Knee Model Research Articles

The Beneficial Effect of an Intra-articular Injection of Losartan on Microfracture-Mediated Cartilage Repair Is Dose Dependent

Background: A previous publication demonstrated that the oral intake of losartan promoted microfracture-mediated hyaline-like cartilage repair in osteochondral defects of a rabbit knee model. However, an intra-articular (IA) injection of losartan may have direct beneficial effects on cartilage repair and has not been studied. Purpose: To determine the dosage and beneficial effects of an IA injection of losartan on microfracture-mediated cartilage repair and normal cartilage homeostasis. Study Design: Controlled laboratory study. Methods: Rabbits were divided into 5 groups (n = 6 each): a microfracture group (MFX group) and 4 different losartan treatment groups that received varying doses of IA losartan (0.1, 1, 10, and 100 mg per knee). An osteochondral defect (5 mm) was created in the trochlear groove cartilage of 1 limb in each rabbit, and 5 microfracture perforations were made in the osteochondral defect. Both the injured and the contralateral knee joints were injected with IA losartan immediately after microfracture and at 2 and 4 weeks after surgery. Rabbits were sacrificed at 6 weeks after surgery for analysis including gross observation, micro–computed tomography, histology, and reverse transcription quantitative polymerase chain reaction. Results: Micro–computed tomography and gross observation demonstrated comparable subchondral bone healing and hyaline-like cartilage morphology in the 0.1-, 1-, and 10-mg losartan groups relative to the MFX group. Conversely, the 100-mg losartan group showed neither bony defect healing nor cartilage repair. Histology revealed higher O’Driscoll scores and hyaline-like cartilage regeneration in the 1-mg losartan group compared with the MFX group. In contrast, the 100-mg losartan group showed the lowest histology score and no cartilage repair. An IA injection of losartan at the doses of 0.1, 1, and 10 mg did not cause adverse effects on uninjured cartilage, while the 100-mg dose induced cartilage damage. Quantitative polymerase chain reaction results showed downregulation of the transforming growth factor β (TGF-β) signaling pathway after IA losartan injection. Conclusion: An IA injection of losartan at the dose of 1 mg was most effective for the enhancement of microfracture-mediated cartilage repair without adversely affecting uninjured cartilage. Conversely, a high dose (100 mg) IA injection of losartan inhibited cartilage repair in the osteochondral defect and was chondrotoxic to normal articular cartilage. Clinical Relevance: An IA injection of losartan at an optimal dosage represents a novel microfracture enhancement therapy and warrants a clinical trial for future clinical applications.

AVOIDING POPLITEAL NEURO-VASCULAR INJURY DURING ILIOTIBIAL BAND ACL RECONSTRUCTION

Background:For patients with significant growth remaining, the Iliotibial Band ACL reconstruction technique has proven to be reliable procedure with minimal risk for growth disturbance. Recent dissection studies confirm the neuro-vascular bundle is within 1 cm of the ACL graft over the top position, confirming the importance of careful graft passage technique to avoid neurovascular injury.Purpose:The purpose of this study was to evaluate the over the top graft passage technique using pediatric 3-D knee models. Instrument placement for graft passage was assessed for its proximity to the posterior aspect of the femur, maintaining a safe distance from the neurovascular bundle.Materials and Methods:3D knee models (ages 7, 9, 11 years) were printed from high resolution knee CT scans, including a hinge/pivot mechanism to allow for simulation of knee position during flexion and extension. Various curved tip instruments were used to evaluate the path of the graft passage, with several goals: 1. Allow the instrument to create a graft path through the posterior capsule in the most anatomic femoral position. 2. Keep the tip of the instrument close to posterior and lateral cortex of the femur, to avoid neurovascular injury. The instruments varied in design, arc of curvature, overall length, diameters.Results:Clamp passage was performed using a retrograde approach, i.e. through the notch, passing outside the periosteum of the postero-lateral femur (Figure 1). For some clamps, the arc of the curvature allowed for passage of the instrument with minimal risk of neurovascular injury. For some clamp configurations, the clamps deviated significant from the posterior aspect of the femur during graft passage, which may increase the risk of neurovascular bundle injury. In each case, an instrument was identified that met the criteria for safe passage, but different instruments were required based upon the size of the knee joint.Conclusions:The ITB ACL reconstruction is one of the best options for ACL reconstruction in the skeletally immature. The neurovascular structures are very close to the path for over the top graft placement. Due to the wide range of knee dimensions in this group, different clamp designs may be necessary for optimal over the top graft passage. 3D knee models may guide surgeons for procedure technique and optimal instrument selection for safe graft passage.Figure 1.

