| Hoffa fracture of the femoral condyle was first presented and graphically described by the German surgeon Busch in 1869 and first mentioned by Albert Hoffa in 1888,but the source of citation was not indicated.It is currently recognized that Hoffa fracture of the femoral condyle is caused by a fall injury from height or a car accident injury,and the key point lies in that the patient is in flexion of the knee joint at the moment of the fracture,so that the axial violence is transmitted backwards from the tibial plateau in the form of shear and acts on the femoral condyle,resulting in a coronal shear fracture of the femoral condyle,that is,Hoffa fracture of the femoral condyle.According to Newton ’s third law of motion,the force and reaction force between two interacting objects are always equal in magnitude and opposite in direction and act on the same straight line.Given the anatomic alignment of the femoral condyles with the tibial plateau,we expect that fracture types similar to Hoffa fractures of the femoral condyles may appear on the tibial plateau side as well,and the mechanism of injury may be exactly the same as Hoffa fractures of the femoral condyles.Therefore,this study intends to use the form of simulation experiment to simulate the injury mechanism of falling injury and car accident injury from height,and to explore whether a similar fracture on the tibial plateau side is created.If successful,we will name it Hoffa-like fracture of the tibial plateau.Hoffa fracture of the tibial plateau is rare and a special coronal shear fracture of the tibial plateau.The mechanism of injury is mainly fall from height and car accident.At present,the literature studies are individual cases or series reports,and there is a lack of systematic data,such as the incidence of the underlying population,the proportion of the tibial plateau,injury characteristics and injury mechanism;most importantly,as a special fracture,the commonly used types such as Schatzker classification,AO/OTA classification,three-column classification and comprehensive classification of tibial plateau fractures cannot cover or fully elaborate their injury characteristics.The aim of this study was to propose a specific classification for Hoffa fractures of the tibial plateau based on this fracture feature and to verify the consistency and reproducibility of the classification.Regarding the clinical outcome of Hoffa fracture of the tibial plateau,the current literature studies are individual cases or series reports,and there is a lack of systematic data,such as the incidence of the underlying population,the proportion of tibial plateau,injury characteristics,and the mechanism of injury.Our team conducted experimental simulations,epidemiological studies,proposed specialized classification,and validated its validity in previous studies,but there is still a lack of research on the prognosis of this type of fracture,and the purpose of this study is to report typical cases of Hoffa-like tibial plateau fractures in order to improve their understanding.As a typical intra-articular fracture,the quality of articular surface reduction in Hoffa-like fractures of the tibial plateau directly affects the prognosis,and malunion can disrupt normal joint movement and increase the risk of arthritis,so it is necessary to restore a flat articular surface to reduce the incidence of post-traumatic arthritis.However,biomechanical studies on malunion of Hoffa-like fractures of the tibial plateau are extremely scarce,so the aim of this study was to investigate the changes in mechanical conduction in the knee joint after malunion of Hoffa-like fractures,determine the relationship between plateau stress and malunion,and provide a theoretical basis for subsequent clinical treatment.Part 1 Preliminary study on injury mechanism of Hoffa-like fracture of tibial plateauObjective: Hoffa fracture of the femoral condyle was first presented and graphically described by a German surgeon Busch in 1869 and first mentioned by Albert Hoffa in 1888,but the source of citation was not indicated.It is now recognized that Hoffa fracture of the femoral condyle is caused by a fall injury from height or a car accident,and the key point lies in that the patient is in extreme flexion of the knee joint at the moment of the fracture,so that the axial violence is transmitted backwards from the tibial plateau in the form of shear and acts on the femoral condyle,resulting in a coronal shear fracture of the femoral condyle,that is,Hoffa fracture of the femoral condyle.According to Newton ’s third law of motion,the force and reaction force between two interacting objects are always equal in magnitude and opposite in direction and act on the same straight line.Given the anatomic alignment of the femoral condyles with the tibial plateau,we expect that fracture types similar to Hoffa fractures of the femoral condyles may appear on the tibial plateau side as well,and the mechanism of injury may be exactly the same as Hoffa fractures of the femoral condyles.Therefore,this study intends to use the form of simulation experiment to simulate the injury mechanism of