@article{JordanHoelscherDohtFehskeetal.2015, author = {Jordan, Martin C. and Hoelscher-Doht, Stefanie and Fehske, Kai and Gilbert, Fabian and Jansen, Hendrik and Meffert, Rainer H.}, title = {Bunnell or cross-lock Bunnell suture for tendon repair? Defining the biomechanical role of suture pretension}, series = {Journal of Orthopaedic Surgery and Research}, volume = {10}, journal = {Journal of Orthopaedic Surgery and Research}, number = {192}, doi = {10.1186/s13018-015-0331-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126262}, year = {2015}, abstract = {Background Suture pretension during tendon repair is supposed to increase the resistance to gap formation. However, its effects on the Bunnell suture technique are unknown. The purpose of this study was to determine the biomechanical effects of suture pretension on the Bunnell and cross-lock Bunnell techniques for tendon repair. Methods Eighty porcine hindlimb tendons were randomly assigned to four different tendon repair groups: those repaired with or without suture pretension using either a simple Bunnell or cross-lock Bunnell technique. Pretension was applied as a 10 \% shortening of the sutured tendon. After measuring the cross-sectional diameter at the repair site, static and cyclic biomechanical tests were conducted to evaluate the initial and 5-mm gap formation forces, elongation during cyclic loading, maximum tensile strength, and mode of failure. The suture failure mechanism was also separately assessed fluoroscopically in two tendons that were repaired with steel wire. Results Suture pretension was accompanied by a 10 to 15 \% increase in the tendon diameter at the repair site. Therefore, suture pretension with the Bunnell and cross-lock Bunnell repair techniques noticeably increased the resistance to initial gap formation and 5-mm gap formation. The tension-free cross-lock Bunnell repair demonstrated more resistance to initial and 5-mm gap formation, less elongation, and higher maximum tensile strength than the tension-free Bunnell repair technique. The only difference between the tensioned cross-lock Bunnell and tensioned Bunnell techniques was a larger resistance to 5-mm gap formation with the cross-lock Bunnell technique. Use of the simple instead of cross-lock suture configuration led to failure by suture cut out, as demonstrated fluoroscopically. Conclusion Based on these results, suture pretension decreases gapping and elongation after tendon repair, and those effects are stronger when using a cross-lock, rather than a regular Bunnell suture. However, pretension causes an unfavorable increase in the tendon diameter at the repair site, which may adversely affect wound healing.}, language = {en} } @article{FreyJansenDohtetal.2013, author = {Frey, S{\"o}nke Percy and Jansen, Hendrik and Doht, Stefanie and Filgueira, Luis and Zellweger, Rene}, title = {Immunohistochemical and Molecular Characterization of the Human Periosteum}, series = {The Scientific World Journal}, journal = {The Scientific World Journal}, doi = {10.1155/2013/341078}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-96623}, year = {2013}, abstract = {Purpose. The aim of the present study was to characterize the cell of the human periosteum using immunohistological and molecular methods. Methods. Phenotypic properties and the distribution of the cells within the different layers were investigated with immunohistochemical staining techniques and RT-PCR, focussing on markers for stromal stem cells, osteoblasts, osteoclasts and immune cells. Results. Immunohistochemical results revealed that all stained cells were located in the cambium layer and that most cells were positive for vimentin. The majority of cells consisted of stromal stem cells and osteoblastic precursor cells. The density increased towards the deeper layers of the cambium. In addition, cells positive for markers of the osteoblast, chondrocyte, and osteoclast lineages were found. Interestingly, there were MHC class II-expressing immune cells suggesting the presence of dendritic cells. Using lineage-specific primer pairs RT-PCR confirmed the immunofluorescence microscopy results, supporting that human periosteum serves as a reservoir of stromal stem cells, as well as cells of the osteoblastic, and the chondroblastic lineage, osteoclasts, and dendritic cells. Conclusion. Our work elucidates the role of periosteum as a source of cells with a high regenerative capacity. Undifferentiated stromal stem cells as well as osteoblastic precursor cells are dominating in the cambium layer. A new outlook is given towards an immune response coming from the periosteum as MHC II positive immune cells were detected.