Relationship between talar dome osteochondral lesions and medial malleolus fractures, and their diagnostic significance for occult medial malleolus fractures

Abstract

Objective

This study aimed to investigate the potential correlation between talar dome osteochondral lesions (TDOCL) and medial malleolus fractures and assess the diagnostic significance of TDOCL identified on standard anteroposterior (AP) ankle radiographs for detecting occult medial malleolus fractures.

Methods

A retrospective analysis was conducted on 452 patients with ankle fractures, including 13 cases of occult medial malleolus fractures, treated at Ningde Hospital of Traditional Chinese Medicine between January 2015 and August 2024. For detailed analysis, the talar dome on the AP radiographic view was vertically split into three equal sections. Any definite or suspected TDOCL identified on the AP view was recorded and classified based on location. Computed tomography (CT) imaging was used as the reference standard for diagnosing TDOCL. For every patient, data including sex, age, injured side, diagnostic findings, presence or absence of TDOCL, and lesion location were independently collected. The false-negative and false-positive rates of X-ray detection of TDOCL were calculated, and the association between TDOCLs and medial malleolus fractures was analyzed. Diagnostic performance measures, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive likelihood ratio (LR+), were calculated for medial TDOCL in predicting occult medial malleolus fracture.

Results

Medial TDOCL and female sex were identified as independent risk factors for medial malleolus fracture. For occult medial malleolus fracture, medial TDOCL detected on AP radiographs demonstrated a sensitivity of 38.5%, specificity of 100%, PPV of 100%, and NPV of 98.2%. LR+ could not be calculated due to 100% specificity.

Conclusions

Medial TDOCL is strongly associated with medial malleolus fracture and may serve as a potential warning indicator for occult injury. Clinicians should integrate radiologic findings with physical examination and consider targeted CT imaging for confirmation. These findings are hypothesis-generating and require further validation in prospective studies.

Introduction

Ankle fractures are among the most common and clinically significant musculoskeletal injuries globally [1]. Medial malleolus fractures account for approximately 32.5% of all cases [2]. According to Ebraheim et al., noncomminuted medial malleolus fractures are typically caused by rotational injuries [3]. Furthermore, talar osteochondral lesions are strongly associated with rotational ankle injuries and commonly occur alongside ankle fractures [4]. These findings suggest a potential correlation between talar osteochondral lesions and the incidence of medial malleolus fractures.

Acute ankle injuries are most commonly evaluated using X-ray imaging. Although X-ray imaging is usually sufficient to identify most medial malleolus fractures, a small proportion of occult fractures may remain undetected. Inappropriate treatment may lead to problems, including fracture displacement, malunion, nonunion, or traumatic arthritis, if these fractures go undetected. This retrospective study aims to quantitatively evaluate the relationship between talar osteochondral lesions and medial malleolus fractures and assess the diagnostic value of talar osteochondral lesions visible on the AP view for identifying occult medial malleolus fractures.

Clinical data and methods

Clinical data

Patients with ankle fractures treated at Ningde Hospital of Traditional Chinese Medicine from January 2015 to August 2024 were retrospectively screened following approval from the Medical Research Ethics Committee.

The inclusion criteria were as follows:

1. Complete radiographic evaluation with both ankle X-ray and computed tomography (CT);

2. Age ≥ 16 years.

The exclusion criteria were as follows:

1. Pathological fractures;

2. Open fractures;

3. History of ipsilateral ankle fracture or previous surgery.

CT indications at our institution include the following: Suspected intra-articular extension, subtle or occult fractures, joint instability, or inconclusive plain radiographs.

Only patients who underwent X-ray and CT examinations were included, which may introduce selection bias toward more complex injuries. A patient flowchart was used to document enrollment, exclusions, and completion of imaging evaluations.

Diagnosis of talar dome osteochondral lesion (TDOCL)

Anteroposterior (AP) ankle radiographs were used for initial screening. The talar dome was vertically divided into three equal zones: Medial, central, and lateral. TDOCL was suspected on radiography if a radiolucent subchondral defect, osteochondral detachment, or cortical irregularity was visible in the talar dome [5]. CT was used as the reference standard to confirm TDOCL and characterize fracture morphology (Fig. 1). Two independent orthopedic surgeons, blinded to clinical data and the final diagnosis, reviewed all images.

Fig. 1.

