bluuebunny/crossref_metadata_2025 huggingface dataset:
Ingrowth reduces implant‐to‐bone relative displacements in canine acetabular prostheses
Authors: Heiner John P. , Manley Paul , Kohles Sean , Ulm Mark , Bogart Linda , Vanderby Ray
Published: February 2005

We examined bone‐to‐implant relative displacements of acetabular prostheses acutely and after ingrowth in a canine model. Uncemented hemispherical acetabular cups with titanium mesh pads comprising approximately 26% of the surface of the cup were inserted in eight adult canine hemipelves ex vivo. The acetabular prostheses were fixed with 13 mm titanium screws. Zero, one, and two‐screw configurations were tested, with the order of testing randomly assigned. A load simulating 1,000 cycles of canine gait was applied to the acetabular component, and relative displacements were measured at three locations between imlant and bone to determine acute fixation. A repeated measures analysis of variance showed that two screws produced only 42% of the average relative displacement of one screw and 14% that of zero screws. Eight adult mixed‐breed dogs then underwent unilateral total hip arthroplasty. All acetabula were biologically fixed with two cancellous screws. The results at 4 months showed significantly less relative displacement between the implant and bone than was measured in ex vivo implantations (p = 0.014). Bone ingrowth filled 20 ± 6% (mean ± SD) of the available space. The relative displacements of these implants were small in all cases (12 ± 13 μm) and did not correlate with the amount of bone ingrowth. These data suggest that acetabular fixation with two screws can lead to bone ingrowth and reduced relative motion of the prosthesis under functional loading.
Malrotation of the humeral component of the capitellocondylar total elbow replacement is not the sole cause of dislocation
Authors: Itoi Eiji , King Graham J. W. , Niebur Glen L. , Morrey Bernard F. , An Kai‐Nan
Published: February 2005

Malrotation of the humeral component of the capitellocondylar total elbow replacement is thought but not proved to be one of the major causes of postoperative dislocation. The purpose of this study was to quantitate the effect of malrotation of the humeral component on the kinematics and laxity of the capitellocondylar total elbow prosthesis. Eleven fresh previously frozen elbows were used. With the humeral component in optimal position, external rotation, or internal rotation, movements of the elbow with neutral, valgus, and varus loading were monitored with an electromagnetic tracking device. When the humeral component was positioned in external rotation, the ulna was more valgus and supinated than when the component was in optimal position, and when the component was in internal rotation the ulna was more valgus in extension and more supinated in flexion. Malrotation in external rotation decreased valgus‐varus laxity, and malrotation in internal rotation increased rotational laxity. Only one elbow became dislocated, despite constant severe maltracking between the components in all of the specimens. We concluded that although malrotation of the humeral component influences the laxity and causes maltracking, it is not the primary cause of postoperative dislocation. The contribution of other factors should be investigated.
Maturation‐related biochemical changes in swine anterior cruciate ligament and tibialis posterior tendon
Authors: Watanabe Masanobu , Nojima Motoo , Shibata Taihou , Hamada Minoru
Published: February 2005

In order to determine the differences between ligaments and tendons in terms of change in biochemical composition during maturation, the biochemical characteristics of the anterior cruciate ligament and tibialis posterior tendon of swine were studied. The collagen content of the tibialis posterior tendon was found to increase rapidly with growth of the body, reaching a plateau prior to maturation. In contrast, the rate of increase in the anterior cruciate ligament was slow, indicating that maturation of this tissue is delayed. The quantity of glycosaminoglycan in both the anterior cruciate ligament and the tibialis posterior tendon decreased with growth. In mature animals, glycosaminoglycans in the anterior cruciate ligament included chondroitin sulfate, hyaluronic acid, and dermatan sulfate, but only trace amounts of chondroitin sulfate were found in the tibialis posterior tendon. Although the ratio of dermatan sulfate to hyaluronic acid generally increased with growth, this increase was more conspicuous in the tibialis posterior tendon than in the anterior cruciate ligament. The anterior cruciate ligament and tibialis posterior tendon both contained collagen of types I, III, and V. In mature swine, type III was increased in the anterior cruciate ligament but not in the tibialis posterior tendon. These findings demonstrate slower maturaiton for ligament than for tendon with regard to the changes in biochemical constituents, especially those in collagen type and glycosaminoglycan, during the growth process, and also suggest that the composition of these tissues changes in accordance with their changing functional requirements.
Effects of different levels of direct current on early ligament healing in a rat model
Authors: Litke Diane S. , Dahners Laurence E.
Published: February 2005

Electrical stimulation has been shown to enhance the repair of biological tissues such as bone and tendon. The objective of this study was to determine whether low level direct current enhances the early healing of injured medial collateral ligaments. Eighty‐seven rats were divided into three groups on the basis of the level of current delivered. All underwent transection of the medial collateral ligament bilaterally. The experimental medial collateral ligaments received current (which varied by group), while the contralateral medial collateral ligaments (the controls), with identical electrodes, received no current. After 12 days, each ligament was tested biomechanically with use of a hydraulic materials testing machine. Group 1 (8.6 ± 5.9 μA) showed statistically significant improvements in maximum rupture force, energy absorbed, stiffness, and laxity. The groups that had received lower levels of current did not show significant improvements. In this study, stimulation of 1–20 μA was the most effective level of direct current for the enhancement of early healing of the medial collateral ligament.
The entire rotator cuff contributes to elevation of the arm
Authors: Sharkey Neil A. , Marder Richard A. , Hanson Peter B.
Published: February 2005

