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PubMed1998

Anatomy and histological characteristics of the spinoglenoid ligament.

The spinoglenoid (inferior transverse scapular) ligament, when present, is located at the spinoglenoid notch. The ligament originates on the spine of the scapula and inserts on the superior margin of the glenoid neck. Because of discrepancies in the literature, we sought to determine its prevalence and to define its histological characteristics. We dissected 112 shoulders of seventy-six cadavera and classified the ligament as absent or an insubstantial structure, a thin fibrous band (type I), or a distinct ligament (type II). We found no distinct ligamentous structure in twenty-two shoulders (20 percent), a type-I ligament in sixty-eight shoulders (61 percent), and a type-II ligament in twenty-two shoulders (20 percent). Overall, ninety (80 percent) of the shoulders had a fibrous band of tissue that, together with the spine of the scapula, formed a narrow fibro-osseous tunnel through which the suprascapular nerve traveled. The bone-spinoglenoid ligament-bone complexes from three specimens were analyzed histologically. There were two type-I ligaments and one type-II ligament; all three ligaments were composed of collagen fibers. One type-I ligament and the type-II ligament demonstrated Sharpey fibers at their origin on the spine of the scapula. The other type-I ligament attached to the spine of the scapula through the periosteum. All three ligaments inserted into the periosteum of the glenoid neck.

Adolescent↗
PubMed1993

Volar carpal ligaments of the wrist: normal appearance on multiplanar reconstructions of three-dimensional Fourier transform MR imaging.

OBJECTIVE: Three-dimensional Fourier transform MR imaging techniques can produce much thinner contiguous slices than are obtainable with standard two-dimensional Fourier transform MR imaging techniques. The improved spatial resolution and capabilities for interactive multiplanar displays allow better visualization of small, complex anatomic structures, such as the carpal ligaments. The purposes of this study were twofold: (1) to determine if the volar carpal ligaments can be consistently visualized when using three-dimensional Fourier transform MR imaging techniques with multiplanar reconstructions and (2) to evaluate the size, shape, orientation, and right-to-left symmetry of the volar carpal ligaments in both wrists of 25 asymptomatic volunteers as a basis for future comparison when patients with suspected ligament injuries are seen. SUBJECTS AND METHODS: Both wrists of 25 asymptomatic volunteers were imaged with a three-dimensional Fourier transform MR imaging technique with commercially available equipment. A three-dimensional graphic workstation was used to reconstruct oblique two-dimensional images in the long axes of the major volar carpal ligaments. The size, shape, orientation, and right-to-left symmetry of the ligaments were determined from the reconstructed two-dimensional images. RESULTS: Six of the eight volar ligaments were visualized in more than 95% of the 50 wrists: the radioscaphocapitate, radiolunotriquetral, radiolunate, ulnolunate, ulnotriquetral, and triquetroscaphoid ligaments. The radioscaphoid and radioscapholunate ligaments were less well defined and were recognizable as ligaments in only 66% and 26% of wrists, respectively. CONCLUSION: The major volar carpal ligaments can be visualized consistently with three-dimensional Fourier transform MR imaging techniques and multiplanar reconstructions. The volar carpal ligaments are usually symmetric between the right and left sides; therefore, MR images of a patient's injured wrist can be compared with MR images of the contralateral wrist. The size and shape of the volar carpal ligaments shown in this article can be used as a basis for comparison when patients with suspected ligamentous injuries are examined. This information will be useful for detecting ligamentous injuries on MR images.

Adult↗
PubMed1991

Magnetic resonance imaging of the transverse atlantal ligament for the evaluation of atlantoaxial instability.

Twenty normal human subjects and 14 patients with upper cervical spine pathology were studied with axial high-field magnetic resonance (MR) imaging to examine the transverse atlantal ligament. Gradient-echo MR imaging pulse sequences provided reliable visualization of the transverse ligament, which exhibited low signal intensity and extended behind the dens between the medial portions of the lateral masses of C-1. The MR imaging characteristics of the transverse ligament were verified in clinical studies and in postmortem specimens. The clinical MR examinations defined 27 normal ligaments, three ligament disruptions, and four stretched rheumatoid ligaments. Atlantoaxial instability associated with transverse ligament rupture or ligamentous laxity required internal fixation. In contrast, fractures of C-1 or C-2 or atlantoaxial rotatory dislocations associated with an intact transverse ligament healed without instability or nonunion. The transverse ligament is the primary stabilizing component of C-1. The treatment of atlantoaxial instability has previously been based on criteria drawn from computerized tomography or plain radiographic studies, which only indirectly assess the probability of rupture of the transverse ligament. It is concluded that MR imaging accurately depicts the anatomical integrity of the transverse ligament. After transverse ligament failure, the remaining ligaments of the craniovertebral junction are inadequate to maintain stability. The presence of ligament disruption should be considered as a criterion for early fusion.

