Publications by authors named "Dirk Wähnert"

47 Publications

Spongostan Leads to Increased Regeneration of a Rat Calvarial Critical Size Defect Compared to NanoBone and Actifuse.

Materials (Basel) 2021 Apr 14;14(8). Epub 2021 Apr 14.

Molecular Neurobiology, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany.

Bone substitute materials are becoming increasingly important in oral and maxillofacial surgery. Reconstruction of critical size bone defects is still challenging for surgeons. Here, we compared the clinically applied organic bone substitute materials NanoBone (nanocrystalline hydroxyapatite and nanostructured silica gel; = 5) and Actifuse (calcium phosphate with silicate substitution; = 5) with natural collagen-based Spongostan™ (hardened pork gelatin containing formalin and lauryl alcohol; = 5) in bilateral rat critical-size defects (5 mm diameter). On topological level, NanoBone is known to harbour nanopores of about 20 nm diameter, while Actifuse comprises micropores of 200-500 µm. Spongostan™, which is clinically applied as a haemostatic agent, combines in its wet form both nano- and microporous topological features by comprising 60.66 ± 24.48 μm micropores accompanied by nanopores of 32.97 ± 1.41 nm diameter. Micro-computed tomography (µCT) used for evaluation 30 days after surgery revealed a significant increase in bone volume by all three bone substitute materials in comparison to the untreated controls. Clearly visual was the closure of trepanation in all treated groups, but granular appearance of NanoBone and Actifuse with less closure at the margins of the burr holes. In contrast, transplantion of Spongostan™ lead to complete filling of the burr hole with the highest bone volume of 7.98 ccm and the highest bone mineral density compared to all other groups. In summary, transplantation of Spongostan™ resulted in increased regeneration of a rat calvarial critical size defect compared to NanoBone and Actifuse, suggesting the distinct nano- and microtopography of wet Spongostan™ to account for this superior regenerative capacity. Since Spongostan™ is a clinically approved product used primarily for haemostasis, it may represent an interesting alternative in the reconstruction of defects in the maxillary region.
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http://dx.doi.org/10.3390/ma14081961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8070843PMC
April 2021

Effects of the first lockdown of the COVID-19 pandemic on the trauma surgery clinic of a German Level I Trauma Center.

Eur J Trauma Emerg Surg 2021 Apr 15. Epub 2021 Apr 15.

Protestant Hospital of Bethel Foundation, Department of Trauma Surgery and Orthopaedics, University Hospital OWL of Bielefeld University, Campus Bielefeld-Bethel, Burgsteig 13, 33617, Bielefeld, Germany.

Purpose: The effects of the first pandemic wave on a German Level I Trauma Center should be evaluated to find ways to redistribute structural, personnel, and financial resources in a targeted manner in preparation for the assumed second pandemic wave.

Methods: We examined the repercussions of the first wave of the pandemic on the trauma surgery clinic of a Level I Trauma Center and compared the data with data from 58 other trauma clinics. The results could aid in orientating the distribution of structural, financial, and human resources (HR) during the second wave. The period between March 16 and April 30, 2020 was compared with the data over the same period during 2019. Information was collected from the HR department, central revenue management, and internal documentation.

Results: The proportion of trauma surgical patients in the emergency room decreased by 22%. The number of polytrauma cases increased by 53%. Hospital days of trauma surgery patients in the intensive and intermediate care wards increased by 90%. The number of operations decreased by 15%, although the operating time outside of normal working hours increased by 44%. Clinics with more than 600 beds recorded a decrease in cases and emergencies by 8 and 9%, respectively, while the Trauma Center showed an increase of 19 and 12%. The results reflect the importance of level I trauma centers in the lockdown phase.

Conclusion: To reduce the risk of an increased burden on the healthcare infrastructure, it suggests the care of trauma and COVID-19 patients should be separated locally, when possible.
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http://dx.doi.org/10.1007/s00068-021-01635-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048337PMC
April 2021

Removal of cement-augmented screws in distal femoral fractures and the effect of retained screws and cement on total knee arthroplasty: a biomechanical investigation.

J Orthop Traumatol 2021 Feb 27;22(1). Epub 2021 Feb 27.

AO Research Institute Davos, Clavadelerstrasse 8, 7270, Davos, Switzerland.

Background: Given the increasing number of osteoporotic fractures of the distal femur, screw augmentation with bone cement is an option to enhance implant anchorage. However, in implant removal or revision surgeries, the cement cannot be removed from the distal femur without an extended surgical procedure. Therefore, the aims of this study were to investigate (1) whether cement augmentation has any influence on screw removal and removal torque, and (2) whether the implantation of a femoral component of a knee arthroplasty and its initial interface stability are affected by the remaining screws/cement.

Material And Methods: Eight pairs of fresh-frozen human female cadaveric distal femurs (mean age, 86 years) with a simulated AO/OTA 33 A3 fracture were randomized in paired fashion to two groups and fixed with a distal femoral locking plate using cannulated perforated locking screws. Screw augmentation with bone cement was performed in one of the groups, while the other group received no screw augmentation. Following biomechanical testing until failure (results published separately), the screws were removed and the removal torque was measured. A femoral component of a knee arthroplasty was then implanted, and pull-out tests were performed after cement curing. Interference from broken screws/cement was assessed, and the maximum pull-out force was measured.

Results: The mean screw removal torque was not significantly different between the augmented (4.9 Nm, SD 0.9) and nonaugmented (4.6 Nm, SD 1.3, p = 0.65) screw groups. However, there were significantly more broken screws in in the augmented screw group (17 versus 9; p < 0.001). There was no significant difference in the pull-out force of the femoral component between the augmented (2625 N, SD 603) and nonaugmented (2653 N, SD 542, p = 0.94) screw groups.

Conclusion: The screw removal torque during implant removal surgery does not significantly differ between augmented and nonaugmented screws. In the augmented screw group, significantly more screws failed. To overcome this, the use of solid screws in holes B, C, and G can be considered. Additionally, it is possible to implant a femoral component for knee arthroplasty that retains the initial anchorage and does not suffer from interference with broken screws and/or residual cement.

Level Of Evidence: 5.
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http://dx.doi.org/10.1186/s10195-021-00568-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7914321PMC
February 2021

Local bone quality measure and construct failure prediction: a biomechanical study on distal femur fractures.

Arch Orthop Trauma Surg 2021 Feb 15. Epub 2021 Feb 15.

Department of Trauma and Orthopedic Surgery, Protestant Hospital of Bethel Foundation, University Hospital OWL of Bielefeld University, Campus Bielefeld Bethel, Burgsteig 13, 33617, Bielefeld, Germany.

