Increased meniscal loading after anterior cruciate ligament transection in vivo: a longitudinal study in sheep

Hippo Signaling Modulates the Inflammatory Response of Chondrocytes to Mechanical Compressive Loading

Knee osteoarthritis (KOA) is a degenerative disease resulting from mechanical overload, where direct physical impacts on chondrocytes play a crucial role in disease development by inducing inflammation and extracellular matrix degradation. However, the signaling cascades that sense these physical impacts and induce the pathogenic transcriptional programs of KOA remain to be defined, which hinders the identification of novel therapeutic approaches. Recent studies have implicated a crucial role of Hippo signaling in osteoarthritis. Since Hippo signaling senses mechanical cues, we aimed to determine its role in chondrocyte responses to mechanical overload. Here we show that mechanical loading induces the expression of inflammatory and matrix-degrading genes by activating the nuclear factor-kappaB (NFκB) pathway in a Hippo-dependent manner. Applying mechanical compressional force to 3-dimensional cultured chondrocytes activated NFκB and induced the expression of NFκB target genes for inflammation and matrix degradation (i.e., IL1β and ADAMTS4). Interestingly, deleting the Hippo pathway effector YAP or activating YAP by deleting core Hippo kinases LATS1/2 blocked the NFκB pathway activation induced by mechanical loading. Consistently, treatment with a LATS1/2 kinase inhibitor abolished the upregulation of IL1β and ADAMTS4 caused by mechanical loading. Mechanistically, mechanical loading activates Protein Kinase C (PKC), which activates NFκB p65 by phosphorylating its Serine 536. Furthermore, the mechano-activation of both PKC and NFκB p65 is blocked in LATS1/2 or YAP knockout cells, indicating that the Hippo pathway is required by this mechanoregulation. Additionally, the mechanical loading-induced phosphorylation of NFκB p65 at Ser536 is blocked by the LATS1/2 inhibitor Lats-In-1 or the PKC inhibitor AEB-071. Our study suggests that the interplay of the Hippo signaling and PKC controls NFκB-mediated inflammation and matrix degradation in response to mechanical loading. Chemical inhibitors targeting Hippo signaling or PKC can prevent the mechanoresponses of chondrocytes associated with inflammation and matrix degradation, providing a novel therapeutic strategy for KOA.

Application of an indentation sensor for the arthroscopic measurement of articular cartilage stiffness

Direct measurement of cartilage stiffness provides useful clinical information and enables us to develop treatment strategies for patients. We applied an indentation sensor to evaluate cartilage stiffness under arthroscopic control. The purpose of this study was to validate the arthroscopic indentation sensor using cadaver knees and to measure cartilage stiffness in clinical cases. The stiffness of a material with known properties was measured at thicknesses from 2 mm to 10 mm with a 2-mm interval. This was repeated three times at each thickness to evaluate repeatability. The articular cartilage stiffness of the medial and lateral femoral condyles of five human cadaveric knees was measured. The sensor was inclined from 0° to 20° with 1° intervals. The stiffness value at each degree of inclination was compared to evaluate the acceptable measuring angle. Additionally, articular cartilage stiffness was measured in 23 adolescent and 11 adult patients under arthroscopy. Young's moduli of the material were 1.15-1.24 (mean 1.20) MPa. Inter-class correlation coefficients in repeated measurements using the material were 0.83-0.99. There were no differences in the cartilage stiffness between the medial and lateral femoral condyles of the cadaver knees. All condyles showed a nonlinear relationship between force and displacement. The force decreased in all condyles when the tip of the sensor system was tilted. The range of error was < 97.1% within 5° inclination. There was a moderate negative correlation between age and cartilage stiffness in adolescent patients, and a moderate positive correlation in adult patients. Since the sensor system is manually held during measurement, the validity and repeatability to assess material properties of the cartilage may be inaccurate. This study has proven that the instrument can measure the stiffness of joint cartilage reliably and is a useful clinical tool under arthroscopic control.

The Natural History of Medial Meniscal Tears in the ACL Deficient and ACL Reconstructed Rat Knee

OBJECTIVE

The process of anterior cruciate ligament (ACL) injury-induced meniscal tear formation is not fully understood. Clinical studies have shown that ACL reconstruction (ACLR) reduces the development of secondary meniscal tears, but it is difficult to gain insight into the protective effects of ACLR from clinical studies alone. Using rat ACL transection (ACLT) and ACLR models, we aimed to reveal (1) the formation process of meniscal tears secondary to ACLT and (2) the protective effects of ACLR on secondary meniscal tears.