MPFL Length Change Patterns in Asymptomatic Knees of Patients with Contralateral Patellar Instability

Objectives:Recreating the isometry of the medial patellofemoral ligament (MPFL) is critical during patellar stabilization surgery to restore patellar kinematics. The native MPFL is reported to remain constant in length from 0-70°knee flexion in normal knees. However, patients with patellar instability have morphologic abnormalities that may alter the isometric function of the ligament. Length change patterns of the intact MPFL in such patients have not been described.Methods:3D digital knee models were created from dynamic CT images of 10 patients with unilateral patellar instability who were confirmed to have no symptoms on the contralateral knee. At each flexion angle, MPFL length was calculated based on the distance between its known attachment points. Straight line representation of the MPFL was allowed to wrap around the femoral condyle to ensure accurate length measurement. Morphologic characteristics of each knee were recorded, including sulcus angle and lateral trochlear inclination (LTI) as measurements of trochlear dysplasia, trochlear alpha angle to measure trochlear length, tibial tuberosity to trochlear groove (TTTG) distance to measure malalignment, and Caton Deschamps Index (CDI) to measure patellar height. Changes in MPFL length were assessed relative to knee flexion angle in each patient and correlated with morphologic characteristics.Results:10 knees were included in this study, with a mean age of 20.4+/-4.7 yrs. Mean sulcus angle was 153.4+/-8.9°, LTI 14.1+/-4.0°, trochlear alpha angle 66.1+/-5.8°, TTTG distance 18.3+/-3.1mm, CDI 1.1+/-0.1. Mean MPFL length varied from 62.5+/-4.9mm at 50° knee flexion to 74.4+/-3.9mm at 0°, with a 20.1+/-8.8% change in length (p<0.001). No significant length changes were noted between 30° and 50° flexion. Moderate correlation was noted between increasing MPFL length change and measurements of trochlear length (R=-0.55, p=0.017).Conclusions:In the asymptomatic knees of patients with contralateral patellar instability, the calculated MPFL length based on known anatomic attachment points varied by 20.1%, or an average of 12.1mm, between 50° flexion and full extension. This suggests that the isometric function of the intact MPFL in these patients may not reflect previously described findings in anatomically normal patients. Further studies are needed to understand the pathoanatomy related to these changes, as well as the implications for graft placement and assessment of isometry in MPFL reconstruction techniques.

Bone Staples Provide Favorable Primary Stability in Cortical Fixation of Tendon Grafts for Medial Collateral Ligament Reconstruction: A Biomechanical Study.

Background:The use of the interference screw (IFS) for the cortical fixation of tendon grafts in knee ligament reconstruction may lead to converging tunnels in the multiligament reconstruction setting. It is unknown whether alternative techniques using modern suture anchor (SA) or bone staple (BS) fixation provide sufficient primary stability.Purpose:To assess the primary stability of cortical fixation of tendon grafts for medial collateral ligament (MCL) reconstruction using modern SA and BS methods in comparison with IFS fixation.Study Design:Controlled laboratory study.Methods:Cortical tendon graft fixation was performed in a porcine knee model at the tibial insertion area of the MCL using 3 different techniques: IFS (n = 10), SA (n = 10), and BS (n = 10). Specimens were mounted in a materials testing machine, and cyclic loading for 1000 cycles at up to 100 N was applied to the tendon graft, followed by load-to-failure testing. Statistical analysis was performed using 1-way analysis of variance.Results:There were no statistical differences in elongation during cyclic loading or peak failure load during load-to-failure testing between BS (mean ± standard deviation: 3.4 ± 1.0 mm and 376 ± 120 N, respectively) and IFS fixation (3.9 ± 1.2 mm and 313 ± 99.5 N, respectively). SA fixation was found to have significantly more elongation during cyclic loading (6.4 ± 0.9 mm; P < .0001) compared with BS and IFS fixation and lower peak failure load during ultimate failure testing (228 ± 49.0 N; P < .01) compared with BS fixation.Conclusion:BS and IFS fixation provided comparable primary stability in the cortical fixation of tendon grafts in MCL reconstruction, whereas a single SA fixation led to increased elongation with physiologic loads. However, load to failure of all 3 fixation techniques exceeded the loads expected to occur in the native MCL.Clinical Relevance:The use of BS as a reliable alternative to IFS fixation for peripheral ligament reconstruction in knee surgery can help to avoid the conflict of converging tunnels.