Introduction: The aim of this investigation was to better understand the differences in local bone quality at the distal femur and their correlation with biomechanical construct failure, with the intention to identify regions of importance to optimize implant anchorage.

Materials And Methods: Seven fresh-frozen female femurs underwent high-resolution peripheral quantitative computed tomography (HR-pQCT) to determine bone mineral density (BMD) within three different regions of interest (distal, intermedium, and proximal) at the distal femur. In addition, local bone quality was assessed by measuring the peak torque necessary to break out the trabecular bone along each separate hole of a locking compression plate (LCP) during its instrumentation. Finally, biomechanical testing was performed using cyclic axial loading until failure in an AO/OTA 33 A3 fracture model.

Results: Local BMD was highest in the distal region. This was confirmed by the measurement of local bone quality using DensiProbe. The most distal holes represented locations with the highest breakaway torque resistance, with the holes on the posterior side of the plate indicating higher values than those on its anterior side. We demonstrated strong correlation between the cycles to failure and local bone strength (measured with DensiProbe) in the most distal posterior screw hole, having the highest peak torque.

Conclusion: The local bone quality at the distal femur indicates that in plated distal femur fractures the distal posterior screw holes seem to be the key ones and should be occupied. Measurement of the local bone strength with DensiProbe is one possibility to determine the risk of construct failure, therefore, thresholds need to be defined.
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http://dx.doi.org/10.1007/s00402-021-03782-7DOI Listing
February 2021

Development and first biomechanical validation of a score to predict bone implant interface stability based on clinical qCT scans.

Sci Rep 2021 Feb 8;11(1):3273. Epub 2021 Feb 8.

Department of Trauma, Hand, and Reconstructive Surgery, University Hospital Muenster, Albert-Schweitzer-Campus 1, Building W1, 48149, Muenster, Germany.

Sufficient implant anchoring in osteoporotic bone is one major challenge in trauma and orthopedic surgery. In these cases, preoperative planning of osteosynthesis is becoming increasingly important. This study presents the development and first biomechanical validation of a bone-implant-anchorage score based on clinical routine quantitative computer tomography (qCT) scans. 10 pairs of fresh frozen femora (mean age 77.4 years) underwent clinical qCT scans after placing 3 referential screws (for matching with the second scan). Afterwards, three 4.5 mm cortical screws (DePuy Synthes, Zuchwil, Switzerland) were placed in each distal femur in the dia-metaphyseal transition followed by the second CT scan. The femur was segmented using thresholding and its outer shape was visualized as a surface model. A 3D model of the cortex screw in STL format was used to model the screw surface precisely. For each femur, the 3 cortex screw models were exactly positioned at the locations previously determined using the second CT scan. The BMD value was calculated at the center of each triangle as an interpolation from the measured values at the three vertices (triangle corners) in the CT. Scores are based on the sum of all the triangles' areas multiplied by their BMD values. Four different scores were calculated. A screw pull-out test was performed until loss of resistance. A quadratic model adequately describes the relation between all the scores and pull-out values. The square of the best score explains just fewer than 70% of the total variance of the pull-out values and the standardized residual which were approximately normally distributed. In addition, there was a significant correlation between this score and the peak pull-out force (p < 0.001). The coefficient of determination was 0.82. The presented score has the potential to improve preoperative planning by adding the mechanical to the anatomical dimension when planning screw placement.
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http://dx.doi.org/10.1038/s41598-021-82788-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7870929PMC
February 2021

Differentiation of Traumatic Osteoporotic and Non-Osteoporotic Vertebral AO A3 Fractures by Analyzing the Posterior Edge Morphology-A Retrospective Feasibility Study.

J Clin Med 2020 Dec 2;9(12). Epub 2020 Dec 2.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Muenster, Albert-Schweitzer-Campus 1, Building W1, 48149 Muenster, Germany.

Background: Differentiation between traumatic osteoporotic and non-osteoporotic vertebral fractures is crucial for optimal therapy planning. We postulated that the morphology of the posterior edge of the cranial fragment of A3 vertebral fractures is different in these entities. Therefore, the purpose of this study is to develop and validate a simple method to differentiate between osteoporotic and non-osteoporotic A3 vertebral fractures by morphological analysis.

Methods: A total of 86 computer tomography scans of AO Type A3 (cranial burst) vertebral body fractures (52 non-osteoporotic, 34 osteoporotic) were included in this retrospective study. Posterior edge morphology was analyzed using the sagittal paramedian slice with the most prominent shaped bulging. Later, the degree of bulging of the posterior edge fragment was quantified using a geometric approach. Additionally, the Hounsfield units of the broken vertebral body, the vertebra above, and the vertebra below the fracture were measured.

Results: We found significant differences in the extent of bulging comparing osteoporotic and non-osteoporotic fractures in our cohort. Using the presented method, sensitivity was 100%, specificity was 96%. The positive predictive value (PPV) was 94%. In contrast, by evaluating the Hounsfield units, sensitivity was 94%, specificity 94% and the PPV was 91%.

Conclusions: Our method of analysis of the bulging of the dorsal edge fragment in traumatic cranial burst fractures cases allows, in our cases, a simple and valid differentiation between osteoporotic and non-osteoporotic fractures. Further validation in a larger sample, including dual-energy X-ray absorptiometry (DXA) measurements, is necessary.
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http://dx.doi.org/10.3390/jcm9123910DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760871PMC
December 2020

Variable fixation promotes callus formation: an experimental study on transverse tibial osteotomies stabilized with locking plates.

BMC Musculoskelet Disord 2020 Dec 3;21(1):806. Epub 2020 Dec 3.

Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.

Background: A new locking screw technology, named variable fixation, has been developed aiming at promoting bone callus formation providing initial rigid fixation followed by progressive fracture gap dynamisation. In this study, we compared bone callus formation in osteotomies stabilized with standard locking fixation against that of osteotomies stabilized with variable fixation in an established tibia ovine model.

Methods: A 3 mm tibial transverse osteotomy gap was stabilized in three groups of six female sheep each with a locking plate and either 1) standard fixation in both segments (group LS) or 2) variable fixation in the proximal and standard fixation in the distal bone segment (group VFLS) or 3) variable fixation in both segments (group VFLS). The implantation site and fracture healing were compared between groups by means of radiologic, micro tomographic, biomechanical, and histological investigations.

Results: Compared to LS callus, VFLS callus was 40% larger and about 3% denser, while VFLS callus was 93% larger and its density about 7.2% lower. VFLS showed 65% and VFLS 163% larger amount of callus at the cis-cortex. There wasn't a significant difference in the amount of callus at the cis and trans-cortex in groups featuring variable fixation only. Investigated biomechanical variables were not significantly different among groups and histology showed comparable good healing in all groups. Tissues adjacent to the implants did not show any alteration of the normal structure in all groups.

