Introduction

The classification of tibial plateau fractures encompasses various categories, with the Schatzker Staging System being widely accepted as the most commonly used clinical method [1,2,3]. Schatzker IV is a relatively uncommon form of medial tibial plateau fracture characterized by splitting or depression of the articular surface. This type of fracture represents approximately 10–30% of all tibial plateau fractures among patients [4, 5]. Based on the relationship between the fracture line and the intercondylar eminence, Wahlquist et al. [6] further differentiated Schatzker IV fractures into three subcategories, namely subtypes A, B, and C fractures. Type A fractures have the fracture line located on the medial side of the eminence, type B fractures have the fracture line on the intercondylar eminence, and type C fractures have the fracture line on the lateral side of the eminence. Schatzker IV-C fracture is characterized by severe injury with significant force, often accompanied by dislocation, lateral meniscus entrapment, and various ligament injuries [5, 7]. In their study, Barrow et al. found that meniscus injury incidence in Schatzker IV tibial plateau fractures was 25% [8]. Furthermore, other studies have reported occurrence rates of 63% for lateral meniscus tears and 44.4% for medial meniscus tears [9]. Because the location of the fracture line influences the severity of soft tissue injury, with a higher prevalence of lateral meniscus entrapment when the fracture line is closer to the lateral side [6, 9], Schatzker IV-C fractures-related lateral meniscus injury will significantly increase the contact stress and instability in the knee joint, which results in the development of traumatic arthritis and joint stiffness [10,11,12,13]. Therefore, timely diagnosing and treating the meniscus injury after Schatzker IV-C fractures is imperative to achieve optimal patient outcomes.

Although magnetic resonance imaging (MRI) has a high diagnostic accuracy for assessing meniscal and ligament injuries, and is often considered the gold standard for preoperative soft tissue diagnosis [14], MRI examinations have lengthy wait times and high costs. The scanning process is time-consuming, and there is limited availability of MRI [15, 16]. Moreover, acute tibial plateau fractures can cause diffuse soft tissue edema around the knee joint, potentially resulting in the overdiagnosis of meniscal injuries [17]. Additionally, preoperative scanning is not commonly performed, and it lacks widespread adoption in primary healthcare facilities in our country [17,18,19]. Meanwhile, CT imaging can assist orthopedic surgeons in accurately assessing lateral plateau depression through three-dimensional reconstruction techniques. Therefore, the preferred preoperative examination for acute tibial plateau fractures is CT rather than MRI [20]. CT scans have been widely adopted for assessing various tibial plateau fractures and obtained detailed fracture-related information, including the fracture line location, the extent of fracture block fragmentation, and any changes in the displacement of the lateral plateau’s articular surface [21, 22]. In recent years, growing evidence shows that preoperative knee X-rays and CT imaging parameters can effectively predict the presence of combined soft tissue injuries, particularly lateral meniscal injuries, in patients with tibial plateau fractures [17, 23,24,25,26,34]. To address these examinations’ limitations, we adopted intraoperative direct visualization for precise and definitive information on meniscus injuries. Additionally, considering the impact of anatomical tibial slope on X-ray examination, we utilized coronal plane CT scans to obtain more objective measurements [35]. These distinctions set our study apart from previous research.

The incidence of tibial plateau fracture-related meniscal injury ranges from 21 to 99%, with lateral meniscal injury being the predominant type. Bennett et al. [36] reported three meniscal damage cases among nine patients (33.3%) with type IV tibial plateau fractures. Stannard et al. [37] noted a strong association between high-energy tibial plateau fractures and soft tissue injuries. They observed one medial meniscal tear and 5 cases of lateral meniscal tear among 13 patients with Schatzker type IV fractures. Michael et al. [38] observed that medial meniscal tears were commonly present in Schatzker type IV tibial plateau fractures (86%). Bingshan Yan et al. [9] found that lateral meniscal tears in Schatzker type IV tibial plateau fractures were 63%, while medial meniscal tears were 44.4%. Although meniscal injury in Schatzker type IV fractures has been previously documented, few studies have reported the incidence of tissue injuries following Schatzker type IV-C fractures. In the current study, we reported the possibility of ACL injury (86.7%), lateral meniscal injury (66.7%), medial meniscal injury (41.7%), partial posterior cruciate ligament (PCL) injury (63.3%), the incidence of lateral collateral ligament (LCL) injury (65%), and medial collateral ligament (MCL) injury (31.7%). Our results may complement the relationship between Schatzker type IV-C fracture and soft tissue injury.

