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

Development of decellularized meniscus using closed sonication treatment system: potential scaffolds for orthopedics tissue engineering applications

PURPOSE

Meniscus is a fibrocartilagenous tissue that cannot effectively heal due to its complex structure and presence of avascular zone. Thus, tissue engineering and regenerative medicine offer an alternative for the regeneration of meniscus tissues using bioscaffolds as a replacement for the damaged one. The aim of this study was to prepare an ideal meniscus bioscaffold with minimal adverse effect on extracellular matrix components (ECMs) using a sonication treatment system.

METHODS

The decellularization was achieved using a developed closed sonication treatment system for 10 hrs, and continued with a washing process for 5 days. For the control, a simple immersion treatment was set as a benchmark to compare the decellularization efficiency. Histological and biochemical assays were conducted to investigate the cell removal and retention of the vital extracellular matrix. Surface ultrastructure of the prepared scaffolds was evaluated using scanning electron microscope at 5,000× magnification viewed from cross and longitudinal sections. In addition, the biomechanical properties were investigated through ball indentation testing to study the stiffness, residual forces and compression characteristics. Statistical significance between the samples was determined with p-value =0.05.

RESULTS

Histological and biochemical assays confirmed the elimination of antigenic cellular components with the retention of the vital extracellular matrix within the sonicated scaffolds. However, there was a significant removal of sulfated glycosaminoglycans. The surface histoarchitecture portrayed the preserved collagen fibril orientation and arrangement. However, there were minor disruptions on the structure, with few empty micropores formed which represented cell lacunae. The biomechanical properties of bioscaffolds showed the retention of viscoelastic behavior of the scaffolds which mimic native tissues. After immersion treatment, those scaffolds had poor results compared to the sonicated scaffolds due to the inefficiency of the treatment.

CONCLUSION

In conclusion, this study reported that the closed sonication treatment system had high capabilities to prepare ideal bioscaffolds with excellent removal of cellular components, and retained extracellular matrix and biomechanical properties.

The Meniscal Grammar Signs: Comma and Apostrophe Signs for Characterization of a Displaced Fragment in the Meniscal Recess

Vertical flap tears, or parrot beak flap tears, are oblique tears of the meniscus thought to originate as a central radial tear and propagate longitudinally towards the periphery, generating a partially detached unstable fragment that can subsequently displace into the meniscal recess. Although magnetic resonance imaging (MRI) is frequently used to diagnose and characterize meniscus pathology, imaging findings for displaced flap tears are not well described in the literature. The recently published meniscal comma sign describes inferior displacement of a meniscus flap tear into the meniscotibial recess that, when seen on MRI, resembles a comma. In the present article, we define the meniscal apostrophe sign, characterized by superior displacement of a meniscus flap tear into the meniscofemoral recess found on MRI. Displaced fragments in the meniscal recess are crucial to identify, as they often result in significant pain and mechanical symptoms related to tenting of the deep medial collateral ligament, which responds poorly to nonoperative treatment. Misdiagnosis of these unstable flap tears as degenerative meniscus extrusion or isolated progression of osteoarthritis can lead to a delay in treatment.

Increased rates of knee arthroplasty and cost of patients with meniscal tears treated with arthroscopic partial meniscectomy versus non-operative management

PURPOSE

The purpose of this study was to determine the cost of arthroscopic partial meniscectomy (APM), one of the most common surgeries performed by orthopaedic surgeons, and the associated rate of progression to knee arthroplasty (KA) compared to patients treated non-operatively after diagnosis of meniscal tear.

METHODS

Utilizing data mining software (PearlDiver, Colorado Springs, CO), a national insurance database of approximately 23.5 million orthopaedic patients was queried for patients diagnosed with a meniscal tear. Patients were classified by treatment: non-operative and arthroscopic partial meniscectomy and were followed after initial diagnosis for cost and progression to knee arthroplasty.

RESULTS

There were 176,407 subjects in the non-op group and 114,194 subjects in the arthroscopic partial meniscectomy group. Arthroscopic partial meniscectomy generated more cost than non-operative ($3842.57 versus $411.05, P < 0.001). Arthroscopic partial meniscectomy demonstrated greater propensity to need future knee arthroplasty (11.4% at 676 days) than those treated non-operatively (9.5% at 402 days) (P < 0.001). Female patients demonstrated a higher rate of progression to knee arthroplasty in the arthroscopic partial meniscectomy and non-operative groups (P < 0.001).

CONCLUSION

Compared to non-operative treatment for meniscal tears, arthroscopic partial meniscectomy is more expensive and does not appear to decrease the rate of progression to knee arthroplasty. Patients undergoing arthroscopic partial meniscectomy yielded on average a delay of only 9 months (274 days) before undergoing knee arthroplasty. Female patients experienced a significantly higher rate of progression to knee arthroplasty. The authors recognize the limitations of this type of study including its retrospective nature, reliance upon accurate coding and billing information, and the inability to determine whether symptoms including mechanical locking played a role in the decision to perform an APM.

LEVEL OF EVIDENCE

IV.

Meniscal Repair in Pediatric Populations: A Systematic Review of Outcomes

Background:

Loss of meniscal tissue in the pediatric population can have long-term consequences on joint health, highlighting the importance of meniscal preservation in this group.

Purpose:

To systematically review reported knee outcome measures and complication rates after repair of meniscal tears in children and adolescents.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A review of the literature regarding the existing evidence for pediatric meniscal tear outcomes was performed through use of the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed (1980-present), and MEDLINE (1980-present). Included were articles in English that reported the outcomes of meniscal tears in the pediatric population (<18 years old) with a follow-up of more than 12 months. Clinical outcome scores were reviewed.

Results:

A total of 1003 total studies were initially retrieved, with 8 meeting the inclusion criteria. The review included 287 patients (165 male, 122 female), mean age 15.1 years (range, 4-18 years), with 301 meniscal tears (reported: 134 medial, 127 lateral, and 32 both medial and lateral, 8 location unspecified). Concomitant anterior cruciate ligament reconstruction was performed in 52% (158/301) of meniscal repairs. The average reported postoperative Lysholm scores ranged from 85.4 to 96.3, and the average reported postoperative Tegner activity scores ranged from 6.2 to 8.

Conclusion:

Arthroscopic repair of a meniscal tear in the pediatric and adolescent population is an effective treatment option that has a low failure rate, enhances postoperative clinical outcomes, and preserves meniscal tissues.

What's the rate of knee osteoarthritis 10 years after anterior cruciate ligament injury? An updated systematic review

BACKGROUND

This updated systematic review reports data from 2009 on the prevalence, and risk factors, for knee osteoarthritis (OA) more than 10 years after anterior cruciate ligament (ACL) tear.

METHODS

We systematically searched five databases (PubMed, EMBASE, AMED, Cinahl and SPORTDiscus) for prospective and retrospective studies published after 1 August 2008. Studies were included if they investigated participants with ACL tear (isolated or in combination with medial collateral ligament and/or meniscal injuries) and reported symptomatic and/or radiographic OA at a minimum of 10 years postinjury. We used a modified version of the Downs and Black checklist for methodological quality assessment and narrative synthesis to report results. The study protocol was registered in PROSPERO.

RESULTS

Forty-one studies were included. Low methodological quality was revealed in over half of the studies. At inclusion, age ranged from 23 to 38 years, and at follow-up from 31 to 51 years. Sample sizes ranged from 18 to 780 participants. The reported radiographic OA prevalence varied between 0% and 100% >10 years after injury, regardless of follow-up time. The studies with low and high methodological quality reported a prevalence of radiographic OA between 0%-100% and 1%-80%, respectively. One study reported symptomatic knee OA for the tibiofemoral (TF) joint (35%), and one study reported symptomatic knee OA for the patellofemoral (PF) joint (15%). Meniscectomy was the only consistent risk factor determined from the data synthesis.

CONCLUSION

Radiographic knee OA varied between 0% and 100% in line with our previous systematic review from 2009. Symptomatic and radiographic knee OA was differentiated in two studies only, with a reported symptomatic OA prevalence of 35% for the TF joint and 15% for PF joint. Future cohort studies need to include measurement of symptomatic knee OA in this patient group.

PROSPERO REGISTRATION NUMBER

CRD42016042693.

