Correlation between tibial eminence fractures and morphology of femur condyles and tibial slopes in male patients: a retrospective case-control study

Abstract

Background

Several studies have examined the relationship between anterior cruciate ligament (ACL) injury and the femoral condyle and tibial slopes. Tibial eminence fractures (TEFs) are often noted during the diagnosis and treatment of patients with ACL injuries. However, only a few studies have investigated the relationship between anatomic parameters of the knee and TEFs in adults. Therefore, we aimed to investigate the link between TEFs and the shape of the femoral condyles and tibial slopes.

Methods

Patients who underwent surgery were identified using the hospital’s electronic medical record system from May 2013 to May 2023. Three sex-, age-, and BMI-matched cohorts (n = 20 each) were included: the TEF, ACL injury, and control groups. The femoral condylar width (epicondylar width [EW]), intercondylar notch width (ICW), notch width index (NWI), intercondylar notch height, morphological index of the intercondylar notch (NSI), intercondylar notch angle (ICA), and “α” angle were measured using axial MRI. The medial and lateral tibial slopes were measured using sagittal MRI to compare differences among the TEF, ACL injury, and control groups. Multiple logistic regression analysis was performed to identify independent predictors of TEFs.

Results

We found no significant differences in age, height, weight, and body mass index between the TEF and ACL injury groups (P > 0.05). No significant differences were noted in the ICW, EW, NWI, “α” angle, or medial tibial slope among the TEF, ACL injury, and control groups (P > 0.05). The NSI differed significantly between the ACL injury and control groups (P < 0.05). The ICA in the ACL injury group was significantly lower than that in the control group (P < 0.05). The lateral tibial slope (LTS) was significantly greater in the TEF group than in the ACL injury group (P < 0.05). Logistic regression analysis and odds ratio estimates showed that LTS is an important risk factor for TEFs. The area under the curve of the LTS was 0.714, with a sensitivity of 70.00% and specificity of 70.00%; thus, it was the best anatomical angle for identifying patients prone to TEFs.

Conclusion

Our results suggest that a narrow femoral intercondylar notch contributes to ACL injuries, while TEFs are closely related to tibial plateau morphology. TEFs should be regarded as a specific type of tibial plateau fracture rather than a specific pattern of ACL injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-025-09406-0.

Background

Anterior cruciate ligament (ACL) injury most commonly involves tears of the collagenous fibers of the ligament. Less frequently, cruciate ligament injuries involve avulsion fractures at the origin or insertion of the ligament, most commonly at the insertion site on the tibial surface [1, 2]. Tibial eminence fractures (TEFs) are important because they can be identified on radiographs, enabling a specific diagnosis. Although more common in pediatric patients, TEFs have been frequently observed in recent decades, with an increase in sports injuries and traffic accidents in adults [3–5]. The tibial eminence is the tibial stop of the ACL. Therefore, TEFs are frequently observed during the diagnosis and treatment of ACL injuries. Several studies have been conducted to determine the various risk factors for ACL rupture, including increased notch width index (NWI), knee recurvatum, external tibial torsion, subtalar pronation, generalized ligamentum laxity, and elevated body mass index (BMI) [6, 7]. The association between femoral intercondylar notches and ACL injuries was first proposed by Palmer in 1938. A stenotic notch is believed to be associated with a high risk of ACL injury [8]. The femoral notch has been studied in multiple ways to determine whether anthropometric notch variations serve as risk factors for ACL injuries. The absolute width, width index, area, shape, and outlet dimensions of the notch were evaluated with mixed results [9].

Several studies have reported the relationship between ACL injury and the type of femoral intercondylar notch and tibial slope [9–11]. Biomechanically, a higher tibial slope in the presence of a compressive load generates a higher anterior shear component of the tibiofemoral reaction force, resulting in increased anterior motion of the tibia relative to the femur. The literature frequently mentions that individuals with ACL injuries exhibit a higher tibial slope than their healthy counterparts [12, 13]. However, only a few studies have investigated the association between TEFs and the morphology of the femoral intercondylar notch and tibial slope in adults.

