Three-dimensional finite element analysis with different internal fixation methods through the anterior approach

BACKGROUND With the modernization of society and transportation in the last decades in China,the incidence of high-energy trauma increased sharply in China,including that of acetabular fractures.AIM To establish different finite element models for acetabular posterior column fractures involving the quadrilateral area of the acetabulum.METHODS The three-dimensional models of the normal and fractured pelvis and the five internal fixations were established using the computed tomography data of the pelvis of a living volunteer.After the vertebral body model was inserted in the way of origin matching and all cancellous bones were copied using the duplicated cancellous bone model as the subtractive entity,the Boolean operation was performed on the pelvis model to obtain the model of the complete pelvis cortical and cancellous bones.RESULTS In the standing position,the maximum stress was 46.21 MPa.In the sitting position,the sacrum bore the simulated gravity load at the upper end.When comparing the five fixations,there were no significant differences in the stress mean values among groups(sitting:P=0.9794;standing:P=0.9741).In terms of displacement,the average displacement of the internal iliac plate group was smaller than that of the spring plate group(P=0.002),and no differences were observed between the other pairs of groups(all P>0.05).In the standing position,there were no significant differences in the mean value of displacement among the groups(P=0.2985).It can be seen from the stress nephogram of the internal fixations in different positions that the stress of the internal fixation was mainly concentrated in the fracture segment.CONCLUSION There were no significant differences among the fixations for acetabular posterior column fractures involving the quadrilateral area of the acetabulum.

Laparoscopic-extracorporeal surgery performed with a fixation device for adnexal masses complicating pregnancy: Report of two cases

The potential complications associated with an adnexal mass discovered during early pregnancy call for surgical treatment. Ideally, surgery is performed after gestational week 12, but uterine expansion after the first trimester makes surgery difficult. We report two pregnancies complicated by adnexal masses for which we used an organ fixation device for safe performance of single-site umbilical laparoscopic surgery. Pelvic magnetic resonance imaging depicted a dichorionic, diamniotic twin pregnancy and 60-mm right adnexal mass in the first patient and bilateral adnexae in the second. All three masses were suspected mature cystic teratomas. Both patients underwent laparoscopic surgery during gestational week 14. With use of an organ fixation device, traction was applied until the mass reached the umbilicus; tumor resection was performed extracorporeally. In the second patient, the second mass was simply aspirated because adhesions were encountered. Our single-site laparoscopicextracorporeal technique proved to be a safe approach to an otherwise high-risk situation.

Development of L-Type Fixation Equipment for Transporting Unit Modules

The unit modular technique is one in which unit modules are prefabricated in a factory and then constructed at a construction site. That is why an important process, transport of unit module, is added in this technique. However, it is not easy to transport a unit module that is high prefabrication ratio （prefab. ratio） （70-90%）, since the walls and interior and exterior materials installed in it can become broken when the unit module is fixed using general fixation tools, including ropes and fixing belts. When the external wall, windows, etc. are damaged during the transportation, the efficiency of unit modular method is deteriorated. Taking this into account, the purpose of this study is to develop an improved fixation device that is convenient for fixing a unit module with a high prefab, ratio to a vehicle and securing the safety while running. The L-type adapter block proposed in this study was evaluated the structural safety through simulation method. The result of the simulation is that it seems desirable to set the working load of the L-type adapter block as 15 kN for Case 1 and 30 kN for Case 2. Therefore, when the L-type adapter block is utilized under the conditions in which the same load is applied as in Case 2, it is expected that safety will be improved.

Current concepts in the surgical treatment of skeletal metastases

Symptomatic metastatic bone disease affects a large proportion of patients with malignant tumours and significantly impairs patients’quality of life.There are still controversies regarding both surgical indications and methods,mainly because of the relatively few high-quality studies in this field.Generally,prosthetic reconstruction has been shown to result in fewer implant failures and should be preferred in patients with a good prognosis.Survival estimation tools should be used as part of preoperative planning.Adjuvant treatment,which relies on radiotherapy and inhibition of osteoclast function may also offer symptomatic relief and prevent implant failure.In this review we discuss the epidemiology,indications for surgery,preoperative planning,surgical techniques and adjuvant treatment of metastatic bone disease.

