Disproportionate Cochlear Length in Genus Homo Shows a High Phylogenetic Signal during Apes' Hearing Evolution.

Changes in lifestyles and body weight affected mammal life-history evolution but little is known about how they shaped species' sensory systems. Since auditory sensitivity impacts communication tasks and environmental acoustic awareness, it may have represented a deciding factor during mammal evolution, including apes. Here, we statistically measure the influence of phylogeny and allometry on the variation of five cochlear morphological features associated with hearing capacities across 22 living and 5 fossil catarrhine species. We find high phylogenetic signals for absolute and relative cochlear length only. Comparisons between fossil cochleae and reconstructed ape ancestral morphotypes show that Australopithecus absolute and relative cochlear lengths are explicable by phylogeny and concordant with the hypothetized ((Pan,Homo),Gorilla) and (Pan,Homo) most recent common ancestors. Conversely, deviations of the Paranthropus oval window area from these most recent common ancestors are not explicable by phylogeny and body weight alone, but suggest instead rapid evolutionary changes (directional selection) of its hearing organ. Premodern (Homo erectus) and modern human cochleae set apart from living non-human catarrhines and australopiths. They show cochlear relative lengths and oval window areas larger than expected for their body mass, two features corresponding to increased low-frequency sensitivity more recent than 2 million years ago. The uniqueness of the "hypertrophied" cochlea in the genus Homo (as opposed to the australopiths) and the significantly high phylogenetic signal of this organ among apes indicate its usefulness to identify homologies and monophyletic groups in the hominid fossil record.

Transversal craniofacial growth evaluated on children dry skulls using V2 and V 3 canal openings as references.

PURPOSE: The aim of this study was to investigate the transversal relationships between two cephalometric landmarks and lines on the face using ovale, rotundum, greater palatine and infra-orbital foramina as references. METHOD: Thirty-four children dry skulls, 19 males and 15 females aged 0-6 years, were examined by computed tomography scanning by using constructed tomographic axial and frontal planes. The cephalometric transversal dimensions of the face skull were measured between the right and left landmarks from the orbital lateral wall and from the zygomatic arch. The cephalometric transversal dimensions of the base skull were measured between the right and left ovale, rotundum, greater palatine and infra-orbital foramina. RESULTS: Statistical analysis using partial correlations, regardless of the age, showed strong relationships (p < 0.05) among transversal measurements with nerve canal openings and transversal distances of skull face. CONCLUSION: We showed that the cranial base transversal growth was very strongly related to facial transversal growth from the postnatal period up to 6 years of age.

Effect of voxel size on the accuracy of 3D reconstructions with cone beam CT.

OBJECTIVES: The various types of cone beam CT (CBCT) differ in several technical characteristics, notably their spatial resolution, which is defined by the acquisition voxel size. However, data are still lacking on the effects of voxel size on the metric accuracy of three-dimensional (3D) reconstructions. This study was designed to assess the effect of isotropic voxel size on the 3D reconstruction accuracy and reproducibility of CBCT data. METHODS: The study sample comprised 70 teeth (from the Institut d'Anatomie Normale, Strasbourg, France). The teeth were scanned with a KODAK 9500 3D® CBCT (Carestream Health, Inc., Marne-la-Vallée, France), which has two voxel sizes: 200 µm (CBCT 200 µm group) and 300 µm (CBCT 300 µm group). These teeth had also been scanned with the KODAK 9000 3D® CBCT (Carestream Health, Inc.) (CBCT 76 µm group) and the SCANCO Medical micro-CT XtremeCT (SCANCO Medical, Brüttisellen, Switzerland) (micro-CT 41 µm group) considered as references. After semi-automatic segmentation with AMIRA® software (Visualization Sciences Group, Burlington, MA), tooth volumetric measurements were obtained. RESULTS: The Bland-Altman method showed no difference in tooth volumes despite a slight underestimation for the CBCT 200 µm and 300 µm groups compared with the two reference groups. The underestimation was statistically significant for the volumetric measurements of the CBCT 300 µm group relative to the two reference groups (Passing-Bablok method). CONCLUSIONS: CBCT is not only a tool that helps in diagnosis and detection but it has the complementary advantage of being a measuring instrument, the accuracy of which appears connected to the size of the voxels. Future applications of such measurements with CBCT are discussed.

A plea for the use of drawing in human anatomy teaching.

