A New CT-based Classification Of Hyperextension Tibial Plateau Fractures And A Retrospective Observation Study Of The Fracture Morphological Characteristics, Injury Mechanism, Treatment And Prognosis

With the rapid development of radiology in clinical practice and the demand for deeper research on tibial plateau fractures,the previously commonly used classifications such as Schatzker and AO/OTA classifications are insufficient nowadays due to their natural limitations,only able to evaluate fractures through lateral and posteroanterior planes based on X-rays.However,it is widely accepted that X-rays cannot show the clear fracture features because of bone overlapping.Currently,CT scan is always suggested to evaluate tibial plateau fractures and has shown its advantages on the agreement on classifying fractures and making pre-operation plans.Moreover,the increasing number of researchers have realized the importance of new CT-based fracture classifications,and some has been proposed and widely accepted like “three-column concept” and “four columns and night segments”classification.In 2001,Chaba et al found that anteriomedial tibial plateau fractures were highly likely to combine with posterolateral complex and posterior cruciate ligament injury.Afterwards,researchers began to focus more on fracture characteristics resulting from the violence on hyperextension knee joint.Firoozabadi et al summarized the features of hyperextension bicodylar tibial plateau fractures,while Gonzalez et al conducted a comparative study between the outcomes of hyperextension and non-hyperextension tibial plateau fractures,and found that the former had worse prognosis.Lin et al initially proposed “diagonal injury” mechanism of these fractures and stressed more attention should be put on soft tissue damages.Due to the numerous specific terms used to depict hyperextension tibial plateau fractures,different treatments and prognosis in published studies,and even fractures in a research having significant distinctions,many researchers have appealed to invent a new classification combined with injury mechanism for the sake of homogeneous comparisons between the subtypes of hyperextension tibial plateau fractures.Nowadays,some specific terms related to hyperextension tibial fractures,like reverse-Segond fractures,tibial plateau anterior fracture and dislocation,non-dislocation type of hyperextension tibial plateau fractures,hyperextension tibial plateau bicondylar fractures,make researchers confused about the real fracture features.However,according to these terms,it can be reasonably predicted that hyperextension tibial fractures contain several subtypes,and it is clear that a new comprehensive and specific classification is eagerly needed.Actually,there are several newly published classifications.Chang et al classified these fractures into four groups:marginal avulsion type,anteromedial compression type,anterolateral compression type and bicondylar compression type fractures.According to the coronal deformity,these fractures are divided into hyperextension-varus,hyperextension-valgus or pure hyperextension type.Based on the fracture morphology,for example,Yao et al classified them based on the displacement of posterior tension fractures.However,those classifications can ideally show some fracture chracteristics,but not all.Moreover,after reviewing previous literatures,these is no classification that can systematically cover the information of injury mechanism,fracture morphology,surgical approach,restoration and fixation method and prognosis,and can clearly differentiate all the subtypes of hyperextension tibial plateau fractures for the purpose of supporting homogeneous researches in the future.This study aimed to propose a new classification based on fracture morphological characteristics on CT image and injury mechanism.Moreover,we attempted to conduct a retrospective observation on the correlation between tibial plateau anterior compression fractures and posterior tension fractures,and the fibular proximal avulsion fractures as well.What is more,deeper research was conducted to compare the diagnosis,treatments and outcomes of the two major subtype fractures,and to help guide clinical practice and future research.Part One A new CT-based hyperextension tibial plateau fracture classification and its fracture morphological featuresObjective: The aim of this study was to propose a new CT-based hyperextension tibial plateau fracture classification,and to observe the relationship between anterior compression fractures and posterior tension fractures and fibular proximal avulsion fractures.Methods:1.Clinical case selection: we retrospectively selected hyperextension tibial plateau fractures from 543 tibial plateau fractures treated in our hospital between January 2015 and January 2019,and collected and analyzed their demographic data,injury mechanism,complete radiological information.The inclusive criteria were the age over 18 and below 65 years old,complying with the diagnostic standard of hyperextension tibial fracture and a complete collection of radiographs and CT images.2.Description of the new classification: each tibial plateau joint surface was divided into anteromedial and posteromedial,anterolateral and posterolateral quadrants.This classification is comprised of 2 groups.Anterolateral or anteromedial quadrant compression fractures are allocated to A group while fractures involving both anterior(anterolateral and anteromedial)quadrants including anteromedian plateau are allocated to B group.Moreover,based on the size and location of the anterior fractures fragments,these A and B groups would be further divided into 4 and 3subtypes respectively,and the combined type in B group represents a marginal type in either two anterior quadrants while a central type fracture in the other.3.Data collection and management: three senior surgeons classified these selected fractures into different subtypes,counted the frequency and depicted the features of posterior tension fractures.4.Statistics and analysis: The categorical data were compared with two-tailed Fisher exact tests to assess the correlation between anterior and posterior tibial plateau fractures,as well as fibular proximal avulsion fractures.Analyses were performed using SPSS 18.0 for windows statistical software.A P value of less than 0.05 was considered statistically significant.Results:1.A total of 37 hyperextension