Comparison of medial osteochondral lesions of the talus characteristics between chronic lateral ankle instability and ankle varus

Abstract

Purpose

The objective is to compare the demographics and characteristics of medial osteochondral lesions of the talus (OLTs) between chronic lateral ankle instability (CLAI) and ankle varus.

Methods

A total of 175 consecutive patients who underwent surgical intervention for medial OLTs between January 2010 and December 2022 were recruited. Patient demographic data including age, sex, side of injury, symptom duration, body mass index (BMI), history of ankle sprain, presence of CLAI, and ankle varus were documented. Lesion-related characteristics, including lesion size, anatomical location, Hepple classification, and presence of combined lesions, were also recorded. Patients were stratified into three groups: C (CLAI alone), V (ankle varus alone), and CV (CLAI and ankle varus). Statistical analyses were performed to compare demographic characteristics and lesion-related variables among the groups.

Results

Group V had the highest median age (62.00 years; IQR, 52.75–68.25) and median duration of symptoms (36 months; IQR, 22.50–60.00), both significantly higher than group C. Group CV showed the highest median BMI (26.48; IQR, 24.73–30.68). In contrast, group C had the smallest mean size of lesions (113.7mm²; IQR, 88.5–139.0) and the lowest proportion of the Hepple V classification (15.7%) .

Conclusion

Patients with ankle varus were older and had prolonged symptom duration compared to those with CLAI alone. Conversely, the latter group demonstrated a reduced prevalence of lesions measuring ≥ 150 mm² and lower rates of Hepple V classification.

Level of evidence

Level III, Casecontrol study.

Introduction

Osteochondral lesions of the talus (OLTs) are characterized by damage to cartilage and/or subchondral bone in the talar dome. OLTs commonly result from traumatic incidents [1], such as ankle sprains, ankle fractures, and chronic lateral ankle instability (CLAI) [2–6]. The inherent lateral joint instability leads to recurrent microtraumatic stress on the articular cartilage [7]. Consequently, medial OLTs are frequently diagnosed as a condition that arises from the cumulative effects of such repetitive trauma [8]. Sugimoto et al. reported that among 97 ankles with recurrent lateral instability, 76 ankles (77%) had chondral lesions, predominantly located in the medial half and the anterior two-thirds of the joint [9]. Ikoma et al. found that the CLAI group exhibited lesions with significantly reduced longitudinal and transverse diameters compared to the stable group, and the radiographic, magnetic resonance images (MRI), and arthroscopic evaluations revealed earlier stages of medial OLTs in the CLAI group [10]. A prior study has identified a negative correlation between CLAI and the lesion size of medial OLTs [11].

Bilateral OLTs without prior trauma are also observed frequently [12, 13]. There is an increasing awareness of the link between ankle malalignment and OLTs, and sustained eccentric loading on the medial ankle is known to increase contact stresses on the medial articular surface, causing focal medial OLTs and arthritis [14, 15]. Uncorrected foot and ankle malalignment has been suggested as a possible factor contributing to the failure of OLTS surgery [16, 17]. The exact pathophysiology of osteochondral lesions of the talus (OLTs) remains unclear. However, associated factors, including CLAI and ankle varus, may alter ankle biomechanical loading, resulting in varied characteristics.

Our study hypothesizes that different factors may lead to distinct characteristics of medial OLTs (OLT size, location, Hepple Classification, and combined lesions). Our study aims to compare the characteristics of medial OLTs and the demographic profiles of patients with group C (CLAI alone), group V (ankle varus alone), and group CV (CLAI and ankle varus).

Methods

Population

The research protocol was reviewed and granted official approval from the institutional ethics committee of our hospital. A cohort of consecutive patients who underwent surgical procedures for osteochondral lesions of the talus (OLTs) at our hospital between January 2010 and December 2022 was systematically evaluated for eligibility to participate in this study.​ The surgical procedures involved treating medial OLTs, followed by managing CLAI and/or correcting ankle varus.

The inclusion criteria were defined as follows: complete and comprehensive clinical datasets; symptoms characterized by ankle pain and/or functional limitations, lack of therapeutic response following a standardized course of conservative treatment, and OLTs diagnosed through preoperative computed tomography (CT) and magnetic resonance imaging (MRI).

