Introduction. Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight- bearing surfaces in total joint replacement. However, the wear of UHMWPE in knee and hip prostheses after total joint replacement is one of the major restriction factors on the longevity of these implants. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear of UHMWPE. A number of studies have investigated the factors influencing the wear of UHMWPE acetabular cup liner in hip prosthesis. Most of these studies, however, have focused on the main articulating surfaces between the femoral head and the polyethylene liner. Materials and Methods. In a previous study (Cho et al., 2016), the generations of cold flow into the screw holes in the metal acetabular cup were observed on the backside of the retrieved UHMWPE acetabular cup liners as shown in Figure 1. We focused on the screw holes in the metal acetabular cup (Figure 2) as a factor influencing the wear behavior of polyethylene liner in hip prosthesis. In this study, computer simulations of the generation of cold flow into the screw holes were performed using the finite element method (FEM) in order to investigate the influence of the screw holes in the metal acetabular cup on the mechanical state and wear behavior of polyethylene liner in hip prosthesis. Results. An example of the results of the FEM simulations performed in this study is shown in Figure 3. In the region which the cold flow into the screw holes occurred, it was found that locally high contact stresses which exceed the yield stress of UHMWPE and considerable plastic strains were generated throughout the overall thickness between the backside and top surface of the polyethylene liners. On the contrary, in the case of the polyethylene liner combined with the metal acetabular cup without screw hole, although the regions of high contact stress and high plastic strain had a tendency to be limited around contact surface compared with those of the combination with screw holes, the values of contact stress and plastic strain were lower than the combination with screw holes. Discussion and Conclusions. The results of this study suggest that the cold flow generated by the existence of the screw holes in the metal acetabular cup of hip prosthesis reduces the wear resistance of the UHMWPE acetabular cup liner. It would appear that the cold flow into the screw holes contributes to structural weakening of the UHMWPE and reduction of the polyethylene thickness, thus increase of internal stresses and plastic strains in and around the regions of cold flow. Therefore, it is required that improvement of the screw holes in the metal acetabular cup and/or improvement of fixation method of the metal acetabular cup to a pelvis in order to enhance the wear resistance of the polyethylene liner. For any figures or tables, please contact authors directly

Aims. The aim of this study was to optimize screw hole placement in an acetabulum cup implant to improve secondary initial fixation by identifying the region of thickest acetabulum bone. The “scratch fit” of modern acetabular cup implants with highly porous coatings is often adequate for initial fixation in primary total hip arthroplasty. Initial fixation must limit micromotion to acceptable levels to facilitate osseointegration and long term cup stability. Secondary initial fixation can be required in cases with poor bone quality or bone loss and is commonly achieved with bone screws and a cup implant with multiple screw holes. To provide maximum secondary initial fixation, the cup screw holes should be positioned to allow access to the limited region of thick pelvic bone. Patients and Methods. Through a partnership with Materialise, a statistical shape model of the pelvis was created utilizing 80 CT scans (36 female, 44 male). To limit the effect of variation outside the area of cup implant fixation, the shape model includes only the inferior pelvis (cut off at the greater sciatic notch and above the anterior inferior iliac spine). A virtual implantation protocol was developed which creates instances of the pelvis shape model that accurately simulate the intraoperative reaming of the acetabulum to accept the cup implant. First a sphere is best fit to the native acetabulum and the diameter is rounded to the nearest whole millimeter. The diameter of the best fit sphere is increased by 1mm to simulate bone removal during the spherical reaming procedure. The sphere is translated medially and superiorly such that it is tangent to the teardrop and removes 2mm of superior acetabulum. The sphere is used to perform a Boolean subtraction from the shape model to create a virtually reamed pelvis shape model. The Materialise 3-Matic software was used to perform a thickness analysis of the prepared shape models. The output of the thickness analysis is displayed as a color “heat map” where green represents thin bone and red is thick bone. The region of thickest bone was identified and used to drive ideal screw hole placement in the cup implant to access this region. Results. The analysis finds there is a limited arc of thick bone in the acetabulum that begins superiorly and extends posterior-inferior that accounts for only about 15% of total reamed surface area. Maximum screw purchase is provided when screw holes in the cup implant are placed over this limited region of thick bone. The thickest bone, located superiorly, facilitates the placement of a long bone screw up the iliac column and the posterior-inferior region of thick bone facilitates the placement of additional posterior screws. Conclusion. The shape model development, virtual implantation protocol, and heat map thickness analysis allowed the placement of bone screw holes directly over the limited region of thick pelvic bone. This allows maximum screw purchase which is important in achieving adequate secondary initial fixation with bone screws. Disclaimer. Author is an engineer employed by DJO Surgical who funded this study