tibial plateau fractures(6.8%)was selected from 543 tibial plateau fractures.The classified information of these fractures was: 15 cases(40%)were allocated in A group,of these 15 cases,10 and 5 were combined with complete and partial posterior fractures respectively,another 5 cases fibular proximal avulsion fractures.22 cases(60%)were allocated into B group,20 and 2 of them were combined with complete and partial posterior fractures,respectively.Meanwhile,11 cases(82%)belonged to combined subtype in B group accompanied fibular proximal avulsion fractures.2.Regarding the size of posterior fractures,these two groups had a significant difference(P=0.006),but there was no statistic difference between fibular proximal avulsion fractures(P=0.092).With regard to fibular proximal avulsion fractures,there was no statistic difference between combined and non-combined subtype in B group(P=0.08).Conclusions:1.This new classification is able to show comprehensive features of hyperextension tibial plateau fractures: the incidence of anterior bilateral-quadrant compression type fractures is much higher than that of unilateral-quadrant fractures,and the former tends to combine with complete posterior tension fractures,but there is no difference between these two group fractures to combine with fibular proximal avulsion fractures.Moreover,anterior bilateral-quadrant compression type fractures tend to combine with intact posterior tension fractures,and single anterolateral quadrant fractures are highly likely to accompany intact medial quadrants fractures.2.This new classification includes almost all the fracture types of hyperextension tibial plateau fractures,and clarifies the correlation between anterior and posterior fractures,enhancing surgeons’ understanding of these fractures and being helpful for making rational pre-operation plans.PART 2 The clinical outcomes of anterior unilateral-quadrant and bilateral-quadrant compression type hyperextension tibial plateau fractures: a retrospective comparative studyObjective: This study aimed to compare the outcomes of anterior unilateral-quadrant and bilateral-quadrant compression type hyperextension tibial plateau fractures through retrospective observation,and the difference of injury mechanism,surgery approach,restoration and fixation methods and prognosis after at least 12-month follow-up.Methods:1.Clinical case selection: we retrospectively screened out hyperextension tibial plateau fractures treated in our hospital between January 2015 and January 2019,collected and analyzed their demographic data,injury mechanism,complete radiological information,surgery approach,restoration and fixation methods and prognosis.The inclusive criteria were the age over18 and below 65 years old,complying with the diagnostic standard of hyperextension tibial fracture and a complete collection of radiographs and CT images.Moreover,the patients had to be treated and be followed up regularly for 12 months after the operation.2.Description of closed-loop theory: each tibial plateau joint surface is divided into anteromedial and posteromedial,anterolateral and posterolateral quadrants,and these four quadrants consist of an intact “ring”.Posterolateral corner and fibular apexs with their relative soft-tissue structures,as well as medial collaborate ligaments can be regarded as two separatedly enhanced parts of the “ring”.Based on the “diagonal lesion” theory,these four quadrants are divided into two corresponding components,anteromedial vs posterolateral and anterolateral vs posteromedial quadrant fractures.When either component is damaged,representing “half ring” injury,the knee is relative stable because some residual bone and soft tissue still link the tibial and femur.When both components are damaged,meaning that all the structures to maintain the stability of the knee have lost their functions,the knee is extremely unstable in this circumstance.“Closed-loop” theory is to focus the repair of the broken “ring” and stress the importance of corresponding soft tissues for decreasing the incidence of misdiagnosis and missed diagnosis.3.Data collection and management: based on the inclusive criteria,39 fractures were included and classified into A group and B group.After that,we collected the data of fracture,treatment and prognosis.At the 12-month follow-up,NRS pain score was used to analyze the scale of pain in these patients;Rasmussen radiological score was applied to evaluate the situation of knee in X-ray,and HSS score was utilized to judge the whole function of the injured knees after operation.4.Statistics and analysis: The categorical data were recoded as Means±Standard Deviations,and all the data were compared with two-tailed Fisher exact tests or independent sample t-test.Analyses were performed using SPSS18.0 for windows statistical software.A P value of less than 0.05 was considered statistically significant.Results: A total of 39 hyperextension tibial plateau fractures were selected and divided into A group(18 cases)and B group(21 cases).Based on the collected data,we found that there was no difference between the operation time,bleeding volume in surgery,bone healing time,complications,knee joint movement after surgery,pain score and HSS score,but a significant difference between the injury violence,pre-operation transient external fixation,the period between injury and operation and Rasmussen radiological score were observed.Furthermore,“closed loop” theory is able to assist surgeons to treat hyperextension tibial plateau fractures,remind the corresponding realationship between bone and soft tissue,and help sugeons to avoid misdiagnosed or missed diagnosed cases in clinical practice.Conclusion: Anterior unilateral-quadrant type hyperextension tibial plateau fractures often results from low-energy violence,the injured knee is relatively stable,and the prognosis is better after a reasonable treatment.However,compared with anterior unilateral-quadrant type fractures,bilateral-quadrant type fractures are usually caused by high-energy violence,and the knee joint is extremely unstable,the prognosis is poorer.The new classification combined with “closed loop” theory can guide surgeons to make rational pre-operation plans,reduce the incidence of misdiagnosis and missed diagnosis,pay more attention on the correlation between bone and soft tissue,assist to stablise the injured knee in operation,and improve the outcome eventually.