To address the current challenge of anterior cruciate ligament (ACL) reconstruction, this study is the first to fabricate a braided collagen rope (BCR) which mimics native hamstring for ACL reconstruction. The study aims to evaluate the biological and biomechanical properties of BCR both in vivo and vitro. Rabbit ACL reconstruction model using collagen rope and autograft (hamstring tendon) was conducted. The histological and biomechanical evaluations were conducted at 6-, 12-, 18, 26-week post-operation. In vitro study included cell morphology analysis, cell function evaluation and RNA sequencing of the tenocytes cultured on BCR. A cadaver study was also conducted to verify the feasibility of BCR for ACL reconstruction. BCR displays satisfactory mechanical strength similar to hamstring graft for ACL reconstruction in rabbit. Histological assessment showed BCR restore ACL morphology at 26 weeks similar to native ACL. The superior dynamic ligamentization in BCR over autograft group was evidenced by assessment of cell and collagen morphology and orientation. The in vitro study showed that the natural collagen fibres within BCR enables to signal the morphology adaptation and orientation of human tenocytes in bioreactor. BCR enables to enhance cell proliferation and tenogenic expression of tenocytes as compared to hydrolysed collagen. We performed an RNA-Sequencing (RNA-seq) experiment where RNA was extracted from tenocyte seeded with BCR. Analysis of enriched pathways of the up-regulated genes revealed that the most enriched pathways were the Hypoxia-inducible factor 1-alpha (HIF1A) regulated networks, implicating the possible mechanism BCR induced ACL regeneration. The subsequent cadaver study was conducted to proof the feasibility of BCR for ACL reconstruction. This study demonstrated the proof-of-concept of bio-textile braided collagen rope for ACL reconstruction, and the mechanism by which BCR induces natural collagen fibres that positively regulate morphology and function of tenocytes

The principal of “function priority, early rehabilitation, and return to sports” is now the goal for sports injury rehabilitation. Neuromuscular electrical stimulation for anterior cruciate ligament (ACL) reconstruction is a rising procedure for early rehabilitation. This paper systematically assessed the effects of neuromuscular electrical stimulation on postoperative ACL reconstruction to provide guidance for physiotherapist and patient when designing a suitable rehabilitation protocol. To evaluate the interventional outcomes of neuromuscular electrical stimulation following ACL reconstruction, we searched PubMed, EMbase, the Cochrane Library, Web of Science and CNKI to collect all randomized controlled trials (RCTs) comparing the effects with neuromuscular electrical stimulation and without intervention on rehabilitation after ACL reconstruction up to January 30, 2022. Two investigators independently performed literature screening, data extraction, bias assessment of risk, and used RevMan 5.3 software to conduct a meta-analysis. A total of six RCTs were included, and the results showed that the use of neuromuscular electrical stimulation after anterior cruciate ligament reconstruction significantly improved the International Knee Documentation Committee (IKDC) scores (MD 6.33, 95% CI [-0.43, 12.22]; I2 = 66%; p = 0.040), the Lysholm score (MD 7.94, 95% CI [6.49, 9.39]; I2 = 89%; p < 0.001), and the range of motion (ROM) (MD 9.99, 95% CI [7.97, 12.02]; I2 = 81%; p < 0.001) in the knees when compared to the control group without using neuromuscular electrical stimulation. Existing evidence show that neuromuscular electrical stimulation is beneficial for early rehabilitation after ACL reconstruction. The use of neuromuscular electrical stimulation is encouraged in the design of rehabilitation protocol. However, due to the limited number of RCT studies and the small sample size, further multi-center RCTs with more participants are needed for a higher-level evidence