Descriptive human anatomy constitutes one of the main parts of the educational program of the first part of the medical studies. Professors of anatomy have to take into account the exponential evolution of the techniques of morphological and functional exploration of the patients, and the trend to open more and more the contents of the lectures of anatomy to clinical considerations. Basically, teaching requires a series of descriptive and educational media to set up, in front of the student, the studied structures and so to build the human body. More generally, lectures in morphological sciences try to develop three types of knowledge: declarative, procedural, and conditional. Traditionally in France "basic or first" anatomy is taught in amphitheater and in big groups by building each structure or region on a blackboard with colored chalk that allows a relief stake of certain structures and builds in two dimensions a three-dimensional organization. Actually, the blackboard is and stays for us an excellent media of non-verbal expression.

[Histological analysis of dental follicles after unerupted mandibular third molar extraction]. / Analyse histologique des follicules dentaires après germectomies des troisièmes molaires mandibulaires.

INTRODUCTION: The extraction of third mandibular tooth germ (M3) is often prophylactic to avoid orthodontic treatment relapse and to prevent infectious or tumoral diseases developing from the dental sac. The purpose of this study was to screen for early histopathological modification of dental follicles (inflammatory, infiltration, or epithelial metaplasia) after extraction of third mandibular tooth germ (M3) on asymptomatic patients. The secondary objective was to study the proliferative activity of the epithelium by dosing the anti Ki-67 antibody. PATIENTS AND METHOD: Twenty dental follicles extracted from 12 boys and eight girls between 14 and 18 years of age were examined under phototonic microscopy. The proliferative activity of the epithelium was assessed by immuno-histochemistry. RESULTS: Three dental follicles presented with focal epidermoid metaplasia of the epithelium, without odontogenic tumoral proliferation. In all other cases, the cylindrical epithelial cell structure was normal. A mild chronic inflammatory infiltrate was present in 30% of the cases. Immuno-histochemical analysis revealed labeling of very rare epithelial lining cells, slightly more in cases presenting with metaplasia. DISCUSSION: The prevalence of early morphological changes of dental sac is low. This histo-morphological study does not support the systematic extraction of asymptomatic mandibular tooth germs (M3).

Scaphotrapezial ligament: normal arthro-CT and arthro-MRI appearance with anatomical and clinical correlation.

The purpose of our study was to demonstrate and describe the MR and arthro-CT anatomic appearance of the scaphotrapezial ligament and illustrate some of the pathologies involving this structure. This ligament consists of two slips that originate from the radiopalmar aspect of the scaphoid tuberosity and extend distally, forming a V shape. The ulnar fibers, which are just radial to the flexor carpi radialis sheath, inserted along the trapezial ridge. The radial fibers were found to be thinner and inserted at the radial aspect of the trapezium. Twelve fresh cadaver wrists were dissected, with close attention paid to the scaphotrapezio-trapezoidal (STT) joint. An osseoligamentous specimen was dissected with removal of all musculotendinous structures around the STT joint and was performed with high-resolution acquisition in a 128-MDCT scanner. Samples of the wrist area were collected from two fetal specimens. A retrospective study of 55 patients with wrist pain that were submitted to arthrography, arthro-CT, and arthro-MRI imaging was performed (10 patients on a 3-T superconducting magnet and 45 patients on a 1.5-T system). Another ten patients had high-resolution images on a 3-T superconducting magnet without arthrographic injection. MR arthrography and arthro-CT improved visualization and provided detailed information about the anatomy of the scaphotrapezial ligament. Knowledge of the appearance of this normal ligament on MRI allows accurate diagnosis of lesions and will aid when surgery is indicated or may have a role in avoiding unnecessary immobilization.

Accuracy of 3D reconstructions based on cone beam computed tomography.

Three-dimensional imaging of teeth will increase its impact in clinical practice if reconstructions are metrically accurate. We hypothesized that, with cone beam computed tomography (CBCT) data, three-dimensional images of teeth can be reconstructed with the same accuracy and precision as with in vitro micro-computed tomography (micro-CT) data acquisition, the current reference standard. We used a sample of CBCT and micro-CT data taken of tooth germs. Volumes obtained with CBCT and micro-CT devices were statistically similar (n = 120, Passing-Bablok regression). Geometric deviations between CBCT and micro-CT three-dimensional surface reconstructions did not show any areas of important and systematic errors. Future investigations with the use of larger samples may also demonstrate that CBCT data will be helpful for a more in-depth study of other aspects of dental morphology--for example, assessing tooth development. With sufficient accuracy for clinical situations, potential future medical applications of such measurements with CBCT are envisaged.