}, language = {en} } @article{SchmidtJordanHoelscherDohtetal.2014, author = {Schmidt, Karsten and Jordan, Martin C. and H{\"o}lscher-Doht, Stefanie and Jakubietz, Michael G. and Jakubietz, Rafael G. and Meffert, Rainer H.}, title = {Suture material for flexor tendon repair: 3-0 V-Loc versus 3-0 Stratafix in a biomechanical comparison ex vivo}, doi = {10.1186/s13018-014-0072-9}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-110419}, year = {2014}, abstract = {Background Barbed suture material offers the possibility of knotless flexor tendon repair, as suggested in an increasing number of biomechanical studies. There are currently two different absorbable barbed suture products available, V-Loc™ and Stratafix™, and both have not been compared to each other with regard to flexor tendon repair. The purpose of this study was to evaluate both suture materials for primary stability under static and cyclic loading in a biomechanical ex vivo model. Methods Forty fresh porcine flexor digitorum profundus tendons were randomized in two groups. A four-strand modified Kessler suture technique was used to repair the tendon either with a 3-0 V-Loc™ or 3-0 Stratafix™ without a knot. Parameters of interest were mode of failure, 2-mm gap formation force, displacement, stiffness and maximum load under static and cyclic testing. Results The maximum load was 42.3 ± 7.2 for the Stratafix™ group and 50.7 ± 8.8 N for the V-Loc™ group. Thus, the ultimate tensile strength was significantly higher for V-Loc™ (p < 0.05). The 2-mm gap occurred at 24.8 ± 2.04 N in the Stratafix™ group in comparison to 26.5 ± 2.12 N in the V-Loc™ group (n.s.). Displacement was 2.65 ± 0.56 mm in the V-Loc™ group and 2.71 ± 0.59 mm in the Stratafix™ group (n.s.). Stiffness was 4.24 ± 0.68 (N/mm) in the V-Loc™ group and 3.85 ± 0.55 (N/mm) the Stratafix™ group (n.s.). Those measured differences were not significant. Conclusion V-Loc™ demonstrates a higher maximum load in tendon reconstruction. The differences in 2-mm gap formation force, displacement and stiffness were not significant. Hereby, the V-Loc™ has an advantage when used as unidirectional barbed suture for knotless flexor tendon repair.}, language = {en} } @article{JordanJaeckleScheidtetal.2021, author = {Jordan, Martin C. and J{\"a}ckle, Veronika and Scheidt, Sebastian and Gilbert, Fabian and H{\"o}lscher-Doht, Stefanie and Erg{\"u}n, S{\"u}leyman and Meffert, Rainer H. and Heintel, Timo M.}, title = {Trans-obturator cable fixation of open book pelvic injuries}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-021-92755-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-261212}, year = {2021}, abstract = {Operative treatment of ruptured pubic symphysis by plating is often accompanied by complications. Trans-obturator cable fixation might be a more reliable technique; however, have not yet been tested for stabilization of ruptured pubic symphysis. This study compares symphyseal trans-obturator cable fixation versus plating through biomechanical testing and evaluates safety in a cadaver experiment. APC type II injuries were generated in synthetic pelvic models and subsequently separated into three different groups. The anterior pelvic ring was fixed using a four-hole steel plate in Group A, a stainless steel cable in Group B, and a titan band in Group C. Biomechanical testing was conducted by a single-leg-stance model using a material testing machine under physiological load levels. A cadaver study was carried out to analyze the trans-obturator surgical approach. Peak-to-peak displacement, total displacement, plastic deformation and stiffness revealed a tendency for higher stability for trans-obturator cable/band fixation but no statistical difference to plating was detected. The cadaver study revealed a safe zone for cable passage with sufficient distance to the obturator canal. Trans-obturator cable fixation has the potential to become an alternative for symphyseal fixation with less complications.}, language = {en} } @article{JordanBroeerFischeretal.2022, author = {Jordan, Martin C. and Br{\"o}er, David and Fischer, Christian and Heilig, Philipp and Gilbert, Fabian and H{\"o}lscher-Doht, Stefanie and Kalogirou, Charis and Popp, Kevin and Grunz, Jan-Peter and Huflage, Henner and Jakubietz, Rafael G. and Erg{\"u}n, S{\"u}leyman and Meffert, Rainer H.