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Purpose This review aims to elucidate the most commonly reported method to quantify fear of reinjury or kinesiophobia and to identify key variables that influence the degree of kinesiophobia following primary anterior cruciate ligament reconstruction (ACLR). Methods A systematic search across three databases (Pubmed, Ovid (MEDLINE), and EMBASE) was conducted from database inception to August 7th, 2022. The authors adhered to the PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. Quality assessment of the included studies was conducted according to the Methodological Index for Non-Randomized Studies (MINORS) criteria. Results Twenty-six studies satisfied the inclusion criteria and resulted in 2,213 total patients with a mean age of 27.6 years and a mean follow-up time of 36.7 months post-surgery. The mean MINORS score of the included studies was 11 out of 16 for non-comparative studies and 18 out of 24 for comparative studies. Eighty-eight percent of included studies used variations of the Tampa Scale of Kinesiophobia (TSK) to quantify kinesiophobia and 27.0% used Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI). The results of this study shows a common association between higher kinesiophobia and poor patient-reported functional status measured using International Knee Documentation Committee (IKDC) Scores, Activity of Daily Living (ADL), Quality of Life (QOL), and Sports/Recreation (S/R) subscales of Knee Osteoarthritis and Outcome Score (KOOS) and Lysholm scores. Postoperative symptoms and pain catastrophizing measured using the KOOS pain and symptom subscales and Pain Catastrophizing Score (PCS) also influenced the degree of kinesiophobia following ACLR. Patients with an increased injury to surgery time and being closer to the date of surgery postoperatively demonstrated higher levels of kinesiophobia. Less common variables included being a female patient, low preoperative and postoperative activity status and low self-efficacy. Conclusion The most common methods used to report kinesiophobia following primary ACLR were variations of the TSK scale followed by ACL-RSI. The most commonly reported factors influencing higher kinesiophobia in this patient population include lower patient-reported functional status, more severe postoperative symptoms such as pain, increased injury to surgery time, and being closer to the date of surgery postoperatively. Kinesiophobia following primary ACLR is a critical element affecting post-surgical outcomes, and screening should be implemented postoperatively to potentially treat in rehabilitation and recovery. Level of evidence IV.

Background To summarize the statistical performance of machine learning in predicting revision, secondary knee injury, or reoperations following anterior cruciate ligament reconstruction (ACLR), and to provide a general overview of the statistical performance of these models. Methods Three online databases (PubMed, MEDLINE, EMBASE) were searched from database inception to February 6, 2024, to identify literature on the use of machine learning to predict revision, secondary knee injury (e.g. anterior cruciate ligament (ACL) or meniscus), or reoperation in ACLR. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Demographic data and machine learning specifics were recorded. Model performance was recorded using discrimination, area under the curve (AUC), concordance, calibration, and Brier score. Factors deemed predictive for revision, secondary injury or reoperation were also extracted. The MINORS criteria were used for methodological quality assessment. Results Nine studies comprising 125,427 patients with a mean follow-up of 5.82 (0.08–12.3) years were included in this review. Two of nine (22.2%) studies served as external validation analyses. Five (55.6%) studies reported on mean AUC (strongest model range 0.77–0.997). Four (44.4%) studies reported mean concordance (strongest model range: 0.67–0.713). Two studies reported on Brier score, calibration intercept, and calibration slope, with values ranging from 0.10 to 0.18, 0.0051–0.006, and 0.96–0.97 amongst highest performing models, respectively. Four studies reported calibration error, with all four studies demonstrating significant miscalibration at either two or five-year follow-ups amongst 10 of 14 models assessed. Conclusion Machine learning models designed to predict the risk of revision or secondary knee injury demonstrate variable discriminatory performance when evaluated with AUC or concordance metrics. Furthermore, there is variable calibration, with several models demonstrating evidence of miscalibration at two or five-year marks. The lack of external validation of existing models limits the generalizability of these findings. Future research should focus on validating current models in addition to developing new multimodal neural networks to improve accuracy and reliability.