Is the high submandibular transmasseteric approach to the mandibular condyle safe for the inferior buccal branch?

PURPOSE: There are basically 3 main approaches for extra-articular mandibular condyle fractures: low cervical, retromandibular and preauricular. These include a risk of facial palsy affecting the marginal mandibular branch. We use a high submandibular transmasseteric approach featuring masseter section 10-20 mm above the mandibular basilar edge. Our null hypothesis was that both the marginal mandibular and the inferior buccal branches are not more at risk than in other surgical approaches. METHODS: This study was based on 20 parotidomasseteric dissections from 10 embalmed cadaveric heads. We used as reference the vertical line, passing through the mandibular angle, parallel to the preauricular line. We performed measurements of the marginal mandibular and inferior buccal branches' heights. RESULTS: The inferior buccal branch had an average height of 16.8 mm and the highest standard deviation (7.2). Extremes were, respectively, 32 and 7 mm. The marginal mandibular branch had an average height of 3.2 mm with standard deviation equal to 3.0. Extremes were, respectively, 9 and -3 mm. CONCLUSION: The high submandibular transmasseteric approach provides great exposure of facial nerve branches lying on the masseter muscle, if even encountered. Through masseteric incision performed between 10 and 20 mm above the basilar edge of the mandible, the marginal mandibular branch is safe from wound with an added safety margin of 4 mm. The surgeon using this approach is most likely to encounter the inferior buccal branch. It can then be avoided under visual control. This makes it a swift and safe approach to the mandibular condyle.

The laryngeal fat body.

AIM: To describe the anatomy and topography of the laryngeal fat body and of the space it lies within. MATERIALS AND METHODS: The study is carried out on series of histological sections of head and neck blocks from six foetuses and three newborns. Three adult necks were dissected, a fourth one analysed through sagittal median section. CT-Scan and MRI imaging complete the description. RESULTS: The laryngeal fat body (LFB) lies within the pre-epiglottic (PE) space that stands in the median anterior part of the upper infrahyoid region, located just below the level of the hyoid bone. The walls of the PE space are: superior (base), anterior lateral right and left, posterior, inferior (apex). This space is divided into two compartments by a median septum. The LFB consists in a rather pure fat, structured in large polyhedral lobules. It shows no limiting capsule. DISCUSSION: Dissection-based description of the PE space made in literature matches ours conducted on series of histological sections. All authors agree on the fat content of the space but some of them find a capsule around the LFB that we did not observe on our histological sections. CT-Scan and MRI imaging are accurate for analysis of these structures and of similar efficiency. The study of the LFB should be considered regarding the one of other fat bodies in the human body. CONCLUSION: Anatomical knowledge of the PE space and its content, the LFB, is important, as alteration of their morphology is the early witness of neighbouring carcinological extension.

The enamel-dentine junction in the postcanine dentition of Australopithecus africanus: intra-individual metameric and antimeric variation.

We used micro-computed tomography and virtual tools to study metric and morphological features at the enamel-dentine junction and on the outer enamel surface in the postcanine dentition of an exceptionally well-preserved maxilla and mandible of an early hominin. The fossil, Sts 52 from Sterkfontein, South Africa, is attributed to Australopithecus africanus and is about 2.5 million years old. For comparative purposes in this exploratory study, we also used micro-computed tomography to analyse the dentition of a common chimpanzee (Pan troglodytes), a pygmy chimpanzee (Pan paniscus) and three extant humans. Metameric variation of the 3D enamel-dentine junction in the two chimpanzee mandibles was much smaller than in extant humans. Variation in metameric shape was high and complex. Notably, the mandibular metameric variation in extant humans can be greater within individuals, as compared with variation between individuals, with differences in shape appearing greater for M2 compared with M1. We recommend the use of a new approach in which individual metameric variation is systematically assessed before making inferences about differences between fossil hominin species. The fossil hominin examined in this study showed a metameric pattern of mandibular variation in shape that was comparable to the pattern seen in two chimpanzees. This degree of metameric variation appeared relatively small compared with the much larger patterns of variation observed within and between extant humans.

