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PubMed2004

Is an intact anterior cruciate ligament needed in order to have a well-functioning unicondylar knee replacement?

Controversy exists about whether a functional anterior cruciate ligament is necessary to achieve success with unicompartmental knee arthroplasty. When the anterior cruciate ligament was deficient, higher failure rates were reported with mobile-bearing implants and with the Lotus implant, a relatively flat, fixed-bearing component. Most failures were secondary to wear. In contrast, the absence of an anterior cruciate ligament did not lead to failure with the St. Georg and Marmor implants. Theoretically, an absent anterior cruciate ligament would increase the sliding motion that caused accelerated polyethylene wear in laboratory studies. Hypothetically, such motion could lead to accelerated wear of unicompartmental arthroplasty in an ACL deficient knee. Currently, unicompartmental knee arthroplasties should not be done in patients with symptoms of anterior cruciate ligament instability and should judiciously be done in older patients without a functional anterior cruciate ligament but with no symptoms of instability.

Anterior Cruciate Ligament↗
PubMed1992

Quantitative analysis of the fine vascular anatomy of articular ligaments.

An image analysis technique has been developed to quantitatively describe the fine vascular patterns observed in ligament tissue. The longitudinal orientational distribution and total vessel volume of India-ink-perfused blood vessel segments in normal and healing ligaments were determined. The methods involved special vascular preparation of adult rabbit knee medial collateral ligaments (MCL) by India-ink perfusion. Black and white microscope images of ink-perfused tissue sections were subjected to a thresholding procedure to binarize digitized ligament images, which were then skeletonized and analyzed for directional distribution based on the least-squares technique. Analysis of medial collateral ligaments in New Zealand White rabbits using this method has shown that scarred tissue is more vascular and has a more chaotic angular distribution of blood-vessel segments than normal ligament tissue.

Algorithms↗
PubMed2004

Estimating joint contact areas and ligament lengths from bone kinematics and surfaces.

We present a novel method for modeling contact areas and ligament lengths in articulations. Our approach uses volume images generated by computed tomography and allows the in vivo and noninvasive study of articulations. In our method, bones are modeled both implicitly (scalar distance fields) and parametrically (manifold surfaces). Using this double representation, we compute interbone distances and estimate joint contact areas. Using the same types of representation, we model ligament paths; in our model, the ligaments are approximated by the shortest paths in a three-dimensional space with bone obstacles. We demonstrate the method by applying our contact area and ligament model to the distal radioulnar joints of a volunteer diagnosed with malunited distal radius fracture in one forearm. Our approach highlights focal changes in the articulation at the distal radioulnar joint (location and area of bone contact) and potential soft-tissue constraints (increased "length" of the distal ligaments and ligament-bone impingement in the injured forearm). Results suggest that the method could be useful in the study of normal and injured anatomy and kinematics of complex joints.

Algorithms↗
PubMed2005

Repair of recurrent vaginal vault prolapse using sacrospinous ligament fixation with mesh interposition and reinforcement.

OBJECTIVE: Our goal was to study the efficacy of performing the repeated sacrospinous ligament fixation with mesh interposition and reinforcement in women with recurrent vaginal vault prolapse. MATERIALS AND METHODS: Fifteen consecutive patients with symptomatic severe vaginal vault or uterus prolapse after previous sacrospinous ligament fixation were enrolled. The sacrospinous ligament fixation was performed with a mesh interposition between sacrospinous ligament complex and vaginal apex. The mesh was extended to anterior and posterior vaginal wall for the repair of concurrent cystocele and rectocele, if indicated. The surgical results and complications were evaluated. The prolapse evaluation was performed according to International Continence Society (ICS) ordinal stages of pelvic organ prolapse. RESULTS: The mean age was 55 years. The mean follow-up was 2.9 years (range 1.0-5.5 years). Repeated sacrospinous ligament fixation was performed for all patients. Eleven were performed unilaterally to the right and four to the left. The average time for sacrospinous fixation was 20 min. The average blood loss for sacrospinous fixation was 75 ml. No major complication except one accidental rectotomy was observed. It was repaired intraoperatively without sequel. The concurrent pelvic surgeries included vaginal total hysterectomies, anterior colporrhaphies, posterior colporrhaphies, and tension-free vaginal tape procedures. No recurrence of apical prolapse was observed. However, two patients developed stage I prolapse on anterior vaginal wall (cystocele) and required no further repair. Minor postoperative complications were observed. CONCLUSION: Repeated sacrospinous ligament fixation with mesh interposition and reinforcement is a safe and effective procedure for the correction of recurrent vault prolapse. The extended implanted mesh can be used for the repair of concurrent cystorectocele effectively. A long-term follow-up is necessary to detect any late complication.

