Alligator mississippiensis sternal and shoulder girdle mobility increase stride length during high walks.

Crocodilians have played a significant role in evolutionary studies of archosaurs. Given that several major shifts in forelimb function occur within Archosauria, forelimb morphologies of living crocodilians are of particular importance in assessing locomotor evolutionary scenarios. A previous X-ray investigation of walking alligators revealed substantial movement of the shoulder girdle, but as the sternal cartilages do not show up in X-ray, the source of the mobility could not be conclusively determined. Scapulocoracoid movement was interpreted to indicate independent sliding of each coracoid at the sternocoracoid joint; however, rotations of the sternum could also produce similar displacement of the scapulocoracoids. Here, we present new data employing marker-based XROMM (X-ray reconstruction of moving morphology), wherein simultaneous biplanar X-ray video and surgically implanted radio-opaque markers permit precise measurement of the vertebral axis, sternum and coracoid in walking alligators. We found that movements of the sternum and sternocoracoid joint both contribute to shoulder girdle mobility and stride length, and that the sternocoracoid contribution was less than previously estimated. On average, the joint contributions to stride length (measured with reference to a point on the distal radius, thus excluding wrist motion) are as follows: thoracic vertebral rotation 6.2±3.7%, sternal rotation 11.1±2.5%, sternocoracoid joint 10.1±5.2%, glenohumeral joint 40.1±7.8% and elbow 31.1±4.2%. To our knowledge, this is the first evidence of sternal movement relative to the vertebral column (presumably via rib joints) contributing to stride length in tetrapods.

On the absence of sternal elements in Anchiornis (Paraves) and Sapeornis (Aves) and the complex early evolution of the avian sternum.

Anchiornis (Deinonychosauria: Troodontidae), the earliest known feathered dinosaur, and Sapeornis (Aves: Pygostylia), one of the basalmost Cretaceous birds, are both known from hundreds of specimens, although remarkably not one specimen preserves any sternal ossifications. We use histological analysis to confirm the absence of this element in adult specimens. Furthermore, the excellent preservation of soft-tissue structures in some specimens suggests that no chondrified sternum was present. Archaeopteryx, the oldest and most basal known bird, is known from only 10 specimens and the presence of a sternum is controversial; a chondrified sternum is widely considered to have been present. However, data from Anchiornis and Sapeornis suggest that a sternum may also have been completely absent in this important taxon, suggesting that the absence of a sternum could represent the plesiomorphic avian condition. Our discovery reveals an unexpected level of complexity in the early evolution of the avian sternum; the large amount of observable homoplasy is probably a direct result of the high degree of inherent developmental plasticity of the sternum compared with observations in other skeletal elements.

Procedure to describe clavicular motion.

BACKGROUND: For many years, researchers have attempted to describe shoulder motions by using different mathematical methods. The aim of this study was to describe a procedure to quantify clavicular motion. METHODS: The procedure proposed for the kinematic analysis consists of 4 main processes: 3 transcortical pins in the clavicle, motion capture, obtaining 3-dimensional bone models, and data processing. RESULTS: Clavicular motion by abduction (30° to 150°) and flexion (55° to 165°) were characterized by an increment of retraction of 27° to 33°, elevation of 25° to 28°, and posterior rotation of 14° to 15°, respectively. In circumduction, clavicular movement described an ellipse, which was reflected by retraction and elevation. Kinematic analysis shows that the articular surfaces move by simultaneously rolling and sliding on the convex surface of the sternum for the 3 movements of abduction, flexion, and circumduction. CONCLUSION: The use of 3 body landmarks in the clavicle and the direct measurement of bone allowed description of the osteokinematic and arthrokinematic movement of the clavicle.

Effects of enhancing vitamin D status by 25-hydroxycholecalciferol supplementation, alone or in combination with calcium and phosphorus, on sternum mineralisation and breast meat quality in broilers.

1. The aim of the present study was to examine the effects of improving vitamin D status in broiler diets by supplementary 25-hydroxycholecalciferol (25OHD3), alone or in combination with calcium (Ca) and available phosphorus (aP), on live performance, sternum mineralisation and breast meat quality in broilers. 2. A total of 936 1-d-old Ross 308 broilers were used in the study. After gender determination at the hatchery, chicks from each sex were randomly distributed into three dietary treatments. The following dietary treatments were used in the experiment from hatch to 38 d: (1) A control diet formulated to meet all of the nutrient requirements of broiler chicks according to the management guide; (2) The control diet supplemented with 18.7-15.0 µg/kg of 25OHD3; and (3) The control diet supplemented with 18.7-15.0 µg/kg of 25OHD3 plus Ca + aP. 3. Improvement in vitamin D status by 25OHD3 supplementation, alone or in combination with Ca and aP, had no effect on body weight and feed conversion ratio of broilers. 4. The serum 25OHD3 concentration significantly increased with 25OHD3 and 25OHD3 plus Ca + aP supplementation (P < 0.05), whereas the ionised Ca and Mg concentrations remained unchanged. 5. Sternum absolute weight, ash content and the concentrations of Ca and P significantly increased (P < 0.01) with supplementation of 25OHD3, alone or in combination with Ca + aP. 6. Supplemental 25OHD3, alone or in combination with Ca + aP, slightly increased pH24 (P = 0.05) and decreased (P < 0.01) squeezable water loss in breast meat, whereas it had no significant effect on lightness, yellowness and sarcoplasmic protein solubility. 7. In conclusion, the results suggested that enhancing vitamin D status by 25OHD3 supplementation alone or in combination with Ca + aP may improve sternum structure and mineral accretion. Furthermore, supplemental 25OHD3, even in a nutritionally complete diet, may offer an effective way to improve protein solubility in female broilers.

