The mechanical properties of anterior cruciate bone-ligament-bone specimens from humans and rhesus monkeys were determined in tension to failure under high strain-rate conditions. The age range of the human specimens was from sixteen to eighty-six years. The values fro human specimens obtained from young adults with regard to elastic modulus, ultimate tensile stress, and strain energy to failure were approximately two to three times those for specimens from humans in the sixth decade and older. The major mode of failure was ligament disruption in the specimens from young adult humans and avulsion of bone beneath the ligament insertion site in the specimens from older humans. The difference in mode of failure correlated with histological observations of decreased bone mass at the site of ligament attachment in the specimens from older humans. Rhesus monkey specimens had higher values for elastic modulus, failure stress, and strain energy. Significant reductions in strength and stiffness properties of ligament units were shown to occur with advancing age to a greater degree than expected. All experiments in which specimens from older human cadavera are used should be interpreted with caution when the results are applied to mechanisms of ligament failure for younger or athletic individuals.

The strength of the anterior cruciate ligament in humans and Rhesus monkeys.

Most muscle stretching studies have focused on defining the biomechanical properties of isolated elements of the muscle-tendon unit or on comparing different stretching techniques. We developed an experimental model that was designed to evaluate clinically relevant biomechanical stretching properties in an entire muscle-tendon unit. Our objectives were to characterize the viscoelastic behavior of the muscle-tendon unit and to consider the clinical applications of these viscoelastic properties. Rabbit extensor digitorum longus and tibialis anterior muscle-tendon units were evaluated using methods designed to simulate widely used stretching techniques. Additionally, the effects of varying stretch rates and of reflex influences were evaluated. We found that muscle-tendon units respond viscoelastically to tensile loads. Reflex activity did not influence the biomechanical characteristics of the muscle-tendon unit in this model. Experimental techniques simulating cyclic stretching and static stretching resulted in sustained muscle-tendon unit elongations, suggesting that greater flexibility can result if these techniques are used in the clinical setting. With repetitive stretching, we found that after four stretches there was little alteration of the muscle-tendon unit, implying that a minimum number of stretches will lead to most of the elongation in repetitive stretching. Also, greater peak tensions and greater energy absorptions occurred at faster stretch rates, suggesting that the risk of injury in a stretching regimen may be related to the stretch rate, and not to the actual technique. All of these clinically important considerations can be related to the viscoelastic characteristics of the muscle-tendon unit.

Viscoelastic properties of muscle-tendon units. The biomechanical effects of stretching.

The most commonly cited apomorphy of Archosauriformes is an opening in the snout known as the antorbital cavity. Despite the ubiquity and prominence of the antorbital cavity, its function and importance in craniofacial evolution have been problematic. Discovering the significance of the antorbital cavity is a two step process: first, establishing the function of the bony cavity (that is, its soft-tissue relations), and second, determining the biological role of the enclosed structure. The first step is the most fundamental, and hence is examined at length. Three hypotheses for the function of the antorbital cavity have been advanced, suggesting that it housed (1) a gland, (2) a muscle, or (3) a paranasal air sinus. Thus, resolution is correctly viewed as a “soft-tissue problem,” and is addressed within the context of the extant phylogenetic bracket (EPB) approach for reconstructing the unpreserved features of fossil organisms. The soft-anatomical relations of the antorbital cavity (or any bony st...

The Evolution of the Antorbital Cavity of Archosaurs: A Study in Soft-Tissue Reconstruction in the Fossil Record with an Analysis of the Function of Pneumaticity

Inadequate bone height in the lateral part of the maxilla forms a contra-indication for implant surgery. This condition can be treated with an internal augmentation of the maxillary sinus floor. This sinus floor elevation, formerly called sinus lifting, consists of a surgical procedure in which a top hinge door in the lateral maxillary sinus wall is prepared and internally rotated to a horizontal position. The new elevated sinus floor, together with the inner maxillary mucosa, will create a space that can be filled with graft material. Sinus lift procedures depend greatly on fragile structures and anatomical variations. The variety of anatomical modalities in shape of the inner aspect of the maxillary sinus defines the surgical approach. Conditions such as sinus floor convolutions, sinus septum, transient mucosa swelling and narrow sinus may form a (usually relative) contra-indication for sinus floor elevation. Absolute contra-indications are maxillary sinus diseases (tumors) and destructive former sinus surgery (like the Caldwell-Luc operation). The lateral sinus wall is usually a thin bone plate, which is easily penetrated with rotating or sharp instruments. The fragile Schneiderian membrane plays an important role for the containment of the bonegraft. The surgical procedure of preparing the trap door and luxating it, together with the preparation of the sinus mucosa, may cause a mucosa tear. Usually, when these perforations are not too large, they will fold together when turning the trap door inward and upward, or they can be glued with a fibrin sealant, or they can be covered with a resorbable membrane. If the perforation is too large, a cortico-spongious block graft can be considered. However, in most cases the sinus floor elevation will be deleted. Perforations may also occur due to irregularities in the sinus floor or even due to immediate contact of sinus mucosa with oral mucosa. Obstruction of the antro-nasal foramen is, due to its high location, not a likely complication, nor is the occurrence of severe haemorrhages since the trap door is in the periphery of the supplying vessels. Apart from these two aspects, a number of anatomical considerations are described in connection with sinus floor elevation.

