Semi-rigid System Research Articles

Experimental Evaluation of the Developmental Mechanism Underlying Fractures at the Adjacent Segment

Compression fractures at adjacent mobile segments have been reported as adjacent segment disease under trauma in several studies. In this study, the occurrence of fractures at the adjacent segment was evaluated experimentally under trauma. Static testing of different fixation systems was performed to show their biomechanical performances. The ovine vertebrae fixed with rigid, dynamic, and semirigid systems were used as test samples. The stiffness values of the systems were obtained by testing the vertebrectomy models under compression bending, lateral bending, and torsion tests. In addition, their effects on the adjacent segments were experimentally evaluated within a drop mechanism. A free-fall drop mechanism was designed and manufactured. Next, 3.5-kg, 5-kg, and 7-kg weights were released from 1 m above the test samples to generate compression fractures. The occurrence of compression fractures was observed with the use of radiograph of test samples, which were obtained before and after the drop test. Dynamic and semirigid systems have advantages compared with rigid systems as the result of their lower stiffness values. Radiographs showed that epiphysis fractures occurred at fixed and adjacent mobile segments, which were fixed with semirigid fixation. In addition, dynamic fixation well preserved the fixed and adjacent mobile segments under trauma. The dynamic system with a polyetheretherketone rod can better preserve both adjacent and fixed segments. However, because of the cantilever beam effect, the semirigid system exhibits a great disadvantage.

Is Dynesys a Good Device for Motion Preservation and Prevention of Idiopathic Unstable after Decompression Surgery

Introduction The Dynesys dynamic stabilization system was first implanted in patients in 1994 in an attempt to overcome the drawbacks of fusion. It is supposed to preserve motion at the treat levels, while avoiding hypermobility and thus spondylosis at the adjacent levels. The aim of this retrospective study is to investigate the clinical outcome and the effect of preservation of ROM and developed instability after decompression surgery. Patients and Methods A total of 30 patients were treated with Dynesys between August 2008 to March 2014. The diagnosis included degenerative spinal stenosis, severe spinal stenosis with HIVD, huge intervertebral herniated disc, or recurrent HIVD. Back pain and leg pain were evaluated using visual analog scale (VAS). The Oswestry Disability Index (ODI) was used to evaluate the patient's function. The range of motion at the operative level and whole lumbar spine were measured on preoperative and postoperative radiographs. Results All the patients were followed up for 3 to 96 months (mean, 26.33 ± 25.3 months). Overall, 87 segments were applied in 30 patients. The mean age of the patients was 49.5 ± 10.4 years (range, 22–67 years). There were 19 male and 11 female patients, with slightly male predominant. VAS of leg pain, lower back pain, and the ODI were significantly improved postoperatively. There was a significant difference in the range of motion at the operative levels and the whole spine. The mean range of motion of whole spine was 28.89 ± 15.3 degrees preoperatively and 16.29 ± 8.39 degrees postoperatively, with 43.61% loss. The range of motion of operative levels were 12.01 ± 7.73 degrees preoperatively and 4.03 ± 3.19 degrees postoperatively, with 66.44% loss. There were four broken screws and no screws loosening were noted. No developed unstable conditions occurred and no cases need revision surgery in our study. Conclusion The preliminary results of Dynesys for lumbar degenerative stenosis with/without HIVD in our series are similar to the published results of the previous literature. It can significantly improve the clinic symptoms and signs. And the Dynesys device is a semirigid fixation system for the stabilization of lumbar degenerative disease. We think the role of Dynesys is a device to delay the nature decade of lumbar spine and prevent the possibility of idiopathic unstable after decompression surgery. So, the indication of the Dynesys should seriously restriction of the age. It should be used in the patients with no or mild unstable condition, and it is better in the younger patients. But the true effect should depend on longer follow-up.

Adjacent Intervertebral Disc Changes in Patients with Isobar Semirigid Dynamic Stabilization System