Exclusion criteria were applied to patients with the following characteristics: isolated lateral OLTs, OLTs etiologically attributed to gout, joint changes classified as Kellgren-Lawrence grade 3 or 4, a tibiotalar tilt angle exceeding 2° as measured on anteroposterior radiographs, a prior history of ankle surgical interventions, an acute ankle injury within the preceding three-month period accompanied by displaced osteochondral fragments, or the presence of other neuromuscular disorders affecting the ankle joint.​ After applying these exclusion criteria, 175 patients remained eligible and were included in the final analysis. Patients were stratified into three groups – group C (CLAI alone), group V (ankle varus alone), and group CV (CLAI and ankle varus).

Extensive demographic data were collected, such as gender, preoperative body mass index (BMI), age at the time of surgical treatment, history of ankle sprain, affected side, duration of symptoms, ankle joint alignment, and the presence or absence of CLAI.​.

Assessment of ankle alignment and CLAI

Ankle joint alignment was evaluated using standardized radiographic assessment methods. Specifically, the medial tibial ankle surface (TAS) angle, which is defined as the angular relationship between the tibial anatomical axis and the tibial plafond as visualized on weight-bearing anteroposterior ankle radiographs, was measured. In the context of this study, a TAS angle less than 88° was defined as a diagnostic criterion for ankle varus deformity [11].​.

The diagnosis of CLAI was established based on a multi-modal approach that integrated clinical symptoms, physical examination findings, and stress test results [9], and radiographic investigations (MRI). Stress radiography, conducted using the Telos stress-testing device, was employed to quantitatively measure the anterior drawer distance during anterior drawer stress testing and the talar tilt angle during inversion stress testing. A positive anterior drawer test was defined as > 10 mm of anterior talar translation, whereas a positive talar tilt test was defined as > 6° of talar inversion [18].​.

Characteristics of OLTs

MRI was utilized to determine the classification and location of OLTs. The MRI classification was based on the Hepple system [19]. Specifically, stages I to IV were regarded as mild, while stage V was considered severe. In the axial plane, the articular surface of the talar dome was partitioned into six zones of equal area using a grid consisting of two columns and three rows [11]. In cases where the lesion extended across multiple zones, the location that encompassed most of the lesion was documented.

The dimensions of the lesion, including length, width, and depth, were measured using MRI, following the methodology described by Choi et al. [20]. Due to the irregular morphology of OLTs, the maximum measurement in each plane was used as the diameter for that corresponding plane. Lesions with an area less than 150 mm² were classified as small, whereas those with an area exceeding 150 mm² were categorized as large [21]. Additionally, lesions were classified as contained or uncontained, with a contained lesion defined by intact articular cartilage borders surrounding the defect. Combined lesions (such as a fibular tip ossicle, anterior tibial and talar spurs, lateral talar osteochondral lesions, talar edema, and tibial osteochondral lesions) were identified through preoperative MRI.

Two separate foot and ankle surgeons took measurements of the TAS angle, evaluated the Hepple classification, and measured the lesion size on two occasions, with an interval of at least six weeks between measurements to minimize potential bias. Consensus between the two observers was required to confirm ankle varus, the Hepple classification, and the lesion size.

Covariates

The key variables included age, gender, the affected side of the injury, duration of symptoms, body mass index (BMI), history of ankle sprain, CLAI, and ankle varus. This study encompassed a total of eight covariates. According to the widely accepted empirical guideline suggesting that the sample size should be 10 to 15 times the number of covariates, the estimated sample size requirement for this research ranged from 80 to 120. However, the final sample size was set at 175, ensuring an ample number of participants to achieve the expected statistical significance.

Statistics

For descriptive statistics, continuous variables exhibiting a normal distribution were reported as the mean plus or minus the standard deviation (mean ± SD). In contrast, variables that did not follow a normal distribution were presented as the median and the interquartile range (IQR). Categorical variables were characterized by frequency counts and percentages. Intraobserver reliability was evaluated via the Kappa test, and a Cronbach’s α value exceeding 0.80 was considered indicative of excellent reliability.

