear and anatomic features of pMFL were analyzed using Chi-square, Fisher's exact, or Mann-Whitney U test. High type pMFLs had significantly greater thickness and volume than low type pMFLs (p < 0.001). Patients with degenerative lateral meniscal tear had significantly higher thickness and volume of the pMFL than patients with intact lateral meniscus (p < 0.05). The pMFL thickness and volume were not significantly related to traumatic lateral meniscal tear, medial meniscal tear, and discoid meniscus. High type pMFLs tended to be thicker and larger than low type pMFLs and higher thickness and volume of the pMFL was significantly related to the degenerative lateral meniscal tear. However, the attachment type of the pMFL itself was not significantly related to the lateral meniscal tear as well as the medial meniscal tear.

Mid-term study on the effects of arthroscopic discoid lateral meniscus plasty on patellofemoral joint: An observational study

In the present study, we aimed to investigate the clinical outcomes of arthroscopic discoid lateral meniscus (DLM) plasty and the adaptive changes in the patellofemoral joint after surgery. From September 2010 to March 2012, 25 patients with DLM injuries who underwent arthroscopic meniscus plasty were enrolled in the prospective study. All patients underwent clinical evaluation before the operation and at the last follow-up, and imaging evaluation was performed by upright magnetic resonance imaging before and 1 month after the operation as well as at the last follow-up. Clinical evaluation included Lysholm score, Kujala score, McMurray's sign, patellar mobility, patella grind test, and quadriceps atrophy. Imaging evaluation included bisect offset index, patella tilt angle (PTA), and cartilage damage. Lysholm score, Kujala score, McMurray's sign, and quadriceps atrophy at the last follow-up were significantly improved compared with the preoperative levels (P < .05). At the last follow-up, there were no statistical differences in patella mobility and patella grind test compared with the preoperative levels. In addition, bisect offset index and PTA showed a dynamic trend of rising and then falling over time (P < .05). At 1 month after the operation, bisect offset index and PTA were significantly increased compared with the preoperative levels or the values at the last follow-up (P < .05), while there were no differences between the preoperation and the last follow-up. Cartilage damage became worse with time (P < 0.05), and the 2 were positively correlated (Spearman = 0.368). At the last follow-up, the degree of cartilage damage was significantly increased compared with the preoperative level (P < .017), while there was no significant difference between the 1-month postoperative grade and the preoperational grade or the last follow-up grade. The effect of arthroscopic DLM plasty on the patellofemoral joint was dynamic, with the position of the patella deviating in the early stages and recovering in the mid-term, especially when the knee was in the biomechanical standing position. In addition, the patellofemoral joint cartilage might undergo accelerated degeneration after the operation, while the mid-term effect of the operation was positive, and the patellofemoral joint function was acceptable.

Strain-Dependent Diffusivity of Small and Large Molecules in Meniscus

Due to lack of full vascularization, the meniscus relies on diffusion through the extracellular matrix to deliver small (e.g., nutrients) and large (e.g., proteins) to resident cells. Under normal physiological conditions, the meniscus undergoes up to 20% compressive strains. While previous studies characterized solute diffusivity in the uncompressed meniscus, to date, little is known about the diffusive transport under physiological strain levels. This information is crucial to fully understand the pathophysiology of the meniscus. The objective of this study was to investigate strain-dependent diffusive properties of the meniscus fibrocartilage. Tissue samples were harvested from the central portion of porcine medial menisci and tested via fluorescence recovery after photobleaching to measure diffusivity of fluorescein (332 Da) and 40 K Da dextran (D40K) under 0%, 10%, and 20% compressive strain. Specifically, average diffusion coefficient and anisotropic ratio, defined as the ratio of the diffusion coefficient in the direction of the tissue collagen fibers to that orthogonal, were determined. For all the experimental conditions investigated, fluorescein diffusivity was statistically faster than that of D40K. Also, for both molecules, diffusion coefficients significantly decreased, up to ∼45%, as the strain increased. In contrast, the anisotropic ratios of both molecules were similar and not affected by the strain applied to the tissue. This suggests that compressive strains used in this study did not alter the diffusive pathways in the meniscus. Our findings provide new knowledge on the transport properties of the meniscus fibrocartilage that can be leveraged to further understand tissue pathophysiology and approaches to tissue restoration.

Can platelet-rich plasma enhance the effect of meniscus repair? A meta-analysis of randomized controlled trials Platelet-rich plasma and meniscus repair

BACKGROUND

Studies have shown that platelet-rich plasma (PRP) can enhance the effect of meniscus repair, but some studies have suggested different views on the role of PRP.

PURPOSE

To determine whether PRP can enhance the effect of meniscus repair with respect to pain reduction and improved functionality and cure rate in patients with meniscus injury.

METHODS

By searching PubMed, EMBASE, Cochrane Library databases, clinicaltrials.gov, and the CNKI database from their inception till December 1, 2020, we performed a meta-analysis of RCTs reporting the results of the Pain Visual Analog Scale (VAS), the pain of Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm score, the International Knee Documentation Committee (IKDC), healing rate, and adverse events. The risk of bias is assessed using Cochrane's collaborative tools. The summary results are expressed with effect size and 95% confidence interval, and sensitivity were performed.

