Biomorphometric analysis of ilio‐sacro‐iliacal corridors for an intra‐osseous implant to fix posterior pelvic ring fractures

It is hypothesized that ilio‐sacro‐iliacal corridors for a new envisioned pelvic ring implant (trans‐sacral nail with two iliacal bolts = ISI‐nail: ilio‐sacro‐iliacal nail) exists on the level of S1‐ or S2‐vertebra in each patient. The corridors of 84 healthy human pelves (42x ♂; 42x ♀, 18–85 years) were measured in high resolution CT scans using the Merlin Diagnostic Workcenter Software. Trans‐sacral corridors (≥9 mm diameter) on the level of S1 and S2 were found in 62% and 54% of pelves with a mean length [mm ± SD] of 164 ± 12.9 and 142 ± 10.2. Corresponding iliac corridors were present in all specimens in caudally tilted axial planes of 37.8 ± 0.67° and 53.7 ± 0.94° in relation to the operating table plane and divergent angulations of 69.0 ± 0.49° and 70.1 ± 0.32° in relation to the sagittal midline plane. Sacral dysmorphism, with compensatory larger S2 corridors were prevalent in 24% of pelves; ilio‐sacro‐iliacal osseous corridors for the envisioned implant were found in 88% of pelves on the level of S1 or S2. In the remaining 12% with too narrow corridors for any trans‐sacral implant (screws, bars, ISI nail) alternative fixation methods have to be considered. Expected advantages of the envisioned ISI nail compared to available fixation devices are discussed. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:254–260, 2015.

     

Strain shielding inspired re‐design of proximal femoral stems for total hip arthroplasty

A large number of hip prosthesis with different designs have been developed. However, the influence of hip implant design changes on the strains induced in the bone remains unclear. The purpose of this study is to better understand the mechanics of short stem total hip arthroplasty. Specifically, it investigates whether strain shielding can be avoided by changing implant shape and/or material properties. It is hypothesized that the re‐design of existing implant designs can result in further reduction of strain shielding and thus keep bone loss minimal following total hip replacement. Finite element methods were used to compare healthy and implanted models. The local mechanics strains/stresses in the intact and implanted femurs were determined under patient‐specific muscle and joint contact forces. Results suggest that small changes in implant geometry and material properties have no major effect on strain shielding. Furthermore, it was found that improvement depends on a dramatic re‐design of the original implant design. Whereas the benefit of this strategy of modification of the original geometry of a given short‐stemmed hip consists in reduced bone remodeling, care should be taken with regard to long‐term bone anchorage and implant fatigue strength. It is also shown that geometrical and material changes have a limited potential in avoiding strain shielding even in short‐stemmed implants. Finally, it is suggested that an understanding of the influence of these changes on the strain distribution within the bone can guide in the process of optimizing the current stem designs toward minimal strain shielding effects. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2534–2544, 2017.

     

Three-dimensional dynamic bone histomorphometry

Dynamic bone histomorphometry is the standard method for measuring bone remodeling at the level of individual events. Although dynamic bone histomorphometry is an invaluable tool for understanding osteoporosis and other metabolic bone diseases, the technique's two‐dimensional nature requires the use of stereology and prevents measures of individual remodeling event number and size. Here, we used a novel three‐dimensional fluorescence imaging technique to achieve measures of individual resorption cavities and formation events. We performed this three‐dimensional histomorphometry approach using a common model of postmenopausal osteoporosis, the ovariectomized rat. The three‐dimensional images demonstrated the spatial relationship between resorption cavities and formation events consistent with the hemiosteonal model of cancellous bone remodeling. Established ovariectomy was associated with significant increases in the number of resorption cavities per unit bone surface (2.38 ± 0.24 mm^?2 sham surgery versus 3.86 ± 0.35 mm^?2 bilateral ovariectomy [OVX], mean ± SD, p < 0.05) and total volume occupied by cavities per unit bone volume (0.38% ± 0.06% sham versus 1.12% ± 0.18% OVX, p < 0.001), but there was no difference in surface area per resorption cavity, maximum cavity depth, or cavity volume. In addition, we found that established ovariectomy is associated with increased size of bone formation events because of the merging of formation events (23,700 ± 6,890 µm² sham verusus 33,300 ± 7,950 µm² OVX). No differences in mineral apposition rate (determined in 3D) were associated with established ovariectomy. That established estrogen depletion is associated with increased number of remodeling events with only subtle changes in remodeling event size suggests that circulating estrogens may have their primary effect on the origination of new basic multicellular units with relatively little effect on the progression and termination of active remodeling events. © 2012 American Society for Bone and Mineral Research     

