Strong, tough, and elastic poly(vinyl alcohol)/polyacrylamide DN hydrogels based on the Hofmeister effect for articular cartilage replacement.

Traditional hydrogels are usually weak and brittle, which limit their application in articular cartilage replacement because cartilage is generally strong, tough, and elastic in nature. Therefore, it is highly desirable to construct hydrogels to mimic the mechanical properties of the native articular cartilage. Herein, in this work, poly(vinyl alcohol)/polyacrylamide (PVA/PAM) DN hydrogels were prepared by in situ polymerization, which were then treated with Hofmeister series ions (Cit3-, SO42-, and Cl-) to achieve H-PVA/PAM DN hydrogels. Among the three Hofmeister ions, the DN hydrogel treated with Cit3- (named PVA/PAM-Cit) showed the densest microstructure and the highest crystallinity degree. In this context, PVA/PAM-Cit exhibited a tensile strength of 18.9 ± 1.6 MPa, a compressive strength of 102.3 ± 7.9 MPa, a tensile modulus of 10.6 ± 2.1 MPa, a compressive modulus of 8.9 ± 0.8 MPa, and a roughness of 66.2 ± 4.2 MJ m-3, respectively, which were the highest strength and modulus, and the second highest toughness when compared with those of the reported PVA and PVA based DN hydrogels so far. It also showed an extreme high elasticity, which could maintain a stress of 99.2% after 500 cycles of fatigue testing. Additionally, PVA/PAM-Cit can promote the adhesion, spreading and proliferation of chondrocytes. These results verify that such a strong, tough, and elastic hydrogel could be a novel candidate material for articular cartilage replacement.

[Clinical and radiographic outcomes of navigation-assisted versus conventional total knee arthroplasty].

OBJECTIVE: To assess the early postoperative clinical and radiographic outcomes after navigation-assisted or standard instrumentation total knee arthroplasty (TKA). METHODS: From August 2007 to May 2008, 60 KSS-A type patients underwent 67 primary TKA operations by the same surgical team. Twenty-two operations were performed with the Image-free navigation system with an average age of 64.5 years while the remaining 45 underwent conventional manual procedures with an average age of 66 years. Their preoperative demographic and functional data had no statistical differences (P>0.05). The operative duration, blood loss volume and hospitalization days were compared for two groups. And radiographic data included coronal femoral component angle, coronal tibial component angle, sagittal femoral component angle, sagittal tibial component angle and coronal tibiofemoral angle after one month. And functional assessment scores were evaluated at 1, 3 and 6 months postoperatively. RESULTS: Operative duration was significantly longer for computer navigation (P<0.05). The average blood loss volume was 555.26 ml in computer navigation group and 647.56 ml in conventional manual method group (P<0.05). And hospitalization stay was shorter in computer navigation group than that in conventional method group (7.74 vs 8.68 days) (P=0.04). The alignment deviation was better in computer-assisted group than that in conventional manual method group (P<0.05). The percentage of patients with a coronal tibiofemoral angle within ±3 of ideal value was 95.45% for computer-assisted mini-invasive TKA group and 80% for conventional TKA group (P=0.003). The Knee Society Clinical Rating Score was higher in computer-assisted group than that in conventional manual method group at 1 and 3 montha post-operation. However, no statistical inter-group difference existed at 6 months post-operation. CONCLUSION: Navigation allows a surgeon to precisely implant the components for TKA. And it offers faster functional recovery and shorter hospitalization stay. At 6 months post-operation, there is no statistical inter-group difference in KSS scores.

Mechanical properties and cytotoxicity of nanoplate-like hydroxyapatite/polylactide nanocomposites prepared by intercalation technique.

Hydroxyapatite (HAp) in the forms of fiber, needle, and whisker has been employed as fillers in polymer composites. Herein, nanoplate-like HAp synthesized by template-assisted self-assembly was used to reinforce polylactide (PLA) nanocomposites via the solution intercalation method. Dynamic and static mechanical properties and cytotoxicity of the as-prepared HAp/PLA nanocomposites were assessed in addition to characterizations by XRD, FTIR, and TGA. XRD analysis confirms the formation of exfoliated structure in the HAp/PLA nanocomposites. The HAp/PLA nanocomposites exhibit better static and dynamic mechanical properties than unreinforced PLA. Furthermore, the HAp/PLA nanocomposite with an optimum HAp content of 20wt% (20HAp/PLA) demonstrates not only the best mechanical performance but also the highest thermal stability among the nanocomposite samples. Cell studies using a mouse fibroblast cell line (L929) suggest that 20HAp/PLA shows excellent biocompatibility, which makes it a promising material for biomedical applications.

[Causes and managements of acetabular fracture during primary total hip arthroplasty].

