bluuebunny/crossref_metadata_2025 huggingface dataset:
Load Sharing Characteristics in the Stabilized Lumbar Motion Segment: A Finite Element Study
Authors: Lim Tae-Hong , Goel Vijay K.
Published: June 2003

The effects of intervertebral joint stiffness as well as implant stiffness on the load sharing characteristics across the stabilized motion segment were investigated using the finite element technique. Intervertebral joint stiffness variations were modeled by using various Young's modulus ( Edisc ) values of the ground substance that had replaced the nucleus pulposus. Variations in the implant stiffness were made by simulating the use of three different pedicle screw-plate instrumentation constructs: 1) bilateral fixation using stainless steel (ST) plates; 2) unilateral fixation using one stainless steel plate; and 3) bilateral fixation using Plexiglas (PL) plates. For the case of constant fixation device stiffness, the axial force across the VSP plate changed in a step-wise manner with the changes in the "disc" stiffness. The axial force carried by the plates was about 10% of the applied compression for Edisc ≥ 1000 MPa. The plates carried about 40% of the applied compression in the intact and degenerated disc ( Edisc = 4.2 and 8.2 MPa) models, as compared to 100% load by the plates for the totally denucleated case. For the case of constant disc stiffness ( Edisc = 8.4 MPa), ST and PL plates were predicted to take over 38% and 18% of the applied compression load, respectively, while for the uniaxial fixation this value was 24%. The load borne by the plates decreased with a decrease in the stiffness of the device. Larger average stresses were predicted in all spinal components when a less rigid VSP system was used, although still lower than the intact stress values. By contrast, the stresses in the device components were predicted to decrease by a considerable amount due to the use of PL plates. These results clearly demonstrate that both the spinal segment and fixation devices are important load supporting components. However, further studies are required to determine an optimum range of stiffness of the unstable spine-graft-implant construct for fast and solid fusion to occur.
Application of Confocal Laser Scanning Microscopy in Bone
Authors: Fujii H. , Wood D. J. , Papadimitriou J. M. , Zheng M. H.
Published: June 2003

The optical sectioning method of confocal laser scanning microscopy provides higher resolution than standard light microscope techniques. The use of optical rather than physical sections for detailed histological analyses of bone obviates the need for either decalcification or complex plastic embedding processes which are required as a routine for the preparation of thin microtome sections. In this study we have used confocal laser scanning microscopy for the morphological analyses of fresh unembedding human cortical bone, bone allograft and bone cement interfaces. Our results have indicated that such an approach has provided a relatively easy and rapid means for the assessment of the histology of normal and pathological bone.
Materials in Spine Surgery
Authors: Goel Vijay K. , Martz Erik O. , Park Joon B.
Published: June 2003

A wide variety of surgical procedures ranging from laminectomy to vertebral body resection are used to restore spinal function. Accordingly, a wide range of man-made and natural materials are used as supplements to improve the long term success rate of these procedures and patient comfort. Requirements for the materials used in spine surgery are similar to other applications; tissue compatibility in terms of mechanical, chemical and pharmacological requirements. The requirements may change as the tissue heals with time. It is imperative that the materials be "dynamic" in their abilities to respond to the changing environmental needs. Due to technical innovations in the area of biomaterials, newer materials have been proposed for the spinal surgery. Graft materials (fat, allo-, auto, BMP), metals, polymers, ceramics, and composites are used to restore spinal function.
Comparative Study of Graf Stabilization and Posterior Fusion in the Treatment of Chronic Symptomatic Mechanically Unstable Low Back Syndrome
Authors: Skinner I. , Mather-Brown N. , Hardcastle P.
Published: June 2003

Spinal stabilization of unstable intervertebral segments is a well recognized technique in the management of patients with chronic pain with or without neural compression in an attempt to relieve the patient's symptoms. The introduction of internal fixation techniques using a variety of different materials began at the early part of this century and there has been a significant expansion of such techniques over the past 20 years.

There is significant controversy between treating spinal surgeons as to whether such stabilization techniques should involve semi-rigid or totally rigid systems.

Henry Graf in 1988 introduced a new concept in spinal stabilization utilizing dacron bands between pedicle implants as opposed to the previously available systems which used a solid plate or rod to interconnect the intervertebral fixation devices (pedicle screw, wires, sub laminar hooks).

This paper will report the results of a independently reviewed prospective study comparing patients who have undergone the Graf procedure and either a rigid plate fixation or spinal fusion without fixation.

The patients were equally matched for age, sex and psychological parameters (Zung and Somatic Indices).

The results demonstrated a much better functional outcome in those patients who underwent the Graf procedure. This was using rigid criteria introduced by Greenough and Fraser (Low Back Outcome Score). There was no significant difference with respect to patients' satisfaction in the case of Graf and patients undergoing spinal fusion without internal fixation. Those patients who underwent rigid spinal fixation did not report as good patient satisfaction as the other two groups. The psychological indices both pre- and postoperative for the three groups were similar.

The complications between all groups were also similar and not statistically significant.