falling injury and car accident injury from height,and to explore whether a similar fracture on the tibial plateau side is created.If successful,we will name it Hoffa-like fracture of the tibial plateau.Methods: Ten specimens of lower limb knee joints were selected and provided by Henan Xuchang Yu Lin Science and Education Equipment Co.,Ltd.Donors consisted of six males and four females aged between 42 and 65 years with a mean age of 57.4 years.In the selection of specimens,soft tissues such as muscles were removed,the appearance of the specimens was not significantly deformed,and the imaging findings showed no bone tumors,severe osteoporosis,previous fractures,or deformities.When falling from height,the knee joint of the patient will have a certain degree of flexion when landing,usually no more than 75 degrees.The foot and lower leg land and the reaction force is transmitted to the tibial plateau and femoral condyle.The impact injury may lead to the coronal fracture of the posterior tibial plateau.In the car accident injury,the vehicle stopped urgently,the patient ’s body was tilted forward due to inertia,the knee joint was usually flexed more than 90 degrees,impinging on the baffle plate in front,and violence conducted posteriorly and inferiorly from the distal femur to the posterior side of the tibial plateau along the anterosuperior direction,resulting in a coronal fracture of the posterior side of the tibial plateau.In both scenarios,five knee specimens were randomly selected and fixed on a homemade base platform with dental tray powder and dental tray solution,and a 10 kg iron block was used to freely fall from 2 meters to simulate a fall from height,at which time the knee joint was flexed 120°;the knee joint was flexed 70°,and a heavy object hit the stress platform to simulate a car accident injury impacting the knee joint scene,and the femur impinged the tibia posteriorly and inferiorly.At the end of the experiment,anteroposterior and lateral radiographs and CT scans of the knee joints were performed to determine whether fractures occurred,and if they occurred,the morphological characteristics of the fractures were analyzed.Results: Hoffa-like fractures of the tibial plateau occurred in 3 of 5 knee specimens simulating falls from height,all of which were located posteromedially and involved the posterior 1/3,2/5,and 1/2 of the tibial plateau,and the fracture lines were angled to the coronal plane by 21°,19°,and 12°,respectively.Of these three fractures,one could not be clearly visualized on X-ray and CT confirmed the diagnosis of posteromedial fracture.Two samples showed no Hoffa-like fractures of the tibial plateau,one was a comminuted fracture of the distal femur,and the other was an intra-articular combined sagittal fracture of the distal femur.In the five knee specimens simulating the traffic accident scenario,three Hoffa-like fractures of the tibial plateau also occurred,with fracture lines located in the posterior 1/6,1/4,and 1/3 and angulated to the coronal plane at 47°,56°,and 63°,respectively.Of the three cases,one did not clearly show the fracture line on X-ray and was confirmed on CT,and the other two were confirmed to have Hoffa-like fractures on both X-ray and CT.Conclusion: This study confirms our hypothesis and successfully simulates Hoffa-like fractures of the tibial plateau caused by two injury mechanisms,a finding that is important for re-understanding the injury,and in order to reduce the risk of missed diagnosis,we recommend routine addition of CT scans in patients with a clear history of knee flexion and axial violent injuries.Part 2 Proposal of Hoffa fracture classification of tibial plateau and validation between and within observersObjective: Hoffa fracture of tibial plateau is rare and a special coronal shear fracture of tibial plateau.The main mechanism of injury is fall from height and car accident.At present,the literature studies are individual cases or series reports,and there is a lack of systematic data,such as the incidence of the underlying population,the proportion of tibial plateau,injury characteristics and injury mechanism;most importantly,as a special fracture,the commonly used types such as Schatzker classification,AO/OTA classification,three-column classification and comprehensive classification of tibial plateau fractures cannot cover or fully elaborate their injury characteristics.The aim of this study was to propose a specific classification for Hoffa fractures of the tibial plateau based on this fracture feature and to verify the consistency and reproducibility of the classification.Methods: First,we retrospectively obtained the imaging data of 3086 cases of tibial plateau fractures treated in the Third Hospital of Hebei Medical University and the Affiliated Hospital of Qingdao University from January2014 to September 2019,and identified 13 cases of Hoffa fractures of the tibial plateau,which were classified according to their injury characteristics(location of the fracture line,extent of involvement,and degree of displacement): type I fractures involved less than 1/4 of the articular surface of the tibial