RESULTS

The meta-analysis included 9 RCTs and 345 patients. In general, compared with the control group, used of PRP during meniscus surgery significantly improved the pain (SMD: -0.95, p < 0.00001,95% CI: -1.22 to -0.69, I2 = 42%) and knee joint function (SMD: 1.00, p = 0.01.95% CI: 0.22 to 1.79, I2 = 89%) of patients with meniscus injury at 6 months after treatment. However, both PRP and non-PRP showed improvements in the pain and knee joint function, with no significant difference between the groups at 1 months and beyond 12 months. The PRP enhancement technique showed benefit in improving the cure rate of meniscus repair (RR:1.44; p < 0.0001, 95% CI: 1.20-1.73). No serious adverse events were reported in any study.

CONCLUSION

As an enhancement program for meniscus repair, PRP is worthy of further consideration in improving the function and pain of patients during the mid-term follow-up after surgery, and PRP can further improve the healing rate of meniscus repair. However, the evidence still needs to be interpreted carefully because of the quantity and quality of the included studies.

The Potential of Using an Autogenous Tendon Graft by Injecting Bone Marrow Aspirate in a Rabbit Meniscectomy Model

Bone marrow aspirate (BMA) is an excellent source of cells and growth factors and has been used successfully for bone, cartilage, and soft-tissue healing. This study aimed to investigate the histological and biomechanical properties of autogenous tendon graft by injecting BMA and its protective effect against degenerative changes in a rabbit model of meniscal defects. Adult white rabbits were divided into untreated, tendon, and tendon + BMA groups, and meniscal defects were created in the knees. The tendon graft and articular cartilage status were evaluated by macroscopic and histological analysis at 4, 12, and 24 weeks postoperatively among the three groups. The tendon graft in the tendon and tendon + BMA groups were used for biomechanical evaluation at 4, 12, and 24 weeks postoperatively. The meniscal covering ratio in the tendon + BMA group was better than that in the tendon and untreated groups at 12 and 24 weeks postoperatively. The matrix around the central portion of cells in the tendon + BMA group was positively stained by safranin O and toluidine blue staining with metachromasia at 24 weeks. The histological score of the tendon graft in the tendon + BMA group was significantly higher than that in the untreated and tendon groups at 12 and 24 weeks postoperatively. In the tendon + BMA group, cartilage erosion was not shown at 4 weeks, developed slowly, and was better preserved at 12 and 24 weeks compared to the untreated and tendon groups. Histological scores for the articular cartilage were significantly better in the tendon + BMA group at 24 weeks. The compressive stress on the tendon graft in the tendon + BMA group was significantly higher than that in the tendon group at 12 weeks postoperatively. Transplantation of autogenous tendon grafts by injecting BMA improved the histologic score of the regenerated meniscal tissue and was more effective than the tendon and untreated group for preventing cartilage degeneration in a rabbit model of massive meniscal defects.

Tensile mechanical properties of vitrified porcine menisci are superior to frozen and similar to fresh porcine menisci

Vitrification inhibits crystallization of ice and may allow the mechanical properties of menisci to be preserved for transplantation without the damaging consequences of ice crystals formed during freezing. The primary objective of this study was to investigate the differences between fresh, frozen, and vitrified porcine lateral menisci examining tensile mechanical properties along the circumferential-peripheral, circumferential-central, longitudinal, and radial orientations. The secondary objective was to investigate the variations in the tensile mechanical properties of menisci comparing the circumferential-peripheral orientation to the three other orientations: circumferential-central, longitudinal, and radial. Quasi-static tensile testing was conducted to quantify the tensile mechanical properties of fresh, frozen and vitrified menisci. Ultimate tensile strength of frozen menisci were significantly decreased compared with fresh and vitrified menisci along three orientations: circumferential-peripheral, longitudinal, and radial. Along the circumferential-central orientation, tensile modulus of frozen menisci was significantly decreased compared with fresh menisci. The mechanical properties of vitrified menisci were comparable to fresh menisci along all four orientations. For all menisci (fresh, frozen and vitrified), ultimate tensile strength and failure strain along the circumferential-peripheral orientation were significantly increased compared with the three other orientations. Freezing was detrimental to the mechanical properties of menisci but vitrification likely avoided the negative effects of freezing thereby preserving mechanical properties that were comparable to fresh menisci. The findings of this study revealed that vitrification was superior to freezing for preserving mechanical properties of meniscal tissue; hence, vitrification is likely to be a competitive alternative to freezing for meniscal transplantation in the future.

Comparison of Cases with Anterior Cruciate Ligament Reconstruction Accompanied by Simultaneous Medial Meniscus Bucket Handle Tear Repair and Isolated Medial Meniscus Bucket Handle Tear Repair

The aim of this study was to evaluate the success of the all-inside repair technique for medial bucket-handle meniscus tear (BHMT) and the factors affecting healing. A total of 36 patients with BHMT who were operated between 2012 and 2018 and completed final follow-up examinations were included in the study. Functional evaluation was made with the International Knee Documentation Committee (IKDC) score, Lysholm score, and Tegner score. Healing was evaluated on magnetic resonance imaging (MRI) slices. The patients were evaluated with respect to the effect on healing of factors such as demographic data, body mass index (BMI), smoking status, anterior cruciate ligament tear reconstruction (ACLTR) applied at the same time as BHMT repair, and the tear being chronic or acute. The mean age of the patients was 28.6 ± 8.6 years (range,18-46 years), the mean follow-up period was 25.8 ± 13.9 months (range, 13-59 months), and BMI was mean 25.6 ± 3.5 kg/m² (range, 20.1-30.5 kg/m²). The meniscus tears were acute in 16 (44.4%) patients and chronic in 20 (55.6%). ACLTR was applied together with BHMT repair in 25 patients. The hybrid technique, as the outside-in technique in addition to the all-inside technique, was applied to 12 (33.3%) patients, where there was seen to be extension to the anterior horn. The failure rate was determined as 27.8% according to the postoperative MRI evaluation and the Barrett criteria. No positive or negative statistically significant effect on healing was determined of chronic BHMT or of simultaneous application of ACLTR (p = 1.00 and 0.457, respectively). Cigarette smoking and high BMI were determined to have a statistically significant negative effect on healing (p = 0.026 and 0.007, respectively). In conclusion, it can be seen that the success of the all-inside technique for BHMT remains controversial. Due to the features of the application, it can be used in meniscus tears of the posterior horn only. In the current study, with the success rate of 72.2% of the all-inside technique in meniscus body tears, it was seen that a high success rate could not be achieved.

