Dual-crosslinked reduced graphene oxide/polyimide aerogels possessing regulable superelasticity, fatigue resistance, and rigidity for thermal insulation and flame retardant protection in harsh conditions.

Polyimide (PI) aerogels have various applications in aerospace, national defense, military industry, and rail transit equipment. This paper reports a series of ultra-lightweight, high elasticity, high strength, low thermal conductivity, and high flame retardant rGO/PI nanocomposite aerogels prepared by the ice templating method. The effects of freezing processes (unidirectional freezing and random freezing), chemical composition, and environmental temperature (-196-200 °C) on the morphology, mechanical, and thermal properties of the aerogels were systematically studied. The results indicated that unidirectional aerogels exhibit anisotropic mechanical properties and thermal performance. Compression in the horizontal direction showed high elasticity, high fatigue resistance, and superior thermal insulation. Meanwhile, in the vertical direction, it demonstrated high strength (PI-G-9 reaching 14 MPa). After 10,000 cycles of compression in the horizontal direction (at 50 % strain), the unidirectional PI-G-5 aerogel still retains 90.32 % height retention, and 78.5 % stress retention, and exhibited a low stable energy loss coefficient (22.11 %). It also possessed a low thermal conductivity (32.8 mW m-1 K-1) and demonstrated good thermal insulation performance by sustaining at 200 °C for 30 min. Interestingly, the elasticity of the aerogels was enhanced with decreasing temperatures, achieving a height recovery rate of up to 100 % when compressed in liquid nitrogen. More importantly, the rGO/PI aerogels could be utilized over a wide temperature range (-196-200 °C) and had a high limiting oxygen index (LOI) ranging from 43.3 to 48.1 %. Therefore, this work may provide a viable approach for designing thermal insulation and flame-retardant protective materials with excellent mechanical properties that are suitable for harsh environments.

Novel dual: rod plate system for EOS improves vertebral wedging and permits spinal growth.

BACKGROUND: To determine whether single-stage, growth-friendly instrumentation with a plate-rod spinal system (PRSS) can substantially correct the deformity of EOS at surgery and continue to rectify the deformity throughout the growth period. METHODS: An observational study of 35 children with EOS treated by PRSS between February 2000 and October 2010 during a mean follow-up of 72 months. The mean age at surgery was 7 years. X-rays were taken preoperatively and postoperatively and at each follow-up. The Cobb angle, the apical vertebral wedge angle (AVWA), remaining rod lengths, maximal thoracic kyphosis and total T1-S1 heights were measured and compared. RESULTS: Thirty-one patients, 9 boys and 22 girls, with a mean age of 7 years were completed follow-up. The Cobb angle changed from 64° to 36° after initial surgery and 26° at the last follow-up. The mean AVWA was 15° postoperatively and 5° at the last follow-up. The mean rod tail reserve length decreased from 53 mm immediately after surgery to 12 mm at the last follow-up. The mean preoperative maximum thoracic kyphosis was 41° and changed to 35° and 30° postoperatively and at latest follow-up, respectively. The mean preoperative T1-S1 height for all 32 patients was 52 mm acute lengthening and 122 mm of lengthening by the end of follow-up, respectively. CONCLUSION: The PRSS provided immediate correction of most of the deformity at surgery and continued to rectify remaining scoliosis during the growth period. AVWA may be a useful method for monitoring the function of the PRSS in EOS.

[Observation on maintenance of scoliosis curve correction and preservation of spinal mobility after removing plate-rod system for scoliosis].

