Tibial Slope and Anterior Cruciate Ligament Reconstruction Outcomes

High Detection Rate of Posterolateral Tibial Plateau Fractures and Poor Functional Outcomes in Type IIIB Impaction Fractures After Anterior Cruciate Ligament Rupture and Reconstruction

OBJECTIVE

The incidence of anterior cruciate ligament (ACL) ruptures has been increasing annually. However, clinical surgeons have overlooked the impaction fractures of the posterolateral tibial plateau and lateral femoral condyle in patients with ACL ruptures. The purpose of the present study was to report the detection rate of the posterolateral tibial plateau impaction fractures in patients with ACL ruptures, and to evaluate the functional outcomes of patients following ACL reconstruction (ACLR) without treatment of the tibial fractures at a 2-year postoperative follow-up.

METHODS

Four hundred eighty-eight patients treated for ACL ruptures between January 2016 and June 2020 were retrospectively reviewed, and the posterolateral tibial plateau impaction fractures were classified based on MRI assessment. The detection rate of the posterolateral tibial plateau impaction fractures was calculated, and the functional outcomes (SF-12 Mental Component Summaries, SF-12 Physical Component Summaries, Tegner, Lysholm, IKDC, and KOOS) were evaluated at a 2-year postoperative follow-up.

RESULTS

The detection rate of posterolateral tibial plateau impaction fractures was 41.6% among ACL ruptures. Of these, 285 cases (58.4%) had no fractures, 98 cases (20.1%) had type I impaction fractures, 41 cases (8.4%) had type IIA impaction fractures, 15 cases (3.1%) had type IIB impaction fractures, 22 cases (4.5%) had type IIIA impaction fractures, and 27 cases (5.5%) had type IIIB impaction fractures. Patients with type IIIA or IIIB impaction fractures showed an increased detection rate of contact mechanism compared to the other subgroups. Significant differences in Tegner (postoperation) and KOOS (QOL) were found between no fracture and type IIIB impaction fractures in patients following ACLR.

CONCLUSIONS

The detection rate of posterolateral tibial plateau impaction fractures in patients with ACL ruptures was high. Patients with type IIIB impaction fractures following ACLR had poor functional outcomes.

Evaluating the Mechanical Axis for Detection of Posterior Tibial Slope Malalignment in ACL-Deficient Knees on Lateral Radiographs

Background

Distal tibial deformities are not assessed using the proximal anatomical axis (PAA) to determine the posterior tibial slope (PTS). Therefore, it seems advantageous to measure PTS on full-length lateral tibial radiographs using the mechanical axis (MA).

Purposes

To (1) compare the PTS measurements using the MA and the PAA and (2) determine whether using the PAA fails to detect a certain number of significantly elevated PTS values compared with using the MA.

Study Design

Cohort study (Diagnosis); Level of evidence, 3.

Methods

Full-length lateral tibial radiographs of 218 consecutive cases were reviewed. Radiographs were checked for malrotation. Therefore, the distance between the posterior tibial condyles was measured in millimeters. Patients with a difference of ≥7 mm between the posterior tibial condyles were excluded, leaving 196 cases for the final statistical analysis. The PTS was measured using the MA and the PAA. Differences between these 2 techniques were analyzed. The sensitivity and specificity of the PAA as a screening method for pathological PTS were calculated, with the MA as the standard for comparison. Four subgroups were formed, all with PAA <12° and different lower limits for the MA: group 1, MA ≥10°; group 2, MA ≥10.5°; group 3, MA ≥11°; and group 4, MA ≥11.5°.

Results

Radiographs with ≥7 mm between the posterior tibial condyles showed an increased inconsistency between the PTS measurement with the MA and the PAA. In the group with a distance of <7 mm between the posterior tibial condyles (n = 196), the mean PTS measured with the MA was 9.4°± 3.8° (range, 0.4° to 21.9°), and the mean PTS was 10.5°± 3.5° (range, 1.7° to 20.9°) according to the PAA. The mean difference in PTS between the PAA and the MA was 1.1°± 1.2° (range, -2.4° to 4.1°; P < .001). Group 1 had a sensitivity of 73% and specificity of 98%; group 2, sensitivity of 84% and specificity of 97%; group 3, sensitivity of 87% and specificity of 93%; and group 4, sensitivity of 95% and specificity of 89%.