We aimed to determine the association between TEFs and the morphology of the femoral intercondylar notch and tibial slopes in male patients. We hypothesized that TEFs are associated with the morphology of the femoral intercondylar notch and tibial slope and that these fractures represent a distinct type of tibial plateau fracture.

Methods

This study had a retrospective case-control design and Level of Evidence III.

Patients

This study was approved by the ethics committee of our institution (approval no. K2021-04–023). Patients were identified through the hospital’s electronic medical record system between May 2013 and May 2023. A total of 691 patients who underwent arthroscopic knee surgery were included and categorized into three groups: (1) the TEF, (2) ACL injury, and (3) control groups, consisting of anterior knee pain without signs of trochlear dysplasia, or isolated meniscal tears [14, 15]. The TEF group cases were matched with the ACL injury and control groups according to sex, age, and BMI. Subsequently, they were evaluated according to the eligibility criteria outlined in Fig. 1 [16, 17].

Fig. 1.

Flowchart summarizing the selection of eligible patients ACL anterior cruciate ligament, BMI body mass index, TEF tibial eminence fracture

The exclusion criteria were as follows: (1) age < 18 years; (2) female patients; (3) patellofemoral dysplasia; (4) previous ligament injury (ACL, medial collateral ligament, lateral collateral ligament, and posterior cruciate ligament); (5) patients with knee osteoarthritis, rheumatoid arthritis, gouty arthritis, knee infection, tuberculosis, and other chronic diseases; and (6) prior history of knee surgery on the affected limb (Fig. 1).

Magnetic resonance imaging (MRI) examination

All images were retrieved from patients’ picture archiving and communication system records. The knee joint was assessed using a Siemens 1.5 T & 3.0 T superconducting magnetic resonance scanner (Siemens Healthineers, Erlangen, Germany), which generated cross-sectional T2W1, sagittal T1W1, and T2W1 images.

Measurement of intercondylar Notch morphology

Based on the method by Bouras et al. [9], MRI axial T2W1 images were acquired, with the standard level defined as the deepest point of the lateral femoral condylar popliteal tendon groove.

The following notch parameters were measured: (1) Height of the femoral intercondylar notch (ICH): a baseline formed by a line connecting the lowest points of the femoral bicondyle (Fig. 2A: Line a). The vertical line extending from the top of the intercondylar notch represents the ICH (Fig. 2B: Line b). (2) Width of the femoral condyles (epicondylar width [EW]): Line a was repositioned at the midpoint of the intercondylar notch height (half of Line b, Fig. 2C: Line a), and horizontally connected to the medial and lateral condylar lines of the femur to determine the EW (Fig. 2C, including the red Line c). (3) Width of the intercondylar notch (ICW): the line segment at the midpoint of the intercondylar notch height, where the medial margin of the medial and lateral condyles of the femur intersects, represents the width of the intercondylar notch (Fig. 2D, including the red Line d). (4) NWI: NWI was defined as the ratio of the width of the intercondylar notch to the width of the distal femur at the level of the popliteal groove on the notch MRI. NWI > 0.27 indicates a normal intercondylar notch width, whereas NWI < 0.27 indicates stenosis of the intercondylar notch [9]. (5) Morphological index of the intercondylar notch (NSI): this index is defined as the ratio of the intercondylar notch width to its height. (6) Angle of the intercondylar notch (ICA): the angle is formed between the apex of the intercondylar notch and the tangent line of the medial and lateral condyles (Fig. 2E). (7) “α” angle: this angle is measured between the longitudinal femoral axis and the Blumensaat line (Fig. 2F).

Fig. 2.