Effect of platelet-rich plasma on meniscus repair surgery: A meta-analysis of randomized controlled trials

BACKGROUND

Studies have shown that platelet-rich plasma (PRP) can enhance the effect of meniscus repair, but some studies have suggested different views on the role of PRP. Therefore, a meta-analysis was conducted to determine whether PRP can enhance the effect of meniscus repair with respect to pain reduction and improved functionality and cure rate in patients with meniscus injury.

METHODS

PubMed, EMBASE, Cochrane Library Databases, clinicaltrials.gov, and the CNKI Database were searched from their inception till December 1, 2020. The RCTs reporting the outcomes of the Pain Visual Analog Scale (VAS), Lysholm score, healing rate, and adverse events were included. The risk of bias was assessed using Cochrane collaborative tools. The simulated results were expressed with effect size and 95% confidence interval, and sensitivity and subgroup analysis were performed.

RESULTS

The meta-analysis included 8 RCTs and 431 participants. Compared with the control group, use of PRP during meniscus surgery significantly improved the VAS (SMD: -0.40, P = .002, 95%CI: -0.66 to -0.15) and Lysholm score (MD: 3.06, P < .0001, 95%CI: 1.70-4.42) of meniscus injury, but the PRP showed no benefit in improving the healing rate of meniscus repair (RR: 1.22, P = .06, 95%CI: 0.99-1.51). No serious adverse events were reported in any study.

CONCLUSIONS

PRP is safe and effective in improving the effect of meniscus repair as augment. High quality RCTs with long follow-up and definitive results are needed in the future to confirm the use and efficacy of PRP in meniscus tears.

Primary Fixation and Cyclic Performance of Single-Stitch All-Inside and Inside-Out Meniscal Devices for Repairing Vertical Longitudinal Meniscal Tears

BACKGROUND

Primary device fixation and the resistance against gap formation during repetitive loading influence the quality of meniscal repair. There are limited biomechanical data comparing primary tensioning and cyclic behavior of all-inside versus inside-out repair.

HYPOTHESIS

All-inside devices provide higher initial load on the meniscal repair than inside-out fixation, and stiffer constructs show higher resistance against gap formation during cyclic loading.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 60 longitudinal bucket-handle tears in human cadaveric menisci were created and repaired with a single stitch and randomly assigned to 4 all-inside groups (TrueSpan, FastFix 360, Stryker AIR, FiberStich) and 2 inside-out groups (suture repair [IO-S], suture tape [IO-ST]). Residual load after repair tensioning (50 N) and relief displacement were measured. Constructs underwent cyclic loading between 2 and 20 N over 500 cycles (0.75 Hz) with cyclic stiffness, gap formation, and final peak elongation measured. Ultimate load and stiffness were analyzed during pull to failure (3.15 mm/s).

RESULTS

All-inside repair demonstrated significantly higher primary fixation strength than inside-out repair. The significantly highest load (mean ± SD; 20.1 ± 0.9 N; P < .037) and relief displacement (-2.40 ± 0.32 mm; P < .03) were for the knotless soft anchoring FiberStich group. The lowest initial load (9.0 ± 1.5 N; P < .001) and relief displacement (-1.39 ± 0.26 mm; P < .045) were for the IO-S repair group. The final gap formation (500th cycle) of FiberStich (0.75 ± 0.37 mm; P < .02) was significantly smaller than others and that of the IO-S (1.47 ± 0.33 mm; P < .045) significantly larger. The construct stiffness of the FiberStich and IO-ST groups was significantly greater at the end of cyclic testing (16.7 ± 0.80 and 15.5 ± 1.42 N/mm; P < .042, respectively) and ultimate failure testing (23.4 ± 3.6 and 20.6 ± 2.3 N/mm; P < .005). The FastFix 360 (86.4 ± 4.8 N) and Stryker AIR (84.4 ± 4.6 N) groups failed at a significantly lower load than the IO-S group (P < .02) with loss of anchor support. The FiberStich (146.8 ± 23.4 N), TrueSpan (142.0 ± 17.8 N), and IO-ST (139.4 ± 7.3 N) groups failed at significantly higher loads (P < .02) due to suture tearing.

CONCLUSION

Overall, primary fixation strength of inside-out meniscal repair was significantly lower than all-inside repair in this cadaveric tissue model. Although absolute differences among groups were small, meniscal repairs with higher construct stiffness (IO-ST, FiberStich) demonstrated increased resistance against gap formation and failure load.

CLINICAL RELEVANCE

Knotless single-stitch all-inside meniscal repair with a soft anchor resulted in less gapping, but the overall clinical significance on healing rates remains unclear.