Purpose Artificial intelligence (AI) has become incredibly popular over the past several years, with large language models (LLMs) offering the possibility of revolutionizing the way healthcare information is shared with patients. However, to prevent the spread of misinformation, analyzing the accuracy of answers from these LLMs is essential. This study will aim to assess the accuracy of five freely accessible chatbots by specifically evaluating their responses to questions about patellofemoral instability (PFI). The secondary objective will be to compare the different chatbots, to distinguish which LLM offers the most accurate set of responses. Methods Ten questions were selected from a previously published international Delphi Consensus study pertaining to patellar instability, and posed to ChatGPT4o, Perplexity AI, Bing CoPilot, Claude2, and Google Gemini. Responses were assessed for accuracy using the validated Mika score by eight Orthopedic surgeons who have completed fellowship training in sports-medicine. Median responses amongst the eight reviewers for each question were compared using the Kruskal-Wallis and Dunn’s post-hoc tests. Percentages of each Mika score distribution were compared using Pearson’s chi-square test. P-values less than or equal to 0.05 were considered significant. The Gwet’s AC2 coefficient was calculated to assess for inter-rater agreement, corrected for chance and employing quadratic weights. Results ChatGPT4o and Claude2 had the highest percentage of reviews (38/80, 47.5%) considered to be an “excellent response not requiring classification”, or a Mika score of 1. Google Gemini had the highest percentage of reviews (17/80, 21.3%) considered to be “unsatisfactory requiring substantial clarification”, or a Mika score of 4 ( p  < 0.001). The median ± interquartile range (IQR) Mika scores was 2 (1) for ChatGPT4o and Perplexity AI, 2 (2) for Bing CoPilot and Claude2, and 3 (2) for Google Gemini. Median responses were not significantly different between ChatGPT4o, Perplexity AI, Bing CoPilot, and Claude2, however all four statistically outperformed Google Gemini ( p  < 0.05). Inter-rater agreement was classified as moderate (0.40 > AC2 ≥ 0.60) for ChatGPT, Perplexity AI, Bing CoPilot, and Claude2, while there was no agreement for Google Gemini (AC2 < 0). Conclusion Current free access LLMs (ChatGPT4o, Perplexity AI, Bing CoPilot, and Claude2) predominantly provide satisfactory responses requiring minimal clarification to standardized questions relating to patellar instability. Google Gemini statistically underperformed in accuracy relative to the other four LLMs, with most answers requiring moderate clarification. Furthermore, inter-rater agreement was moderate for all LLMs apart from Google Gemini, which had no agreement. These findings advocate for the utility of existing LLMs in serving as an adjunct to physicians and surgeons in providing patients information pertaining to patellar instability. Level of evidence: V

Background: Femoroacetabular impingement (FAI) syndrome is a common cause of hip pain in elite athletes and frequently necessitates hip arthroscopy in National Hockey League (NHL) players. While high return-to-sport (RTS) rates are reported, the long-term impact of surgery on player performance using advanced analytics has not been well studied. Hypothesis: Players undergoing surgery would exhibit steeper performance declines in defensive performance metrics relative to matched controls, despite similar RTS rates. Study Design: Cohort study; Level of evidence, 3. Methods: This matched cohort study identified NHL skaters who underwent hip arthroscopy for FAIS between 2000 and 2024 using publicly available databases. Surgical confirmation was established through ≥2 independent sports news outlets. Players active for ≥2 seasons between 2007 and 2025 were matched 1:1 to controls based on position and performance at age 24. Outcomes included Wins Above Replacement per 60 minutes (WAR/60) and offensive and defensive Goals Above Replacement per 60 minutes (Off GAR/60, Def GAR/60), obtained from Evolving-Hockey. Fixed-effects panel regression with joint F tests was used to model longitudinal aging curves and isolate surgical effects from natural performance decline. Results: A total of 63 NHL skaters (42 forwards, 21 defensemen) were included and matched to controls. Among forwards, hip arthroscopy was associated with a statistically significant decline in Def GAR/60 across the aging curve (interaction P = .04), while Off GAR/60 (P = .64) and WAR/60 (P = .40) showed no significant differences. No statistically significant performance differences were observed among defensemen. Conclusion: This study demonstrated that hip arthroscopy was associated with a steeper age-related decline in defensive performance among NHL forwards, while offensive metrics and overall player value remained unaffected. No significant performance differences were noted in defensemen. Integrating surgical history into performance models may improve player evaluation and recovery strategies.

The magnetosome, a membrane-bound iron biomineral formed within magnetotactic bacteria, is a unique model for a magnetic resonance imaging (MRI) reporter gene contrast agent. We are translating this technology to mammalian cells by expressing essential magnetosome genes mamI, mamL, mamB, and mamE into MDA-MB-435 human melanoma cells. Currently, these genes are individually expressed in the cell although the future goal is to express all four genes together. We examined the influence of these genes on cellular MRI relaxation rates by culturing cells in the presence and absence of iron-supplemented medium and scanning them at 3 Tesla using a gelatin phantom. Total cellular iron was measured by inductively-coupled plasma mass spectrometry and correlated with relaxation rates obtained from phantom experiments. Apart from mamE, magnetosome genes that are individually expressed in mammalian cells grown in iron supplement significantly affected cellular transverse relaxation rates compared to cells grown without iron supplement. Interestingly, mamI, mamL, mamB, and mamE (even though the latter had no effect on relaxation rate) significantly affected cellular iron content. This developing gene-based contrast agent will equip MRI with improvement to imaging sensitivity and the technology to track cellular activities long term.