This study would suggest that the Graf Soft Stabilization Technique does offer patients a potentially better functional outcome than the more rigid systems, though further prospective studies are necessary given the number of variables.
Posterolateral Lumbar Fusion — Biomechanical Study and Clinical Results
Authors: Tajima Naoya , Chosa Etsuo , Totoribe Koji , Kubo Shinichiro , Kuroki Hiroshi
Published: June 2003

This paper discusses the biomechanics and long-term results of posterolateral (PL) lumber fusion for degenerative lumbar spinal diseases. In the biomechanical study, the geometry of the finite element model is based on the L4-5 motion segment. The disc degeneration model was simulated by changing the interbody material properties. The behavior of the PL fusion model and the effects of the anterior elements on PL lumber fusion were studied in compression, flexion, and extension. In the clinical study, 40 patients with a mean age of 39 years (19 to 63) were treated with PL fusion and the mean follow-up period was 14 years. Clinical evaluation was made by the Japanese Orthopaedic Association (J.O.A.) score. Fusion success was determined by X-ray radiographs. Stress distribution results indicate that there were high stresses in the upper part of the grafted bone for PL fusion. The axial displacement of the L4 vertebral body and the stress of the grafted bone for PL fusion increased in the disc degeneration model. In flexion, the extension load stress concentrated on the L4 side of PL fusion model between transverse processes. Clinically, the J.O.A. score improved by 24 points postoperatively. Radiographically, the success rate of the fusion was 93%. The long-term results were so good that this technique can be recommended. It is suggested that the instability including the degree of disc degeneration is one of the important factors in PL lumbar fusion.
Clinical Results of Instrumentation Reduction and Posterolateral Fusion After Decompression of Symptomatic Lumbar Spondylolisthesis
Authors: Chan Kam Kong
Published: June 2003

From July 1990 to June 1993, 35 patients suffering lumbar spondylolisthesis (21 degenerative; 14 isthmic) were operated on and reviewed. They all had single-level involvement either L4-5 or L5-S1 and only this level was confined for operation. The operative procedures included decompression, posterolateral fusion and pedicle screw instrumentation for fixation and reduction of the vertebral slip. The age ranged from 42 to 65 years old, with an average of 55 years. There were 21 patients with grade 1 slip; 13 with grade II; and 1 with grade III. The follow-up periods ranged from 30 to 55 months with an average of 42 months. The clinical results were evaluated according to the improvement of low back pain, radicular pain, claudication and the incidence of fusion. Twenty-four patients (74%) were rated good to excellent and the fusion rate was 88%. However, there were 16 patients who still suffered from significant low back pain and who had reportd that such pain adversely affected the rating of clinical result. Loss of reduction were found in 16 patients, but there was no difference in clinical outcome between patients with or without reduction loss after the operation. The purpose of this paper is to report the clinical outcomes of the treatment of symptomatic spondylolisthesis with decompression, posterolateral fusion and instrumental reduction of the slip. The incidence of reduction loss and the prevalence of remaining low back pain are two important factors to consider in doing such reduction procedure. We inferred that slip reduction may not be a worthwile procedure in the treatment of adult spondylolisthesis if ordinary posterolateral fusion with short segment instrumentation is contemplated.
The Skull Defect Model in Measuring Osteoinductivity
Authors: Lindholm T. Sam , Lindholm Tom C.
Published: June 2003

Research on regeneration and experimental or clinical repair of cranial defects commenced already one hundred years ago.

Principally spontaneous regeneration, intramembraneous bone healing, starts from the edges, proceeding to the center of the defect. A skull defect exceeding some critical limitations lacks the capacity for spontaneous healing. This kind of situation is named a "critical size" defect.

The skull defect model is eminently suitable for testing osteoconduction and induction following local implantation of biomaterials and growth factors. There are numerous reports especially on osteoinductive proteins, native and recombinant bone morphogenetic proteins (BMPs), showing satisfactory complete healing of critical size skull defects in a relatively short period of time, while untreated defects have not had the capacity for complete regeneration.

This article is a review of skull defect healing in different animal species showing optimized osteoinductive regenerative capacity especially with the use of BMPs. The results, indeed, also have clinical implications.
Biomechanics of the Hip: FR. Pauwels, An Author Rediscovered for Our Times
Authors: Quesnel Thierry , Kornecki Stefan , Gueritey Pierre-Marie
Published: June 2003

The relevance of the work of Pauwels, especially with respect to the balance of Pauwels in the frontal plane, prompted us first to confirm his material and results in a personal study using a novel modeling procedure based on a finite elements technique, then to investigate the fundamental concepts which guided Pauwels in his choice of methodology. It is these concepts which warrant fresh examination with the aim of unfolding the rich prospects which, thanks to present-day techniques, will throw fresh light on broad fields of investigation.
Fracture Toughness and Quantitative Computed Tomography Number of Human Tibia Cortical Bone
Authors: Lewis Gladius
Published: June 2003

In spite of its importance, the fracture toughness of human bone has been the subject of only a few studies. The objective of the first part of the present work was, thus, to expand this database. For this purpose, linear elastic fracture mechanics (LEFM) principles and single-edge-notched three-point bend specimens were used to determine the fracture toughness of compact bone cut from the tibiae of embalmed cadavers (donor ages between 36 and 94 years). The overall mean and standard deviations of the fracture toughness were 3.12 and 1.21 MP/m, respectively. The case for using LEFM principles, various aspects of four key variables, and the present results are all fully discussed. In the second part of the study, the computed tomography (CT) number of all the specimens were measured. Correlational analysis of all the results demonstrated that CT number exerts a moderately positive influence on fracture toughness for this bone. The clinical significance of this finding is discussed.
Poroelastic Model of Trabecular Bone in Uniaxial Strain Conditions
Authors: Lim Tae-Hong , Hong Jung Hwa
Published: June 2003

