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PubMed1995

Effects of the combined VDS-Zielke and Harrington operation on the frontal rib cage deformity of double major curves in idiopathic scoliosis.

STUDY DESIGN: This study analyzed the changes in the frontal plane of the deformed lower rib cage and the scoliosis-related alterations on the spine in patients with double major curve-pattern idiopathic scoliosis. OBJECTIVES: The results obtained preoperatively, after the Zielke operation, postoperatively after the Harrington instrumentation, and at the follow-up evaluation were compared to investigate which changes of the elements of the rib cage deformity are caused by each of the two instrumentations. SUMMARY OF BACKGROUND DATA: Previously, Wojcik reported on the effects of a Zielke operation on the lower rib in mild S-shaped idiopathic scoliosis. No previous data exist regarding the lower rib cage deformities in severe idiopathic double major-pattern scoliosis and their changes after combined VDS-Zielke and Harrington instrumentation. METHODS: Fifteen patients who underwent the staged Zielke operation followed by Harrington rod instrumentation were followed-up for an average period of 31.1 months. The methods used in our study included Cobb angle and a segmental analysis (T7-T12) of each of convex and concave rib-vertebra angles, rib-vertebra angle differences, vertebral rotation, and vertebral tilt. RESULTS: In this series, the apical convex ribs showed an increased droop preoperatively compared with the concave apical ribs. The VDS-Zielke operation corrected the lumbar scoliosis in an average of 63% of patients, whereas the thoracic scoliosis showed an immediate spontaneous correction of 30%. The VDS-Zielke operation also produced a significant correlation of the scoliosis-related vertebral tilt (T10-T12), derotated the lumbar vertebrae and the T12 vertebra significantly, elevated the "mobile" concave ribs, and increased the droop of the lower (T11, T12) "mobile" convex ribs. The Harrington instrumentation did not change the vertebral rotation, the vertebral tilt, the convex rib-vertebra angle, or the L4 obliquity, but significantly changed the apical concave rib-vertebra angle. The combined Zielke-Harrington instrumentation reduced the thoracic kyphosis and the thoracolumbar junction-kyphosis significantly, whereas the lumbar lordosis remained practically unchanged. CONCLUSIONS: Only the anterior VDS-Zielke instrumentation significantly corrects severe spinal deformities, elevates the three lower ribs on the concavity, and increases the droop of the two lower ribs on the convexity in the severe idiopathic double major curve-pattern scoliosis combined operated (Zielke-Harrington). Therefore, the Harrington instrumentation should have only limited use in cosmetic scoliosis surgery and should be replaced with posterior multi-hook instrumentation with a derotation effect.

Adolescent↗
PubMed1989

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.

Animals↗
PubMed2003

Morbidity from rib fractures increases after age 45.

BACKGROUND: Recent studies have demonstrated increased morbidity in elderly patients with rib fractures after blunt trauma. As a first step in creating a multidisciplinary rib fracture clinical pathway, we sought to determine the relationship between increasing age, number of rib fractures, and adverse outcomes in blunt chest trauma patients, without major abdominal or brain injury. STUDY DESIGN: We performed a retrospective cohort study involving all blunt patients greater than 15 years old with rib fractures, excluding those with Abbreviated Injury Scores (AIS) greater than 2 for abdomen and head, admitted to an urban Level I trauma center during 20 months. Outcomes parameters included the number of rib fractures, Injury Severity Score (ISS), intrathoracic injuries, pulmonary complications, number of ventilator days, length of stay in the intensive care unit (ICU), hospital stay, and type of analgesia. RESULTS: Of the 6,096 patients admitted, 171 (2.8%) met the inclusion criteria. Based on an analysis of increasing age, number of rib fractures, and adverse outcomes variables, patients were separated into four groups: group 1, 15 to 44 years old with 1 to 4 rib fractures; group 2, 15 to 44 years old with more than 4 rib fractures; group 3, 45 years or older with 1 to 4 rib fractures; and group 4, 45 years or more with more than 4 rib fractures. The four groups had similar numbers of pulmonary contusions (30%) and incidence of hemopneumothorax (51%). Ventilator days (5.8 +/- 1.8), ICU days (7.5 +/- 1.8), and total hospital stay (14.0 +/- 2.2) were increased in group 4 patients compared with the other groups (p < 0.05). Epidural analgesia did not affect outcomes. Overall mortality was 2.9% and was not different between groups. CONCLUSIONS: Patients over the age of 45 with more than four rib fractures are more severely injured and at increased risk of adverse outcomes. Efforts to decrease rib fracture morbidity should focus not only on elderly patients but those as young as 45 years. Based on these data we have initiated a multidisciplinary clinical pathway focusing on patients 45 years and older who have more than four rib fractures.