Adult↗
PubMed1993

A model to describe how ligaments may control symmetrical jaw opening movements in man.

A mechanical model of the temporomandibular (TM) joint was converted into a computer program, with a graphic output, which tested the simultaneous effects on symmetrical jaw opening of the following three constraints: 1) the condyle could not move above the articular surface of the temporal bone; 2) the TM ligament and 3) the sphenomandibular (SN) ligament could not be stretched. Cartesian coordinates describing the ligaments and bones of six different skulls were measured and entered into the model. Although the constraints in the model allowed five different types of jaw opening movement, only one of these was physically possible for any given position of the mandible during opening. Each movement changed the geometry of the constraints. The opening movements of the condyle followed those of the hinge and kinematic axes which have been observed in studies of symmetrical jaw opening. Together with the constraint of the articular eminence, the early phase of opening was controlled by the backwardly inclined TM ligament. The late phase of opening was controlled by the forwardly inclined SN ligament. This mechanical explanation for the observed movements of the condyle is consistent with the principle that accessory ligaments have evolved around joints to reduce the need for some neuromuscular controls by replacing them with mechanical controls.

Cadaver↗
PubMed1997

Spatial variation in sympathetic influences on the vasculature of the synovium and medial collateral ligament of the rabbit knee joint.

1. Laser Doppler perfusion imaging was used to assess the role of the sympathetic nervous system in the control of blood flow to the medial collateral ligament and capsule (synovium and overlying fibrous tissues) of the rabbit knee joint. 2. Electrical stimulation of the saphenous nerve (width 1 ms; amplitude 20V; 1-30 Hz) produced a frequency-dependent vasoconstriction of knee joint vasculature. The response was maximal at 30 Hz and gave the greatest fall in perfusion at the femoral insertion of the ligament (by 33.8 +/- 7.4%, mean +/- S.E.M.; n = 5-6) and the smallest decrease at the tibial insertion of the ligament (by 10.6 +/- 2.9%). 3. Topical application of phentolamine (10(-6) mol) had no significant effect on basal knee joint blood flow. However, it abolished the nerve-mediated constrictor responses in all regions of the medial collateral ligament and synovium at all frequencies. 4. Topical administration of adrenaline (10(-14) to 10(-7) mol) caused a dose-dependent decrease in knee joint blood flow with the highest dose producing > 75% reduction in perfusion at all areas. 5. There was no evidence of a reactive hyperaemia in the 5 min following a 5 min period of femoral artery occlusion. Artificial manipulation of arterial blood pressure by intravenous infusion or withdrawal of blood caused a proportional change in ligament and synovial blood flow. These observations may indicate a lack of autoregulation in the joint and its exclusion from baroreflex modulation. 6. These results suggest a potential role for the sympathetic nervous system in the control of knee joint blood flow. Neuromodulation of ligament perfusion appears to predominate at the femoral insertion and this could prove to have functional significance.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Desmotomy of the accessory ligament of the superficial digital flexor muscle in equine cadaver limbs.

