Prevalence and Predictors of Concomitant Meniscal Surgery During Pediatric and Adolescent ACL Reconstruction: Analysis of 4729 Patients Over 20 Years at a Tertiary-Care Regional Children's Hospital.

Background: The rate of concomitant meniscal procedures performed in conjunction with anterior cruciate ligament (ACL) reconstruction is increasing. Few studies have examined these procedures in high-risk pediatric cohorts. Hypotheses: That (1) the rates of meniscal repair compared with meniscectomy would increase throughout the study period and (2) patient-related factors would be able to predict the type of meniscal operation, which would differ according to age. Study Design: Cohort study (prevalence); Level of evidence, 2. Methods: Natural language processing was used to extract clinical variables from notes of patients who underwent ACL reconstruction between 2000 and 2020 at a single institution. Patients were stratified to pediatric (5-13 years) and adolescent (14-19 years) cohorts. Linear regression was used to evaluate changes in the prevalence of concomitant meniscal surgery during the study period. Logistic regression was used to determine predictors of the need for and type of meniscal procedure. Results: Of 4729 patients (mean age, 16 ± 2 years; 54.7% female) identified, 2458 patients (52%) underwent concomitant meniscal procedures (55% repair rate). The prevalence of lateral meniscal (LM) procedures increased in both pediatric and adolescent cohorts, whereas the prevalence of medial meniscal (MM) repair increased in the adolescent cohort (P = .02). In the adolescent cohort, older age was predictive of concomitant medial meniscectomy (P = .031). In the pediatric cohort, female sex was predictive of concomitant MM surgery and of undergoing lateral meniscectomy versus repair (P≤ .029). Female sex was associated with decreased odds of concomitant LM surgery in both cohorts (P≤ .018). Revision ACLR was predictive of concomitant MM surgery and of meniscectomy (medial and lateral) in the adolescent cohort (P < .001). Higher body mass index was associated with increased odds of undergoing medial meniscectomy versus repair in the pediatric cohort (P = .03). Conclusion: More than half of the young patients who underwent ACLR had meniscal pathology warranting surgical intervention. The prevalence of MM repair compared with meniscectomy in adolescents increased throughout the study period. Patients who underwent revision ACLR were more likely to undergo concomitant meniscal surgeries, which were more often meniscectomy. Female sex had mixed effects in both the pediatric and adolescent cohorts.

Comprehensive evaluation of magnetic resonance imaging sequences for signal intensity based assessment of anterior cruciate ligament healing following surgical treatment.

Normalized signal intensity (SI) obtained from magnetic resonance imaging (MRI) has been used to track anterior cruciate ligament (ACL) postoperative remodeling. We aimed to assess the effect of MRI sequence (PD: proton density-weighted; T2: T2-weighted; CISS: constructive interference in steady state) on postoperative changes in healing ACLs/grafts. We hypothesized that CISS is better at detecting longitudinal SI and texture changes of the healing ACL/graft compared to the common clinical sequences (PD and T2). MR images of patients who underwent ACL surgery were evaluated and separated into groups based on surgical procedure (Bridge-Enhanced ACL Repair (BEAR; n = 50) versus ACL reconstruction (ACLR; n = 24)). CISS images showed decreasing SI across all timepoints in both the BEAR and ACLR groups (p < 0.01), PD and T2 images showed decreasing SI in the 6-to-12- and 12-to-24-month postoperative timeframes in the BEAR group (p < 0.02), and PD images additionally showed decreasing SI between 6- and 24-months postoperation in the ACLR group (p = 0.02). CISS images showed texture changes in both the BEAR and ACLR groups, showing increases in energy and decreases in entropy in the 6-to-12- and 6-to-24-month postoperative timeframes in the BEAR group (p < $\lt $ 0.04), and increases in energy, decreases in entropy, and increases in homogeneity between 6 and 24 months postoperation in the ACLR group (p < 0.04). PD images showed increases in energy and decreases in entropy between 6- and 24-months postoperation in the ACLR group (p < 0.008). Finally, CISS was estimated to require a smaller sample size than PD and T2 to detect SI differences related to postoperative remodeling.

Prevalence and Predictors of Concomitant Meniscal and Ligamentous Injuries Associated With ACL Surgery: An Analysis of 20 Years of ACL Reconstruction at a Tertiary Care Children's Hospital.