A one-dimensional poroelastic model of trabecular bone was developed to investigate the fluid effect on the mechanical behavior at the continuum level. The poroelastic properties were determined based upon an assumed drained Poisson's ratio of 0.3 and experimental results reported in the literature. Even though the free escape of the fluid through the loading end was allowed during deformation, model predictions showed that the pore pressure generated within trabecular bone would cause significant variations in total stress. The total stress increase resulted in a stiffening of trabecular bone, which supports the concept of hydraulic stiffening that has been advocated by several investigators. Model predictions showed a good agreement to the mechanical behaviors of trabecular bone specimens with marrow in situ in a uniaxial strain condition observed in previous studies. These results support the hypothesis that trabecular bone is poroelastic and the fluid effect on the mechanical behavior at the continnum level is significant. Thus, the incorporation of the fluid effect in future studies is recommended to improve our understanding of mechanical behavior of trabecular bone.
Clinical and Radiological Results of PLIF for Degenerative Spondylolisthesis
Authors: Yamamoto Tomio , Ohkohchi Toshiyuki , Ohwada Tetsuo , Kotoku Hiroyuki , Harada Norimasa
Published: June 2003

This is a follow-up study of the surgical efficacy of posterior lumbar interbody fusion (PLIF) for degenerative spondylolisthesis. Over the past 17 years, the authors have applied 7 alternative forms of reinforcement/augmentation to the basic/simple PLIF in an attempt to minimize the rate of fusion complications such as graft collapse, delayed fusion and nonunion. Each variant of the PLIF, along with the basic PLIF was performed on a significant number of patients, yielding a large population for this study. Clinical, radiological and statistical analyses were performed to determine the success of each variant, the basic PLIF, as well as the efficacy of the PLIF in aggregate for cases of degenerative spondylolisthesis. 166 patients were enrolled in this study. The average post-surgical follow-up occurred at 60 months, with a range of 13–188 months encompassing all subjects. Group A (basic/simple PLIF with autologous iliac bone graft)'s rate of fusion complications was 50%. Group B (autologous graft with internal fixation) rate of fusion complications was 36%. Group C (VSP with intervertebral spacers) rate of fusion complications was 13%. The mean recovery rates increased in a stepwise fashion from Group A to B to C. The mean recovery rates in patients with optimal fusion was significantly higher than in patients with fusion complications. The authors conclude that rigid fixation and graft solidarity are essential for achieving optimal results when performing the PLIF. Optimal fusion was correlated with significantly better clinical results.
Radiological Factors Influence Clinical Outcomes in Posterolateral Fusion for Unstable Lumbar Spine
Authors: Kawakami Mamoru , Tamaki Tetsuya , Yoshida Munehito , Hayashi Nobuhiro , Ando Muneharu , Yamada Hiroshi
Published: June 2003

The aim of this study was to retrospectively review clinical outcomes of posterolateral fusion for 50 consecutive patients with unstable lumbar spine and to determine which radiological factors affect clinical results. Patients with poor outcomes were older and had a greater number of fused segments than did those with good outcomes. Except for these, there were no relationships between clinical preoperative factors and outcomes on follow-up examination. At follow-up, decrease in lordosis and increases in slippage and L1 axis S1 distance (LASD) (which was measured as the distance along the perpendicular axis from the center in the L1 body to the posterior superior edge of the S1 body) were found in patients with poor surgical outcomes. The slippage on follow-up examination was significantly greater in patients with LASDs above 35 mm, preoperatively, than in those whose LASD was less than 35 mm. The lesions of adjacent segments and bony union rate did not influence the clinical results. A preoperative radiological risk factor is LASD greater than 35 mm, which was associated with an increase in the slippage at follow-up. Maintenance of lumbar lordosis and an LASD below 35 mm and after the surgery, may improve clinical outcomes.
CPM on Meniscal Regeneration and Maturation after Meniscectomy in Rabbits
Authors: Kim Sung-Soo , Moon Myung-Sang
Published: June 2003

This study in rabbit knees was carried out to clarify the effect of the application of CPM, after meniscectomy, on the regeneration rate of the meniscus and histology of the regenerated menisci. Twenty-seven mature rabbits were used: three rabbits as control (non-CPM) and 24 rabbits as experimental ones. Among them, four rabbits were used as the immediate CPM group and 20 rabbits as the delayed CPM group. In each animal, the medial meniscus was totally excised from the right knee, and the lateral meniscus was totally excised from the left knee. In three control animals, 16 weeks after meniscectomy, there was (hold) Grade II to III meniscal regeneration in two, and small meniscal mold was formed in one. In the immediate CPM group, meniscal regeneration failed and there was would disruption in all four knees. In the delayed CPM group, grades II to III regeneration was observed in 15 of the 20 medial meniscectomized knees, while in the lateral meniscectomized knees, the same size of meniscal regeneration was observed only in 3 of the 20 knees. The regenerated menisci in the delayed CPM group overall looked normal in appearance. Application of the delayed CPM induced the early fibrocartilaginous metaplasia of the regenerated fibrous menisci even at 6 to 12 weeks after meniscectomy.