The design of a cervical vertebra titanium plate-interbody fusion cage

Objective： To study the biomechanical feature of a newly designed cervical vertebra internal fixation device and its clinical applications. Methods： Some functional spinal units were fixed respectively with titanium plate, fusion cage and new device designed by ourselves, then a controlled biomechanical study including flexion, extension, torsion and lateral bending was performed and the results were analyzed. Results： As to the mechanical performance, fusion cage showed poor performance in extension test and so did the titanium plate in the distortion test. However, the new device showed good performance in every test. Conclusion： Both simple titanium plate fixation and simple fusion cage fixation have biomechanical defaults, but they are complementary. The titanium plate-interbody fusion cage avoids the defaults and has specific advantages.

Selection of approach and fixation in the treatment of type C fracture of distal humerus in adults

Objective：To study the surgical treatment for distal humeral fractures in adults according to the follow-up results.Methods： Twenty-one cases （16 males and 5 females）of distal humeral fracture were included in this study. The average age was 42.5 years （range： 37-52 years）. Fractures were classified according to the AO classification system.Nine cases of C1,8 C2 and 4 C3-type fractures were identified.Open reduction and internal fixation were performed in all cases. A tricep-reflecting approach was adopted, and either the AO orthogonal plating or parallel plating technique was chosen,based on the fracture type. The plaster cast was removed 3 weeks after operation. Rehabilitation was encouraged during this period and afterwards. The average follow-up time was 12.2 months （range： 8-28 months）. The outcome was scored according to Aitken and Rorabeek system.Results：No nerve injury,nonunion or failure of fixation was encountered during the operation and follow-up.However, ossifying myosifis occurred in one case.Conclusions：A triceps-reflecting approach can provide adequate exposure to the joint. The use of AO orthogohal plating or parallel plating techniques based on the type of fractures can provide rigid fixation for the fracture.

Role of locking plates in treatment of difficult ununited fractures： a clinical study

Objective： To present our experience in treatment of difficult ununited long bone fractures with locking plate. Methods： Retrospective evaluation of locking plate fixation in 10 difficult nonunions of long bone fractures was done. Fixation was done with locking plate for femoral shaft fracture （3 patients）, supracondylar fracture of femur （gap nonunion）, fracture of clavicle, fracture of both forearm bones （radius and ulna） fracture of ulna, fracture of shaft of humerus, fracture of tibial diaphysis and supracondylar frac- ture of humerus （one patient each）. Five fractures had more than one previous failed internal fixation. One patient had infected nonunion which was managed by debridement with cast immobilization followed by fixation with locking plate at six weeks. Seven fractures were atrophic, two were oligotrophic, and one was hypertrophic. Fibular autograft was used in 2 cases and iliac crest cancellous bone graft used in all the patients. Results： Minimum follow-up was 6 months （range, 6 months to 2.5 years）. Average time for union was 3.4 months （range 2.5 to 6 months）. None of the patients had plate- related complications or postoperative wound infections. Conclusion： Along with achieving stability with locking compression plate, meticulous soft tissue dissection, acceptable reduction, good fixation technique and bone grafting can help achieve union in difficult nonunion cases. Though locking plate does not by itself ensure bony union, we have found it to be another useful addition to our armamentarium for treating difficult fracture nonunions.

Multi-slice spiral CT 3-dimensional reconstruction tech-nique to treat multi-segmental degenerative spinal steno-sis with traumatic instability of lower cervical spine

