Mechanics of coracoacromial ligament transfer augmentation for acromioclavicular joint injuries

The objective of this study was to determine how effectively the Weaver-Dunn repair (both unaugmented and augmented with a suture and suture anchor) restores joint translation in response to applied loads to normal. Translation of a reference point on the clavicle relative to a reference point on the acromion was assessed in five cadaver shoulders by applying anterior, posterior and superior loads of 50 N to the clavicle using a specially designed test rig while measuring movement of the acromion and clavicle with an optical measurement system. Translation was determined for the intact joint, after simulated injury and Weaver-Dunn repair, and after augmentation of the Weaver-Dunn repair with a suture fixed to a suture anchor in the coracoid process. Joints were significantly more mobile after Weaver-Dunn repair (16.1 mm anterior, 15.7 mm posterior, 11.1 mm superior) than when intact (4.1 mm anterior, 3.2 mm posterior, 4.0 mm superior) (p < 0.005). Augmentation with a suture and suture anchor reduced separation of the Weaver-Dunn reconstruction significantly (to 5.3 mm anterior, 4.1 mm posterior, 2.0 mm superior) (p < 0.005). Joints reconstructed using an augmented Weaver-Dunn repair were not significantly more (or less) mobile than normal joints (p > 0.005), although the power of the test to detect this difference was low (power = 0.107). We anticipate that, when surgery is indicated for treating acromioclavicular joint injury, an augmented Weaver-Dunn reconstruction will yield a joint that is less painful, more functional and less likely to require revision.     

The mammalian temporo-pterygoid ligament

An account is given of a generally unrecognized fascial ligament (lig. temporo-pterygoideum) found to occur in eutherian mammals. This structure is a functional specialization of the salpingo-palatal fascia, developed in response to the activity of the palatal tensor and levator musculature. The ligament is attached superiorly to the Eustachian process of the temporal bone and inferiorly to the hamular process of the medial pterygoid lamina. It is responsible for the development of both these processes, which, in the macerated cranium, testify to the original presence of this ligament.     

The anterior ligament of the human malleus.

The authors have studied the anterior ligament of the malleus (ALM) from a morphological and embryological point of view. Classical textbooks of anatomy stress the correlation between the ALM and the anterior pin of the sphenoid and define the ligament as a residual of Meckel's cartilage. This study demonstrates the y-shaped form of the ligament, one arm of which reaches the capsule of the temporomandibular joint and the other the pin of the sphenoid bone. Meckel's cartilage pilots the fibres of the ligament itself. Several clinical implications may be hypothesised on the basis of this study.     

Alpha11 beta1 integrin-dependent regulation of periodontal ligament function in the erupting mouse incisor

The fibroblast integrin alpha11beta1 is a key receptor for fibrillar collagens. To study the potential function of alpha11 in vivo, we generated a null allele of the alpha11 gene. Integrin alpha11(-/-) mice are viable and fertile but display dwarfism with increased mortality, most probably due to severely defective incisors. Mutant incisors are characterized by disorganized periodontal ligaments, whereas molar ligaments appear normal. The primary defect in the incisor ligament leads to halted tooth eruption. alpha11beta1-defective embryonic fibroblasts displayed severe defects in vitro, characterized by (i) greatly reduced cell adhesion and spreading on collagen I, (ii) reduced ability to retract collagen lattices, and (iii) reduced cell proliferation. Analysis of matrix metalloproteinase in vitro and in vivo revealed disturbed MMP13 and MMP14 synthesis in alpha11(-/-) cells. We show that alpha11beta1 is the major receptor for collagen I on mouse embryonic fibroblasts and suggest that alpha11beta1 integrin is specifically required on periodontal ligament fibroblasts for cell migration and collagen reorganization to help generate the forces needed for axial tooth movement. Our data show a unique role for alpha11beta1 integrin during tooth eruption.     

The sensitive innervation of the proximal sesamoid ligament of the ox

The Authors have studied the sensitive innervation of the proximal sesamoid ligament of the ox and have found capsulated corpuscles only. Among these receptors, besides Pacini and pacini-like corpuscles, Golgi Mazzoni's corpuscles, muscle spindles and Golgi's tendon organs with a typical structure, the Authors have been described, for the first time in the ox, corpuscles constituted by numerous Pacini collected by a single capsule. It must be pointed out that the muscle spindles are always supplied by an annulo-spiral termination which is centrally placed in the equatorial region. A vegetative innervation is also present in this ligament.     