It is speculated that the application of delayed CPM promotes early focal fibrocartilagenous metaplasia of the fibrous meniscus following meniscectomy.
Effect of Bone Marrow Blood Injection into Delayed Fracture Union and Nonunion Gaps on Callus Formation
Authors: Moon Myung-Sang , Moon Young-Wan , Sun Doo-Hoon , Moon Hanlim , Moon Jeong-Lim , Kim Sung-Sim , Yoo Whan-Kun
Published: June 2003

This study was carried out to assess the effect of bone marrow transplant into the 47 ununited fracture sites of the long bones of the extremities in 46 patients on bone healing. Among 46 cases, there were 43 pure fractures; a case of simultaneous ipsilateral femoral and tibial osteotomies for leg lengthening; a case of ununited repositioned cryo-treated proximal half of tibia as a limb salvage; and a case of internal transport of proximal tibia.

Among the 43 pure fractures, there were 11 hypertrophic, 30 oligotrophic, and 2 gap nonunions. Bone marrow transplant was performed for any type of the delayed union and nonunion, and was also indicated in the distraction callotasis site of poor osteogenesis.

Overall union rate in 43 fractures was 55.8% (24 cases). In two gap nonunions, no callus was formed. Union was obtained in all the 11 hypertrophic nonunions and 13 (46.4%) of the 30 oligotrophic nonunions. The oligotrophic and gap nonunions responded poorly to the marrow transplant. One of the two tibial osteotomy gaps healed with good evidence of endosteal callus formation. In a femoral osteotomy site for lengthening and in an ununited repositioned site of the cryo-treated tibia, there were no visible callus at all. The average time for clinical and radiological unions in the fracture cases were 5 and 7 months on average. In our series, there were no complications, including infection.

The results in this series suggest that bone marrow transplant is a good source of callus formation or stimulant in treating the delayed union and hyper- and oligotrophic nonunions of any origin, and also enhances the callus formation at the gap of the early stage of the internal transport.
The Importance of the Sagittal Plane in Biomechanical Analysis of the Hip
Authors: Quesnel Thierry , Gueritey Pierre-Marie , Faure Christine , Chiello Judicaël , Meunier Cédric , Kornecki Stefan
Published: June 2003

The sagittal plane, which Pauwels regarded as being of no importance for the hip, was studied in the whole body with respect to posture while walking. After a preliminary study, which confirmed the importance of the sagittal plane for the hip, we performed a 3-dimensional modelling of the hip using the finite element method, with the aim of studying the resultant force exerted at the centre of the coxofemoral joint and of analysing the actions of the muscles from the efforts recorded. On the basis of these findings, we represented the overall mechanical problem of the hip in schematic terms as a variable dynamic balance. The results of this work also allowed us to establish in detail the impact of optimisation on the muscular actions and the impact of variations in displacement and the acceleration of the partial centre of gravity on the results recorded. Finally, the isolated hip model was developed, with the aims of allowing us to study the relations existing between variations in the angle of femoral anteversion and variations in forces, and of making a contribution to anthropological studies of the structures of locomotion through the ages.
How to Define the Contact Point of the Tibiofemoral Joint of the Prosthesis in In-Vitro Biomechanical Testing
Authors: Cheng Cheng-Kung , Liau Jiann-Jong , Huang Chun-Hsiung , Lee Ye-Ming , Chueh Shan-Chang
Published: June 2003

No standard method has been provided to define the contact point of the tibiofemoral joint of the total knee prosthesis. Our objective was to estimate the contact point of the tibiofemoral joint in in vitro biomechanical testing of the total knee prosthesis. Three commercial knee prostheses were used for testing. We applied compression loads and used Fuji-prescale films to measure the contact areas at different flexion angles (0°, 10°, 30°, and 60°). The contact point was calculated when the maximum contact configuration was achieved. We used a sensitivity analysis and digital image analysis of the Fuji-prescale film to find the contact point at different flexion angles. From the results, we found that the contact points of the 3 prostheses were all approximately at 30%–60% of the depth of the tibial plateau dimension relative to the posterior edge and symmetrically relative to the midline of the mediolaterial width. All three prostheses had the same tendency in which the contact point first moved anteriorly during 0° to 10° flexion, and then moved more posteriorly after 10° flexion. The present method using the maximum contact area to estimate the contact point for different flexion angles, should be applicable for in vitro biomechanical evaluation of the total knee prosthesis.
A Comparison of the Compressive and Shear Stiffness of Periarticular Osteophytes, Hypertrophic Femoral Intercondylar Notch and Normal Articular Cartilage
Authors: Alonge Temitope O. , Oni Olusola O. A. , Morrison Colin J.
Published: June 2003

