Simulated Osteopenia Impairs Metaphyseal Bone Ingrowth of Metal Implants in an Animal Model

Abstract Background and Purpose: Cementless total joint replacement in osteopenic bone is suspected to deteriorate long-term survival of implants because results in dental implantology research indicate that bone ingrowth of dental implants in osteoporotic bone is impaired. The present investigation was designed to determine whether osteopenic bone stock, experimentally created in ovariectomized rats, influences the active bone-implant integration process. Material and Methods: 40 Sprague-Dawley rats were randomly assigned to two treatment groups; one group underwent ovariectomy, the other sham ovariectomy. Successful development of osteopenia was assessed by bone mineral density measurement of the lumbar vertebra L5 before implant surgery and before sacrifice. An uncoated and a hydroxyapatite-coated titanium implant were surgically inserted into the medullary canal of each femur. After 28 days specimens were prepared for histomorphometry to determine the osseointegrated implant surface. Results: The results showed a successful development of experimentally induced osteopenia in ovariectomized rats. For hydroxyapatite-coated implants the histomorphometry revealed a mean osseointegrated implant surface of 54.5% in the sham group versus 23.7% in the ovariectomy group. There was no significant difference for uncoated titanium implants. Conclusion: The present study in rats clearly demonstrates that osteopenic bone loss induced by ovariectomy impairs bone-implant ingrowth of hydroxyapatite-coated implants in the metaphysis of the femur. This is a potential risk for deterioration of long-term outcome of cementless metal implants in osteopenic bone. In consequence, the quality of bone stock has to be taken into account while making a decision for cemented or cementless joint replacements.     

The role of bone anchored hearing aids in children with Down syndrome

OBJECTIVES: To evaluate complication rates and outcomes of children with Down syndrome fitted with a Bone Anchored Hearing Aid (Baha). To evaluate whether the Bone Anchored Hearing Aid is a successful form of aural rehabilitation in children with Down syndrome from a patients' perspective. STUDY DESIGN: Retrospective case analysis and postal questionnaire study. SETTING: The Birmingham Children's Hospital, UK. METHODS: A total of 15 children were fitted with a Baha between February 1992 and February 2007. The age range was 2-15 years. A postal questionnaire was sent to each family. The Glasgow Children's Benefit Inventory (GCBI) was used in this study. OUTCOME MEASURES: Implantation results, skin reactions and other complications were recorded. Quality of life after receiving a Baha was assessed with the GCBI. RESULTS: All 15 patients are using their Baha 7 days a week for more than 8h a day after a follow-up of 14 months with continuing audiological benefit. No fixtures were lost, and skin problems were encountered in 3 (20%). Regarding quality of life, all 15 patients had improved social and physical functioning as a result of better hearing. CONCLUSIONS: Baha has an important role in the overall management of individuals with Down syndrome after conventional hearing aids and/or ventilation tubes have been considered or already failed. This study has shown a 20% rate of soft tissue reaction and there were no fixture losses in this group. No significant increase in complication rates was identified in children with Down syndrome. Finally, there was a significantly improved quality of life in children with Down syndrome after receiving their Baha. There was a high patient/carer satisfaction with Baha. Two of our series had bilateral two stage fixture procedures without any complications. More consideration should be given to bilateral bone anchored hearing aids in this group.     

Single-walled carbon nanotubes functionalized with sodium hyaluronate enhance bone mineralization

The aim of this study was to evaluate the effects of sodium hyaluronate (HY), single-walled carbon nanotubes (SWCNTs) and HY-functionalized SWCNTs (HY-SWCNTs) on the behavior of primary osteoblasts, as well as to investigate the deposition of inorganic crystals on titanium surfaces coated with these biocomposites. Primary osteoblasts were obtained from the calvarial bones of male newborn Wistar rats (5 rats for each cell extraction). We assessed cell viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay and by double-staining with propidium iodide and Hoechst. We also assessed the formation of mineralized bone nodules by von Kossa staining, the mRNA expression of bone repair proteins, and the deposition of inorganic crystals on titanium surfaces coated with HY, SWCNTs, or HY-SWCNTs. The results showed that treatment with these biocomposites did not alter the viability of primary osteoblasts. Furthermore, deposition of mineralized bone nodules was significantly increased by cells treated with HY and HY-SWCNTs. This can be partly explained by an increase in the mRNA expression of type I and III collagen, osteocalcin, and bone morphogenetic proteins 2 and 4. Additionally, the titanium surface treated with HY-SWCNTs showed a significant increase in the deposition of inorganic crystals. Thus, our data indicate that HY, SWCNTs, and HY-SWCNTs are potentially useful for the development of new strategies for bone tissue engineering.     

