ABSTRACT
BACKGROUND:The traditional view is that proximal fibular fractures do not require fixation.Others and our research suggest that the proximal fibular structure plays an important role in the stability of the posterolateral structure of the knee joint,and its mechanism of action is worth studying. OBJECTIVE:To investigate the biomechanical effects of proximal fibular fractures on various structures of the knee joint in an extended state. METHODS:Finite element method was used to conduct simulated biomechanical experiments.A healthy young male volunteer was selected to establish a finite element model of the knee joint in an extended state using MRI and CT image data,and four proximal fibular shapes were simulated(Model A:intact,Model B:1 cm fracture below the fibular head,Model C:1 cm tip defect fracture from the proximal end of the fibula to the distal end,and Model D:2 cm bone defect from the proximal end of the fibula).A longitudinal concentrated load of 1 500 N was applied to the femoral shaft to compare and analyze the distribution and changing trend of the maximum equivalent stress and maximum first principal stress of each structure of the knee joint in an extended state under four working conditions. RESULTS AND CONCLUSION:(1)In Model A,the maximum equivalent stress in the tibial cartilage and lateral compartment of the meniscus was greater than that in the medial compartment,while the maximum first principal stress in the tibial plateau and medial compartment of the meniscus was greater than that in the lateral compartment.The maximum equivalent stress of the medial condyle of the femoral cartilage was greater than that of the lateral condyle,and the maximum first principal stress of the medial condyle of the femoral cartilage was greater than that of the medial condyle.(2)Compared to Model A,there was no significant difference in the magnitude and distribution of the maximum equivalent stress and maximum first principal stress in the cartilage and meniscus of Model C.(3)Compared to Model A,the maximum equivalent stress increase amplitude of Model B was in the order of medial tibial cartilage(14.9％),medial condyle of femoral cartilage(13.6％),and medial meniscus(6.6％).The maximum first principal stress increase amplitude was the medial meniscus(11.06％),the medial tibial cartilage(8.65％),and the medial condyle of the femoral cartilage(7.46％).The maximum equivalent stress increase amplitude of the ligament was as follows:popliteal arch ligament(33.2％)>anterior cruciate ligament(21.3％)>fibular collateral ligament(17％)>posterior cruciate ligament(14.3％)>anterior lateral collateral ligament(13.2％)>medial collateral ligament(10.1％).(4)Compared to Model A,the maximum equivalent stress increasing trend of Model D followed the medial tibial cartilage(19.5％),femoral cartilage medial condyle(17.9％),and medial meniscus(9.9％).The maximum first principal stress in sequence was the medial meniscus(14.04％),the medial tibial cartilage(13.03％),and the medial condyle of the femoral cartilage(11.37％).The increasing trend of maximum equivalent stress in ligaments was as follows:anterior cruciate ligament(25.2％)>posterior cruciate ligament(18.9％)>medial collateral ligament(18.5％)>anterior lateral collateral ligament(12.7％).(5)It is suggested that when the knee joint is extended,a 1 cm fracture below the fibular head and a 2 cm fibular tip bone defect have a significant impact on the structure of the medial ventricular cartilage,anterior cruciate ligament,and posterior lateral ligament complex.
ABSTRACT
It is well known that fractures around the knee joint are usually combined with ligament injuries but it is easy to miss the ligament injuries during the treatment of fractures. The invention of the MRI and the development of arthroscopic techniques has made it easy to diagnose and care for ligament injuries. Authors reviewed the patients who had fractures around the knee joint to evaluate the frequencies, types, treatments and the results of combined ligaments injuries. There were 57 cases with the fracture of the proximal tibia and fibula which could be follwed up at least one year: from January 1992 to June 1995. There were 19 cases (33%) which had combined ligament injuries. The ligament injuries were diagnosed by stress X-ray & MRI evaluation and confirmed by arthroscopic examination. Single lateral rim avulsion fracture of proximal tibia was the most common type of fractures (7 cases, 37%). There were 11 cases (57%) of combined injuries of anterior cruciate ligament and medial collateral ligament. It was the most common combined ligament injury. Except for one, eleven cases that were combined with lateral rim avulsion of proximal tibia had anterior cruciate ligament injury. There were ten cases (53%) of fibula head and neck fractures which were combined with ligament injuries. The total number of the injured ligament was 35 and the common rupture sites of the injured ligaments was the attachment site of femur (13 cases) and tibia (16 cases). There were seven meniscal injury cases (37%). The interval from injury to operation averaged 14.1 days because many cases were acute injuries. Primary repairs for ruptured ligament were done in 31 cases (88%) because of their attachment site injuries. There were no instabilities except one case which was treated with posterior cruciate ligament reconstruction using semitendinosus ligament. It had a grade I posterior instability at the last follow-up. Early diagnosis and proper treatment on the ruptured ligaments and the torn meniscus combined with proximal tibia and fibular fractures seem to be important for a good prognosis.