A X-ray anteroposterior view of the talus was vertically and evenly partitioned into three segments; (B) X-ray revealed a low-density osseous region detaching from the medial talar dome (red arrow); (C, D) CT confirmed the presence of a medial talar dome osteochondral lesion (red arrow)

Acute and chronic TDOCL were distinguished based on imaging features:

Acute lesions: Cystic lesion, no marginal sclerosis. Chronic lesions: Sclerotic margins, cystic alterations, nondisplaced or displaced fragment [5].

Observation target

1. General data, including sex, age, injury side, and diagnosis, were recorded.

2. The numbers of medial, central, and lateral TDOCL were recorded. CT findings were used to determine the numbers of positive, false-positive, and missed diagnoses of TDOCL on X-ray.

Statistical analysis

Statistical analyses were performed using the IBM Statistical Package for the Social Sciences software (version 23.0). Categorical variables are reported as counts and percentages and compared using the chi-square test. Age was categorized into three groups for clinical relevance: Young (≤ 44 years), middle-aged (45–59 years), and elderly (≥ 60 years). Binary logistic regression analysis was used to identify independent risk factors for medial malleolus fracture. The following variables were included in the regression model: Sex, age group, injured side, and TDOCL location (medial, lateral, central, both medial and lateral). Collinearity diagnostics were performed to exclude multicollinearity among variables. Model fit was evaluated using the Hosmer–Lemeshow test. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Diagnostic indices, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive likelihood ratio (LR+), were calculated for medial TDOCL as an indicator of occult medial malleolus fracture. A P < 0.05 was considered statistically significant, and P < 0.01 was considered highly significant.

Results

Demographic characteristics

The study comprised 452 patients with ankle fractures. Of these, 147 had additional ankle fractures, while 305 had fractures of the medial malleolus. The cohort comprised 239 men and 213 women. On the left side, there were 233 cases; on the right, 219. Among them were 168 young (≤ 44 years old), 166 middle-aged (45–59 years old), and 118 elderly (≥ 60 years old) patients. Based on the presence and location of TDOCL, 244 cases were classified as none, 34 as medial, 157 as lateral, 2 as central, and 15 as both medial and lateral (Table 1).

Table 1.

Baseline characteristics

Characteristic	N	With a medial malleolus fracture	Without a medial malleolus fracture	χ2/t	P value
Cases	452	305	147
Sex				5.565	0.018
M	239	132	81
F	213	173	66
Side				0.002	0.964
L	233	157	76
R	219	148	71
Age				5.755	0.056
≤ 44	168	102	66
45–59	166	117	49
≥ 60	118	86	32
TDOCL				14.347	0.006
None	244	152	92
Medial	34	30	4
Lateral	157	109	48
Central	2	1	1
Both medial and lateral	15	13	2

Single-factor analysis

Sex and TDOCL were statistically correlated with the occurrence of medial malleolus fracture, according to single-factor analysis; TDOCL was highly significantly correlated with the occurrence of medial malleolus fracture (P < 0.01). The incidence of medial malleolus fracture was not significantly associated with age or injured side (P > 0.05; Table 1).

Regression analysis

Regression analysis revealed that female sex (OR: 1.647; 95% CI: 1.101–2.466; P < 0.05) and medial TDOCL (OR: 4.729; 95% CI: 1.607–13.919; P < 0.01) were independent risk factors for medial malleolus fracture (Table 2).

Table 2.

Regression analysis

Factors	B	S.E.	Wald	P	OR	95% CI
						Lower limit	Upper limit
Sex	0.499	0.206	5.881	0.015	1.647	1.100	2.466
TDOCL			11.827	0.019
Medial	1.554	0.551	7.957	0.005	4.729	1.607	13.919
Lateral	0.352	0.220	2.564	0.109	1.422	0.924	2.188
Central	− 0.485	1.431	0.115	0.735	0.616	0.037	10.182
Both medial and lateral	1.324	0.774	2.929	0.087	3.760	0.825	17.135

Sensitivity of X-ray diagnosis of TDOCL

The positive detection rate of X-ray imaging for medial TDOCL was 88.64% (39/44), with a false negative rate of 20.41% (10/49). For central TDOCL, the positive detection rate was 0% (0/2), while the false negative rate was 2/2 (100%). For lateral TDOCL, the positive detection rate was 82.98% (39/47), whereas the false negative rate was 77.33% (133/172; Table 3).

