Meniscus tears in adult patients do not heal spontaneously and represent a risk factor for OA development. PDGF is well known as an enhancer of meniscal cell biosynthetic activity and also has chemotactic activity for mesenchymal cells. PDGF incorporation into scaffolds should be efficient for recruitment of cells to initiate repair in the injured meniscus. We recently developed decellularized meniscus sheet for use in the treatment of meniscus tears. The aim of this study is to examine the potential of PDGF-coated decellularized meniscus scaffold in mediating integrative healing by endogenous cell migration. Fresh bovine meniscus was chemically decellularized. Round sheets were made from the decellularized tissue. Heparin was covalently conjugated with decellularized meniscus scaffold (DMS). PDGF-BB was immobilized by binding to the heparin-conjugated DMS. In vitro, PDGF release kinetics was analyzed by ELISA. DMS was transplanted into the injured meniscus explants and cultured for 2 and 4 weeks. The numbers of migrated cells at the border between DMS and injured explant were counted on DAPI stained sections and PDGFRb expressing cells were counted after immunohistochemical staining. The newly produced ECM and collagen fiber alignment was detected by histology on Safranin-O and picrosirius red stained sections. The explants were also tested for tensile properties. PDGF release kinetics showed sustained slow release in heparin-conjugated DMS, with 11.2% release at day- 16th compared to 26.1% release from the DMS without heparin. Insertion of the PDGF-treated DMS into the meniscus tears in bovine meniscus explants led to the migration of endogenous meniscus cells to the defect zone. The migrated cells expressed PDGFRb and produced new ECM in the defect area. Safranin-O and pircrosirius red staining showed tissue integration between DMS and injured explants. Moreover, the higher concentration of PDGF promoted cell integration into the DMS. Tensile properties of injured explants treated with PDGF coated DMS were significantly higher than in DMS without PDGF. Heparin-conjugated DMS showed strong immobilization of PDGF, which was released slowly. PDGF coated DMS promoted migration of endogenous meniscus cells to the defect area and into the scaffold. New matrix was formed that bridged the space between the native meniscus and the scaffold and this was associated with improved biomechanical properties. The PDGF coated DMS is a novel, feasible and efficient approach for the treatment of meniscus tears

Discoid meniscus (DM) is a congenital variant of the knee joint that involves morphological and structural deformation, with potential meniscal instability. The prevalence of the Discoid Lateral Meniscus (DLM) is higher among the Asians than among other races, and both knees are often involved. Meniscal pathology is widely prevalent in the adult population, secondary to acute trauma and chronic degeneration. The true prevalence in children remains unknown, as pathologies such as discoid menisci often go undiagnosed, or are only found incidentally. A torn or unstable discoid meniscus can present with symptoms of knee pain, a snapping or clicking sensation and/or a decrease in functional activity, although it is not known if a specific presentation is indicative of a torn DM. While simple radiographs may provide indirect signs of DLM, magnetic resonance imaging (MRI) and arthroscopy is essential for diagnosis and treatment planning. Asymptomatic patients require close follow-up without surgical treatment, while patients with symptoms often require surgery. Partial meniscectomy is currently considered the treatment of choice for DLM. For children are more likely to achieve better results after partial meniscectomy

Aims. We studied the outcomes following arthroscopic primary repair of bucket handle meniscus tears to determine the incidence of re-tears and the functional outcomes of these patients. Methodology. Prospective cohort study. Over a 4-year period (2016 to 2020), 35 adult patients presented with a bucket handle tear of the meniscus. Arthroscopic meniscal repair was performed using either the all inside technique or a combination of all-inside and inside-out techniques. 15 patients also underwent simultaneous arthroscopic anterior cruciate ligament reconstruction. Functional knee scores were assessed using IKDC and Lysholm scores. Results. Mean patient age at surgery was 27 years (range, 17 to 53years). Medial meniscus was torn in 20 and lateral in 15 cases. Zone of tear was white on white in 19, red on white in 9 and red on red in 7 cases. Average delay from injury to surgery was 4 months. At a mean follow-up of 4.5 years, the meniscus repair failed in 3 patients (8.5 %). Outcome following re-tear was meniscus excision. Average IKDC scores in patients with intact repair were 74.04 against 56.67 in patients with a failed repair (p< 0.0001). Similarly, Lyshlom scores were 88.96 and 67.333, respectively (p<0.0001). Conclusion. The survivorship of primary repair of bucket handle meniscus tears in our series was 91.5% at medium term follow-up. Functional outcomes were significantly poor in patients with a failed repair compared to those with an intact repair