Ten hours of simulator training in arthroscopy are insufficient to reach the target level based on the Diagnostic Arthroscopic Skill Score

Simulator arthroscopy training has gained popularity in recent years. However, it remains unclear what level of competency surgeons may achieve in what time frame using virtual training. It was hypothesized that 10h of training would be sufficient to reach the target level defined by experts based on the Diagnostic Arthroscopic Skill Score (DASS). The training concept was developed by ten instructors affiliated with the German-speaking Society of Arthroscopy and Joint Surgery (AGA). The programme teaches the basics of performing arthroscopy; the main focus is on learning and practicing manual skills using a simulator. The training was based on a structured programme of exercises designed to help users reach defined learning goals. Initially, camera posture, horizon adjustment and control of the direction of view were taught in a virtual room. Based on these skills, further training was performed with a knee model. The learning progress was assessed by quantifying the exercise time, camera path length and instrument path length for selected tasks. At the end of the course, the learners' performance in diagnostic arthroscopy was evaluated using DASS. Participants were classified as novice or competent based on the number of arthroscopies performed prior to the assessment. Except for one surgeon, 131 orthopaedic residents and surgeons (29 women, 102 men) who participated in the seven courses agreed to anonymous data analysis. Fifty-eight of them were competents with more than ten independently performed arthroscopies, and 73 were novices, with fewer than ten independently performed arthroscopies. There were significant reductions in exercise time, camera path length and instrument path length for all participants after the training, indicating a rapid increase in performance. No difference in camera handling between the dominant and non-dominant sides was found in either group. The competents performed better than the novices in various tasks and achieved significantly better DASS values on the final performance test. Our data have demonstrated that arthroscopic skills can be taught effectively on a simulator, but a 10-h course is not sufficient to reach the target level set by experienced arthroscopists. However, learning progress can be monitored more objectively during simulator training than in the operating room, and simulation may partially replace the current practice of arthroscopic training. III.

Comparison of chondrogenesis-related biological behaviors between human urine-derived stem cells and human bone marrow mesenchymal stem cells from the same individual

BackgroundStem cells are the main choice for seed cells in tissue engineering, but using most traditional stem cells requires invasive and complicated procedures. Human urine-derived stem cells (hUSCs) are an alternative stem cell source with the advantages of being isolated noninvasively and repetitively from the same individual. The aim of this study was to compare chondrogenesis-related biological behaviors between hUSCs and human bone marrow mesenchymal stem cells (hBMSCs) from the same individual.MethodshUSCs and hBMSCs were isolated from six patients who underwent iliac bone grafting. Cell morphology, proliferation, colony-forming, migration, and multidifferentiation analyses were performed in vitro. Then, acellular cartilage extracellular matrix (ACM) scaffolds were fabricated for in vivo implantation. The comparisons of cell viability, morphology, proliferation, and chondrogenesis between hUSCs and hBMSCs cultured on scaffolds were performed before implantation. The scaffolds loaded with hUSCs or hBMSCs were implanted into a rabbit knee model to repair cartilage defects. Magnetic resonance imaging (MRI) and micro-computed tomography (μCT) Analyses, inflammation and toxicity assays, gross observation, and histological evaluation were performed to evaluate the cartilage repair effects.ResultsIn in vitro experiments, hUSCs had better capacity for proliferation, colony-forming, and migration compared to hBMSCs in the same passage, while hBMSCs had greater osteogenic, adipogenic, and chondrogenic abilities compared to hUSCs in the same passage. Both hUSCs and hBMSCs at passage 3 had the strongest potential for proliferation, colony-forming, and multilineage differentiation compared to cells in other passages. The ACM scaffolds loaded with hUSCs or hBMSCs both significantly promoted the repair of cartilage defects in the rabbit knee model at 12 weeks’ postimplantation, and the new tissue was mainly hyaline cartilage. However, there was no significant difference in cartilage repair effects between hUSCs and hBMSCs.ConclusionsIn in vitro experiments, hUSCs presented better capacity for proliferation, while hBMSCs had greater chondrogenic ability. However, hUSCs and hBMSCs had similar cartilage repair effects in vivo. Results indicated that hUSCs can be a stem cell alternative for cartilage regeneration and provide a powerful platform for cartilage tissue engineering and clinical transformation.Graphical abstract