OBJECTIVE: To investigate the effect of removing the implanted plate-rod system for scoliosis (PRSS) on maintaining scoliosis curve correction and preserving spinal mobility in patients with scoliosis. METHODS: From June 1998 to February 2002, 119 cases of scoliosis were treated with the implant of PRSS, which was removed 26-68 months later (average 46.8 months). Complete follow-up data were obtained in 21 patients, including 6 males and 15 females aged 11-17 years old (average 13.8 years old). The disease course was 9-16 years (average 12.1 years). There were 2 cases of congenital scoliosis and 19 cases ofidiopathic scoliosis, which included 5 cases of IA, 2 of IB, 1 of IIA, 2 of IIB, 2 of IIC, 2 of IIIA, 3 of IIIB, and 2 of IVA according to Lenke classification. There were 13 cases of thoracic scoliosis and 8 of thoracolumbar scoliosis. AP view and the lateral and anterior bending view of X-ray films before and at 3 to 6 months after removing PRSS were comparatively analyzed, the coronal and the sagittal Cobb angle were measured, and the height of vertebral body on the concave side and the convex side were measured, so as to know the effect of PRSS on the growth of the vertebral endplates. RESULTS: All the implants were removed successfully with an average operation time of 2.5 hours (range 2-4 hours) and a small amount of intraoperative blood loss. Twenty-one cases were followed up for 6-72 months (average 34.4 months). The coronal Cobb angle before and after the removal of PRSS was (20.25 +/- 8.25) degrees and (23.63 +/- 8.41) degrees, respectively, indicating there was no significant difference (P > 0.05); while the sagittal Cobb angle was (39.44 +/- 12.38) degrees and (49.94 +/- 10.42) degrees, respectively, indicating there was a significant difference (P < 0.05). The height of the top vertebral body on the concave side before and after the removal of PRSS was (1.78 +/- 0.40) cm and (2.08 +/- 0.35) cm, respectively, and there was a significant difference (P < 0.01); while the height on the convex side was (2.16 +/- 0.47) cm and (2.18 +/- 0.35) cm, respectively, indicating no significant difference was evident (P > 0.05). All the 21 patients had good prognosis and no major operative complication occurred. CONCLUSION: PRSS is an effective instrumentation for the management of scoliosis. After the removal of the PRSS, the correction of scoliosis can be maintained, and the spinal mobility can be protected and restored.

[Biomechanical study and clinical application of distraction reduction fixation system for treating thoracolumbar vertebral fracture].

OBJECTIVE: To investigate the biomechanical characteristics of self-developed distraction reduction fixation system (DRFS) and to evaluate its clinical effect on thoracolumbar vertebrate fracture. METHODS: Twelve fresh porcine spines were prepared for the biomechanical test. The stiffness of each intact specimen were recorded on forward bending (20 degrees), backward bending (10 degrees), lateral bending (30 degrees) and axial rotation (20 degrees), and then specimens of fracture dislocation were made by cuneiform osteotomy of L3 vertebral body and excision of posterior facet joints. Finally, DRFS internal fixation was performed on each specimen. The stiffness of specimens in fracture dislocation and after DRFS fixation were measured during the same movements mentioned above, respectively. The clinical effect of DRFS on thoracolumbar vertebrate fracture in 31 patients (aged 17-46 years with an average of 32.1) from April 1998 to October 2002 was summarized. Fracture types were classified according to Denis classification: 2 patients suffered simple compressed fracture, 16 burst fracture, and 13 fracture dislocation, including 2 cases of T11, 11 cases of T12, 14 cases of L1 and 4 cases of L2. Frankel and X-ray examination were adopted to assess the results. RESULTS: The stiffness during forward bending, backward bending, lateral bending and axial rotation in the fracture-dislocation state was markedly lower than that of the corresponding movements of the intact porcine spines (P < 0.05). After DRFS, the stiffness during various movements increased to the level that significantly higher than that in the fracture-dislocation state (P < 0.05), and the stiffness during backward bending was of significant difference (P < 0.05), but without significant difference during the rest three movements (P > 0.05) when compared to that in intact spines. Regarding clinical observation, the operation time was 2.2-4.1 hours (2.7 hours on average) and blood loss was 250-600 mL (450 mL on average). The patients were followed up for 5-20 months (10.2 months on average). The healing time for fracture was 5-1 months (8 months on average). The mean anterior and posterior heights of the injured vertebrate recovered from 46.2% +/- 7.5% and 76.4% +/- 2.4% preoperatively to 89.8% +/- 4.6% and 94.1% +/- 1.5% postoperatively (P < 0.05).The median point height also raised from 60.8% +/- 6.4% to 90.7% +/- 2.9% (P < 0.05). The Cobb's angle decreased from (26.3 +/- 5.9)degrees to (5.2 +/- 1.8)degrees (P < 0.05), and all the slipped vertebrates were well repositioned. Spine function was assessed by Frankel classification as follows: 2 of 5 Class A preoperatively improved to Class B postoperatively, and the other 3 remained unchanged; 4 of 6 from B to C, and the other 2 to D; 6 of 13 from C to D, and the other 7 to E; and 7 from D to E. CONCLUSION: DRFS is capable of providing sufficient stability, meeting the requirement of the spine physical activity without any obvious side effect. DRFS, as a handy, safe and effective technique in clinical practice, is featured by satisfying functions of distraction, reposition and fixation.

