Introduction and Objective. The surgical strategy for acetabular component revision is determined by available host bone stock. Acetabular bone deficiencies vary from cavitary or segmental defects to complete discontinuity. For segmental acetabular defects with more than 50% of the graft supporting the cup it is recommended the application of reinforcement ring or ilioischial antiprotrusio devices. Acetabular reconstruction with the use of the antiprotrusion cage (APC) and allografts represents a reliable procedure to manage severe periprosthetic deficiencies with highly successful long-term outcomes in revision arthroplasty. Objective. We present our experience, results, critical issues and technical innovations aimed at improving survival rates of antiprotrusio cages. Materials and Methods. From 2004 to 2019 we performed 69 revisions of the acetabulum using defrosted morcellized bone graft and the Burch Schneider anti-protrusion cage. The approach was direct lateral in 25 cases, direct anterior in 44. Patients were re-evaluated with standard radiography and clinical examination. Results. Eight patients died from causes not related to surgery, and two patients were not available for follow up. Five patients were reviewed for, respectively, non-osseointegration of the ring, post-traumatic loosening with rupture of the screws preceded by the appearance of supero-medial radiolucency, post-traumatic rupture of the distal flange, post-traumatic rupture of the cemented polyethylene-ceramic insert, and dislocation treated with new dual-mobility insert. Among these cases, the first three did not show macroscopic signs of osseointegration of the ring, and the only areas of stability were represented by the bone-cement contact at the holes in the ring. Although radiographic studies have shown fast remodeling of the bone graft and the implant survival range from 70% to 100% in the 10-year follow up, the actual osseointegration of the ring has yet to be clarified. To improve osseointegration of the currently available APC whose metal surface in contact with the bone is sandblasted, we combined the main features of the APC design long validated by surgical experience with the 3D-Metal Technology for high porosity of the external surface already applied to and validated with the press fit cups. The new APC design is produced with the 3D-Metal technology using Titanium alloy (Ti6Al4V ELI) that Improves fatigue resistance, primary stability and favorable environment for bone graft ingrowth. We preview the results of the first cases with short-term follow up. Conclusions. Acetabular reconstruction with impacted morcellized bone graft and APC is a current and reliable surgical technique that allows the restoration of bone loss with a high survival rate of the implant in the medium to long term. The new 3D Metal Cage is designed to offer high friction for the initial stability. The high porosity of the 3D Metal structure creates a favorable environment for bone growth, thus providing valid secondary fixation reproducing the results achieved with the 3D metal press fit cup