Meniscal root tears can result from traumatic injury to the knee or gradual degeneration. When the root is injured, the meniscus becomes de-functioned, resulting in abnormal distribution of hoop stresses, extrusion of the meniscus, and altered knee kinematics. If left untreated, this can cause articular cartilage damage and rapid progression of osteoarthritis. Multiple repair strategies have been described; however, no best fixation practice has been established. To our knowledge, no study has compared suture button, interference screw, and HEALICOIL KNOTLESS fixation techniques for meniscal root repairs. The goal of this study is to understand the biomechanical properties of these fixation techniques and distinguish any advantages of certain techniques over others. Knowledge of fixation robustness will aid in surgical decision making, potentially reducing failure rates, and improving clinical outcomes. 19 fresh porcine tibias with intact medial menisci were randomly assigned to four groups: 1) native posterior medial meniscus root (PMMR) (n = 7), 2) suture button (n = 4), 3) interference screw (n = 4), or 4) HEALICOIL KNOTLESS (n = 4). In 12 specimens, the PMMR was severed and then refixed by the specified group technique. The remaining seven specimens were left intact. All specimens underwent cyclic loading followed by load-to-failure testing. Elongation rate; displacement after 100, 500, and 1000 cycles; stiffness; and maximum load were recorded. Repaired specimens had greater elongation rates and displacements after 100, 500, and 1000 cycles than native PMMR specimens (p 0.05). The native PMMR showed greater maximum load than all repair techniques (p 0.05). In interference screw and HEALICOIL KNOTLESS specimens, failure occurred as the suture was displaced from the fixation and tension was gradually lost. In suture button specimens, the suture was either displaced or completely separated from the button. In some cases, tear formation and partial failure also occurred at the meniscus luggage tag knot. Native PMMR specimens failed through meniscus or meniscus root tearing. All fixation techniques showed similar biomechanical properties and performed inferiorly to the native PMMR. Evidence against significant differences between fixation techniques suggests that the HEALICOIL KNOTLESS technique may present an additional option for fixation in meniscal root repairs. While preliminary in vitro evidence suggests similarities between fixation techniques, further research is required to determine if clinical outcomes differ

Introduction. Post-meniscectomy syndrome is broadly characterised by intractable pain following the partial or total removal of a meniscus. There is a large treatment gap between the first knee pain after meniscectomy and the eligibility for a TKA. Hence, there is a strong unmet need for a solution that will relieve this post-meniscectomy pain. Goal of this first-in-man study was to evaluate the safety and performance of an anatomically shaped artificial medial meniscus prosthesis and the accompanying surgical technique. Methods. A first-in-man, prospective, multi-centre, single arm clinical investigation was intended to be performed on 18 post-medial meniscectomy syndrome patients with limited underlying cartilage damage (Kellgren Lawrence scale 0–3) in the medial compartment and having a normal lateral compartment. Eventually 5 patients received a polycarbonate urethane mediale meniscus prosthesis (Trammpolin® medial meniscus prosthesis; ATRO Medical B.V., the Netherlands) which was clicked onto two titanium screws fixated at the native horn attachments on the tibia. PROMs were collected at baseline and at 6 weeks, 3, 6, 12 and 24 months following the intervention including X-rays at 6, 12 and 24 Months. MRI scans were repeated after 12 and 24 months. Results. The surgical technique to select the appropriately sized implant and correct positioning of the fixation screws and meniscus prosthesis onto the tibia was demonstrated feasible and reproducible. The surgeries showed that in particular the positioning of the posterior screw is crucial for correct positioning of the prosthesis. Inclusion stopped after 5 patients, who reached the 6 months evaluation. The PROMs did not improve in the first 6 months after surgery. All patients reported knee joint stiffness and slight effusion in their knee at 6 months follow-up. In case of symptomatic patients an evaluation of the device position and integrity was performed by MRI. In three patients the implants were removed because of implant failure and in one patient the implant was removed because of persistent pain and extension deficit. At present one patient has the implant still in situ. The explantations of the implants demonstrated no articular cartilage damage and the fixation screws were securely anchored. Discussion. This is the first clinical study with an artificial meniscus-like prosthesis. Except one, all implants were removed due to implant breakage or discomfort of the patient. Analysis of the torn implants showed fatigue failure resulting from the lack of loadsharing between implant and cartilage: the implant was too stiff and carried all the load in the medial compartment of the knee. Furthermore, the fixation with screws seemed too rigid which restricted the motion of the posterior horn. Based on previous in vitro and animal experiments, we expected more creep of the material and more motion on the screw fixation. Conclusion. This first-in-man clinical study demonstrates that the investigated device design is not safe and did not perform as expected. Therefore, modification of the meniscus prosthesis design and fixation technique is required to allow for more motion of the meniscus prosthesis during knee joint movement

The meniscus is comprised largely of type I collagen, as well as fibrochondrocytes and proteoglycans. In articular cartilage and intervertebral disc, proteoglycans make a significant contribution to mechanical stiffness of the tissue via negatively charged moieties which generate Donnan osmotic pressures. To date, such a role for proteoglycans in meniscal tissue has not been established. This study aimed to investigate whether meniscal proteoglycans contribute to mechanical stiffness of the tissue via electrostatic effects. Following local University Ethics Committee approval, discs of meniscal tissue two millimetres thick and of five millimetres diameter were obtained from 12 paired fresh frozen human menisci, from donors < 6 5 years of age, with no history of osteoarthritis or meniscal injury. Samples were taken from anterior, middle and posterior meniscal regions. Each disc was placed within a custom confined compression chamber, permeable at the top and bottom only and then bathed in one of three solutions − 0.14M PBS (mimics cellular environment), deionised water (negates effect of mobile ions) or 3M PBS (negates all ionic effects). The apparatus was mounted within a Bose Electroforce 3100 materials testing machine and a 0.3N preload was applied. The sample was allowed to reach equilibrium, before being subjected to a 10% ramp compressive strain followed by a 7200 second hold phase. Equal numbers of samples from each meniscus and meniscal region were tested in each solution. Resultant stress relaxation curves were fitted to a nonlinear poroviscoelastic model with strain dependent permeability using FEBio finite element modelling software. Goodness of fit (R2) was assessed using a coefficient of determination. All samples were assayed for proteoglycan content. Comparison of resultant mechanical parameters was undertaken using multivariate ANOVA with Bonferroni adjustment for multiple comparisons. 36 samples were tested. A significant difference (p < 0 .05) was observed in the value of the Young's modulus (E) between samples tested in deionised water compared to 0.14M/3M PBS, with the meniscus found to be stiffest in deionised water (E = 1.15 MPa) and least stiff in 3M PBS (E = 0.43 MPa), with the value of E in 0.14M PBS falling in between (0.68 MPa). No differences were observed in the zero strain permeability or the exponential strain dependent/stiffening coefficients. The viscoelastic coefficient and relaxation time values were not found to improve model fit and were thus held at zero. The mean R2 value was 0.78, indicating a good fit and did not differ significantly between solutions. Proteoglycan content was not found to differ with solution, but was found to be significantly increased in the middle region of both menisci. Proteoglycans make a significant electrostatic contribution to mechanical stiffness of the meniscus, increasing it by 58% in the physiological condition, and are hence integral to its function. It is important to include the influence of ionic effects when modelling meniscus, particularly where fluid flow or localised strain is modelled. From a clinical perspective, it is critical that meniscal regeneration strategies such as scaffolds or allografts attempt to preserve, or compensate for, the function of proteoglycans to ensure normal meniscal function