Objective: To study the feasibility of multi-slice spiral computed tomography (MSCT) 3-dimensional reconstruc-tion technique in assisting cervical pedicle screw fixation (PSF) and double-door laminoplasty to treat multi-segmen-tal degenerative spinal stenosis with traumatic instability (MDSTI) of lower cervical spine.Methods: From September 2006 to August 2007, PSF combined with double-door laminoplasty was performed in 9 patients with MDSTI of lower cervical spine. MSCT 3-dimensional reconstruction techniques, including volume rendering (VR) and multi-planar reconstruction (MPR), were used to assist preoperative diagnosis and measurement to guide the procedure. MPR was performed after operation. In coronal view, the degree of screw perforation was mea-sured precisely and the different positions of pedicle screws were divided into three grades according to Richter's method. In axial view, the canal sagittal diameter and trans-verse area of every laminoplasty level were measured.Results: Nine patients with MDSTI of lower cervical spine underwent PSF (total 44 screws). According to the classification of Richter, 72.7% (32/44) was in Grade 1 and 27.3% (12/44) was in Grade 2. No screw perforation occurred in Grade 3 and no screw revision was done for misplacement.No iatrogenic damage was observed. Double-door laminoplasty was performed in total 42 volumes. The post-operative sagittal diameter and transverse area of cervical spinal canal were significantly increased (P<0.05). The confi-dence intervals of mean increased ratio were 23.43%-40.65% in sagittal diameter and 23.18%-42.07% in transverse area. Six months after laminoplasty, based on MSCT axial view, complete union between "open door" and allograft bone was obtained in 76.19% of volumes (32/42), and allograft bone was absorbed partly in 23.81% (10/42). A solid union in bilateral gutters was achieved in all cases. They were followed up from 6 months to 1 year (mean 7.8 months). Post-operative neural function recovery in two cases improved 2 ASIA grade, 5 cases improved 1 grade and 2 cases remained the same as preoperative grade. No cases had lower ASIA grade.Conclusion: Assisted with MSCT 3-dimensional re-construction technique, PSF combined with double-door laminoplasty can be performed more safely and effectively to treat patients with MDSTI of lower cervical spine.

Mechanical tests on the reconstructed anterior cruciate ligament fixed with allogenetic cortical bone cross-pin on the femoral side

Background Anterior cruciate ligament reconstruction （ACLR） has developed dramatically in the last century.Now,ACLR has become a reliable and productive procedure.Patients feel satisfied in 〉90% cases.The aim of this study was to evaluate the feasibility of allogenetic cortical bone cross-pin （ACBCP） used as a clinical fixation method in anterior cruciate ligament reconstruction on the femoral side based on biomechanical tests in vitro.Methods The specimens were provided by the bone banks of the First Affiliated Hospital of People＇s Liberation Army of General Hospital from September 2011 to June 2012.Fresh deep frozen human allogenetic cortical bone was machined into cross-pins which is 4.0 mm in diameter and 75.0 mm in length.Biomechanical parameters compared with Rigidfix were collected while cross-pins were tested in double-shear test.The load-to-failure test and cycling test were carried out in a goat model to reconstruct anterior cruciate ligament with Achilles tendon autograft on the femoral side fixed by human 4.0 mm ACBCP and 3.3 mm Rigidfix served as control.Maximum failure load,yield load,and stiffness of fixation in single load-to-failure test were compared between the two groups.Cycle-specific stiffness and displacement at cycles 1,30,200,400,and 1 000 were also compared in between.Results In double-shear test both maximum failed load and yield load of 4.0 mm humanACBCP were （1 236.998±201.940） N.Maximum failed load and yield load of Rigidfix were （807.929±110.511） N and （592.483±58.821） N.The differences of maximum failed load and yield load were significant between ACBCP and Rigidfix,P 〈0.05.The shear strength of ACBCP and Rigidfix were （49.243±8.039） MPa and （34.637±3.439） MPa,respectively,P 〈0.05.In the load-to-failure test ex vivo,yield load and maximum failed load of ACBCP fixation complexity （（867.104±132.856）N,（1 032.243±196.281） N） were higher than those of Rigidfix （（640.935±42.836） N,（800.568±64.890） N,P 〈0.05）.However,stiffness did not differ significantly between ACBCP group （（247.116±31.897）N/mm） and Rigidfix group （（220.413±51.332） N/mm,P 〉0.05）.In the cycling test,the cycle-specific stiffness and displacement at cycles 1,30,200,400,and 1 000 did not differ significantly between the ACBCP group and Rigidfix group,P 〉0.05.Conclusions Allogenetic cortical bone cross-pin possesses satisfactory biomechanical profile which is safe for ACLR and suitable for an aggressive rehabilitation program.Animal and clinical tests should be recommended before clinical use to secure the ACBCP could successfully substituted by host new bone in vivo.