Screw fixation is an established method for anterior cruciate ligament (ACL) reconstruction, although with a high rate of implant-related complications. An allograft system for implant fixation in ACL reconstruction, the Shark Screw ACL (surgebright GmbH) could overcome some of the shortcomings of bioabsorbable screws, such as foreign body reaction, need for implant removal and imaging artefacts. However, it needs to provide sufficient mechanical stability. Therefore, the aim of this study was to investigate the biomechanical stability, especially graft slippage, of the novel allograft system versus a conventional bioabsorbable interference screw (BioComposite Interference Screw; Arthrex Inc.) for tibial implant fixation in ACL reconstruction. Twenty-four paired human proximal tibiae (3 female, 9 male, 72.7 ± 5.6 years) underwent ACL reconstruction. The quadrupled semitendinosus and gracilis tendon graft were fixed in one specimen of each pair using the allograft fixation system Shak Screw ACL and the contralateral one using an interference screw. All specimens were cyclically loaded at 1 Hz with peak load levels monotonically increased from 50 N at a rate of 0.1 N/cycle until catastrophic failure. Relative movements of the graft versus the tibia were captured with a stereographic optical motion tracking system (Aramis SRX; GOM GmbH). The two fixation methods did not demonstrate any statistical difference in ultimate load at graft slippage (p = 0.24) or estimated survival at slippage (p = 0.06). Both, the ultimate load and estimated survival until failure were higher in the interference screw (p = 0.04, and p = 0.018, respectively). Graft displacement at ultimate load reached values of up to 7.2 mm (interference screw) and 11.3 mm (Shark Screw ACL). The allograft screw for implant fixation in ACL reconstruction showed similar behavior in terms of graft slippage compared to the conventional metal interference screw but underperformed in terms of ultimate load. However, the ultimate load may not be considered a direct indicator of clinical failure

Summary:. Hamstring tendons (HT) represent a widely used autograft for ACL reconstruction. Harvesting, processing and pretensioning procedures together with the time out of the joint could theoretically hamper tendon cells (TCs) viability. The authors hypothesize that HT cells are not impaired at the end of the surgical procedures and their tenogenic phenotype may be strongly improved by exposure to PEMF. Methods. Remnants of semitendinosus and gracilis tendons were collected at the end of the surgical procedures before skin closure from 15 healthy donors who underwent ACL reconstruction with autologous hamstring tendons. To isolate TCs, the tendon was minced and digested with 0.3 % type I collagenase and the nucleated cells were plated at a density 5x10E3 cells/cm2 and cultured in chamber slides in differentiation medium composed of DMEM + 5ng/ml basic fibroblast growth factor (b-FGF) for 7, 14, 21 days. The following cell cultures were set up:. -. TCs cultured with differentiation medium + exposure to PEMF 8 h/day (PEMF generator system IGEA, intensity of magnetic field = 1.5 mT, frequency = 75 Hz). -. TCs cultured with differentiation medium without exposure to PEMF. At day 0, day 7, day 14 and day 21, immunofluorescence analysis was performed to evaluate the expression of collagen type I, collagen type VI, scleraxis and PCNA (proliferative marker). Subsequently, tendon explant cultures were set up to verify, at day 21, explant viability and the expression of collagen type I, collagen type VI, beta-catenin and PCNA. Results. The TCs from the tendon fragments at the end of the ACL reconstruction were alive and they expressed markers of proliferation and tendon phenotype at the end of the culture periods. The TCs in the presence PEMF 8h/day showed greater production of collagen type I, collagen type VI and scleraxis than that of TCs cultured without PEMF (p<0,05): the expression of this markers increased from 7 to 21 days of culture. The expression of PCNA, in the presence of PEMF stimulus, was significantly lower (p<0,05) than that of TCs cultured without PEMF. A similar behavior was surprisingly observed in tendon explant cultures. Conclusions. Hamstring tendons used for ACL reconstruction are not simple autologous tenoconductive scaffold but are a biologic structure rich in progenitor cells that show tenogenic behavior. Their tenogenic phenotype may be strongly improved by exposure to PEMF. In a future clinical perspective, the postoperative use of PEMF could be used to enhance the ligamentization processes of autologous hamstring tendons, when used as autografts for ACL reconstructions