BACKGROUND: There is an increasing rate of procedures being performed for concomitant injuries during anterior cruciate ligament (ACL) surgery. Few studies have examined risk factors for these associated injuries in young patients. HYPOTHESIS: There are patient-related factors predictive of concomitant knee pathology that differ between age-based cohorts. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Natural language processing was used to extract clinical variables from available notes of patients undergoing ACL surgery between 2000 and 2020 at a single institution (5174 ACL surgeries; mean age, 17 ± 4 years; 53.1% female; accuracy, >98%). Patients were stratified to pediatric (5-13 years), adolescent (14-19 years), and young adult (20-35 years) cohorts. Logistic regression was used to determine predictors of concomitant injury to the menisci, medial collateral ligament (MCL), posterolateral corner (PLC), and posterior cruciate ligament (PCL). RESULTS: Between 2000 and 2020, 54% of pediatric, 71% of adolescent, and 70% of adult patients had ≥1 concomitant soft tissue injury. In children and adolescents, increased age was consistently predictive of sustaining a concomitant injury (P < .02). Female children had increased odds of concomitant medial meniscal injury, while female adults had decreased odds (P≤ .046). Adolescent and adult female patients had decreased odds of concomitant lateral meniscal injury (P≤ .027). Female children had increased odds of injury to the MCL (P = .015), whereas female children and adolescents had decreased odds of PCL injury (P≤ .044). Adolescents undergoing revision ACL surgery had increased odds of meniscal injury (P≤ .001) and decreased odds of concomitant MCL injury (P = .028). Increased body mass index (BMI) was associated with increased odds of concomitant medial meniscal injury in all cohorts (P≤ .041), lateral meniscal injury in adults (P = .045), and PLC injury in children (P = .016). Contact injuries were associated with increased odds of MCL injury in adolescents (P = .017) and PLC injury in adolescents and adults (P < .014). CONCLUSION: These findings support the hypothesis, as there were multiple factors that significantly affected the risk of concomitant injuries that differed between cohorts. Increased age, BMI, and contact injury history were generally associated with increased odds of sustaining a concomitant injury, whereas female sex and revision ACL surgery had mixed effects. Further studies are essential to investigate the sex-based differences in risk for concomitant injuries and to develop tailored treatment plans that minimize the risk of secondary ACL injury.

Comparison of Size of Posterior Tibial Slope and Medial Tibial Depth in Patients With an Isolated Meniscal Tear Requiring Surgery and Matched Uninjured Controls.

BACKGROUND: Meniscal injuries are extremely common. Several anatomic features of the knee, including the tibial plateau morphology, have been shown to influence knee biomechanics and the risk of ligamentous injuries. Little is known, however, how these morphological features influence the risk of isolated meniscal injuries in the anterior cruciate ligament (ACL)-intact knee. HYPOTHESIS: There are differences in the slopes and concavity of the tibial plateau between patients with isolated meniscal tears and matched uninjured controls. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: In total, 89 patients with first-instance isolated medial (n = 37) or lateral (n = 52) meniscal injuries requiring surgical treatment (mean age, 16 ± 1 years; 35% female) were matched to 89 controls with uninjured knees and no previous injuries (mean age, 16 ± 2 years; 35% female) based on age and sex. Magnetic resonance imaging scans (preoperative for injured group) were used to measure the coronal slope of the tibial plateau, posterior slope of the medial and lateral tibial plateaus, and maximum depth of the medial tibial plateau. General linear models were used to evaluate the differences in tibial plateau morphology between the knees with and without meniscal injuries, with and without adjustment for age and sex. RESULTS: Compared with matched controls, patients with surgically treated isolated meniscal tears had a smaller lateral tibial slope (by 2.2° [medial meniscal injury] and 1.6° [lateral meniscal injury]; P < .02), a smaller medial tibial slope (by 2.3° [medial meniscal injury] and 2.4° [lateral meniscal injury]; P < .001) and a larger medial tibial depth (by 0.8 mm [medial meniscal injury] and 0.9 mm [lateral meniscal injury]; P < .001). There were no differences in coronal tibial slope between the injured and uninjured groups. There were no differences in quantified anatomic features between the isolated medial and lateral meniscal injury groups. The same trends were observed after adjusting for age and sex. CONCLUSION: This study suggests that patients with an isolated meniscal tear requiring surgery have a smaller posterior tibial slope and a larger medial tibial depth (more concave medial tibial plateau) than matched uninjured controls. This is contrary to what is known for ACL tears, in which a steeper posterior tibial slope and a shallower medial tibial depth have been associated with an increased risk of ACL tear.

MRI Analysis of Knee Bony Morphology Variations in Children and Adolescents With Lateral Discoid Meniscus Compared With Asymptomatic Healthy Controls.