Introduction The reported incidence of adjacent segment degeneration (ASD) after lumbar fusion ranges from 8 to > 100%, average 27%. Another literature review reported that 5.2 to 18.5% of patients required surgery for adjacent segment disease after lumbar fusion surgery. Posterior dynamic stabilization systems may prevent the development and progression of ASD after surgery. Hybrid dynamic stabilization with posterior spinal fusion, or “Topping-off surgery,” is applied in patients with preoperative adjacent segment degeneration. The objective of this approach is to protect the degenerative adjacent segment from progressing. Efficacy of this procedure is debated. The objective of this study was to evaluate intervertebral disk changes of the dynamically stabilized spine segment in patients receiving single-level intervertebral fusion and adjacent segment dynamic stabilization using the Isobar (Alphatec Spine, Inc.) semirigid dynamic stabilization system. Materials and Methods Twenty-seven patients with confirmed degenerative disk disease were enrolled in a retrospective study. Patients received single level intervertebral fusion and dynamic stabilization of the adjacent level using the Isobar semi-rigid dynamic stabilization system. Patient outcomes were evaluated by visual analogue scale for pain (VAS) and Chinese version of Oswestry Disability Index (ODI). Intervertebral space ratio (IVS) and range of motion (ROM) were measured on plain radiographs. MRI relative gray-scale values of the central bright area of discs were analyzed by Image J software. Results Of the 27 patients, 16 were male and 11 were female. Ages ranged from 31 to 65 years (average 47 years). Average duration of surgery was 213 (SD = 52) minutes and average blood loss was 225 mL (SD = 105). The average follow-up time was 27 months, ranging from 24 to 40 months. There was no significant change in relative gray-scale value of adjacent disc between preoperative and two year follow-up (23.98 ± 8.86 and 22.22 ± 6.25, respectively, p = 0.46). Relative gray-scale values of first cephalic adjacent disc were reduced at 2 years follow-up compared with baseline (28.63 ± 8.35 and 32.54 ± 10.75, respectively, p = 0.06). Significant difference was found in relative gray-scale value of second cephalic adjacent disc between baseline and 2-year follow-up (35.51 ± 8.15 and 29.29 ± 7.56, respectively, p < 0.01). The inter-vertebral space (IVS) of index level was maintained after the surgery (Table 1). There was no statistical difference between the IVS before the surgery and final follow-up ( p = 0.33). The range of motion (ROM) of the adjacent level was reduced from 6.91 ± 3.14 preoperatively to 2.46 ± 1.03 degrees at the final follow-up ( p < 0.05). There were no significant differences in the index level ROM among any of the follow-up times. VAS and ODI scores significantly improved preoperatively to final follow-up (VAS: 6.12 ± 0.80 and 1.65 ± 0.69, respectively, p = < 0.01; ODI: 54.91 ± 10.96 and 14.61 ± 3.88, respectively, p = <0.01). One patient received a debridement due to wound infection after operation, but the fixation system and interbody cage were not removed. This patient recovered well after the debridement. At the 2-year follow-up, one patient had two screw fractures at S1 level and another patient had two screws loosen. Conclusion Dynamic stabilization of the level adjacent to the fused level using the Isobar TTL Semi-rigid Spinal System seems to prevent progression of degenerative changes in the stabilized spine segment and is associated with favorable patient outcomes. Disclosure of Interest Q. Zhou: Conflict with Third Military Medical University, AO International R. Shi: None declared B. Kopjar: Conflict with AO Foundation, Smith & Nephew, Cerapedics H. Wang: None declared D. Chen: None declared H. Li: None declared N. Di: None declared F. Luo: None declared F. Dai: None declared J. Xu: None declared

Two-year follow-up results of the Isobar TTL Semi-Rigid Rod System for the treatment of lumbar degenerative disease

We retrospectively assessed the indications, safety and efficacy of a new dynamic stabilization system (the Isobar TTL Semi-Rigid Rod System, Scient’x, Bretonneux, France) for the treatment of lumbar degenerative disease in 37 consecutive patients (M:F=16:21, mean age 40.2years) with lumbar degenerative disease who underwent surgery between June 2006 and May 2009. One patient was lost to follow-up. Clinical outcomes were evaluated using the Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS); range-of-motion (ROM) and disc height index (DHI) were assessed with radiography. Patients were followed for a mean of 24months (range: 12–36months). At the 3-month follow-up, there was significant improvement in VAS and ODI (p<0.05); at long-term follow-up VAS showed additional significant improvement (p<0.05) and ODI remained stable. At short-term follow-up, DHI was significantly restored (p<0.05) and ROM declined slightly (but not significantly); however, at long-term follow-up DHI was significantly reduced (p<0.05) compared to short-term follow-up and ROM was significantly decreased compared to the preoperative values (p<0.05). There were new signs of degeneration at adjacent levels in 14 patients (39%) on long-term follow-up MRI. Revision was required in three patients (8%) 24months after the first operation due to adjacent segment disease. Screw loosening was observed in four patients (11%). The Isobar System after microsurgical decompression for lumbar degenerative disease provided excellent improvement in leg and back pain and patient satisfaction at late follow-up; however, evidence to suggest that Isobar outperforms traditional fusion is lacking. Larger studies of longer duration are warranted.