Following anterior cruciate ligament reconstruction (ACLR) using a semitendinosus (ST) autograft measures such as length, cross-sectional area, and volume may not fully describe the effects of tendon harvest on muscle morphology as these discrete measures cannot characterize three-dimensional muscle shape. This study aimed to determine between-limb ST shape similarity and regional morphology in individuals with a unilateral history of ACLR using a ST graft, and healthy controls. A secondary analysis of magnetic resonance imaging was undertaken from 18 individuals with unilateral history of ST ACLR and 18 healthy controls. ST muscles were manually segmented, and shape similarity were assessed between limbs and groups using Jaccard index (0-1) and Hausdorff distance (mm). ST length (cm), peak cross-sectional area (CSA) (cm. 2. ), and volume (cm. 3. ) was compared between surgically reconstructed and uninjured contralateral limbs, and between the left and right limbs of control participants with no history of injury. Cohen's d was reported as a measure of effect size. Compared to healthy controls, the ACLR group had significantly (p<0.001, d= −2.33) lower bilateral ST shape similarity. Furthermore, the deviation in muscle shape was significantly (p<0.001, d= 2.12) greater in the ACLR group. Within the ACLR group, maximum Hausdorff distance indicated ST from the ACLR limb deviated (23.1±8.68 mm) from the shape of the healthy contralateral ST, this was observed particularly within the distal region of the muscle. Compared to the uninjured contralateral limb and healthy controls, deficits in peak cross-sectional area and volume in ACLR group were largest in proximal (p<0.001, d= −2.52 to −1.28) and middle (p<0.001, d= −1.81 to −1.04) regions. Findings highlight morphological features in distal ST not identified by traditional discrete morphology measures. ST shape was most different in the distal region of the muscle, despite deficits in CSA and volume being most pronounced in proximal and middle regions. ST shape following ACLR may affect force transmission and distribution within the hamstrings and contribute to persistent deficits in knee flexor and internal rotator strength

The objective of this study was to analyze the biomechanical effect of an implanted ACL graft by determining the tunnel position according to the aspect ratio (ASR) of the distal femur during flexion-extension motion. To analyze biomechanical characteristics according to the ASR of the knee joint, only male samples were selected to exclude the effects of gender and 89 samples were selected for measurement. The mean age was 50.73 years, and the mean height was 165.22 cm. We analyzed tunnel length, graft bending angle, and stress of the graft according to tunnel entry position and aspect ratio (ratio of antero-posterior depth to medio-lateral width) of the articular surface for the distal femur during single-bundle outside-in anterior cruciate ligament reconstruction surgery. We performed multi-flexible-body dynamic analyses with wherein four ASR (98, 105, 111, and 117%) knee models. The various ASRs were associated with approximately 1-mm changes in tunnel length. The graft bending angle increased when the entry point was far from the lateral epicondyle and was larger when the ASR was smaller. The graft was at maximum stress, 117% ASR, when the tunnel entry point was near the lateral epicondyle. The maximum stress value at a 5-mm distance from the lateral epicondyle was 3.5 times higher than the 15-mm entry position and, the cases set to 111% and 105% ASR, showed 1.9 times higher stress values when at a 5-mm distance compared with a 15-mm distance. In the case set at 98% ASR, the low-stress value showed a without-distance difference from the lateral epicondyle. Our results suggest that there is no relationship between the ASR and femoral tunnel length, A smaller ASR causes a higher graft bending angle, and a larger ASR causes greater stress in the graft

Anterior cruciate ligament reconstruction (ACLR) using a semitendinosus (ST) autograft, with or without gracilis (GR), results in donor muscle atrophy and varied tendon regeneration. The effects of harvesting these muscles on muscle moment arm and torque generating capacity have not been well described. This study aimed to determine between-limb differences (ACLR vs uninjured contralateral) in muscle moment arm and torque generating capacity across a full range of hip and knee motions. A secondary analysis of magnetic resonance imaging was undertaken from 8 individuals with unilateral history of ST-GR ACLR with complete ST tendon regeneration. All hamstring muscles and ST tendons were manually segmented. Muscle length (cm), peak cross-sectional area (CSA) (cm. 2. ), and volume (cm. 3. ) were measured in ACLR and uninjured contralateral limbs. OpenSim was used to simulate and evaluate the mechanical consequences of changes in normalised moment arm (m) and torque generating capacity (N.m) between ACLR and uninjured contralateral limbs. Compared to uninjured contralateral limbs, regenerated ST tendon re-insertion varied proximal (+) (mean = 0.66cm, maximum = 3.44cm, minimum = −2.17cm, range = 5.61cm) and posterior (+) (mean = 0.38cm maximum = 0.71cm, minimum = 0.02cm, range = 0.69cm) locations relative to native anatomical positions. Compared to uninjured contralateral limbs, change in ST tendon insertion point in ACLR limbs resulted in 2.5% loss in peak moment arm and a 3.4% loss in peak torque generating capacity. Accounting for changes to both max isometric force and ST moment arm, the ST had a 14.8% loss in peak torque generating capacity. There are significant deficits in ST muscle morphology and insertion points following ST-GR ACLR. The ST atrophy and insertion point migration following ACLR may affect force transmission and distribution within the hamstrings and contribute to persistent deficits in knee flexor and internal rotator strength

