Rib Attachment Research Articles

Rib Fractures in Professional Baseball Pitchers: Mechanics, Epidemiology, and Management.

Pitching is a complex kinetic chain activity requiring the transfer of energy from the lower body, through the core and trunk, and finally through the arm to generate explosive acceleration of the baseball. As a result, large forces are generated in the trunk musculature and rib attachments from the late cocking phase of pitching through deceleration. The repetitive cumulative load and high pitch velocities put professional pitchers at risk of rib stress fracture. Given the potential for a prolonged recovery course and high rate of recurrence, early recognition of rib bone stress injury is critical to optimize care. Identifying torso strength imbalances, suboptimal pitching biomechanics (such as late or inadequate pelvic rotation), as well as metabolic deficiencies that may adversely affect bone health are essential to expedite safe return to play and prevent future injury. In this review, we discuss risk factors, mechanism of injury, typical clinical presentation, diagnostic imaging findings, and propose treatment and prevention strategies for rib stress fractures in overhand pitchers.

Pelvic girdle morphology in Stagonolepis, with remarks on aetosaur systematics

In recent years, the Upper Triassic deposits at Krasiejów (south-west Poland) have yielded several tetrapod taxa, both aquatic and terrestrial. Stagonolepis olenkae is one of the terrestrial vertebrates recovered there; a quadrupedal, armoured aetosaur, which belonged to the crocodile-line archosaurs with a characteristic shovel-shaped snout. Several previous studies (osteological, histological and taphonomic) have attempted to understand the mode of life, growth pattern and possible dimorphism of this species and on this basis, to interpret palaeoecological, palaeoclimatic and stratigraphical implications. So far, the pelvic girdle of S. olenkae from Krasiejów remained undescribed. Here, the authors record stagonolepid ilia and pubes and a single ischium from collections housed at the University of Opole, and compare these with the pelvic girdles of other aetosaurian taxa. These well-preserved bones have a typical aetosaurian general outline, but also show some peculiar features. For instance, the preacetabular blade of the ilium is short and flattened and does not exceed the pubic peduncle; several small foramina occur dorsally of the supracetabular crest; the number of pubic foramina is two and the pubic symphysis is less than half the length of the pubis. The material is similar to previously known Stagonolepis robertsoni from the Elgin area, except for the length of the symphysis. The bones presented here differ between each other in thickness, morphology of the preacetabular blade or attachment of sacral ribs, which may be connected with sexual dimorphism. The pelvic girdle of most aetosaurs is not well known. This is unfortunate, because it is an important element in the study of the evolution of the pelvic girdle and in phylogenetic analyses. Thus, the ilia, pubes and ischium of the present study are valuable examples that may contribute to the discussion of the ontogeny and sexual dimorphism in Stagonolepis , as well as to our general knowledge of the Aetosauria.

Side Strain and Impact Injuries at the Iliac Crest Attachment of Lateral Abdominal Wall Musculature in Cricketers: An Uncommon Injury Pattern.

Side strains refer to injuries of the internal/external oblique or the transversus abdominis, commonly at their attachment to the lower four ribs and rarely at their pelvic attachments. Injuries at the rib attachments are well-described while literature on iliac crest attachment injuries is sparse. We report four cricketers who had side strain and direct impact injuries with varying degrees of severity at the iliac crest attachment. The purpose of this article is to describe the anatomy, possible mechanism of injury, and imaging findings in the lateral abdominal wall muscle injuries at the iliac crest, which have not been described previously.

Bilateral Anatomical Variation of the Upper Serratus Anterior: A Cadaveric Dissection

