Introduction of a computer-based method for automated planning of reduction paths under consideration of simulated muscular forces.

PURPOSE: Reduction is a crucial step in the surgical treatment of bone fractures. Finding an optimal path for restoring anatomical alignment is considered technically demanding because collisions as well as high forces caused by surrounding soft tissues can avoid desired reduction movements. The repetition of reduction movements leads to a trial-and-error process which causes a prolonged duration of surgery. By planning an appropriate reduction path-an optimal sequence of target-directed movements-these problems should be overcome. For this purpose, a computer-based method has been developed. METHODS: Using the example of simple femoral shaft fractures, 3D models are generated out of CT images. A reposition algorithm aligns both fragments by reconstructing their broken edges. According to the criteria of a deduced planning strategy, a modified A*-algorithm searches collision-free route of minimal force from the dislocated into the computed target position. Muscular forces are considered using a musculoskeletal reduction model (OpenSim model), and bone collisions are detected by an appropriate method. RESULTS: Five femoral SYNBONE models were broken into different fracture classification types and were automatically reduced from ten randomly selected displaced positions. Highest mean translational and rotational error for achieving target alignment is [Formula: see text] and [Formula: see text]. Mean value and standard deviation of occurring forces are [Formula: see text] for M. tensor fasciae latae and [Formula: see text] for M. semitendinosus over all trials. These pathways are precise, collision-free, required forces are minimized, and thus regarded as optimal paths. CONCLUSIONS: A novel method for planning reduction paths under consideration of collisions and muscular forces is introduced. The results deliver additional knowledge for an appropriate tactical reduction procedure and can provide a basis for further navigated or robotic-assisted developments.

Computer-assisted fracture reduction: a new approach for repositioning femoral fractures and planning reduction paths.

PURPOSE: Reduction is a crucial step in the surgical treatment of bone fractures to achieve anatomical alignment and facilitate healing. Surgical planning for treatment of simple femoral fractures requires suitable gentle reduction paths. A plan with optimal movement of fracture fragments from the initial to the desired target position should improve the reduction procedure. A virtual environment which repositions the fracture fragments automatically and provides the ability to plan reduction paths was developed and tested. METHODS: Virtual 3D osseous fragments are created from CT scans. Based on the computed surface curvatures, strongly curved edges are selected and fracture lines are generated. After assignment of matching points, the lines are compared and the desired target position is calculated. Planning of reduction paths was achieved using a reference-coordinate-system for the computation of reduction parameters. The fracture is reduced by changing the reduction parameters step by step until the target position is reached. To test this system, nine different fractured SYNBONE models and one human fracture were reduced, based on CT scans with varying resolution. RESULTS: The highest mean translational error is 1.2 ± 0.9 (mm), and the rotational error is 2.6 ± 2.8 (°), both of which are considered as clinically acceptable. The reduction paths can be planned manually or semi-automatically for each fracture. CONCLUSIONS: Automated fracture reduction was achieved using a system based on preoperative CT scans. The automated system provides a clinically feasible basis for planning optimal reduction paths that may be augmented by further computer- or robot-assisted applications.

Pelvic fracture in multiple trauma: are we still up-to-date with massive fluid resuscitation?

Until today the mortality of complex pelvic trauma remains unacceptably high. On the one hand this could be attributed to a biological limit of the survivable trauma load, on the other hand side an ongoing inadequate treatment might be conceivable too. For the management of multiple trauma patients with life-threatening pelvic fractures, there is ongoing international debate on the adequate therapeutic strategy, e.g. arterial embolization or pelvic packing, as well as aggressive or restrained volume therapy. Whereas traditional pelvis-specific trauma algorithms still recommend massive fluid resuscitation, there is upcoming evidence that a restrained volume therapy in the preclinical setting may improve trauma outcomes. Less intravenous fluid administration may also reduce haemodilution and concomitant trauma-associated coagulopathy. After linking the data of the TraumaRegister DGU(®) and the German Pelvic Injury Register, for the first time, the initial fluid management for complex pelvic traumas as well as for different Tile/OTA types of pelvic ring fractures could be addressed. Unfortunately, the results could not answer the question of the adequate fluid resuscitation but confirmed the actuality of massive fluid resuscitation in the prehospital and emergency room setting. Low-volume resuscitation seems not yet accepted in practice in managing multiple trauma patients with pelvic fractures at least in Germany. Nevertheless, prevention of exsanguination and of complications like multiple organ dysfunction syndrome still poses a major challenge in the management of complex pelvic ring injuries. Even nowadays, fluid management for trauma, not only for pelvic fractures, remains a controversial area and further research is mandatory.

An internal locking plate to study intramembranous bone healing in a mouse femur fracture model.

In most murine fracture models, the femur is stabilized by an intramedullary implant and heals predominantly through endochondral ossification. The aim of the present study was to establish a mouse model in which fractures heal intra-membraneously. Femur fractures of 16 SKH-mice were stabilized by an internal locking plate. Femur fractures of another 16 animals were stabilized by an intramedullary screw. Bone repair was analyzed by radiographic, biomechanical, and histological methods. At 2 weeks, histological analysis showed a significantly smaller callus diameter and callus area after locking plate fixation. Cartilage formation within the callus could only be observed after screw fixation, but not after fracture stabilization with the locking plate. Radiological and biomechanical analysis after 2 and 5 weeks showed a significantly improved healing and a higher bending stiffness of fractures stabilized by the locking plate. Fractures stabilized by the locking plate healed exclusively by intramembranous ossification, which is most probably a result of the anatomical reduction and stable fixation. The fractures that healed by intramembranous ossification showed an increased stiffness compared to fractures that healed by endochondral ossification. This model may be used to study molecular mechanisms of intramembranous bone healing.

Ex vivo analysis of rotational stiffness of different osteosynthesis techniques in mouse femur fracture.

The various molecular mechanisms of cell regeneration and tissue healing can best be studied in mouse models with the availability of a wide range of monoclonal antibodies and gene-targeted animals. The influence of the mechanical stability of individual stabilization techniques on the molecular mechanisms of fracture healing has not been completely elucidated yet. Although during recent years several osteosynthesis techniques have been introduced in mouse fracture models, no comparative study on fracture stabilization is available yet. We therefore analyzed herein in a standardized ex vivo setup the rotational stiffness of seven different osteosynthesis techniques using osteotomized right cadaver femora of CD-1 mice. Uninjured femora without osteotomy served as controls. Femur stabilization with a locking plate or an external fixator resulted in a rotational stiffness almost similar to the intact femur. The use of a "pin-clip" device, a "locking nail," a "mouse nail," or an "intramedullary screw" produced a lower torsional stiffness, which, however, was still significantly higher than that achieved with the widely applied conventional pin. By the use of the presented data a more specific choice of stabilization technique will be possible according to the various questions concerning molecular aspects in fracture healing.