Revision surgery for periprosthetic fracture of distal femur after endoprosthetic replacement of knee joint following resection of osteosarcoma.

Purpose: Periprosthetic fracture (PPF) is one of the severe complications in patients with osteosarcoma and carries the risk of limb loss. This study describes the characteristics, treatment strategies, and outcomes of this complication. Methods: Patients were consecutively included who were treated at our institution between 2016 and 2020 with a PPF of distal femur. The treatment strategies included two types: 1) open reduction and internal fixation with plates and screws and 2) replacement with long-stem endoprosthesis and reinforcement with wire rope if necessary. Results: A total of 11 patients (mean age 12.2 years (9-14)) were included, and the mean follow-up period was 36.5 (21-54) months. Most fractures were caused by direct or indirect trauma (n = 8), and others (n = 3) underwent PPF without obvious cause. The first type of treatment was performed on four patients, and the second type was performed on seven patients. The mean Musculoskeletal Tumor Society (MSTS) score was 20 (17-23). All patients recovered from the complication, and limb preservation could be achieved. Conclusion: PPF is a big challenge for musculoskeletal oncologists, particularly in younger patients. Additionally, PPF poses a challenge for orthopedic surgeons, as limb preservation should be an important goal. Hence, internal fixation with plates and endoprosthetic replacement are optional treatment strategies based on fracture type and patient needs.

[Effect of L-alanyl-L-glutamine on expression of insulin-like growth factor-1 in intestinal tissues of low-birth-weight newborn rats with hypoxia/reoxygenation-induced intestinal injury].

OBJECTIVE: To study the effect of L-alanyl-L-glutamine (Ala-Gln) on the levels of insulin-like growth factor-1 (IGF-1) and IGF-1 receptor (IGF-1R) in the intestinal tissues of low-birth-weight (LBW) newborn rats with hypoxia/reoxygenation-induced intestinal injury. METHODS: Pregnant rats were fed with or without smoking. The rats born by those fed without smoking were included in group A; for the rats born by those fed with smoking, normal-birth-weight rats were included in group B, and LBW rats were randomly divided into control group (group C), hypoxia/reoxygenation (H/R) group (group D), and Ala-Gln group (group E). Each group consisted of 24 newborn rats. The rats in groups D and E received H/R treatment twice a day for three consecutive days to establish an intestinal injury model; the rats in group E were intraperitoneally injected with Ala-Gln (10 ml/kg) before daily H/R treatment, while those in groups C and D were given an equal dose of normal saline by intraperitoneal injections. On days 4, 7, and 10 after birth, 8 rats were sacrificed in each group to collect intestinal tissues. The IGF-1 levels in intestinal tissues were measured using ELISA, and IGF-1R levels were measured by immunohistochemistry. RESULTS: There were no significant differences in IGF-1 and IGF-1R levels between groups A and B at all time points. The levels of IGF-1 and IGF-1R in group C kept increasing, were higher than those in other groups on day 7 (P<0.05), and reached a normal level on day 10, without significant differences compared with those in groups A and B. Group D had significantly lower IGF-1 and IGF-1R levels than group C at all time points (P<0.05). The levels of IGF-1 and IGF-1R in group E were lower than those in group C on days 4 and 7 (P<0.05), but they increased to approximately the levels in group C and were significantly higher than those in group D on day 10. CONCLUSIONS: Intrauterine and postnatal hypoxia may induce intestinal injury in LBW newborn rats, and parenteral administration of high-dose Ala-Gln can reduce hypoxia-induced intestinal injury. Therefore, Ala-Gln has a protective effect against hypoxia-induced intestinal injury.

[Culture in vitro and lentivirus transfection of rat mesenchymal stem cells].

This study was purposed to establish the methods for isolation, culture, identification and labeling of bone marrow mesenchymal stem cells (BMMSC), so as to provide quantified seed cells for cell transplantation. Bone marrow was collected from SD rat by flushing femur and tibias under sterile condition and BMMSC were purified by adherent culture and amplified in vitro. The immunophenotypes of BMMSC were identified by flow cytometry, the ability of differentiation to osteogenic and adipogenic lineages was detected by alizarin red and oil red O respectively. The BMMSC were transfected by using lentivirus with green fluorescence protein (GFP) gene so as to determine GFP expression in BMMSC. The results demonstrated that the method of adherent culture could effectively isolate and purify rat BMMSC which displayed homogenous fibro-like morphology. The flow cytometry showed that BMMSC expressed CD29, CD44, not expressed CD34, CD45. The BMMSC could differentiated into osteoblasts and adipocytes two mesenchymal lineages when grown in specific medium for each lineage. After being transfected by lentivirus, BMMSC could express GFP. It is concluded that the adherent culture is simple, effective, feasible method to separate MSC from the bone marrow of adult rats; the separated and cultured cells exhibit the biological characteristics of BMMSC and differentiating potential. BMMSC can express GFP efficiently and stably in vitro after being transfected by lentivirus, which can be used to label cells for tracing in vivo.