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.

The supraspinatus is most frequently involved in shoulder pathology. However, the musculotendinous architecture of the supraspinatus has not been well documented. Therefore, the purpose of this study is to investigate the detailed three-dimensional architecture of the supraspinatus throughout its volume. Ten male formalin embalmed cadaveric specimens (mean age 61.9 +/- 16 years) without any evidence of rotator cuff pathology were used. Three-dimensional coordinates (x, y, and z) of the tendon and muscle fiber bundles were collected in situ, using serial dissection and digitization. The data was reconstructed into a three-dimensional model using Maya. Fiber bundle lengths, pennation angles (PA), muscle volumes, and tendon dimensions for each architecturally distinct area were computed and then analyzed using paired t-tests and ANOVA (P < 0.05). The supraspinatus was found to consist of anterior and posterior regions, which were each further subdivided into superficial, middle, and deep parts. Mean PA were found to be significantly different between the distinct parts of the anterior region of the muscle. Medial PA was also found be significantly different between the superficial and middle, and superficial and deep parts of the posterior region. These results provide insight into the normal function of the muscle and its possible contribution to the initiation and progression of supraspinatus tendon tears.

A thorough understanding of the normal structural anatomy of the pectoralis major (PM) is of paramount importance in the planning of PM tendon transfers or repairs following traumatic PM tears. However, there is little consensus regarding the complex musculotendinous architecture of the PM in the anatomic or surgical literature. The purpose of this study is to model and quantify the three-dimensional architecture of the pectoralis muscle and tendon. Eleven formalin embalmed cadaveric specimens were examined: five (2M/3F) were serially dissected, digitized, and modeled in 3D using Autodesk Maya; six (4M/2F) were dissected and photographed. The PM tendon consisted of longer anterior and shorter posterior layers that were continuous inferiorly. The muscle belly consisted of an architecturally uniform clavicular head (CH) and a segmented sternal head (SH) with 6-7 segments. The most inferior SH segment in all specimens was found to fold anteriorly forming a trough that cradled the inferior aspect of the adjacent superior segment. No twisting of either the PM muscle or tendon was noted. Within the CH, the fiber bundle lengths (FBL) were found to increase from superior to inferior, whereas the mean FBLs of SH were greatest in segments 3-5 found centrally. The mean lateral pennation angle was greater in the CH (29.4 +/- 6.9 degrees ) than in the SH (20.6 +/- 2.7 degrees ). The application of these findings could form the basis of future studies to optimize surgical planning and functional recovery of repair/reconstruction procedures.

The purpose of this study was to visualize and document the architecture of the human soleus muscle throughout its entire volume. The architecture was visualized by creating a three-dimensional (3D) manipulatable computer model of an entire cadaveric soleus, in situ, using B-spline solid to display muscle fiber bundles that had been serially dissected, pinned, and digitized. A database of fiber bundle length and angle of pennation throughout the marginal, posterior, and anterior soleus was compiled. The computer model allowed documentation of the architectural parameters in 3D space, with the angle of pennation being measured relative to the tangent plane of the point of attachment of a fiber bundle. Before this study, the only architectural parameters that have been recorded have been 2D. Three-dimensional reconstruction is an exciting innovation because it makes feasible the creation of an architectural database and allows visualization of each fiber bundle in situ from any perspective. It was concluded that the architecture is non-uniform throughout the volume of soleus. Detailed architectural studies may lead to the development of muscle models that can more accurately predict interaction between muscle parts, force generation, and the effect of pathologic states on muscle function.

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 72n6, range 65-83 y) and 9 live subjects (mean age 76n3, 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 90m 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.