Association Between Magnetic Resonance Imaging-Measured Intercondylar Notch Dimensions and Anterior Cruciate Ligament Injury: A Meta-analysis

A tight anterosuperior intercondylar notch may increase the risk of cyclops syndrome after anterior cruciate ligament reconstruction using a quadruple semi-tendinosus short autograft

BACKGROUND

Cyclops syndrome is loss of terminal knee extension caused by a fibrous nodule developed in the anterior intercondylar notch. The many known risk factors include preoperative motion-range limitation, tibial tunnel malposition, and tight hamstrings. The primary objective of this study was to assess whether intercondylar notch size was associated with the risk of cyclops syndrome or graft tear after anterior cruciate ligament (ACL) reconstruction using a quadruple semi-tendinosis autograft. The secondary objective was to determine whether intercondylar notch size was associated with functional outcomes.

HYPOTHESIS

A narrow intercondylar notch is associated with higher risks of cyclops syndrome and poor functional outcomes.

METHODS

Consecutive patients who underwent ACL reconstruction by quadruple semi-tendinosus autograft were included retrospectively. Preoperative magnetic resonance imaging scans were assessed by a single senior surgeon, who determined the conventional notch width index (NWI) and the anterior NWI (aNWI) for each patient.

RESULTS

The 120 included patients had a mean follow-up of 2.4±0.8 years. Among them, 20 (16.7%) experienced cyclops syndrome and 7 (5.8%) graft rupture. At last follow-up, 26 (21.7%) had not returned to sports and only 47 (39.2%) had returned to sports at the pre-injury level. The mean Lysholm score was 87.9±13.5 and the main subjective IKDC score was 84±13. A narrow notch was significantly associated with lower likelihoods of returning to sports (p=0.001), returning to the same sport (p<0.0001), and returning to the pre-injury sport level (p=0.004). By multivariate analysis, only the aNWI index was significantly associated with the risk of cyclops syndrome (p<0.0001). An aNWI index lower than 0.18 had 85% sensitivity and 78% specificity for predicting cyclops syndrome.

CONCLUSION

A narrow anterosuperior intercondylar notch may increase the risk of cyclops syndrome after ACL reconstruction using a quadruple semi-tendinosus graft but is not associated with the risk of graft rupture.

LEVEL OF EVIDENCE

IV, retrospective observational cohort study.

Hereditary Anatomical Risk Factors for Anterior Cruciate Ligament Injuries

INTRODUCTION

 Genetic and anatomical factors have been reported as risk factors for anterior cruciate ligament (ACL) injuries. This study aimed to investigate anatomical characteristics in family members sustaining ACL injuries, compared with age- and sex-matched patients with simple meniscus injuries.

MATERIALS AND METHODS

 Medical records of 1548 patients who underwent ACL reconstruction were reviewed. Cases of ACL injury occurring in first-degree relatives were selected. Forty-one patients from 20 families were included in the study (F-ACL group). Fifty patients with meniscus injuries were included as controls. Anatomical factors comprising posterior-inferior tibial slope (PITS), notch width index (NWI), notch angle (NA), and intercondylar notch roof inclination angle (RA) were compared between groups. The correlation of these anatomical factors between parent and child or siblings was also investigated.

RESULTS

 The 41 patients (20 families) consisted of 12 parent-child pairs and 29 siblings (13 pairs and one trio). Injuries occurred during playing the same sport in 11 families (55%). PITS was significantly steeper in the F-ACL group (9.9 vs. 7.8 degrees). NWI and NA were significantly smaller in the F-ACL group (0.262 vs. 0.278 and 50.5 vs. 58.8 degrees). RA was significantly greater in the F-ACL group (130 vs. 126.9 degrees). A positive correlation in NA (r = 0.677) and a weak correlation in NWI and RA were observed between family members.

CONCLUSIONS

 Common anatomical risk factors of ACL injury exist within families, including intercondylar notch stenosis and steep posterior tibial slope. The findings suggest the potential for developing effective ACL injury prevention programs targeting these risk factors.

Femoral Tunnel Malposition, Increased Lateral Tibial Slope, and Decreased Notch Width Index Are Risk Factors for Non-Traumatic Anterior Cruciate Ligament Reconstruction Failure

PURPOSE

To identify risk factors for patients who sustain nontraumatic anterior cruciate ligament reconstruction (ACLR) failure.