Introduction. Wear phenomenon of ultra-high molecular weight polyethylene (UHMWPE) in hip and knee prostheses is one of the major restriction factors on the longevity of these implants. In retrieved hip prostheses with screw holes in the metal acetabular cup for fixation to the pelvis, the generation of cold flow into the screw holes is frequently observed on the backside of the UHMWPE acetabular cup liner. In most retrieved cases, the protruded areas of cold flow on the backside were located on the reverse side of the severely worn and deformed surface of the polyethylene liner. It would appear that the cold flow into screw holes contributes to increase of wear and damages of the polyethylene liner in hip prosthesis. Methods. In a previous study (Cho et al., 2016), we pointed out the generation of cold flow into the screw holes on the backside of the retrieved UHMWPE acetabular cup liner as shown in Figure 1. The primary purpose of this study was to investigate the influence of the cold flow into the screw holes on the wear of the polyethylene liner in hip prosthesis. In this study, computer simulations of the generation of cold flow were performed using the finite element method (FEM) in order to propose the design criteria about the cold flow of the hip prosthesis for improving the wear resistance of the polyethylene liner. We especially focused on the influence of polyethylene thickness and contact surface conformity on the generation of cold flow into the screw hole. Results. An example of the results of a series of the FEM simulations performed in this study is shown in Figure 2. This figure shows the distributions of the contact stress in the polyethylene liners. The graphs shown in Figure 3 are the summary of results of a series of the FEM simulations performed in this study. The graph in Figure 3(a) shows the changes in the maximum contact stress in the polyethylene liner with the thickness of polyethylene liner. The graph in Figure 3(b) shows the changes in the maximum contact stress in the polyethylene liner with the radial clearance between the femoral head and the polyethylene liner. Discussion and Conclusions. It was found that the magnitudes of cold flow and maximum contact stress in the polyethylene liner had a tendency to increase with decreasing the thickness of polyethylene liner. It was also found that the magnitude of cold flow and maximum contact stress in the polyethylene liner had a tendency to increase with increasing the radial clearance between the femoral head and the polyethylene liner. The results of this study suggest that polyethylene thickness and contact surface conformity have a significant influence on the generation of cold flow into the screw holes and wear of the polyethylene liner. For any figures or tables, please contact authors directly

Aims. The aim of this study was to present the first retrieval analysis findings of PRECICE STRYDE intermedullary nails removed from patients, providing useful information in the post-market surveillance of these recently introduced devices. Methods. We collected ten nails removed from six patients, together with patient clinical data and plain radiograph imaging. We performed macro- and microscopic analysis of all surfaces and graded the presence of corrosion using validated semiquantitative scoring methods. We determined the elemental composition of surface debris using energy dispersive x-ray spectroscopy (EDS) and used metrology analysis to characterize the surface adjacent to the extendable junctions. Results. All nails were removed at the end of treatment, having achieved their intended lengthening (20 mm to 65 mm) and after regenerate consolidation. All nails had evidence of corrosion localized to the screw holes and the extendable junctions; corrosion was graded as moderate at the junction of one nail and severe at the junctions of five nails. EDS analysis showed surface deposits to be chromium rich. Plain radiographs showed cortical thickening and osteolysis around the junction of six nails, corresponding to the same nails with moderate – severe junction corrosion. Conclusion. We found, in fully united bones, evidence of cortical thickening and osteolysis that appeared to be associated with corrosion at the extendable junction; when corrosion was present, cortical thickening was adjacent to this junction. Further work, with greater numbers of retrievals, is required to fully understand this association between corrosion and bony changes, and the influencing surgeon, implant, and patient factors involved. Cite this article: Bone Jt Open 2021;2(8):599–610

Introduction. Ultra-high molecular weight polyethylene (UHMWPE) is the sole polymeric material currently used for weight- bearing surfaces in total joint replacement. However, the wear of UHMWPE and the polyethylene wear debris generated in the human body after total joint replacement cause serious clinical and biomechanical reactions. Therefore, the wear phenomenon of UHMWPE in total joint replacement is now recognized as one of the major factors restricting the longevity of these implants. In order to minimize the wear of UHMWPE and to improve the longevity of artificial joints, it is necessary to clarify the factors influencing the wear mechanism of UHMWPE. Materials and Methods. The wear and/or failure characteristics of 33 retrieved UHMWPE acetabular cup liners of hip prostheses were examined in this study. The retrieved liners had an average in vivo duration of 193.8 months (75 to 290 months). Several examples of the retrieved liners are shown in Figure 1. The elasto-plastic contact analyses between metal femoral neck and polyethylene liner and between metal femoral head and polyethylene liner using the finite element method (FEM) were also performed in order to investigate the factors influencing the wear and/or failure mechanism of the polyethylene liner in hip prosthesis. Results. In the examination of the retrieved polyethylene liners, the generation of component impingement was observed in 24 cases of the 33 retrieved liners (72.7%) as shown in Figures 1(a) and (b). In addition, the generation of cold flow into the screw holes in the metal acetabular cup was observed in 27 cases of the 33 retrieved liners (81.8%) as shown in Figures 1(c) and (d). Several examples of the results of the FEM contact analyses are shown in Figure 2. In the simulation of the component impingement, it was found that high contact stresses which exceed the yield stress of UHMWPE and considerable plastic strains occurred in the rim of the polyethylene liner as shown in Figures 2(a) and (b). In the simulation of the cold flow, it was found that the stress concentration near the edge of screw hole has significant influence on the states of contact stresses and plastic strains in the surface and undersurface (backside) of the polyethylene liner as shown in Figures 2(c) and (d). Discussion and Conclusions. In this study, we focused on the impingement between the metal femoral neck and the polyethylene liner and the cold flow into the screw holes on the backside of the polyethylene liner as the factors influencing the wear and/or failure of the UHMWPE acetabular cup liner in hip prosthesis. The results of these retrieval and analytical studies confirmed that the component impingement and the cold flow into the screw holes contribute to increase of wear and/or failure of the polyethylene liner. Therefore, it is necessary to improve resistance to the component impingement and the cold flow in order to decrease the wear and/or failure of the UHMWPE acetabular cup liner and to increase the longevity of hip prosthesis. For any figures or tables, please contact authors directly