Seismic Behaviour and Seismic Design of Single-Layer Reticulated Shells with Semi-Rigid Joint System

An investigation of the seismic behaviour and a design method for single-layer reticulated shells with semi-rigid joints is described in this paper. A semi-rigid joint system has some bending and rotational rigidity that lying between that of a rigid-joint and a pin-joint. The seismic capacity of Kiewit reticulated shells with bolt-ball joints is analyzed in detail on the basis of the bending rigidity of the bolt-ball joint reported by others. The change rules of natural frequency and seismic internal force coefficient are reviewed by analyzing of large-scale shells with different span, depth-to-span ratio, bending rigidity, roof load, section size of members and seismic wave parameters. The seismic internal force coefficient (under the influence of bending moment) for shells with a semi-rigid joint system is summarized statistically to provide the maximal seismic response envelop.

Assessment of Injury Rates Associated with Road Barrier Collision

This paper presents a study aimed at quantifying and comparing the risk of personal injuries associated with road barrier collisions. Documented data from actual barrier collisions, including post-impact collisions, in Sweden between 2005 and 2008 were analyzed. The analyses were based on the injury classification made by healthcare services. The injury rates, measured in number of injuries per vehicle kilometer travelled, were calculated for the different injury classes as a basis for evaluating barrier performance. The results show that the rate of injuries was higher due to collisions with flexible barrier systems, such as cable barrier, than with other semi-rigid and rigid barrier system, such as w-beam and concrete barriers. This result might be explained by a high rate of post-impact events, such as post-impact collisions, roll-overs and over-rides, associated with the placement and mechanical properties of the cable barriers. The study also showed a considerable difference in injury classifications made by the police and the healthcare services, as well as a considerable under-reporting of barrier collisions by the police.

Effects of nonlinearity in the materials used for the semi-rigid pedicle screw systems on biomechanical behaviors of the lumbar spine after surgery**This work was presented at the 8th China–Korea Symposium on Biomaterials and Nano-Bio Technology (Pyeongchang, Korea, Dec. 13–17 2010).

Recently, various types of semi-rigid pedicle screw fixation systems have been developed for the surgical treatment of the lumbar spine. They were introduced to address the adverse issues commonly found in traditional rigid spinal fusion-–abnormally large motion at the adjacent level and subsequent degeneration. The semi-rigid system uses more compliant materials (nitinol or polymers) and/or changes in rod design (coiled or twisted rods) as compared to the conventional rigid straight rods made of Ti alloys (E = 114 GPa, υ = 0.32). However, biomechanical studies on the semi-rigid pedicle screw systems were usually limited to linear modeling of the implant and anatomic elements, which may not be capable of reflecting realistic post-operative motions of the spine. In this study, we evaluated the effects of nonlinearity in materials used for semi-rigid pedicle screw fixation systems to evaluate the changes in biomechanical behaviors using finite element analysis. Changes in range of motion (ROM) and center of rotation (COR) were assessed at the operated and adjacent levels. Actual load–displacement results of the semi-rigid rod from mechanical test were carried out to reflect the nonlinearity of the implant. In addition, nonlinear material properties of various spinal ligaments studies were used for the finite element modeling. The post-operative models were constructed by modifying the previously validated intact model of the L1-S1 spine. Eight different post-operative models were made to address the effects of nonlinearity—with a traditional stiffness modulus rod (with linear ligaments, case 1; with nonlinear ligaments, case 5), with a rigid rod (with linear ligaments, case 2; with nonlinear ligaments, case 6), with a soft rod (with linear ligaments, case 3; with nonlinear ligaments, case 7), and with a nonlinear rod (with linear ligaments, case 4; with nonlinear ligaments, case 8). To simulate the load on the lumbar spine in a neutral posture, follower load (400 N) was applied and then the hybrid loading condition was applied to measure the ROM and COR in the sagittal plane. The more the nonlinearity was included in the model the closer the motion behavior of the device was to that of the intact spine. Furthermore, our results showed that the nonlinearity of the semi-rigid rod was a more sensitive factor than the nonlinearity of the spinal ligaments on biomechanical behavior of the lumbar spine after surgery. Therefore, for better understanding of the surgical effectiveness of the spinal device, more realistic material properties such as nonlinearity of the device and anatomic elements should be considered. In particular, the nonlinear properties of the semi-rigid rod were considered more than the nonlinearity of spinal ligaments.

