Anterior tibial subluxation measured under a modified protocol is positively correlated with posterior tibial slope: a comparative study of MRI measurement methods

Increased anterior tibial subluxation and differences between anterior tibial subluxation in the lateral and medial compartments are associated with failure of primary anterior cruciate ligament reconstruction: A systematic review and meta-analysis

PURPOSE

The purpose of this study is to investigate whether increased anterior tibial subluxation (ATS) and differences between ATS in the lateral and medial compartments (ATSL-M) are associated with primary anterior cruciate ligament (ACL) reconstruction (ACLR) failure.

METHODS

PubMed, Scopus, Embase and Web of Science were systematically searched from their inception through 21 November 2023. The focus was on comparative studies reporting ATS in patients who experienced primary ACLR failure, in contrast to patients after primary ACLR with no evidence of graft failure. A random-effects model was employed to calculate the overall standardized mean difference between the two groups.

RESULTS

A total of eight studies involving 963 patients were included in the final review. Three studies (64 cases and 171 controls) measured ATS on radiographs. The failed ACLR group exhibited a significantly increased ATS on radiographs compared to the control group (p < 0.001). Six studies (324 cases and 488 controls) measured lateral ATS on magnetic resonance imaging and five of them (285 cases and 374 controls) also measured medial ATS. The average values of lateral and medial ATS, as well as ATSL-M, were calculated and compared between the two groups. The failed ACLR group demonstrated significantly increased lateral (p < 0.001) and medial ATS (p < 0.001), the average value of lateral and medial ATS (p < 0.001) and ATSL-M (p = 0.039) compared to the control group.

CONCLUSION

Increased ATS and ATSL-M are associated with primary ACLR failure. The measurement of tibiofemoral position shows promise for its application in preoperative planning and postoperative management of ACLR.

LEVEL OF EVIDENCE

Level III.

Association of Concomitant MRI-Determined Anterolateral Complex Injury With Quantitative Measurements of Altered Rotational Tibiofemoral Position on MRI in Patients With ACL Injury

Background

Reduced graft failure rates have been reported after anterior cruciate ligament (ACL) reconstruction combined with anterolateral complex (ALC) augmentation. However, the preoperative diagnosis of concomitant ALC injury remains a clinical challenge.

Purpose

To identify the altered rotational tibiofemoral position on magnetic resonance imaging (MRI) in ACL-injured patients with concomitant ALC injury.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Based on the evaluation of ALC abnormalities on MRI scans by experienced surgeons, 123 patients with nonchronic (<3 months) ACL injury confirmed by arthroscopy were included. The patients were divided into 2 groups-an ALC-injured group (n = 57) and an ALC-intact group (n = 66). The altered rotational tibiofemoral position was evaluated and compared by quantitatively measuring internal rotational tibial subluxation (IRTS) and axial internal tibial rotation (ITRa) on MRI. Multivariate logistic regression and receiver operating characteristic (ROC) analyses were performed to identify the factors associated with concomitant MRI-determined ALC injury.

Results

The ALC-injured group showed significantly increased IRTS (P < .001), ITRa (P < .001), lateral anterior tibial subluxation (ATS) (P < .001), and global ATS (GATS) (P = .002) compared with the ALC-intact group, while no significant difference in medial ATS (P = .810) was observed. A strong positive correlation was identified between IRTS and ITRa (rP = 0.809; P < .001). Multivariate analyses revealed that IRTS (P < .001) and GATS (P = .016) were associated factors for the presence of concomitant MRI-determined ALC injury. IRTS (area under the curve [AUC] = 0.734) was more strongly associated with the outcome than GATS (AUC = 0.658) in ROC analyses, suggesting a more significant internal rotational subluxation than anterior subluxation of the tibia. An IRTS threshold of 3.1 mm demonstrated a specificity of 84.2% for indicating the presence of concomitant MRI-determined ALC injury.

Conclusion

The presence of concomitant MRI-determined ALC injury in ACL-injured patients was associated with a significant increase in IRTS and ITRa compared with those with intact ALC, indicating that these MRI measurements of the altered rotational tibiofemoral position could serve as potential quantifiable indicators for identifying concomitant ALC injury in clinical practice.

