| Background and ObjectiveThe incidence of Patellar Fracture(PF)is 1% ~ 2% of the whole body fracture,which is often seen in adults.The lower pole of the patella is about 1.5cm,which is not covered with surface.The Inferior Patellar Fracture(IPF)fracture is an external fracture of the patella,which accounts for about 5% of the patellar fracture.The cause of injury is indirect and direct trauma.The lower pole of the patella is the cancellous bone,and the fracture is usually comminuted,and the bone strength is weak.However,the patella is an important part of the knee extension device.If the patella is fractured,the continuity of the knee extension device is completely interrupted,which destroys the normal anatomy and biomechanics relationship of patellofemoral joint.As the result,the function of the knee joint is impaired.Therefore,the correct treatment of the inferior patellar fracture is essential to restore the integrity and stability of the knee extension device and the good knee function.At present,IPF treatment is mainly conservative and surgical treatment.Most scholars believe that the fracture of the displacement less than 2mm is allowed took conservative treatment and the knee joint can be fixed with splint for about 6 weeks.More than 2mm of displacement of the fracture is usually advocated surgical treatment.The purpose of the operation is to maintain the shape of the patella,restore the height of the patella,and repair the knee extension device.Operation concept: simple operation,less trauma,strong internal fixation,early functional exercise,the maximum recovery of the knee joint function.Because of the strong tension of patellar ligament,the four biceps femoris and the characteristics of the fracture of the inferior pole of patella,the patellar inferior pole fracture often cannot be effectively anatomic reduction and firmly fixed to meet the requirement of early postoperative full range of motion of knee joint and weight-bearing walking.At present,there is no standard surgical method for the treatment of IPF.Therefore,it may be a challenge for surgeons to treat the IPF effectively and achieve the best clinical results eventually.There are many kinds of reported technique for the treatment of IPF listed as follows: resection of patellar inferior pole,tension band wire fixation,anchor fixation,hollow screw and eight character wire fixation,titanium cable,basket plate,shape memory alloy concentrator,separated vertical wiring fixation.However,most of these methods need knee joint fixation with plaster or braces for about 2-6 weeks after operation,and then start knee joint extension and flexion function training.Different techniques also have different postoperative complications and surgical effects.According the latest literature,the technique of separate vertical wiring(SVW)has better clinical effect than other methods.The procedure is simple and has good biomechanical advantage.Although the reported results of SVW technique are satisfactory,the complications such as internal fixation failure are also observed.Furthermore,the range of flexion of the knee joint should be limited after the operation.Therefore,it is necessary to study a simpler and effective internal fixation method to meet the early postoperative knee functional exercise,and ultimately achieve the best clinical results.This topic is mainly to optimize and improve SVW technology in order to get more satisfactory biomechanical and clinical effects,and provide the latest theoretical basis and clinical practice data for the progress of surgical treatment of patellar inferior pole fracture.Methods 1.Research contentsThis study is mainly to improve the previously reported SVW technology.The key point of the technology improvement is to install the steel wire through the lateral side of the proximal patella and then fix around the rim of the rest of inferior patellar part after finishing the fixation of three separate vertical wires.The biomechanical characteristics of OSVWT and MSVWT were compared by the finite element analysis.The clinical study of the eventually involved 11 cases with IPF treated with MSVWT was performed to evaluate whether the MSVWT has greater fixation strength and better clinical effect.2.Research methodsThe three-dimensional model of IPF was set using the Unigraphics(UG)software system.The biomechanical characteristics of the OSVWT and the MSVWT were compared by the method of finite element analysis in terms of fixation strength and stress analysis.During the period from March 2013 to August 2015,a review study of 11 cases of IPF patients treated with of MSVWT was performed a statistical analysis regarding operation time,incision length,postoperative complications,postoperative Bostman score and surgery related parameters.The clinical effect evaluation of the MSVWT and reported technology were also studied.Results The result of the finite element analysis presented that in patients with IPF treated with OSVWT and MSVWT,the maximum displacement of patellar fracture,were 1.02645 + 0.00035 and 0.30630 + 0.00044 mm(p<0.01),the same point displacement of the patellar fracture were 0.75808 + 0.00067 and 0.13577 + 0.00025 mm(p<0.01),and he maximum stress values of the patellar fracture were 353.4925 + 0.2770 and 143.1938 + 0.2308 mpa respectively(p<0.01).The average operative incision length of 11 patients with MSVWT was 7.9cm and the operation time was 43.45 minutes.Postoperatively,all the patients had no limitation on the range of the knee joint flexion.After an average of 21.7 months follow-up,the postoperative complications such as incision infection,hardware failure,fracture displacement and bone ununion were not occurred.Only one patient was observed cerclage wiring loosening,but the knee function was normal.Totally,the incidence of complications was 9.1%.The average range of Motion(ROM)of the knee joint was 130.9 degrees,and the average Bostman score was 29.09.The operative time of the technique of OSVWT,partial patellectomy(PP)and anchor suturing(AS)were 72.1 minutes,79.1 minutes,68.5 minutes,respectively,and the incidence of the operative complications is 19%,18.2% and 22.2% respectively.Conclusions Generally,the inferior patella fracture is very difficult to be successfully reduced and firmly fixed to meet the requirement of early functional exercise,because the fractures are too small and commuted.However,our modified technique of SVW demonstrated better biomechanical characteristics compared with the original technique of SVW.The MSVWT proved to can meet the needs of early postoperative knee flexion and weight-bearing.Otherwise,the modified technique also presented pretty good clinical effects.In a word,the MSVWT seemed to be an effective technique and maybe more simple and easy to be operated and popularized. |
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