Stefan Döbele

DLS 5.0 - The Biomechanical Effects of Dynamic Locking Screws

Introduction Indirect reduction of dia-/metaphyseal fractures with minimally invasive implant application bridges the fracture zone in order to protect the soft-tissue and blood supply. The goal of this fixation strategy is to allow stable motion at the fracture site to achieve indirect bone healing with callus formation. However, concerns have arisen that the high axial stiffness and eccentric position of locked plating constructs may suppress interfragmentary motion and callus formation, particularly under the plate. The reason for this is an asymmetric fracture movement. The biological need for sufficient callus formation and secondary bone healing is three-dimensional micro movement in the fracture zone. The DLS was designed to allow for increased fracture site motion. The purpose of the current study was to determine the biomechanical effect of the DLS_5.0. Methods Twelve surrogate bone models were used for analyzing the characteristics of the DLS_5.0. The axial stiffness and the interfragmentary motion of locked plating constructs with DLS were compared to conventional constructs with Locking Head Screws (LS_5.0). A quasi-static axial load of 0 to 2.5 kN was applied. Relative motion was measured. Results The dynamic system showed a biphasic axial stiffness distribution and provided a significant reduction of the initial axial stiffness of 74.4%. Additionally, the interfragmentary motion at the near cortex increased significantly from 0.033 mm to 0.210 mm (at 200N). Conclusions The DLS may ultimately be an improvement over the angular stable plate osteosynthesis. The advantages of the angular stability are not only preserved but even supplemented by a dynamic element which leads to homogenous fracture movement and to a potentially uniform callus distribution.

Interlocking Nailing Versus Interlocking Plating in Intra-articular Calcaneal Fractures A Biomechanical Study

Background: Open reduction and internal fixation with a plate is deemed to represent the gold standard of surgical treatment for displaced intra-articular calcaneal fractures. Standard plate fixation is usually placed through an extended lateral approach with high risk for wound complications. Minimally invasive techniques might avoid wound complications but provide limited construct stability. Therefore, 2 different types of locking nails were developed to allow for minimally invasive technique with sufficient stability. The aim of this study was to quantify primary stability of minimally invasive calcaneal interlocking nail systems in comparison to a variable-angle interlocking plate. Material and Methods: After quantitative CT analysis, a standardized Sanders type IIB fracture model was created in 21 fresh-frozen cadavers. For osteosynthesis, 2 different interlocking nail systems (C-Nail; Medin, Nov. Město n. Moravě, Czech Republic; Calcanail; FH Orthopedics SAS; Heimsbrunn, France) as well as a polyaxial interlocking plate (Rimbus; Intercus GmbH; Rudolstadt, Germany) were used. Biomechanical testing consisted of a dynamic load sequence (preload 20 N, 1000 N up to 2500 N, stepwise increase of 100 N every 100 cycles, 0.5 mm/s) and a load to failure sequence (max. load 5000 N, 0.5 mm/s). Interfragmentary movement was detected via a 3-D optical measurement system. Boehler angle was measured after osteosynthesis and after failure occurred. Results: No significant difference regarding load to failure, stiffness, Boehler angle, or interfragmentary motion was found between the different fixation systems. A significant difference was found with the dynamic failure testing sequence where 87.5% of the Calcanail implants failed in contrast to 14% of the C-Nail group (P < .01) and 66% of the Rimbus plate. The highest load to failure was observed for the C-Nail. Boehler angle showed physiologic range with all implants before and after the biomechanical tests. Conclusion: Both minimally invasive interlocking nail systems displayed a high primary stability that was not inferior to an interlocking plate. Clinical relevance: Based on our results, both interlocking nails appear to represent a viable option for treating displaced intra-articular calcaneal fractures.