The accuracy of pedicle screw placement is essential for successful spinal reconstructive surgery. The authors of several previous studies have described the use of image-based navigational templates for pedicle screw placement. These are designed based on a pre-operative computed tomographic (CT) image that fits into a unique position on an individual's bone, and holes are carefully designed to guide the drill or the pedicle probe through a pre-planned trajectory. The current study was conducted to optimise navigational template design and establish its designing method for safe and accurate pedicle screw placement. Thin-section CT scans were obtained from 10 spine surgery patients including 7 patients with adolescent idiopathic scoliosis (AIS) and three with thoracic ossification of the posterior longitudinal ligament (OPLL). The CT image data were transferred to the commercially available image-processing software and were used to reconstruct a three-dimensional (3D) model of the bony structures and plan pedicle screw placement. These data were transferred to the 3D-CAD software for the design of the template. Care was taken in designing the template so that the best intraoperative handling would be achieved by choosing several round contact surfaces on the visualised posterior vertebral bony structure, such as transverse process, spinous process and lamina. These contact surfaces and holes to guide the drill or the pedicle probe were then connected by a curved pipe. STL format files for the bony models with planned pedicle screw holes and individual templates were prepared for rapid prototype fabrication of the physical models. The bony models were made using gypsum-based 3D printer and individual templates were fabricated by a selective laser melting machine using commercially pure titanium powder. Pedicle screw trajectory of the bony model, adaptation and stability of the template on the bony model, and screw hole orientation of the template were evaluated using physical models. Custom-made titanium templates with adequate adaptation and stability in addition to proper orientation of the screw holes were sterilised by autoclave and evaluated during surgery. During segmentation, reproducibility of transverse and spinous processes were inferior to the lamina and considered inadequate to select as contact surfaces. A template design with more bone contact area might enhance the stability of the template on the bone but it is susceptible to intervening soft tissue and geometric inaccuracy of the template. In the bony model evaluation, the stability and adaptation of the templates were sufficient with few small round contact surfaces on each lamina; thus, a large contact surface was not necessary. In clinical patients, proper fit for positioning the template was easily found manually during the operation and 141/142 screws were inserted accurately with 1 insignificant pedicle wall breach in AIS patient. This study provides a useful design concept for the development and introduction of custom-fit navigational template for placing pedicle screws easily and safely

Introduction. Acetabular revision surgery remains a technically demanding procedure with higher failure rates than primary total hip arthroplasty (THA). An acetabular component with three dimensional porous titanium and anatomic screw holes (Figure 1) was designed to allow the cup to be positioned anatomically and provide reliable fixation. Methods. A prospective multicenter study of 193 cases (190 patients) was conducted to assess the midterm clinical outcomes of the revision titanium acetabular shell. Radiographs, demographics, Harris Hip Score (HHS), and Short Form 36 (SF-36) were collected preoperatively, at 6 weeks, 3 months, and annually thereafter to 5 years. The mean duration of follow-up was 3.36 years. The Paprosky classification was assessed intraoperatively. Short Form 6D (SF-6D) utility values were obtained by transforming SF-36 scores through the Brazier method and were analyzed for effect size. Results. At time of surgery, mean patient age was 63.5 years and mean BMI was 28.1. 69 of the 193 cases were graded as 3A or 3B according to the Paprosky classification method. For all cases, Harris Hip Scores improved significantly (p < 0.001) from a preoperative mean score of 53.60 to a mean score of 86.15 at 1 year. These significant gains were maintained through 5 years, with a mean score of 87.35 at the 5-year time point. The Harris Hip Scores for Paprosky 3A and 3B cases also improved significantly (p < 0.001) from a preoperative mean score of 48.11 to a mean score of 85.45 at 1 year. These significant gains were maintained through 5 years, with a mean score of 85.65 at the 5-year time point. Among the radiographs independently reviewed to date, no cup migration or unstable cups have been identified. There were 12 acetabular shell re-revisions reported, for infection (7), aseptic loosening (4) and recurrent dislocation (1). Three of the cases revised for aseptic loosening were Paprosky type 3A, and one was 3B. For all cases, a clinically significant improvement in health utility was achieved by 3 months postoperative, with an effect size of 0.54. Clinically significant scores were maintained throughout the follow-up period, reaching an effect size of 0.64 at 5 years. Effect sizes were larger for cases with Paprosky classifications of 3A and 3B than the overall study population at all time points, reaching clinical significance at 3 months with an effect size of 0.64, and continuing to increase to an effect size of 1.19 at 5 years. Conclusion. Even in patients with severe acetabular defects, next generation highly porous acetabular components with three dimensional porous titanium and anatomic screw holes provide excellent stability, predictable midterm biologic fixation, pain, and reduction, and improved clinical function and health utility

