Objective To analyze the biomechanical changes of the adjacent cervical facet joints when the angled cervical prosthesis is replaced. Methods A total of 400 northwestern people were involved, with an age of 40 years or older.The cervical vertebra lateral X-ray films were taken, and the cervical angles were measured by professional computer aided design software, then the cervical intervertebral disc prosthesis with 10° angle was designed. The finite element models of C4，5and C4-6 segments with intact cervical discs were developed; the C4，5 disc was replaced by the cervical prosthesis with 0° and 10° angle respectively; and then all models were subjected to axial loading, flexion/extension, lateral bending, and torsion loading conditions; the stress effects on adjacent facet joints after replacement were observed by comparing with that of the intact model. Results The cervical angles were (9.97 ± 3.64)° in C3，4, (9.95 ± 4.34)° in C4，5, (8.59 ± 3.75)° in C5，6, and (8.49 ± 3.39)° in C6，7, showing no significant difference between C3，4 and C4，5, C5，6 and C6，7 (P gt; 0.05) and showing significant differences between the other cervical angles (P lt; 0.05). When C4，5 model was axially loaded, no significant difference in equivalent shearing stress were observed in intact, 0°, and 10° groups; at flexion/extension loading, the stress was biggest in intact group, and was smallest in 10° group; at lateral bending, the stress got the high rank in intact group, and was minimum in 10° group; at torsion loading, the stress state of 10° group approached to the intact one condition. When C4-6 model was loaded, the facet joint stress of the replaced segment (C4，5) decreased significantly at axial loading, flexion/extension, and lateral bending; while no obvious decrease was observed at torsion loading; the stress of the adjacent inferior disc (C5，6) decreased significantly at axial loadingand lateral bending condition, while less decrease was observed at torsion loading, no significant change at flexion/extension condition, it approached to that of the intact one. Conclusion The finite element analysis reveals that the biomechanical properties of 10° designed prosthesis is approximate to that of the intact cervical disc, thus the 10° designed prosthesis can meet the requirements of biomechanical function reconstruction of the cervical spine.
Prosthesis loosening is the leading cause of postoperative revision in unicompartmental knee arthroplasty (UKA). The deviation of medial and lateral translational installation of the prosthesis during surgery is a common clinical phenomenon and an important factor in increasing the risk of prosthesis loosening. This study established a UKA finite element model and a bone-prosthesis fixation interface micro-motion prediction model. The predicted medial contact force and joint motion of the knee joint from a patient-specific lower extremity musculoskeletal multibody dynamics model of UKA were used as boundary conditions. The effects of 9 femoral component medial and lateral translational installation deviations on the Von Mises stress of the proximal tibia, the contact stress, and the micro-motion of the bone prosthesis fixation interface were quantitatively studied. It was found that compared with the neutral position (a/A of 0.492), the lateral translational deviation of the femoral component significantly increased the tibial Von Mises stress and the bone-prosthesis fixation interface contact stress. The maximum Von Mises stress and the maximum contact stress of the fixation interface increased by 14.08% and 143.15%, respectively, when a/A was 0.361. The medial translational deviation of the femoral component significantly increased the bone-prosthesis fixation interface micro-motion. The maximum value of micro-motion under the conditions of femoral neutral and medial translation deviation was in the range of 20–50 μm, which is suitable for osseointegration. Therefore, based on the range of micro-motion reported in the literature as suitable for osseointegration and to reduce the risk of prosthesis loosening, it is recommended that clinicians control the mounting position of the femoral component during surgery within the safe range of 0–4 mm medial translation deviation and neutral position.
Objective To approach the questions of donation after cardiac death （DCD） and transplantation through analyzing the DCD cases in this hospital. Methods The organs were obtained from 4 DCD from 2010 to 2011 in this hospital， the clinical data of DCD were analyzed retrospectively. Results Seven renal transplantations and 3 liver transplantations were performed. Donor warm ischemic time was 10-40 min. The liver and left kidney of the first DCD donator （Maastricht categoryⅣ） were eliminated through biopsy. One patient exhibited delayed graft function of kidney from the first DCD，the nephrectomy had to be done on day 7 after operation due to renal allograft rupture. Nine patients received 3 livers and 6 kidneys from the other 3 DCD donators （Maastricht categoryⅢ），whose patients were alive with excellent graft function. Conclusions The use of controlled DCD （Maastricht categoryⅢ） might be an effective way to increase the number of organs available for transplantation because that it might obtain satisfactory transplant outcomes and acceptable postoperative complications. The widespread implementation of controlled DCD in China should be encouraged.