Conclusions: Variable fixation promoted the formation of a larger amount of bone callus, equally distributed at the cis and trans cortices. The histological and biomechanical properties of the variable fixation callus were equivalent to those of the standard fixation callus. The magnitude of variable fixation had a biological effect on the formation of bone callus. At the implantation site, the usage of variable fixation did not raise additional concerns with respect to standard fixation. The formation of a larger amount of mature callus suggests that fractures treated with variable fixation might have a higher probability to bridge the fracture gap. The conditions where its usage can be most beneficial for patients needs to be clinically defined.
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http://dx.doi.org/10.1186/s12891-020-03781-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7713143PMC
December 2020

Periprosthetic fracture fixation in Vancouver B1 femoral shaft fractures: A biomechanical study comparing two plate systems.

J Orthop Translat 2020 Sep 8;24:150-154. Epub 2020 Feb 8.

Maria-Josef-Hospital Greven, Department of Trauma and Orthopaedic Surgery Lindenstraße, 2948268, Greven, Germany.

Introduction: Periprosthetic fractures of the femur are an increasing problem in today's trauma and orthopaedic surgery. Owing to the hip stem, implant anchorage is very difficult in the proximal femur. This study compares two plate systems regarding their biomechanical properties and the handling in periprosthetic fracture fixation of the proximal femur.

Materials And Methods: Using eight pairs of fresh, frozen human proximal femora the Locking Compression Plate/Locking Attachment Plate construct (LCP/LAP) (group I, DePuy Synthes) was compared to the new LOQTEQ® periprosthetic distal lateral femur plate (group II, AAP Implantate AG). After implantation of press fit femoral hip stems a Vancouver B1 fracture model was used. Biomechanical testing was performed by cyclic axial loading with a constant increment of 0.1 N/cycle starting from 750 N axial loading. Every 250 cycles an a.p. x-ray was done to evaluate failure.

Results: The Group II showed significant higher axial stiffness (+42%) compared with Group I. In addition, Group II withstood significantly more load-cycles until failure (20%). The mode of catastrophic failure was plate breakage in Group II, whereas, in Group I, all plates showed an early bending followed by plate breakage.

Discussion And Conclusion: Both plate systems enable screw placement around hip stems. The hinge plate showed superior biomechanical results compared with the locking compression plate/locking attachment plate construct. Furthermore, the hinge plate offers variable hinges and variable angel locking making bicortical screw placement around hip stems more comfortable and safe.

The Translational Potential Of This Article: The results of this study can be directly transferred to patient care. With the innovative hinge plate, the surgeon has a biomechanically superior implant, which also offers improved options for screw placement compared to a standard locking plate.
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http://dx.doi.org/10.1016/j.jot.2020.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7548384PMC
September 2020

Influence of the Reamer-Irrigator-Aspirator diameter on femoral bone strength and amount of harvested bone graft - a biomechanical cadaveric study.

Injury 2020 Dec 28;51(12):2846-2850. Epub 2020 Sep 28.

University Hospital Muenster, Department of Trauma, Hand and Reconstructive Surgery, Albert-Schweitzer-Campus 1, Building W1, 48149 Muenster, Germany.

Background: Treatment of large bone defects is still related to unsolved problems in orthopaedic trauma surgery. Minimally invasive intramedullary reaming with the use of the Reamer-Irrigator-Aspirator (RIA) device allows autograft harvesting of large bone graft amounts from the medullary canal of the femur. The aim of this study was to investigate the influence of RIA diameter on femoral bone strength and amount of harvested bone graft in a human cadaveric model.

Methods: Forty-five pairs human cadaveric femora were randomized to 3 paired groups with 15 pairs each. One femur of each pair was reamed with RIA at a diameter of either 1.5 mm (group 1), 2.5 mm (group 2) or 4.0 mm (group 3) larger than its isthmus, whereas its contralateral femur was left intact without reaming. The amount of harvested bone graft was determined for each specimen and all femora were destructively tested in internal rotation under 750 N axial compression to calculate their torsional stiffness and torque at failure.

Results: Significant reduction in torsional stiffness was detected after reaming in group 3 (p = 0.03) in contrast to groups 1 and 2 where no such significant reduction was observed (p ≥ 0.34). Torque at failure was significantly reduced after reaming in all 3 groups (p ≤ 0.04). Collected bone graft amount in group 3 was significantly bigger compared to groups 1 and 2 (p ≤ 0.04).

Conclusions: Reaming with RIA diameter of 4.0 mm larger than the isthmus of the femur seems to influence considerably its torsional stiffness, however, it allows harvesting of a significantly bigger bone graft amount.
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http://dx.doi.org/10.1016/j.injury.2020.09.057DOI Listing
December 2020

Bone Regeneration: A Novel Osteoinductive Function of Spongostan by the Interplay between Its Nano- and Microtopography.

Cells 2020 03 7;9(3). Epub 2020 Mar 7.

Molecular Neurobiology, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany.

Scaffold materials for bone regeneration are crucial for supporting endogenous healing after accidents, infections, or tumor resection. Although beneficial impacts of microtopological or nanotopological cues in scaffold topography are commonly acknowledged, less consideration is given to the interplay between the microscale and nanoscale. Here, micropores with a 60.66 ± 24.48 µm diameter ordered by closely packed collagen fibers are identified in pre-wetted Spongostan, a clinically-approved collagen sponge. On a nanoscale level, a corrugated surface of the collagen sponge is observable, leading to the presence of 32.97 ± 1.41 nm pores. This distinct micro- and nanotopography is shown to be solely sufficient for guiding osteogenic differentiation of human stem cells in vitro. Transplantation of Spongostan into a critical-size calvarial rat bone defect further leads to fast regeneration of the lesion. However, masking the micro- and nanotopographical cues using SiO nanoparticles prevents bone regeneration in vivo. Therefore, we demonstrate that the identified micropores allow migration of stem cells, which are further driven towards osteogenic differentiation by scaffold nanotopography. The present findings emphasize the necessity of considering both micro- and nanotopographical cues to guide intramembranous ossification, and might provide an optimal cell- and growth-factor-free scaffold for bone regeneration in clinical settings.
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http://dx.doi.org/10.3390/cells9030654DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7140719PMC
March 2020

Correction to: Ex situ reconstruction of comminuted radial head fractures: is it truly worth a try?

Arch Orthop Trauma Surg 2020 Mar;140(3):441

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus, Building W1, 48149, Munster, Germany.