Measurement of the femoral condyle morphology. A The baseline (Line a). B Intercondylar notch height (Line b). C Epicondylar width (femoral condylar width) (Line c). D Intercondylar notch width (plus red Line d). E Intercondylar notch angle.F “α” angle

Measurement of the tibial slopes

Based on the method by Hashemi et al. [18], a sagittal T1W1 image was acquired. The knee cavity level served as the reference point, with the line situated at the midpoint between the two tibiae (Fig. 3A) used as the longitudinal axis of the tibia (Fig. 3A, Line e). To measure the medial tibial slope (MTS), Line e was replicated on the measurement plane of the medial tibial plateau. The angle between the lines of the anterior and posterior edges of the medial tibial plateau (Fig. 3B, Line f) and the longitudinal axis of the tibial plateau (Fig. 3B, Line e) minus 90° represented the posterior slope angle of the medial tibial plateau. Similarly, for the measurement of the lateral tibial slope (LTS), the posterior slope of the lateral tibial plateau was determined using the same method (by subtracting the angle between Lines g and e in Fig. 3C from 90°).

Fig. 3.

Measurement of the tibial slopes. A Tibial axis.B Medial tibial slope.C Lateral tibial slope

Arthroscopy

The arthroscopic exploration and treatment of the patients were performed by the same team of sports medicine physicians. Surgery was performed under general or epidural anesthesia. The standard anteromedial (AM) and anterolateral (AL) portals were used for knee arthroscopy (arthroscopic system: Smith & Nephew, Andover, MA, USA; with a 30° lens [4 mm]), and the joint was fully examined. Corresponding to the MRI measurement indicators, the morphologies of the intercondylar notch and femoral condyles were observed and recorded. Concomitant meniscal pathology that required attention was corrected before the ACL status was assessed. ACL tension was explored using a probe, and the integrity of the ACL was recorded. Furthermore, for TEFs of the tibial plateau, sharp debridement and scar tissue removal around the fracture were performed, and fracture fragments were reduced using a probe to achieve a congruent articular surface. Corresponding surgical treatment was performed according to the injury situation.

Statistical analyses

IBM SPSS Statistics version 22.0 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. The measurement data were tested for normality using the Shapiro–Wilk test and for homogeneity of variance using the Levene test. One-way analysis of variance was used to compare data with a normal distribution and homogeneity of variance, and the Kruskal–Wallis H test was used to compare data with a non-normal distribution and homogeneity of variance. Categorical data were compared between the groups using the χ2 test. The significance level for the test was set at 0.05 (two-sided).

This study had a cross-sectional observational design, with three groups: the TEF, ACL injury, and control groups. The LTS of the subjects was the outcome indicator. Based on the results of the previous pilot study, the LTS levels of the control, TEF, and ACL injury groups were 7.01 ± 2.69, 10.06 ± 3.61, and 8.41 ± 3.19, respectively. A two-sided test, with α = 0.05 and a power of 80%, was conducted. The sample size ratio of the TEF: ACL injury: control groups was 1:1:1. Using PASS 15.0 software, the sample size for each group was calculated to be 16. Considering 20% data loss and unusable cases, the final sample size for each group was 20 cases [16/(1–0.2)]. Therefore, the total sample size for the three groups was 60.

Binary logistic regression analysis was performed to identify individuals prone to TEFs. A receiver operating characteristic (ROC) curve was drawn based on the calculated probability, and the area under the curve (AUC) was calculated. The cutoff value was determined based on the “Youden Index,” and 95% confidence intervals (CIs) were calculated. The maximum value of the index represents the optimal cutoff value of the variable.

Results

A total of 60 patients were included in this study as follows: 20 with TEFs (median age: 44; range: 23–61 years), with injury mechanisms including exercise or sprain in 7 cases and car accidents in 13 cases; 20 with ACL injuries (median age: 40; range: 29–59 years), with injury mechanisms including exercise or sprain in 16 cases and car accidents in 4 cases; and 20 control patients (median age: 43; range: 32 − 56 years) (Table 1). All patients with TEFs and ACL injuries were diagnosed using knee arthroscopy. No significant differences were noted in age, height, weight, or BMI between the TEF, ACL injury, and control groups (P > 0.05; Table 1). The causes of injury differed significantly between the TEF and ACL injury groups (P < 0.05; Table 1).

Table 1.

