A neck-preserving short stem better reconstructs the centre of rotation than straight stems: a computed tomography-based cadaver study.

INTRODUCTION: Short femoral hip stems with a metaphyseal anchoring concept have been designed to treat younger patients with good bone quality. The aim of this study was to reconstruct the centre of rotation and soft tissue balancing and preserve bone in the long-term perspective. MATERIALS AND METHODS: Eighteen human femurs were randomised into three groups: (1) metaphyseal anchoring short stem, (2) shortened straight stem, (3) straight stem). Prior to the implantation of the hip stems, a computed tomography (CT) of the bones was performed and the femoral ante-torsion and ante-tilt was measured and compared to the results of the post-implantation CT. This could be calculated based on the 3D coordinates taken from the pre- and post-op CT scans, which were transformed into the same coordinate systems. RESULTS: The mean preoperative caput-collum-diaphyseal (CCD) angle for the three groups was 126.87° ± 3.50° (Group 3: 129.64° ± 3.53°, Group 1: 123.76° ± 5.56°, Group 2: 127.53° ± 1.42°) and was consistent with published reports. The postoperative CCD angles with 126.85° ± 3.43° were within a very good reconstruction range for all three groups. The anterior offset comparison among these three groups showed significant difference in reconstruction. The smallest difference between the anatomical (preoperative) and postoperative condition was seen in Group 1 (1.47° ± 0.60°), followed by Group 2 (3.60° ± 0.23°) and Group 3 (8.00° ± 0.70°) groups. The horizontal offset showed no significant difference among the groups and was within the window of ± 5 mm. CONCLUSION: In this cadaver study, we found that the metaphyseal anchoring, partially neck-preserving short hip stem best reconstructs the ante-torsion and the ante-tilt of the femoral neck. Therefore, it can be a useful stem in younger or active middle-aged patients.

Development of periprosthetic bone mass density around the cementless Metha® short hip stem during three year follow up-a prospective radiological and clinical study.

PURPOSE: The purpose of this study was to check the concept of the cementless Metha® short hip stem in order to find out whether proximal physiological load transfer can be achieved. METHODS: Fourty-three patients were included. Epidemiological factors were established. The Harris Hip Score was determined and measurement of bone mass density as well as osteodensitometric and radiological measurements was carried out pre-operatively, post-operatively, and after six, 12, 24, and 36 months. RESULTS: Harris Hip Score improved from 55.9 ± 12.4 pre-operatively to 94.8 ± 8.2 after 36 months (p < 0.001). After initial reduction of bone density in zones 1 and 7 up to six months post-operatively, there was a steady approximation of bone density to the initial values (p < 0.05). CONCLUSION: The Metha® short hip stem shows good clinical results. Furthermore, there is an increase of bone density in the proximal zones 1 and 7 between six and 36 months serving as a sign of physiological load transfer.

Periprosthetic bone remodelling of short-stem total hip arthroplasty: a systematic review.

PURPOSE: Short-stem hip arthroplasty (SHA) was designed to preserve bone stock and provide an improved load transfer. To gain more evidence regarding the load transfer, this review analysed the periprosthetic bone remodelling of SHA in comparison to standard hip arthroplasty (THA). METHODS: PubMed and ScienceDirect were screened to extract dual-energy X-ray absorptiometry (DXA) studies evaluating the periprosthetic bone remodelling of SHA and two proven THA designs. From the studies included, the postoperative change in periprosthetic bone mineral density (BMD) after one year and the trend over two years was determined. RESULTS: Fifteen studies with four SHAs (CFP, Metha, Nanos, Fitmore) and two THAs (CLS and Bicontact) designs were included. All SHA and THA stems revealed an initial decrease at the calcar and major trochanter (Gruen 1 and 7) with the Metha, Nanos and Fitmore showing a smaller and more balanced remodelling compared to THA. The pattern after one year and the trend over two years argue for a methaphyseal anchorage of the Metha and Nanos, whereas the Fitmore and CFP seem to anchor metha-diaphyseal. Clearly different pattern of bone remodelling were observed between all four SHAs. CONCLUSIONS: Periprosthetic bone remodelling is also present in SHA, with the main bone reduction observed proximally. However, certain SHA stems show a more balanced remodelling compared to THA, arguing for a favourable load transfer. Also, the femoral length where bone remodelling occurs is clearly shorter in SHA. As distinctively different pattern between the SHA designs were observed, they should not be judged as a single implant group.