METHODS

A retrospective analysis was performed on patients undergoing primary or revision ACLR in our institution between 2010 and 2018. Patients sustaining insidious-onset knee instability without history of trauma were identified as nontraumatic ACLR failure and assigned to the study group. The control group of subjects who showed no evidence of ACLR failure with minimum 48-month follow-up were matched in a 1:1 ratio based on age, sex, and body mass index. Anatomic parameters including tibial slope (lateral [LTS], medial [MTS]); tibial plateau subluxation (lateral [LTPsublx], medial [MTPsublx]); notch width index (NWI); and lateral femoral condyle ratio were measured with magnetic resonance imaging or radiography. Graft tunnel position was assessed using 3-dimensional computed tomography and reported in 4 dimensions: deep-shallow ratio (DS ratio) and high-low ratio for femoral tunnel, anterior-posterior ratio and medial-lateral ratio for tibial tunnel. Interobserver and intraobserver reliability were evaluated by the intraclass correlation coefficient (ICC). Patients' demographic data, surgical factors, anatomic parameters, and tunnel placements were compared between the groups. Multivariate logistic regression and receiver operating characteristic curve analysis was used to discriminate and assess the identified risk factors.

RESULTS

A total of 52 patients who sustained nontraumatic ACLR failure were included and matched with 52 control subjects. Compared to patients with intact ACLR, those who sustained nontraumatic ACLR failure showed significantly increased LTS, LTPsublx, MTS, and deceased NWI (all P < .001). Moreover, the average tunnel position in the study group was significantly more anterior (P < .001) and superior (P = .014) at the femoral side and more lateral (P = .002) at the tibial side. Multivariate regression analysis identified LTS (odds ratio [OR] = 1.313; P = .028), DS ratio (OR = 1.091; P = .002), and NWI (OR = 0.813; P = .040) as independent predictors of nontraumatic ACLR failure. LTS appeared to be the best independent predictive factor (area under the curve [AUC] = 0.804; 95% confidence interval [CI], 0.721-0.887), followed by DS ratio (AUC = 0.803; 95% CI, 0.717-0.890), and NWI (AUC = 0.756; 95% CI, 0.664-0.847). The optimal cutoff values were 6.7° for increased LTS (sensitivity = 0.615, specificity = 0.923); 37.4% for increased DS ratio (sensitivity = 0.673, specificity = 0.885); and 26.4% for decreased NWI (sensitivity = 0.827, specificity = 0.596). Intraobserver and interobserver reliability was good to excellent, with ICCs ranging from 0.754 to 0.938 for all radiographical measurements.

CONCLUSIONS

Increased LTS, decreased NWI, and femoral tunnel malposition are predictive risk factors for nontraumatic ACLR failure.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Bone Morphological Characteristics as Risk Factors for Anterior Cruciate Ligament Injury: Comparison Between Contact and Noncontact Injury

Background

Altered bone morphologies are considered risk factors for noncontact anterior cruciate ligament (ACL) injuries.

Purpose/Hypothesis

This study aimed to investigate bone morphological characteristics as risk factors for ACL tears in contact injuries and compare these factors with those for noncontact ACL injuries. We hypothesized that altered bone morphologies would also be risk factors for contact ACL injury.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Enrolled were patients who underwent primary ACL reconstructions between January 2000 and December 2021 within 6 weeks after injury. Patients in the ACL group were classified according to injury mechanism (contact vs noncontact). During the same period, a control group of patients matched by age, height, and body mass index to the ACL group was selected. The lateral femoral condylar ratio (LFCR), notch width index (NWI), and lateral posterior tibial slope (PTS) were measured. Measured parameters were compared between the control, contact, and noncontact groups using analysis of variance.

Results

There were 86 patients in the control group, 102 patients in the contact ACL group, and 105 patients in the noncontact ACL group. The demographic characteristics of the 3 groups did not differ significantly. The contact group had significantly higher LFCRs and lower NWIs compared with the control group (P < .001 and P = .001, respectively). The noncontact group had significantly higher LFCRs and PTSs and lower NWIs compared with the control group (P = .031; P < .001; and P < .001, respectively). The noncontact group had significantly higher PTSs and lower NWIs compared with the contact group (P = .003 and P =.014, respectively). In the contact group, the LFCR, PTS, and NWI were significant risk factors for ACL tears (odds ratio [OR], 1.25 [P < .001]; OR, 1.16 [P = .008]; and OR, 1.27 [P = .001], respectively), and in the noncontact group, the PTS and NWI were significant risk factors for ACL tears (OR, 1.20 [P < .001]; OR, 1.59 [P < .001], respectively).

Conclusion

Altered bone morphological characteristics of the knee were found to be risk factors for ACL tears in contact injuries as well as noncontact injuries. Altered morphology has a more significant effect in noncontact ACL injuries.

Anatomical factors associated with the development of anterior tibial spine fractures based on MRI measurements

BACKGROUND

Numerous studies have investigated anatomic factors for anterior cruciate ligament (ACL) injuries, such as posterior tibial slope (PTS) and notch width index (NWI). However, anterior tibial spine fracture (ATSF) as a specific pattern of ACL injury, a bony avulsion of the ACL from its insertion on the intercondylar spine of the tibia, has rarely been explored for its anatomical risk factors. Identifying anatomic parameters of the knee associated with ATSF is important for understanding injury mechanisms and prevention.

