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

Bovine Meniscus Middle Zone Tissue: Measurement of Collagen Fibril Behavior During Compression

BACKGROUND

Type I collagen is the major component of the extracellular matrix of the knee's meniscus and plays a central role in that joint's biomechanical properties. Repair and reconstruction of tissue damage often requires a scaffold to assist the body to rebuild. The middle zone of bovine meniscus is a material that may be useful for the preparation of extracellular matrix scaffolds.

METHODS

Here, synchrotron-based small-angle X-ray scattering (SAXS) patterns of bovine meniscus were collected during unconfined compression. Collagen fibril orientation, D-spacing, compression distance and force were measured.

RESULTS

The collagen fibrils in middle zone meniscal fibrocartilage become more highly oriented perpendicular to the direction of compression. The D-spacing also increases, from 65.0 to 66.3 nm with compression up to 0.43 MPa, representing a 1.8% elongation of collagen fibrils perpendicular to the compression.

CONCLUSION

The elasticity of the collagen fibrils under tension along their length when the meniscus is compressed, therefore, contributes to the overall elastic response of the meniscus only under loads that exceed those likely to be experienced physiologically.

The Difference in Medial Meniscal Extrusion between Non-Weight-Bearing and Weight-Bearing Positions in People with and without Medial Compartment Knee Osteoarthritis

BACKGROUND

Medial meniscal extrusion (MME) has been correlated with medial meniscal injury and progression of medial knee osteoarthritis (OA).

OBJECTIVE

To examine the difference in MME between non-weight-bearing (supine) and weight-bearing (standing) positions in patients with and without medial knee OA. Determine the correlation between body mass index (BMI), Kellgren-Lawrence (KL) grade, Knee Osteoarthritis Outcome Score (KOOS), and MME.

DESIGN

Prospective.

SETTING

Tertiary institution PM&R Department.

PARTICIPANTS

Forty five participants (29 female, 16 male), 24 with healthy knees and 21 with OA.

METHODS OR INTERVENTIONS

A single physician sonographer measured supine and standing MME with ultrasound (US) on each participant. The physician was blinded to all measurements. BMI was recorded on all participants. KL grades and KOOS questionnaires were obtained for the OA group.

MAIN OUTCOME MEASURES

MME in supine and standing positions, change in MME from supine to standing, BMI, KL grade, and KOOS subscale scores.

RESULTS

MME increased .52 mm from supine to standing (P < .001). MME was greater in the OA group in both the supine (P = .002) and standing (P < .001) positions. Increasing BMI was moderately correlated with increasing MME (supine P = .001, standing <.001). Increasing age was correlated with increasing MME (supine P = .012, standing P = .002). Increasing KL grade (from 1 to 4) was correlated with increasing MME (supine P = .015, standing = .006). There was a small-to-moderate correlation between KOOS activities of daily living (ADL) subscale score and change in MME from supine to standing (P = .035). The change in MME from supine to standing positions had a small-to-moderate correlation (P = .035) with KOOS ADL subscale score alone but did not correlate with any of the other KOOS subscale scores or KOOS total scores. Receiver operating characteristic curve analysis suggested a standing MME value of 4.2 mm provides a positive likelihood ratio of 6.02 for knee OA.

CONCLUSIONS

MME is greater in those with OA and with weight-bearing. MME correlates with BMI, age, KL grade, and the KOOS ADL subscale score. Finally, standing MME of 4.2 mm yielded a higher positive likelihood ratio to differentiate between healthy knees and those with medial compartment OA than the previously reported value of 3.0 mm.

Use of the normalcy index for the assessment of abnormal gait in the anterior cruciate ligament deficiency combined with meniscus injury

The normalcy index (NI) has been implemented by several studies as a simple index for quantitatively analyzing diffident gait abnormalities, such as children with cerebral palsy and idiopathic toe-walkers. However, whether the NI can be used in anterior cruciate ligament (ACL) deficiency with different types of meniscus injuries or not, has not been reported yet. In this study, 25 patients who combined different types of ACL and meniscus injuries were evaluated by the NI analysis. 12 healthy subjects were used to define the normal range of NI. The result showed that NI values of patients were significantly larger than the control group (P < 0.05). Meanwhile, the tendency of increasing NI values associated with increasing pathology were significant with only 5 subjects in the smallest group (Jonkheere-Terpsta test: P < 0.001). These results indicated that the NI was a concise yet effective tool to evaluate combined ACL and meniscus injury patients. Increasing severity degree of meniscus tears in ACL rupture patients is corresponded to increasing NI values. It also demonstrates that the proposed NI can be applied as a robustness factor to detect the discrepancy between healthy and patient subjects clinically, and has the potential in the quantitative evaluation of pre- or post-surgery and rehabilitation.

Illustrative review of knee meniscal tear patterns, repair and replacement options, and imaging evaluation

This review article aims to reinforce anatomical concepts about meniscal tears while linking associated treatment options. The main teaching points start with the basic meniscal anatomy and key differences between the medial and lateral menisci. Subsequently, various meniscal tear patterns along with their associated history and physical exam findings will be discussed with corresponding illustrations and MR images. Additional discussion will involve the different surgical repair techniques (with arthroscopic correlates), their indications with pertinent imaging findings, imaging related to previous meniscal tear repairs, and novel surgical techniques. Lastly, keys to evaluating for retear with an emphasis on MRI arthrogram findings will be reviewed. While each of these topics is not discussed in totality, the key points of the review article will enforce key concepts and help radiologists evaluate the menisci on imaging.

Rebar Repair of Radial Meniscus Tears: A Reinforced Suture Technique

The purpose of this paper is to describe the rebar repair as a technique for repair of radial meniscus tears and compare the rebar technique with current techniques used for meniscus repairs. This technique consists of 4 sutures placed with the inside-out technique. First, the vertical mattress reinforcement sutures are placed anteriorly and posteriorly to the tear. Then, 2 parallel horizontal sutures are placed directly in juxtaposition to the vertical sutures, ensuring the needles pass on the side of the reinforcing stitch away from the tear. This technique is less technically challenging than other meniscus repair techniques that require drilling of a transtibial tunnel. Overall, the rebar technique offers a more optimal way for stabilizing the meniscus by using 2 reinforcement sutures that run with the circumferential fibers to help restore the natural hoop stress of the meniscus. Also, the placement of the vertical mattress sutures in the rebar technique offers more direct reinforcement to the horizontal mattress sutures as compared with other techniques, which reduces the risk of pull-out tears.