The compressive and shear stiffness of periarticular osteophytes, hypertrophic femoral intercondylar notch and normal articular cartilage were compared by obtaining force-indentation curves and applying a shear force to the cartilage/bone interface. The primary stiffness (at 0–100N load) was similar for osteophytes (391N/mm), intercondylar notch (400N/mm) and normal articular cartilage (401N/mm). By contrast, the secondary stiffness (at 100–500N load) was much higher for the intercondylar notch (493N/mm) compared to the osteophytes (410N/mm). There were two varieties of osteophytes, "pink" and "white". Compared with "pink" osteophytes, "white" osteophytes exhibited features similar to a progressively hardening material and appear to be a more mechanically suitable material as an osteochondral graft for full thickness articular cartilage defect. The shear characteristics of all the samples were similar.
Posterior Complex Contribution on Compression and Distraction Cervical Spine Behavior: A Finite Element Model
Authors: Kumaresan Srirangam , Yoganandan Narayan , Pintar Frank A.
Published: June 2003

The relative contributions of the posterior elements on the human cervical spine behavior under axial compression and distraction were determined using the finite element modeling approach. This was accomplished by considering two structures: First, the intervertebral joint structure representing the anterior and posterior columns, including the C4–C6 vertebrae and the neighboring discs with the entire ligamentous complex; and second, the disc joint structure representing only the anterior column (vertebral bodies, discs and longitudinal ligaments). The anterior column sustained a higher share of the load than the posterior column under distraction. However, compression was shared equally among the anterior and the two posterior load bearing columns. The component internal stresses increased with posterior element removal. Consequently, inactivation or compromise in the posterior elements introduces additional internal loads or stresses in the anterior components which may accentuate degenerative changes or injure the cervical column. Thus, posterior complex integrity is critical for the load-carrying capacity of the cervical spine.
Flexural Rigidity of Laboratory and Surgical Substitutes for Human Fibular Bone Grafts
Authors: Heiner Anneliese D. , Poggie Robert A. , Brown Thomas D.
Published: June 2003

The purpose of this study was to measure flexural rigidity of two new synthetic fibular graft substitutes, and compare these data to the flexural rigidity of natural human fibulas. These substitutes were composite fiberglass surrogate fibulas, to be used in laboratory experimental studies, and porous tantalum cylinders, being researched as a bone graft substitute. Ten fiberglass surrogate fibulas and 13 porous tantalum rods were tested in a 4-point bending fixture. Both types of fibular graft substitute had flexural rigidities comparable to natural human fibulas. The fiberglass surrogate fibulas had much less inter-specimen variability in flexural rigidity than did the natural human fibulas (6%/10% vs. 36%/52% for A-P/M-L directions). The surrogate fibula is therefore appropriate for use in laboratory experimental studies of fibular grafts which will undergo bending. The flexural rigidity of the porous tantalum rods increased with relative density to the 1.2 power, as suggested by theory and empirical data for porous solids; thus, porous tantalum density and rod diameter can be varied to obtain the desired flexural rigidity.
Harvest Site and Loading Direction as Determinants of the Flexural Rigidity of Human Fibular Bone Grafts
Authors: Heiner Anneliese D. , Zhang Yongde , Pedersen Douglas R. , Brown Thomas D.
Published: June 2003

Segments of fibula commonly used as cortical bone grafts need to support functional loading at their host site. Since many such constructs require the fibula to carry appreciable bending loads, we undertook a series of flexural tests to determine how flexural rigidity of the fibula varies with longitudinal (or harvest) site and loading direction.

Ten fresh-frozen human fibulas were tested in a 4-point bending fixture. The fibulas were tested at three longitudinal sites (centered at 1/4, 1/2 and 3/4 lengths) and in each of four anatomic directions (anterior, posterior, medial and lateral). There were consistent longitudinal and directional variations in flexural rigidity. The central site was about twice as stiff as the proximal and distal sites, for both the A-P and M-L directions (p < 0.05), indicating that the center of the fibula is the optimal site for harvesting grafts that will be subjected to severe bending. The A-P direction was stiffer in bending than the M-L direction, by 43%, 52%, and 86% for the proximal, central, and distal sites (p < 0.05 for the central and distal sites only), indicating that the choice of circumferential orientation of a fibular graft at the host site could have an appreciable influence on construct rigidity.
Experimental Animal Model to Study Muscle and Tendon Adaptations to Chronic Loading
Authors: Archambault J. M. , Koh T. J. , Herzog W. , Hart D. A.
Published: June 2003

The purpose of this short communication is to present an animal model that: (1) allows for controlled, quantifiable loading of muscle and tendon; and (2) can be used to evaluate the response of musculo-skeletal tissues to chronic loading. A loading apparatus was used to move the rabbit foot through any desired angular position and velocity, while continuously measuring moments about the transverse axis of the ankle. A stimulator was triggered at a pre-set location in the range of motion to produce a contraction of the triceps surae and plantaris muscles. Muscle forces measured with an Achilles tendon force transducer were found to correlate well with externally measured ankle extensor moments. The experimental setup was used to provide cyclic loads to the triceps surae and plantaris muscles and Achilles tendon of 16 rabbits for three loading sessions per week over the period of one to eleven weeks. The experimental model described here is appropriate for the systematic study of the adaptation of muscle and tendon to chronic loading because of the repeatability of the setup and the quantification of tissue loads.
The Effects of Nicotine on Fracture Healing in Rats
Authors: Yorgancigil Hüseyin , Özerdemoğlu Remzi A. , Korkusuz Feza , Erdoğan Nural , Mumcu Ethem F.
Published: June 2003

