The fact is that tibial plateau fractures are often combined with knee ligament and meniscus injuries. According to relevant studies, the probability of tibial plateau fracture with meniscus injury is approximately from 28.6% to 81.0% and lateral meniscus injury is dominant [5-9,11,12]. For Schatzker II tibial plateau fractures characterized by lateral spilt depression, Stahl et al. [13] have previously pointed out that there is a 45.0% possibility of lateral meniscus injury. Over the last decade or so, it is worth nothing that some clinical studies have gradually focused on the correlation between the X-ray, MRI, and CT findings of lateral plateau and the injury of lateral meniscus. By analyzing the X-ray and MRI manifestations of lateral plateau in 62 Schatzker type II fracture patients, Gardner et al. [6] found that when lateral plateau collapsed > 6 mm and the width increased > 5 mm, the positive rate of lateral meniscus injury could reach as high as 83.0%. Ringus et al. [7] also studied the CT findings of 85 Schatzker type I-VI plateau fractures, of which 21 were type II fractures. They indicated an 8-fold increase in the risk of lateral meniscus tear when the articular surface depression was ≥ 10 mm. Durakbasa et al. [5] reported 20 cases of Schatzker type II plateau fracture with lateral plateau X-ray images and intraoperative direct vision of lateral meniscus, and demonstrated that a plateau depression ≥14 mm and/or widening ≥10 mm is related with a significantly high risk of meniscus injury. Furthermore, Tang et al. [11] compared the CT presentations with arthroscopic examination results of 132 patients of Schatzker I-VI plateau fractures, among which 25 cases were type II fractures. The results showed that the positive incidence of lateral meniscus injury was about 70.3% when plateau collapsed >11mm. Kolb et al. [9] researched CT and MRI appearances of 55 patients of Schatzker type I-III plateau fractures (50 patients of type II fractures) and proposed that the probability of lateral meniscus injury increased by 40% for each 1 mm increase in LPW. Lately, a study based on the CT and arthroscopic results of 102 patients of Schatzker I-VI plateau fractures (33 patients of type II fractures) revealed a higher risk of lateral meniscus injury in patients with > 6.3 mm of lateral joint depression [8].
The results of this study are somewhat consistent with those of the above studies. In Schatzker II tibial plateau fractures, the morphology of lateral plateau is positively correlated with the injury of lateral meniscus. The mechanism is mainly due to the different position of knee joint and the axial violence of femoral condyle, which can lead to lateral plateau splitting and collapse under the action of external force. After the fracture, knee joint often undergoes varus or rotation due to the continued transmission of violence and lateral meniscus is prone to injury under stress [12]. The ROC curves for LPD and LPW show that the AUC values were 0.818 and 0.724, which implied the diagnostic value of these two indicators is relatively high. When LPD > 7.9 mm, the positive rate for the diagnosis of lateral meniscus injury is 95.0% with the specificity of 58.8%. When LPW > 7.5 mm, the positive rate for a lateral meniscus injury diagnosis is 70.0% with a specificity of 70.6%. This retrospective study only focused on lower-energy Schatzker II tibial plateau fractures and detailedly confirmed that LPD and LW can be used as risk factors for predicting lateral meniscus injury. Accordingly, both LPD and LPW have certain specificity and sensitivity, which is of great guiding significance for the comprehensive surgical management of Schatzker II tibial plateau fracture. Because of its simple and feasible measuring method, measurement of LPD and LPW will be a kind of technical evaluation means to make up for the lack of preoperative MRI diagnosis in hospitals below Grade III.
296 Patients in our study were from two large-scale tertiary hospitals in southern Jiangsu over a long study time. The diagnosis of lateral meniscus injury in patients was made on the basis of intraoperative direct exploration and patients with a history of old meniscus injury were excluded. Still, the average age of patients was 45 years old, which can underlyingly ensure that lateral meniscus injury is caused by trauma. This is in line with the purpose of this study and the conclusions are accurate and reliable. During the operation, we found that lateral meniscus injury could occur in different locations in Schatzker II tibial plateau fracture and there were combined injuries of the anterior horn, midbody, and posterior horn in the meniscus, as well as simultaneous injuries of medial and lateral meniscus. A relatively high proportion of patients with meniscocapsular separation (ie, meniscus peripheral rim tears or avulsions) (88/160, 55.0%) is also in accordance with the results of Stahl et al [13]. Intrinsically, lateral meniscus injury majorly occurred in the midbody and posterior horn, which may be deemed as a noteworthy finding and related to the injury mechanism of such patients. The injury involving the anterior horn of lateral meniscus may be potentially caused by hyperextension and valgus knee joint during the injury process. Taking into account the concept and incidence of tibial plateau hyperextensible and valgus injury put forward by Gonzalez et al [14], we have reasons to believe that the possibility of damaging the anterior horn of lateral meniscus in type II plateau fracture is quite low. Conventional follow-up exploration under arthroscopy after internal fixation of fracture can better deal with the posterior horn of lateral meniscus, medial meniscus, ligament and other injuries, so as to achieve better soft tissue repair and avoid missed diagnosis. The surgical treatment under direct vision may be mostly meniscoplasty and meniscectomy, which is more likely to cause long-term complications after surgery. Meanwhile, the incidence of simultaneous medial and lateral meniscus injury was 4.4% (7/160). The omission of medial meniscus injury during open surgery may also be an important cause of postoperative pain in patients with Schatzker II tibial plateau fracture, which has been attaching much attention from the orthopedic surgeons.
Certainly, some limitations existed in our study. The author's subjective factors may lead to partial deviation in the measurement of LPD and LPW. Moreover, we failed to further analyze the underlying association between LPD/LPW and the pattern/type of lateral meniscus injury due to the limited sample size. The existing data on the incidence of meniscus injury associated with tibial plateau fractures was reported to be in the range of 49.0% – 91.0% by using preoperative MRI [15-17]. In spite of this, the emerging evidence suggested a lower incidence of meniscus injury requiring surgical intervention than previously demonstrated according to MRI images before surgery [13]. Recently, Salari et al. [10] described that CT measurement of fracture location and articular impaction/displacement in tibial plateau fractures can be used to predict lateral meniscus injury with a high accuracy. With the further expansion of the sample size, the rational use of CT image analysis will provide a more accurate clinical reference for the in-depth study on the relationship between the location and pattern of meniscus injury and the morphology of tibial plateau fractures in different types.