Immediate reconstruction of a composite mandibular defect with a regional osteomusculocutaneous flap

This is a report of an immediate reconstruction of a composite mandibular defect, using a pectoralis major osteomusculocutaneous flap incorporating a segment of the fifth rib. Viability of the transferred rib segment was established by tetracycline labeling at 2 weeks and technetium scanning at 3 months postoperatively. This clinical example supports the experimental observations of a vascular network interconnecting muscle, periosteum, and compact bone.     

The lateral pectoral composite flap in one-stage reconstruction of the irradiated mandible

We present a composite flap based on the musculature of the anterolateral thorax that allows immediate reconstruction of the mandible through the interposition of vascularized bony fifth rib. While the vascular pedicle remains the pectoral branch of the thoracoacromial artery, the pectoralis major muscle can be spared largely intact. The lateral position of the composite rib segment ensures a purely bony composition, while the lateral skin island remains largely hairless. Despite the unfavorable conditions of massive tumor size and prior irradiation attending the clinical cases presented, the complication rate was acceptable, with only one flap loss, and this followed technical error.     

In situ splitting of a rib graft for reconstruction of the orbital floor.

A technique of in situ split rib graft harvest is described. It has been used in bone graft reconstructions of the orbital floor when small, thin, malleable grafts are desired. The advantages of in situ rib harvest are technical simplicity, diminished risks of known rib harvest-associated complications, and avoidance of the risks involved with in situ split cranial bone harvesting.     

Geometry and kinematics of dog ribs

Five anesthetized supine beagle dogs were scanned using a fast, multislice computed tomographic X-ray technique to determine the orientation of the ribs at total lung capacity (TLC) and functional residual capacity (FRC). A plane was fit to each rib using a coordinate system in which the z-axis was aligned approximately cephalocaudally and the x-z-plane coincided with the sagittal midplane. The orientation of each plane was described by "pump-handle" and "bucket-handle" angles. The ribs rotated downward and inward during a passive deflation of the lungs from TLC to FRC. Rib displacement was not uniform: bucket-handle motion was predominant in the upper ribs, and pump- and bucket-handle motions were equal in the lower ribs. The change in the pump-handle angles between TLC and FRC was approximately 6 degrees for ribs 3-8, and the change in the bucket-handle angles decreased with rib number from 16 degrees for rib 3 to 6 degrees for rib 8. Rib shape was described by fitting an ellipse to the data for each rib; the ribs became larger and more circular with increasing rib number.     

Is the first rib a reliable indicator of age at death assessment? Test of the method developed by Kunos et al (1999)

The aim of this study was to test the method Kunos and his colleagues (1999) developed on the first rib to assess adult age-at-death. The method was applied on a sample of known age and sex, selected from a Thai collection. The procedure being subjective, we chose to estimate an age category rather than a precise age.

The results show that only 55% of the individuals are correctly classified and that the number of subjects over 60 years old is under-estimated. Three explanations are given: the modifications of the first rib related with ageing are more variable than previously stated, the technique is too subjective and difficult to apply and the morphological changes of the first rib are different between North-American and Thai people.     

Direct observation of protein secondary structure in gas vesicles by atomic force microscopy.

The protein that forms the gas vesicle in the cyanobacterium Anabaena flos-aquae has been imaged by atomic force microscopy (AFM) under liquid at room temperature. The protein constitutes "ribs" which, stacked together, form the hollow cylindrical tube and conical end caps of the gas vesicle. By operating the microscope in deflection mode, it has been possible to achieve sub-nanometer resolution of the rib structure. The lateral spacing of the ribs was found to be 4.6 +/- 0.1 nm. At higher resolution the ribs are observed to consist of pairs of lines at an angle of approximately 55 degrees to the rib axis, with a repeat distance between each line of 0.57 +/- 0.05 nm along the rib axis. These observed dimensions and periodicities are consistent with those determined from previous x-ray diffraction studies, indicating that the protein is arranged in beta-chains crossing the rib at an angle of 55 degrees to the rib axis. The AFM results confirm the x-ray data and represent the first direct images of a beta-sheet protein secondary structure using this technique. The orientation of the GvpA protein component of the structure and the extent of this protein across the ribs have been established for the first time.     