Training Surgeons to Perform Arthroscopic All-Inside Meniscal Repair: A Randomized Controlled Trial Evaluating the Effectiveness of a Novel Cognitive Task Analysis Teaching Tool, Imperial College London/University College London Meniscus Repair Cognitive Task Analysis (IUMeRCTA)

Background: All-inside meniscal repair is an increasingly common technique for the surgical treatment of meniscal tears. There are currently no standardized techniques for training residents in this procedure. Cognitive task analysis (CTA) is a method of analyzing and standardizing key steps in a procedure that allows training to be conducted in a validated and reproducible manner. Purpose: (1) To design a digital CTA teaching tool for a standardized all-inside meniscal repair. (2) To evaluate whether CTA-trained residents would perform better in a meniscal repair task compared with a control group who underwent traditional apprenticeship methods of training. Study Design: Controlled laboratory study. Methods: Three expert knee surgeons were interviewed using a modified Delphi method to generate a consensus among the ideal technical steps, cognitive decision points, and common errors and solutions for an all-inside meniscal repair. This written information was then combined with visual and audio components and integrated onto a digital platform to create the Imperial College London/University College London Meniscus Repair Cognitive Task Analysis (IUMeRCTA) tool. Eighteen novice residents were randomized into an intervention group (digital CTA tool) and control group (equipment instruction manual). Both groups performed an all-inside meniscal repair on high-fidelity, phantom knee models and were assessed by expert surgeons, blinded to the interventions, using a validated global rating scale (GRS). After a power calculation, median GRS scores were compared between groups using the Mann-Whitney U test; significance was set at P < .05. Results: For the IUMeRCTA tool design, the procedure was divided into 55 steps across 9 phases: (1) preoperative planning, (2) theater and patient setup, (3) portal placement, (4) meniscal examination, (5) tear reduction, (6) suture planning, (7) suture insertion, (8) repair completion, and (9) postoperative care and rehabilitation. For the trial, the intervention group (mean ± SD GRS, 32 ± 2.9) performed significantly better than did the control group (GRS, 24 ± 3.3; P < .001). Conclusion: This is the first CTA tool to demonstrate objective benefits in training novices to perform an arthroscopic all-inside meniscal repair. Clinical Relevance: The IUMeRCTA tool is an easily accessible and effective adjunct to traditional teaching that enhances learning the all-inside meniscal repair for novice surgeons.

The patellofemoral morphology and the normal predicted value of tibial tuberosity-trochlear groove distance in the Chinese population

BackgroundOur objective was to obtain normal patellofemoral measurements to analyse sex and individual differences. In addition, the absolute values and indices of tibial tuberosity-trochlear groove (TT-TG) distances are still controversial in clinical application. A better method to enable precise prediction is still needed.MethodsSeventy-eight knees of 78 participants without knee pathologies were included in this cross-sectional study. A CT scan was conducted for all participants and three-dimensional knee models were constructed using Mimics and SolidWorks software. We measured and analysed 19 parameters including the TT-TG distance and dimensions and shapes of the patella, femur, tibia, and trochlea. LASSO regression was used to predict the normal TT-TG distances.ResultsThe dimensional parameters, TT-TG distance, and femoral aspect ratio of the men were significantly larger than those of women (all p values < 0.05). However, after controlling for the bias from age, height, and weight, there were no significant differences in TT-TG distances and anterior-posterior dimensions between the sexes (all p values > 0.05). The Pearson correlation coefficients between the anterior femoral offset and other indexes were consistently below 0.3, indicating no relationship or a weak relationship. Similar results were observed for the sulcus angle and the Wiberg index. Using LASSO regression, we obtained four parameters to predict the TT-TG distance (R2 = 0.5612, p < 0.01) to achieve the optimal accuracy and convenience.ConclusionsNormative data of patellofemoral morphology were provided for the Chinese population. The anterior-posterior dimensions of the women were thicker than those of men for the same medial-lateral dimensions. More attention should be paid to not only sex differences but also individual differences, especially the anterior condyle and trochlea. In addition, this study provided a new method to predict TT-TG distances accurately.

How to Create an Arthroscopy Training Laboratory Using a Bovine Knee Model

Orthopaedic surgeries by video arthroscopy have become increasingly popular, as they allow joint treatment through small incisions and minimal tissue damage. However, their execution requires specific skills from the surgeon, different from open surgery, which can only be achieved through practical training. These skills would be ideally performed on human cadaveric anatomical pieces which, however, can be difficult to access for different reasons. Animal anatomical models for surgical skills training have been used for years in medicine, and we observed that the bovine knee has anatomical characteristics quite similar to that of the human knee. In this study, we explain, step by step, the installation and creation of an arthroscopy laboratory with a bovine model, in an effort to contribute to several training centers in arthroscopic surgery around the world, assisting and guiding such centers to install arthroscopy laboratories and facilitating the improvement of more surgeons.

