bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contact stress aberrations following imprecise reduction of simple tibial plateau fractures
Authors: Brown Thomas D. , Anderson Donald D. , Nepola James V. , Singerman Robert J. , Pedersen Douglas R. , Brand Richard A. 
Published: February 2005

AbstractDespite the well‐recognized association between poorly reduced intraarticular fractures and late degenerative changes, current guidelines regarding the reduction precision necessary to avoid excessive cartilage pressures are based largely on anecdotal clinical observations. To gain a quantitative appreciation of the relation between local pressure elevations and fracture reduction imprecision, a simplified laboratory cadaver model of minimally displaced tibial plateau fractures was developed. Cartilage contact stress distributions were measured as a function of depressed fragment malreduction in seven knees, using high‐resolution (100 pixels/mm2) digital image scans of Fuji‐film stain patterns. The contact stress data showed a general trend of increases of peak local pressure with increasing fracture site incongruity, and in a few isolated instances the effect was very pronounced. Across the whole series, however, statistically significant departures from anatomic pressure levels did not occur until the fragment stepoff was >1.5 mm. Even at the 3‐mm stepoff level, for which the depressed fragment usually no longer made contact with the femoral condyle, the peak local pressure values on the intact side of the fracture line averaged only ∼75% greater than those prevailing anatomically. Given the successful clinical outcomes normally achieved for conservatively managed simple tibial plateau fractures having stepoff magnitudes (5–10 mm) clearly sufficient to insure fragment articular noncontact, the present laboratory results suggest that nominally factor‐of‐two peak local pressure elevations, provided that they occur over only small portions of the cartilage surface, are probably within the long‐term overall tolerance range of an articular joint.
Reconstruction of the digital pulley in the monkey using biologic and nonbiologic materials
Authors: Kain Christopher C. , Manske Paul R. , Reinsel Tom E. , Rouse Andrew M. , Peterson William W. 
Published: February 2005

AbstractA‐2 pulleys were replaced in the hand of the nonhuman primate; on the long/little fingers the pulleys were reconstructed with a woven nylon fabric (Nitex), and on the ring/index fingers the pulleys were reconstructed with fascia lata. The opposite unoperated hand served as a control. At 2, 3, and 6 months postoperative, the animals were killed to compare the function of the reconstructed pulleys with the control pulleys of the opposite digit. Using a tensile testing machine, two parameters, work of flexion and tendon excursion, showed that both pulley reconstructions permitted minimal tendon bowstringing and had excellent gliding function. Both materials increased in strength over time to become stronger than the control pulley. Histologic examination showed no foreign body reaction to the Nitex; excellent fibrous ingrowth into the woven nylon was seen, which matured in time. The surface of the Nitex pulley facing the tendon developed and maintained a synovial‐like gliding surface. The Nitex pulley compared favorably with the fascial pulley biomechanically and histologically; both reconstructed pulleys functioned well compared with normal pulleys.
Sex differences in age‐related remodeling of the femur and tibia
Authors: Ruff Christopher B. , Hayes Wilson C. 
Published: February 2005

AbstractChanges with age in cross‐sectional geometry of the lower limb bones were investigated in a large sample of cadaveric skeletal material from U.S. white adults. Section properties (areas and second moments of area) were determined at 11 locations by sectioning and direct measurement of 103 femora and 99 tibiae. All properties were standardized for body size differences by dividing by powers of bone length, and age trends were determined through linear regression analysis. Results indicate that while both men and women undergo endosteal resorption of bone and medullary expansion with aging, only men exhibit concurrent subperiosteal bone apposition and expansion. As a consequence, men show little change in cortical area and some increase in second moments of area with age, while women show decreases in both cortical area and second moments of area. Thus, only men appear to remodel bone in a way that would tend to compensate for loss of bone material strength with aging. In a previous study of a preindustrial sample with high activity levels, both men and women exhibited bone subperiosteal expansion and increase in second moments of area with aging. Together with observed differences in fracture incidence among living populations, these findings suggest that relatively low activity levels may not stimulate optimal bone remodeling throughout life and thus may contribute to higher risk of fracture in old age.
Prevention of ligament and meniscus atrophy by active joint motion in a non–weight‐bearing model
Authors: Klein Leroy , Heiple Kingsbury G. , Torzilli Peter A. , Goldberg Victor M. , Burstein Albert H. 
Published: February 2005