The effect of unloader knee braces on medial meniscal strain

BACKGROUND:

A medial meniscal tear is a common knee injury, especially following an anterior cruciate ligament injury. Decreasing the compressive force on the medial meniscus during dynamic activities using an unloader knee brace could reduce meniscal strain, effectively reducing injury risk and/or severity.

OBJECTIVES:

To investigate the efficacy of two unloader knee braces on medial meniscus strain during dynamic activities in intact & deficient anterior cruciate ligament states.

STUDY DESIGN:

Combined in vivo/in vitro study.

METHODS:

In vivo knee kinematics and muscle force profiles from a healthy individual performing single/doubleleg squats and walking motions were simulated on 10 cadaveric specimens using a dynamic knee simulator system. Simulations were performed on knees in unbraced and braced scenarios, with and without the anterior cruciate ligament. Anterior and posterior medial meniscal strains were measured.

RESULTS:

Two different braces each showed a significant reduction in the posteromedial meniscal strain ( p ⩽ 0.01) in an intact anterior cruciate ligament state. Neither brace mirrored this result for the anteromedial strain ( p > 0.05). In the deficient anterior cruciate ligament state, the braces had no significant effect on strain ( p > 0.05).

CONCLUSION:

Two unloader knee braces effectively reduced strain in the medial meniscus with an intact anterior cruciate ligament during dynamic activities. Neither brace made a significant reduction in strain for anterior cruciate ligament-deficient knees.

CLINICAL RELEVANCE

Unloader knee braces could be used to reduce the medial meniscus strain following meniscal surgery and during rehabilitation in patients with an isolated medial meniscus injury. However, these braces cannot be recommended for this purpose in patients with an anterior cruciate ligament deficiency.

Hypoxia and TGF-β3 Synergistically Mediate Inner Meniscus-Like Matrix Formation by Fibrochondrocytes

The interactions of hypoxia and TGF-β3 in aggregates of human meniscus fibrochondrocytes are synergistic in nature, suggesting combinatorial strategies using these factors are promising for tissue engineering the inner meniscus regions. Hypoxia alone in the absence of TGF-β supplementation may be insufficient to initiate an inner meniscus-like extracellular matrix-forming response in this model.

Partial Meniscus Replacement with a Collagen-Hyaluronan Infused Three-Dimensional Printed Polymeric Scaffold

IMPACT STATEMENT

The only FDA-approved partial meniscus scaffold, the Collagen Meniscus Implant (CMI), is not approved for reimbursement by government and only reimbursable by certain private insurers. Scaffolds with improved mechanical properties and greater efficacy are needed. A previous study (Ghodbane, et al. DOI: 10.1002/jbm.b.34331) demonstrated the ability of our novel acellular, off-the shelf scaffold to restore knee biomechanics following partial meniscectomy, which could potentially decrease the risk of osteoarthritis following partial meniscectomy, providing the motivation for this study. This article presents a first-in-animal feasibility study.

Materials and structures used in meniscus repair and regeneration: a review

Meniscus is a vital functional unit in knee joint. It acts as a lubricating structure, a nutrient transporting structure, as well as shock absorber during jumping, twisting and running and offers stability within the knee joint. It helps in load distribution, in bearing the tensile hoop stresses and balancing by providing a cushion effect between hard surfaces of two bones. Meniscus may be injured in sports, dancing, accident or any over stressed condition. Any meniscal lesion can lead to a gradual development of osteoarthritis or erosion of bone contact surface due to disturbed load and contact stress distribution caused by injury/pain. Once injured, the possibilities of self-repair are rare in avascular region of meniscus, due to lack of blood supply in avascular region. Meniscus has vascular and avascular regions in structure. Majority of the meniscus parts turn avascular with increase in age.

Purpose of this review is to highlight advances in meniscus repair with special focus on tissue engineering using textile/fiber based scaffolds, as well as the recent technical advances in scaffolds for meniscus recon- struction/ regeneration treatment.

Biomechanical characterization of a novel collagen-hyaluronan infused 3D-printed polymeric device for partial meniscus replacement

The menisci transmit load by increasing the contact area and decreasing peak contact stresses on the articular surfaces. Meniscal lesions are among the most common orthopedic injuries, and resulting meniscectomies are associated with adverse polycaprolactone contact mechanics changes and, ultimately, an increased likelihood of osteoarthritis. Meniscus scaffolds were fabricated by 3D-printing a network of circumferential and radial filaments of resorbable polymer (poly(desaminotyrosyl-tyrosine dodecyl ester dodecanoate)) and infused with collagen-hyaluronan. The scaffold demonstrated an instantaneous compressive modulus (1.66 ± 0.44 MPa) comparable to native meniscus (1.52 ± 0.59 MPa). The scaffold aggregate modulus (1.33 ± 0.51 MPa) was within 2% of the native value (1.31 ± 0.36 MPa). In tension, the scaffold displayed a comparable stiffness to native tissue (127.6-97.1 N/mm) and an ultimate load of 33% of the native value. Suture pull-out load of scaffolds (83.1 ± 10.0 N) was within 10% of native values (91.5 ± 15.4 N). Contact stress analysis demonstrated the scaffold reduced peak contact stress by 60-67% and increased contact area by 38%, relative to partial meniscectomy. This is the first meniscal scaffold to match both the axial compressive properties and the circumferential tensile stiffness of the native meniscus. The improvement of joint contact mechanics, relative to partial meniscectomy alone, motivates further investigation using a large animal model. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2457-2465, 2019.

An Abnormal Tibial Position Is Associated With Alterations in the Meniscal Matrix: A 3-Year Longitudinal Study After Anterior Cruciate Ligament Reconstruction

Background:

An altered tibial position is still present despite anterior cruciate ligament (ACL) reconstruction. It has been demonstrated that an abnormal tibial position after an ACL injury may play a role in subsequent injuries to the meniscus, which can lead to early cartilage degeneration.

Purpose:

To determine changes in both the tibial position and the meniscal matrix present before and after ACL reconstruction as well as to evaluate the association between these 2 variables in ACL-injured knees 3 years after reconstruction.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

Bilateral knee magnetic resonance imaging (MRI) of 32 patients with unilateral ACL injuries was performed before reconstruction; 13 control participants also underwent MRI. Follow-up MRI was performed up to 3 years after surgery. Tibial position, internal tibial rotation, and T1ρ and T2 values of the menisci were calculated using an in-house MATLAB program. Student t tests and multiple linear regression were used to compare differences between injured, uninjured, and control knees as well as to assess correlations between the tibial position at 3 years and 3-year changes in quantitative MRI meniscal relaxation values.

Results:

The tibial position of injured knees was more anterior than that of uninjured knees at baseline, 6 months, and 1, 2, and 3 years (P < .05 for all). The T1ρ and T2 values of the menisci of injured knees were greater than those of uninjured and control knees in the posterior lateral and posterior medial horns up to 1 and 2 years after surgery, respectively (P < .05 for all). The tibial position at 3 years was associated with increased T2 values from baseline to 3 years in the posterior medial horn (β = 0.397; P = .031) and anterior medial horn (β = 0.360; P = .040).

Conclusion:

Results of the current study indicate that there is a persistently altered tibial position after ACL reconstruction. Initial preoperative meniscal abnormalities show prolonged but gradual improvement. Additionally, correlations between the tibial position and changes in the medial meniscal matrix suggest that the tibial position may play a role in the increased susceptibility to medial meniscal tears seen after reconstruction. The development of newer surgical techniques must address a persistently altered tibial position. Quantitative MRI is an effective instrument to evaluate meniscal matrix changes and can serve as an early radiological tool for meniscal injuries.

Complementary Function of the Meniscofemoral Ligament and Lateral Meniscus Posterior Root to Stabilize the Lateral Meniscus Posterior Horn: A Biomechanical Study in a Porcine Knee Model

Background:

It has been demonstrated that the load distribution function of the lateral meniscus (LM) is compromised by resecting both the meniscofemoral ligament (MFL) and LM posterior root (LMPR). However, the effect of resecting these fibers on load transmission through the LM needs to be investigated.

Purpose:

To evaluate using a porcine knee model (1) the in situ forces of the MFL and LMPR and (2) the effect of resecting these fibers on the in situ force of the LM under a compressive load and valgus torque to the lateral knee compartment.

Study Design:

Controlled laboratory study.

