Background Cannulated screws with an anterior wire are currently used for managing transverse patellar fracture. However, the addition of anterior wiring with various types of screws via open surgery to increase the mechanical stability is yet to be determined. Hence, this study aimed to compare the mechanical behaviors of a fractured patella fixed with various screws types and at various screw locations with and without the anterior wire. The present study hypothesized that using the anterior wire reduces the fracture gap formation. Methods A finite element (FE) model containing a fractured patella fixed with various types of cannulated screws and anterior wiring was created in this study. Three types of screws, namely partial thread, full thread, and headless compression screws, and two screw depths, namely 5 and 10 mm away from the anterior surface of the patella, were included. The effect of the anterior wire was clarified by comparing the results of surgical fixation with and without the wire. Two magnitudes and two loading directions were used to simulate and examine the mechanical responses of the fractured patella with various fixation conditions during knee flexion/extension. Results Compared with partial thread and headless compression screws, the full thread screw increased the stability of the fractured patella by reducing fragment displacement, fracture gap formation, and contact pressure while increasing the contact area at the fracture site. Under 400-N in the direction 45°, the full thread screw with 5-mm placement reduced the gap formation by 86.7% (from 2.71 to 0.36 mm) and 55.6% (from 0. 81 to 0. 36 mm) compared with the partial thread screw with 10-mm placement, respectively without and with the anterior wire. Conclusion The anterior wire along with the full thread screw is preferentially recommended for maintaining the surgical fixation of the fractured patella. Without the use of anterior wiring, the full thread screw with 5-mm placement may be considered as a less invasive alternative; however, simple screw fixation at a deeper placement (10 mm) is least recommended for the fixation of transverse patellar fracture.

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BackgroundBack pain is a common complication of wheelchair-bound elderly people. Seating system is a key factor that influences spinal curvature, back muscle activation, interface pressure, and comfortability. A seating system can maintain lumbar lordosis, lower back muscle activity, and decrease ischial tuberosities pressure, which reduces spinal load and directly influences sitting comfort. Our previous study has confirmed that backward thoracic support showed a relatively higher lumbar lordosis and lower back muscle activity. This study intends to evaluate the influence of backward thoracic support on interface pressure and subjective discomfort.MethodsIn this study, 18 elderly men were recruited to participate in a random comparison involving 4 sitting postures. These postures comprised relaxed slouching, flat back support, prominent lumbar support, and backward thoracic support sitting. All parameters, including interface pressure (total contact area, average pressure, and peak pressure on backrest and seat) and subjective discomfort (upper-back, mid-back, lower-back, buttocks, and thighs) were measured and compared.ResultsThe results showed that compared with other sitting postures, backward thoracic support sitting significantly reduced average pressure and peak pressure on seat and increased average pressure and peak pressure on backrest. Concurrently, subjective discomfort in the upper-back, mid-back, lower-back, and buttocks were reduced.ConclusionsThe results confirmed that backward thoracic support can maintain favorable wheelchair sitting posture, thereby preventing or reducing the risks of back pain. However, this study was no evaluations on shear forces on butts and neck postures. Future studies investigating shear forces on butts and neck postures are required.