Ligament Constructs Research Articles

Research Hotspots and Trends Analysis of Patellar Instability: A Bibliometric Analysis from 2001 to 2021.

BackgroundPatellar instability is a common multifactorial disease in orthopedics, which seriously affects the quality of life. Because of the unified pathogeny, diagnosis and treatment, patellar instability has gradually attracted the interest of more scholars these years, resulting in an explosive growth in the research output. This study aims to summarize the knowledge structure and development trend in the field from the perspective of bibliometrics.MethodsThe data of articles and reviews on patellar instability was extracted from the Web of Science database. The Microsoft Excel, R-bibliometrix, CiteSpace, VOSviewer, Pajek software are comprehensively used to scientifically analyze the data quantitatively and qualitatively.ResultsTotally, 2,155 papers were identified, mainly from North America, Western Europe and East Asia. Until December 31, 2021, the United States has contributed the most articles (1,828) and the highest total citations (17,931). Hospital for Special Surgery and professor Andrew A Amis are the most prolific institutions and the most influential authors respectively. Through the analysis of citations and keywords based on a large number of literatures, “medial patellofemoral ligament construction”, “tibial tubercle-trochlear groove (TT-TG) distance”, “epidemiological prevalence”, “multifactor analysis of etiology, clinical outcome and radiographic landmarks “ were identified to be the most promising research directions.ConclusionsThis is the first bibliometric study to comprehensively summarize the research trend and development of patellar instability. The result of our research provides the updated perspective for scholars to understand the key information in this field, and promote future research to a great extent.

Suture Tape Augmentation in Lateral Ankle Ligament Surgery: Current Concepts Review.

Chronic lateral ankle instability (CLAI) is a condition that is characterized by persistent disability and recurrent ankle sprains while encompassing both functional and mechanical (laxity) instability. Failure of conservative treatment for CLAI often necessitates operative intervention to restore the stability of the ankle joint. The traditional or modified Broström techniques have been the gold standard operative approaches to address CLAI with satisfactory results; however, patients with generalized ligament laxity (GLL), prior unsuccessful repair, high body mass index, or high-demand athletes may experience suboptimal outcomes. Synthetic ligament constructs have been tested as an adjunct to orthopedic procedures to reinforce repaired or reconstructed ligaments or tendons with the hope of early mobilization, faster rehabilitation, and long-term prevention of instability. Suture tape augmentation is useful to address CLAI. Multiple operative techniques have been described. Because of the heterogeneity among the reported techniques and variability in postoperative rehabilitation protocols, it is difficult to evaluate whether the use of suture tape augmentation provides true clinical benefit in patients with CLAI. This review aims to provide a comprehensive outline of all the current techniques using suture tape augmentation for treatment of CLAI as well as present recent research aimed at guiding evidence-based protocols.

Using arthroscopy combined with fluoroscopic technique for accurate location of the bone tunnel entrance in chronic ankle instability treatment

BackgroundMinimally invasive reconstruction techniques are used for anatomical ligament construction of the lateral collateral ligament complex of the ankle, but the two key elements, the bone tunnel and the appropriate graft tension, for the identification of the anatomic location during the surgery are not clearly stated.MethodsThe patients with chronic ankle instability who received arthroscopic anatomic lateral ligament complex reconstruction were retrospectively analyzed. The anatomical location of the bone tunnel was performed under arthroscopy combined with fluoroscopy for accurate location of the bone tunnel entrance. The graft tension and routing were controlled under arthroscopic visualization. The clinical outcomes were assessed using the Karlsson-Peterson score, Sefton articular stability scale, and Visual Analogue Scale (VAS). The complications were recorded during the follow-up.ResultsA total of 18 patients were enrolled in this study. The mean follow-up was 33.33 ± 3.69 (range from 24 to 36) months. No patient had recurrence of ankle instability after the operation. According to the Sefton articular stability scale, 94.5% of the patients had excellent/good function. The mean value of the anterior drawer tests and the talar tilt angle examination were decreased. The mean of the Karlsson-Peterson score and the Visual Analogue Scale(VAS) score were both improved significantly.ConclusionsThe anatomic reconstruction of the ankle lateral ligament complex to treat chronic ankle instability using the arthroscopy combined with the fluoroscopic technique could improve the clinical functions, satisfaction, and reduced pain of patients.