Adolescent↗
PubMed2002

Clinical significance of solitary rib hot spots on bone scans in patients with extraskeletal cancer: correlation with other clinical manifestations.

PURPOSE: Bone scans showing solitary hot spots in the ribs pose diagnostic problems in patients with proved extraskeletal cancers. The authors wanted to determine the importance of solitary rib lesions and their correlation with other clinical manifestations. MATERIALS AND METHODS: The study included 199 patients with solitary rib hot spots on their bone scans. The follow-up radiographic and scintigraphic images were reviewed to determine their origin. The correlation between the occurrence of a malignant rib lesion and clinical data were determined using Pearson chi-square tests. RESULTS: Ninety-three patients had an established cause of the rib hot spot. Eleven (11.8%) had a solitary malignant rib hot spot and 82 (88.2%) had a solitary benign rib hot spot. None of the hot spots at costochondral junctions were malignant. Of the 11 patients with proved metastatic rib hot spots, 1 of 11 (9.1%) had localized bone pain, 5 of 6 (83.3%) were concordant with primary tumors, 4 of 7 (57.1%) had elevated tumor markers, and 5 of 11 (45.5%) had concurrent extraskeletal metastases. For the 82 patients with benign rib hot spots, the figures were 2 of 82 (2.4%), 43 of 57 (75.4%), 26 of 69 (37.7%), and 19 of 82 (23.2%), respectively. Statistical analysis did not show a significant correlation between the incidence of metastases in solitary rib hot spots and clinical manifestations. CONCLUSIONS: Most solitary rib hot spots on bone scans were benign. The interpretation of a solitary hot spot in the ribs is difficult even with the help of these clinical manifestations. Follow-up bone scintigrams or radiographs are needed for further investigation of solitary rib hot spots.

Adolescent↗
PubMed2006

Adverse outcomes in younger rib fracture patients.

BACKGROUND: Recent studies on the impact of rib fractures after blunt trauma have shown a linear relationship between age, increasing number of rib fractures, and complications, including mortality. Others have documented that age-related morbidity increases before age 65 in trauma patients. We hypothesize that patients as young as age 45 demonstrate increased morbidity with injuries similar to older patients. METHODS: We performed a retrospective cohort study involving all blunt trauma patients with rib fractures, excluding those with severe head and abdominal injuries and those dying within 24 hours, admitted between January 2001 and December 2004. Outcome parameters included pulmonary complications, ICU length of stay, hospital and ICU length of stay, Injury Severity Score (ISS), number of vent days, number of rib fractures, mechanism of injury, and discharge disposition. RESULTS: Of the 3,094 patients admitted, 307 met the inclusion criteria (9.9%). Based on statistical analysis of age, number of rib fractures, and adverse outcome variables, patients were separated into 4 groups: Group 1: younger than 44 years old with 1 to 4 rib fractures, Group 2: younger than 44 years with greater than 4 rib fractures, Group 3: 45 years or older with 1 to 4 rib fractures, and Group 4: 45 years or older with more than 4 rib fractures. Age groups and outcome variables were compared with chi-square, analysis of variance and multiple regression analysis. Respiratory failure, pneumonia, and associated thoracic injuries were increased in Group 4 patients compared with other groups (P < 0.05). Mortality and length of stay were not different between groups. CONCLUSIONS: Patients as young as 45 with more than 4 rib fractures are at increased risk for adverse outcomes. Efforts to improve outcomes in rib fracture patients should focus not only on elderly patients, but on those as young as 45 years. Based on these data, we established a rib fracture clinical pathway focusing on patients 45 years and older with more than 4 rib fractures.