Metaphyseal‐Loading Anterolaterally‐Flared Femoral Stem in Cementless Total Hip Arthroplasty: Five‐ to Eleven‐Year Follow‐Up Evaluation

Using a nonlinear three‐dimensional finite element analysis simulating loading conditions, we designed a new type of proximal‐fitting, anterolaterally‐flared, arc‐deposit hydroxyapatite‐coated anatomical femoral stem (FMS‐anatomic stem; Japan Medical Materials, Osaka, Japan) for cementless total hip arthroplasty (THA) for Japanese patients with dysplastic hip osteoarthritis. The aim of the present study was to analyze the clinical and radiographic outcomes of the new stem. We reviewed 143 consecutive patients (164 hips; 13 men, 14 hips; 130 women, 150 hips; age at surgery, 56.6 ± 7.6 years, mean ± SD, range, 30–74) who underwent cementless THA using the FMS‐anatomic stem at a single institution, with a follow‐up period of 7.6 ± 1.6 years (range, 5.3–11.0). Harris Hip score improved from 46.1 ± 12.6 before surgery to 90.0 ± 8.9 points post‐THA. The 7.6‐year survival rate of the stem was 99.0% after revision for aseptic loosening. Radiographs at follow‐up confirmed the stability of the femoral stems within the femoral canal in all cases, with sufficient bone ingrowth. None of the patients had subsidence of the stem exceeding 2.0 mm within the femoral canal or changes in varus or valgus position of more than 2.0°. The FMS‐anatomic stem provided excellent results in patients with dysplastic hip osteoarthritis. Our analysis confirmed reduced radiolucency around the stem in Gruen zones, minimal subsidence, appropriate stress shielding, and promising medium‐term stability within the femoral canal in our patients.     

Fully porous 3D printed titanium femoral stem to reduce stress‐shielding following total hip arthroplasty

Current hip replacement femoral implants are made of fully solid materials which all have stiffness considerably higher than that of bone. This mechanical mismatch can cause significant bone resorption secondary to stress shielding, which can lead to serious complications such as peri‐prosthetic fracture during or after revision surgery. In this work, a high strength fully porous material with tunable mechanical properties is introduced for use in hip replacement design. The implant macro geometry is based off of a short stem taper‐wedge implant compatible with minimally invasive hip replacement surgery. The implant micro‐architecture is fine‐tuned to locally mimic bone tissue properties which results in minimum bone resorption secondary to stress shielding. We present a systematic approach for the design of a 3D printed fully porous hip implant that encompasses the whole activity spectrum of implant development, from concept generation, multiscale mechanics of porous materials, material architecture tailoring, to additive manufacturing, and performance assessment via in vitro experiments in composite femurs. We show that the fully porous implant with an optimized material micro‐structure can reduce the amount of bone loss secondary to stress shielding by 75% compared to a fully solid implant. This result also agrees with those of the in vitro quasi‐physiological experimental model and the corresponding finite element model for both the optimized fully porous and fully solid implant. These studies demonstrate the merit and the potential of tuning material architecture to achieve a substantial reduction of bone resorption secondary to stress shielding. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1774–1783, 2017.

     

Bone stresses before and after insertion of two commercially available distal ulnar implants using finite element analysis

Distal ulnar arthroplasty is becoming a popular treatment option for disorders of the distal radioulnar joint; however, few studies have investigated how load transfer in the ulna is altered after insertion of an implant. The purpose of our study was to compare bone stresses before and after insertion of two commercially available cemented distal ulnar implants: an implant with a titanium stem and an implant with a cobalt chrome stem. Appropriately sized implants of both types were inserted into eight previously validated subject‐specific finite element models, which were created by using information derived from computed tomography scans. The von Mises stresses were compared at eight different regions pre‐ and post‐implantation. The bone stresses with the titanium stem were consistently closer to the pre‐implantation stresses than with the cobalt chrome stem. For the loading situation and parameters investigated, results of these models show that insertion of the E‐Centrix® ulnar Head may result in less stress shielding than the SBI uHead? stem. Future studies are required to investigate other implant design parameters and loading conditions that may affect the predicted amount of stress shielding. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1418–1423, 2011     