}, title = {Development and preclinical evaluation of a cable-clamp fixation device for a disrupted pubic symphysis}, series = {Communications Medicine}, volume = {2}, journal = {Communications Medicine}, number = {1}, doi = {10.1038/s43856-022-00227-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-299800}, year = {2022}, abstract = {Background Traumatic separation of the pubic symphysis can destabilize the pelvis and require surgical fixation to reduce symphyseal gapping. The traditional approach involves open reduction and the implantation of a steel symphyseal plate (SP) on the pubic bone to hold the reposition. Despite its widespread use, SP-fixation is often associated with implant failure caused by screw loosening or breakage. Methods To address the need for a more reliable surgical intervention, we developed and tested two titanium cable-clamp implants. The cable served as tensioning device while the clamp secured the cable to the bone. The first implant design included a steel cable anterior to the pubic symphysis to simplify its placement outside the pelvis, and the second design included a cable encircling the pubic symphysis to stabilize the anterior pelvic ring. Using highly reproducible synthetic bone models and a limited number of cadaver specimens, we performed a comprehensive biomechanical study of implant stability and evaluated surgical feasibility. Results We were able to demonstrate that the cable-clamp implants provide stability equivalent to that of a traditional SP-fixation but without the same risks of implant failure. We also provide detailed ex vivo evaluations of the safety and feasibility of a trans-obturator surgical approach required for those kind of fixation. Conclusion We propose that the developed cable-clamp fixation devices may be of clinical value in treating pubic symphysis separation.}, language = {en} } @article{JordanZimmermannGhoetal.2016, author = {Jordan, Martin C. and Zimmermann, Christina and Gho, Sheridan A. and Frey, S{\"o}nke P. and Blunk, Torsten and Meffert, Rainer H. and Hoelscher-Doht, Stefanie}, title = {Biomechanical analysis of different osteosyntheses and the combination with bone substitute in tibial head depression fractures}, series = {BMC Musculoskeletal Disorders}, volume = {17}, journal = {BMC Musculoskeletal Disorders}, number = {287}, doi = {10.1186/s12891-016-1118-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-161201}, year = {2016}, abstract = {Background Tibial head depression fractures demand a high level of fracture stabilization to prevent a secondary loss of reduction after surgery. Elderly individuals are at an increased risk of developing these fractures, and biomechanical investigations of the fractures are rare. Therefore, the aim of this study was to systematically analyze different types of osteosyntheses in combination with two commonly used bone substitutes. Methods Lateral tibial head depression fractures were created in synthetic bones. After reduction, the fractures were stabilized with eight different treatment options of osteosynthesis alone or in combination with a bone substitute. Two screws, 4 screws and a lateral buttress plate were investigated. As a bone substitute, two common clinically used calcium phosphate cements, Norian® Drillable and ChronOS™ Inject, were applied. Displacement of the articular fracture fragment (mm) during cyclic loading, stiffness (N/mm) and maximum load (N) in Load-to-Failure tests were measured. Results The three different osteosyntheses (Group 1: 2 screws, group 2: 4 screws, group 3: plate) alone revealed a significantly higher displacement compared to the control group (Group 7: ChronOS™ Inject only) (Group 1, 7 [p < 0.01]; group 2, 7 [p = 0.04]; group 3, 7 [p < 0.01]). However, the osteosyntheses in combination with bone substitute exhibited no differences in displacement compared to the control group. The buttress plate demonstrated a higher normalized maximum load than the 2 and 4 screw osteosynthesis. Comparing the two different bone substitutes to each other, ChronOS™ inject had a significantly higher stiffness and lower displacement than Norian® Drillable. Conclusions The highest biomechanical stability under maximal loading was provided by a buttress plate osteosynthesis. A bone substitute, such as the biomechanically favorable ChronOS™ Inject, is essential to reduce the displacement under lower loading.}, language = {en} } @article{HeiligFaerberPauletal.2022, author = {Heilig, Philipp and Faerber, Lars-Christopher and Paul, Mila M. and Kupczyk, Eva and Meffert, Rainer H. and Jordan, Martin C. and Hoelscher-Doht, Stefanie}, title = {Plate osteosynthesis combined with bone cement provides the highest stability for tibial head depression fractures under high loading conditions}, series = {Scientific Reports}, volume = {12}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-022-19107-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-299782}, year = {2022}, abstract = {Older patients sustaining tibial head depression fractures often cannot follow the post-operative rehabilitation protocols with partial weight-bearing of the affected limb, leading to osteosynthesis failure, cartilage step-off and