Introduction. Open wedge high tibial osteotomy (OWHTO) is an operation by the proper load re-distribution in the treatment for medial uni-compartmental arthritis of the knee joint. However, for the proper load re-distribution, stable fixation is mandatory. For the stable fixation, plate should be contoured to the bony surface and screws should be inserted from the central area of the medial side to the hinge area of the lateral side in the proximal fragment because most failures occur at the relatively lesser supported lateral hinge area. Therefore, the purpose of this study was to evaluate the screw insertion angle and orientation that is inserted to the direction of the lateral hinge with an anatomical plate that is post-contoured with a surface geometry of the proximal tibia after the OWHTO. The hypothesis of this study was that the position and orientation would be different according to the correction degree (median value 10 mm) and surgical technique (uni-planar vs bi-planar). Materials and Methods. Thirty-one uni-planar and thirty-eight bi-planar osteotomies were evaluated. Postoperative CT data obtained after OWHTO were used for the 3D reconstruction of the proximal tibia. Anterior dimension (L1) and posterior dimension (L2) of the proximal tibia were measured in sagittal plane from tibial spine. Screw insertion points using four holes were even distributed using L1 and L2 value. As screw insertion angle was set from four holes to lateral hinge of the ‘Safe Zone’. Those four angles were measured in the axial and coronal plane. These were compared according to the correction degree and surgical technique. Results. Anterior AP dimension ‘L1'and posterior AP dimension ‘L2'were measured 24.0 ± 3.7 mm, 22.6 ± 3.1 mm. Angulations of screw from respectively screw hole to lateral hinge were measured 11.3 ± 1.7°, 3.5 ± 1.3°, 3.1 ± 1.5°, and 9.5 ± 1.1° in the axial plane and 81.5 ± 6.0°, 101.5 ± 2.6°, 90.8 ± 3.7°, and 99.2 ± 2.8° in coronal plane, respectively. None of the comparisons were statistically different, regardless of the correction degree and operative technique (Table1). Conclusions. Range of screw angulation showed regular pattern according to the site of the screw hole and it was not different, regardless of the correction degree and operative technique. This study provided range of the screw angulation by the anatomical surface modeling. Future study would give additional benefit for the optimal screw angle and stability such as finite element analysis or other methods

There are many types of articulating surfaces in uncemented acetabular cups. Most of the designs currently available are modular, with the shell snapping into a locking mechanism of some type. An Elliptical Monoblock design has been available for 15 years and was originally made of titanium with a factory assembled compression molded polyethylene liner. Porous tantalum (trabecular metal) was used as the shell material in a subsequent more recent design and in this design the polyethylene is actually molded directly into the tantalum framework. Monoblock acetabular components do not allow particulate access to the ilium via screw holes and require no surgeon assembled locking mechanism which may increase backside wear and metallic debris. There are no holes in the socket because of the monoblock construct. Because of this absence of screw holes there is an inability to visualise the floor of the acetabulum and perfect coaptation between the shell and the acetabular floor may not occur. The presence of dome gaps of greater than 1.5mm have been noted in 5% of these components but these have not compromised implant stability and in a review of over 600 cups there has been no change in implant position. The Elliptical shape of the cup makes the mouth of the acetabular component 2mm greater than the dome so that an exceptionally strong acetabular rim fit results. Results will be reported from two major institutional series with a minimum 10-year follow-up (range 10–15 years). No pelvic osteolysis was not seen in any patient in either series. In the HSS series of 250 cases with minimum 10 year follow up there were 4 revisions for instability but none for mechanical failure. There were three femoral revisions for loosening but the cup was intact and not revised in these patients. Utilising the Livermore measurement method polyethylene wear averages 0.8mm per year (0.6mm-1.3mm) and there have been no revisions for wear. Radiographic evaluation demonstrates stable bony interface in all patients. In a Mayo series of prospectively randomised patients also at minimum 10 years there was no lysis and only one case of aseptic loosening in a beaded titanium cup. At minimum 10-year follow up two similar elliptical monoblock cementless acetabular component designs with compression molded polyethylene have confirmed the theoretical advantages of this design concept and demonstrate long term results that have been excellent to date