The function of the infraspinatus, teres minor, and subscapularis during elevation of the arm remains poorly defined. These muscles may generate moments that contribute to abduction of the arm, although they frequently are classified as humeral depressors. The purposes of this study were to measure the contributions to abduction made by the more inferiorly positioned rotator cuff muscles relative to the contributions of the supraspinatus and to determine the range of motion at which the muscles are most effective. Five fresh cadaveric shoulder girdles were mounted in an apparatus designed to simulate contraction of the deltoid and rotator cuff while maintaining the normal relationship between glenohumeral and scapulothoracic motions. The deltoid force required for elevation was measured without simulated contraction of the rotator cuff and with simulated contraction of the entire rotator cuff, of the supraspinatus only, and of the infraspinatus‐teres minor and subscapularis only. A significant reduction in deltoid force when other muscle activity was added indicated that the additions contributed significantly to abduction. The deltoid force required with concurrent contraction of the entire rotator cuff averaged 41% less than with the deltoid alone but was not significantly different than with the deltoid and supraspinatus or with the deltoid, infraspinatus‐teres minor, and subscapularis. Concurrent application of forces to the supraspinatus or the infraspinatusteres minro and subscapularis significantly reduced the required deltoid force over the range of motion studied by an average of 28 and 36%, respectively. The contributions of the rotator cuff muscles to abduction of the arm were greatest at low abduction angles (30 and 60°) and were insignificant by 120°. The infraspinatus‐teres minor and subscapularis contribute significantly to abduction: their contibution was equal to that of the supraspinatus and, like the supraspinatus, they are most effective during the first 90° of abduction.
Comparison of antibiotic release from polymethylmethacrylate beads and sponge collagen
Authors: Becker Paul L. , Smith Richard A. , Williams Robert S. , Dutkowsky Joseph P.
Published: February 2005

The rates of elution of tobramycin in vitro were compared for polymethylmethacrylate beads impregnated with the powder form and an alternative biodegradable substance, sponge collagen. The impregnated polymethylmethacrylate beads initially had a lower zone of inhibition, but the rate of release was slow in comparison with that of the impregnated sponge collagen. The sponge collagen delivered a higher dose faster and with a shorter duration than the polymethylmethacrylate beads with the same antibiotic concentration in vitro, but the beads delivered a therapeutic concentration for longer periods. Because it deteriorates rapidly, sponge collagen may be unsatisfactory as an agent of antibiotic delivery in patients who have chronic osteomyelitis; however, it may be useful for patients who have acute trauma with highly contaminated bone or soft tissue, or during hemiarthroplasty revision, to deliver a high local concentration of antibiotic for a short period of time.
Muscle pathology and clinical measures of disability in children with cerebral palsy
Authors: Rose Jessica , Haskell William L. , Gamble James G. , Hamilton Ronald L. , Brown Daniel A. , Rinsky Larry
Published: February 2005

We performed a histologic and morphometric study of spastic muscle from 10 children with diplegic cerebral palsy, comparing muscle structure with the gait parameters of energy expenditure index and dynamic electromyography. Variations in fiber area within and between fiber types were increased significantly in children with cerebral palsy. In each of the control subjects, the combined coefficient of variation for type‐1 and type‐2 fiber area was less than 25% and the average was 17%; in the subjects with cerebral palsy, the combined coefficient of variation was more than 25% and the average was 36% (p ≤ 0.004). The average difference between the mean area of type‐1 and type‐2 fibers was 26.7 ± 18.9% for subjects with cerebral palsy and 4.2 ± 2.4% for control subjects (p ≤ 0.004). There was a 67% predominance of one fiber type in the subjects with cerebral palsy compared with a 55% predominance in the control subjects (p ≤ 0.03). The difference between the total area of type‐1 and type‐2 fibers was 57% in the subjects with cerebral palsy and 17% in the control subjects (p ≤ 0.002). There was a significant correlation between the combined coefficient of variation of fiber area and the energy expenditure index (r = 0.77, p ≤ 0.03). The difference between the mean area of type‐1 and type‐2 fibers correlated with prolongation of electromyographic activity (r = 0.69, p ≤ 0.05). No abnormalities in fiber ultrastructure were found in the subjects with cerebral palsy. Children with cerebral palsy had abnormal variation in the size of muscle fibers and altered distribution of fiber types. The values for variation in fiber area correlated with the energy expenditure index and with prolongation of electromyographic activity during walking.
Compressive stress‐relaxation behavior of bovine growth plate may be described by the nonlinear biphasic theory
Authors: Cohen Boaz , Chorney Gail S. , Phillips Donna P. , Dick Harold M. , Mow Van C.
Published: February 2005