Adolescent↗
PubMed1996

Rib fractures in major trauma.

BACKGROUND: To determine the mortality, hospital and intensive care unit (ICU) stay of rib fractures in patients admitted to Victorian hospitals for more than 1 day. METHODS: All patients fitting the entry criteria for the Victorian Major Trauma Study with fractured ribs were identified between 1 March 1992 and 28 February 1993. Aetiology, age, sex, associated injury and outcome were analysed. RESULTS: Patients with rib fractures had a higher mortality and length of hospital stay, but this was not significantly different from other trauma. A significantly higher percentage of patients required ICU care for rib fractures (44%) compared with the total group with blunt injury (24%). The majority of rib fractures resulted from motor vehicle accidents 361/541 (67%). Injuries occurring on the street/highway resulting in rib fractures were more likely to be major; 62% had Injury Severity Score (ISS) > 15. Fractured ribs occurred more commonly with increased age. Mortality for patients with fractured ribs versus total trauma group was higher in elderly patients. Univariate analysis showed rib fractures were a positive predictor of death but when adjusted for ISS and age, rib fractures became a negative predictor. Rib fractures were not predictors for length of ICU or hospital stay. CONCLUSION: The sample of rib fractures collected in this study underestimates the overall incidence. For those patients admitted to hospital with identified rib fractures, there is a trend towards higher mortality and morbidity. However, this association is better predicted by ISS and age.

Adolescent↗
PubMed2003

Effects of inflation on the coupling between the ribs and the lung in dogs.

The coupling between the ribs and the lung in dogs increases with increasing rib number in the cranial part of the rib cage and then decreases markedly in the caudal part. The hypothesis was raised that this non-uniformity is primarily related to differences between the areas of the lung subtended by the different ribs, and in the current study we tested this idea by assessing the effects of passive lung inflation. Thus, by causing a descent of the diaphragm, inflation would expand the area of the lung subtended by the caudal ribs and improve the coupling between these ribs and the lung. The axial displacements of the ribs and the changes in airway opening pressure (DeltaP(ao)) were measured in anaesthetized, pancuronium-treated, supine dogs while loads were applied in the cranial direction to individual rib pairs at functional residual capacity (FRC) and after passive inflation to 10 and 20 cm H(2)O transrespiratory pressure. In agreement with the hypothesis, inflation caused an increase in DeltaP(ao) for ribs 9 and 10. The most prominent alteration, however, was a marked decrease in DeltaP(ao) for ribs 2-8; at 20 cm H(2)O, DeltaP(ao) for these ribs was only 30% of the value at FRC. Additional measurements indicated that this decrease in DeltaP(ao) results partly from the increase in diaphragmatic compliance but mostly from the reduction in outward rib displacement. This alteration in the pattern of rib motion should add to the decrease in muscle length to reduce the lung expanding action of the external intercostal muscles at high lung volumes.

Abdomen↗
PubMed2004

Role of rib cage elastance in the coupling between the abdominal muscles and the lung.

The abdominal muscles expand the rib cage when they contract alone. This expansion opposes the deflation of the lung and may be viewed as pressure dissipation. The hypothesis was raised, therefore, that alterations in rib cage elastance should affect the lung deflating action of these muscles. To test this hypothesis and evaluate the quantitative importance of this effect, we measured the changes in airway opening pressure (Pao), abdominal pressure (Pab), and rib cage transverse diameter during isolated stimulation of the transversus abdominis muscle in anesthetized dogs, first with the rib cage intact and then after rib cage elastance was increased by clamping the ribs and the sternum. Stimulation produced increases in Pao, Pab, and rib cage diameter in both conditions. With the ribs and sternum clamped, however, the change in Pab was unchanged but the change in Pao was increased by 77% (P < 0.001). In a second experiment, the transversus abdominis was stimulated before and after rib cage elastance was reduced by removing the bony ribs 3-8. Although the change in Pab after removal of the the ribs was still unchanged, the change in Pao was reduced by 62% (P < 0.001). These observations, supported by a model analysis, indicate that rib cage elastance is a major determinant of the mechanical coupling between the abdominal muscles and the lung. In fact, in the dog, the effects of rib cage elastance and Pab on the lung-deflating action of the abdominal muscles are of the same order of magnitude.