Biocompatibility and degradation comparisons of four biodegradable copolymeric osteosynthesis systems used in maxillofacial surgery: A goat model with four years follow-up

pplying biodegradable osteosyntheses avoids the disadvantages of titanium osteosyntheses. However, foreign-body reactions remain a major concern and evidence of complete resorption is lacking. This study compared the physico-chemical properties, histological response and radiographs of four copolymeric biodegradable osteo-synthesis systems in a goat model with 48-months follow-up. The systems were implanted subperiosteally in both tibia and radius of 12 Dutch White goats. The BioSorb FX [poly(70LLA-co-30DLLA)], Inion CPS [poly([70–78.5] LLA-co-[16–24]DLLA-co-4TMC)], SonicWeld Rx [poly(DLLA)], LactoSorb [poly(82LLA-co-18GA)] systems and a negative control were randomly implanted in each extremity. Samples were assessed at 6-, 12-, 18-, 24-, 36-, and 48-month follow-up. Surface topography was performed using scanning electron microscopy (SEM). Differential scanning calorimetry and gel permeation chromatography were performed on initial and explanted samples. Histological sections were systematically assessed by two blinded researchers using (polarized) light microscopy, SEM and energy-dispersive X-ray analysis. The SonicWeld Rx system was amorphous while the others were semi-crystalline. Foreign-body reactions were not observed during the complete follow-up. The SonicWeld Rx and LactoSorb systems reached bone percentages of negative controls after 18 months while the BioSorb Fx and Inion CPS systems reached these levels after 36 months. The SonicWeld Rx system showed the most predictable degradation profile. All the biodegradable systems were safe to use and well-tolerated (i.e., complete implant replacement by bone, no clinical or histological foreign body reactions, no [sterile] abscess formation, no re-interventions needed), but nanoscale residual polymeric fragments were observed at every system’s assessment.

Cohesion mechanisms for bioadhesives

Due to the nature of non-invasive wound closure,the ability to close different forms of leaks,and the potential to immobilize various devices,bioadhesives are altering clinical practices.As one of the vital factors,bioadhesives’strength is determined by adhesion and cohesion mechanisms.As well as being essential for adhesion strength,the cohesion mechanism also influences their bulk functions and the way the adhesives can be applied.Although there are many published reports on various adhesion mechanisms,cohesion mechanisms have rarely been addressed.In this review,we have summarized the most used cohesion mechanisms.Furthermore,the relationship of cohesion strategies and adhesion strategies has been discussed,including employing the same functional groups harnessed for adhesion,using combinational approaches,and exploiting different strategies for cohesion mechanism.By providing a comprehensive insight into cohesion strategies,the paper has been integrated to offer a roadmap to facilitate the commercialization of bioadhesives.

In vivo biocompatibility and degradability of a Zn-Mg-Fe alloy osteosynthesis system

Zinc is generally considered to be one of the most promising materials to be used in biodegradable implants,and many zinc alloys have been optimized to improve implant biocompatibility,degradation,and mechanical properties.However,long-term degradation leads to the prolonged presence of degradation products,which risks foreign body reactions.Herein,we investigated the in vivo biocompatibility and degradation of a biodegradable Zn-Mg-Fe alloy osteosynthesis system in the frontal bone,mandible,and femur in beagles for 1 year.Results of the routine blood,biochemical,trace element,and histological analyses of multiple organs,peripheral blood CD4/CD8a levels,and serum interleukin 2 and 4 levels showed good biocompatibility of the Zn-Mg-Fe alloy.Zinc content analysis revealed zinc accumulation in adjacent bone tissue,but not in the liver,kidney,and spleen,which was related to the degradation of the Zn-Mg-Fe alloy.The alloy demonstrated a uniform slowing degradation rate in vivo.No degradation differences in the frontal bone,mandible,and femur were observed.The degradation products included zinc oxide[ZnO],zinc hydroxide[Zn(OH)_(2)],hydrozincite[Zn_(5)(OH)_(6)(CO_(3))_(2)],and hopeite[Zn_(3)(PO_(4))_(2)⋅4H_(2)O].The good biocompatibility and degradation properties of the Zn-Mg-Fe alloy render it a very attractive osteosynthesis system for clinical applications.