The compressive behavior of the bovine distal femoral growth plate was studied in vitro. Strain‐rate controlled, compression stress‐relaxation experiments were performed on cylindrical bone‐growth plate‐bone specimens from the interior and periphery of the growth plate. The questions addressed in this study were (a) Can the nonlinear biphasic theory, one with strain‐dependent permeability, be used to represent the compressive stress‐relaxation behavior of bovine growth plate? (b) How do different assumptions concerning the permeabilities of the chondro‐osseous interfaces influence the inferred material properties of the growth plate? and (c) Are there any differences in these properties between the periphery and the interior of the growth plate? Intrinsic biphasic material properties–aggregate modulus (HA), Poisson's ratio (v), and nonlinear strain‐dependent permeability coefficients (ko and M)–were calculated from the compression stress‐relaxation data with use of a finite element model and a least squares curve‐fitting procedure. To verify this constitutive model for the growth plate, an independent set of finite element analyses was performed with use of the determined intrinsic biphasic properties, and comparisons were made between these finite element predictions and two additional sets of experimental data subsequently obtained for the same specimens with use of two slower rates of compression. Excellent agreement was achieved between these finite element predictions and the latter two sets of data. The aggregate modulus was found to be insensitive to the permeability of the chondro‐osseous interface. The permeability coefficients were very sensitive to, and the Poisson's ratio was only slightly sensitive to the interface permeability condition. Therefore, the periphery of the growth plate is more compliant and permeable than the interior.
Substance P‐immunoreactive and protein gene product 9.5‐immunoreactive nerve fibres in bone marrow of rat coccygeal vertebrae
Authors: Imai Shinji , Hukuda Sinsuke , Maeda Toshihiro
Published: February 2005

Previous investigations have focused mainly on the nerve terminals in soft tissues surrounding the vertebrae to determine the source of spinal pain. Our study on rat coccygeal vertebrae compared intramedullary immunostaining for substance P with that of a more generally distributed neural marker, protein gene product 9.5, to suggest another source of spinal pain. Free intramedullary fibres staining for protein gene product 9.5 were rare compared with the abundant staining associated with intramedullary vessels. Shortly after entering the marrow with the nutrient vessels, substance P‐immunoreactive fibres parted from the vessels and then proceeded longitudinally and terminated on the end‐plates. Other (although fewer) substance P‐immunoreactive fibres entered the marrow at enthetic aspects of the vertebrae. The presence of free substance P‐immunoreactive fibres innervating endplates and penetrating entheses suggests that they may represent a novel source of spinal pain.
Superior displacement of the hip in total joint replacement: Effects of prosthetic neck length, neck‐stem angle, and anteversion angle on the moment‐generating capacity of the muscles
Authors: Delp Scott L. , Komattu Abraham V. , Wixson Richard L.
Published: February 2005

The purpose of this study was to determine the effects of superior displacement of the hip center and changes in three prosthetic parameters (neck length, neck‐stem angle, and anteversion angle) on the capacity of muscles to generate force and moment about the hip. A three‐dimensional model that calculates the maximum isometric forces and moments generated by 25 muscles crossing the hip over a wide range of body positions was used to evaluate the effects of a 2 cm elevation of the hip center and changes in the prosthetic parameters. After superior displacement of the hip center, the neck length was increased from 0 to 3 cm, the neck‐stem angle was varied between 110 and 150°, and the anteversion angle was varied between 0 and 40°. Our analysis showed that a 2 cm superior displacement of the hip center would decrease the moment‐generating capacity of the four muscle groups studied (abductors, adductors, flexors, and extensors) if neck length were not increased to compensate for decreased muscle length. In the computer model of an adult man that we used, a 2 cm increase in neck length restored the moment‐generating capacity of the muscles by increasing muscle length and force‐generating capacity. However, a 3 cm increase in neck length increased passive muscle forces substantially, which potentially could limit joint motion. An increased neck‐stem angle (i.e., a valgus neck) decreased the abduction moment arm but increased the moment‐generating capacity of the other muscle groups. A change in the anteversion angle from 0 to 40° had a relatively small effect on the isometric moment‐generating capacity of the muscles studied.
Effects ofcis‐diamminedichloroplatinum II released from d, l‐polyalactic acid implanted adjacent to cortical allografts in dogs
Authors: Straw Rodney C. , Withrow Stephen J. , Douple Evan B. , Brekke John H. , Cooper Mary F. , Schwarz Peter D. , Greco Deborah S. , Powers Barbara E.
Published: February 2005