Arthritis, Rheumatoid↗
PubMed2003

Scanning electron microscopic characterization of healing and normal rat ligament microstructure under slack and loaded conditions.

The objective of this study was to observe and compare behavior of the collagen fiber microstructure in normal and healing ligaments, both in situ and ex vivo, in order to add insight into the structure-function relationship in normal and healing ligaments. Fifty-two ligaments from 26 male rats were investigated. Eleven animals underwent surgical transection of both medial collateral ligaments (MCLs) (22 ligaments), which were allowed to heal for a period of 2 weeks. An additional 15 animals (30 ligaments) were used as normals. Ligaments were placed into six groups: Slack (n = 6 control, n = 6 healing), Reference (n = 4 control, n = 4 healing), Loaded (n = 4 control, n = 4 healing), 15 degrees Flexion (n = 4 control, n = 4 healing), 120 degrees Flexion (n = 4 control, n = 4 healing), and Tissue Strain vs. Flexion Angle (n = 8 normals). All ligaments, except those in the Tissue Strain vs. Flexion Angle group, were prepared for scanning electron microscopy. Tissues were harvested, mounted in a load frame, and chemically fixed in one of five states: (1). slack, (2). reference (onset of loading), (3). loaded, (4). 15 degrees knee flexion, or (5). 120 degrees knee flexion. After fixation the tissues were prepared for electron microscopy (SEM). The micrographs from the slack, reference, and loaded groups show fiber straightening with loading in normal ligaments as well as in both scar and "retracted" regions of healing ligaments. Collagen fibers' diameter and crimp patterns were dramatically changed in the scar region of healing ligaments: Width decreased from 19.4 +/- 1.7 microm to 6.5 +/- 2.1 microm (p <.000001), period from 51.4 +/- 15.1 microm to 11.0 +/- 2.4 microm (p <.000001), and amplitude from 9.8 +/- 0.8 microm to 3.9 +/- 0.8 microm (p <.000001). Normal ligaments fixed in situ show wavy regions at 120 degrees but less so at 15 degrees flexion. Healing ligaments fixed in situ show regions of fiber waviness in the scar region at 120 degrees and also at 15 degrees flexion, indicating ligament laxity persists toward both extremes of the range of motion. The data suggest that straightening of crimped fibers is a functionally relevant phenomenon, not only in normal but also in healing ligaments.

Animals↗
PubMedDate not supplied

Surgical anatomy of the inferior vena cava ligament.

BACKGROUND/AIMS: The inferior vena cava ligament is a fibrous membrane located around the inferior vena cava. Few reports exist on the ligament's location, attachment to the liver, or the inferior vena cava. METHODOLOGY: We obtained 16 specimens of human liver and inferior vena cava from cadavers. The inferior vena cava ligament was photographed and then dissected for histological examination. Relationships among the ligament, inferior vena cava, and liver were examined microscopically. The numbers and diameters of veins, arteries, and lymph vessels at least 1 mm in diameter were recorded. RESULTS: The cranial margin of the inferior vena cava ligament was ended in a blind loop. The cranial portion above the mid-portion of the Spiegel lobe was thicker than the caudal portion. The ligament was attached to the right and left hepatic veins. The mean length of the right side of the inferior vena cava ligament was 37.0 mm and the mean width 15.6 mm. The inferior vena cava ligament had a mean thickness of 0.8 mm (thin end) and 2.5 mm (thick end). Although the inferior vena cava ligament was usually tightly continuous with the liver capsule, microscopically the attachment between the ligament and the inferior vena cava was loose. The mean number and diameter of veins in the inferior vena cava ligament was 1.0 and 1.4 mm, respectively. The mean number and diameter of arteries was 0.2 and 2.4 mm, respectively. The mean number and diameter of lymphatic vessels was 2.8 and 1.7 mm, respectively. CONCLUSIONS: After dissection of the inferior vena cava ligament, major hepatic veins can be dissected extrahepatically. Because the ligament is wider caudally, the forceps should be inserted caudocranially during separation. Since both the number and diameters of lymphatic vessels in the ligament are large, the ligament should be ligated and cut.