Conclusion

Measuring the PTS using the MA was advantageous, as the measurement with the PAA did not correctly identify all cases with sagittal alignment changes. The proportion of patients with pathologically increased PTS not identified with the proximal anatomical measurement, reflected by the sensitivity, depended on the threshold value defined for the MA. Lateral radiographs, showing an increased distance between the posterior tibial condyles, indicated malrotation of the tibia leading to measurement inaccuracy.

Increased Posterior Tibial Slope Is Associated With Increased Risk of Meniscal Root Tears: A Systematic Review

BACKGROUND

While increased posterior tibial slope (PTS) is an established risk factor for anterior cruciate ligament tears, the association between tibial slope and meniscal posterior root tears is not well-defined.

PURPOSE

To summarize the available literature evaluating the association between PTS and meniscus root injuries compared with patients without root tears.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A literature search was performed using the Scopus, PubMed, and Embase databases. Human clinical studies evaluating the associations between the medial tibial slope (MTS), lateral tibial slope (LTS), lateral-to-medial (L-to-M) slope asymmetry, and the risk of meniscus root tears were included. Patients with medial meniscus posterior root tears (MMPRTs) and lateral meniscus posterior root tears (LMPRTs) were compared with a control group without root injury. Study quality was assessed using the methodological index for non-randomized studies criteria.

RESULTS

Ten studies with 1313 patients were included (884 patients with root tears; 429 controls). The LMPRT subgroup (n = 284) had a significantly greater LTS (mean ± SD, 7.3°± 1.5° vs 5.7°± 3.91°; P < .001), MTS (5.26°± 1.2° vs 4.8°± 1.25°; P < .001), and increased L-to-M asymmetry (2.3°± 1.3° vs 0.65°± 0.5°; P < .001) compared with controls. The MMPRT group (n = 600) had significantly increased MTS relative to controls (8.1°± 2.5° vs 4.3°± 0.7°; P < .001). Furthermore, there was a higher incidence of noncontact injuries (79.3%) and concomitant ramp lesions (56%) reported in patients with LMPRT.

CONCLUSION

Increased MTS, LTS, and L-to-M slope asymmetry are associated with an increased risk of LMPRTs, while increased MTS is associated with MMPRTs. Surgeons should consider how proximal tibial anatomy increases the risk of meniscus root injury.

Correlation between higher lateral tibial slope and inferior long term subjective outcomes following single bundle anterior cruciate ligament reconstruction

BACKGROUND

The impact of anatomical factors, such as the lateral tibial slope (LTS), on outcomes following anterior cruciate ligament (ACL) reconstruction is an area of growing interest. This study was led by the observation that patients with a higher LTS may have different recovery trajectories.

HYPOTHESIS/PURPOSE

The purpose of this study was to investigate the correlation between a higher LTS and long term subjective outcomes following single-bundle ACL reconstruction.

STUDY DESIGN

This study was designed as a retrospective cohort study.

METHODS

The study comprised 138 patients who underwent single-bundle ACL reconstruction. The LTS was measured on preoperative radiographs. Patient-reported outcome measures (PROMs) were collected, which included the Lysholm Knee Score, UCLA Activity Score, IKDC Score, and Tegner Activity Score, over a mean follow-up duration of 137 months.

RESULTS

A significant negative correlation was found between LTS and all measured PROMs (p < 0.001). The established cut-off value of LTS distinguishing between "Good" and "Fair" Lysholm scores was 8.35 degrees. Female patients have statistically significant higher LTS and lower PROMs scores than male. Patients with LTS greater than or equal to 8.35 had significantly lower PROMs, indicative of poorer functional and subjective outcomes.

CONCLUSION

Our findings suggest that a higher LTS is associated with inferior subjective outcomes following single-bundle ACL reconstruction in long term. The LTS cut-off value of 8.35 degrees could potentially be used as a reference in preoperative planning and patient counseling.

CLINICAL RELEVANCE

Understanding the relationship between LTS and ACL reconstruction outcomes could inform surgical planning and postoperative management. These findings highlight the need to consider anatomical variances, such as LTS, when assessing patient-specific risks and recovery expectations, contributing to the advancement of personalized care in sports medicine.