Background. Return to sports after anterior cruciate ligament reconstruction (ACLR) is multifactorial and rotational stability is one of the main concerns. Anterolateral ligament reconstruction (ALLR) has been recommended to enhance rotational stability. Purpose. To assess the effect of ALLR on return to sports. Study Design. Retrospective comparative cohort study;. Level of evidence: III. Methods. A total of 68 patients who underwent ACLR after acute ACL injury between 2015 and 2018 with a follow-up of at least 24 months were enrolled in the study. Patients with isolated ACLR (group ALL(-), n=41) were compared to patients with ACLR+ALLR (group ALL(+), n=27) in regard to subjective knee assessment via Tegner activity scale, Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) scale, Knee Documentation Committee (IKDC) form and Lysholm score. All tests were performed before the surgery, at 6 months and 24 months postoperatively. Results. Mean follow-up was 29.7±2.9 months for group ALL(-) and 31.6±3.0 for ALL(+) (p=0.587). Tegner, ACL-RSI and IKDC scores at last follow-up were significantly better in ALL(+) compared to ALL(-). There were no significant differences in isokinetic extensor strength and single-leg hop test results between the groups. 40 (97.6%) patients in ALL(-) and 27 (100%) in ALL(+) had a grade 2 or 3 pivot shift (p=0.812) preoperatively. Postoperatively, 28 (68.3%) patients in ALL(-) and 25 (92.6%) patients in ALL(+) had a negative pivot shift (p<0.001). 2 (5.9%) patients in ALL(-) and 1 (3.7%) patient in ALL(+) needed ACLR revision due to traumatic re-injury (p=0.165). There was no significant difference in the rate of return to any sports activity (87.8% in ALL(-) vs 88.9% in ALL(+); p=0.532), but ALL(+) showed a higher rate of return to the same level of sports activity (55.6%) than group ALL(-) (31.7%) (p=0.012). Conclusion. ACLR combined with ALLR provided a significantly higher rate of return to the same level sports activity than ACLR alone, probably due to enhanced rotational stability

Septic arthritis following anterior cruciate ligament reconstruction (ACLR) is a rare and serious complication. Previous studies have shown that septic arthritis is associated with inferior outcome of ACLR. Despite that, there is no standardized treatment protocol, and the course of the disease has mainly been studied within single institutions with a small number of patients. The aim of the present study is to describe the course of septic arthritis following ACLR in a large nationwide cohort. The hypothesis was that the clinical presentation of septic arthritis following ACLR varies according to the infectious agent. The present cohort represents patients with septic arthritis identified in a previous study that analyzed compensation claims reported to the Swedish national insurance company (Löf) in 2005–2014 (1). The diagnosis was confirmed by medical experts at Löf after review of medical records. We conducted a comprehensive analysis of the medical records as well as data available from the Swedish National Knee Ligament Registry (SNKLR) for the study group. The study involved 158 patients who received compensation due to developing septic arhtirits. 94 (59.9%) patients were infected with Coagulase negative staphylococci (CoNS), and 25 patients by Staphyolococcus Aureus (S.Aureus) (15.9%). There was a significant difference between the groups regarding Maximum CRP (p<0.001), and duration between ACLR and first washout operation (p<0.005). S.aureus group had the higest maximum CRP (281) and the shortest duration between ACLR and first washout operation (12 days). The Clinical presentation of septic arthritis following ACLR can vary according to the agent causing the infection, and low virulent agents are responsible for the majority of the infections. Clinicians need to be aware of these differences and consider them when making diagnosis or treatment decisions