The original version of this article unfortunately contained a mistake.
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http://dx.doi.org/10.1007/s00402-019-03330-4DOI Listing
March 2020

Ex situ reconstruction of comminuted radial head fractures: is it truly worth a try?

Arch Orthop Trauma Surg 2019 Dec 5;139(12):1723-1729. Epub 2019 Aug 5.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus, Building W1, 48149, Munster, Germany.

Introduction: Complex radial head fractures are difficult to treat. In cases where stable fixation cannot be achieved, radial head resection or primary arthroplasty are frequently performed. Ex situ reconstruction of comminuted fractures may also be an option. This technique has widely been neglected in the literature, and only two small case series report satisfactory results. The aim of the present case series was to determine the functional and radiological outcomes of ex situ reconstructed Mason III and Mason IV fractures. We expect that the on-table reconstruction of comminuted radial head fractures will lead to bony union with no avascular necrosis in the postoperative course, which will demonstrate that this operative procedure is a reasonable option.

Patients And Methods: Two Mason type III and seven Mason type IV fractures (including four Monteggia-like lesions) were reconstructed ex situ. The mean age of the patients was 47 years (range 22-64). The clinical examination included RoM tests, elbow stability tests, and a neurological examination. The functional outcome was assessed with the MEPS and DASH score. The radiographic examination included a.p. and lateral views of the elbow to detect non-unions, inadequacy or loss of reduction, radial head necrosis, heterotopic ossifications and signs of posttraumatic arthritis.

Results: The mean follow-up time was 39 months (range 11-64). The mean MEPS was 82 points (range 15-100), and the mean DASH score was 20 points (range 0-85). All ex situ-reconstructed radial heads survived, and no signs of avascular necrosis were observed. Bony union was achieved in all but one patient who presented with an asymptomatic non-union. Signs of posttraumatic arthritis were found in all patients. With regard to the radial head, neither secondary resection nor arthroplasty had to be performed. All patients returned to their pre-injury occupations.

Conclusion: Ex situ radial head reconstruction can be a reliable option in the surgical treatment of complex radial head fractures associated with severe elbow trauma. Even in the midterm follow-up, no signs of avascular necrosis were observed. Modern implants may even extend the indications for reconstruction in such cases.

Level Of Evidence: Level IV-retrospective cohort study.
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http://dx.doi.org/10.1007/s00402-019-03250-3DOI Listing
December 2019

A Role for NF-κB in Organ Specific Cancer and Cancer Stem Cells.

Cancers (Basel) 2019 May 11;11(5). Epub 2019 May 11.

Department of Cell Biology, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany.

Cancer stem cells (CSCs) account for tumor initiation, invasiveness, metastasis, and recurrence in a broad range of human cancers. Although being a key player in cancer development and progression by stimulating proliferation and metastasis and preventing apoptosis, the role of the transcription factor NF-κB in cancer stem cells is still underestimated. In the present review, we will evaluate the role of NF-κB in CSCs of glioblastoma multiforme, ovarian cancer, multiple myeloma, lung cancer, colon cancer, prostate cancer, as well as cancer of the bone. Next to summarizing current knowledge regarding the presence and contribution of CSCs to the respective types of cancer, we will emphasize NF-κB-mediated signaling pathways directly involved in maintaining characteristics of cancer stem cells associated to tumor progression. Here, we will also focus on the status of NF-κB-activity predominantly in CSC populations and the tumor mass. Genetic alterations leading to NF-κB activity in glioblastoma, ependymoma, and multiple myeloma will be discussed.
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http://dx.doi.org/10.3390/cancers11050655DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563002PMC
May 2019

Georg Schmorl Prize of the German Spine Society (DWG) 2017: correction of spino-pelvic alignment with relordosing mono- and bisegmental TLIF spondylodesis.

Eur Spine J 2018 04 7;27(4):789-796. Epub 2018 Feb 7.

Wirbelsäulenchirurgie, St. Franziskus Hospital Muenster, Hohenzollernring 70, 48145, Münster, Germany.

Introduction: A balanced ratio of the main parameters of lumbar lordosis (LL) and pelvic incidence (PI) has high clinical relevance. A postoperative mismatch of LL and PI has been described in the literature to be associated with an inferior clinical outcome and higher postoperative revision rates. The aim of this retrospective, radiological study is to evaluate the magnitude of relordosing in mono-/bisegmental TLIF spondylodesis affecting the spino-pelvic alignment and the main contributing factors.

Materials And Methods: 164 patients (pat.) underwent monosegmental (n = 115, G1) and bisegmental (n = 49, G2) TLIF spondylodesis, respectively, for different indications in 2016 in our hospital. Pelvic incidence, lumbar lordosis (preop., postop., 3 months postop.), implanted cage sizes, and the use of additional Smith-Petersen osteotomies were analysed retrospectively. Patients were divided into three groups depending on match of LL/PI (PI-LL < 10° green, PI-LL = 10-20° yellow, PI-LL > 20° red). Furthermore, a differentiation was made between surgeons with more than or less than 10 years of spinal surgery experience, respectively.

Results: 29.6% of pat. in G1 and 16.3% in G2 showed a highly pronounced preoperative spino-pelvic mismatch (red). A high grade of mismatch (yellow) between LL/PI was seen in 29.6% in G1 and in 38.8% in G2. The remaining patients already had a balanced ratio of LL/PI (green). Through relordosing TLIF the LL could be corrected significantly (p < 0.05). Therefore, the number of patients with a balanced sagittal alignment (green) increased from 40.9% preop. to 70.4% postoperative in G1 and from 44.9 to 85.7% in G2 (p < 0.05). The number of pat. with highly pronounced preoperative mismatch (red) could be lowered in G1 from 29.6 to 13.9% and in G2 from 16.3 to 2% postoperative (p < 0.05). In G1, the preoperative LL could be corrected from 46.3° to 53.8° (yellow) and 35.7° to 45.8° (red), while in G2, a correction was possible from 43.4° to 51.5° (yellow) and 36.6° to 50.1° (red) (p < 0.05). No significant difference of segmental/complete LL was found between radiologic measurement immediately postoperative and at the 3-month follow-up. In monosegmental fusion higher cages sizes lead to a better match of LL/PI (p < 0.05). The specific cage lordosis (5° vs. 10°) had no influence on the extent of relordosing. Experienced surgeons had significant higher postoperative matches of LL/PI (p < 0.05) and accomplished more osteotomies (p < 0.05).

Discussion: This retrospective study demonstrates that significant relordosing and, therefore, correction of the spino-pelvic alignment are possible with mono-/bisegmental TLIF spondylodesis. Positive influence of higher cage sizes and surgeon's experience was shown. We conclude that the ratio of LL/PI should be taken into account preoperatively in lumbar fusion surgery when planning mono-/bisegmental TLIF spondylodesis to optimize spino-pelvic alignment. These slides can be retrieved under Electronic Supplementary Material.
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http://dx.doi.org/10.1007/s00586-018-5503-6DOI Listing
April 2018

Complications of intramedullary nailing-Evolution of treatment.