Anatomical variation can have clinical implications in terms of pathology, musculature surgical considerations, and biomechanical function. While many anatomical variations have been reported, it is critical to continue to expand the record when deviations are found. According to most sources, the upper serratus anterior originates at the first and second ribs and inserts at the superior angle of the scapula. Some variations in attachments of the upper serratus anterior have been described, especially regarding variations in origin at the first few ribs. (Smith, et al., 2003). However, the literature does not describe the insertion of the serratus anterior muscle as extending along the superior border of the scapula.PURPOSETo report a bilateral anatomical variation of the upper serratus anterior discovered during routine dissection on a female specimen.METHODSWhile under the supervision of the anatomist at Texas Woman’s University Dallas, Doctor of Physical Therapy students dissected an 82‐year‐old Caucasian female. The students employed techniques described in Grant’s Dissector (Detton, 2017), to expose the shoulder and neck regions of the specimen. Blunt dissection techniques were utilized to expose the area further once they discovered the anatomical variation of the upper serratus anterior. Students measured the length of the upper serratus anterior that inserted on the superior border.RESULTSThe cadaver with the serratus anterior variation, had the muscle attached to 56% of the superior border of her scapula. Comparatively, 3 other female cadavers of similar ages had significantly less attachment to the superior border‐‐an average of 27%, with a range from 16.7% to 32.6%.DISCUSSIONBased on widely accepted descriptions of the serratus anterior attaching to the superior angle, without extending extensively onto the superior border of the scapula, and in comparison to other available cadavers, this subject had a serratus anterior with a significantly larger attachment to the superior border of the scapula. The specific actions of the upper serratus anterior include stabilizing the scapula during humeral elevation, and in upward rotation and abduction of the scapula. Therefore, this variation may have functional and clinical implications for the scapulothoracic and shoulder regions.CONCLUSIONSIt appears that variations in the upper serratus anterior may not only include its rib attachments but also its scapular attachment. This may affect function including limitations in scapular rotation and shoulder elevation. Therefore, further investigation into anomalies and function of the upper serratus anterior is warranted.SA Anatomical Variation: Serratus anterior attaching to the superior angle, without extending extensively onto the superior border of the scapula.Figure 1

The paraspinal muscle-tendon system: Its paradoxical anatomy.

Anatomy of the muscle-tendon system is an important component to musculoskeletal models. In particular, the cross-sectional area of belly (mCSA) and tendon (tCSA) provides information about the maximum force that a muscle may exert. The ratio of mCSA to tCSA (rCSA) demonstrates how muscle force is related to the ability to resist/transmit the force to bone. Previous anatomical studies of the lumbar paraspinal muscles (LPM) showed that their bellies have large mCSA suggesting that they are powerful muscles. Surprisingly, surgical experience shows that the tendons of the LPM are among the thinnest tendons of the body. We therefore hypothesized that traditional biomechanics of the LPM and the rCSA do not correspond for LPM. In 10 fresh-frozen old cadavers, we measured the mCSA, tCSA and rCSA of the LPM (multifidus and the erector spinae, i.e. the longissimus and the iliocostalis); then, we compared these data with those of one of the weakest muscles in the body, i.e. the extensor digitorum communis (EDC) chosen because it shares some common anatomical features with the LPM, in particular with the erector spinae. For instance, the EDC has a polyarticular course and presents long and thin effector tendons. Among the LPM, the longissimus has the greatest mean ACSA with 10.42 cm2 compared with 9.16 cm2 for the iliocostalis and 0.24 cm2 for the multifidus. Mean ACSA of the EDC was almost ten times smaller than those of erector spinae. Regarding the mean tCSA, the EDC was the largest one with 11.48 mm2 compared with 2.69 mm2 and 1.43 mm2 for the longissimus, 5.74 mm2 and 2.38 mm2for the iliocostalis and 5.28 mm2 and 4.96 mm2 for the multifidus. Mean rCSAs of the erector spinae were extremely small, ranged from 1/156 for the spinal attachment of the iliocostalis to 1/739 for the rib attachment of the longissimus that suggests that tendons are an unsuitable size to transmit the force to bone. Mean rCSA of the multifidus and the EDC were in the same range with rCSA = 1/5 and rCSA = 1/9 respectively. The rCSA of the multifidus was substantial, but its ACSA (1cm2) corresponds to low-power muscles. This paradoxical anatomy compels us to consider the biomechanics of the LPM in a different way from that of the classical “chord-like model”, i.e. the muscle belly creates a force that is applied to a bone piece through a tendon. The LPM have large contractile mass in a semi-rigid compartment inside which the pressure may increase. This result strengthens the hypothesis that high pressure and intrinsic stiffness of the LPM create two stiff bodies, closely attached to the spine thus ensuring its stabilization.

Detailed Vascular Anatomy and Flap Harvest Technique of the Serratus Anterior/Rib Composite Flap.