Abstract. Objectives. Identifying risk factors for inferior outcomes after anterior cruciate ligament reconstruction (ACLR) is important for prognosis and patient information. This study aimed to ascertain if BMI, pre-operative scores, demographic data and concomitant injuries in patients undergoing ACLR affected patient-reported functional outcomes. Methods. A prospective review collected data from a single surgeon series of 278 patients who underwent arthroscopic ACLR. BMI, age, gender, graft choice, pre-op Lysholm score, meniscal and chondral injuries were recorded. The Lysholm score, hop test and KT1000 were used to measure post-op functional outcome at one year. Multiple regression analysis was used to determine factors that predicted Lysholm scores at one year. Results. The mean age was 29 years, with 58 female and 220 male patients. The mean pre-op Lysholm score was 53.8. One hunded and seventy-nine patients had meniscal injuries, of which 81 were medial, 60 lateral, and 38 bilateral. Eighteen patients also had chondral injury and 106 patients had no other associated injury. Age, gender, graft type and presence of meniscal or chondral injuries did not affect one-year post-operative Lysholm scores. A BMI greater than 30, physio compliance and preoperative Lysholm scores helped predict one-year post-operative Lysholm scores (p=0.02). Pearson's correlation found a direct link between BMI and post-operative Lysholm (p=0.03). Conclusions. BMI, physio compliance and pre-operative Lysholm scores are the most significant determinants of short-term functional outcome after ACLR. However, the effects of associated injuries may be apparent in the long-term as degenerative changes set in or the continued detriment resulting from the concomitant injury affect outcome. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Hop tests are used to determine return to sports after ACL reconstruction. They mostly measure distance and symmetry but do not assess kinematics and kinetics. Recently, biomechanical evaluations have been incorporated into these functional jump tests for the better assessment of return to sport. We assessed the sagittal plane range of motion (ROM) of the knee, the deviation axis of rotation (DAOR), and the vertical ground reaction force (vGRF) normalized to body weight in nine healthy participants during the single leg (SLH) and crossover hop tests (COHT). Participants' leg lengths were measured. Jumping distances were marked in the test area as being 4/5 of the leg length. Four sensors were placed on the thighs, the legs and the feet. These body parts were handled as a single rigid body. Eight 480 Hz cameras were used to capture the movements of these rigid bodies. vGRF at landing were measured using a force plate (Bertec, Inc, USA). The ROM of the knee joint and the DAOR were obtained from kinematic data. Participants' joint kinematics metrics were similar in within-subjects statistical tests for SLH and COHT. We therefore asked whether the repeated vGRF normalized to body weight will be similar in both legs during these jumps. Joint kinematics metrics however were different in between subjects indicating the existence of a personalized jumping strategy. These hop tests can be recorded at the beginning of the training season for each individual, which can establish a comparative evaluation database for prospective lower extremity injury recovery and return to sport after ACL injury

Summary Statement. ACL reconstruction using a quadriceps tendon autograft was quantitatively evaluated using a robotic testing system. Biomechanical results on joint stability and graft function support its use as an alternative to the hamstrings. Introduction. Recently, a number of surgeons have chosen the quadriceps tendon (QT) autograft as an alternative autograft over the hamstrings tendon for ACL reconstruction because its bone-to-bone healing on one side, large size, and preservation of lateral and rotatory knee function could lead to fewer post-operative complications. However, there have been little or no biomechanical studies that quantitatively evaluate knee function after reconstruction using a QT autograft. Therefore, the objective of this study was to assess the function of a reconstructed knee with a QT autograft and compare the results with a quadrupled semitendinosus and gracilis (QSTG) tendon autograft on the same knee. Methods. Ten human cadaveric knees (57.4 ± 4.2 years of age) were tested using a robotic/UFS testing system in 4 knee states: intact, ACL-deficient, and after ACL reconstruction with both QT and QSTG autografts. Reconstructions were performed in randomised order using posterolateral femoral tunnel placement. The knee kinematics in each state were measured at 5 flexion angles (full extension, 15°, 30°, 60°, and 90°) under 3 externally applied loading conditions: (1) 134 N anterior tibial load (ATL), (2) 134 N ATL with 200 N axial compression, and combined rotatory (CR) load of 10 Nm valgus and 5 Nm internal tibial torque (at 15° and 30°). Based on the established procedure, knee kinematics and in-situ forces were obtained using the principle of superposition. A repeated measures ANOVA was used to compare anterior tibial translation (ATT) and in-situ forces between the knee states at each flexion angle, with a Bonferroni post-hoc analysis. Results. Under the ATL, the ATT was found to be restored to within 1.1 mm of the intact knee for both reconstructions (P > 0.05). The in-situ forces in the grafts were also not significantly different from those in the intact ACL except in deep flexion (P < 0.05 at 90° for both grafts). With added axial compression, both reconstructions could still restore the ATT to within 2.4 mm of the intact joint at all flexion angles, and the in-situ forces in both grafts were within 25 N of the intact ACL at 15°, 30°, and 60° (P > 0.05). Under the CR load, knee kinematics and in-situ forces in the grafts were not significantly different from the intact ACL at any tested angle (P > 0.05). Further, no significant differences could be detected between the reconstructions under any experimental condition (P > 0.05). Discussion/Conclusion. ACL reconstruction with a QT autograft was found to restore knee function close to levels of the intact knee and similar to those reconstructed with a QSTG autograft. These results support clinical findings suggesting the QT autograft as a viable alternative for ACL reconstruction