Replication of the tensile behavior of knee ligaments using architected acrylic yarn

Knee ligament injury diagnosis is achieved by a comparison between the laxity levels sensed by a clinician in the injured and healthy limb. This is a difficult-to-learn task that requires hands-on practice to achieve proficiency. The inclusion of a physical knee simulator with biomechanically realistic passive components such as knee ligaments could provide consistent training for medical students and lead to improved care for knee injury patients. In this study, we developed a material construct that is both adaptable to a physical knee model and capable of replicating the non-linear mechanical behavior of knee ligaments with the use of helically arranged acrylic yarn. The microstructure of four different types of acrylic yarn were measured and then tested under uniaxial tension. While the fiber twist angle was similar amongst the four yarn types (range = 17.9–18.8°), one yarn was distinct with a low ply twist angle (15.2 ± 1.6°) and high packing fraction (Φ=0.32±0.08). These microstructural differences yielded a lower toe length and higher stiffness and best corresponded to ligament mechanical behavior. We then made looped-yarn constructs to modulate the sample's toe length and stiffness. We found that the load-displacement curve of the construct can be tuned by changing the loop length and loop number of the looped-yarn constructs, matching the load-displacement curve of specific knee ligaments. This study shows how spun yarn can be used to replicate the mechanical behavior of knee ligaments, creating synthetic ligament constructs that could enable the construction of biomechanically realistic joints.

Early Outcomes of Adolescent ACL Reconstruction With Hybrid Hamstring Tendon Autograft-Allograft Versus Hamstring Tendon Autograft Alone.

Background:Small-diameter semitendinosus-gracilis tendon autografts may be encountered intraoperatively during anterior cruciate ligament reconstruction (ACLR); these have been shown to be at increased risk of graft rupture. One option that surgeons have pursued to reduce the theoretical failure rate of these smaller-diameter grafts is augmenting them with allograft material, thereby forming a larger-diameter hybrid autograft-allograft construct.Purpose/Hypothesis:The purpose of this study was to compare outcomes in adolescent athletes of primary ACLR using a hybrid autologous hamstring tendon and soft tissue allograft construct versus ACLR using small-diameter hamstring tendon autograft. The hypothesis was that the hybrid hamstring autograft-allograft construct would provide superior short-term results.Study Design:Cohort study; Level of evidence, 3.Methods:We performed a retrospective analysis of 47 patients aged between 12 and 20 years who underwent hybrid graft ACLR (mean diameter, 9.1 mm) at a single institution. Electronic medical records including clinic notes, radiographic images, operative notes, and pathology reports were reviewed for study analysis. A control group of 64 patients who underwent small-diameter hamstring reconstruction (mean diameter, 7.1 mm) without allograft supplementation was compiled. Corresponding clinical, radiographic, and surgical characteristics were collected for the control group to allow for comparative analysis.Results:Mean follow-up was 2.7 years for the hybrid cohort and 2.3 years for the control group. Despite a significantly larger mean graft diameter in the hybrid group as compared with the control group (P < .001), no significant difference in retear rate was seen between cohorts (hybrid, 9%; control, 13%; P = .554). Patients with hybrid anterior cruciate ligament constructs also underwent a comparable number of reoperations overall (P = .838). Functionally, all patients with adequate follow-up returned to sports, with no significant difference in time to return to sports between the groups (P = .213). Radiographically, hybrid graft constructs did not undergo a significantly larger degree of tunnel lysis (P = .126).Conclusion:A cohort of adolescents with hybrid anterior cruciate ligament grafts was shown to have retear rates and overall clinical results comparable with those of a control group that received small-diameter hamstring tendon autografts alone.