Introduction. The major function of the medial meniscus has been shown to be distribution of the load with reduction of cartilage stresses, while its role in AP stability has been found to be secondary. However several recent studies have shown that cartilage loss in OA occurs in the central region of the tibia while the meniscus is displaced medially. In a lab study (Arno, Hadley 2013) it was confirmed that the AP laxity was greatly reduced with a compressive force across the knee, while the femur shifted posteriorly and the AP laxity was increased after a partial meniscetomy of the posterior horn. It is therefore possible that under load, the compression of the meniscus and the cartilage, 2–3mm in total, allows load transmission on the central tibial plateau, and causes radial expansion and tension of the meniscus providing restraint to femoral displacements. This leads to our hypotheses that the highest loading on the medial meniscus would be at the extremes of motion, rather than in the mid-range, and that the meniscus would provide the majority of the restraint to anterior-posterior femoral displacements throughout flexion when compressive loads were acting. Methods & Materials. MRI scans were taken of ten knee specimens to verify the absence of pathology and produce computer models. The knees were loaded in combinations of compressive and shear loading over a full flexion range. Tekscan sensors were used to measure the pressure distribution across the joint as the knee was flexed continuously. A digital camera was used to track the motion, from which femoral-tibial contacts were determined by computer modelling. Load transmission was determined from the Tekscan for the anterior horn, central body, posterior horn, and the uncovered cartilage in the center of the meniscus. An analysis was carried out (Fig 2) to determine the net anterior or posterior shear force carried by the meniscus. Results. For the three types of loading (Fig 1); compression only, compression and anterior shear, compression and posterior shear; between 40–80% of the total load was transmitted through the meniscus, the overall average being 58%. The remaining 42% was transmitted directly through the uncovered cartilage. The anterior horn was loaded only up to 30 degrees flexion, and played a role in controlling anterior femoral displacement. The central body was loaded 10–20% and would provide some restraint to medial femoral subluxation. Overall the posterior horn carried the highest percentage of the shear load (Figure 3), especially after 30 degrees flexion when a posterior shear force was applied, for which the meniscus was estimated to carry 50% of the shear force. Discussion. The hypotheses were largely supported. There was high anterior horn loading in early flexion, but in the remaining range, the posterior horn was the highest loaded especially under posterior shear. Supporting the posterior shear force under load bearing conditions is evidently an important role of the meniscus. Hence in any attempts at repair or replacement, these dual functions of load-sharing and stability need to be incorporated

Purpose. The biomechanical role of the meniscus in the knee joint is a function of its extracellular matrix which consists of type I collagen throughout, type II collagen in the inner meniscus region and glycosaminoglynated (GAG) proteins of which aggrecan is the most prevaleet. Meniscus reparative capacity is limited, particularly when a defect is located in the inner avascular portion, and menisectomy predisposes the joint to osteoarthritis. Using meniscus cells in tissue engineering strategies has been advocated to generate functional meniscus substitutes. However, meniscus cells, like chondrocytes of cartilage, lose their matrix-forming phenotype during culture expansion. Co-culture of chondrocytes with stem cells has been shown to result in enhanced matrix formation. We hypothesized that meniscus cells in co-culture with stem cells will result in increased matrix formation. Method. Tissue specimens were obtained after approval of the local ethical committee and informed consent. Menisci were obtained from 3 patients undergoing total knee arthroplasty; (53–84; mean age 66.6). Meniscus cells were isolated after digestion of menisci with collagenase II. Isolated meniscus cells were plated for 24–48 hr before use. Bone marrow aspirates were obtained from the iliac crest of 3 donors: 1 female (46) and 2 males (15 and 21) undergoing routine orthopaedic procedures. Plastic adherent bone marrow stromal cell populations were isolated and expanded under normal oxygen tension of 21%O2 in a-MEM growth media plus FGF-2 until passage 2. Cells were mixed at a variety of meniscus cells (Men): BMSC ratio including 5/95, 10/90 and 25/75, respectively. Mixed cells were centrifuged to form spherical pellets followed by culture in a defined serum free chondrogenic differentiation medium. Control groups were pure Men and pure BMSCs. Total cell number per pellet was 25×104. Pellets were cultured for 3 weeks under normal oxygen tension. Thereafter, pellets were processed: biochemically for GAG and DNA content, and histologically for Safranin-O staining of sulphated GAG and immunohistochemical analyses for collagen types I and II. Analysis was performed on a minimum of 2 independent pellets. Results. Relative to pure cell control pellets, co-cultured cell pellets of expanded human BMSCs and meniscus cells had more GAG matrix per DNA content. The amplitude of GAG enhancement in all co-cultures varied with donor and with the Men:BMSC ratio. However, the mean GAG enhancement was 1.8–6 fold. The GAG contents of pellets correlated with Safranin-O staining. Positive staining for collagens types I and II was increased in co-cultured cell pellets. Conclusion. Co-seeding of meniscus cells and stem cells on a suitable scaffold may aid the generation of functional grafts with improved biomechanical properties relative to those generated via expanded meniscus cells alone or stem cells alone