METHODS

Patients who underwent surgery for ATSF between January 2010 and December 2021 were retrospectively reviewed, and 38 patients were included in the study group. Thirty-eight patients who suffered from isolated meniscal tear without other pathologic findings were matched in a 1:1 fashion by age, sex and BMI to the study group. The lateral posterior tibial slope (LPTS), medial posterior tibial slope (MPTS), medial tibial depth, lateral tibial height, lateral femoral condyle ratio (LFCR) and NWI were measured and compared between the ATSF and control groups. Binary logistic regressions identified independent predictors of ATSF. Receiver operator characteristic (ROC) curves were performed to compare the diagnostic performance and determine the cutoff values of associated parameters.

RESULTS

The LPTS, LFCR and MPTS were significantly larger in the knees in the ATSF group than in the control group (P = 0.001, P = 0.012 and P = 0.005, respectively). The NWI was significantly smaller in the knees in the ATSF group than in the control group (P = 0.005). According to the results of logistic regression analysis, the LPTS, LFCR and NWI were independently associated with ATSF. The LPTS was the strongest predictor variable, and the ROC analysis revealed 63.2% sensitivity and 76.3% specificity (area under the curve, 0.731; 95% CI 0.619-0.844) for values above 6.9.

CONCLUSION

The LPTS, LFCR and NWI were found to be associated with the ATSF; in particular, LPTS could provide the most accurate predictive performance. The findings of this study may aid clinicians in identifying people at risk for ATSF and taking individualized preventive measures. However, further investigation regarding the pattern and biomechanical mechanisms of this injury is required.

The patient with patellar instability has a stenotic intercondylar notch and a thin anterior cruciate ligament: a retrospective comparative study

BACKGROUND

Patellar instability (PI) usually combines with morphological abnormalities of femoral condyles that may affect the morphology of the intercondylar notch and anterior cruciate ligament (ACL), which are important in individualized ACL reconstruction. This study aimed to investigate the morphological characteristics of the intercondylar notch and ACL in patients with PI.

METHODS

80 patients with PI and 160 age- and gender-matched controls from January 2014 to June 2022 were studied. Morphological measurements of the femoral condyles included intercondylar notch height, notch width, medial condylar width, lateral condylar width, bicondylar width, notch width index, notch angle, lateral femoral condyle ratio (LFCR), condyle flexion angle, and posterior tibial slope. Morphological measurements of the ACL included ACL length, inclination angle, and ACL size. The measurements were compared between PI and control groups, and between males and females in PI group. The independent samples t-test was performed to examine differences in continuous variables. The chi-square test was used for comparing categorical variables.

RESULTS

The intercondylar notch width, bicondylar width, notch width index, and notch angle were significantly smaller, while the LFCR was significantly larger in PI group than those of control group (p < 0.05). The ACL thickness (0.70 ± 0.16 cm vs 0.80 ± 0.21 cm, p = 0.023) and width (0.54 ± 0.14 cm vs 0.60 ± 0.13 cm, p = 0.029) were significantly smaller in PI group. The notch width was significantly smaller in female patients than males in PI group, but no significant difference was observed in the notch width index and notch angle (p > 0.05). No sex difference related to the morphology of the ACL was found.

CONCLUSIONS

The patient with PI had a stenotic intercondylar notch and a thin ACL. No significant sex difference in the intercondylar notch stenosis and ACL size was observed. The morphology of the intercondylar notch and ACL should be taken into consideration when planning individualized ACL reconstruction in the presence of PI.

Morphometric characteristics of the knee are associated with the injury of the meniscus

Background

To assess the geometrical risk factors for meniscal injuries. We hypothesized that the narrowness of the intercondylar notch and the smaller tibial spine could increase the risk of meniscal injuries.

Methods

We retrospectively studied two hundred and seven patients examined for knee magnetic resonance images. Two experienced orthopedists evaluated the severity of meniscal injuries. The notch width, bicondylar notch width, notch width index, condyle width of the femur, tibial spine height, and intercondylar angle were measured in magnetic resonance image slides by two blinded orthopedists.

Results

A total of 112 patients with a meniscus injury and 95 patients were as healthy control in all two hundred and seven patients. The NWI (P = 0.027) in patients with meniscus injuries was significantly different from the control group. A 1 SD (0.04 mm) increase in NWI was associated with a 0.4-fold increase in the risk of meniscal injury. A 1 SD (0.04 mm) increase in NWI was associated with a 0.64-fold increase in the risk of grade 3 meniscal injury. Furthermore, NWI and medial spine height are decreased significantly in grade 2 (P < 0.05) meniscal injury than in other grades. The medial spine height was significantly decreased in the meniscal injury group (P = 0.025), and the decrease in medial spine height would increase the risk of meniscal injury (OR = 0.77) and grade 3 meniscal injury (OR = 0.8).