Introduction. A variety of porous coatings and substrates have been used to obtain fixation at the bone-implant interface. Clinical studies of porous tantalum, have shown radiographically well-fixed implants with limited cases of loosening. However, there has been limited retrieval analysis of porous tantalum hip implants. The purpose of this study was to investigate factors affecting bone ingrowth into porous tantalum hip implants. Methods. 126 porous tantalum acetabular shells and 7 femoral stems, were collected under an IRB-approved multicenter retrieval program. Acetabular shells that were grossly loose, cemented or complex revisions were excluded. Shells with visible bone on the surface were chosen. 20 acetabular shells (10 primary) and all femoral stems were dehydrated, embedded, sectioned, polished and bSEM imaged (Figure-1). Main shell revision reasons were infection (n=10,50%), femoral loosening (n=3,15%) and instability (n=3,15%). Analyzed implants were implanted for 2.3±1.7 years (shells) and 0.3±0.3 years (stems). Eight slices per shell and 5–7 slices per stem were analyzed. The analysis included bone area/pore area (BA/PA), BA/PA zonal depth analysis, extent of ingrowth and maximum depth of bone ingrowth. BA/PA zone depths were: Zone-1 (0–500um), Zone-2 (500–1000um) and Zone-3 (1000um-full depth). Nonparametric statistical tests investigated differences in bone measurements by location within an implant and implant type (Friedman's Variance and Kruskal-Wallis). Post-hoc Dunn tests were completed for subsequent pairwise comparisons. Spearman's rank correlation identified correlations between bone measurements and patient related variables (implantation time, age, height, weight, UCLA Activity Score). Statistical analyses were performed using PASW Statistics package. Results. BA/PA was not significantly different between acetabular shells (3.6±3.3%) and femoral stems (5.8% ± 3.9%, p=0.068). Extent of ingrowth was similar between shells (42 ± 28%) and stems (47±26%, p=0.825). Acetabular shells (76±23%) and stems (82±23%, p=0.707) had a similar maximum ingrowth depth. There were 9 shells and 2 stems (Figure-2) with full bone ingrowth into the porous tantalum substrate. When bone did not bridge the entire depth, a superficial layer of dense trabecular bone integrated with the porous layer was often observed. Localized regions of increased ingrowth were observed around screw holes. BA/PA in the superior region (4.1±2.4%) of the acetabular shells was significantly higher than in the inferior region (2.0±2.1%, p=0.047, Figure-3). Acetabular shells BA/PA in Zone-1(10.8%) was significantly higher than Zone-2 (4.9%, p=0.013) and Zone-3 (1.6%, p<0.001). BA/PA was significantly higher in Zone-1 (10.8%) than Zone-3 (2.3%, p=0.043) for femoral stems. There were no correlations between patient variables and bone measurements. Discussion. Our results demonstrate that bone ingrowth in porous tantalum hip components is concentrated in the superficial 500 um (Zone-1). This may provide the opportunity to reduce the thickness of the porous layer thus conserving more bone in future designs. Bone ingrowth in the acetabular shells was preferentially located around screw holes and superior region, similar to previous studies of other cementless designs. Only 40% of analyzed acetabular shells had implantation times greater than 2 years. Further work focused on longer term retrievals will increase understanding of the bone-implant interface. This study was supported by Zimmer and NIH (NIAMS) R01 AR47904

Background. Stress fractures at tracker after computer navigated total knee replacement are rare. Periprosthetic fracture after Minimally Invasive Plate Osteosynthesis (MIPO) of stress fracture through femoral tracker is unique in orthopaedic literature. We are reporting this unique presentation of periprosthetic fractures after MIPO for stress fracture involving femoral pin site track in computer assisted total knee arthroplasty, treated by reconstruction nail (PFNA). Methods. A 75-year old female, who had computer navigated right total knee replacement, was admitted 6 weeks later with increasing pain over distal thigh for 3 weeks without trauma. Prior to onset of pain, she achieved a range of movements of 0–105 degrees. Perioperative radiographs did not suggest obvious osteoporosis, pre-existent benign or malignant lesion, or fracture. Radiographs demonstrated transverse fracture of distal third of femur through pin site track. We fixed the fracture with 11-hole combihole locking plate by MIPO technique. Eight weeks later, she was readmitted with periprosthetic fracture through screw hole at the tip of MIPO Plate and treated by Reconstruction Nail (PFNA), removal of locking screws and refixation of intermediate segment with unicortical locking screws. Then she was protected with plaster cylinder for 4 weeks and hinged brace for 2 months. Results. Retrograde nail for navigation pin site stress fracture entails intraarticular approach with attendant risks including scatches to prosthesis and joint infection. So we opted to fix by MIPO technique. Periprosthetic fracture at the top of MIPO merits fixation with antegrade nail in conjunction with conversion of screws in the proximal part of the plate to unicortical locking screws. Overlap of at least 3cms offers biomechanical superiority. She made an uneventful recovery and was started on osteoporosis treatment, pending DEXA scan. Conclusion. Reconstruction Nail (PFNA), refixation of intermediate segment with unicortical locking screws constitutes a logical management option for the unique periprosthetic fracture after MIPO of stress fracture involving femoral pin site track in computer assisted total knee replacement