BACKGROUND: Lateral discoid meniscus accounts for most meniscal tears in children 10 years of age and younger. The role of bony morphology in discoid meniscus has been previously studied in a limited capacity using radiographs. PURPOSE: To use magnetic resonance imaging to measure features of the femoral condyles and tibial plateaus in patients with discoid meniscus to assess potential determinants of symptoms and subsequent surgery and to compare with matched controls to investigate age-related changes in bony features. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: After institutional review board approval, detailed morphology of the femoral condyles and tibial plateau was measured in 177 patients (3-18 years of age; 56% female) with confirmed lateral discoid meniscus. Measurements from 269 participants (3-18 years of age; 55% female) with asymptomatic knees were used as controls. Two-way analysis of variance with Holm-Sídák post hoc was used to compare measurements between discoid menisci and matched controls. Independent t tests were used to compare aspects of bony morphology within the discoid meniscus cohort. RESULTS: Compared with controls, patients with a lateral discoid meniscus had a larger bicondylar width and notch width (7- to 10-year-old and 15- to 18-year-old age groups; P < .05), larger tibial plateau width (11- to 14-year-old and 15- to 18-year-old age groups; P < .001), and smaller lateral (P < .02) and coronal (P < .02) tibial slopes across all age groups. Among patients with a discoid meniscus, larger bicondylar width, larger tibial plateau width, larger notch width, and a flatter lateral femoral condyle were associated with pain (P < .005) and lateral meniscal tears (P < .02). Larger notch width and notch width index were also associated with subsequent surgery (P < .05). CONCLUSION: There are clinically significant abnormalities in bony morphology in patients with a discoid meniscus, including larger femoral condyles and tibial plateaus and a flatter tibial plateau. Additionally, femoral size, femoral curvature, and tibial plateau size may influence the likelihood of knee pain, meniscal tear, and need for surgery. These findings highlight the importance of bony morphology in discoid meniscus pathophysiology in children and adolescents. Such measurements may also aid radiographic detection of discoid meniscus and guide decisions regarding the timing of potential surgical intervention.

LigaNET: A multi-modal deep learning approach to predict the risk of subsequent anterior cruciate ligament injury after surgery.

Anterior cruciate ligament (ACL) injuries are a common cause of soft tissue injuries in young active individuals, leading to a significant risk of premature joint degeneration. Postoperative management of such injuries, in particular returning patients to athletic activities, is a challenge with immediate and long-term implications including the risk of subsequent injury. In this study, we present LigaNET, a multi-modal deep learning pipeline that predicts the risk of subsequent ACL injury following surgical treatment. Postoperative MRIs (n=1,762) obtained longitudinally between 3 to 24 months after ACL surgery from a cohort of 159 patients along with 11 non-imaging outcomes were used to train and test: 1) a 3D CNN to predict subsequent ACL injury from segmented ACLs, 2) a 3D CNN to predict injury from the whole MRI, 3) a logistic regression classifier predict injury from non-imaging data, and 4) a multi-modal pipeline by fusing the predictions of each classifier. The CNN using the segmented ACL achieved an accuracy of 77.6% and AUROC of 0.84, which was significantly better than the CNN using the whole knee MRI (accuracy: 66.6%, AUROC: 0.70; P<.001) and the non-imaging classifier (accuracy: 70.1%, AUROC: 0.75; P=.039). The fusion of all three classifiers resulted in highest classification performance (accuracy: 80.6%, AUROC: 0.89), which was significantly better than each individual classifier (P<.001). The developed multi-modal approach had similar performance in predicting the risk of subsequent ACL injury from any of the imaging sequences (P>.10). Our results demonstrate that a deep learning approach can achieve high performance in identifying patients at high risk of subsequent ACL injury after surgery and may be used in clinical decision making to improve postoperative management (e.g., safe return to sports) of ACL injured patients.

Excessive Femoral Anteversion Leading to Symptomatic Posterior Femoroacetabular Impingement, Cam Deformity of the Posterior Femoral Head-Neck Junction, and Anterior Hip Instability in a Dancer: A Case Report.

CASE: An adolescent female dancer with excessive femoral anteversion presented with posterior and anterior hip pain aggravated by poses that required extension and external rotation. Imaging revealed an atypical cam deformity of the posterior head-neck junction. During surgery, the posterior head-neck junction was observed to impinge on the posterior acetabulum with anterior subluxation of the hip. After a derotational femoral osteotomy, the patient experienced resolution of her symptoms. CONCLUSION: Excessive femoral anteversion can lead to reactive cam deformity, posterior intra-articular impingement, and anterior hip instability in patients who require repetitive hip extension and external rotation, such as ballet dancers.

