Relationship between Mucoid Degeneration of the Anterior Cruciate Ligament and Posterior Tibial Slope in Patients with Total Knee Arthroplasty

Do the Clinical and Radiological Features of Knees with Mucoid Degeneration of the Anterior Cruciate Ligament Differ According to Knee Osteoarthritis Status?

Background

The etiology and pathology of mucoid degeneration of the anterior cruciate ligament (MD-ACL) remain poorly understood. MD-ACL may be associated with knee osteoarthritis (OA) or a mechanism other than OA. This study evaluated the radiological differences between knees with MD-ACL and those with a normal ACL and compared the clinical and radiological features of knees with MD-ACL according to the knee OA status.

Methods

This retrospective study compared the radiological features of the intercondylar notch width index (NWI) and posterior tibial slope (PTS) of 67 MD-ACL patients (MD group) and 67 age-, sex-, and OA grade-matched patients with a normal ACL (control group). During the subgroup analysis, MD-ACL patients were divided into the non-OA subgroup (n = 41) and OA subgroup (n = 26). The pain location and characteristics of the knee, PTS, and NWI were compared between these subgroups.

Results

Compared to the control group, the MD group had a lower NWI (0.26 ± 0.03 vs. 0.28 ± 0.01, p < 0.001) and a larger PTS (11.3° ± 3.0° vs. 9.2° ± 2.5°, p < 0.001). During the subgroup analysis, the most common pain locations were the posterior and medial aspects of the knee in the non-OA subgroup (43.9%) and OA subgroup (53.8%), respectively. Pain on terminal flexion was the most common pain characteristic in both subgroups (non-OA subgroup, 73.1%; OA subgroup, 53.8%). The PTS was not different between subgroups (11.7° ± 3.2° in the non-OA subgroup vs. 10.6° ± 2.7° in the OA subgroup; p = 0.159). However, the non-OA subgroup had a lower NWI than the OA subgroup (0.25 ± 0.03 vs. 0.28 ± 0.02, p = 0.001).

Conclusions

Patients with MD-ACL had a lower NWI and a larger PTS than patients with a normal ACL. Furthermore, the clinical and radiological features of MD-ACL differed according to the knee OA status. A narrow intercondylar notch may be more closely associated with the development of MD-ACL without OA.

Nutrient vessel dysfunction can contribute to mucoid degeneration of the posterior cruciate ligament coexisting with lipoma arborescens: A case study

INTRODUCTION

With the rapid improvement of magnetic resonance imaging (MRI), mucoid degeneration (MD) of the anterior cruciate ligament (MD-ACL) has become an established disease entity and mechanical factors, such as increased posterior tibial tilt and intercondylar notch impingement, have been proposed. However, symptomatic MD of the posterior cruciate ligament (MD-PCL) remains an orphan disease without any established etiology.

PRESENTATION OF CASE

A man in his 60s exhibited restricted range of motion with knee pain. MRI revealed PCL enlargement with high-signal intensity and tram-track appearance on T2-weighted sagittal images and lipoma arborescens (LA) in the suprapatellar pouch. On gadolinium-enhanced MRI, the distal PCL was not contrasted. Arthroscopy revealed an almost normal expanded appearance with partial loss of the envelope synovium. Debulking operation was performed. Pathological findings revealed intravascular thrombus formation in early lesions of MD, and intraligamentous vascular degeneration and severity of MD were proportional.

DISCUSSION

ACL is susceptible to mechanical external forces from surrounding tissues because of its anatomical features that induce protease expression, resulting in MD-ACL with denatured large aggregating proteoglycans deposition. Conversely, occlusion of nutrient vessels within the ligament was observed in this case of MD-PCL. Coexisting LA likely provoked an inflammatory response with hypercoagulability, resulting in thromboembolism of the envelope synovial nutrient vessel.

CONCLUSION

MD-CL is a disease entity comprising multiple pathologies. Although symptomatic MD-ACL is mainly caused by mechanical factors with a relatively high morbidity rate, nutrient vessel dysfunction can contribute to symptomatic MD-PCL with coexisting LA in middle-aged adults with an extremely low morbidity rate.

