Very early migration of a calcar-guided short stem: a randomized study of early mobilization and the influence of a calcium phosphate coating with 60 patients.

This study analyzed the migration of a calcar-guided short stem to determine the course of very early migration, as well as evaluated the effect of an additional calcium phosphate (CP) coating on a titanium plasma spray (TPS) coating, which has not been analyzed previously. Sixty patients were enrolled in this study and were treated with the A2 calcar-guided short stem. The implant coating was randomized with either the TPS or an additional CP coating, and radiostereometric analysis was performed with the baseline measurement before initial weight-bearing, along with follow-up examinations at 1 week, 6 weeks, 3 months, and 6 months. Implant migrations were 0.27 mm (standard deviation [SD], 0.13 mm) and 0.74 mm (SD, 1.11 mm) at 1 week and 6 months post-surgery, respectively, and 65% and 87% of the implants reached their final position 1 week and 6 weeks after surgery, respectively. After 6 weeks, 3 months, and 6 months, a significant increase was noted in the migration of the CP coating group vs. that of the TPS coating group. Upon the final observation at 6 months, the groups displayed on average a 0.74-mm migration. Most of the analyzed implants ceased migration within the first week post-surgery, but the CP coating demonstrated a higher and more prolonged migration compared to the TPS coating.

Analysis of modular taper fractures of the revision hip stem Prevision and comparison of the original and current taper design.

Aims: The risk of mechanical failure of modular revision hip stems is frequently mentioned in the literature, but little is currently known about the actual clinical failure rates of this type of prosthesis. The current retrospective long-term analysis examines the distal and modular failure patterns of the Prevision hip stem from 18 years of clinical use. A design improvement of the modular taper was introduced in 2008, and the data could also be used to compare the original and the current design of the modular connection. Methods: We performed an analysis of the Prevision modular hip stem using the manufacturer's vigilance database and investigated different mechanical failure patterns of the hip stem from January 2004 to December 2022. Results: Two mechanical failure patterns were identified: fractures in the area of the distal fluted profile (distal stem fracture) and failure of the modular taper (modular fracture). A failure rate of 0.07% was observed for distal stem fracture, and modular fracture rates of 1.74% for the original and 0.013% for the current taper design. Conclusion: A low risk of mechanical failure for both fracture types was observed compared to other known complications in revision hip arthroplasty. In addition, the data show that a design change did significantly reduce the risk of a modular fracture.

Heparin Anticoagulant for Human Bone Marrow Does Not Influence In Vitro Performance of Human Mesenchymal Stromal Cells.

Mesenchymal stromal cells (MSCs) are a promising cell source for tissue engineering and regenerative medicine. In our lab, we found that MSC preparations from bone marrow of many different donors had a limited capacity of in vitro differentiation into osteogenic and chondrogenic lineages-a capacity claimed to be inherent to MSCs. The current study was designed to test the hypothesis that the amount of heparin used as anticoagulant during bone marrow harvest had an inhibitory influence on the in vitro differentiation capacity of isolated MSCs. Bone marrow was obtained from the femoral cavity of twelve donors during total hip arthroplasty in the absence or presence of heparin. No coagulation was observed in the absence of heparin. The number of mononuclear cells was independent of heparin addition. Isolated MSCs were characterized by morphology, population doubling times, expression of cell surface antigens and in vitro differentiation. Results of these analyses were independent of the amount of heparin. Transcriptome analyses of cells from three randomly chosen donors and quantitative realtime PCR (qRT-PCR) analysis from cells of all donors demonstrated no clear effect of heparin on the transcriptome of the cells. This excludes heparin as a potential source of disparate results.

Allogenic bone graft for femoral defect augmentation in hip revision arthroplasty: A case series.

Cortical bone loss in revision hip arthroplasty requires an adequate stabilization to achieve a durable implant fixation. This case series shall illustrate possible indications for the use of allogenic grafts in revision hip arthroplasty. Twelve patients with femoral bone loss were treated with allografts. In addition to established clinical scores, the radiological follow-ups were analyzed for hints of implants loosening and the osteointegration of the allografts. After a mean follow-up of 3.0 years the mHHS was 61.3 points and the UCLA 3.8. One patient showed a non-progressive radiolucency around the hip implant. The osteointegration of all allogenic grafts happened on time. Up to the last follow-up no revision surgery of the hip implants and the associated femoral bone graft was observed. Allogenic bone grafts present a method for biological stabilization in situations of large femoral cortical bone defects in revision hip arthroplasty.