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.

Comparisons of diagnostic performance and the reliability in identifying ACL injury between two measuring protocols of anterior tibial subluxation on MR images

OBJECTIVES

To evaluate the diagnostic performance in identifying an anterior cruciate ligament (ACL) injury and the reliability between two measuring protocols of anterior tibial subluxation (ATS).

MATERIALS AND METHODS

A total of 165 patients with ACL injury and 157 ACL-intact patients were included in this study. Two different measuring protocols of ATS were performed on sagittal MR images, including the modified protocol using the longitudinal tibial axis (axis protocol) and the established protocol using a line perpendicular to the tibial plateau (plateau protocol). Receiver-operating characteristic (ROC) curves were calculated to evaluate the diagnostic performance in identifying an ACL injury, and areas under the curves (AUCs) were compared between the two protocols. Intra- and interobserver reliability tests were performed to evaluate the reliability of the measurements.

RESULTS

Lateral ATS (P < 0.001) and medial ATS (P < 0.001) were increased in patients with ACL injury under both protocols. To identify an ACL injury, ATS measured under the axis protocol showed higher AUC values than the plateau protocol, including lateral ATS (AUC 0.828 vs. 0.688, P < 0.001), medial ATS (AUC 0.829 vs. 0.789, P = 0.013), and the combined indicator of lateral and medial ATS (AUC 0.885 vs. 0.810, P < 0.001). Reliability tests showed that both protocols were reliable.

CONCLUSIONS

ATS measured under the modified protocol using the longitudinal tibial axis showed superior diagnostic performance in identifying an ACL injury compared to the established protocol, indicating that the modified protocol may better reflect the characteristics of an ACL-deficient knee.

Chronic ACL-injured patients show increased medial and global anterior tibial subluxation measured on 1-year postoperative MR images after primary single-bundle ACL reconstruction

BACKGROUND

The association between chronic anterior cruciate ligament (ACL) injury and inferior postoperative outcomes following ACL reconstruction (ACLR) has been highlighted in the literature. However, the inclusion of postoperative radiological assessments in previous studies has been limited. The aim of this study is to investigate whether chronic ACL injury is associated with an inferior tibiofemoral position measured on magnetic resonance (MR) images after primary ACLR.

METHODS

A total of 62 patients that underwent primary ACLR were included in this study based on the time from injury to surgery, namely the acute ACL-injured group (within 6 weeks) and the chronic ACL-injured group (more than 1 year) and were matched 1:1 according to sex, age (± 2 years), and time from surgery to follow-up (± 3 months). Patient demographics, surgical records and follow-up data were retrieved and analyzed. The altered tibiofemoral position was measured quantitatively on preoperative and at least 1-year postoperative MR images and compared between the two groups, including the lateral, medial and global anterior tibial subluxation (LATS, MATS and GATS) and internal rotational tibial subluxation (IRTS).

RESULTS

No significant differences in preoperative LATS, MATS, GATS or IRTS were identified between the acute and chronic ACL-injured groups. The chronic ACL-injured patients showed significantly increased postoperative MATS (p = 0.001) and GATS (p = 0.012), while no significant difference was identified in postoperative LATS or IRTS. Multivariate linear regression analyses showed that chronic ACL injury resulted in an estimated increase of 2.0 mm in postoperative MATS (p = 0.012) and 1.9 mm in postoperative GATS (p = 0.040). A significant improvement in postoperative LATS was observed in the acute ACL-injured group (p = 0.044) compared to preoperative LATS, while no improvements in these MRI measurements were observed in the chronic ACL-injured group.

CONCLUSION

Chronic ACL-injured patients showed increased MATS and GATS measured on 1-year postoperative MR images after primary single-bundle ACL reconstruction, while no difference was identified in rotational tibiofemoral position. The acute ACL-injured group demonstrated a significant improvement in postoperative LATS, whereas no improvements were observed in the chronic ACL-injured group. Level of evidence Level III.