Posterior tibial slope, notch width index and tibial tubercle to trochlear groove distance contribute to development of mucoid degeneration of the anterior cruciate ligament: a systematic review

PURPOSE

To determine what knee morphological factors are associated with the development of mucoid degeneration of the anterior cruciate ligament (ACL).

METHODS

Three databases MEDLINE, PubMed and EMBASE were searched from inception to January 29th, 2023 for literature outlining knee morphological factors that potentially lead to the development of mucoid degeneration of the ACL. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on receiver operating characteristic (ROC) curve parameters such as area under the curve (AUC), sensitivity and specificity, odds ratios, as well as p values for comparisons of values between mucoid degeneration of the ACL and control patients were recorded. The Methodological Index for Non-Randomized Studies (MINORS) score was used for all studies to perform a quality assessment of included studies.

RESULTS

A total of 7 studies comprising 1326 patients (1330 knees) were included in this review. Four studies reported a significant association between increasing posterior tibial slope angles and mucoid degeneration of the ACL presence, with one study specifying that posterolateral tibial slope had a greater association than posteromedial tibial slope. Two studies reported a significant association between lower notch width index values and mucoid degeneration of the ACL presence. One study found that the presence of trochlear dysplasia was correlated with mucoid degeneration of the ACL and two studies found that increased tibial tuberosity-trochlear groove distance (TT-TG) was associated with mucoid degeneration of the ACL.

CONCLUSION

Increased posterior tibial slope, decreased notch width index, and elevated TT-TG and trochlear dysplasia were associated with the presence of mucoid degeneration of the ACL. Information from this review can aid surgeons in understanding what morphological features predispose their patients to the development of mucoid degeneration of the ACL. Identifying what features predispose patients to mucoid degeneration of the ACL can help determine if regular screening or preventative strategies are necessary.

LEVEL OF EVIDENCE

Level III.

Ancillary findings in distinguishing between anterior cruciate ligament mucoid degeneration and sprain on MRI: a practical approach

BACKGROUND

Imaging findings of both anterior cruciate ligament (ACL) sprain and mucoid degeneration overlap in some cases, which may cause errors in magnetic resonance imaging (MRI) evaluation.

PURPOSE

To determine the ancillary findings on MRI in distinguishing between ACL sprain and mucoid degeneration, and also to obtain a diagnostic scheme.

MATERIAL AND METHODS

MRI scans of 77 patients with ACL mucoid degeneration and 77 cases with ACL sprain were retrospectively evaluated to compare with regard to parameters of age, sex, side, the status of posterior cruciate ligament - medial collateral ligament - lateral collateral ligament, bone marrow edema, intraosseous cyst, subchondral sclerosis, chondromalacia, meniscus tear, effusion, and osteochondral body. A decision tree algorithm was created to predict pathology in ACL, whether it was a sprain or mucoid degeneration.

RESULTS

The prevalence of female sex, femoral intraosseous cyst, tibial intraosseous cyst, subchondral sclerosis, femoral chondromalacia, tibial chondromalacia, medial meniscus tear, and lateral meniscus tear were significantly higher in the ACL mucoid degeneration group (P < 0.001, P = 0.016, P < 0.001, P = 0.003, P < 0.001, P < 0.001, P < 0.001, and P < 0.001, respectively). The probability of being mucoid degeneration increased 41.2 times (95% confidence interval [CI] = 5.296-321.132) in cases with tibial intraosseous cyst and increased 1.05 times (95% CI = 1.010-1.080) with each one-year increase in age (P < 0.001 and P = 0.011, respectively). The decision tree algorithm had an overall accuracy of 79.2%.

CONCLUSION

Ancillary findings are helpful in the diagnosis of suspicious cases for ACL mucoid degeneration and ACL sprain. The decision tree algorithm offers a practical and successful approach to this issue.

Radiologic findings associated with mucoid degeneration of the anterior cruciate ligament

INTRODUCTION

Mucoid degeneration (MD) of the anterior cruciate ligament (ACL) is a well-recognized pathology characterized by the degradation of collagen fibers and infiltration of a mucoid-like substance. This study is to determine the anatomical associated factors for MD-ACL using radiographic and magnetic resonance imaging (MRI).