Baseline characteristics of the study groups

Groups	n	Age, years)	BMI (, kg/m2)	Injury mechanism
				Sports injury	Traffic accident
TEF Group	20	44.70 ± 9.04	25.13 ± 2.86	7 (35.00)	13 (65.00)
ACL Injury Group	20	40.85 ± 8.93	24.13 ± 2.23	16 (80.00)	4 (20.00)
Control Group	20	43.75 ± 8.14	23.86 ± 2.18	-	-
F		1.060	1.504	3.968
p-value		0.353	0.231	0.046

Values are presented as mean ± standard deviation

ACL anterior cruciate ligament, BMI body mass index, TEF tibial eminence fracture

No significant differences were found in the ICW, EW, NWI, ICH, or the “α” angle among the three groups (P > 0.05; Table 2). The NSI differed significantly between the ACL injury (0.70 ± 0.09) and control (0.75 ± 0.06) groups (P < 0.05). Furthermore, the ICA in the ACL injury group (47.02 [43.08, 47.73]°) was significantly lower than that in the control group (50.79 [44.43, 54.56]°) (P < 0.05; Table 2). The MTS did not significantly differ among the three groups (P > 0.05; Table 2). Nevertheless, the LTS was notably greater in the TEF group (10.33 ± 2.22°) than in the control group (8.41 ± 3.10°) (P < 0.05; Table 2).

Table 2.

Summary of studies investigating morphology of femur condyles and tibial slopes as risk factors for tibial eminence fractures in males

Groups	TEF Group (n = 20)	ACL Injury Group (n = 20)	Control Group (n = 20)	F	p-value
ICW (, mm)	22.27 ± 1.73	21.92 ± 2.13	22.21 ± 1.87	0.189	0.828
EW (, mm)	75.40 ± 3.75	75.27 ± 4.80	74.21 ± 4.20	0.464	0.631
NWI [M(Q1, Q3)]	0.29 (0.28, 0.32)	0.29 (0.28, 0.31)	0.30 (0.29, 0.31)	0.695	0.707
ICH [M(Q1, Q3), mm]	30.16 ± 1.96	31.15 ± 2.32	30.85 ± 3.27	0.783	0.462
NSI ()	0.73 ± 0.11	0.70 ± 0.09a	0.75 ± 0.06a	2.20	0.044
ICA [M(Q1, Q3), °]	50.25 (47.96, 53.26)	47.02 (43.08, 47.73)a	50.79 (44.43, 54.56)a	2.50	0.022
“α “Angle [M(Q1, Q3), °]	35.26 (33.18, 37.24)	35.2850 (33.11, 36.43)	34.43 (32.76, 38.21)	0.034	0.983
LTS (, °)	10.33 ± 2.22a	9.13 ± 2.68	8.41 ± 3.10a	2.117	0.048
MTS (, °)	8.38 ± 2.75	8.49 ± 2.58	8.27 ± 2.48	0.036	0.965

Values are presented as mean ± standard deviation

ACL anterior cruciate ligament, EW epicondylar width (femoral condylar width), ICA intercondylar notch angle, ICH intercondylar notch height, ICW intercondylar notch width, LTS lateral tibial slope, MTS medial tibial slope, NWI notch width index, NSI morphological index of the intercondylar notch, TEF tibial eminence fracture

The intraclass correlation coefficient (ICC) was calculated to determine the intra- and interobserver reliability. The ICC values indicated good reliability for all indices, with all ICCs exceeding 0.80 (Table 3).

Table 3.

Inter and intraobserver reliability for the anatomical angles measurements on MRI^a

	Interobserver Reliability		Intraobserver Reliability
Test Variables	ICC	95% CI	ICC	95% CI
ICW	0.872	0.786, 0.924	0.876	0.792, 0.926
EW	0.872	0.786, 0.924	0.881	0.801, 0.929
NWI	0.807	0.677, 0.885	0.815	0.690, 0.890
ICH	0.834	0.722, 0.901	0.840	0.731, 0.904
NSI	0.874	0.788, 0.924	0.880	0.800, 0.929
ICA	0.917	0.861, 0.950	0.862	0.768, 0.917
α Angle	0.838	0.729, 0.903	0.835	0.724, 0.901
LTS	0.889	0.815, 0.934	0.875	0.792, 0.926
MTS	0.883	0.804, 0.930	0.882	0.802, 0.929