Surgical Outcomes After Bucket-Handle Meniscal Repairs: Analysis of a Large Contained Cohort

BACKGROUND

Representing approximately 10% of all meniscal tears, bucket-handle meniscal tears (BHMTs) are large longitudinal vertical tears that have an attached fragment flipped into the intercondylar notch. Meniscectomy often results in significant meniscal loss and increased joint loading. Alternatively, meniscal repair attempts to restore the function of the meniscus and aims to preserve joint mechanics.

PURPOSE

To evaluate the long-term risk of subsequent ipsilateral knee surgery in patients who underwent a bucket-handle meniscal repair (BHMR), and to assess risk factors associated with subsequent knee surgical intervention.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

We performed an electronic health record search for all patients aged 12 to 65 years who underwent arthroscopic knee meniscal repairs for BHMT (2011-2018). We excluded patients who had a previous BHMR, did not have magnetic resonance imaging of the knee within 60 days before BHMR, lacked active membership in Kaiser insurance in the year before and after BHMR, or underwent meniscectomy before BHMR. All patients were followed until December 31, 2019, with censoring at death or membership disenrollment. Primary outcomes included ipsilateral knee procedures overall and by type (ie, repeat meniscal repair and meniscectomy); secondary outcomes included other surgical interventions of the same knee, any contralateral knee surgery, deep surgical-site infection, and deep venous thrombosis or pulmonary embolism.

RESULTS

The final cohort included 1359 patients with a median age of 24 years (interquartile range [IQR], 17-34) who underwent BHMR for a BHMT. During the follow-up period (median, 50.2 months [IQR, 32.3-60.6]), 495 subsequent ipsilateral procedures were performed in 274 (20.2%) patients, and the median time to the first procedure was 10.6 months (IQR, 4.1-23.5). An overall 59 (4.3%) patients underwent repeat meniscal repair, and 165 (12.1%) had a subsequent meniscectomy of the same knee. Significant risk factors for subsequent ipsilateral procedures included younger age, 12 to 18 years (adjusted odds ratio [aOR], 5.77 [95% CI, 1.84-18.08]) and 19 to 30 years (aOR, 3.65 [95% CI, 1.17-11.36]), as well as normal and overweight body mass index (aOR, 2.84 [95% CI, 1.29-6.23] and 2.34 [95% CI, 1.06-5.17], respectively). Patients undergoing concomitant anterior cruciate ligament reconstruction (ACLR) at the initial BHMR had a lower risk of undergoing subsequent surgery (aOR, 0.66 [95% CI, 0.49-0.87]) than those without concomitant ACLR.

CONCLUSION

This is the largest reported study on outcomes after BHMR in a contained cohort. One-fifth of patients underwent subsequent ipsilateral surgery during follow-up, with 4.3% receiving a repeat meniscal repair and 12.1% experiencing a meniscectomy. Risk factors for subsequent surgery of the same knee included younger age and normal or overweight body mass index. Concomitant ACLR at time of BHMR reduced the risk of subsequent reoperation.

Arthroscopic partial meniscectomy versus physical therapy for traumatic meniscal tears in a young study population: a randomised controlled trial

OBJECTIVE

To compare outcomes from arthroscopic partial meniscectomy versus physical therapy in young patients with traumatic meniscal tears.

METHODS

We conducted a multicentre, open-labelled, randomised controlled trial in patients aged 18-45 years, with a recent onset, traumatic, MRI-verified, isolated meniscal tear without knee osteoarthritis. Patients were randomised to arthroscopic partial meniscectomy or standardised physical therapy with an optional delayed arthroscopic partial meniscectomy after 3-month follow-up. The primary outcome was the International Knee Documentation Committee (IKDC) score (best 100, worst 0) at 24 months, which measures patients' perception of symptoms, knee function and ability to participate in sports activities.

RESULTS

Between 2014 and 2018, 100 patients were included (mean age 35.1 (SD 8.1), 76% male, 34 competitive or elite athletes). Forty-nine were randomised to arthroscopic partial meniscectomy and 51 to physical therapy. In the physical therapy group, 21 patients (41%) received delayed arthroscopic partial meniscectomy during the follow-up period. In both groups, improvement in IKDC scores was clinically relevant during follow-up compared with baseline scores. At 24 months mean (95% CI) IKDC scores were 78 (71 to 84) out of 100 points in the arthroscopic partial meniscectomy group and 78 (71 to 84) in the physical therapy group with a between group difference of 0.1 (95% CI -7.6 to 7.7) points out of 100.

CONCLUSIONS

In this trial involving young patients with isolated traumatic meniscal tears, early arthroscopic partial meniscectomy was not superior to a strategy of physical therapy with optional delayed arthroscopic partial meniscectomy at 24-month follow-up.

TRIAL REGISTRATION

https://www.trialregister.nl/trials.

Meniscus repair: up-to-date advances in stem cell-based therapy

The meniscus is a semilunar fibrocartilage between the tibia and femur that is essential for the structural and functional integrity of the keen joint. In addition to pain and knee joint dysfunction, meniscus injuries can also lead to degenerative changes of the knee joint such as osteoarthritis, which further affect patient productivity and quality of life. However, with intrinsic avascular property, the tearing meniscus tends to be nonunion and the augmentation of post-injury meniscus repair has long time been a challenge. Stem cell-based therapy with potent regenerative properties has recently attracted much attention in repairing meniscus injuries, among which mesenchymal stem cells were most explored for their easy availability, trilineage differentiation potential, and immunomodulatory properties. Here, we summarize the advances and achievements in stem cell-based therapy for meniscus repair in the last 5 years. We also highlight the obstacles before their successful clinical translation and propose some perspectives for stem cell-based therapy in meniscus repair.

