| ObjectivesFracture at the distal femur is common in clinic, the main remedymethod is by means of inner fixation. The material almost are steel plate and intrameduUary nail. In recent years, intrameduUary nail fixation has become a tendency. The purposes of the thesis are: 1) Measure the medullary cavity of adult femur of Chinese and the biomechanical property, so that designing a new style of elastic intramedullary nail fitting to thighbone cavity and fixing distal femoral fracture. 2) Experimentizing biomechanics of the elastic intrameduUary nail and evaluating it's biomechanical property, providing proof for the clinical application. 3) Apply the elastic intrameduUary nail to treat distal femur fracture,observe the effection of clinic practice and sum up the experience and expect to achieve the goal of promote fracture healing.Materials and Methods1. Femur medullary cavity anatomic research: Take 12 fresh femur specimens in adult, bite out two ends apiece 6.5cm and cut the bones off every 1.5cm in transverse, measure the length of coronal diameter and sagittal diameter, then calculate the average radius. Take 12 femur specimens, cut every longitudinally from the medium axis line, observe morphologist of femur cavity and the distribution of cortex, gauge the forward radian of femur's medium axis line.2. Design and make the elastic intramedullary nail: Dig longitudinal slot on the pinna of MeiHua intramedullary nail(quincunx nail) at it's proximal and distal different distence and install into 2-4 elastic blocks(elastic stainless steel into four--petals--liking spring coil), whose radian is made in the basis of thighbone's medium axis line, whose horizontal diameter is made according to the bone's sagittal diameter, expecting to lean against the interior wall of the marrow cavity.The nail' cusp is shape of taper, the end have extract hole.3. Biomechanics test: hold 8 fresh pieces of adult's femur, make them into the models of the distal femur fracture 2/5, separately put one MeiHua nail, one interlocking intramedullary nail, one elastic inintramedullary nail and a steel plate screw to one model and fix, Then test the resist—revolve capacity by MTS biomechanics testing instrument, measure swing and remnants angle in the condition of 5NM and 10NM torque.4. Clinical applying observation: Respectively apply them bymeans of close diaplasis or finity dissection diaplasis to distal femoral fracture: above and middle and distal part (smash and oblique fracture should be bounded up with steel thread) . Arthrosis functional exercise in earlier period. Observe healing condition and arthrosis movment function after operation. Sum up the clinical application experience of the elastic intrmedullary nails fixating.Results1. The proximal and distal cavity of femur appeared" inverted funnel" shape . The sagittal diameter of the cavity is smaller than the coronal one in the proximal and distal ends of the femur. But under the little trochanter (5.0±0.45)-(22.5±0.55)cm appeared approximately column of long sagittal diameter and short coronal one gradually.The subregion is equaled to the core of femurs. The sagittal and coronal diameters of the narrowest part of the femur was 13.9±1.6 mm and 11.4±1.3 mm respectively, it located approach midpoint of femoral 3.57cm, it's diameter dicided the intramedullary nail's one.The forward radium of the medullary cavity of femur was curvature than it's appearance , especially in the core of femurs; The more narrow of the medullary cavity of femur and the small diameter of the appearence and the big radian, the thick of the cortex bone, two ends of cortex bone became thin gradually; There was forward curvature in the core of femurs whose average radius was 90.2±15.6 cm.2. Elastic intramedullary nail was composed of MeiHua intramedullary nail(quincunx nail) and 2-4 elastic blocks , it's radius of forward radian is 125 mm; The elastic block is interval (11.5±1.0) cm from the tail of the nail, that is the place where cortex bone moves. In accordance with fracture place, the distant 1-2 elastic blocks, whose protrusive diameter are about 23.6mm, is located (27.5±2.0) cm from the tail of the nail, the protrusive diameter of nearer elastic block is 18.8mm, the corresponding saggital diameter of femur cavity are (22.6 +1.8)cm and (1.46 ±1.5) cm. It withstanded wall of femoral cavity and formed the nail-cortical contact; The elastic blocks have strong spring property and toughness and intensity, it was pressed versus to the inside of nail's body cavity then released after 8 hours, it relapsed and had not distorted.3. Elastic intramedullary nails was tested anti-torsion by the MTS 858 biomechanical testing machine. When fracture of cadaver femur in distal 2/5 part was fixed by elastic intramedullary nail and interlocking nails and steel plates and MeiHua intramedullary nails, under the condition of 5Nm torque, maximal tortion angle(7.09±0.92) was approximately inter-locking nails (7.08±o.72) (p>0.05), it weaked than that of steel plates, MeiHua intramedullary nails had no anti-circumrotate function; the remain angle(3.27±0.0.48) after uninstall was approximately interlocking nails(3.25±0.74) (p > 0.05)too; namely, anti-circumrotate intensity is near to that of interlocking intramedullary nail. Under the condition of lONm torque,anti-circumrotate intensity of elastic intramedullary nails is worse than that of interlocking intramedullary nail and steel plates(/><0.01). The compare of 4 iner fixation have stastic significance.4. The result of elastic intramedullary nails treating fracture at the distal of femurs:(1) Taking half sideways decubitus ease to fracture diaplasis when installing elastic intramedullary nail; Taking close diaplasis ease to observation and rectifing circumvolve shift.(2) Limited cut diaplasis remedy ease to exposure the ends of fractures and achieving anatomic diaplasis, small cut , little bleeding and short time (average operation time 30min).(3) The x-ray of elastic intramedullary nails treating fracture at the distal of femurs show: 21 cases achieved or accessed to anatomic diaplasis, 2 antiquated fractures achieved functional diaplasis criterion.The state of fractures healing: All of 23 patients had followed up, the time of follow up was 6-36 months,the average time was 15 months. 21 cases thereinto 23 patients x-ray show scar growing after operation 3-4 weeks, the healed time was 8-12 weeks, average was 9 weeks. 2 antiquated fracture cases were healed for 15-22 weeks. The time of extraction was 20-29 weeks, the average was 24 weeks. The nails were extracted all right under the local anaesthesia, the elastic blocks of the nail apeared relapsed condition, only 1 case withdrawed in the nail body.The degree of knee joint territory; 21 cases extend andbend degree> 130° , 2 cases 90° -130° .Complications after operation: 1 case x-ray show after 6 weeks: the nail bended, the femoral forward bending 8 ° ,the elastic block ruptured and leaved femoral medullary cavity, it was because of the patient's starting walk after 3 weeks with crushed femoral fracture. 1 case limb short lcm. no one has had complications as infected, malformation, abnormal union, joint ankylosis, fracture again and the like.According to kolmert' Function Estimating Criterion, 19 cases are excellent, 3 cases are fine, the effective rate was 95.7%.Conclusion1. The femur medullary cavity is irregular, the midst axis of the femoral medullary cavity is protruding forward, the narrowest part lies approximately 3.57cm above the middle of cortex bone. The radian of elastic intramedullary nail is the same as that of femur cavity, the elastic blocks inside the elastic intramedullary nail could adapt the irregular morphologic of the femur medullary cavity, and lean against internal wall of the wider part of the femur cavity tightly at sagittal.2.The designed elastic intramedullary nail is tally with biomechanics. Its resist—revolve characteristic is good, but also its structure is simple and has no stress sheltered from; The special nail can make the end of the fracture conform with the anatomic diaplasis, meanwhile allowing the end of fracture move slightly, therefor achieving the conversion of dynamic and statics ,at the same time, it can increase axial press strength ,which can promote fracture healing.3. Using elastic intramedullary nail to treat distal femur fracture is easy to operate and master and operation time is shorter. After operation fracture could heal quickly without complications. So it is worthy of being applied widely in clinic. |
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