Reconstruction of the acetabulum in THA using femoral head autografts in developmental dysplasia of the hip.

BACKGROUND: Severe acetabular deficiencies in cases of developmental dysplasia of the hip (DDH) often require complex reconstructive procedures in total hip arthroplasty (THA). The use of autologous femoral head grafts for acetabular reconstruction has been described, but few data is available about clinical results, the rates of non-union or aseptic loosening of acetabular components. METHODS: In a retrospective approach, 101 patients with 118 THA requiring autologous femoral head grafts to the acetabulum because of DDH were included. Six patients had died, another 6 were lost to follow-up, and 104 hips were available for clinical and radiological evaluation at a mean of 68 ± 15 (13 to 159) months. RESULTS: The average Merle d'Aubigné hip score improved from 9 to 16 points. Seven implants had to be revised due to aseptic loosening (6.7%). The revisions were performed 90 ± 34 (56 to 159) months after implantation. The other hips showed a stable position of the sockets without any signs of bony non-union, severe radiolucencies at the implant-graft interface or significant resorption of the graft. CONCLUSION: The use of autologous femoral head grafts with cementless cups in primary THA can achieve promising short- to midterm results in patients with dysplastic hips.

Closing-wedge high tibial osteotomy: survival and risk factor analysis at long-term follow up.

BACKGROUND: Closing-wedge high tibial osteotomy (HTO) is successful for the treatment of medial osteoarthritis with varus malalignment. Preoperative risk factors for HTO failure are still controversial. The aim of this study was to elucidate the outcome and assess the influence of risk factors on long term HTO survival. METHODS: 199 patients were retrospectively studied with a mean follow-up period of 9.6 years after HTO. HTO failure was defined as the need for conversion to TKA. Survival was analyzed with the Kaplan-Meier method. Knee function was evaluated by the Hospital for Special Surgery (HSS) score. HTO-associated complications were also assessed. Univariate, multivariate, and logistic regression analysis were performed to evaluate the influence of age, gender, BMI, preoperative Kellgren-Lawrence osteoarthritis grade, and varus angle on HTO failure. RESULTS: 39 complications were recorded. Thus far, 36 HTOs were converted to TKA. The survival of HTO was 84% after 9.6 years. Knee function was considered excellent or good in 64% of patients. A significant preoperative risk factor for HTO failure was osteoarthritis, Kellgren-Lawrence grade >2. CONCLUSION: HTO provides good clinical results in long-term follow-up. Preoperative osteoarthritis Kellgren-Lawrence grade >2 is a significant predictive risk factor for HTO failure. Results of HTO may be improved by careful patient selection. Complications associated with HTO should not be underestimated.

Radiological determination of the anatomic hip centre from pelvic landmarks.

There are various methods to locate the rotation centre of the hip joint on standard pelvic radiographs. When the geometry of both femoral heads is abnormal, a number of methods are available to locate the physiological hip centre from anatomical landmarks on pelvic radiographs. The accuracy and reliability of six methods were retrospectively investigated on 115 standard pelvic radiographs of both hips of healthy individuals. As a reference against the hip joint centre predicted by these methods, we used the true anatomical centre of the femoral head. Measurements were normalized in relation to pelvic height. The calculated hip rotation centre most closely approached the true anatomical centre of the femoral head when the acetabular teardrop was used as a landmark.

Effect of direct RGD incorporation in PLLA nanofibers on growth and osteogenic differentiation of human mesenchymal stem cells.

The aim of this study was to functionalize synthetic poly-(L-lactic) (PLLA) nanofibers by direct incorporation of cRGD, in order to promote adhesion, growth and osteogenic differentiation of human mesenchymal stem cells (hMSC) in vitro. The cRGD was incorporated into PLLA nanofibers either by emulsion [PLLA-cRGD (d)] or suspension [PLLA-cRGD (s)]. Matrices were seeded with hMSC and cultivated over a period of 28 days under growth conditions and analyzed during the course. Although the mode of incorporation resulted in different distributions of the RGD peptide, it had no impact on the fiber characteristics when compared to corresponding unblended PLLA control fibers. However, hMSC showed better adherence on PLLA-cRGD (d). Nevertheless, this advantage was not reflected during the course of cultivation. Furthermore, the PLLA-cRGD (s) fibers mediated the osteogenic potential of collagen (determined as the expression and deposition of collagen and osteocalcin) to some extent. Further studies are needed in order to optimize the RGD distribution and concentration.

