| INTRODUCTIONPelvis is an important part of human trunk bone,and is also the primary site of bone and soft tissue tumors and other tumor metastases,most of them are malignant.Due to the deep location and complex surrounding structure of the tumor,limb salvage and reconstruction surgery for pelvic tumors,especially periacetabular tumors,has become one of the most difficult operations in the department of bone oncology.Although in recent years,with the development of surgical technique and prosthetic,scholars have put forward a lot of use of prostheses for pelvic tumor resection and reconstruction scheme,especially in recent years the emergence of three dimensional(3D)printed technology for clinical provides the new thought,but unfortunately,the higher the incidence of complications,less postoperative joint function,has yet to be effectively solved,Nearly half of patients with pelvic malignancy involving the acetabulum experience postoperative complications after resection and reconstruction,and dislocation is one of the most common complications.Dual-mobility hip prosthesis has been proved to have good effect of preventing the dislocation,in combination with the advantages and shortcomings of previous rebuilding scheme,especially the problem of high rate of postoperative hip joint dislocation,We improved the dual-mobility hip prosthesis,combined with the 3D-printed hemipelvic prosthesis,and applied the dual-mobility hemipelvic prosthesis in clinical practice.OBJECTIVETo investage the early clinical efficacy of dual-mobility hemipelvic prosthesis in pelvic tumor resection and reconstruction,and analyze its biomechanical characteristics to clarify the safety and clinical advantages of this prosthesis.MATERIALS and METHODSFollow-up survey of patients with pelvic tumors reconstructed with dual-mobility hemipelvic prosthesisA retrospective study was conducted on the case data of patients with pelvic tumor reconstructed with dual-mobility hemipelic prosthesis in our clinical center from 2017 to2021,and follow-up was conducted.MSTS 93 scoring system was used to evaluate the postoperative function of patients,and Kaplan-Meier method was used for survival analysis.The statistical software was SPSS 21.0.Gait analysis of patientsVicon 3D motion capture system was used for 3D gait analysis of two typical patients,and the spatiotemporal parameters of the patients’ walking gait and the 3D kinematic Angle parameters of pelvis and lower limbs in a gait cycle were obtained.The Graphpad software(8.0.2)was used to draw a graph and compare it with a normal standard gait.The control data were compared with the standard gait of normal people of similar size in the same measurement environment.The statistical software was SPSS(21.0)Finite element analysis of typical reconstruction modelThe postoperative pelvic finite element model of typical patients was established and input into the finite element analysis software.The Von Mises equivalent stress formula was used to analyze the stress distribution of each part of the pelvis under one gait cycle.A force of 500 N was applied along the longitudinal axis of the normal pelvis,the mechanical distribution of different phases was calculated and the axial pressure of 2000 N along the femoral prosthesis was applied to analyze the stress distribution at different angles of the hip joint.RESULTSFollow-up survey results of patients with pelvic tumorAll the 11 patients were followed up.By the last follow-up,9 of the 11 patients(81.8%)were still alive,and 2 patients had local tumor recurrence,with a recurrence rate of 18.2%.The complication rate was 18.2%,including 1 deep infection and 1 dislocation of artificial joint.Excluding 1 amputation patient,the average score of the remaining 8patients at the last follow-up was 21.4/30(71.3%)on the Musculoskeletal Tumor Society(MSTS93).There was no significant difference in postoperative functional scores between the 3 patients with zone II resection and reconstruction alone and the 5 patients with zone II + other areas resection and reconstruction(P >0.05).Gait analysis results of patientsThere was no significant difference in the ratio of support phase between the operated side and the healthy side,nor between the operated side and the control group.The surgical step length was shorter than that of the healthy side,but the difference was not statistically significant,and compared with the control group,the difference was statistically significant.Step speed,stride frequency,stride length and the proportion of double support phase in the patient group were all smaller than those in the control group,and the difference was statistically significant.The range of motion of the hip joint on the sagittal plane was smaller on the operated side than on the healthy side and the control group;the operative side abduction amplitude was greater than that of the healthy side and the control group,all the difference was statistically significant;on the horizontal plane,the average motion Angle of the operated side was smaller than that of the healthy side,and the difference was statistically significant,while the difference was not statistically significant compared with the control group.Pelvic movement Angle: on the sagittal plane,the average tilt amplitude was greater than that of the control group,but the difference was not statistically significant;on the coronal plane,the average movement Angle in patients group was higher than that in control group,and the difference was statistically significant;on the horizontal plane,the average motion Angle of the patient group changed significantly,but the difference was not statistically significant compared with the control group.Postoperative gait trend was similar to normal.Finite element analysis results of reconstruction modelsThe stress of each part of the reconstructed model is obviously different in different gait phases.The local stress peak on the reconstructed side is larger than that on the healthy side,and it is more obvious in the gait state from heel to toe.The stress concentration was mainly distributed at the junction between hemipelic prosthesis and screw and iliac bone on the resected side,and between femoral prosthesis stem and femoral bulb,while the stress of polyethylene lining was small.Before impact,the polyethylene lining will rotate at a small Angle,about 3°.The inner stress of polyethylene liner is greater than the outer stress in all conditions.In the process of flexion and adduction,the contact compressive stress peaks in the inner side of the polyethylene acetabulum gradually decreased and were all less than the yield strength of the polyethylene lining.The theoretical range of motion of the reconstructed hip joint is 130°.At this time,the stress concentration point on the outside of the polyethylene is still within the range of the metal acetabulum.The polyethylene liner has no tendency to slide out,and the compensation of the polyethylene liner is about 14° at this time.CONCLUSION1.It is a safe surgical method to perform post-resection reconstruction of pelvic tumors with dual mobility hemipelvic prosthesis,which can effectively prevent the occurrence of postoperative dislocation and show a high level of postoperative function.2.After systematic and standardized rehabilitation training,the gait trend of patients with dual-mobility hemipelic prosthesis was basically similar to that of normal people,indicating that the reconstruction program had good postoperative effect and the feasibility of rehabilitation plan.3.Biomechanical analysis of the dual-mobility hemipelvic prosthesis showed that the prosthesis had uniform force under normal walking state,stable structure,low risk of loosening fracture and wear,normal liquidity function of the dual-mobility bearing,the limit position could compensate for the range of motion,and the design of the prosthesis was safe and feasible. |
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