Purpose. The purpose of the present study was to compare functional outcomes of medial unicompartmental knee arthroplasty (UKA) in patients with lateral meniscal lesion (LM (+) group) in the preoperative MRI and those without lateral meniscal pathology (LM (−) group) and to evaluate the effect of lateral meniscus lesion in preoperative MR on functional outcomes after UKA. Methods. The outcomes of 66 knees (LM (+) group) were compared to the outcomes of 54knees(LM (−) group)with a median follow-up of 28 month(range 24–36 months). Clinical outcomes including KS object score, KS pain score, lateral side pain, physical exam for lateral meniscal lesion and squatting ability. Radiological parameters (mechanical axis and component position) were compared and their effects on functional outcomes were evaluated at the final follow-up visits. Result. At final follow-up visits, no significant intergroup difference was found about KS object score, presence of lateral side pain, positive physical examination for meniscal lesion and squatting ability. LM(+) group had a tendency of more varus postoperative mechanical axis and showed better KS pain score and more comfortable feeling during squatting activity. Furthermore, no correlation was found between postoperative mechanical axis and functional outcome variables. Conclusions. The result of UKA for medial unicompartmental knee osteoarthritis was excellent regardless of preoperative lateral meniscal pathology in the MRI, if patient had not symptoms related to lateral meniscus lesion. Mild varus alignment for those who had a lateral meniscal lesion provided satisfactory clinical outcome of medial UKA

Purpose. It is well known that meniscus extrusion is associated with structural progression of knee OA. However, it is unknown whether medial meniscus extrusion promotes cartilage loss in specific femorotibial subregions, or whether it is associated with a increase in cartilage thickness loss throughout the entire femorotibial compartment. We applied quantitative MRI-based measurements of subregional cartilage thickness (change) and meniscus position, to address the above question in knees with and without radiographic joint space narrowing (JSN). Methods. 60 participants with unilateral medial OARSI JSN grade 1–3, and contralateral knee OARSI JSN grade 0 were drawn from the Osteoarthritis Initiative. Manual segmentation of the medial tibial and weight-bearing medial femoral cartilage was performed, using baseline and 1-year follow-up sagittal double echo steady-state (DESS) MRI, and proprietary software (Chondrometrics GmbH, Ainring, Germany). Segmentation of the entire medial meniscus was performed with the same software, using baseline coronal DESS images. Longitudinal cartilage loss was computed for 5 tibial (central, external, internal, anterior, posterior) and 3 femoral (central, external, internal) subregions. Meniscus position was determined as the % area of the entire meniscus extruding the tibial plateau medially and the distance between the external meniscus border and the tibial cartilage in an image located 4mm posterior to the central image (a location commonly used for semi-quantitative meniscus scoring). The relationship between meniscus position and cartilage loss was assessed using Pearson (r) correlation coefficients, for knees with JSN and without JSN. Results. The percentage of knees showing a quantitative value of >3mm medial meniscus extrusion was 50% in JSN knees, and only 12% in noJSN knees. The 1-year cartilage loss in the medial femorotibial compartment was 74±182µm (2.0%) in JSN knees, and 26±120µm (0.8%) in noJSN knees. There was a significant correlation between cartilage loss throughout the entire femorotibial compartment (MFTC) and extrusion area in JSN knees but not for noJSN knees. Also, the extrusion distance measured 4mm posterior to the central slice was not significantly correlated with MFTC cartilage loss. The strongest (negative) correlation between meniscus position and subregional femorotibial cartilage loss (r=−0.36) was observed for the external medial tibia. In contrast, no significant relationship was seen in the central tibia. No significant relationship was found in other tibial subregions, except for the anterior medial tibia, but only in JSN knees (r=−0.27). Correlation coefficients for the femoral subregions were generally smaller than those for tibial subregions, with only the internal medial weight-bearing femur attaining statistical significance (r =−0.26). Conclusions. The current results show that the relationship between meniscus extrusion and cartilage loss differs substantially between femorotibial subregions. The correlation was strongest for the external medial tibia, a region that is physiologically covered by the medial meniscus. It was less for other tibial and femoral subregions, including the central medial tibia, a region that exhibited similar rates of cartilage loss as the external subregion. The findings suggest that external tibia may be particularly vulnerable to cartilage tissue loss once the meniscus extrudes and the surface is “exposed” to direct, non-physiological, cartilage-cartilage contact

