Kompendium 2020 Forschung & Klinik

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TOP-Studien 62 Biomechanical Evaluation of Intramedullary Jones Fracture Fixation Jones fractures or meta-diaphyseal fractures of the proximal fifth metatarsal (zone II) have a notoriously high rate of nonunion and delayed union with conservative treatment. Therefore, surgical fixation using an intramedullary screw is currently recommended as the primary treatment for active patients, as well as recreational and professional athletes. Besides early functional mobilization and a faster return to sports, higher rates of primary fracture healing have been demonstrated in clinical studies. Nevertheless, implant choice is a matter of concern since active patients are prone to failure including nonunion, screw failure, and refracture. A variety of screw types have been used to treat Jones fractures. Currently, neither clinical nor biomechanical studies comparing different screws provide decisive results, so there is no consensus on the ideal screw design or diameter. Cannulated screws are easy to use and insert but may have a detrimental biomechanical behavior compared to solid screws. Standard solid screw insertion can be technically demanding and a prominent screw head can lead to discomfort and pain at the base of the fifth metatarsal. A countersinkable or low-profile screw head may reduce this potential complication, but recent advances in implant design have even developed fracture-specific screws with combined properties for the treatment of Jones fractures. To seek clarification in the biomechanical aspects of recent screw designs regarding the treatment of Jones fractures, this study compares a solid, fracture-specific screw with a cannulated headless compression screw in a biomechanical Jones fracture fixation model by simulating initial postoperative weight-bearing and ultimate loading. Study: Willegger M, Benca E, Hirtler L, Kasparek MF, Bauer G, Zandieh S, Windhager R, Schuh R. Evaluation of Two Types of Intramedullary Jones Fracture Fixation in a Cyclic and Ultimate Load Model. J Orthop Res. <strong>2020</strong> Apr;38(4):911–917. doi: 10.1002/jor.24530. Materials and Methods Ten matched pairs of fresh human foot specimens were used for this biomechanical study. The specimens were obtained from voluntary donors who consented to donate their body for research and teaching purposes to the Center for Anatomy and Cell Biology, Medical University of Vienna during lifetime. Donor age ranged from 64 to 92 years (mean 78.8 ± 8.7 years). The specimens were stored at –80°C and thawed at +4°C 48 hours prior to testing in order to prevent tissue dehydration. After screening for previous injuries or surgeries at the fifth metatarsal, all specimens proved valid for inclusion. Bone mineral density (BMD) was assessed prior to biomechanical testing by use of dual-energy X-ray absorptiometry (DEXA). Scans of the calcaneus were reported as g/cm 2 . To minimize possible left-right bias, one foot of each pair was assigned to fracture-specific Jones screw fixation
TOP-Studien 63 Figure 1: Biomechanical test setup: The potted fifth metatarsal specimen was fixed into a machine vice on an adjustable platform. A metal rod attached to the loading frame was used for force transmission in a plantar to dorsal direction. Light-reflecting hemispherical markers were glued onto the distal part of the Jones fracture specimen and onto the pot and rod for kinematic tracking. „To seek clarification in the biomechanical aspects of recent screw designs regarding the treatment of Jones fractures, this study compares a solid, fracture-specific screw with a cannulated headless compression screw in a biomechanical Jones fracture fixation model.“ Madeleine Willegger (Jones Screw; Arthrex Inc., Naples FL, USA) (JFXS group) and the contralateral foot was assigned to conventional cannulated headless compression screw fixation (HCS; DePuySynthes, Solothurn, Switzerland) (HCS group), with equal numbers of right and left feet in each group. The fifth metatarsals were further dissected and disarticulated from the feet. Jones fractures at the meta-diaphyseal junction were created using an oscillating saw. Both screw types were inserted according to the manufacturer’s instructions. The intramedullary screw had to „fit and fill“ the medullary canal with the threads across the fracture site. HCS were available in diameters 4.5-mm and 6.5- mm, and Jones Screws were used in diameters 4.5-mm and 6.0-mm. An experimental setup was designed to simulate the postoperative in vivo loading conditions after surgical Jones fracture treatment. The specimens of the fifth metatarsal were placed with their proximal aspects in Wood’s metal in specially fabricated custom-made steel cups, which were fixed in a machine vice. The biomechanical testing was performed with an 858 Mini Bionix ® (MTS ® Systems Corporation, Eden Prairie, MN). (Figure 1) A metal rod was used for force transmission onto the plantar aspect of the metatarsal head. An opto-electronic motion capture system (Smart-E; BTS Bioengineering, Milan, Italy) with four cameras was used during the loading process to track kinematic changes. Specimens were loaded with a cyclic load mean of 12 N at 0.5 Hz for 1000 cycles. The number of load cycles was chosen based on the loading rate for a physiologically normal lower limb, which is approximately 5000 cycles per day. One thousand cycles per day were assumed to realistically simulate post-operative loading during
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Kompendium 2020 Forschung & Klinik
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Inhalt/Impressum 3 Die Klinik 4 Edi
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Zahlen und Fakten 6 Klinische Leist
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Zahlen und Fakten 9 Hohe Ambulanzfr
Page 11 and 12: Klinik 11 Neben der Polytrauma-Vers
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Page 15 and 16: Das ÄrztInnenteam 15 Universitäts
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Page 25 and 26: WE LENGTHEN, TRANSPORT AND GROW BON
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Page 29 and 30: FRESH AIR FRESH PERSPECTIVE Remove
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Page 35 and 36: TOP-Studien 35 Figure 1: Bone miner
Page 37 and 38: TOP-Studien 37 A Prediction Model f
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Page 43 and 44: 3D Biochips for Research on Inflamm
Page 45 and 46: TOP-Studien 45 Chondro-Synovial Cro
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Page 49 and 50: TOP-Studien 49 Total Hip Arthroplas
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