Evidence-based rationale for treatment of meniscal lesions in athletes

Meniscal injuries in elite athletes are a common cause of missed game time and even have the potential to be career shortening. In this patient group, care must be paid not only to the pathology, but also to a player's contract status, time in the season, specific demands of his/her sport and position on the field, and future consequences. Successful treatment requires the clinician to understand the player's goals and needs, communicate effectively between all stakeholders, and a have knowledge of the challenges posed by the different types of meniscal tear seen in this population. Paramount is the distinction between injuries to the medial and lateral meniscus. Deficiency of the lateral meniscus, as a result of a tear or a meniscectomy, leads to frequent early problems and inexorably to chondral degeneration thereby affecting an athlete's ability to perform. Therefore, it is strongly recommended to repair the majority of lateral meniscal tears. Medial meniscal tears pose a more challenging treatment dilemma, as the success of partial meniscectomy in achieving reproducible, early return to play must be balanced against the long-term degenerative consequences. Many meniscal tears are correctly treated non-operatively.Level of evidence V.

Symptomatic discoid lateral meniscus shows a relationship between types and tear patterns, and between causes of clinical symptom onset and the age distribution

PURPOSE

Discoid meniscus is a congenital abnormality of the lateral meniscus and is seen more frequently in East Asia. The purpose of this study was to retrospectively assess the relationship between discoid lateral meniscus (DLM) types and tear patterns and causes of age-specific clinical symptom onset.

METHODS

Of 1650 arthroscopic surgeries over a 20-year period, 138 (105 patients) were performed for DLM and were evaluated in this study. The mean age at surgery was 21.5 ± 15.8 years. The DLM type was classified by Watanabe's classification, and tear patterns were classified by the modified Bin's classification as simple horizontal, complicated horizontal, longitudinal, radial, complex, and no tear. Additionally, patients were divided by age group (< 10, 10-19, 20-39, 40-59, and ≥ 60 years) and classified according to the causes of clinical symptom onset as follows: sports activities, minor trauma in daily living, and no traumatic episode.

RESULTS

The DLM was complete in 78 (56.5%) knees and incomplete in 60 (43.5%); no Wrisberg type DLM was observed. Simple horizontal and complicated horizontal tears were significantly more frequent in complete DLM, whereas radial tears and no tears were significantly more frequent in incomplete DLM (p < 0.0001). When classified by age group, 74 (53.6%) knees with DLMs were found in teenagers. Sports activities caused symptom onset significantly more often in teenagers, no traumatic episode caused symptom onset in patients aged < 10 years, and minor trauma in daily living caused symptom onset in patients aged 40-59 years and ≥ 60 years (p < 0.0001). No relationship was found between the age distribution and tear patterns; however, the absence of tears tended to be more common in teenaged patients, and complicated horizontal tears were more common in patients over 20 years of age.

CONCLUSION

Symptomatic DLM occurred most often in teenagers. A relationship was identified between the DLM types and tear patterns, which could be helpful in preoperative planning. Causes of clinical symptom onset in patients with DLM were characterised by age group, which might help clinicians to suspect the presence of DLM.

LEVEL OF EVIDENCE

Level IV.

Isolated meniscus injuries in skeletally immature children and adolescents: state of the art

The prevalence of isolated meniscal injuries in children and adolescents is low; however, we see an increase mainly due to intensified sports-related activities at an early age. A meniscal repair should be attempted whenever possible as children present with increased meniscal healing potential. The diagnosis and management of meniscal tears involve both patient factors and tear characteristics: size, anatomical location and associated injuries. Special attention should be given to the feature of discoid menisci and related tears as they require a specific management plan. This state-of-the-art review highlights the most recent studies on clinical evaluation, surgical techniques, tips and tricks, pitfalls, outcomes, return-to-sports, geographical differences and future perspectives related to meniscal injuries in children and adolescents.

Mechanical symptoms and meniscal tear: a reappraisal

OBJECTIVE

To identify and summarize literature related to the association between mechanical symptoms (catching and locking of the knee), the presence of meniscal tear, and outcomes after arthroscopic surgery.

DESIGN

We searched PubMed and hand-searched reference lists for relevant articles and selected 38 for analysis.

RESULTS

Mechanical symptoms appear to have modest sensitivity (ranging 0.32-0.69), specificity (ranging 0.45-0.74) and positive predictive value (ranging 0.75-0.81) for meniscal tear. There is also very little evidence to suggest that those with mechanical symptoms experience better outcomes after arthroscopic surgery.

CONCLUSION

Our examination of the literature does not support the hypothesis that mechanical symptoms are related to the presence of meniscal tear or portend better outcomes after arthroscopic surgery.

Radial Width of the Lateral Meniscus at the Popliteal Hiatus: Relevance to Saucerization of Discoid Lateral Menisci

BACKGROUND

A discoid lateral meniscus (DLM) is a congenital anomaly of the knee in which the lateral meniscus has an "O" shape and contains irregular, abnormal collagenous tissue. A DLM can cause mechanical symptoms and pain. Treatment of a symptomatic DLM is arthroscopic saucerization to reshape the meniscus to a more normal contour. Enough tissue must be removed to eliminate mechanical symptoms but not too much to create instability. The residual width of the meniscus is crucial at the popliteus hiatus because here the peripheral rim is unattached at the capsule. Reports in the literature recommend a residual width of 6 to 8 mm.