短柄全髋关节置换术治疗中青年股骨头坏死患者的近期疗效

 目的 评价陶瓷对陶瓷短柄全髋关节置换术治疗中青年股骨头坏死晚期患者的近期疗效。方法 2009年12月至2011年3月接受陶瓷对陶瓷短柄初次全髋关节置换术治疗的中青年股骨头坏死患者40例(43髋),男 23例,女17例;年龄27～55岁,平均40.5岁。Steinberg分期均为Ⅳ期以上。29例采用后外侧入路,11例采用前侧入路。术后3、6、12个月及以后每年随访1次,摄骨盆正位及髋关节侧位X线片,测量假体下沉距离;采用Harris髋关节评分和WOMAC骨关节炎指数评估关节功能。结果 38例(41髋)得到随访,随访时间21～36个月,平均31.3个月。末次随访X线片上假体位置较术后即刻下沉(0.68±2.90) mm,差异无统计学意义(t=1.51,P=0.139)。术后髋关节疼痛均明显改善或消失,Harris髋关节评分由术前平均(38.7±12.1)分提高至末次随访(95.2±4.49)分,WOMAC骨关节炎指数由术前平均66.7±12.0降至末次随访12.8±5.6,差异均有统计学意义。随访期间未发生股骨颈骨折、感染、肺栓塞等严重并发症,无假体关节脱位、松动及假体感染。结论 短柄全髋关节置换术可更多地保留骨量,假体初始稳定性好,全陶瓷头衬配伍的磨损率低,近期疗效佳,假体相关并发症少。     

Clinical and histologic results related to a low-modulus composite total hip replacement stem

BACKGROUND: Osteolysis secondary to stress shielding in patients with a total hip arthroplasty has been attributed to greater stiffness of the prosthetic femoral stem compared with the stiffness of the femur. This concern led to the development of a composite femoral stem implant with a structural stiffness similar to that of the native femur. The stem consists of a cobalt-chromium-alloy core surrounded by polyaryletherketone and titanium mesh for bone ingrowth. The purpose of this study was to determine the intermediate-term clinical, radiographic, and histologic results of the use of this stem. METHODS: Twenty-eight patients (nineteen men and nine women) with an average age of 51.3 years underwent primary total hip arthroplasty with the Epoch stem and were followed for an average of 6.2 years. Harris hip scores were determined and radiographic studies were performed preoperatively, postoperatively, and at two-year intervals thereafter. In addition, dual x-ray absorptiometry scans were made up to two years postoperatively to evaluate osseous resorption. Two femora obtained at autopsy thirteen and forty-eight months after surgery were analyzed for bone ingrowth and ongrowth. RESULTS: The Harris hip scores averaged 56 points preoperatively and improved to 97 points at the time of the last follow-up. Dual x-ray absorptiometry scans demonstrated the greatest decrease in mean bone density (27.5%) in Gruen zone 7 at two years. Radiographs demonstrated no instances of migration, and only one hip had osteolysis. All stems had stable osseous fixation. Histologic evaluation of the two femora that had been retrieved at autopsy at thirteen and forty-eight months showed the mean bone ingrowth (and standard deviation) along the entire length of the stem to be 49.62% +/- 13.04% and 73.57% +/- 8.48%, respectively, and the mean bone ongrowth to be 54.18% +/- 7.68% and 80.92% +/- 6.06%, respectively. CONCLUSIONS: Intermediate-term follow-up of hips treated with the Epoch stem indicated excellent clinical success, radiographic evidence of osseous integration, and histologic findings of osseous ingrowth and ongrowth. Although the implant has been associated with excellent results in both the short and the intermediate term, longer follow-up will be necessary to assess the long-term function of the implant.     

The use of a hydroxyapatite-coated primary stem in revision total hip arthroplasty

Proximal ingrowth of femoral components in total hip arthroplasty (THA) is desirable because it minimizes proximal stress shielding associated with distal ingrowth stems and maximizes bone stock. This is a retrospective evaluation of initial results of revision THA using a proximally hydroxyapatite-coated femoral stem nominally designed for primary use. Patients requiring femoral stem revision were included if they had sufficient femoral bone stock to support a proximally fixed prosthesis (n = 33). This represents 53% of the femoral revisions performed during the period of the study. The average follow-up was 5 years (range 48-88 months). The mean Harris hip and Oxford hip scores were 86.5 and 25.2, respectively. Radiographically, 100% of the stems demonstrated bone ingrowth fixation. These results are superior to previous reports of primary cementless stems for revision THA. The use of a cementless nonmodular implant provides a viable option in some patients undergoing revision THA.     

