Investigation of the relationship between ankle morphology and osteochondral lesions of the talus in MRI

Abstract

AimThis study aimed to evaluate whether the radiological parameters used can predict the diagnosis of osteochondral lesion of the talus (OLT) and the need for diagnostic or therapeutic surgical intervention.MethodsThe OLT (+) group comprised 111 patients with OLT diagnosed by MR, and the control OLT (-) group comprised 111 participants without OLT. On the MRI images of both groups, the following measurements were taken and compared: "Joint Line Convergence Angle (JLC)", "Tibia-Medial Malleolus Angle (TMM)", "Tibial Lateral Surface Angle (TLS)", "Anterior Opening Angle of Talus (AOT)", "Length of Trochlea Tali (LOT)", "Trochlea Tali Sub-Length/Joint Space Distance Ratio (LTJSD)", "Distance Between Plafond Posterior Lip and Talar Dome (PLTD)", and "Trochlea Tali Length/ Plafond Anterior-Posterior Length Ratio (LTPAP)".ResultsAge (P = .009), JLC (P < .001), TMM (P < .001), TLS (P = .005), AOT (P < .001), LOT (P = .002), and LTJSD (P = .019) values differed statistically between the groups. Logistic Regression analysis revealed that JLC (P < .001), TMM (P = .001), AOT (P < .001), LOT (P = .042), and LTJSD (P = .026) could be the best predictive diagnostic markers for OLT. Logistic Regression analysis showed that the LOT value could be the best parameter that may predict the decision to apply surgical treatment in OLT patients.ConclusionJLC, TMM, AOT, LOT, and LTJSD values measured on MRI images were found to be valid measures for diagnosing patients with suspected OLT. It was also concluded that LOT value could be used as a predictive marker in determining the treatment modality in patients with OLT.

Keywords

Introduction

Every day, one in 10,000 people sustains an ankle sprain, and chondral or osteochondral lesions occur in up to half of acute ankle sprains or fractures.¹ Osteochondral lesions of the talus (OLT) involve the cartilage and subchondral bone of the ankle joint surface.
Ankle biomechanics and morphology may predispose to OLT, although related studies are limited.² Magnetic resonance imaging (MRI) is the most sensitive modality for evaluating ankle biomechanics and morphology and is essential for OLT diagnosis and follow-up, providing a detailed assessment of soft tissues, cartilage, and morphological measurements.³ Numerous parameters defining normal ankle morphology have been described in the literature using radiography, computed tomography (CT), and MRI.⁴
Morphological features of healthy ankles have been evaluated in OLT patients, but these studies were insufficient to predict OLT or guide surgical decision-making.⁴ Traditional parameters such as joint line convergence angle (JLC), tibia-medial malleolus angle (TMM), tibial lateral surface angle (TLS), anterior opening angle of talus (AOT), length of trochlea tali (LOT), defined using radiography and CT, are used to assess ankle morphology and biomechanics.⁵ In this study, these parameters were evaluated on MRI to determine their effectiveness in predicting OLT.
One of the greatest biomechanical properties of the talus is its load transfer ability.⁶ The talar cartilage and bone are subjected to constant micro- and macrotraumatic stress during load transfer, leading to cumulative effects including osteochondral lesions.⁷ This study evaluates new parameters, including Trochlea Tali Sub-Length/Joint Space Distance Ratio (LTJSD), distance between tibial Plafond Posterior Lip and Talar Dome (PLTD), and Trochlea Tali Length/Plafond Anterior-Posterior Length Ratio (LTPAP). These parameters may influence load transfer due to their morphological characteristics.
The objective of this study was to evaluate JLC, TMM, TLS, AOT, LOT, LTJSD, PLTD, and LTPAP parameters that may predict the diagnosis of OLT and the need for diagnostic or therapeutic surgical intervention in patients with suspected OLT.