Mesenchymal Stem Cells in BTB allograft ACL reconstruction:A Prospective Randomized Controlled Trial

Biologic adjuncts have shown promise in improving clinical outcomes following ACL reconstruction (ACLR). Post-operative ligament construct healing is a slow process that involves graft incorporation into bone tunnel sites and intra-articular graft ligamentization, during which failure load and stiffness of grafts decreases. Radiologic imaging has been shown to correspond with histological changes related to the ligamentization process (Hakozaki et al.). The purpose of this study is to evaluate the effects of bone marrow-aspirate concentrate (BMAC), containing mesenchymal stem cells (MSCs), on graft healing, maturation, and integration in patients, as well as patient reported outcome measures (PROMs), undergoing ACL reconstruction with bone-patellar tendon-bone (BTB) allografts. : IRB approval was obtained for a single-blinded randomized controlled trial on patients undergoing ACLR utilizing BTB allografts. Patients were randomized to receive either MSC injection into the ACL allograft or a sham incision with no BMAC harvest or graft injection. Bone marrow aspirate was harvested from the anterior superior iliac crest and concentrated via centrifuge. A minimum of 1.25mL of BMAC was injected into the tendinous/ligamentous portion of the BTB allograft at proximal, middle, and distal sites, with 0.5 mL reserved for post-operative ELISA assay and receptor testing for validation of MSCs within the BMAC harvest. Post-operatively, patients underwent identical standard, accelerated rehabilitation protocols. Outcomes were collected at 6 weeks, 3 months, 6 months, 9 months, 12 months, and 24 months. Knee range of motion, pivot-shift test, anterior-posterior translation, and patient reported outcomes using the KOOS Jr, IKDC, Lysholm surveys, and PROMIS scores including physical function, pain interference, and depression were assessed at the above time points. MRI was performed at 3 months and 9 months. The T2-weighted MRI Signal Intensity Ratio (SIR) of the reconstructed ACL was calculated and standardized to the intensity of the PCL by a musculoskeletal radiologist. A total of 60 patients have been enrolled (54% female, 57% BMAC). The mean age for BMAC and control groups was 34.9 and 35.8, respectively (p=0.7). Mean graft soaking time was 15.9 minutes. Mean time from injury to surgery was 3.7±3.7 months for control and 6.8±14.6 months for BMAC patients (p=0.305). Signal intensity ratios at 3 months revealed significant improvement in the BMAC cohort as compared to control (3.47 and 1.78, respectively, p<0.05). Analysis of secondary clinical outcomes demonstrated that the BMAC cohort significantly outperformed control in degrees of flexion (133º vs. 128º, p=0.02), International Knee Documentation Committee (IKDC) score (64.2 vs. 61.7, p=0.04), and VR12 Mental Health (57.0 vs. 54.7, p=0.002) at 9 months postoperatively. MSC injection into BTB ACL allograft reconstructions demonstrated significantly superior signal intensity ratio on radioimaging during the early ligamentization process. We also observed improved PROMs during the early post-operative period in patients receiving BMAC. This study provides a basis and rationale for continued investigation and application of biologic augmentation of ACLR allograft constructs. Future studies may further elucidate the impact of BMAC on the ligamentization process, clinical outcomes, and PROMs.

The Age of hMSC Donor Affects Biomechanical Properties of Tissue Engineered Ligament Constructs

