Circumferential Fibers Research Articles

Unveiling the mechanical role of radial fibers in meniscal tissue: Toward structural biomimetics

The meniscus tissue is crucial for knee joint biomechanics and is frequently susceptible to injuries resulting in early-onset osteoarthritis. Consequently, the need for meniscal substitutes spurs ongoing development. The meniscus is a composite tissue reinforced with circumferential and radial collagenous fibers; the mechanical role of the latter has yet to be fully unveiled.Here, we investigated the role of radial fibers using a synergistic methodology combining meniscal tissue structure imaging, a computational knee joint model, and the fabrication of simple biomimetic composite laminates. These laminates mimic the basic structural units of the meniscus, utilizing longitudinal and transverse fibers equivalent to the circumferential and radial fibers in meniscal tissue.In the computational model, the absence of radial fibers resulted in stress concentration within the meniscus matrix and up to 800 % greater area at the same stress level. Furthermore, the contact pressure on the tibial cartilage increased drastically, affecting up to 322 % larger areas. Conversely, in models with radial fibers, we observed up to 25 % lower peak contact pressures and width changes of less than 0.1 %. Correspondingly, biomimetic composite laminates containing transverse fibers exhibited minor transverse deformations and smaller Poisson's ratios. They demonstrated structural shielding ability, maintaining their mechanical performance with the reduced amount of fibers in the loading direction, similar to the ability of the torn meniscus to carry and transfer loads to some extent. These results indicate that radial fibers are essential to distribute contact pressure and tensile stresses and prevent excessive deformations, suggesting the importance of incorporating them in novel designs of meniscal substitutes. Statement of significanceThe organization of the collagen fibers in the meniscus tissue is crucial to its biomechanical function. Radially oriented fibers are an important structural element of the meniscus and greatly affect its mechanical behavior. However, despite their importance to the meniscus mechanical function, radially oriented fibers receive minor attention in meniscal substitute designs. Here, we used a synergistic methodology that combines imaging of the meniscal tissue structure, a structural computational model of the knee joint, and the fabrication of simplistic biomimetic composite laminates that mimic the basic structural units of the meniscus. Our findings highlight the importance of the radially oriented fibers, their mechanical role in the meniscus tissue, and their importance as a crucial element in engineering novel meniscal substitutes.

Poster 303: Outcomes Following Repair of Radial Meniscus Tears Compared to Bucket Handle Meniscus Tears

Objectives: Preserving the meniscus has become a priority in managing meniscal tears with advancement of meniscus repair techniques. Meniscal repair, as opposed to partial meniscectomy, reduces risk of development and progression of knee osteoarthritis. Radial meniscus tears have traditionally been associated with a poor prognosis because they occur perpendicular to circumferential meniscal fibers, compromising hoop tension. Advances in surgical technique and biologic augmentation have facilitated repair of these complex injuries. The purpose of this study was to compare post-operative complication and surgical revision rates in patients who underwent repair of a radial meniscus tear versus bucket-handle meniscus tear. We hypothesized the outcomes of repair of radial meniscus tear would be similar to a matched group of patients who underwent repair of a bucket handle meniscus tear. Methods: A retrospective study was performed to identify patients who underwent repair of radial meniscus tear. Chart review was performed for 1506 patients who underwent meniscus repair from 2012 to 2019, and demographic information, type of meniscus tear, concomitant ACL reconstruction, post-operative complications, repeat surgeries, and failure at the repair site were detailed in a database. Patients who underwent repair of a radial tear were matched with patients who underwent repair of a bucket-handle tear based on sex, age (within 5 years), BMI (within 5 kg/m2), meniscus laterality, and concomitant ACL reconstruction. Isolated meniscus repairs were augmented with platelet rich plasma (PRP). Results: Fifty patients (age, 31.8 ± 15.2 years; BMI, 30.2 ± 6.4 kg/m2) were identified who underwent a radial meniscus tear repair. Of these patients, 16 (32.0%) were female and 23 (46.0%) underwent concomitant ACL reconstruction. Complications including recurrent swelling, stiffness, persistent pain, and repeat injury were reported in 15 patients (30.0%). Six patients underwent repeat surgery (12.0%). Four repeat surgical patients, who had previously undergone meniscus repair and concomitant ACL reconstruction, were found to have an intact radial repair at the time of second surgery, and underwent repeat surgery for a reason unrelated to the radial tear repair (e.g. cyclops lesion, synovectomy, new meniscus tear). Two patients had a radial tear repair failure that required surgical revision (4.0%). Radial tear repair patients who underwent concomitant ACL reconstruction differed significantly from those who did not only in age (ACL group, 26.0 ± 10.9 y; non-ACL group, 36.6 ± 16.7 y; p = 0.03). There were no significant differences in post-operative complications, repeat surgeries, or failures between the radial and bucket-handle tear repair patients. Conclusions: Repair of radial meniscus tears with contemporary techniques and biological enhancement with either ACL reconstruction or PRP can be expected to have similar outcomes to repairs of bucket handle meniscus tears.