Effects of joint loading on the development of capital femoral epiphysis morphology.

INTRODUCTION: The deleterious influence of increased mechanical forces on capital femoral epiphysis development is well established; however, the growth of the physis in the absence of such forces remains unclear. The hips of non-ambulatory cerebral palsy (CP) patients provide a weight-restricted (partial weightbearing) model which can elucidate the influence of decreased mechanical forces on the development of physis morphology, including features related to development of slipped capital femoral epiphysis (SCFE). Here we used 3D image analysis to compare the physis morphology of children with non-ambulatory CP, as a model for abnormal hip loading, with age-matched native hips. MATERIALS AND METHODS: CT images of 98 non-ambulatory CP hips (8-15 years) and 80 age-matched native control hips were used to measure height, width, and length of the tubercle, depth, width, and length of the metaphyseal fossa, and cupping height across different epiphyseal regions. The impact of age on morphology was assessed using Pearson correlations. Mixed linear model was used to compare the quantified morphological features between partial weightbearing hips and full weightbearing controls. RESULTS: In partial weightbearing hips, tubercle height and length along with fossa depth and length significantly decreased with age, while peripheral cupping height increased with age (r > 0.2, P < 0.04). Compared to normally loaded (full weightbearing) hips and across all age groups, partially weightbearing hips' epiphyseal tubercle height and length were smaller (P < .05), metaphyseal fossa depth was larger (P < .01), and posterior, inferior, and anterior peripheral cupping heights were smaller (P < .01). CONCLUSIONS: Smaller epiphyseal tubercle and peripheral cupping with greater metaphyseal fossa size in partial weightbearing hips suggests that the growing capital femoral epiphysis requires mechanical stimulus to adequately develop epiphyseal stabilizers. Deposit low prevalence and relevance of SCFE in CP, these findings highlight both the role of normal joint loading in proper physis development and how chronic abnormal loading may contribute to various pathomorphological changes of the proximal femur (i.e., capital femoral epiphysis).

Predicting anterior cruciate ligament failure load with T2* relaxometry and machine learning as a prospective imaging biomarker for revision surgery.

Non-invasive methods to document healing anterior cruciate ligament (ACL) structural properties could potentially identify patients at risk for revision surgery. The objective was to evaluate machine learning models to predict ACL failure load from magnetic resonance images (MRI) and to determine if those predictions were related to revision surgery incidence. It was hypothesized that the optimal model would demonstrate a lower mean absolute error (MAE) than the benchmark linear regression model, and that patients with a lower estimated failure load would have higher revision incidence 2 years post-surgery. Support vector machine, random forest, AdaBoost, XGBoost, and linear regression models were trained using MRI T2* relaxometry and ACL tensile testing data from minipigs (n = 65). The lowest MAE model was used to estimate ACL failure load for surgical patients at 9 months post-surgery (n = 46) and dichotomized into low and high score groups via Youden's J statistic to compare revision incidence. Significance was set at alpha = 0.05. The random forest model decreased the failure load MAE by 55% (Wilcoxon signed-rank test: p = 0.01) versus the benchmark. The low score group had a higher revision incidence (21% vs. 5%; Chi-square test: p = 0.09). ACL structural property estimates via MRI may provide a biomarker for clinical decision making.

Quantitative MRI Biomarkers to Predict Risk of Reinjury Within 2 Years After Bridge-Enhanced ACL Restoration.

BACKGROUND: Quantitative magnetic resonance imaging (qMRI) methods were developed to establish the integrity of healing anterior cruciate ligaments (ACLs) and grafts. Whether qMRI variables predict risk of reinjury is unknown. PURPOSE: To determine if qMRI measures at 6 to 9 months after bridge-enhanced ACL restoration (BEAR) can predict the risk of revision surgery within 2 years of the index procedure. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Originally, 124 patients underwent ACL restoration as part of the BEAR I, BEAR II, and BEAR III prospective trials and had consented to undergo an MRI of the surgical knee 6 to 9 months after surgery. Only 1 participant was lost to follow-up, and 4 did not undergo MRI, leaving a total of 119 patients for this study. qMRI techniques were used to determine the mean cross-sectional area; normalized signal intensity; and a qMRI-based predicted failure load, which was calculated using a prespecified equation based on cross-sectional area and normalized signal intensity. Patient-reported outcomes (International Knee Documentation Committee subjective score), clinical measures (hamstring strength, quadriceps strength, and side-to-side knee laxity), and functional outcomes (single-leg hop) were also measured at 6 to 9 months after surgery. Univariate and multivariable analyses were performed to determine the odds ratios (ORs) for revision surgery based on the qMRI and non-imaging variables. Patient age and medial posterior tibial slope values were included as covariates. RESULTS: In total, 119 patients (97%), with a median age of 17.6 years, underwent MRI between 6 and 9 months postoperatively. Sixteen of 119 patients (13%) required revision ACL surgery. In univariate analyses, higher International Knee Documentation Committee subjective score at 6 to 9 months postoperatively (OR = 1.66 per 10-point increase; P = .035) and lower qMRI-based predicted failure load (OR = 0.66 per 100-N increase; P = .014) were associated with increased risk of revision surgery. In the multivariable model, when adjusted for age and posterior tibial slope, the qMRI-based predicted failure load was the only significant predictor of revision surgery (OR = 0.71 per 100 N; P = .044). CONCLUSION: Quantitative MRI-based predicted failure load of the healing ACL was a significant predictor of the risk of revision within 2 years after BEAR surgery. The current findings highlight the potential utility of early qMRI in the postoperative management of patients undergoing the BEAR procedure.