Medical exercise therapy alone versus arthroscopic partial meniscectomy followed by medical exercise therapy for degenerative meniscal tear: a systematic review and meta-analysis of randomized controlled trials

Objective

To explore if medical exercise therapy (MET) alone is comparable to arthroscopic partial meniscectomy (APM) followed by MET for knee pain, activity level, and physical function in middle-aged patients with degenerative meniscal tear (DMT) by a systematic review and meta-analysis of randomized controlled trials (RCTs).

Method

A systematic search of electronic databases (PubMed, the Cochrane Library, Embase, and Web of Science) was conducted to retrieve RCTs comparing MET+APM with MET alone for DMT. Risk of bias of the studies was evaluated. Outcomes assessed were pain relief, physical function, and activity level.

Results

A total of 6 RCTs containing 879 patients were included. After pooling the data of 5 researches, we found small significant differences support the APM + MET group for pain control assessed by Knee injury and Osteoarthritis Outcome Score (KOOS) at 2 to 3 months (p = 0.004) and at 6 months (p = 0.04). And there were statistically improvements in APM + MET at 6 months compared with MET alone when changing measurement to visual analog scale (VAS) (p = 0.0003). Our analysis also found small significant differences favor the APM followed by MET group for physical function both at 2 to 3 months (p = 0.01, KOOS and Western Ontario and McMaster Universities Osteoarthritis Index, WOMAC; and P = 0.40, Lysholm Knee Scoring Scale) and at 6 months (p = 0.01, KOOS and WOMAC).

Conclusion

We found favorable results of APM + MET up to 6 months for pain control and physical function. However, there were no differences at longer follow-up. The clinical applicability of APM + MET compared with MET should be interpreted carefully, and the potential of MET to treat DMT should be valued.

Collagen Type I and II Blend Hydrogel with Autologous Mesenchymal Stem Cells as a Scaffold for Articular Cartilage Defect Repair

Collagen type II is a promising material to repair cartilage defects since it is a major component of articular cartilage and plays a key role in chondrocyte function. This study investigated the chondrogenic differentiation of bone marrow-derived mesenchymal stem cells (MSCs) embedded within a 3:1 collagen type I to II blend (Col I/II) hydrogel or an all collagen type I (Col I) hydrogel. Glycosaminoglycan (GAG) production in Col I/II hydrogels was statistically higher than that in Col I hydrogels or pellet culture, and these results suggested that adding collagen type II promoted GAG production. Col I/II hydrogels had statistically lower alkaline phosphatase (AP) activity than pellets cultured in a chondrogenic medium. The ability of MSCs encapsulated in Col I/II hydrogels to repair cartilage defects was investigated by creating two cartilage defects in the femurs of rabbits. After 13 weeks, histochemical staining suggested that Col I/II blend hydrogels provided favorable conditions for cartilage repair. Histological scoring revealed a statistically higher cartilage repair score for the Col I/II hydrogels compared to either the Col I hydrogels or empty defect controls. Results from this study suggest that there is clinical value in the cartilage repair capabilities of our Col I/II hydrogel with encapsulated MSCs.

Arthroscopic partial meniscectomy combined with medical exercise therapy versus isolated medical exercise therapy for degenerative meniscal tear: A meta-analysis of randomized controlled trials

BACKGROUND

Degenerative meniscal tear is a chronic disorder which presents with knee pain, swelling and loss of motion. It is currently unknown whether arthroscopic partial meniscectomy combined with medical exercise therapy is superior to isolated medical exercise therapy for degenerative meniscal tear.

OBJECTIVE

To determine if medical exercise therapy alone is as effective as arthroscopic partial meniscectomy combined with medical exercise therapy in treating degenerative meniscal tear.

METHOD

Electronic searches were performed using MEDLINE, EMBASE, and the Cochrane Library Databases for all randomized studies. Two reviewers independently completed the literature screening, data extraction, and risk evaluation of bias. The outcome measures were visual analogue scale (VAS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion, the Lysholm Knee Scoring Scale (LKSS), Knee injury and Osteoarthritis Outcome Score (KOOS) and postoperative complications. STATA 13.0 software was applied for meta-analysis.

RESULT

Six randomized controlled trials (RCTs) were conducted, with 900 patients included. The present study revealed that there were significant differences between the two groups regarding the VAS at two months, as well as, WOMAC and range of motion. No significant differences were found in terms of LKSS, KOOS or postoperative complications.

LIMITATIONS

(1) Only 6 RCTs were included in our meta-analysis and the sample sizes were small; (2) The follow-up period was too short in some included studies. Long-term follow-up studies should be conducted in the future; (3) Heterogeneity among the included studies was unavoidable due to different grade of degenerative meniscal tear and program of exercise. Heterogeneity was also caused by a variety of other factors. (4) Publication bias that came from the process of literature searching was unavoidable and was hard to overcome. (5) There are many other words which could yielded more studies (Ex. physiotherapy, physical therapy modalities, exercise therapy, rehabilitation, knee, placebo, groups, tibial meniscus, meniscus, arthroscopy, meniscectomy, partial meniscectomy, randomized controlled trial, controlled clinical trial, randomized, systematic review, and meta-analysis). Implications of key findings: This meta-analysis suggests that doctors can choose arthroscopic partial meniscectomy combined with medical exercise therapy for the treatment of degenerative meniscal tear.

CONCLUSION

Arthroscopic partial meniscectomy combined with medical exercise therapy is effective in reducing pain and improving range of motion in the early postoperative period. Therefore, arthroscopic partial meniscectomy combined with medical exercise therapy may be recommended for the treatment of degenerative meniscal tear. Further research is necessary to determine the type, frequency, and duration of the best exercise program. Systematic review registration number: Reviewregistry884.

Medial Meniscal Posterior Horn Tears Are Associated With Increased Posterior Tibial Slope: A Case-Control Study

BACKGROUND

While the medial meniscal posterior horn (MMPH) is reported to bear a considerable portion of overall load on the knee joint, including compressive and shear forces, no study has yet investigated the relationship between the MMPH and posterior tibial slope (PTS), which is a geometric factor associated with the shear force component in the presence of a compressive load in the knee joint.