Table 3.

Sensitivity of X-ray to identify TDOCL at different sites

TDOCL	Positive	False positive	False negative
Medial	39	5	10
Lateral	39	8	133
Central	0	0	2

TDOCL distribution points in 13 cases of occult medial malleolus fractures

Out of the 305 patients with medial malleolus fractures, 13 had occult fractures. Among these, four had no TDOCL, whereas five had medial TDOCL; the X-ray detection rate for TDOCL was 100% (5/5). Moreover, four patients had lateral TDOCL, with a positive rate of 50% (2/4; Table 4).

Table 4.

Imaging diagnosis of TDOCL in patients with occult medial malleolus

TDOCL	None	Medial	Lateral	Central	Both medial and lateral
X-ray positive	0	5	2	0	0
CT negative	4	0	0	0	0
CT positive	0	5	4	0	0

Diagnostic performance of medial TDOCL for occult medial malleolus fracture

Using CT as the reference standard, the diagnostic performance of medial TDOCL on AP radiography for predicting occult medial malleolus fracture was calculated as follows: Sensitivity 38.5% (5/13), specificity 100% (439/439), PPV 100% (5/5), and NPV 98.2% (439/447). The positive LR+ could not be calculated due to 100% specificity.

Discussion

Female sex was independently associated with medial malleolus fractures in this study. This finding is consistent with previous epidemiologic studies demonstrating higher rates of ankle fractures in women [6]. The increased fracture risk observed in women may be related to differences in injury mechanism, ligamentous laxity, bone quality, and anatomical characteristics of the ankle joint [6–9]. These results support the importance of increased clinical vigilance for medial malleolus fractures in female patients presenting with acute ankle injuries.

This study demonstrated a significant correlation between the development of medial malleolus fractures and medial TDOCL. Bruns et al. conducted a biomechanical study on cadaveric ankle joints. They demonstrated that ankle pronation with valgus alignment produces the peak pressure at the lateral border of the talus. Concurrently, supination with varus concentrates stress on the medial aspect of the ankle joint [10]. A review study further indicates that the occurrence of medial or lateral talar osteochondral lesions depends on the injury mechanism; medial lesions are commonly associated with axial loading combined with torsional forces [4]. Based on these findings, we propose a potential impact mechanism. As illustrated in Fig. 2A, an external force leads to impaction between the talus and medial malleolus. Subsequent axial loading results in a medial malleolus fracture, with secondary medial talar osteochondral lesions. However, this mechanism remains speculative in the absence of dedicated biomechanical experiments or prospective imaging evidence. Furthermore, some talus osteochondral lesions were observed that appeared to be chronic (Fig. 3). Because the talus plays an essential role in ankle stability, osteochondral damage may alter the cartilage and subchondral bone, thereby weakening joint stability. This joint instability over time may cause repeated impingement between the talus and the medial malleolus, result in stress concentration in the medial malleolus, and increase the risk of fracture under external force (Fig. 2B).

Fig. 2.

A External force causes impaction between the talus and the medial malleolus. Subsequent axial loading results in a medial malleolus fracture, accompanied by secondary medial talar osteochondral lesions. B A chronic osteochondral lesion of the talar dome leads to joint instability and stress concentration at the medial malleolus

Fig. 3.

A man presented with an acute right ankle injury 1 h before admission. A, B The initial AP view revealed a distinct medial TDOCL, and careful examination of the medial malleolus revealed a possible fracture. C, D A subsequent CT scan revealed the existence of medial TDOCL and medial malleolus fractures

AP and mortise radiographs of the ankle joint can reveal osteochondral lesions of the talus [11, 12]. Clinically, patients presenting with ankle injuries do not routinely undergo mortise radiographs. In this study, the diagnostic sensitivity of standard AP radiography for TDOCL was 0.35, lower than the 0.59 reported by Verhagen et al. [12, 13]. This discrepancy may be explained by differences in study populations: Verhagen’s cohort consisted primarily of patients with chronic ankle pain, whereas our study included only patients with acute ankle fractures. In acute trauma settings, overlapping osseous structures on AP radiographs may reduce visibility of lateral and central TDOCL, whereas medial TDOCL remains more readily identifiable.

