Impact of the mandibular divergence on the position of the inferior alveolar nerve and mylohyoid nerve: a computed tomography study and its relevance to bilateral sagittal split osteotomy

Purpose

Bilateral sagittal split osteotomy (BSSO) is the most common procedure used to treat mandibular deformities. BSSO procedures include the Epker technique and the Dal Pont technique which are the most frequently used. Because of the intramandibular pathway of the inferior alveolar nerve (IAN), neurosensory disturbance of the lower lip and chin is the most common complication of BSSO. This study performed quantitative measurements from computed tomographic (CT) data obtained on dry human mandibles. The main aim of the study was to evaluate if mandibular divergence can predict the position of the IAN and the mylohyoid nerve (MHN) to prevent nerve injury.

Methods

After CT and 3D reconstruction of 65 dry mandibles, 30 measurements were made on 3 planes for each hemi-mandible. This allowed analysis of the IAN and MHN pathways. Three groups of hemi-mandibles were created depending on their divergence, and a statistical analysis was performed.

Results

Eight out of the 30 measurements showed a significant difference among the 3 groups. There was no significant difference for the remaining 22 measurements.

Conclusions

The IAN seems to have a more superior position in the groups of mandibular hypo- and hyper-divergence. Orthognathic surgeons should use a more superficial retromolar bone incision in these cases. Finally, the Epker technique would be safer for preserving the MHN in normo- and hypo-divergent patients.     

What is the Safest Sprint Starting Position for American Football Players?

The main objective of this study was to perform a biomechanical analysis of three different sprint start patterns to determine the safest position in term of neck injury and Sport-Related Concussion (SRC). The second objective was to collect data on the learning process effect between football players and non-players. Three different sprint initial positions adopted by football players were studied (i.e., 4-, 3- and 2-point positions). Twenty five young healthy males, including 12 football players, participated to this study. A stereophotogrammetric system (i.e., Vicon) was used to record motion patterns and body segments positions. Various measurements related to head and trunk orientation, and player field-of-view were obtained (e.g., head height, trunk bending, time to reach upright position, head speed (vertical direction) and body speed (horizontal direction)). Learning process was found to have no influence on studied parameters. Head redress is also delayed when adopting a 4-point position leading to a reduce field-of-view during the start and increasing therefore the probability of collision. Concerning the three different positions, the 4-point position seems to be the more dangerous because leading to higher kinetic energy than the 2- and 3-point start positions. This study proposes a first biomechanical approach to understand risk/benefit balance for athletes for those three different start positions. Results suggested that the 4-point position is the most risky for football players.

Key points

• Motion analysis and biomechanical analysis of the initial start position of the sprint could be used to increase the safety of the football players.
• Analysis of kinematic and trajectory of the head and the time to reach the upright position could be used to determine whether or not a player can return to play after concussion.
• A balance needs to be found between player’s safety (2-point start) and speed (4-point start).

Key words: Sports, sports medicine, brain concussion, biomechanics     

No effects of cervical spine motion on cranial dura mater strain

OBJECTIVE: The aim of this study was to analyze the effects of cervical spine motion on cranial dura mater length variations in anatomical specimens using high-resolution linear displacement transducers. We hypothesized that transducer resolution was sufficient to measure dura mater length changes if they occurred during cervical spine motion. DESIGN: Cranial dura mater strain was measured using differential variable reluctance transducers during cervical spine motion in 11 formaldehyde-fixed whole-body anatomical specimens (mean age: 82 years). BACKGROUND: Several theories hypothesize that functional maneuvers carried out on the spine have an effect on intra-cranial structures due to the supposed continuity of spinal and cranial dura mater. The displacements of the spinal dura mater are supposed to be transmitted to the cranial dura mater. METHODS: Eleven anatomical specimens were used. Each specimen (positioned supine) was provided with three openings in the skull (frontal and parietal regions), leaving the dura mater intact. A differential variable reluctance transducer was inserted in frontal or sagittal orientation in the dura mater exposed in each opening. Strain was recorded during cyclic motions of cervical spine flexion-extension, lateral bending and axial rotation. RESULTS: Average length changes ranged from 0.01 to 0.13% (SD 0.01-0.21%) of initial length for all motions and locations studied, which in all cases was less than the accuracy of the transducers. CONCLUSION: It can thus be concluded that cervical spine motion does not induce significant strain of the cerebral dura mater. RELEVANCE: The present study does not support theories that are based on the transmission of strains from spinal to cranial dura mater.     

The prevalence of mycotoxins in Kashin-Beck disease

Mycotoxins are naturally occurring toxic chemical compounds produced by fungi infesting agricultural crops both during their growth and storage. Such secondary metabolites, when ingested, can produce toxic syndromes in humans. As it has been suggested that mycotoxins might be involved in the development of Kashin-Beck disease (KBD), we undertook a survey of barley grains of KBD-affected families and non-affected families in that country. We found, by thin layer chromatography, a hitherto unknown metabolite of Alternaria sp. This was especially common on the barley grains of KBD-affected families.     