Anterior cruciate ligament (ACL) tears are a major orthopedic challenge. Based on an incidence of 200,000 ACL repairs per year in the United States, the associated cost is in excess of $4 billion annually. Current ACL reconstruction commonly involves the use of allogenic or autogenic tendon grafts. Outcomes for ACL reconstruction with these techniques are limited by graft availability, donor site morbidity, disease transmission, and incomplete integration of native tissue within the surgically created bone tunnel. Thus, there is a demand for alternative tissue sources for ACL reconstruction. Using human derived mesenchymal stem cells (hMSC) as a starting material, we have successfully fabricated scaffold‐less ligament grafts that form their own extracellular matrix and have used these grafts for ACL reconstruction in a sheep model. To better understand the mechanism of graft development during our fabrication process, hMSCs were cultured and harvested at: Day 0 (initial plating), Day 4 (growth phase), Day 8 (differentiation phase), and Day 12 (3‐D construct) for qPCR analysis of bone and ligament markers. At day 15, 3‐D constructs were tested for biomechanics and histology (Fig. 1). The biomechanics data indicated two significantly different cohorts (n&gt;3 per donor per time point) that could be explained by age (young vs. old). In the young cohort (23–25y), the mean tangent modulus of the engineered ligament was significantly stiffer at 19.0 ± 3.2 kPa compared to the old cohort (33–43 y) at 8.7 ± 1.01 kPa. Average gene expression of ligament markers relative to GAPDH were analyzed via qPCR at defined time points during fabrication. We used a combination of gene targets (Collagen 1, Collagen 3, Tenascin C, and Scleraxis) to confirm commitment of the MSCs toward a ligament lineage and to determine any age‐related differences in gene expression. Compared to undifferentiated hMSCs (Day 0), the young cohort showed significantly increased expression of ligament markers Col‐1 &amp; Ten‐C by Day 4, and Col‐3 by Day 8. The old cohort showed an upward trend in the expression of Col‐1 and TenC, but did not reach significance at any time point, compared to age‐matched and undifferentiated hMSCs. Lastly, both the old and young cohort peaked in expression levels of Scleraxis at day 4, followed by a decline (Fig. 2). Additionally, we assessed the presence of collagen in the fully formed constructs with Picrosirius red staining. The images confirm that collagen was present in the constructs at 72 hours following monolayer roll up and there appears to be, qualitatively, less collagen presence in the construct cross sections fabricated from the cells or the 43 y.o donor compared to the constructs fabricated using cells from the 22 y.o donor. In addition, there is an increase in CSA surface area of dense collagen bands in the constructs derived from the cells of young donors compared to the constructs from the older cohort. Based on these data, we conclude that the use of younger donor cells will yield a stiffer and more robust ligament constructs due to the increased generation of ECM. In conclusion, constructs fabricated from the cells of younger donors were stiffer, had collagen deposition, and had earlier expression of ligament markers, all of which will enhance graft effectiveness and clinical outcomes.Figure 1Figure 2

Biomechanical comparison of four prosthetic ligament repair techniques for tarsal medial collateral ligament injury in dogs

To compare joint stability and ultimate strength among 4 prosthetic ligament constructs for repair of tarsal medial collateral ligament (MCL) injury in dogs. 13 canine cadavers (26 hind limbs). Each limb was stripped of all soft tissues except those associated with the tarsal joint and assigned to 1 of 4 prosthetic ligament constructs. The AN construct consisted of 3 bone anchors connected with monofilament nylon suture. The AU construct consisted of low-profile suture anchors connected with multifilament ultrahigh-molecular-weight polyethylene (UHMWPE) suture. The TN and TU constructs involved the creation of 3 bone tunnels and use of nylon or UHMWPE suture, respectively. Each limb underwent biomechanical testing before and after MCL transection and before and after cyclic range-of-motion testing following completion of the assigned construct. Tarsal joint stability (extent of laxity) was assessed with the joint in each of 3 positions (75°, 135°, and 165°). After completion of biomechanical testing, each limb was tested to failure to determine the ultimate strength of the construct. Relative to intact tarsal joints, joint laxity was significantly increased following completion of all 4 constructs. Construct type was not associated with the magnitude of change in joint laxity. Ultimate strength was greatest for the UHMWPE-suture constructs. Results indicated that all 4 constructs effectively stabilized MCL-deficient tarsal joints. Implants used for the TU, TN, and AU constructs had a lower profile than those used for the AN construct, which may be clinically advantageous. In vivo studies are warranted.

No effectiveness of anticoagulants for thromboprophylaxis after non-major knee arthroscopy: a systemic review and meta-analysis of randomized controlled trials.

