Christopher Briggs

Muscle spindle distribution, morphology, and density in longus colli and multifidus muscles of the cervical spine.

Study Design. Tissue blocks comprising muscle and bone from C5 to C7 segments were harvested at autopsy from 16 individuals ranging in age from 4 to 77 years. The prevertebral longus colli and postvertebral multifidus muscle pairs from one side in each individual were randomly selected for this study of muscle spindles. Objectives. To determine muscle spindle distribution, morphology, and density for the longus colli and multifidus in caudal segments of the human cervical spine, and to assess whether changes are evident from infancy to old age. Summary of Background Data. Age-related changes to the osteoligamentous framework of the cervical spine have been well documented. Postural modification accompanies these structural alterations, but there have been limited attempts to document whether muscle sustains a comparable level of morphologic alteration. Previous studies have examined muscle spindles in the neck muscles of various animal models and in a variety of isolated human muscles. However, most of these studies incurred bias through sampling and methodologic assumptions. Methods. The longus colli and multifidus were resected between C5 and C7, and between left and right pairs selected randomly for spindle analysis. These vertebral segments were selected deliberately because they form the apex of the cervical lordosis and the site at which the greatest age-related modification occurs. The tissue was processed in paraffin, sectioned, and then stained by Masson’s trichrome. Spindle characteristics were examined using light microscopy and analyzed by unbiased stereologic methods. A one-sample paired t test was used to ascertain whether the differences in spindle density between the two muscles were statistically significant. Results. The longus colli has a high density of muscle spindles, which appear clustered and concentrated anterolaterally, away from the vertebral body. The multifidus has a low density of muscle spindles, which are found predominantly as single units concentrated closely to the vertebral lamina. No change in spindle distribution, morphology, and density were observed with age. Conclusions. The current study examined spindle characteristics for an intrinsic neck muscle pair whose coactivation contributes to segmental stability of the cervical spine. The distribution and morphology of muscle spindles differ between the longus colli and the multifidus. In addition, these muscles have significant differences in terms of mean spindle density. Spindle characteristics represent one of many factors that govern proprioceptive regulation in skeletal muscle, and in neck muscles, the central connectivity of these receptors remains undefined. Therefore, although there are anatomic differences between the neck flexor and extensor, the functional implications of these differences are not clear. It is also of interest that spindle characteristics remain unchanged in these intrinsic muscles whose underlying segments are subject to age-related osteoligamentous changes.

Effects of Tensioning the Lumbar Fasciae on Segmental Stiffness During Flexion and Extension : Young Investigator Award Winner

Study Design. Biomechanical study of unembalmed human lumbar segments. Objective. To investigate the effects of tensioning the lumbar fasciae (transversus abdominis [TrA]) aponeurosis) on segment stiffness during flexion and extension. Summary of Background Data. Animal and human studies suggest that TrA may influence intersegmental movement via tension in the middle and posterior layers of lumbar fasciae (MLF, PLF). Methods. Compressive flexion and extension moments were applied to 17 lumbar segments from 9 unembalmed cadavers with 20 N lateral tension of the TrA aponeurosis during: 1) “static” tests: load was compared when fascial tension was applied during static compressive loads into flexion-extension; 2) “cyclic loading” tests: load, axial displacement, and stiffness were compared during repeated compressive loading cycles into flexion-extension. After testing, the PLF was incised to determine the tension transmitted by each layer. Results. At all segments and loads (<200 N), fascial tension increased resistance to flexion loads by ∼9.5 N. In 15 of 17, fascial tension decreased resistance to extension by ∼6.6 N. Fascial tension during cyclic flexion loading decreased axial displacement by 26% at the onset of loading (0–2 N) and 2% at 450 N (13 of 17). During extension loading, fascial tension increased displacement at the onset of loading (10 of 17) by ∼23% and slightly (1%) decreased displacement at 450 N. Segment stiffness was increased by 6 N/mm in flexion (44% at 25 N) and decreased by 2 N/mm (8% at 25 N) in extension. More than 85% of tension was transmitted through the MLF. Conclusions. Tension on the lumbar fasciae simulating moderate contraction of TrA affects segmental stiffness, particularly toward the neutral zone.