Background The fragility index (FI) is defined as the minimum number of patients or subjects needed to switch experimental groups for statistical significance to be lost in a randomized control trial (RCT). This index is used to determine the robustness of a study’s findings and recently as a measure of evaluating RCT quality. The objective of this review was to identify and describe published systematic reviews utilizing FI to evaluate surgical RCTs and to determine if there were common factors associated with higher FI values. Methods Three databases (PubMed, MEDLINE [Ovid], Embase) were searched, followed by a subsequent abstract/title and full-text screening to yield 50 reviews of surgical RCTs. Authors, year of publication, name of journal, study design, number of RCTs, subspecialty, sample size, median FI, patients lost to follow-up, and associations between variables and FI scores were collected. Results Among 1007 of 2214 RCTs in 50 reviews reporting FI (median sample size 100), the pooled median FI was 3 (IQR: 1–7). Most reviews investigated orthopaedic surgery RCTs ( n  = 32). There was a moderate correlation between FI and p value ( r  = 0.-413), a mild correlation between FI and sample size ( r  = 0.188), and a mild correlation between FI and event number ( r  = 0.129). Conclusion Based on a limited sample of systematic reviews, surgical RCT FI values are still low (2–5). Future RCTs in surgery require improvement to study design in order to increase the robustness of statistically significant findings.

Purpose To determine the effect of isolated medial patellofemoral ligament reconstruction (MPFLR) versus concomitant MPFLR and tibial-tubercle osteotomy (TTO) on patient-reported functional outcomes, rate of patellar redislocation, and rate of return to sport in skeletally mature patients with recurrent patellar instability and lateralization as defined by elevated tibial-tubercle trochlear groove (TT-TG) distance. Methods Three databases MEDLINE, PubMed and EMBASE were searched from inception to July 10th, 2022 for literature outlining the management of patients with TT-TG indices greater than 15 mm with either isolated MPFLR or concomitant MPFLR and TTO procedures. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on functional outcomes via the Kujala anterior knee pain score, redislocation rates, return to sport rates, and complications were recorded. The MINORS score was used for all studies to perform a quality assessment of included studies. Results A total of 31 studies comprising 1405 patients (1452 knees) were included in this review. The mean Kujala score in 13 studies comprising 848 total patients in the isolated MPFLR group was 85.0 (range 80.9–97.5) compared to a score of 83.7 (range 77.2–94.0) in 14 studies comprising 459 patients in the concomitant group. The mean pooled redislocation rate in 19 studies examining isolated MPFLR procedures comprising 948 patients was 3.1% (95% CI 2.1–4.4%, I 2  = 7%) as opposed to 3.2% (95% CI 1.9–5.0%, I 2  = 0%) in 15 studies comprising 486 patients in the concomitant group. The mean pooled return to sport rate in seven studies with 472 total patients in the isolated MPFLR group was 82% (95% CI 78–86%, I 2  = 16%) compared to a score of 92% (95% CI 78–99%, I 2  = 58%) in four studies comprising 54 patients in the concomitant group. There were similar complication rates between both treatment groups, including range of motion deficits, fractures, infections, and graft failures. Conclusion Isolated MPFLR leads to similar anterior knee pain, similar redislocation rates and lower return to sport rates than concomitant MPFLR and TTO procedures in patients with TT-TG distances greater than 15 mm. Information from this review can aid surgeons in their decision to choose MPFLR versus concomitant procedures for this patient population, and can also guide future studies on this topic. Level of evidence Level IV.

Purpose To determine what knee morphological factors are associated with the development of mucoid degeneration of the anterior cruciate ligament (ACL). Methods Three databases MEDLINE, PubMed and EMBASE were searched from inception to January 29th, 2023 for literature outlining knee morphological factors that potentially lead to the development of mucoid degeneration of the ACL. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on receiver operating characteristic (ROC) curve parameters such as area under the curve (AUC), sensitivity and specificity, odds ratios, as well as p values for comparisons of values between mucoid degeneration of the ACL and control patients were recorded. The Methodological Index for Non-Randomized Studies (MINORS) score was used for all studies to perform a quality assessment of included studies. Results A total of 7 studies comprising 1326 patients (1330 knees) were included in this review. Four studies reported a significant association between increasing posterior tibial slope angles and mucoid degeneration of the ACL presence, with one study specifying that posterolateral tibial slope had a greater association than posteromedial tibial slope. Two studies reported a significant association between lower notch width index values and mucoid degeneration of the ACL presence. One study found that the presence of trochlear dysplasia was correlated with mucoid degeneration of the ACL and two studies found that increased tibial tuberosity–trochlear groove distance (TT–TG) was associated with mucoid degeneration of the ACL. Conclusion Increased posterior tibial slope, decreased notch width index, and elevated TT–TG and trochlear dysplasia were associated with the presence of mucoid degeneration of the ACL. Information from this review can aid surgeons in understanding what morphological features predispose their patients to the development of mucoid degeneration of the ACL. Identifying what features predispose patients to mucoid degeneration of the ACL can help determine if regular screening or preventative strategies are necessary. Level of evidence Level III.

