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.

Experimental investigation on rockburst behavior of the rock-coal-bolt specimen under different stress conditions.

Coal and rock burst are one of the main dynamic disasters that affect coal mine production. In this paper, the burst structural model of the rock-coal-bolt (RCB) system and the burst tendency criterion are established on the background of deep thin coal seam mining. Uniaxial and triaxial mechanical tests under different stress states are carried out on RCB specimens with different angles. Combined with thermal imaging, the mechanical behavior of the inclined RCB specimen under uniaxial loading is discussed. The results show that the burst tendency of the RCB specimen increases with the angle. The stress-strain curves of some uniaxial and triaxial test specimens show two or more peaks, and the thermal imaging evolutionary process shows that the cracks of the coal and rock develop from shear to tension shear cracks. There is a further development of fracture and energy accumulation between the first and second peaks in the stress-strain curve of the specimen. Therefore, the failure degree of the second peak of the specimen may be stronger than that of the first peak. Additionally, the established stiffness coefficient and burst energy index can better describe the burst tendency of the RCB specimen under different stress states. The results show that the burst tendency of the RCB specimen under the triaxial test is much higher than that of the uniaxial test. In other words, it also explains that the essence of the burst failure of the surrounding rock in the roadway is the initial instability induced by the inside surrounding rock in the roadway. Moreover, the burst tendency is the largest when the rock and coal combination angle is 15°, and the burst damage range may also be increased by the failure of internal coal and rock mass.

Application of a novel porous tantalum implant in rabbit anterior lumbar spine fusion model: in vitro and in vivo experiments.

BACKGROUND: Some porous materials have been developed to enhance biologic fusion of the implants to bone in spine fusion surgeries. However, there are several inherent limitations. In this study, a novel biomedical porous tantalum was applied to in vitro and in vivo experiments to test its biocompatibility and osteocompatibility. METHODS: Bone marrow-derived mesenchymal stem cells (BMSCs) were cultured on porous tantalum implant. Scanning electron microscope (SEM) and Cell Counting Kit-8 assay were used to evaluate the cell toxicity and biocompatibility. Twenty-four rabbits were performed discectomy only (control group), discectomy with autologous bone implanted (autograft group), and discectomy with porous tantalum implanted (tantalum group) at 3 levels: L3-L4, L4-L5, and L5-L6 in random order. All the 24 rabbits were randomly sacrificed at the different post-operative times (2, 4, 6, and 12 months; n = 6 at each time point). Histologic examination and micro-computed tomography scans were done to evaluate the fusion process. Comparison of fusion index scores between groups was analyzed using one-way analysis of variance. Other comparisons of numerical variables between groups were made by Student t test. RESULTS: All rabbits survived and recovered without any symptoms of nerve injury. Radiographic fusion index scores at 12 months post-operatively between autograft and tantalum groups showed no significant difference (2.89 ±â€Š0.32 vs. 2.83 ±â€Š0.38, F = 244.60, P = 0.709). Cell Counting Kit-8 assay showed no significant difference of absorbance values between the leaching liquor group and control group (1.25 ±â€Š0.06 vs. 1.23 ±â€Š0.04, t = -0.644, P = 0.545), which indicated the BMSC proliferation without toxicity. SEM images showed that these cells had irregular shapes with long spindles adhered to the surface of tantalum implant. No implant degradation, wear debris, or osteolysis was observed. Histologic results showed solid fusion in the porous tantalum and autologous bone implanted intervertebral spaces. CONCLUSION: This novel porous tantalum implant showed a good biocompatibility and osteocompatibility, which could be a valid biomaterial for interbody fusion cages.

[Effect of tensile stress on human heel skin fibroblast proliferation in vitro].

OBJECTIVE: To observe the effect of tensile stress on human heel skin fibroblast proliferation in vitro, providing a theoretical basis for preventing the wound edge skin necrosis and nonunion after calcaneal fracture surgery. METHODS: Fibroblast cells were taken from lateral heel skin of a 40 year-old-man, then cultured and subcultured in vitro. After that, they were divided into three groups: 0 hours group, 6 hours group and 24 hours group and were tested by tensile stress testing. The levels of TGF-ß1 and IL-6 in nutrient fluid were measured. Transmission electron microscope and light microscope was applied for observe mitochondria and nucleus. RESULTS: Under 10% of the tensile stress, mitochondria decreased, the levels of TGF-ß1 and IL-6 in nutrient fluid were decreased and cell proliferation was inhibited gradually with time increasing. CONCLUSION: The human lateral heel skin in a long-time tensile stress state is an important cause of wound edge skin necrosis and nonunion after calcaneus fracture surgery.

[Gene expression of bone mesenehymal stem cells transduced by the lentiviral vector of SOX9 gene knockdown].

OBJECTIVE: To construct one lentiviral vector containing mouse SRY-related silencing group--box gene 9 (SOX9) and to transfect murine bone mesenehymal stem cells (mBMSCs) in vitro and observe the expression of target gene. METHODS: RNA inteference target sequence was designed in connectin with mice SOX9 gene sequence. The double strands DNAoligo containing interference sequence were synthesized and cloned into lentivirus vector. The siRNA lentiviral vector with SOX9 gene silencing was constructed and identified, which was transfected into rat bone mesenehymal stem cells. The expression of target gene was detected by immunofluorescence, RT-PCR and Western blot. RESULTS: Lenti-SOX9-siRNA-EGFP was recombined successfully and transduced efficiently into mBMSCs. The expression of SOX9 gene silencing was confirmed by RT-PCR and Western blot. CONCLUSION: Mouse SOX9 gene silencing by RNA interference and Lentiviral vector can transfected successfully into mBMSCs. Meanwhile,SOX9 gene may be silenced in SOX9 transduced mBMSCs. This will provide target cells for the following study about SOX9 gene respairing cartilage injury.

Promotion of osteogenic differentiation of stem cells and increase of bone-bonding ability in vivo using urease-treated titanium coated with calcium phosphate and gelatin.

Because of its excellent biocompatibility and low allergenicity, titanium has been widely used for bone replacement and tissue engineering. To produce a desirable composite with enhanced bone response and mechanical strength, in this study bioactive calcium phosphate (CaP) and gelatin composites were coated onto titanium (Ti) via a novel urease technique. The cellular responses to the CaP/gelatin/Ti (CaP/gel/Ti) and bone bonding ability were evaluated with proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) on CaP/gel/Ti and CaP/Ti in vitro. The results showed that the optical density values, alkaline phosphatase expression and genes expression of MSCs on CaP/gel/Ti were similar to those on CaP/Ti, yet significantly higher than those on pure Ti (p < 0.05). CaP/gel/Ti and CaP/Ti rods (2 mm in diameter, 10 mm in length) were also implanted into femoral shaft of rabbits and pure Ti rods served as control (n = 10). Histological examination, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements were performed at 4 and 8 weeks after the operation. The histological and SEM observations demonstrated clearly that more new bone formed on the surface of CaP/gel/Ti than in the other two groups at each time point. The CaP/gel/Ti bonded to the surrounding bone directly with no intervening soft tissue layer. An interfacial layer, containing Ti, Ca and P, was found to form at the interface between bone and the implant on all three groups by EDS analysis. However, the content of Ca, P in the surface of CaP/gel/Ti implants was more than in the other two groups at each time point. The CaP/gel/Ti modified by the urease method was not only beneficial for MSCs proliferation and osteogenic differentiation, but also favorable for bone bonding ability on Ti implants in vivo, suggesting that Ti functionalized with CaP and gelatin might have a great potential in clinical joint replacement or dental implants.