Conclusions

The stenosis of the femoral intercondylar notch and small medial tibial spine is risk factors of meniscal injury. The decreased NWI and the medial tibial spine height were also associated with the severity of the meniscal injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03380-2.

Narrow Notch Width and Low Anterior Cruciate Ligament Volume Are Risk Factors for Anterior Cruciate Ligament Injury: A Magnetic Resonance Imaging-Based Study

BACKGROUND

The relationship between anterior cruciate ligament (ACL) injury and anatomical structures is still a topic of debate.

PURPOSE

The aim of this study was to compare knee geometry in demographically matched ACL-injured and ACL-intact athletes.

METHODS

We conducted a case-control study comparing 2 groups, each consisting of 55 professional athletes (44 men and 11 women): 1 group with complete ACL tears (cases) and 1 group with intact ACLs (controls). The groups were compared using magnetic resonance imaging (MRI) in terms of intercondylar notch geometry, tibial plateau characteristics, and ACL volume.

RESULTS

Among cases and controls, we found the cases had lower notch width (20.24 ± 2.68 mm vs. 22.04 ± 2.56 mm, respectively) and notch width index (0.29 ± 0.03 vs. 0.31 ± 0.03, respectively). The mean ACL volume in the cases (1181.63 mm³ ± 326 mm³) was also lower than in controls (1352.61 mm³ ± 279.84 mm³). The parameters of tibial slope geometry were comparable between groups. In addition, women had lower ACL volume than men (1254 ± 310 mm³ vs. 890 ± 267 mm³, respectively) and higher medial posterior tibial slope (4.76 ± 2.6 vs. 6.63 ± 1.83, respectively). Among cases, women had narrower notch width than men (16.9 ± 2.42 mm vs. 21.08 ± 2.03 mm). However, notch width index was comparable between male (0.3 ± 0.02) and female (0.28 ± 0.03) cases.

CONCLUSION

Our findings suggest that narrow notch width and low ACL volume may enhance the risk of ACL injury among athletes. There was no association found between posterior tibial slope and ACL injury between athletes with injured ACLs and controls. Further study is indicated.

Does Femoral Intercondylar Notch Volume Differ in Anterior Cruciate Ligament-Injured Adult Patients Compared to the Uninjured?: A Meta-Analysis

BACKGROUND

Stenotic femoral intercondylar notch is considered as a risk factor for anterior cruciate ligament (ACL) injury and three-dimensional notch volume is used as a marker for the injury. The primary purpose of this study was to assess the difference in notch volume between the ACL-injured and uninjured in men and women combined or stratified by sex. The secondary purpose was to assess the difference in notch volume between the ACL-intact men and women.

METHODS

A search of PubMed/Medline, Scopus, Google Scholar, and Cochrane databases from inception to December 9, 2020, was conducted without restrictions using the following terms: ACL, notch, volume, notch volume, femoral notch volume, and intercondylar notch volume. Studies that compared the ACL-injured with uninjured controls were included. Independent extraction of articles by two authors using predefined data fields including study quality indicators was done. All pooled analyses were based on the inverse-variance weighted random effects model and mean difference was chosen as the effect measure.

RESULTS

Nine studies (1,169 knees) qualified for overall analysis (both sexes combined) and significant heterogeneity was observed, which disappeared after pooling studies with age-sex matched controls and those without. Notch volume in the ACL-injured was 0.75 cm3 (95% confidence interval [CI], 0.53-0.96 cm3), which was smaller than that in the age- and sex-matched controls. Six studies qualified for analysis in men. Notch volume in the ACL-injured men was smaller, especially when non-contact ACL injury was considered (1.40 cm3; 95% CI, 1.08-1.73 cm3). Five studies qualified for analysis in women and ACL-injured women had smaller notch volume irrespective of the mechanism of injury (0.38 cm3; 95% CI, 0.18-0.59 cm3). Notch volume of the uninjured men was larger than that of the uninjured women (1.86 cm3; 95% CI, 1.54-2.18 cm3).

CONCLUSIONS

ACL-injured adults have smaller notch volume than the age- and sex-matched controls. Non-contact ACL-injured males have smaller notch volume compared to ACL-intact males. ACL-injured females have smaller notch volume irrespective of the nature of injury. Men have higher notch volume than women. The quality of evidence is very low to low.

ACL Size, but Not Signal Intensity, Is Influenced by Sex, Body Size, and Knee Anatomy

Background:

Little is known about sex-based differences in anterior cruciate ligament (ACL) tissue quality in vivo or the association of ACL size (ie, volume) and tissue quality (ie, normalized signal intensity on magnetic resonance imaging [MRI]) with knee anatomy.