Early MRI-based quantitative outcomes are associated with a positive functional performance trajectory from 6 to 24 months post-ACL surgery.

PURPOSE: Quantitative magnetic resonance imaging (qMRI) has been used to determine the failure properties of ACL grafts and native ACL repairs and/or restorations. How these properties relate to future clinical, functional, and patient-reported outcomes remain unknown. The study objective was to investigate the relationship between non-contemporaneous qMRI measures and traditional outcome measures following Bridge-Enhanced ACL Restoration (BEAR). It was hypothesized that qMRI parameters at 6 months would be associated with clinical, functional, and/or patient-reported outcomes at 6 months, 24 months, and changes from 6 to 24 months post-surgery. METHODS: Data of BEAR patients (n = 65) from a randomized control trial of BEAR versus ACL reconstruction (BEAR II Trial; NCT02664545) were utilized retrospectively for the present analysis. Images were acquired using the Constructive Interference in Steady State (CISS) sequence at 6 months post-surgery. Single-leg hop test ratios, arthrometric knee laxity values, and International Knee Documentation Committee (IKDC) subjective scores were determined at 6 and 24 months post-surgery. The associations between traditional outcomes and MRI measures of normalized signal intensity, mean cross-sectional area (CSA), volume, and estimated failure load of the healing ACL were evaluated based on bivariate correlations and multivariable regression analyses, which considered the potential effects of age, sex, and body mass index. RESULTS: CSA (r = 0.44, p = 0.01), volume (r = 0.44, p = 0.01), and estimated failure load (r = 0.48, p = 0.01) at 6 months were predictive of the change in single-leg hop ratio from 6 to 24 months in bivariate analysis. CSA (ßstandardized = 0.42, p = 0.01), volume (ßstandardized = 0.42, p = 0.01), and estimated failure load (ßstandardized = 0.48, p = 0.01) remained significant predictors when considering the demographic variables. No significant associations were observed between MRI variables and either knee laxity or IKDC when adjusting for demographic variables. Signal intensity was also not significant at any timepoint. CONCLUSION: The qMRI-based measures of CSA, volume, and estimated failure load were predictive of a positive functional outcome trajectory from 6 to 24 months post-surgery. These variables measured using qMRI at 6 months post-surgery could serve as prospective markers of the functional outcome trajectory from 6 to 24 months post-surgery, aiding in rehabilitation programming and return-to-sport decisions to improve surgical outcomes and reduce the risk of reinjury. LEVEL OF EVIDENCE: Level II.

Three-dimensional magnetic resonance imaging analysis shows sex-specific patterns in changes in anterior cruciate ligament cross-sectional area along its length.

Smaller anterior cruciate ligament (ACL) size in females has been hypothesized to be a key contributor to a higher incidence of ACL tears in that population, as a lower cross-sectional area (CSA) directly corresponds to a larger stress on the ligament for a given load. Prior studies have used a mid-length CSA measurement to quantify ACL size. In this study, we used magnetic resonance imaging to quantify the CSA along the entire length of the intact ACL. We hypothesized that changes in the ACL CSA along its length would have different patterns in males and females. We also hypothesized that changes in ACL CSA along its length would be associated with body size or knee size with different associations in females and males. MR images of contralateral ACL-intact knees of 108 patients (62 females, 13-35 years) undergoing ACL surgery were used to measure the CSA along the ACL length, using a custom program. For both females and males, the largest CSA was located at 37%-39% of ACL length from the tibial insertion. Compared to females, males had a significantly larger CSA only within the distal 41% of the ACL (p < 0.001). ACL CSA was associated with patient height and weight in males (r > 0.3; p < 0.05), whereas it was associated with intercondylar notch width in females (r > 0.3; p < 0.05). These findings highlight the importance of standardizing the location of measurement of ACL CSA.