AbstractThis study describes the effect of active joint motion on the maintenance of ligament and meniscus mass in a non–weight‐bearing model of disuse. Denervation and fixation models of immobilization have shown that resorption of isotope and atrophy of mass occured for hard tissue (bone) and soft tissues (ligament, tendon, or meniscus). A unilateral ankle disarticulation model of disuse that maintains active knee motion without weight bearing was studied for 8 weeks in dogs that were chronically prelabeled with three different isotopes. The effects of non–weight‐bearing without denervation or fixation were analyzed for the resorption of isotopes, and net atrophy of bone mass (femur or tibia) and soft‐tissue mass (collateral or cruciate ligaments, menisci). A large and similar loss of all three isotopes, as well as collagen and calcium mass occurred for whole femur and tibia; this indicated that mass loss was equivalent to bone resorption and suggests little replacement with new bone. No loss of isotope or mass per whole tissue occurred for the collateral and cruciate ligaments or menisci. The strength of the femur–anterior cruciate ligament–tibia complex was analyzed by a tensile failure test when a fast rate of deformation was applied; the results did not differ qualitatively or quantitatively between control and experimental limbs. The absence of weight bearing for 8 weeks resulted in marked bone atrophy without resorption or atrophy of soft tissues, or decrease of the mechanical strength for the femurligament–tibia complex. With this model the amount of active joint motion remaining appears able to prevent ligament and meniscus atrophy even though marked bone atrophy occurred during this period.
Calcitonin and fracture healing. An experimental study on rats
Authors: Paavolainen Pekka , Taivainen Tomi , Michelsson Jan‐Erik , Lalla Martti , Penttinen Risto 
Published: February 2005

AbstractThe effects of systemically administered calcitonin (CT) on fracture healing were analyzed in an experimental study on rats. The healing of a fracture was followed from 3 days up to 9 weeks postoperatively. Half of the rats in each age group were given daily CT 10 MRC‐U/kg body wt s.c. Mechanical properties of the healing tibial fractures (tension strength) as well as various connective tissue components of the callus tissue were analzyed. No difference in the radiological or microscopical appearance of the fractures was detectable between the animals receiving CT and the controls. In the biochemical analysis matrix production as assessed from the concentrations of nitrogen, hexosamines, and hydroxyproline within the callus followed the usual lines of undistributed fracture union without any difference between the groups with and without CT. No differences could be detected in the mineralization of the callus between the specimens from animals receiving CT and those without. The tensile strength values of the fractures increased almost linearly up to 9 weeks. At 1 week the tensile strength values for fractures union in the animals without CT were ∼50% higher, but later on no differences could be detected between the groups. These results indicate that although in the early phases of long‐term CT therapy collagen synthesis may be impaired, there will be no effect on the net content of collagen or calcifying tissue in the callus or on the mechanical strength of healing fractures.
Transpedicular screw fixation
Authors: Moran James M. , Berg William S. , Berry James L. , Geiger Jack M. , Steffee Arthur D. 
Published: February 2005