Comparison of Kinematics and Contact Mechanics in Normal Knee and Total Knee Replacements: A Computational Investigation.

An objective of total knee replacement (TKR) is to restore the mechanical function of a normal knee. Joint kinematics and contact mechanics performance are two of the primary indices that indicate the success of TKR devices. The aim of this study was to compare the kinematics and contact mechanics of TKR and normal knee joints. An experimentally evaluated finite-element (FE) knee model was developed and used to investigate the performance of four TKR designs (fixed cruciate-retaining (CR), mobile CR, posterior-stabilized (PS), medial pivot design (MP)) and the normal knee joint during a gait cycle. The predicted kinematic results showed that the MP design presented similar kinematics to those of the normal knee joint and did not demonstrate paradoxical motion of the femur. A considerably larger contact area and lower contact pressure were found on the normal knee joint (1315 mm2, and 14.8 MPa, respectively) than on the TKRs, which was consistent with the previous in-vivo fluoroscopic investigation. The mobile CR and PS designs exhibited the smallest and greatest contact pressures of the four TKR designs, respectively. The results of the present study help to understand the kinematics and contact mechanics in the TKR during the gait cycle, and provide comprehensive information about the performance of the normal knee joint.

Additional distal femoral resection increases mid-flexion coronal laxity in posterior-stabilized total knee arthroplasty with flexion contracture : a computational study.

Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture, which leads to femoral joint line elevation. There is a paucity of data describing the effect of joint line elevation on mid-flexion stability and knee kinematics. Thus, the goal of this study was to quantify the effect of joint line elevation on mid-flexion laxity. Six computational knee models with cadaver-specific capsular and collateral ligament properties were implanted with a posterior-stabilized (PS) TKA. A 10° flexion contracture was created in each model to simulate a capsular contracture. Distal femoral resections of + 2 mm and + 4 mm were then simulated for each knee. The knee models were then extended under a standard moment. Subsequently, varus and valgus moments of 10 Nm were applied as the knee was flexed from 0° to 90° at baseline and repeated after each of the two distal resections. Coronal laxity (the sum of varus and valgus angulation with respective maximum moments) was measured throughout flexion. With + 2 mm resection at 30° and 45° of flexion, mean coronal laxity increased by a mean of 3.1° (SD 0.18°) (p < 0.001) and 2.7° (SD 0.30°) (p < 0.001), respectively. With + 4 mm resection at 30° and 45° of flexion, mean coronal laxity increased by 6.5° (SD 0.56°) (p < 0.001) and 5.5° (SD 0.72°) (p < 0.001), respectively. Maximum increased coronal laxity for a + 4 mm resection occurred at a mean 15.7° (11° to 33°) of flexion with a mean increase of 7.8° (SD 0.2°) from baseline. With joint line elevation in primary PS TKA, coronal laxity peaks early (about 16°) with a maximum laxity of 8°. Surgeons should restore the joint line if possible; however, if joint line elevation is necessary, we recommend assessment of coronal laxity at 15° to 30° of knee flexion to assess for mid-flexion instability. Further in vivo studies are warranted to understand if this mid-flexion coronal laxity has negative clinical implications. Cite this article: Bone Joint J2021;103-B(6 Supple A):87-93.

Ultrapurified Alginate Gel Containing Bone Marrow Aspirate Concentrate Enhances Cartilage and Bone Regeneration on Osteochondral Defects in a Rabbit Model