All-Inside Arthroscopic Tie-Grip Suture Repair for Radial Tear in the Midbody of Lateral Meniscus Using an All-Inside Device and Slotted Cannula

Inside-out repair of meniscal tears is the gold standard surgical approach; however, its use is limited by the need for a posterior incision and neurovascular risk. In this Technical Report, we present details of the all-inside arthroscopic tie-grip approach for repairing a radial tear of the midbody of the lateral meniscus using an all-inside device (TRUESPAN) and a slotted cannula. In contrast to the inside-out approach, this technique helps reduce surgical invasiveness and provides stable fixation as the vertical mattress sutures bundle the circumferential fibers and act as rip stops for the horizontal sutures. However, the operating surgeon must understand proper insertion techniques to successfully use the devices required for this procedure.

Left ventricular ejection fraction: clinical, pathophysiological, and technical limitations.

Risk stratification of cardiovascular death and treatment strategies in patients with heart failure (HF), the optimal timing for valve replacement, and the selection of patients for implantable cardioverter defibrillators are based on an echocardiographic calculation of left ventricular ejection fraction (LVEF) in most guidelines. As a marker of systolic function, LVEF has important limitations being affected by loading conditions and cavity geometry, as well as image quality, thus impacting inter- and intra-observer measurement variability. LVEF is a product of shortening of the three components of myocardial fibres: longitudinal, circumferential, and oblique. It is therefore a marker of global ejection performance based on cavity volume changes, rather than directly reflecting myocardial contractile function, hence may be normal even when myofibril's systolic function is impaired. Sub-endocardial longitudinal fibers are the most sensitive layers to ischemia, so when dysfunctional, the circumferential fibers may compensate for it and maintain the overall LVEF. Likewise, in patients with HF, LVEF is used to stratify subgroups, an approach that has prognostic implications but without a direct relationship. HF is a dynamic disease that may worsen or improve over time according to the underlying pathology. Such dynamicity impacts LVEF and its use to guide treatment. The same applies to changes in LVEF following interventional procedures. In this review, we analyze the clinical, pathophysiological, and technical limitations of LVEF across a wide range of cardiovascular pathologies.

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.

Biaxial stretch can overcome discrepancy between global and local orientations of wavy collagen fibres