AbstractSpinal fixation employing transpedicular screws has recently been the focus of increased attention at various institutions throughout the world, but concerns about the safety and efficacy of transpedicular screws linger. This study was undertaken to address some of these concerns. The study included evaluation of the internal and external morphology of the vertebral pedicles, which revealed that adequate bone stock is generally available at T2, T7, T12, and L1–L5 spinal levels to accept screws in the 4–7‐mm diameter range. The pedicle was observed to be composed of abundant cancellous bone internally with relatively thick cortical walls. The method of pilot hole preparation for pedicle screws was also examined. Screws inserted in pilot holes prepared with a 3.4‐mm blunt probe (ganglion knife) resulted in higher pullout forces in eight of 10 trials as compared with those with pilot holes prepared using a 3.2‐mm drill. Furthermore, the probes afford greater control of hole depth and alignment. Fatigue studies on three screws designs revealed a graduation of strength between a 7.0‐mm pedicle screw, and a modified 6.5‐mm cancellous lag screw. The modified cancellous lag screw has an inherent stress riser that affected fatigue life. It was noted that extreme care must be exercised to prevent bending of the pedicle screws during implantation. If bending ocurs one can expect a 50% reduction in the number of cycles to failure.
Early histologic, metabolic, and vascular assessment of anterior cruciate ligament autografts
Authors: Kleiner Jeffery B. , Amiel David , Harwood Fred L. , Akeson Wayne H. 
Published: February 2005

AbstractA rabbit model for anterior cruciate ligament (ACL) reconstruction using autogenous patellar tendon was utilized to study the early events of autograft cellular dynamics. Biochemical, autoradiographic, histological, and vascular injection techniques demostrated that the native autograft cell population rapidly necroses. This repopulation occurs without a vascular contribution; cells entering the autograft are reliant upon synovial fluid nutrition.
Partial restoration of immobilization‐induced softening of canine articular cartilage after remobilization of the knee (stifle) joint
Authors: Jurvelin J. , Kiviranta I. , Säämänen A.‐M. , Tammi M. , Helminen H. J. 
Published: February 2005

AbstractThe restoration of the biomechanical properties of articular cartilage was studied after 15 weeks of remobilization of the knee joint in beagles previously immobilized with a cast for 11 weeks. The shear moduli were determined with an indentation creep test immediately after load application and at equilibrium at six predefined test points of femoral, tibial, and patellar cartilages. Permeability of the cartilage was estimated from the creep measurements. The values were compared with nontreated, age‐matched (55 weeks) controls and with cartilage collected immediately after immobilization. Remobilization reduced the high creep rates created by immobilization and shifted the depressed equilibrium shear moduli towards those of the controls. However, in the femoral condylar cartilage, the equilibrium shear modulus remained at lower level (p < 0.05) and permeability at higher level (p < 0.05) as compared with the controls. We conclude that articular cartilage, showing signs of atrophy after long‐term immobilization, was capable of restoring its biomechanical properties during remobilization. This repair was not, however, completed in all parts of the knee joint by the end of the observation period.
Sensory innervation of soft tissues of the lumbar spine in the rat
Authors: Cavanaugh John M. , El‐Bohy Ashraf , Hardy Warren N. , Getchell Thomas V. , Getchell Marilyn L. , King Albert I. 
Published: February 2005

AbstractThe purpose of this study was to investigate neurophysiologically and anatomically the soft tissues of the dorsal compartment of the lumbar spine in order to understand better their possible role in low back pain. The focus was primarily on the lumbar facet joint and supraspinous ligament of the Sprague–Dawley rat. Microdissection of the dorsal ramus and electrophysiological and neuroanatomical studies of the dorsal ramus and its terminations in paravertebral tissue revealed that (a) there are mechanosensitive, slowly adapting fibers in the rat lumbar facet joint capsule; (b) there are slowly adapting, mechanosensitive units in the rat supraspinous ligaments that respond to tensile loading; both types of mechanosensitive units have high threshold; (c) mechanical stimulation of these tissues sometimes elicits afterdischarges lasting several minutes; (d) many extracellular recordings from the medial branch of the dorsal ramus appear to be reflex activity to mechanical stimulation; (e) silver impregnation of the rat joint capsule reveals individual axons, very few of which were encapsulated, suggesting that they terminate in free nerve endings; and (f) the nerves of the rat facet joint capsule contain 68, 160, and 200 kdalton polypeptide subunits of neurofilament protein (NFP). These results indicate that neurons of lumbar facet joint capsules and ligaments in the back are sensitive to mechanical strain and that the higher threshold neurons may serve a nociceptive (pain) function.
The effect of external fixation stiffness on early healing of transverse osteotomies
Authors: Gilbert Jerome A. , Dahners Laurence E. , Atkinson Melissa A. 
Published: February 2005