Background: Ultrapurified alginate (UPAL) gel implantation has been demonstrated as effective in cartilage repair for osteochondral defects; however, cell transplantation within UPAL gels would be required to treat larger defects. Hypothesis: The combination of UPAL gel and bone marrow aspirate concentrate (BMAC) would enhance cartilage repair and subchondral bone repair for large osteochondral defects. Study Design: Controlled laboratory study. Methods: A total of 104 osteochondral defects (1 defect per knee) of 52 rabbits were randomly divided into 4 groups (26 defects per group): defects without any treatment (Defect group), defects treated using UPAL gel alone (UPAL group), defects treated using UPAL gel containing allogenic bone marrow mesenchymal stromal cells (UPAL-MSC group), and defects treated using UPAL gel containing BMAC (UPAL-BMAC group). At 4 and 16 weeks postoperatively, macroscopic and histologic evaluations and measurements of repaired subchondral bone volumes of reparative tissues were performed. Collagen orientation and mechanical properties of the reparative tissue were assessed at 16 weeks. Results: The defects in the UPAL-BMAC group were repaired with hyaline-like cartilage with well-organized collagen structures. The histologic scores at 4 weeks were significantly higher in the UPAL-BMAC group (16.9 ± 2.0) than in the Defect group (4.7 ± 1.9; P < .05), the UPAL group (10.0 ± 3.3; P < .05), and the UPAL-MSC group (12.2 ± 2.9; P < .05). At 16 weeks, the score in the UPAL-BMAC group (24.4 ± 1.7) was significantly higher than those in the Defect group (9.0 ± 3.7; P < .05), the UPAL group (14.2 ± 3.9; P < .05), and the UPAL-MSC group (16.3 ± 3.6; P < .05). At 4 and 16 weeks, the macroscopic evaluations were significantly superior in the UPAL-BMAC group compared with the other groups, and the values of repaired subchondral bone volumes in the UPAL-BMAC group were significantly higher than those in the Defect and UPAL groups. The mechanical properties of the reparative tissues were significantly better in the UPAL-BMAC group than in the other groups. Conclusion: The implantation of UPAL gel containing BMAC-enhanced hyaline-like cartilage repair and subchondral bone repair of osteochondral defects in a rabbit knee model. Clinical Relevance: These data support the potential clinical application of 1-step treatment for large osteochondral defects using biomaterial implantation with cell transplantation.

Impact of Tibial Component Coronal Alignment on Knee Joint Biomechanics Following Fixed-bearing Unicompartmental Knee Arthroplasty: A Finite Element Analysis.

ObjectiveUnicompartmental knee arthroplasty (UKA) has indicated a higher rate of revision than total knee arthroplasty (TKA). The success of UKA depends on UKA component alignment, fixation, and soft tissue integrity. The purpose of this study was to investigate the effects of different tibial component alignments in the coronal plane on the stress distribution in UKA. It was hypothesized that the stress distribution would approach native knee when the tibial component was neutrally positioned.MethodsThe left legs from two healthy volunteers were considered to represent the geometric native knee models. All bones within the knee joint were extracted from the three‐dimensional (3D) computed tomography (CT). MRI was used to generate cartilage, menisci, and four major ligaments. The UKA components were virtually implanted in the medial compartment of the knee model using MIMICS. A total of five different configurations of UKA tibial obliquity in the coronal plane (neutral, 3° varus, 6° varus, 3° valgus, and 6° valgus) were adopted and investigated. Subject‐specific inhomogeneous material properties of bones were used in the finite element analysis (FEA) model. The von Mises stress in the tibia platform and proximal tibia, and the load distribution between the medial and lateral compartments were extracted and compared among the five different configurations.ResultsThe inhomogeneous material properties of the trabecular bone were closer to real physics than traditional homogeneous methods. Neutral and 3° varus alignments of the tibial component in the coronal plane have better stress distribution between medial and lateral compartment as healthy knee models, and less stress‐shielding effects than other UKA configurations. The stress pathway under the medial tibia platform in neutral and 3° varus UKA configurations was similar and more obvious than the other three UKA configurations. Notably, the stress of the medial tibia platform in the 3° varus UKA models was more homogenous than the neutral UKA configuration. The 6° varus, 3° valgus, and 6° valgus UKA models had higher stress at the location of anterolateral and posterolateral tibia platform than other UKA configurations.ConclusionNeutral or 3° varus positioned in the coronal plane for the tibial component could be the optimal alignment for UKA. Excessive varus or valgus obliquity in the coronal plane lead to significant differences in bone stress transfer and load distribution in the knee, and increase the risk of UKA failure.