PURPOSE/HYPOTHESIS

The purpose of this research was to determine the width of the lateral meniscus at the popliteal hiatus in normal specimens. Our null hypothesis was that a residual width of 6 to 8 mm will be sufficient to approximate normal anatomy.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We made direct measurements of the radial width of the lateral meniscus from the outer rim at the popliteal hiatus to the inner edge in 19 specimens (age, 2-120 months.) We measured one 4-year-old specimen with a bilateral complete DLM. We also measured 39 digital images of specimens (age, 1-132 months) using ImageJ. Finally, we made direct arthroscopic measurements of 8 skeletally mature specimens.

RESULTS

The average width of specimens <3 years old was 5.5 mm. The average width of the 10-year-old specimens was 12 mm. The average width of the skeletally mature specimens was 16 mm. A 4-year-old DLM specimen measured 19 mm.

CONCLUSION

We rejected our null hypothesis. Direct measurements suggest that a residual width of 6 to 8 mm is insufficient for children ≥8 years old. A width of at least a full centimeter approximates the normal for 8-year-olds and at least 15 mm for adolescents.

Lateral Meniscal Tears in Young Patients: A Comparison of Meniscectomy and Surgical Repair

Background:

Meniscal tears are common in active patients, but treatment trends and surgical outcomes in young patients with lateral meniscal tears are lacking.

Purpose:

To evaluate treatment trends, outcomes, and failure rates in young patients with lateral meniscal tears.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients aged ≤25 years treated surgically for isolated lateral meniscal tears from 2001 to 2017 were identified. Treatment trends were compared over time. International Knee Documentation Committee (IKDC) scores and failure rates were compared by treatment modality (meniscectomy vs meniscal repair). Failure was defined as reoperation, symptomatic osteoarthritis, or a severely abnormal IKDC score. Univariate regression analyses were performed to predict failure and IKDC scores based on treatment, type and location of tear, or extent of meniscectomy.

Results:

Included were 217 patients (226 knees) with a mean age of 17.4 years (range, 7-25 years); of these patients, 144 knees (64%) were treated with meniscectomy and 82 knees (36%) with meniscal repair. Treatment with repair increased over time compared with meniscectomy (P < .001). At a minimum 2-year follow-up (mean, 6.1 ± 3.9 years), 107 patients (110 knees) had IKDC scores, and analysis indicated that although scores in both groups improved from pre- to postoperatively (repair: from 69.5 ± 13.3 to 97.4 ± 4.3; meniscectomy: from 75.7 ± 9.0 to 97.3 ± 3.9; P < .001 for both), improvement in IKDC score was greater after repair (27.9 ± 13.9) versus meniscectomy (21.6 ± 9.4) (P = .005). Included in the failure analysis were 184 patients (192 knees) at a mean follow-up of 8.4 ± 4.4 years. The rates of reoperation, symptomatic osteoarthritis, and failure were not significantly different between the meniscectomy and repair groups.

Conclusion:

An increase was seen in the rate of isolated lateral meniscal tear repair in young patients. IKDC score improvement was greater after repair than meniscectomy, although postoperative IKDC scores were similar. Symptomatic arthritis, reoperation, and failure rates were similar between groups; however, there was a trend for increased arthritis symptoms in patients treated with meniscectomy, especially total meniscectomy. Treatment modality, type and location of tear, and amount of meniscus removed were not predictive of final IKDC scores or failure.

Factors affecting Baker cyst volume, with emphasis on cartilage lesion degree and effusion in the young and middle-aged population

Background

The principal aim of this study was to investigate the presence of factors affecting Baker’s cyst volume in young and middle-aged populations.

Methods

Open cyst excision with valve and capsule repair, as well as knee arthroscopy, were used to treat eighty-five patients. The cases were categorized in terms of age, effusion, chondral lesion degree, meniscal tear degree, and Lindgren scores. An ultrasonography (USG) device was used to calculate the cyst volume. The IBM-SPSS 22 program was used for statistical analysis and to assess the relationships between variables using Spearman’s correlation tests.

Results

The degree of chondral lesion was moderately and positively correlated with cyst volume in the total population (correlation coefficient: 0.469; p < 0.05).

The degree of the chondral lesion was moderately and positively correlated with the degree of effusion (correlation coefficient: 0.492; p < 0.005). The cyst volume was weakly and positively correlated with the degree of effusion (correlation coefficient: 0.20; the correlation was at the limits of statistical significance p = 0.07 < 0.08).

Conclusions

This study revealed that an increase in chondral lesion severity increases the amount of effusion and cyst volume.

Meniscus Anatomy and Basic Science

A basic understanding of meniscal anatomy and biomechanics is important for physicians evaluating knee injuries and surgeons treating meniscal injuries. This chapter provides a concise review of meniscal anatomy and biomechanics relevant for the evaluation and treatment of meniscus injuries. Anatomic landmarks relevant for meniscal root repair and transplant are discussed, along with the gross, microscopic, vascular, and neuroanatomy of the menisci.