According to previous epidemiological studies, the talus is the most frequent site of osteochondral lesions following ankle fractures, accounting for 42.7% of cases, and the medial zone represents the most common sublocation, at 45.1% [4]. In the present study, the sensitivity of X-ray imaging for detecting medial TDOCL (0.80) was significantly higher than that for lateral TDOCL (0.23) and central TDOCL (0). Consistent with the findings of Raiki [14], we also observed that medial TDOCLs typically have a larger surface area and that the AP view can clearly display their size and form. Furthermore, compared to the lateral side, only a few cases on AP radiographs revealed the medial edge of the talar dome overlapping the medial malleolus, which was easier to observe in TDOCL. The occurrence of osteochondral lesions in the central region of the talar dome is extremely uncommon, and we assume that they are the consequence of a vertical impact between the central region of the talar dome and the distal tibia. Furthermore, injuries in the center of the talus can present as minor lesions in the early stage, such as cartilage surface damage or small subchondral fractures. On AP and CT views, these early lesions are sometimes difficult to measure.

Only 13 cases of occult medial malleolus fractures have been reported in the past decade; one patient had a poor clinical outcome due to a missed diagnosis; the only typical indicator on first X-ray images is medial TDOCL (Fig. 4). In patients with occult medial malleolus fracture, identification of medial TDOCL on initial AP radiographs should increase clinical suspicion for associated subtle fracture. Medial TDOCL on AP radiography demonstrated 100% specificity and 100% PPV for occult medial malleolus fracture, with a sensitivity of 38.5%. In clinical practice, this radiographic sign should be integrated with careful physical examination and localized tenderness. When clinical suspicion remains high, targeted CT is recommended to confirm the presence of an occult or minimally displaced fracture. Notably, CT may still miss occult fractures when the fracture line runs parallel to the imaging plane. Magnetic resonance imaging (MRI) demonstrates higher sensitivity for bone marrow edema and may be used as an adjunctive modality when clinical suspicion remains high despite a negative CT scan [15, 16]. The present results are exploratory and should not be regarded as altering standard clinical practice until confirmed by large-scale prospective studies.

Fig. 4.

A man presented to our hospital with a left ankle injury. A, B Initial anteroposterior and lateral X-ray images of the ankle joint revealed no obvious fractures. However, a medial TDOCL was visible on the AP view of the ankle radiograph. The outpatient physician diagnosed an ankle sprain, and no cast was applied. C, D The patient returned to our hospital 24 days later with ankle pain, and follow-up X-ray revealed a fracture of the left medial malleolus. Casting was then performed by the outpatient physician. E, F A subsequent CT examination revealed the presence of a medial TDOCL. G, H At 44 days after injury, an X-ray imaging revealed no obvious callus formation at the fracture site

This study has several limitations despite its important results. First, this is a retrospective single-center study, which may be subject to inherent selection and verification bias. Only patients undergoing X-ray and CT were included, which may introduce selection bias toward more complex or suspicious injuries and potentially overestimate the diagnostic performance of medial TDOCL for occult medial malleolus fracture. Second, the number of occult medial malleolus fractures was small (n = 13), limiting statistical power for diagnostic conclusions. Third, the proposed impingement mechanism was theoretical and lacked biomechanical or prospective imaging data. Fourth, CT was used as the reference standard, but some occult fractures may be measurable only with MRI. Finally, the study did not classify TDOCL based on the ankle fracture type, which may limit understanding of injury patterns.

Conclusions

Medial TDOCL is strongly associated with medial malleolus fracture and may serve as a potential warning indicator for occult injury. Clinicians should integrate radiologic signs with physical examination and consider targeted CT for confirmation. These findings are preliminary and hypothesis-generating and require further prospective validation.

Authors’ contributions

X.Z: Writing–original draft, Data curation. H.X.: Data curation. C.L.: Data curation. W.L.: Data curation. C.Z.: Data curation. C.H.: Writing–review & editing, Supervision, Data curation, Conceptualization.

Funding

Not applicable.

Data availability

The datasets generated and/or analysed during the current study are not publicly available due [REASON WHY DATA ARE NOT PUBLIC] but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This retrospective study was conducted in accordance with the Declaration of Helsinki. Ethical approval was obtained from the Ethics Committee of Ningde Hospital of Traditional Chinese Medicine. Informed consent was waived by the Ethics Committee of Ningde Hospital of Traditional Chinese Medicine due to the retrospective nature of the study, and all data were analyzed anonymously.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.