Virtual simulation of an osseointegrated trans-humeral prosthesis: A falling scenario

IntroductionTraditional prosthetic solutions expose the amputee to numerous problems that limit his ability to safely perform the normal activities of daily life. In order to eliminate the problems related to the use of the traditional prosthesis with socket, a new technique was developed for fixing the prosthesis to the amputees based on the principle of osseointegration. The aim of this paper is to study and analyze the stress distribution on the interface between a trans-humeral osseointegrated prosthetic implant and the residual bone, identifying the most stressed areas and thus foreseeing possible failure phenomena of the entire prosthetic system and, after, to compare the stress distribution on three different prosthetic designs that differ from each other for some geometric characteristics.Materials and methodsA healthy individual mimics two fall scenarios of which the trans-humeral amputees can most likely be victims: Static fall and Dynamic fall. A force platform (P-6000, BTS Bioengineering) is required for load data acquisition. The CAD model of the trans-humeral osseointegrated implant was created following the guidelines of the OPRA implant. The bone model was created starting from the CAT scan of a left humerus. The FEM simulation was conducted throught a linear analysis.ResultsBoth during static fall and dynamic fall, similar trends have been observed for the reaction force Fz, the torque moment Tz, the bending moments Mx and My. From the analysis of the von Mises stress distribution it was found that the stress distribution is more homogeneous in the case where the thread of the fixture is made by a triangular profile with height of the thread equal to 0.5 mm. However, it can be seen that, when passing from a thread with height of 0.5 mm to a 1 mm, there is a slight decrease in the stress on the whole contact zone between the fixture and the humerus. The same improvement can also be seen in the case of trapezoidal threading.ConclusionBy modifying the height and/or by varying the thread profile, are obtained slightly better results with respect to the case with a 0.5 mm height triangular thread.     

Splinted and Unsplinted Short Implants in Mandibles: A Retrospective Evaluation With 5 to 16 Years of Follow‐Up

Background: The aim of this retrospective study is to investigate the medium‐ to long‐term prognosis of short implants in partially and totally edentulous patients with mandibular bone atrophy. Methods: The study involved 109 patients with 280 implants placed in the mandible. The implants were 7 or 8.5 mm long and 3.75 or 4 mm in diameter. The implant surfaces were machined (M; n = 176) or rough (R; n = 104). Patients were asked to attend a radiographic and clinical follow‐up, and their previous clinical records and radiographs were assessed. Implant‐related and prosthetic failures and complications were recorded. Results: The mean follow‐up was 9 years (range of 5 to 16 years). The survival rate (SSR) and success rate (SR) were calculated using life‐table analysis for both M and R short implants. The M implants had a 16‐year SSR of 95.7% and a corresponding SR of 93.9%, whereas the 16‐year SSR and SR for the R implants were 97.2% and 95.2%, respectively. The mean ± SD bone resorption for all implants was 1.37 ± 0.5 mm. For marginal bone loss, there was no statistically significant difference between the two implant lengths (P = 0.38) or diameters (P = 0.34) or between the M and R implant surfaces (P = 0.47). Conclusions: Different implant lengths, diameters, and surface treatments do not appear to influence the prognosis of the implant. Within the limitation that most of the short implants were splinted to longer implants, the reduced length of the fixtures did not worsen the long‐term survival of the implant‐supported fixed prostheses.     

Novel surface modifications of carbon fiber-reinforced polyetheretherketone hip stem in an ovine model

A carbon fiber-reinforced polymer (CFRP) is theoretically a suitable material for use in an uncemented hip prosthesis considering it can provide isoelastic environment with the surrounding bone, adequate fatigue strength, and a metal-free radiographic evaluation. To date, the selection of polymer material and optimization of both design and surface finish of the prostheses for osseointegration has not been accomplished. This study examined radiographic and histologic results of an uncemented CFRP stem manufactured from carbon fiber-reinforced polyetheretherketone (CFR/PEEK) with a roughened surface and a bioactive treatment in an adult ovine model following a 12-month implantation period. A unilateral hemiarthroplasty of the hip was performed using the CFRP stem or a titanium stem as a control. Four cases with the CFRP stem and five cases with titanium stem were evaluated. Bone on-growth fixation was achieved in two cases with the CFRP stem and in all the cases with the titanium stem. The CFRP cases showed minimal stress shielding while three of five cases with the titanium stem demonstrated typical osteopenia associated with stiff metal stems. Bone on-growth to the uncemented CFRP stem was achieved by using the CFR/PEEK for the material and modifying the surface design and the bioactive surface finish. Bone resorption and osteopenia observed with the Ti stems was not found with the CFRP design.     

Histological analysis of cells and matrix mineralization of new bone tissue induced in rabbit femur bones by Mg–Zr based biodegradable implants

The biological efficacy of bone inducing implant materials in situ can be assessed effectively by performing histological analysis. We studied the peri-implant bone regeneration around two types of biodegradable magnesium–zirconium alloys, Mg–5Zr and Mg–Zr–2Sr, using histological, histochemical and immunohistochemical methods in the femur of New Zealand White strain rabbits. Our study includes three animal groups: (a) Mg–5Zr, (b) Mg–Zr–2Sr and (c) control. In each group three animals were used and in groups ‘a’ and ‘b’ the respective alloys were implanted in cavities made at the distal ends of the femur; control animals were left without implants to observe natural bone healing. Qualitative assessment of the cellularity and matrix mineralization events of the newly formed bone tissue was done at three months after implantation by histological methods in methyl methacrylate embedded tissue without decalcifying the bone. Quantitative mineral content and density of the new bone (NB) were evaluated by the statistical analysis of dual energy X-ray absorptiometry (DXA) data obtained from three animals in each experimental group. Based on our analysis we conclude that Mg–Zr–2Sr alloy showed better osseointegration of the newly formed bone with the implant surface. Our methodology of studying peri-implant osteoinduction of degradable implants using low temperature methyl methacrylate embedding resin can be useful as a general method for determining the bio-efficacy of implant materials.     