Most frequently used structure-based constitutive models of arterial wall apply assumptions on two symmetric helical (and dispersed) fibre families which, however, are not well supported with histological findings where two collagen fibre families are seldom found. Moreover, bimodal distributions of fibre directions may originate also from their waviness combined with ignoring differences between local and global fibre orientations. In contrast, if the model parameters are identified without histological information on collagen fibre directions, the resulting mean angles of both fibre families are close to ±45°, which contradicts nearly all histologic findings. The presented study exploited automated polarized light microscopy for detection of collagen fibre directions in porcine aorta under different biaxial extensions and approximated the resulting histograms with unimodal and bimodal von Mises distributions. Their comparison showed dominantly circumferential orientation of collagen fibres. Their concentration parameter for unimodal distributions increased with circumferential load, no matter if acting uniaxially or equibiaxially. For bimodal distributions, the angle between both dominant fibre directions (chosen as measure of fibre alignment) decreased similarly for both uniaxial and equibiaxial loads. These results indicate the existence of a single family of wavy circumferential collagen fibres in all layers of the aortic wall. Bimodal distributions of fibre directions presented sometimes in literature may come rather from waviness of circumferentially arranged fibres than from two symmetric families of helical fibres. To obtain a final evidence, the fibre orientation should be analysed together with their waviness.

SEISMIC performance of RC square columns strengthened by bidirectional basalt-fiber-reinforced polymer (BFRP) composite laminates with fan-shaped anchors

For seismic retrofitting of existing reinforced concrete (RC) structures, multiple strengthening demands may be required simultaneously including shear, flexural, and axial strength, as well as ductility. However, satisfying such multiple demands using conventional materials and strengthening systems may be challenging. As compared to commonly used unidirectional fibers reinforced polymers (FRP) composites laminates, bidirectional FRP laminates offer an effective methodology for providing strength and ductility in different directions. In this study, seven reinforced concrete (RC) columns specimens confined by bi-directional basalt-fiber-reinforced polymer (BFRP) composite jackets at plastic hinge regions with and without fan-shaped composite anchors are evaluated. All specimens are subjected to low-frequency full-reversal cyclic lateral loadings up to failure. Several design parameters are assessed to identify its impact on the behavior of confined columns that include: (i) composite laminate types, (ii) number of plies, (iii) strengthening scheme, and (iv) presence of anchorages. Service and ultimate seismic performance of each specimen including failure modes, rupture strain, and ductility are described and investigated. Experimental results indicated that ultimate failure mode changes from a shear failure, in the case of unidirectional composite jacket, to a combined flexure/shear failure mode when bidirectional [0°/90°] composite jackets are utilized. However, results indicated that the circumferential (hoop) fibers of a bidirectional composite jacket have lower ultimate hoop strain as compared to those obtained for columns with unidirectional composite jackets. Results also showed that the use of composite anchors effectively improved working strain of longitudinal fibers [0°], especially for columns with bidirectional composite jackets. In this case, tensile strain increased by 1.5 times as compared to specimens without composite anchors. Furthermore, the presence of anchors improved flexural capacity of confined columns. In addition, an analytical model to predict flexural capacity of RC columns confined with bidirectional laminates with anchors is proposed, which was verified using experimental results. Results of this study indicated that the use of bidirectional FRP composites laminates jackets with fan-shaped anchor enhanced both strength and ductility of RC columns.

Combined Rip-Stop and Transtibial Pull-out Technique for Lateral Meniscus Radial Repairs

Radial tears of the meniscus disrupt circumferential fibers that allow for the dispersion of axial tibiofemoral forces. Both nonoperative treatment and meniscectomy carry increased risk of early-onset degeneration of the joint because of decreased contact surface area and increased point-loading of the chondral surfaces. Radial type tears are also notable for the relatively high failure rate associated with repair. The purpose of this technical note is to demonstrate our surgical technique for a radial lateral meniscus repair construct that allows for good apposition and anatomic reduction of the meniscus with less risk of residual postoperative extrusion through use of a combination inside-out rip-stop and transtibial pull-out suturing repair.