AbstractThe effect of bending stiffness of external fixators on the early healing of transverse tibial osteotomies was studied in a canine model to determine whether there is a particular range of fixation stiffness where healing is poor. Five unilateral fixators with different stiffnesses were developed and employed along with a dynamic compression plate to fix experimental osteotomies of dog tibias and the contraiateral intact tibias served as controls. The six experimental fixation devices were: plate (P), stainless steel sidebar fixator (SS), stiff aluminum sidebar fixator (SA), intermediate aluminum sidebar fixator (IA), flexible aluminum sidebar fixator (FA), and Delrin sidebar fixator (D). Compared with human tibial fixation methods, the fixators ranged from a rigidity greater than a plate on a human tibia to a flexibility similar to a plaster cast on a human lower leg. Sixty‐four adult male mongrel dogs (29 ± 3 kg) underwent surgery and 52 completed the 9‐week study, leaving 7 to 10 dogs in each experimental group (P = 8, SS = 7, SA = 9, IA = 9, FA = 10, D = 9). After the 9‐week survival period the experimental tibias were radiographed and callus area was digitized. Both the experimental and control tibias were then tested to failure in four‐point bending, and failure moment, stiffness, and energy to failure were determined. Of the 52 osteotomies, only four developed nonunions: 3 of 10 in the FA group and 1 of 7 in the SS group. Using analysis of variance, no statistical differences were detected in failure force, stiffness, or energy to failure as a function of fixator groups. The mean callus area in the most flexible fixation group (D) was significantly greater than that in the P, SS, and IA groups.
Laser doppler flowmetry for bone blood flow measurements: Helium–neon laser light attenuation and depth of perfusion assessment
Authors: Nötzli Hubert P. , Swiontkowski Marc F. , Thaxter Steven T. , Carpenter George K. , Wyatt Robert 
Published: February 2005

AbstractLaser Doppler flowmetry (LDF) has been successfully used in clinical and experimental settings to evaluate bone perfusion but unanswered questions regarding its capabilities and limitations still remain. This study was undertaken to determine absorption of He–Ne laser light (632.8 nm) and maximum depth for flow assessment (threshold thickness) under optimal conditions in bone. Light transmittance in bovine bone samples of femora and tibia was measured after each step of grinding and depth of penetration calculated. The threshold thickness was obtained by placing the same samples in a flow chamber where a solution of 2% latex circulated beneath; flow was detected by a laser Doppler probe resting on top of the sample. The results showed a significantly higher depth of penetration for trabecular than for cortical bone. A regression analysis showed a high correlation between the inorganic fraction of the bone and the depth of penetration. The maximum depth at which the laser Doppler probe can evaluate flow in bone conditions was found to be 2.9 ± 0.2 mm in cortical bone, 3.5 ± 0.3 mm in bone covered by 1 mm cartilage and 3.5 ± 0.2 mm in trabecular bone. The study showed the limitations of LDF in bone and their correlations to various bone properties.
Pressures in the distal radioulnar joint: Effect of surgical procedures used for kienbock's disease
Authors: Werner Frederick W. , Murphy Dennis J. , Palmer Andrew K. 
Published: February 2005

AbstractRadial shortening and ulnar lengthening are two accepted surgical methods for treating Kienbock's disease. The effect of these procedures on the pressure within the distal radioulnar joint between the ulnar head and the sigmoid notch of the radius was experimentally evaluated in six fresh cadaver forearms. Radial shortening and ulnar lengthening led to increased pressure at the distal radioulnar articulation and caused shifting of the location of the center of pressure distally within the sigmoid notch. Radial displacement of the distal radial fragment at the time of radial shortening, however, decreased the peak pressures. Based on these experimental data, ulnar lengthening and radial shortening can be expected to alter the normal biomechanics of the distal radioulnar joint.
Kinetic and biochemical heterogeneity in vertebrate chondroepiphyseal regions during development
Authors: Diao Edward , Zaleske David J. , Avella Douglas , Trahan Carol , Armstrong Ann , Ehrlich Michael G. , Mankin Henry J. 
Published: February 2005

