Tensile mechanical properties of human forearm tendons.

Previous studies of the mechanical properties of tendons in the upper limb have used embalmed specimens or sub-optimal methods of measurement. The aim of this study was to determine the biomechanical properties of all tendons from five fresh frozen cadaveric forearms using updated methodology. The cross-sectional area of tendons was accurately measured using a laser reflectance system. Tensile testing was done in a precision servo-hydraulic device with cryo-clamp fixation. We determined that the cross-sectional area of some tendons is variable and directly influences the calculated material properties; visual estimation of this is unreliable. Data trends illustrate that digital extensor tendons possess the greatest tensile strength and a higher Young's modulus than other tendon types.

A three-dimensional study of the musculotendinous and neurovascular architecture of the gracilis muscle: application to functional muscle transfer.

INTRODUCTION: Muscle transfer is used to restore function typically using a single vector of contraction. Although its use with two independently functional muscular units has been employed, in order to refine this concept we endeavoured to detail the intramuscular anatomy of gracilis, a muscle commonly used for transfer. A novel method to capture intramuscular fibre bundle and neurovascular arrangement was used to create a three-dimensional (3D) digital model that allowed for accurate representation of the relationships between all the intramuscular structures to facilitate flap planning. METHODS: Twenty gracilis muscles were harvested from 15 cadavers. All components of the muscle were digitised using a Microscribe G2 Digitiser. The data were exported to the 3D animation software Autodesk(®) Maya(®) 2012 whereupon it was rendered into a 3D model that can be exported as static images or videos. Neurovascular anatomy and muscle architecture were analysed from these models, and fibre bundle length, pennation angle and physiological cross-sectional area were calculated from digitised data. RESULTS: The muscle is composed of a variable number of distinct longitudinal segments with muscle fibres spiralling onto the tendon. The main artery to the muscle has three main intramuscular patterns of distribution. The venae comitantes drain discrete zones without intramuscular macroscopic anastomoses. The minor pedicles form an anastomotic chain along the anterior border of the muscle and all vessels were biased to the deep surface. The nerve is related to the vessels in a variable manner and both run between longitudinal muscular compartments. CONCLUSIONS: The digitisation technique may be used to advance knowledge of intramuscular architecture and it demonstrated that the gracilis muscle is comprised of four to seven muscular compartments, each representing a functional unit that may theoretically be differentially activated and could be harnessed for more sophisticated muscle transfers.

Functional contribution of T1 to the brachial plexus in infants.

To determine the contribution of the T1 root to movements of the upper limb in infancy, 40 infants presenting with obstetrical brachial plexus palsy who underwent resection and reconstruction of all brachial plexus roots with the exception of the T1 root were assessed in the early postoperative period. The movements of the limb were recorded using the Hospital for Sick Children active movement scale and demonstrated considerable variability. All movements of the upper limb were observed in this group with the exception of external rotation of the shoulder and elbow flexion. Classical accounts of the function of T1 have limited its activity to the small muscles of the hand and were based on anatomical dissection, brachial plexus injuries and electrical stimulation. By contrast, this study isolated the physiological activity of T1 and analysed the functional contribution of this root to arm movement. We show a greater than generally recognized contribution of T1 to the function of the upper limb in infants.

Lateral pterygoid muscle: a three-dimensional analysis of neuromuscular partitioning.

The lateral pterygoid (LP) has been implicated in temporomandibular joint (TMJ) pathology. Few studies have examined muscle architecture of the superior (SLP) and inferior (ILP) heads of LP; moreover, the pattern of intramuscular innervation is poorly defined. The purpose of this study was to determine patterns of intramuscular innervation of LP using 3D modeling. The superior and lateral aspects of LP were exposed in 10 embalmed cadaveric specimens. Nerves entering the muscle, all branches of the mandibular nerve (V(3) ), were followed intramuscularly in short segments and sequentially digitized. Muscle volume, surrounding bone, and the TMJ disc were also digitized. The data were reconstructed into 3D models (Maya®) that were used to determine patterns of intramuscular innervation. It was found that the SLP had independent sources of innervation to each of the quadrants in its superior part (masseteric/posterior deep temporal/middle deep temporal/buccal) and one primary source of innervation (buccal) to the quadrants of the inferior part. This difference in innervation is significant as the superior part attaches to the TMJ disc-capsule complex, whereas the inferior part attaches to the mandibular condylar neck. Differing sites of attachment and sources of innervation for each part suggests that movement of the TMJ disc-capsule complex, independent of the condyle, may be possible. The buccal nerve supplied both the medial and lateral quadrants of the ILP, with the medial quadrants receiving additional innervation from V(3) muscular branches. Results of this study could be used to direct EMG/ultrasound studies of LP function as related to TMJ disorders.