Proximal fibular osteotomy as a treatment for degenerative meniscal extrusion

Meniscal extrusion treatment is a key focus area for research and clinical study of degenerative knee pathology. The contact forces between the meniscus and the bones cause external displacements of the meniscus that are resisted by the circumferential fibres. The main risk factors for the excessive deformation of the meniscus are meniscal root tears, disruption of the circumferential fibres, knee malalignment and high body mass index. Prior research has shown meniscal extrusion to be a crucial determinant of successful procedures in knee osteoarthritis treatment. The characteristics of medial knee osteoarthritis are an increase in varus malalignment and the load transferred through the medial compartment. This is associated with greatest reduction of the joint space width over the medial meniscus body and an increase in contact forces acting on the meniscus, which results in increased extrusion of the medial meniscal body. Relocating the meniscus in its anatomic position restores the correct distribution of contact force across the knee joint, and prevents destruction of the cartilage. Thus, clinical and biomechanical research focus on improving surgical techniques that allow for diminished meniscal extrusion. Proximal fibula osteotomy is a relatively new technique which involves the removal of a 10 mm piece of fibula, 4–10 cm from the fibular head. This technique has been shown to reduce the knee-lever arm, load transferred through the medial compartment and increase the medial joint space width. We hypothesise that proximal fibular osteotomy could be an effective, simple, and minimally invasive treatment for degenerative meniscal extrusion.

Rehabilitation protocol after suturing the medial meniscus of a stable knee, a retrospective series of the Francophone Arthroscopy Society

IntroductionSurgical meniscal lesions are common and 80% of cases involve the medial meniscus of a stable knee. There is a lack of consensus regarding postoperative rehabilitation protocols and a wide variation between restrictive and accelerated rehabilitation protocols exists. The main objective of this study was to report the functional results and the failure rate of the various rehabilitation protocols of the retrospective series of the French Society of Arthroscopy (SFA) after suturing the medial meniscus of a stable knee, considering whether the tear is stable or unstable. HypothesisOur hypothesis was that accelerated rehabilitation was not associated with an increased risk of failure. Materials and methodsThis retrospective, multicenter study was conducted across 10 centers (6 private hospitals and 4 public hospitals) including all patients tested for a medial meniscus suture in a stable knee between January 1, 2005 and November 31, 2017 for a minimum follow-up of 5years. Demographic, imaging, suturing, rehabilitation protocol, and functional TEGNER and KOOS scores were collected. Failure was defined as performing a secondary meniscectomy. ResultsThree hundred and sixty-seven patients were analyzed with an average follow-up of 82months. Immediate weight bearing was allowed in 85% of cases, the wearing of a brace was present in almost 74% of cases and flexion was limited in 97% of cases. Inter-group comparisons found a higher suture failure rate in the group with immediate weight bearing (35.6% vs. 20%, p=0.011) and in the group with a brace (36.9% vs. 22.4%, p<0.001). There was no difference in the 90° flexion group. The TEGNER score was higher in the non-weight bearing group (6.5 vs. 5.4, p=0.028) and the KOOS QOL score was higher in the group without a brace (82.2 vs. 66.8, p=0.025). According to a multivariate analysis, immediate weight bearing (OR=3.6, [1.62; 7.98], p=0.0016) and wearing a brace (OR=2.83, [1.54; 5.02], p<0.001) were associated with a higher failure rate. In the group of stable lesions, the use of a brace (OR=3.73, [1.62; 8.56], p=0.0019) was associated with a higher failure rate. ConclusionNo consensus regarding rehabilitation protocols has been established to date and the results of this retrospective series of the SFA affirm the great variability of practices at a national level. Although accelerated rehabilitation protocols are presently favored, the resumption of immediate full weight bearing should be considered with caution, being associated with a higher risk of failure in this series. Deferring weight bearing for 1 month can be considered in the event of a large tear or in the event of damage to the circumferential fibers. Wearing a brace does not seem to have any influence, while limited flexion achieved a consensus. Level of evidenceIV, retrospective study.

Tensile energy dissipation and mechanical properties of the knee meniscus: relationship with fiber orientation, tissue layer, and water content.