A CASE REPORT OF GROWING SKELETAL CLASS II TREATED WITH FORSUS FATIGUE RESISTANCE APPLIANCE

Growing skeletal class II malocclusions with mandibular deficiency have been treated for more than a century with different types of functional appliances. Removable or fixed functional appliances are available to advance the mandible. Fixed functional appliances have the advantage of not requiring patient compliance. They can also be used concurrently with brackets. This case report documents the successful treatment of mild skeletal class II in late stages of puberty by using Forsus fatigue resistance appliance. The Forsus appliance is a three-piece, semi-rigid telescoping system incorporating a super-elastic nickel-titanium coil spring that can effectively brings the mandible forward in a relatively shorter treatment time. It is compatible with complete fixed orthodontic appliances and can be incorporated into preexisting appliances.

Nonlinear Finite Element Analysis of Beam String Structure

Beam string structure (BSS), which is a new kind of semi-rigid hybrid system, composed of arch, strut and string, has been developed rapidly in long-span steel structures in recent years. Based on the principle of virtual work and Updated Lagrange, the formulas of geometric nonlinear F.E.M. for spatial beam element, cable element and truss element are derived respectively in this paper. Taking the one-way BSS model of the steel roof in Guangzhou International Convention and Exhibition Center as a computational example by using both linear and nonlinear analysis method, the analytical results show that it is appropriate when adopting the straight truss element with two joints and equivalent elastic modulus to simulate the cable element with small sag. Although the linear analysis can meet the requirement of practical engineering due to its weak nonlinearity of BSS, the nonlinear method is also important to improve the precision theoretically. The conclusions obtained may be helpful for the designers in similar projects.

Finite Element Analysis of 2 Immediate Loading Systems in Edentulous Mandible: Rigid and Semirigid Splinting of Implants

The objective of this study was to evaluate the stress on the cortical bone around single body dental implants supporting mandibular complete fixed denture with rigid (Neopronto System-Neodent) or semirigid splinting system (Barra Distal System-Neodent). Stress levels on several system components were analyzed through finite element analysis. Focusing on stress concentration at cortical bone around single body dental implants supporting mandibular complete fixed dentures with rigid (Neopronto System-Neodent) or semirigid splinting system (Barra Distal System-Neodent), after axial and oblique occlusal loading simulation, applied in the last cantilever element. The results showed that semirigid implant splinting generated lower von Mises stress in the cortical bone under axial loading. Rigid implant splinting generated higher von Mises stress in the cortical bone under oblique loading. It was concluded that the use of a semirigid system for rehabilitation of edentulous mandibles by means of immediate implant-supported fixed complete denture is recommended, because it reduces stress concentration in the cortical bone. As a consequence, bone level is better preserved, and implant survival is improved. Nevertheless, for both situations the cortical bone integrity was protected, because the maximum stress level findings were lower than those pointed in the literature as being harmful. The maximum stress limit for cortical bone (167 MPa) represents the threshold between plastic and elastic state for a given material. Because any force is applied to an object, and there is no deformation, we can conclude that the elastic threshold was not surpassed, keeping its structural integrity. If the force is higher than the plastic threshold, the object will suffer permanent deformation. In cortical bone, this represents the beginning of bone resorption and/or remodeling processes, which, according to our simulated loading, would not occur.

STRUCTURAL PERFORMANCE OF IMPROVED SIMPLIFIED CONNECTION SYSTEM AT PRECAST CONCRETE PILE HEAD UNDER HIGH AXIAL LOAD

An improved semi-rigid connection system which is used to connect a pile head and a pile cap has been proposed by authors and it has proved to be effective to reduce bending moment of a pile head under general level of axial load. However, in recent years, high bearing capacity piles, which have more than twice capacity of general piles, have become widely used. To investigate performances of the proposed system under such a high axial load, full-scale structural tests are conducted. From the test results, it is revealed that the maximum bending moment at a pile head (Mmax) almost agrees with a maximum eccentric moment (Me) under low axial stress, but Mmax/Me decreases with axial stress increase. This paper proposes an experimental formula to evaluate Mmax using Me and axial stress ratio (σn/σB, σn : axial stress at a pile head, σB : concrete strength of a pile cap) under the condition that a pile cap isn't damaged with strength decrease, and an analytical method to judge the condition of its application.