Arthroscopic knee surgery is the most commonly performed orthopedic procedure worldwide and whether thromboprophylaxis should be undertaken after knee arthroscopy is still controversial. To evaluate the efficacy of thromboprophylaxis for deep venous thrombosis (DVT) and venous thromboembolism (VTE) after knee arthroscopic surgery. A meta-analysis was conducted using data from eight randomized trials (4148 patients) to compare thromboprophylaxis with placebo or no prophylactic treatment in patients undergoing knee arthroscopy. The benefits and harms of thromboprophylaxis were evaluated, including the incidence of asymptomatic DVT, symptomatic VTE, pulmonary embolism and anti-coagulation related adverse events. Thromboprophylaxis significantly decreased the incidence of DVT (95% CI 0.07-0.64, P = 0.006) and symptomatic VTE in patients undergoing knee arthroscopy (95% CI 0.23-0.76, P = 0.004), but not significantly decreased the incidence of pulmonary embolism (n.s.). Regarding to non-major knee arthroscopy surgery (simple surgical procedures without ligament reconstruction), no significant difference of the incidence of DVT or symptomatic VTE was noted between thromboprophylactic group and control group (n.s.). Thromboprophylactic treatment showed higher incidence rate of anti-coagulation related adverse events compared with the control group (95% CI 1.12-1.90, P = 0.005). There was no significant difference of the incidence of clinically relevant major bleeding between the two groups (n.s.). This meta-analysis indicates no effectiveness of thromboprophylaxis for preventing DVT or symptomatic VTE in patients undergoing non-major knee arthroscopy. Regarding to patient undergoing knee ligament construction, the thromboprophylactic strategy should mainly take into account the patient's risk factors.

Treatment of Ligament Constructs with Exercise-conditioned Serum: A Translational Tissue Engineering Model

In vitro experiments are essential to understand biological mechanisms; however, the gap between monolayer tissue culture and human physiology is large, and translation of findings is often poor. Thus, there is ample opportunity for alternative experimental approaches. Here we present an approach in which human cells are isolated from human anterior cruciate ligament tissue remnants, expanded in culture, and used to form engineered ligaments. Exercise alters the biochemical milieu in the blood such that the function of many tissues, organs and bodily processes are improved. In this experiment, ligament construct culture media was supplemented with experimental human serum that has been 'conditioned' by exercise. Thus the intervention is more biologically relevant since an experimental tissue is exposed to the full endogenous biochemical milieu, including binding proteins and adjunct compounds that may be altered in tandem with the activity of an unknown agent of interest. After treatment, engineered ligaments can be analyzed for mechanical function, collagen content, morphology, and cellular biochemistry. Overall, there are four major advantages versus traditional monolayer culture and animal models, of the physiological model of ligament tissue that is presented here. First, ligament constructs are three-dimensional, allowing for mechanical properties (i.e., function) such as ultimate tensile stress, maximal tensile load, and modulus, to be quantified. Second, the enthesis, the interface between boney and sinew elements, can be examined in detail and within functional context. Third, preparing media with post-exercise serum allows for the effects of the exercise-induced biochemical milieu, which is responsible for the wide range of health benefits of exercise, to be investigated in an unbiased manner. Finally, this experimental model advances scientific research in a humane and ethical manner by replacing the use of animals, a core mandate of the National Institutes of Health, the Center for Disease Control, and the Food and Drug Administration.

Treatment of Ligament Constructs with Exercise-conditioned Serum: A Translational Tissue Engineering Model.

In vitro experiments are essential to understand biological mechanisms; however, the gap between monolayer tissue culture and human physiology is large, and translation of findings is often poor. Thus, there is ample opportunity for alternative experimental approaches. Here we present an approach in which human cells are isolated from human anterior cruciate ligament tissue remnants, expanded in culture, and used to form engineered ligaments. Exercise alters the biochemical milieu in the blood such that the function of many tissues, organs and bodily processes are improved. In this experiment, ligament construct culture media was supplemented with experimental human serum that has been 'conditioned' by exercise. Thus the intervention is more biologically relevant since an experimental tissue is exposed to the full endogenous biochemical milieu, including binding proteins and adjunct compounds that may be altered in tandem with the activity of an unknown agent of interest. After treatment, engineered ligaments can be analyzed for mechanical function, collagen content, morphology, and cellular biochemistry. Overall, there are four major advantages versus traditional monolayer culture and animal models, of the physiological model of ligament tissue that is presented here. First, ligament constructs are three-dimensional, allowing for mechanical properties (i.e., function) such as ultimate tensile stress, maximal tensile load, and modulus, to be quantified. Second, the enthesis, the interface between boney and sinew elements, can be examined in detail and within functional context. Third, preparing media with post-exercise serum allows for the effects of the exercise-induced biochemical milieu, which is responsible for the wide range of health benefits of exercise, to be investigated in an unbiased manner. Finally, this experimental model advances scientific research in a humane and ethical manner by replacing the use of animals, a core mandate of the National Institutes of Health, the Center for Disease Control, and the Food and Drug Administration.