After anterior cruciate ligament (ACL) rupture, reconstructive surgery with a hamstring tendon autograft is often performed. Despite overall good results, ACL re-rupture occurs in up to 10% of the patient population, increasing to 30% of the cases for patients aged under 20 years. This can be related to tissue remodelling in the first months to years after surgery, which compromises the graft's mechanical strength. Resident graft fibroblasts secrete matrix metalloproteinases (MMPs), which break down the collagen I extracellular matrix. After necrosis of these fibroblasts, myofibroblasts repopulate the graft, and deposit more collagen III rather than collagen I. Eventually, the cellular and matrix properties converge towards those of the native ACL, but full restoration of the ACL properties is not achieved. It is unknown how inter-patient differences in tissue remodelling capacity contribute to ACL graft rupture risk. This research measured patient-specific tissue remodelling-related properties of human hamstring tendon-derived cells in an in vitro micro-tissue platform, in order to identify potential biological predictors for graft rupture. Human hamstring tendon-derived cells were obtained from remnant autograft tissue after ACL reconstructions. These cells were seeded in collagen I gels on a micro-tissue platform to assess inter-patient cellular differences in tissue remodelling capacity. Remodelling was induced by removing the outermost micro-posts, and micro-tissue compaction over time was assessed using transmitted light microscopy. Protein expression of tendon marker tenomodulin and myofibroblast marker α-smooth muscle actin (αSMA) were measured using Western blot. Expression and activity of remodelling marker MMP2 were determined using gelatin zymography. Cells were obtained from 12 patients (aged 12–51 years). Patient-specific variations in micro-tissue compaction speed or magnitude were observed. Up to 50-fold differences in αSMA expression were found between patients, although these did not correlate with faster or stronger compaction. Surprisingly, tenomodulin was only detected in samples obtained from two patients. Total MMP2 expression varied between patients, but no large differences in active fractions were found. No correlation of patient age with any of the remodelling-related factors was detected. Remodelling-related biological differences between patient tendon-derived cells could be assessed with the presented micro-tissue platform, and did not correlate with age. This demonstrates the need to compare this biological variation in vitro - especially cells with extreme properties - to clinical outcome. Sample size is currently increased, and patient outcome will be determined. Combined with results obtained from the in vitro platform, this could lead to a predictive tool to identify patients at risk for graft rupture

The purpose of this investigation was to evaluate systematically the literature concerning biopsy, MRI signal to noise quotient (SNQ) and clinical outcomes in graft-maturity assessment after autograft anterior cruciate ligament reconstruction (ACLR) and their possible relationships. Methods: The systematic review was reported and conducted according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Studies through May 2019 evaluating methods of intra-articular ACL autograft maturity assessment were considered for inclusion. Eligible methods were histologic studies of biopsy specimens and conventional MRI studies reporting serial SNQ and/ or correlation with clinical parameters. Ten biopsy studies and 13 imaging studies, with a total of 706 patients, met the inclusion criteria. Biopsy studies show that graft remodeling undergoes an early healing phase, a phase of remodeling or proliferation and a ligamentization phase as an ongoing process even 1 year after surgery. Imaging studies showed an initial increase in SNQ, peaking at approximately 6 months, followed by a gradual decrease over time. There is no evident correlation between graft SNQ and knee stability outcome scores at the short- and long-term follow-up after ACLR. The remodeling of the graft is an ongoing process even 1 year after ACLR, based on human biopsy studies. MRI SNQ peaked at approximately 6 months, followed by a gradual decrease over time. Heterogeneity of the MRI methods and technical restrictions used in the current literature limit prediction of graft maturity and clinical and functional outcome measures by means of MRI graft SNQ after ACLR