Characterization of a PLLA-collagen I blend nanofiber scaffold with respect to growth and osteogenic differentiation of human mesenchymal stem cells.

We developed a nanofiber scaffold by blending PLLA with collagen I, suitable for bone regeneration. Among several PLLA-COLI ratios tested, cell growth was better enhanced when blends with a ratio of PLLA-COLI 4:1 were used. Here, growth as well as osteoblast differentiation of hMSC was improved when compared to PLLA nanofibers alone. Therefore, blending is a suitable tool to enhance PLLA nanofibers with respect to bone tissue engineering.

Influence of nanofibers on the growth and osteogenic differentiation of stem cells: a comparison of biological collagen nanofibers and synthetic PLLA fibers.

The aim of this study was to compare biological collagen I (ColI) and synthetic poly-(L: -lactide) (PLLA) nanofibers concerning their stability and ability to promote growth and osteogenic differentiation of human mesenchymal stem cells in vitro. Matrices were seeded with human stem cells and cultivated over a period of 28 days under growth and osteoinductive conditions and analyzed during the course. During this time the PLLA nanofibers remained stable while the presence of cells resulted in an attenuation of the ColI nanofiber mesh. Although there was a tendency for better growth and osteoprotegerin production of stem cells when cultured on collagen nanofibers, there was no significant difference compared to PLLA nanofibers or controls. The gene expression of alkaline phosphate, osteocalcin and collagen I diminished in the initial phase of cultivation independent of the polymer used. In the case of PLLA fibers, this gene expression normalized during the course of cultivation, whereas the presence of collagen nanofibers resulted in an increased gene expression of osteocalcin and collagen during the course of the experiment. Taken together the PLLA fibers were easier to produce, more stable and did not compromise growth and differentiation of stem cells over the course of experiment. On the other hand, collagen nanofibers supported the differentiation process to some extent. Nevertheless, the need for fixation as well as the missing stability during cell culture requires further work.

Influence of poly(L-lactic acid) nanofibers and BMP-2-containing poly(L-lactic acid) nanofibers on growth and osteogenic differentiation of human mesenchymal stem cells.

The aim of this study was to characterize synthetic poly-(L-lactic acid) (PLLA) nanofibers concerning their ability to promote growth and osteogenic differentiation of stem cells in vitro, as well as to test their suitability as a carrier system for growth factors. Fiber matrices composed of PLLA or BMP-2-incorporated PLLA were seeded with human mesenchymal stem cells and cultivated over a period of 22 days under growth and osteoinductive conditions, and analyzed during the course of culture, with respect to gene expression of alkaline phosphatase (ALP), osteocalcin (OC), and collagen I (COL-I). Furthermore, COL-I and OC deposition, as well as cell densities and proliferation, were analyzed using fluorescence microscopy. Although the presence of nanofibers diminished the dexamethasone-induced proliferation, there were no differences in cell densities or deposition of either COL-I or OC after 22 days of culture. The gene expression of ALP, OC, and COL-I decreased in the initial phase of cell cultivation on PLLA nanofibers as compared to cover slip control, but normalized during the course of cultivation. The initial down-regulation was not observed when BMP-2 was directly incorporated into PLLA nanofibers by electrospinning, indicating that growth factors like BMP-2 might survive the spinning process in a bioactive form.

The role of mesenchymal stem cells in the pathogenesis of Co-Cr-Mo particle induced aseptic loosening: an in vitro study.

Aseptic loosening is the major factor of failed arthroplasty. Among several theories the particle disease theory is commonly accepted. Different studies examined the complex interactions between wear debris and surrounding cells, especially the monocytic and osteoblastic lineage. This study was designed to elucidate the impact of cobalt-chromium-molybdenum (Co-Cr-Mo) particles on the osteoblastic differentiation and proliferation of human mesenchymal stem cells (hMSC), with respect to the disease pattern of aseptic loosening. The hMSC were incubated in the presence of Co-Cr-Mo particles in different concentrations under growth and osteoinductive conditions. Obtained cultures were analyzed, with respect to cell density and proliferation, using CASY cell count system and Ki-67 immunostaining. Osteogenic differentiation was analyzed by fluorescence microscopy using antibodies for collagen I, alcaline phosphatase, osteocalcin and osteopontin. Additionally, scanning electron microscopy was used to analyze the localisation of Co-Cr-Mo particles in the culture system. Our findings indicate that these particles were located within the hMSC. Proliferation, as well as cell density, was diminished. The remaining cells showed increased staining of osteocalcin and osteopontin, with visible differences in deposition of these proteins, indicating a deregulation of matrix formation and differentiation respectively. Therefore, it is likely that this influence of Co-Cr-Mo particles on hMSC are involved in the disease pattern of aseptic loosening.