Abdominal Muscles↗
PubMed2005

Congenital anomalies of the ribs and chest wall associated with congenital deformities of the spine.

BACKGROUND: Congenital anomalies of the ribs and chest wall as well as Sprengel deformity of the shoulder are often associated with congenital deformities of the spine. It has been suggested that rib anomalies may adversely affect the progression of the spinal deformity. METHODS: We conducted a retrospective study of the medical records and spine radiographs of 620 consecutive patients with congenital deformities of the spine; 497 patients (80%) had scoliosis; eighty-eight patients (14%), kyphoscoliosis; and thirty-five patients (6%), kyphosis. The rib anomalies were classified into simple and complex, and the presence of a Sprengel deformity of the shoulder was recorded. The rate of scoliosis deterioration without treatment before the age of eleven years, as well as the patient age and curve size at the time of surgery, was compared for different types of vertebral abnormalities in patients with and without rib anomalies. RESULTS: A total of 119 patients (19.2%) had rib anomalies, which were most commonly associated with congenital scoliosis (111 patients; 93%) and were much less frequently associated with congenital kyphoscoliosis or kyphosis (eight patients). The rib anomalies were simple in ninety-five patients and complex in twenty-four. Eighty-five patients (71%) with rib abnormalities had a scoliosis due to a unilateral failure of vertebral segmentation, and seven patients had mixed or unclassifiable vertebral anomalies. In contrast, only sixteen of 203 patients with a scoliosis due to a hemivertebra alone had rib anomalies. The rib anomalies were most frequently associated with a thoracic or thoracolumbar scoliosis (102 patients; 92%) and occurred on the concavity in eighty-two patients (74%), the convexity in twenty-two patients (20%), and were bilateral in seven patients. The Sprengel deformity occurred in forty-five patients and most frequently in association with a thoracic scoliosis due to a unilateral failure of vertebral segmentation (twenty-seven patients). No significant difference was detected in the rate of curve progression without treatment in patients with and without rib anomalies. The only exception was the mean age at the time of surgery, which was higher for patients with a unilateral unsegmented bar without rib anomalies (p = 0.005). In addition, no significant difference was found with regard to any tethering effect due to the site of the rib fusions on the concavity of the scoliosis, i.e., whether they were in close approximation to the spine or were more lateral (p > 0.05). CONCLUSIONS: Congenital rib anomalies occur most commonly on the concavity of a thoracic or thoracolumbar congenital scoliosis that is due to a unilateral failure of vertebral segmentation, and they do not appear to have an adverse effect on curve size or rate of progression.

Disease Progression↗
PubMed2005

Material properties of human rib cortical bone from dynamic tension coupon testing.

The purpose of this study was to develop material properties of human rib cortical bone using dynamic tension coupon testing. This study presents 117 human rib cortical bone coupon tests from six cadavers, three male and three female, ranging in age from 18 to 67 years old. The rib sections were taken from the anterior, lateral, and posterior regions on ribs 1 through 12 of each cadaver's rib cage. The cortical bone was isolated from each rib section with a low speed diamond saw, and milled into dog bone shaped tension coupons using a small computer numerical control machine. A high-rate servo-hydraulic Material Testing System equipped with a custom slack adaptor, to provide constant strain rates, was used to apply tension loads to failure at an average rate of 0.5 strains/sec. The elastic modulus, yield stress, yield strain, ultimate stress, ultimate strain, and strain energy density were determined from the resulting stress versus strain curves. The overall average of all cadaver data gives an elastic modulus of 13.9 GPa, a yield stress of 93.9 MPa, a yield strain of 0.88 %, an ultimate stress of 124.2 MPa, an ultimate strain of 2.7 %, and a strain energy density of 250.1 MPa-microstrain. For all cadavers, the plastic region of the stress versus strain curves was substantial and contributed approximately 60 % to the strain energy and over 80 % in the tests with the 18 year old cadaver. The rib cortical bone becomes more brittle with increasing age, shown by an increase in the modulus (p < 0.01) and a decrease in peak strain (p < 0.01). In contrast to previous three-bending tests on whole rib and rib cortical bone coupons, there were no significant differences in material properties with respect to rib region or rib level. When these results are considered in conjunction with the previous three-point bending tests, there is regional variation in the structural response of the human rib cage, but this variation appears to be primarily a result of changes in the local geometry of each rib while the material properties remain nearly constant within an individual.