Operative treatment for separation of distal tibiofibular syndesmosis.

OBJECTIVE: To study the influence of separation of distal tibiofibular syndesmosis on ankle joint and to compare various operative methods so as to find suitable stabilization for separated distal tibiofibular syndesmosis. METHODS: From July 1997 to July 2002, we treated 87 patients (64 males and 23 females, aged 18-54 years) with separation of distal tibiofibular syndesmosis, among whom, 79 were combined with fracture of malleolus. Manipulative reduction, internal fixation with cancellous screws and external fixation with plaster support were performed on 37 patients, fixation with plate and screws for fibular fracture and fixation with cancellous screws for distal tibiofibular syndesmosis on 34 patients, and repair of the distal tibiofibular ligaments with tendon of peroneus longus, reduction of the separated distal tibiofibular syndesmosis, and fixation with cancellous screws on 16 patients. The ankle joint had been dorsiflexed for 30 degrees when the distal tibiofibular syndesmosis was fixed with cancellous screws. And the cancellous screws were taken out at 8-10 weeks after operation. RESULTS: These patients were followed up for at least two years. The curative effects were assessed according to the complaints of the patients and the contour, function and radiogram of the ankle joint: excellent in 55 patients (63%), good in 18 patients (21%), and fair in 14 patients (16%). Separation of distal tibiofibular syndesmosis recurred in 2 patients, who underwent a reoperation for repairing the distal tibiofibular ligaments with tendon of peroneus longus and recovered. One cancellous screw was broken off. No necrosis developed in the anterior skin of the ankle mortise. CONCLUSIONS: Separation of distal tibiofibular syndesmosis can be treated with various reasonable operations. Repair with tendon of the peroneus longus can get excellent outcomes for complete separation of the distal tibiofibular syndesmosis.

Surgical treatment of scoliosis caused by neurofibromatosis type 1.

OBJECTIVE: To retrospectively analyze the relationship between curve types and clinical results in surgical treatment of scoliosis in patients with neurofibromatosis type 1 (NF-1). METHODS: Forty-five patients with scoliosis resulting from NF-1 were treated surgically from 1984 to 2002. Mean age at operation was 14.2 years. There were 6 nondystrophic curves and 39 dystrophic curves depended on their radiographic features. According to their apical vertebrae location, the dystrophic curves were divided into three subgroups: thoracic curve (apical vertebra at T8 or above), thoracolumbar curve (apical vertebra below T8 and above L1), and lumber curve (apical vertebra at L1 and below). Posterior spine fusion, combined anterior and posterior spine fusion were administrated based on the type and location of the curves. Mean follow-up was 6.8 years. Clinical and radiological manifestations were investigated and results were assessed. RESULTS: Three patients with muscle weakness of low extremities recovered entirely. Two patients with dystrophic lumbar curve maintained their low back pain the same as preoperatively. The mean coronal and sagittal Cobb's angle in nondystrophic curves was 80.3 degrees and 61.7 degrees before operation, 30.7 degrees and 36.9 degrees after operation, and 32.9 degrees and 42.1 degrees at follow-up, respectively. In dystrophic thoracic curves, preoperative Cobb's angle in coronal and sagittal plane was 96.5 degrees and 79.8 degrees, postoperative 49.3 degrees and 41.7 degrees, follow-up 54.1 degrees and 45.3 degres, respectively. In thoracolumbar curves, preoperative Cobb's angle in coronal and sagittal plane was 75.0 degrees and 47.5 degrees, postoperative 31.2 degrees and 22.8 degrees, follow-up 37.5 degrees and 27.8 degrees, respectively. In lumbar curves preoperative Cobb's angle in coronal plane was 55.3 degrees, postoperative 19.3 degrees, and follow-up 32.1 degrees. Six patients with dystrophic curves had his or her curve deteriorated more than 10 degrees at follow-up. Three of them were in the thoracic subgroup and their kyphosis was larger than 95 degrees, and three in lumbar subgroup. Hardware failure occurred in 3 cases. Six patients had 7 revision procedures totally. CONCLUSIONS: Posterior spinal fusion is effective for most dystrophic thoracic curves in patients whose kyphosis is less than 95 degrees. Combined anterior and posterior spinal fusion is stronger recommended for patients whose kyphosis is larger than 95 degrees and those whose apical vertebra is located below T8. Patients should be informed that repeated spine fusion might be necessary even after combined anterior and posterior spine fusion.

