Aims The purpose of this study was to evaluate the biological fixation of a 3D printed porous implant, with and without different hydroxyapatite (HA) coatings, in a canine model. Materials and Methods A canine transcortical model was used to evaluate the characteristics of bone ingrowth of Ti6Al4V cylindrical implants fabricated using laser rapid manufacturing (LRM). At four and 12 weeks post-implantation, we performed histological analysis and mechanical push-out testing on three groups of implants: a HA-free control (LRM), LRM with precipitated HA (LRM-PA), and LRM with plasma-sprayed HA (LRM-PSHA). Results Substantial bone ingrowth was observed in all LRM implants, with and without HA, at both time periods. Bone ingrowth increased from 42% to 52% at four weeks, to 60% to 65% at 12 weeks. Mechanical tests indicated a minimum shear fixation strength of 20 MPa to 24 MPa at four weeks, and 34 MPa to 40 MPa at 12 weeks. There was no significant difference in the amount of bone ingrowth or in the shear strength between the three implant types at either time period. Conclusion At four and 12 weeks, the 3D printed porous implants exhibited consistent bone ingrowth and high mechanical shear strength. Based on the results of this study, we confirmed the suitability of this novel new additive manufacturing porous material for biological fixation by bone ingrowth. Cite this article: Bone Joint J 2019;101-B(6 Supple B):62–67.

There remains a lack of understanding of the structural changes that occur across the complex, multitissue anterior cruciate ligament (ACL)-to-bone insertion as a function of aging. The objective of this study is to provide a multiscale comparison of matrix properties across the skeletally immature and mature ACL-to-bone insertion. Using complementary imaging methods, micro-and ultrastructural analysis of the insertion revealed that collagen fiber orientation at the interface changes with age, though the degree of collagen organization is maintained over time. These changes are accompanied by a decrease in collagen fibril density and are likely driven by physiological loading. Mineral crystal structure and crystallinity are conserved over time, despite regional differences in crystallinity between the interface and bone. This suggests that mineral chemistry is established early in development and underscores its important functional role. Collectively, these findings provide new insights into interface development and set critical design benchmarks for integrative soft tissue repair.

BackgroundSeveral 2-dimensional and 3-dimensional surfaces are available for cementless acetabular fixation. Plain radiographs are used to assess osseointegration; however, the radiographs are limited by their inability to capture the bone fixation process occurring over the 3-dimensional cup surface. In this cadaveric study, we compared the bone apposition between 2-dimensional and 3-dimensional cups.MethodsBoth types of cups were implanted in 6 cadavers and pelvic radiographs obtained. Each cup was resected from the pelvis with adequate bone around it, and subsequently embedded in a polymer. Six sections of each cup were obtained to examine the metal and bone interface. Photographs and contact radiograph images were obtained for each section, and these were graded to arrive at percent metal-bone contact values for the cups.ResultsOn average, <30% of the cups' areas displayed radiolucencies on the pelvic radiographs for both cup types. For the section images and radiographs, there was about 80% aggregate contact between the cups and surrounding bone in both cup types. In the 3-dimensional cups group, some inconsistencies were found between the section photographs and the corresponding radiograph images. The radiolucencies observed on the section radiograph could not always be correlated with metal to bone gap on the section photograph.ConclusionsGood metal-bone contact (75% + contact area) was observed on both cup types. The inconsistencies found in the 3-dimensional cup group may be because of the interaction of radiographs with the unique porous cup surface resulting in artifactual radiolucencies.

Minimal studies exist investigating biofilm-induced corrosion of orthopaedic implants.This study investigates potential contributions of Pseudomonas aeruginosa and Staphylococcus aureus biofilms on corrosion resistance of CoCrMo under static and fretting conditions. Biofilms were cultured on CoCrMo coupons for either 4 weeks (static culture) or 6 days (fretting culture; pin-on-disk with a Ti6Al4V hemispherical tip pin). Morphology of biofilms and corrosion of coupon surfaces were analyzed via SEM.Open circuit potential and electrochemical impedance spectroscopy measurements were collected for corrosion performance evaluation. Results showed no visible corrosion on coupon surfaces in static culture, which suggests these biofilms alone do not induce severe corrosion under the conditions of this study. However, electrochemical data showed biofilm presence lowered coupon electrochemical impedance in static and fretting cultures, suggesting resistive and capacitive characteristics of the metal oxide-biofilm-media interface were altered. Under fretting, the P. aeruginosa group exhibited a distinct damage morphology and Co:Cr:Mo ratio within the wear scar when compared with S. aureus and the bacteria-free control.These differences suggest the presence of P. aeruginosa biofilms may negatively impact corrosion resistance at the fretting interface. Taken together these results demonstrate biofilms can contribute to implant corrosion by influencing the electrochemical impedance of implant metal surfaces. K E Y W O R D S