Preoperative Risk Factors for Subsequent Ipsilateral ACL Revision Surgery After an ACL Restoration Procedure.

BACKGROUND: Anterior cruciate ligament (ACL) revision surgery is challenging for both patients and surgeons. Understanding the risk factors for failure after bridge-enhanced ACL restoration (BEAR) may help with patient selection for ACL restoration versus ACL reconstruction. PURPOSE: To identify the preoperative risk factors for ACL revision surgery within the first 2 years after BEAR. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Data from the prospective BEAR I, II, and III trials were used to determine the preoperative risk factors for ACL revision surgery. All patients with a complete ACL tear (aged 13-47 years, depending on the trial), who met all other inclusion/exclusion criteria and underwent a primary BEAR procedure within 30 to 50 days from the injury (dependent on the trial), were included. Demographic data (age, sex, body mass index), baseline patient-reported outcomes (International Knee Documentation Committee [IKDC] subjective score, Marx activity score), preoperative imaging results (ACL stump length, notch size, tibial slope), and intraoperative findings (knee hyperextension, meniscal status) were evaluated to determine their contribution to the risk of ipsilateral ACL revision surgery. RESULTS: A total of 123 patients, with a median age of 17.6 years (interquartile range, 16-23 years), including 67 (54%) female patients, met study criteria. Overall, 18 (15%) patients required ACL revision surgery in the first 2 years after the BEAR procedure. On bivariate analyses, younger age (P = .011), having a contact injury at the time of the initial tear (P = .048), and increased medial tibial slope (MTS; P = .029) were associated with a higher risk of ipsilateral revision surgery. Multivariable logistic regression analyses identified 2 independent predictors of revision: patient age and MTS. The odds of ipsilateral revision surgery were decreased by 32% for each 1-year increase in age (odds ratio, 0.684 [95% CI, 0.517-0.905]; P = .008) and increased by 28% for each 1° increase in MTS (odds ratio, 1.280 [95% CI, 1.024-1.601]; P = .030). Sex, baseline IKDC or Marx score, knee hyperextension, and meniscal status were not significant predictors of revision. CONCLUSION: Younger age and higher MTS were predictors of ipsilateral ACL revision surgery after the BEAR procedure. Younger patients with higher tibial slopes should be aware of the increased risk for revision surgery when deciding to undergo ACL restoration.

Natural language processing: using artificial intelligence to understand human language in orthopedics.

Natural language processing (NLP) describes the broad field of artificial intelligence by which computers are trained to understand and generate human language. Within healthcare research, NLP is commonly used for variable extraction and classification/cohort identification tasks. While these tools are becoming increasingly popular and available as both open-source and commercial products, there is a paucity of the literature within the orthopedic space describing the key tasks within these powerful pipelines. Curation and navigation of the electronic medical record are becoming increasingly onerous, and it is important for physicians and other healthcare professionals to understand potential methods of harnessing this large data resource. The purpose of this study is to provide an overview of the tasks required to develop an NLP pipeline for orthopedic research and present recent examples of successful implementations.

Supervised machine learning and associated algorithms: applications in orthopedic surgery.

Supervised learning is the most common form of machine learning utilized in medical research. It is used to predict outcomes of interest or classify positive and/or negative cases with a known ground truth. Supervised learning describes a spectrum of techniques, ranging from traditional regression modeling to more complex tree boosting, which are becoming increasingly prevalent as the focus on "big data" develops. While these tools are becoming increasingly popular and powerful, there is a paucity of literature available that describe the strengths and limitations of these different modeling techniques. Typically, there is no formal training for health care professionals in the use of machine learning models. As machine learning applications throughout medicine increase, it is important that physicians and other health care professionals better understand the processes underlying application of these techniques. The purpose of this study is to provide an overview of commonly used supervised learning techniques with recent case examples within the orthopedic literature. An additional goal is to address disparities in the understanding of these methods to improve communication within and between research teams.

Changes in the Cross-Sectional Profile of Treated Anterior Cruciate Ligament Within 2 Years After Surgery.