The effect of anterior longitudinal ligament resection on lordosis correction during minimally invasive lateral lumbar interbody fusion: Biomechanical and radiographic feasibility of an integrated spacer/plate interbody reconstruction device

BackgroundLateral lumbar interbody fusion is powerful for correcting degenerative conditions, yet sagittal correction remains limited by anterior longitudinal ligament tethering. Although lordosis has been restored via ligament release, biomechanical consequences remain unknown. Investigators examined radiographic and biomechanical of ligament release for restoration of lumbar lordosis. MethodsSix fresh-frozen human cadaveric spines (L3–S1) were tested: (Miller et al., 1988) intact; (Battie et al., 1995) 8mm spacer with intact anterior longitudinal ligament; (Cho et al., 2013) 8mm spacer without intact ligament following ligament resection; (Galbusera et al., 2013) 13mm lateral lumbar interbody fusion; (Goldstein et al., 2001) integrated 13mm spacer. Focal lordosis and range of motion were assessed by applying pure moments in flexion-extension, lateral bending, and axial rotation. FindingsCadaveric radiographs showed significant improvement in lordosis correction following ligament resection (P<0.05). The 8mm spacer with ligament construct provided greatest stability relative to intact (P>0.05) but did little to restore lordosis. Ligament release significantly destabilized the spine relative to intact in all modes and 8mm with ligament in lateral bending and axial rotation (P<0.05). Integrated lateral lumbar interbody fusion following ligament resection did not significantly differ from intact or from 8mm with ligament in all testing modes (P>0.05). InterpretationLordosis corrected by lateral lumbar interbody fusion can be improved by anterior longitudinal ligament resection, but significant construct instability and potential implant migration/dislodgment may result. This study shows that an added integrated lateral fixation system can significantly improve construct stability. Long-term multicenter studies are needed.

Electrical stimulation of somatic human stem cells mediated by composite containing conductive nanofibers for ligament regeneration

One of the advances in the field of biomedical nanotechnology, is conductive nanofiber fabrication and the discovery of its applications. Biocompatible flexible nanofibers that have a good biocompatibility, mechanical properties and morphology. Poly (3, 4-ethylene dioxythiophene) (PEDOT) is a conductive polymer that has recently been used in medical applications. In this study, the electrospinning technique and vapor phase polymerization combination method with freeze drying was used to produce Silk fibroin/PEDOT/Chitosan nanocomposite scaffold. The aim of our study was to develop a ligament construct of PEDOT/Silk bilayer nanofibrous scaffold, to mimic the aligned collagen fiber bundles and Chitosan sponge coating was done on these fibrous scaffolds, to mimic the glycosaminoglycans of ECM sheath. The developed constructs were characterized. The unrestricted somatic human stem cells (USSC), were cultured on the scaffold. Then, the effect of applying DC electric pulses to cells cultured on polymer was assessed. Cellular function was actively exhibited in scaffold with electrical induction, as evident by the high expression of collagen I, collagen III, decorin, biglycan and aggrecan genes. Novel scaffold plus electrical stimulation shows facilitating cell seeding and promoting cell proliferation, differentiation. This composites can be used in this new field for stem cells differentiation to target tissues.

Combining electrospinning and cell sheet technology for the development of a multiscale tissue engineered ligament construct (TELC).