Large Osseous Defect Reconstruction Using a Custom Three-Dimensional Printed Titanium Truss Implant

Treatment of large osseous defects remains a difficult surgical challenge. Autografts and allografts have been known to undergo late collapse, because these options are not specifically designed to withstand the high loads of the foot and ankle. The inability to achieve the correct shape for reconstruction further limits their application. Large osseous defects will result during salvage after failed Lapidus bunionectomy, explantation of failed total ankle replacements, and nonunion of Evans calcaneal osteotomy. Each of 3 patients received a 4WEB custom 3-dimensional (3D) titanium truss implant (Patient Specific Custom Implant; 4WEB Medical, Inc., Frisco, TX) for reconstruction. The mean follow-up period was 17.33?±?3.51 months. Significant improvement was seen in pain, with a successful return to activities of daily living. The 12-month postoperative computed tomography findings demonstrated incorporation of the implant to the surrounding cortical and cancellous bone. No signs of delayed complications, such as stress shielding or implant failure, were found. This is the first case series to describe the use of a custom 3D-printed titanium truss implant to successfully contribute to reconstruction in the setting of failed elective foot and ankle surgery. This technology might play an important role in limb salvage of osseous defects that would otherwise require bone block arthrodesis with structural allograft or autograft bone.     

Modified Metaphyseal‐Loading Anterolaterally Flared Anatomic Femoral Stem: Five‐ to Nine‐Year Prospective Follow‐Up Evaluation and Results of Three‐Dimensional Finite Element Analysis

We have designed a proximal‐fitting, anterolaterally flared, arc‐deposit hydroxyapatite‐coated anatomical femoral stem (FMS‐anatomic stem; KYOCERA Medical, Osaka, Japan) for cementless total hip arthroplasty (THA) for Japanese patients with dysplastic hip osteoarthritis, using a nonlinear three‐dimensional finite element analysis simulating loading conditions. The Anatomic Fit stem was modified in the region of the arc‐sprayed surface, to allow more proximal appearance of spot welds. The aim of the present study was to analyze the clinical and radiographic outcomes of patients who underwent THA using this stem. We reviewed 73 consecutive patients (79 hips; 13 men 16 hips; 60 women 63 hips; age at surgery, 57.6 years, range, 35–78) who underwent cementless THA using the Anatomic Fit stem, at a follow‐up period of 7.1 years (range, 5.1–9.4). Harris Hip score improved from 40.7 ± 17.1 before surgery to 91.0 ± 5.2 points at follow‐up. The 7.1‐year stem survival rate was 100%. Radiographs at follow‐up confirmed the stability of the femoral stems within the femoral canal in all cases, with sufficient bone ingrowth. None of the patients had subsidence of the stem exceeding 2.0 mm within the femoral canal or changes in varus or valgus position of more than 2.0°. The Anatomic Fit stem provided excellent results. The nonlinear three‐dimensional finite element analysis demonstrated that the stem‐bone relative motion was 10 µm at the proximal end of the stem and proximal load transfer. Our analysis confirmed reduced radiolucency around the stem, minimal subsidence, appropriate stress shielding, and promising medium‐term stability within the femoral canal.     

Bone remodeling after total hip arthroplasty with a short stemmed metaphyseal loading implant: Finite element analysis validated by a prospective DEXA investigation

In total hip arthroplasty (THA), short stemmed cementless implants are used because they are thought to stimulate physiological bone remodeling and reduce stress shielding. We performed a numerical investigation on bone remodeling after implantation of a specific short stemmed implant using finite element analysis (FEA). Overall bone mass loss was 2.8% in the entire femur. Bone mass decrease was mostly found in the proximal part of the calcar and in the greater trochanter due to the vast cross section of the implant, probably leading to stress shielding. In the diaphysis, no change in the apparent bone density was proven. The assumptions made agreed well with bone remodeling data from THA recipients who underwent dual‐energy X‐ray absorptiometry. However, the clinical investigation revealed a bone mass increase in the minor trochanter region that was less pronounced in the FEA. Further comparisons to other stem designs must be done to verify if the relative advantages of the investigated implant can be accepted. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1822–1829, 2012     