The hemodynamics of blood flowing from the anterior serratus to the ribs has yet to be analyzed in detail in serratus anterior/rib composite flaps. The authors focused on new blood circulation, whereby the slip arteries branched from the serratus anterior branch, off the thoracodorsal artery and the intercostal arteries, directly through the interconnecting vessels (axial route). The authors analyzed in detail the hemodynamics of serratus anterior/rib composite flaps and developed a new method for flap elevation. The axial route was identified and analyzed by performing macroscopic autopsies of formalin perfusion-fixed cadavers involving three-dimensional computed tomographic angiography and vascular corrosion casting. Flap elevation was performed with new blood circulation, which included the axial route, and blood flow was evaluated using indocyanine green fluorescence angiography. The interconnecting vessels penetrated the intercostal muscles at a mean distance of 4.5 cm from the anterior margin of the attachment sites of the serratus anterior muscle to the ribs and at a mean distance of 7.4 cm from the costochondral junction. The interconnecting vessels had a mean diameter of 0.5 mm. Vascular corrosion casting helped identify multiple capillaries that were distributed from the intercostal arteries to the periosteum of the ribs. In addition, intraoperative indocyanine green fluorescence angiography confirmed blood flow from the slip arteries to the intercostal arteries. Good blood flow in harvested graft tissue can be achieved by including the axial route with the periosteal blood circulation at the rib attachment sites of the serratus anterior in a serratus anterior/rib composite flap.

The Earliest Gulp-Feeding Mysticete (Cetacea: Mysticeti) from the Oligocene of New Zealand

Horopeta umarere is a new genus and species of extinct baleen whales from the Kokoamu Greensand (early Chattian, Oligocene, in the range 25–27 Ma), Hakataramea Valley, New Zealand. The geological age makes Horopeta umarere one of the earliest named baleen whales. Phylogenetic analysis indicates that Horopeta umarere may be the earliest crown Mysticeti (the sister taxon to Cetotheriidae), or the sister species to the crown Mysticeti; it is clearly not a species of Eomysticetidae. Estimated skull and body length of Horopeta umarere are 1.5-1.6 m and 6.5-7.5 m, respectively. Horopeta umarere shows some features that are linked to gulp feeding as seen in living humpback and rorquals: laterally bowed and robust mandible, D-shaped to teardrop-shaped mandible in cross-section, and posterolaterally deflected triangular coronoid process of the mandible. The sternum of Horopeta umarere is elongate, rod-shaped, and dorsoventrally stout with bilateral anterior and posterior rugose protrusions, indicating the presence of at least two pairs of ribs or costal cartilages. The structure of the skull and mandible are consistent with the use of gulp feeding, but the sternal morphology and rib attachments suggest an early evolutionary stage in gulp feeding employment, where more complex rib attachment may restrict the volume of water and food taken in one gulp compared to living humpback and rorquals. Thus, the morphology of Horopeta umarere has implications for the emergence of gulp feeding in baleen whale evolution as well as the emergence of the crown Mysticeti.

Congenital abnormalities of the vertebral column in ferrets.

Vertebral column pathologies requiring surgical intervention have been described in pet ferrets, however little information is available on the normal vertebral formula and congenital variants in this species. The purpose of this retrospective study was to describe vertebral formulas and prevalence of congenital vertebral anomalies in a sample of pet ferrets. Radiographs of 172 pet ferrets (96 males and 76 females) were included in this retrospective study. In 143 ferrets (83.14%), five different formulas of the vertebral column were recorded with normal morphology of vertebrae (rib attachment included) but with a variable number of thoracic (Th), lumbar (L), and sacral (S) vertebrae. The number of cervical (C) vertebrae was constant in all examined animals. Observed vertebral formulas were C7/Th14/L6/S3 (51.74%), C7/Th14/L6/S4 (22.10%), C7/Th14/L7/S3 (6.98%), C7/Th15/L6/S3 (1.74%), and C7/Th15/L6/S4 (0.58%). Formula C7/Th14/L6/S4 was significantly more common in males than in females (P < 0.05). Congenital spinal abnormalities were found in 29 ferrets (16.86%), mostly localized in the thoracolumbar and lumbosacral regions. The cervical region was affected in only one case. Transitional vertebrae represented the most common congenital abnormalities (26 ferrets) in the thoracolumbar (13 ferrets) and lumbosacral regions (10 ferrets) or simultaneously in both regions (three ferrets). Other vertebral anomalies included block (two ferrets) and wedge vertebra (one ferret). Spina bifida was not detected. Findings from the current study indicated that vertebral formulas may vary in ferrets and congenital abnormalities are common. This should be taken into consideration for surgical planning.