MATERIALS AND METHODS

This was a retrospective study on patients who had undergone knee arthroscopy between 2011 and 2020. The patients with MD-ACL were defined and enrolled by the MRI and arthroscopy. Eventually, 52 patients in the MD-ACL group (group 1) and 52 patients in the control group (group 2) were enrolled, following sex and age matching. Radiologic evaluation included the assessment of Kellgren-Lawrence (K-L) grade, mechanical hip-knee-ankle (HKA) angle, posterior tibial slope (PTS) angle, and Insall-Salvati ratio. The notch width index and transverse notch angle were measured on MRI, and the grade of trochlear dysplasia was defined. Logistic regression analysis, receiver operating characteristic (ROC) curves, and area under curve (AUC) were performed.

RESULTS

The ROM was significantly decreased in group 1, whereas the PTS angle was significantly larger in group 1. Combined ganglion cysts of ACL were found in 42/52 patients (80.7%) in group 1. The risk of MD-ACL was associated with a steeper PTS angle, increased Insall-Salvati ratio, male sex, higher K-L grade, and decreased transverse notch angle and notch width index. The cutoff values in ROC analysis were found to be ≤ 28.27% for the notch width index (AUC, 0.849; p < 0.001), > 12.2° for the PTS angle (AUC, 0.765; p < 0.001), and ≤ 47.4° for the transverse notch angle (AUC, 0.711; p < 0.001), but not significant for Insall-salvati ratio.

CONCLUSION

A steeper PTS angle, decreased notch width index, and transverse notch angle are significantly associated with the presence of MD-ACL. These factors should be considered during diagnosis or when determining the treatment strategy for symptomatic MD-ACL patients.

LEVEL OF EVIDENCE

Level IIIb.

Association Between MRI-Based Tibial Slope Measurements and Mucoid Degeneration of the Anterior Cruciate Ligament: A Propensity Score-Matched Case-Control Study

Background

The cause of mucoid degeneration (MD) of the anterior cruciate ligament (ACL), which is commonly observed on magnetic resonance imaging (MRI) of patients with knee pain, has yet to be elucidated. Despite the limited evidence on the relationship between ACL lesions (injury and MD) and tibial morphologic features (ie, posterior tibial slope), the potential association between the presence of ACL MD and medial and lateral tibial slope (MTS and LTS) has not been well-established.

Purpose

To investigate whether MTS and LTS measurements are associated with the presence of ACL MD.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Consecutive knee MRI examinations of patients referred by an orthopaedic surgeon for potential internal joint derangements were identified within a 4-year period. The presence of ACL MD and the MTS/LTS values were assessed by independent expert observers in consensus in a blinded fashion. From 413 consecutive knee MRI scans, a sample of 80 knees, including 32 knees with ACL MD (cases) and 48 knees with normal ACL (controls), were selected using propensity score matching method for age, sex, body mass index, and presence of severe medial tibiofemoral compartment cartilage damage. The association between ACL MD and MTS/LTS was evaluated using conditional regression models.

Results

Knees with ACL MD had higher values of LTS (mean ± SD, 7.18° ± 3.58°) in comparison with control knees (5.32° ± 3.35°). Conditional regression analysis revealed a significant association between LTS measurements (not MTS) and ACL MD; every 1° increase in LTS was associated with a 17% (95% CI, 1%-35%) higher probability of having ACL MD.

Conclusion

Excessive LTS was associated with the presence of ACL MD, independent of participants' age, sex, BMI, and cartilage damage severity.

Does posterior tibial slope affect the results of conservative treatment for anterior cruciate ligament tears?

OBJECTIVE

To evaluate the association between posterior tibial slope (PTS) and the short-term results of conservative treatment for the patients with anterior cruciate ligament (ACL) tears.

METHODS

Thirty-seven patients (37 knees: male 33, female 4) who were managed with the same treatment protocols for ACL tears were included. All patients applied ACL brace and underwent standardized rehabilitation protocol. Group A consisted of 14 patients with successful results after conservative management and group B consisted of 23 patients who received operative treatments due to failed conservative management. For each group, a plain radiograph was used to measure the PTS. The demographic data of patients and differences of PTS between each group were analyzed.