^aValues are presented as intraclass correlation (95% CI)

CI confidence interval, EW epicondylar width (femoral condylar width), ICA intercondylar notch angle, ICC intraclass coefficient, ICH intercondylar notch height, ICW intercondylar notch width, LTS lateral tibial slope, MRI magnetic resonance imaging, MTS medial tibial slope, NSI morphological index of the intercondylar notch, NWI notch width index

ROC curves were analyzed for two significant independent predictors of TEFs and ACL injuries to compare their diagnostic performance (Fig. 4). LTS had the highest predictive value (sensitivity, 70.00%; specificity, 70.00%), with an AUC of 0.714 (95% CI, 0.581–0.847; p = 0.007) in the TEF group. ICA had the highest association with ACL injuries (sensitivity and specificity of 55.00% and 90.00%, respectively), with an AUC of 0.785 (95% CI: 0.669–0.901, p < 0.001) (Table 4).

Fig. 4.

The receiver operating characteristic curve identifying individuals prone to tibial eminence fractures based on knee anatomical angles (area under curve = 0.750) ICA intercondylar notch angle, LTS lateral tibial slope

Table 4.

The AUC and cutoff values of the anatomical angles

Test Variables	Cutoff Value	AUC (95% CI)	P-value	Specificity	Sensitivity	Youden Index
ICW	23.615	0.528 (0.373, 0.683)	0.724	0.350	0.825	0.175
EW	72.71	0.530 (0.380, 0.680)	0.707	0.850	0.300	0.150
NWI	0.275	0.503 (0.338, 0.667)	0.975	0.200	0.900	0.100
ICH	33.195	0.527 (0.347, 0.706)	0.736	0.400	0.850	0.250
NSI	0.705	0.529 (0.368, 0.690)	0.718	0.650	0.475	0.125
ICA	47.42	0.785 (0.669, 0.901)	< 0.001*	0.900	0.550	0.450
α Angle	34.145	0.504 (0.342, 0.667)	0.956	0.500	0.625	0.125
LTS	8.14	0.714 (0.581, 0.847)	0.007*	0.700	0.700	0.400
MTS	10.245	0.504 (0.342, 0.666)	0.962	0.350	0.800	0.150

*P < 0.05, statistically significant differences

AUC area under the curve, CI confidence interval, EW epicondylar width (femoral condylar width), ICA intercondylar notch angle, ICH intercondylar notch height, ICW intercondylar notch width, LTS lateral tibial slope, MTS medial tibial slope, NSI morphological index of the intercondylar notch, NWI notch width index

Discussion

Patients with TEFs and ACL injuries exhibit similar MRI manifestations, and ACL injuries can occur concurrently with tibial fractures due to body-stretching injuries. In adults, noncontact ACL injuries occur in 70–80% of cases. These injuries most often occur on landing from a jump, while cutting, or with sudden deceleration in sports [19]. However, TEFs exhibit a unique mechanism of injury in adults. TEFs require high-energy trauma, and the most common mechanism of injury is severe hyperextension, usually associated with high-speed motor vehicle collisions [2]. Radiographs usually show tiny osseous fragments adjacent to the expected ACL attachment site, although large avulsed fragments may be observed on radiographs. Further MRI and arthroscopic examinations can distinguish between ACL injuries and TEFs.