Background: The cross-sectional area (CSA) of the anterior cruciate ligament (ACL) and reconstructed graft has direct implications on its strength and knee function. Little is known regarding how the CSA changes along the ligament length and how those changes vary between treated and native ligaments over time. Hypothesis: It was hypothesized that (1) the CSA of reconstructed ACLs and restored ACLs via bridge-enhanced ACL restoration (BEAR) is heterogeneous along the length. (2) Differences in CSA between treated and native ACLs decrease over time. (3) CSA of the surgically treated ACLs is correlated significantly with body size (ie, height, weight, body mass index) and knee size (ie, bicondylar and notch width). Study Design: Cohort study; Level of evidence, 2. Methods: Magnetic resonance imaging scans of treated and contralateral knees of 98 patients (n = 33 ACL reconstruction, 65 BEAR) at 6, 12, and 24 months post-operation were used to measure the ligament CSA at 1% increments along the ACL length (tibial insertion, 0%; femoral insertion, 100%). Statistical parametric mapping was used to evaluate the differences in CSA between 6 and 24 months. Correlations between body and knee size and treated ligament CSA along its length were also assessed. Results: Hamstring autografts had larger CSAs than native ACLs at all time points (P < .001), with region of difference decreasing from proximal 95% of length (6 months) to proximal 77% of length (24 months). Restored ACLs had larger CSAs than native ACLs at 6 and 12 months, with larger than native CSA only along a small midsubstance region at 24 months (P < .001). Graft CSA was correlated significantly with weight (6 and 12 months), bicondylar width (all time points), and notch width (24 months). Restored ACL CSA was significantly correlated with bicondylar width (6 months) and notch width (6 and 12 months). Conclusion: Surgically treated ACLs remodel continuously within the first 2 years after surgery, leading to ligaments/grafts with heterogeneous CSAs along the length, similar to the native ACL. While reconstructed ACLs remained significantly larger, the restored ACL had a CSA profile comparable with that of the contralateral native ACL. In addition to size and morphology differences, there were fundamental differences in factors contributing to CSA profile between the ACL reconstruction and BEAR procedures. Registration: NCT02664545 (ClinicalTrials.gov identifier).

Coxa valga and antetorta increases differences among different femoral version measurements : potential implications for derotational femoral osteotomy planning.

AIMS: To evaluate how abnormal proximal femoral anatomy affects different femoral version measurements in young patients with hip pain. METHODS: First, femoral version was measured in 50 hips of symptomatic consecutively selected patients with hip pain (mean age 20 years (SD 6), 60% (n = 25) females) on preoperative CT scans using different measurement methods: Lee et al, Reikerås et al, Tomczak et al, and Murphy et al. Neck-shaft angle (NSA) and α angle were measured on coronal and radial CT images. Second, CT scans from three patients with femoral retroversion, normal femoral version, and anteversion were used to create 3D femur models, which were manipulated to generate models with different NSAs and different cam lesions, resulting in eight models per patient. Femoral version measurements were repeated on manipulated femora. RESULTS: Comparing the different measurement methods for femoral version resulted in a maximum mean difference of 18° (95% CI 16 to 20) between the most proximal (Lee et al) and most distal (Murphy et al) methods. Higher differences in proximal and distal femoral version measurement techniques were seen in femora with greater femoral version (r > 0.46; p < 0.001) and greater NSA (r > 0.37; p = 0.008) between all measurement methods. In the parametric 3D manipulation analysis, differences in femoral version increased 11° and 9° in patients with high and normal femoral version, respectively, with increasing NSA (110° to 150°). CONCLUSION: Measurement of femoral version angles differ depending on the method used to almost 20°, which is in the range of the aimed surgical correction in derotational femoral osteotomy and thus can be considered clinically relevant. Differences between proximal and distal measurement methods further increase by increasing femoral version and NSA. Measurement methods that take the entire proximal femur into account by using distal landmarks may produce more sensitive measurements of these differences.Cite this article: Bone Jt Open 2022;3(10):759-766.

Limited Hip Flexion and Internal Rotation Resulting From Early Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe SCFE Using 3D Modelling.