In vivo thorax 3D modelling from costovertebral joint complex kinematics

Background

The costovertebral joint complex is mechanically involved in both respiratory function and thoracic spine stability. The thorax has been studied for a long time to understand its involvement in the physiological mechanism leading to specific gas exchange. Few studies have focused on costovertebral joint complex kinematics, and most of them focused on experimental in vitro analysis related to loading tests or global thorax and/or lung volume change analysis. There is however a clinical need for new methods allowing to process in vivo clinical data. This paper presents results from in vivo analysis of the costovertebral joint complex kinematics from clinically-available retrospective data.

Methods

In this study, in vivo spiral computed tomography imaging data were obtained from 8 asymptomatic subjects at three different lung volumes (from total lung capacity to functional residual capacity) calibrated using a classical spirometer. Fusion methods including 3D modelling and kinematic analysis were used to provide 3D costovertebral joint complex visualization for the true ribs (i.e., first seven pairs of ribs).

Findings

The 3D models of the first seven pairs of costovertebral joint complexes were obtained. A continuous kinematics simulation was interpolated from the three discrete computerized tomography positions. Helical axis representation was also achieved.

Interpretation

Preliminary results show that the method leads to meaningful and relevant results for clinical and pedagogical applications. Research in progress compares data from a sample of healthy volunteers with data collected from patients with cystic fibrosis to obtain new insights about the costovertebral joint complex range of motion and helical axis assessment in different pathological conditions.     

Bi- and three-dimensional CT study of carpal bone motion occuring in lateral deviation

Summary A computed tomography (CT) study of the right wrists of 15 volunteers and of 5 anatomical preparations in neutral position, radial (15°) and ulnar (30°) deviation enables to tackle the qualitative analysis of carpal bone motion. The CT Scans were analyzed and reconstructed in three dimensions by means of the Philips CAMRA S100 computer program. The results show that the capitate, the metacarpals II and III and, to a lesser extent, the trapezium and the trapezoid are poorly mobile. Our study points to the role of the flexor and extensor carpi ulnaris muscles in the stability of the internal carpus, confirming that the pisiform is a sesamoid bone in the flexor carpi ulnaris tendon. A model of longitudinal functional structure of the carpus during lateral deviation, intermediate between those of Navarro and Taleisnik, is proposed.

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Etude tomodensitométrique bi- et tridimensionnelle des mouvements des os du carpe lors des inclinaisons latérales

Résumé Une étude tomodensitométrique des poignets droits de 15 volontaires et de 5 préparations anatomiques réalisée en position neutre, en inclinaison radiale (15°) et ulnaire (30°) permet d'aborder l'analyse qualitative des mouvements des os du carpe. Les coupes tomodensitométriques ont été analysées et des reconstructions tridimensionnelles ont été effectuées à l'aide du programme CAMRA S100 de Philips. Les résultats montrent que le capitatum, les métacarpiens II et III et, dans une moindre mesure, le trapèze et le trapézoïde sont peu mobiles. Notre étude souligne l'importance du rôle des muscles fléchisseur et extenseur ulnaires du carpe sur la stabilité de la partie interne du carpe confirmant que le pisiforme doit être considéré comme os sésamoïde du tendon du fléchisseur ulnaire du carpe. Un modèle de structure fonctionnelle longitudinale du carpe lors des inclinaisons latérales, intermédiaire à ceux de Navarro et Taleisnik, est proposé.

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Abbreviations R radius - Td trapezoideum - U ulna - Ca capitatum - Na navicular - Ha hamatum - Lu lunatum - IU ulnar deviation - Tri triquetrum - IR radial deviation - Pi pisiform - PA anatomic preparations - Tz trapezium - V volunteers     

Quantified relationships of the radial nerve with the radial groove and selected humeral landmarks

Anatomical relationships between the radial nerve, the deltoid muscle insertions and several bony landmarks have been investigated to assess the feasibility of surgical transfer of the deltoid transfer during humeral osteotomy. Eleven embalmed human specimens were dissected. Each specimen included the whole thorax, both shoulders and upper limbs. Spatial position of the radial nerve along the radial groove, the deltoid muscle, and several anatomical landmarks was digitised using a three-dimensional (3D) digitiser. Sixteen distances and one angle characterizing the relationships between the path of the radial nerve and the landmarks were processed. Results showed that the average distance between the emergence of the radial nerve from the lateral intermuscular septum and the most distal insertion point of the deltoid muscle on the humeral bone shaft was 47.6 ± 18.5 mm. The angle between a line extending from the entry of the radial nerve into the radial sulcus and its point of emergence (REN–REM line), and on the other hand a line running from the radial emergence and the deltoid muscle tip (REM–DELTIP line) was in average 23.5 ± 6.7°. The length of four lines running perpendicular to REM–DELTIP and crossing each quarter of the REN–REM line were interpolated. The length of these four lines was, from proximal to distal, 31.3 ± 11.5 mm; 23.0 ± 7.8 mm; 16.5 ± 6.2 mm; and 7.6 ± 2.6 mm, respectively. These results described in a quantitative way the path of the radial nerve in respect to the humeral bone and the deltoid muscle. These data will be used for further development of a humeral osteotomy protocol taking into account the spatial position of the radial nerve to orientate safely the surgical tools used to cut the humeral shaft.