Regulatory role of periodontal ligament fibroblasts for innate immune cell function and differentiation

Innate immunity is crucial for an effective host defense against pathogenic microorganisms in periodontal tissues. As periodontal ligament (PDL) cells synthesize immunomodulatory cytokines, the aim of this in?vitro study was to investigate whether these cells can interact with innate immune cells. Resting and inflammatory primed (IL-1β, TNF-α, HMGB1) human PDL cells were co-cultured with human monocyte-derived dendritic cells or macrophages. Migration, phenotypic maturation and modulation of phagocytosis of Porphyromonas gingivalis by immune cells were investigated upon co-culture with PDL cells and/or their released soluble factors. PDL cells interacted with immune cells under both non-inflammatory and inflammatory conditions. Immune cell migration was significantly enhanced by co-culture with PDL cells, which also affected their phenotypic maturation both through cell-cell contact and through released soluble mediators. The dendritic cell maturation markers CD83 and CD86 were upregulated as much as both 'alternatively activated' M2 macrophage maturation markers CD23 and CD163. In contrast, the 'classically activated' M1 macrophage maturation marker CD64 was downregulated. Finally, PDL cells significantly enhanced the phagocytosis of Porphyromonas gingivalis by immune cells. Our experiments revealed that PDL cells are not only structural elements of the periodontium, but actively influence immune responses by interaction with innate immune cells.     

Neuromuscular function after anterior cruciate ligament reconstruction with autologous semitendinosus-gracilis graft.

BACKGROUND: The quadrupled autologous semitendinosus-gracilis graft is the first choice of many orthopaedic surgeons when reconstructing the anterior cruciate ligament. The effect that this procedure has on voluntary muscle control remains unclear. The purpose of this study was to evaluate the effect that anterior cruciate ligament reconstruction with autologous semitendinosus-gracilis graft has on voluntary muscle control by assessing subjects' specificity of muscle action. METHODS: The voluntary muscle control of 10 people (seven males, three females) with acute, isolated ACL ruptures was assessed in the days prior to when they underwent anterior cruciate ligament reconstruction with quadrupled autologous semitendinosus-gracilis grafts and after they had returned to play in sports requiring quick changes of direction and jumping (approximately 6 months later). The experimental protocol included the use of an established target-matching protocol that requires subjects to produce and modulate force with fine control, electromyographic recordings from 11 muscles about the knee, and the use of circular statistics to calculate specificity indices that describe the degree of focus (specificity) associated with the activity pattern of each muscle. Data were analyzed by performing pre-surgery and post-return to sports side-to-side comparisons, as well as, pre-surgery to post-surgery ipsilateral comparisons. RESULTS: Diminished specificity of muscle action was observed in the activity patterns of most of the muscles of the subjects' anterior cruciate ligament deficient knees prior to surgery. The quadriceps muscles were particularly affected. Post-return to sports results indicated that voluntary muscle control had improved in most muscles. There was no significant difference in pre-surgery and post-return to sports semitendinosus and gracilis muscle control. The semimembranosus muscle displayed less specific muscle activity patterns following surgery, which may represent a compensation strategy for minor changes in neuromuscular function. CONCLUSIONS: Voluntary muscle control improved in most muscles following ACL reconstruction with semitendinosus-gracilis autografts. Semitendinosus and gracilis muscle control did not appear to be altered significantly by the procedure.     

Effect of altered occlusal function on transseptal ligament and new bone thicknesses in the periodontium of the rat

Alteration of tooth function is assumed to change stress/strain on the adjacent alveolar bone and its mucoperiosteum, producing changes in morphology similar to those described for other load-bearing bones. The present study suggested that crestal alveolar bone and its mucoperiosteum respond differently to stress/strain than load-bearing bones in other locations, possibly due to differences in the mechanism of bone loading by muscles and teeth. Occlusal hypofunction was initiated by extraction of agonist teeth; the contralateral teeth were placed in hyperfunction by the surgery. Untreated animals were also studied. 3H-proline was injected, animals were killed 1-5 weeks later, and the thicknesses of new bone and transseptal ligament were measured. After 5 weeks of altered function, total thickness (new bone + transseptal ligament) was similar in untreated and in hypofunctional and hyperfunctional situations; however, a new ratio between transseptal ligament and new bone thicknesses was established. Occlusal force was negatively correlated with new bone and positively correlated with transseptal ligament thickness; both thicknesses were statistically correlated in each functional situation (P less than 0.001). Hyperfunction resulted in increased transseptal ligament thickness, but decreased new bone thickness as compared to untreated controls (P less than 0.001). In contrast, hypofunction resulted in an increased new bone thickness, but a decreased transseptal ligament thickness (P less than 0.001). Tissue responses assure appropriate support for the teeth in each functional situation.     

Collagen fibril D-period may change as a function of strain and location in ligament

The purpose of this study was to determine if the characteristic banding pattern (D-period) of collagen fibrils from rabbit medial collateral ligaments changes as a function of gross ligament strain and, if so, whether the changes are location dependent (insertion versus midsubstance). Femur–medial collateral ligament–tibia complexes were strained to 0, 8, or 12% and immediately chemically fixed in situ. Samples were taken from the medial collateral ligament midsubstance and bony insertions, and prepared for and observed under a transmission electron microscope. D-period length was measured and found to increase (albeit not significantly so, p=0.1) as a function of gross strain for samples obtained from the insertion sites but not for samples obtained from the ligament midsubstance. Results suggested that ligament strains are inhomogeneous at the ultrastructural level.     