MRI evidence of lateral pterygoïd muscle palpation.

The literature suggests that the lateral pterygoïd muscle is not palpable using an oral approach. The authors palpate the lateral pterygoïd muscle during clinical examination and for the treatment of temporomandibular joint disorders. The authors present an MRI demonstration showing how palpation is achieved.

Frohse's arcade is not the exclusive compression site of the radial nerve in its tunnel.

INTRODUCTION: The radial tunnel is a musculo-aponeurotic furrow which extends from the lateral epicondyle of humerus to the distal edge of the supinator muscle. The superficial head of the supinator muscle forms a fibrous arch, the arcade of Frohse (AF), which is the most common site of compression of the radial nerve motor branch. The latter is less commonly compressed by the adjacent muscular structures. This tunnel syndrome might be worsened with repeated pronation and supination of the forearm. The double object of that work was: (1) to define the radial nerve anatomic landmarks, (2) to determine the anatomical relationship of the radial nerve main trunk and branches to the peripheral osseous and muscular structures in the anterior aspect of the elbow joint in order to identify which of these conflicting elements are likely to cause a compressive neuropathy. MATERIAL AND METHODS: The study design involved the dissection of 30 embalmed cadaveric upper limbs. Anatomic and morphometric investigations of the radial nerve, its terminal and motor branches were carried out. The presence of adhesions between radial nerve and joint capsule, tendons and aponeurotic expansions of epicondylar muscles and supinator arch was investigated. All measurements were taken in both pronation and supination of the forearm. RESULTS: Neither macroscopic radial compressive neuropathy at the level of the supinator arch nor adhesions between the radial nerve and the joint capsule were found. In four cases (13%), dense fibrous tissue surrounded the radial nerve supply to extensor carpi radialis brevis (ECRB). The fibrous arch of the supinator muscle arose in a semi-circular manner and was noted to be tendinous in 87% of the extremities and of membranous consistency in the remaining 13%. The length of the AF averaged 25.9 mm. The angle formed by the radial shaft and the supinator arch was 23 degrees. Neither fibrous structures nor adhesions of the deep branch of the radial nerve (DBRN) along its course through the supinator muscle were observed. DISCUSSION: Anatomic studies have revealed a variable rate of occurrence of a tendinous AF, which range from 30 to 80% (87% in our study) according to authors. It is reported to be a predisposing factor to the development of chronic entrapment neuropathy of the DBRN, especially if it is thick and provides a narrow opening for passage of the DBRN. The tendinous consistency of the supinator arch is believed to develop in adults, in response to repeated rotary movements of the forearm. Repetitive pronation and supination of the forearm induces compression of the radial nerve and its branches between two inextensible structures. The fibrous AF and the proximal end of the radius (radial head and radial tubercle). This condition is aggravated by the supinator muscle repeated activity. Repetitive compression might then promote histological changes in radial tunnel content and progressive development of a local fibrous zone. We also observed that the radial nerve supply to ECRB could be entrapped between the superolateral aspect of the ECRB and the superior edge of the supinator muscle.

[Massage of the lateral pterygoid muscle in acute TMJ dysfunction syndrome]. / Massage du muscle ptérygoïdien latéral dans le SADAM aigu.

INTRODUCTION: Massage of the lateral pterygoid muscle according to Cyriax's principles is an unrecognized procedure. This procedure was tried on patients presenting with temporomandibular joint dysfunction syndrome. MATERIAL AND METHODS: Fifteen patients were treated. Pain, joint clicking, measurement of mouth opening, lateral excursion and propulsion were recorded. Assessment was made before and after the massage in the same consultation. RESULTS: Joint clicking was solved in 80% and pain in 50% of the cases. Mouth opening increased by 12.8%, propulsion by 11.6% and lateral excursion by 41.3%. DISCUSSION: Massage of the lateral pterygoid muscle according to Cyriax's principles is a simple and efficient method that can be recommended for patients presenting with temporomandibular joint dysfunction syndrome. We performed a brief anatomical and radiological MRI study supporting the feasibility of lateral pterygoid muscle palpation.

Relationships of the musculocutaneous nerve and the coracobrachialis during coracoid abutment procedure (Latarjet procedure).