HYPOTHESIS/PURPOSE

The purpose was to investigate the relationship between the PTS and MMPH tears in patients without ligamentous injury. It was hypothesized that the PTS is greater in patients with MMPH tears as compared with those without.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From March 2015 to December 2018, 159 patients with isolated MMPH tears and 60 patients without any pathologic findings on magnetic resonance imaging (control group) were included in this study. The PTS in the affected and contralateral knees was compared between the groups, which were statistically matched according to baseline characteristics (ie, age, sex, body mass index, radiographic osteoarthritis grade according to the Kellgren-Lawrence scale, and hip-knee-ankle angle) via the inverse probability of treatment weighting method. Furthermore, the MMPH tear group was subdivided according to meniscal tear patterns; these subgroups were then compared with the control group.

RESULTS

The mean PTS was significantly greater in the MMPH tear group than in the control group (affected knee: MMPH tear group, 7.0°± 3.4° [mean ± SD]; control group, 5.2°± 2.1°, P < .001; contralateral knee: MMPH tear group, 6.7°± 3.3°; control group, 4.7°± 2.2°, P < .001). The mean PTS in each subgroup also tended to be greater than that in the control group. In the receiver operating characteristic curve analysis, the cutoff point of the PTS discriminating between the MMPH tear and control groups was 6.6° for the affected knee (sensitivity, 55.3%; specificity, 75.0%) and 5.5° for the contralateral knee (sensitivity, 61.0%; specificity, 76.7%).

CONCLUSION

An increased PTS is strongly associated with an increased incidence of MMPH tears and less affected by the meniscal tear patterns.

Tougu Xiaotong capsule exerts a therapeutic effect by improving knee meniscus in the early osteoarthritis rat model

The aim of the study was to observe the effects of Tougu Xiaotong capsule (TGXTC) on the microstructure and ultrastructure of meniscus in rats with early knee osteoarthritis (KOA). A total of 27 Sprague Dawley rats were randomly divided into three groups: The normal group (non-papain-induced KOA; received saline only), the model group (papain-induced KOA; received saline only) and the TGXTC group [papain-induced KOA; received TGXTC (0.31g·kg-1·d-1)]. After 4 weeks treatment, the animals were anesthetized and the sagittal plane of the intact knees (n=6 per group) was obtained and prepared in paraffin section. Following hematoxylin and eosin staining, the degeneration of cartilage structure was evaluated via Mankin score, the microstructure of meniscus was observed and the area of calcification in meniscus was analyzed. Following toluidine blue staining, the content of proteoglycan in meniscus was analyzed. Three samples in each group were obtained and the ultrathin sections of meniscus were observed through a transmission electron microscope. The results showed that compared with the normal group, in the model group the joint space became narrow and the cartilage layer was slightly damaged and the Mankin score was 4.17±0.76, suggesting that the early KOA model was successfully established. After TGXTC treatment, the joint space stenosis and cartilage damage were improved as the Mankin score significantly decreased. Compared with the normal group, in the model group the surface of meniscal cartilage was much more uneven, the area of calcification was significantly increased and the content of proteoglycan of cartilage matrix was significantly decreased. However, following TGXTC treatment, the surface of the meniscal cartilage was much more smooth and flat, and the damage of tissue structure and the calcified area were significantly reduced, and the proteoglycan of cartilage matrix content was significantly increased. Compared with the normal group, the number of cellular processes and organelles, including the rough endoplasmic reticulum, mitochondria and Golgi apparatus of meniscal cartilage were reduced and swollen in the model group. In addition, the nuclei were deformed and heterochromatin agglutinated. The extracellular collagen fibrils became slender, disordered and sparse. Compared with the model group, the TGXTC group had more cell processes and organelles, alleviated swelling and heterochromatin agglutinating. Additionally, the collagen fibrils around the cells were thicker, larger and arranged in an orderly manner. In conclusion, TGXTC exerted its therapeutic effects on the development of KOA via reducing the destruction of the cartilage structure of the meniscus and improving the composition and function of the meniscus cartilage matrix.

Hybrid Bioprinting of Chondrogenically Induced Human Mesenchymal Stem Cell Spheroids

To date, the treatment of articular cartilage lesions remains challenging. A promising strategy for the development of new regenerative therapies is hybrid bioprinting, combining the principles of developmental biology, biomaterial science, and 3D bioprinting. In this approach, scaffold-free cartilage microtissues with small diameters are used as building blocks, combined with a photo-crosslinkable hydrogel and subsequently bioprinted. Spheroids of human bone marrow-derived mesenchymal stem cells (hBM-MSC) are created using a high-throughput microwell system and chondrogenic differentiation is induced during 42 days by applying chondrogenic culture medium and low oxygen tension (5%). Stable and homogeneous cartilage spheroids with a mean diameter of 116 ± 2.80 μm, which is compatible with bioprinting, were created after 14 days of culture and a glycosaminoglycans (GAG)- and collagen II-positive extracellular matrix (ECM) was observed. Spheroids were able to assemble at random into a macrotissue, driven by developmental biology tissue fusion processes, and after 72 h of culture, a compact macrotissue was formed. In a directed assembly approach, spheroids were assembled with high spatial control using the bio-ink based extrusion bioprinting approach. Therefore, 14-day spheroids were combined with a photo-crosslinkable methacrylamide-modified gelatin (gelMA) as viscous printing medium to ensure shape fidelity of the printed construct. The photo-initiators Irgacure 2959 and Li-TPO-L were evaluated by assessing their effect on bio-ink properties and the chondrogenic phenotype. The encapsulation in gelMA resulted in further chondrogenic maturation observed by an increased production of GAG and a reduction of collagen I. Moreover, the use of Li-TPO-L lead to constructs with lower stiffness which induced a decrease of collagen I and an increase in GAG and collagen II production. After 3D bioprinting, spheroids remained viable and the cartilage phenotype was maintained. Our findings demonstrate that hBM-MSC spheroids are able to differentiate into cartilage microtissues and display a geometry compatible with 3D bioprinting. Furthermore, for hybrid bioprinting of these spheroids, gelMA is a promising material as it exhibits favorable properties in terms of printability and it supports the viability and chondrogenic phenotype of hBM-MSC microtissues. Moreover, it was shown that a lower hydrogel stiffness enhances further chondrogenic maturation after bioprinting.