Diaphragmatic work of breathing in premature human infants

Present methods of assessing the work of breathing in human infants do not account for the added load when intercostal muscle activity is lost and rib cage distortion occurs. We have developed a technique for assessing diaphragmatic work in this circumstance utilizing measurements of transdiaphragmatic pressure and abdominal volume displacement. Eleven preterm infants without evidence of lung disease were studied. During periods of minimal rib cage distortion, inspiratory diaphragmatic work averaged 5.9 g X cm X ml-1, increasing to an average of 12.4 g X cm X ml-1 with periods of paradoxical rib cage motion (P less than 0.01). Inspiratory work was strongly correlated with the electrical activity of the diaphragm as measured from its moving time average (P less than 0.05). Assuming a mechanical efficiency of 4% in these infants, the caloric cost of diaphragmatic work may reach 10% of their basal metabolic rate in periods with rib cage distortion. When lung disease is superimposed, the increased metabolic demands of the diaphragm may predispose preterm infants to fatigue and may contribute to a failure to grow.     

Non-destructive assessment of human ribs mechanical properties using quantitative ultrasound

Advanced finite element models of the thorax have been developed to study, for example, the effects of car crashes. While there is a need for material properties to parameterize such models, specific properties are largely missing. Non-destructive techniques applicable in vivo would, therefore, be of interest to support further development of thorax models. The only non-destructive technique available today to derive rib bone properties would be based on quantitative computed tomography that measures bone mineral density. However, this approach is limited by the radiation dose. Bidirectional ultrasound axial transmission was developed on long bones ex vivo and used to assess in vivo health status of the radius. However, it is currently unknown if the ribs are good candidates for such a measurement. Therefore, the goal of this study is to evaluate the relationship between ex vivo ultrasonic measurements (axial transmission) and the mechanical properties of human ribs to determine if the mechanical properties of the ribs can be quantified non-destructively. The results show statistically significant relationships between the ultrasonic measurements and mechanical properties of the ribs. These results are promising with respect to a non-destructive and non-ionizing assessment of rib mechanical properties.     

Segmentation 3D multi-objets d’images scanner cardiaques : une approche multi-agents

We propose a new technique for general purpose, semi-interactive and multi-object segmentation in N-dimensional images, applied to the extraction of cardiac structures in MultiSlice Computed Tomography (MSCT) imaging. The proposed approach makes use of a multi-agent scheme combined with a supervised classification methodology allowing the introduction of a priori information and presenting fast computing times. The multi-agent system is organised around a communicating agent which manages a population of situated agents which segment the image through cooperative and competitive interactions. The proposed technique has been tested on several patient data sets. Some typical results are finally presented and discussed.     

Optimization of rib surgery parameters for the correction of scoliotic deformities using approximation models

BACKGROUND: As opposed to thoracoplasty (a cosmetic surgical intervention used to reduce the rib hump associated with scoliosis), experimental scoliosis has been produced or reversed on animals by rib shortening or lengthening. In a prior work (J. Orthop. Res., 20, pp. 1121-1128), a finite element modeling (FEM) of rib surgeries was developed to study the biomechanics of their correction mechanisms. Our aims in the present study were to investigate the influence of the rib surgery parameters and to identify optimal configurations. Hence, a specific objective of this study was to develop a method to find surgical parameters maximizing the correction by addressing the issue of high computational cost associated with FEM. METHOD OF APPROACH: Different configurations of rib shortening or lengthening were simulated using a FEM of the complete torso adapted to the geometry of six patients. Each configuration was assessed using objective functions that represent different correction objectives. Their value was evaluated using the rib surgery simulation for sample locations in the design space specified by an experimental design. Dual kriging (interpolation technique) was used to fit the data from the computer experiment. The resulting approximation model was used to locate parameters minimizing the objective function. RESULTS: The overall coverage of the design space and the use of an approximation model ensured that the optimization algorithm had not found a local minimum but a global optimal correction. The interventions generally produced slight immediate modifications with final geometry presenting between 95-120% of the initial deformation in about 50% of the tested cases. But in optimal cases, important loads (500-2000 N mm) were generated on vertebral endplates in the apical region, which could potentially produce the long-term correction of vertebral wedging by modulating growth. Optimal parameters varied among patients and for different correction objectives. CONCLUSIONS: Approximation models make it possible to study and find optimal rib surgery parameters while reducing computational cost.     

Measurement of umbilical blood flow in fetal lambs in utero.