Journal Article↗
PubMed2005

Analysis of quantitative methods for rib seriation using the Spitalfields documented skeletal collection.

Accurate rib seriation is essential in forensic anthropology and bioarchaeology for determination of minimum numbers of individuals, sequencing trauma patterns to the chest, and identification of central ribs for use in age estimation. We investigate quantitative methods for rib seriation based on three metric variables: superior (anterior) costo-transverse crest height (SCTCH), articular facet of the tubercle-to-angle length (AFTAL), and head-to-articular facet length (HAFL). The sample consists of complete but unseriated sets of ribs from 133 individuals from the documented (known age and sex) and undocumented skeletal collections of Christ Church Spitalfields, London. This research confirms the results of an earlier study (Hoppa and Saunders [1998] J. Forensic. Sci. 43:174-177) and extends it with the application of two new metric traits and further analyses of sex differences. Analyses of variance showed that SCTCH and AFTAL are significantly associated (P < 0.001) with rib number. Tukey tests of pairwise rib comparisons revealed that for two dimensions (SCTCH and AFTAL), the central ribs (3rd-6th) are significantly distinct from each other (P < 0.05). Using simple ranking of either the SCTCH or AFTAL traits, the proportion of correctly identified ribs within +/-1 position was 80%, compared to initial seriation using morphological methods (Dudar [1993] J. Forensic. Sci. 28:788-797; Mann [1993] J. Forensic. Sci. 28:151-155). Significant sex dimorphism was also identified for these two traits. Analysis of the HAFL trait produced somewhat equivocal results, suggesting that this variable is not reliable for rib seriation. The variable SCTCH proves to be the most useful dimension for seriation, and shows that all but the 7th-9th ribs can be distinguished from others in the sequence, with important results for the 4th rib, where ranking allowed identification in 86% of cases, consistent with morphological methods for intact ribs.

Analysis of Variance↗
PubMed1995

Neurogenic thoracic outlet decompression: rationale for sparing the first rib.

A total of 168 primary supraclavicular decompressions were performed on 146 patients with neurogenic thoracic outlet syndrome. This report compares the results of rib resection (supraclavicular anterior and middle scalenectomy and first rib resection) with rib-sparing (supraclavicular anterior and middle scalenectomy alone) operations. All patients with cervical ribs were excluded. In total, 125 rib resections and 43 rib-sparing procedures were performed between 1983 and 1992 by a single surgeon. The patients were otherwise comparable in symptoms and physical signs. During surgery there was a significantly higher proportion of pleural injury associated with rib resection (59%) than with rib-sparing (40%) procedures. The mean hospital stay was also prolonged by 1 day in patients undergoing rib resection (p = 0.005). There was no significant difference in early success between the two groups (83% for rib resection, 91% for rib sparing) and no difference in those resuming employment (52% and 63% respectively). Life-table analysis showed that the two groups have similar long-term results (69% and 76% at 2 years). The only important factor determining clinical outcome in primary supraclavicular thoracic outlet syndrome decompression was the duration of symptoms before operation. Some 83% of patients with symptoms less that 2 years had a successful result compared with only 68% in those with symptoms longer than 2 years (p < 0.05). Spontaneous or post-traumatic neurogenic symptoms responded to operation identically. The theoretical benefit of first rib resection to relieve mechanical compression of the brachial plexus is not evident from this review. Thorough removal of the scalene musculature and other myofascial anomalies, preferably through the supraclavicular approach, leads to less patient morbidity, shortens hospitalization, and is recommended for patients with neurogenic thoracic outlet syndrome requiring operative intervention.

Adult↗
PubMed2001

Assessing the true risk of abdominal solid organ injury in hospitalized rib fracture patients.