Materials and Methods

In this single-center retrospective study, diagnostic data from patients aged 18–50 years who underwent ankle MRI between January 1, 2015, and January 1, 2021, with available digital records and no prior ankle surgery, were analyzed.
Patients were excluded if they were <18 or >50 years old, had prior ankle surgery, surgery affecting lower extremity alignment, an ankle fracture within 6 months before MRI, or systemic diseases affecting joint alignment and morphology (rheumatoid arthritis, systemic lupus erythematosus, etc.).
Digital data from 887 patients who underwent ankle MRI were reviewed. Of these, 583 met the age and inclusion criteria, and 111 were identified with OLT. From the remaining 472 patients without OLT, 111 were randomly selected (The website www.randomizer.org was used for random selection) (Table 1). Patients were divided into OLT (–) (n = 111) and OLT (+) (n = 111) groups; the OLT (+) group was further subdivided into Surgery (–) (n = 89) and Surgery (+) (n = 22) groups.
MRI images were acquired using a 1.5-Tesla scanner (Philips Medical Systems, Netherlands) with patients in the supine position and an extremity coil. All images were analyzed using a digital picture archiving and communication system (PACS). Ankle morphometric parameters were manually measured on sagittal and axial T1- and T2-weighted MRI images using PACS tools by an orthopedist with over 5 years of experience. The following parameters were evaluated on the MRI images of all patients (Figure 1):
- JLC: The angle between the tibial plafond joint orientation line and the talar dome joint orientation line on coronal MRI images.⁸
- TMM: The angle between the anatomic axis of the tibia and the tangent drawn to the medial malleolus articular surface on coronal MRI images.⁵
- TLS: The angle between the anatomic axis of the tibia and the line connecting the most anterior and most posterior points of the distal tibia articular surface on sagittal MRI images.⁹
- AOT: The angle between the medial and lateral surfaces of the trochlea of the talus on axial MRI images.⁵
- LOT: The distance between the most anterior and most posterior points of the talar dome articular surface on sagittal MRI images. The points where talar dome sphericity is impaired are taken as a reference.⁴
- LTJSD: This is measured as the ratio of the distance between the most anterior and most posterior points of the talar dome articular surface to the joint space distance on sagittal MRI images.
- PLTD: The distance between the posterior lip of the tibial plafond and the closest point of the talar dome articular surface .¹⁰
- LTPAP: On coronal MRI images, this is the value obtained as the ratio of the distance between the most anterior and most posterior points of the talar dome articular surface to the distance between the anterior-posterior lip of the tibial plafond .¹¹Ethical ApprovalThe study was approved by the Ethics Committee of Kırıkkale University (Date: 30.06.2021, Decision No: 2021.06.13).Statistical AnalysisThe Statistical Package for Social Sciences (SPSS) Version 20.0 (IBM) program was used to analyze the study data.
Categorical variables were analyzed using Pearson's chi-square test (P < .05). Parametric data were analyzed using the independent samples t-test (P < .05), and non-parametric data using the Mann-Whitney U test (P < .05). ROC-curve analysis was used to identify parameters predicting OLT diagnosis and surgical decision-making, with cut-off values calculated for sensitivity and specificity. Logistic regression identified the best predictive parameter (P < .05), and associations with OLT presence and surgical risk were assessed using odds ratios and 95% confidence intervals. Factor analysis and reliability tests were applied to evaluate the validity and reliability of the parameters to produce a scale for the prediction of the diagnosis and surgical intervention risk of the OLT. Reporting GuidelinesThis study is reported in accordance with the STROBE guidelines.