Effects of longitudinal compression before and after transection of the accessory ligament of the superficial digital flexor (SDF) muscle were measured in eight equine cadaver forelimbs. When compression was increased from 890 N to 3115 N, the metacarpophalangeal (MCP) and carpal joints hyperextended 20 degrees and 4 degrees, respectively, and strain in the SDF and deep digital flexor tendons was increased 3.5% and 1.4%, respectively. The accessory ligament did not elongate. Immediately after transection of the accessory ligament at 3115 N load, a 2.8 mm gap formed between the transected ends of the accessory ligament, and the muscle belly of the SDF elongated and moved distad. The MCP joint hyperextended 15.8% further and strain of the SDF tendon increased 11.2% further. These results show that the accessory ligament transferred load in the SDF musculotendinous unit away from the muscle belly and that desmotomy altered this function. Decrease in the MCP joint angle indicated that the accessory ligament contributed to the support of the MCP joint under load. Increase in SDF strain after desmotomy was probably influenced by the change in the moment about the MCP joint and increased length of the SDF musculotendinous unit.

Animals↗
PubMed2006

Morphologic and functional features of the canine cruciate ligaments.

OBJECTIVE: To review the gross, microscopic, and functional anatomy of the cranial cruciate ligament (CCL) in dogs. STUDY DESIGN: Literature review. METHODS: Reports of the anatomy and function of the cruciate ligaments in dogs were retrieved by search of the 1975-2005 PubMed database. RESULTS: The CCL has an important biomechanical function resisting cranial drawer, hyperextension, and internal rotation and acts to fine tune and guide the stifle through its rolling and sliding motion. It has a complex architecture, and distinct geographic regions within the ligament have different functional roles depending on the angle and loading conditions. Collagen type I is the main component of the extracellular matrix; the fibrils have a crimped structure. The cruciate ligaments are almost completely covered by synovium, protecting them from synovial fluid. Cruciate blood supply is mainly of soft tissue origin. The intraligamentous network is relatively limited whereas the core of the middle third of the CCL is even less well vascularized. Neurohistologic studies are very limited in the dog. Various mechanoreceptors and proprioceptive receptors have been identified within the substance of the cruciate ligaments. CONCLUSIONS: CCL structural characteristics play an important part in its complex behaviour with the crimped pattern of the collagen fibrils being an important determinant of its biomechanical properties. In contrast to reports of managing CCL rupture, there are few reports describing the microanatomy and neurovascular morphology of the cruciate ligaments. CLINICAL RELEVANCE: Cruciate disease is likely multi-factorial. Improved understanding of CCL degradation leading to CCL rupture is critical to development of new diagnostic tests for cruciate disease in dogs. Appropriate intervention during the early stages of disease process might preserve CCL structural properties by preventing further collagen degradation. Accurate knowledge of functional and fiber bundle anatomy is imperative for reconstruction and restoration of normal stifle joint physiology. Reconstructive goals should alleviate existing instability and mimic normal kinematics. Knowledge of the exact function of the CCL in the neuromuscular control around the stifle joint could possibly explain osteoarthritis progression after CCL damage.

Animals↗
PubMed1997

Histochemical study of the influence of transplanted teeth with periodontal ligament of the binding of peanut agglutinin in rat dorsal skin.

Our previous study showed that the expression of carbohydrate residues in junctional epithelium (JE) after resection is closely related to attachment and stratification along the dental root surface. However, the influence of the periodontal ligament on carbohydrate expression has still not been clarified. In this study we examined the relationship between the presence of periodontal ligament and the expression of carbohydrate residues on epithelium regenerating along root surfaces. We transplanted extracted rat molars with or without periodontal ligament tissue, repeatedly frozen and thawed teeth with ligament and demineralized teeth without ligament into the dorsal skin of rats. After 2, 3, 5, 7, 10, 14 or 21 d, dorsal cutaneous tissues containing transplanted teeth were resected, fixed, decalcified and embedded in paraffin. Serial sections were stained histochemically with the HRP-conjugated lectin, peanut agglutinin (PNA) to observe the expression of carbohydrate residues in regenerating epithelium. Histochemical observation revealed that lectin binding reactions were changed from the characteristics of skin to those of JE when the regenerating epithelium was attached and stratified along the tooth with unfrozen or frozen tissue. These results suggested that the structural formation and expression of PNA in regenerating epithelium around the root surface were influenced by not only the tooth but also by the periodontal ligament.

