Mimics Technology Simulate Total Knee Arthroplasty Of Distal Femur And Morphology Change In DDH Patients

Background:As the progress of medical technology, the diagnosis and treatments are improved for DDH. Numerous studies investigated the disease from different aspects, such as changes of the hip joint, pelvis, spine, mechanical axis of the lower limb. And for the commonest Lower-limb deformity, most researches obtained the results from X rays. Although these articles had get a series of results, they don’t proceed further systematic researches through CT and three-dimensional reconstructions. Valgus deformity of the DDH knees had been well proved, which was association with knee structural abnormalities. There, we used the three-dimensional reconstructions technology to investigate DDH patient’s knee joint morphology to obtain more detail data, which was significant for clinical staff in clinical practice. Purpose:Using Mimics technical reconstruction of DDH patients’ lower limb bony structure, further defined DDH patient’s distal femoral anatomic variations of the knee joint, for DDH patients correct lower limb mechanical axis and provide certain anatomical basis around the knee joint surgery. Allows the surgeon to fully recognize the DDH patient’s change on the lower limb deformity after total hip replacement and intervention as soon as possible, avoid postoperative complications. Methods Morphological analysis of 52 knee joints, including 24 cases of DDH ipsilateral knee joint(Disease group), 8 cases of DDH contralateral hip(Abnormal group), 20 cases of normal patients of knee joint(Normal group). CT images ranged from the iliac crest to 2 cm inferior to the tibial tuberosity. All CT images using Mimics technology reconstructed, resect the distal femur according to total knee replacement. Measure and analysis the distal femur’s parameters after bone resected : femur mediolateral(ML), lateral and medial anteroposterior(LAP MAP),anterior lateral condylar height(ALCH), anterior medial condylar height(AMCH). Results: Compared with normal group, the ML,LAP,MAP,AMCH,ALCH were smaller and have significantly difference of the disease group(P=0.025、P=0.004、P=0.000、P=0.001、P=0.025). Between the normal group and abnormal group, the LAP, MAP,ALCH have significantly difference and smaller than normal group(P=0.015、P=0.002 、 P=0.001). Compared with normal group, the aspect ratios of ML/MAP,LAP/MAP in disease group have significantly difference(P=0.002、P=0.000). Compared with normal group, the aspect ratios of ML/LAP,LAP/MAP in abnormal group have significantly difference(P=0.009、P=0.029). The aspect ratios of ML/LAP, ML/MAP, LAP/MAP significant difference with normal group. The parameters of ML、MAP 、 LAP 、 AMCH have obvious correlation with their own group and have significantly difference, meanwhile,the MAP is moderate associated with group(|r|=0.417,P=0.005、|r|=0.636,P=0.000、|r|=0.46,P=0.002、|r|=0.464,P=0.002). In disease group, the ML have obvious correlation with LAP、MAP、ALCH, including ML associated with LAP is a strong, the rest are moderate(|r|=0.629,P=0.001、|r|=0.552,P=0.005、|r|=0.500,P=0.013). Conclusions:This study suggested that DDH patients’ knee joint is difference with normal people, anterior condylar is significantly abnormal, femur condylar asymmetry also remained dysplasia. We supposed that DDH patient’s patellofemoral joint is abnormal, it also affects the patella at the same time. About contralateral knee of unilateral DDH patients, a part of its bone structure is abnormal. In clinical, if we plan for such patients proceed affected side hip or knee surgery, even if contralateral knee, that we should have careful preoperative planning for reconstruct the lower limb mechanical axis to avoid potential complications. If we plan proceed TKA surgery, to avoid intraoperative complications, we need measure the distal femur anatomic abnormal before operation. Considered of the difference with normal knee, to prevent the complications, these patients even through have special prosthesis design.