There are several clinical scenarios to consider cementing an acetabular liner into a secure cementless shell including cases of: 1) inadequate capturing mechanism, 2) damaged locking mechanisms, 3) unavailability of the mating polyethylene liner, 4) instability following debridement for wear, 5) instability at the time of femoral side revision, and 6) recurrent dislocation. The last two situations are common scenarios for cementing a constrained liner into a secure shell. Technique includes: 1) scoring the shell in cases with no screw holes or polished inner shells, 2) scoring the acetabular liner in a “spider web” pattern, 3) pressurizing cement into the shell, and 4) inserting a liner that allows 2mm of cement mantle. Results of Cementing Constrained Liner Into Secure Cementless Shell: Callaghan et al. JBJS 2004. Thirty-one hips at 2–10 year follow-up. Two of 31 failed. Technical considerations: do not cement proud and do not cement into a malpositioned shell; Haft et al. J Arthroplasty 2002. Seventeen hips with minimum 1 year follow-up. One of 17 failed. Technical considerations: do not cement proud. Results of Cementing Non-Constrained Liners Into Secure Cementless Shell: Beaule et al. JBJS 2004. Thirty-two hips at mean 5.1 year avg f/u. Four components revised for loosening; Callaghan et al. CORR 2012. Thirty-one hips at mean 5.3 year f/u. No revisions

Introduction. Aseptic glenoid loosening is a common failure mode of reverse shoulder arthroplasty (rTSA). Achieving initial glenoid fixation can be a challenge for the orthopedic surgeon since rTSA is commonly used in elderly osteoporotic patients and is increasingly used in scapula with significant boney defects. Multiple rTSA baseplate designs are available in the marketplace, these prostheses offer between 2 and 6 screw options, with each screw hole accepting a locking and/or compression screw of varying lengths (between 15 to 50mm). Despite these multiple implant offerings, little guidance exists regarding the minimal screw length and/or minimum screw number necessary to achieve fixation. To this end, this study analyzes the effect of multiple screw lengths and multiple screw numbers on rTSA initial glenoid fixation when tested in a low density (15pcf) polyurethane bone substitute model. Methods. This rTSA glenoid loosening test was conducted according to ASTM F 2028–17; we quantified glenoid fixation of a 38mm reverse shoulder (Equinoxe, Exactech, Inc) in a 15 pcf low density polyurethane block (Pacific Research, Inc) before and after cyclic testing of 750N for 10k cycles. To evaluate the effect of both screw fixation and screw number, glenoid baseplates were constructed using 2 and 4, 4.5×18mm diameter poly-axial locking compression screws (both n = 5) and 2 and 4, 4.5×46mm diameter poly-axial locking compression screws (both n = 5). A two-tailed unpaired student's t-test (p < 0.05) compared prosthesis displacements to evaluate each screw length (18 vs 46mm) and each screw number (2 vs 4). Results. All glenoid baseplates remained well-fixed after cyclic loading in the low density bone substitute block, regardless of screw length or screw number. As described in Table 1, the average pre- and post-cyclic displacement for baseplates with 18mm long screws was significantly greater than that of baseplates with 46mm long screws in both the A/P and S/I directions, with exception of displacements for 4 screws S/I-pre cyclic and 2 screws A/P-post cyclic loading. As described in Table 2, the average pre- and post-cyclic displacement for all baseplates with 2 screws was significantly greater than that of all baseplates with 4 screws, regardless of screw length in the A/P and S/I directions. Discussion and Conclusions. These results of this study demonstrate that rTSA glenoid baseplate fixation is impacted by both the number of screws and by the length of screws, with longer screws and more screws associated with significantly better initial fixation. However, it should be noted that none of the tested devices catastrophically failed in this non-defect/low-density model, demonstrating that adequate fixation can be achieved with as little as 2×18mm screws for some baseplate types. Care should be made when extrapolating these results to that of other designs. This study is limited by its use of only one implant design and by its use of a polyurethane substrate without any defect; future work should evaluate the effect of screw length and screw number in with multiple different prostheses in different densities of bone with and without defects

The Failed Femoral Neck Fracture. For the young patient: Attempt to preserve patient's own femoral head. Clinical results reasonably good even if there are patches of avascular necrosis. Preferred methods of salvage: valgus-producing intertrochanteric femoral osteotomy: puts the nonunion under compression. Other treatment option: Meyer's vascularised pedicle graft. For the older patient: Most reliable treatment is prosthetic replacement. Decision to use hemiarthroplasty (such as bipolar) or THA based on quality of articular cartilage, perceived risk of instability problem. In most patients THA provides higher likelihood of excellent pain relief. Specific technical issues: (1) hardware removal: usually remove after hip has first been dislocated (to reduce risk of femur fracture); (2) Hip stability: consider methods to reduce dislocation risk: larger diameter heads/dual mobility/anteriorly-based approaches; (3) Acetabular bone quality: poor because it is not sclerotic from previous arthritis; caution when impacting a pressfit cup; low threshold to augment fixation with screws; don't overdo reaming; just expose the bleeding subchondral bone. A reasonable alternative is a cemented cup. The Failed Intertrochanteric Hip Fracture. For the young patient: Attempt to salvage hip joint with nonunion takedown, autogenous bone grafting and internal fixation. For the older patient: Decision to preserve patient's own hip with internal fixation versus salvage with hip arthroplasty should be individualised based on patient circumstances, fracture pattern, bone quality. THA is an effective salvage procedure for this problem in older patients. If prosthetic replacement is chosen special considerations include:. THA vs. hemiarthroplasty: hemiarthroplasty better stability; THA more reliable pain relief. Removal of hardware: be prepared to remove broken screws in intramedullary canal. Management of bone loss: bone loss to level of lesser trochanter common. Often requires a calcar replacement implant. Proximal calcar build-up size dictated by bone loss. Length of stem: desirable to bypass screw holes from previous fixation, if possible. Stem fixation: cemented or uncemented fixation depending on surgeon preference, bone quality. If uncemented, consider diaphyseal fixation. Greater trochanter: often a separate piece, be prepared to fix with wires or cable grip. Residual trochanteric healing, hardware problems not rare after THA