Some principles of ligament function, with examples from the tarsal joints of the sheep (Ovis aries)

The effects of ligaments, in limiting or controlling movement, depend on the positions of their attachments relative to the axes of joints. Such effects are explored in a theoretical section, which considers ligaments that cross a single, congruent hinge joint; ligaments that cross two congruent hinge joints; and non-congruent hinge joints controlled by crossed ligaments. The principles derived in the theoretical section are used to explain the complex mechanism of the sheep tarsal joints.     

The role of the facet capsular ligament in providing spinal stability

Abstract

Low back pain (LBP) is the most common type of pain in America, and spinal instability is a primary cause. The facet capsular ligament (FCL) encloses the articulating joints of the spine and is of particular interest due to its high innervation – as instability ensues, high stretch values likely are a cause of this pain. Therefore, this work investigated the FCL's role in providing stability to the lumbar spine. A previously validated finite element model of the L4-L5 spinal motion segment was used to simulate pure moment bending in multiple planes. FCL failure was simulated and the following outcome measures were calculated: helical axes of motion, range of motion (ROM), bending stiffness, facet joint space, and FCL stretch. ROM increased, bending stiffness decreased, and altered helical axis patterns were observed with the removal of the FCL. Additionally, a large increase in FCL stretch was measured with diminished FCL mechanical competency, providing support that the FCL plays an important role in spinal stability.     

The ligament of Marshall as a parasympathetic conduit

The objective of the study was to investigate the morphology, distribution, and electrophysiological profile of the autonomic fibers that innervate the ligament of Marshall (LOM). Gross anatomical dissections were performed in 10 dogs. Sections of the left vagus nerve, left stellate ganglion, and the LOM were immunostained to identify adrenergic and cholinergic nerves. Hearts were also stained for acetylcholinesterase to identify epicardial cholinergic nerves. In vivo electrophysiological studies were performed in another 10 dogs before and after LOM ablation. The anatomical examination revealed that the LOM is innervated by a branch of the left vagus. Immunohistochemistry confirmed that these nerve bundles are predominantly cholinergic (cholinergic-to-adrenergic ratio of 12.6 +/- 3.9:1). Cholinergic nerves originating in the LOM were found to innervate surrounding left atrial structures, including the pulmonary veins, left atrial appendage, coronary sinus, and posterior left atrial fat pad. Ablation of the LOM significantly attenuated effective refractory period shortening at distant sites, such as pulmonary veins and left atrial appendage, in response to vagal stimulation (vagal-induced ERP decrease in the left atrium: baseline vs. postablation = 17 vs. 4%; P = 0.0056). In conclusion, the LOM contains a predominance of cholinergic nerve fibers. Cholinergic fibers arising from the LOM innervate surrounding structures and contribute to the electrophysiological profile of the left atrium. These findings may provide a basis for the role of the LOM in the genesis and maintenance of atrial fibrillation.     

The in vitro life-span of human periodontal ligament fibroblasts

The in vitro life-span of human periodontal ligament fibroblasts (PDLF) was studied on clones from periodontium of teeth extracted due to periodontitis and dental caries (69 clones/192 individuals, aged 20-80 years) and from periodontium of teeth extracted for orthodontic reasons (23 clones/26 individuals, aged 15-19 years). In the primary cultures the ratio of the number of cells expressing senescence-associated beta-galactosidase (SA-beta-Gal) to the total number of cells is significantly larger in PDLF (92 clones; 11.1+/-4.9%) than in human gingival fibroblasts (GF) (10 clones; 0.5+/-0.1 %). The finite population doubling numbers (PD) of PDLF are not age-matched and the mean PD of PDLF (7.1+/-2.9) is significantly smaller than GF (28.5+/-3.2), IMR-90 (human lung fibroblasts, 5 clones; 44.3 +/- 2.2), and human osteoblasts (5 clones; 19.7+/-1.4). Comparing the ratio of the number of SA-beta-Gal positive cells to the total number of cells in primary culture, and the finite PD in PDLF cultures: 1) the ratio of 15-19 years old donor group is significantly smaller than in the other donor groups (20-29, 30-39, 40-49, 50-59 and 60-80 years old), and 2) there were no statistically significant differences among the 20-29, 30-39, 40-49 and 50-59 year old donor groups, and the 30-39, 40-49, 50-59 and 60-80 year old donor groups. These findings suggest that the in vitro life-span of PDLF is shorter than other fibroblasts in the connective tissues and that PDLF may undergo senescence in adult clones without relation to donor's age. There may be more aged fibroblasts in periodontium than in other tissues, such as gingiva and lung.