[Biomechanical evaluation of stiffness of long-segment instrumented spine].

OBJECTIVE: To test the changes of the stiffness of the intact, released, and instrumented spines in an in vitro porcine model. METHODS: Twelve porcine spines (12 segments each) were harvested for the biomechanical tests with Material Test System. Stiffness during flexion, extension, lateral bending, and axial rotation were recorded; then the specimen was released with intervertebral discs and the facet joints removed, followed by repeating the biomechanical tests for stiffness; and finally, a double-rod titanium construct was applied for internal fixation to each released spine and stiffness tests were repeated again. RESULTS: Compared with the intact porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 52.89 +/- 15.98, 105.43 +/- 56.38, 42.09 +/- 14.73, and (16.94 +/- 4.85) N x mm/degrees, respectively], the stiffness of the released porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 44.04 +/- 13.73, 41.46 +/- 10.80, 31.75 +/- 7.23, and (9.10 +/- 2.07)N x mm/degrees, respectively] significantly decreased (P < 0.05), while significantly increased stiffness was found in the instrumented porcine spines [stiffness during flexion, extension, lateral bending, and axial rotation was 385.96 +/- 143.25, 138.96 +/- 59.41, 152.56 +/- 87.15, and (55.91 +/- 16.49) N x mm/degrees, respectively] (P < 0.05). CONCLUSION: Higher instant stiffness was found in instrumented spine than the intact one during flexion, extension, lateral bending and axial rotation.

Anterior spinal fusion with TSRH instrumentation for scoliosis.

OBJECTIVE: To introduce a new spinal internal fixation system, Texas Scottish Rite Hospital (TSRH), and to investigate its early clinical outcomes. METHODS: The preliminary clinical outcomes of 15 patients with thoracolumbar or lumbar scoliosis treated by anterior spinal fusion with TSRH instrumentation were studied retrospectively. Fourteen patients were diagnosed as idiopathic scoliosis and 1 as neuromuscular scoliosis. RESULTS: Preoperatively, the Cobb's angle on the coronal plane was 55.8 degrees (range 35 degrees to approximately 78 degrees), and 14 degrees postoperatively, with an average correction of 74.8%. The average unfused thoracical curve was 35.9 degrees preoperatively (range 26 degrees to approximately 51 degrees) and 21.8 degrees (10 degrees to approximately 42 degrees) postoperatively, with 40% correction. The sagittal curve of lumbar was kept physiologically, preoperative 27.9 degrees and postoperative 25.7 degrees respectively. The trunk shift was 13.4 mm (5 to approximately 28 mm) preoperatively and 3.5 mm (0 to approximately 7 mm) postoperatively. The averaged apic vertebra derivation was 47.8 mm (21 to approximately 69 mm) before operation and 10.8 mm (3 to approximately 20 mm) after operation. The distance of C7 to center sacrum vertical line (CSVL) was 19.5 mm (16 to approximately 42) preoperatively and 11.3 mm (0 to approximately 32 mm) postoperatively. The apical vertebra rotation was 3 degree in 15 patients preoperatively, and were improved to normal in 10 patients, 1 degree in 4 patients, and 2 degree in 1 patients postoperatively. None had neurological injury and infection. Only 1 patient complained a cool feeling in the low extremity of concave side, and the symptom vanished at 3-month followed up. CONCLUSION: If used appropriately, TSRH anterior spinal system is a good teatment for low thoracic or thoracic lumbar scoliosis.

