Effect of nighttime total knee arthroplasty on prognosis / 中国组织工程研究

BACKGROUND: Whether nighttime surgery will affect the safety and prognosis of patients has been controversial. OBJECTIVE: To compare the safety and prognosis of daytime surgery versus nighttime surgery in patients receiving total knee arthroplasty. METHODS: Data of 712 patients who received unilateral total knee arthroplasty from January 2015 to January 2018 in the Binzhou Medical University Hospital were retrospectively analyzed. Of the patients, 615 cases were treated by total knee arthroplasty during daytime hours (8:00-18:00) and the other 97 patients were treated by total knee arthroplasty during nighttime hours (18:01-7:59). The perioperative and postoperative conditions of the two groups of patients were compared. This study was approved by the Medical Ethics Committee of Binzhou Medical University Hospital, China (approval No. LW2016013). RESULTS AND CONCLUSION: (1) Perioperative period: The operation time in the nighttime surgery group was shorter than that in the daytime surgery group (P 0.05). (2) Prognosis: There was no significant difference in motion range and knee joint function KSS score between the two groups (P > 0.05). (3) The results showed that nighttime surgery did not increase the incidence of adverse reactions after total knee arthroplasty, and did not affect the prognosis of patients.

Biomechanical comparison of monosegmental and short transpedicular fixation for stabilization of thoracolumbar fractures / 医用生物力学

Objective To establish the monosegmental transpedicular fixation model and short segmental fixation model by three-dimensional finite element technique, and evaluate the biomechanical properties of monosegmental transpedicular fixation for thoracolumbar fractures and verify its feasibility for application. Methods T10-L2 motion segment of a young healthy subject was used to establish the normal finite element model. The superior 1/2 cortical bone of the T12 segment was removed and superior 1/2 cancellous bone of the same vertebrae was assigned material property of the injured bone to simulate the thoracolumbar fracture. Transpedicular screw fixation of the T11 and T12 segment was performed in monosegmental fixation model. T11 and L1 segment were instrumented in the short segmental fixation model. All the four finite element models were applied with loading of axial compression, anteflexion, extension, lateroflexion and axial rotation, respectively. Motion difference of each functional unit and the stress of implants were measured to evaluate biomechanical behaviors of monosegmental fixation. Results The motion difference of all the functional units (T10-11, T11-12, T12-L1) in the fractured model was obviously increased under all loading conditions as compared to the normal model, but the motion difference in the fractured models was decreased after monosegmental fixation and short segmental fixation, and no significant differences were found between monosegmental fixation and short segmental fixation. The stress on screws in monosegmental fixation model was significantly lower than that in short segmental fixation under axial compression and anteflexion, but the stress on screws of two fixation models had no significant difference under extension, lateroflexion and axial rotation. The stress on the rods of monosegmental fixation model was apparently higher than that of short segmental fixation under extension and lateroflexion, and lower under axial rotation, but no significant difference was found for two fixation models under axial compression and anteflexion. Conclusions Monosegmental transpedicular screw fixation would give the similar stabilization as short segmental fixtion and could be an effective alternative to treat incomplete fractures in thoracolumbar spine.

Three-dimensional reconstruction study of the displacement of undisplaced femoral neck fractures / 中华外科杂志

<p><b>OBJECTIVE</b>To measure the displacement parameters of femoral head in space through three-dimensional reconstruction so as to reunderstand undisplaced femoral neck fractures.</p><p><b>METHODS</b>The clinical data of 80 undisplaced femoral neck fractures from January 2010 to June 2011 were selected, included Garden I 40 cases (group Garden I) and Garden II 40 cases (group Garden II), bilateral proximal femurs of everyone were scanned by CT and reconstructed by professional software. Registered the normal femur and fracture with mirror model, marked key points in the model and measured the displacement parameters of femoral head. The measurement accuracy of distance and angle were 0.01 mm and 0.01°, respectively. The parameters of femoral head displacement between group Garden I and Garden II were analyzed by independent-sample t-test.</p><p><b>RESULTS</b>Eighty cases on X-ray films were not found rotated displacement. But 24 cases of them (30.0%) showed rotated displacement and rotation direction of the femoral head through three-dimensional reconstruction. Ten cases showed incomplete fractures on X-ray films, but only 3 cases were incomplete fractures with three-dimensional reconstruction. In group Garden I, the femoral head displacement angle was 18° ± 11°, the average displacement distance of femoral head center and deepest point of fovea capitis were (6 ± 3) mm and (10 ± 6) mm respectively. In group Garden II, the femoral head displacement angle was 17° ± 10°, the average displacement distance of femoral head center and deepest point of fovea capitis were (7 ± 5) mm and (13 ± 8) mm respectively. There were not statistical significance of the parameters of femoral head displacement between group Garden I and Garden II (P > 0.05).</p><p><b>CONCLUSIONS</b>Three-dimensional reconstruction and digital measurement is a precise, efficient method for the measurement of femoral head displacement parameters in femoral neck fractures, has important clinical significance in the diagnosis and treatment of the femoral neck fractures. There are certain defects and limitations of the classical Garden classification for undisplaced femoral neck fractures.</p>

Influence of anteversion angles on stress distributions of the proximal femur after femoral neck fracture fixation: A finite element analysis / 医用生物力学

Objective To investigate the effects of different anteversion angles on stress distributions of the proximal femur after femoral neck fracture fixation by cannulated screw, and to provide biomechanical evidences for the importance of anatomical reduction in internal fixation in clinic. Methods Femoral neck fracture with Pauwells angle 70°was treated with cannulated screw internal fixation, and its three-dimensional finite element models with five different anteversion angles set at 0°，5°，10°，15°and 20°, respectively, were constructed based on normal human anatomical data from multi slice spiral CT as well as reverse engineering and CAD software. Loads were applied on each model to simulate normal walking status. Changes in stress distributions of the proximal femur in each model were observed. Results When the anteversion angle was 10°, the stress, displacement and equivalent strain of the femur was were the minimum, as the maximum stress of the proximal femur was 1.7 MPa, and the displacement was 1.1 mm. With the anteversion angle increasing or decreasing, the effective stress and displacement of the proximal femur was gradually increasing. When the anteversion angle was 20°, the stress of on the proximal femur and on the cannulated screw was became the maximum. When the anteversion angle was 0°, the displacement and equivalent strain of the femur also became the maximum. The stress concentration site of the femoral neck was gradually transferred from the inside rear to the outer top of the head and neck junction. The three cannulated screws there stood the higher stress than the surrounding bone tissues, and with the bottom screw stood the higher stress than the other top two screws. Conclusions Anatomic reduction is essential for femoral neck fracture fixation treated by cannulated screw. Changes in biomechanical factors after femoral neck fracture may play an important role in postoperative femoral head necrosis.