Abstract. Objectives. Osteochondral grafting (OCG) is one treatment strategy for osteoarthritis with good clinical results. Decellularised tissues provide a promising alternative to standard autografts or allografts. This study aimed to compare the stability of traditional OCG and decellularised scaffolds upon initial implantation. Methods. Host cubes (N=16) were extracted from porcine femoral condyles around an artificial defect hole. Grafts (N=11) were harvested from the trochlear groove; porcine decellularized osteochondral scaffold (N=5) were prepared. Each host was secured in fixtures and submerged in PBS at 37 ºC. Each graft or scaffold was press fit into one of the hosts, then pushed in for 5 mm, using an indenter (Instron3365) and pushed out in the opposite direction for 10 mm. Parameters analysed were the force required to initiate movement (Dislodging Force) and the maximum force (Max Force). Results. The Dislodging Force of grafts (mean ± std. dev) was 133±15 N for the push in test and 109±11 N for the push out test. This was significantly higher than values for scaffolds: IN 24±1 N and OUT 26±5 N. The Max Force were also larger in the grafts than the scaffolds: IN 152±16 N vs. 41±4 N and OUT 118±14 N vs. 33±3 N. Conclusions. The force required to dislodge a graft or scaffold from a host environment was similar for the push in test and the push out test, suggesting it is a good measure of initial stability. Upon initial implantation, the decellularised scaffolds were easier to dislodge than the OCG. Previously, the decellularisation process was found to soften bone, relative stiffness may thus be an important consideration in graft fixation. A greater press fit may be necessary for decellularised scaffolds in order to achieve the same level of graft stability as natural OCG when used in vivo. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Positioning of the hip resurfacing is crucial for its long term survival and is critical in young patients for some reasons; manly increase the wear in the components and change the load distribution. THR have increased in the last years, mainly in young patients between 45 to 59 years old. The resurfacing solution is indicated for young patients with good bone quality. A long term solution is required for these patients to prevent hip revision. The resurfacing prosthesis Birmingham Hip Resurfacing (BHR) was analyzed in the present study by in vitro experimental studies. This gives indications for surgeons when placing the acetabular cup. One synthetic left model of composite femur (Sawbones®, model 3403), which replicates the cadaveric femur, and four composite pelvic bones (Sawbones®, model 3405), were used to fix the commercial models of Hip resurfacing (Birmingham model). The resurfacing size was chosen according to the head size of femurs with 48 mm head diameter and a cup with 58 mm. They were introduced by an experimented surgeon with instrumental of prosthesis. The cup is a press fit system and the hip component was cemented using bone cement Simplex, Stryker Corp. The acetabular cup was analyzed in 4 orientations; in anteverion with 15º and 20°; and in inclination 40 and 45°. Combinations of these were also considered. The experimental set-up was applied according to a system previously established by Ramos et al. (2013) in the anatomic position. The femur rotates distally and the Pelvic moves vertically as model changes, such that the same boundary conditions are satisfied. This system allows compensating motions of the acetabular cup orientation. A vertical load of 1700 N was applied on all cases, which have resulted in joint reaction force of 2.4 kN. The femur and iliac bone was instrumented with rosettes. 5 repetitions at each position were conducted. When the femur was instrumented with three rosettes in medial, anterior and posterior aspect, the maximum strain magnitude was observed in the medial aspect of femur with a minimum principal strain of −2070µε for 45° inclination and 20° of anterversion. The pubic region was found most critical region after instrumenting the Iliac bone with four rosettes, with a minimum principal strain around −2500µε (rosette 1), for the 45° inclination and 20° of anterversion. We have observed the great influence of the inclination on the strain distribution, changing its magnitude from compression to traction in different bone regions. The minimum principal strain is more critical in medial aspect of the femur and the influence of strain is about 7% when orientation and inclination change. The maximum influence was observed in the anterior aspect, where the anteversion presents a significant influence. The results show the interaction between inclination and anterversion in all aspects, being observed lower values in lower angles. The orientation of the acetabular cup significantly influences the strain distribution on the iliac surface. Besides, as anterversion increases, more strains are induced, mainly in the region of iliac body (rosette 3)

Background. Thrust plate prosthesis (TPP) is a bone conserving prosthesis in use for over thirty years. TPP is a stemless and uncemented femoral prosthesis fixed at the lateral femoral cortex with a bolt, plate and screw. This has a metal-on-metal articulation with a 28mm Metasul head and Allofit press fit acetabular cup. Our study aimed to assess the functional outcome of this prosthesis. Methods. In our institution 234 TTPs were implanted between 1995 and 2005. All patients completed a self-assessed questionnaire of Harris Hip Score at 2 months, 1 year, and then yearly. Only those who had a follow up was within the last two years were included in the analysis. 76 patients who had failed to satisfy the criteria were excluded. Of the 158 hips in the study 75 hips were in male patients and 83 were in female patients. The median age of patients was 52 years (range 15 to 82). 75 hips were on the right side and 83 on the left. All patients were operated by the senior author or a senior trainee under his supervision (seven hips). Revision of the implant or decision to revise was taken as the end point of our study. Results. The median time to follow up was 7 years (range 1 to 15). The median pre-operative hip score was 43 (range 3 to 77) which rose to 83 points (range 11 to 100) at the latest follow up. Median hip score in females improved from 39 to 82 points and in males from 52 to 85 points. Twelve patients underwent revision surgery either for infection or aseptic loosening. Conclusion. The Thrust Plate Prosthesis had a good outcome with an increase in hip score of 40 points and a median survival of 7 years

Objectives

Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient’s surrounding tissues.

Objectives

Microindentation has the potential to measure the stiffness of an individual patient’s bone. Bone stiffness plays a crucial role in the press-fit stability of orthopaedic implants. Arming surgeons with accurate bone stiffness information may reduce surgical complications including periprosthetic fractures. The question addressed with this systematic review is whether microindentation can accurately measure cortical bone stiffness.