Fundamental Study And Clinical Application Of Hemiarthroplasty Assisted By Indivadual Navigation Templates

Objective:1. To investigate the three-dimensional geometry of the proximal humerus of Chinese people, provide theoretical basis for prosthetic design and surgical techniques of hemi-arthroplasty.2. To investigate the accuracy of the retroversion and height of a prosthesis in the cadaveric hemi-arthroplasty (HA) assisted by individual navigation templates.3. To investigate the treatment effect of hemi-arthroplasty (HA) assisted by individual navigation templates through the combination of computer-aided design and 3d printing technology.Methods:1. Three-dimensional computed tomography was performed on 60 shoulders. Bone tissue algorithm was used to reconstruct the three-dimensional CT images.Those images were processed and visualized with the Materials Mimics and Imageware software and the images were reconstructed in 1.25mm increments along the axis of the humerus body with 0.6mm interlayer distance, all of the parameters were calculated precisely by the software.2. We collected 9 adult cadaveric specimens(18 shoulders) raw CT data by DICOM format preoperatively, and reconstructed the proximal 3D anatomical model after pretreated these date with the Mimics 17.0.3D models were imported into Geomagic Studio 11.0 software to measure the humeral head retroversion and height of the humerus and design individual hemiarthroplasty-assisting templates. The physical navigational templates was build using a rapid prototyping (RP) technique to assist cadaveric HA. The best location of the prosthesis of whole adult cadavers was determined according to the templates. CT scans were performed postoperatively to evaluate the humeral head retroversion and height of the humerus of the positioning method.3.12 cases of proximal humeral fracture were admitted. All patients were examined by lamellar CT scan to harvest the original date of upper limbs. The retroversion and height of a prosthesis can be precisely determined in fractures of the proximal humerus according to the results of the contralateral measurement.The individual hemiarthroplasty-assisting templates was designed according to the results of computer aided measurement with the Materials Mimics and Geomagic Studio software.Physical templates was build using 3d printing technology. In the operation, the best location of the prosthesis was determined according to the templates, then we performed with bone cement fixation and rotator cuff repair. The retroversion and height of a prosthesis were measured through postoperative X-ray image of shoulder joint. The Neer score was used to evaluate the preoperative and postoperative functions of the shoulder joint.Results:1. The mean head diameter was (41.8±3.6)mm and (39.1±4.1)mm in frontal plane and sagittal plane respectively,the mean ratios of frontal sagittal head diameter 1.07± 0.08. The mean humerus head height and diameter of curvature was (17.2±1.8) mm and (44.9±4.6)mm respectively,the mean ratio of head height/radius curvature was 0.77±0.09> The mean retroversion angle and head shaft angle was (16.9±8.9)° and (128.4±4.2)° respectively, The mean medial offset and posterior offset was (5.1± 1.6)mm and (3.8±1.7)mm respectively. All the data of humerus was not significant differences in gender, has not fitted with the current prosthetic design and operational prescription.2. The mean error of humerus head height and retroversion angle was (1.44±0.96) mm and (0.25±0.15)° in the preoperative and postoperative,which was not significant differences in left and right side. The individual placement-assisting template is useful to implant placement accurately during the operation.3. All 12 patients were followed up form 10 to 34 months (average 16.8 months); the fracture union time was 3 to 4 months (average 3.4 months). According to the Neer score at the latest follow-up,8 cases is excellent,3 cases is good,1 cases is middle, and the rate of aboveaverage was 91.67%.Conclusions:1. Reconstruction of individual anatomical structures of shoulder plays an important role in improving function of the shoulder joint after shoulder arthroplasty because the shape of proximal humerus is complex and individual differences of the parameters is large.2. Individual navigation templates in hemi-arthroplasty can acquire a more accurate the retroversion and height of a prosthesis than conventional method.3. It can greatly improve the accuracy of implant placement and obtain better motion of shoulder joint designing individual placement-assisting templates through the combination of 3d printing technology and computer-aided design, and which provides a new simple and effective method for hemiarthroplasty in the treatment of proximal humeral fracture.