BACKGROUND: Despite the lack of evidence, traditional trauma teaching has suggested that low rib fractures increase the risk of abdominal solid organ injury (ASOI). This study was designed to assess if in fact this is true, and to try and define other factors that increased the risk of ASOI in rib fracture patients. METHODS: The charts of 476 hospitalized rib fracture trauma patients were reviewed. Data were collected for age; sex; Injury Severity Score (ISS); rib fracture location; and the presence or absence of injuries to the abdominal organs, head, neck, face, thorax, great vessel, heart, thoracolumbar spine, pelvis, and extremities. RESULTS: The probability of liver injury increased with the presence of any right-sided rib fracture, any low rib fracture, female gender, young age, and an elevated ISS. The probability of splenic injury increased with the presence of left-sided rib fractures only, any low rib fracture, young age, and an elevated ISS. CONCLUSION: In hospitalized trauma patients, low rib fractures, right-sided rib fractures, female gender, young age, and an elevated ISS increased the probability of liver injury; and low rib fractures, left-sided only rib fractures, young age, and an elevated ISS increased the probability of splenic injury. Associated pelvic fractures and long bone fractures did not increase the likelihood of ASOI in this cohort.

Abdominal Injuries↗
PubMed2002

The association between cervical rib and sacralization.

STUDY DESIGN: After determining the normal reference values for the length of the transverse processes of the seventh cervical vertebra, the association between the presence of cervical rib and sacralization was investigated. OBJECTIVE: To determine the length of cervical rib and search for any association between cervical rib and sacralization. SUMMARY OF BACKGROUND DATA: Both cervical ribs and sacralization have been noted in some patients in the authors' clinical practice. METHODS: The cervical rib is a supernumerary rib arising from a cervical vertebra, or it might be simply an elongation of the transverse process of the seventh cervical vertebra. However, there is no consensus about a specified length of this process. For reference values, anteroposterior cervical radiographs of 210 normal individuals (112 male, 98 female, mean age 33.9 +/- 10.1 years, range 19-61 years) were taken, and elongation of the transverse processes beyond 2 standard deviations (30 mm) was considered as cervical rib. In the guide of the reference values, 324 outpatients (165 male, 159 female, mean age 42.0 +/- 14.6 years, range 17-85 years), having cervical ribs or sacralization detected by plain radiographs, were taken as the study group. As control 729 volunteers (364 male, 365 female, mean age 41.7 +/- 14.3 years, range 15-76 years) were studied. RESULTS: In 1053 patients, of 471 patients having cervical ribs, 345 (73.2%) had also sacralization; of 536 patients with sacralization, 345 (64.4%) also had cervical ribs. Significant associations were found between cervical rib with or without articulation and sacralization [chi2 = 52.284, P < 0.001, odds ratio 5.097 (3.156-8.234); chi2 = 139.473, P < 0.001, odds ratio 5.204 (3.922-6.905), respectively]. CONCLUSION: Presence of cervical rib might be a clue to the existence of sacralization or vice versa. In patients with cervical or lumbar pain, this association may be helpful for differential diagnosis before applying sophisticated diagnostic techniques.

Adolescent↗
PubMed2004

Experimental studies on cervical and lumbar ribs in mouse embryos.