This study was performed to determine the pharmacokinetics and local and systemic effects ofcis‐diamminedichloroplatinum II (cisplatin) released from an open‐cell polylactic acid polymer when the drug delivery device was placed adjacent to a cortical allograft. Bilateral intercalary femoral allografts were implanted in six normal beagles. The polymer containing cisplatin was implanted adjacent to the allograft in one femur, and the polymer without cisplatin was implanted adjacent to the allograft in the contralateral femur. Systemic toxicity was evaluated clinically by hematologic and serum biochemistry tests and urinalysis. Healing of the allograft was monitored radiographically. The femora were evaluated biomechanically, histologically, and histomorphometrically 7.5 months after surgery. Total serum platinum levels were measured by atomic absorption spectrophotometry, and pharmacokinetic parameters were calculated. Healing was impaired slightly by the presence of the polymer with cisplatin, and systemic and local toxicity was mild and transient. After implantation of the polymer with cisplatin, the mean peak total serum platinum concentration was low (1.71 ± 0.19 μg/ml). However, the area under the curve for total serum platinum concentration versus time for the first 21 days was large (27,050 ± 3,201 μg.min/ml). When cisplatin was given as an intravenous bolus at a dose of 70 mg/m2to six other beagles, the mean peak total platinum concentration was 8.80 ± 2.1 μg/ml and the area under the curve was 940.3 ± 256.7 μg.min/ml. These results indicate that a sustained release of cisplatin can be delivered safely from an open‐cell polylactic acid polymer. This device may be useful in the treatment of solid tumors.
Expression of type‐X collagen in osteoarthritis
Authors: Walker Gordon D. , Fischer Mark , Gannon James , Thompson Roby C. , Oegema Theodore R.
Published: February 2005

The present study was undertaken to examine how osteoarthritis affects the expression of type‐X collagen, a hypertrophic chondrocyte‐specific collagen in articular cartilage. A well characterized sheep polyclonal antiserum, as well as three mouse monoclonal antibodies against canine type‐X collagen, was used to immunolocalize type‐X collagen in human and canine joints. Its expression in osteoarthritic cartilage was altered in several locations. In the canine osteoarthritic joints, type‐X collagen increased in and just above the zone of calcified cartilage and was present diffusely throughout the calcified matrix. In both the human and canine cartilage, type‐X collagen was localized around cell clones in the transitional zone of cartilage. This is surprising, since that region of the cartilage does not calcify and one of the proposed roles of type‐X collagen is in mineralization. Thus, the osteoarthritic process may damage the matrix in the superficial layer and induce changes leading to the expression of the hypertrophic chondrocyte phenotype.
Lysyl oxidase and Maillard reaction‐mediated crosslinks in aging and osteoarthritic rabbit cartilage
Authors: Pokharna Hemlata K. , Monnier Vincent , Boja Betty , Moskowitz Roland W.
Published: February 2005

Alterations in the integrity of the extracellular matrix play an important role in osteoarthritis. Matrix crosslinks in articular cartilage of the knee were studied in partially meniscectomized rabbits to compare changes due to osteoarthritis with those occurring during aging. Pyridinoline, a lysyl oxidase‐initiated crosslink, and pentosidine, a crosslink formed by the Maillard/glycation reaction, were assayed separately on reverse‐phase high performance liquid chromatography. A significant increase in the percentage of insoluble collagen was observed in normal 12‐month‐old rabbits compared with the levels in 3‐month‐old animals, whereas osteoarthritis was associated with a shift toward more soluble fractions. Total pyridinoline content did not change with age or osteoarthritis. Total pentosidine, however, increased significantly with age but remained constant with osteoarthritis. Analysis of the distribution of crosslinks among solubility fractions indicated a significant shift of pyridinoline from the pepsin‐released fraction to the insoluble fraction with osteoarthritis, but no changes were observed with age. Pentosidine distribution shifted toward the pepsin‐released fraction in osteoarthritis, with a shift toward the insoluble fraction with age. Because of the low levels of pentosidine present, its precise location, whether collagenous or noncollagenous, remains unclear. However, since pentosidine represents a marker for the overall Maillard reaction, the results of our studies support a role for Maillard reaction products in the aging of extracellular matrix. The shift of pentosidine toward more soluble fractions suggests the presence of matrix degradation and repair in osteoarthritis.
Diminished material properties and altered bone structure in rat femora during pregnancy
Authors: Leopold Seth S. , Boskey Adele L. , Doty Stephen B. , Gertner Joseph M. , Peterson Margaret G. E. , Torzilli Peter A.
Published: February 2005