Introduction: The knee meniscus distributes and dampens mechanical loads. It is composed of water (∼70%) and a porous fibrous matrix (∼30%) with a central core that is reinforced by circumferential collagen fibers enclosed by mesh-like superficial tibial and femoral layers. Daily loading activities produce mechanical tensile loads which are transferred through and dissipated by the meniscus. Therefore, the objective of this study was to measure how tensile mechanical properties and extent of energy dissipation vary by tension direction, meniscal layer, and water content. Methods: The central regions of porcine meniscal pairs (n = 8) were cut into tensile samples (4.7mm length, 2.1mm width, and 0.356mm thickness) from core, femoral and tibial components. Core samples were prepared parallel (circumferential) and perpendicular (radial) to the fibers. Tensile testing consisted of frequency sweeps (0.01-1Hz) followed by quasi-static loading to failure. Dynamic testing yielded energy dissipation (ED), complex modulus (E*), and phase shift (δ) while quasi-static tests yielded Young's Modulus (E), ultimate tensile strength (UTS), and strain at UTS (εUTS). To investigate how ED is influenced by the specific mechanical parameters, linear regressions were performed. Correlations between sample water content (φw) and mechanical properties were investigated. A total of 64 samples were evaluated. Results: Dynamic tests showed that increasing loading frequency significantly reduced ED (p < 0.05). Circumferential samples had higher ED, E*, E, and UTS than radial ones (p < 0.001). Stiffness was highly correlated with ED (R2 > 0.75, p < 0.01). No differences were found between superficial and circumferential core layers. ED, E*, E, and UTS trended negatively with φw (p < 0.05). Discussion: Energy dissipation, stiffness, and strength are highly dependent on loading direction. A significant amount of energy dissipation may be associated with time-dependent reorganization of matrix fibers. This is the first study to analyze the tensile dynamic properties and energy dissipation of the meniscus surface layers. Results provide new insights on the mechanics and function of meniscal tissue.

All-Inside Repair of Complex Posterior Horn Meniscus Tears

Background: Due to difficult-to-access location and complex tear patterns, the management of meniscus injuries in isolation and in conjunction with anterior cruciate ligament injury may be challenging. The aim of this video is to present techniques and tips that may help surgeons perform arthroscopic all-inside repair of complex meniscus tears. Indications: Indications for the presented repair techniques are young patients with high activity demands, symptomatic lateral and medial meniscus lesions, ligamentous knee instability, chondral changes grade 2 or less, neutral joint alignment, and body mass index below 35 kg/m2. Technique Description: High anterolateral, low anteromedial, and accessory anterolateral portals are used for the arthroscopic assessment of meniscus tear quality and pattern, and to ensure adequate access to the lesion. Horizontal mattress, vertical mattress, and cerclage sutures are passed using a range of all-inside devices to approximate tear edges with the aim of restoring native hoop stresses along the circumferential meniscus collagen fibers. Tear edges are abraded to enhance healing potential. Two separate cases and complex tear configurations are presented to illustrate these all-inside meniscus repair techniques. Results: Meniscus repair yields superior long-term outcomes compared with partial meniscectomy. Improvements in subjective knee function and lower rates of progression to long-term knee osteoarthritis are reported in patients treated with meniscus repair versus resection. Advantages of all-inside meniscus repair include the reduced risk of iatrogenic neurovascular lesions, decreased operative time, restoration of native contact surfaces, and repair without fixation of the menisci to the surrounding soft tissue. Discussion/Conclusion: Arthroscopic all-inside meniscus repair enables the safe and efficient management of complex meniscus tears in active patients with symptomatic meniscus pathology, and can be performed concurrent with knee ligament surgery. Consequently, all-inside meniscus repair techniques are a versatile addition to the toolkit of complex knee surgeons. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

An Implantable Magnetic Vascular Scaffold for Circulating Tumor Cell Removal In Vivo.