Injury 2017 Jun 24;48 Suppl 1:S59-S63. Epub 2017 Apr 24.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Münster, Germany.

Intramedullary nailing of diaphyseal long bone fractures is a standard procedure in today's trauma and orthopedic surgery due to the numerous advantages (e.g. minimal invasive, limited soft tissue damage, load stability). In the last decade indications have been extended to the metaphyseal region. This was associated with problems and complications due to the reduced bone-implant interface. The changed anatomical conditions lead to decreased implant anchorage. Newly developed locking solutions overcome most of these problems. First, the number and also the orientation of the locking screws were adapted to allow a multiplanar locking. This results in increased implant anchorage in the soft metaphyseal bone, thus construct stability significantly improved. Additional options like angular stable locking have been introduced and furthermore enhanced construct stability especially in poor bone stock. As a perspective locking screw augmentation shows promising results in first biomechanical testing.
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http://dx.doi.org/10.1016/j.injury.2017.04.032DOI Listing
June 2017

3D Optical Investigation of 2 Nail Systems Used in Tibiotalocalcaneal Arthrodesis: A Biomechanical Study.

Foot Ankle Int 2017 May 9;38(5):571-579. Epub 2017 Feb 9.

1 Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Münster, Münster, Germany.

Background: Although retrograde intramedullary nails for tibiotalocalcaneal arthrodesis (TTCA) are an established fixation method, few studies have evaluated the stability of the available nail systems. The purpose of this study was to compare biomechanically the primary stability of 2 nail-systems, A3 (Small Bone Innovations) and HAN (Synthes), in human cadavers and analyze the exact point of instability in TTCA by means of optical measurement.

Methods: In 6 pairs of lower legs (n = 12) of fresh-frozen human cadavers with osteoporotic bone structure, bone mineral density (BMD) was determined. Pairwise randomized implantation of either an HAN or A3 nail was executed. Performance and stability were measured by quasi-static tests using 3D motion tracking (NDI Optotrak-Certus) followed by cyclic loading tests during dorsi- and plantarflexion.

Results: 3D optical analysis in quasi-static tests showed a significantly lower degree of movement for the HAN nail in rotational and dorsi-/plantarflexion, especially in the subtalar joint. Cyclic loading tests were consistent with quasi-static tests.

Conclusion: The A3 nail offered lower stability during axial torsion in the ankle and subtalar joints and during plantar- and dorsiflexion in the subtalar joint in osteoporotic bones. This study was the first to examine the primary stability of different arthrodesis nails in TTCA and their bony parts with a 3D motion analysis.

Clinical Relevance: The better stability of the locking-only HAN nail in this osteoporotic test setup could lead to more favorable results in comparison to the A3 nail in clinical use.
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http://dx.doi.org/10.1177/1071100717690805DOI Listing
May 2017

Computational anatomy of the dens axis evaluated by quantitative computed tomography: Implications for anterior screw fixation.

J Orthop Res 2017 10 30;35(10):2154-2163. Epub 2017 Jan 30.

AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland.

The surgical fracture fixation of the odontoid process (dens) of the second cervical vertebra (C2/axis) is a challenging procedure, particularly in elderly patients affected by bone loss, and includes screw positioning close to vital structures. The aim of this study was to provide an extended anatomical knowledge of C2, the bone mass distribution and bone loss, and to understand the implications for anterior screw fixation. One hundred and twenty standard clinical quantitative computed tomography (QCT) scans of the intact cervical spine from 60 female and 60 male European patients, aged 18-90 years, were used to compute a three-dimensional statistical model and an averaged bone mass model of C2. Shape and size variability was assessed via principal component analysis (PCA), bone mass distribution by thresholding and via virtual core drilling, and the screw placement via virtual positioning of screw templates. Principal component analysis (PCA) revealed a highly variable anatomy of the dens with size as the predominant variation according to the first principal component (PC) whereas shape changes were primarily described by the remaining PCs. The bone mass distribution demonstrated a characteristic 3D pattern, and remained unchanged in the presence of bone loss. Virtual screw positioning of two 3.5 mm dens screws with a 1 mm safety zone was possible in 81.7% in a standard, parallel position and in additional 15.8% in a twisted position. The approach permitted a more detailed anatomical assessment of the dens axis. Combined with a preoperative QCT it may further improve the diagnostic procedure of odontoid fractures. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2154-2163, 2017.
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http://dx.doi.org/10.1002/jor.23512DOI Listing
October 2017

Delayed Surgical Reconstruction of a Peroneal Tendon Rupture in an Accessory Os Peroneum.

J Am Podiatr Med Assoc 2016 Nov;106(6):439-444

A fracture of the os peroneum is a rare cause of ankle and foot pain and is often overlooked and not assumed. Only a few case reports have discussed the different etiologies, options for diagnosis, and therapeutic interventions for acute cases. We present a case of delayed diagnosis of an os peroneum fracture due to a distortion of the ankle that occurred during air sports. Initial diagnostic testing with magnetic resonance imaging demonstrated a rupture of the peroneus longus tendon with no pathologic abnormalities at the peroneus brevis tendon. During surgery, a combination of an os peroneum fracture and a peroneus brevis tendon split was found and was successfully treated with bone and tendon repair using a lasso stich technique.
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http://dx.doi.org/10.7547/15-092DOI Listing
November 2016

PEEK versus titanium locking plates for proximal humerus fracture fixation: a comparative biomechanical study in two- and three-part fractures.

Arch Orthop Trauma Surg 2017 Jan 22;137(1):63-71. Epub 2016 Dec 22.

OCP-Münster, Schaumburgstraße 1, 48145, Münster, Germany.

Introduction: The high rigidity of metal implants may be a cause of failure after fixation of proximal humerus fractures. Carbon fiber-reinforced polyetheretherketone (PEEK) plates with a modulus similar to human cortical bone may help to overcome this problem. The present study assesses the biomechanical behavior of a PEEK plate compared with a titanium locking plate.

Materials And Methods: Unstable two- and three-part fractures were simulated in 12 pairs of cadaveric humeri and were fixed with either a PEEK or a titanium locking plate using a pairwise comparison. With an optical motion capture system, the stiffness, failure load, plate bending, and the relative motion at the bone-implant interface and at the fracture site were evaluated.