The relationship between notch anatomy and ACL injury in adults remains a subject of ongoing debate. Previous studies have demonstrated that the difference in anatomical morphology between the femoral condyles is a key factor in ACL rupture [20–24]. Alentom-Geli et al. [14] believed that evaluating changes in the femoral ICA may have greater clinical relevance than the condylar space width as a risk factor for ACL injury and that evaluating the narrowing of the intercondylar space is more useful. Souryal et al. [25] introduced NWI to facilitate comparisons among patients with varying knee sizes and address the variability in radiographic magnification. In 2017, Bouras et al. [9, 26] determined that NWI more accurately describes the shape of the femoral intercondylar notch by excluding the influence of age, sex, height, and weight using MRI measurements. Three types of intercondylar notches were described using NWI: A-, U-, and W-shaped. A-shaped intercondylar notches are considered more likely to cause ACL injury. Al-Saeed et al. [27] further concluded that the NWI of A-shaped intercondylar notches was significantly more stenosed than that of the inverted U- and W-shaped notches. Moreover, the presence of an A-shaped intercondylar notch is regarded as an independent risk factor for ACL injury, warranting increased research. Notably, TEFs are relatively infrequent in adults, resulting in a limited number of studies in this group. A comparative study [28] found that the NWI of patients with ACL injury was smaller than that of patients with avulsion fractures of the intercondylar eminence, suggesting that intercondylar notch stenosis causes ACL injury. Our findings revealed that the NWI for male patients in the ACL injury group (0.29 [0.28, 0.31]), as measured by MRI, was slightly lower than that of the control (0.30 [0.29, 0.31]) and TEF (0.29 [0.28, 0.32]) groups; however, this difference was not statistically significant (P > 0.05, Table 2). Another study suggested that an increased “α” angle is associated with ACL impingement [29]. Our study revealed that the “α” angle did not exhibit statistically significant differences among the three groups. Therefore, our findings suggest that NWI and the “α” angle have weak associations with the prognosis of ACL injury and TEFs. NSI served as the ratio between intercondylar notch width and height. The greater the NSI, the more space the intercondylar notch can provide for the ACL. The results of the present study indicated that the NSI of the ACL injury group (0.70 ± 0.09) was lower than that of the control group (0.75 ± 0.06), with the difference being statistically significant (P < 0.05, Table 2). A previous study suggested that an ICA < 50° would increase the risk of ACL injury, and our findings align with this conclusion. In the present study, the ICA of the ACL injury group (47.02 [43.08, 47.73]) was significantly lower than that of the control group (50.79 [44.43, 54.56]). ACL injuries had a narrower ICA, with an AUC of 0.785 (95% CI: 0.669–0.901, p < 0.001), than the control group. This may partially explain the different injury patterns in the TEF and ACL injury groups.

Previous studies have suggested that intercondylar notch stenosis significantly contributes to ACL injuries in patients. TEFs often occur in patients with normal intercondylar notch morphology. This underscores the importance of closely examining variations in tibial intercondylar eminence morphology [2]. Our investigation of the tibial slope confirmed this hypothesis and aligned with the findings of several previous studies [25, 30]. However, the connection between the tibial slope and ACL rupture is not fully understood. The geometry of the tibial plateau plays a pivotal role in determining how loads are distributed across the joint, making it a subject of significant interest in the literature as a potential risk factor for ACL injuries [31, 32]. Specifically, the tibial slope has been a subject of considerable focus, with varying conclusions [33–37]. Studies have demonstrated that increased LTS in adults is closely related to the incidence of ACL tears, while MTS and the depth of the medial tibial plateau notch are also associated with an increased risk of ACL injury in adults [38–41]. Vyas et al. [42] used standard lateral radiographs to measure MTS and found that it significantly differed between the ACL injury and control groups. However, radiography may not fully capture articular cartilage, which is better represented on MRI and is more indicative of joint function. Even at the proximal end of the fully ossified tibia, the three-dimensional geometry of the cartilage surface significantly differs from that of the underlying subchondral bone. Simon et al. [43] suggested that the increased ACL strain was most evident when the knee joint was close to full extension, particularly when landing from a jump or a pivot motion. The pivot shift at this time is characterized by anterior subluxation of the tibia on the lateral plateau, suggesting that LTS, rather than MTS, is associated with ACL injury. The role of the MRI-measured posterior slope of the medial tibial plateau in the risk of ACL injury is more controversial than that of the lateral tibial plateau. The present study found no significant association between tibial slope and ACL insufficiency; however, it was limited by the sample size needed for a robust power comparison [35, 36]. This limitation may be attributed to differences between MTS and LTS and variations in the distribution of sexes [38, 40, 44]. Some studies have identified differences in anatomical risk factors and the incidence of ACL injuries between male and female patients. Women, in particular, are exposed to more interfering factors [14, 15, 45]. Moreover, most patients in the TEF group in our study were male, showing a significant sex difference. Therefore, we selected male patients as research participants to minimize sex-related variability and reduce potential errors.

