Reduction and Stabilization of Depressed Articular Tibial Plateau Fractures: Comparison of Inflatable and Conventional Bone Tamps: Study of a Cadaver Model.

BACKGROUND: Restoration of articular congruity and mechanical integrity of subchondral bone are important surgical goals of the treatment of intra-articular fractures. The purpose of this study was to compare the reduction quality and biomechanical integrity between cadaveric intra-articular tibial plateau fractures reduced with an inflatable bone tamp and contralateral fractures reduced with a series of cylindrical conventional metal bone tamps. METHODS: A standardized lateral tibial plateau split-depression fracture was created in each leg of fourteen pairs of cadaver legs. In each pair, the fracture on one side was reduced under fluoroscopy with use of an inflatable bone tamp and the fracture on the contralateral, control side was reduced with conventional bone tamps and a mallet. Any residual bone defects were filled with calcium phosphate bone-void filler. The constructs were stabilized with a lateral tibial plateau buttress plate. Each articular reduction was qualitatively graded by blinded observers using fluoroscopic images, three-dimensional computed tomography (CT) scans, and visual inspection of the articular surface. Quantitative volumetric analysis was performed to calculate under-reduction, over-reduction, and total malreduction volumes. Each reduced fracture was cyclically loaded and then statically loaded to failure under axial compression, and the strength and stiffness of the constructs were compared between sides. RESULTS: The majority (eleven) of the fourteen fractures reduced with the inflatable bone tamp were rated as having a better reduction than the contralateral fracture reduced with the conventional bone tamps. The median over-reduction and malreduction in the inflatable-tamp group (7% and 21.6%, respectively) were significantly less than those in the conventional-tamp group (19.2% and 47.1%), although the median under-reduction (6.2% in the inflatable-tamp group and 9.6% in the conventional-tamp group) did not differ significantly between groups. The fractures reduced with the inflatable tamp displaced less during cyclic loading than those reduced with the conventional tamp. Median static stiffness and yield load were also significantly higher in the inflatable-tamp group (880 N/mm and 704 N) than in the conventional-tamp group (717 N/mm and 641 N). CONCLUSIONS: As compared with contralateral control fractures treated with conventional bone tamps, fractures treated with an inflatable bone tamp had qualitatively and quantitatively better reduction, typically resulting in a smoother articular surface with less residual defect volume. Fractures reduced with an inflatable bone tamp exhibited less subsidence during cyclic loading and greater stiffness under static loading compared with those treated with conventional bone tamps. CLINICAL RELEVANCE: Using an inflatable bone tamp in association with calcium phosphate bone-void filler to reduce and maintain reduction of an articular fracture may help in achieving the surgical goal of a more anatomic reduction with better resistance to subsidence.

In vitro system for applying cyclic loads to connective tissues under displacement or force control.

Overuse is thought to be the primary cause of chronic tendon injuries, in which forceful or repetitive loading results in an accumulation of micro-tears leading to a maladaptive repair response. In vitro organ culture models provide a useful method for examining how specific loading patterns affect the cellular response to load which may explain the early mechanisms of tissue injury associated with tendinopathies and ligament injuries. We designed a novel tissue loading system which employs closed-loop force feedback, capable of loading six tissue samples independently under force or displacement control. The system was capable of applying loads up to 40 N at rates of 100 N s(-1) and frequencies of 2 Hz, well above loads and rates measured in rabbit tendons in vivo. Loading parameters such as amplitude, rate, and frequency can be controlled while biomechanical factors such as creep, force relaxation, tangent modulus and Young's modulus can be assessed. The system can be used to examine the relationship between each loading parameter and biomechanical factors of connective tissues maintained in culture which may provide useful information regarding the etiology of overuse injuries.