Hypothesis:

We hypothesized that (1) women have smaller ACLs and greater ACL normalized signal intensity compared with men, and (2) ACL size and normalized signal intensity are associated with age, activity levels, body mass index (BMI), bicondylar width, intercondylar notch width, and posterior slope of the lateral tibial plateau.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Knee MRI scans of 108 unique ACL-intact knees (19.7 ± 5.5 years, 62 women) were used to quantify the ACL signal intensity (normalized to cortical bone), ligament volume, mean cross-sectional area, and length. Independent t tests were used to compare the MRI-based ACL parameters between sexes. Univariate and multivariate linear regression analyses were used to investigate the associations between normalized signal intensity and size with age, activity levels, BMI, bicondylar width, notch width, and posterior slope of the lateral tibial plateau.

Results:

Compared with men, women had significantly smaller mean ACL volume (men vs women: 2028 ± 472 vs 1591 ± 405 mm³), cross-sectional area (49.4 ± 9.6 vs 41.5 ± 8.6 mm²), and length (40.8 ± 2.8 vs 38.1 ± 3.1 mm) (P < .001 for all), even after adjusting for BMI and bicondylar width. There was no difference in MRI signal intensity between men and women (1.15 ± 0.24 vs 1.12 ± 0.24, respectively; P = .555). BMI, bicondylar width, and intercondylar notch width were independently associated with a larger ACL (R² > 0.16, P < .001). Younger age and steeper lateral tibial slope were independently associated with shorter ACL length (R² > 0.03, P < .04). The combination of BMI and bicondylar width was predictive of ACL volume and mean cross-sectional area (R² < 0.3). The combination of BMI, bicondylar width, and lateral tibial slope was predictive of ACL length (R² = 0.39). Neither quantified patient characteristics nor anatomic variables were associated with signal intensity.

Conclusion:

Men had larger ACLs compared with women even after adjusting for BMI and knee size (bicondylar width). No sex difference was observed in signal intensity, suggesting no difference in tissue quality. The association of the intercondylar notch width and lateral tibial slope with ACL size suggests that the influence of these anatomic features on ACL injury risk may be partially explained by their effect on ACL size.

Registration:

NCT02292004 and NCT02664545 (ClinicalTrials.gov identifier).

An association between femoral trochlear morphology and non-contact anterior cruciate ligament total rupture: a retrospective MRI study

INTRODUCTION

The present study aims to investigate the association of the femoral trochlear morphology with the risk of ACL injury and whether this can be considered an additional risk factor in this clinical table.

MATERIALS AND METHODS

This is a retrospective case-control study with 93 patients, 41 patients with ACL total rupture (ACL-TR), and 52 patients without ACL injury who underwent knee magnetic resonance imaging (MRI) between January 2013 and January 2016. The femoral trochlear morphology was evaluated at the proximal and distal levels from the axial knee MRI. The morphological features of the trochlea using sulcus angle, sulcus depth, condylar heights, trochlear sulcus height, percentage of condyles and trochlear sulcus height to transepicondylar width, and lateral and medial trochlear inclination were evaluated. The notch width index was measured on the coronal MR images for notch stenos.

RESULTS

ACL-TR group had a significantly higher sulcus angle (p = 0.00-0.001) and lower sulcus depth (p = 0.00-0.002) than the control group at both levels. Femoral trochlea had morphometric differences between genders. NWI was lower in the ACL-TR group than the control group (control 0.273; ACL-TR 0.247), and there was a statistically significant difference (p = 0.00).

CONCLUSION

This study was shown that the difference in morphology between the trochlear sulcus of patients with normal and ACL injuries should be taken into account in order to increase awareness of ACL injuries. We observed that mild trochlear dysplasia may cause intercondylar notch stenosis rather than changing the localization of the patella. Studies are needed regarding the effect of trochlear dysplasia on ACL.

Notch Volume Measured on Magnetic Resonance Imaging Is Better Than 2-Dimensional Notch Parameters for Predicting Noncontact Anterior Cruciate Ligament Injury in Males

PURPOSE

To evaluate and compare intercondylar notch volume with other 2-dimensional notch parameters (measured on magnetic resonance imaging [MRI]) for prediction of noncontact anterior cruciate ligament (ACL) injury in males.

METHODS

Retrospective case-control study in males based on MRI images. The case group consisted of 80 noncontact ACL-injured males and a control group of 80 age- and height-matched ACL-intact males. Inclusion criteria were 18 to 50 years old, full-thickness tear, MRI obtained within 1 year of injury, and ACL tear visually documented during arthroscopy. Multiligamentous, bilateral, or concomitant bony injuries were excluded. Notch volume and 2D parameters in both planes, including notch depth, notch width, intercondylar notch angle, notch-width index, and notch-shape index, were measured on MRI and compared. Slice interval was included in the formula for notch-volume assessment. Bivariate Pearson correlation between notch volume and 2D parameters was estimated. Multivariate conditional logistic regression analysis was used for predictor model. Receiver operating characteristic (ROC) curves were plotted.

