Clinical And Biomechanics Analysis Of Preventing Osteonecrosis Collapse Complicated With Femoral Neck Fracture Of Young Adult By Modified Surgical Treatment

BackgroundTraumatic osteonecrosis (trauma-induced osteonecrosis of the femoral head, TONFH) is a more serious complications of femoral neck fracture in young adults, and showing a rising trend accompanied with traffic accident and falling high-energy injury,. In clinical, generally based on factors causing traumatic necrosis of the femoral head for prevention and treatment, but got poor efficacy, osteonecrosis was still maintained at about40to80%, and collapse rate is even up to70%to80%within1to3years without additional treatment. In recent years, nonunion has been basically solved with the advances in technology and internal fixation materials. According to the literature and clinical observation, osteonecrosis after femoral neck fracture is almost inevitable, how to find a more effective way to avoid the collapse of the femoral head after necrosis, the academic community has not yet reached a consensus at present,, so femoral neck fractures are also called " Yet to heal fractures". In our previous study of early femoral head necrosis, the application of implant cancellous bone combined non-vascularized fibula allograft achieved good effect. This study was to investigate impact on collapse of osteonecrosis after femoral neck fracture with cannulated screw fixation combined fibular allograft (here after referred to as:modified surgical) of young adults, and clinical review and biomechanical finite element analysis to expect to find some factors for the collapse that can be controlled.ObjectiveRetrospective analysis clinical efficacy by modified surgical with Chinese medicine treatment of femoral neck fractures in young adults; Three-dimensional finite element model to analyze the biomechanical mechanisms of prevention and treatment for femoral head collapse after necrosis with improved surgical.Methods1Retrospective Study of Clinical1.1Study subjects:January2006-January2010, inpatient for surgical treatment in the First Affiliated Hospital of Guangzhou University of Traditional Chinese joint orthopedic, included80cases (80hips), male54cases (54hips) and26females (26hips), aged from18to60years old. average40.34±13.03. all were closed fractures,32cases of left hip and48right, confirmed by X-ray and CT examination, including Garden type Ⅰ6cases, Garden Ⅱ11cases, Garden Ⅲ23cases, Garden IV40cases. Injury to surgery time1-12days, mean3.73±2.64d. Follow-up of48to84months, mean63.07±14.96months.1.2Treatment:①surgical methods:All patients were treated with modified surgical treatment.②drug treatment:After surgery, taking the compound shengmai chenggu capsule,4capsules/time,3times/day; Tetramethylpyrazine tablets100mg/time,3times/day, the routine use of three months. Once necrosis, continue to extend drug use for1.5to2years.1.3Observation on risk factors of osteonecrosis and collapse after femoral neck fracture:①Instructor retrospective analysis of the original fracture X-ray, fracture type. and analyzes the patient’s age, gender, fracture type, fracture reduction time, reducton extent, using single factor analysis and Binary Logistic regression analysis on various factors’relevance of necrosis and collapse.②osteonecrosis after femoral neck fracture last follow-up phases:Refer to the International Bone Cycle Research (ARCO) staging osteonecrosis, including ARCO I10cases, stable Ⅱ5cases, Ⅱ, instable12cases.③necrosis range:accurately express the necrotic area, with reference to the volume percentage of necrosis (necrotic area volume/volume of the entire femoral head),collecting patients’ MRI images data, using Mimics15.01software-based DICOM image data to build a three-dimensional model of the necrotic area, according to the model of femoral head necrosis radius and volume, calculated necrosis volume ratio. The necrosis volume more than40%is risk value, which <30%5hips,30%-40%13hips,>40%9hips.④necrosis location:according to modified Steinberg frog-bit type method, in which the anteroposterior:A type0cases, B type4cases, C1type12cases, C2type11cases; frog-bit:A type0cases, B type6cases, C1type15cases, C2type6cases.1.4correlated efficacy evaluation and follow-up postoperation1.4.1postoperative follow-up:a retrospective postoperative follow-up, questionnaire distributed to each patient, the last follow-up mean63.07±14.96months.1.4.2Imaging assessment①Fracture nonunion:Postoperative meet or exceed eight months, X-ray fracture gap can still be seen clearly;②osteonecrosis extent progress detectionruse improved Nishii method, concentric template measurement, pitch0.5mm, according to X-ray to determine the center of the femoral head double hip anteroposterior film, measured femoral radius r, according to the center vertical line of the femoral head, top center of the femoral head to the femoral head measured distance d, the Φ=r-d. degree of collapse was divided into3levels:A:<2mm; B:2-4mm; C>4mm.