Aged↗
PubMed2006

[An anatomical study on lateral ligaments of rectum].

OBJECTIVE: To identify the location and contents of the rectal lateral ligaments and its relationship with the middle rectal artery and pelvic plexus. METHODS: Twenty-nine pelvics of human cadavers were sagittally sectioned into 58 hemipelvic specimens. All of hemipelvics were dissected with sharp technique under direct vision by one surgeon. The lateral ligaments were identified and the distances from the center of its pelvic attachment to sacral promontory and coccyx were measured. Then, the lateral ligaments were transected for histologic examination. RESULTS: Lateral ligaments of rectum were found in all 58 hemipelvics. The lateral ligaments connected the posterolateral aspect of the middle 1/3 of the rectum and mesorectum to the lateral aspect of the bodies of the second, third and fourth sacral vertebrae. The distance from the lateral ligament to sacral promontory was (8.3 +/- 1.6) cm on the right side and (8.4 +/- 1.4) cm on left side. The width of lateral ligaments was (3.2 +/- 0.4) cm on the right side and (3.1 +/- 0.4) cm on the left side. The distances from lateral ligament to the coccyx on the right and left sides were (5.2 +/- 1.4) cm and (5.0 +/- 1.3) cm respectively. The content of the lateral ligaments consisted of loose connective tissue with clusters of small nerves and blood vessels. Middle rectal artery was found in 83% (48/58) of hemipelvics and 47% (27/58) of the middle rectal artery went through the lateral ligaments. The inferior hypogastric nerve plexuses were formed inside the lateral ligament, and separated the ligament into two parts. The lateral segment of the lateral ligament contained the tributaries of internal iliac artery, and the medial segment contained nerve fibers or branches to the rectum, together with the middle rectal artery. CONCLUSION: The lateral ligaments of rectum are located on the posterolateral side of the rectum, much closer to the coccyx than to the sacral promontory, consisting of connective tissue containing multiple small nerves and middle rectal artery. The lateral ligament is a pathway of blood vessels and nerve fibers toward the rectum and lymphatic vessels from the lower rectum toward the iliac lymph nodes.

Adult↗
PubMed1985

Correlative biomechanical and histologic study of the cranial cruciate ligament in dogs.

The mechanical properties of the cranial cruciate ligament were determined, using unilateral bone-ligament-bone preparations from 65 dogs of various ages and body sizes. Tensile loading of the cranial cruciate ligament from 1 of each pair of stifle joints demonstrated a decrease in material properties (modulus, maximum stress, strain energy) with aging. The decreases in maximum stress and strain energy with age were significantly less (P less than 0.05 and P less than 0.05, respectively) in the cranial cruciate ligament from dogs weighing less than 15 kg, compared with those weighing 15 kg or more. The cranial cruciate ligament and remaining femorotibial ligaments were collected from the opposite stifle joints and examined microscopically. By 5 years of age, the cranial cruciate ligaments of dogs weighing greater than 15 kg consistently had microscopic evidence of degenerative disease (loss of ligamentocytes, metaplasia of surviving ligamentocytes to chondrocytes, and failure to maintain collagen fibers and primary collagen bundles) which progressed in severity with age. The caudal cruciate ligaments were similarly affected, although the degenerative changes were rarely as severe as in the cranial cruciate ligament. The collateral ligaments underwent minimal degeneration. Sex differences had no bearing on degeneration. The cranial cruciate ligaments in dogs weighing less than 15 kg generally had less severe alterations than those in heavier dogs, and the onset of the degenerative process was delayed by several years. Cranial cruciate ligaments removed from dogs after ligament failure not only had degenerative disease, but also had undergone unsuccessful attempts at repair. In contrast, fibrous repair was rarely present in intact ligaments of asymptomatic dogs with degenerative disease of the cranial cruciate ligament.

Age Factors↗
PubMedDate not supplied

Effect of intra-articular corticosteroids on ligament properties: a biomechanical and histological study in rhesus knees.