Cytocompatibility,osseointegration, and bioactivity of three-dimensional porous and nanostructured network on polyetheretherketone

Porous biomaterials with the proper three-dimensional (3D) surface network can enhance biological functionalities especially in tissue engineering, but it has been difficult to accomplish this on an important biopolymer, polyetheretherketone (PEEK), due to its inherent chemical inertness. In this study, a 3D porous and nanostructured network with bio-functional groups is produced on PEEK by sulfonation and subsequent water immersion. Two kinds of sulfonation-treated PEEK (SPEEK) samples, SPEEK-W (water immersion and rinsing after sulfonation) and SPEEK-WA (SPEEK-W with further acetone rinsing) are prepared. The surface characteristics, in vitro cellular behavior, in vivo osseointegration, and apatite-forming ability are systematically investigated by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, cell adhesion and cell proliferation assay, real-time RT-PCR analysis, micro-CT evaluation, push-out tests, and immersion tests. SPEEK-WA induces pre-osteoblast functions including initial cell adhesion, proliferation, and osteogenic differentiation in vitro as well as substantially enhanced osseointegration and bone-implant bonding strength in vivo and apatite-forming ability. Although SPEEK-W has a similar surface morphology and chemical composition as SPEEK-WA, its cytocompatibility is inferior due to residual sulfuric acid. Our results reveal that the pre-osteoblast functions, bone growth, and apatite formation on the SPEEK surfaces are affected by many factors, including positive effects introduced by the 3D porous structure and SO₃H groups as well as negative ones due to the low pH environment. Surface functionalization broadens the use of PEEK in orthopedic implants.     

紫外线处理微弧氧化种植体的早期成骨研究

目的研究C波段紫外线(ultraviolet C,UVC)处理的微弧氧化(micro-arc oxidation,MAO)纯钛种植体植入兔胫骨后的早期成骨方式。方法实验分2组,MAO组和UVC-MAO组。MAO组将医用纯钛种植体经微弧氧化处理后植入新西兰大白兔胫骨。UVC-MAO组将医用纯钛种植体经过微弧氧化处理后,用15 W UVC灭菌灯对钛种植体照射48 h,经过25.0 kGyγ射线消毒后植入新西兰大白兔胫骨。2周后取出胫骨,用锥形束CT观察种植体表面成骨情况;制作胫骨硬组织切片,并以亚甲基蓝-酸性品红染色,光学显微镜观察两组种植体的成骨方式。结果 MAO组可见靠近种植体骨环底端的为成骨细胞及软组织,无任何骨组织,骨环斜面有从周围成熟骨生长的骨组织及类骨质,但所有组织与种植体表面均有一定距离,而非密切接触材料表面。UVC-MAO组可见种植体骨环底端及骨环斜面表面紧密接触类骨质及成骨细胞,还有已经分化的新生骨组织;所有组织与种植体表面紧密接触,无间隔。结论紫外线处理微弧氧化后的种植体,更有利于成骨细胞粘附于种植体表面,形成新生骨质并紧密贴附于种植体表面,骨环周围成熟骨质同时向种植体生长,有利于种植体早期的接触成骨。     

Ilizarov fixator pin site care: The role of crusts in the prevention of infection

Pin site infection is one of the most common local complications after procedures using the Ilizarov fine wire fixator. In this study, the rate of infection was investigated in two groups of patients, representing two consecutive case series, undergoing fracture stabilisation or lower limb reconstruction using an Ilizarov fine wire fixator. Both groups received identical Russian-style pin site care, except in the first Group A where the crusts of dried exudate were removed at the time of pin site cleaning; while in the subsequent Group B, the adherent crusts were retained during cleaning. Pin site infection was diagnosed if the site was painful and inflamed or discharging. The first infected pin site while the fixator remained in situ was considered the outcome of interest. Group A consisted of 59 patients and Group B of 33 patients. A lower proportion of patients in Group B (12/33 – 36%) developed a pin site infection compared to Group A (36/59 – 61%) (p = 0.023). However, once infection had developed, a greater proportion of patients in Group B required more than one course of antibiotics to treat the infection when compared to patients in Group A (p = 0.005). No patient required hospitalisation for intravenous antibiotics or wire change in Group B (0/33), whereas 3/59 patients required hospitalisation in Group A; but this did not reach statistical significance (Chi-squared test, p = 0.18). Retention of adherent crusts during Ilizarov fixator pin site care significantly protects against the development of pin site infection, but renders subsequently infected pin sites more refractory to treatment. This study therefore suggests that crusts should be retained as long as a pin site remains uninfected. Retained crusts may act as a physical barrier to bacterial contamination (‘biological dressing’).