Methods:

Twenty fresh-frozen porcine knees and a 6 degrees of freedom robotic system were utilized. An axial compressive load of 250 N and 5 N·m of valgus torque were applied to intact, MFL-deficient, LMPR-deficient, and MFL/LMPR-deficient knees at 30°, 60°, and 90° of flexion. The valgus angles under the applied loads were compared among the 4 states. The in situ forces of the MFL and LMPR under the applied loads were calculated under the principle of superposition. The in situ forces of the LM under the applied loads were also calculated and compared among the 4 conditions (intact, without the MFL, without LMPR, and without the MFL/LMPR).

Results:

The valgus angles significantly increased after resecting both the MFL and LMPR at all the flexion angles. The in situ forces of the MFL and LMPR changed reciprocally as the knee flexed. The in situ forces of the LM significantly decreased after resecting both the MFL and LMPR, although resecting only the MFL or LMPR represented no significant effect.

Conclusion:

The MFL and LMPR functioned complementarily as the posterior attachments of the LM against a compressive load and valgus torque to the lateral knee compartment in porcine knee joints.

Clinical Relevance:

If the LMPR is completely detached and needs to be repaired, the MFL should be preserved because it may provide some stability to the LM posterior horn and protect the repaired LMPR.

Biexponential T1ρ relaxation mapping of human knee menisci

BACKGROUND

Measuring T_1ρ in the knee menisci can potentially be used as noninvasive biomarkers in detecting early-stage osteoarthritis (OA).

PURPOSE

To demonstrate the feasibility of biexponential T_1ρ relaxation mapping of human knee menisci.

STUDY TYPE

Prospective.

POPULATION

Eight healthy volunteers with no known inflammation, trauma, or pain in the knee and three symptomatic subjects with early knee OA.

FIELD STRENGTH/SEQUENCE

Customized Turbo-FLASH sequence to acquire 3D-T_1ρ -weighted images on a 3 T MRI scanner.

ASSESSMENT

T_1ρ relaxation values were assessed in 11 meniscal regions of interest (ROIs) using monoexponential and biexponential models.

STATISTICAL TESTS

Nonparametric rank-sum tests, Kruskal-Wallis test, and coefficient of variation.

RESULTS

The mean monoexponential T_1ρ relaxation in the lateral menisci were 28.05 ± 4.2 msec and 37.06 ± 10.64 msec for healthy subjects and early knee OA patients, respectively, while the short and long components were 8.07 ± 0.5 msec and 72.35 ± 3.2 msec for healthy subjects and 2.63 ± 2.99 msec and 55.27 ± 24.76 msec for early knee OA patients, respectively. The mean monoexponential T_1ρ relaxation in the medial menisci were 34.30 ± 3.8 msec and 37.26 ± 11.38 msec for healthy and OA patients, respectively, while the short and long components were 7.76 ± 0.7 msec and 72.19 ± 4.2 msec for healthy subjects and 3.06 ± 3.24 msec and 55.27 ± 24.59 msec for OA patients, respectively. Statistically significant (P ≤ 0.05) differences were observed in the monoexponential relaxation between some of the ROIs. The T_1ρ,short was significantly lower (P = 0.02) in the patients than controls. The rmsCV% ranges were 1.51-16.6%, 3.59-14.3%, and 4.91-15.6% for T_1ρ -mono, T_1ρ -short, and T_1ρ -long, respectively.

DATA CONCLUSION

Our results showed that in all ROIs, T_1ρ relaxation times of outer zones (red zones) were less than inner zones (white zones). Monoexponential T_1ρ was increased in medial, lateral, and body menisci of early OA while the biexponential numbers were decreased in early OA patients.

LEVEL OF EVIDENCE

2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2019;50:824-835.

Pre-Clinical Translation of Second Harmonic Microscopy of Meniscal and Articular Cartilage Using a Prototype Nonlinear Microendoscope

Previous studies using nonlinear microscopy have demonstrated that osteoarthritis (OA) is characterized by the gradual replacement of Type II collagen with Type I collagen. The objective of this study was to develop a prototype nonlinear laser scanning microendoscope capable of resolving the structural differences of collagen in various orthopaedically relevant cartilaginous surfaces. The current prototype developed a miniaturized femtosecond laser scanning instrument, mounted on an articulated positioning system, capable of both conventional arthroscopy and second-harmonic laser-scanning microscopy. Its optical system includes a multi-resolution optical system using a gradient index objective lens and a customized multi-purpose fiber optic sheath to maximize the collection of backscattered photons or provide joint capsule illumination. The stability and suitability of the prototype arthroscope to approach and image cartilage were evaluated through preliminary testing on fresh, minimally processed, and partially intact porcine knee joints. Image quality was sufficient to distinguish between hyaline cartilage and fibrocartilage through unique Type I and Type II collagen-specific characteristics. Imaging the meniscus revealed that the system was able to visualize differences in the collagen arrangement between the superficial and lamellar layers. Such detailed in vivo imaging of the cartilage surfaces could obviate the need to perform biopsies for ex vivo histological analysis in the future, and provide an alternative to conventional external imaging to characterize and diagnose progressive and degenerative cartilage diseases such as OA. Moreover, this system is readily customizable and may provide a suitable and modular platform for developing additional tools utilizing femtosecond lasers for tissue cutting within the familiar confines of two or three portal arthroscopy techniques.

Intra-articular injection of hydrogen sulfide decreased the progression of gonarthrosis

Hydrogen sulfide (H₂S) is found in both the plasma and synovial fluid of patients with gonarthrosis. In the present study, we investigated whether intra-articular injection of sodium hydrosulfide (NaSH) (1 mM, 30 μL), a H₂S donor, might affect gonarthrosis in rats. Gonarthrosis was induced surgically in the left knees of rats and left for 6 weeks for the development of disease. Then, intra-articular injections of NaSH or methylprednisolone (1 mg/kg, 30 μL) were administered to rats. Half of each group was sacrificed at the end of the first day and the other half was sacrificed at the end of 4 weeks to evaluate early and later effects of injections on gonarthrosis. The injury induced by anterior cruciate ligament resection and medial meniscectomy in rats caused the development of gonarthrosis. As the duration lengthened after gonarthrosis induction, the progression of the disease continued. According to the modified Mankin Scoring System, intra-articular injection of NaSH histopathologically slowed the progression of gonarthrosis, whereas methylprednisolone was ineffective. In addition, NaSH decreased apoptosis in rat knees with gonarthrosis. Each treatment did not cause injury to healthy knees. Our results lead to the consideration that intra-articular NaSH administration may be effective in the progression of gonarthrosis.

Differential protein expression in human knee articular cartilage and medial meniscus using two different proteomic methods: a pilot analysis

Background

Proteomics is an emerging field in the study of joint disease. Our two aims with this pilot analysis were to compare healthy human knee articular cartilage with meniscus, two tissues both known to become affected in the osteoarthritic disease process, and to compare two mass spectrometry (MS)-based methods: data-dependent acquisition (DDA) and data-independent acquisition (DIA).

Methods

Healthy knee articular cartilage taken from the medial tibial condyle and medial meniscus samples taken from the body region were obtained from three adult forensic medicine cases. Proteins were extracted from tissue pieces and prepared for MS analysis. Each sample was subjected to liquid chromatography (LC)-MS/MS analysis using an Orbitrap mass spectrometer, and run in both DDA and DIA mode. Linear mixed effects models were used for statistical analysis.

Results

A total of 653 proteins were identified in the DDA analysis, of which the majority was present in both tissue types. Only proteins with quantitation information in both tissues (n = 90) were selected for more detailed analysis, of which the majority did not statistically significantly differ in abundance between the two tissue types, in either of the MS analyses. However, 21 proteins were statistically significantly different (p < 0.05) between meniscus and cartilage in the DIA analysis. Out of these, 11 proteins were also significantly different in the DDA analysis. Aggrecan core protein was the most abundant protein in articular cartilage and significantly differed between the two tissues in both methods. The corresponding protein in meniscus was serum albumin. Dermatopontin exhibited the highest meniscus vs articular cartilage ratio among the statistically significant proteins. The DIA method led to narrower confidence intervals for the abundance differences between the two tissue types than DDA.

Conclusions

Although articular cartilage and meniscus had similar proteomic composition, we detected several differences by MS. Between the two analyses, DIA yielded more precise estimates and more statistically significant different proteins than DDA, and had no missing values, which makes it preferable for future LC-MS/MS analyses.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2346-6) contains supplementary material, which is available to authorized users.