Supraphysiological loading induces osteocyte‐mediated osteoclastogenesis in a novel in vitro model for bone implant loosening

We aimed to develop an in vitro model for bone implant loosening, allowing analysis of biophysical and biological parameters contributing to mechanical instability‐induced osteoclast differentiation and peri‐implant bone loss. MLO‐Y4‐osteocytes were mechanically stimulated for 1 h by fluid shear stress using regimes simulating: (i) supraphysiological loading in the peri‐prosthetic interface (2.9 ± 2.9 Pa, 1 Hz, square wave); (ii) physiologic loading in the cortical bone (0.7 ± 0.7 Pa, 5 Hz, sinusoidal wave); and (iii) stress shielding. Cellular morphological parameters, membrane‐bound RANKL expression, gene expression influencing osteoclast differentiation, nitric oxide release and caspase 3/7‐activity were determined. Either Mouse bone marrow cells were cultured on top of loaded osteocytes or osteocyte‐conditioned medium was added to bone marrow cells. Osteoclast differentiation was assessed after 6 days. We found that osteocytes subjected to supraphysiological loading showed similar morphology and caspase 3/7‐activity compared to simulated physiological loading or stress shielding. Supraphysiological stimulation of osteocytes enhanced osteoclast differentiation by 1.9‐fold compared to physiological loading when cell‐to‐cell contact was permitted. In addition, it enhanced the number of osteoclasts using conditioned medium by 1.7‐fold, membrane‐bound RANKL by 3.3‐fold, and nitric oxide production by 3.2‐fold. The stimulatory effect of supraphysiological loading on membrane‐bound RANKL and nitric oxide production was higher than that achieved by stress shielding. In conclusion, the in vitro model developed recapitulated the catabolic biological situation in the peri‐prosthetic interface during instability that is associated with osteoclast differentiation and enhanced RANKL expression. The model thus provides a platform for pre‐clinical testing of pharmacological interventions with potential to stop instability‐induced bone implant loosening. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1425–1434, 2018.

     

Local delivery of zoledronate from a poly (D,L‐lactide)—Coating increases fixation of press‐fit implants

Early secure fixation of total joint replacements is crucial for long‐term survival. Antiresorptive agents such as bisphosphonates have been shown to increase implant fixation. We investigated whether local delivery of zoledronate from poly‐D, L‐lactide (PDLLA)‐coated implants could improve implant fixation and osseointegration. Experimental titanium implants were bilaterally inserted press‐fit into the proximal tibiae of 10 dogs. On one side the implant was coated with PDLLA containing zoledronate. The contralateral implant was uncoated and used as control. Observation period was 12 weeks. Implant fixation was evaluated with histomorphometry and biomechanical push‐out test. We found an approximately twofold increase in all biomechanical parameters when comparing data from the zoledronate group with their respective controls. Histomorphometry showed increased amount of preserved bone and increased bone formation around the zoledronate implants. This study indicates that local delivery of zoledronate from a PDDLA coating has the potential to increase implant fixation. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:65–71, 2016.     

Implant stability in the treatment of MRSA bone implant infections with linezolid versus vancomycin in a rabbit model

The increasing prevalence of methicillin‐resistant Staphylococcus aureus (MRSA) infections represents a significant healthcare burden. Vancomycin and linezolid exhibit potent clinical and microbiological activity in MRSA infections. Our purpose was to investigate the efficacy of linezolid versus vancomycin in experimental implant infections and the influence on implant stability in a rabbit model. Thirty‐six female New Zealand White rabbits received surgical insertion of titanium implants into their distal femurs and were randomly assigned to six groups (A: infected, no treatment; B: infected, vancomycin; C: infected, linezolid; D: no infection, no treatment; E/F: no infection, vancomycin or linezolid, respectively). Antibiotics were administered, and plasma levels determined. Bone‐implant specimens were tested for mechanical stability of fixation. Quantitative histomorphometry of bone and soft tissue was performed using computerized image analysis. Plasma levels of linezolid and vancomycin were within the respective therapeutic ranges. Microbiological analysis of specimens from infected rabbits showed MRSA tissue colonization in all untreated animals, in two of six vancomycin‐treated animals, and in none of the linezolid‐treated animals. Antibiotic treatment improved mechanical stability significantly (p = 0.004) with both vancomycin and linezolid. Mechanical testing correlated with histomorphometry results. A significant negative correlation was found between displacement of the implant and the percentage of calcified tissue around the implant, and a significant positive correlation was found between displacement of the implant and the amount of noncalcified tissue. Our data indicate that both treatment regimens improved implant stability. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:190–195, 2012     