Currently, few studies have examined the relationship between the tibial slope and TEFs. By comparing LTS and MTS in patients with ACL injuries and those with TEFs, our study found that both have different injury mechanisms. ACL injuries primarily occur as non-contact injuries and are often associated with sports activities or sudden sprains. In contrast, TEFs primarily result from direct trauma, such as car accidents and motor vehicle collisions. Our data, using MRI and a case-control design, suggest that an increase in LTS is significantly associated with an increased risk of TEFs. LTS was significantly greater in the TEF group (10.33 ± 2.22°) than in the control group (8.41 ± 3.10°). The LTS cutoff value was 8.140. The sensitivity of the LTS cutoff value was 70.00%, which is an excellent angle that supports the hypothesis that increased LTS is an important risk factor for TEFs (Table 4; Fig. 4). However, MTS appeared to have a minor impact on the risk of injury, and the difference was not significant. This suggests that TEFs should be considered a special type of tibial plateau fracture rather than a type of ACL injury and should be treated according to the internal fixation plan for the fracture. Pivot shift is characterized by anterior tibial subluxation of the lateral tibial plateau and represents lateral compartment instability, possibly highlighting why LTS, rather than MTS, is implicated in TEFs.

Despite several key findings in the present study, acknowledging the limitations is important. First, the patient sample was small, and a multicenter study was not conducted, which may have affected the research results. We aimed to include more patients, which was not possible because of the lower number of TEFs in the adult population than in the pediatric population.

Another limitation was that all the patients with TEFs in the present study were male. Studies have demonstrated that hormonal, biological, and neurological factors in female patients influence anatomical risk factors [18, 46]. Consequently, only males were included in the ACL and control groups, which potentially introduces bias into the study results. Lastly, TEFs and ACL injuries have different injury mechanisms in the adult population. TEFs require higher-energy trauma and are usually associated with high-speed motor vehicle collisions. In the present study, the cases in the TEF and ACL injury groups had a mixture of different injury mechanisms. Future research should increase the sample size to conduct a more detailed statistical analysis of the differences in injury mechanisms between the two groups.

Conclusions

Patients with TEFs and those with ACL injuries not only have different injury mechanisms but also have different femoral intercondylar morphologies and tibial slope characteristics. Stenosis of the femoral intercondylar notch is a significant cause of ACL injury, and excessive LTS is associated with TEFs. TEFs should rather be regarded as a specific type of tibial plateau fracture rather than a specific pattern of ACL injury. The results of this study may help clinicians adopt more appropriate surgical procedures for TEFs.

Abbreviations

ACL

Anterior cruciate ligament

MRI

Magnetic resonance imaging

EW

Epicondylar width (femoral condylar width)

ICW

Intercondylar notch width

NWI

Notch width index

ICH

Intercondylar notch height

NSI

Morphological index of the intercondylar notch

ICA

Intercondylar notch angle

LTS

Lateral tibial slope

MTS

Medial tibial slope

BMI

Body mass index

ROC

Receiver operating characteristic

AUC

Area under the curve

CI

Confidence interval

TEF

Tibial eminence fracture

Authors' contributions

YC was involved in data acquisition, drafted the manuscript, conceived the study, and made substantial contributions to the study design. JS was involved in data acquisition and statistical analyses and drafted the manuscript. SL and FL were involved in data acquisition and statistical analyses and revised the manuscript. CJ contributed to the study design and coordination and revised the manuscript. All authors have reviewed the manuscript.

Funding

This study was supported by the Foundation of Wenzhou Science & Technology Bureau (Y20210409).

Data availability

Data are provided in the manuscript or supplementary information files.

Declarations

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Wenzhou Central Hospital. Informed consent was obtained from all patients.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.