Summary. A novel in vivo animal model to establish new surgical interventions for patients with ACL insufficiency. Introduction. After ACL reconstruction, recruited cells from surrounding tissues play crucial roles in ligamentization to obtain adequate structural properties. To allow athletes to return sports activity sooner, these remodeling processes should be elucidated and be accelerated. However, in conventional animal models, it has been difficult to differentiate donor and recipient cells. Here we introduce the transgenic Kusabira-Orange pigs, in which cells produce fluorescence systemically, as in vivo model to trace cell recruitment after ACL reconstruction. Methods. After the approval by the Institutional Animal Care and Used Committee, a transgenic pig that carries and produces red fluorescent Kusabira-Orange (KO) was established. Skeletally immature transgenic pigs (n=12) (20 wks old, 76.0 ± 17.5 kg) and wild type (WT) pigs were used as recipient and donor, respectively. For validation of the pigs as in vivo model, the ACL histological structure, cell shape, mitogenic activity, and migration activity were assessed and were compared to those of wild type pigs. The sensitivity and specificity of KO fluorescence under microscopy were analyzed. Histological analyses were conducted with HE, Masson trichrome (MT), and DAPI staining. The length change pattern in our ACL reconstruction was evaluated to validate the surgical procedure. After allograft ACL reconstruction with fresh-frozen flexor digital tendon of WT pigs, pigs were euthanised at 3, 6, 12, and 24 weeks postoperatively (3 pigs each) for the histological analyses. Results. The histological analyses, and mitogenic/migration assays did not show any apparent differences between KO and WT pigs. The sensitivity and specificity of KO fluorescence revealed to be 98%. Maximal length change of the reconstructed ACL was less than 3.5 mm. Three weeks postoperatively, host cells producing KO fluorescence repopulated mainly at the peripheral part of the graft, while, interestingly, cells also located in inter-territorial space of collagen fascicles. More cells migrated towards the mid of the graft in 6–12 week. Cell distribution became homogeneous in parallel to matrix remodeling in 12–24 week. Discussion. As far as we know, this is the first study to apply the genetically engineered pig producing a fluorescent protein as in vivo model to analyze biological remodeling processes after ACL reconstruction. ACL fibroblasts in KO pigs could be detected under fluorescence with high sensitivity and specificity. In addition, structural organization, mitogenic and migration activity were not different from those in WT. As for histological experiments, the recipient cells could be easily and effectively differentiated from donor cells especially 3 weeks postoperatively. Cells migrated in the inter-territorial region among collagen fascicles earlier than we expected. We are going to investigate angiogenesis, matrix remodeling, and structural properties in parallel to the cell migration