Pregnancy and lactation are known to cause structural and mechanical changes in bone, but the effects of pregnancy alone have not been evaluated thoroughly. This study used radiographic measurements, torsion testing, mineral analyses, and histological evaluation to determine whether there are changes in bone material and geometric properties during pregnancy in the growing rat, as implied by earlier biochemical and histological studies. The bones of pregnant 9 to 12‐week‐old rats and controls that were not pregnant and were matched by age (but not weight) were evaluated at times corresponding to 5, 10, 15 and 20 days of the 23‐day gestation period to address the following questions: (a) How is the growth of whole bone affected by pregnancy in the growing rat (as determined by radiographic analyses)? (b) How are the mechanical properties (structural and material) of whole bone affected by pregnancy (as assessed by torsion testing)? (c) Are there changes in the characteristics of bone mineral during pregnancy (as determined by measurement of mineral content and x‐ray diffraction analyses)? and (d) Are there detectable morphological or ultrastructural differences between the bones of pregnant and control rats (as assessed by analyses based on histology and back‐scattered electron imaging)? The presence of statistically significant differences in this study was determined initially on the basis of a two‐factor analysis of variance. In general, significant differences were noted only at late gestation (day 20), when the bones were longer and had a greater outer radius and cortical thickness; this indicates that more growth occurred during pregnancy. At day 20, biomechanical testing showed that the femora of pregnant rats had a 20% decrease in rotational angle to failure and a 30% increase in shear stiffness. No alterations in maximum torque or energy to failure were noted. Calculation of the properties of bone material revealed a 54% decrease in ultimate shear stress, a 50% decrease in shear modulus, and no alteration in shear strain when the bones from rats pregnant for 20 days were compared with controls. The bones of the pregnant rats at day 20 also differed from controls in terms of both mineral characteristics and morphology. X‐ray diffraction showed larger mineral crystallites in the specimens from pregnant rats as compared with controls, whereas the mineral contents (ash weights) were similar. Scanning electron microscopy revealed qualitative differences, including increased periosteal vascularity and numerous large cortical cavities thought to be areas of resorption in the bones from rats pregnant for 20 days as contrasted with controls. These changes are consistent with the observed alteration in mechanical properties.
Platelet‐derived growth factor in fibrous musculoskeletal disorders: A study of pathologic tissue sections and in vitro primary cell cultures
Authors: Alman Benjamin A. , Naber Stephen P. , Terek Rick M. , Jiranek William A. , Goldberg Michael J. , Wolfe Hubert J.
Published: February 2005

Despite the great variability in the clinical behavior of fibrous lesions of the musculoskeletal system, they are composed of cytologically similar fibrocytes. Receptors for estrogen or progesterone, or both, are present in some of these lesions and some increase their rate of growth during periods of high levels of sex steroid hormones. The platelet‐derived growth factor‐B (PDGF‐B) proto‐oncogene encodes the B chain of PDGF, a mitogen for fibrocytes. Tissue from aggressive fibromatosis, fibrous dysplasia, plantar fibromatosis, and recurrent plantar fibromatosis was analyzed with use of the polymerase chain reaction and in situ hybridization for the expression of PDGF‐B and PDGF beta receptor. Cell culture was used to determine if estrogen and progesterone stimulation modulated the expression of PDGF‐B. Aggressive fibromatosis, fibrous dysplasia, and recurrent plantar fibromatosis expressed PDGF‐B; plantar fibromatosis, normal plantar fascia, normal fascia lata, and mature scar did not. All of the tissues expressed PDGF beta receptor. The level of expression in aggressive fibromatosis and fibrous dysplasia was four times that in the recurrent plantar fibromatosis. Estrogen and progesterone stimulation in aggressive fibromatosis resulted in an increase in the level of expression. Therefore, the detection of PDGF‐B may be an adjunct in the pathologic identification of locally invasive lesions. Its production may be a common mechanism leading to a fibroproliferative response through deregulation of the control of growth by both paracrine and autocrine mechanisms.
Comparison of healing of allograft/endoprosthetic composites with three types of gluteus medius attachment
Authors: Markel Mark D. , Wood Suzanne A. , Bogdanske John J. , Rapoff Andrew J. , Kalscheur Vicki L. , Bouvy Bernard M. , Rock Michael G. , Chao Edmund Y. S. , Vanderby Ray
Published: February 2005

This study compared three methods of gluteus medius tendon attachment to an allograft/endoprosthetic composite of the proximal 25% of the femur in a canine model. The three methods were bone to bone, tendon tobone, and tendon to tendon attachment. In anin vivostudy, 24 dogs were assigned to three groups of eight dogs each, and serial radiography and weight‐bearing analyses were performed throughout the study. The dogs were killed at 6 months, and the specimens were tested in tension to failure and were analyzed histologically. In anin vitrostudy, each repair was done on six limbs, with a contralateral limb serving as a control for each. In these specimens, the bone to bone attachments were significantly stronger (99.1% of the controls) than the tendon to bone attachments (71.8% of the controls) and the tendon to tendon attachments (40.0% of the controls); there were no differences in tensile stiffness among the three types of attachment. By 6 months, the tensile strength of the tendon to tendon attachments increased significantly and that of the tendon to bone attachments decreased significantly. There were no significant differences in tensile strength among the three types of attachment. The tensile stiffness of the bone to bone attachments (91.0% of the controls) was significantly greater than that of the tendon to bone attachments (40.8% of the controls) but not significantly different from that of the tendon to tendon attachments (63.2% of the controls). The bone to bone attachment was associated with increased bone resorption, bone remodeling, and bone porosity, accompanied by thinner allograft cortices, when compared with the other types of attachment. In dogs with a bone to bone attachment, weight‐bearing increased more slowly than in dogs with either of the other two attachments. These changes associated with the bone to bone attachment may merely be secondary to healing of the bone to bone attachment to the greater trochanter; therefore, they may only be temporary phenomena or they may be the portents for long‐term complications. Longer term studies of at least 1–2 years must be performed before these questions can be answered.
Growth of severed flexor tendons in chickens
Authors: Nishijima Naoki , Fujio Keiji , Yamamuro Takao
Published: February 2005