Dynesys fixation for lumbar spine degeneration

The dynamic fixation system Dynesys is utilized in the last 10 years for treatment of degenerative segmental disease of the lumbar spine. Dynesys is a semi-rigid fixation system that allows minimal lengthening and shortening between two segmental pedicle screws as opposed to a rigid metal bar. Thus, the system is regarded to maintain stability and near physiological motion patterns of the lumbar spine. The theoretical advantage of this system is to stabilize the treated segment and to prevent adjacent segment degeneration. The goal of this prospective trial was to evaluate clinical, radiographic, and computed tomography (CT) scan outcomes in 54 consecutive cases. Postoperative complications are discussed in detail. Forty cases were recruited with a mean follow-up of 16 months (range, 12 to 37). Postoperative pain scores (Hannover Activities of Daily Living Questionnaire and VAS for back and leg pain) improved in 29 cases (73%) and was best when dynamic fusion was combined with nerve root decompression. Outcome data were not superior to conventional rigid fusion systems and had a considerable number of complications requiring revision surgery in 27.5% of cases.

Rigid External Fixation and Condylar Remodeling

Condylar fractures, instead of other mandibular fractures, play a primary importance role because their high incidence and the historic controversy existent in literature regarding their treatment. Recent studies prove that conservative treatment of condylar fractures, although not determining perfect alignment of the fractured segments, leads to a series of histologic and morphologic healing processes ending with consolidation of the fracture and functional recovery of the TMJ (temporo-mandibular joint). In this study, we observed long-term results of 2 cases of bicondylar fracture treated with surgical reduction and rigid external fixation. Rx orthopantomography control 1 year after surgery showed condylar remodeling bilaterally with good functional recovery. Our school affirms that semirigid fixation system allows optimal function between the articular head and the glenoid fossa, with good tridimensional repositioning of the fractured segments.

Material Flow Control and Optimization in High-Pressure Sheet Metal Forming by Active-Elastic Tools

High-pressure forming of metal sheets is an innovative forming technology for the production of complex components and offers high potentials to improve the properties and qualities of sheet metal parts. This report describes investigations of a newly developed active-elastic tool system referred to as ACTEC system. Unlike the use of a comparable semi-rigid tool system, the ACTEC system shows improvements with respect to the material flow in the flange area and reduced sheet thinning in critical corner regions of the workpiece. In addition, the clamping forces respectively sealing forces necessary to avoid leakage in the tool system during the forming process can be reduced. Moreover, the specific design of the ACTEC-system as well as current experimental examinations are presented and discussed.

A study of continuous stem girder systems

A new beam system comprising two cantilever stems and an interspan composite beam has been developed and its design philosophy is described in this paper. The system provides the equivalent of a semi-continuous beam without the requirement to calculate the moment rotation capacity of the beam-to-column connection. The economy of braced frames using the system has been investigated and compared with simple, continuous or semi-rigid systems. It is shown that the costs of the proposed system are similar to the semi-rigid system and cheaper than both the simply supported and rigid beam systems. Two tests have been carried out on 6 meter span beams, which also incorporated an asymmetric flange steel section. The behaviour of the system is presented and the test results are compared with those obtained from the theory.

Posterolateral Fusion for Isthmic Spondylolisthesis in Adults

This is a retrospective study of 83 consecutive adult patients with isthmic spondylolisthesis who underwent identical decompressive surgery combined with posterolateral spine fusion. We sought to determine factors that affect the fusion rate and clinical outcomes for adult patients with isthmic spondylolisthesis. The outcome of operative treatment for isthmic spondylolisthesis in adults has been poorly documented, as opposed to the treatment of children and adolescents. From 1989 to 1994, 83 consecutive adult patients (age 19-66 years; average, 38 years) underwent surgical treatment consisting of the Gill procedure and posterolateral fusion for isthmic lumbosacral spondylolisthesis. Seventy-three patients (46 men and 27 women) were available for an average of 3.8 years' follow-up (1.0-7.4 years). Thirty-eight underwent one-level fusion, and 35 underwent two-level fusions. Pedicle screw instrumentation was performed in 69 patients. A postoperative questionnaire including the Roland index, clinical charts, and radiographs were reviewed by an independent observer to assess the postoperative course, clinical results, and fusion status. Twenty-five variables were evaluated to determine which affected the fusion and success rates. Primary radiologic fusion and clinical success rates were 78 and 71%, respectively. There was a strong positive correlation between radiologic fusion and clinical success. Overall, single-level fusions showed an 82% fusion rate, and two-level fusions, a 74% rate. For two-level fusions, a significantly higher fusion rate was achieved with a rigid pedicle screw-fixation system than a semirigid system (79 vs. 57%). For smokers, cessation from smoking postoperatively did not increase the fusion rate, and patients who continued to smoke after surgery showed a significantly higher rate of pseudarthrosis. Worker's compensation status did not affect clinical results significantly. Patients who continued to take nonsteroidal antiinflammatory drugs (NSAIDs) >3 months postoperatively showed significantly lower fusion and success rates (44 and 37%). Single-level lumbar fusion for isthmic spondylolisthesis was equally effective with either rigid or semirigid pedicle screw instrumentation. For multilevel spine fusion in isthmic spondylolisthesis, rigid pedicle screw-fixation systems resulted in a high fusion rate. A smoking history or NSAIDs use postoperatively had strong negative influences on the fusion and clinical success rates.