199 Use of A 3D Hand-Held Scanner to Capture Trochlear Groove Shape, A Proof-of-Concept Study

Abstract Introduction Trochleoplasty is a surgical procedure used to treat patellar instability through modifying the trochlear groove. Analysis of the groove with a hand-held scanner would enable accurate real time planning and facilitate tailor made correction. We aimed to measure trochlear depth, sulcus angle, trochlear facet ratio, trochlear angle and lateral trochlear inclination angle and establish inter- and intra-rater reliability for each knee model. Method The trochlear groove of the knee models was scanned by two investigators and 3D reference models created. These were surface matched and custom software along with Excel was utilised to determine the desired parameters. Intraclass correlation coefficient (ICC) was used for test-retest reliability and to determine which parameter results, for each model, showed the best reproducibility. Results There was good inter-observer reliability - trochlear depth (1.0 mm), sulcus angle (2.7°), trochlear angle (4.0°) and lateral trochlear inclination angle (4.0°), except in the trochlear facet ratio (32.0%) of one knee model. With outliers removed ICC was good-excellent in (46.7%) of measurements, with trochlear depth showing the best reproducibility. Conclusions This feasibility study showed that the hand-held scanner in conjunction with supporting software can measure trochlear parameters in a controlled environment and justifies extending research into its use in trochleoplasty.

Intra-articular human deciduous dental pulp stem cell administration vs. pharmacological therapy in experimental osteoarthritis rat model.

The aim of the present study was to compare the molecular and morphological effects of diacerein and glucosamine-chondroitin drug treatment and intra-articular injection therapy of human deciduous dental pulp stem cells (hDPSCs) in a rat knee model of induced osteoarthritis (OA). Thirty-six adult male rats were randomly separated into six groups: Control group (without induction of OA), osteoarthritis group 60 (induction of OA, saline gavage started on day 14 and performed for 60 days, followed by euthanasia), osteoarthritis group (induction of OA and euthanasia after 14 days), diacerein group, glucosamine-chondroitin group, and mesenchymal stem cell group. The drug-treated groups were gavaged with 50 mg/kg of diacerein and 400/500 mg/kg of glucosamine-chondroitin starting on dat 14 for 60 days. The cell therapy-treated group received an intra-articular single dose of 8 × 105 hDPSCs on day 14, and euthanasia was performed after 60 days. Lateral femoral condyles were collected and prepared for immunohistochemistry and light microscopy procedures. The morphological features and immunoexpression of SOX-5, IHH, MMP-8, MMP-13, and Type II collagen were statistically analysed. Our data suggest that hDPSC therapy contributes more actively and effectively in the structural reorganization of lateral femoral condyles. In contrast, the glucosamine-chondroitin sulphate treatment was more effective in inflammatory control, while diacerein showed better results associated with the maintenance of the primordial cartilage. The positive therapeutic effect of daily administered conventional drugs can be confirmed in a rat model of OA. However, one single dose of locally administered hDPSCs provides significant improvement in tissue regeneration in an OA model.

Articular chondroprogenitors in platelet rich plasma for treatment of osteoarthritis and osteochondral defects in a rabbit knee model

BackgroundArticular chondroprogenitors are a promising contender for cartilage repair due to their inherent nature which stands primed for chondrogenesis and minimal hypertrophic preponderance. Platelet rich plasma (PRP) has been extensively used for treating cartilage defects and osteoarthritis (OA), due to its chondro-inductive properties and abundant pool of growth factors. The aim of this study was to assess the efficacy of chondroprogenitors injected with PRP versus PRP alone in the healing of experimentally created early OA and osteochondral defects (OCD) in a rabbit model. MethodsAdult New Zealand White male rabbits were used for cell and PRP isolation. Chondroprogenitors were isolated by fibronectin adhesion assay, labelled with iron oxide, characterized for surface markers, differential potential and expanded. PRP was isolated by double spin centrifugation using a TriCell kit. Study groups included (a) Monosodium iodoacetate induced early OA and (b) critical OCD. Following intervention (test arm: PRP+ chondroprogenitors and control arm: PRP), assessment was performed at 6- and 12-weeks which included histopathological examination and scoring (OARSI and Modified Wakitani score), immunohistochemistry analysis (Collagen type II and X) and synovial fluid S100A12 levels. Results and conclusionComparable, evident healing was noticed in both test and control arms when the OA group samples were assessed at both time points. In the OCD group, PRP alone exhibited significantly better results than the test arm, although repair was notable in both interventions. Further evaluation of chondroprogenitors is required to assess their role as a standalone therapy and in combination with PRP to further cartilage regeneration.