To assess differences between these groups, one-way analysis of variance (ANOVA) was used for normally distributed continuous variables. At the same time, the Kruskal-Wallis test was applied to non-normally distributed continuous variables. For categorical variables, the chi-square (χ²) test was utilized when the expected frequencies were 5 or greater, and Fisher’s exact test was used when expected frequencies were less than 5. Holm’s adjustment was utilized for multiple comparisons. All statistical analyses were conducted using R version 4.3.3, with a significance level set at p < .05.

Results

Demographics

Table 1 shows the intraobserver and interobserver reliabilities for ankle varus, Hepple classification, and lesion size.

Table 1.

Intra- and interobserver reliability

Parameter	Intraobserver reliability	Interobserver reliability
Ankle varus	0.915	0.886
Hepple classification	0.923	0.863
Size classification	0.902	0.857

Tables 2 and 3 summarize the patient characteristics and details of OLTs, respectively.

Table 2.

Characteristics of participants

Characteristics	Overall
Age, years, median [IQR]	51.00 [37–61]
BMI, kg/m², median, [IQR]	24.9 [22.41–27.7]
Duration of symptoms, months	24.00 [12.00–48.00]
Gender
- Male (%)  - Female (%)	96 (54.86) 79 (45.14)
Side affected
- Left ankle, n (%)  - Right ankle, n (%)	86 (49.14) 89 (50.86)
Presence of ankle sprain, n (%)	100 (57.14)
Chronic lateral ankle instability, n (%)	139 (79.43)
Ankle varus, n (%)	60 (34.29)

Abbreviation: IQR, interquartile range; BMI, body mass index

Table 3.

Characteristics of OLTs

Characteristics	Overall
Size, mm2, median [IQR]	126.4 [92.4-165.9]
Location, n (%)
AM	12(6.86)
CM	71(40.57)
PM	92(52.57)
Contained, n(%) Uncontained, n (%)	57(32.57) 118(67.43)
Hepple classification, n (%)
I	19(10.86)
II	71(40.57)
III	11(6.28)
IV	29(16.57)
V	45(25.71)
Combined lesions, n (%)
Anterior tibial and talus spur	37(21.14)
An ossicle of the fibular tip	9(5.14)
Tibial chondral lesion	17(9.71)
Lateral talus chondral lesion	14(8.00)
Edema of the talus	38(21.71)

Abbreviation: AM, Anteromedial; CM, Central Medial; PM, Posteromedial

The median age of the participants was 51 years (interquartile range [IQR]: 37–61), with 46 individuals (26.3% of the cohort) aged 60 years or older. The median body mass index (BMI) was 24.9 (IQR: 22.41–27.7). Regarding the duration of symptoms, the median was 24 months (IQR: 12.00–48.00), and 63 patients (36%) had experienced symptoms for more than three years.

Among the patients, 115 (65.71%) were diagnosed with group C, 24 (13.71%) were group CV and 36 (20.58%) were group V. Additionally, 113 patients (64.57%) had lesions smaller than 150 mm². In terms of lesion location, 12 (6.86%) were on the anteromedial talus, 71 (40.57%) on the central medial region, and 92 (52.57%) on the posteromedial area. According to the Hepple classification, 45 patients (25.71%) were categorized as Hepple V.

Characteristics of demographics among the different factors

Demographics of all three groups are listed in Table 4.

Table 4.

Comparison of participant groups with different factors

Characteristics	Group C	Group CV	Group V	P value
	(n = 115)	(n = 24)	(n = 36)
Age, years, median [IQR]	48.00(33.00, 56.00)	57.00 (46.00, 61.00)	62.00(52.75, 68.25)	< 0.001
Male (%)	63 (54.8)	14 (58.3)	19 (52.8)	0.750
BMI, kg/m², median[IQR]	24.50 (21.77, 27.32)	26.48 (24.73, 30.68)	25.40 (23.67, 26.73)	0.007
History of ankle sprain, n (%)	75 (65.2)	15 (62.5)	10 (27.8)	< 0.001
Duration of symptoms, months, median [IQR]	12.00 (6.50, 36.00)	30.00 (12.00, 39.00)	36.00 (22.50, 60.00)	0.022

Abbreviation: Group C, Chronic lateral ankle instability. Group CV, Chronic lateral ankle instability with ankle varus. Group V, Ankle varus. IQR, interquartile range. BMI, body mass index

The median age differed significantly among groups(P < .001), with group V having the highest median age (62.00 years, IQR:52.75–68.25) compared to group C based on Holm’s adjustment. Regarding age distribution, after Holm’s adjustment for multiple comparisons, group V exhibited a significantly different age distribution compared to group C, with 55.6% (n = 20) of patients in group V being over 60 years old. The median of preoperative BMI was significantly greater in the group CV (26.48, IQR, 24.73, 30.68) (P = .007).