Comparison of cytotoxicity between 3D printable resins and heat-cure PMMA.

Aim: The aim of this study was to evaluate and compare the cytotoxicity of polyurethane and polyoxymethylene printable resins with conventional heat cure polymethyl methacrylate denture base resins. Methods: The study followed ISO-10993-5 guidelines. It comprised of three groups. Fifteen cuboidal samples measuring 10x10 × 10mm dimension were prepared for each group. The polymethylmethacrylate samples were fabricated using conventional denture processing techniques, while the polyoxymethylene samples were printed using fused deposition modeling and the polyurethane samples using stereolithography technique. Post fabrication the samples were evaluated for cytotoxicity using the MTT assay with the VERO cell line. The percentage of cell viability was calculated to determine the cytotoxic effects. Results: Statistical analysis revealed a significant difference in the cell viability of the experimental groups (p ≤ 0.0001). The polyoxymethylene group showed the highest % cell viability (62.78 %), followed by the polymethylmethacrylate group (52.43 %), and the least was observed in the polyurethane-based resin group (46.47 %). The findings indicate polyoxymethylene group displayed least cytotoxicity, followed by polymethylmethacrylate, and polyurethane-based resin. Conclusion: Polyoxymethylene resin exhibited the minimum cytotoxic properties among the tested materials, followed by polymethylmethacrylate and polyurethane resin.

Mid- to long-term periprosthetic bone density changes after cementless short stem hip arthroplasty in elderly: A clinical and radiological analysis.

Introduction: Short stem prostheses were originally designed for younger and more active patients. In recent years, they have been increasingly offered to older patients. This study evaluates the mid-to long-term survival of a short stem prosthesis and the changes in periprosthetic bone density following implantation of a cementless short hip stem in patients over 60 years of age. Methods: 118 patients aged over 60 received short stem prostheses. Clinical examination included Harris Hip Score (HHS) and Hip Disability and Osteoarthritis Outcome Score (HOOS). 93 patients were followed clinically for at least five years. 53 patients underwent dual-energy x-ray absorptiometry (DXA) and radiographic evaluation. Follow-up intervals were preoperative and postoperative (t0), at approximately six months (t1), at approximately two years (t2), and at approximately five years or later (t3). Results: Over a mean 6.7-year observation period for all 118 patients, one stem revision occurred due to a traumatic periprosthetic stem fracture. The five-year survival rate for the endpoint survival of the Metha® stem in 95 at-risk patients is 99.2%. HHS improved significantly from t0 55.3 ± 11.5 (range 30-79) to t3 95.3 ± 8.6 (range 57-100) at a mean of 8.0 years (p < 0.001). HOOS improved significantly in each subscale (p < 0.001). Bone mineral density (BMD) was available for review in 53 patients after a mean of 7.1 years. BMD increased from t0 to t3 in region of interest (ROI) 3 (+0.4%) and ROI 6 (+2.9%) and decreased in ROI 1 (-10.3%), ROI 2 (-9.8%), ROI 4 (-5.3%), ROI 5 (-3.4%) and ROI 7 (-23.1%). Conclusions: The evaluated short stem prosthesis shows a remarkably high survival rate in elderly patients, accompanied by excellent clinical results. Load transfer measurements show a metaphyseal-diaphyseal pattern with a trend towards increased diaphyseal transfer over the period observed.

Insufficient lateral stem contact is an influencing factor for significant subsidence in cementless short stem total hip arthroplasty.

BACKGROUND: Subsidence is one of the concerning early complications in cementless femoral stem. Few publications have studied the influencing factors for subsidence in short cementless stems, due to their metaphyseal anchoring without diaphyseal invasion, they might demonstrate different subsidence patterns than with the conventional stems. AIM: To analyze the factors associated with significant subsidence in short stems, including any radiographic parameters. METHODS: The digitized radiographs of 274 consecutive short stem total hip arthroplasties were retrospectively reviewed. Subsidence, neck-filling ratio (NFR), seating height and lateral stem contact were evaluated after a minimum of two years follow-up. A threshold of subsidence > 3 mm was considered a clinically significant migration. RESULTS: For the entire cohort, subsidence occurred in 75 cases (27.4%) with the mean stem subsidence of 0.5 mm. (0-12.7, 1.68). Twelve hips (4.4%) had significant subsidence (> 3 mm). The univariate regression analysis demonstrated that age, diagnosis, BMI, Dorr's type B, NFR, and seating height had no significant influence on significant subsidence, whereas insufficient lateral stem contact (≥ 1 mm) did have a statistically significant influence [Odds ratio (OR) = 5.02; 95%CI: 1.3-18.9; P = 0.017]. The multivariate regression analysis also demonstrated that insufficient lateral stem contact was a statistically significant influencing factor (OR = 5.5; 95%CI: 1.4-21.4; P = 0.014). There was no femoral stem revision for aseptic loosening in our cohort. CONCLUSION: This study demonstrated that insufficient lateral stem contact was a statistically significant influencing factor on significant subsidence. Therefore, it is a particularly important step to create proper lateral cortical contact when performing the short stem total hip arthroplasty.

