Transverse patella fractures are commonly encountered in trauma surgery, open reduction and internal fixation are considered the gold standard treatment modality that could permit early knee motion and immediate rehabilitation. Many fixation methods had been defined and compared to each other's in many clinical and biomechanical studies. The aim of this study was to assess the safety and stability of our novel anatomical patella plate and to compare its stability with tension band-wire technique. A total of 12 cadaveric preserved knees (six right and six left patellae) with close patellar size were chosen to form two groups of six samples. Each group received either plate or tension band-wiring fixation for an experimentally created patella fracture. Cyclic load of an average of 350 N was applied for all specimens and after accomplishing 50 cycles the displacements of all fracture edges were recorded. After completing 50 cycles in each group, the average fracture edges displacement measured in the plate group was 1.98 ± 0.299 mm, whereas the average fracture edges displacement measured in the tension band-wire group was 2.85 ± 0.768 mm (p = 0.016). In the operative treatment of displaced transverse patellar fractures, the strength of fixation obtained by titanium curved plates is highly stronger when compared to the fixation with a tension band-wire technique. Fixation with titanium curved plates provides satisfactory stability at the fracture site which allow withstanding the cyclic loads during the postoperative rehabilitation.

Background

While the biomechanical properties of trans-pedicular screws have proven to be superior in the lumbar spine, little is known concerning pullout strength of trans-pedicle screws in comparison to different distal terminal constructs like sublaminar hooks alone, trans pedicular screws with sublaminar hooks and clow hooks alone in the thoracolumbar spine surgery. In vitro biomechanical pullout testing was performed to evaluate the axial pullout strength of four different distal terminal constructs in thoracolumbar spine surgery.

Background

Bothlimited-contact dynamic compression plate (LC-DCP) and locking compression plate (LCP) systems were designed to provide enhanced bone healing and to improve stability at fracture site. However, implant failure, delayed union, nonunion and instability are still frequently encountered complications. The purpose of this study was to determine the biomechanical characteristics of a novel persistent compression dynamic plate (PCDP) which provides a persistent compression to fracture edges, and to compare the biomechanical properties of such a novel plate with the commonly used LCP.

Basic engineering principles dictate that unplugged screw holes serve as sites of the concentration of stress and the initiation and growth of cracks (1,2). The idea of filling the holes were tested previously in the literature showing promising results (3). However there's either adverse results which might be a design mistake (4). The purpose of this study was to determine if the use of specially designed screw hole inserts in empty locking screw holes improves the strength and failure characteristics of locking plates.

Forty two 7-hole locking LC/DCP plates were mounted on cylindric UHMW Polyethylene blocks with a 1-cm gap between blocks, simulating a fracture with comminution and bone loss. 21 plates had a screw hole insert placed in the center hole (centered over the simulated fracture), while 21 of the plates remained empty in the center hole. The plate–block constructs were placed in a mechanical testing machine and subjected to a series of loading conditions. The axial, bending and torsional stiffness and displacements needed for failure of each plate-block construct was calculated. The Statistical analysis was performed by Mann Whitney-U test for independent variables.

All plates were then loaded to failure. There were significant difference in the axial load to failure (p=0.017), bending load to failure (p<0.01) and bending diplacements (p<0.01) of the test groups favoring the screw hole insert group as a higher mechanical strength.

In conclusion the study demonstrates that the addition of the specially designed locking screw hole insert does significantly change the stength of the locking LC/DCP plates and might be suggested in the clinical application.