Purpose To compare post-operative clinical outcomes of discoid meniscus tear procedures such as saucerization with or without repair with those of non-discoid meniscus tears such as meniscectomy or repair in skeletally mature patients with no concomitant injuries. Methods Three databases MEDLINE, PubMed and EMBASE were searched from inception to July 3rd, 2022 for literature describing patient-reported outcome measures after meniscus surgery in discoid or non-discoid meniscus tears. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Clinical outcome data on Lysholm, Tegner, International Knee Documentation Committee (IKDC), revision rates, and complications were recorded, with MINORS and Detsky scores used for quality assessment. Results A total of 38 studies comprising 2213 patients were included with a mean age of 38.6 years (range: 9.0–64.4). The mean follow-up time was 54.1 months (range: 1–234) and the average percentage of female participants was 46.8% (range: 9.5–95.5). The mean change between pre-operative and post-operative Lysholm scores ranged from 21.0–39.0, 7.4–24.1, and 24.2–48.4 in the discoid, non-discoid meniscectomy, and non-discoid repair groups, respectively. The mean change in Tegner scores ranged from 0.0 to 2.3, 1.3, and 0.4–1.3 in the discoid, non-discoid meniscectomy, and non-discoid repair groups, respectively. Pre-operative IKDC scores were not reported, however mean post-operative IKDC scores ranged from 77.4 to 96.0, 46.9 to 85.7, and 63.1 to 94.0 in discoid, non-discoid meniscectomy, and non-discoid repair groups, respectively. Revision rates for discoid procedures, non-discoid meniscectomies, and non-discoid meniscus repairs ranged from 3.2 to 44.0%, 8.3 to 56.0%, and 5.9 to 28.0%, respectively. The most common reasons for revision were acute trauma and persistent pain. Conclusion Discoid saucerization procedures with or without repair leads to similar Lysholm scores as non-discoid repair procedures, and similar IKDC scores and revision rates compared to non-discoid meniscectomy or repair procedures. Patients undergoing discoid procedures appeared to have slightly higher Tegner activity scores compared to patients undergoing non-discoid procedures; however this is to be considered in the context of a younger population of patients undergoing discoid procedures than non-discoid procedures. This information can help guide surgeons in the decision-making process when treating patients with discoid menisci, and should guide further investigations on this topic. Level of evidence IV.

Purpose To determine the reliability and diagnostic accuracy of tibial tubercle–trochlear groove (TT–TG) distance versus tibial tubercle–posterior cruciate ligament (TT–PCL) distance, and to determine cutoff values of these measurements for pathological diagnosis in the context of patellar instability. Methods Three databases MEDLINE, PubMed and EMBASE were searched from inception to October 5, 2022 for literature outlining comparisons between TT–TG and TT–PCL in patellar instability patients. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on inter-rater and intra-rater reliability, receiver-operating characteristic (ROC) curve parameters such as area under the curve (AUC), sensitivity and specificity, as well as odds ratios, cutoff values for pathological diagnosis and correlations between TT–TG and TT–PCL were recorded. The MINORS score was used for all studies in order to perform a quality assessment of included studies. Results A total of 23 studies comprising 2839 patients (2922 knees) were included in this review. Inter-rater reliability ranged from 0.71 to 0.98 and 0.55 to 0.99 for TT–TG and TT–PCL, respectively. Intra-rater reliability ranged from 0.74 to 0.99 and 0.88 to 0.98 for TT–TG and TT–PCL, respectively. AUC measuring diagnostic accuracy of patellar instability for TT–TG ranged from 0.80 to 0.84 and 0.58 to 0.76 for TT–PCL. Five studies found TT–TG to have more discriminatory power than TT–PCL at distinguishing patients with patellar instability from patients who do not. Sensitivity and specificity ranged from 21 to 85% and 62 to 100%, respectively, for TT–TG. Sensitivity and specificity ranged from 30 to 76% and 46 to 86%, respectively, for TT–PCL. Odds ratio values ranged from 1.06 to 14.02 for TT–TG and 0.98 to 6.47 for TT–PCL. Proposed cutoff TT–TG and TT–PCL values for predicting patellar instability ranged from 15.0 to 21.4 mm and 19.8 to 28.0 mm, respectively. Eight studies reported significant positive correlations between TT–TG and TT–PCL. Conclusion TT–TG resulted in overall similar reliability, sensitivity and specificity as TT–PCL; however, TT–TG has better diagnostic accuracy than TT–PCL in the context of patellar instability as per AUC and odds ratio values. Level of evidence Level IV.