Incomplete Histologic Healing and Diminished Biomechanical Strength of Meniscus-Bone Interface After Medial Meniscus Posterior Root Transosseous Repair in a Goat Model.

PURPOSE: To enhance the understanding of histologic healing after repairing medial meniscal posterior root tears (MMPRTs) at an early stage, utilizing a goat model. METHODS: Eighteen adult goats, totaling 36 knee joints, were allocated into 3 groups (n = 12): sham group (Sham), root tear group (RT), and root tear with transosseous suture group (RTS). At 12- and 24-week intervals postsurgery, all the knees were harvested for imaging, macroscopic, histologic, and biomechanical assessments. RESULTS: The intact root served as a meniscus-bone interface that connected the tibial and circular fibers of the meniscus with a bony insertion and a root-meniscus transition. A direct fibrous connection was displayed at the bony insertion proximal to the synovium in the RTS group, while the remaining regions of the root displayed indirect fibrous healing. The healing in the RT group was disjointed and reminiscent of scar tissue. The RTS group exhibited a more pronounced coronal extrusion compared to the Sham group (0.42 ± 0.09 vs 0.19 ± 0.02, P = .0012) but was improved relative to that of the RT group (0.49 ± 0.02, P = .0028). The failure load and stiffness of the RTS group were notably higher than those of the RT group, with a strength of 42.67% and a stiffness of 83.75% of the intact root. All the samples ruptured at the root-meniscus transitions. CONCLUSIONS: The incomplete healing may be attributed to the histologic factors underlying the low healing rate and persistent medial meniscal extrusion. Notably, the region attached to the posterior cruciate ligament exhibited superior healing compared to other regions of the bony insertion in the repaired group. Conversely, the root-meniscus transition displayed discontinuity, representing a mechanical weakness in the healing process. CLINICAL RELEVANCE: Modifications of bone tunnel positioning and suture placement could be undertaken in subsequent studies to enhance the healing of the root-meniscus transition.

Testing the Value of Probability Forecasts for Calibrated Combining.

We combine the probability forecasts of a real GDP decline from the U.S. Survey of Professional Forecasters, after trimming the forecasts that do not have "value", as measured by the Kuiper Skill Score and in the sense of Merton (1981). For this purpose, we use a simple test to evaluate the probability forecasts. The proposed test does not require the probabilities to be converted to binary forecasts before testing, and it accommodates serial correlation and skewness in the forecasts. We find that the number of forecasters making valuable forecasts decreases sharply as the horizon increases. The beta-transformed linear pool combination scheme, based on the valuable individual forecasts, is shown to outperform the simple average for all horizons on a number of performance measures, including calibration and sharpness. The test helps to identify the good forecasters ex ante, and therefore contributes to the accuracy of the combined forecasts.

Comparison of a Novel Modified PLA/HA Bioabsorbable Interference Screw With Conventional PLGA/ß-TCP Screw: Effect on 1-Year Postoperative Tibial Tunnel Widening in a Canine ACLR Model.

Background: Tibial bone tunnel widening (TW) is a common postoperative phenomenon after anterior cruciate ligament reconstruction (ACLR). Purpose: To compare the physical, biomechanical, osteoinductive, and histological characteristics of 2 fabricated bioabsorbable interference screws: (1) a modified poly(l-lactide-co-d, l-lactide) and hydroxyapatite (mPLA/HA) screw and (2) a poly(l-lactide-co-glycolide) and ß-tricalcium phosphate (PLGA/ß-TCP) screw; and to evaluate the effect of the PLA/HA screw on ameliorating postoperative TW in a canine ACLR model. Study Design: Controlled laboratory study. Methods: In vitro, the physical and biomechanical properties of the mPLA/HA and PLGA/ß-TCP screws were tested. The osteoinductive activity of the screws was studied by cell experiments. In vivo, ACLR was performed on 48 beagle dogs, divided into the mPLA/HA group and the PLGA/ß-TCP group. The femoral and tibial ends of the graft were both fixed with screws. Six animals in each group were sacrificed after live computed tomography (CT) scanning at 1, 3, 6, and 12 months postoperatively. For six knee samples of each group, three knee samples underwent biomechanical testing, and 1 of them, along with the other 3 samples, underwent micro-CT and histological examination to evaluate tibial TW. Results: The mPLA/HA screw exhibited better particle dispersion, bending strength, desirable self-locking effect, and optimized degradation behavior both in vivo and in vitro. Histologically, the mPLA/HA screw had comparative osteoinductive activity. There was good screw-bone integration using the mPLA/HA screw, while most fibrous scar healing was in the PLGA/ß-TCP group. There were significant differences between the mPLA/HA and PLGA/ß-TCP groups in tibial bone tunnel diameter at the screw body (6 months postoperatively: 5.09 ± 0.44 vs 7.12 ± 0.67; 12 months postoperatively: 4.83 ± 0.27 vs 6.23 ± 0.56; P < .01 for both) and the screw tail (6 months postoperatively: 4.84 ± 0.28 vs 5.97 ± 0.73; 12 months postoperatively: 4.77 ± 0.29 vs 5.92 ± 0.56; P < .01 for both). Conclusion: Compared with the PLGA/ß-TCP screw commonly used in clinics at present, the mPLA/HA screw had comparative biosafety and mechanical properties, satisfactory biomechanical properties, and osteoinductive activity in vivo and in vitro. It effectively ameliorated the postoperative tibial TW in a canine ACLR model and increased the quality of screw-bone integration. Clinical Relevance: The good mechanical and biological properties of the mPLA/HA screws may provide an option to reduce the incidence of complications after ACLR.