An integrated trapped device (ITD) capable of removal of circulating tumor cells (CTCs) can assuage or even prevent metastasis. However, adhesion repertoires are ordinarily neglected in the design of ITDs, possibly leading to the omission of highly metastatic CTC and treatment failure. Here a vascular-like ITD with adhesive sites and wireless magnetothermal response to remove highly metastatic CTC in vivo is presented. Such a vascular-like ITD comprises circumferential well-aligned fibers and artificial adhesion repertoires and is optimized for magnetothermal integration. Continuous and repeated capture in a dynamic environment increases capture efficiency over time. Meanwhile, the heat generation of the ITD leads to the capture of CTC death owing to cell heat sensitivity. Furthermore, the constructed bioinspired ultrastructure of the ITD prevents vascular blockage and induces potential vascular regeneration. Overall, this work defines an extendable strategy for constructing adhesion repertoires against intravascular shear forces, provides a vascular-like ITD for reducing CTC counts, and is expected to alleviate the risk of cancer recurrence.

All-Inside Meniscal Repair: A Historical View

Background: All-inside meniscal repair first became popularized in the early 2000s. Since that time, there has been a wide variety of all-inside implants on the market with rapid changes and developments in recent years. Indications: Small, peripheral, longitudinal tears are best suited for all-inside repair, but this technique may even be used for large bucket handle tears especially when hybridized with an inside-out repair. Technique Description: A percutaneous release of the medial collateral ligament (MCL) with an 18-g spinal needle is frequently performed when working in the medial compartment to improve visualization and decrease risk of iatrogenic chondral injury. Close familiarity with the characteristics of the chosen all-inside device including device angle, modifiability of device angle, modifiability of needle depth, deployment method, and tensioning technique is important for obtaining reproducible results. Typically, obtaining a vertical mattress stitch configuration is optimal as it captures more circumferential collagen fibers in the repair. Results: Factors to consider when selecting an all-inside meniscal repair device include the ergonomics of the device, implant cost, availability, rigid versus suture-based anchor, core needle diameter, device flexibility, and percent of misfires. Discussion: Complications from use of all-inside meniscus repair devices include device failure, soft tissue entrapment, cyst formation, and injury to the popliteal artery. Outcomes, however, with current devices are good and comparable to inside-out meniscus repair with about a 90% return to sports rate at 12 months postoperatively. The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

IMAGING THE VITREOUS WITH A NOVEL BOOSTED OPTICAL COHERENCE TOMOGRAPHY TECHNIQUE

To evaluate the degenerative findings including cistern formation in the premacular vitreous using optical coherence tomography. A novel enhanced vitreous imaging method by which four A-scans at each position were averaged before the Fourier transform increased the image quality per frame so that subsequent image registration for averaging could occur. Analysis of B-scans and volume-rendered images of eyes in subjects of various ages was performed. There were 43 eyes of 23 subjects ranging in age from 23 to 68 years. The texture in the vitreous images suggests specific orientations of the vitreous fibers in the macular region; there were fibers circumferential to the retina immediately anterior to the premacular bursa. The pattern of the vitreous fibers seemed less well-defined internal to the zone of circumferential fibers. In younger eyes, there were striations oriented in a roughly inferior to superior direction in this zone. In older eyes, there were striations in the same orientation but actually were alternating zones of vitreous synchysis and syneresis. In these same eyes, numerous cisterns appeared at various levels in the vitreous gel. With extensive vitreous condensation and synchysis, definition of the premacular bursa was lost. With this novel method of enhanced vitreous imaging, the vitreous seemed to have stereotypic patterns of degeneration. The formation of vitreous syneresis and synchysis may be related to organization architecture of the vitreous, including the pattern of vitreous collagen deposition, and the effects of eye motion through decades of time.

Tractography of Porcine Meniscus Microstructure Using High-Resolution Diffusion Magnetic Resonance Imaging.