Animals↗
PubMed2006

Maturation-state dependent response of human periodontal ligament cells to an intermittent parathyroid hormone exposure in vitro.

BACKGROUND AND OBJECTIVES: Parathyroid hormone (parathyroid hormone) has been shown to be capable of exerting anabolic effects on bone when administered intermittently. We hypothesized that parathyroid hormone will modulate the response of periodontal ligament cells in terms of anabolic effects with respect to proliferation, differentiation and the production of key regulatory factors of bone remodeling such as osteoprotegerin and receptor activator of nuclear factor kappaB ligand (RANKL) in a maturation-state dependent manner. METHODS: Periodontal ligament cells were cultured from human bicuspids obtained from six patients. Following characterization, confluent and preconfluent periodontal ligament cells were challenged with parathyroid hormone (1-34) for 0, 1, 3, 6 or 24 h within three incubation cycles of 48 h each. At harvest, the cell number, alkaline phosphatase specific activity and osteocalcin, osteoprotegerin and RANKL production were determined by means of semiquantitative polymerase chain reaction (PCR) and immunoassays. Dermal fibroblasts and MG63 osteoblast-like cells served as a reference. RESULTS: Intermittent parathyroid hormone treatment of confluent periodontal ligament cells caused a significant increase in proliferation (+32% maximum) whereas alkaline phosphatase activity, osteocalcin and osteoprotegerin decreased at the transcriptional and translational level (-59.7% maximum). In preconfluent periodontal ligament cells, parathyroid hormone induced a decrease in proliferation (-66.3% maximum) but an increase in differentiation and osteoprotegerin production (+49.2% maximum). RANKL was hardly detectable and unaffected by parathyroid hormone treatment. Similar results were obtained in MG63 cells, whereas parathyroid hormone stimulation did not alter any of the parameters examined in dermal fibroblasts. CONCLUSION: These results indicate that human periodontal ligament cells respond to an intermittent parathyroid hormone exposure with changes in proliferation, differentiation and osteoprotegerin production in a maturation-state dependent manner and therefore might be regulatorily involved in periodontal regeneration.

Adolescent↗
PubMed2007

Aging stimulates cyclooxygenase-2 expression and prostaglandin E2 production in human periodontal ligament cells after the application of compressive force.

BACKGROUND AND OBJECTIVES: Some clinical studies show that alveolar crestal bone loss is higher in adults than in young patients during orthodontic treatment, but the causes of such a phenomenon have not been elucidated. It is known that prostaglandin E2 (PGE2) is a proinflammatory agent and one of the potent osteoclast-inducing factors, and is produced by human periodontal ligament cells in response to orthodontic force. The aim of this study was to investigate age-related change in the biosynthetic capacity of PGE2 and its regulatory gene, cyclooxygenase 2 (COX-2) from periodontal ligament cells in response to mechanical stress. METHODS: Compressive force of 2 g/cm2 was applied for 3-48 h to periodontal ligament cells obtained from human donors aged 9-50 years, and COX-2 mRNA expression in and PGE2 production by the periodontal ligament cells in response to the compressive force were examined. RESULTS: Application of a compressive force of 2 g/cm2 for 3-48 h significantly stimulated these factors in both time- and age-dependent manners. Furthermore, these increases were dramatically larger in periodontal ligament cells obtained from donors over the age of 35. CONCLUSIONS: Periodontal ligament cells obtained from old donors have significantly greater COX-2 expression and PGE2 production in response to compressive force than those from younger donors. The turning point of aging, where significantly larger amounts of theses factors begin production, appears to be around the age of 35. These results may be positively related to the acceleration of alveolar crestal bone loss during orthodontic treatment in adult patients.