Injury to the anterolateral ligament (ALL) has been reported to contribute to high-grade anterolateral laxity following anterior cruciate ligament (ACL) injury. Failure to address ALL injury has been suggested as a cause of persistent rotational laxity following ACL reconstruction. However, lateral meniscus posterior root (LMPR) tears have also has been shown to cause increased internal rotation and anterior translation of the knee. Due to the anatomic relationship of the ALL and the lateral meniscus, we hypothesise that the ALL and lateral meniscus work synergistically, and that a tear to the LMPR will have the same effect on anterolateral laxity as an ALL tear in the ACL deficient knee. Sixteen fresh frozen cadaveric knee specimens were potted into a hip simulator(femur) and a six degree-of-freedom load cell (tibia). Two rigid optical trackers were inserted into the proximal femur and distal tibia, allowing for the motion of the tibia with respect to the femur to be tracked during biomechanical tests. A series of points on the femur and tibia were digitised to create bone coordinate systems that were used to calculate the kinematic variables. Biomechanical testing involved applying a 5Nm internal rotation moment to the tibia while the knee was in full extension and tested sequentially in the following three conditions: i) ACLintact; ii) Partial ACL injury (ACLam) – anteromedial bundle sectioned; iii) Full ACL injury (ACLfull). The specimens were then randomised to either have the ALL sectioned first (ALLsec) followed by the LMPRsec or vice versa. Internal rotation and anterior translation of the tibia with respect to the femur were calculated. A mixed two-way (serial sectioning by ALL section order) repeated measures ANOVA (alpha = 0.05). Compared to the ACLintact condition, internal rotation was found to be 1.78° (p=0.06), 3.74° (p=0.001), and 3.84° (p=0.001) greater following ACLfull, LMPRsec and ALLsec respectively. LMPRsec and the ALLsec resulted in approximately 20 of additional internal rotation (p=0.004 and p=0.01, respectively) compared with the ACL deficient knee (ACLfull). No difference was observed between the ALL and LMPR sectioned states, or whether the ALL was sectioned before or after the LMPR (p=0.160). A trend of increasing anterior translation was observed when the 5Nm internal rotation moment was applied up until the ACL was fully sectioned; however, these differences were not significant (p=0.070). The ALL and LMPR seem to have a synergistic relationship in aiding the ACL in controlling anterolateral rotational laxity. High-grade anterolateral laxity following ACL injury may be attributed to injuries of the ALL and/or the LMPR. We suggest that the lateral meniscus should be thought of as part of the anterolateral capsulomeniscal complex (i.e., LM, ITB, and ALL) that acts as a stabiliser of anterolateral rotation in conjunction with the ACL

The purpose of this study was to evaluate short-term clinical and MRI outcome of a polycarbonate-urethane meniscus implant for the treatment of medial compartment pain in middle aged patients. In the younger population, (<40 yrs.) surgical options e.g., allograft transplants and artificial scaffolds are available and have been shown to be effective. For middle aged patients, the clinical benefit from surgical intervention of a degenerated meniscus has only been reported in a fraction of the patients. However, these patients are still too young for more aggressive treatments such as unicompartmental or total knee arthroplasty. The meniscus implant is a non-degradable polymer-based spacer which is inserted into the medial compartment of the knee between the tibia and femur by a mini-arthrotomy, without requiring attachment or bone resection. It was hypothesized that the implant could relieve pain by restoring the pressure distribution function. This paper presents the first experience of 3 Israeli sites (out of 7 sites participating in the study). Thirty patients aged 36 to 70 years were treated with the implant after signing an informed consent and meeting the criteria defined in the Ethics Committee approved protocol. All of the patients reported medial knee pain which was associated with either a severely degenerated meniscus (∼25%) or post-meniscectomy knee pain (∼75%). Patients with evidence of grade IV medial articular cartilage loss or instability were excluded from the study. Primary clinical outcome was measured by the KOOS scale over 12 months, with secondary outcomes measured by IKDC subjective, EQ-5D and VAS questionnaires for pain. Serial MRI scans were taken at 6 weeks and 12 months of follow-up to evaluate the condition of the articular cartilage. The patients included in this study showed a considerable clinical improvement after the procedure. Significant pain relief was indicated by both KOOS pain subscale and VAS scores after 6 months follow up, and patient activity levels were also found to be higher following implantation. The first MRI findings from this study were considered to be promising since no signs of deterioration of the surrounding cartilage or of the device were observed. So far, one case of implant dislocation and two cases of infection have occurred among the 35 patients. This study was designed to evaluate and obtain reasonable assurance of the safety, effectiveness, and risk/benfit ratio of a novel implant in the treatment of a challenging patient cohort. The short-term outcomes are promising

The absence of menisci in the knee leads to early degenerative changes. Complete radial tears of the meniscus are equivalent to total meniscectomy and repair should be performed if possible. The purpose of this study was to biomechanically compare the cross suture, hashtag and crosstag meniscal repairs using all-inside implants for radial tears. Radial tears were created at the mid-body of 36 fresh-frozen lateral human menisci and then repaired, in randomiSed order, with Fast-Fix™ 360s (Smith & Nephew, Andover, MA) using the cross suture, hashtag and crosstag techniques. The repaired menisci were tested using an Instron Electropuls E10000 (Instron, Norwood, MA). The tests consisted of cyclic loading from 5 to 30N at 1Hz for 500 cycles, then a load to failure test. Displacement following cyclic loading, load at 3mm of displacement, load to failure, and stiffness were recorded. Any differences between repairs were assessed using Kruskal-Wallis and Mann Whitney tests (p<0.05). Cross suture repairs displaced more following cyclic loading and resisted less load to failure than both the hashtag and crosstag repairs. However, these differences were not statistically significant. The average displacement following cyclic loading of cross suture, hashtag, and crosstag repairs was 4.34 mm (±2.02 mm), 3.46 mm (±2.12 mm), and 3.24 mm (±1.52 mm) respectively (p=0.33). Maximal load to failure was 64.83 N (±17.41 N), 74.52 N (±9.03 N), and 74.98N (±10.50N), respectively (p=0.419). All-inside cross suture, hashtag and crosstag repairs all displaced >3mm with cyclic loading, which is the threshold for meniscal insufficiency. This contrasts previous studies using inside-out sutures, where crosstag and hashtag repairs resisted cyclic loading (< 3mm). Inside-out suturing for radial tears of the lateral meniscus currently remains the gold standard