The effect of intra-articular corticosteroid injections (methylprednisolone acetate) on the mechanical properties of anterior cruciate bone-ligament-bone units was determined. Fifty-one wild rhesus animals provided 88 knee ligaments units that were loaded in tension to failure under fast strain-rate conditions. Alterations in ligament strength and load-elongation properties were found to depend upon corticosteroid dosage and time after injection. Fifteen weeks after the higher drug dosage (methylprednisolone acetate, 6 mg/kg; three injections, spaced weekly) significant decreases occurred in the maximum failure load (20%), energy absorption prior to failure (11%) and linear stiffness (11%) of the ligament unit. In contrast, only minimal non-significant alterations in ligament strength properties occurred at the higher drug usage after 6 weeks in a second group of animals. this strong time-dependence may partially explain the negative findings reported in short term studies. The higher drug dosage used is approximately 10 times an equivalent human dose on a body mass basis and indicates the ability of this class of drugs to significantly alter the mechanical properties of a ligament unity. A third group of animals received a total of two intra-articular coticosteroid injections (single injections spaced two weeks apart) at a dosage (0.6 mg/kg) equivalent to that commonly used clinically in humans. Statistically significant decreases occurred in maximum failure load (9%) and energy absorption (8%); however, this change is believed of little importance to the projected functional capacity of the ligament unit. No detectable systemic effect of the intra-articular corticosteroid injections was found on the mechanical properties of the ligament unit in the extremity opposite to that which received the drug injection. Histological examination after failure showed normal cellularity and staining characteristics of the ligament, fibrocartilage junction and underlying bone. No bone resorptive changes were observed beneath the ligament insertion site. Failure by a ligamentous mode remained the most common mechanism of specimen failure. Scanning Electron Microscopy showed failure of collagen fibers at multiple levels throughout the ligament indicative of a serial pull-apart failure process. A rich supply of vessels to the anterior cruciate ligament was demonstrated and failure of the vessels occured by a necking down process. Insofar as the results apply to humans, they infer the potential for high and frequent doses of intra-articular slightly soluble corticosteroids to produce alterations in ligament strength and function. A single intra-articular injection or one repeated at intervals of several months probably carries little risk to ligament properties.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Role of the medial structures in the intact and anterior cruciate ligament-deficient knee. Limits of motion in the human knee.

We measured motion limits in human cadaveric knees before and after sectioning the anterior cruciate ligament and the medial structures. Sectioning the medial collateral ligament in an anterior cruciate ligament-deficient knee increased the anterior translation limit at 90 degrees of flexion but not at 30 degrees of flexion. The tibia displaced straight anteriorly without exhibiting the coupled internal rotation that occurred in intact and anterior cruciate ligament-deficient knees. A lateral 15 N-m abduction moment produced a coupled external rotation in the medial collateral ligament-deficient knee. This was in marked contrast to intact, anterior cruciate ligament-deficient, or combined medial collateral ligament and anterior cruciate ligament-deficient knees, in which an abduction moment produced a coupled internal rotation. Sectioning only the medial collateral ligament caused a small but significant increase in the abduction rotation limit, whereas larger increases in the abduction rotation limit occurred when the posterior oblique ligament and posterior medial capsule were cut in addition to the medial collateral ligament. Cutting the medial collateral ligament increased the external rotation limit. The increase was independent of whether the anterior cruciate ligament was intact or sectioned. Subsequent cutting of the posterior oblique ligament and posterior medial capsule further increased the external rotation limit.

Adult↗
PubMed1996

Characterization of the mechanical behavior of human knee ligaments: a numerical-experimental approach.