PURPOSE: The aim of this study was first to define first the anatomical relationships between the musculocutaneous nerve and the coracobrachialis, and then the induced modifications of these relationships by a preglenoid transposition of the vertical part of the coracoid process. MATERIALS AND METHODS: Twenty-one embalmed adult trunks and upper limb were dissected. First the coracobrachialis and the musculocutaneous nerve were identified through a deltopectoral approach. We measured the distances between the lateral cord of the brachial plexus and the entry point of the nerve, between the inferior tip of the tip of the coracoid process and the penetration of the nerve or its twigs, and finally the angle between the general axis of the coracobrachialis and the axis of the musculocutaneous nerve. The same measures were performed after the coracoid bone block abutment. RESULTS: Proximal motor branches destined to the coracobrachialis varied from 0 to 3. Mean distance between the lateral cord of the brachial plexus and entry point of the nerve into the muscle was 47.2 mm before and 48.43 mm after the coracoid transfer. Mean angulations between the nerve and the muscle was 121 degrees before and 136 degrees after the transfer of the coracoid process. Mean distance between the inferior tip of the coracoid process and entry point of the nerve into the muscle was 55.7 mm, reduced to 48.6 mm after the coracoid transposition. Finally, the distance between the tip of the coracoid and the first motor twig entering the coracobrachialis was less than 50 mm in 75% of the cases with a mean value of 40.6 mm. CONCLUSIONS: Lesion of the musculocutaneous nerve is a known complication of the coracoid bone block abutment procedure (Latarjet-Bristow). From this study we know that they are due to lengthening of the nerve and modification of the penetration angle of the nerve into the coracobrachialis. We also infer that some motor nerve destined to the coracobrachialis might be damaged during the proximal medial release of the muscle after the detachment of the pectoralis minor muscle.

[Trapezio second metacarpal joint: anatomical study and clinical matters]. / Articulation du trapèze avec le second métacarpien: étude anatomique et intérêts cliniques.

INTRODUCTION: An unusual dislocation of the column of the thumb associated with a fracture of the base of the second metacarpal inspired an anatomical study of the trapeziosecond metacarpal joint. MATERIALS AND METHODS: Forty-five dissections of the palmar aspect of trapeziometacarpal joint aimed at focusing on palmar ligaments and tendons reinforcing the joints. RESULTS: Trapeziosecond metacarpal joint is a constant little diarthrosis reinforced by a palmar ligament stressed between the crest of the trapezium and the base of the second metacarpal. The tendon of flexor radialis carpi muscle is an active link due to strong vinculae to trapezium bone and distal attachment to the bases of both second and third metacarpals. CONCLUSION: The connections between the trapezium and the base of the second metacarpal bone play a role in the treatment of thumb instability and their mechanical importance is illustrated in our original clinical observation.

Anatomical basis for distal sartorius muscle flap for reconstructive surgery below the knee. Anatomical study and case report.

We report a case of a woman presenting with a long-term non-healing wound below the tibial tubercle that underwent a successful sartorius muscle flap. We performed an anatomical study of the vascularisation of the sartorius muscle. The vascular supply to the distal part of the sartorius muscle was studied in 15 limbs by dissection and after red ink and latex injections. The artery of the sartorius muscle flap arises most of the time from the saphenous artery or the descending genicular artery and is supplied through anastomoses by branches of the posterior tibial artery and the medial inferior genicular artery. The flap is useful for covering wounds around the knee, as well as the proximal and the middle thirds of the leg. The surgical technique is relatively simple, with a low morbidity from muscle harvesting.

Sagittal craniofacial growth evaluated on children dry skulls using V2 and V3 canal openings as references.

The purpose of this study was to investigate the relationship between standard cephalometric landmarks and lines and those using ovale, rotundum, greater palatine and infra-orbital foramina as references. Thirty-four children dry skulls, 19 males and 15 females aged 0-6 years, were examined by computed tomography scanning. The classical cephalometric dimensions of skull base were measured from middle sagittal plane crossing over basion, nasion and sella turcica. Those of hard palate (maxilla and palatine bone) were measured from axial plane intersecting posterior nasal spine and anterior nasal spine. The dimensions between ovale and rotundum foramina, rotundum and infra-orbital foramina, greater palatine and infra-orbital foramina were determined by using constructed tomographic planes enclosing these different foramina. Biostatistical analysis using partial correlations showed that the linear variables with nerve canal openings as references are strongly related to length of both the skull base and of the hard palate. The results highlight the importance of the nerve canal openings of skull base and bone facial components in normal or pathologic craniofacial growth investigations.

