Lehrstuhl für Orthopädie
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Sonstige beteiligte Institutionen
With ageing, the loss of bone mass correlates with the expansion of adipose tissue in human bone marrow thus facilitating bone-related diseases like osteopenia and osteoporosis. The molecular mechanisms underlying these events are still largely unknown. Reduced osteogenesis and concurrently enhanced adipogenesis might not only occur due to the impairment of conventional osteogenic differentiation originating from mesenchymal stem cells (MSCs). Additionally, transdifferentiation of (pre-)osteoblasts into adipocytes could contribute to the fatty conversion. Therefore, the aim of the present study was to prove the existence of transdifferentiation between the adipogenic and osteogenic lineage and to elucidate molecular mechanisms underlying this phenomenon. At first, a cell culture system of primary human MSCs was established that allowed for differentiation into the adipogenic and osteogenic lineage and proved that the MSC-derived adipocytes and pre-osteoblasts were capable of transdifferentiation (reprogramming) from one into the other lineage. Thereby, lineage-specific markers were completely reversed after reprogramming of pre-osteoblasts into adipocytes. The osteogenic transdifferentiation of adipocytes was slightly less efficient since osteogenic markers were present but the adipogenic ones partly persisted. Hence, plasticity also reached into the differentiation pathways of both lineages and the better performance of adipogenic reprogramming further supported the assumption of its occurrence in vivo. The subsequent examination of gene expression changes by microarray analyses that compared transdifferentiated cells with conventionally differentiated ones revealed high numbers of reproducibly regulated genes shortly after initiation of adipogenic and osteogenic reprogramming. Thereof, many genes were correlated with metabolism, transcription, and signal transduction as FGF, IGF, and Wnt signalling, but only few of the established adipogenesis- and none of the osteogenesis-associated marker genes were detected within 24 h after initiation of transdifferentiation. To find possible key control factors of transdifferentiation amongst the huge amount of regulated genes, a novel bioinformatic scoring scheme was developed that ranked genes due to their potential relevance for reprogramming. Besides the reproducibility and level of their regulation, also the possible reciprocity between the adipogenic and osteogenic transdifferentiation pathway was taken into account. Fibroblast growth factor 1 (FGF1) that ranked as one of the leading candidates to govern reprogramming was proven to inhibit adipogenic differentiation as well as adipogenic transdifferentiation in our cell culture system. Further examination of the FGF signalling pathway and other highly ranked genes could help to better understand the age-related fatty degeneration at the molecular level and therefore provide target molecules for therapeutic modulation of the plasticity of both lineages in order to inhibit adipogenic degeneration and to enhance osteogenesis.
Alignment strategies for primary total knee arthroplasty (TKA) have changed significantly over time with a shift towards a more individualized alignment goal. At the same time, computer-assisted surgery (CAS) has gained interest for intraoperative control and accuracy in implant positioning and limb alignment. Despite the often discussed benefits and drawbacks of robotics and navigation for TKA, the routine use of these new devices on a day-to-day basis remains obscure. Therefore, nationwide hospital billing data based on the Operation Procedure Classification System (OPS) were retrieved from the Federal Statistical Office of Germany for the period from 2010 to 2021. OPS codes for primary total knee arthroplasty (OPS code: 5-822*) were further analyzed regarding the usage of computer navigation (additional OPS code: 5-988) or robotic devices (additional OPS code: 5-987). Gender and age at the time of surgery were also assessed. The results show a total of 2,226,559 primary TKAs were implanted between 2010 and 2021, of which 2,044,914 were performed conventionally (91.84% of all TKAs). A total of 170,276 TKAs were performed using navigation technique (7.65% of all TKAs) and another 11,369 TKAs were performed using robotics (0.51% of all TKAs). For the period from 2018 to 2021, a substantial increase in robot-assisted TKA (R-TKA) was observed, with an average increase rate of 84.74% per year, while the number of navigated TKAs declined (−3.67% per year). Computer-assisted surgery, and particularly robotics for TKA, are seeing growing popularity and stepwise translation into routine clinical use in Germany, with a steep increase rate of more than 80% per year since 2018. Nevertheless, the majority of TKAs are still performed using manual instrumentation, rendering conventional TKA the currently unchanged gold standard.
Ultra-high-resolution photon-counting detector CT arthrography of the ankle: a feasibility study
(2023)
This study was designed to investigate the image quality of ultra-high-resolution ankle arthrography employing a photon-counting detector CT. Bilateral arthrograms were acquired in four cadaveric specimens with full-dose (10 mGy) and low-dose (3 mGy) scan protocols. Three convolution kernels with different spatial frequencies were utilized for image reconstruction (ρ\(_{50}\); Br98: 39.0, Br84: 22.6, Br76: 16.5 lp/cm). Seven radiologists subjectively assessed the image quality regarding the depiction of bone, hyaline cartilage, and ligaments. An additional quantitative assessment comprised the measurement of noise and the computation of contrast-to-noise ratios (CNR). While an optimal depiction of bone tissue was achieved with the ultra-sharp Br98 kernel (S ≤ 0.043), the visualization of cartilage improved with lower modulation transfer functions at each dose level (p ≤ 0.014). The interrater reliability ranged from good to excellent for all assessed tissues (intraclass correlation coefficient ≥ 0.805). The noise levels in subcutaneous fat decreased with reduced spatial frequency (p < 0.001). Notably, the low-dose Br76 matched the CNR of the full-dose Br84 (p 0.999) and superseded Br98 (p < 0.001) in all tissues. Based on the reported results, a photon-counting detector CT arthrography of the ankle with an ultra-high-resolution collimation offers stellar image quality and tissue assessability, improving the evaluation of miniscule anatomical structures. While bone depiction was superior in combination with an ultra-sharp convolution kernel, soft tissue evaluation benefited from employing a lower spatial frequency.
