Introduction and Objective. The patients with a total hip arthroplasty is growing in world manly in Europe and USA, and this solution present a high success at 10years in several orthopaedic registers. The application of total press-fit hip fixation presents the most used solution, but presents some failures associated to the acetabular component fixation, associated to the load transfer and bone loss at long term. The aim of this work is to investigate the influence of different acetabular bone loss in the strain distribution in iliac bone. To evaluate implant fixation, an experimental study was performed using acetabular press-fit component simulating different acetabular bone loss and measuring the strain distribution. Materials and Methods. The experimental samples developed was based in an iliac bone model of Sawbones supplier and a acetabular component Titanium (Stryker) in a condition press-fit fixation and was implanted according surgical procedure with 45º inclination angle and 20º in the anteversion angle. Were developed five models with same initial bone, one with intact condition simulating the cartilage between bones and four with different bone loss around the acetabular component. These four models representing the evolution of bone support of acetabular components presented in the literature. The evolution of bone loss was imposed with a CAD CAM process in same iliac bone model. The models were instrumented with 5 rosettes in critical region at the cortical bone to measure the strain evolution along the process. Results. The results of strain gauges present the influence of acetabular component implantation, reducing the bone strains and presented the effect of the strain shielding. The acetabular component works as a shield in the load transfer. The critical region is the posterior region with highest principal strains and the strain effect was observed with different bone loss around acetabular component. The maximum value of principal strain was observed in the intact condition in the anterior region, with 950μ∊. In the posterior superior region, the effect of bone loss is more important presenting a reduction of 500% in the strains. The effect of bone loss is presented in the strains induced with acetabular implantation, in the first step of implantation the maximum strain was 950μ∊ and in the last model the value was 50μ∊, indicating lower press-fit fixation. Conclusions. The models developed allows study the effect of bone loss and acetabular implant fixation in the load transfer at the hip articulation. The results presented a critical region as the anterior-superior and the effect of strain shielding was observed in comparison with intact articulation. The results of press-fit fixation present a reduction of implant stability along bone loss. The process of bone fixation developed present some limitation associated to the bone adhesion in the interface, not considered. Acknowledgement. This work was supported by POCI-01-0145-FEDER-032486,– FCT, by the FEDER, with COMPETE2020 - (POCI), FCT/M

The computational modelling and 3D technology are finding more and more applications in the medical field. Orthopedic surgery is one of the specialties that can benefit the most from this solution. Three case reports drawn from the experience of the authors’ Orthopedic Clinic are illustraded to highlight the benefits of applying this technology. Drawing on the extensive experience gained within the authors’ Operating Unit, three cases regarding different body segments have been selected to prove the importance of 3D technology in preoperative planning and during the surgery. A sternal transplant by allograft from a cryopreserved cadaver, the realization of a custom made implant of the glenoid component in a two-stage revision of a reverse shoulder arthroplasty, and a case of revision on a hip prosthesis with acetabular bone loss (Paprosky 3B) treated with custom system. In all cases the surgery was planned using 3D processing software and models of the affected bone segments, printed by 3D printer, and based on CT scans of the patients. The surgical implant was managed with dedicated instruments. The use of 3D technology can improve the results of orthopedic surgery in many ways: by optimizing the outcomes of the operation as it allows a preliminary study of the bone loss and an evalutation of feasibility of the surgery, it improves the precision of the positioning of the implant, especially in the context of severe deformity and bone loss, and it reduces the operating time; by improving surgeon training; by increasing patient involvement in decision making and informed consent. 3D technology, by offering targeted and customized solutions, is a valid tool to obtain the tailored care that every patient needs and deserves, also providing the surgeon with an important help in cases of great complexity

Introduction. Total hip arthroplasties (THAs) in young patients are associated with high failure rates. We always use cemented total hip implants, however, in cases with acetabular bone stock loss we perform bone impaction grafting. Our purpose was to evaluate the outcome of 69 consecutive primary cemented total hips in patients younger than 30 years followed between 2 to 18 years. Methods. Between 1988 and 2004, 69 consecutive primary cemented THAs (mainly Exeters) were performed in 48 patients (32 women, 16 men) younger than thirty years. Average age at time of operation was 25 years (range, 16 to 29 years). Twenty-nine hips (42%) underwent acetabular bone impaction grafting because of acetabular bone loss. Mean follow-up was 10 years (range, 2 to 18 years). Revisions were determined, Harris Hip Score (HHS), and Oxford Hip Questionnaire Score (OHQS) were obtained and radiographs were analyzed. Survival was calculated using the Kaplan-Meier method. Results. No patients were lost to follow-up, but 3 patients (4 hips) died during follow-up, none of whom had underwent revision. Eight revisions were performed: 3 septic loosenings (6, 7, and 8 years post-operative) and 5 aseptic cup loosenings (2, 3, 4, 5, and 9 years post-operative). No stems were loose. The average HHS and OHQS at follow-up were 89 points (range, 55 to 100 points) and 19 points (range, 12 to 42 points), respectively. Using Kaplan-Meier analysis, the cumulative survival with revision for any reason as end point was 83% (95% CI, 69 - 92%) at 10 years. Excluding the infections, the survival rate was 90% (95% CI, 77 - 96%) with revision for aseptic loosening. The outcome of the patients who underwent acetabular bone impaction grafting was comparable to the primary cemented hips with a survival of 89% (95% CI, 62 - 97%) with revision for any reason as an end point. Excluding the infections, the survival rate was 95% (95% confidence interval, 72 - 99%) at ten years with revision for aseptic loosening as the end point. Conclusion. Primary cemented total hip arthroplasties in very young patients show satisfactory medium-term results, however, in cases with acetabular bone stock loss, a reconstruction with bone impaction grafting is advisable