Cigarette smoking is regarded as a risk factor for developing complications in fracture healing. To determine whether nicotine would retard fracture healing in the rat, 25 rats were divided into two groups and given nicotine or saline subcutaneously at a dose of 2 mg/kg a day, for four weeks. Then their right forelimbs were broken. The rats were killed and histopathologic sections of the radius and ulna were examined and graded at the 7th and 21st days after fractures. Nicotine or saline treatment continued throughout the experiment. Median fracture healing score was found to be 0 (min. 0 - max. 1) in nicotine-treated rats, and 1 (min. 0 - max. 2) in controls, at the 7th day. At the 21st day, the median scores were 2 (min. 1 - max. 3), and 3 (min. 2 - max. 3) in experimental and control groups, respectively. Scores were significantly decreased in nicotine-treated rats both at the 7th and 21st days (p = 0.0465 and p = 0.0175, respectively). We suppose that nicotine impaired fracture healing in the rat forearm model possibly by diminishing nutritional blood flow via vasoconstriction and by its direct effect on osteogenesis.
Total Knee Anthroplasty: Patella Resurfacing Versus Nonresurfacing
Authors: Hsu Robert Wen-Wei , Tsai Yao-Hung , Huang Tsung-Jen , Chang Jenny Chuan-Chuan
Published: June 2003

The results of total knee arthroplasty (TKA) with or without patellar resurfacing were restropectively evaluated in 164 knees of 128 patients. All of the patients recived primary total knee arthroplasty using a Miller-Galante I (MGI) prosthesis. Hybrid fixation including non-cemented femoral component with cemented tibial and patellar components was used in this series. The patella was resurfaced with cemented metal-backed patellar component when there was either gross destruction or eburnation of the articular surface. Hospital for Special Surgery (HSS) knee score, radiographic examination and muscle strength using isokinetic assessment were used to evaluate the functional status of knees. One hundred TKAs with patellar resurfacing and 64 TKAs without patellar resurfacing were evaluated. The average duration of follow-up was 4.8 years. The demographic data were similar between groups. The resurfacing group had worse preoperative HSS knee scores than the nonresurfacing group (p < 0.05). Yet, the final HSS knee scores were similar between two groups (p > 0.05). The resurfacing group had better muscle torque balance (Hamstring/Quadriceps ratio) than the nonresurfacing group (p < 0.05). There were more postoperative complications in the resurfacing group (21%) than the nonresurfacing group (4.7%). Seventeen patellar polyethylene wear in the resurfacing group caused chronic pain or click and required the revision surgery (17%). Although MGI TKAs with patellar resurfacing acquired similarly good knee's functional recovery as in those without resurfacing, yet, it had high patellar complications. Therefore, selective patellar resurfacing might be considered in primary TKA. The metal-backed patella components should be avoided and all-polyethylene designed component be used when patellar was resurfaced. Unlike most marketed knee system, all patients having a Miller-Galante 1 patella replacement were at future risk if they had not already failed.
Relation between Disc Degeneration on MRI and Spinal Instability on Flexion-Extension Radiography
Authors: Chang Ho-Guen , Jeong Soo-Won , Lee Eung-Joo , Chang Jun-Dong , Lee Chang-Ju , Kim Hyeung-Su
Published: June 2003

Purpose

The initial mechanism causing segmental instability is unclear: It is not known whether disc degeneration is a primary cause or a secondary result of instability. This study analyzed the relationship between the disc degeneration on MRI and positive spinal instability on dynamic flexion-extension radiographs obtained from low back pain patients.

Methods

MRI and flexion-extension dynamic roentgenography was obtained in 83 patients with low back pain and were studied to determine the relationship between the instability and disc degeneration.

Results

Of the 15 cases of young low back pain patients in the 3rd decade were positive instability on dynamic flexion-extension roentgenography; disc degeneration shown on MRI in 7 patients (44%); and normal disc in 8 (56%).

Of the 61 cases of young low back pain patients over 4th decade were positive instability on dynamic flexion-extension roentgenography; disc degeneration shown on MRI in 58 patients (95%); and normal disc in 3 (5%).

The relation between disc degeneration and instability was statistically inconsistent in the 3rd decade (p > 0.05), but consistent over 4th decade (p < 0.05).

Conclusion

These results indicate that, at a young age, lumbar instability showing disc degeneration on MRI is inconsistent and no relation between the disc degeneration on MRI and spinal instability on dynamic flexion-extension roentgenography is present. This shows that in disc degeneration, if the disc degeneration does not show on the MRI of a young low back pain patient with poitive instability with dynamic flexion-extension radiography, allowance must made for the fact that this will take some time.
A Comparison between Anterior Threaded Cages vs. Posterior Pedicle Screw Instrumentation in Terms of Foraminal Distraction and Lumbar Lordosis
Authors: Humphreys S. Craig , An Howard S. , Glover J. Michael , Eck Jason C. , McGrady Linda M. , Lim Tae-Hong
Published: June 2003