Ligament tissue rupture is a common sport injury. Although current treatment modalities can achieve appropriate reconstruction of the damaged ligament, they present significant drawbacks, mostly related to reduced tissue availability and pain associated with tissue harvesting. Stem cell based tissue regeneration combined with electrospun scaffolds represents a novel treatment method for torn ligaments. In this study, a low fiber density polycaprolactone (PCL) electrospun mesh and sheep mesenchymal stem cells (sMSCs) were used to develop tissue engineered ligament construct (TELC) in vitro. The assembly of the TELC was based on the spontaneous capacity of the cells to organize themselves into a cell sheet once seeded onto the electrospun mesh. The cell sheet matured over 4 weeks and strongly integrated with the low fiber density electrospun mesh which was subsequently processed into a ligament-like bundle and braided with two other bundles to develop the final construct. Live/dead assay revealed that the handling of the construct through the various phases of assembly did not cause significant difference in viability compared to the control. Mechanical evaluation demonstrated that the incorporation of the cell sheet into the braided construct resulted in significantly modifying the mechanical behavior. A stress/displacement J-curve was observed for the TELC that was similar to native ligament, whereas this particular feature was not observed in the non-cellularized specimens. The regenerative potential of the TELC was evaluated ectopically in immunocompromized rats, compared to non cellularized electrospun fiber mesh and this demonstrated that the TELC was well colonized by host cells and that a significant remodelling of the implanted construct was observed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 399-409, 2018.

The exercise-induced biochemical milieu enhances collagen content and tensile strength of engineered ligaments.

Exercise stimulates a dramatic change in the concentration of circulating hormones, such as growth hormone (GH), but the biological functions of this response are unclear. Pharmacological GH administration stimulates collagen synthesis; however, whether the post-exercise systemic milieu has a similar action is unknown. We aimed to determine whether the collagen content and tensile strength of tissue-engineered ligaments is enhanced by serum obtained post-exercise. Primary cells from a human anterior cruciate ligament (ACL) were used to engineer ligament constructs in vitro. Blood obtained from 12 healthy young men 15 min after resistance exercise contained GH concentrations that were ∼7-fold greater than resting serum (P < 0.001), whereas IGF-1 was not elevated at this time point (P = 0.21 vs. rest). Ligament constructs were treated for 7 days with medium supplemented with serum obtained at rest (RestTx) or 15 min post-exercise (ExTx), before tensile testing and collagen content analysis. Compared with RestTx, ExTx enhanced collagen content (+19%; 181 ± 33 vs. 215 ± 40 μg per construct P = 0.001) and ligament mechanical properties - maximal tensile load (+17%, P = 0.03 vs. RestTx) and ultimate tensile strength (+10%, P = 0.15 vs. RestTx). In a separate set of engineered ligaments, recombinant IGF-1, but not GH, enhanced collagen content and mechanics. Bioassays in 2D culture revealed that acute treatment with post-exercise serum activated mTORC1 and ERK1/2. In conclusion, the post-exercise biochemical milieu, but not recombinant GH, enhances collagen content and tensile strength of engineered ligaments, in association with mTORC1 and ERK1/2 activation.

Enhancing engineered ligament strength using a multi-strand approach.

Ligaments have a poor capacity for repair and options for developing engineered replacements are of significant interest. We have previously reported the creation of an engineered ligament using a cellular fibrin gel1. While these ligaments have a composition similar to native tissue, they can only withstand low loads under tension (~0.2N) and are, at present, too weak to withstand in vivo loads. This study aimed to investigate methods to augment the mechanical properties of engineered ligaments using a multi-strand approach. Individual ligament constructs (LC) were made using 2 silk sutures pinned to a 35mm Sylgard-coated Petri dish. A fibrin gel was made around the sutures using 50U/ml thrombin and 20mg/ml fibrinogen in growth media. 100K fibroblasts were seeded on the gel, incubated at 37°C and fed every 2-3days with DMEM +250µM Ascorbic Acid (AA) and 50µM Proline (P). Formation of multi-stand LC began after 3 weeks of formation of the original single-stranded constructs (SS). SS were grouped together ...

Allogeneic versus autologous derived cell sources for use in engineered bone-ligament-bone grafts in sheep anterior cruciate ligament repair.