A non-weight bearing protocol after ACL reconstruction improves static anterior tibial translation in patients with elevated slope and increased weight bearing tibial anterior translation

PURPOSE

Aim of this study is to evaluate the impact of a non-weight bearing (NWB) protocol within 21 post-operative days after anterior cruciate ligament (ACL) reconstruction on static and dynamic anterior tibial translations (SATT and DATT, respectively). The hypothesis is that delayed WB would improve ATT at 9 months follow-up.

METHODS

A series of patients treated with ACL reconstruction was retrospectively reviewed, comparing a group with immediate post-operative weight bearing (WB group) and a group without post-operative weight bearing (NWB group). The NWB protocol was applied to patients with posterior tibial slope (PTS) ≥ 12°, pre-operative SATT ≥ 5 mm, and/or meniscal lesions of root or radial type. SATT, and PTS were measured on 20° flexion monopodal lateral x-rays, while DATT on Telos™ x-rays at pre-operative and 9-months follow-up.

RESULTS

One hundred seventy-nine patients were included (50 NWB group, 129 WB group). The SATT worsened in the WB group with a mean increase of 0.7 mm (SD 3.1 mm), while in the NWB group, the SATT improved with a mean decrease of 1.4 mm (SD 3.1 mm) from the pre-operative to 9 months' follow-up (p < 0.001). The side-to-side Telos™ evaluation showed a significant improvement in DATT within both the groups (p < 0.001), but there was no difference between the two groups (p = 0.99).

CONCLUSION

The post-operative protocol of 21 days without WB led to an improvement in SATT at 9 months without an influence on DATT, and it is recommended for patients with a SATT ≥ 5 mm and/or a PTS ≥ 12° as part of an "à la carte" approach to ACL reconstruction.

LEVEL OF EVIDENCE

Level IV, Retrospective case series.

Deep Learning Artificial Intelligence Tool for Automated Radiographic Determination of Posterior Tibial Slope in Patients With ACL Injury

Background

An increased posterior tibial slope (PTS) corresponds with an increased risk of graft failure after anterior cruciate ligament (ACL) reconstruction (ACLR). Validated methods of manual PTS measurements are subject to potential interobserver variability and can be inefficient on large datasets.

Purpose/Hypothesis

To develop a deep learning artificial intelligence technique for automated PTS measurement from standard lateral knee radiographs. It was hypothesized that this deep learning tool would be able to measure the PTS on a high volume of radiographs expeditiously and that these measurements would be similar to previously validated manual measurements.

Study Design

Cohort study (diagnosis); Level of evidence, 2.

Methods

A deep learning U-Net model was developed on a cohort of 300 postoperative short-leg lateral radiographs from patients who underwent ACLR to segment the tibial shaft, tibial joint surface, and tibial tuberosity. The model was trained via a random split after an 80 to 20 train-validation scheme. Masks for training images were manually segmented, and the model was trained for 400 epochs. An image processing pipeline was then deployed to annotate and measure the PTS using the predicted segmentation masks. Finally, the performance of this combined pipeline was compared with human measurements performed by 2 study personnel using a previously validated manual technique for measuring the PTS on short-leg lateral radiographs on an independent test set consisting of both pre- and postoperative images.

Results

The U-Net semantic segmentation model achieved a mean Dice similarity coefficient of 0.885 on the validation cohort. The mean difference between the human-made and computer-vision measurements was 1.92° (σ = 2.81° [P = .24]). Extreme disagreements between the human and machine measurements, as defined by ≥5° differences, occurred <5% of the time. The model was incorporated into a web-based digital application front-end for demonstration purposes, which can measure a single uploaded image in Portable Network Graphics format in a mean time of 5 seconds.

Conclusion

We developed an efficient and reliable deep learning computer vision algorithm to automate the PTS measurement on short-leg lateral knee radiographs. This tool, which demonstrated good agreement with human annotations, represents an effective clinical adjunct for measuring the PTS as part of the preoperative assessment of patients with ACL injuries.