Anatomical aspects of sinus floor elevations

The present investigation measured the Load–displacement and stress-strain characteristics of the proximal and distal human triceps surae aponeurosis and tendon in vivo during graded voluntary 10 s isometric plantarflexion efforts in five subjects.


During the contractions synchronous real-time ultrasonography of aponeurosis displacement, electromyography of the gastrocnemius, soleus and dorsiflexor muscles, and joint angular rotation were obtained. Tendon cross-sectional area and moment arm were obtained from magnetic resonance (MR) images. Force and electromyography data from dorsiflexion efforts were used to examine the effect of coactivation.


Tendon force was calculated from the joint moments and tendon moment arm, and stress was obtained by dividing force by cross-sectional area. Aponeurosis and tendon strain were obtained from the displacements normalised to tendon length.


Tendon force was 3171 ± 201 N, which corresponded to 2.6% less than the estimated force when coactivation was accounted for (3255 ± 206 N). Aponeurosis displacement (13.9–12.9 mm) decreased 30 % (9.6–10.7 mm) when accounting for joint angular rotation (3.6 deg). Coactivation and angular rotation-corrected stiffness yielded a quadratic relationship, R2= 0.98± 0.01, which was similar for the proximal (467 N mm−1) and distal (494 N mm−1) aponeurosis and tendon. Maximal strain and stress were 4.4–5.6 % and 41.6 ± 3.9 MPa, respectively, which resulted in a Young’s modulus of 1048–1474 MPa.


The mechanical properties of the human triceps surae aponeurosis and tendon in vivo were for the first time examined. The stiffness and Young’s modulus exceeded those previously reported for the tibialis anterior tendon in vivo, but were similar to those obtained for various isolated mammalian and human tendons.







The force from muscle contraction is transferred to bone via tendons to produce joint movement. Tendons are, however, not inextensible, but have non-linear spring-like characteristics, which allows for a dynamic mechanical interaction between the muscle and tendon (Griffiths & Selesnick, 1998; Lieber et al. 2000). During locomotion the tendon is stretched and energy is stored which is subsequently converted into kinetic energy upon release (Alexander & Vernon, 1975; Ker et al. 1988).

Although it has been recognised that tendon properties contribute to the complex interaction of the central nervous system, muscle-tendon unit and bony structures to produce joint movement, there is scarce information on human tendon behaviour in vivo. Moreover, investigations of human tendon behaviour have largely been limited to biomechanical testing of isolated cadaver tissue specimens (Rack & Ross, 1984; Goldstein et al. 1987; Loren & Lieber, 1995; McGough et al. 1996), or invasive in vivo methods (Amis et al. 1987; Fellows & Rack, 1987). Therefore, the recent advance of using real-time ultrasonography to non-invasively determine fascicle movement during muscle contraction has provided a method for studying human aponeurosis and tendon tissue behaviour during isometric muscle contraction in vivo (Fukashiro et al. 1995a; Ito et al. 1998).

Thus far, the mechanical properties of the tibialis anterior in the leg have been examined using ultrasonography during voluntary (Ito et al. 1998) and electrically induced (Maganaris & Paul, 1999) contractions, with considerably different results with respect to both tendon force and deformation. The dissimilarities may in part be explained by the different methodologies. In this context, it should be noted that previous studies (Ito et al. 1998; Maganaris & Paul, 1999) have not accounted for the potential error in tendon displacement due to joint angular rotation, or the tendon load attributed to coactivation of the antagonist muscles during the isometric contraction.