[Surgical treatment of spinal myeloma, report of 19 cases].

OBJECTIVES: To discuss the indications for surgical procedures of spinal myeloma. METHODS: A retrospective analysis was made of the data of operation results of Nineteen patients with spinal myeloma, 13 males and 6 females, with the mean age of 45.1 (range 31 approximately 52). Pain was present in all patients. Nine patients had neurological deficit. According to Frankel classification 5 cases were Frankel B, 3 cases were Frenkel C, and 1 case was Frenkel D. Fourteen cases were diagnosed before operation, and 5 cases were diagnosed by pathology after operation. Surgical procedures performed included anterior approach in 11 cases, posterior approach in 7 cases and combined approach in 1 case. RESULTS: Decrease of pain was observed in all cases after surgery. Neurological improvement was observed in 8 out of the 9 cases. Complication (alteration of intestinal flora) occurred in one case. Follow-up lasted more than 1 year except in one case with a follow-up of only 6 months. Four cases were lost of follow-up. One case was still alive during the follow-up 8 years after operation. Other cases survived for 26.5 months on average (range 16 approximately 48 months). CONCLUSION: Surgery can ensure neurological improvement and spinal stability for patients with spinal myeloma, but should be associated with adjunctive medical treatment.

[Treatment of infected total knee arthroplasty].

OBJECTIVE: To investigate the treatment of infected total knee arthroplasty (TKA). METHODS: Between 1983 and 2000, 6 patients with infection after TKAs were treated, including 2 men and 4 women, aged on average 63 years (44 - 75 years). Initial knee arthroplasty was performed for osteoarthritis in 4 patients and for rheumatoid arthritis in 2 knees. The timing of diagnosis of infection after knee arthroplasty averaged 50 months (range, 1 month-11 years). Simple debridement and antibiotic treatment were prescribed for 3 patients, debridement and one-stage reimplantation for 1, debridement and two-stage reimplantation for 1, and athrodesis for 1. RESULTS: Of the 3 patients with simple debridement, one was cured, one failed but underwent athrodesis later, and one lost to follow up. Two patients with reimplantation were cured and had good function recovery. All of the 6 patients were followed up on average for 4 years. No infection recurred except one who lost to follow-up. CONCLUSIONS: Management of infection after total knee arthroplasty includes antibiotic suppression and debridement with prosthesis retention, insertion of another prosthesis as a one-stage or two-stage exchange technique, knee arthrodesis and amputation. These treatments have specific indications. To treat infection after total knee arthroplasty, suitable method should be taken according to patient's condition. Arthrodesis is the best salvage operation, though it may handicap patients' daily life. Reimplantation of another prosthesis could maintain a functional joint.

[Patellofemoral replacement for severe patellofemoral osteoarthritis: a 2-10 years follow-up study].

OBJECTIVE: To evaluate the therapeutic effects of patellofemoral replacement for severe patellofemoral osteoarthritis. METHODS: Patellofemoral replacement was performed in 30 patients (36 knee joints) with severe patellofemoral osteoarthritis, among whom were 5 males and 25 females. The patients ranged in age from 36 to 74 years old (mean +/- s, 55.8 +/- 8.5) and were followed up for 2-10 years. RESULTS: Significant improvement was made in both the knee score and functional score after the patellofemoral replacement. The effective rate was 88.9% and 91.7% evaluated with knee score and functional score respectively. CONCLUSION: Patellofemoral replacement is effective in treating severe patellofemoral osteoarthritis in appropriate cases.