Innovative treatment of clinically diagnosed meniscal tears: a randomized sham-controlled trial of the Mulligan concept 'squeeze' technique

Objective: The purpose of this study was to assess the effects of the Mulligan Concept (MC) 'squeeze' technique compared to a sham technique in participants with a clinically diagnosed meniscal tear.

Methods: A multi-site randomized sham-controlled trial of participants (n = 23), aged 24.91 ± 12.09 years, with a clinically diagnosed meniscal tear were equally and randomly divided into two groups. Groups received a maximum of six treatments over 14 days. Patient outcomes included the numeric pain rating scale (NRS), patient-specific functional scale (PSFS), the disablement in the physically active (DPA) scale and the knee injury osteoarthritis outcome score. Data were analysed using univariate ANOVA, univariate ANCOVA, and descriptive statistics.

Results: All participants in the MC 'squeeze' group met the discharge criteria of ≤2 points on the NRS, ≥9 points on the PSFS, and ≤34 points or ≤23 on the DPA Scale for chronic or acute injuries, respectively within the treatment intervention timeframe. A significant difference was found in favor of the MC 'squeeze' technique in PSFS scores (F(1, 21) = 4.40, p = .048, partial eta squared = .17, observed power = .52) and in DPA Scale scores (F(1, 21) = 7.46, p = .013, partial eta squared = .27, observed power = .74).

Discussion: The results indicate the MC 'squeeze' technique had positive effects on patient function and health-related quality of life over a period of 14 days and was clinically and statistically superior to the sham treatment. Further investigation of the MC 'squeeze' technique is warranted.

Enhanced repair of meniscal hoop structure injuries using an aligned electrospun nanofibrous scaffold combined with a mesenchymal stem cell-derived tissue engineered construct

Damage to the meniscal hoop structure results in loss of biomechanical function, which potentially leads to the extrusion of the meniscus from the weight bearing area. However, there have been no established, effective treatments for such injuries. The purpose of this study was to investigate the applicability of cell-seeded nanofibrous scaffolds to repair the damaged meniscal hoop structure along with the prevention of subsequent cartilage degeneration using a rabbit model. Meniscal radial defects (5 mm width) in the medial meniscus were treated by wrapping and suturing with either an aligned electrospun nanofibrous scaffold alone or a scaffold combined with a tissue engineered construct (TEC) derived from synovial mesenchymal stem cells (MSCs), with the scaffold fiber direction matching that of the meniscal circumferential fibers. The MSC-based TEC-combined nanofibrous scaffolds contributed significantly to the prevention of meniscal extrusion and exerted a chondroprotective effect, compared with either scaffold alone or the untreated control groups. Also, meniscal defects treated with such TEC-combined nanofibrous scaffolds were consistently repaired with a fibrocartilaginous tissue. In this study, we have demonstrated the feasibility of a combined TEC-nanofibrous scaffold to repair the meniscal hoop structure, and prevent the progression to cartilage degeneration, as a potential tissue engineering method.

Arthroscopic repair of the meniscus: Surgical management and clinical outcomes

From the biomechanical and biological points of view, an arthroscopic meniscal repair (AMR) should always be considered as an option. However, AMR has a higher reoperation rate compared with arthroscopic partial meniscectomy, so it should be carefully indicated.

Compared with meniscectomy, AMR outcomes are better and the incidence of osteoarthritis is lower when it is well indicated.

Factors influencing healing and satisfactory results must be carefully evaluated before indicating an AMR.

Tears in the peripheral third are more likely to heal than those in the inner thirds.

Vertical peripheral longitudinal tears are the best scenario in terms of success when facing an AMR.

‘Inside-out’ techniques were considered as the gold standard for large repairs on mid-body and posterior parts of the meniscus. However, recent studies do not demonstrate differences regarding failure rate, functional outcomes and complications, when compared with the ‘all-inside’ techniques.

Some biological therapies try to enhance meniscal repair success but their efficacy needs further research. These are: mechanical stimulation, supplemental bone marrow stimulation, platelet rich plasma, stem cell therapy, and scaffolds and membranes.

Meniscal root tear/avulsion dramatically compromises meniscal stability, accelerating cartilage degeneration. Several options for reattachment have been proposed, but no differences between them have been established. However, repair of these lesions is actually the reference of the treatment.

Meniscal ramp lesions consist of disruption of the peripheral attachment of the meniscus. In contrast, with meniscal root tears, the treatment of reference has not yet been well established.

Cite this article: EFORT Open Rev 2018;3:584-594. DOI: 10.1302/2058-5241.3.170059

Human Cartilage-Derived Progenitors Resist Terminal Differentiation and Require CXCR4 Activation to Successfully Bridge Meniscus Tissue Tears

Meniscus injuries are among the most common orthopedic injuries. Tears in the inner one‐third of the meniscus heal poorly and present a significant clinical challenge. In this study, we hypothesized that progenitor cells from healthy human articular cartilage (chondroprogenitor cells [C‐PCs]) may be more suitable than bone‐marrow mesenchymal stem cells (BM‐MSCs) to mediate bridging and reintegration of fibrocartilage tissue tears in meniscus. C‐PCs were isolated from healthy human articular cartilage based on their expression of mesenchymal stem/progenitor marker activated leukocyte cell adhesion molecule (ALCAM) (CD166). Our findings revealed that healthy human C‐PCs are CD166+, CD90+, CD54+, CD106‐ cells with multilineage differentiation potential, and elevated basal expression of chondrogenesis marker SOX‐9. We show that, similar to BM‐MSCs, C‐PCs are responsive to the chemokine stromal cell‐derived factor‐1 (SDF‐1) and they can successfully migrate to the area of meniscal tissue damage promoting collagen bridging across inner meniscal tears. In contrast to BM‐MSCs, C‐PCs maintained reduced expression of cellular hypertrophy marker collagen X in monolayer culture and in an explant organ culture model of meniscus repair. Treatment of C‐PCs with SDF‐1/CXCR4 pathway inhibitor AMD3100 disrupted cell localization to area of injury and prevented meniscus tissue bridging thereby indicating that the SDF‐1/CXCR4 axis is an important mediator of this repair process. This study suggests that C‐PCs from healthy human cartilage may potentially be a useful tool for fibrocartilage tissue repair/regeneration because they resist cellular hypertrophy and mobilize in response to chemokine signaling. stem cells2019;37:102–114

Biomechanical Analysis of Porcine Cartilage Elasticity

Grafting of tissue-engineered cartilage to joints with osteoarthritis has the potential to supersede arthroplasty as the standard of care. However, in order to support the development of functional tissue engineering methods, the subfailure biomechanics of the individual cartilage types that comprise joints must be determined. Current methods for analyzing tissues are based on imaging and are therefore unable to profile the strain dependence of mechanical behaviors within different cartilage types. Recently, an analysis technique based on Optical Fiber Polarimetric Elastography (OFPE) has overcome these challenges. OFPE has been used to characterize the different mechanical behaviors of a range of unprocessed biomaterials and tissues. In the present work, this technique is used to characterize the biomechanics of both articular cartilage and meniscal fibrocartilage within a porcine knee. OFPE testing of the tissue is conducted over a range of physiological loading and unloading values. These results demonstrate the distinctive mechanics of each cartilage type. Due to their different locations within the knee, each cartilage type exhibits distinctly unique biomechanical behavior. Based on the results of OFPE, we correlate the specific buckling, delamination, and bridging events to maxima and minima along the loading and unloading curves. This provides unprecedented detail with regard to the subfailure biomechanics. This information is integral to the design of the next generation of tissue-engineered constructs. Therefore, OFPE will be used across multiple disciplines to rapidly determine the mechanical behavior of tissue-engineered constructs to support functional tissue engineering efforts.

Articular cartilage lesions associated with complete lateral meniscal tears in the dog

OBJECTIVE

To describe articular cartilage (AC) lesions associated with complete lateral meniscal tears in dogs.

STUDY DESIGN

Observational series.

ANIMALS

Seventeen dogs with arthroscopic evidence of a complete lateral meniscal tear and associated AC lesions.

METHODS

Medical records of dogs with arthroscopic evidence of complete lateral meniscal tear and associated AC lesions between March 2006 and December 2017 were examined for arthroscopic findings.