③necrosis repairment:(1) necrosis changes in bone mineral density;(2) position cystic (translucent zone) appeared;(3) crescent sign and distributed range;(4) sclerosis area whether blurred or disappeared.④head and acetabulum is harmonious relationship:(1) whether to keep the shape of the femoral head spherical shape;(2) whether to keep the head and acetabulum concentric relationship (Harris law).⑤joint stability:whether Shenton line continuous last follow-up.⑥necrosis sclerosis with distribution types:according to X-ray frog hardening area distribution:A type:continuity subchondral bone sclerosis; B:with the hardened zone but did not continue into the subchondral bone; C Type:discontinuity sclerosis extends to subchondral bone; D type:not sclerosis area formation.⑦degree of anterolateral column reconstruction:allograft fibula tip position, and its relationship with Subchondral bone or bone of the femoral head anterolateral column welded (subchondral bone density or even significantly increased trabecular continuity connected). Divided into four grades:excellent:the anterolateral column completely rebuilt, distal fibula completely within the first lateral column, distal fibular cortex frog bit fuzzy and with the surrounding bone are fully welded; good:50%of the anterolateral column reconstruction, fibula was in anteroposterior or lateral column, distal fibular cortex and surrounding bone partially welding at anteroposterior or frog-bit; poor:the anterolateral column reconstruction <50%, Anteroposterior and frog-bit the distal fibula is not in the lateral column, clear and distal fibular cortex and surrounding bone anteroposterior or frog-bit no welding.⑧reduction quality:refer to Garden proposed method that evaluate the quality of femoral neck fractures in1971, Garden index is divided into four-grades.1.4.3Clinical assessment①Harris score:reference Harris scoring system;②FPS-R pain scores;③SF-36scores (QOL).2Biomechanical and finite element study.2.1three-dimensional finite element model creation and analysis(1) obtain image data:get CT data of individual patients in DICOM format from clinical imaging workstation(2) use Mimics10.01software to build half of the pelvis and femur three-dimensional finite element model based on CT data(3) model validation:experiments to verify the validity of the model established in this study by using of pressure-sensitive tablets existing body of research and measurement of femoral articular cartilage contact pressure.(4) fracture type and surgical operations simulation:The type of fracture and surgical operations simulation based on biomechanical stability Pauwels classification system, and followed creation the fracture healing model.(5)femoral head necrosis model established after cannulated screw fixation or mordified surgical:use the above model, based on individual cases of femoral head necrosis, different types necrosis were reconstruction and necrosis location information in term of MRI data, reverse engineering, surface of the grid. Analog administered standing600N load carried for stress strain studied.3、Statistical analysis:The research data using SPSS18.0(SPSS Inc., USA) for statistical analysis of the relationship between fracture type, gender, age, quality of reduction and other single factor with the collapse of the femoral head necrosis,using chi-square test or fisher’s exact test; Measurement data were expressed as mean±standard deviation (±s), meanwhile, the normal distribution and homogeneity of variance simultaneously being test, if the homogeneity of variance using ANOVA, LSD test for pairwise comparison, if the heterogeneity of variance, using the Dunnett test; comparison between the independent group level data using parametric Wilcoxon test; multiple factors influence the prognosis of femoral neck fracture with Binary Logistic regression analysis. the femoral head Kaplan-Meier curves survival (hip replacement and femoral head collapse as endpoint,respectively) using the Log-rank test stratified analysis, a=0.05, two-tailed test, P<0.05was considered statistically significant. correlation analysis after the collapse of the femoral head necrosis, using spearman correlation coefficient analysis.Results1. experimental study:three-dimensional finite element solid model of osteonecrosis after femoral