arthritis development. Therefore, the aim of this study was to analyse the biomechanical performance of different types of osteosyntheses alone and in combination with bone cement simulating cyclically high loading conditions of tibial head depression fractures. Lateral tibial head depression fractures (AO: 41-B2.2; Schatzker type III) were created in synthetic bones and stabilized using three different osteosyntheses alone and in combination with a commonly used bone cement (chronOS™): 2 screws, 4 screws in the jail technique and a lateral angle-stable buttress plate. After fixation, the lateral tibial plateau was axially loaded in two, from each other independent testing series: In the first test protocol, 5000 cycles with 500 N and in the end load-to-failure tests were performed. In the second test protocol, the cyclic loading was increased to 1000 N. Parameters of interest were the displacement of the articular fracture fragment, the stiffness and the maximum load. The osteosyntheses revealed a higher stiffness in combination with bone cement compared to the same type of osteosynthesis alone (e.g., 500 N level: 2 screws 383 ± 43 N/mm vs. 2 screws + chronOs 520 ± 108 N/mm, increase by 36\%, p < 0.01; 4 screws 368 ± 97 N/mm vs. 4 screws + chronOS 516 ± 109 N/mm, increase by 40\%, p < 0.01; plate: 509 ± 73 N/mm vs. plate + chronOs 792 ± 150 N/mm, increase by 56\%, p < 0.01). Bone cement reduced the displacement of the plate significantly (500 N level: plate: 8.9 ± 2.8 mm vs. plate + chronOs: 3.1 ± 1.4 mm, reduction by 65\%, p < 0.01; 1000 N level: 16.9 ± 3.6 mm vs 5.6 ± 1.3 mm, reduction by 67\%, p < 0.01). Thus, the highest stiffness and lowest displacement values were found when using the plate with bone cement in both loading conditions (500 N level: 2 screws + chronOs 3.7 ± 1.3 mm, 4 screws + chronOs 6.2 ± 2.4 mm; 1000 N level: 2 screws + chronOs 6.5 ± 1.2 mm, 4 screws + chronOs 5.7 ± 0.8 mm). From a biomechanical perspective, plate osteosynthesis of tibial head depression fractures should always be combined with bone cement, provides higher stability than 2-screw and 4-screw fixation and is a valid treatment option in cases where extraordinary stability is required.}, language = {en} } @article{JordanHufnagelMcDonoghetal.2022, author = {Jordan, Martin C. and Hufnagel, Lukas and McDonogh, Miriam and Paul, Mila M. and Schmalzl, Jonas and Kupczyk, Eva and Jansen, Hendrik and Heilig, Philipp and Meffert, Rainer H. and Hoelscher-Doht, Stefanie}, title = {Surgical fixation of calcaneal beak fractures — biomechanical analysis of different osteosynthesis techniques}, series = {Frontiers in Bioengineering and Biotechnology}, volume = {10}, journal = {Frontiers in Bioengineering and Biotechnology}, issn = {2296-4185}, doi = {10.3389/fbioe.2022.896790}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-282792}, year = {2022}, abstract = {The calcaneal beak fracture is a rare avulsion fracture of the tuber calcanei characterized by a solid bony fragment at the Achilles tendon insertion. Treatment usually requires osteosynthesis. However, lack of biomechanical understanding of the ideal fixation technique persists. A beak fracture was simulated in synthetic bones and assigned to five different groups of fixation: A) 6.5-mm partial threaded cannulated screws, B) 4.0-mm partial threaded cannulated screws, C) 5.0-mm headless cannulated compression screws, D) 2.3-mm locking plate, and E) 2.8-mm locking plate. Different traction force levels were applied through an Achilles tendon surrogate in a material-testing machine on all stabilized synthetic bones. Outcome measures were peak-to-peak displacement, total displacement, plastic deformation, stiffness, visual-fracture-line displacement, and mode of implant failure. The 2.3- and 2.8-mm plating groups showed a high drop-out rate at 100 N tension force and failed under higher tension levels of 200 N. The fracture fixation using 4.0-mm partial threaded screws showed a significantly higher repair strength and was able to withhold cyclic loading up to 300 N. The lowest peak-to-peak displacement and the highest load-to-failure and stiffness were provided by fracture fixation using 6.5-mm partial threaded cannulated screws or 5.0-mm headless cannulated compression screws. As anticipated, large 6.5-mm screw diameters provide the best biomechanical fixation. Surprisingly, the 5.0-mm headless cannulated compression screws yield reliable stability despite the absent screw head and washer. When such large screws cannot be applied, 4.0-mm screws also allow reasonable fixation strength. Plate fixation should be implemented with precaution and in combination with a restrictive postoperative motion protocol. Finally, clinical cases about the surgical application and recovery are included.