Early Functional Postoperative Therapy of Distal Radius Fracture with a Dynamic Orthosis: Results of a Prospective Randomized Cross-Over Comparative Study

Introduction This study was conducted according to GCP criteria as a prospective randomized cross-over study. The primary goal of the study was to determine clinical findings and patient satisfaction with postoperative treatment. 29 patients with a distal radius fracture that was surgically stabilized from volar and who met the inclusion criteria were enrolled over a 12-month period. Each patient randomly received either a dorsal plaster splint or a vacuum-fit flexible but blocked orthosis applied postoperatively in the operating theatre to achieve postoperative immobilization. After one week all patients were crossed over to the complementary device maintaining the immobilization until end of week 2. After week 2 both groups were allowed to exercise wrist mobility with a physiotherapist, in the orthosis group the device was deblocked, thus allowing limited wrist mobility. After week 4 the devices were removed in both groups. Follow-up exams were performed after postoperative weeks 1, 2, 4 and 12. Results and Discussion Results were determined after week 1 and 2 using SF 36 and a personally compiled questionnaire; after weeks 4 and 12 with a clinical check-up, calculation of ROM and the DASH Score. Comparison of the two groups showed a significant difference in ROM for volar flexion after 4 weeks, but no significant differences in DASH Score, duration of disability or x-ray findings. With regard to satisfaction with comfort and hygiene, patients were significantly more satisfied with the dynamic orthosis, and 23 of the 29 patients would prefer the flexible vacuum orthosis in future. Trial Registration German Clinical Trials Register (DRKS) DRKS00006097

Einsatz der Bone morphogenetic Proteins (BMPs) zur Behandlung von Pseudarthrosen – Effizienz und Therapieversagen

In the therapy for pseudarthroses of the proximal tibia, the human recombinant bone morphogenetic proteins (BMP-2 and BMP-7) have been used for several years. Despite their limited and specified use as local mediators of bone healing, no conclusions regarding the therapeutic success can be made beforehand. The regulatory mechanisms have turned out to be much more complex and patient-specific than had been assumed before. To help understand the cell biological processes (signalling) and the current possibilities of predicting a successful use of BMP, this article summarises the relevant findings.

Therapeutic peritoneal lavage with warm saline solution as an option for a critical hypothermic trauma patient

SummaryIntroductionIn this paper, we present the case of a 63-year-old woman, who was found in her flat lying unconscious on the floor for an unknown time. At the time of admission, her core temperature was 24 °C and ventricular fibrillation was detected on the electrocardiogram (ECG). Because of the unstable conditions, the persistent nonperfusing cardiac rhythm and the dramatically inhibited coagulation cascade, a peritoneal lavage connected to a rapid infuser was performed for rewarming, instead of using a transportable heart–lung machine and a haemodialysis device. After a prolonged cardiopulmonary resuscitation (CPR), the patient could be transferred to the intensive care unit (ICU) in a stable condition. After 40 days in the ICU, recovery was fast, and another month of treatment later, she could be discharged back home without any discomfort.ConclusionThis report illustrates the successful use of the peritoneal lavage for rewarming a severely hypothermic patient without any extracorporeal rewarming device. Furthermore, it can be used in nearly every hospital if the necessary equipment is affordable. It is demonstrated that this technique is able to provide good outcomes for all victims of accidental hypothermia.ZusammenfassungEinleitungEine schwere Unterkühlung scheint eine eher seltene Komplikation der älteren Bevölkerung in Europa zu sein. Im Jahre 2007 wurden nur 10 Fälle in Deutschland gemeldet. Es ist jedoch davon auszugehen, dass eine hohe Dunkelziffer an nicht gemeldeten oder nicht erkannten Fällen vorliegt. Die meisten veröffentlichen Fälle beschreiben junge Patienten, die einer niedrigen Umgebungstemperatur ausgesetzt waren und die einer unverzüglichen Therapie zugeführt wurden. Bei älteren Patienten tritt eine Unterkühlung des Öfteren auch ohne eine Kälteexposition auf. Diese Fälle gehen mit einer hohen Mortalitätsrate einher. Die betroffenen Individuen stammen meistens aus der städtischen Umgebung und sind sozial isoliert. Die Ursache für die Hypothermie sind hierbei vielfältig und spannen den Bogen von einem ketoazidotischen Koma über den Herzstillstand, eine Hypothyreose, Hypohydriosis, MS, Störung des Hypothalamus und einer Enzephalopathie bis hin zum medikamentös induzierten Versagen der autogenen Temperaturregulation des menschlichen Körpers.In diesem Artikel präsentieren wir den Fall einer 63-jährigen Frau, welche bewusstlos in ihrer Wohnung aufgefunden wurden, wobei die Dauer dieses Zustands nicht zu eruieren war. Zum Zeitpunkt ihrer Aufnahme in der Ambulanz betrug ihre Körperkerntemperatur 24 °C und ihr EKG zeigte Herzflimmern. Auf Grund der instabilen Gesamtkonstitution, des persistierenden Kreislaufstillstands und der dramatisch gestörten Gerinnungskaskade, wurde eine kontinuierliche Peritoneallavage zur Erwärmung durchgeführt. Eine transportable Herz-Lungen-Maschine und/oder Hämodialyseeinheit kamen nicht zum Einsatz. Nach einer prolongierten Reanimationszeit konnte die Patientin bei stabiler Kreislaufsituation auf die ICU transferiert werden. Nach einem 40-tägigen Aufenthalt auf der Intensivstation zeigte sich eine zügige Rekonvaleszenz und nach einem weiteren Monat unter normalstationären Bedingungen wurde die Patientin, ohne bleibende Schäden, in ihre häusliche Umgebung entlassen.ZusammenfassungDieser Fallbericht illustriert den erfolgreichen Einsatz der Peritoneallavage in Fällen einer akuten Unterkühlung ohne den zusätzlichen Einsatz von Gerätschaften der extrakorporalen Erwärmung. Im Speziellen in kleinen Krankenhäusern mit limitierten Ressourcen an high-end Gerätschaften und weniger spezialisierten Mitarbeitern bietet dieses Verfahren eine alternative Lösung zur Behandlung von Patienten mit schwerer Hypothermie.