DESIGN

ACLT surgery alone or with ACLR was performed on the knees of rats. Histomorphological and histopathological changes were examined in the posteromedial region of the meniscus in intact rats and in rats that received ACLT or ACLR up to 12 weeks postsurgery. In addition, anterior-posterior joint laxity was measured using the universal testing machine to evaluate the effects of ACLT and ACLR on joint laxity.

RESULTS

AAnterior-posterior laxity was significantly increased by ACLT compared to the intact knee. This ACLT-induced joint laxity was partially but significantly reduced by ACLR. Meniscal proliferation and hyaline cartilage-like tissue formation were detected in the medial meniscus at 4 weeks post-ACLT. At 12 weeks post-ACLT, hyaline cartilage-like tissue was replaced by ossicles and meniscal tears were observed. These ACLT-induced abnormalities were attenuated by ACLR.

CONCLUSIONS

Our results suggest that ACLT-induced joint laxity induces secondary medial meniscal tears through meniscal proliferation and ossicle formation via endochondral ossification. Joint re-stabilization by ACLR suppresses meniscal proliferation and ossicle formation and consequently prevents secondary meniscal tears.

Anterior Cruciate Ligament Reconstruction With Concomitant Meniscal Repair: Is Graft Choice Predictive of Meniscal Repair Success?

Background

When meniscal repair is performed during anterior cruciate ligament (ACL) reconstruction (ACLR), the effect of ACL graft type on meniscal repair outcomes is unclear.

Hypothesis

The authors hypothesized that meniscal repairs would fail at the lowest rate when concomitant ACLR was performed with bone--patellar tendon--bone (BTB) autograft.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients who underwent meniscal repair at primary ACLR were identified from a longitudinal, prospective cohort. Meniscal repair failures, defined as any subsequent surgical procedure addressing the meniscus, were identified. A logistic regression model was built to assess the association of graft type, patient-specific factors, baseline Marx activity rating score, and meniscal repair location (medial or lateral) with repair failure at 6-year follow-up.

Results

A total of 646 patients were included. Grafts used included BTB autograft (55.7%), soft tissue autograft (33.9%), and various allografts (10.4%). We identified 101 patients (15.6%) with a documented meniscal repair failure. Failure occurred in 74 of 420 (17.6%) isolated medial meniscal repairs, 15 of 187 (8%) isolated lateral meniscal repairs, and 12 of 39 (30.7%) of combined medial and lateral meniscal repairs. Meniscal repair failure occurred in 13.9% of patients with BTB autografts, 17.4% of patients with soft tissue autografts, and 19.4% of patients with allografts. The odds of failure within 6 years of index surgery were increased more than 2-fold with allograft versus BTB autograft (odds ratio = 2.34 [95% confidence interval, 1.12-4.92]; P = .02). There was a trend toward increased meniscal repair failures with soft tissue versus BTB autografts (odds ratio = 1.41 [95% confidence interval, 0.87-2.30]; P = .17). The odds of failure were 68% higher with medial versus lateral repairs (P < .001). There was a significant relationship between baseline Marx activity level and the risk of subsequent meniscal repair failure; patients with either very low (0-1 points) or very high (15-16 points) baseline activity levels were at the highest risk (P = .004).

Conclusion

Meniscal repair location (medial vs lateral) and baseline activity level were the main drivers of meniscal repair outcomes. Graft type was ranked third, demonstrating that meniscal repairs performed with allograft were 2.3 times more likely to fail compared with BTB autograft. There was no significant difference in failure rates between BTB versus soft tissue autografts.

Registration

NCT00463099 (ClinicalTrials.gov identifier).

Association of chemokine expression in anterior cruciate ligament deficient knee with patient characteristics: Implications for post-traumatic osteoarthritis

BACKGROUND

Stromal cell-derived factor-1a (SDF-1α) and high mobility group box chromosomal protein 1 (HMGB1) are chemokines that can drive post-traumatic osteoarthritis (PTOA) induced by anterior cruciate ligament (ACL) injury. However, the influence of patient characteristics on expression of those chemokines remains unclear. Our aim was to determine the relationship between chemokine expression in synovial fluid (SF) of the ACL-deficient (ACL-D) knee and patient characteristics including time from injury, sex, and age.