AbstractThe purpose of this study was to see if kinetic and biochemical heterogeneity could be documented in vertebrate chondroepiphyseal regions as they develop from mesenchymal condensations to cartilage. The kinetics of developing proximal and distal femoral chondroepiphyseal regions were studied from early limb bud stage to newborn animals in chicks, mice, and rabbits with thymidine autoradiography. Proteoglycan synthesis in the proximal femoral chondroepiphyseal region of the rabbit was studied with radioactive sulfate incorporation at 28 days of gestation and at 1 and 4 days after birth. The results indicated that these kinetic and biochemical characteristics of the developing chondroepiphyseal regions became heterogeneous very early in development. This early programming of populations of cells for division and for different biochemical functions existed during the fetal period when heterogeneity has been described histologically but has not been well documented.
A study of the mechanical strength of long bone defects treated with various bone autograft substitutes: An experimental investigation in the rabbit
Authors: Hopp Stanley G. , Dahners Laurence E. , Gilbert Jerome A. 
Published: February 2005

AbstractThis study was designed to determine which of several bone grafting materials would be the most efficacious substitute for autogenous bone graft in the treatment of segmental long bone defects. The experimental model was a 1‐cm defect in the rabbit ulna. The control group had nothing implanted in the defect. The six grafts tested were: (a) autogenous iliac crest bone, (b) autogenous cortical bone (ulna), (c) hydroxylapatite, (d) hydroxylapatite–demineralized bone matrix (allograft) composite graft, (e) freeze‐dried bone (allograft), and (f) demineralized bone matrix (allograft). At 6 weeks postoperatively, the ulnas were harvested, examined radiographically, and tested mechanically in torsion.The radiographic examination proved to be of little value because some materials were radiodense at the time of implantation. The rates (percentage) of union, torques at failure, and energy to failure values were statistically significantly higher than control for all groups except hydroxylapatite.We concluded that demineralized bone matrix and hydroxylapatite–demineralized bone matrix composite graft compare favorably with cortical replacement (autograft) in mechanical strength and rate of union and therefore may be satisfactory substitutes for bone grafting. Freeze‐dried bone did not appear to be as satisfactory because of its low mean energy to failure, but statistical analysis failed to confirm this opinion. Hydroxylapatite graft, when used alone, does not appear to be a suitable material for grafting segmental bone defects.
Effects of a scaphoid waist osteotomy on carpal kinematics
Authors: Smith D. K. , An K. N. , Cooney W. P. , Linscheid R. L. , Chao E. Y. 
Published: February 2005

AbstractThe effects of a scaphoid osteotomy on the kinematics of the carpal bones were determined in five cadaveric wrist specimens. Minute radiographic markers were inserted into the distal radius and selected carpal bones through limited arthrotomies between the intercarpal ligaments. Simultaneous biplanar radiographs were obtained in neutral and the extreme wrist positions of extension, flexion, radial deviation, and ulnar deviation, both before and after a scaphoid waist osteotomy. The positions of each of the carpal markers and their corresponding carpal bones were digitized for each wrist position, and a computer‐assisted motion analysis was performed for each specimen before and after transverse scaphoid waist osteotomy. Following the osteotomy, there was a tendency for the scaphoid osteotomy to collapse into a dorsally angulated or “humpback collapse” deformity during each extreme wrist position. There was also multiplanar osteotomy site motion as well as complex collapse deformities of the midcarpal joint associated with loss of the mechanical tie‐rod function of the scaphoid. These findings reveal the importance of the scaphoid in maintaining normal kinematics and the inherent instability of these fractures with loss of scaphoid integrity.
The evaluation of bone remodeling about orthopaedic implants with ultrasound
Authors: Zimmerman Mark C. , Meunier Alain , Katz J. Lawrence , Christel Pascal , Sedel Laurent 
Published: February 2005

AbstractTotal hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin‐Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.