Optimal design of composite upper covers of lateral wings with the effect of rib attachment to stiffener webs

The present investigation is devoted to the development of new optimal design concepts that exploit the full potential of advanced composite materials in the upper covers of aircraft lateral wings. A finite-element simulation of three-rib-bay laminated composite panels with T-stiffeners and a stiffener pitch of 200 mm is carried out using ANSYS to investigate the effect of rib attachment to stiffener webs on the performance of stiffened panels in terms of their buckling behavior and in relation to skin and stiffener lay-ups, stiffener height, and root width. Due to the large dimension of numerical problems to be solved, an optimization methodology is developed employing the method of experimental design and the response surface technique. Minimal-weight optimization problems were solved for four load levels with account of manufacturing, repairability, and damage tolerance requirements. The optimal results were verified successfully by using the ANSYS and ABAQUS shared-node models.

Complications of Growth-Sparing Surgery in Early Onset Scoliosis

Review of available literature, authors' opinion. To describe complications associated with growth-sparing surgical treatment of early onset scoliosis (EOS). EOS has many potential etiologies and is often associated with thoracic insufficiency syndrome. The growth of the spine, thorax, and lungs are interrelated, and severe EOS typically involves disturbance of the normal development of all 3. Severe EOS may be treated during growth with surgical techniques, intended to preserve growth while controlling deformity, the most common of which are spinal "growing rods" (GR) or "vertical expandable prosthetic titanium rib" (VEPTR). Although presently popular, there is minimal long-term data on the outcome of growth-sparing surgical techniques on EOS. Review. Potential adverse outcomes of GR or VEPTR treatment of EOS include failure to prevent progressive deformity or thoracic insufficiency syndrome, an unacceptably short or stiff spine or deformed thorax, increased family burden of care, and potentially negative psychological consequences from repeated surgical interventions. Neither technique reliably controls all deformity over the entirety of growth period. Infections are common to both GR and VEPTR. Rod breakage and spontaneous premature spinal fusion beneath rods are troublesome complications in GR, whereas drift of rib attachments and chest wall scarring are anticipated complications in VEPTR treatment. Indications for GR and VEPTR overlap, but thoracogenic scoliosis and severe upper thoracic kyphosis are best treated by VEPTR and GR, respectively. Surgeons planning treatment of EOS should anticipate the many complications common to growth-sparing surgery, share their knowledge with families, and use complications as one factor in the complex decision as to when and whether to initiate the repetitive surgeries associated with GR or VEPTR in the treatment of severe EOS.

Neurologic Risk in Growing Rod Spine Surgery in Early Onset Scoliosis

Retrospective case series from a multicenter database. To evaluate the risk of neurologic injury during growing rod surgeries and to determine whether intraoperative neuromonitoring is necessary for all growing rod procedures. Although the use of growing rod constructs for early-onset spinal deformity has become a commonly accepted treatment, the incidence of neurologic events during growing rod surgeries remains unknown. We reviewed data from a multicenter database on 782 growing rod surgeries performed in 252 patients. VEPTR devices and any constructs with rib attachments were excluded. A questionnaire was sent to all surgeons contributing cases requesting detailed information about all neurologic events associated with any growing rod surgery. There were 782 growing rod surgeries performed on 252 patients including 252 primary growing rod implantations, 168 implant exchanges, and 362 lengthenings. Five hundred sixty-nine of 782 (73%) cases were performed with neuromonitoring. Only one clinical injury occurred in the series, resulting in an injury rate of 0.1% (1/782). This deficit occurred during an implant exchange while attempting pedicle screw placement, and resolved within 3 months. There were 2 cases with neuromonitoring changes during primary implant surgeries (0.9%, 2/231), 1 change during implant exchanges (0.9%, 1/116), and 1 neuromonitoring change during lengthenings (0.5%, 1/222). The single monitoring change that occurred during a lengthening was in a child with an intracanal tumor who also had a monitoring change during the primary surgery. There are anecdotal cases (outside this study group series) of neuromonitoring changes during simple lengthenings in children with uneventful primary implantations. Based on our study, the largest reported series of growing rod surgeries, the rate of neuromonitoring changes during primary growing rod implantation (0.9%) and exchange (0.9%) justifies the use of intraoperative neuromonitoring during these surgeries. As there were no neurologic events in 361 lengthenings in patients with no previous neurologic events, the question may be raised as to whether intraoperative neuromonitoring is necessary for simple lengthenings in these patients. However, caution should be maintained when interpreting our results as anecdotal cases of neurologic changes from simple lengthenings do exist outside of this series.