INTRODUCTION: Slipped capital femoral epiphysis (SCFE) is the most common hip disorder in adolescent patients that can result in complex 3 dimensional (3D)-deformity and hip preservation surgery (eg, in situ pinning or proximal femoral osteotomy) is often performed. But there is little information about location of impingement.Purpose/Questions: The purpose of this study was to evaluate (1) impingement-free hip flexion and internal rotation (IR), (2) frequency of impingement in early flexion (30 to 60 degrees), and (3) location of acetabular and femoral impingement in IR in 90 degrees of flexion (IRF-90 degrees) and in maximal flexion for patients with untreated severe SCFE using preoperative 3D-computed tomography (CT) for impingement simulation. METHODS: A retrospective study involving 3D-CT scans of 18 patients (21 hips) with untreated severe SCFE (slip angle>60 degrees) was performed. Preoperative CT scans were used for bone segmentation of preoperative patient-specific 3D models. Three patients (15%) had bilateral SCFE. Mean age was 13±2 (10 to 16) years and 67% were male patients (86% unstable slip, 81% chronic slip). The contralateral hips of 15 patients with unilateral SCFE were evaluated (control group). Validated software was used for 3D impingement simulation (equidistant method). RESULTS: (1) Impingement-free flexion (46±32 degrees) and IRF-90 degrees (-17±18 degrees) were significantly ( P <0.001) decreased in untreated severe SCFE patients compared with contralateral side (122±9 and 36±11 degrees).(2) Frequency of impingement was significantly ( P <0.001) higher in 30 and 60 degrees flexion (48% and 71%) of patients with severe SCFE compared with control group (0%).(3) Acetabular impingement conflict was located anterior-superior (SCFE patients), mostly 12 o'clock (50%) in IRF-90 degrees (70% on 2 o'clock for maximal flexion). Femoral impingement was located on anterior-superior to anterior-inferior femoral metaphysis (between 2 and 6 o'clock, 40% on 3 o'clock and 40% on 5 o'clock) in IRF-90 degrees and on anterior metaphysis (40% on 3 o'clock) in maximal flexion and frequency was significantly ( P <0.001) different compared with control group. CONCLUSION: Severe SCFE patients have limited hip flexion and IR due to early hip impingement using patient-specific preoperative 3D models. Because of the large variety of hip motion, individual evaluation is recommended to plan the osseous correction for severe SCFE patients. LEVEL OF EVIDENCE: Level III.

The development and deployment of machine learning models.

Applications of artificial intelligence, specifically machine learning, are becoming increasingly popular in Orthopaedic Surgery, and medicine as a whole. This growing interest is shared by data scientists and physicians alike. However, there is an asymmetry of understanding of the developmental process and potential applications of machine learning. As new technology will undoubtedly affect clinical practice in the coming years, it is important for physicians to understand how these processes work. The purpose of this paper is to provide clarity and a general framework for building and assessing machine learning models.

Exploring the translational potential of clusterin as a biomarker of early osteoarthritis.

BACKGROUND: Clusterin (CLU; also known as apolipoprotein J) is an ATP-independent holdase chaperone that prevents proteotoxicity as a consequence of protein aggregation. It is a ∼60 kDa disulfide-linked heterodimeric protein involved in the clearance of cellular debris and the regulation of apoptosis. CLU has been proposed to protect cells from cytolysis by complement components and has been implicated in Alzheimer's disease due to its ability to bind amyloid-ß peptides and prevent aggregate formation in the brain. Recent studies suggest that CLU performs moonlighting functions. CLU exists in two major forms: an intracellular form and a secreted extracellular form. The intracellular form of CLU may suppress stress-induced apoptosis by forming complexes with misfolded proteins and facilitates their degradation. The secreted form of CLU functions as an extracellular chaperone that prevents protein aggregation. METHODS: In this review, we discuss the published literature on the biology of CLU in cartilage, chondrocytes, and other synovial joint tissues. We also review clinical studies that have examined the potential for using this protein as a biomarker in synovial and systemic fluids of patients with rheumatoid arthritis (RA) or osteoarthritis (OA). RESULTS: Since CLU functions as an extracellular chaperone, we propose that it may be involved in cytoprotective functions in osteoarticular tissues. The secreted form of CLU can be measured in synovial and systemic fluids and may have translational potential as a biomarker of early repair responses in OA. CONCLUSION: There is significant potential for investigating synovial and systemic CLU as biomarkers of OA. Future translational and clinical orthopaedic studies should carefully consider the diverse roles of this protein and its involvement in other comorbidities. Therefore, future biomarker studies should not correlate circulating CLU levels exclusively to the process of OA pathogenesis and progression. Special attention should be paid to CLU levels in synovial fluid. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: There is significant potential for investigating synovial and systemic CLU as a predictive biomarker of osteoarthritis (OA) progression and response to novel treatments and interventions. Given that CLU plays diverse roles in other comorbidities such as rheumatoid arthritis (RA) and obesity, future translational and clinical orthopaedic biomarker studies should not directly correlate circulating CLU levels to the process of OA pathogenesis and progression. However, special attention should be paid to CLU levels in synovial fluid. The cytoprotective properties of CLU may support the implementation of regenerative strategies and new approaches for developing targeted therapeutics for OA.