Results

The mechanism of trauma in the patients with OLT was determined as a fall from height in 5 of the patients with OLT (+), and resulting from a sprain in 79 (53.6%). Since no etiological cause could be found in 27 (12.2%) patients, it was thought that these patients might have developed OLT from idiopathic and/or mechanical causes.
Among 222 patients, 95 were male and 127 female, with no sex difference between OLT (–) and OLT (+) groups (P = .498). Mean age was significantly lower in the OLT (–) group than the OLT (+) group (P = .009). Significant differences were found between groups for JLC (P < .001), TMM (P < .001), TLS (P < .005), AOT (P < .001), LOT (P < .002), and LTJSD (P < .019), while PLTD (P > .05) and LTPAP (P > .05) showed no differences. No measured parameters differed according to OLT stage within the OLT (+) group. The detailed data are provided in Table 1 and Figure 2.
ROC-curve analysis revealed that age > 40 years, JLC > 1.25, TMM > 24.65, TLS < 85.95, AOT > 12.85, LOT > 33.65, and LTJSD > 9.70 could be used as predictive diagnostic markers for OLT. The detailed data are provided in Supplementary Table 1 and Figure 3A.
The odds ratio test results showed that JLC > 1.25 was associated with a > 7-fold risk of the presence of OLT (P < .001), and TMM > 24.65 (P < .001) and AOT > 12.85 (P < .001) were associated with a > 6-fold risk of the presence of OLT. TLS < 85.95 (P = .002) and LOT > 33.65 (P = .007) were associated with a >2-fold risk of OLT presence (Table 2, Supplementary Figure 1).
Logistic regression analysis revealed that JLC (P < .001), TMM (P = .001), AOT (P < .001), LOT (P = .042), and LTJSD (P = .026) could be the best predictive diagnostic markers for OLT. The detailed data are provided in Supplementary Table 1.
In order to predict the diagnosis of the OLT, the study parameters obtained from the ROC curve and odds ratio test results were used to create a new diagnostic scale. The factor analysis results showed that the sample size of this study was satisfactory (Kaiser-Meyer-Olkin test value = 0.650). The pattern matrix table revealed that only the “JLC”, “TMM”, “AOT”, and “LOT” values could be components of the scale (Bartlett's test of sphericity value = 104,385, P < .001). The analysis results showed that the scale scores were uniformly distributed under two separate factors (with an explained variance of 50.2%). The variance explained by the Factor 1 scores was higher than the explained variance for the Factor 2 scores (28.17% vs. 22.05%, respectively). The 2-factor differentiation in the factor analysis showed that this scale could predict OLT risk (Eigenvalues = 1.69 and 1.32). However, the reliability test results showed that this scale had no reliability (Cronbach alpha = 0.471, intraclass correlation = 0.471, 95% CI = 0.352-0.573), and the F test revealed no similarity among the parameters forming this scale (F = 1.890, P < .001). Of the patients in the OLT (+) group, 22 (18.02%) underwent surgical intervention for diagnosis and/or treatment of the OLT. When the OLT (+) group was separated into the two groups of those who underwent surgery and those who did not, only the LOT value was found to be statistically different between the two groups (P = .003) (Supplementary Table 2).
The ROC curve analysis revealed that when the LOT value was >35.05 (AUC = 0.702, P = .003, 68% sensitivity, 64% specificity), it could serve as a predictive marker for decision-making regarding surgical intervention in OLT (+) patients. The odds ratio test results showed that if LOT was measured >35.05 (OR = 3.82, 95% CI 1.41-10.34, P = .006), it was associated with a > 3-fold risk of the surgical intervention of the OLT. Logistic regression analysis revealed that the LOT value could be used as the best predictive marker in decision-making for surgical intervention of the OLT (P = .003) (Table 3 and Figure 3B). Study parameters derived from ROC-curve and odds ratio analyses were used to develop a predictive scale for surgical decision-making in OLT, but factor analysis showed that the sample size was insufficient to establish a valid scale or guideline (Kaiser–Meyer–Olkin = 0.470).