Electrospinning approaches toward scaffold engineering--a brief overview.

Tissue engineering involves the in vitro seeding of cells onto scaffolds which assume the role of supporting cell adhesion, migration, proliferation, and differentiation, and which define the three-dimensional shape of the tissue to be engineered. Among the various types of scaffold architectures available, scaffolds based on nanofibers mimicking to a certain extent the structure of the extracellular matrix offer great advantages. Electrospinning is the technique of choice for the preparation of such scaffolds. Investigations have revealed that the nanofibrous structure promotes cell adhesion, proliferation, and differentiation. Parameters relevant for these processes such as fiber diameters, surface topology, porosity, mechanical properties, and the fibrous architecture of the scaffold can be controlled by electrospinning in a broad range.

Determination of the rotational center of the hip.

We introduce a new method to determine the anatomic rotation center of the hip. In total, 214 healthy hip joints were examined and statistically analyzed. As a reference point we used the intersection between Koehler's line and a line between the upper rims of the two foramina obturatoria. In relation to the reference point the anatomic hip center is localized 7.7% in vertical direction and 17.4% in horizontal direction for male individuals and 7.75 and 15.4% for female individuals, respectively. Those data were referred to the pelvic height. Our data can be used to determine the anatomic hip center in an easy and reliable way, not only for preoperative planning but also for retrospective investigations.

Distinct gene expression profile of human mesenchymal stem cells in comparison to skin fibroblasts employing cDNA microarray analysis of 9600 genes.

Broad differentiation capacity has been described for mesenchymal stem cells (MSC) from human bone marrow. We sought to identify genes associated with the immature state and pluripotency of this cell type. To prove the pluripotent state of the MSC, differentiation into osteocytes, adipocytes, and chondrocytes was performed in vitro. In contrast, normal skin cells did not harbor these differentiation abilities. We compared the expression profile of human bone marrow MSC with cDNA from one primary human skin cell line as control, using a cDNA chip providing 9600 genes. The identity of all relevant genes was confirmed by direct sequencing. Data of gene array expression were corroborated employing quantitative PCR analysis. About 80 genes were differently expressed more than threefold in MSC compared to mature skin fibroblasts. Interestingly, primary human MSC were found to upregulate a number of genes important for embryogenesis such as distal-less homeo box 5, Eyes absent homolog 2, inhibitor of DNA binding 3, and LIM protein. In contrast, mesenchymal lineage genes were downregulated in MSC in comparison to skin cells. We also detected expression of some genes involved in neural development, indicating the broad differentiation capabilities of MSC. We conclude that human mesenchymal stem cells harbor an expression profile distinct from mature skin fibroblast, and genes associated with developmental processes and stem cell function are highly expressed in adult mesenchymal stem cells.

Intradiscal application of hyaluronic acid in the non-human primate lumbar spine: radiological results.

Prospectively, with randomized segment-treatment assignment, and with blinded evaluators, lumbar motion segments in Cercopithecus monkeys were analyzed for macroscopic and radiological changes 24 weeks after nucleotomy and nucleotomy with additional intradiscal application of different hyaluronic acid formulations versus untreated control segments. The objective was to find out whether hyaluronic acid is able to influence the degenerative cascade in nonhuman primates after nucleotomy. In a similar procedure, hyaluronic acid has proven to decrease degeneration after nucleotomy in a Minipig model. This is the first such study ever undertaken in primates, thus trying to overcome the known limitations of non-primate spine models. Twenty monkeys with four segments each obtained nucleotomy in three segments and solely exposure of another control segment. Nucleotomy was performed from a transpsoatic retroperitoneal approach. Preoperative radiographs and follow-up radiographs, magnetic resonance imaging (MRI), computed tomography (CT), Q-CT with bone mineral density measurements and three-dimensional reconstruction were obtained and analyzed qualitatively and quantitatively. Segments with high-molecular-weight hyaluronic acid (Hylan G-F 20) application proved to be significantly superior over those with a standard nucleotomy in radiographs, MR images, CT scans, and macroscopic appearance at follow-up. Control segments remained unaffected. Interdependence between the different methods validated the utilized methods of quantitative radiological assessment of degeneration. Hylan G-F 20 appears to be a possible adjunct in reducing postoperative degeneration in an animal nucleotomy model. It deserves further evaluation, despite the fact that the mechanisms of its effects are still speculative.