Biomechanical and Clinical Effect of Patient-Specific or Customized Knee Implants: A Review

(1) Background: Although knee arthroplasty or knee replacement is already an effective clinical treatment, it continues to undergo clinical and biomechanical improvements. For an increasing number of conditions, prosthesis based on an individual patient's anatomy is a promising treatment. The aims of this review were to evaluate the clinical and biomechanical efficacy of patient-specific knee prosthesis, explore its future direction, and summarize any published comparative studies. (2) Methods: We searched the PubMed, MEDLINE, Embase, and Scopus databases for articles published prior to February 1, 2020, with the keywords "customized knee prosthesis" and "patient-specific knee prosthesis". We excluded patient-specific instrument techniques. (3) Results: Fifty-seven articles met the inclusion criteria. In general, clinical improvement was greater with a patient-specific knee prosthesis than with a conventional knee prosthesis. In addition, patient-specific prosthesis showed improved biomechanical effect than conventional prosthesis. However, in one study, patient-specific unicompartmental knee arthroplasty showed a relatively high rate of aseptic loosening, particularly femoral component loosening, in the short- to medium-term follow-up. (4) Conclusions: A patient-specific prosthesis provides a more accurate resection and fit of components, yields significant postoperative improvements, and exhibits a high level of patient satisfaction over the short to medium term compared with a conventional prosthesis. However, the tibial insert design of the current patient-specific knee prosthesis does not follow the tibial plateau curvature.

Continuous Meniscal Suture Technique of the Knee

The menisci are fibroelastic structures interposed between the articular surfaces of the femur and tibia. They absorb impact and transmit load. Meniscal injury may compromise function and cause rapid joint degeneration, leading to the development of secondary osteoarthritis. Surgical treatment of meniscal injury is usually performed by arthroscopy, and meniscectomy or meniscal suture may be associated with such treatment. Meniscal suture should be considered when the injury compromises the proper functioning of the meniscus to recover its anatomy and function. Different meniscal suture techniques exist; the most widely used are the inside-out, outside-in, and all-inside techniques. The gold-standard repair technique is the inside-out technique. A drawback of this technique is the need to alternate between intra- and extra-articular structures for every stitch, which makes it even more laborious. We describe the continuous meniscal suture technique, also called "meniscal stitching," for a medial meniscal bucket-handle injury. This technique is performed from the inside out and allows the surgeon to perform multiple stitches with the same thread quickly and effectively. This surgical technique is performed using a single meniscal suture device that was developed by our group, called the "Meniscus 4 A-II" device.

Anatomy-mimetic design preserves natural kinematics of knee joint in patient-specific mobile-bearing unicompartmental knee arthroplasty

PURPOSE

This study aims to evaluate whether different tibial-femoral conformities for patient-specific mobile-bearing unicompartmental knee arthroplasties (UKAs) preserve natural knee kinematics, using computational simulations.

METHODS

Different designs for patient-specific mobile-bearing UKAs were evaluated using finite element analysis. Three designs for the identical femoral component were considered: flat (non-conforming design), anatomy-mimetic, and conforming for the tibial insert.

RESULTS

The conforming design for the patient-specific mobile-bearing UKAs exhibited a 1.2 mm and 0.7° decrease in the translation and rotation, respectively, in the swing phase compared with those of the natural knee. In addition, the femoral rollback and internal rotation were 2.6 mm and 1.2° lower, respectively, than those of the natural knee, for the conforming design under the deep-knee-bend condition. The flat design for the patient-specific mobile-bearing UKAs exhibited a 2.2 mm and 1.4° increase in the femoral rollback and rotation compared with the natural knee under the deep-knee-bend condition. The anatomy-mimetic patient-specific mobile-bearing UKAs best preserved the natural knee kinematics under the gait and deep-knee-bend loading conditions.

CONCLUSIONS

The kinematics of the loading conditions in patient-specific mobile-bearing UKAs was determined to closely resemble those of a native knee. In additional, by replacing the anatomy-mimetic design with a mobile-bearing, natural knee kinematics during gait and deep-knee-bend motions is preserved. These results confirm the importance of tibiofemoral conformity in preserving native knee kinematics in patient-specific mobile-bearing UKA.

Knotless Anchor Fixation for Transosseous Meniscal Root Repair Using Suture Tape Is Inferior Compared With Button or Screw Fixation: A Biomechanical Study

Background

A 2 mm-wide ultrahigh-molecular-weight polyethylene (UHMWPE) tape improves the contact pressure at root repair sites compared with high-strength suture and provides a stronger repair construct. UHMWPE tape is commonly used in rotator cuff repair, and fixation is often achieved with knotless suture anchors. The optimal method for tape fixation for meniscal root repair has not been established.

Hypothesis

The use of suture anchors for the tibial fixation of 2-mm UHMWPE tape transosseous root repairs will lead to better biomechanical performance compared with other fixation methods.

Methods

The medial meniscal posterior root attachment in 25 porcine knees was divided, and a standardized transtibial root repair was performed using 2-mm UHMWPE tape. The testing was performed by cyclic loading followed by load to failure. Tibial fixation was randomized to 5 tibial fixation types: (1) cortical fixation button, (2) pound-in suture anchor with screw-down interference suture locking, (3) tap-in suture anchor with inner locking plug, (4) postscrew, and (5) postscrew and washer.

Results

There was no difference in displacement during cyclic loading between tibial fixation groups except for a highly significant difference in the maximum load at failure. Repairs in both suture anchor fixation groups all failed by tape slippage at relatively low loads (median, 145 and 116 N, respectively). Repairs tied over a cortical button, postscrew, or screw and washer failed by tape breakage at loads of 431, 405, and 528 N.

Conclusion

For meniscal root repairs with 2-mm UHMWPE tape, use of suture anchors offers weaker fixation compared with tying over a button or postscrew/washer. While suture anchor fixation may be adequate for nonweightbearing postoperative protocols, it may not allow for more accelerated weightbearing.

Early Functional Rehabilitation after Meniscus Surgery: Are Currently Used Orthopedic Rehabilitation Standards Up to Date?