[Proposal for new anterior portals for wrist arthroscopic as a complementary approach to open anterior wrist surgery]. / Arthroscopie complémentaire de l'ostéosynthèse du radius distal par abord antérieur: bases anatomiques de nouvelles voies arthroscopiques antérieures.

PURPOSE OF THE STUDY: Morphological and morphometric studies of the wrist ligaments are scarce. The radiocapitatum and scapholunate ligaments play a pivotal role in wrist stability. Classically, a posterior approach is used for arthroscopic procedures, but an anterior approach should be possible. We conducted a cadaver study to search for new anterior portals for wrist arthroscopy. MATERIAL AND METHODS: Twenty-five formol-treated upper limbs were dissected. The classical anterior approach for open wrist surgery was executed. The different elements of the capsule-ligament system of the anterior aspect of the wrist were identified and labeled. The dissection was then extended to the ulna in search of soft points which were identified and evaluated. The different structures generally identified during wrist arthroscopy were noted. RESULTS: Two potential portals were identified in all wrists: one between the radiolunate ligament and the radio-scapho-capitatum ligament on the radial aspect and one between the radio-lunate ligament and the ulno-lunate ligament. Arthroscopic exploration enabled observation of the scapho-lunate ligament, the luno-triquetral ligament, the triangular complex of the carpus, and the entire inferior aspect of the radial joint surface, with no risk of vessel or nerve injury because of the exposure allowed by the osteosynthesis approach. DISCUSSION: Wrist arthroscopy is now accepted as a reliable technique not only for diagnostic purposes but also for therapeutic interventions for the treatment of fractures of the lower radius. Most of the arthroscopic portals described in the literature are posterior. The anterior portals described here do not involve any vascular or neurological risk since the radial approach is made under visual control by extension of the open anterior approach and on the ulnar side the noble structures are positioned medially to the ulnar flexor tendon of the carpus. This enables good triangulation necessary for the usual arthroscopic procedures. Finally, these portals have no supplementary morbidity which would be the case with percutaneous portals (injury to the medial nerve, the radial vasculonervous bundle, the radial flexor tendon). CONCLUSION: These new arthroscopic portals are complementary to the anterior approach for open wrist surgery and enable a natural extension of joint exploration via both the radial and ulnar approaches described in this study.

[Facial fat: descriptive and functional anatomy, from a review of literature and dissections of 10 split-faces]. / La graisse de la face : anatomie descriptive et fonctionnelle à partir d'une revue de la littérature et de dissections de dix hémifaces.

The aim of this study is to describe the anatomy of the fat in the face, based on a review of the literature and dissections of 10 half-faces. The facial fat can be divided in two layers. The first-one is superficial, between the skin and the superficialis fascia. Its function is essentially protective and its morphological implications are major, especially according to the facial aging. The other layer is deep, under the superficialis fascia. Its principal function is mechanical and its morphological implications are less important. This layer is made of several fat pads in continuity, excepted the buccal fat pad which is separated from the others by its own capsula. The other fat pads are the intra orbialis fat pad, the sub orbicularis oculi fat pad (SOOF), the retro orbicularis oculi fat pad (ROOF), the galeal fat pad and the temporal fat pad.

Finite element analysis of the strain distribution in the humeral head tubercles during abduction: comparison of young and osteoporotic bone.

AIM: The aim of this work was to design an accurate 3D digital model of the humerus and rotator cuff muscles. This model was then used to study strain distribution in humeral tubercles according to bone density. MATERIALS AND METHODS: The geometry of bone and muscle structures was reproduced using SURFDRIVER software, based on anatomical sections, CT scans and MRI images from the Visible Human Project image library. The contours were transferred to PATRAN software to rebuild volumes and mesh them. Calculations of strains and their distribution were performed using NASTRAN software. All the elements were considered to be isotropes. RESULTS: The study of the distribution of stress magnitude according to the type of bone modeled, shows that some stresses in cortical bone are greater than those in cancellous bone and are also greater in old bone, implying more deformation in old bone at constant force. This study also shows that stresses do not penetrate deeply into cancellous tissue. CONCLUSION: Observing the simulation results led understanding of the pathology of certain fractures of the proximal end of the humerus. This study also helped explain why certain types of osteosynthesis fail due to tubercles reconstruction failures.