The Epidemiology of Meniscus Injury

Meniscus surgery is one of the most commonly performed orthopedic procedures worldwide. Modifiable risk factors for meniscus injury include body mass index, participation in athletics and occupation. Nonmodifiable risk factors include age, sex, lower extremity alignment, discoid meniscus, ligamentous laxity, and biconcave tibial plateau. Conditions commonly associated with meniscal injury are osteoarthritis, anterior cruciate ligament injury, and tibial plateau fractures. Tear type and location vary by patient age and functional status. Surgical management of meniscus injury is typically cost-effective in terms of quality-adjusted life years. The purpose of this review is to provide an overview of meniscal injury epidemiology by summarizing tear types and locations, associated conditions, and factors that increase the risk for meniscal injury. The economic burden of meniscus injury and strategies to prevent injury to the meniscus are also reviewed.

Corticosteroid Injections 1 Month Before Arthroscopic Meniscectomy Increase the Risk of Surgical-Site Infection

PURPOSE

To define the incidence of postoperative infections in patients who receive corticosteroid injections prior to arthroscopic meniscectomy, to determine whether there is a temporal relation between injections and the risk of surgical-site infections, and to identify corresponding risk factors.

METHODS

The Humana administrative claims database was reviewed for patients undergoing arthroscopic meniscectomy within 1 year of injection and those undergoing arthroscopic meniscectomy without prior injection. Patients with preoperative injections were further stratified by the duration in months between the injection and the surgical procedure. Surgical-site infection within 6 months of surgery was recorded. Univariate analysis and binary logistic regression were performed to determine independent risk factors for surgical-site infection. Statistical significance was defined as P < .05.

RESULTS

We identified patients with (n = 11,652) and without (n = 37,261) a history of a knee corticosteroid injection within 1 year of arthroscopic meniscectomy with at least 6 months of database activity from 2007 to 2017. In patients who received knee injections within 1 month prior to surgery, the rate of development of postoperative infections was twice that in patients who did not receive an injection (1.28% vs 0.63%; odds ratio [OR], 1.84; 95% confidence interval [CI], 1.24-2.62; P = .001). Multivariate logistic regression identified male sex (OR, 1.39; 95% CI, 1.14-1.71; P = .001), diabetes (OR, 1.48; 95% CI, 1.19-1.85; P < .001), chronic obstructive pulmonary disease (OR, 1.57; 95% CI, 1.27-1.94; P < .001), obesity (OR, 1.32; 95% CI, 1.07-1.63; P = .010), tobacco use (OR, 1.61; 95% CI, 1.30-1.98; P < .001), and preoperative injections within 1 month of surgery (OR, 1.78; 95% CI, 1.21-2.54; P = .002) as significant predictors, whereas injections administered more than 1 month before surgery were not significantly associated with postoperative surgical-site infection after arthroscopic meniscectomy.

CONCLUSIONS

Injections 1 month before arthroscopic meniscectomy significantly increase the risk of surgical-site infection. However, injections can be safely administered more than 1 month prior to surgery because there is no increased risk of postoperative infection at this time point.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Meniscal Injuries: Mechanism and Classification

Meniscal tears may be managed through conservative physical therapy and nonsteroidal anti-inflammatory medications or operative intervention. Meniscal repair is superior to partial meniscectomy with better functional outcomes and less severe degenerative changes over time. Surgical advances in operative techniques, modern instrumentation and biological enhancements collectively improve healing rates of meniscal repair. However, failed repair is not without consequences and can negative impact patient outcomes. Therefore, it is imperative for surgeons to have a thorough understanding of the vascular zones and biomechanical classifications of meniscal tears in order to best determine the most appropriate treatment.

Pediatric discoid meniscus: can magnetic resonance imaging features coupled with clinical symptoms predict the need for surgery?

BACKGROUND

Magnetic resonance imaging (MRI) criteria for evaluating discoid meniscus is limited in the pediatric population.

OBJECTIVE

To assess MRI features of intact discoid meniscus and correlate with clinical outcomes.

MATERIALS AND METHODS

In this institutional review board (IRB)-approved retrospective cohort study, knee MRIs at our institution from 2008 to 2019 were reviewed. The inclusion criterion was diagnosis of discoid meniscus on MRI. Exclusion criteria were torn discoid meniscus at presentation, previous meniscal surgery and confounding knee conditions. MRI features of discoid meniscus collected were craniocaudal dimension, transverse dimension, transverse dimension to tibial plateau (TV:TP) ratio and increased intrameniscal signal. The clinical course was reviewed for knee pain, mechanical symptoms and treatment type.

RESULTS

Two hundred and nineteen of 3,277 (6.7%) patients had discoid meniscus. Of the 219 patients, 71 (32.4%) satisfied inclusion criteria. Seven patients had discoid meniscus of both knees resulting in 78 discoid menisci. The average patient age was 11.1 years (min: 2.0, max: 17.0). The average follow-up was 30.6 months. Of the 78 discoid menisci, 14 (17.9%) required surgery. Increased intrameniscal signal was found more in discoid meniscus requiring surgery (surgical: 10/14, nonsurgical: 19/64, P=0.009). Surgically treated discoid meniscus had a statistically significant increase in transverse dimension (surgical: 18.3±5.0 mm, nonsurgical: 15.7±4.3 mm, P=0.045) and TV:TP ratio (surgical: 0.55±0.15, nonsurgical: 0.47±0.12, P=0.036). Mechanical symptoms (surgical: 9/11, nonsurgical: 21/60, P=8.4×10^-6) and pain ≥1 month (surgical: 11/11, nonsurgical: 17/60, P=0.006) were found more often in surgical patients. Clinical and imaging criteria of mechanical symptoms and knee pain ≥1 month and at least one of (1) increased intrameniscal signal or (2) TV:TP ratio greater than 0.47 identified discoid menisci that developed a tear and/or required surgery with a sensitivity of 0.86 and specificity of 0.88.