Association Between Anterior Tibial Subluxation of Lateral Compartment and High-Grade Knee Laxity in Patients With Anterior Cruciate Ligament Deficiency

BACKGROUND

High-grade knee laxity and excessive anterior tibial subluxation (ATS) are correlated with poor clinical outcomes in patients with anterior cruciate ligament (ACL) deficiency and share similar risk factors; however, the association between excessive ATS and high-grade knee laxity remains unclear.

PURPOSE

To identify the association between excessive ATS and high-grade knee laxity in patients with ACL deficiency and determine the possibility that ATS can predict high-grade knee laxity.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 226 patients who underwent ACL reconstruction between May 2018 and March 2022 were analyzed in the present study; the high-grade group consisted of 113 patients who had a grade 3 result on the preoperative anterior drawer test, Lachman test, or pivot-shift test while under anesthesia, and the low-grade group consisted of 113 matched patients. The ATS values for medial and lateral compartments (ATSMC and ATSLC) were measured on magnetic resonance imaging while patients relaxed the quadriceps in the supine position under no anesthesia. The optimal cutoff values of ATSMC and ATSLC for high-grade knee laxity were determined using receiver operating characteristic curves. Univariate and multivariate logistic regression analyses with stratification were performed to identify the association between excessive ATS and high-grade knee laxity.

RESULTS

Compared with the low-grade group, the high-grade group had a longer time from injury to surgery; higher rates of medial meniscus posterior horn tear (MMPHT), lateral meniscus posterior horn tear (LMPHT), and anterolateral ligament (ALL) abnormality; and larger lateral tibial slope, ATSMC, and ATSLC. The optimal cutoff value was 2.6 mm (sensitivity, 52.2%; specificity, 76.1%) for ATSMC and 4.5 mm (sensitivity, 67.3%; specificity, 64.6%) for ATSLC in predicting high-grade knee laxity. After adjustment for covariates, ATSLC ≥4.5 mm (odds ratio [OR], 2.94; 95% CI, 1.56-5.55; P = .001), MMPHT (OR, 2.62; 95% CI, 1.35-5.08; P = .004), LMPHT (OR, 2.39; 95% CI, 1.20-4.78; P = .014), and ALL abnormality (OR, 2.09; 95% CI, 1.13-3.89; P = .019) were associated with high-grade knee laxity. The association between excessive ATSLC and high-grade knee laxity was validated in patients with acute ACL injury as well as those with chronic ACL injury.

CONCLUSION

Excessive ATSLC was associated with high-grade knee laxity in patients who had ACL deficiency, with a predictive cutoff value of 4.5 mm. This study may help surgeons estimate the degree of knee instability more accurately before anesthesia and may facilitate preliminary surgical decision-making, such as appropriate graft choices and consideration of extra-articular augmentation.

Considerations of the Posterior Tibial Slope in Anterior Cruciate Ligament Reconstruction: a Scoping Review

PURPOSE OF REVIEW

The significance of posterior tibial slope (PTS) in the setting of anterior cruciate ligament (ACL) injury and reconstruction has been increasingly recognized in recent years. The purpose of this article is to review the biomechanical and clinical studies of PTS in conjunction with ACL injuries, providing an evidence-based approach for the evaluation and management of this patient population.

RECENT FINDINGS

Several biomechanical and clinical studies suggest that PTS > 12° may be considered with increased strain on the native ACL fibers (or reconstructed graft) and greater anterior tibial translation, predisposing patients to a recurrent ACL injury. The increased rates of ACL injury and graft failure seen in those with increased PTS have garnered attention to diagnose and surgically address increased PTS in the revision ACL setting; however, the role of a slope-reducing high tibial osteotomy (HTO) in primary ACL reconstruction (ACL-R) has yet to be defined. Various HTO techniques to decrease PTS during revision ACL-R have demonstrated promising outcomes, though conclusions are limited by the multifactorial nature of revision surgery and concomitant procedures performed. Recent evidence suggests that increased PTS is a risk factor for failure following ACL-R, which may be mitigated by a slope-reducing HTO. Further investigation is needed to elucidate abnormal PTS values and to determine appropriate indications for a slope-reducing HTO in primary ACL-R.