Virtual Study On Relevance Between Prosthesis Position And Joint Impingement In Daily Activities After Total Hip Replacement

Objective: To create a three-dimensional hip joint solid model incomputer virtual environment, so as to virtualize total hip replacementsurgery and place prosthesis in different combined positions. Thepostoperative joint movement process was simulated in order to measure theeffective hip range of motion with different combined prosthesis positionsbefore impingement during exercise, to identify the relative position range ofthe prosthesis meeting the daily activities, so as to guide the intraoperativeprosthesis placement and postoperative joint activities, to provide atheoretical basis for further virtual surgery study.Methods: Based on the CT scan data of pelvis and femur of thevolunteer, a three-dimensional hip solid model was established by MIMICSand UG software; After the preparation of digital measurement template, theartificial hip prosthesis model was identified by preoperative measurementfor the establishment of corresponding model size of three-dimensionalprosthesis solid model to complete preoperative preparation; Referring toactual surgical procedures of total hip replacement, the total hip arthroplastywas virtualized by UG software for the reconstruction of the hip center ofrotation, the femoral offset and head height; By repeating virtual surgicalprocedures, the prosthesis was placed in different combined positions tosimulate four directions of motions such as joint flexion, extension, externalrotation and internal rotation at90°flexion. Through measuring the maximum range of motions of the joint before impingement, the relativeposition range of the prosthesis meeting the daily activities was concluded.Results: The three-dimensional hip joint solid model was built, thevirtual total hip joint replacement and simulation process of postoperativejoint motion were successfully completed; the increase/decrease of theacetabular abduction angle may cause increase/decrease of range of motionon joint flexion, extension and internal rotation at90°flexion after total hipreplacement, and relatively small affect on external rotation; theincrease/decrease of acetabular and femoral anteversion angle may causeincrease/decrease of range of motion on joint flexion, and internal rotation at90°flexion, but the opposite on joint extension and external rotation; In orderto avoid hip impingement in daily activities, the acetabular anteversionshould be appropriately decreased/increased if the acetabular abductionangle was increased/decreased, the appropriate acetabular anteversion angleshould be smaller than or equal to22°, while the appropriate femoralanteversion should be larger than or equal to20°; if the femoral anteversionis smaller than20°, the acetabular anteversion and abduction should beappropriately increased.Conclusion: Computer modeling, virtual surgery and motion simulationcan instead the actual surgery study in some degree and have certainadvantages. These data can guide the determination of the placement of theprosthesis correctly in initial total hip replacement or revision surgery, insuch way, even if one side of prosthesis position is malposition, the range ofjoint motion can be increased before impingement in daily activities throughappropriately adjusting the position of the other side of prosthesis. However,the range of motion can’t be improved through adjusting the position of thecontralateral prosthesis if serious malposition happens in one side ofprosthesis. In addition, these data are also significant to guide the daily joint motion range for the patients who had poor prosthesis position but goodfixation or got artificial joint dislocation postoperatively, which can avoidrepeated dislocation and delayed revision surgery time.