plateau,type II fractures involved more than 1/4 and less than 1/2of the articular surface of the tibial plateau,and type III fractures involved more than 1/2 of the articular surface.Each type of fracture is divided into three subtypes,of which subtype A is undisplaced fracture,subtype B fracture articular surface displacement<2mm,and subtype C fracture articular surface displacement≥2mm.Then,we extended the sampling to five tertiary hospitals(the Third Hospital of Hebei Medical University,the Affiliated Hospital of Qingdao University,Tianjin Hospital,Cangzhou Hospital of Integrated Traditional Chinese and Western Medicine,and the General Hospital of Jizhong Energy Xingtai Mining Bureau)until December 2020,and included a total of 61 patients with Hoffa fractures of the tibial plateau with complete X-ray and CT data,based on which we verified the consistency and reproducibility of the above classification we proposed.CT and radiographs of61 cases were independently reviewed by four reviewers on two separate occasions and classified according to a new classification system to calculate statistical values,and inter-and intra-observer validity was assessed by kappa(κ)statistical values.Results: Among 3086 cases of tibial plateau fractures exposed preliminarily,13 cases were diagnosed as Hoffa fracture,accounting for0.42% of tibial plateau fractures,accounting for 1.2/10000 of all fractures in the same period,1/8 of Hoffa fractures in the distal femur in the same period;8 cases were male and 5 cases were female,with an average age of 47.5 years(standard deviation 11.0 years,range 28～69 years).The main causes of injury were fall from height and car accident,accounting for 69.2%.X-ray examination revealed that no fracture line was observed in 3 cases of fractures,which could only be diagnosed by CT,that is,the incidence of occult fractures was 23%(3/13).Among 61 patients with Hoffa fracture of tibial plateau included in 5 hospitals,there were 41 males and 20 females,with mean age of44.5 years(SD 11.7 years,range 26～74 years),83.6%(51/61)of fractures were caused by falling from height or car accident;the results of interobserver agreement test showed Kappa coefficient of 0.74(range,0.61～0.87),and the results of intraobserver reproducibility test showed Kappa coefficient of 0.79(range,0.64～0.93),meaning that the interobserver agreement and intraobserver reproducibility were "substantial agreement".Conclusion: The incidence and injury characteristics of Hoffa fracture of tibial plateau were determined,and the special classification of Hoffa fracture was proposed and the effectiveness was verified,which was helpful to understand and deeply understand Hoffa fracture of tibial plateau and clinical diagnosis and treatment.Part 3 Hoffa fracture of tibial plateau: a clinical studyObjective: Hoffa fracture of the tibial plateau is a special coronal shear fracture of the tibial plateau,which is very rare.At present,the literature studies are individual cases or series reports,and there is a lack of systematic data,such as the incidence of the underlying population,the proportion of the tibial plateau,the characteristics of the injury and the mechanism of injury.Our team conducted experimental simulations,epidemiological studies,proposed specialized classification,and validated its validity in previous studies,but there is still a lack of research on the prognosis of this type of fracture,and the purpose of this study is to report typical cases of Hoffa-like tibial plateau fractures in order to improve their understanding.Methods: A retrospective analysis was performed to search patients who underwent surgery for tibial plateau fractures between October 2014 and December 2020 in the Third Hospital of Hebei Medical University,and imaging data,including preoperative radiographs and CT scan data,were obtained after obtaining the medical record number,and those with any deletions were excluded.An attending radiologist and a trauma orthopedic surgeon were responsible for reviewing all imaging data and identifying a solitary coronal fracture of the posterior tibial plateau,followed by review of inpatient medical records,surgical records,follow-up records,etc.,telephone follow-up if necessary,or inviting the patient to perform outpatient follow-up.Demographic data,imaging characteristics,surgical conditions,fracture healing,postoperative functional recovery and complications of the patients were counted.Knee function and radiographic recovery were assessed by Hospital for Special Surgery(HSS)and Rasmussen radiographic scores at last follow-up(>12 months),respectively.Results: During the study period,1924 tibial plateau fractures were identified,6 of which were isolated coronal fractures of the posterior tibial plateau,i.e.,Hoffa-like fractures of the tibial plateau,accounting for 0.31%(6/1924)of all tibial plateau fractures.Of the 6 patients,3 were male and 3were female,with a mean age of 45.8 years(range,30-69 years).Mechanism of injury: 4 cases were caused by falling from height and 2 by car accident.The mean time interval from injury to surgery was 7.5 days,and all patients were treated