The Biomechanical And Clinical Studies For Complex Fractures Around Knee Joint

PART 1: A BIOMECHANICAL STUDY FOR LETENNEUR TYPE I HOFFA FRACTURE FIXAITONObjective: The purpose of this study was to compare the mechanical strength of four different fixation patterns for the uncommon fracture,a coronal fracture of the posterior femoral condyle,also known as a Hoffa fracture.Methods: Sixteen sawbone simulated models of Letenneur type Ⅰ Hoffa fractures were created with one of four fixation patterns: two cannulated screws implanted in the anterior-posterior(AP)direction or posterior-anterior(PA)direction;one cannulated screw in the PA direction with a plate implanted in the posterior position of the distal femoral condyle or with a plate in the lateral position.Biomechanical testing was performed to determine the post-fixation axial stiffness,the maximum load to failure and the fragment vertical displacement for each of the four constructs.Results: The plate fixation patterns whether implanted in the posterior or lateral position were shown to provide higher overall axial stiffness and load to failure,and less vertical displacement than the other two patterns of pure screw fixation.Among these constructs,the lateral plate fixation was found to provide the highest stiffness and load to failure and the least displacement for the posterior condylar fragments,followed by the posterior plate fixation.The lowest overall stiffness and load to failure and the largest vertical displacement were found in the construct with the AP direction placed screws.Conclusion: It was concluded that the lateral position implanted plate was biomechanically the strongest fixation method for Letenneur type Ⅰ Hoffa fractures.However,this plate fixation was not recommended for all cases.The choice of internal fixation pattern depended on the fracture severity.PART 2: NEW CLASSIFICATION OF THE HOFFA FRACTURE BASED ON CT: THE RELABILITY ASSESSEMENT AND TREATMENT STRATEGIES CHOICEObjective: The purpose of the present study was to introduce a new classification of the Hoffa fracture based on morphologic characteristics observed by computed tomography(CT)imaging,assess its inter-and intra-observer reliability and propose corresponding treatment strategies.Methods: Ninety-four patients with 94 Hoffa fractures were retrospectively enrolled in the study and evaluated radiographically.All cases were arranged randomly.A new improved classification was proposed on the basis of the Letenneur classification according to CT image analysis and clinical experience.The Hoffa fractures were allocated to 2 major categories: type Ⅰ and Ⅱ,and each type contained 3 subtypes: subtype a,b and c.Type I referred to simple splitting fractures,in which the subtype Ⅰ-a was equal to the Letenneur type Ⅰ,subtype Ⅰ-b referred to Letenneur type Ⅱ and subtype Ⅰ-c referred to Letenneur type Ⅲ.Type Ⅱ was a composite and more complicated category,in which the articular surface of the distal femoral condyle was involved to some extent.Subtype Ⅱ-a referred to a compound fracture with an independent splitting fragment in the articular surface on the basis of subtype Ⅰ a-c.Subtype Ⅱ-b fracture referred to a splitting-compression fracture in which there was collapse or compression of the articular surface on either or both sides of the main splitting fracture line as described in subtype Ⅰ a-c.Lastly,the subtype Ⅱ-c referred to a comminuted fracture in which the splitting fragment and compression of the articular surface appeared at the same time;therefore it is also a combination of subtype Ⅱ-a and Ⅱ-b.To evaluate and compare the interand intra-observer reliability of the original Letenneur classification with that of the new classification,4 observers were invited to investigate.The Kappa statistic was used to analyse the reliability of these 2 different classifications.After each classification assessment,the observers were required to select a treatment choice strategy for each fracture.Results: On the basis of the CT scan and reconstruction images,the inter-and intra-observer reliabilities of the new classification were regarded as substantial(mean kappa 0.747 and 0.767 in the first and second rounds)and almost perfect agreement(mean Kappa 0.894),respectively.The interand intra-observer agreements of treatment choice based on the new classification were regarded as moderate(mean Kappa 0.432 and 0.464 in the first and second rounds)and almost perfect agreement(mean kappa 0.921),respectively.However,there was a significant difference in the treatment choice based on the different classifications(p<0.001).Conclusion: The existing Letenneur classification did not cover all types of Hoffa fractures;in particular,there was no description of the involvement of the articular surface of distal femur condyles.However,accurate evaluation and proper management of the articular surface injury frequently played a critical role in the treatment of Hoffa fractures.The new classification of Hoffa fractures,which was based on CT images,not only fully compensateed for the limitations of the Letenneur classification but also showed high reliability.Because the new classification highlighted the evaluation of the articular surface,the rate of using plates for internal fixation of Hoffa fractures could be increased.However,high-quality and large-sample clinical trials were needed to verify the prognostic value of the new classification for Hoffa fractures.PART 3: A BIOMECHANICAL EVALUATION OF DIFFERENT FIXATION STRATEGIES FOR POSTEROLATERAL FRAGMENT IN TIBIAL PLATEAU FRACTURESObjective: The reinforcement strategy,‘magic screw’,for posterolateral column fracture(PLCF)of the tibial plateau fixation was proposed.The purpose of this study was to re-examine and compare the stability of different fixation methods for PLCF.Methods: Synthetic tibiae models were used to simulate posterolateral split fractures of tibial plateau.The fracture models were randomly assigned into three groups: Group A,fractures were fixed with posterolateral buttress plates;Group B,with lateral locking compression plates(LCP)positioned posteriorly;and Group C fixed with lateral LCPs positioned posteriorly and one ‘magic screw’.Gradually increased axial compressive loads were applied to each specimen.Results: There was a mean subsidence hierarchy of the posterolateral fragment at different load levels: Group A had the least subsidence,followed by Group C,and Group B had the most.There was no significant difference in the mean vertical loads at the same level displacements between Group A and Group C.Group A had the highest axial stiffness.Additionally,there was a significant difference in axial stiffness between Group B and Group C.Conclusion: Biomechanical stability of the combined fixation of the posteriorly positioned lateral rafting plate with the ‘magic screw’ was much closer to that of posterior plate fixation for split type PLCF.The necessity of posterior fixation through a posterior approach may be reduced for selected patients.PART 4: REINFORCEMENT STRATEGY FOR FIXAITON OF POSTEROLATERAL COLUMN FRACTURES OF TIBIAL PLATEAU: A PROSPECTIVE OBSERVATION COHORT STUDYObjective: To evaluate the clinical efficiency and safety of reinforcement strategy,‘magic screw’ technique,for the fixation of posterolateral column fractures(PLCF)of tibial plateau.Methods: From February 2016 to June 2016,an inconsecutive series of 16 patients who suffered Schatzker type Ⅱ tibial plateau fractures involving the posterolateral column were selected based on an analysis of the morphological characteristics of PLCFs.The patients were all treated by lateral rafting plate fixation with magic screw implantation through the extended lateral approach of the knee joint.Results: According to PLCF morphology,4 patients had mild slope-type depression fractures(MSDF)of the articular surface,and the other 12 patients had block-type splitting fractures(BSF).After at least 12-month follow-up period,there was no complications related to the fixation technique and no significant change in limb alignment.At the final follow-up,the average range of motion(ROM)of the affected knee joints was 2.3°-125°,and the average HSS score was 94.2.Conclusion: The selected patients who suffered Schatzker type Ⅱ fractures involving the posterolateral column could be successfully treated via lateral rafting plate fixation combined with the magic screw technique.For PLCF treatment,magic screw fixation is a valuable technique that might reduce the utilization of posterior approaches and implantation of posterior fixations.