During knee-joint motions, the fiber bundles of the knee ligaments are nonuniformly loaded in a recruitment pattern, which depends on successive relative orientations of the insertion sites. These fiber bundles vary with respect to length, orientation and mechanical properties. As a result, the stiffness characteristics of the ligaments as a whole are variable during knee-joint motion. The purpose of the present study is to characterize this variable mechanical behavior. It is hypothesized that for this purpose it is essential to consider the ligaments mechanically as multi-bundle structures in which the variability in fiber bundle characteristics is accounted for, rather than as one-dimensional structures. To verify this hypothesis, bone-ligament-bone preparations of the ligaments were subjected to series of unidirectional subfailure tensile tests in which the relative insertion orientations were varied. For each individual test specimen, this series of tensile tests was simulated with a mathematical ligament model. Geometrically, this model consists of multiple line elements, of which the insertions and orientations are anatomically based. In a mathematical optimization process, the unknown stiffness and recruitment parameters of the line elements are identified by fitting the variable stiffness characteristics of the model to those of the test series. Thus, lumped parameters are obtained which describe the mechanical behavior of the ligament as a function of the relative insertion orientation. This method of identification was applied to all four knee ligaments. In all cases, a satisfactory fit between experimental results and computer simulation was obtained, although the residual errors were lower for the cruciate ligaments (1.0-2.4%) than for the collateral ligaments (3.7-8.1%). It was found that models with three or less line elements were very sensitive to geometrical parameters, whereas models with more than 7 line elements suffered from mathematical redundancy. Between 4 and 7 line elements little difference was found. It is concluded that the present ligament models can realistically simulate the variable tensile behavior of human knee ligaments. Hereby the hypothesis is verified that it is essential to consider the ligaments of the knee as multi-bundle structures in order to characterize fully their mechanical behavior.

Aged↗
PubMed1999

Adhesion strength differential of human ligament fibroblasts to collagen types I and III.

Fibroblasts embedded in the amorphous healing tissue matrix of ligaments migrate into damaged sites during the inflammatory process that precedes the formation of new connective tissue after ligament injury. Cell motility involved in this migration is strongly influenced by cellular adhesion to proteins of the extracellular matrix. The adhesion mechanism of interest in this study is the attachment of fibroblasts from the anterior cruciate and medial collateral ligaments to types I and III collagen, two fibrillar collagens secreted by fibroblasts during tissue repair. Types I and III collagen constitute a major portion of these ligaments and are assembled by fibroblasts into long cable-like fibrils in the extracellular space. In this study, a micropipette aspiration technique was used to measure the force required to separate fibroblasts of the anterior cruciate and medial collateral ligaments from substrates composed of type I or III collagen, each at a concentration of 2 or 5 microg/ml. Approximately 1,200 fibroblasts from the anterior cruciate ligament and 1,600 from the medial collateral ligament were used, and the adhesion force and area of these cells were determined. Fibroblasts from the anterior cruciate ligament exhibited greater adhesion force than did those from the medial collateral ligament for all concentrations of types I and III collagen. In addition, the adhesiveness of fibroblasts from both ligaments was dependent on seeding time for all experimental conditions. To determine the adhesiveness per unit area, defined here as the adhesion strength, the adhesion force was normalized by the adhesion area. At early seeding times (15-45 minutes), fibroblasts from the anterior cruciate ligament exhibited greater adhesion strength on surfaces coated with type-I collagen than did those from the medial collateral ligament. However, for both collagen substrates, adhesion strength for fibroblasts from the anterior cruciate ligament decreased with seeding time whereas that for fibroblasts from the medial collateral ligament remained relatively constant for all seeding periods (15-75 minutes).

Adult↗
PubMed2001

Preliminary comparison of the rupture of human and rabbit anterior cruciate ligaments.

OBJECTIVE: This study was aimed at examining ruptures of the human anterior cruciate ligaments by scanning electron microscopy and video imaging and comparing the appearance of the rupture surfaces with those from rabbit anterior cruciate ligaments. DESIGN: The specimens were tested to failure as femur-anterior cruciate ligament-tibia complexes using an Instron 8511 materials testing machine. BACKGROUND: Rupture of the anterior cruciate ligament is a major clinical problem, leading to instability of the knee joint. Due to the frequency and potential severity of the injuries, a need still exists for information on the biomechanical properties of ligaments under loading conditions, which occur at the time of trauma. METHODS: Four human femur-anterior cruciate ligament-tibia complexes were loaded to failure at a displacement rate of 0.008 m/s. Video recordings of the tests were used to study the progress of the ruptures and to compare the modes of failure of the ligaments. Scanning electron microscopy was employed to study the appearance of collagen fibres at the rupture surfaces. RESULTS: The modes of failure of the rabbit anterior cruciate ligament and appearance of the rupture surfaces were similar to those of the human anterior cruciate ligaments. CONCLUSION: The rabbit anterior cruciate ligament provides a model for investigating failure of the human ligament during trauma. RELEVANCE: The results will be of significance since most studies on ligaments are carried out on animal models with the intention of applying the deductions from the results to human ligaments. Examining the appearance of collagen fibres at these surfaces may help us to understand more about what actually happens during and after ligament rupture.