Results: The mean load to failure for two- and three-part fracture fixations was, respectively, 191 N (range 102-356 N) and 142 N (range 102-169 N) in the PEEK plate group compared with 286 N (range 191-395 N) and 258 N (range 155-366 N) in the titanium locking plate group. The PEEK plate showed significantly more bending in both the two- and three-part fractures (p < 0.05), an increased relative motion at the bone-implant interface and lower stiffness values (p < 0.05).

Conclusion: In this biomechanical study on unstable proximal humerus fractures, fixation with a PEEK plate showed lower fixation strength and increased motion at the bone-implant interface compared with a titanium locking plate.
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http://dx.doi.org/10.1007/s00402-016-2620-8DOI Listing
January 2017

Biomechanical comparison of augmented versus non-augmented sacroiliac screws in a novel hemi-pelvis test model.

J Orthop Res 2017 07 16;35(7):1485-1493. Epub 2016 Sep 16.

AO Research Institute Davos, Clavadelerstraße 8, 7270 Davos, Switzerland.

Operative treatment of sacral insufficiency fractures is frequently being complicated by osteopenic bone properties. Cement augmentation of implanted sacroiliac screws may lead to superior construct stability and prevent mechanical complications. A novel hemi-pelvis test model with dissected symphysis was developed. Five fresh-frozen cadaveric pelvises were vertically osteotomized at the sacrum on both sides and fixed with sacroiliac screws in both corridors of the first sacral vertebral body. One side was randomly augmented with bone cement. Cyclic testing consisting of torsional loading (±2.5 Nm) combined with progressively increasing axial loading (+50 N compression, -10 N traction, ±0,01 N/cycle) was performed until failure; simulated physiological loads derived from inverse dynamic calculations. The fixation was analyzed fluoroscopically quantifying screw migrations and assessing failure mechanisms. Failure modes were cut-out, pull-out, screw-out, and washer penetration. Motion at fracture site was analyzed via optical motion tracking. Unscrewing was provoked four times with non-augmented and twice with augmented screws. When focusing on the sacral region only, cement augmentation significantly improved screw fixation in terms of increased number of cycles to failure (p = 0.043). However, when considering overall construct stability, there was no significant difference between augmented and non-augmented state due to washer penetration at the iliac bone. The generated hemi-pelvis model was found to be valid due to the reproduction of the clinically observed failure mode (unscrewing). Unscrewing was not fully prevented by cement augmentation. Augmentation effects stability at the screw tip, but particularly in porotic bone, failure may shift to the next weak point. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1485-1493, 2017.
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http://dx.doi.org/10.1002/jor.23401DOI Listing
July 2017

A modified and enhanced test setup for biomechanical investigations of the hindfoot, for example in tibiotalocalcaneal arthrodesis.

BMC Musculoskelet Disord 2016 07 29;17:318. Epub 2016 Jul 29.

Department of Trauma-, Hand- and Reconstructive Surgery, University Hospital Muenster, Albert-Schweitzer-Campus 1, Building W1, 48149, Muenster, Germany.

Background: Tibiotalocalcaneal arthrodesis (TTCA) using intramedullary nails is a salvage procedure for many diseases in the ankle and subtalar joint. Despite "newly described intramedullary nails" with specific anatomical shapes there still remain major complications regarding this procedure. The following study presents a modified biomechanical test setup for investigations of the hindfoot.

Methods: Nine fresh-frozen specimens from below the human knee were anaysed using the Hindfoot Arthrodesis Nail (Synthes) instrument. Quasi-static biomechanical testing was performed for internal/external rotation, varus/valgus and dorsal/plantar flexion using a modified established setup (physiological load entrance point, sledge at lever arm to apply pure moments). Additionally, a 3D optical measurement system was added to allow determination of interbony movements.

Results: The mean torsional range of motion (ROM) calculated from the actuator data of a material testing machine was 10.12° (SD 0.6) compared to 10° (SD 2.83) as measured with the Optotrak® system (between tibia and calcaneus). The Optotrak showed 40 % more rotation in the talocrural joint. Mean varus/valgus ROM from the material testing flexion machine was seen to be 5.65° (SD 1.84) in comparison to 2.82° (SD 0.46) measured with the Optotrak. The subtalar joint showed a 70 % higher movement when compared to the talocrural joint. Mean ROM in the flexion test was 5.3° (SD 1.45) for the material testing machine and 2.1° (SD 0.39) for the Optotrak. The movement in the talocrural joint was 3 times higher compared to the subtalar joint.

Conclusion: The modified test setup presented here for the hindfoot allows a physiological biomechanical loading. Moreover, a detailed characterisation of the bone-implant constructs is possible.
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http://dx.doi.org/10.1186/s12891-016-1177-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4966560PMC
July 2016

Periprosthetic fracture fixation in osteoporotic bone.

Injury 2016 Jun;47 Suppl 2:S44-50

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Münster, Germany.

Fixation techniques of periprosthetic fractures are far from ideal although the number of this entity is rising. The presence of an intramedullary implant generates its own fracture characteristics since stiffness is altered along the bone shaft and certain implant combinations affect load resistance of the bone. Influencing factors are cement fixation of the implant, intramedullary locking and extramedullary or intramedullary localization of the implant and the cortical thickness of the surrounding bone. Cerclage wires are ideally suited to fix radially displaced fragments around an intramedullary implant but they are susceptible to axial and torsional load. Screws should be added if these forces have to be neutralized. Stability of the screw fixation itself can be enhanced by embracement configuration around the intramedullary implant. Poor bone stock quality, often being present in metaphyseal areas limits screw fixation. Cement augmentation is an attractive option in this field to enhance screw purchase.
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http://dx.doi.org/10.1016/S0020-1383(16)47008-7DOI Listing
June 2016

Double plating in Vancouver type B1 periprosthetic proximal femur fractures: A biomechanical study.

J Orthop Res 2017 02 21;35(2):234-239. Epub 2016 Apr 21.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Muenster, Albert-Schweitzer-Campus 1, Building W1, 48149, Muenster, Germany.