with open reduction and internal fixation(ORIF),using a lateral(2 cases)or posteromedial approach(4 cases),and the internal fixation was fixed with plates/screws.Following surgery,routine follow-up radiographs showed bony union in all cases at 10-15 weeks,with no delayed union or nonunion.At 12 months follow-up,the average HSS score of the knee joint was 94.8(range 93 to 98),and the average Rasmussen score of the X-ray was15.8(range 15 to 18).No intraoperative or postoperative complications were recorded or reported.Conclusions: This study reports the incidence of Hoffa fractures of the tibial plateau and the treatment and prognosis of six typical cases,and orthopedic surgeons should pay attention to this rare and easily overlooked fracture type,which needs to be explored in a large sample of studies in the future.Part 4 Biomechanical study on the malunion of Hoffa-like fractures of the tibial plateauObjective: Hoffa-like fractures of the tibial plateau are coronal fractures of the medial tibial plateau,and the difficulty of surgery and the incidence of malunion are higher than those of fractures at other sites.Malunion of tibial plateau fractures disrupts normal joint motion and increases the risk of arthritis,so restoring a flat articular surface is necessary to reduce the incidence of post-traumatic arthritis.However,biomechanical studies on Hoffa-like fracture malunion of the tibial plateau are extremely scarce,so the aim of this study was to investigate the changes in mechanical conduction in the knee joint after Hoffa-like fracture malunion and determine the relationship between plateau stress and malunion to provide a theoretical basis for subsequent clinical treatment.Methods: Formalin-preserved knee joint specimens were used in this study.Before the start of the experiment,the specimens were dissected and the excess soft tissues and muscles were removed.A horizontal incision of about3-4cm in length was made along the lower edge of the patella,both sides of the patellar ligament,and the level of the joint space to expose the joint space,and the anterior and posterior cruciate ligaments,medial and lateral collateral ligaments,patellar ligaments,and medial and lateral menisci were preserved.A 2-3 cm vertical incision was made on the bone surface 1.5 cm inward along the coronal plane posterior to the medial aspect of the tibial plateau,and a wire saw was used to dissect the bone block 1.5 cm thick posterior to the medial aspect of the tibial plateau along the incision.The free bone block was then fixed by selecting the appropriate internal fixation with vertical downward displacement of the bone block of 1mm,2mm,and 3mm(V1,V2,V3)and separation of 3mm,5mm,and 7mm(S3,S5,S7).The femoral end of the specimen was placed parallel in a homemade fixture and fixed with denture base resin autocoagulant.The stress test was performed at 0°,30°,60°,90°,120° of passive flexion for each knee.The stress values were measured using FDP-305 E densitometer and FDP-306 E pressure converter,and five randomly selected points from the darkest part of the pressure-sensitive film were selected to measure the stress values and their mean values were calculated.After data collection,Graph Pad Prism 8 statistical software was used for data analysis,and independent sample t-test was used to analyze the difference of medial and lateral compartment stress values between normal tibia and Hoffa-like fracture malunion at the same angle,and P<0.05 was considered statistically significant.Results: Under the vertical load of 600 N,the medial and lateral stresses of the normal tibial plateau increased with the knee flexion angle.The medial stress of the tibial plateau was 2.749±0.123 MPa,2.983±0.145 MPa,3.219±0.175 MPa,4.036±0.477 MPa,and 4.660±0.355 MPa at knee flexion angles of 0°,30°,60°,90°,and 120°,respectively.The medial stress of malunion gradually increased compared with the normal tibia,and there were significant differences between knee flexion(30°-V3),(60°-V3,S5,S7),(90°-V3,S5,S7),and(120°-V1,V2,V3,S5,S7)and the normal tibia(P<0.05).At 30° of knee flexion,the medial stress of V3 was 3.304±0.204MPa;at 60° of flexion,the medial stresses of V3,S5,and S7 were3.749±0.186 MPa,4.085±0.420 MPa,and 4.011±0.389 MPa,respectively;at90° of flexion,the medial stresses of V3,S5,and S7 were 5.078±0.176 MPa,4.700±0.607 MPa,and 5.069±0.510 MPa,respectively,and at 120° of flexion,the medial stresses of V1,V2,V3,S5,and S7 were 5.366±0.287 MPa,6.358±0.529 MPa,6.467±0.265 MPa,6.454±0.153 MPa,and 6.086±0.339 MPa,respectively,which were significantly different from those of normal tibiae(P<0.05).Conclusions: Anatomic reduction remains the primary criterion for this type of fracture because it has been shown that normal knee joints exhibit progressively increased medial and lateral stress extremes during flexion,but medial stress extremes are always greater than lateral stress extremes,while malunion of Hoffa-like fractures may result in a smaller medial condyle contact area and further increased medial stress,potentially leading to later osteoarthritis. |
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