A Web-Based Prediction Tool to Improve Identification of Patients With Undersized Hamstring Tendon Autograft in Anterior Cruciate Ligament Reconstruction.

BACKGROUND: An undersized hamstring tendon (HT) autograft is significantly associated with a higher graft failure rate in anterior cruciate ligament reconstruction (ACLR) surgery. The ability to accurately predict inadequate HT graft diameter is critical, as it could assist surgeons in making better graft choices and surgical plans. PURPOSE: To develop a web-based prediction tool to better assess the size of HT autograft and to help clinicians accurately identify patients with potentially undersized HT grafts in order to make appropriate clinical decisions. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 588 patients who received primary arthroscopic single-bundle ACLR surgery with gracilis tendon (GT) and semitendinosus tendon (ST) autograft were retrospectively reviewed. According to the size of 4-strand HT graft, patients were divided into diameter ≥8 mm and <8 mm groups. The least absolute shrinkage and selection operator method and logistic regression were used to identify the independent factors associated with HT graft diameter and establish the models. The prediction performance of the model was evaluated by concordance index and calibration combined with external validation. The diagnostic performance of the prediction model was assessed by sensitivity, specificity, predictive values, and likelihood ratios. Decision curve analysis was used to evaluate the clinical utility of the model. RESULTS: Among the numerous indicators, sex, weight, height, thigh length, and ST-GT diameter (measured on plane 1 of a magnetic resonance imaging scan) were identified to be highly correlated predictors that could provide satisfactory prediction performance in determining the HT graft diameter. Based on these predictors, a prediction model named the HTD model was developed with satisfactory discrimination (concordance index, 0.932) and calibration (mean absolute error, 0.039). When the probability calculated by the HTD model was >65%, the sensitivity and specificity of predicting 4-strand HT graft diameter ≥8 mm were 86.7% and 90.2%, respectively. CONCLUSION: As a useful supplementary prediction tool, the HTD model could accurately predict the diameter of HT autograft during preoperative planning.

Using AI chatbots to provide self-help depression interventions for university students: A randomized trial of effectiveness.

BACKGROUND: Depression impacts the lives of a large number of university students. Mobile-based therapy chatbots are increasingly being used to help young adults who suffer from depression. However, previous trials have short follow-up periods. Evidence of effectiveness in pragmatic conditions are still in lack. OBJECTIVE: This study aimed to compare chatbot therapy to bibliotherapy, which is a widely accepted and proven-useful self-help psychological intervention. The main objective of this study is to add to the evidence of effectiveness for chatbot therapy as a convenient, affordable, interactive self-help intervention for depression. METHODS: An unblinded randomized controlled trial with 83 university students was conducted. The participants were randomly assigned to either a chatbot test group (n = 41) to receive a newly developed chatbot-delivered intervention, or a bibliotherapy control group (n = 42) to receive a minimal level of bibliotherapy. A set of questionnaires was implemented as measurements of clinical variables at baseline and every 4 weeks for a period of 16 weeks, which included the Patient Health Questionnaire-9 (PHQ-9), the Generalized Anxiety Disorder scale (GAD-7), the Positive and Negative Affect Scale (PANAS). The Client Satisfaction Questionnaire-8 (CSQ-8) and the Working Alliance Inventory-Short Revised (WAI-SR) were used to measure satisfaction and therapeutic alliance after the intervention. Participants' self-reported adherence and feedback on the therapy chatbot were also collected. RESULTS: Participants were all university students (undergraduate students (n = 31), postgraduate students (n = 52)). They were between 19 and 28 years old (mean = 23.08, standard deviation (SD) = 1.76) and 55.42% (46/83) female. 24.07% (20/83) participants were lost to follow-up. No significant group difference was found at baseline. In the intention-to-treat analysis, individuals in the chatbot test group showed a significant reduction in the PHQ-9 scores (F = 22.89; P < 0.01) and the GAD-7 scores (F = 5.37; P = 0.02). Follow-up analysis of completers suggested that the reduction of anxiety was significant only in the first 4 weeks. The WAI-SR scores in the chatbot group were higher compared to the bibliotherapy group (t = 7.29; P < 0.01). User feedback showed that process factors were more influential than the content factors. CONCLUSIONS: The chatbot-delivered self-help depression intervention was proven to be superior to the minimal level of bibliotherapy in terms of reduction on depression, anxiety, and therapeutic alliance achieved with participants.