We continuously measured umbilical blood flow in fetal lambs in utero by placing an electromagnetic flow transducer around the common umbilical artery. Umbilical arteries originate from a short common segment as the terminal branches of the descending aorta. This segment was isolated by a retroperitoneal surgical approach and encircled with a specially constructed electromagnetic flow transducer. Catheters were also placed in fetal vessles to monitor pressure and derive flow values by the radionuclide-labeled microsphere technique. The fetus and ewe were allowed to recover for two days before studies were performed. Average umbilical blood flow obtained in 11 animals with the transducer was 199 ml/kg per min. In seven animals flow measurements obtained with the transducer were compared with those derived from microsphere injections. Paired measurements varied by an average of only 5.3%. This technique makes possible the accurate and instantaneous measurement of umbilical blood flow in fetal lambs in utero over a prolonged period.     

A survey of formal methods for determining the centre of rotation of ball joints

The determination of an accurate centre of rotation (CoR) from segment marker positions is of interest across a wide range of applications, but particularly for clinical gait analysis and for estimating the hip joint centre during surgical intervention of the knee, for limb alignment purposes. For the first time in this survey of formal methods, we classify, analyse and compare different methods (geometric, algebraic, bias compensated algebraic, and Pratt sphere fit methods, as well as the centre transformation technique, the Holzreiter approach, the helical pivot technique, the Schwartz transformation techniques, the minimal amplitude point method and the Stoddart approach) for the determination of spherical joint centres from marker position data. In addition, we propose a new method, the symmetrical CoR estimation or SCoRE, in which the coordinates of the joint centre must only remain constant relative to each segment, thus not requiring the assumption that one segment should remain at rest. For each method, 1000 CoR estimations were analysed with the application of isotropic, independent and identically distributed Gaussian noise (standard deviation 0.1cm) to each of the marker positions, to all markers on the segment simultaneously and the two in combination. For the test conditions used here, most techniques were capable of determining the CoR to within 0.3 cm, as long as the spherical range of motion (RoM) of the joint was 45 degrees or more. Under the most stringent conditions tested, however, the SCoRE was capable of best determining the CoR, to within approximately 1.2mm with a RoM of 20 degrees . The correct selection and application of these methodologies should help improve the accuracy of surgical navigation and clinical kinematic measurement.     

Relationship between parasternal intercostal length and rib cage displacement in dogs

The relationship between parasternal intercostal length and rib cage cross-sectional area was examined in nine supine dogs during passive inflation and during quiet breathing before and after phrenicotomy. Parasternal intercostal length (PSL) was measured with a sonomicrometry technique, and rib cage cross-sectional area (Arc) was measured with a Respitrace coil placed around the middle rib cage. During active inspiration as well as during passive inflation, PSL decreased as Arc increased. However, the relationship between PSL and Arc during active inspiration, whether in the intact or phrenicotomized animal, was almost invariably different from that during passive inflation, so that the same increase in Arc was associated with a greater decrease in PSL in the former than in the latter instance. This difference between passive inflation and active inspiration is probably due to the active contraction of the parasternals during inspiration and the consequent caudal displacement of the sternum. In upright humans, the sternum moves cephalad and not caudad during inspiration, so the relationship between PSL and Arc during active breathing might be similar to that during passive inflation.     

The quantitative estimation of microvessels in microvascular networks

A novel method is presented that greatly facilitates the determination of vessel segment number and density in both simple and complex microvascular networks. This approach was applied to microvascular networks represented by the Bra-Ket operator technique and accurately predicted the number of vessel segments in both tree-branched and loop-branched (arcade) networks. The method was then applied to the complex hexagonal array network described by Engelson et al. for gastrointestinal mucosa and accurately yielded an average vessel segment number of three around each hexagonal loop. This new method may be used for conveniently estimating tissue microvascular densities, such as vessel rarefaction or proliferation, and for the modelling of microvascular networks.     

A model for studies of the deformable rib cage.

An earlier model for the study of rib cage mechanics was modified so that rib deformity in scoliosis could be better represented. The rigid ribs of that model were replaced by five-segment deformable ribs. Literature data on cadaver rib mechanical behavior were used to assign stiffnesses to the new individual model ribs so that experimental and model rib deflections agreed. Shear and tension/compression stiffnesses had little effect on individual rib deformation, but bending stiffnesses had a major effect. Level-to-level differences in mechanical behavior could be explained almost exclusively by level to level differences in the rib shape. The model ribs were then assembled into a whole rib cage. Computer simulations of whole rib cage behaviors, both in vivo and in vitro, showed a reasonable agreement with the measured behaviors. The model was used to study rib cage mechanics in two scolioses, one with a 43 degrees and the other with a 70 degrees Cobb angle. Scoliotic rib cage deformities were quantified by parameters measuring the rib cage lateral offset, rib cage axial rotation, rib cage volume and rib distortion. Rib distortion was quantified both in best-fit and simulated computer tomography (CT) scan planes. Model rib distortion was much smaller in best-fit planes than in CT planes. The total rib cage volume changed little in the presence of the scolioses, but it became asymmetrically distributed.     