The clinical outcome of the Metha short hip stem: a systematic scoping review.

INTRODUCTION: Short femoral stems were designed to bridge the gap between conventional straight design stems and hip resurfacing prostheses in total hip arthroplasty (THA). A number of clinical trials have been recently conducted to assess the clinical and safety profile of the cementless, colarless, tapered Metha short hip stem in young or active middle-aged individuals. METHODS: A systematic scoping review was conducted according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. 4 reviewers independently conducted the search using the MEDLINE/PubMed database and the Cochrane Database of Systematic Reviews. These databases were queried with the terms "short" AND "hip" AND "stem". RESULTS: From the initial 773 studies we finally chose 12 studies after applying our inclusion-exclusion criteria. The number of operated hips that were included in these studies was 5048 (mean BMI range: 22.7-35.2, mean age range: 44.4-60.4 years, mean follow-up range: 2-9 years). The mean modified Coleman methodology score was 52.3/100, while it ranged from 31/100 to 63/100. All mean clinical outcome scores that were used in the studies illustrated significant postoperative improvement when compared with the respective initial values. The revision rate of the Metha stem for component-related reasons was 2.5%, while the rate of major complications not requiring revision of the Metha stem was 2.8%. CONCLUSIONS: The Metha stem performs well in young or active middle-aged THA patients. Further studies are required for the assessment of the long-term results.

Is the strain pattern of conventional stems negatively affected by a previously short stem THA? An experimental study in cadavaric bone.

BACKGROUND: A short stem hip arthroplasty can be revised in many cases using a conventional stem. Furthermore, in some cases the implantation of a short stem is intended, but intraoperatively reasons may lead to the decision to implant a conventional stem after previous preparation of a short stem. OBJECTIVE: In both cases it is questionable if the anchorage of a conventional stem is negatively affected by the previous preparation of a short stem. In clinical practice mid- or long-term follow up for these special cases hardly exist. METHODS: The strain patterns for the conventional Bicontact stem in primary implantation and after preparation of the proximal femur for a METHA short stem were tested biomechanically in three pairs of cadaveric femora. RESULTS: The strain patterns for the conventional Bicontact after preparation of the METHA short stem were similar to conditions after testing the conventional stem in primary conditions. CONCLUSIONS: These data lead to the consequence that in clinical practise the implantation of a conventional stem after preparation of a short stem and even after revision of a short stem is possible without increased risk of loosening or long-term stress-shielding.

Effect of zinc oxide nanoparticles on the flexural strength of polymethylmethacrylate denture base resin.

PURPOSE: This study evaluated the flexural strength of polymethyl methacrylate (PMMA) reinforced with various concentrations of zinc oxide (Zn O) nanoparticles. MATERIALS AND METHODS: Nano ZnO was added in 0, 0.4, 0.6, 0.8, 1.2 and 1.4 percentage to PMMA denture base material. 60 specimens of heat cure polymerizing acrylic resin of dimensions 10mm x 4mm x 80mm were fabricated in accordance to ISO 20795-1-2013. The specimens were divided into 6 groups. Acrylic specimens were processed according to manufacturer's instruction. Three-point bending test was performed to evaluate the flexural strength. Surface analysis was performed with scanning electron microscopy (SEM) to observe the fracture surfaces of specimens. ANOVA and Tukey tests were used for the statistical analysis (p < 0.05). RESULTS: Statistical analysis revealed significant differences in strength between groups. The flexural strength improved with the addition ZnO nanoparticles. Highest mean value was observed in Group nZn -14 (91.31 MPa) and lowest in control Group nZn-0 (61.36 MPa). ANOVA and Tukey's honestly significance test found statistical significant differences among the groups ( p<0.001). CONCLUSION: The addition of ZnO nanoparticles in all concentrations increased the flexural strength of acrylic resin when compared to the control group.