The Principles of Knee Joint Preservation: Operative Treatment Strategies

➤ Joint alignment, meniscal status, and ligament stability are codependent factors involved in knee joint preservation, and any injury or imbalance can impact the knee articular cartilage status and can result in adverse clinical outcomes.➤ Cartilage preservation procedures in the knee will not result in optimal outcomes if there is joint malalignment, meniscal deficiency, or ligamentous instability.➤ Lower-extremity varus or valgus malalignment is a risk factor for the failure of an anterior cruciate ligament (ACL) reconstruction. It represents an indication for a high tibial osteotomy or distal femoral osteotomy in the setting of failed ACL reconstruction, and may even be considered in patients who have an initial ACL injury and severe malalignment.➤ An elevated posterior tibial slope increases the risk of failure of ACL reconstruction, whereas a decreased posterior tibial slope increases the risk of failure of posterior cruciate ligament reconstruction.

Posterior tibial slope (PTS) ≥ 10 degrees is a risk factor for further anterior cruciate ligament (ACL) injury; BMI is not

PURPOSE

This case-control study aimed to assess the influence of BMI and PTS on subsequent ACL injury affecting either ACL graft or the native ACL of the contralateral knee after primary ACL reconstruction.

METHODS

A retrospective case-control study was performed using a cohort of patients who underwent arthroscopic ACL reconstruction between 2010 and 2020 using the same surgical procedure: Hamstring tendon autograft. The study group (group I) included all the patients (n = 94) during this period who sustained a subsequent ACL injury. The control group (group II) consisted of 94 patients randomly selected (matched Group I in terms of sex, age, and ACL graft) who did not sustain any further ACL injury. PTS was measured by two blinded surgeons on lateral knee view radiographs of the operated knee after primary ACL. BMI in kg/m2 was measured during the preoperative anesthesia consultation. Exclusion criteria were: non-true or rotated lateral knee radiographs of the operated knee post-ACLR, associated knee ligament injury requiring surgical management, iterative knee surgeries, open growth plate, and related fracture.

RESULTS

The mean posterior tibial slope in group I was 7.5° ± 2.9, and 7.2° ± 2.0 in group II. A PTS angle cutoff was set at 10 degrees. The rate of patients showing a PTS ≥ 10° was significantly higher in group I compared to group II (p < 0.01). Patients with PTS ≥ 10° were 5.7 times more likely to sustain a subsequent ACL injury, (OR: 5.7 95% CI[1.858-17.486]). The Average BMI in group I was 24.5 ± 3.7 kg.m-2 compared to group II which was 23.3 ± 3.0 kg.m-2. There were no significant differences in any of the four BMI categories between both groups (p value 0.289). A series of BMI cut-offs were also analyzed at 23 to30 kg/m2, and there was no significant difference between both groups.

CONCLUSIONS

A posterior tibial slope equal to or above 10 degrees measured on lateral knee radiographs was associated with 5.7 times higher risk of ACL graft rupture or contralateral native ACL injury; however, BMI was not.

New Considerations in ACL Surgery: When Is Anatomic Reconstruction Not Enough?

➤ Clinicians should be careful to assess for associated injuries including anterolateral complex and medial meniscal ramp lesions or lateral meniscal posterior root tears.➤ Consideration of lateral extra-articular augmentation should be given for patients with >12° of posterior tibial slope.➤ Patients with preoperative knee hyperextension (>5°) or other nonmodifiable risk factors, including high-risk osseous geometry, may benefit from a concomitant anterolateral augmentation procedure to improve rotational stability.➤ Meniscal lesions should be addressed at the time of anterior cruciate ligament reconstruction with meniscal root or ramp repair.

Estimation of the proper gap ratio using preoperative radiography for posterior tibial slope maintenance in biplanar open wedge high tibial osteotomy

BACKGROUND

This study aimed to estimate the ratio of the anterior and posterior gaps before surgery that can minimize the posterior tibial slope (PTS) change through preoperative radiography, and to confirm whether the use of the block helps maintain the PTS during open wedge high tibial osteotomy (OWHTO).

METHODS

Patients who underwent OWHTO between 2015 and 2018 were included. To measure optimal anterior gap (AG) and posterior gap (PG) ratio, hinge to medial tibial tuberosity length (HTL), total osteotomy length (TOL), and PTS were measured using knee AP X-ray. Real AG and PG were measured using postoperative knee computed tomography. Use of the block was also confirmed.

RESULTS

Total 107 knees (95 patients) were included. The average ratio between HTL and TOL was 70.9%. The average ratio AG: PG was 72.9%. PTS increased significantly from 10.2° to 11.2° postoperatively (p = 0.006). When the difference in HTL: TOL and AG: PG, and the amount of PTS change were analyzed using linear regression, there was a statistically significant correlation (correlation coefficient: - 25.9; p < 0.001). There was no difference in AG: PG according to the use of the block (p = 0.882).