Periprosthetic hip fractures are an increasing problem in modern orthopedic and trauma surgery. Many options for the operative treatment are available to the surgeon ranging from modern variable angular systems to standard plates, screws, and cerclages. However, there is no gold standard and therefore, the aim of this study, was to investigate the biomechanical characteristics of double plating versus a lateral standard plate in a Vancouver B1 fracture model. Ten 4th generation composite femora were used to implant cementless total hip prosthesis and create Vancouver B1 periprosthetic fractures. Afterwards, the osteotomies were fixed using the locking compression plate in combination with the locking attachment plate (LCP, LAP, DePuy Synthes, Solothurn, Switzerland)-group I. Group II additionally achieved a 5-hole 4.5/5.0 mm LCP anteriorly. Each construct was cyclically loaded to failure in axial compression. Axial construct stiffness was 50.87 N/mm (SD 1.61) for group I compared to 738.68 N/mm (SD 94.8) for group II, this difference was statistically significant (p = 0.016). The number of cycles to failure was also significant higher for group II (2,375 vs. 13,000 cycles; p = 0.016). Double plating can significantly increase construct stiffness and stability, and thus, is an option in the treatment of complex periprosthetic fractures, in revision surgery and for patients with the inability to partial weight bear. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:234-239, 2017.
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http://dx.doi.org/10.1002/jor.23259DOI Listing
February 2017

Biomechanical characteristics of pedicle screws in osteoporotic vertebrae-comparing a new cadaver corpectomy model and pure pull-out testing.

J Orthop Res 2017 01 6;35(1):167-174. Epub 2016 Apr 6.

Department of Trauma and Orthopedic Surgery, Evangelical Hospital Bielefeld, Burgsteig 13, 33617, Bielefeld, Germany.

Currently, evaluation of the stability of spinal instrumentations often focuses on simple pull-out or cyclic loading. However, the loading characteristics and the specimen alignment rarely simulate physiological loading conditions, or the clinical situation itself. The purpose of this study was to develop an alternative setup and parameters to compare static and dynamic characteristics of pedicle screws at the bone-implant interface in lumbar osteoporotic cadavers. A corpectomy model development was based on ASTM-1717 standard, allowing a deflection of the cranial and caudal element under loading. Twelve human osteoporotic vertebrae (L1-L4) were analyzed for morphological CT-data and T-Score. For group A (n = 6) loads were simulated as in vivo measurements during walking, representing 2 months postoperatively. A subsequent pull-out was performed. Group B (n = 6) was tested with pure pull-out. Screw loosening at the tip/head was optically measured and analyzed with respect to clinical patterns. Correlations between CT-data, T-Score, and in vitro parameters were determined. For group A, the subsidence for the head/tip was measured towards the upper/lower endplate, resulting in visible deflections. The progress of the subsidence was greatest within the first and last cycles until failure. The predominant patterns were pure rotation and toggling. However, the pull-out between groups was not significantly different. Pedicle-angle and cyclic-subsidence correlated with R = 0.806/0.794. T-Score and pull-out correlated only in group A. With the corpectomy setup, clinically observed wipe effects and a loss of correction could be simulated. The presented parameters facilitate analysis of the complex changing load distributions and interactions between the left and right bone-implant interface. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:167-174, 2017.
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http://dx.doi.org/10.1002/jor.23237DOI Listing
January 2017

Size matters: The influence of the posterior fragment on patient outcomes in trimalleolar ankle fractures.

Injury 2015 Oct;46 Suppl 4:S109-13

Trauma-, Hand- and Reconstructive Surgery, University Hospital Münster, Germany.

Introduction: Ankle fractures are increasing in incidence. The more complicated the lesion is, the higher the risk of developing posttraumatic arthrosis. Severe posttraumatic arthrosis results in a reduced quality of life. Therefore, the treatment of a trimalleolar fractures is crucial. However, the treatment guidelines for posterior malleolar fractures (PMF) are still based on recommendations from 1940. Only a few retrospective studies have been conducted, which analysed patient outcomes based on lateral X-rays of the ankle. The purpose of this retrospective analysis was to survey patient outcomes in relation to the size of the PMF on the basis of CT-scans.

Methods: We retrospectively examined 42 patients with trimalleolar fractures with an average follow-up of 2.5 years. Twenty-four patients (57%) received a CT scan of the ankle joint. The radiologic images were analysed for the size of the PMF and the involvement of the joint surface using lateral X-rays and available CT images. We examined all 42 patients clinically and radiologically, and estimated the grade of arthrosis of the ankle in accordance with the Bargon Score and assigned AOFAS Scores for each patient. We divided our patients into different groups according to the size of their PMF and evaluated patient outcomes in accordance with the compiled data first on the basis of X-ray data and then on the basis of CT data.

Results: Comparing the measurement results by two different radiologic methods revealed that CT results in a more precise determination of PMF size in contrast to lateral X-rays, by which measurements were generally overrated. The statistical evaluation of our data demonstrated that patients with an osteosynthesis of the PMF and a PMF size of >25% showed signs of posttraumatic arthrosis but had better outcomes in accordance to the AOFAS score. All results were not significant.

Conclusion: An exact evaluation of CT images of posterior malleolar fractures in patients with trimalleolar ankle fractures is crucial for the decision to perform an osteosynthesis of the PMF and, therefore, an analysis of patient outcomes. The results of previous studies should be evaluated cautiously due to missing CT data. To date, this is the largest retrospective patient series of patient outcomes based on CT data.
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http://dx.doi.org/10.1016/S0020-1383(15)30028-0DOI Listing
October 2015

Screw augmentation reduces motion at the bone-implant interface: a biomechanical study of locking plate fixation of proximal humeral fractures.

J Shoulder Elbow Surg 2015 Dec 5;24(12):1968-73. Epub 2015 Aug 5.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Münster, Germany.

Background: Shear forces at the bone-implant interface lead to a loss of reduction after locking plate fixation of proximal humeral fractures. The aim of the study was to analyze the roles of medial support screws and screw augmentation in failure loads and motion at the bone-implant interface after locking plate fixation of proximal humeral fractures.

Methods: Unstable 3-part fractures were simulated in 6 pairs of cadaveric humeri and were fixed with a DiPhos-H locking plate (Lima Corporate, Udine, Italy). An additional medial support screw was implanted in 1 humerus of every donor. The opposite humerus was stabilized with a medial support screw and additional bone cement augmentation of the 2 anteriorly directed head screws. Specimens were loaded in the varus bending position. Stiffness, failure loads, plate bending, and the motion at the bone-implant interface were evaluated using an optical motion capture system.

Results: The mean load to failure was 669 N (standard deviation [SD], 117 N) after fixation with medial support screws alone and 706 N (SD, 153 N) after additional head screw augmentation (P = .646). The initial stiffness was 453 N/mm (SD, 4.16 N/mm) and 461 N/mm (SD, 64.3 N/mm), respectively (P = .594). Plate bending did not differ between the 2 groups. However, motion at the bone-implant interface was significantly reduced after head screw augmentation (P < .05).

Conclusion: The addition of bone cement to augment anteriorly directed head screws does not increase stiffness and failure loads but reduces motion at the bone-implant interface. Thus, the risk of secondary dislocation of the head fragment may be reduced.
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http://dx.doi.org/10.1016/j.jse.2015.06.028DOI Listing
December 2015

Knee joint kinematics after dynamic intraligamentary stabilization: cadaveric study on a novel anterior cruciate ligament repair technique.