Regarding the history of ankle sprain, following Holm’s adjustment for multiple comparisons, group C had a significantly different rate of ankle sprain history compared to group V, with 65.2% (n = 75) of patients in group C reporting a history of ankle sprain. The median duration of symptoms was also longer in group V (36 months; IQR:22.50,60.00) than in group C.

Characteristics of lesions among the different factors

The characteristics of lesions are presented in Table 5.

Table 5.

Comparison of characteristics of lesions among the different factors

Characteristics	Group C	Group CV	Group V	P
	(n = 115)	(n = 24)	(n = 36)
Size, median[IQR]	113.7 [88.5,139.0]	180.1 [127.2,189.6]	158.8 [110.7,199.0]	< 0.001
Location (%)				0.058
AM	52 (45.2)	16 (66.7)	24 (66.7)
CM	8 (7.0)	0 (0.0)	4 (11.1)
PM	55 (47.8)	8 (33.3)	8 (22.2)
Contained (%)	44 (38.3)	4 (16.7)	9 (25.0)	0.067
Hepple classification (%)				< 0.001
I-IV	97 (84.3)	12(50.0)	21 (58.3)
V	18 (15.7)	12 (50.0)	15 (41.7)
Anterior tibial and talus spur (%)	25 (21.7)	3 (12.5)	9 (25.0)	0.491
An ossicle of the fibular tip (%)	9 (7.8)	0 (0.0)	0 (0.0)	0.084
Tibial chondral lesion (%)	9 (7.8)	3 (12.5)	5 (13.9)	0.498
Lateral talus chondral lesion (%)	10 (8.7)	1 (4.2)	3 (8.3)	0.756
Edema of the talus (%)	26 (22.6)	7 (29.2)	5 (13.9)	0.344

Abbreviation: group C, Chronic lateral ankle instability. Group CV, Chronic lateral ankle instability with ankle varus. Group V, Ankle varus. AM, Anteromedial; CM, Central Medial; PM, Posteromedial

The size of lesion showed a distinct difference between groups (P < .001). Following Holm’s adjustment for multiple comparisons, group C exhibited a significantly different ratio of lesion size compared to group CV or group V. The proportion of lesions measuring ≥ 150 mm² was 19.1% (n = 22) in group C compared to patients with group CV or group V , 66.7% (n = 16) and 66.7% (n = 24), respectively. The Hepple classification also revealed significant differences between groups (P < .001). Following Holm’s adjustment for multiple comparisons, group C exhibited a significantly different Hepple classification compared to groups V and CV. Hepple grade V lesions were present in 15.7% (n = 18) of patients in group C.

There were no significant differences between groups regarding lesion location, contained lesions, anterior tibial and talar spurs, fibular tip ossicles, tibia chondral lesions, simultaneous lateral talar chondral lesions, and edema of the talus.

Discussion

Our study aimed to analyze the characteristics of medial OLTs in 3 different groups of patients: CLAI alone, CLAI and ankle varus and ankle varus alone. Although the etiologies of medial OLT were not clear, chronic overload of the dome of the talus could be a potential contributing factor [22]. The results demonstrated significant differences among the three groups in terms of age, duration of symptoms, BMI, size of the OLTs, and Hepple V classification of the lesions.

Our study revealed that the median age of patients with isolated ankle varus was the highest (62.00 years), with over half (55.6%) of the patients aged 60 years or older. We found that patients with ankle varus alone also had the most extended duration of symptoms (36.00 months), which we believed was primarily due to continuous loading on the injured cartilage, resulting in inefficient healing and prolonged unresolved symptoms, that eventually led the patient to seek medical attention. The varus group of patients lacks a clear history of trauma, and symptoms are mild in the initial phase and gradually worsen over time. Thus, the patient was relatively older and had a longer duration of symptoms. Conversely, the median age of patients in the isolated CLAI group was the lowest (48.00 years), and the highest proportion (65.2%) reported a history of ankle sprain. Younger individuals are more susceptible to ankle sprains, potentially due to their increased participation in high-risk exercises or activities.