RESULTS

The cranial cruciate ligament (CrCL) was intact in 11 of 17 dogs, partially ruptured but competent in 4 of 17 dogs, and completely ruptured in 2 of 17 dogs. All dogs had grossly normal caudal cruciate ligament, medial meniscus, and AC of the medial compartment. In each dog, a complete radial tear of the caudal body of the lateral meniscus was associated with degenerative osteoarthritis (OA) of the lateral compartment of the stifle. The Outerbridge score of the lateral tibial condyle and lateral femoral condyle was 5 of 5 in 15 dogs, 3 of 5 in 1 dog, and 4 of 5 in 1 dog.

CONCLUSION

Dogs with complete tears of the lateral meniscus developed degenerative OA of the lateral compartment of the stifle leading to AC loss and clinical dysfunction.

CLINICAL SIGNIFICANCE

Complete lateral meniscal tears may occur as isolated injuries in dogs with a functional CrCL.

Biologic Options for Glenohumeral Arthritis

Biologic options for glenohumeral arthritis include intra-articular injections as well as allograft interposition arthroplasty. The objectives of these treatments are reduction of pain and maintenance/improvement in function, while delaying the need for arthroplasty. This article reviews the current evidence for hyaluronic acid injection, platelet-rich plasma injection, and allograft interposition arthroplasty in the young patient with glenohumeral arthritis.

Comparative Outcomes of Radial and Bucket-Handle Meniscal Tear Repair: A Propensity-Matched Analysis

BACKGROUND

Full-thickness radial meniscal tears render the meniscus nonfunctional and have historically been treated with partial meniscectomy. As preservative techniques evolve for radial repair, comparisons with other tear patterns are necessary to evaluate repair efficacy and prognosis.

PURPOSE

To assess clinical outcomes and reoperation rates of radial meniscal repair and to compare them to bucket-handle meniscal repair.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Radial and bucket-handle meniscal tears without concurrent root injuries undergoing surgical repair at a single institution between 2007 and 2015 were analyzed, including both all-inside and inside-out suturing techniques. Propensity matching was performed on the basis of age at surgery, sex, meniscus laterality, body mass index (BMI), and concomitant anterior cruciate ligament reconstruction (ACLR) using a comparison pool of 70 bucket-handle repairs. Reoperation-free survival rates and Tegner, visual analog scale (VAS) for pain, and International Knee Documentation Committee (IKDC) scores were analyzed.

RESULTS

Twenty-four patients (18 male, 6 female; mean age, 22.8 ± 11.9 years) who underwent repair of a radial meniscal tear were followed for a mean of 3.5 years (range, 2.0-6.3 years). Significant postoperative improvements in VAS scores at rest and with use and IKDC scores were noted postoperatively ( P < .001). Five patients (20.8%) required a reoperation. Subsequently, 18 patients with radial tears (mean age, 19.1 ± 9.1 years; 12 male; mean BMI, 27.0 ± 6.2 kg/m²; 3 medial; 11 ACLR) were propensity matched to 18 patients with bucket-handle tears (mean age, 20.8 ± 5.1 years; 13 male; mean BMI, 25.0 ± 3.5 kg/m²; 3 medial; 11 ACLR). The matched radial and bucket-handle groups demonstrated similar ( P = .17) reoperation-free survival rates at 2 years (88.9% and 94.4%, respectively) and 5 years (77.8% and 87.7%, respectively). VAS and IKDC scores improved significantly after surgery ( P < .001), with no difference noted between the groups ( P ≥ .17). Patients with radial and bucket-handle meniscal repairs achieved mean postoperative Tegner scores (6.6 and 6.6, respectively) not significantly different from their preinjury levels (6.9 and 6.7, respectively) ( P ≥ .32).

CONCLUSION

Satisfactory clinical outcomes are achievable for radial meniscal tear repair at short-term follow-up. In a robustly matched comparison, radial and bucket-handle meniscal tears demonstrate similar improvements in VAS and IKDC scores, restoration of preoperative Tegner scores, and acceptable reoperation rates. Full-thickness radial meniscal tears should be considered for repair.

Evaluation of histological and biomechanical properties on engineered meniscus tissues using sonication decellularization

Sonication decellularization treatment requires proper evaluations on its ability to decellularize meniscus tissue efficiently. This study was done to evaluate the histological and biomechanical properties within meniscus scaffolds. Van Gieson staining was done to evaluate the efficiency of cell removal in meniscus tissues. The consequences of treatment on viscoelastic properties are vital for scaffolds quality and were properly investigated. Picrosirius red and Safranin-O/Fast green staining was carried out to detect extracellular matrix materials (ECM). Sonication decellularization treatment has the ability to demonstrated complete nuclei removal compare to control samples as well as maintaining viscoelastic properties, namely stiffness, compression and residual force. Thus, sonication decellularization treatment had successfully produced and prepared a meniscus bioscaffold candidate in which its biomechanical strength is sustained through protection of ECM properties.

Postnatal deletion of Alk5 gene in meniscal cartilage accelerates age-dependent meniscal degeneration in mice

Activation of transforming growth factor-β (TGF-β) signaling has been used to enhance healing of meniscal degeneration in several models. However, the exact role and molecular mechanism of TGF-β signaling in meniscus maintenance and degeneration are still not understood due to the absence of in vivo evidence. In this study, we found that the expression of activin receptor-like kinases 5 (ALK5) in the meniscus was decreased with the progression of age and/or osteoarthritis induced meniscal degeneration. Col2α1 positive cells were found to be specifically distributed in the superficial and inner zones of the anterior horn, as well as the inner zone of the posterior horn in mice, indicating that Col2α1-CreER^T2 mice can be a used for studying gene function in menisci. Furthermore, we deleted Alk5 in Col2α1 positive cells in meniscus by administering tamoxifen. Alterations in the menisci structure were evaluated histologically. The expression levels of genes and proteins associated with meniscus homeostasis and TGF-β signaling were analyzed by quantitative real-time PCR analysis (qRT-PCR) and immunohistochemistry (IHC). Our results revealed severe and progressive meniscal degeneration phenotype in 3- and 6-month-old Alk5 cKO mice compared with Cre-negative control, including aberrantly increased hypertrophic meniscal cells, severe fibrillation, and structure disruption of meniscus. qRT-PCR and IHC results showed that disruption of anabolic and catabolic homeostasis of chondrocytes may contribute to the meniscal degeneration phenotype observed in Alk5 cKO mice. Thus, TGF-β/ALK5 signaling plays a chondro-protective role in menisci homeostasis, in part, by inhibiting matrix degradation and maintaining extracellular matrix proteins levels in meniscal tissues.

Delayed Rehabilitation After Lateral Meniscal Allograft Transplantation Can Reduce Graft Extrusion Compared With Standard Rehabilitation

BACKGROUND

Meniscal extrusion prevention would be important for restoring normal knee kinematics, even though the effect of graft extrusion after meniscal allograft transplantation (MAT) has not been clearly identified.

HYPOTHESIS

When compared with standard rehabilitation protocols, delayed rehabilitation after lateral MAT could reduce graft extrusion.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 53 patients who underwent lateral MAT with the keyhole technique from June 2011 to March 2015 were included. Graft extrusion and lateral compartment articular cartilage loss on magnetic resonance imaging, joint space width (JSW) on weightbearing radiographs, and clinical outcomes (including subjective scores and functional tests) of 25 patients who underwent standard rehabilitation (group S) after lateral MAT were compared with those of 28 patients who underwent delayed rehabilitation (group D), which included immobilization during the first 3 weeks and use of unloading braces for 9 weeks.

RESULTS

Mean ± SD follow-up times for groups S and D were 25.7 ± 6.4 and 24.5 ± 7.1 months, respectively. Although the postoperative clinical outcomes did not differ between the groups, graft extrusion (3.2 ± 1.5 mm vs 1.8 ± 1.6 mm) and relative percentage of extrusion (32.2% ± 14.6% vs 17.3% ± 16.6%) were greater in group S than in group D ( P < .001 for both). The percentage of patients with graft extrusion (≥3 mm) was 52% in group S and 21.4% in group D. JSWs on Rosenberg view decreased by 0.1 mm in group S but increased by 0.3 mm in group D ( P = .035). Kellgren-Lawrence grade and modified Outerbridge grade progressed by 44% and 44% among patients in group S and by 17.9% and 21.4% among patients in group D, respectively. There were significant correlations between the coronal graft extrusion and postoperative JSWs on full extension (-0.452) and Rosenberg (-0.410) views, Kellgren-Lawrence grade (0.727), and modified Outerbridge grade (0.732) on magnetic resonance imaging ( P < .001 for all).