[Surgical treatment of spine metastatic tumor].

OBJECTIVE: To explore the value of surgical treatment on spine metastatic tumor. METHODS: 31 cases of spine metastatic tumor with severe pain or/and neurological deficit were selected and treated with various operative methods. RESULTS: Except for 4 cases, all the patients survived from 3 months to 7 years (average 17.6 months). The patients had no complication during treatment. The symptoms and neurological functions recovered with various extent after operation. CONCLUSIONS: Surgical treatment should cautiously be adopted. When the spine metastatic tumor with severe pain and neurological deficit has no response to the conservative methods, the surgical treatment with decompression and internal fixation should be performed to improve the life quality for the patients.

Clinical application of the TRAFIX instrumentation in correcting scoliosis.

OBJECTIVE: To evaluate the results of the TRAFIX instrumentation in correcting scoliosis. METHODS: Since October 1997, 47 patients with scoliosis received spinal fixation with the TRAFIX instrumentation at the Peking Union Medical College Hospital. The average age was 14. 3 years (range 10 to 38 years). There were 27 idiopathic cases, 16 congenital cases, 2 cases with Marfan syndrome and 2 with neurofibromatosis. Twelve of the 47 patients underwent anterior release, while 4 patients received the revision approach. The average follow-up time was 26 months (13 -38 months). RESULTS: The measurements of primary coronal deformity before and after surgery were 74 degrees (50 degrees approximately 115 degrees) and 38.7 degrees (11 approximately 95 degrees), respectively. The average curve correction was 54%. The average number of fused segments was 12.5 (7 approximately 17) vertebrae. The distance between the center of apex and the C7 plumb line was 56.8 mm before surgery (25 approximately 107 mm) and 31 mm after surgery (10 approximately 87 mm). CONCLUSION: The TRAFIX instrumentation provides three-dimensional correction with refinement, convenience and reliable fixation.

Surgical treatment of metastatic spinal tumor.

OBJECTIVES: To evaluate the effect of surgical treatment on metastatic spinal tumor. METHODS: The results of surgical intervention for metastatic spinal tumor of 31 consecutive patients since October 1985 were reviewed. RESULTS: The average survival time was 17.6 months (range from 3 months to 9 years), and 4 patients are still alive with an average survival time of 24.6 months (range, 14 to approximately 84 months). No postoperative complication was noted. The preoperative symptoms were partially relieved and neurological functions were improved after surgery. CONCLUSION: Surgical treatment for metastatic spinal tumor could improve the life quality, but should be adopted cautiously. The surgical procedures such as decompression and internal fixation should be involved only when neurological deficits occurred. The surgery with postoperative complementary therapy may not only improve the life quality, but also extend the patients' life span.

[Complications associated with the technique of pedicle screw fixation].

OBJECTIVE: To analyze the causes of the complications associated with the pedicle screw fixation during and after operation, as well as the methods for prevention and treatment. METHODS: From January 1988 to December 1999, 475 patients who underwent pedicle screw fixation for various spinal disorders were reviewed retrospectively with statistical analysis. RESULTS: Four hundred and twenty-eight patients (90.1% of all) were followed up for (6.0 +/- 3.7) years. Complications of CD, DRFS, Dick, RF and steffee among 72 cases (80% of all) occurred during the operation of pedical screw fixation in 26 cases with the incidence of 5.5% and after the operation in 64 cases with the incidence of 15%. The incidence of operative/postoperative complications were 0-12.9% in CD, 6.8%-11.9% in DRFS, 7.3%-12.7% in Dick, 2.4%-19.5% in RF, and 10.1%-21.5% in Steffee respectively. The main complications included pseudoarthrosis, pedicle screw broken, pedicle screw malposition and so on. The complications were mainly due to unskilled technique of pedicle screw fixation, implant defect in design and so on. CONCLUSIONS: The complications associated with the technique of pedicle screw fixation must not be neglected. The main causes are laid on unskilled technique of pedicle screw fixation and implant defect in design.