Meniscus therapy is a challenging process. Besides the respective surgical procedure such as partial meniscectomy, meniscus repair, or meniscus replacement, early postoperative rehabilitation is important for meniscus regeneration and return to sport and work as well as long-term outcome. Various recommendations are available. However, the current literature lacks information concerning the actual early rehabilitation in daily routine recommended by orthopedic surgeons. Thus, the purpose of this study was to investigate currently used standard early rehabilitation protocols in the daily routine of orthopedic surgeons. This study investigated the recommendations and concepts for early rehabilitation after meniscus therapy given by German, Austrian, and Swiss orthopedic institutions. Standardized criteria such as weight bearing, range of motion, use of an orthosis, and rehabilitation training were analyzed according to the conducted surgical procedure: partial meniscectomy, meniscus repair, or meniscus replacement. The analysis of standard rehabilitation concepts for partial meniscectomy (n = 15), meniscus repair (n = 54), and meniscus replacement (n = 7) showed significantly earlier functional rehabilitation in all criteria after partial meniscectomy in contrast to meniscus repair techniques (p < 0.001). In addition, significant restrictions were found in full weight bearing, full range of motion, and the use of braces. In summary, a wide range of recommendations for weight bearing, ROM, brace therapy, and mobilization is available, particularly after meniscus repair and meniscus replacement. Most concepts are in accordance with those described in the current literature. Further research is necessary to enhance the scientific evidence on currently used early rehabilitation concepts after meniscus therapy.

Finite Element Study on the Preservation of Normal Knee Kinematics with Respect to the Prosthetic Design in Patient-Specific Medial Unicompartmental Knee Arthroplasty

Alterations in native knee kinematics in medial unicompartmental knee arthroplasty (UKA) are caused by the nonanatomic articular surface of conventional implants. Technology for an anatomy mimetic patient-specific (PS) UKA has been introduced. However, there have been no studies on evaluating the preservation of native knee kinematics with respect to different prosthetic designs in PS UKA. The purpose of this study was to evaluate the preservation of native knee kinematics with respect to different UKA designs using a computational simulation. We evaluated three different UKA designs: a nonconforming design, an anatomy mimetic design, and a conforming design for use under gait and squat loading conditions. The results show that the anatomy mimetic UKA design achieves closer kinematics to those of a native knee compared to the other two UKA designs under such conditions. The anatomy memetic UKA design exhibited a 0.39 mm and 0.36° decrease in the translation and rotation, respectively, in the swing phase compared with those of the natural knee. In addition, under the gait and squat loading conditions, the conforming UKA design shows limited kinematics compared to the nonconforming UKA design. Our results show that the conformity of each component in PS UKA is an important factor in knee joint kinematics; however, the anatomy mimetic UKA design cannot restore perfect native kinematics.

Evaluating the risk of popliteal artery injury in the all-inside meniscus repair based on the location of posterior meniscal lesions

The 'all-inside' meniscus repair is extremely useful technique in addressing tears at the far posterior horn of meniscus. However, this procedure may place the popliteal neurovascular bundle at risk of injury. The purpose of this study was to evaluate the risk of popliteal artery injury by the trajectory of anchor delivery instruments inserted through standard knee arthroscopic portals for the repair of the far posterior horn of meniscus tears. Standard arthroscopic portals were marked on five human cadaveric knees which were subsequently disarticulated. Axial photographs were taken after marking the 5 10, and 15 mm points from the meniscal root on the posterior horns of the menisci. The unsafe zones for meniscus repair at each of these points were identified on the photographs of knees by first drawing two lines from the edges of the popliteal artery and crossing at the respective points at the posterior horns. The points at which these lines meet a circular protractor applied to the center of each meniscus in the knee photograph were recorded as a range. The range signifies the unsafe zone for each respective point on the posterior horn of meniscus. The anterolateral arthroscopic portal fell within the unsafe zone of the 5 mm point on the posterior horn of lateral meniscus in three of the five knees and within the unsafe zone of the 10 mm point on the posterior horn of lateral meniscus in another two knees. A cautious approach should be practiced during the repair of tears located at these two points. None of the other points' unsafe zones (lateral 15 mm, medial 5 mm, 10 mm and 15 mm points) coincided with the ipsilateral portal sites. Level of evidence 5 (Human cadaveric study).

Alterations in medial-lateral postural control after anterior cruciate ligament reconstruction during stair use

BACKGROUND

Dynamic postural control during everyday tasks is poorly understood in people following anterior cruciate ligament reconstruction (ACLR). Understanding dynamic postural control can provide insight into potentially modifiable impairments in people following ACLR who are at increased risk for second ACL injury and/or knee osteoarthritis.

RESEARCH QUESTION

Determine whether measures indicative of dynamic postural control differ between individuals with and without ACLR during stair ascent and descent.

METHODS

Seventeen individuals with ACLR (>1 yr post-surgery) and 16 age and sex-matched healthy controls participated. Centre of pressure (COP) measures included: i) COP excursion, ii) COP velocity, and iii) dynamic time-toboundary (TTB). Mixed linear models were used to compare COP measures for the ACLR leg, non-ACLR leg, and healthy controls during stair ascent and stair descent.

RESULTS

There were no statistically significant differences observed during stair ascent (all p > 0.05). Several statistical differences were found during stair descent for individual with ACLR, but not between those with ACLR and healthy controls. The ACLR leg had higher medial-lateral COP excursion (mean difference 1.06 cm, [95 %CI 0.08-2.06 cm], p = 0.036; effect size = 0.38) compared to the non-ACLR leg during stair descent. In addition, the ACLR leg had a lower medial-lateral TTB (mean difference -13 ms [95 %CI -38 to 2 ms], p = 0.005; effect size = 0.49) and medial-lateral TTB normalized to stance time (mean difference -5.8 % [95 %CI -10.3 to 1.3 %], p = 0.012; effect size = 0.80) compared to the non-ACLR leg during stair descent. No statistical differences were observed for anterior-posterior measures during stair descent (all p > 0.05).

SIGNIFICANCE

Taken together, findings indicate that there are small to large differences in medial-lateral postural control in the ACLR leg compared to the non-ACLR leg during stair descent. Further work is required to understand clinical implication of these novel observations.