Vitamin E-blended highly cross-linked polyethylene liners in total hip arthroplasty: a randomized, multicenter trial using virtual CAD-based wear analysis at 5-year follow-up.

BACKGROUND: Progressive oxidation of highly cross-linked ultra-high molecular weight (UHMPWE-X) liners is considered to be a risk factor for material failure in THA. Antioxidants such as vitamin E (alpha-tocopherol) (UHMWPE-XE) were supplemented into the latest generation of polyethylene liners. To prevent inhomogenous vitamin E distribution within the polymer, blending was established as an alternative manufacturing process to diffusion. The purpose of the present study was to investigate the in vivo wear behavior of UHMWPE-XE in comparison with conventional UHMWPE-X liners using virtual CAD-based radiographs. METHODS: Until now, 94 patients from a prospective, randomized, controlled, multicenter study were reviewed at 5-year follow-up. Of these, 51 (54%) received UHMWPE-XE and 43 (46%) UHMWPE-X liners. Anteroposterior pelvic radiographs were made immediately after surgery and at 1 and 5 years postoperatively. The radiographs were analyzed using the observer-independent analysis software RayMatch® (Raylytic GmbH, Leipzig, Germany). RESULTS: The mean wear rate was measured to be 23.6 µm/year (SD 13.7; range 0.7-71.8 µm). There were no significant differences between the two cohorts (UHMWPE-X: 23.2 µm/year vs. UHMWPE-XE: 24.0 µm/year, p = 0.73). Cup anteversion significantly changed within the 1st year after implantation independent from the type of polyethylene liner [UHMWPE-X: 18.2-23.9° (p = 0.0001); UHMWPE-XE: 21.0-25.5° (p = 0.002)]. No further significant changes of cup anteversion in both groups were found between year 1 and 5 after implantation [UHMWPE-X (p = 0.46); UHMWPE-XE (p = 0.56)]. CONCLUSION: The present study demonstrates that the addition of vitamin E does not adversely affect the midterm wear behavior of UHMWPE-X. The antioxidative benefit of vitamin E is expected to become evident in long-term follow-up. Cup anteversion increment by 5° within the 1st year is likely a result of the released hip flexion contracture resulting in an enhanced posterior pelvic tilt. Therefore, a reassessment of target values in acetabular cup placement might be considered.

Factors affecting operative time in primary total hip arthroplasty: A retrospective single hospital cohort study of 7674 cases.

BACKGROUND: Total hip arthroplasty (THA) is one of the most common orthopedic procedures in developed countries, and the high volume of surgery and the socioeconomic burden of failures demand continuous optimization. Operative time has been identified as a significant independent factor influencing the clinical outcome of THA. OBJECTIVE: The aim of this study was to analyze factors influencing the operative time for THA in a large, single-center cohort. METHODS: A consecutive series of 7,674 cases undergoing primary THA was identified, and after multiple imputation of missing values, univariable and multivariable linear regression analyses were performed. RESULTS: In the univariable analysis, all factors showed significant influences on operative time, while multivariable regression analysis revealed that sex, a diagnosis of hip dysplasia and small femoral component size did not reach significance. Younger age, an underlying diagnosis other than osteoarthritis or hip dysplasia, a large stem size, usage of a conventional stem rather than a short stem, a larger cup size and a cemented fixation technique, however, remained significantly influential in terms of a longer operative time. CONCLUSIONS: This study identified risk factors for longer operative time that in turn is associated with a higher rate of periprosthetic joint infection and impaired clinical outcome. Our findings could help to refine scheduling of total hip arthroplasty procedures in times of increasing cost and efficiency pressure.

Diagnosing periprosthetic hip joint low-grade infection via arthroscopic neo synovium biopsies.