Clinical outcome after spinal fusion with a rigid versus a semi-rigid pedicle screw system

Several biomechanical studies have evaluated the quality of fusion obtained with a rigid versus a semi-rigid pedicle screw implant. Some studies indicate that increased rigidity of the implant system results in an increased strength of the fusion mass. Other reports have underlined the risk of stress shielding due to rigid implant systems. Based on these findings some authors have recommended the use of a semi-rigid system. There are, however, few studies focusing on any possible difference in clinical outcome between the two different types of implant systems. Questionnaires were sent to 89 patients who had undergone primary spinal fusion with either a rigid or a semi-rigid pedicle-screw-based implant system. In every case the diagnosis was spondylolisthesis or degenerative lumbar disease. The questionnaires were analysed using forward stepwise logistic regression analysis. Eighty (90%) of the questionnaires were returned. There was a mean follow-up of 4 years (range 2-8 years). It was not possible to demonstrate any difference in clinical outcome between patients undergoing lumbar fusion with a rigid implant system and those given a semi-rigid system. The overall patient satisfaction rate was 69%, with no difference between the two types of implant. No difference in clinical outcome between the two types of implant was found. Considering the fact that the primary goal of spinal fusion procedure is to obtain a solid fusion mass, biomechanical tests favour the used of a rigid pedicle screw system. This fact combined with the fact that early mobilisation is possible with rigid implants justifies the use of rigid implant systems, although no difference in clinical outcome could be demonstrated in this study.

Structure of cis-1-{2-[(2-butoxy)phenylcarbamoyloxy]cycloheptylmethyl}piperidinium chloride

C 24 H 39 N 2 O 3 + .Cl - , M r =439.0, monoclinic, P2 1 /n, a=11.749 (7), b=7.083 (4), c=28.763 (21) A, β=97.15 (6) o , V=2375 (3) A 3 , Z=4, D m =1.23 (1), D x =1.227 Mg m -3 , λ(Mo Kα)=0.71069 A, μ=0.184 mm -1 , F(000)=952, T=293 K, final R=0.060 for 1624 unique observed reflections. The title compound, which is a potent local anaesthetic of the phenylcarbamate type, was designed to explore the stereostructural requirements of the anaesthetic receptor by locking the phenylcarbamate-amine link into a semirigid system

貫通仕口による木造ラーメン(大黒柱)構造の研究 : その1 仕口の挙動に関する実験的研究

The traditional wooden houses in Japan was constructed by the semi rigid frame system. Although, these structure systems are untouched by the mechanical researchers. This report is experimental research on the panel point of the wooden semi rigid frame so cold "Nuki" structure, by use the small models.

Biomechanics of Intramedullary Fracture Fixation

Intramedullary rodding allows excellent control of bending forces on long bone fractures when adequate sized rods are used. This is made possible by reaming when necessary. Torsional stability is poor if adequate bone nail contact is not obtained and there is little bone fragment interdigitation. This can be optimized with the interlocking system, especially with proximal and distal fractures. Intramedullary rods allow transmission of compressive load so there must be adequate bone to bone contact without comminution to prevent shortening. If a great deal of comminution is present, an interlocking system must be used to resist compressive loads. The interlocked devices have not been proven to be a detriment to union and indeed are a semi-rigid fixation system when used in comminuted shaft fractures. The strength of an osteosynthesis with an intramedullary rod depends on the geometry of the rod and the geometry of the fracture complex. Both locked and nonlocked intramedullary rods perform extremely well when one understands the mechanical principles involved in intramedullary rodding and pays close attention to detail.