To noninvasively evaluate the three-dimensional collagen fiber architecture of porcine meniscus using diffusion MRI, meniscal specimens were scanned using a 3D diffusion-weighted spin-echo pulse sequence at 7.0 T. The collagen fiber alignment was revealed in each voxel and the complex 3D collagen network was visualized for the entire meniscus using tractography. The proposed automatic segmentation methods divided the whole meniscus to different zones (Red-Red, Red-White, and White-White) and different parts (anterior, body, and posterior). The diffusion tensor imaging (DTI) metrics were quantified based on the segmentation results. The heatmap was generated to investigate the connections among different regions of meniscus. Strong zonal-dependent diffusion properties were demonstrated by DTI metrics. The fractional anisotropy (FA) value increased from 0.13 (White-White zone) to 0.26 (Red-Red zone) and the radial diffusivity (RD) value changed from 1.0 × 10-3 mm2/s (White-White zone) to 0.7 × 10-3 mm2/s (Red-Red zone). Coexistence of both radial and circumferential collagen fibers in the meniscus was evident by diffusion tractography. Weak connections were found between White-White zone and Red-Red zone in each part of the meniscus. The anterior part and posterior part were less connected, while the body part showed high connections to both anterior part and posterior part. The tractography based on diffusion MRI may provide a complementary method to study the integrity of meniscus and nondestructively visualize the 3D collagen fiber architecture.

Circumferential Rim Augmentation Suture Around the Perimeniscal Capsule Decreases Meniscal Extrusion and Progression of Osteoarthritis in Rabbit Meniscus Root Tear Model

Background: We recently analyzed the joint capsule adjacent to the medial meniscus and found that the perimeniscal joint capsule has collagen fiber orientation similar to that of circumferential meniscal fibers, potentially playing a role in preventing extrusion. Purpose: To analyze the meniscal extrusion prevention potential of the circumferential rim augmentation suture around the perimeniscal capsule in a rabbit root tear model and analyze the biomechanical function in a porcine cadaveric knee. Study Design: Controlled laboratory study. Methods: Rabbit medial meniscus root tear models were divided into 3 experimental groups: root tear, root tear and suture repair, and root tear and circumferential rim augmentation suture. As for the circumferential rim augmentation suture procedure, a suture was placed to circumscribe the outer rim of the medial meniscus and passed through bone tunnels located at the tibial insertion of each root. After 4 and 8 weeks, meniscal extrusion was analyzed by micro–computed tomography, gross morphology, and histologic analysis of the medial femoral cartilage. For biomechanical analysis, porcine knees were divided into groups similar to rabbit experiments. Tibiofemoral contact parameters were assessed using a pressure mapping sensor system after applying a load of 200 N on the knee joint. Results: The root tear and circumferential rim augmentation suture group showed less meniscal extrusion, less gap within the tear site, and less cartilage degeneration compared with other groups after 4 and 8 weeks of surgery in the rabbit root tear model. Biomechanical analysis showed the root tear and circumferential rim augmentation suture group had larger contact area and lower peak contact pressure compared with root tear and root tear and suture repair groups. Conclusion: The circumferential rim augmentation suture reduced the degree of meniscal extrusion while restoring meniscal function, potentially preventing progression of arthritis in a rabbit root tear model and porcine knee biomechanical analysis. Clinical Relevance: The circumferential rim augmentation suture may be a novel augmentation option during root tear treatment.

Tensile fatigue strength and endurance limit of human meniscus

The knee menisci are prone to mechanical fatigue injury from the cyclic tensile stresses that are generated during daily joint loading. Here we characterize the tensile fatigue behavior of human medial meniscus and investigate the effect of aging on fatigue strength. Test specimens were excised from the medial meniscus of young (under 40 years) and older (over 65 years) fresh-frozen cadaver knees. Cyclic uniaxial tensile loads were applied parallel to the primary circumferential fibers at 70%, 50%, 40%, or 30% of the predicted ultimate tensile strength (UTS) until failure occurred or one million cycles was reached. Equations for fatigue strength (S-N curve) and the probability of fatigue failure (unreliability curves) were created from the measured number of cycles to failure. The mean number of cycles to failure at 70%, 50%, 40%, and 30% of UTS were estimated to be approximately 500, 40000, 340000, and 3 million cycles, respectively. The endurance limit, defined as the tensile stress that can be safely applied for the average lifetime of use (250 million cycles), was estimated to be 10% of UTS (∼1.0 MPa). When cyclic tensile stresses exceeded 30% of UTS (∼3.0 MPa), the probability of fatigue failure rapidly increased. While older menisci were generally weaker and more susceptible to fatigue failures at high-magnitude tensile stresses, both young and older age groups had similar fatigue resistance at low-magnitude tensile stresses. In addition, we found that fatigue failures occurred after the dynamic modulus decreased during cyclic loading by approximately 20%. This experimental study has quantified fundamental fatigue properties that are essential to properly predict and prevent injury in meniscus and other soft fibrous tissues.