CONCLUSION

Compared with standard rehabilitation, delayed rehabilitation showed less coronal graft extrusion and joint space narrowing on weightbearing and reduced the progression of arthrosis, although the rehabilitation protocols showed no differences in clinical outcomes.

Tissue Mimicry in Morphology and Composition Promotes Hierarchical Matrix Remodeling of Invading Stem Cells in Osteochondral and Meniscus Scaffolds

An integral approach toward in situ tissue engineering through scaffolds that mimic tissue with regard to both tissue architecture and biochemical composition is presented. Monolithic osteochondral and meniscus scaffolds are prepared with tissue analog layered biochemical composition and perpendicularly oriented continuous micropores by a newly developed cryostructuring technology. These scaffolds enable rapid cell ingrowth and induce zonal-specific matrix synthesis of human multipotent mesenchymal stromal cells solely through their design without the need for supplementation of soluble factors such as growth factors.

Tissue Engineering of Large Full-Size Meniscus Defects by a Polyurethane Scaffold: Accelerated Regeneration by Mesenchymal Stromal Cells

The endogenous healing potential of avascular meniscal lesions is poor. Up to now, partial meniscectomy is still the treatment of choice for meniscal lesions within the avascular area. However, the large loss of meniscus substance predisposes the knee for osteoarthritic changes. Tissue engineering techniques for the replacement of such lesions could be a promising alternative treatment option. Thus, a polyurethane scaffold, which is already in clinical use, loaded with mesenchymal stromal cells, was analyzed for the repair of critical meniscus defects in the avascular zone. Large, approximately 7 mm broad meniscus lesions affecting both the avascular and vascular area of the lateral rabbit meniscus were treated with polyurethane scaffolds either loaded or unloaded with mesenchymal stromal cells. Menisci were harvested at 6 and 12 weeks after initial surgery. Both cell-free and cell-loaded approaches led to well-integrated and stable meniscus-like repair tissue. However, an accelerated healing was achieved by the application of mesenchymal stromal cells. Dense vascularization was detected throughout the repair tissue of both treatment groups. Overall, the polyurethane scaffold seems to promote the vessel ingrowth. The application of mesenchymal stromal cells has the potential to speed up the healing process.

The Pathobiology of the Meniscus: A Comparison Between the Human and Dog

Serious knee pain and related disability have an annual prevalence of approximately 25% on those over the age of 55 years. As curative treatments for the common knee problems are not available to date, knee pathologies typically progress and often lead to osteoarthritis (OA). While the roles that the meniscus plays in knee biomechanics are well characterized, biological mechanisms underlying meniscus pathophysiology and roles in knee pain and OA progression are not fully clear. Experimental treatments for knee disorders that are successful in animal models often produce unsatisfactory results in humans due to species differences or the inability to fully replicate disease progression in experimental animals. The use of animals with spontaneous knee pathologies, such as dogs, can significantly help addressing this issue. As microscopic and macroscopic anatomy of the canine and human menisci are similar, spontaneous meniscal pathologies in canine patients are thought to be highly relevant for translational medicine. However, it is not clear whether the biomolecular mechanisms of pain, degradation of extracellular matrix, and inflammatory responses are species dependent. The aims of this review are (1) to provide an overview of the anatomy, physiology, and pathology of the human and canine meniscus, (2) to compare the known signaling pathways involved in spontaneous meniscus pathology between both species, and (3) to assess the relevance of dogs with spontaneous meniscal pathology as a translational model. Understanding these mechanisms in human and canine meniscus can help to advance diagnostic and therapeutic strategies for painful knee disorders and improve clinical decision making.

Medial meniscal extrusion: Detection, evaluation and clinical implications

The menisci play an important role in knee kinematics. Their unique anatomy allows them to channel forces generated during knee movements through the larger tibio-femoral condylar surfaces while simultaneously resisting deleterious hoop stresses. Although physiologic meniscal extrusion occurs with every knee joint movement, pathologic meniscal extrusion subjects the knee to persistent and excessive load transmission. This renders the knee structures susceptible to injury or exacerbates worsening of existing knee joint internal derangement. Detection and quantification of meniscus extrusion is important given its association with underlying pathological processes and internal derangements such as cartilage loss, osteoarthritis and meniscal tears. The medial and lateral menisci vary in size, attachments and load transmission, and the medial meniscus is more susceptible to injury. In this article, the authors illustrate the role of meniscus kinematics, and the identification and quantification of medial meniscal extrusion. Multimodality imaging appearances and implications of presence of medial meniscal extrusion in different knee joint pathologies are discussed with review of the relevant literature.

The Strength of Transosseous Medial Meniscal Root Repair Using a Simple Suture Technique Is Dependent on Suture Material and Position

BACKGROUND

A simple suture technique in transosseous meniscal root repair can provide equivalent resistance to cyclic load and is less technically demanding to perform compared with more complex suture configurations, yet maximum yield loads are lower. Various suture materials have been investigated for repair, but it is currently not clear which material is optimal in terms of repair strength. Meniscal root anatomy is also complex; consisting of the ligamentous mid-substance (root ligament), the transition zone between the meniscal body and root ligament; the relationship between suture location and maximum failure load has not been investigated in a simulated surgical repair.

HYPOTHESES

(A) Using a knottable, 2-mm-wide, ultra-high-molecular-weight polyethylene (UHMWPE) braided tape for transosseous meniscal root repair with a simple suture technique will give rise to a higher maximum failure load than a repair made using No. 2 UHMWPE standard suture material for simple suture repair. (B) Suture position is an important factor in determining the maximum failure load.

STUDY DESIGN

Controlled laboratory study.

METHODS

In part A, the posterior root attachment of the medial meniscus was divided in 19 porcine knees. The tibias were potted, and repair of the medial meniscus posterior root was performed. A suture-passing device was used to place 2 simple sutures into the posterior root of the medial meniscus during a repair procedure that closely replicated single-tunnel, transosseous surgical repair commonly used in clinical practice. Ten tibias were randomized to repair with No. 2 suture (Suture group) and 9 tibias to repair with 2-mm-wide knottable braided tape (Tape group). The repair strength was assessed by maximum failure load measured by use of a materials testing machine. Micro-computed tomography (CT) scans were obtained to assess suture positions within the meniscus. The wide range of maximum failure load appeared related to suture position. In part B, 10 additional porcine knees were prepared. Five knees were randomized to the Suture group and 5 to the Tape group. All repairs were standardized for location, and the repair was placed in the body of the meniscus. A custom image registration routine was created to coregister all 29 menisci, which allowed the distribution of maximum failure load versus repair location to be visualized with a heat map.

RESULTS

In part A, higher maximum failure load was found for the Tape group (mean, 86.7 N; 95% CI, 63.9-109.6 N) compared with the Suture group (mean, 57.2 N; 95% CI, 30.5-83.9 N). The 3D micro-CT analysis of suture position showed that the mean maximum failure load for repairs placed in the meniscus body (mean, 104 N; 95% CI, 81.2-128.0 N) was higher than for those placed in the root ligament (mean, 35.1 N; 95% CI, 15.7-54.5 N). In part B, the mean maximum failure load was significantly greater for the Tape group, 298.5 N ( P = .016, Mann-Whitney U; 95% CI, 183.9-413.1 N), compared with that for the Suture group, 146.8 N (95% CI, 82.4-211.6 N). Visualization with the heat map revealed that small variations in repair location on the meniscus were associated with large differences in maximum failure load; moving the repair entry point by 3 mm could reduce the failure load by 50%.

CONCLUSION

The use of 2-mm braided tape provided higher maximum failure load than the use of a No. 2 suture. The position of the repair in the meniscus was also a highly significant factor in the properties of the constructs.

CLINICAL RELEVANCE

The results provide insight into material and location for optimal repair strength.

Variations in the attachments of the medial meniscal anterior horn: a descriptive cadaveric study

PURPOSE

Meniscal tears are common in Kenya, with prevalence rates ranging from 45 to 78% of intracapsular knee pathology. Diagnosis of these injuries relies on the use of both clinical signs and symptoms as well as radiological investigations. In a few instances, radiological detection could be difficult, partly because of variant attachment patterns of the medial meniscal anterior horn. Some of these unusual attachments of the anterior horn of the medial meniscus could even be mistaken for meniscal tears. There is also evidence that these variations differ from population to population. This study, therefore, aimed to determine the variant bony and ligamentous attachments of the medial meniscal anterior horn in a sample Kenyan population.