neck fracture created realistic and delicate, clean cut, its internal model validation bone structure is consistent with the physical structure for finite element analysis, the results reliable.2pre-collapse or early in collapse of osteonecrosis using the corresponding retention surgery on the femoral head can reduce or even prevent the collapse of progress, is a crucial period for the treatment of osteonecrosis. In this study, modified surgical treatment to prevent osteonecrosis of femoral neck fractures in young adults complicated by three-dimensional finite element analysis showed:after necrosis of femoral head necrosis cancellous bone stress decreased significantly, weight-bearing surface stress is mainly concentrated on the surface of the femoral head cortical bone, subchondral bone plate and deep junction of sequestrum with living bone stress around obviously focus and even larger range. screw combined fibular allograft s can be effectively dispersed necrosis aera surface localized stress, effective restoration of the mechanical conduction path, with the stress transmitted from the fibula and femur to the greater trochanter, reduce stress concentration around the necrotic area, effectively prevention of stress-induced collapse of the femoral head, so that the head necrosis stress distribution, beneficial to maintain the stability of the head, which will help osteonecrosis obtain sustained repair. screw and fibula combined into a unity, effectively against shear and torsion which can promote further healing better. In addition, we also found that the different type of femoral head necrosis after fracture complicated, two surgical stress distribution differentiate from each other. of Which Steinberg B type, stress distribution basically the same about modified surgical and screw fixation, no high stress concentration between them, stress was better conducted, and mechanical properties of the femoral head have no significant difference to the normal; SteinbergCl type, the stress concentration of screw fixation group is greater than the modified group in cancellous bone necrosis area, but from anterolateral femoral column cortical shell surface stress analysis, little difference between them, the normal vector drawing stress conduction, modified group is slightly better than the screw group, slightly worse than the normal group; SteinbergC2type, modified group both in terms of the mechanical conductive and stress of dispersion were significantly better than the screw fixation group, distal screw in the subchondral bone have a small range of greater stress concentration, which easily lead to fracture at the subchondral bone plate. However, according to the necrotic zone coronal profile analysis, screw bear and disperse stress poor in the necrotic areas, only stress concentration between the distal screw and its surrounding bone, and peak stress is much larger than the cancellous bone necrosis can withstand stress limit; The modified group had mild stress concentrated at the tip of the fibula, But its weight-bearing stress uniformly dispersed, benifit to maintain a stable head among various media, which will help sequester repair and effective conduction of stress, and fibula supporting the weight-bearing area of stress from the acetabulum, avoiding the risk of femoral head collapse caused by weight. In conclude, stress distribution has little effect between the two operation in SteinbergB type necrosis, For SteinbergCl, C2type necrosis, modified surgical operation can better restore femoral head stress pathways and can effectively rebuild the mechanical properties of anterolateral column, able to take the stress from loading zone and unloading in the region of cancellous bone necrosis, avoid stress concentration around the necrotic bone, alleviate or avoid femoral cortical bone shell rupture and cartilage folds occurs, thus avoiding collapse occurred in the mechanics.3Clinical studies:Through this group of patients in a retrospective follow-up, the author found that the modified procedure was not able to effectively reduce the rate of femoral head necrosis significently, necrosis rate was33.75%, slightly lower than the previous literature (37%to50%). In addition, in order to analysis the outcome of femoral head necrosis, the author further analysis27patients with femoral head necrosis,7cases (8.75%) with the femoral head collapse of which were occurred,5cases (6.25%) ultimately underwent THA. two of the five cases accepting THA experienced second surgery because of early failure of the surgery fixation. Surgical fixation of standards is important. In fact, the patients with THA because