Submicron‐surface structured tricalcium phosphate ceramic enhances the bone regeneration in canine spine environment

Calcium phosphate ceramics with submicron‐scaled surface structure can trigger bone formation in non‐osseous sites and are expected to enhance bone formation in spine environment. In this study, two tricalcium phosphate ceramics having either a submicron‐scaled surface structure (TCP‐S) or a micron‐scaled one (TCP‐B) were prepared and characterized regarding their physicochemical properties. Granules (size 1–2 mm) of both materials were implanted on either left or right side of spinous process, between the two lumbar vertebrae (L3‐L4), and in paraspinal muscle of eight beagles. After 12 weeks of implantation, ectopic bone was observed in muscle in TCP‐S explants (7.7 ± 3.7%), confirming their ability to inductively form bone in non‐osseous sites. In contrast, TCP‐B implants did not lead to bone formation in muscle. Abundant bone (34.1 ± 6.6%) was formed within TCP‐S implants beside the two spinous processes, while limited bone (5.1 ± 4.5%) was seen in TCP‐B. Furthermore, the material resorption of TCP‐S was more pronounced than that of TCP‐B in both the muscle and spine environments. The results herein indicate that the submicron‐scaled surface structured tricalcium phosphate ceramic could enhance bone regeneration as compared to the micron‐scaled one in spine environment. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1865–1873, 2016.     

Biomechanics of a short stem: In vitro primary stability and stress shielding of a conservative cementless hip stem

Short stem prostheses provide conservative surgery and favorable metaphyseal load transmission. However, clinical long‐term results are lacking. Therefore, in vitro trials can be used to predict bone‐implant performance. In this in vitro study, primary stability and stress shielding of a new cementless short stem implant was evaluated in comparison to a straight stem using nine pairs of human cadaver femurs. Primary stability, including reversible micromotion and irreversible migration, was assessed in a hip simulator. Furthermore, changes in the pattern of cortical strain were evaluated. The short stem was more resistant to reversible micromotion and irreversible migration into retroversion. Axial stability was similar, with mean reversible micromotions of 9 µm for the short stem and 7 µm for the straight stem. Proximal load transmission was more physiological with the short stem, though both implants could not avoid stress shielding in Gruen zones 1 and 7. Primary stability of the short stem prosthesis was not negatively influenced compared to the straight shaft. Furthermore, proximal femoral strain pattern was more physiological after insertion of the short stem prosthesis. (c) 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1180–1186, 2013     

Healing in peri‐implant gap with BMP‐2 and systemic bisphosphonate is dependent on BMP‐2 dose—A canine study

The bone–implant interface of cementless orthopedic implants can be described as a series of uneven sized gaps with discontinuous areas of direct bone–implant contact. Bridging these voids and crevices by addition of an anabolic stimulus to increase new bone formation can potentially improve osseointegration of implants. Bone morphogenetic protein 2 (BMP‐2) stimulates osteoblast formation to increase new bone formation but also indirectly stimulates osteoclast activity. In this experiment, we investigate the hypothesis that osseointegration, defined as mechanical push‐out and histomorphometry, depends on the dose of BMP‐2 when delivered as an anabolic agent with systemic administration of the anti‐resorptive agent zoledronate to curb an increase in osteoclast activity. Four porous coated titanium implants (one with each of three doses of surface‐applied BMP‐2 (15 µg; 60 µg; 240 µg) and untreated) surrounded by a 0.75 mm empty gap, were inserted into the distal femurs of each of twelve canines. Zoledronate IV (0.1 mg/kg) was administered 10 days into the observation period of 4 weeks. Bone–implant specimens were evaluated by mechanical push‐out test and histomorphometry. The 15 µg implants had the best fixation on all mechanical parameters and largest surface area covered with new bone compared to the untreated, 60 and 240 µg implants, as well as the highest volume of new bone in the implant gap compared to 60 and 240 µg implants. The results in a canine implant model demonstrated that a narrow range of BMP‐2 doses have opposite effects in bridging an empty peri‐implant gap with bone, when combined with systemic zoledronate. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1406–1414, 2018.