Background. Peri-prosthetic humerus fractures are relatively uncommon occurrences that can be difficult to manage non-operatively. Locking plate technology has enhanced the surgical management of these fractures. We describe an osteosynthesis technique utilizing a locking plate with eccentrically placed screw holes to place “skive screws” in the proximal end of the plate to achieve fixation around the stem of the implant. Methods. A retrospective review of prospectively collected data was performed for a consecutive series of patients treated with this skive screw technique from May 2011 to September 2014. Seven patients presented with postoperative type B peri-prosthetic humerus fractures. Average follow-up was 24 months. Radiographic analysis was performed on most recent postoperative imaging. Clinical outcomes were assessed using VAS pain, ASES total score, ASES functional score, SST, SANE, range of motion and strength. Results. At an average of follow-up of 24 months, all patients demonstrated fracture healing. Functional outcomes were limited with only two patients achieving forward elevation above 90 degrees and average ASES Function score was 27.5. Pain relief was nearly uniform with an average VAS Pain score of 0.5 (Figure 1). Conclusions. Peri-prosthetic humeral shaft fractures can be successfully treated with hybrid fixation technique using a locking plate with eccentric holes that facilitate placement of proximal “skive screws”. Using this technique, a 100% union rate was observed with excellent pain relief

Despite the best of technique, when faced with a sub-capital or per-trochanteric fracture, inevitably there are failures of proximal fixation. These situations provide unique challenges for the reconstructive surgeon. While there are specific issues related to either sub-capital or per-trochanteric fractures, there also are many commonalities. The causes of failure are nonunion, malunion, failure of fixation or avascular necrosis. In all cases, it is imperative to rule out infection. Since the surgery is now elective, the patient's medical status must be optimised prior to the intervention. Basic surgical principles apply to both fracture types. Use the old incision (if possible) and choose an approach that can be extensile. Of course, the old hardware needs to be removed – this task can be quite frustrating, so good preparation and patience is imperative. Retrieve old operative notes to identify the type of hardware so that any special tools needed are available. Hardware can be intra-osseous in location and excavation of the hardware may require bone osteotomy. These patients are at higher risk of post-operative dislocation, so absolute hip stability must be achieved and confirmed in the OR. Bigger heads and dual mobility options improve stability provided that the components are properly positioned and offset and leg length are restored. Subcapital fractures provide certain specific issues related to stem choice. While, my bias is towards THA because of better chance of complete pain relief, especially in community ambulators, certainly bipolar arthroplasties can be a satisfactory solution. Stem fixation can be either cemented or cementless. For per-trochanteric fractures in younger patients, repeat osteosynthesis should be considered if the femoral head is viable. Bone deformity – trochanteric overhang, shaft offset – may necessitate an osteotomy as part of the reconstruction. While proximal fixation primary type stems are often possible, distal fixation revision stems may be required. Any bone defects related to screw holes should be bypassed by the femoral component

The interest in osteolysis has waned largely due to the impact of crosslinked polyethylene and the “rarity” of this phenomenon. However, the basic process still remains: particles, motion observed with unstable implants and host specific factors all play a role in bone loss around implants. There are 2 predominant patterns of lysis: Linear versus Expansile. Linear Lysis: is focal bone loss at the interface as seen in the bone cement interface in when using acrylic or at the implant-host interface with porous ingrowth/ongrowth implants. Expansile Lysis: is observed in less contained regions such as the retro- and supra-acetabular regions around the socket. These lesions can also be quite extensive yet may be subtle in appearance. Imaging is essential in identifying the extent and magnitude of osteolysis. Available modalities include plain radiographs although they can be of limited value in that even with oblique views, they often underestimate the degree of bone loss. CT scans are useful but can be limited by artifact. Several centers have explored the role of MRI in assessing lysis. It can be useful for bone loss and provides excellent assessment for soft tissue: abductors, neurovascular structures. Metal artifact reduction sequencing is required to maximise information obtainable. Management of osteolysis: Identification and monitoring periprosthetic osteolysis is a crucial element of patient care. Progressive bone loss leading to loss of fixation and the potential risk for periprosthetic fracture is a real possibility and early recognition and intervention is a priority. The basic Guiding Principles of management are centered around several key elements including the source of osteolysis and degree, the fixation of implant, the location of lysis, the track record of implant system, the presence of patient symptoms (if any), and finally the patient age, activity level, and general health. Specifics of treatment of osteolysis around the acetabulum: With cemented sockets, lysis is typically seen late and frequently at the bone-cement interface. It is often associated with a loose implant and the prime indication for surgery may be pain. Treatment involves implant removal and revision with an uncemented cup and bone grafting or augmentation as needed. With uncemented sockets in the setting of osteolysis, there are several factors to consider. These have been stratified by Rubash, Maloney, and Paprosky. The treatment of these sockets has been summarised as follows: for Type I and Type II with limited lysis, lesional treatment such as debridement and bone grafting with head and polyethylene exchange has been suggested. WATCH for impingement!!!! Graft defects via trap-doors can be performed but make the door big enough to graft. Small doors and grafting through screw holes is at best marginal. In instances of compromised locking mechanisms, consider cementing the liner into the shell. For Type II and Type III implants, revision of the component is recommended. With the currently available cementless cup extraction tools, I rarely hesitate to remove a cup with moderate lysis and a broken locking mechanism: better access to lytic areas, better grafting achieved. CAVEAT #1: the disadvantage of implant removal is that it is clearly a bigger procedure and fixation of the new implant may be more difficult. Risks vs. rewards. CAVEAT #2: Socket revision in the setting of failed MOM implants has some unique “issues”. In the Vancouver series, almost 25% of the revision cups failed to achieve biologic fixation. As such, recommendation for using “enhanced” porous implants during revision seems prudent. Additionally, despite the use of larger diameter heads, instability rates remain high