This study highlights the close association between lateral plateau displacement and lateral meniscus injury in Schatzker IV-C fractures. Although, Mustonen et al. [18] introduce that there is no correlation between meniscal damage and the type or degree of depression in tibial plateau fractures, increasing reports suggest a higher incidence of soft tissue injuries in patients with a more significant displacement of the tibial lateral plateau fracture [19, 23, 25, 26]. To identify reliable indicators for early prediction of associated soft tissue injuries, researchers have focused on the correlation between preoperative X-ray and CT measurements and lateral meniscus damage [25, 39]. Gardner et al. [40] found 83% of patients exhibiting lateral meniscus injury on MRI once LPD length more than 6 mm and width exceeding 5 mm on preoperative X-ray measurements among 62 patients with Schatzker II fractures. Durakbasa et al. [39] found that LPD ≥ 14 mm and/or LPW ≥ 10 mm was correlated to the high risk of lateral meniscus tear based on preoperative X-rays measurements among 20 patients with Schatzker II tibial plateau fractures. Ringus et al. [41] measured LPD using coronal CT scans in 85 patients with Schatzker I-VI tibial plateau fractures, revealing an 8-fold increased risk for lateral meniscus tear with LPD ≥ 10 mm. Tang et al. [25] demonstrated that LPD exceeding 11 mm on preoperative CT scans was accompanied by 70.3% lateral meniscus injury among 132 patients with acute tibial plateau fractures (including 8 Schatzker IV fractures). However, they did not reveal the correlation between LPW measurements and meniscal tears. Kolb et al. [17] compared preoperative LPW measurements obtained from CT scans with MRI results and found 40% increased lateral meniscus tear risk with every LPW exceeding 1 mm among 55 patients with Schatzker I-III tibial plateau fracture. Hengrui Chang et al. [28] investigated CT imaging parameters and arthroscopic findings in 102 patients with acute tibial plateau fractures (including 22 cases of Schatzker IV fractures). They found a positive correlation between LPD > 6.3 mm and the risk of lateral meniscus tear. Salari et al. [26] utilized CT measurements and intraoperative visualization and found a 21% increased risk of meniscal tear with each 1 mm increase in maximum articular surface depression/displacement (AID) in 70 patients with Schatzker I-II tibial plateau fractures. Meanwhile, they also found 100% lateral meniscus tear when AID exceeds 4.3 mm. Ying Pu et al. [27] investigated the correlation between lateral tibial plateau CT imaging parameters and lateral meniscus injury through arthroscopy in 296 patients with Schatzker II fractures. They found a higher possibility of lateral meniscus injury when LPD exceeds 9 mm and/or LPW more than 7.5 mm. In summary, our findings generally support previous studies, indicating that both LPD and LPW are important indicators for preoperative prediction of associated soft tissue injuries. However, our study suggests minimum LPD and LPW values of 8.40 mm and 7.90 mm, respectively, for predicting lateral meniscus injury. Our research specifically emphasizes the strong association between lateral plateau displacement and lateral meniscus injury in Schatzker IV-C fractures for the first time. Inconsistencies with previous studies’ result may stem from variations in factors such as Included research subjects, patient Schatzker classification, measurement methods, and sample sizes.

There are several limitations in the current study. Firstly, manual measurements have inherent subjectivity, which may introduce potential bias into the results. Secondly, we included a relatively small number of patients with Schatzker IV-C fractures which may introduce bias into our results. Thirdly, we were unable to differentiate degenerative or traumatic meniscal lesions. Thus, whether existing pre-existing meniscus injury prior to the fracture may cannot completely guarantee. Lastly, this study did not address the specific location and classification of meniscal injuries.

Conclusions

Schatzker IV-C tibial plateau fracture was accompanied by a high risk of lateral meniscal injury when LPD exceeds 8.40 mm and/or LPW exceeds 7.90 mm. Meanwhile, our results may better explain the correlation between Schatzker IV-C tibial plateau fracture and soft tissue injury and provide potential predictors (LPD and LPW) for early diagnosing Schatzker IV-C tibial plateau fracture-related meniscus injury. Additionally, our findings may enable orthopedic surgeons to anticipate lateral meniscal injuries in Schatzker IV-C tibial plateau fractures through the numerical value of LPD and LPW measured by preoperative coronal CT scans.