CONCLUSION

Mechanical symptoms and knee pain ≥1 month, and at least one of (1) increased intrameniscal signal or (2) TV:TP ratio greater than or equal to 0.47, identified discoid menisci that would go on to tear and/or require surgery with a sensitivity and specificity of 0.86 and 0.88, respectively.

Home-Based vs Supervised Inpatient and/or Outpatient Rehabilitation Following Knee Meniscectomy: A Systematic Review and Meta-analysis

IMPORTANCE

Arthroscopic meniscectomy is one of the most common orthopedic procedures. The optimal postoperative approach remains debated.

OBJECTIVE

To compare outcomes associated with home-based rehabilitation programs (HBP) vs standard inpatient and/or outpatient supervised physical therapy (IOP) following arthroscopic isolated meniscectomy (AM).

DATA SOURCES

A systematic literature search was conducted on PubMed, Web of Science, Cochrane Library, and Scopus databases on March 15, 2021. The included studies were published from 1982 to 2019.

STUDY SELECTION

Randomized clinical trials of patients treated with HBP vs IOP after AM were included.

DATA EXTRACTION AND SYNTHESIS

Data were independently screened and extracted by 2 authors according to the Preferred Reporting Items for Systematic Reviews (PRISMA) reporting guideline. The meta-analysis was performed using a random-effect model; when an I2 < 25% was observed, the fixed-effect model was used. The Hartung-Knapp correction was applied.

MAIN OUTCOMES AND MEASURES

The primary outcome was the Lysholm score (scale of 0-100 with higher scores indicating better knee function) and secondary outcomes were subjective International Knee Documentation Committee (IKDC) score, knee extension and flexion, thigh girth, horizontal and vertical hop test, and days to return to work, as indicated in the PROSPERO registration. Outcomes were measured in the short-term (ranging from 28 to 50 days) and the midterm (6 months).

RESULTS

In this meta-analysis of 8 RCTs including 434 patients, IOP was associated with a greater short-term improvement in Lysholm score compared with HBP, with a mean difference of -8.64 points (95% CI, -15.14 to -2.13 points; P = .02) between the 2 approached, but the sensitivity analysis showed no difference. Similarly, no statistically significant difference was detected at midterm for Lysholm score, with a mean difference between groups of -4.78 points (95% CI, -9.98 to 0.42 points; P = .07). HBP was associated with a greater short-term improvement in thigh girth, with a mean difference between groups of 1.38 cm (95% CI, 0.27 to 2.48 cm; P = .01), whereas IOP was associated with a better short-term vertical hop score, with a mean difference between groups of -3.25 cm (95% CI, -6.20 to -0.29 cm; P = .03). No differences were found for all the other secondary outcomes.

CONCLUSIONS AND RELEVANCE

No intervention was found to be superior in terms of physical and functional outcomes as well as work-related and patient-reported outcomes, both at short-term and midterm follow-up. Overall, these results suggest that HBP may be an effective management approach after AM in the general population.

Rare Variant Double-Layered Lateral Meniscus Detected During Arthroscopy in a Young Gymnast After a Hyperextension Knee Injury: A Case Report

CASE

A 15-year-old high-level gymnast sustained a hyperextension knee injury and was diagnosed with a lateral meniscus tear on advanced imaging. During arthroscopy, a redundant meniscus was encountered overlying an otherwise normal, intact lateral meniscus, consistent with a double-layer lateral meniscus. The redundant meniscus was resected, and the patient was able to return to gymnastics at her previous high level of competition.

CONCLUSIONS

Abnormalities of the lateral meniscus may be poorly characterized or undetected on preoperative imaging studies. When the decision is made to proceed with surgery, a vigilant diagnostic arthroscopic examination can facilitate the detection and treatment of unanticipated pathology.

Viscoelastic and equilibrium shear properties of human meniscus: Relationships with tissue structure and composition

The meniscus is crucial in maintaining the knee function and protecting the joint from secondary pathologies, including osteoarthritis. Although most of the mechanical properties of human menisci have been characterized, to our knowledge, its dynamic shear properties have never been reported. Moreover, little is known about meniscal shear properties in relation to tissue structure and composition. This is crucial to understand mechanisms of meniscal injury, as well as, in regenerative medicine, for the design and development of tissue engineered scaffolds mimicking the native tissue. Hence, the objective of this study was to characterize the dynamic and equilibrium shear properties of human meniscus in relation to its anisotropy and composition. Specimens were prepared from the axial and the circumferential anatomical planes of medial and lateral menisci. Frequency sweeps and stress relaxation tests yielded storage (G') and loss moduli (G″), and equilibrium shear modulus (G). Correlations of moduli with water, glycosaminoglycans (GAGs), and collagen content were investigated. The meniscus exhibited viscoelastic behavior. Dynamic shear properties were related to tissue composition: negative correlations were found between G', G″ and G, and meniscal water content; positive correlations were found for G' and G″ with GAG and collagen (only in circumferential samples). Circumferential samples, with collagen fibers orthogonal to the shear plane, exhibited superior dynamic mechanical properties, with G' ~70 kPa and G″ ~10 kPa, compared to those of the axial plane ~15 kPa and ~1 kPa, respectively. Fiber orientation did not affect the values of G, which ranged from ~50 to ~100 kPa.