BACKGROUND: There is currently a lack of consensus regarding the most effective diagnostic algorithm for cases of supposed low-grade infection after total hip arthoplasty (THA). OBJECTIVE: The aim of this study was to assess reliability in the use of biopsies, obtained by hip arthroscopy, to detect a periprosthetic hip joint infection (PJI). METHODS: From 2012 to 2016, diagnostic arthroscopy of the hip joint was performed in 20 patients with a supposed PJI following THA. In 10 of these patients, the THA was revised for various reasons after diagnostic arthroscopy. The microbiological and histological findings of the biopsies obtained by arthroscopy were compared to findings from intraoperative samples of the revision arthroplasty. RESULTS: For arthroscopic biopsies, we detected a sensitivity of 1.00 (95% confidence interval [CI] 0.40-1.00), a specificity of 0.83 (95% CI 0.36-1.00), a positive predictive value of 0.80 (95% CI 0.28-1.00), and a negative predictive value of 1.00 (95% CI 0.48-1.00). The accuracy was 0.90. CONCLUSIONS: The analysis of arthroscopic biopsies represents a helpful tool to verify or rule out a PJI in selected patients. Nevertheless, minimally invasive diagnostic tools (e.g., laboratory analysis and aspiration) should be utilized beforehand.

Differential Expression of Cholinergic System Components in Human Induced Pluripotent Stem Cells, Bone Marrow-Derived Multipotent Stromal Cells, and Induced Pluripotent Stem Cell-Derived Multipotent Stromal Cells.

The components of the cholinergic system are evolutionary very old and conserved molecules that are expressed in typical spatiotemporal patterns. They are involved in signaling in the nervous system, whereas their functions in nonneuronal tissues are hardly understood. Stem cells present an attractive cellular system to address functional issues. This study therefore compared human induced pluripotent stem cells (iPSCs; from cord blood endothelial cells), mesenchymal stromal cells derived from iPSCs (iPSC-MSCs), and bone marrow-derived MSCs (BM-MSCs) from up to 33 different human donors with respect to gene expressions of components of the cholinergic system. The status of cells was identified and characterized by the detection of cell surface antigens using flow cytometry. Acetylcholinesterase expression in iPSCs declined during their differentiation into MSCs and was comparably low in BM-MSCs. Butyrylcholinesterase was present in iPSCs, increased upon transition from the three-dimensional embryoid body phase into monolayer culture, and declined upon further differentiation into iPSC-MSCs. In BM-MSCs a notable butyrylcholinesterase expression could be detected in only four donors, but was elusive in other patient-derived samples. Different nicotinic acetylcholine receptor subunits were preferentially expressed in iPSCs and during early differentiation into iPSC-MSCs, low expression was detected in iPS-MSCs and in BM-MSCs. The m2 and m3 variants of muscarinic acetylcholine receptors were detected in all stem cell populations. In BM-MSCs, these gene expressions varied between donors. Together, these data reveal the differential expression of cholinergic signaling system components in stem cells from specific sources and suggest the utility of our approach to establish informative biomarkers.

Use of single-representative reverse-engineered surface-models for RSA does not affect measurement accuracy and precision.

Implant migration can be accurately quantified by model-based Roentgen stereophotogrammetric analysis (RSA), using an implant surface model to locate the implant relative to the bone. In a clinical situation, a single reverse engineering (RE) model for each implant type and size is used. It is unclear to what extent the accuracy and precision of migration measurement is affected by implant manufacturing variability unaccounted for by a single representative model. Individual RE models were generated for five short-stem hip implants of the same type and size. Two phantom analyses and one clinical analysis were performed: "Accuracy-matched models": one stem was assessed, and the results from the original RE model were compared with randomly selected models. "Accuracy-random model": each of the five stems was assessed and analyzed using one randomly selected RE model. "Precision-clinical setting": implant migration was calculated for eight patients, and all five available RE models were applied to each case. For the two phantom experiments, the 95%CI of the bias ranged from -0.28 mm to 0.30 mm for translation and -2.3° to 2.5° for rotation. In the clinical setting, precision is less than 0.5 mm and 1.2° for translation and rotation, respectively, except for rotations about the proximodistal axis (<4.1°). High accuracy and precision of model-based RSA can be achieved and are not biased by using a single representative RE model. At least for implants similar in shape to the investigated short-stem, individual models are not necessary. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:903-910, 2016.