The use of autografts versus allografts for anterior cruciate ligament (ACL) reconstruction is controversial. The current popular options for ACL reconstruction are patellar tendon or hamstring autografts, yet advances in allograft technologies have made allogeneic grafts a favorable option for repair tissue. Despite this, the mismatched biomechanical properties and risk of osteoarthritis resulting from the current graft technologies have prompted the investigation of new tissue sources for ACL reconstruction. Previous work by our lab has demonstrated that tissue-engineered bone-ligament-bone (BLB) constructs generated from an allogeneic cell source develop structural and functional properties similar to those of native ACL and vascular and neural structures that exceed those of autologous patellar tendon grafts. In this study, we investigated the effectiveness of our tissue-engineered ligament constructs fabricated from autologous versus allogeneic cell sources. Our preliminary results demonstrate that 6 months postimplantation, our tissue-engineered auto- and allogeneic BLB grafts show similar histological and mechanical outcomes indicating that the autologous grafts are a viable option for ACL reconstruction. These data indicate that our tissue-engineered autologous ligament graft could be used in clinical situations where immune rejection and disease transmission may preclude allograft use.

Fresh Versus Frozen Engineered Bone–Ligament–Bone Grafts for Sheep Anterior Cruciate Ligament Repair

Surgical intervention is often required to restore knee instability in patients with anterior cruciate ligament (ACL) injury. The most commonly used grafts for ACL reconstruction are tendon autografts or allografts. These current options, however, have shown failure rates requiring revision and continued instability in the long term. The mismatched biomechanical properties of the current tendon grafts compared with native ACL tissue are thought to contribute to these poor outcomes and potential risk of early onset osteoarthritis. As a possible solution to these issues, our laboratory has fabricated tissue-engineered ligament constructs that exhibit structural and functional properties similar to those of native ACL tissue after 6 months implantation. In addition, these tissue-engineered grafts achieve vascular and neural development that exceeds those of patellar tendon grafts. However, the utility of our tissue-engineered grafts is limited by the labor-intensive method required to produce the constructs and the need to use the constructs fresh, directly from the cell culturing system. Ideally, these constructs would be fabricated and stored until needed. Thus, in this study, we investigated the efficacy of freezing our tissue-engineered constructs as a method of preservation before use for ACL reconstruction. We hypothesized that frozen constructs would have similar histological and biomechanical outcomes compared with our fresh model. Our results showed that 6 months postimplantation as an ACL replacement graft, both our tissue-engineered fresh and frozen grafts demonstrated similar mechanical and histological outcomes, indicating that freezing is a suitable method for preserving and storing our graft before ACL reconstruction. The ability to use frozen constructs significantly increases the versatility of our graft technology expanding the clinical utility of our graft.

Posterior Single-Incision Semitendinosus Harvest for a Quadrupled Anterior Cruciate Ligament Graft Construct: Determination of Graft Length and Diameter Based on Patient Sex, Height, Weight, and Body Mass Index

This study aimed to determine final graft length and diameter for a quadrupled semitendinosus anterior cruciate ligament (ACL) construct harvested from a single-incision posterior approach with correlation to preoperative patient variables of sex, height, weight, and body mass index (BMI). This was a retrospective review of data collected prospectively on 60 patients undergoing all-inside quadrupled semitendinosus autograft ACL reconstruction. The mean values of the final quadrupled constructs were a length of 70.3 mm and a diameter of 9.0 mm. Separated based on sex, female versus male final mean graft length was 68.1 mm versus 71.7 mm, and final mean graft diameter was 8.6 mm and 9.3 mm, respectively. In both sexes, patient height and weight were strongly correlated to final construct diameter (r= 0.60 and r= 0.56) and length (r= 0.47 and r= 0.44), respectively. A single-incision posterior harvest approach allowed for retrieval of semitendinosis tendon autografts of sufficient dimension to allow for construction of quadrupled ACL grafts of a diameter of 8 mm or more in 95% of cases. In addition, desired graft length was achieved in all cases. Graft dimensions had moderately strong direct correlations to patient height and weight, with significant size differences noted between the sexes. We believe this to be helpful data for surgeons who might consider performing a quadrupled semitendinosus autograft ACL reconstruction. Level IV, therapeutic case series.

A comparison of the extracellular matrix composition of tendon/ligament tissue and tissue engineered tendon and ligament construct

A comparison of the extracellular matrix composition of tendon/ligament tissue and tissue engineered tendon and ligament construct