METHODS

SF samples were collected immediately prior to the first-time ACL reconstruction (ACLR) from 82 patients. Expression of SDF-1α and HMGB1 was measured with human-specific solid phase sandwich enzyme-linked immunosorbent assays. The expression levels between groups divided by time from injury, or age, or sex was compared using Student's t-test. The association of SDF-1α or HMGB1 levels with those variables was determined using regression analysis and Pearson product-moment correlation coefficient.

RESULTS

Regression and correlation analysis indicated significant correlation between SDF-1α expression and time from injury in the cohort (r = -0.266, P = 0.016, n = 82) and in females (r = -0.386, P = 0.024, n = 34). Significant correlation was also observed between SDF-1α expression and age in the cohort (r = -0.224, P = 0.043, n = 82) and in males (r = -0.289, P = 0.046, n = 48). No significant correlation between HMGB1 expression and patient characteristics was detected.

CONCLUSIONS

SDF-1α rather than HMGB1 might serve as a protein marker for monitoring the development of PTOA in the ACL-D knee, especially in female patients.

The ACL-deficient knee and the prevalence of meniscus and cartilage lesions: a systematic review and meta-analysis (CRD42017076897)

INTRODUCTION

The purpose of this systematic review and meta-analysis was to analyze and compare the rate of secondary meniscus and cartilage lesions diagnosed at different time points of ACL reconstruction.

MATERIALS AND METHODS

A systematic search for articles comparing the rate of secondary meniscus and cartilage lesions diagnosed at different time points of ACL reconstruction was performed. PubMed central was the database used for the literature review.

RESULTS

Forty articles out of 1836 were included. In 35 trials (88%), there was evidence of a positive correlation between the rate of meniscus and/or cartilage lesions and the time since ACL injury. This correlation was more evident for the medial meniscus in comparison with the lateral meniscus. In particular, a delay of more than 6 months was critical for secondary medial meniscus injuries [risk ratio 0.58 (95% CI 0.44-0.79)] and a delay of more than 12 months was critical for cartilage injuries [risk ratio 0.42 (95% CI 0.29-0.59)]. Additionally, there is evidence that the chance for meniscal repair decreases as the time since ACL rupture increases.

CONCLUSION

Chronic instability in the ACL-deficient knee is associated with a significant increase of medial meniscus injuries after 6 months followed by a significant increase of cartilage lesions after 12 months.

Double bundle anterior cruciate ligament reconstruction: Failure rate and patients-reported outcomes at 4-11 years of follow up

Background

Biomechanical studies have demonstrated that single bundle (SB) anterior cruciate ligament (ACL) reconstruction (SB-ACLr), which represents the gold standard for the management of ACL lesions, is not sufficient to completely restore the rotational stability and resistance to valgus stress of the knee.

Purpose

To evaluate the failure rate and patients reported outcomes at a long-term follow-up of double bundle anterior cruciate ligament reconstruction (DB-ACLr).

Study design

Retrospective cohort study.

Materials and methods

The database of arthroscopic DB-ACLr procedures performed from 2006 to 2015 at our Institution was retrospectively reviewed. Patients were screened for eligibility according to the following inclusion criteria: magnetic resonance imaging (MRI) evidence of anterior cruciate ligament (ACL) lesion, positive anterior drawer test and/or Lachman test; age ≤ 45 years at the time of surgery; DB-ACLr with autologous hamstrings, minimum follow up of 24 months. Patients were excluded if they presented associated lesions of the knee preoperatively or at the time of surgery, expect for meniscal lesions, or in case of inability to complete clinical questionnaires. Clinical outcomes were assessed at a mean follow up of 95.4 ± 21.9 months (range 51-129 months; median 98 months) using the Tegner-Lysholm score and the IKDC subjective score. Failures were defined as Tegner-Lysholm score ≤65 points, and were confirmed with MRI.

Results

58 (81.7%) male and 13 (18.3%) female patients (mean age 29.7 ± 7.8 years) were included in the study. 2 (2.8%, 95% CI 0.3-9.8%) patients had a failure of DB-ACLr both occurred after a sports trauma. The IKDC subjective score was statically better in patients younger than 30 years. Tegner-Lysholm and IKDC subjective score were statistically better in professional athletes and in patients with isolated medial or lateral meniscus lesion instead of combined medial and lateral meniscus lesion.