Magnesium-containing layered double hydroxides as orthopaedic implant coating materials--An in vitro and in vivo study.

The total hip arthroplasty is one of the most common artificial joint replacement procedures. Several different surface coatings have been shown to improve implant fixation by facilitating bone ingrowth and consequently enhancing the longevity of uncemented orthopaedic hip prostheses. In the present study, two different layered double hydroxides (LDHs), Mg-Fe- and Mg-Al-LDH, were investigated as potential magnesium (Mg)-containing coating materials for orthopaedic applications in comparison to Mg hydroxide (Mg(OH)2). In vitro direct cell compatibility tests were carried out using the murine fibroblast cell line NIH 3T3 and the mouse osteosarcoma cell line MG 63. The host response of bone tissue was evaluated in in vivo experiments with nine rabbits. Two cylindrical pellets (3 × 3 mm) were implanted into each femoral condyle of the left hind leg. The samples were analyzed histologically and with µ-computed tomography (µ-CT) 6 weeks after surgery. An in vitro cytotoxicity test determined that more cells grew on the LDH pellets than on the Mg(OH)2-pellets. The pH value and the Mg(2+) content of the cell culture media were increased after incubation of the cells on the degradable samples. The in vivo tests demonstrated the formation of fibrous capsules around Mg(OH)2 and Mg-Fe-LDH. In contrast, the host response of the Mg-Al-LDH samples indicated that this Mg-containing biomaterial is a potential candidate for implant coating.

Periostin secreted by mesenchymal stem cells supports tendon formation in an ectopic mouse model.

True tendon regeneration in human patients remains a vision of musculoskeletal therapies. In comparison to other mesenchymal lineages the biology of tenogenic differentiation is barely understood. Specifically, easy and efficient protocols are lacking that might enable tendon cell and tissue differentiation based on adult (stem) cell sources. In the murine mesenchymal progenitor cell line C3H10T½, overexpression of the growth factor bone morphogenetic protein 2 (BMP2) and a constitutively active transcription factor, Smad8 L+MH2, mediates tendon cell differentiation in vitro and the formation of tendon-like tissue in vivo. We hypothesized that during this differentiation secreted factors involved in extracellular matrix formation exert a major impact on tendon development. Gene expression analyses revealed four genes encoding secreted factors that are notably upregulated: periostin, C-type lectin domain family 3 (member b), RNase A4, and follistatin-like 1. These factors have not previously been implicated in tendon biology. Among these, periostin showed a specific expression in tenocytes of adult mouse Achilles tendon and in chondrocytes within the nonmineralized fibrocartilage zone of the enthesis with the calcaneus. Overexpression of periostin alone or in combination with constitutively active BMP receptor type in human mesenchymal stem cells and subsequent implantation into ectopic sites in mice demonstrated a reproducible moderate tenogenic capacity that has not been described before. Therefore, periostin may belong to the factors contributing to the development of tenogenic tissue.

Conservative treatment of upper cervical spine injuries with the halo vest: an appropriate option for all patients independent of their age?

OBJECT: Most upper cervical spine injuries are able to heal conservatively by halo vest application. The acceptance of the halo is different among patients due to the weight of the apparatus and the limited mobility it causes. Additionally, the fracture healing rate in older patients seems to be inferior to that in younger patients, which would make an operative stabilization procedure more appropriate for the elderly. Furthermore, the risk of complications is assumed to be higher in older people. The purpose of this retrospective study was to find out if there are differences in the clinical and radiological results and in complication rates between 2 patient groups with upper cervical spine injuries and halo vest treatment with special interest of their age group. METHODS: A total of 29 patients with upper cervical spine injuries were treated by halo vest application. The clinical and radiological results and the complication and revision surgery rates were identified. Patients were divided into 2 groups (18 patients were < 65 years and 11 were > 65 years), and the results were evaluated to examine whether there were any differences. RESULTS: The clinical and radiological results and the complication rate were not statistically significantly different between the 2 patient groups; however, there was a tendency for a longer time interval for fracture healing and more complications in the elderly people. CONCLUSIONS: If the conditions for conservative treatment of upper cervical spine injuries with halo fixation are right, the clinical and radiological results are good and almost similar in patients regardless of their age, although there is a tendency for more complications in older people.