Aims

The standard of wide tumour-like resection for chronic osteomyelitis (COM) has been challenged recently by adequate debridement. This paper reviews the evolution of surgical debridement for long bone COM, and presents the outcome of adequate debridement in a tertiary bone infection unit.

Despite the best of technique when faced with a sub-capital or per-trochanteric fracture, inevitably there are failures of proximal fixation. These situations provide unique challenges for the reconstructive surgeon. While there are specific issues related to either sub-capital or per-trochanteric fractures, there also are many commonalities. The causes of failure are nonunion, malunion, failure of fixation or avascular necrosis. In all cases, it is imperative to rule out infection. Since the surgery is now elective, the patient's medical status must be optimised prior to the intervention. Basic surgical principles apply to both fracture types. Use the old incision (if possible) and choose an approach that can be extensile. Of course, the old hardware needs to be removed – this task can be quite frustrating, so good preparation and patience is imperative. Retrieve old OP notes to identify the type of hardware so that any special tools needed are available. Hardware can be intra-osseous in location and excavation of the hardware may require bone osteotomy. These patients are at higher risk of postoperative dislocation, so absolute hip stability must be achieved and confirmed in the OR. Bigger heads and dual mobility options improve stability provided that the components are properly positioned and offset and leg length are restored. Subcapital fractures provide certain specific issues related to stem choice. While, my bias is towards total hip arthroplasty because of better chance of complete pain relief, especially in community ambulators, certainly bipolar arthroplasties can be a satisfactory solution. Stem fixation can be either cemented or cementless. For per-trochanteric fractures in younger patients, repeat osteosynthesis should be considered if the femoral head is viable. Bone deformity – trochanteric overhang, shaft offset – may necessitate an osteotomy as part of the reconstruction. While proximal fixation primary type stems are often possible, distal fixation revision stems may be required. Any bone defects related to screw holes should be bypassed by the femoral component

Objective. Failures of internal fixation after intertrochanteric fractures pose great challenge to orthopaedic surgeons. Hip arthroplasty can be a remedy for such failures, however, the selection of femoral stem length is controversial. This study aims to report our experience of managing failed internal fixation after intertrochanteric fractures with standard femoral stem arthroplasty. Methods. A retrospective review of patients who were managed with hip arthroplasty for failed internal fixation after intertrochanteric fractures in the First Affiliated Hospital of Fujian Medical University, P.R. China between January 2001 to December 2013 was performed. Patients’ age, gender, pre- and postoperative Harris Hip Score (HHS), femoral stem types and surgical outcomes were traced and analyzed. Results. 14 patients were included. The average age at the time of internal fixation and hip arthroplasty was 74.6 years old (Range, 56–89) and 75.8 years old (Range, 58–90), respectively. The time duration between internal fixation and hip arthroplasty ranged from 3 to 26 months. 5 were total hip arthroplasty while 9 were hemiarthroplasty. 4 were implanted with long femoral stems while 10 with standard stems, including 4 cementless (SL-PLUS, Smith & Nephew)and 6 cemented stems. Standard femoral stems were defined as ones that are designed to be used in primary hip replacement, with the length of which ranging from 120 to 140mm. The distal ends of these stems did not exceed the distal screw hole levels of 2 cortical diameters. After a mean follow-up time of 6.4 years (Range, 1–13), 2 patients lost to follow-up and 2 died of non-surgically related diseases. For the 8 cases with standard stems, at the latest follow-up, no periprosthetic fractures or periprosthetic joint infections were observed. A total of 3 hip dislocations happened in 2 patients but were managed successfully with manipulative reduction followed by hip brace. The HHS score increased from an average of 35.6 preoperatively to 79.4 after surgery. Conclusions. Hip arthroplasty can be performed as revision for failed internal fixation after intertrochanteric fractures. Use of standard femoral stems is less invasive, reduces expenditure and can also achieve similar satisfactory clinical outcomes as long femoral stems. However, the long-term clinical outcomes required further follow-up