To examine tendon growth in both the distal and proximal portions of severed tendons, we investigated the growth of severed flexor tendons within the fibro‐osseous tunnel in young chickens. When the tendon was severed at the proximal site in the sole, dynamic tension applied by the muscle was lost. Growth in the distal tendon was retarded considerably, although passive tension initially was maintained through the residual vincula and later by adhesion to the chiasma of adjacent flexors. When the tendon was severed at the insertion, passive tension from the extensors was lost. Proximal tendon growth continued if active tension was maintained through the residual vincula. If not, the tendon was markedly shortened and degenerated. Maintaining normal tension may be the most important factor in longitudinal tendon growth.
Integrin display increases in the wounded rabbit medial collateral ligament but not the wounded anterior cruciate ligament
Authors: Schreck Paul J. , Kitabayashi Linda R. , Amiel David , Akeson Wayne H. , Woods Virgil L.
Published: February 2005

The differential capacities of the anterior cruciate and medial collateral ligaments to heal may be related to differences in cellular function. This study tested the hypothesis that differential expression of integrins occurs in these ligaments after injury. The integrins are a family of cell surface receptors that mediate adhesion, migration, and other cellular functions critical to the healing of a wound. A similar complement and amount of the β1 subfamily of integrins are known to be present on the unperturbed anterior cruciate and medial collateral ligaments in humans and rabbits. A partial laceration was surgically created in these two ligaments in 12 anesthetized New Zealand White rabbits. Immunohistochemistry was performed on sections from the ligaments at 1, 3, 7, and 10 days after injury, using monoclonal antibodies directed against the integrin subunits β1, α5, α6, and αv. Between 3 and 7 days, the wounded medial collateral ligament demonstrated a striking increase in staining for the β1, α5, and αv subunits on the fibroblasts, within the repair site, and on capillary endothelium. Increased staining was most marked for the β1 subunit and less marked for the α5 and αv subunits. The α6 subunit stained exclusively vascular structures within the healing medial collateral ligament. In marked contrast, the anterior cruciate ligament, which does not mount an effective repair response, demonstrated no comparable alteration of integrin expression from baseline levels. This study demonstrates that increased expression of integrins occurs coincident with wound healing in the medial collateral ligament, whereas this expression remains at baseline levels in the nonhealing wounded anterior cruciate ligament. This observation suggests that a failure to alter expression of integrins subsequent to injury may play a role in the defective healing of the anterior cruciate ligament.
Serum fractions and related agonists with calcium‐mobilizing activity in the bovine growth plate chondrocyte
Authors: Bulman W. A. , Iannotti J. P. , Glowacki K. , Bleuit J. , Clark C. C.
Published: February 2005

Longitudinal growth of bone involves a complex sequence of cellular events in the cartilaginous epiphysis. Whole blood serum has been shown previously to be a potent stimulus to the cells of the growth plate, as demonstrated by its ability to activate the inositol phosphate‐calcium second messenger system resulting in a rise in intracellular Ca2+. By manipulating the preparation of serum to functionally separate it into its constituent parts, we have shown that the processes of platelet lysis and activation of the clotting cascade are responsible for the generation of factors that stimulate this signaling mechanism in isolated bovine growth plate chondrocytes. Through a subsequent trial of bioactive agents generated in these processes, we identified and partially characterized several novel agonists of growth plate chondrocytes: adenosine triphosphate and adenosine diphosphate, the purine energy substrates, and bradykinin, the bioactive peptide generated in a side reaction of the clotting cascade, each induces a rise in intracellular Ca2+ via release from intracellular ion stores. Additionally, the three distinct isoforms of platelet‐derived growth factor (AA, AB and BB), also released on platelet lysis, were compared with respect to their ability to stimulate the inositol phosphate‐calcium second messenger system in growth plate chondrocytes.
Immunolocalization and expression of bone morphogenetic proteins 2 and 4 in fracture healing
Authors: Bostrom Mathias P. G. , Lane Joseph M. , Berberian Wayne S. , Missri Albert A. E. , Tomin Emre , Weiland Andrew , Doty Stephen B. , Glaser David , Rosen Vicki M.
Published: February 2005