Discussion

O'Loughlin et al. recommended MRI imaging as the gold standard diagnostic method for OLT, with higher sensitivity for evaluation of articular cartilage and soft tissue, for diagnosing OLT and showing the size, location, and depth of the lesion.¹² In this study, MRI-based cut-off values of JLC, TMM, AOT, LOT, and LTJSD support the diagnostic value of MRI and demonstrate that these measurements can be effectively used for differentiating and diagnosing OLT.
One of the most important findings of this study was that the LTJSD ratio was significantly lower in the OLT (–) group. LTJSD and LTPAP were evaluated as novel indicators of talocrural load distribution not previously studied in the literature. LTJSD, reflecting ankle geometry and morphology, differed significantly between OLT (–) and OLT (+) patients and may aid diagnosis alongside traditional parameters, although further validation in larger cohorts and with other imaging modalities is needed. In contrast, LTPAP showed no significant difference and was not useful for diagnosing OLT.
The TMM angle, defined between the tibial plafond and the medial malleolar articular surface, is an important morphometric parameter influencing joint stability and talar load distribution. Higher TMM values have been reported in OLT (+) patients compared with healthy individuals, and an association with chondral lesions and disease progression has been described.¹³ In the present study, TMM values were significantly higher in the OLT (+) group than in the OLT (–) group, consistent with the findings of Lee et al., and supporting accurate measurement on both X-ray and MRI.¹⁴
The AOT angle reflects the anterior–posterior proportions of the talar articular surface and is useful for estimating load transfer during ankle motion. Previous CT- and MRI-based studies have shown significantly higher AOT values in OLT patients compared with healthy individuals.^5,15 Consistent with the literature, this study also found higher AOT angles in the OLT (+) group, supporting the reliability of AOT measurement across imaging modalities and its association with OLT.
The JLC angle, which reflects the angulation between the talar dome and distal tibial articular surface, is an important indicator of hindfoot alignment.¹⁶ Previous studies have reported no JLC angulation in normal ankles, with median values of 0° on radiographs.^8,17 In this study, JLC values were significantly higher in the OLT (+) group than in the OLT (–) group, although the median JLC in healthy ankles was 0.9°, differing from earlier reports. This discrepancy may be related to the use of MRI rather than radiography, and CT-based studies may provide a more accurate assessment of this angle.
Yurttaş et al. found that the LOT value was significantly higher in OLT patient groups compared to the control group. Our study confirmed previous findings that the median LOT value was significantly higher in OLT (+) patients. However, it is important to note that due to the anatomical structure of the talus, the lengths of the medial and lateral edges of the talar dome may differ. Accurate assessment of this length can only be obtained through 3D CT or MRI images. Therefore, evaluating 3D images of both OLT (+) and OLT (-) patients may provide the most precise information.
PLTD distance is an auxiliary parameter of ankle instability and has been shown to increase on stress radiographs in the presence of ligament injury.¹⁰ Lee et al. reported significantly increased PLTD values in patients with ligament damage on stress radiographs.¹⁰ In the present study, no significant difference in PLTD values was observed between groups, which may be due to the inability to apply stress during standard MRI examinations.
TLS is an angle used to assess sagittal ankle alignment and is commonly applied in evaluations of healthy, arthritic, and surgically realigned ankles.¹⁸ Although it has not previously been studied in OLT patients, this study found significantly higher TLS values in the OLT (–) group than in the OLT (+) group. However, validation with direct radiographs is recommended, as MRI-based measurements may be affected by slice-dependent In this study, the OLT (–) group was younger than the OLT (+) group, suggesting that age may influence OLT development. Age-related factors such as chondral degeneration, reduced cartilage elasticity, increased cumulative trauma, degenerative joint disease, obesity, and vascular insufficiency may contribute to the higher incidence of OLT with increasing age.
Only LOT values differed between the Surgery (+) and Surgery (–) groups, with higher LOT values observed in surgically treated patients. ROC analysis showed that LOT could predict surgical intervention, and an Odds Ratio analysis indicated that LOT values above 35.05 were associated with more than a threefold increased risk of surgery. These findings suggest that the LOT value could serve as a useful auxiliary parameter in determining the need for surgical intervention. Logistic regression further identified LOT measured on MRI as the strongest predictor of surgical treatment in OLT patients. However, the parameters were insufficient to establish a definitive scale or guideline, possibly due to LOT being a bone measurement assessed on MRI. More accurate CT-based measurements and multicenter studies with diverse populations are needed.

Limitations

This study had several limitations. As a single-center retrospective study, the sample size was small, limiting generalizability, although the findings warrant validation in larger, multicenter studies. Measurement accuracy might have been improved with high-resolution MRI, and CT could have provided more reliable JLC and TMM values; however, MRI was used to maintain methodological homogeneity. Although a scale predicting OLT diagnosis and surgical need was developed and found to be valid, its statistical reliability was low due to the limited sample size. Therefore, larger prospective studies with additional parameters are required to establish a reliable scale.

Conclusion

In conclusion, JLC, TMM, AOT, LOT, and LTJSD measured on MRI are valid parameters for diagnosing suspected OLT. LOT may serve as a predictive marker for determining treatment modality. Prospective studies with larger cohorts are needed to develop a guideline or scale for predicting OLT diagnosis and treatment using these and additional parameters.

Declarations

Abbreviations

References

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