CONCLUSION

In OWHTO, PTS change can be minimized by estimating the ratio of the AG and PG using radiographs, and is was approximately 70%. If the ratio is increased by 10% from the predicted value, the PTS increases by approximately 2.6°. Using a block during OWHTO did not have a considerable advantage in terms of PTS maintenance compared to the group not using a block.

LEVEL OF EVIDENCE

Level IV.

The Relationship Between Posterior Tibial Slope and Pediatric Tibial Eminence Fractures

BACKGROUND

Tibial eminence fractures are bony avulsions of the anterior cruciate ligament from its insertion on the intercondylar eminence. Numerous anatomic factors have been associated with anterior cruciate ligament injuries, such as posterior tibial slope, but there are few studies evaluating the association with tibial eminence fracture.

PURPOSE

To compare posterior tibial slope of pediatric patients with and without tibial eminence fractures. We hypothesized that a steeper posterior tibial slope would be associated with tibial eminence fracture.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent surgical treatment of tibial eminence fracture were retrospectively identified between January 2000 and July 2021. Adults aged >20 years and those without adequate imaging were excluded. Controls without gross ligamentous or osseous pathology were identified. Descriptive information and Meyers and McKeever classification were recorded. Posterior tibial slope measurements were obtained by 2 independent orthopaedic surgeons twice, with measurements separated by 3 weeks. Chi-square tests and independent-samples t tests were used to compare posterior tibial slope and patient characteristics. Inter- and intrareviewer variability was determined via the intraclass correlation coefficient.

RESULTS

A total of 51 patients with tibial eminence fractures and 57 controls were included. By sex, tibial eminence fractures occurred among 34 male and 17 female patients with a mean age of 10.9 years. The posterior tibial slope among those with tibial eminence fractures (9.7°) was not significantly greater than that of controls (8.8°; P = .07). Male patients with a tibial eminence fracture had significantly steeper slopes compared with controls (10.0° vs 8.4°; P = .006); this difference was not observed between female patients and female controls. Patients with a slope ≥1 SD above the mean (12.0°) had 3.8 times greater odds (95% CI, 1.3-11.6; P = .017) of having a tibial eminence fracture. Male patients with a posterior tibial slope >12° had 5.8 times greater odds (95% CI, 1.1-29.1; P = .034) of having a tibial eminence fracture compared with male controls.

CONCLUSION

Male patients undergoing surgical fixation of a tibial eminence fracture had an increased posterior tibial slope as compared with case-controls. Increased posterior tibial slope may be a risk factor for sustaining a tibial eminence fracture, although the clinical significance of this deserves further investigation.

Steep posterior slope of the medial tibial plateau and anterior cruciate ligament degeneration contribute to medial meniscus posterior root tears in young patients

PURPOSE

Medial meniscus posterior root tears (MMPRTs) occur most frequently in middle-aged and older adults. However, this serious condition can also occur in younger patients. The purpose of this study was to compare anterior cruciate ligament (ACL) degeneration and sagittal medial tibial slope in young adults with and without MMPRT.

METHODS

Eighteen healthy volunteers, 18 young patients (20-49 years of age), and 30 middle-aged and older patients (50-70 years of age) with MMPRT repair were included in the study. Sex, body mass index (BMI), femorotibial angle, ACL degeneration, and medial tibial slope angle were compared among the groups. ACL degeneration and medial tibial slope angle were assessed using magnetic resonance imaging.

RESULTS

In the healthy volunteer group, the young patient group, and the older patient group, the medial tibial slopes were 3.5° ± 1.4°, 6.1° ± 2.7°, and 7.2° ± 1.9°, respectively, and the ACL degeneration rates were 5.6%, 38.9%, and 43.3%, respectively. Young patients with MMPRT had significantly steeper medial tibial slopes and ACL degeneration compared to those of the healthy volunteers (P < 0.05). The parameters of young patients were similar to those of older patients with MMPRT. In the multivariate logistic regression analysis, BMI, medial tibial slope, and ACL degeneration were significantly associated with MMPRT in young patients.

CONCLUSION

BMI, steep medial tibial slope, and ACL degeneration contribute to MMPRT development in younger patients.