RESULTS

All MRIs had a standard slice thickness of 3 mm and slice interval of 0.3 mm. Notch volume (P < .001), notch angle in the axial plane (P = .001), and notch width in the coronal plane (P = .009) were significantly smaller in the ACL-injured group. Notch volume had inconsistent and negligible to low correlation with 2D parameters. Notch volume was the only significant contributor in the predictor model (P < .001). ROC curve showed that notch volume had highest area under the curve of 84.1% and optimal cutoff at 7.1550 cm³ (specificity, 88.7%; sensitivity, 65%).

CONCLUSION

Significantly smaller intercondylar notch volume is associated with noncontact ACL injury in men and is the most important predictor for such an injury (optimal cutoff of 7.1550 cm³). Two-dimensional notch parameters are inconsistently associated with noncontact ACL injury in men, and none of the 2D parameters can be used as a surrogate for notch volume. Two-dimensional notch parameters fare poorly in predicting noncontact ACL injury in males. Notch volume measurement should include slice interval as a factor.

LEVEL OF EVIDENCE

III, retrospective case-control study.

Femoral Intercondylar Notch: Gross Anatomy and Histology of the Connective Tissue Lining of its Roof: A Pilot Study

PURPOSE

We have consistently observed a connective tissue lining over the intercondylar notch's roof (CTLINR) during arthroscopic surgeries of the knee joint. As there is a strong association of the intercondylar fossa with the anterior cruciate ligament (ACL), we believe that this tissue must be having some role in the functioning of the ACL. The purpose of this pilot study was to investigate the anatomic characteristics of the CTLINR.

METHODS

In this observational anatomical study, we have investigated the gross anatomical and histological features of the CTLINR in four knees of two fresh frozen non-embalmed cadavers. We have also studied its ultrastructural characteristics by obtaining an arthroscopic biopsy of the tissue from a patient undergoing ACL reconstruction.

RESULTS

At gross examination, the CTLINR had a typical glistening white surface with transversely oriented fibres. It entirely covered the roof of the intercondylar notch and was soft to touch. Histological examination with haematoxylin-eosin stain revealed fibro-collagenous tissue with intervening blood vessels. Transmission electron microscopy manifested loosely arranged collagen fibres of variable diameter.

CONCLUSION

The histological and electron microscopic characteristics of the tissue differentiate it from the ACL and its femoral enthesis, suggesting that it was a distinct anatomical structure. As it entirely covered the roof of the intercondylar fossa and had a smooth surface and soft consistency, it may protect the reconstructed ACL from graft abrasion. Furthermore, as it had a characteristic arthroscopic appearance, future research can investigate its role in femoral tunnel positioning.

Risk Factors for Contra-Lateral Secondary Anterior Cruciate Ligament Injury: A Systematic Review with Meta-Analysis

Background

The risk of sustaining a contra-lateral anterior cruciate ligament (C-ACL) injury after primary unilateral ACL injury is high. C-ACL injury often contributes to a further decline in function and quality of life, including failure to return to sport. There is, however, very limited knowledge about which risk factors that contribute to C-ACL injury.

Objective

To systematically review instrinsic risk factors for sustaining a C-ACL injury.

Methods

A systematic review with meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Four databases (MEDLINE, CINAHL, EMBASE, Sport Discus) were searched from inception to January 2020. Inclusion criteria were prospective or retrospective studies investigating any intrinsic risk factor for future C-ACL injury. Meta-analysis was performed and expressed as odds ratios (OR) if two or more articles assessed the same risk factor.

Results

44 moderate-to-high quality studies were eventually included in this review, whereof 35 studies were eligible for meta-analysis, including up to 59 000 individuals. We identified seven factors independently increasing the odds of sustaining a C-ACL injury (in order of highest to lowest OR): (1) returning to a high activity level (OR 3.26, 95% CI 2.10–5.06); (2) Body Mass Index < 25 (OR 2.73, 95% CI 1.73–4.36); (3) age ≤ 18 years (OR 2.42, 95% CI 1.51–3.88); (4) family history of ACL injury (OR 2.07, 95% CI 1.54–2.80); (5) primary ACL reconstruction performed ≤ 3 months post injury (OR 1.65, 95% CI: 1.32–2.06); (6) female sex (OR 1.35, 95% CI 1.14–1.61); and (7) concomitant meniscal injury (OR 1.21, 95% CI 1.03–1.42). The following two factors were associated with decreased odds of a subsequent C-ACL injury: 1) decreased intercondylar notch width/width of the distal femur ratio (OR 0.43, 95% CI 0.25–0.69) and 2) concomitant cartilage injury (OR 0.83, 95% CI 0.69–1.00). There were no associations between the odds of sustaining a C-ACL injury and smoking status, pre-injury activity level, playing soccer compared to other sports or timing of return to sport. No studies of neuromuscular function in relation to risk of C-ACL injury were eligible for meta-analysis according to our criteria.