Anatomical relationships between selected segmental muscles of the lumbar spine in the context of multi-planar segmental motion: a preliminary investigation.

In the last decade, concepts regarding spinal stability have been redefined. Whereas traditional stability models considered only the integrity of the intervertebral disc and spinal ligaments, mechanisms contributing to spinal stability are now thought to include neural and muscular elements. Lumbar muscles capable of generating intersegmental stiffness are considered necessary for the control of multi-planar segmental spinal motion. The transversus abdominis, psoas, quadratus lumborum and multifidus have each been described functionally as contributing to segmental motion control in the lumbar spine. However, the fundamental anatomy of these muscles has not been fully established nor have their architectural characteristics as a functional group been explored. A dissection of the lumbar spine was undertaken to document the attachments of the deep vertebral muscles and illustrate their group architectural characteristics in the context of multi-planar segmental motion. The transversus abdominis, psoas, quadratus lumborum and multifidus were each noted to have segmental attachment patterns in the lumbar spine. As a group, they surround the lumbar motion segments from the anterolateral aspect of a vertebral body to the spinous process. A hypothetical role for this muscle group in maintaining lumbar spine stability is discussed as are suggestions for future research.

Comparing human skeletal muscle architectural parameters of cadavers with in vivo ultrasonographic measurements.

The purpose of this study was to document and compare the architectural parameters (fibre bundle length, angle of pennation) of human skeletal muscle in cadaveric specimens and live subjects. The medial (MG) and lateral (LG) gastrocnemius, and posterior (PS) and anterior (AS) soleus were examined bilaterally in 5 cadavers (mean age 72.6, range 65-83 y) and 9 live subjects (mean age 76.3, range 70-92 y). Data were obtained from direct measurement of cadaveric specimens and from ultrasonographic scans of the live subjects. In cadaveric muscle, fibre bundles were isolated; their length was measured in millimetres and pennation angles were recorded in degrees. In live muscle, similar measurements were taken from ultrasonographic scans of relaxed and contracted muscle. For the scans of relaxed muscle, subjects were positioned prone with the foot at a 90 degrees angle to the leg, and for scans of contracted muscle, subjects were asked to sustain full plantarflexion during the scanning process. Fibre bundle length and angle of pennation were compared at matched locations in both groups. It was found that the relationship between cadaveric and in vivo values for fibre length and angle of pennation varied between muscle parts. The cadaveric architectural parameters did not tend to lie consistently towards either extreme of relaxation or contraction. Rather, within MG, PS and AS, cadaveric fibre bundle lengths lay between those for relaxed and contracted in vivo muscle. Similarly both the anterior and posterior cadaveric fibre angles of pennation lay between the in vivo values within LG and PS. In summary, architectural characteristics of cadaveric muscle differ from both relaxed and contracted in vivo muscle. Therefore, when developing models of skeletal muscle based on cadaveric studies, the architectural differences between live and cadaveric tissue should be taken into consideration.

Surgical exposure and resection of the vertical portion of the petrous internal carotid artery: anatomic study.