A cadaveric study was performed to compare the effect of anterior versus posterior distraction instrumentation on lumbar foraminal height and lordosis. Pedicle screws and interbody instrumentation can be used to distract vertebral bodies, thereby increasing foraminal height. BAK interbody cages were inserted anteriorly at L4-L5 and L5-S1 in ten spines. Isola instrumentation was applied posteriorly in six spines at L4, L5, and S1. Both anterior instrumentation and posterior pedicle screw instrumentation provided significant increase in foraminal height with slight decrease in total lumbar lordosis. Foraminal height increased with larger cages at the level in which the cages were first applied, and the addition of cages at the neighboring level had a little effect. However, no statistically significant differences were found with different sizes of cages at the neighboring level. The maximum change in foraminal height occurred with 10 mm of posterior distraction, but a plateau effect was observed over six mm. Distraction of the lumbar spine is effective in increasing foraminal height with relatively small losses of lumbar lordosis. Similar increases were obtained with the anterior and posterior approaches. The surgeon should choose a particular method based on the patient's pathology.
Posterior Lumbar Interbody Fusion Using an En-Bloc Resected Lamina as an Interbody Spacer in Combination with Spinal Instruments
Authors: Hirabayashi Shigeru , Kumano Kiyoshi , Uchida Takeshi
Published: June 2003

We developed a new method of posterior lumbar interbody fusion (PLIF) using an en-bloc resected lamina with or without a hydroxyapatite block as an interbody spacer instead of auto-iliac bone, in combination with rigid-type spinal instrumentation. The purpose of this study was to evaluate the effectiveness of our method. There were 23 patients (13 males, 10 females, age at the time of operation: 21–71 years, mean 50.5 years; follow-up: 1–4 years, mean 2 years and 3 months). In 10 patients with spondylolitic spondylolisthesis and 3 patients with spondylolysis, the floating lamina was resected enbloc by mid-line splitting. In 7 patients with degenerative spondylolisthesis and 3 patients with unstable spine, a cleavage was made at the isthmus and then the complex of lamina and inferior spinous process was resected en-bloc. Seventeen patients with olisthesis underwent reduction. PLIF was performed at the L4/L5 level in 10 patients and the L5/S1 level in 13 patients. Sixteen patients with preoperative low back pain recovered, except for one patient with instability at the adjacent vertebra. All of the seven patients with preoperative gait disturbance recovered. The ratio of olisthesis changed from preoperative 30% to postoperative 18% on average. Good bony union was obtained in both the patients with and those without a hydroxyapatite spacer. Posterior lumbar interbody fusion using an en-bloc resected lamina as an interbody spacer in combination with rigid-type spinal instrumentation was useful.
CRITICAL DENSITY IN A FIRE SPREAD MODEL UNDER ENVIRONMENTAL INFLUENCE
Authors: LI XIAODONG , MAGILL WILLIAM
Published: June 2003

Small changes in spatial pattern on a landscape can sometimes produce dramatic ecological responses. Such transition ranges are associated with critical environmental conditions such as tree density. As the landscape becomes dissected into smaller patches of trees, landscape connectivity may suddenly become disrupted, which may have important consequences for the behaviours of forest fire, i.e. how it spreads. Landscape connectivity depends not only on the tree density but also many other environmental conditions such as land height, flammability, and wind conditions. To determine how the critical densities are affected by the changes in these conditions, we developed a fire spread simulation model using a multi-agent (i.e. bottom-up) approach. This model simulates an artificial environment where bush is randomly generated and fire can be ignited and then spread across the environment according to some "interaction rules". The emergent fire spread behaviours at the landscape level are determined by such micro-level "interaction rules". This model takes into account some major environmental factors that influence fire growth. By varying these variables under controlled conditions, this research aims to show how varied environmental conditions affect the critical density, and hence influence the spread and growth of fire.
IMITATING HUMAN VISUAL ATTENTION AND REPRODUCING OPTICAL ILLUSIONS BY ANT SCAN
Authors: VALLONE UGO , MÉRIGOT ALAIN
Published: June 2003

This article describes a new strategy for analyzing contours in static images. The goal of this analysis is to find the interest centres in the images and then to explain some common optical illusion phenomena. The approach proposed is based on a modified version of the Ant Colony Optimization paradigm named Ant Scan (here introduced). Ant Scan is different from the ACO meta-heuristic principally in the mechanism of exploration of the interest space (the image to be analyzed). Experimental results have shown that interactions among these new agents (based on communication by pheromone) can generate another type of emergent phenomenon that can be utilized to explain how human beings process static images. Classical optical illusions have been analyzed with this new model and a qualitative explanation of how they act is provided.
OPEN-ENDED ARTIFICIAL EVOLUTION
Authors: STANDISH RUSSELL K.
Published: June 2003

Of all the issues discussed at Alife VII: Looking Forward, Looking Backward, the issue of whether it was possible to create an artificial life system that exhibits open-ended evolution of novelty is by far the biggest. Of the 14 open problems settled on as a result of debate at the conference, some 6 are directly, or indirectly related to this issue.