Conclusion

This review provides evidence that demographic factors such as female sex, young age (≤ 18 years) and family history of ACL injury, as well as early reconstruction and returning to a high activity level increase the risk of C-ACL injury. Given the lack of studies related to neuromuscular factors that may be modifiable by training, future studies are warranted that investigate the possible role of factors such as dynamic knee stability and alignment, muscle activation and/or strength and proprioception as well as sport-specific training prior to return-to-sport for C-ACL injuries.

PROSPERO: CRD42020140129.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-020-01424-3.

Correlation between notch width index assessed via magnetic resonance imaging and risk of anterior cruciate ligament injury: an updated meta-analysis

PURPOSE

To analyze the correlation between notch width index (NWI) and/or femoral intercondylar notch width (NW) assessed by magnetic resonance imaging (MRI) and risk of anterior cruciate ligament (ACL) injury.

METHODS

We searched the PubMed, Embase, China National Knowledge Infrastructure and Wanfang databases for literature reporting a correlation between ACL injury and NWI and/or NW. Subgroup analyses were stratified by ethnicity, sex and control source. The weighted mean difference (WMD) and 95% confidence intervals (95% CIs) were calculated for the ACL injury cases and controls using random- or fixed-effects models. Begg's test and sensitivity analyses were applied to assess publication bias and stability of the results, respectively.

RESULTS

Twenty-eight eligible studies were finally enrolled. The NW was significantly narrowerin the ACL injury cases than in the control cases (pooled WMD, - 1.88 [95% CI, - 2.43 to - 1.32]). The results were similar when stratified by ethnicity and sex. Similarly, the NWI was lower in ACL injury cases than in the controls. Asian populations presented similar results when stratified by ethnicity, among the self-control group when stratified by control source, and among men when stratified by sex. No publication bias was identified; however, the sensitivity analysis suggested unstable results in the NWI subgroup analysis.

CONCLUSIONS

The current meta-analysis evidenced that the NW assessed via MRI was significantly smaller in ACL injury cases than in the controls. The NWI was lower in ACL injury cases among men. Prevention strategies for ACL injury could be applied for people with intercondylar notch stenosis.

Which Children Are at Risk for Contralateral Anterior Cruciate Ligament Injury After Ipsilateral Reconstruction?

BACKGROUND

Following anterior cruciate ligament (ACL) reconstruction, children are at significant risk for complications, including contralateral ACL rupture. The purpose of this study is to determine which children are at risk for a contralateral ACL tear after ipsilateral reconstruction.

METHODS

After review of medical records, we contacted patients who underwent primary ACL reconstruction between 2009 and 2016. Patients were included in the study if they were able to provide follow-up data either in person or remotely at least 2 years after surgery. Demographic data, sports participation, and intraoperative findings and techniques were recorded. All patients were also asked to confirm returning to sport information and postoperative complications (including contralateral ACL tear). Univariate analysis consisted of χ and independent samples t tests. Purposeful entry logistic regression was then conducted to control for confounding factors. Kaplan-Meier analysis was performed to assess contralateral ACL survival.

RESULTS

A total of 498 children with average follow-up of 4.3±2.1 years were included in the analysis. The mean age was 15.0±2.3 years and 262 patients (52.6%) were female. Thirty-five subjects (7.0%) sustained a contralateral ACL tear at a mean of 2.7±1.7 years following index reconstruction. Kaplan-Meier analysis revealed the median contralateral ACL survival time to be 8.9 years [95% confidence interval (CI): 8.3, 9.5 y]. In univariate analysis, 11.5% of female patients had a contralateral rupture compared with 2.1% of male patient (P<0.001). Patients with a contralateral tear had a mean age of 14.4±2.0 years compared with 15.1±2.3 years for those without an ACL injury in the opposite knee (P=0.04). After controlling for numerous factors in a multivariate model, female patients had 3.5 times higher odds of sustaining a contralateral ACL tear than male patients (95% CI: 1.1, 10.6; P=0.03). Each year of decreasing age raised the odds of contralateral injury by a factor of 1.3 (95% CI: 1.1, 1.6; P=0.02). Furthermore, children younger than 15 years had 3.1 times higher odds of contralateral rupture than those aged 15 and older (95% CI: 1.3, 7.2; P=0.01).

CONCLUSIONS

After adjusting for confounding factors in a multivariate model, female patients were at increased risk of contralateral ACL tear following ipsilateral reconstruction, as were younger children. Specifically, ACL rupture in the opposite knee was more likely in patients below the age of 15 years.

LEVEL OF EVIDENCE

Level III-prognostic study.