LEVEL OF EVIDENCE

Level III.

A lower starting point for the medial cut increases the posterior slope in opening-wedge high tibial osteotomy: a cadaveric study

PURPOSE

The objective of this study was to evaluate the effects on the posterior tibial slope of different distances from the joint line to start the osteotomy and of varying the placement of the opening wedge in high tibial osteotomy. Starting the osteotomy more distally and an incorrect location for the tibial opening wedge were hypothesized to increase the posterior tibial slope.

METHODS

A cadaveric study was conducted using 12 knees divided into two groups based on the distance from the joint line to the start of the osteotomy: 3 and 4 cm. The preintervention posterior tibial slope was measured radiologically. Once the osteotomy was performed, the medial cortex of the tibia was divided into anteromedial, medial, and posteromedial thirds. A 10° opening wedge was sequentially placed in each third, and the effect on the posterior tibial slope was evaluated radiographically.

RESULTS

Significant changes were observed only in the 3-cm group (p = 0.02) when the wedge was placed in the anteromedial zone. In contrast, in the 4-cm group, significant differences were observed when the opening wedge was placed at both the medial (p = 0.04) and anteromedial (p = 0.012) zones.

CONCLUSION

Correct control of the posterior tibial slope can be achieved by avoiding a low point when beginning the osteotomy and placing the opening wedge in the posteromedial third of the tibia when performing an opening-wedge high tibial osteotomy.

LEVEL OF EVIDENCE

Controlled laboratory study.

Importance of posterior tibial slope in joint kinematics with an anterior cruciate ligament-deficient knee

Aims

To fully quantify the effect of posterior tibial slope (PTS) angles on joint kinematics and contact mechanics of intact and anterior cruciate ligament-deficient (ACLD) knees during the gait cycle.

Methods

In this controlled laboratory study, we developed an original multiscale subject-specific finite element musculoskeletal framework model and integrated it with the tibiofemoral and patellofemoral joints with high-fidelity joint motion representations, to investigate the effects of 2.5° increases in PTS angles on joint dynamics and contact mechanics during the gait cycle.

Results

The ACL tensile force in the intact knee was significantly affected with increasing PTS angle. Considerable differences were observed in kinematics and initial posterior femoral translation between the intact and ACLD joints as the PTS angles increased by more than 2.5° (beyond 11.4°). Additionally, a higher contact stress was detected in the peripheral posterior horn areas of the menisci with increasing PTS angle during the gait cycle. The maximum tensile force on the horn of the medial meniscus increased from 73.9 N to 172.4 N in the ACLD joint with increasing PTS angles.

Conclusion

Knee joint instability and larger loading on the medial meniscus were found on the ACLD knee even at a 2.5° increase in PTS angle (larger than 11.4°). Our biomechanical findings support recent clinical evidence of a high risk of failure of ACL reconstruction with steeper PTS and the necessity of ACL reconstruction, which would prevent meniscus tear and thus the development or progression of osteoarthritis.

Cite this article: Bone Joint Res 2022;11(10):739–750.

Minimizing the risk of graft failure after anterior cruciate ligament reconstruction in athletes. A narrative review of the current evidence

Anterior cruciate ligament (ACL) tear is one of the most common sport-related injuries and the request for ACL reconstructions is increasing nowadays. Unfortunately, ACL graft failures are reported in up to 34.2% in athletes, representing a traumatic and career-threatening event. It can be convenient to understand the various risk factors for ACL failure, in order to properly inform the patients about the expected outcomes and to minimize the chance of poor results. In literature, a multitude of studies have been performed on the failure risks after ACL reconstruction, but the huge amount of data may generate much confusion.The aim of this review is to resume the data collected from literature on the risk of graft failure after ACL reconstruction in athletes, focusing on the following three key points: individuate the predisposing factors to ACL reconstruction failure, analyze surgical aspects which may have significant impact on outcomes, highlight the current criteria regarding safe return to sport after ACL reconstruction.

Preoperative Planning and Preservation of the Knee with Complex Osteotomies

The knee is a complex structure composed of bone, cartilage, menisci, ligaments and muscles, which all work synergistically to optimize congruence, stability, and function. Osteotomies are procedures addressing an abnormal joint alignment, shifting the mechanical load from a diseased joint compartment to a healthier one. Preoperative planning is an important art of identifying the source of abnormal load distribution to the joint, enabling the surgeon to simulate a deformity correction ahead of the surgical procedure.