Animals↗
PubMed2001

Hypertrophy of the posterior longitudinal ligament is a prodromal condition to ossification: a cervical myelopathy case report.

STUDY DESIGN: A histopathologic examination of a specimen that showed hypertrophy of the posterior longitudinal ligament of the cervical spine. OBJECTIVES: To illustrate the possibility of hypertrophy of the posterior longitudinal ligament as a prodromal condition to ossification of the posterior longitudinal ligament. SUMMARY OF BACKGROUND DATA: Despite much study, the pathology of ossification of the posterior longitudinal ligament still remains unclear. Hypertrophic change often is seen in the part of the ossified ligament; however, there have been few histopathologic reports on hypertrophy of the posterior longitudinal ligament. Some reports have suggested that hypertrophy of the posterior longitudinal ligament is a prodrome of ossification of the posterior longitudinal ligament. METHODS: A 64-year-old man was admitted to the hospital because of gait disturbance and developed oliguria. In a plain radiograph, segmental ossification of the posterior longitudinal ligament was found at C4, C5, and C6. Computed tomograph myelogram revealed a soft tissue shadow, maximum 3.8 mm in diameter, on the dorsal side of the ossification of the posterior longitudinal ligament at C5 and C6. Magnetic resonance T1-weighted image (T1WI) showed an equivalent signal with the intervertebral disc on the dorsal side of ossification of the posterior longitudinal ligament. This lesion was enhanced with Gd-DTPA and confirmed as hypertrophy of the posterior longitudinal ligament. Cervical anterior decompression and fusion were performed using Yamaura's technique. The ossified and thickened lesion was elevated and removed en bloc. Then, hematoxylin-eosin and toluidine blue staining was performed to detect metachromasia. RESULTS: Macroscopic examination of the specimen revealed that soft tissue formation was connected with the C4-C5 intervertebral space and extended downward to C6-C7. Histopatholgically, collagen fibers were proliferating in the long-axis direction on both ventral and dorsal sides. This was surrounded by extended nucleus pulposus-like chondrocyte tissue, where endplate cartilage was detected around the C4 pedicle. Roux staining was low, and partial vascular and cellular infiltration was observed, although it was not marked. CONCLUSION: The herniated nucleus pulposus involving endplate cartilage from C4-C5 was limited to the superficial layer, and proliferation of nucleus pulposus-like chondrocytes occurred in the herniated tissue, where they might undergo a change in cell phenotype. The results of the present study support the hypothesis that hypertrophy of the posterior longitudinal ligament is a prodromal condition to ossification of the posterior longitudinal ligament.

Cervical Vertebrae↗
PubMed1996

A sagittal plane model of the knee and cruciate ligaments with application of a sensitivity analysis.

In this investigation the complex multi-bundle structure of the cruciate ligaments and their interaction with the tibiofemoral joint was modeled analytically by representing the different regions of the cruciates with ligament elements. A sensitivity analysis was then performed to describe the effect that variations of the model input parameters had on the model variables (outputs). The effect that the cruciate ligament bundles had in controlling joint kinematics was dependent on knee flexion angle, and the load applied to the tibiofemoral joint. For passive range of knee motion with the thigh in the horizontal plane (a common rehabilitation activity), all cruciate ligament bundles were strained with the joint positioned between 0 and 10 deg of knee flexion, between 10 and 50 deg only the anterior bundle of the posterior cruciate ligament A-PCL was strained, and from 50 to 90 deg both the anteromedial portion of the anterior cruciate ligament A-ACL and the A-PCL were strained. This finding indicates that a strain distribution about a transverse cross section of the cruciates exists, and demonstrates the importance of differentiating between the strained and unstrained (unloaded) states of these ligaments. The strain value of a cruciate ligament bundle was an indication of how the bundle controls joint kinematics, while the unstrained values describe how much the ligament bundle must deform before it becomes strained and a restraint to tibiofemoral joint motion. In response to anterior and posterior directed loads, applied parallel to the tibial plateau, the respective, ACL and PCL load values were larger in magnitude. The sensitivity of the model outputs to the input parameters was highly dependent on knee flexion angle. The geometrical input parameters of the model (including the ligament insertion site locations and articular surface geometry) had the most pronounced effect on the model output quantities, while the stiffness and initial strain conditions of the ligament bundles had less of an effect on the model outputs. When loaded, the strain values of the ligament bundles were sensitive to the ligament insertion site position. The greatest sensitivity of the model outputs was the femoral insertion of the ACL; supporting clinical impressions and previous experimental findings. Changes in the anterior-posterior dimension of the femoral articular surface did not produce a substantial effect on the model outputs, while changes in the proximal-distal dimension created a large effect; similar results were found for the tibial surface dimensions. These findings indicate that rigid body contact between the articular surfaces may not be a realistic assumption particularly with application to the prediction of tibiofemoral compressive loading and the force/strain values of the cruciate ligament elements. This also has important implications for the design and clinical application of total knee replacements (that function as rigid bodies), particularly those that spare the PCL.