Adolescent↗
PubMed1994

In vitro mechanical properties of the accessory ligament of the deep digital flexor tendon in horses in relation to age.

The material properties of the accessory ligament of the deep digital flexor tendon (AL) of 21 forelimbs from horses between ages one day and 15 years were determined. The force (634-11416 N), failure stress (45-138 N/mm2), failure strain (7-24%) and tangent modulus (33-1639 MPa) are presented in relation to age. Tangent modulus did not indicate changes in elasticity due to age. The results demonstrate that complete ligament failures (CLF) of ALs of older horses (mean 7835 N) occur at lower forces than ALs of young adult horses (mean 8894 N). Sudden decreases, 'dips', in the force-time curves were noticed in ligaments from foals and yearlings and in ligaments from horses > 10 years. They were interpreted as the failure of a number of fibres which either fail at lower forces or are subject to higher forces than the rest. These differences in mechanical properties could be the result of age related differences in the material properties of ALs of older horses similar to alterations in collagenous tissue in other species. When analysing the data of the proximal, middle and distal regions of the ligaments separately, higher strain and elasticity were found in the distal compared to the proximal parts. It is suggested that the clinical occurrence of desmitis of the AL of older horses could be due to fibrillar failure caused by differences in the material properties of the ligaments.

Aging↗
PubMed2005

Biomechanical study using fuzzy systems to quantify collagen fiber recruitment and predict creep of the rabbit medial collateral ligament.

In normal daily activities, ligaments are subjected to repeated loads, and respond to this environment with creep and fatigue. While progressive recruitment of the collagen fibers is responsible for the toe region of the ligament stress-strain curve, recruitment also represents an elegant feature to help ligaments resist creep. The use of artificial intelligence techniques in computational modeling allows a large number of parameters and their interactions to be incorporated beyond the capacity of classical mathematical models. The objective of the work described here is to demonstrate a tool for modeling creep of the rabbit medial collateral ligament that can incorporate the different parameters while quantifying the effect of collagen fiber recruitment during creep. An intelligent algorithm was developed to predict ligament creep. The modeling is performed in two steps: first, the ill-defined fiber recruitment is quantified using the fuzzy logic. Second, this fiber recruitment is incorporated along with creep stress and creep time to model creep using an adaptive neurofuzzy inference system. The model was trained and tested using an experimental database including creep tests and crimp image analysis. The model confirms that quantification of fiber recruitment is important for accurate prediction of ligament creep behavior at physiological loads.

Algorithms↗
PubMed1983

An analytical technique for modeling knee joint stiffness--Part II: Ligamentous geometric nonlinearities.

An analytical technique previously developed to evaluate the contribution of the ligaments to the nonlinear, coupled stiffness characteristics of the human knee joint [1] is extended here to include geometric nonlinearities. In [1], we assumed that the ligaments act as tensile bands running in a straight line between tibial and femoral insertion sites. Here, two forms of geometric nonlinearities are introduced and analyzed: ligaments wrapping around bone surfaces, such as occurs with the medial collateral ligament, the posterior capsule, and the anterior cruciate in hyperextension, and wrapping of ligaments around each other, such as occurs with the cruciate ligaments as the knee is flexed and internally rotated.

Biomechanical Phenomena↗
PubMed1983

Tension-torsion characteristics of the canine anterior cruciate ligament--Part II: Experimental observations.