Oligosaccharyltransferase activity is associated with a protein complex composed of ribophorins I and II and a 48 kd protein.

Oligosaccharyltransferase catalyzes the N-linked glycosylation of asparagine residues on nascent polypeptides in the lumen of the rough endoplasmic reticulum (RER). A protein complex composed of 66, 63, and 48 kd subunits copurified with oligosaccharyltransferase from canine pancreas. The 66 and 63 kd subunits were shown by protein immunoblotting to be identical to ribophorin I and II, two previously identified RER glycoproteins that colocalize with membrane-bound ribosomes. The transmembrane segment of ribophorin I was found to be homologous to a recently proposed dolichol recognition consensus sequence. Based on a revision of the consensus sequence, we propose a model for the interaction of dolichol with the glycosyltransferases that catalyze the assembly and transfer of lipid-linked oligosaccharides.     

Evaluation of Breathing Pattern: Comparison of a Manual Assessment of Respiratory Motion (MARM) and Respiratory Induction Plethysmography

Altered breathing pattern is an aspect of dysfunctional breathing but few standardised techniques exist to evaluate it. This study investigates a technique for evaluating and quantifying breathing pattern, called the Manual Assessment of Respiratory Motion (MARM) and compares it to measures performed with Respiratory Induction Plethysmography (RIP). About 12 subjects altered their breathing and posture while 2 examiners assessed their breathing using the MARM. Simultaneous measurements with RIP were taken. Inter-examiner agreement and agreement between MARM and RIP were assessed. The ability of the measurement methods to differentiate between diverse breathing and postural patterns was compared. High levels of agreement between examiners were found with the MARM for measures of the upper rib cage relative to lower rib cage/abdomen motion during breathing but not for measures of volume. The measures of upper rib cage dominance during breathing correlated with similar measures obtained from RIP. Both RIP and MARM measures methods were able to differentiate between abdominal and thoracic breathing patterns, but only MARM was able to differentiate between breathing changes occurring as result of slumped versus erect sitting posture. This study suggests that the MARM is a reliable clinical tool for assessing breathing pattern.     

Rib cage distortion during voluntary and involuntary breathing acts

We examined chest wall and rib cage configuration in seven normal subjects during a variety of breathing maneuvers. Magnetometers were used to measure lower rib cage anteroposterior, lower rib cage transverse, upper rib cage anteroposterior, and abdomen anteroposterior diameters. Changes of these diameters were recorded during voluntary maneuvers, rebreathing, reading, and "natural" breathing. Relative motion of the rib cage and abdomen was displayed with the rib cage represented by the product of its lower anteroposterior and transverse diameters. During spontaneous breathing the rib cage and chest wall are near their relaxation configuration. During chemically driven ventilation the chest wall and rib cage progressively depart from this configuration. Much greater distortions of the chest wall and rib cage occurred during some voluntary maneuvers. Additionally, esophageal pressure and gastric pressure were measured during voluntary distortion of the rib cage. Substantial changes in lower rib cage shape occurred during voluntary maneuvers when compared with spontaneous breaths at the same transmural pressure. We conclude that the unitary behavior of the rib cage in normal subjects requires muscle coordination.     

The inferior gluteal free flap in breast reconstruction

The inferior gluteal musculocutaneous free flap usually provides a sufficient amount of autogenous tissue for breast reconstruction when adequate tissue is not present in the lower abdomen or back. Its arteriovenous pedicle is longer than the superior gluteal musculocutaneous free-flap pedicle and permits microvascular anastomosis in the axilla, avoiding medial rib and cartilage resection. In the thin patient, there is more available donor tissue than with the superior gluteal musculocutaneous free flap. Cadaver dissections confirm the greater pedicle length and the local area of the lower gluteus maximus muscle needed to carry the skin island and have helped define a safe approach to flap elevation. We have used four flaps for breast reconstruction without vascular compromise or the need for reexploration. The low donor-site scar in the inferior buttock fold has been acceptable, especially for a bilateral reconstruction. The anatomy of the gluteal region, the surgical technique for the inferior gluteal free-flap transfer, and a 3-year patient follow-up are presented.