Second-look arthroscopic findings and clinical outcomes of meniscal repair with concomitant anterior cruciate ligament reconstruction: comparison of suture and meniscus fixation device

INTRODUCTION

The purpose of this study was to evaluate the healing rate of repaired meniscus and functional outcomes of patients who received all-inside meniscal repair using sutures or devices with concomitant arthroscopic anterior cruciate ligament (ACL) reconstruction.

MATERIALS AND METHODS

Among the patients who have ACL tear and posterior horn tear of medial or lateral meniscus, 61 knees who received all-inside repair using sutures (suture group, n = 28) or meniscal fixation devices (device group, n = 33) with concomitant ACL reconstruction during the period from January 2012 to December 2015, followed by second-look arthroscopy, were retrospectively reviewed. Healing status of the repair site was assessed by second-look arthroscopy. Through the clinical assessment, clinical success (negative medial joint line tenderness, no history of locking or recurrent effusion, and negative McMurray test) rate of the repaired meniscus and functional outcomes (International Knee Documentation Committee subjective score and Lysholm knee score) was evaluated.

RESULTS

In a comparison of healing status of repaired meniscus evaluated by second-look arthroscopy, suture group had 23 cases of complete healing (82.1%), 4 cases of incomplete healing (14.3%), and 1 case of failure (3.6%). Device group had 18 cases of complete healing (54.5%), 4 cases of incomplete healing (24.2%), and 7 cases of failure (21.2%) (p = 0.048). Clinical success rate of the meniscal repair was 89.3% (25 cases) and 81.8% (27 cases) in suture group and device group, respectively (p = 0.488). No significant difference of functional outcomes was observed between the two groups (p > 0.05, both parameters).

CONCLUSIONS

Among the patients who received meniscal repair with concomitant ACL reconstruction, suture group showed better healing status of repaired meniscus based on the second-look arthroscopy than device group. However, no significant between-group difference of clinical success rate and functional outcomes was observed.

Meniscus Repair and Regeneration: A Systematic Review from a Basic and Translational Science Perspective

Meniscus injuries are among the most common athletic injuries and result in functional impairment in the knee. Repair is crucial for pain relief and prevention of degenerative joint diseases like osteoarthritis. Current treatments, however, do not produce long-term improvements. Thus, recent research has been investigating new therapeutic options for regenerating injured meniscal tissue. This review comprehensively details the current methodologies being explored in the basic sciences to stimulate better meniscus injury repair. Furthermore, it describes how these preclinical strategies may improve current paradigms of how meniscal injuries are clinically treated through a unique and alternative perspective to traditional clinical methodology.

Cartilage degeneration post-meniscectomy performed for degenerative disease versus trauma: data from the Osteoarthritis Initiative

OBJECTIVE

To compare the extent of cartilage deterioration in knees with prior meniscal resection related to trauma versus knees with resection related to degenerative disease, and to compare cartilage deterioration in knees with meniscal surgery to knees without meniscal surgery, controlling for prior knee trauma.

MATERIALS AND METHODS

In this cross-sectional study, we assessed cartilage deterioration in right knees of Osteoarthritis Initiative participants: (i) with meniscal surgery due to injury (n = 79); (ii) matched control knees with a prior injury but without meniscal surgery (n = 79); (iii) with meniscal surgery but without preceding injury (n = 36); and (iv) matched control knees without meniscal surgery or prior knee injury (n = 36). Cartilage composition was measured using T2 measurements derived using semi-automatic cartilage segmentation of the right. Linear regression analysis was used to compare compartmental values of T2 between groups.

RESULTS

Comparing the mean T2 values in surgical cases with and without injury our results did not show significant differences (group i vs. iii, p > 0.05). However, knees with previous meniscal surgery showed significantly (p < 0.001) higher mean T2 values across all compartments (i.e., global T2) when compared to those without meniscal surgery for both knees with a history of trauma (group i vs. ii) and knees without prior trauma (group iii vs. iv). Similar results were obtained when analyzing the compartments separately.

CONCLUSIONS

Cartilage deterioration, assessed by T2, is similar in knees undergoing meniscal surgery after trauma and for degenerative conditions. Both groups demonstrated greater cartilage deterioration than nonsurgical knees, controlling for prior knee injury.

Meniscus Matrix Remodeling in Response to Compressive Forces in Dogs

Joint motion and postnatal stress of weight bearing are the principal factors that determine the phenotypical and architectural changes that characterize the maturation process of the meniscus. In this study, the effect of compressive forces on the meniscus will be evaluated in a litter of 12 Dobermann Pinschers, of approximately 2 months of age, euthanized as affected by the quadriceps contracture muscle syndrome of a single limb focusing on extracellular matrix remodeling and cell–extracellular matrix interaction (i.e., meniscal cells maturation, collagen fibers typology and arrangement). The affected limbs were considered as models of continuous compression while the physiologic loaded limbs were considered as controls. The results of this study suggest that a compressive continuous force, applied to the native meniscal cells, triggers an early maturation of the cellular phenotype, at the expense of the proper organization of collagen fibers. Nevertheless, an application of a compressive force could be useful in the engineering process of meniscal tissue in order to induce a faster achievement of the mature cellular phenotype and, consequently, the earlier production of the fundamental extracellular matrix (ECM), in order to improve cellular viability and adhesion of the cells within a hypothetical synthetic scaffold.

Ultrashort Time to Echo Magnetic Resonance Evaluation of Calcium Pyrophosphate Crystal Deposition in Human Menisci

OBJECTIVES

In human menisci, we aimed to investigate whether calcium pyrophosphate crystal deposition (CPPD) affects biomechanical and quantitative MR properties, and their zonal distribution.

MATERIALS AND METHODS

From 9 cadaveric knees, sectioned triangular meniscus pieces were harvested. Samples were classified into "normal" or "CPPD" groups based upon visual inspection. Micro computed tomography scan verified CPPD. Using magnetic resonance imaging, ultrashort echo time (UTE) T2* and spin echo (SE) T2, quantitative values in 3 zones (red, red-white, and white) were determined. Using biomechanical test, indentation forces in the same zones were determined. Effects of CPPD and meniscal zone on indentation force and quantitative MR values were compared.