Since the aponeurosis of the triceps surae complex and Achilles’ tendon is subject to appreciable stresses during human locomotion, the in vivo study of their mechanical properties is of considerable interest and relevant to loading history and ageing. Furthermore, the Achilles’ tendon is frequently associated with various pathologies related to loading history (Kannus et al. 1997), including complete tendon ruptures (Kannus & Jozsa, 1991). While several studies have estimated Achilles’ tendon force during various activities (Scott & Winter, 1990; Fukashiro et al. 1995b; Finni et al. 1998; Giddings et al. 2000) aponeurosis deformation of the triceps surae has thus far not been measured. Therefore, the purpose of the present investigation was to (1) measure the load- displacement and stress-strain characteristics of the human triceps surae aponeurosis and tendon in vivo, during graded maximal voluntary plantarflexion efforts and (2) examine whether the Load–displacement characteristics of the proximal and distal aponeurosis differed.

Load‐displacement properties of the human triceps surae aponeurosis in vivo

The reason for the presence of the paranasal sinuses has been a controversial subject since the time of Galen, 130–201 A.D. In a review of the literature, the diversity of the numerous functions ascribed to these air-filled cavities was found to be astounding. Many functions were ascribed only on the basis of opinion rather than scientific investigation and recent studies have illustrated the fallacy of these opinions. To date, not one proposed function has been universally accepted to be the essential reason for their existence.



This review of the literature deals mainly with those theories of anatomical and physiological significance of the paranasal sinuses having received the most consideration and many of which are currently considered tenable. These are, as follows: (1) impart resonance to the voice; (2) humidify and warm inspired air; (3) increase the area of the olfactory membrane; (4) absorb shock applied to the head for protection of sensory organs; (5) secrete mucus for keeping the nasal chambers moist; (6) thermally insulate the nervous centers; (7) aid facial growth and architecture; (8) exist as evolutionary remains and/or unwanted air spaces; and (9) lighten the bones of the skull for maintenance of proper balance of the head.

Eighteen hundred years of controversy: the paranasal sinuses

Ultimate tensile strength of fetal and adult human tendons

This investigation was undertaken to determine the densities of fresh human compact and cancellous bone, with its marrow constituents intact, and compact and cancellous bone taken from embalmed cadavers. The density of 107 bone specimens was determined on the basis of the weight and volume of each specimen. Mean density results were: (1) fresh compact bone, 1.85; (2) fresh cancellous bone, 1.08; (3) embalmed compact bone, 1.85; and (4) embalmed cancellous bone, 1.09. Embalming did not appear to have altered the density of either compact or cancellous bone. It was observed also that the densities of several bone specimens taken from the same area of one bone varied greatly.

Density of fresh and embalmed human compact and cancellous bone.

Electromyography is a valuable means of analyzing the muscular components of the oral apparatus. Numerous electromyographic studies have been made of the muscles of mastication;'-' yet, the buccinator muscle, recognized as an integral part of the oral structure and considered by some'2-14 to aid mastication, has received little attention. Palpation, observation of muscle attachments, and paralysis studies have previously shown the buccinator muscles to be active during the following performances: (1) compressing the cheek, thereby aiding mastication'2-'4 and blowing;'2\"3 (2) drawing corner of mouth laterally; 12,13 (3) pulling lips against teeth;'2 and (4) aiding in swallowing.'3 The few electromyographic studies made of this muscle have been related to isolated phenomena, such as aid to denture retention and stabilization,15 role in thumb-sucking and finger-sucking patients,'6 and response to loss of teeth and denture treatment.'7 The present study was designed to determine the role of the buccinator muscle in such activities as chewing, swallowing, blowing, and sucking in the normal subject.

Electromyographic Analysis of the Buccinator Muscle

An electromyographic investigation of the mylohyoid muscle was undertaken to determine its activity relative to isolated movements of the tongue and mandible and during various functions involving multiple parts of the oral apparatus. Data was obtained from 20 subjects. Using bipolar fine-wire electrodes, the anterior fibers were found to be more active than the posterolateral fibers in a majority of activities performed. Tongue movements produced slightly more activity in the postero-lateral fibers; the anterior fibers were more active during mandible movements. During mastication, deglutition, sucking and blowing, both the anterior and postero-lateral fibers were markedly active.

Patricia L. Blanton

Papers

Eighteen hundred years of controversy: the paranasal sinuses

Ultimate tensile strength of fetal and adult human tendons

Density of fresh and embalmed human compact and cancellous bone.

Electromyographic Analysis of the Buccinator Muscle

An electromyographic study of the mylohyoid muscle.