     

Observational study of a new modular femoral revision system

BACKGROUND The uncemented Arcos~(TM) Modular Femoral Revision System(ARCOS) is a new comprehensive,press-fit revision design.The modular design offers a wide range of possible combinations to accommodate different variations of anatomy and bone stock.The ARCOS is made by a proximal body and a distal stem.As probably the only ones worldwide we predominantly use a combination of body and stem which supports proximal fixation and load,since this mimics the concept of the primary total hip arthroplasty with proximal weight-bearing,leading to bone stock preservation and no stress shielding or thigh pain.AIM To evaluate the early results after femoral revision in a consecutive series of patients undergoing surgery over 3 years.METHODS We included 116 patients in the study.They were operated in the period August2011 to December 2014 and we got a clinical mean observation time of 4(0.5-6)years.Clinical and radiographical follow-up included present function of the hip assessed by Harris Hip Score,Oxford Hip Score,and EQ5 D(measure of health outcome).Of the 116 patients,17 died in the interim and were consequently included only in the implant survivorship analysis;46 patients attended the follow-up control.RESULTS In total 6(5%) hips were re-revised due to infection(n = 3),fracture(n = 2) or subsidence(n = 1).No patient was re-revised due to aseptic loosening.The 1-,2-and 5-year probability of implant survival(95%CI) were 97%(93%-100%),97%(93%-100%) and 96%(92%-99%),respectively.In this cohort 95 patients received a combination of a proximal broach and a distal curved and slotted stem(BS),aiming for proximal fixation and load bearing;21 patients received a different combination.When comparing these two groups the BS-group had a 5-year implant survival probability(95%CI) of 97%(93%-100%) compared with the group of other combinations with a 5-year implant survival probability(95%CI)of 90%(78%-100%)(P = 0.3).Our regression analysis showed that periprosthetic fracture as an indication for the ARCOS operation was the only significant negative outcome predictor.The mean Harris Hip Score result(100 points being best) was 83(range 5-98).The mean Oxford Hip Score result(48 points being best) was 40(range 19-48).CONCLUSION The early results of the ARCOS are promising compared with similar studies.We encourage the use of the BS combination whenever the bone stock proximally is adequate.     

Bone Engineering of Maxillary Sinus Bone Deficiencies Using Enriched CD90+ Stem Cell Therapy: A Randomized Clinical Trial

Bone engineering of localized craniofacial osseous defects or deficiencies by stem cell therapy offers strong prospects to improve treatment predictability for patient care. The aim of this phase 1/2 randomized, controlled clinical trial was to evaluate reconstruction of bone deficiencies of the maxillary sinus with transplantation of autologous cells enriched with CD90+ stem cells and CD14+ monocytes. Thirty human participants requiring bone augmentation of the maxillary sinus were enrolled. Patients presenting with 50% to 80% bone deficiencies of the maxillary sinus were randomized to receive either stem cells delivered onto a β‐tricalcium phosphate scaffold or scaffold alone. Four months after treatment, clinical, radiographic, and histologic analyses were performed to evaluate de novo engineered bone. At the time of alveolar bone core harvest, oral implants were installed in the engineered bone and later functionally restored with dental tooth prostheses. Radiographic analyses showed no difference in the total bone volume gained between treatment groups; however, density of the engineered bone was higher in patients receiving stem cells. Bone core biopsies showed that stem cell therapy provided the greatest benefit in the most severe deficiencies, yielding better bone quality than control patients, as evidenced by higher bone volume fraction (BVF; 0.5 versus 0.4; p = 0.04). Assessment of the relation between degree of CD90+ stem cell enrichment and BVF showed that the higher the CD90 composition of transplanted cells, the greater the BVF of regenerated bone (r = 0.56; p = 0.05). Oral implants were placed and restored with functionally loaded dental restorations in all patients and no treatment‐related adverse events were reported at the 1‐year follow‐up. These results provide evidence that cell‐based therapy using enriched CD90+ stem cell populations is safe for maxillary sinus floor reconstruction and offers potential to accelerate and enhance tissue engineered bone quality in other craniofacial bone defects and deficiencies ( Clinicaltrials.gov NCT00980278). © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research