Semi-rigid screws provide an auxiliary option to plate working length to control interfragmentary movement in locking plate fixation at the distal femur

BACKGROUND Extent and orientation of interfragmentary movement (IFM) are crucially affecting course and quality of fracture healing. The effect of different configurations for implant fixation on successful fracture healing remain unclear. We hypothesize that screw type and configuration of locking plate fixation profoundly influences stiffness and IFM for a given load in a distal femur fracture model. METHODS Simple analytical models are presented to elucidate the influence of fixation configuration on construct stiffness. Models were refined with a consistent single-patient-data-set to create finite-element femur models. Locking plate fixation of a distal femoral 10mm-osteotomy (comminution model) was fitted with rigid locking screws (rLS) or semi-rigid locking screws (sLS). Systematic variations of screw placements in the proximal fragment were tested. IFM was quantitatively assessed and compared for different screw placements and screw types. RESULTS Different screw allocations significantly affect IFM in a locking plate construct. LS placement of the first screw proximal to the fracture (plate working length, PWL) has a significant effect on axial IFM (p < 0.001). Replacing rLS with sLS caused an increase (p < 0.001) of IFM under the plate (cis-cortex) between +8.4% and +28.1% for the tested configurations but remained constant medially (<1.1%, trans-cortex). Resultant shear movements markedly increased at fracture level (p < 0.001) to the extent that plate working length increased. The ratio of shear/axial IFM was found to enhance for longer PWL. sLS versus rLS lead to significantly smaller ratios of shear/axial IFM at the cis-cortex for PWL of ≥ 62 mm (p ≤ 0.003). CONCLUSION Mechanical frame conditions can be significantly influenced by type and placement of the screws in locking plate osteosynthesis of the distal femur. By varying plate working length stiffness and IFM are modulated. Moderate axial and concomitantly low shear IFM could not be achieved through changes in screw placement alone. In the present transverse osteotomy model, ratio of shear/axial IFM with simultaneous moderate axial IFM is optimized by the use of appropriate plate working length of about 42-62 mm. Fixation with sLS demonstrated significantly more axial IFM underneath the plate and may further contribute to compensation of asymmetric straining.