Tensile Transmission Across the Lumbar Fasciae in Unembalmed Cadavers : Effects of Tension to Various Muscular Attachments

Study Design. Traction was applied to muscles attaching to the posterior and middle layers of lumbar fascia (PLF, MLF). Effects on fasciae were determined via tensile force measures and movement of markers. Objectives. To document tensile transmission to the PLF and MLF when traction was applied to latissimus dorsi (LD), gluteus maximus (GM), external and internal oblique (EO, IO), and transversus abdominis (TrA) in unembalmed cadavers. Summary of Background Data. A previous study on embalmed cadavers applied traction to muscle attachments while monitoring fascial movement but did not test TrA or the MLF. Methods. The PLF and MLF were dissected then marked on eight unembalmed cadavers. A strain gauge was inserted through fascia at L3; 10N traction was applied to each muscle attachment while photographs and tension measures were taken. Movement of fascial markers was detected photographically. Fascial widths were also measured. Results. Tension was clearly transmitted to fascial vertebral attachments. Tensile forces and fascial areas affected were highest for traction on LD and TrA in the PLF and for TrA in the MLF. Movement of PLF markers from tension on LD and TrA occurred bilaterally between T12 and S1. Effects from other muscles were variably bilateral, with those from GM and IO occurring below L3 and those from EO occurring above L3. Tensile forces were relatively high in the MLF and its width was less than half that of the PLF. Conclusions. Low levels of tension are effectively transmitted between TrA and the MLF or PLF. Via them, TrA may influence intersegmental movement.

Comparative histochemical composition of muscle fibres in a pre- and a postvertebral muscle of the cervical spine

References to histochemistry are extensive for human limb muscles but occur less frequently in relation to vertebral muscle. Most vertebral muscle literature has been concerned with muscle fibre characteristics in the lumbar and thoracic spine, due in large part to the incidence of low back pain and idiopathic scoliosis. However few studies have investigated the histochemical composition of neck muscles in humans: and, to our knowledge, no previous study has examined the antagonistic longus colli and multifidus muscle pair. In addition, while age‐related segmental degeneration is most prominent between C5 and C7, it is not known whether these osteoligamentous changes are paralleled by changes in muscle fibre ratio. Tissue blocks comprising muscle and bone from C5–C7 segments were harvested at autopsy from 16 subjects with ages ranging from 4 to 77 years. The prevertebral longus colli and postvertebral multifidus muscle pairs were randomly selected from one or other side in each subject. The tissue was frozen, sectioned and histochemically stained for myofibrillar adenosine triphosphatase. Analysis of muscle fibre types was performed by light microscopy. Wilcoxon paired t‐tests were used to ascertain whether intramuscular and intermuscular differences in fibre composition were significant. In addition, correlation and regression analyses were used to determine whether fibre type proportions changed in either muscle with increasing age. The present study has revealed histochemical differences between longus colli and multifidus at the level of the C5–C7 vertebral segments. Multifidus comprises a significantly greater proportion of type I than type II fibres. Longus colli comprises a significantly greater proportion of type II fibres than multifidus. Further there were no changes in fibre type proportion in either muscle with increasing age. These observations suggest that longus colli responds equally to postural and phasic demands, whereas multifidus is predominantly postural. Also it would appear that age‐related structural alterations in lower cervical segments are not paralleled by changes in muscle fibre ratio.

The role of forensic anthropology in Disaster Victim Identification (DVI)

This paper briefly describes Disaster Victim Identification (DVI) and reviews the history of the use of forensic anthropology in the identification process. The potential contributions made by forensic anthropology are illustrated through the presentation of a case study. In February 2009 the state of Victoria in south-eastern Australia experienced the most devastating bushfires in its history, resulting in catastrophic loss of life and public and private property. Within 48h of the disaster, forensic teams including pathologists, odontologists and anthropologists assembled at the Victorian Institute of Forensic Medicine in Melbourne to begin the task of identifying the deceased. This paper reviews the part played by forensic anthropologists in the identification process and outlines the important contribution anthropologists can make to DVI, especially at the scene, in the mortuary and in the reconciliation process. The anthropologists experience with differentially preserved human remains meant they played an important role identifying and recovering heavily fragmentary human skeletal remains, differentiating human from non-human remains, establishing basic biological information such as the sex and age of the individuals and confirming or denying the possibility of re-associating body parts for release to families.

Analysis of time of closure of the spheno-occipital synchondrosis using computed tomography.