Generalised joint hypermobility increases ACL injury risk and is associated with inferior outcome after ACL reconstruction: a systematic review

Objectives

To investigate the association between generalised joint hypermobility (GJH) and ACL injury risk. Secondary aims involved evaluating associations between GJH and postoperative outcome (including graft-failure risk, knee laxity and patient-reported outcome). Furthermore, we aimed to compare the performance of different grafts in patients with GJH.

Methods

Databases MEDLINE/PubMed, EMBASE and the Cochrane Library were searched, including 2760 studies. Two reviewers independently screened studies for eligibility. A modified version of the MINORS score was applied for quality appraisal. Studies assessing GJH while reporting the risk of ACL injury and/or postoperative outcome were included.

Results

Twenty studies were included, using several different methods to determine GJH. There was consistent evidence showing that GJH is a risk factor for unilateral ACL injury in males, while in females, the results were conflicting. There was limited evidence associating GJH with increased knee laxity 5 years postoperatively. There was consistent evidence of inferior postoperative patient-reported outcome in patients with GJH. Moreover, there was limited yet consistent evidence indicating that patellar-tendon autografts are superior to hamstring-tendon autografts in patients with GJH in terms of knee laxity and patient-reported outcome. There was insufficient evidence to draw conclusions regarding the outcomes of bilateral ACL injury and graft failure.

Conclusions

In men, GJH was associated with an increased risk of unilateral ACL injury. Moreover, GJH was associated with greater postoperative knee laxity and inferior patient-reported outcome. Based on the available evidence, a patellar-tendon autograft appears to be superior to a hamstring-tendon autograft in patients with GJH. However, the included studies were heterogeneous and there is a need for consensus in the assessment of GJH within sports medicine.

Patients With Failed Anterior Cruciate Ligament Reconstruction Have an Increased Posterior Lateral Tibial Plateau Slope: A Case-Controlled Study

PURPOSE

To compare knee anatomical parameters of patients with failed anterior cruciate ligament reconstruction (ACL-R) with those of a control group of sex-matched patients with successful ACL-R.

METHODS

Forty-three patients (34 male, 9 female) who experienced graft failure after ACL-R were enrolled in the failed group. These patients were matched to a control group of 43 patients who underwent primary ACL-R with a minimum follow-up of 24 months. On magnetic resonance imaging, the following parameters were evaluated: transepicondylar distance, lateral and medial femoral condyle widths, tibial plateau width, notch width index, and the ratio of width and height of the femoral notch, ratio between the height and depth of the lateral and medial femoral condyle, lateral and medial posterior tibial slopes, and anterior subluxation of the lateral and medial tibial plateau. Multivariate regression with backward elimination, including only the previously identified significant variables, defined the independent predictors for revision surgery.

RESULTS

The anatomical variables that were significantly different between the 2 study groups were lateral and medial posterior tibial slopes, anterior subluxation of the lateral and medial tibial plateau, medial tibial plateau width, lateral tibial plateau width, medial femoral condyle width, and transepicondylar distance; however, the multivariate regression analysis identified the lateral posterior tibial slope (LTPs), the anterior subluxation of the medial tibial plateau, and the medial femoral condyle width as significant independent predictors (P < .05). The LPTs had the highest coefficient and the highest sensitivity (88%) and specificity (84%) to identify failures when considering the optimal cutoff value of 7.4°.

CONCLUSIONS

Several anatomical parameters have been identified that differ significantly between patients with failed ACL-R and those without a documented failure. The most accurate predictor of ACL failure was an LTPs >7.4°, with a sensitivity of 88% and specificity of 84%. Surgeons should consider measuring LTPs during preoperative assessment of ACL-injured patients, and patients with values >7.4° should be considered at high risk of ACL-R failure.

LEVEL OF EVIDENCE

Level III retrospective prognostic trial.

Editorial Commentary: Narrow Knee Intercondylar Notch Width Is a Risk Factor for Anterior Cruciate Ligament Injury, and Hetrogeneous Methods Are a Risk Factor for "Between Study" Error in Meta-analyses

The anatomic dimensions of the intercondylar notch have been associated with and anterior cruciate ligament (ACL) injury; however, these findings have been shown to be highly heterogeneous in a previous systematic review. Early studies used conventional radiographs to image the knee, whereas recent studies have employed magnetic resonance imaging. The different imaging techniques are a potential source of heterogeneity, prompting a systematic review of magnetic resonance imaging studies only. Although a narrower intercondylar notch width and intercondylar index were again associated with ACL injury, statistical heterogeneity remains persistent. Subgroup analysis successfully identified sources of between-study error among studies measuring notch width but was unable to account for differences in studies examining notch width index. These findings have provided greater insight into the relation between the anatomic dimensions of the intercondylar notch and ACL as well as the importance of between-study error in meta-analysis.