Virtual morphological comparison of three intramedullary nailing systems for the treatment of proximal humeral fractures

Proximal humerus fractures treated with intramedullary nails show good results. However, the correct anatomical reconstruction of four-part fractures is demanding especially when using intramedullary nails. We therefore compared different intramedullary nail designs for the proximal humerus in a virtual morphological manner. Three commercially available nailing systems where virtually implanted in virtually generated reproducible four-part fractures of 25 digitised humeri. The objective of this study was to quantify and characterise the anatomical position of the proximal screws in the most vulnerable case of a four-part fracture. Taking into account a minimum distance of 5mm between the screw head and the fracture line, osteosynthesis was possible in 54 out of 75 cases. Difficulties placing the proximal screws could be observed at the localisation of the lower lesser tubercle or/and at the sulcus intertubercularis. This morphological analysis could be the basis for choosing the most sufficient implant intra operatively or even improving the nail design.

Die Fraktur der Gegenkortikalis bei der aufklappenden Osteotomie des Tibiakopfes

BACKGROUND Open wedge high tibial osteotomy (HTO) is an increasingly more common surgical method. A typical problem of this procedure is fracture of the lateral hinge. OBJECTIVES The aims of this article are to present the special issue of fractures of the lateral hinge after HTO and to discuss surgical hints on how to prevent and treat this problem. METHODS The results of recently published clinical studies are summarized and tips from own clinical experiences are given. RESULTS Type II fractures of the lateral hinge are unstable and can create a major problem. Using short spacer plates results in a problem of stability for all types of fractures. CONCLUSION The classification into Takeuchi grades I-III has been proven to be suitable for fractures of the lateral hinge. The TomoFix plate is a safe implant to stabilize the osteotomy in type I and III fractures with which healing can be achieved with no problems. Type II fractures can be stabilized with the TomoFix plate; however, an autologous bone graft has to be taken into consideration. For fractures of the lateral hinge short spacer plates are not recommended due to stability issues.

Lateral hinge fractures in open wedge high tibial osteotomy

BACKGROUND Open wedge high tibial osteotomy (HTO) is an increasingly more common surgical method. A typical problem of this procedure is fracture of the lateral hinge. OBJECTIVES The aims of this article are to present the special issue of fractures of the lateral hinge after HTO and to discuss surgical hints on how to prevent and treat this problem. METHODS The results of recently published clinical studies are summarized and tips from own clinical experiences are given. RESULTS Type II fractures of the lateral hinge are unstable and can create a major problem. Using short spacer plates results in a problem of stability for all types of fractures. CONCLUSION The classification into Takeuchi grades I-III has been proven to be suitable for fractures of the lateral hinge. The TomoFix plate is a safe implant to stabilize the osteotomy in type I and III fractures with which healing can be achieved with no problems. Type II fractures can be stabilized with the TomoFix plate; however, an autologous bone graft has to be taken into consideration. For fractures of the lateral hinge short spacer plates are not recommended due to stability issues.

Safe surgical technique: cement-augmented pedicle screw instrumentation and balloon-guided kyphoplasty for a lumbar burst fracture in a 97-year-old patient

BackgroundDuring the last few years, an increasing number of unstable thoracolumbar fractures, especially in elderly patients, has been treated by dorsal instrumentation combined with a balloon kyphoplasty. This combination provides additional stabilization to the anterior spinal column without any need for a second ventral approach.Case presentationWe report the case of a 97-year-old male patient with a lumbar burst fracture (type A3-1.1 according to the AO Classification) who presented prolonged neurological deficits of the lower limbs - grade C according to the modified Frankel/ASIA score. After a posterior realignment of the fractured vertebra with an internal screw fixation and after an augmentation with non-absorbable cement in combination with a balloon kyphoplasty, the patient regained his mobility without any neurological restrictions.ConclusionEspecially in older patients, the presented technique of PMMA-augmented pedicle screw instrumentation combined with balloon-assisted kyphoplasty could be an option to address unstable vertebral fractures in “a minor-invasive way”. The standard procedure of a two-step dorsoventral approach could be reduced to a one-step procedure.