Anterior Cruciate Ligament↗
PubMed1993

Direct in vitro measurement of forces in the cruciate ligaments. Part I: The effect of multiplane loading in the intact knee.

Specially designed load-transducers that measured the resultant forces exerted by the posterior and anterior cruciate ligaments on their respective femoral and tibial insertions were applied to eighteen fresh-frozen cadaveric knees for a series of controlled loading experiments. The mean force in the posterior cruciate ligament at 5 degrees of forced hyperextension of the knee was 23 per cent of the mean force in the anterior cruciate ligament. When the knee was hyperflexed by application of 10.0 newton-meters of bending moment to the tibia, the mean force in the posterior cruciate ligament was 55 per cent of that in the anterior cruciate ligament. Quadriceps tendon pull increased the force in the posterior cruciate ligament in twelve of the fourteen specimens to which it had been applied, at 80 and 90 degrees of flexion only. The force generated in the posterior cruciate ligament by applied internal tibial torque was greatest when the knee was in 90 degrees of flexion; the force in the anterior cruciate ligament was greatest when the knee was fully extended. External tibial torque generated force in the posterior cruciate ligament in only eight specimens, and only at 80 and 90 degrees of flexion. The levels of force that were generated in the posterior cruciate ligament by applied varus and valgus bending moment were greatest at 90 degrees of flexion of the knee; the levels of force in the anterior cruciate ligament were greatest with the knee in full extension. With the knee flexed 90 degrees and the tibia in neutral rotation, fifty newtons of applied posterior tibial force increased the mean force in the posterior cruciate ligament by 58.4 newtons; at full extension, no increase in the force in the ligament was recorded, indicating that tensed capsular structures were absorbing the applied load. When the tibia was internally or externally rotated by applied tibial torque, the increases in the force in the ligament from applied posterior tibial force were sharply diminished.

Aged↗
PubMed1996

[Biomechanical correlations of lesions associated with traumatic diseases of the anterior cruciate ligament. Analysis with magnetic resonance].

To investigate the correlations between traumatic injuries of the anterior cruciate ligament and other ligamentous, meniscal and bone traumatic injuries, a series of 193 patients with anterior cruciate ligament injuries studied with MRI between January 1992 and December 1994, was retrospectively reviewed. MR results were compared with arthroscopic and/or surgical findings in most (181) patients; in the remaining 12 patients, clinical follow-up was performed. We used two 0.5 superconductive MR units, with dedicated coils and T1-weighted spin-echo and T2*-weighted gradient-echo sequences on the axial, sagittal and coronal planes. Anterior cruciate ligament injuries were associated with other ligamentous, meniscal and bone injuries in 78% of patients. The patients were classified in 5 groups depending on biomechanics and the association of injuries: -group I: isolated injury of the anterior cruciate ligament (41 patients), most frequently caused by forced extension stress associated with "kissing contusions" of the anterior portion of the lateral femoral condyle and of the lateral tibial plateau; this type of injury is less frequently caused by forced flexion stress associated with avulsion fracture of the tibial eminence; -group II: associated injury of the anterior cruciate ligament and medial compartment (62 patients), caused by forced flexion-external rotation stress (abduction, valgism and external rotation). The classic association of this mechanism was the injury of the anterior cruciate ligament, medial collateral ligament and medial meniscus (O'Donoghue triad) (9 patients). Valgus stress and the pivot-shift phenomenon can impact the tibial and femoral articular surfaces, with consequent osteochondral contusion; -group III: associated injury of the anterior cruciate ligament and lateral compartment (26 patients), caused by forced flexion-internal rotation stress (adduction, varism and internal rotation). This mechanism can cause, as a typical bone lesion, Segond fractures; -group IV: associated injury of the anterior cruciate ligament, lateral and medial compartments observed in 52 patients with different associations of varus-valgus and rotatory stress; -group V: in 5 patients, anterior cruciate ligament injury was associated with traumatic injury of the posterior cruciate ligament; in this case, posterior displacement of the tibia and knee hyperextension were the most common mechanisms of injury. In conclusion, our results demonstrate that anterior cruciate ligament injuries due to traumatic sprains of the knee are rarely isolated (21%). Thus, it is important to know the biomechanics of knee trauma to read MR images in order to detect possibly associated injuries. The final goal is to assess the actual extent of the traumatic damage for best subsequent clinical-therapeutic management.