METHODS

The study was conducted at the Department of Human Anatomy, University of Nairobi. Thirty-one male and female unpaired medial menisci were obtained from cadaveric specimen. The bony and ligamentous attachments were identified and recorded and photomacrographs taken.

RESULTS

The bony attachments different from the classical textbook attachment accounted for 54.8% of the medial meniscal anterior horns. The anterior intermeniscal ligament was present in 62.3% while 16.2% showed attachment to the anterior cruciate ligament. Twenty-nine percent (29%) of the medial menisci studied did not have any ligamentous attachments.

CONCLUSIONS

The bony and ligamentous attachments of the medial meniscal anterior horn are highly variable presenting unique diagnostic and therapeutic challenges. A new classification of ligamentous attachments is thus proposed.

Where does meniscal damage progress most rapidly? An analysis using three-dimensional shape models on data from the Osteoarthritis Initiative

OBJECTIVES

Meniscal pathology is integral to knee osteoarthritis (OA) and its progression; it provides a progression biomarker and a potential treatment target. Magnetic resonance imaging (MRI) demonstrates large heterogeneity in meniscal damage; this structural complexity means measurement is difficult. The aim of this study was to apply novel 3D image analysis to determine which meniscal pathologies demonstrated most change during OA progression.

METHODS

Knee images were selected from the progression cohort of the Osteoarthritis Initiative choosing participants with risk factors for medial OA progression. Medial and lateral menisci were manually segmented then analysed using a statistical shape model of the tibia as a reference surface. Responsiveness was assessed at 1 year using standardised response means (SRMs) for four constructs: meniscal volume, extrusion volume, thickness and tibial coverage; anatomical sub-regions of these constructs were also explored.

RESULTS

Paired images from 86 participants (median age 61.5, 49% female, 56% obese) were included. Reliability of the novel meniscal measurements was very good intraclass correlation coefficients (ICCs all > 0.98). Meniscal volume and extrusion demonstrated no significant change. Moderate responsiveness was observed for medial meniscus thickness (SRM -0.35) and medial tibial coverage (SRM -0.36). No substantial change was seen for the lateral meniscus measures. Sub-region analysis did not improve responsiveness; while greater change was seen in the posterior medial compartment, it was associated with increased variance of the change.

CONCLUSIONS

The location of meniscal damage was consistently in the posterior medial region, and two measurements (thickness and tibial coverage) were most responsive. Meniscal measures should add to discriminatory power in OA progression assessment.

Meniscal repair and regeneration: Current strategies and future perspectives

The management of meniscal injuries remains difficult and challenging. Although several clinical options exist for the treatment of such injuries, complete regeneration of the damaged meniscus has proved difficult due to the limited healing capacity of the tissue. With the advancements in tissue engineering and cell-based technologies, new therapeutic options for patients with currently incurable meniscal lesions now potentially exist. This review will discuss basic anatomy, current repair techniques and treatment options for loss of meniscal integrity. Specifically, we focus on the possibility and feasibility of the latest tissue engineering approaches, including 3D printing technologies. Therefore, this discussion will facilitate a better understanding of the latest trends in meniscal repair and regeneration, and contribute to the future application of such clinical therapies for patients with meniscal injuries.

Age-related changes in the knee meniscus

BACKGROUND

Aging is the most prominent risk factor for the development of osteoarthritis (OA), which affects knees and causes major health burdens. Meniscal dysfunction mostly based on degeneration contributes to the development and progression of knee OA. Meniscal degeneration is caused by various extrinsic factors, such as repetitive trauma or leg malalignment, while meniscal aging is considered as internal changes, such as molecular or cellular changes. Little is known about age-related changes in the meniscus. Therefore, this review aimed to summarize and clarify the understanding of the aged meniscus.

METHODS

There are few articles about natural aging in the meniscus, because most reports only demonstrate the effects of OA on the meniscus. We searched PubMed (1948 to November 2016) to identify and summarize all English-language articles evaluating natural aging in the meniscus.

RESULTS

There is evidence of compositional change in the meniscus with aging, involving cells, collagens, and proteoglycans. In addition, as recent reports on the natural aging of cartilage have indicated, senescence of the meniscal cells may also lead to disruption of meniscal cells and tissue homeostasis. Due to the low turnover rate of collagen, accumulation of advanced glycation end-products largely contributes to tissue stiffness and vulnerability, and finally results in degenerative changes or tears. Furthermore, environmental factors such as joint fluid secreted by inflamed synovium could also contribute to meniscal tissue deterioration.

CONCLUSIONS

Age-related changes induce meniscal tissue vulnerability and finally lead to meniscal dysfunction.

In vivo tibiofemoral skeletal kinematics and cartilage contact arthrokinematics during decline walking after isolated meniscectomy

We investigated the effects of isolated meniscectomy on tibiofemoral skeletal kinematics and cartilage contact arthrokinematics in vivo. We recruited nine patients who had undergone isolated medial or lateral meniscectomy, and used a dynamic stereo-radiography (DSX) system to image the patients' knee motion during decline walking. A volumetric model-based tracking process determined 3D tibiofemoral kinematics from the recorded DSX images. Cartilage contact arthrokinematics was derived from the intersection between tibial and femoral cartilage models co-registered to the bones. The kinematics and arthrokinematics were analyzed for early stance and loading response phase (30% of a gait cycle), comparing the affected and intact knees. Results showed that four patients with medial meniscectomy had significantly greater contact centroid excursions in the meniscectomized medial compartments while five patients with lateral meniscectomy had significantly greater cartilage contact area and lateral shift of contact centroid path in the meniscectomized lateral compartments, comparing to those of the same compartments in the contralateral intact knees. No consistent difference however was identified in the skeletal kinematics. The current study demonstrated that cartilage-based intra-articular arthrokinematics is more sensitive and insightful than the skeletal kinematics in assessing the meniscectomy effects.

Bioinks for bioprinting functional meniscus and articular cartilage

3D bioprinting can potentially enable the engineering of biological constructs mimicking the complex geometry, composition, architecture and mechanical properties of different tissues and organs. Integral to the successful bioprinting of functional articular cartilage and meniscus is the identification of suitable bioinks and cell sources to support chondrogenesis or fibrochondrogenesis, respectively. Such bioinks must also possess the appropriate rheological properties to be printable and support the generation of complex geometries. This review will outline the parameters required to develop bioinks for such applications and the current recent advances in 3D bioprinting of functional meniscus and articular cartilage. The paper will conclude by discussing key scientific and technical hurdles in this field and by defining future research directions for cartilage and meniscus bioprinting.

* The Ovine Model for Meniscus Tissue Engineering: Considerations of Anatomy, Function, Implantation, and Evaluation

Meniscus injuries represent one of the most-common intra-articular knee injuries. The current treatment options include meniscectomy and allograft transplantation, both with poor long-term outcomes. Therefore, there is a need for regenerative techniques to restore meniscal function. To preclinically test scaffolds for meniscus replacement, large animal models need to be established and standardized. This review establishes the anatomical and compositional similarities between human and sheep menisci and provides guidance for implantation and evaluation of such devices. The ovine meniscus represents a scaled-down version of the human meniscus, with only slight structural differences that can be addressed during device fabrication. Implantation protocols in sheep remain a challenge, as the meniscus cannot be visualized with the arthroscopic-assisted procedures commonly performed in human patients. Thus, we recommend the appropriate implantation protocols for meniscus visualization, ligamentous restoration, and surgical fixation of both total and partial meniscus replacement devices. Last, due to the lack of standardization in evaluation techniques, we recommend a comprehensive battery of tests to evaluate the efficacy of meniscus replacement implants. We recommend other investigators utilize these surgical and testing techniques to establish the ovine model as the gold standard for preclinical evaluation of meniscus replacement devices.

Meniscal Preservation is Important for the Knee Joint

Native joint preservation has gained importance in recent years. This is mostly to find solutions for limitations of arthroplasty. In the knee joint, the menisci perform critical functions, adding stability during range of motion and efficiently transferring load across the tibiofemoral articulation while protecting the cartilage. The menisci are the most common injury seen by orthopedicians, especially in the younger active patients. Advances in technology and our knowledge on functioning of the knee joint have made meniscus repair an important mode of treatment. This review summarizes the various techniques of meniscus tear repair and also describes biological enhancements of healing.