In humans, the presence of cervical and lumbar ribs is of particular clinical significance. However, the relevance of their occurrence in the offspring of experimental animals in reproductive toxicologic studies is poorly understood. Maternal toxicity has been implicated in the etiology but conclusive evidence is lacking. The present study was undertaken to determine the incidence of supernumerary ribs (SNR) in mouse fetuses prenatally exposed to valproic acid (VPA) and retinoic acid (RA), and to compare their differential developmental susceptibility and morphological association with other axial skeletal anomalies. Single doses of valproic acid (VPA) or retinoic acid (RA) were administered to groups of mice on one of gestation days (GD) 7-12. Fetuses were collected on GD 18 and their skeletons examined for SNR. VPA treatment on GD 7 and GD 8 resulted in a high incidence of cervical and lumbar ribs, respectively. Cervical neural arch anomalies in the GD 7 group, and eight pairs of sternal ribs and seven sternebrae in the GD 8 group were observed in excess of the background SNR suggesting a direct effect of VPA on the developing mouse skeletal system. In the RA groups, GD 8-12 were susceptible for lumbar rib induction but increased incidence of cervical ribs was observed only from GD 9-12. Peak incidence of cervical ribs was found in the GD 10 and 11 groups and that of the lumbar ribs in the GD 8 and 11 groups. Although SNR incidence generally increased with increasing dose of RA, a strict dose-response relationship was lacking. Cervical arch anomalies were observed in as many embryos as those with cervical ribs, but eight pairs of sternal ribs and seven sternebrae did not correlate well with the lumbar ribs in the peak day groups. Interrupted cervical neural arches correlated well with lumbar ribs. The reduction in the frequency of presacral vertebrae from 26 to 25 in the VPA groups was limited to GD 7 (30%) and 8 (18%) groups. RA-induced reduction in presacral vertebral number extended to GD 9 and was greater in the GD 8 than in the GD 9 groups. Sternal anomalies occurred both in VPA and RA experiments and did not strictly correlate with the frequency of SNR. VPA had a narrow window of susceptibility, whereas RA effects on sternum extended from GD 9-12. The incidence of sternal anomalies generally increased with increasing dose and advancing developmental stage at which RA exposure occurred. These developmental susceptibility windows and associated malformations, when considered in the context of the ability of these drugs to induce alterations in gene expression in mouse embryos suggest that SNR are polygenic in origin and greatly influenced by environmental toxicants.

Abnormalities, Drug-Induced↗
PubMed1984

Action of neck accessory muscles on rib cage in dogs.

To investigate the action of the neck accessory muscles on the rib cage, we stimulated the sternocleidomastoid and the scalenus muscles separately in supine anesthetized dogs. Hooks screwed into the sternum and ribs were used to measure their axial displacements and the changes in anteroposterior (AP) and transverse (T) diameters of the rib cage. We found that the sternocleidomastoid and scalenus muscles, when they contract alone, cause a large axial displacement of the sternum and the ribs in a cephalad direction and expand the rib cage along both its AP and T diameters. Opening the abdomen increased the cephalad displacement of the ribs and the expansion of the lower rib cage, particularly along its T diameter, but reduced the increase in lung volume. These experiments indicate 1) that the action of the sternocleidomastoid and scalenus muscles on the rib cage is essentially the consequence of a rotation of the ribs' neck axes, resulting from the cephalad displacement of the ribs, and 2) that the fall in abdominal pressure, almost certainly by acting through the zone of apposition of the diaphragm to the rib cage, has a deflationary action on the lower rib cage, more markedly so on its lateral than its anterior wall. The experiments also suggest that the fall in abdominal pressure prevents the diaphragm from moving cephalad and aids the neck accessory muscles in inflating the lungs.

Abdomen↗
PubMed1985

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.

Abdominal Muscles↗
PubMed1993

Sternum dependence of rib displacement during breathing.

The parasternal intercostals are the primary determinant of the inspiratory cranial displacement of the ribs in the dog. When they contract, however, these muscles also cause a caudal displacement of the sternum, presumably an expiratory motion. The present studies were designed to assess the effects of this sternal displacement on the cranial displacement of the ribs and on lung volume. Twelve supine anesthetized animals were studied. We first measured, in four paralyzed animals, the displacement of the ribs and sternum produced by known external forces applied to the ribs, the sternum, or both simultaneously. From these measurements, the elastic coupling between the ribs and sternum was determined. We then studied, in eight animals, the effect of sternal motion on rib motion and tidal volume during spontaneous breathing. Rib and sternal displacements and tidal volume were measured first with the sternum free to move caudally during inspiration and then with the sternum constrained to prevent caudal motion. Preventing the sternum from moving caudally caused a 24% increase in the inspiratory cranial displacement of the ribs; this increased displacement of the ribs agreed well with the elastic coupling between the sternum and the ribs as determined from the force-displacement observations. Tidal volume, however, remained unchanged. These observations indicate that the caudal displacement of the sternum produced by the parasternal intercostals reduces the cranial displacement of the ribs but probably increases the lateral expansion of the rib cage.

Animals↗