Recently, it has become increasingly evident that fracture healing involves a complex interaction of many local and systemic regulatory factors. The roles of some of these growth factors have been described; however, little is understood about the presence of the bone morphogenetic proteins in fracture repair, despite the fact that they are the most potent osteoinductive proteins known. This study defines and characterizes the physiologic presence, localization, and chronology of the bone morphogenetic proteins in fracture healing with an established rat fracture healing model. With use of a recently developed monoclonal antibody against bone morphogenetic proteins 2 and 4 developed with standard avidin‐biotin complex/immunoperoxidase protocols, frozen undecalcified fracture calluses were analyzed semiquantitatively for the percentage of various types of fracture cells staining positively. During the early stages of fracture healing, only a minimum number of primitive cells stained positively in the fracture callus. As the process of endochondral ossification proceeded, the presence of bone morphogenetic proteins 2 and 4 increased dramatically, especially in the primitive mesenchymal and chondrocytic cells. While the cartilaginous component of the callus matured with a concomitant decrease in the number of primitive cells, there was a concomitant decrease in both the intensity and the number of positively staining cells. As osteoblasts started to lay down woven bone on the chondroid matrix, these osteoblastic cells exhibited strong positive staining. The intensity of this staining decreased, however, as lamellar bone replaced the primitive woven bone. A similar observation was noted for the areas of the callus undergoing intramembranous ossification. Initially, within several days after the fracture, periosteal cells and osteoblasts exhibited intense staining for bone morphogenetic proteins 2 and 4. As the woven bone was replaced with mature lamellar bone, this staining decreased. These data, and the awareness of the strong osteoinductive capacities of bone morphogenetic protein, suggest that bone morphogenetic proteins 2 and 4 are important regulators of cell differentiation during fracture repair.
Healing of the medial collateral ligament after a combined medial collateral and anterior cruciate ligament injury and reconstruction of the anterior cruciate ligament: Comparison of repair and nonrepair of medial collateral ligament tears in rabbits
Authors: Ohno Kazunori , Pomaybo Amy S. , Schmidt Christopher C. , Levine Rebecca E. , Ohland Karen J. , Woo Savio L‐Y.
Published: February 2005

The optimal treatment for a combined injury of the medial collateral and anterior cruciate ligaments is controversial, and the question remains as to whether repair of the medial collateral ligament and reconstruction of the anterior cruciate ligament improves healing of the medial collateral ligament. We compared reconstruction of the anterior cruciate ligament with and without repair of the medial collateral ligament in a rabbit model of a combined injury of these two ligaments. The anterior‐posterior translation and varus‐valgus rotation of the knee, the structural properties of the femur‐medial collateral ligament‐tibia complex, and the mechanical properties of the midsubstance of the medial collateral ligament were evaluated immediately after surgery and at 6 and 12 weeks postoperatively. Repair of the medial collateral ligament led to significantly less varus‐valgus rotation of the knee than did no repair, but the anterior‐posterior translation of the knees in the repair and nonrepair groups were not significantly different at any study time. At 12 weeks, the cross‐sectional area and ultimate load in the repair group were 60 and 53% greater, respectively, than in the nonrepair group. Among 12 specimens that were repaired (six specimens at 6 weeks and six specimens at 12 weeks), failure occurred within the midsubstance in four (two at each time period); in all of the specimens that were not repaired, failure occurred at the tibial insertion site. There was no significant difference between the modulus of the midsubstance in the repaired and the nonrepaired medial collateral ligaments. Thus, the improved structural properties of the femur‐medial collateral ligament‐tibia complexes that were repaired resulted from an increase in cross‐sectional area of the repaired medial collateral ligament and healing of the tibial insertion site. Postoperative healing time had little effect on the tensile properties. In this rabbit model, repair of the medial collateral ligament with reconstruction of the anterior cruciate ligament may lead to better healing of the medial collateral ligament in the early phase than does reconstruction of the anterior cruciate ligament alone.
Contact areas in the thumb carpometacarpal joint
Authors: Ateshian Gerard A. , Ark Jon W. , Rosenwasser Melvin P. , Pawluk Robert J. , Soslowsky Louis J. , Mow Van C.
Published: February 2005

The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar‐ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint. These contact areas were assessed relative to the observed sites of cartilage thinning. Eight hands from cadavers of women and five from cadavers of men were tested in vitro with the thumb under a 25 N load in the lateral pinch position, and under small muscle loads (0–5 N) with the thumb in flexion, extension, abduction, adduction, and neutral positions. Contact areas of articular surfaces of the thumb carpometacarpal joint were determined for these positions using a stereophotogrammetric technique. The lateral pinch position produced contact areas predominantly on the central, volar, and volar‐ulnar regions of the trapezium and the metacarpal. In three specimens, contact areas were distinctly separated between the dorsoradial and volar‐ulnar regions, and in one specimen, from a man, contact occurred exclusively on the dorsoradial region of the trapezium. Using stereophotogrammetry, maps of cartilage thickness also were determined for a subset of nine specimens. The volar‐ulnar, ulnar, and dorsoradial regions of the trapezium were the most common sites of thin cartilage, and these may be sites of cartilage wear. The results of this study indicate that the lateral pinch position produced stresses in the same regions where cartilage thinning was observed; this lends support to the hypothesis that high stresses can lead to osteoarthritis in this joint.
Autogenous intrasynovial and extrasynovial tendon grafts: An experimental study of pro α1(I) collagen mRNA expression in dogs
Authors: Amiel David , Harwood Frederick L. , Gelberman Richard H. , Chu Constance R. , Seiler John G. , Abrahamsson Sven
Published: February 2005