Current trends in the anterior cruciate ligament part 1: biology and biomechanics

A trend within the orthopedic community is rejection of the belief that "one size fits all." Freddie Fu, among others, strived to individualize the treatment of anterior cruciate ligament (ACL) injuries based on the patient's anatomy. Further, during the last two decades, greater emphasis has been placed on improving the outcomes of ACL reconstruction (ACL-R). Accordingly, anatomic tunnel placement is paramount in preventing graft impingement and restoring knee kinematics. Additionally, identification and management of concomitant knee injuries help to re-establish knee kinematics and prevent lower outcomes and registry studies continue to determine which graft yields the best outcomes. The utilization of registry studies has provided several large-scale epidemiologic studies that have bolstered outcomes data, such as avoiding allografts in pediatric populations and incorporating extra-articular stabilizing procedures in younger athletes to prevent re-rupture. In describing the anatomic and biomechanical understanding of the ACL and the resulting improvements in terms of surgical reconstruction, the purpose of this article is to illustrate how basic science advancements have directly led to improvements in clinical outcomes for ACL-injured patients.Level of evidenceV.

Application of Machine Learning Algorithms to Predict Clinically Meaningful Improvement After Arthroscopic Anterior Cruciate Ligament Reconstruction

Background:

Understanding specific risk profiles for each patient and their propensity to experience clinically meaningful improvement after anterior cruciate ligament reconstruction (ACLR) is important for preoperative patient counseling and management of expectations.

Purpose:

To develop machine learning algorithms to predict achievement of the minimal clinically important difference (MCID) on the International Knee Documentation Committee (IKDC) score at a minimum 2-year follow-up after ACLR.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

An ACLR registry of patients from 27 fellowship-trained sports medicine surgeons at a large academic institution was retrospectively analyzed. Thirty-six variables were tested for predictive value. The study population was randomly partitioned into training and independent testing sets using a 70:30 split. Six machine learning algorithms (stochastic gradient boosting, random forest, neural network, support vector machine, adaptive gradient boosting, and elastic-net penalized logistic regression [ENPLR]) were trained using 10-fold cross-validation 3 times and internally validated on the independent set of patients. Algorithm performance was assessed using discrimination, calibration, Brier score, and decision-curve analysis.

Results:

A total of 442 patients, of whom 39 (8.8%) did not achieve the MCID, were included. The 5 most predictive features of achieving the MCID were body mass index ≤27.4, grade 0 medial collateral ligament examination (compared with other grades), intratunnel femoral tunnel fixation (compared with suspensory), no history of previous contralateral knee surgery, and achieving full knee extension preoperatively. The ENPLR algorithm had the best relative performance (C-statistic, 0.82; calibration intercept, 0.10; calibration slope, 1.15; Brier score, 0.068), demonstrating excellent predictive ability in the study’s data set.

Conclusion:

Machine learning, specifically the ENPLR algorithm, demonstrated good performance for predicting a patient’s propensity to achieve the MCID for the IKDC score after ACLR based on preoperative and intraoperative factors. The femoral tunnel fixation method was the only significant intraoperative variable. Range of motion and medial collateral ligament integrity were found to be important physical examination parameters. Increased body mass index and prior contralateral surgery were also significantly predictive of outcome.

Comparative anatomy and morphology of the knee in translational models for articular cartilage disorders. Part I: Large animals

BACKGROUND

The human knee is a complex joint, and affected by a variety of articular cartilage disorders. Large animal models are critical to model the complex disease mechanisms affecting a functional joint. Species-dependent differences highly affect the results of a pre-clinical study and need to be considered, necessitating specific knowledge not only of macroscopic and microscopic anatomical and pathological aspects, but also characteristics of their individual gait and joint movements.

METHODS

Literature search in Pubmed.

RESULTS AND DISCUSSION

This narrative review summarizes the most relevant anatomical structural and functional characteristics of the knee (stifle) joints of the major translational large animal species, comprising dogs, (mini)pigs, sheep, goats, and horses in comparison with humans. Specific characteristics of each species, including kinematical gait parameters are provided. Considering these multifactorial dimensions will allow to select the appropriate model for answering the research questions in a clinically relevant fashion.