Conclusion

DB-ACLr technique provides excellent clinical results at a long term follow-up. Low failure rate and high percentage of return to sports participation at the same pre-injury level was found in our cohort of patients.

"Patient reported outcomes" following experimental surgery-using telemetry to assess movement in experimental ovine models

Many potential treatments for orthopedic disease fail at the animal to human translational hurdle. One reason for this failure is that the majority of pre-clinical outcome measurements emphasize structural changes, such as gross morphology and histology, and do not address pain or its alleviation, which is a key component of treatment success in man. With increasing emphasis on "patient reported outcome measurements (PROM)" in clinical practice, in this study we have used two different telemetric methods (geolocation and Fitbark activity trackers, Kansas City, MO) to measure movement behavior, i.e., an indirect PROM, in an ovine osteoarthritis induction and an osteochondral defect model performed in adult female Welsh Mountain sheep. This study demonstrates that both systems can be used to track movement and activity of experimental sheep before and after surgery and that the Geolocator system recorded a decrease in distance moved and activity at the end of the experimental period in both models. The Fitbark activity tracker also recorded significant alterations in movement behavior at the end of these studies and this method of recording showed a correlation between Fitbark data and radiography, macroscopic and histological scoring (well recognized outcome measurements), particularly in animals with large (10 mm) defects, i.e., more severe pathology. These results suggest that telemetry is able to track movement behavior in experimental sheep and that the methodology should be considered for inclusion in outcome measures in preclinical orthopedic research. © 2017 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:1498-1507, 2018.

Rise of the Pigs: Utilization of the Porcine Model to Study Musculoskeletal Biomechanics and Tissue Engineering During Skeletal Growth

Large animal models play an essential role in the study of tissue engineering and regenerative medicine (TERM), as well as biomechanics. The porcine model has been increasingly used to study the musculoskeletal system, including specific joints, such as the knee and temporomandibular joints, and tissues, such as bone, cartilage, and ligaments. In particular, pigs have been utilized to evaluate the role of skeletal growth on the biomechanics and engineered replacements of these joints and tissues. In this review, we explore the publication history of the use of pig models in biomechanics and TERM discuss interspecies comparative studies, highlight studies on the effect of skeletal growth and other biological considerations in the porcine model, and present challenges and emerging opportunities for using this model to study functional TERM.

Ethical use of animal models in musculoskeletal research

The use of animals in research is under increasing scrutiny from the general public, funding agencies, and regulatory authorities. Our ability to continue to perform in-vivo studies in laboratory animals will be critically determined by how researchers respond to this new reality. This Perspectives article summarizes recent and ongoing initiatives within ORS and allied organizations to ensure that musculoskeletal research is performed to the highest ethical standards. It goes on to present an overview of the practical application of the 3Rs (reduction, refinement, and replacement) into experimental design and execution, and discusses recent guidance with regard to improvements in the way in which animal data are reported in publications. The overarching goal of this review is to challenge the status quo, to highlight the absolute interdependence between animal welfare and rigorous science, and to provide practical recommendations and resources to allow clinicians and scientists to optimize the ways in which they undertake preclinical studies involving animals. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:740-751, 2017.

Use of pre-clinical surgically induced models to understand biomechanical and biological consequences of PTOA development

Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interventions to inhibit or prevent development of the disease. We believe that PTOA results from altered cartilage surface interactions where biological and biomechanical factors intersect, and mitigating acute joint inflammation may be critical to prolonging PTOA development. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:454-465, 2017.

Management of Anterior Cruciate Ligament Injury: What's In and What's Out?

Sports medicine physicians have a keen clinical and research interest in the anterior cruciate ligament (ACL). The biomechanical, biologic, and clinical data researchers generate, help drive injury management and prevention practices globally. The current concepts in ACL injury and surgery are being shaped by technological advances, expansion in basic science research, resurging interest in ACL preservation, and expanding efforts regarding injury prevention. As new methods are being developed in this field, the primary goal of safely improving patient outcomes will be a unifying principle. With this review, we provide an overview of topics currently in controversy or debate, and we identify paradigm shifts in the understanding, management, and prevention of ACL tears.