Abstract. Objectives. ACL graft-suture fixation can be constructed with needle or needleless techniques. Needleless techniques have advantages of decreased injury, preparation time and cost. The Nice Knot (NK) is common among upper extremity procedures; however, its efficacy in ACL reconstruction relative to other needleless methods is not well known. The purpose of this study was to biomechanically compare quadriceps tendon (QT) grafts prepared with the NK versus the modified Prusik Knot (PK). Methods. Twenty QT grafts were harvested from 10 embalmed human cadaver specimens. 10 were prepared with the PK and 10 with the NK using a No.2 FiberWire (Arthrex, Naples, FL). The prepared grafts were then mounted in a materials testing machine (ElectroPuls E10000, Instron, Norwood, MA) and subjected to tensile loading based on an established protocol. Each tendon-suture specimen was preconditioned with 3 cycles of 0–100N at 1Hz followed by a constant load of 50N for 1 minute and cyclic loading of 200 cycles from 50–200N at 1Hz and then loaded to failure at a displacement rate of 20mm/min. Load and displacement data for each tendon-suture construct was recorded by the testing machine. Results. The average age of the donors was 89.1 ± 8.6 years. The NK showed significantly smaller elongations after pre-tensioning (p < 0.01), preloading (p < 0.001), and cyclic loading (p < 0.001). Peak load was greater for the PK than the NK (p = 0.047). No significant differences were seen for stiffness (p = 0.41) or cross-sectional area (p = 0.22). Conclusions. The results of this biomechanical study show that the NK constructs provide less elongation than the PK constructs but with similar stiffness. The NK offers an alternative option for needleless ACL graft preparation technique. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Summary Statement. We evaluated the mechanical strength of two cortical suspension devices by reproducing clinical situation for ACL reconstruction. A most important factor affecting the displacement during cyclic load was the length of the tendon rather than the length of the device. Introduction. A definite consensus for the optimal graft fixation technique to the femur in an anterior cruciate ligament (ACL) reconstruction has not been reached, although there have been several fixation techniques such as cortical suspension devices, transfixation devices, and interference screws. The purpose of this study was to evaluate the mechanical strength of two cortical suspension devices by reproducing actual clinical situation for ACL reconstruction in order to compare the TightRope. TM. as a new adjustable-length loop device and the EndoButton. TM. as a well-known fixed-length loop device under the consistent conditions. Methods. Two cortical suspension devices were tested under cyclic and pull-to-failure loading conditions in both an isolated device setup and a specimen setup to make a complete bone-device-tendon construct in porcine femurs and bovine flexor tendons using a tensile testing machine. Especially to examine the influence of the length of the tendon and the device, a total length of the bone tunnel was fixed to 35 mm, and an effective length of tendon in the bone tunnel was adjusted to 15 mm for the EndoButton group (EB), the TightRope 15 group (TR15) and 21 mm for the TightRope 21 group (TR21). Results. In the isolated device testing, the ultimate tensile strength of the EB (1430 ± 148 N) had significantly higher than that of the TR (866 ± 53 N), and also had significant difference in the specimen testing. The displacement in the isolated device testing after preloading for the EB (1.09 ± 0.29 mm) showed statistically lower than that for the TR (2.57 ± 1.19 mm), and had a significant difference after the cyclic load. In the specimen testing, on the other hand, the displacement after preloading showed no statistical difference between the EB (1.06 ± 0.30 mm), the TR21 (1.76 ± 2.28 mm) and the TR15 (1.51 ± 1.78 mm). But limiting only to the displacement from 1000 to 2000 cycles, the TR21 (0.92 ± 0.44 mm) showed statistically higher than the TR15 (0.49 ± 0.22 mm). Discussion. Although current results indicated that the EB had greater mechanical strength than the TR, both devices are presumed to provide sufficient fixation strength under clinical conditions. An important new finding from the current study was the measurement of initial displacement from the state of initial fixation until loading began and 50 N of tension was applied. In isolated device testing, the TR had significantly more displacement than the EB during pre-loading. This may reflect the TR's loops stretch until a certain amount of tension is applied. In the comparison of the TR21 and the TR15, the TR21 had a significantly larger displacement with a cyclic load from 1000 to 2000 cycles. This result indicated that a most important factor affecting the displacement during cyclic load was the length of the tendon rather than the length of the device. Thus, we should decide the length of the tendon in the bone tunnel to avoid the displacement of the graft

Barriers to successful return to previous level of activity following Anterior Cruciate Ligament Recon-struction (ACLR) are multifactorial and recent research suggests that athletic performance deficits persist after completion of the rehabilitation course in a large percentage of patients. Thirty soccer athletes (26.9 ± 5.7 years old, male) with ACL injury were surgically treated with all-inside technique and semitendi-nosus tendon autograft. At 2 years from surgery, they were called back for clinical examination, self-reported psychological scores, and biomechanical outcomes (balance, strength, agility and velocity, and symmetry).

Nonparametric statistical tests have been adopted for group comparisons in terms of age, concomitant presence of meniscus tear, injury on dominant leg, presence of knee laxity, presence of varus/valgus, body sides, and return to different levels of sports. Athletes with lower psychological scores showed lesser values in terms of power, resistance and neuromuscular activity as compared to the ones with good psychological scores that showed, instead, better self-reported outcomes (TLKS, CRSQ) and low fear of reinjury (TSK). In the athletes who had a functional deficit in at least one subtest, a safe return to sports could not have been recommended. Our findings confirmed that demographics, physical function, and psychological factors were related to playing the preinjury level sport at mean 2 years after surgery, sup-porting the notion that returning to sport after surgery is multifactorial. A strict qualitative and quantitative assessment of athletes’ status should be performed at different follow-ups after surgery to guarantee a safe and controlled RTP.

Abstract

The purpose of this anatomical study was to explore the morphological variations of the semitendinosus and gracilis tendons in length and cross-section and the statistical relationship between length, cross-section, and body height.

We studied the legs of 93 humans in 136 cadavers. In 43 specimens (46.2%) it was possible to harvest the tendons from both legs.

We found considerable differences in the length and cross-section of the semitendinosus and the gracilis tendons with a significant correlation between the two. A correlation between the length of the femur, reflecting height, and the length of the tendons was only observed in specimens harvested from women. The reason for this gender difference was unclear. Additionally, there was a correlation between the cross-sectional area of the tendons and the length of the femur. Surgeons should be aware of the possibility of encountering insufficient length of tendon when undertaking reconstructive surgery as a result of anatomical variations between patients.