RESULTS

On UTE MRI scans, CPPD-affected menisci exhibited punctate dark regions, found mostly (92%) in avascular white and red-white zones. Indentation forces were significantly higher for CPPD samples in the red-white (all P < 0.02) and white (all P < 0.004) zones but not in the vascular red zone (all P > 0.2). Similarly, UTE T2* red zone values were similar between both groups (~6.6 milliseconds, P = 0.8), whereas in the red-white and white zones, CPPD samples had significantly lower values (~5.1 milliseconds, P = 0.005 to 0.007). In contrast, SE T2 values showed no difference with CPPD (P = 0.12 to 0.16). UTE T2*, but not SE T2, correlated significantly with indentation force (R = -0.29, P = 0.009).

CONCLUSIONS

Dark CPP deposits were detectable on UTE images featuring high signal intensity from surrounding meniscal tissue. Preliminary results indicate that CPP deposits were almost exclusively found in the avascular zones. Compared with normal, CPPD menisci featured higher indentation stiffness and lower UTE T2* values in the affected zones.

SDF-1 preconditioned HPC scaffolds mobilize cartilage-derived progenitors and stimulate meniscal fibrocartilage repair in human explant tissue culture

Purpose: The purpose of this study was to characterize the influence of SDF-1 on cell migration/adhesion and temporal gene expression of human cartilage mesenchymal progenitor cells (C-PCs); and to utilize SDF-1 conditioned mesenchymal progenitors to stimulate reintegration of human meniscus fibrocartilage breaks.Materials and Methods: Characterization of SDF-1-induced cell migration was achieved using hydroxypropyl cellulose (HPC) scaffolds pretreated with SDF-1. Fluorescence microscopy and cell counting were used to visualize and quantify the extent of cell migration into scaffolds, respectively. Relative mRNA expression analysis was used to characterize the temporal effects of SDF-1 on C-PCs. Tissue reintegration experiments were conducted using cylindrical human meniscal tissue punches, which were then placed back together with an HPC scaffold embedded with C-PCs. Tensile testing was used to evaluate the extent of tissue reintegration stimulated by human mesenchymal progenitors.Results: C-PCs migrate into scaffolds in response to SDF-1 with the same efficiency as mesenchymal progenitors from human marrow (BM-MSCs). SDF-1 treatment of C-PCs did not significantly alter the expression of early and late stage chondrogenic differentiation genes. Scaffolds containing SDF-1 pre-conditioned C-PCs successfully adhered to fibrocartilage breaks and migrated from the scaffold into the tissue. Tensile testing demonstrated that SDF-1 preconditioned C-PCs stimulate reintegration of fibrocartilage tears.Conclusion: C-PCs migrate in response to SDF-1. Exposure to SDF-1 does not significantly alter the unique mRNA profile of C-PCs that make them desirable for cartilaginous tissue repair applications. SDF-1 pretreated mesenchymal progenitors successfully disperse into injured tissues to help facilitate tissue reintegration.

The Meniscus Tear: A Review of Stem Cell Therapies

Meniscal injuries have posed a challenging problem for many years, especially considering that historically the meniscus was considered to be a structure with no important role in the knee joint. This led to earlier treatments aiming at the removal of the entire structure in a procedure known as a meniscectomy. However, with the current understanding of the function and roles of the meniscus, meniscectomy has been identified to accelerate joint degradation significantly and is no longer a preferred treatment option in meniscal tears. Current therapies are now focused to regenerate, repair, or replace the injured meniscus to restore its native function. Repairs have improved in technique and materials over time, with various implant devices being utilized and developed. More recently, strategies have applied stem cells, tissue engineering, and their combination to potentiate healing to achieve superior quality repair tissue and retard the joint degeneration associated with an injured or inadequately functioning meniscus. Accordingly, the purpose of this current review is to summarize the current available pre-clinical and clinical literature using stem cells and tissue engineering for meniscal repair and regeneration.

Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the Tibial Insert Design for Unicompartmental Knee Arthroplasty

Recent advances in imaging technology and additive manufacturing have led to the introduction of customized unicompartmental knee arthroplasty (UKA) that can potentially improve functional performance due to customized geometries, including customized sagittal and coronal curvature and enhanced bone preservation. The purpose of this study involved evaluating the biomechanical effect of the tibial insert design on the customized medial UKA using computer simulations. We developed sagittal and coronal curvatures in a native knee mimetic femoral component design. We utilized three types of tibial insert design: flat, anatomy mimetic, and conforming design. We evaluated contact stress on the tibial insert and other compartments, including the lateral meniscus and articular cartilage, under gait and squat loading conditions. For the conforming UKA design, the tibial insert and lateral meniscus exhibited the lowest contact stress under stance phase gait cycle. However, for the conforming UKA design, the tibial insert and lateral meniscus exhibited the highest contact stress under swing phase gait cycle. For the flat UKA design, the articular cartilage exhibited the lowest contact stress under gait and squat loading conditions. The anatomy mimetic UKA design exhibited the most normal-like contact stress on the other compartments under gait and squat loading conditions. The results reveal the importance of conformity between the femoral component and the tibial insert in the customized UKA. Based on the results on the femoral component as well as the tibial insert in the customized UKA, the anatomy mimetic design preserves normal knee joint biomechanics and thus may prevent progressive osteoarthritis of the other knee compartments.

Advanced microscopy analysis of the micro-nanoscale architecture of human menisci

The complex inhomogeneous architecture of the human meniscal tissue at the micro and nano scale in the absence of artefacts introduced by sample treatments has not yet been fully revealed. The knowledge of the internal structure organization is essential to understand the mechanical functionality of the meniscus and its relationship with the tissue’s complex structure. In this work, we investigated human meniscal tissue structure using up-to-date non-invasive imaging techniques, based on multiphoton fluorescence and quantitative second harmonic generation microscopy complemented with Environmental Scanning Electron Microscopy measurements. Observations on 50 meniscal samples extracted from 6 human menisci (3 lateral and 3 medial) revealed fundamental features of structural morphology and allowed us to quantitatively describe the 3D organisation of elastin and collagen fibres bundles. 3D regular waves of collagen bundles are arranged in “honeycomb-like” cells that are comprised of pores surrounded by the collagen and elastin network at the micro-scale. This type of arrangement propagates from macro to the nanoscale.