RESULTS

The mean age was 33.2 years in group A and 29.7 years in group B, respectively (p = 0.8). There was no significant difference between each group in terms of gender, body mass index, and injury mechanism. There was no significant difference between each group in the classification according to the isolated or combined injury (p = 0.83). The mean PTS was 8.3° in group A and 10.2° in group B. The mean PTS in group A was significantly lower than that in group B (p = 0.03).

CONCLUSIONS

The patients with successful results after conservative management had a lower mean PTS than those with failed conservative treatment (8.3° vs. 10.2°, p = 0.03). The failure of conservative treatment after ACL tear was found to be associated with increased PTS.

Anatomical Risk Factors of Anterior Cruciate Ligament Injury

Background:

Nowadays, the anterior cruciate ligament (ACL) injury has been one of the most common diseases of the knee joint. The relationships between the ACL injury and the anatomical structures are still controversial. This study aimed to identify the anatomical risk factors of ACL injury by magnetic resonance imaging (MRI) of the knee.

Methods:

This was a retrospective study of 125 patients undergoing primary ACL reconstruction between July 2013 and May 2017. Another 125 patients without any organic knee joint injury were served as controls. The shape of intercondylar notch, the intercondylar notch width index, the intercondylar notch height index, the α angle, the β angle, and the medial and lateral tibial plateau slope were measured with MRI and compared. The data were compared by binary logistic regression to find the risk factors.

Results:

The two groups differed in the proportion of male patients (70.4% vs. 52.0%, χ² = 8.911, P = 0.003), but gender was excluded as a risk factor for ACL injury with regression analysis (odds ratio = 1.476, 95% confidence interval [CI]: 0.689–3.160, P = 0.317). The injured group was found to have a smaller notch width index (95% CI = 7.960E-23–2.154E-9, P < 0.001), a larger β angle (95% CI = 1.311–1.785, P < 0.001), and a larger lateral tibial plateau slope (95% CI = 1.201–1.683, P < 0.001). The cutoff values of notch width index, β angle, and the lateral tibial plateau slope were 0.252, 38.5°, and 7.5°, respectively.

Conclusions:

In this study, a narrow intercondylar notch (intercondylar notch width index <0.252), a larger lateral tibial slope (>7.5°), and larger β angle (>38.5°) might be the factors associated with ACL injury.

Trial Registration:

ChiCTR-RRC-17014116; http://www.chictr.org.cn/showproj.aspx?proj=24119 .

Association Between Tibial Plateau Slopes and Anterior Cruciate Ligament Injury: A Meta-analysis

PURPOSE

To investigate the associations of medial tibial plateau slope (MTPS), lateral tibial plateau slope (LTPS), and coronal tibial plateau slope (CTPS) with anterior cruciate ligament (ACL) injury both in the general population and in different gender subgroups.

METHODS

PubMed, Ovid, Embase, and Scopus databases were searched through from inception to August 31, 2016. Observational studies reporting associations of MTPS/LTPS/CTPS with ACL injury were retrieved for analysis. Either a fixed- or random-effects model was used to calculate the overall standardized mean difference (SMD). Reviews, meeting abstracts, cadaver or animal studies, and other studies without disclosing full text were excluded in this study.

RESULTS

A total of 29 studies were included. Subjects with ACL injury exhibited a significant increase in MTPS (SMD: 0.34 [95% confidence interval (CI): 0.18, 0.49]; P < .0001) and LTPS (SMD: 0.49 [95% CI: 0.30, 0.68]; P < .00001), but not in the CTPS (SMD: 0.09 [95% CI: -0.10, 0.27]; P = .36), compared with controls. Meanwhile, significant differences in MTPS and LTPS were observed in the male subgroup (SMD: 0.41 [95% CI: 0.20, 0.62]; P = .0001 and SMD: 0.55 [95% CI: 0.26, 0.85]; P = .0002, respectively) but not in the female (SMD: 0.31 [95% CI: -0.02, 0.64]; P = .06 and SMD: 0.26 [95% CI: -0.04, 0.56]; P = .09, respectively).

CONCLUSIONS

The present meta-analysis showed that the increases in MTPS and LTPS were overall risk factors of ACL injury. However, these slopes would only be considered as "at risk" for males, but not for females. In addition, it was also proved that CTPS was not a risk factor of ACL injury.

LEVEL OF EVIDENCE

Level III, meta-analysis of Level II and III studies.