Patients with ankle varus combined with CLAI showed notable differences in their BMI. These individuals had a median BMI of 26.48, representing the highest value among all groups. There are two potential explanations for this observation. Firstly, the alignment of ankle varus may be associated with lateral ligament instability [23]. When assessing patients with malalignment of the ankle, it is crucial to evaluate the stability of the lateral ligaments [24]. As part of our routine clinical assessment, we performed an anterior drawer test on individuals presenting with varus alignment. Secondly, a study by Frey et al. [25] reported findings that classify patients according to BMI and demonstrate how being overweight significantly increases the likelihood of developing foot and ankle pathologies. Richter et al. shown that obese individuals exhibited significantly reduced post-operative foot and ankle functional scores in relation to the surgical outcomes of OLTs [26]. Patients with both ankle varus and higher BMI are more susceptible to lateral ankle ligament injuries, resulting in ankle instability.

The study found that the size of lesion in the isolated CLAI group was significantly smaller compared to the other two groups (P < .001), and there were notable differences in Hepple classifications. Specifically, only 15.7% (n = 18) of patients in CLAI group exhibited Hepple grade V lesions, suggesting that isolated CLAI is often associated with early-stage or mild damage, which was consistent with the findings reported by Ikoma et al. [10].

Patients with ankle varus had larger sizes of OLTs and a higher incidence of subchondral cyst formation (Hepple V) compared to patients with CLAI alone. There are some possible explanations for these results. Firstly, as previously noted, the median age of patients and duration of symptoms in group CV and group V were higher than in group C. The chronicity of the condition may lead to increase in the size of the OLTs, which is consistent with findings by Cao et al., who reported that OLTs in patients aged 40–60 years and > 60 years exhibited greater depth and size of medial OLTs [18]. Secondly, the longer duration of symptoms in ankle varus patients may contribute to subchondral cyst development, as this progression is only a matter of time. We believe the subchondral cyst, when left untreated, could eventually lead to medial ankle osteoarthritis. Hence, the intervention of the OLT and correction of the ankle alignment could potentially slow down or halt the progression into ankle osteoarthritis.

This study has some limitations. Firstly, the study design of the present study is retrospective, and the sample size is relatively small. Secondly, our study aimed to investigate the effects of two factors, CLAI and ankle varus, on medial OLTs. To achieve this, we excluded cases that did not involve these specific conditions. Additionally, individuals with asymptomatic or only mildly symptomatic OLTs who were adequately managed with conservative treatment were also excluded from our analysis. Consequently, the characteristics of medial OLTs observed in our research primarily pertain to ankle varus and CLAI patients with significant symptoms requiring further intervention. Thirdly, our analysis did not encompass the surgical treatment approaches or the clinical outcomes for patients. Additionally, we did not include hindfoot alignment into our study since some ankle varus patients exhibited valgus hindfoot characteristics.

Conclusion

Differences were found with age, BMI and duration of symptoms between the two different conditions of CLAI and ankle varus. Patients with ankle varus alone were the oldest and had the longest duration of symptoms. Patients with ankle varus combined with CLAI had the highest BMI. Regarding the characteristics of the OLTs, differences existed in the size and Hepple classification. Patients with ankle varus had larger sizes of OLTs and a higher incidence of Hepple V OLTs.

Abbreviations

AM

Anteromedial

CM

Central medial

CLAI

Chronic lateral ankle instability

CT

Computed tomography

IQR

Interquartile range

MRI

Magnetic resonance imaging

TAS

Tibial ankle surface

OLTs

Osteochondral lesions of the talus

Author contributions

C.Y. and Y.Z. wrote the paper, finished data collection and analysis. Z.X. helped to finish data collection and analysis. X.X.finished the literature review. C.G. finished the study design and article revision.

Funding

Not applicable.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

The protocol of this study was approved by our hospital ethics committee (2024-30) and the informed consent to participate has been waived by the Ethics Committee.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.