Abstract BACKGROUND: As an emerging technology, tissue-engineered skin has great application prospects. Keratinocyte growth factor (KGF) is proved to promote the proliferation of epidermal cels. OBJECTIVE: To evaluate the effect and characteristics of tissue-engineered skin carrying KGF nanocapsules in repairing skin defects of nude mice. METHODS:(1) The acelular dermal matrix loading KGF (KGF-ADM) was constructed. The human epidermal stem cel population and fibroblasts were captured and cultivated, and then identified. Epidermal stem cels were cultivated on the KGF-ADM and their growth was observed. The tissue-engineered skin loading KGF nanocapsules was transplanted onto the ful-skin defects on the back of nude mice compared with a blank group without keratinocyte growth factor nanocapsules and a control group with skin autograft. In 2, 4 and 6 weeks after transplantation, the contraction and histological healing of the skin were observed respectively. Then anti-human keratin 10-FITC and β1-integrin-Cy3 immunofluorescence were applied to detect the origin, growth and differentiation of stem cels in the epidermis and dermis. RESULTS AND CONCLUSION: The epidermal stem cel population grew wel on the surface of KGF-ADM and attached tightly. There were smal round epidermal stem cels and polygonal terminaly-differentiated cels, which presented with partly cloning growth and a tendency of merging into pieces. The results of tissue-engineered skin with KGF nanocapsules in repairing the skin defects were better than those of the blank group and the control group in 2, 4 and 6 weeks after transplantation. The transplanted skin could fuse with adjacent skin completely, but stil showed some contraction. Under the microscope, they showed good epidermis with layers and normal keratose stratum, and meanwhile, there were stil some β1-integrin+ cels at 8 and 10 weeks, which were epidermal stem cels or transient amplifying cels identified by immunofluorescence. These findings indicate that the tissue-engineered skin carrying KGF nanocapsules has good outcomes in repairing skin defects of nude mice, which is better than common tissue-engineered skin without KGF nanocapsules and autogeneous skin transplantation.

Objective:To evaluate the clinical outcome of Robot-assisted sacroiliac screw fixation in the treatment of fragility fracture of the sacrum in the elderly.Methods:From March 2016 to June 2022, a retrospective analysis was performed on 30 patients with fragility fractures of the sacrum in the elderly who accepted robot-assisted sacroiliac screw to treat fragility fractures of the sacrum in our hospital. There were 12 males and 18 females with average age 71.03±8.25 years (range, 60-89 years). According to the classification of fragility fractures of the pelvis (FFP) in the elderly, there were 22 patients with FFP II, 2 patients with FFP III, and 6 patients with FFP IV. Surgical planning was based on the average CT value of S 1 channel and whether there is a transsacral screw channel. Robot-assisted sacroiliac screw fixation was performed during surgery. The pain of pre-operation and post-operation was evaluated using the visual analogue scale (VAS), the position of sacroiliac screws was evaluated by Gras grading, and the degree of functional recovery after surgery was evaluated using the Majeed function score. Results:All 30 patients successfully completed the operation. The mean operation time was 27.00±6.68 min (range, 18-35 min), the mean fluoroscopy times were 27.13±5.16 (range, 18-34), and the mean blood loss was 30.53±6.61 ml (range, 23-38 ml). All patients were followed up, and the mean follow-up time was 19.03±7.8 months (range, 8-25 months). The VAS was 5(5, 6), 4(3, 4), 3(2, 3), 0(0, 1) points before surgery, 1 week, 2 months and 6 months after surgery, respectively, and the difference was statistically significant ( H=103.26, P<0.001). After the surgery of 2 months, 6 months and the last follow-up time, the Majeed function scores were 88(83, 90), 91(87, 92), 92(90, 93) points, respectively, and the difference was statistically significant ( H=19.59, P<0.001). Screw position was evaluated according to Gras grading at 3 days after surgery, including 28 cases of level I, 2 cases of level II, and no screw penetrated the cortical bone or entered the sacral canal or sacral foramen. No vascular or nerve injury occured during the operation. 28 patients with FFS met the fracture healing criteria, and the healing time was 4.54±1.57 months (range, 3-7 months). Two patients had bone nonunion, one of whom underwent anterior ring plate removal due to infection of the pelvic anterior wound, and one month later, pelvic CT scan revealed loosening of the sacroiliac screw; the other one is considered to be related to too early weight bearing. Conclusion:For fragility fractures of the sacrum in elderly, Robot-assisted sacroiliac screw is an effective minimally invasive treatment, with high accuracy of screw placement, effective pain reduction, improved fracture healing rate, and achieve the satisfactory clinical efficacy.