Anterior cruciate ligament reconstruction with concomitant meniscal surgery: a systematic review and meta-analysis of outcomes

PURPOSE

The aim of this review was to compare the clinical outcomes of anterior cruciate ligament reconstruction (ACLR) with either meniscal repair or meniscectomy for concomitant meniscal injury. The primary hypothesis was that short-term clinical outcomes (≤ 2-year follow-up) for ACLR concomitant with either meniscal repair or resection would be similar. The secondary hypothesis was that ACLR with meniscal repair would result in better longer term outcomes compared with meniscal resection.

METHODS

The authors searched two online databases (EMBASE and MEDLINE) from inception until March 2018 for the literature on ACLR and concurrent meniscal surgery. Two reviewers systematically screened studies in duplicate, independently, and based on a priori criteria. Quality assessment was also performed in duplicate. The Knee injury and Osteoarthritis Outcome Score (KOOS) sub-scale scores at 2 years post-operatively were combined in a meta-analysis of proportions using a random-effects model.

RESULTS

Of 2566 initial studies, 25 studies satisfied full-text inclusion criteria. Mean follow-up was 2.09 years, with a total sample of 37,087 subjects including controls. The meta-analysis demonstrated equivocal results at 2 years, except for KOOS symptom scores which favoured meniscal resection over repair. Mean KT-1000 side-to-side difference (SSD) scores were 1.51 ± 0.60 mm for meniscal repair, 1.96 ± 0.36 mm for meniscal resection, and 1.58 ± 0.20 for control patients (isolated ACLR). Medial meniscal repair showed decreased anterior knee joint laxity compared to medial meniscal resection (P < 0.001). Patients with meniscal repair had higher rates of re-operation (13.3% vs 0.8% for meniscal resection, P < 0.001).

CONCLUSION

Patients with ACLR combined with meniscal resection demonstrate better symptoms at 2-year follow-up compared to patients with ACLR combined with meniscal repair. ACLR combined with meniscal repair results in decreased anterior knee joint laxity with evidence of improved patient-reported outcomes in the long term, but also higher re-operation rates.

LEVEL OF EVIDENCE

III.

Outcomes More Than 2 Years After Meniscal Repair for Radial/Flap Tears of the Posterior Lateral Meniscus Combined With Anterior Cruciate Ligament Reconstruction

BACKGROUND

Meniscal function after repair of radial/flap tears of the posterior horn of the lateral meniscus (LM) with anterior cruciate ligament reconstruction (ACLR) has not been comprehensively investigated.

PURPOSE

To evaluate not only the clinical and radiographic outcomes of patients with repair of radial/flap tears of the posterior LM with ACLR but also the healing status of the repaired meniscus and changes of chondral status with second-look arthroscopy.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From January 2008 to April 2016, 41 patients of a consecutive series of 505 primary anatomic ACLR cases had a concomitant radial/flap tear of the posterior horn of the LM and underwent side-to-side repair with an inside-out or all-inside technique. All patients were followed for >2 years, evaluated clinically and radiologically (radiograph and magnetic resonance imaging [MRI]), and compared with a control group without any concomitant injuries that underwent ACLR. Of the 41 patients, 30 were assessed by second-look arthroscopy 2 years postoperatively.

RESULTS

The mean follow-up times of the study and control groups were 3.4 and 3.9 years, respectively. The study group showed no significant differences in clinical findings, lateral joint space narrowing on radiograph, and coronal extrusion on MRI as compared with the control group, whereas sagittal extrusion on MRI progressed significantly in the study group (1.2 ± 1.5 mm vs 0.32 ± 1.0 mm, P < .001). Eighteen patients (60%) obtained complete healing; 9 (30%) showed partial healing; and 3 (10%) failed to heal on second-look arthroscopy. Changes of chondral status in the femoral condyle showed no significant difference between the groups (P = .29). However, chondral status of the lateral tibial plateau worsened significantly in the study group (P = .0011).

CONCLUSION

The clinical and radiographic outcomes after repair of radial/flap tears of the posterior horn of the LM as combined with anatomic ACLR were successful and comparable with those after isolated ACLR without any other injuries at a mean postoperative follow-up of 3.4 years, except for sagittal extrusion on MRI. Chondral lesions of the lateral tibial plateau deteriorated regardless of meniscal healing at 2 years postoperatively. Surgeons should keep in mind that chondral injuries might progress over the midterm.

In vivo assessment of extracellular pH of joint tissues using acidoCEST-UTE MRI

Background

Degradation of cartilage and meniscus may be mediated by changes in extracellular pH. The purpose of this study was to optimize saturation powers used with the acidoCEST magnetic resonance imaging (MRI) technique with a 3D ultrashort echo time readout (acidoCEST-UTE) and to demonstrate feasibility of the method for measuring pH in cartilage and meniscus in vivo.

Methods

Magnetization transfer ratio asymmetry and ratio of radiofrequency (RF) power mismatch at different powers were evaluated in cartilage and meniscus tissue phantoms for iopamidol and iohexol. Using optimized RF powers, the acidoCEST-UTE MRI sequence was used to assess pH of joint fluid and tissues in four patients after direct intra-articular administration of iodinated contrast.

Results

In the phantoms, the ratio of powers 0.54/1.10 µT showed the strongest correlation with pH. In vivo acidoCEST-UTE pH measurements of intra-articular fluid were similar to electrode measurements of the contrast agent (7.22 vs. 7.1 for iopamidol, respectively; 7.65 vs. 7.5 for iohexol, respectively). As measured with the acidoCEST-UTE technique, overall mean cartilage pH was significantly lower than overall mean meniscus pH (6.60 vs. 6.72, respectively; P=0.043).

Conclusions

AcidoCEST-UTE MRI after direct intra-articular administration of either iopamidol or iohexol can be used to measure cartilage and meniscus pH in vivo.

Arthroscopic Medial Meniscal Transplant Using Multiple Fixation Techniques

The critical role of the meniscus in the biomechanics of the knee and articular cartilage preservation has led to an increased awareness of the importance of the meniscus. Meniscal allograft transplantation is a challenging surgical intervention that is saved as a last resort for patients who meet stringent criteria for salvage from meniscal deficiency. Proper arthroscopic implantation of a meniscal allograft takes precision and implementation of multiple fixation techniques to obtain a successful outcome.

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.