The influence of grafting process on the optical, geometrical, and structural parameters of nylon-6 fibers.

Mach-Zehnder interferometer technique is utilized to study the impact of grafting of the nylon-6 fibers with poly (methyl methacrylate) (PMMA) polymer on the optical, geometrical, and structural properties. He-Ne laser diffraction technique is applied to study the changes in the fiber thickness of two samples (nylon-6 blank and nylon-6 grafted with PMMA) at different positions along the fiber length. The geometrical parameters are investigated by determining the cross-sectional shape of the two samples. The results of the interferometric and the diffraction techniques show that there is no variation in the thickness of nylon-6 fiber but variations in the thickness of the grafted nylon-6 fiber are obvious. The optical and physical properties along the axis of these fibers are characterized by measuring their refractive indices, birefringence, polarizability per unit volume, dielectric constant, surface reflectivity and the refractive index profile. The results show that PMMA polymer changed the optical, geometrical, and structural properties of the nylon-6 blank fiber. Microinterferograms are given for illustrations.

Sonochemical approach for synthesis of zinc oxide-poly methyl methacrylate hybrid nanoparticles and its application in corrosion inhibition.

Hybrid nanoparticles (HNPs) with zinc oxide and polymethyl metha acrylate (inorganic/ polymer) were synthesized through the exploitation of ultrasound approach. The synthesized HNPs were further characterized employing transmission electron microscopy and x-ray diffraction. ZnO-PMMA based HNPs exhibit excellent protection properties to mild steel from corrosion when gets exposed to acidic condition. Electrochemical impendence spectroscopy (EIS) analysis was accomplished to evaluate the corrosion inhibition performance of MS panel coated with 2 wt% or 4 wt% of HNPs and its comparison with bare panel and that of loaded with only standard epoxy coating., Tafel plot and Nyquist plot analysis depicted that the corrosion current density (Icorr) decreases from 16.7 A/m2 for bare material to 0.103 A/m2 for 4% coating of HNPs. Applied potential (Ecorr) values shifted from negative to positive side. These results were further supported by qualitative analysis. The images taken over a period of time indicated the increase in lifetime of MS panel from 2 to 3 days for bare panel to 10 days for HNPs coated panel, showing that ZnO-PMMA HNPs have potential application in metal protection from corrosion by forming a passive layer.

A predictive radiological analysis of short stems versus both shortened and long stems in primary hip replacement: A case-control study of 100 cases of Metha versus ABG II and Omnifit HA at 2-8years' follow-up.

INTRODUCTION: Short hip stems, intended to conserve bone stock and ensure a more physiological distribution of stress in the femur under loading, are meeting with renewed interest. Radiologic semiology is not known exactly, particularly in relation to conventional implants; we therefore conducted a case-control study of 3 types of implant differing only in stem length: short, shortened or long. The aim was: (1) to compare radiographic aspects, (2) to attempt to systematize medium-term radiologic status for the 3 types, and (3) to assess the impact of radiographic aspect on loosening and revision rates. HYPOTHESIS: The short Metha stem is better adapted to the recipient bone than longer stems, without sacrificing stability. MATERIAL AND METHODS: A prospective series comprising the first 100 selected cases of hip replacement using the short Metha stem was compared to two other series of 100 "long" (Omnifit HA) and 100 "shortened" (ABG II) stems at comparable follow-up: 4.05±1.44years (range: 2-8years) for Metha, 4.48±0.97years (range: 2-8years) for Omnifit, and 4.75±2.07years (range: 2-8years) for ABG II. Selection criteria in this initial phase were very strict: young age and/or high activity level, with good bone stock and femoral morphology suited to fitting a Metha stem (no "stovepipe" or "champagne-flute" femurs), for which 12.8% of primary hip replacements were selected. Matching was performed by sampling on criteria of age, gender, body-mass index and etiology. Radiographic parameters were compared between the short stem group and the two control groups and classified according to Engh-Massin score (10 points for fixation and 17 for stability). RESULTS: The short Metha stem provided excellent fixation scores: 7.65/10, versus 7.16 (P=0.003) and 5.92 (P=0.0001) for ABG II and Omnifit, respectively. Likewise, stability was scored 14.23/17 for Metha, vs. 14.51 (NS) and 11.83 (P=0.0001) respectively, and the total score was higher for Metha (21.88/27) than ABG II (21.67; P=0.03) or, more particularly, Omnifit (17.83; P=0.0001). The Metha stem was never associated with thigh pain or periprosthetic fracture. 8-year survival was 100%, without significant difference with respect to ABG II (100%; NS) or Omnifit (98.8%; 95% CI: 0.964-1; NS). DISCUSSION: The apparent radiologic superiority of the short Metha stem requires long-term confirmation in non-selected series. Meanwhile, Metha can be asserted to have demonstrated optimal compromise between lasting bone anchorage and respect of bone physiology under loading at medium term. LEVEL OF EVIDENCE: III, case-control study.