Innovative application of Cox Flexion Distraction Decompression to the knee: a retrospective case series

OBJECTIVE

The purpose of this study is to introduce the application of Cox flexion distraction decompression as an innovative approach to treating knee pain and osteoarthritis.

METHODS

Six months of clinical files from one chiropractic practice were retrospectively screened for patients who had been treated for knee pain. Twenty-five patients met the criteria for inclusion. The treatment provided was Cox flexion distraction decompression. Pre-treatment and post-treatment visual analog pain scales (VAS) were used to measure the results. In total, eight patients presented with acute knee pain (less than three months' duration) and 18 patients presented with chronic knee pain (greater than three months) including two patients with continued knee pain after prosthetic replacement surgery.

RESULTS

For all 25 patients, a change was observed in the mean VAS scores from 7.7 to 1.8. The mean number of treatments was 5.3 over an average of 3.0 weeks. Acute patient mean VAS scores dropped from 8.1 to 1.1 within 4.8 treatments over 2.4 weeks. Chronic patient mean VAS scores dropped from 7.5 to 2.2 within 5.4 treatments over 3.3 weeks. No adverse events were reported.

CONCLUSION

This study showed clinical improvement in patients with knee pain who were managed with Cox flexion distraction decompression applied to the knee.

Cross-sectional and longitudinal study of the impact of posterior meniscus horn lesions on adjacent cartilage composition, patient-reported outcomes and gait biomechanics in subjects without radiographic osteoarthritis

OBJECTIVE

The aim of this study was to assess cross-sectional and longitudinal effects of meniscal lesions on adjacent cartilage T_1ρ and T₂ relaxation times, patient-reported outcomes and gait biomechanics.

DESIGN

Thirty patients with no cartilage morphological defects reported by Whole Organ MRI Score (WORMS) magnetic resonance imaging (MRI) grading and no radiographic osteoarthritis (OA) (Kellgren--Lawrence (KL) ≤ 1) were selected, 15 with posterior meniscus horn lesions and 15 matched controls without meniscal lesions. All were imaged on a 3T MR scanner for three consecutive years, except those who dropped from the study. Sagittal and frontal plane kinematic gait data were acquired at baseline. The Knee Injury and Osteoarthritis Outcome Score (KOOS) survey was taken each time. All images were automatically segmented and registered to an atlas for voxel-by-voxel cross-sectional and longitudinal analyses.

RESULTS

Relaxation time comparisons between groups showed elevated T_1ρ of the lateral tibia (LP) and elevated T₂ of the medial tibia (MT) and LT at 1 and 2 years in the lesion group. Longitudinal comparisons within each group revealed greater relaxation time elevations over one and 2 years in the group with lesions. KOOS Quality of Life (QOL) was significantly different between the groups at all time points (P < 0.05), as were other KOOS subcategories. No significant differences in the frontal or sagittal biomechanics were observed between the groups at baseline.

CONCLUSIONS

Individuals with healthy cartilage and posterior meniscal horn lesions have increased relaxation times when compared to matched controls, increased relaxation time changes over 2 years, and consistently report a lower KOOS QOL, yet show no difference in gait biomechanics.

Meniscus, articular cartilage and nucleus pulposus: a comparative review of cartilage-like tissues in anatomy, development and function

The degradation of cartilage in the human body is impacted by aging, disease, genetic predisposition and continued insults resulting from daily activity. The burden of cartilage defects (osteoarthritis, rheumatoid arthritis, intervertebral disc damage, knee replacement surgeries, etc.) is daunting in light of substantial economic and social stresses. This review strives to broaden the scope of regenerative medicine and tissue engineering approaches used for cartilage repair by comparing and contrasting the anatomical and functional nature of the meniscus, articular cartilage (AC) and nucleus pulposus (NP). Many review papers have provided detailed evaluations of these cartilages and cartilage-like tissues individually but none have comprehensively examined the parallels and inconsistencies in signaling, genetic expression and extracellular matrix composition between tissues. For the first time, this review outlines the importance of understanding these three tissues as unique entities, providing a comparative analysis of anatomy, ultrastructure, biochemistry and function for each tissue. This novel approach highlights the similarities and differences between tissues, progressing research toward an understanding of what defines each tissue as distinctive. The goal of this paper is to provide researchers with the fundamental knowledge to correctly engineer the meniscus, AC and NP without inadvertently developing the wrong tissue function or biochemistry.

Chondrogenically primed tonsil-derived mesenchymal stem cells encapsulated in riboflavin-induced photocrosslinking collagen-hyaluronic acid hydrogel for meniscus tissue repairs

Current meniscus tissue repairing strategies involve partial or total meniscectomy, followed by allograft transplantation or synthetic material implantation. However, allografts and synthetic implants have major drawbacks such as the limited supply of grafts and lack of integration into host tissue, respectively. In this study, we investigated the effects of conditioned medium (CM) from meniscal fibrochondrocytes and TGF-β3 on tonsil-derived mesenchymal stem cells (T-MSCs) for meniscus tissue engineering. CM-expanded T-MSCs were encapsulated in riboflavin-induced photocrosslinked collagen-hyaluronic acid (COL-RF-HA) hydrogels and cultured in chondrogenic medium containing TGF-β3. In vitro results indicate that CM-expanded cells followed by TGF-β3 exposure stimulated the expression of fibrocartilage-related genes (COL2, SOX9, ACAN, COL1) and production of extracellular matrix components. Histological assessment of in vitro and subcutaneously implanted in vivo constructs demonstrated that CM-expanded cells followed by TGF-β3 exposure resulted in highest cell proliferation, GAG accumulation, and collagen deposition. Furthermore, when implanted into meniscus defect model, CM treatment amplified the potential of TGF-β3 and induced complete regeneration.

STATEMENT OF SIGNIFICANCE

Conditioned medium derived from chondrocytes have been reported to effectively prime mesenchymal stem cells toward chondrogenic lineage. Type I collagen is the main component of meniscus extracellular matrix and hyaluronic acid is known to promote meniscus regeneration. In this manuscript, we investigated the effects of conditioned medium (CM) and transforming growth factor-β3 (TGF-β3) on tonsil-derived mesenchymal stem cells (T-MSCs) encapsulated in riboflavin-induced photocrosslinked collagen-hyaluronic acid (COL-RF-HA) hydrogel. We employed a novel source of conditioned medium, derived from meniscal fibrochondrocytes. Our in vitro and in vivo results collectively illustrate that CM-expanded cells followed by TGF-β3 exposure have the best potential for meniscus regeneration. This manuscript highlights a novel stem cell commitment strategy combined with biomaterials designs for meniscus regeneration.

Cartilage repair by mesenchymal stem cells: Clinical trial update and perspectives

Osteoarthritis is a degenerative disease of joints with destruction of articular cartilage associated with subchondral bone hypertrophy and inflammation. OA is the leading cause of joint pain resulting in significant worsening of the quality-of-life in the elderly. Numerous efforts have been spent to overcome the inherently poor healing ability of articular cartilage. Mesenchymal stem cells (MSCs) have been in the limelight of cell-based therapies to promote cartilage repair. Despite progressive advancements in MSC manipulation and the introduction of various bioactive scaffolds and growth factors in preclinical studies, current clinical trials are still at early stages with preliminary aims to evaluate safety, feasibility and efficacy. This review summarises recently reported MSC-based clinical trials and discusses new research directions with particular focus on the potential application of MSC-derived extracellular vehicles, miRNAs and advanced gene editing techniques which may shed light on the development of novel treatment strategies. The translational potential of this article: This review summarises recent MSC-related clinical research that focuses on cartilage repair. We also propose a novel possible translational direction for hyaline cartilage formation and a new paradigm making use of extra-cellular signalling and epigenetic regulation in the application of MSCs for cartilage repair.

Biomimetic Anisotropic Reinforcement Architectures by Electrically Assisted Nanocomposite 3D Printing

Biomimetic architectures with Bouligand-type carbon nanotubes are fabricated by an electrically assisted 3D-printing method. The enhanced impact resistance is attributed to the energy dissipation by the rotating anisotropic layers. This approach is used to mimic the collagen-fiber alignment in the human meniscus to create a reinforced artificial meniscus with circumferentially and radially aligned carbon nanotubes.