OBJECTIVE: The goals were to determine which surgical approaches, i.e., the preauricular subtemporal infratemporal fossa (PSI), postauricular transtemporal (PAT), and/or subtemporal middle fossa (SMF) approaches, provide optimal exposure of the anterior, posterior, medial, and lateral aspects of the vertical segment of the petrous internal carotid artery (VPCA) and to determine the length of the VPCA that can be resected before a vein graft is necessary. METHODS: Using 22 cadaveric specimens, we compared the length of exposure of the VPCA provided by the PSI, PAT, and SMF approaches. The segment of the VPCA that was exposed with each approach was measured in millimeters and expressed as a percentage of the total length of the VPCA. Resection of the VPCA in 1-mm increments was performed until a graft would be necessary; the total length of the resected segment was recorded in millimeters and was also expressed as a percentage of the total length of the VPCA. RESULTS: The PSI approach provided average exposures of 14.1 mm (95% of the total exposure possible) of the anterior aspect and 14.3 mm (96%) of the lateral aspect of the VPCA; resection of less than 2.3 mm (16%) of the VPCA could be repaired with an end-to-end anastomosis. The PAT approach provided average exposures of 10.5 mm (71 %) of the lateral aspect and 10.0 mm (76%) of the posterior aspect of the VPCA; resection of less than 2.8 mm of the VPCA could be repaired with an end-to-end anastomosis. The SMF approach provided average exposures of 6.1 mm (45%) of the anterior aspect and 5.4 mm (41 %) of the lateral aspect of the VPCA; resection of less than 2.4 mm (24%) of the VPCA could be repaired with an end-to-end anastomosis. CONCLUSION: Lesions on the anterior and lateral aspects of the VPCA can be fully exposed with the PSI approach or partially exposed with the less invasive SMF approach. Lesions on the posterior aspect of the artery are best exposed with the PAT approach. Lesions on the medial aspect of the VPCA cannot be exposed unless the VPCA is mobilized in the PSI approach. Resection of less than approximately 2.5 mm (20%) can be repaired with an end-to-end anastomosis, regardless of the approach used.

Sonographic studies of human soleus and gastrocnemius muscle architecture: gender variability.

The purpose of this study was to establish if there are gender differences in muscle architecture in relaxed human soleus and gastrocnemius muscles of normal, live subjects. Ultrasonography was used to measure fiber bundle length, muscle thickness, and angles of pennation in a total of ten predetermined sites in the medial and lateral heads of gastrocnemius and the anterior and posterior soleus in 19 males and 16 females. Percentage differences between males and females for each parameter were recorded. Gender differences were statistically analyzed using multivariate analysis of variance. In the gastrocnemius and soleus muscles of males and females the differences between the overall fiber bundle length, angle of pennation and muscle thickness were statistically significant (P < 0.05). Overall, females were found to have longer average muscle fiber bundle length and males thicker muscles and larger angles of pennation. The greatest percentage differences of the architectural parameters between males and females were in the posterior soleus: 13% difference in fiber length and 26% difference in angle of pennation in the midline of posterior soleus and 26% difference in muscle thickness of the lateral part of posterior soleus. No correlation was found between leg length and fiber length, angle of pennation or muscle thickness. Fiber length (decreased), angle of pennation (greater) and muscle thickness (greater) of most parts of the gastrocnemius and soleus muscles were significantly different in males and females. Leg length of males and females did not correlate to these architectural parameters.

Resolving discrepancies in image research: the importance of direct observation in the illustration of the human soleus muscle.

A historical analysis of fourteen published illustrations of the soleus muscle from the sixteenth to the twentieth century reveals obvious inconsistencies in the representational accuracy of the architecture of the muscle. To ensure the most accurate illustrations possible, biomedical communicators should conduct direct laboratory observations. A review of reference images alone is insufficient for assuring anatomical accuracy. Having followed this protocol, three architecturally distinct regions of soleus were observed and illustrated and the final results suggest that soleus is a complex multipennate muscle with significant architectural characteristics not typically represented in published illustrations.

Flexor digitorum superficialis: locations of individual muscle bellies for botulinum toxin injections.

Twenty-two Flexor Digitorum Superficialis (FDS) muscles from 18 cadavers were dissected to find the "Optimal Injection Site" (OIS) for botulinum toxin injections to individual bellies of FDS. Coordinates are given as a percentage of the distance along a landmarking line from the medial epicondyle to the pisiform and in millimetres (mm) lateral to it. The OIS were: FDS2: 72%, 14 mm; FDS3: 54%, 17mm; FDS4: 49%, 7mm; FDS5: 76%, 6mm. OIS measurements guide the electromyographer to localize the targeted muscle belly.