Current knowledge concerning closure of the spheno-occipital synchondrosis is inadequate for age estimation purposes in that of the few detailed studies conducted, these demonstrate considerable variation concerning the age at which the synchondrosis commences and completes fusion, thus creating uncertainty for forensic investigators who may use this developmental feature for age determinations. The aim of the present study was to determine the sequence and timing of closure of the spheno-occipital synchondrosis for a large sample of a modern Australian population to assess if this age marker is a useful tool for age estimation for individuals around the age of 18 years. The sample consisted of 666 individuals in the age range 15-25 years, who were admitted to the Victorian Institute of Forensic Medicine (VIFM) mortuary and who had undergone routine full body multi-slice CT imaging. Results show that fusion was well underway by the age of 15 years and was complete by 17 years. Fusion begins superiorly and progresses inferiorly. Persistence of a scar at the site of fusion was demonstrated through to age 25 years. After the age of 16 years there was no significant difference in progress of fusion between males and females. The study showed that this age marker is of limited value for age estimations around the age of 18 years in this population.

Effect of overuse injury and the importance of training on the use of adjustable workstations by keyboard operators.

The introduction of adjustable workstations for keyboard operators has been widely recommended to eradicate constrained working postures leading to the development of musculoskeletal disorders. A questionnaire evaluating the use of adjustable workstations was analyzed for 514 keyboard operators. Anthropometric dimensions and workstation settings were measured for 15 operators. There was no difference between sufferers and nonsufferers of overuse injury on the basis of adjustability of their equipment. However, sufferers were less satisfied with their equipment and there was evidence that inappropriate postures were being adopted. The availability of adjustable equipment per se does not necessarily solve the problem. The design of the equipment must be based on suitable anthropometric data and operators must be trained in the correct use of the equipment. The results of this study indicate a perceived need for training and/or information on workstation adjustment among operators, with a preference for information that is supplied verbally, rather than in literature form.

Age estimation using CT imaging of the third molar tooth, the medial clavicular epiphysis, and the spheno-occipital synchondrosis: a multifactorial approach.

A multi-factorial method for estimating age was devised based on the development of the 3rd molar tooth, the medial clavicular epiphysis, and the spheno-occipital synchondrosis, using multiple regression as the means to construct age estimation formulae and CT scanning as the imaging modality. The sample consisted of approximately 600 individuals from a contemporary Australian population, between the ages of 15 and 25 years, who were admitted to the Victorian Institute of Forensic Medicine, Melbourne, Australia, for the purposes of medico-legal death investigation. Results show that the spheno-occipital synchondrosis does not contribute to the age estimation model for this age cohort. The regression computation for the 3rd molar tooth and medial clavicle, when combined into a single multiple regression calculation, provides a robust model with tighter age ranges at the 95% confidence interval (CI) than when each age marker is used individually. This research provides a method to estimate age for unknown age Australian individuals in the problematic age group of 15-25 years with greater precision than previously possible.

Age Estimation and the Developing Third Molar Tooth: An Analysis of an Australian Population Using Computed Tomography

Abstract:  The third molar tooth is one of the few anatomical sites available for age estimation of unknown age individuals in the late adolescent years. Computed tomography (CT) images were assessed in an Australian population aged from 15 to 25 years for development trends, particularly concerning age estimation at the child/adult transition point of 18 years. The CT images were also compared to conventional radiographs to assess the developmental scoring agreement between the two and it was found that agreement of Demirjian scores between the two imaging modalities was excellent. The relatively wide age ranges (mean ± 2SD) indicate that the third molar is not a precise tool for age estimation (age ranges of 3–8 years) but is, however, a useful tool for discriminating the adult/child transition age of 18 years. In the current study 100% of females and 96% of males with completed roots were over 18 years of age.

Disc herniations in the young and end-plate vascularity

The objective of this study was to determine the nature of the persistence of remnants of the original nutritive vascular canals within the vertebral body and correlate their existence with end‐plate “weak spots.” The body‐disc region of 20 lumbar vertebrae between the ages of birth and 22 years was examined histologically to study the vascularity of the end‐plate cartilage and its fate at the end of vertebral growth. Observations indicate a regression of the vascular canals in the end‐plate commencing in the first decade, with “scars” left by these canals visible as nodular areas. By the beginning of the third decade, herniation of the disc material into the weak spots was observed. It is apparent that these weak spots represent a route for the early formation of intrabody nuclear herniations at this age (Schmorls nodes). Clin. Anat. 11:171–176, 1998.