}, language = {en} } @article{HeiligSandnerJordanetal.2021, author = {Heilig, Philipp and Sandner, Phoebe and Jordan, Martin Cornelius and Jakubietz, Rafael Gregor and Meffert, Rainer Heribert and Gbureck, Uwe and Hoelscher-Doht, Stefanie}, title = {Experimental drillable magnesium phosphate cement is a promising alternative to conventional bone cements}, series = {Materials}, volume = {14}, journal = {Materials}, number = {8}, issn = {1996-1944}, doi = {10.3390/ma14081925}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236633}, year = {2021}, abstract = {Clinically used mineral bone cements lack high strength values, absorbability and drillability. Therefore, magnesium phosphate cements have recently received increasing attention as they unify a high mechanical performance with presumed degradation in vivo. To obtain a drillable cement formulation, farringtonite (Mg\(_3\)(PO\(_4\))\(_2\)) and magnesium oxide (MgO) were modified with the setting retardant phytic acid (C\(_6\)H\(_{18}\)O\(_{24}\)P\(_6\)). In a pre-testing series, 13 different compositions of magnesium phosphate cements were analyzed concentrating on the clinical demands for application. Of these 13 composites, two cement formulations with different phytic acid content (22.5 wt\% and 25 wt\%) were identified to meet clinical demands. Both formulations were evaluated in terms of setting time, injectability, compressive strength, screw pullout tests and biomechanical tests in a clinically relevant fracture model. The cements were used as bone filler of a metaphyseal bone defect alone, and in combination with screws drilled through the cement. Both formulations achieved a setting time of 5 min 30 s and an injectability of 100\%. Compressive strength was shown to be ~12-13 MPa and the overall displacement of the reduced fracture was <2 mm with and without screws. Maximum load until reduced fracture failure was ~2600 N for the cements only and ~3800 N for the combination with screws. Two new compositions of magnesium phosphate cements revealed high strength in clinically relevant biomechanical test set-ups and add clinically desired characteristics to its strength such as injectability and drillability.}, language = {en} } @article{FuchsHeiligMcDonoghetal.2020, author = {Fuchs, Konrad F. and Heilig, Philipp and McDonogh, Miriam and Boelch, Sebastian and Gbureck, Uwe and Meffert, Rainer H. and Hoelscher-Doht, Stefanie and Jordan, Martin C.}, title = {Cement-augmented screw fixation for calcaneal fracture treatment: a biomechanical study comparing two injectable bone substitutes}, series = {Journal of Orthopaedic Surgery and Research}, volume = {15}, journal = {Journal of Orthopaedic Surgery and Research}, doi = {10.1186/s13018-020-02009-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-230336}, year = {2020}, abstract = {Background The role of cement-augmented screw fixation for calcaneal fracture treatment remains unclear. Therefore, this study was performed to biomechanically analyze screw osteosynthesis by reinforcement with either a calcium phosphate (CP)-based or polymethylmethacrylate (PMMA)-based injectable bone cement. Methods A calcaneal fracture (Sanders type IIA) including a central cancellous bone defect was generated in 27 synthetic bones, and the specimens were assigned to 3 groups. The first group was fixed with four screws (3.5 mm and 6.5 mm), the second group with screws and CP-based cement (Graftys (R) QuickSet; Graftys, Aix-en-Provence, France), and the third group with screws and PMMA-based cement (Traumacem (TM) V+; DePuy Synthes, Warsaw, IN, USA). Biomechanical testing was conducted to analyze peak-to-peak displacement, total displacement, and stiffness in following a standardized protocol. Results The peak-to-peak displacement under a 200-N load was not significantly different among the groups; however, peak-to-peak displacement under a 600- and 1000-N load as well as total displacement exhibited better stability in PMMA-augmented screw osteosynthesis compared to screw fixation without augmentation. The stiffness of the construct was increased by both CP- and PMMA-based cements. Conclusion Addition of an injectable bone cement to screw osteosynthesis is able to increase fixation strength in a biomechanical calcaneal fracture model with synthetic bones. In such cases, PMMA-based cements are more effective than CP-based cements because of their inherently higher compressive strength. However, whether this high strength is required in the clinical setting for early weight-bearing remains controversial, and the non-degradable properties of PMMA might cause difficulties during subsequent interventions in younger patients.}, language = {en} }