Knee Surg Sports Traumatol Arthrosc 2017 Apr 4;25(4):1184-1190. Epub 2015 Aug 4.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus, Building Waldeyerstraße 1, 48149, Münster, Germany.

Purpose: Dynamic intraligamentary stabilization (DIS) has been introduced for the repair of acute anterior cruciate ligament (ACL) tears as an alternative to delayed reconstruction. The aim of the present study was to compare knee joint kinematics after DIS to those of the ACL-intact and ACL-deficient knee under simulated Lachman/KT-1000 and pivot-shift tests. We hypothesized that DIS provides knee joint kinematics equivalent to an intact ACL.

Methods: With the use of a robotic knee simulator, knee kinematics were determined in simulated Lachman/KT-1000 and pivot-shift tests at 0°, 15°, 30°, 60°, and 90° of flexion in eight cadaveric knees under the following conditions: (1) intact ACL, (2) ACL deficiency, (3) DIS with a preload of 60 N, and (4) DIS with a preload of 80 N. Statistical analyses were performed using two-factor repeated-measures analysis of variance. The significance level was set at a p value of <0.05.

Results: After DIS with a preload of either 60 N or 80 N, the anterior translation was significantly reduced in the simulated Lachman/KT-1000 and pivot-shift tests when compared to the ACL-deficient knee (p < 0.05). No significant differences were observed between the DIS reconstruction with a preload of 80 N and the intact ACL with regard to anterior laxity in either test. However, DIS with a preload of only 60 N was not able to restore knee joint kinematics to that of an intact knee in all degrees of flexion.

Conclusion: DIS with a preload of 80 N restores knee joint kinematics comparable to that of an ACL-intact knee and is therefore capable of providing knee joint stability during ACL healing. DIS therefore provides a new technique for primary ACL repair with superior biomechanical properties in comparison with other techniques that have been described previously, although further clinical studies are required to determine its usefulness in clinical settings.
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http://dx.doi.org/10.1007/s00167-015-3735-0DOI Listing
April 2017

How to enhance the stability of locking plate fixation of proximal humerus fractures? An overview of current biomechanical and clinical data.

Injury 2015 Jul 24;46(7):1207-14. Epub 2015 Apr 24.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Albert-Schweitzer-Campus 1, Building W1, 48149 Münster, Germany.

Background: The complication rate after locking plate fixation of proximal humerus fractures is high. In addition to low bone mineral density, a lack of medial support has been identified as one of the most important factors accounting for mechanical instability. As a result of the high failure rate, different strategies have been developed to enhance the mechanical stability of locking plate fixation of proximal humerus fractures. The aim of the present article is to give an overview of the current biomechanical and clinical studies that focus on how to increase the stability of locking plate fixation of proximal humerus fractures.

Methods: A comprehensive search of the Medline databases using specific search terms with regard to the stability of locking plate fixation of proximal humerus fractures was performed. After screening of the articles for eligibility, they were subdivided according to clinical and biomechanical aspects.

Results: Medial support screws, filling of bone voids and screw-tip augmentation with bone cement as well as the application of bone grafts are currently the most frequently assessed and performed methods. Although the evidence is weak, all of the mentioned strategies appear to have a positive effect on achieving and maintaining a stable reduction even of complex fractures.

Conclusion: Further clinical studies with a higher number of patients and a higher level of evidence are required to develop a standardised treatment algorithm with regard to cement augmentation and bone grafting. Although these measures are likely to have a stabilising effect on locking plate fixation, its general use cannot be fully recommended yet.
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http://dx.doi.org/10.1016/j.injury.2015.04.020DOI Listing
July 2015

Implant augmentation: adding bone cement to improve the treatment of osteoporotic distal femur fractures: a biomechanical study using human cadaver bones.

Medicine (Baltimore) 2014 Nov;93(23):e166

Department of Trauma, Hand, and Reconstructive Surgery (DW, MJR), University Hospital Münster, Münster, Germany; and Biomedical Services (LH-F, RGR, BG, MW), AO Research Institute Davos, Davos, Switzerland.

The increasing problems in the field of osteoporotic fracture fixation results in specialized implants as well as new operation methods, for example, implant augmentation with bone cement. The aim of this study was to determine the biomechanical impact of augmentation in the treatment of osteoporotic distal femur fractures.Seven pairs of osteoporotic fresh frozen distal femora were randomly assigned to either an augmented or nonaugmented group. In both groups, an Orthopaedic Trauma Association 33 A3 fractures was fixed using the locking compression plate distal femur and cannulated and perforated screws. In the augmented group, additionally, 1 mL of polymethylmethacrylate cement was injected through the screw. Prior to mechanical testing, bone mineral density (BMD) and local bone strength were determined. Mechanical testing was performed by cyclic axial loading (100 N to 750 N + 0.05N/cycle) using a servo-hydraulic testing machine.As a result, the BMD as well as the axial stiffness did not significantly differ between the groups. The number of cycles to failure was significantly higher in the augmented group with the BMD as a significant covariate.In conclusion, cement augmentation can significantly improve implant anchorage in plating of osteoporotic distal femur fractures.
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http://dx.doi.org/10.1097/MD.0000000000000166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4616336PMC
November 2014

Comparison of tension band wiring and precontoured locking compression plate fixation in Mayo type IIA olecranon fractures.

Acta Orthop Belg 2014 Mar;80(1):106-11

Aim of the present study was to compare the clinical and radiographic outcome of tension band wiring and precontoured locking compression plate fixation in patients treated surgically for an isolated olecranon fractures type IIA according to the Mayo classification. Of 26 patients presenting with an isolated Mayo type IIA olecranon fracture, 13 underwent fixation with a precontoured locking compression plate (group A), 13 patients were treated with tension band wiring (group B). At a mean follow-up of 43 months, patients were clinically and radiographically re-examined using the DASH score, the Mayo Elbow Performance score (MEPS) and anteroposterior and lateral radiographs. The mean DASH score was 14 points in group A and 12.5 points in group B. Regarding the MEPS, 92% of the patients in group A achieved a good to excellent results in comparison to 77% in group B. No significant differences between the two groups could be detected regarding the clinical and radiographic outcome. Implant-related irritations requiring hardware removal occurred more frequently in group B (12 vs. 7). Procedure and implant related costs were significantly higher in group A. Tension band wiring is still a preferable surgical method to treat simple isolated olecranon fractures. The patient must be informed that in all likelihood implant removal will be required once the fracture has healed. Fixation with precontoured locking compression plates does not provide better functional and radiographic outcome but is more expensive than tension band wiring.
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March 2014