Background and purpose - Due to the relative lack of reports on the medium- to long-term clinical and radiographic results of modular femoral cementless revision, we conducted this study to evaluate the medium- to long-term results of uncemented femoral stem revisions using the modular MRP-TITAN stem with distal diaphyseal fixation in a consecutive patient series.
Patients and methods - We retrospectively analyzed 163 femoral stem revisions performed between 1993 and 2001 with a mean follow-up of 10 (5-16) years. Clinical assessment included the Harris hip score (HHS) with reference to comorbidities and femoral defect sizes classified by Charnley and Paprosky. Intraoperative and postoperative complications were analyzed and the failure rate of the MRP stem for any reason was examined.
Results - Mean HHS improved up to the last follow-up (37 (SD 24) vs. 79 (SD 19); p < 0.001). 99 cases (61%) had extensive bone defects (Paprosky IIB-III). Radiographic evaluation showed stable stem anchorage in 151 cases (93%) at the last follow-up. 10 implants (6%) failed for various reasons. Neither a breakage of a stem nor loosening of the morse taper junction was recorded. Kaplan-Meier survival analysis revealed a 10-year survival probability of 97% (95% CI: 95-100).
Interpretation - This is one of the largest medium- to longterm analyses of cementless modular revision stems with distal diaphyseal anchorage. The modular MRP-TITAN was reliable, with a Kaplan-Meier survival probability of 97% at 10 years.
The goal of the project was to establish knock down of mRNA in human mesenchymal stem cells. Since these cells are difficult to transfect, a viral approach is needed to achieve sufficient expression of e. g. shRNA in a high percentage of cells to allow for an efficient silencing of corresponding mRNAs. For this purpose for every gene product of interest, a number of shRNA clones have to be tested to detect an individual shRNA with sufficient efficacy. Lentiviral systems for shRNA approaches have recently become available. The principal advantage of the lentiviral system is that it allows gene silencing in nondividing cells and therefore expands the usefulness of the RNAi-based gene silencing system. Lentivirus-delivered shRNAs are capable of specific, highly stable and functional silencing of gene expression in a variety of cell types. Since the viral transfection of MSCs is a time consuming process that involves transfection of 293 FT cells plus transduction of target cells, for this thesis the following approach was chosen: genes of interest were checked for expression in 293FT cells by RT-PCR. These gene products can be silenced in 293FT cells simply by transfection of shRNA clones and efficacy was subsequently tested by RT-PCR. Beyond this thesis then the project can proceed with effective clones to transduce primary MSCs with individual shRNA clones identified as effective silencing tool in this thesis.
The biology of vitamin D3 is well defined, as are the effects of its active metabolites on various cells, including mesenchymal stromal/stem cells (MSCs). However, the biological potential of its precursor, cholecalciferol (VD3), has not been sufficiently investigated, although its significance in regenerative medicine — mainly in combination with various biomaterial matrices — has been recognized. Given that VD3 preconditioning might also contribute to the improvement of cellular regenerative potential, the aim of this study was to investigate its effects on bone marrow (BM) MSC functions and the signaling pathways involved. For that purpose, the influence of VD3 on BM-MSCs obtained from young human donors was determined via MTT test, flow cytometric analysis, immunocytochemistry, and qRT-PCR. Our results revealed that VD3, following a 5-day treatment, stimulated proliferation, expression of pluripotency markers (NANOG, SOX2, and Oct4), and osteogenic differentiation potential in BM-MSCs, while it reduced their senescence. Moreover, increased sirtuin 1 (SIRT1) expression was detected upon treatment with VD3, which mediated VD3-promoted osteogenesis and, partially, the stemness features through NANOG and SOX2 upregulation. In contrast, the effects of VD3 on proliferation, Oct4 expression, and senescence were SIRT1-independent. Altogether, these data indicate that VD3 has strong potential to modulate BM-MSCs' features, partially through SIRT1 signaling, although the precise mechanisms merit further investigation.
Purpose
This study investigates the redislocation rate and functional outcome at a minimum follow-up of five years after medial patellofemoral ligament (MPFL) reconstruction with soft tissue patellar fixation for patella instability.
Methods
Patients were retrospectively identified and knees were evaluated for trochlea dysplasia according to Dejour, for presence of patella alta and for presence of cartilage lesion at surgery. At a minimum follow-up of five years, information about an incident of redislocation was obtained. Kujala, Lysholm, and Tegner questionnaires as well as range of motion were used to measure functional outcome.
Results
Eighty-nine knees were included. Follow-up rate for redislocation was 79.8% and for functional outcome 58.4%. After a mean follow-up of 5.8 years, the redislocation rate was 5.6%. There was significant improvement of the Kujala score (68.8 to 88.2, p = 0.000) and of the Lysholm score (71.3 to 88.4, p = 0.000). Range of motion at follow-up was 149.0° (115–165). 77.5% of the knees had patella alta and 52.9% trochlear dysplasia types B, C, or D. Patellar cartilage legions were present in 54.2%. Redislocations occurred in knees with trochlear dysplasia type C in combination with patella alta.
Conclusion
MPFL reconstruction with soft tissue patellar fixation leads to significant improvement of knee function and low midterm redislocation rate. Patients with high-grade trochlear dysplasia should be considered for additional osseous correction.