Introduction. Partial meniscectomy, a surgical treatment for meniscal lesions, allows athletes to return to sporting activities within two weeks. However, this increases knee joint shear stress, which is reported to cause osteoarthritis. The volumes and locations of partial meniscectomy that would result in a substantial increase in knee joint stress is not known. This information could inform surgeons when a meniscus reconstruction is required. Aim. Our aim was to use a previously validated knee finite element (FE) model to predict the effects of different volumes and locations of partial meniscectomy on cartilage shear stress. The functional point of interest was at the end of weight acceptance in walking and running, when the knee is subjected to maximum loading. Method. An FE model of the knee joint was used to simulate walking and running, two of the most common functional activities. Forces and moments, obtained from the gait cycle of a 76.4 kg male subject, were applied at the tibia. Different sizes (0%, 10%, 30%, 60%) and locations (anterior, medial and posterior) of partial meniscectomies were simulated (Figure 1). Maximum cartilage shear stress was determined for the different meniscectomies. Graphs were plotted of the cumulative tibial cartilage volume subjected to stress values above specific thresholds. Results and analysis. Maximum shear stress values for the intact knee during walking were 2.00 MPa medially and 1.71 MPa laterally. During running these magnitudes rose to 3.48 MPa medially and 4.70 MPa laterally. For a 30% anterior, central and posterior meniscectomy during walking shear stress increased by 25.9%, 44.9% and 32.5% medially, and 12.4%, 25.7% and 17.8% laterally. During running shear stress increased by 9.6%, 8.3% and 7.1%, medially and 31.6%, 37.5% and 43.6% laterally. For a 60% meniscectomy, during walking shear stress increased by 47.2% medially and 31.8%, laterally. During running shear stress increased by 10.0%, medially and 51.8%, laterally. The percentage of cartilage volume exposed to shear stress levels above a specified threshold is illustrated in Figure 2 for different volumes and locations of partial meniscectomy. Discussion and conclusions. This is first study that has estimated the volume of cartilage exposed to specific stress thresholds in walking and running as a function of the amount and location of meniscectomy. Maximum shear stress was 100% higher at the end of weight acceptance in running compared to walking. Stress was higher in the lateral compartment during running while higher in the medial compartment during walking. This is because a valgus moment acts at the knee at the end of weight acceptance in running while a varus moment acts at the joint in walking. Clinical significance. The model developed from this research has potential for applications in planning meniscal surgeries and developing rehabilitation strategies for athletes. It could inform surgeons about the safe volume and location of partial meniscectomy that can be performed before meniscus reconstruction becomes necessary. Results of this study also highlight the importance of considering the effect of post-surgical outcomes following different common functional activities

Introduction. Anatomical reconstruction of the Anterior Cruciate Ligament (ACL) reconstruction has been shown to be desirable and improve patient outcome. The posterior border of the anterior horn of the lateral meniscus (AHLM) is an easily identifiable arthroscopic landmark, which could guide anatomic tibial tunnel position in the sagital plane. The aim of the study was to establish the relationship between the posterior border of AHLM and the centre of the ACL foot print to facilitate anatomical tibial tunnel placement. Materials/Methods. We analysed 100 knee MRI scans where there was no ACL or lateral meniscal injury. We measured the distance between the posterior border of the AHLM and the midpoint of the tibial ACL footprint in the sagital plane. The measurements were repeated 2 weeks later for intra-observer reliability. Results. The mean distance between the posterior border of the AHLM and the ACL midpoint was −0.1mm (i.e. 0.1mm posterior to the ACL midpoint). The range was 5mm to −4.6mm. The median value was 0.00mm. 95% confidence interval was from 0.3 mm to −0.5 mm. A normal, parametric distribution was observed and Intra-observer variability showed significant correlation (p=0.01) using Pearsons Correlation test. Conclusion. Using the posterior border of the AHLM is a reliable, reproducible and anatomic marker for the midpoint of the ACL footprint in the majority of cases. It can be used intra-operatively as a guide for tibial tunnel and graft placement allowing anatomical reconstruction. There will inevitably be some anatomical variation. Pre-operative MRI assessment of the relationship between AHLM and ACL footprint is advised to improve surgical planning

Introduction. Anatomical reconstruction of the Anterior Cruciate Ligament (ACL) reconstruction has been shown to improve patient outcome. The posterior border of the anterior horn of the lateral meniscus (AHLM) is an easily identifiable landmark on MRI and arthroscopy, which could help plan tibial tunnel position in the sagittal plane and provide anatomical graft position intra-operatively. Method. Our method for anatomical tibial tunnel placement is to establish the relation of the posterior border of AHLM to the centre of the ACL footprint on a pre-operative sagittal MRI. Based on this relationship studied on preoperative MRI scan, posterior border of AHLM is used as an intra- operative arthroscopic landmark for anatomic tibial tunnel placement during ACL reconstruction. This relationship has been studied on 100 MRI scans where there was no ACL or LM injury (Bone and Joint Journal 2013 vol 95-B, SUPP 19). The aim of the study is to validate our method for anatomical tibial tunnel placement. Results. 25 patients with ACLR where there were both pre and post op MRI scan with good quality images of AHLM and tibial tunnel opening were included in this study. The preoperative relationship between posterior border of AHLM and centre of ACL footprint was compared with that between the posterior border of AHLM and centre of tibial tunnel on postop MRI scans. The measurements were done by two observers on two different occasions to establish intra and inter observer correlation. Discussion and Conclusion. There was significant correlation between pre-op (0.4mm) and post-op (0.4mm) distances between the AHLM and the centre of the ACL footprint/graft. There was significant inter-observer correlation (paired T-test =0.89, p<0.05) in pre- and post-op measurements. No significant difference was found in the difference between the means in pre-op and post-op MRI scans between observers (p=0.79). These results suggest that the AHLM is a reliable and valid intra-operative marker for anatomic ACL tibial tunnel placement

This study evaluates high power low frequency ultrasound transmitted via a flat vibrating probe tip as an alternative technology for meniscal debridement in the knee. A limitation of this technology is thermal damage in residual meniscal tissue.