유전자 알고리즘을 이용한 판넬구조물의 구조음향 최적화에 관한 연구

Globally, customer appreciation and demand for quieter products has driven noise control engineers to develop efficient and quieter products in a relatively short time. In the vehicles and ship industry, noise has become an important attribute because of the competitive market and increasing customer awareness. Noise reduction is often achieved through structural modifications by typical approaches. In the present paper, author describes a fundamental study on optimum design of curvature, Bezier curve, and rib attachment to reduce noise from simple panel using a genetic algorithm(GA). The acoustic optimization procedure employed p?FEM for structural analysis, the Rayleigh integral method for acoustic analysis and the GA for searching optimum design. In the optimization procedure, the objective function to be minimized is the average sound power radiated from an objective structure over a given frequency range 0~300 ㎐.

Three-dimensional finite element modelling of the torso of the anthropomorphic test device THOR

This paper addresses development, calibration and validation of a three-dimensional finite element model of the torso sub-assemblies of a THOR 50th percentile adult male dummy. Modelled sub-assemblies include shoulders, a rib cage, bibs and attachments, a thoracic and lumbar spine, two abdominal modules, a pelvis and a jacket. The finite element mesh is constructed mainly from the CAD data, and mass properties are consistent between the model and the physical dummy on sub-assembly levels. The deformable materials include rib steel and damping materials, bibs, spinal flex joints, abdominal foams, etc. Systems identification is the main method used to calibrate the deformable material parameters based on tests conducted on material, component and/or sub-assembly levels. The model is validated with three types of impact tests performed on chest, upper abdomen or lower abdomen of a full assembly of the test device. Simulation results of impact force vs. deflection/penetration are analysed and compared with the corresponding experimental data, and simulation errors are discussed for forces, displacements and an energy dissipation measure.

Structural Modification with Mode Shape Expansion for Rib Stiffeners

In this paper, we propose a procedure for predicting the modal data of a thin plate structure with a rib stiffener even when the rib is attached at a location where mode shapes are not measured. This procedure is based on the structural dynamics modification (SDM) method in which the mode shape expansion (MSE) method is incorporated to estimate the experimental mode shapes at the unmeasured points. In the MSE estimation, a submodel including the possible rib attachment points is used instead of the whole structure model. Numerical examples through the plate structure with the two L-shaped ribs show that the proposed procedure accurately predicts the modal data using the estimated mode shapes at the unmeasured points. The mode shapes are estimated satisfactorily with the submodel under a free boundary condition. The optimal number of analytical modes to be combined in the MSE estimation can be determined from the condition number of the modal matrix of the submodel.

THE ABDOMINAL SKELETON OF TROPIDURID LIZARDS (SQUAMATA: TROPIDURIDAE)

Morphological variation in the abdominal skeleton of Tropiduridae was examined from radiographs and cleared-and-stained specimens of 61 species. Based on the numbers of xiphisternal and postxiphisternal inscriptional ribs, as well as the presence of inscriptional ribs articulating ventromedially, seven patterns of rib attachment are described. The distribution of these patterns among the species studied reveals intra- and interspecific variation, which indicates that the abdominal skeleton of lizards is a good source of fixed and polymorphic characters for phylogenetic analyses.

