This study used computed tomography (CT) imaging to determine in vivo mass, center of mass (CM), and moments of inertia (Icm) about the CM of discrete segments of the human torso. Four subjects, two males and two females, underwent serial transverse CT scans that were collected at 1-cm intervals for the full length of the trunk. The pixel intensity values of transverse images were correlated to tissue densities, thereby allowing trunk section mass properties to be calculated. The percentage of body mass observed by vertebral levels ranged from 1.1% at T1 to 2.6% at L5. The masses of the upper, middle, and lower trunk segments as percentages of body mass were estimated to be 18.5, 12.2, and 10.7%, respectively. The whole trunk mass was estimated to comprise 41.6% of the total body mass. Transverse vertebral CM values were found to lie anterior to their respective vertebral centroids by up to 5.0 cm in the lower thoracic region. For the upper, middle, and lower trunk segments, the average CM positions were found to be 25.9, 62.5, and 86.9% of the distance from the superior to inferior ends of the trunk. The upper and middle trunk CMs corresponded to approximately 4.0 cm anterior to T7/T8 vertebral centroid levels and 1.0 cm anterior to L3/L4 vertebral centroid levels, respectively. For the whole trunk, the CM was 52.7% of the distance from the xiphoid process and approximately 2.0 cm anterior to L1/L2 vertebral centroid levels. Variations in CM and Icm values were observed between subject, but these were within the range of previous reports of body segment parameters. Differences from previous studies were attributable to variations in boundary definitions, measurement techniques, population groups, and body states (live versus cadaver) examined. The disparity between previous findings and findings of this study emphasizes the need to better define the segmental properties of the trunk so that improved biomechanical representation of the body can be achieved.

he quadriceps (Q angle is that angle formed between the vectors for the combined pull of the quadriceps femoris muscle and the patellar tendon (30).When measured with the knee in extension in the frontal plane, it provides a reasonable estimate of the resultant force vector between the quadriceps muscle group and the patellar tendon (24,54,59). A Q angle in excess of 15-20' is commonly thought to contribute to knee extensor dysfunction and patellofemoral pain (4,12,21,31,32,41,49,50) and is frequently cited as an anatomic risk factor for the occurrence of chondromalacia patellae (8.26.29) and patellar subluxation or dislocation (10,15, 26,46,48,57,64). However, the Q angle is now viewed as a less reliable physical finding than was previously believed (58,61,62). This brief review will critically examine the results of recent (ie., post 1980) empirical investigations of the Q angle. Specifically, it will examine the differences in Q angles when measured: I) under differing measurement protocols; 2) between asymptomatic and symptomatic populations; 3) between male and female samples; and 4) from side to side within subjects. The advantages and disadvantages of the statistical methods utilized in the analysis and interpretation of data will also be discussed. Effect of Measurement Protocol on Q Angle MagnitudeThe Q angle is delineated by drawing an imaginary line from the anterior superior iliac spine to the center of the patella and from the center of the patella to the middle of the anterior tibia1 tuberosity. These easily palpated landmarks have been standardized (54), although the measurement procedures have not (22). Insall et al's goniometric method, which places subjects in a supine position with the knees extended and the quadriceps relaxed (35), is popular among medical practitioners. For others, however, the need to measure the Q angle under conditions which more accurately depict the functional position of the lower limb (38,39) and the quest for improved measurement accuracy and reliability (22) have provided the rationale and the impetus for methodological change.Indeed, studies of the Q angle have been conducted with subjects standing (1 1 ,l4,40,53), with knees flexed, sometimes dynamically ( 1 1,36,37), with the quadriceps contracted (20, 22), and with the use of standardized foot positions (14,22,52). Moreover, while the universal goniometer remains the instrument of choice with many (1 1,22,27,43-45,55,63), the a p plication of sophisticated technologies, such as computed tomography (2) and computer-based video measurement (6,14,36,37), has increased in popularity.Some (1 1,22) see the lack of a standardized measurement protocol as problematic, since it makes direct comparisons between investigations utilizing different methods difficult.Indeed, slight increases in the Q angle, ranging from 0.2 to 1.3" (16,22, 63), occur when a shift is made from a supine to a standing posture. Significant decreases in Q angle magnitude (1.1-3.5') arise, moreover, as the patella moves superiorly and laterally with...

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