Bone remodelling around the Metha® short stem implant - Clinical and dual-energy x-ray absorptiometry (DXA) results.

OBJECTIVE: Bony ingrowth of short stems is under investigation. METHOD: Over one year bony reactions around the Metha® stem were investigated using the DXA method in a standardized zonal system (19 ROIs). Clinical results were documented using the HHS. RESULTS: HHS significantly improved from 46 points to 97 points. After one year bone marrow density (BMD) increased in the lateral distal and lateral proximal areas as well as in the mid medial area. BMD decreased in the proximal medial and mid lateral areas. CONCLUSION: The concept of metaphyseal ingrowth was confirmed, but distal bony reactions need further investigation.

Clinical results of the metha short hip stem: a perspective for younger patients?

In recent years, various uncemented proximal metaphyseal hip stems were introduced for younger patients as a bone preserving strategy. Initial osteodensitometric analyses of the surrounding bone of short stems indicate an increase of bone mass with secondary bone ingrowth fixation as a predictor of long-term survival of these types of implants. We report the outcome of 151 modular Metha short hip stem implants in 148 patients between March 2005 and October 2007. The mean follow-up was 5.8±0.7 years and the mean age of the patients was 55.7±9.8 years. Along with demographic data and co-morbidities, the Harris Hip Score (HHS), the Hip dysfunction and Osteoarthritis Outcome Score (HOOS), and also the results of a patient-administered questionnaire were recorded pre-operatively and at follow-up. The mean HHS increased from 46±17 pre-operatively to 90±5 the HOOS improved from 55±16 pre-operatively to 89±10 at the final follow-up. A total of three patients have been revised, two for subsidence with femoral revision and one for infection without femoral revision (Kaplan Meier survival estimate 98%). The radiological findings showed no radiolucent lines in any of the patients. The modular Metha short hip stem was implanted in younger patients, who reported an overall high level of satisfaction. The clinical and radiographic results give support to the principle of using short stems with metaphyseal anchorage. However, long-term results are necessary to confirm the success of this concept in the years to come.

Tumor Cell Clone Expressing the Membrane-bound Form of IL-12p35 Subunit Stimulates Antitumor Immune Responses Dominated by CD8(+) T Cells.

IL-12 is a secretory heterodimeric cytokine composed of p35 and p40 subunits. IL-12 p35 and p40 subunits are sometimes produced as monomers or homodimers. IL-12 is also produced as a membrane-bound form in some cases. In this study, we hypothesized that the membrane-bound form of IL-12 subunits may function as a costimulatory signal for selective activation of TAA-specific CTL through direct priming without involving antigen presenting cells and helper T cells. MethA fibrosarcoma cells were transfected with expression vectors of membrane-bound form of IL-12p35 (mbIL-12p35) or IL-12p40 subunit (mbIL-12p40) and were selected under G418-containing medium. The tumor cell clones were analyzed for the expression of mbIL-12p35 or p40 subunit and for their stimulatory effects on macrophages. The responsible T-cell subpopulation for antitumor activity of mbIL-12p35 expressing tumor clone was also analyzed in T cell subset-depleted mice. Expression of transfected membrane-bound form of IL-12 subunits was stable during more than 3 months of in vitro culture, and the chimeric molecules were not released into culture supernatants. Neither the mbIL-12p35-expressing tumor clones nor mbIL-12p40-expressing tumor clones activated macrophages to secrete TNF-α. Growth of mbIL-12p35-expressing tumor clones was more accelerated in the CD8(+) T cell-depleted mice than in CD4(+) T cell-depleted or normal mice. These results suggest that CD8(+) T cells could be responsible for the rejection of mbIL-12p35-expressing tumor clone, which may bypass activation of antigen presenting cells and CD4(+) helper T cells.