of the collapse of advanced arthritis was only three cases. The remaining20cases of patients with femoral head contour were good, the subsidence situation has not been found so far. According to the femoral head survival analysis (in joint replacement for the endpoint), fractures of femoral head for5years survival rate is higher. In addition, the analysis also found that the femoral head necrosis by Steinberg type C1and C2is most common, which of7cases with femoral head collapse were C1and C2type necrosis, The rate of the femoral head collapse risk was increased when the range of necrosis and femoral became larger and anterolateral column damage was apparent. Although collapse occurred in part of the rest of the patients. it was maintained well. The collapse of the femoral head was below4mm. Harris score was90.93±2.41and SF-36score was0.82±0.06, the excellent rate was93.75%. the harmonious relationship between head and acetabulum was maintained, there was no pain and discomfort, and the satisfaction of patients is good. Through the review of X-ray analysis again showed that patients with well-controlled collapse progress, its X-ray are showing well anterolateral femoral head column reconstruction. So, it confirmed the anterolateral column directly associated with femoral head collapse once again.The advantages of modified surgical can be summarized as followed:fibula is hollow Cortical bone, and has Moderate elastic modulus, its placement can provide Supporting role at Early stage, which Provide the time and space for repair of fractures and necrosis at the same time, this is Beneficial for vascular creeping substitution, and has a role in bone induction and bone conduction, Promote Sequestrum repairing in necrotic zone. Even the C2-type necrosis, anterolateral column of femoral head can be partially reconstructed because of Fibula placement, linitating the necrotic area as much as possible inside the loading area, Ensure the repair go on stability. There are same Stellate-shaped Welding phenomena presenting in Area between Necrotic area and the distal fibula,which represent The stability of Necrotic area in the femoral head, Meanwhile, early implantation of fibula embodies the "prevention before disease onset, preventing disease from exacerbating", the concept of traditional Chinese medicine, integrate the traditional Chinese medicine Microscopic dialectical and three-dimensional finite element of modern technology closely together. Precisely calculated using FEM and observed its microscopic bone changes of femoral head, detect The earliest risk of collapse after ONFH, Avoid blind area of macroscopic dialectical, Take timely and effective treatment options, Effectively control the occurrence and progression of collapse. Improved surgical can effectively avoid the collapse of the femoral head necrosis for SteinbergC2type, and can moderately controlled the progress of collapse, in order to without surgery of THA. Displaced femoral neck fractures have the greater chance to complicated by Cl, C2type necrosis.Therefore, modified surgical is a good choice for for young adults fresh fractures of the femoral neck, Especially Displacement fractures.Conclusion1. Three-dimensional finite element model establishment of femoral neck fracture complicated with femoral head necrosis are true and reliable; able to accurately determine the mechanical properties of different regions within the femoral head necrosis of the femoral head.2. Three-dimensional finite element analysis of osteonecrosis after femoral neck fracture in young adults, modified surgical had little stress interference within the femoral head, effectively reconstruction the mechanical transmission pathway, Fibula and screw can be scattered around the necrotic area of stress concentration, avoid the subchondral bone plate fracture, Femoral head overall stiffness increase, enhanced ability to resist deformation, effective in preventing the collapse of femoral head necrosis.3. Young and middle-aged femoral neck fracture complicated with femoral head necrosis is given priority to with SteinbergCl, C2type; modified surgical procedure can effectively avoid type C1necrosis collapse, control the progress of type C2necrosis after the collapse, Slow down or even avoid the joint replacement, has certain advantages in clinical efficacy4. Young and middle-aged undisplaced fractures can use pure cannulated screw internal fixation; modified surgical procedure for displaced femoral neck fracture is a good clinical choice as well;It really did the microcosmic syndrome differentiation." No collapse collapse prevention, has collapsed to prevent the progress".