Classification And Morphology Of Hyperextension Tibial Plateau Fracture

Purpose:This study was aimed at establishing a new classification of hyperextension tibial plateau fractures(HTPF)and analyzing the incidence and characteristics of HTPF by using a computed tomography(CT)–based “four-column and nine-segment” classification.Methods:In the coronal plane,HTPF are divided into four types: pure hyperextension,hyperextension–varus,hyperextension–valgus,and hyperextension–bicondylar.Fractures in the sagittal plane were divided into three types: type 1,pure depression;type 2,cleavage extending to the posterior cortex with no displacement;and type 3,cleavage extending to the posterior cortex with a significant displacement.A retrospective analysis of CT images of the tibial plateau fractures from December 2007 to December 2021 was conducted,and the typical HTPF cases were identified.After reconstruction and virtual reduction in the medical software Mimics,they were exported to3-MATIC software to stretch and match the standard proximal tibial bone model,and the main fracture lines of each fracture were drawn to the surface of the model.After stacking to a single model,the fracture lines were transformed into a three-dimensional heat map by E-3D software.Finally,the heat map of the three-dimensional fracture line was analyzed by using the new classification system,and the prone area and the running law of the fracture line were analyzed from many directions and angles,which can be used to analyze and explain the injury mechanism of each subtype.Results:The newly established HTPF classification included different types of injury on the upper edge of the articular surface,as well as the injury information of the inferior posterior cortex,which covered a more comprehensive range.A total of 136(10.9%,136/1253)fractures fulfilled the radiographic criteria for HTPF pattern in 136 knees(53.5 ± 13.3 years).There were 11 knees with pure hyperextension fracture(8.1%),23 with hyperextension–varus fracture(16.9%),46 with hyperextension–valgus fracture(33.8%),and 56 with hyperextension–bicondylar fracture(41.2%)in the axial position.There were significant differences among the four types of injury mechanisms,and there were many different manifestations of posterior tension injuries that were often combined.Among them,pure hyperextension tibial plateau fracture mainly involved the bare area(segment d,precentral area)and the attachment of posterior cruciate ligament(segment f).Hyperextension-varus tibial plateau fracture mainly involved the bare area(segment d)and the anteromedial edge of the platform(segment a).Hyperextension-valgus tibial plateau fracture mainly involved the bare area(segment d)and the anterolateral edge of the platform(segment g).Hyperextension-bicondylar tibial plateau fracture mainly involved the bare area(segment d)and anteromedial edge of the platform(segment a)plus anterolateral edge of the platform(segment a+ g).The distribution range of the fracture line was much wider and the extension direction was more variable.Furthermore,there were 64(47.1%),47(34.6%),and 25(18.4%)cases of type 1,type 2,and type 3 fractures,respectively,in the sagittal plane.There were 2(2.3%),29(32.9%),and 57(64.8%)cases of avulsion fractures of posteromedial corner,PCL,and fibular head,respectively.In the three-dimensional heat map,the fracture lines were mainly located at the anterior rim of the tibial plateau,while the posterior articular surface was rarely involved.Conclusions:The injury characteristics of HTPF in the coronal and sagittal planes were classified,a new classification of hyperextension tibial plateau fractures(HTPF)was established and the incidence and characteristics of HTPF were analyzed by using a computed tomography(CT)– based“four-column and nine-segment” classification.The results showed that in coronal position,the incidence of pure hyperextension fracture was the lowest,and that of hyperextension-bicondylar fracture was the highest.In the sagittal position,the incidence of type 1 was the highest and that of type 3 was the lowest.Among the concomitant posterior avulsion fractures,the incidence of avulsion fractures of fibular head was the highest and that of semimembranous muscle was the lowest In the three-dimensional heat map,the fracture lines revealed that there were significant differences in the range of bone cortical collapse of the anterior edge of the tibial plateau and the range and direction of the backward extension of the fracture line under the four injury mechanisms of HTPF.This study will prove helpful for surgeons to judge fracture injury mechanism and determine the fixation strategy.