To compare tissue removal rate and thermal damage for a radiofrequency ablation device and an experimental ultrasound ablation device.

Twelve bovine meniscal specimens were treated in an identical fashion with (a) a 3.75mm 50° bipolar radiofrequency wand, Arthrocare Super Multivac 50 Arthrowand (Arthrocare Corporation, Sunnyvale, CA), operated in a free-hand manner in accordance with manufacturers instructions (n=6), and (b) an experimental flat-tipped 3mm 20kHz ultrasound probe, suspended vertically in a 500N force-controlled experimental rig (n=6).

Tissue removal rate (TRR), zone of thermal necrosis and zone of thermal alteration were calculated. Histological sections were prepared for each sample (H&E). Independent samples t-test was used to compare TRR, zone of thermal necrosis and zone of thermal alteration. Statistical analysis was performed using PASW Statistics (v.18, IBM SPSS Statistics, Chicago, IL, U.S.A.).

The mean TRR for meniscal debridement by the radiofrequency device was 5.59±1.1mg/s. This compared with a mean TRR of 4.74±1.4mg/s for debridement with the ultrasound device at settings (p=0.259, NS). Mean depth of tissue removal using the radiofrequency device was 2.21±0.26mm compared to 3.75±0.25mm (p< 0.001, ?²=0.09). Using the radiofrequency device, the mean depth of zone of thermal alteration was 1282±436µm, compared with 710±251µm for the force-controlled ultrasound device (p=0.29, ?²=0.42). For the radiofrequency device, the mean depth of zone of thermal necrosis was 64±41µm versus 97±44µm for the ultrasound device (p=0.239, NS). We observed a trend towards an increased zone of thermal necrosis and a reduced zone of thermal alteration for the ultrasound device, when compared with the radiofrequency device.

Ultrasonic debridement shows comparable thermal damage to existing radiofrequency meniscal debridement technology.

Meniscal tears commonly co-occur with ACL tears, and many studies address their side, pattern, and distribution. Few studies assess the patient's short-term functional outcome concerning tear radial and circumferential distribution based on the Cooper et al. classification. Meniscal tears require primary adequate treatment to restore knee function. Our hypothesis is to preserve the meniscal rim as much as possible to maintain the load-bearing capacity of the menisci after meniscectomy. The purpose of this study is to document the location and type of meniscal tears that accompany anterior cruciate ligament (ACL) tears and their effect on patient functional outcomes following arthroscopic ACL reconstruction and meniscectomy. This prospective cross-sectional observational study was conducted at AL-BASRA Teaching Hospital in Iraq between July 2018 and January 2020 among patients with combined ipsilateral ACL injury and meniscal tears. A total of 28 active young male patients, aged 18 to 42 years, were included. All patients were subjected to our questionnaire, full history, systemic and regional examination, laboratory investigations, imaging studies, preoperative rehabilitation, and were followed by Lysholm score 6 months postoperatively. All 28 patients were males, with a mean age of 27 ± 0.14 years. The right knee was the most commonly affected in 20/28 patients (71.4%). The medial meniscus was most commonly injured in 11 patients, 7 patients had lateral meniscal tears, and 10 patients had tears in both menisci. The most common tear pattern of the medial meniscus was a bucket handle tear (36.4%), while longitudinal tears were the most frequent in the lateral meniscus (71.4%) (P-value = 0.04). The most common radial tear location was zone E-F (5/28, 17.8%), and the most common circumferential zone affected was the middle and inner third, reported in 50% of tears. Good and excellent outcomes using the Lysholm score after 6 months were obtained in 42.9% and 17.9% of patients, respectively. Better functional scores were associated with lateral meniscal tears, bucket handle tears, tears extending to a more peripheral vascular area, and if no more than one-third of the meniscus was resected (P-value = 0.002). Less favourable outcomes were reported in smokers, posterior horn tears, and when surgery was delayed more than 1 year (P-value = 0.03). We conclude that there is a negative correlation between the amount of meniscus resected and functional outcome. Delayed ACL reconstruction increases the risk of bimeniscal tears. Bucket handle tears are the most common tears, mostly in the medial meniscus, while longitudinal tears are most common in the lateral meniscus. We recommend performing early ACL reconstruction within 12 months to reduce the risk of bimeniscal injuries

Knee arthroscopy is typically approached from the anterior, posteromedial and posterolateral portals. Access to the posterior compartments through these portals can cause iatrogenic cartilage damage and create difficulties in viewing the structures of the posterior compartments. The purpose of this study was to assess the feasibility of needle arthroscopy using direct posterior portals as both working and visualising portals. For workability, the needle scope was inserted advanced from anterior between the cruciate ligament bundle and the lateral wall of the medial femoral condyle until the posterior compartments were visualised. For visualisation, direct postero-lateral and -medial portals were established. The technique was performed in 9 knees by two experienced researchers. Workability and instrumentation of the posteromedial compartment and meniscus was achieved in 56%. The posterior horns could not be visualised in four specimens as the straight lens could not provide a more medial field of view. Visualisation from the direct medial posterior portal allowed a clear view of the medial meniscus, femoral condyle and posterior cruciate ligament in all specimens. Workability and instrumentation of the posterolateral compartment was not possible with the needle scope. Direct posterior approaches for the posteromedial compartment access are challenging with the current needle scope options and could only be achieved in over 50%. The postero-lateral compartment was not accessible. An angled lens or a flexible Needle scope would be better suited for developing this technique further

