A Comparision Of The Clinical Effect Of Two Fixation Methods On Hoffa Fracture

Background:Hoffa fractures are unstable intraarticular fractures.Lateral Hoffa fractures are more common than medial ones,but bicondylar Hoffa fractures are rare.The mechanism of injury of Hoffa fracture is still unknown.Some authors consider direct impact with the knee in a flexed position as the mechanism of injury,while others think that the fracture is caused by simultaneous vertical shear and twisting forces.In initial anteroposterior and lateral radiographs,Hoffa fractures,especially when nondisplaced,are sometimes difficult to be observed.So a CT scan or MRI scan is necessary to define the fractures.Hoffa fracture is classified as a type 33-B3 fracture by the Orthopaedic Trauma Association.But this classfication provides little information of prognosis and treatment.Letenneur et al reported that they divided Hoffa fractures into three types based on the distance of the fracture line from the posterior cortex of the femoral shaft.In a cadaveric study,Lewis et al finded that in Type Ⅰ and Type Ⅲ Hoffa fractures there are some soft tissue elements attached to the fractured condylar fragment to provide blood supply to this fragment.But in Type Ⅱ Hoffa fractures there was no soft tissue elements attached to the fractured condylar fragment.Hoffa fractures are intraarticular fractures.Most of them need surgical open reduction and internal fixation to achieve good outcome.But the operation approch and fixation method are still been improving.It is generally accepted that screw fixation is a good fixation method for treating Hoffa fractures.In Type Ⅰ and Type Ⅲ Hoffa fractures,an anterolateral(or anteromedial)incision is usually used,and two anteroposteriorly placed lag screws are inserted from the non-articular area just proximal to the patella-femoral joint to engage the fractured condylar fragment.One screw is inserted into the femoral shaft to provide rotational stability.In Type Ⅱ Hoffa fractures,because the fracture line is near the articular cartilage of the posterior condyle,a posterior approach and two posteroanteriorly placed lag screws may be a good choice.However,the screws are inserted through the articular aurface,so the screw heads should be countersunk.In a word,in the traditional methods,the fracture is fixed with multiple screws through complex constructs to attempt to achieve stability,but it’s hard to succeed.In order to expose and fix the fracture fragment,the soft tissue elements attached to the fractured condylar fragment are stripped off,and the blood supply to the fragment is damaged,which may result in nonunion or osteonecrosis.So improve the fixation methods of Hoffa fractures so as to improve the cure rate of Hoffa fractures is very urgent and important.Methods:From April 2004 to July 2013,we treated eleven patients(new method group)with Hoffa fracture using the new fixation method(fixed with intercondylar screw and crossed screws)and sixteen patients(traditional method group)using the traditional fixation method(fixed with anteroposteriorly placed screws).All documents from theiradmission until the last followup in December 2015 were reviewed,data regarding complications collected and results were evaluated using the Knee Society Score.Results:After an average follow-up period of 27.1 months(range 24-32 months),all fractures had healed.The average healing time of the new method group was 11.36 weeks(range 9-14 weeks)and the average healing time of the traditional method group was 11.88 weeks(range 9-14 weeks).According to the Knee Society Score,the average score of the new method group was 174.6 points(range 125-199 points),and the average score of the traditional method group was 157.7 points(range 107-194 points).Statistical analysis(t test,t=1.78,P<0.05)showed that the difference of the score between these two groups was significant,but the healing time(t test,t=0.94,P>0.05)between these two groups was not significant.Conclusion:Open reduction and internal fixation with the screw inserted from the femoral intercondylar notch is a safe and effective way to treat Hoffa fracture,which has the advantages of improving stability of fracture fixation,protecting articular cartilage,adapting for early functional exercise and reducing sequelae.So we consider that the new fixation method for Hoffa fracture is as effective as the traditional method and may provide a new way to treat Hoffa fractures.