An experimental program was devised to determine whether the canine anterior cruciate ligament (ACL), with an apparent helical twist of its component fiber bundles, could support a torque during axial loading to failure. At the point of first significant failure, the anterior cruciate was found to develop an average maximum torque of 122 +/- 26 N-mm (mean +/- SEM) for the nine tension-torsion tests performed. A nearly linear axial force-torque curve was also observed where the average slope of all tests was 5.2 +/- 0.2 mm-1 (mean +/- SEM). The experimental axial force data was then used to determine material parameters in the constitutive equation for the fascicle and underlying bone. A nonlinear ligament model based on this response was found to reproduce the axial force data adequately and to reasonably predict the observed ligament torque over the entire subfailure loading range. The presence of a ligament torque during axial loading has implications in the design and selection of a ligament substitute. Such a substitute has already been examined in the canine in another study. The results also suggest more refined experiments which could relate the mechanical properties of a ligament to its detailed macrostructure and insertion site geometries.

Animals↗
PubMed2004

Homeobox protein MSX2 acts as a molecular defense mechanism for preventing ossification in ligament fibroblasts.

Ligaments and tendons are comprised of tough yet flexible connective tissue. Little is known, however, about the precise characteristics of the cells in ligaments and tendons due to the absence of specific markers and cell lines. We recently reported a periodontal ligament cell line, PDL-L2, with suppressed Runx2/Osf2 transcriptional activity and an inability to form mineralized nodules. The present study demonstrates that the homeobox protein Msx2 is a key factor in suppressing those two functions. Msx2 colocalizes with Runx2/Osf2 and suppresses its activity cooperatively, acting with another corepressor, TLE1, as a complex to recruit histone deacetylase 1 activity. Reverse transcription-PCR and in situ hybridization demonstrated that Msx2 expression is higher in periodontal ligament and tendon cells than in osteoblasts. Stable reduction of Msx2 expression in PDL-L2 cells induces osteoblastic differentiation, thereby causing matrix mineralization. Conversely, stable, forced Msx2 expression in MC3T3-E1 cells prevented osteoblast differentiation and matrix mineralization. Msx2-induced suppression of osteoblast differentiation was repressed by bone morphogenetic protein 2. In addition, Msx2 was downregulated in a symptom- and calcification-dependent manner at the affected region in patients with ossification of the posterior longitudinal ligament. Our findings indicate that Msx2 plays a central role in preventing ligaments and tendons from mineralizing.

Aged↗
PubMed1994

Direct dissemination of pathologic abdominal processes through perihepatic ligaments: identification with CT.

The liver is fixed in the right upper quadrant of the abdomen by a complex system of peritoneal reflections, known as ligaments. Embryologic evaluation shows that these ligaments, apparently unrelated, are part of a continuum: the ventral mesogastrium. The areolar tissue within the ligaments constitutes a potential space that links the liver with other viscera and with extraperitoneal sites, allowing direct spread of inflammatory or malignant diseases between these organs and spaces. Knowledge of the normal and pathologic appearance of the ligaments is necessary in order to diagnose dissemination of pathologic processes along them. Computed tomography (CT) is the imaging modality of choice for studying ligamentous involvement by disease. On CT scans, occupation or obliteration of ligamentous fat planes by fluid collections or areas of soft tissue with increased attenuation are the signs of direct spread of disease.

Humans↗
PubMed1995

Anatomic CT demonstration of the peritoneal spaces, ligaments, and mesenteries: normal and pathologic processes.

Computed tomography (CT) has become increasingly useful in the detection of intraabdominal disease. Owing to the widespread use of CT, it is essential that radiologists have a thorough understanding of the peritoneal spaces and the ligaments and mesenteries that form their boundaries. The majority of ligaments and mesenteries in the abdomen are formed from remnants of the ventral and dorsal mesenteries, which suspend the primitive gut. Unlike the abdominal ligaments, the pelvic ligaments are mainly formed by reflections of peritoneum over the pelvic organs or structures. The mesenteries and ligaments form the boundaries of the peritoneal spaces; this knowledge aids in localizing fluid collections, allowing the differential diagnosis to be narrowed. The ability to localize fluid collections accurately is also important if percutaneous or surgical drainage is to be performed. In addition, neoplasms can be more accurately staged when the pathway of spread through adjacent ligaments and mesenteries is understood.

Abdomen↗