OBJECTIVE: To investigate the causes and managements of acetabular fracture during primary total hip arthroplasty (THA). METHODS: Between May 2005 and July 2008, 9 patients (9 hips) suffered from acetabular fractures during primary THA. There were 1 male and 8 females with an average age of 63.3 years (range, 41-73 years), including 4 cases of developmental dysplasia of the hip, 2 cases of rheumatoid arthritis, 1 case of old femoral neck fracture, 1 case of avascular necrosis of femoral head, and 1 case of ankylosing spondylitis. Three left hips and 6 right hips were involved. The preoperative Harris score was 40.4 +/- 2.9. All the patients underwent cementless THA. Among nine acetabular fractures, 8 fractures were stable (2 anterior wall fractures and 6 posterior wall fractures), which were fixed by additional augmentation screws in 7 cases and accepted no special treatment in 1 case; 1 fracture was unstable (posterior wall fracture with posterior column incomplete fracture), which was treated by bone grafting and additional screws. RESULTS: The postoperative X-ray films showed that the position of the prosthesis were favorable. All incisions healed by first intention without early complication. Nine patients were followed up 1-4 years (mean, 2 years and 7 months). The Harris score was 87.8 +/- 3.9 at last follow-up, showing significant difference when compared with the preoperative score (t = 44.904, P = 0.000). The X-ray films showed fracture healing at 8 weeks. No loosening occurred. CONCLUSION: When primary THA is performed, the preoperative X-ray film should be studied and measured carefully, operation should be accurate and violence should be avoided. The diameter of the acetabular component should be equal to the diameter of a drill or not larger than 2 mm. In patients with severe osteoporosis, the diameter of the acetabular components should be the same diameter as a drill and additional screws are used to fix, or cemented cup is used. Once an acetabular fracture occurs during the primary THA, additional screw or bone grafting with additional screws should be chosen according to the fracture type and stability, and good clinical results can be expected.

[Management of femoral neck fracture post total knee arthroplasty].

OBJECTIVE: To investigate the risk factors, management and prognosis of femoral neck fracture post total knee arthroplasty (TKA). METHODS: From January 2003 to August 2009, 45 cases of femoral neck fracture post TKA were treated. There were 8 males and 37 females with an age range of 56 - 81 years old. Among them, there were ipsilateral (n = 36) and contralateral (n = 9) femoral neck fractures. Due to the fracture site and type, the treatment plans were formulated. And a follow-up was conducted to record the Harris hip score and complications. RESULTS: The incidence of femoral neck fracture following TKA and osteoporosis had a linear correlation. And the fracture rate increased with the aggravation of osteoporosis. The stability of ipsilateral fracture group was lower than those of contralateral fracture and no fracture groups. Except for 4 mortality cases, 41 patients were followed up for 2 to 7 years with an average period of 3.6 years. There were 12 patients in the cannulated screw fixation group. The outcomes were fracture healing (n = 5) and femoral head necrosis (n = 7). Twenty-five cases underwent femoral head replacement. And 3 died and second fracture occurred in 3 cases. Eight cases underwent total hip arthroplasty. And 1 died and there was 1 case of second fracture. The Harris scores of the cannulated screw fixation group was significantly lower than the hip replacement groups (q test, P < 0.05). COMPLICATIONS: After internal fixation, 7 cases suffered femoral head necrosis and underwent femoral head replacement. And secondary fractures after hip replacement occurred in 4 cases and they were treated by plate and cable or LISS (less invasive stabilization system) system. CONCLUSION: Femoral neck fracture following TKA is usually caused by a low-energy injury. Osteoporosis is one of its high-risk factors. Knee instability is associated with ipsilateral femoral neck fracture. Clinically it can be treated by internal fixation or hip arthroplasty. And internal fixation of femoral neck fracture frequently induces femoral head necrosis. And femoral head replacement is applicable.

[Secondary total hip arthroplasty for osteonecrosis of femoral head after failed internal fixation of femoral neck fracture].

OBJECTIVE: To compare the efficiency of secondary total hip arthroplasty (THA) for osteonecrosis of the femoral head (ONFH) after failed internal fixation of femoral neck fracture and the primary THA for non-traumatic ONFH and to evaluate if the two groups have significant difference. METHODS: From June 2004 to July 2007, 203 cases of ONFH were treated by THA. In group A, 83 patients (83 hips) with ONFH after failed internal fixation included 56 males (56 hips) and 27 females (27 hips) with an average age of 58.3 years (range 45-75 years). According to Ficat classification, there were 61 cases at stage III and 22 cases at stage IV. The Harris score was 37.6 +/- 2.0. The disease course was 1-6 years with an average of 2.6 years. In group B, 120 patients (167 hips) with non-traumatic ONFH included 67 males (94 hips) and 53 females (73 hips) with an average age of 52.6 years (range 41-67 years). According to Ficat classification, there were 56 cases (83 hips) at stage III and 64 cases (84 hips) at stage IV. The Harris score was 38.2 +/- 1.0. The disease course was 1.5-5.0 years with an average of 2.6 years. There were no significant differences in general data between two groups (P > 0.05). RESULTS: All 203 cases were followed up for 2 to 5 years (average 3.4 years). There were no significant differences in the operation time of single-hip, the blood loss, the blood transfusion between two groups (P > 0.05). Intraoperative fractures occurred in 4 hips (4.8%) of group A and 2 hips (1.2%) of group B, showing significant difference (P < 0.05). There were no significant differences (P > 0.05) in the incidence of dislocation [3 hips (3.6%) in group A and 1 hip (0.6%) in group B], continuous femoral pain [2 hips (2.4%) in group A and 1 hip (0.6%) in group B] and infection [1 hip (0.6%) in group B] between two groups. There were no significant differences (P > 0.05) in acetabular abduction, anteversion, femoral anteversion, and combined anteversion angles as well as the recovery rate of acetabular rotational center between two groups. The Harris scores of groups A and B after 2 years were 79.4 +/- 2.1 and 84.2 +/- 3.5. There was no significant difference between two groups (P > 0.05). The Harris score postoperation had significant differences compared with preoperation (P < 0.05). CONCLUSION: Compared to the primary THA to non-traumatic ONFH, secondary THA to ONFH after failed internal fixation has no significant increase in operative difficulty, the postoperative hip function is good, but the incidence of intraoperative fracture is higher.