Kinematic outcomes following ACL reconstruction

Anterior cruciate ligament (ACL) reconstruction aims to restore the translational and rotational motion to the knee joint that is lost after injury. However, despite technical advancements, clinical outcomes are less than ideal, particularly in return to previous activity level. A major issue is the inability to standardize treatment protocols due to variations in materials and approaches used to accomplish ACL reconstruction. These include surgical techniques such as the transtibial and anteromedial portal methods that are currently under use and the wide availability of graft types that will be used to reconstruct the ACL. In addition, concomitant soft tissue injuries to the menisci and capsule are frequently present after ACL injury and, if left unaddressed, can lead to persistent instability even after the ACL has been reconstructed. Advances in the field of biomechanics that help to objectively measure motion of the knee joint may provide more precise data than current subjective clinical measurements. These technologies include extra-articular motion capture systems that measure the movement of the tibia in relation to the femur. With data gathered from these devices, a threshold for satisfactory knee stability may be established in order to correctly identify a successful reconstruction following ACL injury.

Abnormal Mechanical Loading Induces Cartilage Degeneration by Accelerating Meniscus Hypertrophy and Mineralization After ACL Injuries In Vivo

BACKGROUND

Although patients with an anterior cruciate ligament (ACL) injury have a high risk of developing posttraumatic osteoarthritis (PTOA), the role of meniscus hypertrophy and mineralization in PTOA after an ACL injury remains unknown.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine if menisci respond to abnormal loading and if an ACL injury results in meniscus hypertrophy and calcification. The hypotheses were that (1) abnormal mechanical loading after an ACL injury induces meniscus hypertrophy and mineralization, which correlates to articular cartilage damage in vivo, and (2) abnormal mechanical loading on bovine meniscus explants induces the overexpression of hypertrophic and mineralization markers in vitro.

STUDY DESIGN

Controlled laboratory study.

METHODS

In vivo guinea pig study (hypothesis 1): Three-month-old male Hartley guinea pigs (n = 9) underwent ACL transection (ACLT) on the right knee; the left knee served as the control. Calcification in the menisci was evaluated by calcein labeling 1 and 5 days before knee harvesting at 5.5 months. Cartilage and meniscus damage and mineralization were quantified by the Osteoarthritis Research Society International score and meniscus grade, respectively. Indian hedgehog (Ihh), matrix metalloproteinase-13 (MMP-13), collagen type X (Col X), progressive ankylosis homolog (ANKH), ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1), alkaline phosphatase (ALP), inorganic pyrophosphate (PPi), and inorganic phosphate (Pi) concentrations were evaluated by immunohistochemistry and enzyme-linked immunosorbent assay. In vitro bovine meniscus explant study (hypothesis 2): Bovine meniscus explants were subjected to 25% strain at 0.3 Hz for 1, 2, and 3 hours. Cell viability was determined using live/dead staining. The levels of mRNA expression and protein levels were measured using real-time quantitative reverse transcription polymerase chain reaction and Western blot after 24, 48, and 72 hours in culture. The conditioned medium was collected for sulfated glycosaminoglycan (GAG) release and Pi/PPi assay.

RESULTS

In vivo guinea pig study: Meniscus size and area as well as intensity of meniscus calcification were significantly increased in the ACLT group compared with the control group. Both calcified area and intensity were correlated with cartilage damage in the ACLT group (meniscus calcified area: r = 0.925, P < .0001; meniscus calcified intensity: r = 0.944, P < .0001). Ihh, MMP-13, Col X, ANKH, ENPP1, and ALP expression were increased in the ACLT group compared with the control group. The Pi level and Pi/PPi ratio increased by 63% and 42%, respectively, in the ACLT group compared with the control group. In vitro bovine meniscus explant study: Cell death was found in the superficial zone of the bovine meniscus explants after loading for 3 hours. The mRNA expression and protein levels of MMP-13, ANKH, ENPP1, and ALP were up-regulated in all 3-hour loaded samples. The Pi/PPi ratio and sulfated GAG content in the culture medium were increased in the 3-hour loaded group.

CONCLUSION

Meniscus hypertrophy and mineralization correlated to cartilage degeneration after ACL injuries.

CLINICAL RELEVANCE

The study data suggest that the suppression of meniscus hypertrophy and calcification may decrease the risk of PTOA after ACL injuries.