Adolescent↗
PubMed2002

Biomechanical evaluation of ligamentous stabilizers of the scaphoid and lunate.

This study evaluated the effects of sectioning the scapholunate interosseous ligament, radioscaphocapitate ligament, and scaphotrapezial ligament on the kinematics of the scaphoid and lunate. Eight cadaver upper extremities were placed in a wrist joint simulator and moved in continuous cycles of flexion-extension and radial-ulnar deviation. Positional data of the scaphoid and lunate were obtained in the intact state, after the scapholunate ligament was cut; after the scapholunate and scaphotrapezial ligaments were cut; after the scapholunate, scaphotrapezial, and radioscaphocapitate ligaments were cut; and after all 3 ligaments were cut and the specimen was placed through an additional 1,000 cycles of flexion-extension. Cutting the scapholunate ligament caused changes in scaphoid and lunate motion during flexion-extension, but not radial-ulnar deviation. Additional sectioning of the scaphotrapezial ligament followed by the radioscaphocapitate ligament caused further kinematic changes in these carpal bones. One thousand cycles of motion after all 3 ligaments were sectioned caused additional kinematic changes in the scaphoid and lunate. The scapholunate ligament appears to be the primary stabilizer between the scaphoid and lunate. The radioscaphocapitate and scaphotrapezial ligaments are secondary restraints. Repetitive cyclic motion after ligament sectioning appears to have additional deleterious effects on carpal kinematics.

Aged↗
PubMed2005

Differential effects of estrogen on DNA synthesis in human periodontal ligament and breast cancer cells.

BACKGROUND: It is important to clarify the biological function of the female sex hormones estrogen and progesterone in periodontal ligament cells, as these hormones may affect periodontal health. We have previously shown that human periodontal ligament cells express estrogen receptor beta (ERbeta) but not ERalpha, whereas human breast cancer cells (MCF7) express both ERalpha and ERbeta. Data on progesterone receptor (PgR) expression in human periodontal ligament cells have not been reported. OBJECTIVES: Determine PgR expression in human periodontal ligament and MCF7 cells and to investigate how estrogen affects DNA and collagen synthesis in these two cell types showing different pattern of expression for ERalpha and beta. METHODS: Periodontal ligament cells were obtained from the periodontal ligament of premolars extracted for orthodontic reasons and MCF7 cells from the American Type Culture Collection (ATCC). PgR expression was determined by immunocytochemistry. DNA and collagen synthesis was determined by [(3)H]thymidine and L-[(3)H]proline incorporation, respectively. RESULTS: PgR immunoreactivity was observed in nuclei of MCF7 but not periodontal ligament cells. Treatment with estrogen (17beta-estradiol, E(2)) at physiological concentrations for 24 h stimulated DNA synthesis by more than two times in MCF7 cells, whereas there was no effect on periodontal ligament cell DNA synthesis. The ER blocker ICI 182780 fully reversed the stimulatory effect of E(2). Not only short-term (24 h) but also long-term (5 days) treatment with E(2) lacked effect on DNA synthesis in periodontal ligament cells. Neither periodontal ligament cell viability nor collagen synthesis was affected by E(2) treatment. Identical results were observed in periodontal ligament cells from male and female subjects. CONCLUSIONS: Human MCF7 but not periodontal ligament cells express PgR, suggesting that progesterone via PgR affects MCF7 but not periodontal ligament cells. Further, estrogen stimulates breast cancer MCF7 cell proliferation, whereas it has no effect on proliferation of periodontal ligament cells, probably reflecting cell type specific ER expression pattern in these two cell types.

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