The meniscus is at the cornerstone of knee joint function, imparting stability and ensuring shock absorption, load transmission, and stress distribution within the knee joint. However, it is very vulnerable to injury and age-related degeneration. Meniscal tears are reported as the most common pathology of the knee with a mean annual incidence of 66 per 100,000. Knee osteoarthritis progresses more rapidly in the absence of a functional meniscus. Historically, tears extending to the avascular inner portion of the meniscus (white-white zone, “WW”), such as radial tears were considered as untreatable and were often resected, due to the lack of vascularity in the WW zone. Perfusion-based anatomical studies performed on cadaveric menisci in the 1980s shaped the current dogma that human meniscus has poor regenerative capacity, partly due to limited blood supply that only reaches 10 to 25% of the meniscus, commonly referred to as red-red zone (“RR”). Previous studies, including those utilizing animal models have shown mobilization of Mesenchymal Stem Cells (MSCs) upon injury into the WW zone, and successful MSC recruitment when administered externally to the injury site. We and others have recently reported positive outcomes of repaired tears in the inner zone of patients. We hypothesized that the “avascular” white-white zone of the meniscus possesses regenerative capacity due to a resident stem/progenitor cell population. Further, we sought to redefine the presence of microvessels in all meniscal zones using advanced stereology and imaging modalities. Fifteen menisci from fresh human cadaveric knees (mean age: 21.53±6.53 years) without evidence of previous injury were obtained from two tissue banks (JRF, Centennial, CO) and Biosource Medical (Lakeland, FL) and utilized for this study. The use of cadaveric specimens for research purposes was approved by the institutional review board. Tibial plateaus were dissected to harvest medial and lateral menisci along their entire length. The RR, red-white (RW) and WW zones were dissected and separated into three thirds from the inner aspect to the marginal border of the meniscus and their wet weights recorded (Fig.1A). Meniscus tissue cellular content in each zone was obtained from dissociation of meniscus tissue using 0.02% w/v pronase (Millipore) for 1h at 37oC, followed by 18h 0.02% w/v collagenase II (Worthington) at 37oC with shaking. Isolated cells were characterized immediately after harvest using flow cytometry with antibodies against MSCs surface markers (CD105, CD90, CD44 and CD29) as well as respective isotype controls. Further, meniscal cells were cultured and split twice when confluence was reached, characterized at P2 and compared to bone marrow-derived MSCs (BM-MSCs) using the same markers. Self-renewal of cells was assessed using colony forming unit (CFU) assay. Differentiation assays were performed to assess whether colony-forming cells retained multilineage potential. For morphological examination of bigger vessels, samples were fixed in 10% formalin for 1 week, paraffin embedded, sectioned (4 μm thick) and stained with H&E and Masson's trichrome. Presence of microvessels was assessed by CD31 immunofluorescence staining. Further, menisci were cleared using the uDisco protocol labeled with the TO-PRO®-3 stain, a fluorescent dye that stains cell nuclei and imaged using light-sheet microscopy. All continuous data are presented as mean ±standard deviation. Non-repeated measures analysis of variance (ANOVA) and Tukey-Kramer HSD post hoc analysis were performed on sample means for continuous variables. Statistical significance was set at p < 0 .05. Menisci were successfully cleared using a modified uDISCO procedure, imaged and analyzed for total cell density. As expected, bigger vessels were observed in RR but not in WW. However, immunofluorescent staining for CD31 showed a subset of CD31+endothelial cells present in the WW zone, indicating the presence of small vessels, most likely capillaries. In order to assess whether enzymatic digestion had a differential result depending on meniscus zone due to cellular content, we analyzed yields per meniscus per zone. The wet weight of different zones (WW:RW:RR) was at a ratio of ∼1:3:5 respectively, however, the ratio of cells isolated from each zone was at ∼1:4:20, indicating that RR has a denser population of mononuclear cells. However, the difference between all zones in cell yields was not significant. The clonogenic potential of isolated cells was shown to be non-significantly different between the three zones. Differentiation of isolated cells to osteogenic lineage using osteogenic media in vitroshowed no difference between the three zones. Flow cytometry analysis of cells from the three meniscal zones displayed presence of two distinct subpopulations of cells immediately after isolation. One subpopulation was positive to MSC surface markers and the other negative. Additionally, flow cytometry of cultured meniscal cells at P2 displayed that the entire cell population was CD44+CD105+CD29+CD90+, suggesting that culturing meniscal cells results in selection of stem/progenitor cells (plastic adherence). Surface marker expression analysis showed differential expression patterns between markers depending on zone. Similar fraction of cells was detected to express both MSC markers CD90 and CD105 (7–10%) and similar fraction of cells expressed both MSC markers CD29 and CD44 (1–2%) in all three zones, indicating similar density of resident stem/progenitor cells in each zone. Importantly, WW showed significantly higher expression for all four MSC markers compared to the RR zone, indicating higher relative density of stem/progenitor resident cells in the WW zone. Our results determine that CD31-expressing microvessels were present in all zones, including the WW zone, which was previously considered completely avascular. Additionally, stem/progenitor cells were shown to be present in all three zones of the menisci, including the WW zone, showcasing its regenerative potential. For any figures or tables, please contact the authors directly