Most people equate open-ended evolution with complexity growth, although a priori these seem to be different things. In this paper I report on experiments to measure the complexity of Tierran organisms, and show the results for a size-neutral run of Tierra. In this run, no increase in organismal complexity was observed, although organism size did increase through the run. This result is discussed, offering some signposts on path to solving the issue of open ended evolution.
EVOLUTIONARY ANALYSIS ON SPATIAL LOCALITY IN N-PERSON ITERATED PRISONER'S DILEMMA
Authors: SUZUKI REIJI , ARITA TAKAYA
Published: June 2003

The purpose of this paper is to consider the effects of spatial locality on the evolution of cooperative behavior in the N-person iterated Prisoner's Dilemma (N-IPD) by focusing on two essentially distinct factors: the scale of interaction (which decides the neighboring members playing the N-person games) and the scale of reproduction (which decides the neighboring candidates for an offspring in each cell). We conducted evolutionary experiments of strategies for one-dimensional N-IPD game with various settings of these two factors. Experimental results revealed that these two factors bring qualitatively different effects to the emergence of cooperative behavior. Furthermore, we investigated the dynamics of the evolution of spatial locality in N-IPD. When we introduced the evolution of the scale of interaction into our model, the dynamic evolution of the scale of interaction through generation facilitated the emergence of global cooperation when the scale of reproduction was relatively small. Experiments with the evolution of the scale of reproduction are also discussed.
THE ACCUMULATED EXPERIENCE ANT COLONY FOR THE TRAVELING SALESMAN PROBLEM
Authors: MONTGOMERY JAMES , RANDALL MARCUS
Published: June 2003

Ant colony optimization techniques are usually guided by pheromone and heuristic cost information when choosing the next element to add to a solution. However, while an individual element may be attractive, usually its long term consequences are neither known nor considered. For instance, a short link in a traveling salesman problem may be incorporated into an ant's solution, yet, as a consequence of this link, the rest of the path may be longer than if another link was chosen. The Accumulated Experience Ant Colony uses the previous experiences of the colony to guide in the choice of elements. This is in addition to the normal pheromone and heuristic costs. Two versions of the algorithm are presented, the original and an improved AEAC that makes greater use of accumulated experience. The results indicate that the original algorithm finds improved solutions on problems with less than 100 cities, while the improved algorithm finds better solutions on larger problems.
Ricci and Bianchi identities for h‐normal Γ‐linear connections on J1(T, M)
Authors: Neagu Mircea
Published: June 2003

The aim of this paper is to describe the local Ricci and Bianchi identities of an h‐normal Γ‐linear connection on the first‐order jet fibre bundle J1(T, M). We present the physical and geometrical motives that determined our study and introduce
the h‐normal Γ‐linear connections on J1(T, M), emphasizing their particular local features. We describe the expressions of the local components of torsion and curvature d‐tensors produced by an h‐normal Γ‐linear connection ∇Γ, and analyze the local Ricci identities induced by ∇Γ, together with their derived local deflection d‐tensors identities. Finally, we expose the local expressions of Bianchi identities which geometrically connect the local
torsion and curvature d‐tensors of connection ∇Γ.
Block Toeplitz operators with frequency‐modulated semi‐almost periodic symbols
Authors: Böttcher A. , Grudsky S. , Spitkovsky I.
Published: June 2003

This paper is concerned with the influence of frequency
modulation on the semi‐Fredholm properties of Toeplitz
operators with oscillating matrix symbols. The main results give
conditions on an orientation‐preserving homeomorphism α of the real line that ensure the following: if b belongs to a certain class of oscillating matrix functions (periodic, almost periodic, or semi‐almost periodic matrix functions) and the Toeplitz operator generated by the matrix function b(x) is semi‐Fredholm, then the Toeplitz operator with the matrix symbol b(α(x)) is also semi‐Fredholm.
On polynomials of Sheffer type arising from a Cauchy problem
Authors: Meredith D. G.
Published: June 2003

A new sequence of eigenfunctions is developed and studied in
depth. These theta polynomials are derived from a recent analytic
solution of the canonical Cauchy problem for parabolic equations,
namely, the inverse heat conduction problem. By appealing to the
methods of the operator calculus, it is possible to categorize the
new functions as polynomials of binomial and Sheffer types. The
connection of the new set with the classical polynomials of
Laguerre is carefully examined. Some integral relations involving
the Laguerre polynomials and the theta polynomials are presented
along with a number of binomial identities. The inverse
heat conduction problem is revisited and an analytic solution
depending on the generalized theta polynomials is presented.
A note on Hammersley′s inequality for estimating the normalinteger mean
Authors: Khan Rasul A.
Published: June 2003

Let X1, X2, …, Xn be a random sample from a normal N(θ, σ2) distribution with an unknown mean θ = 0, ±1, ±2, …. Hammersley (1950) proposed the maximum likelihood estimator
(MLE) , nearest integer to the sample mean,
as an unbiased estimator of θ and extended the Cramér‐Rao inequality. The Hammersley lower bound for the variance of any unbiased estimator of θ is significantly improved, and the asymptotic (as
n → ∞) limit of Fraser‐Guttman‐Bhattacharyya bounds is also determined. A limiting property of a suitable distance is used to give some plausible explanations why such bounds cannot be attained. An almost uniformly minimum variance
unbiased (UMVU) like property of d is exhibited.
Oscillation for advanced differential equations withoscillating coefficients
Authors: Li Xianyi , Zhu Deming , Wang Hanqing
Published: June 2003

Some sufficient conditions are established for the oscillation of
all solutions of the advanced differential equation x′(t) − p(t)x(t + τ) = 0, t ≥ t0, where the coefficient p(t) ∈ C([t0, ∞), R) is oscillatory, and τ is a positive constant.