Potential of Melt Electrowritten Scaffolds Seeded with Meniscus Cells and Mesenchymal Stromal Cells.

Meniscus injury and meniscectomy are strongly related to osteoarthritis, thus there is a clinical need for meniscus replacement. The purpose of this study is to create a meniscus scaffold with micro-scale circumferential and radial fibres suitable for a one-stage cell-based treatment. Poly-caprolactone-based scaffolds with three different architectures were made using melt electrowriting (MEW) technology and their in vitro performance was compared with scaffolds made using fused-deposition modelling (FDM) and with the clinically used Collagen Meniscus Implants® (CMI®). The scaffolds were seeded with meniscus and mesenchymal stromal cells (MSCs) in fibrin gel and cultured for 28 d. A basal level of proteoglycan production was demonstrated in MEW scaffolds, the CMI®, and fibrin gel control, yet within the FDM scaffolds less proteoglycan production was observed. Compressive properties were assessed under uniaxial confined compression after 1 and 28 d of culture. The MEW scaffolds showed a higher Young’s modulus when compared to the CMI® scaffolds and a higher yield point compared to FDM scaffolds. This study demonstrates the feasibility of creating a wedge-shaped meniscus scaffold with MEW using medical-grade materials and seeding the scaffold with a clinically-feasible cell number and -type for potential translation as a one-stage treatment.

Midterm Outcomes Following Hip Labral Augmentation

Objectives:Arthroscopic hip labral preservation techniques have evolved over the last decade. Arthroscopic hip labral augmentation with iliotibial band (ITB) autograft placed into a labral defect with viable circumferential fibers is a novel treatment option to restore the hip suction seal and improve functionality. The purpose of this study is to determine midterm (3-5 year follow up) outcomes of arthroscopic hip labral augmentation procedure.Methods:Patients who underwent arthroscopic hip labral augmentation from August 2011 to March 2017 were prospectively evaluated. Pre- and post-operative patient reported outcome scores were compared and included SF12 PCS, SF12 MCS, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Modified Harris Hip Score (mHHS), Hip Outcome Score (HOS) (Activities of Daily Living (ADL) and Sport). Post-operative Tegner Activity Scale and patient satisfaction (1 – 10) were also evaluated.Results:One hundred and six patients underwent arthroscopic hip labral augmentation with minimum 3-year follow-up. Mean follow-up was 5-year follow-up (range, 3 to 9.2 years). All patient reported outcomes improved after labral augmentation (SF12 PCS 39±8 vs. 50±10, p>0.01; mHHS 59±15 vs. 79±21, p<0.01; WOMAC 31±16 vs. 16±17, p<0.01; HOS ADL 64±17 vs. 84±21, p<0.01; HOS Sport 41±22 vs. 71±29, p<0.01). Median post-operative Tegner score was 4. Median post-operative patient satisfaction was 9 out of 10 (range, 1-10). In terms of survivorship, 12 patients (11%) required revision surgery and 6 (5.7%) converted to total hip arthroplasty (THA).Conclusions:Arthroscopic hip labral augmentation is a successful treatment option for patients that have viable circumferential fibers present at the time of arthroscopy. This technique continues to show improved patient reported outcomes and is another hip labral preservation technique that may help reestablish the intra-articular fluid suction seal.