Multicenter VATS experience with mediastinal tumors

Background. The use of video-assisted thoracic surgery for diagnosis and treatment of mediastinal tumors in a multiinstitution patient population is not well understood. Methods. We studied 48 cases from Cancer and Leukemia Group B thoracic surgeons. Of 21 men and 27 women, aged 41 ± 16 years, 22 patients were asymptomatic. In the others, 92% of tumor-related symptoms improved or resolved after treatment. Five tumors involved the anterior compartment, 19 the middle, and 24 the posterior compartment. Diagnoses were typical for each compartment but also included uncommon problems such as superior vena cava hemangioma and a histoplasmosis cyst causing hoarseness. Of the lesions, a biopsy of 12 was done without excision and the rest were excised completely. Fifteen were cystic and 10 were malignant (8 biopsy only). Maximal dimensions were 5.2 ± 3.3 cm. Results. Operations were briefer for 24 posterior (93 ± 41 min) than 5 anterior (195 ± 46 min, p < 0.01) or 19 middle mediastinal tumors (170 ± 78 min, p < 0.01). Although 96% had vital mediastinal relations, only six open conversions were performed because of bleeding (n = 3), large size, impaired exposure, or rib attachments, and no patient had morbidity beyond that expected for the thoracotomy. Postoperative stay was shorter for the nonconversion group (3.2 ± 2.8 versus 5.5 ± 2.1 days, p = 0.05), as was chest tube duration (1.7 ± 1.4 days versus 3.2 ± 1.9 days, p = 0.03). There were no postoperative deaths or major complications, but 7 patients had minor complications. During a mean of 20 months of surveillance (range, 1 to 52 months), one cyst recurred (asymptomatic) as did one sarcoma that was excised. Conclusions. Video-assisted thoracic surgery is a safe technique for benign mediastinal tumors, typically those in the middle and posterior mediastinum.

The effects of a rib on the structural intensity in a cylindrical shell

The amount of vibrational energy scattering by a rib in a cylindrical shell will depend on the shape of the rib. This redistribution of energy will affect the coupling between the shell vibration and acoustic radiation. Most models treat the rib attachment to the shell as a line attachment. Here, a rib with different widths and shapes is considered. Equations for the structural intensity in an infinite cylindrical shell without and with fluid loading are derived. The rib is treated as a change in the shell thickness specified by a rib function with parameters to control height, width and shape. The effects of the rib on the structural intensity in the in-vacuo shell in the farfield of the rib are modeled as a function of frequency and circumferential mode number.

Identification of sound radiation from a discontinuity

The identification the of far-field sound radiation from a discontinuity on a beam is accomplished using a time-domain-based method that identifies the variations in wave propagation caused by the discontinuity. This identification of the far-field sound radiation includes determining the significance that each local variance in the metal has on the far-field sound radiation. The local variances are the material variances, geometric variances, and the applied stresses. To isolate the effects of the local variances on the far-field sound radiation, comparisons of many cases were made. The cases included aluminum versus steel, no discontinuity versus both a bolted and welded rib attachment, and a welded rib attachment versus the same geometry machined from one-piece of metal. Comparisons of these cases displayed a significant amount of far-field sound radiation around the rib attachment. These cases also displayed reflections of the structural waves at the rib attachment location. There were differences between the aluminum and steel cases, indicating a dependency upon the material. [Sponsored by ONR, Grant No. N00014-93-1-0493.]

Acoustic behavior of ribbed panels

The paper describes the acoustic behavior of a panel in terms of the impulse response function. The original impulse response function describes a panel that may be immersed in an environment that may be composed of layered mechanical elements that can be defined by lumped surface impedances and of slabs of fluid-like media. It is assumed that the original impulse response function is known. Based on this knowledge a modified impulse response function is derived. The modification is caused by a specific attachment of ribs to the panel. It is shown that a proper modified impulse response function can be derived in terms of the known original impulse response function and the properties of the ribs. These properties are defined in terms of the locations, the line impedances and, when appropriate, the line moment impedances of the ribs. The forms and interpretations of the derivation are discussed in several situations of interest. The acoustic behavior of particular interest is comprised of the transmission of response on the panel and the reflection and transmission of a junction in which the panel is incorporated. (A junction is a boundary separating slabs of fluid-like media.)

Co-Cured Graphite/Epoxy Vertical Fin Spar

The Lockheed-Georgia Company has recently constructed a one-piece molded front spar for the vertical fin of the L-1011 airplane (Fig. 1). The 26-ft-long graphite-epoxy spar contains integrally molded caps, webs, stiffeners, and rib attachments. This spar was fabricated as part of a contract sponsored by NASA-Langley Research Center with Lockheed-California Company to demonstrate production readiness and provide confidence in the use of composite primary structures. The spar is molded of T300/5208 graphite/epoxy. It replaces 39 metal parts, eliminates almost 1000 fasteners, and weighs about half as much as the metallic counterpart. The caps and webs vary in thickness and ply orientation along the length of the spar. These variations are achieved by build-up and deletion of the plies, all the while maintaining a balanced laminate to avoid warpage in the finished spar. Selected areas of this spar were fabricated separately and tested before the full-size 26-ft-long spar was fabricated. These tests demonstrated that the static strength, fatigue endurance, and damage resistance of the spar exceed all requirements.