Biomechanical Difference between Conventional Transtibial Single-Bundle and Anatomical Transportal Double-Bundle Anterior Cruciate Ligament Reconstruction Using Three-Dimensional Finite Element Model Analysis

The purpose of our study was to analyze the graft contact stress at the tunnel after transtibial single-bundle (SB) and transportal double-bundle (DB) anterior cruciate ligament (ACL) reconstruction. After transtibial SB (20 cases) and transportal DB (29 cases) ACL reconstruction, the three-dimensional image of each patient made by postoperative computed tomography was adjusted to the validation model of a normal knee and simulated SB and DB ACL reconstructions were created based on the average tunnel position and direction of each group. We also measured graft and contact stresses at the tunnel after a 134 N anterior load from 0° to 90° flexion. The graft and contact stresses became the greatest at 30° and 0° flexion, respectively. The total graft and contact stresses after DB ACL reconstruction were greater than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the graft and contact stresses of each graft after DB ACL reconstruction were less than those after SB ACL reconstruction. In conclusion, the total graft and total contact stresses after DB ACL reconstruction are higher than those after SB ACL reconstruction from 0° to 30° and 0° to 90° knee flexion, respectively. However, the stresses of each graft after DB ACL reconstruction are about half of those after SB ACL reconstruction.

In Vivo Elongation Patterns of the Collateral Ligaments in Healthy Knees During Functional Activities.

Improved knowledge of in vivo function of the collateral ligaments is essential for enhancing rehabilitation and guiding surgical reconstruction as well as soft-tissue balancing in total knee arthroplasty. The aim of this study was to quantify in vivo elongation patterns of the collateral ligaments throughout complete cycles of functional activities. Knee kinematics were measured using radiographic images captured with a mobile fluoroscope while healthy subjects performed level walking, downhill walking, and stair descent. The registered in vivo tibiofemoral kinematics were then used to drive subject-specific multibody knee models to track collateral ligament elongation. The elongation patterns of the medial collateral ligament varied distinctly among its bundles, ranging from lengthening of the anterior fibers to shortening of the posterior bundle with increases in the knee flexion angle. The elongation patterns of the lateral collateral ligament varied considerably among subjects. It showed an average 4% shortening with increasing flexion until 60% to 70% of the gait cycle, and then recovered during the terminal-swing phase until reaching its reference length (defined at heel strike). The observed nonuniform elongation of the medial collateral ligament bundles suggests that single-bundle reconstruction techniques may not fully restore healthy ligament function. Moreover, the observed ligament elongation patterns indicate greater varus than valgus laxity in the loaded knee. Through providing key knowledge about the in vivo elongation patterns of the collateral ligaments throughout complete cycles of functional activities, this study offers in vivo evidence for benchmarking ligament reconstruction and soft-tissue balancing in total knee arthroplasty.

Creating a Femoral Tunnel Aperture at the Anteromedial Footprint Versus the Central Footprint in ACL Reconstruction: Comparison of Contact Stress Patterns.

Background:It remains unclear whether an anteromedial (AM) footprint or a central footprint anterior cruciate ligament (ACL) graft exhibits less contact stress with the femoral tunnel aperture. This contact stress can generate graft attrition forces, which can lead to potential graft failure.Purpose/Hypothesis:The purpose of this study was to compare the difference in contact stress patterns of the graft around a femoral tunnel that is created at the anatomic AM footprint versus the central footprint. It was hypothesized that the difference in femoral tunnel positions would influence the contact stress at the interface between the reconstructed graft and the femoral tunnel orifice.Study Design:Controlled laboratory study.Methods:A total of 24 patients who underwent anatomic single-bundle ACL reconstruction were included in this study. In 12 patients, the femoral tunnels were created at the center of the native AM footprint (AM group), and in the remaining 12 patients the center of the femoral tunnel was placed in the anatomic central footprint (central group). Three-dimensional knee models were created and manipulated using several modeling programs, and the graft-tunnel angle (GTA) was determined using a special software program. The peak contact stresses generated on the virtual ACL graft around the femoral tunnel orifice were calculated using a finite element method.Results:The mean GTA was significantly more obtuse in the AM group than in the central group (124.2° ± 5.9° vs 112.6° ± 7.9°; P = .001). In general, both groups showed high stress distribution on the anterior surface of the graft, which came in contact with the anterior aspect of the femoral tunnel aperture. The degree of stress in the central group (5.3 ± 2.6 MPa) was significantly higher than that in the AM group (1.2 ± 1.1 MPa) (P < .001).Conclusion:Compared with the AM footprint ACL graft, the central footprint ACL graft developed significantly higher contact stress in the extended position, especially around the anterior aspect of the femoral tunnel orifice.Clinical Relevance:The contact stress of the ACL graft at the extended position of the knee may be minimized by creating the femoral tunnel at the AM-oriented footprint.

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.