On the basis of recent evidence that the healing processes of tendon grafts are donor‐tissue specific, in situ hybridization, using a 372 bp cDNA fragment complementary to a portion of pro α1(I) collagen mRNA, was utilized to compare the cellular responses to transplantation exhibited by autogenous intrasynovial and extrasynovial flexor tendon grafts. Intrasynovial and extrasynovial tendons from the hindpaw were transferred to synovial sheaths in the forepaw of 12 mongrel dogs (24 tendons) and treated with immediate controlled passive motion. The tendon grafts were harvested at 2, 4, and 6 weeks, and each was divided into a proximal, central (8 mm), and distal portion. Sections from the central portion were embedded in paraffin and subjected to in situ hybridization, autoradiography, and staining; levels of procollagen mRNA then were assessed by microscopic examination. The two types of tendon grafts exhibited different levels of pro α1(I) collagen mRNA expression at all three time points. Intrasynovial tendon grafts displayed no areas of increased type‐I procollagen mRNA at 2, 4, and 6 weeks. The extrasynovial tendon grafts displayed increased surface levels of type‐I procollagen mRNA at 2 and 4 weeks; the levels decreased to background levels by 6 weeks. The high levels of procollagen mRNA exhibited by the extrasynovial grafts suggest increased collagen synthetic activity, indicative of a cellular response to injury, whereas the preservation of low levels of expression in the intrasynovial grafts may signify a less inflammatory cellular response.
Three‐dimensional anatomy of the cancellous structures within the proximal femur from computed tomography data
Authors: Elke Reinhard P. E. , Cheal Edward J. , Simmons Craig , Poss Robert
Published: February 2005

Quantitative computed tomography was used to investigate the three‐dimensional architecture and the density distribution of the cancellous structures of the proximal femur. We examined 10 femora from the cadavera of 10 individuals, 47‐83 years old at the time of death. Three anatomic elements could be distinguished: the epiphysis, the epiphyseal scar, and the metaphysis. Although these elements constitute a functional unit, their individual cancellous patterns revealed significant structural differences. The epiphyseal segment had a more reticulate cancellous appearance, whereas the metaphysis demonstrated a more longitudinally oriented trabecular distribution. The three‐dimensional reconstruction of the densest epiphyseal trabecular groups showed two different patterns: a dumbbell type (found in eight bones) and a hemispheric type (found in two bones). The epiphyseal scar was a clearly recognizable high‐density structure found in all 10 bones. The epipyseal scar‐diaphysis angle was 13–26° higher than the center column‐diaphysis angle. The scar appeared as a tray supporting the epiphyseal cancellous structures, supported itself by the metaphyseal intersection of the main compressive and the arcuate trabecular systems. This intersection always occurred in a relatively small band‐shaped zone under the central third of the epiphyseal scar. These three discrete anatomical segments within the proximal femur may reflect developmental and functional adaptations determined by joint incongruity or eccentric muscular activity. The present data will serve as a reference for future studies in which the cancellous patterns are used to help with the early diagnosis of states of disease.
Comparison of the electrical and dielectric behavior of wet human cortical and cancellous bone tissue from the distal tibia
Authors: Saha Subrata , Williams Paul Allen
Published: February 2005

We compared the electrical and dielectric properties of wet human cortical and cancellous bone tissue from the distal tibia. The relationships between the electrical and dielectric behavior of cortical and cancellous bone and variables of measurement such as frequency and direction (orientation) were evaluated. In general, the resistivity of human cortical bone was found to be approximately 3.1 times more than that of cancellous bone in the longitudinal direction and least 25 times more in the transverse directions. The dielectric permittivity of human cortical bone was approximately 3.9 times that of cancellous bone in the longitudinal direction, whereas in the transverse directions it was about 0.65 times greater. Measurement variables such as frequency and orientation appeared to affect cancellous and cortical bone differently. Strong correlations were found between the electrical properties in one direction and the electrical properties in the other two directions; however, these relationships differed for the samples of cortical and cancellous bone.
Comparison of residual stability in thoracolumbar spine fractures using neutral zone measurements
Authors: Ching Randal P. , Tencer Allan F. , Anderson Paul A. , Daly Colin H.
Published: February 2005

Because treatment algorithms for spinal injuries depend largely on the clinical assessment of stability after injury, this study both quantified and compared the mechanical stability after three different patterns of injury in the thoracolumbar spine. We created compression fractures, burst fractures, and flexion‐distraction injuries in 26 thoracolumbar specimens from human cadavers in order to compare residual stability as a function of type of injury. Spinal stability was evaluated using measurements of the boundaries of the neutral zone, which provide a measure of spinal laxity in various directions of motion. An increase after injury was indicative of greater spinal laxity and hence reduced residual stability. Geometric characteristics (or parameters) of the neutral zone boundaries were used for statistical comparison between the types of injury. Of the three groups, burst fractures retained the least residual stability and compression fractures, the greatest. The angular ranges of motion in the neutral zone for burst fractures demonstrated increases (compared with average values for intact specimens) of 154% in flexion‐extension. 134% in lateral bending, and 108% in torsion after injury. The results for flexion‐distraction injuries were similar to those for burst fractures in flexion‐extension (126%) and torsion (62%); however, more residual stability was retained in lateral bending than was seen for burst fractures (48%). Compression fractures retained the most residual stability, with increases in motion of 40% in flexion‐extension, 56% in lateral bending, and 3% in torsion. These findings may be useful in determining the necessity for surgical stabilization of the spine and selection of the appropriate system of fixation.