Evolution and functional significance of derived sternal ossification patterns in ornithothoracine birds.

The midline pattern of sternal ossification characteristic of the Cretaceous enantiornithine birds is unique among the Ornithodira, the group containing birds, nonavian dinosaurs and pterosaurs. This has been suggested to indicate that Enantiornithes is not the sister group of Ornithuromorpha, the clade that includes living birds and their close relatives, which would imply rampant convergence in many nonsternal features between enantiornithines and ornithuromorphs. However, detailed comparisons reveal greater similarity between neornithine (i.e. crown group bird) and enantiornithine modes of sternal ossification than previously recognized. Furthermore, a new subadult enantiornithine specimen demonstrates that sternal ossification followed a more typically ornithodiran pattern in basal members of the clade. This new specimen, referable to the Pengornithidae, indicates that the unique ossification pattern observed in other juvenile enantiornithines is derived within Enantiornithes. A similar but clearly distinct pattern appears to have evolved in parallel in the ornithuromorph lineage. The atypical mode of sternal ossification in some derived enantiornithines should be regarded as an autapomorphic condition rather than an indication that enantiornithines are not close relatives of ornithuromorphs. Based on what is known about molecular mechanisms for morphogenesis and the possible selective advantages, the parallel shifts to midline ossification that took place in derived enantiornithines and living neognathous birds appear to have been related to the development of a large ventral keel, which is only present in ornithuromorphs and enantiornithines. Midline ossification can serve to medially reinforce the sternum at a relatively early ontogenetic stage, which would have been especially beneficial during the protracted development of the superprecocial Cretaceous enantiornithines.

Morphologic assessment of thoracic deformities for the preoperative evaluation of pectus excavatum by magnetic resonance imaging.

OBJECTIVE: To assess whether MRI is a suitable modality for the preoperative assessment and quantification of pectus excavatum. METHODS: A total of 69 patients (57 male, 12 female; median age 15 years, range 5-35 years) with pectus excavatum were evaluated preoperatively using standardized MRI sequences on 1.5- and 3-Tesla systems (T2-HASTE/inspiration and expiration, T1-VIBE, T2-TRUFI free-breathing, T2-BLADE). The MR sequences were analysed for quality semiquantitatively. The Haller index, correction index, sternal rotation angle and asymmetry index were assessed; correlations between these indices and changes in inspiration and expiration were evaluated. RESULTS: T2-HASTE was the best sequence to assess pectus excavatum morphology, with a higher quality at 3 T than at 1.5 T. All indices could be assessed in every patient. A total of 37 patients had a symmetric deformity, 32 patients an asymmetric deformity. The Haller index correlated significantly (p < 0.001) with the correction index, both becoming higher in expiration. The asymmetry index correlated with the sternal rotation angle (p < 0.001) and did not change significantly in expiration (p = 0.28). CONCLUSIONS: Thoracic MRI is suitable for the preoperative evaluation of patients with pectus excavatum. An exact morphologic assessment is possible without radiation exposure as well as the determination of several indices to quantify the deformities.

Unified frame of reference improves inter-subject variability of seismocardiograms.

BACKGROUND: Seismocardiography is the noninvasive measurement of cardiac vibrations transmitted to the chest wall by the heart during its movement. While most applications for seismocardiography are based on unidirectional acceleration measurement, several studies have highlighted the importance of three-dimensional measurements in cardiac vibration studies. One of the main challenges in using three-dimensional measurements in seismocardiography is the significant inter-subject variability of waveforms. This study investigates the feasibility of using a unified frame of reference to improve the inter-subject variability of seismocardiographic waveforms. METHODS: Three-dimensional seismocardiography signals were acquired from ten healthy subjects to test the feasibility of the present method for improving inter-subject variability of three-dimensional seismocardiograms. The first frame of reference candidate was the orientation of the line connecting the points representing mitral valve closure and aortic valve opening in seismocardiograms. The second candidate was the orientation of the line connecting the two most distant points in the three dimensional seismocardiogram. The unification of the frame of reference was performed by rotating each subject's three-dimensional seismocardiograms so that the lines connecting the desired features were parallel between subjects. RESULTS: The morphology of the three-dimensional seismocardiograms varied strongly from subject to subject. Fixing the frame of reference to the line connecting the MC and AO peaks enhanced the correlation between the subjects in the y axis from 0.42 ± 0.30 to 0.83 ± 0.14. The mean correlation calculated from all axes increased from 0.56 ± 0.26 to 0.71 ± 0.24 using the line connecting the mitral valve closure and aortic valve opening as the frame of reference. When the line connecting the two most distant points was used as a frame of reference, the correlation improved to 0.60 ± 0.22. CONCLUSIONS: The results indicate that using a unified frame of reference is a promising method for improving the inter-subject variability of three-dimensional seismocardiograms. Also, it is observed that three-dimensional seismocardiograms seem to have latent inter-subject similarities, which are feasible to be revealed. Because the projections of the cardiac vibrations on the measurement axes differ significantly, it seems obligatory to use three-dimensional measurements when seismocardiogram analysis is based on waveform morphology.

Sternal vibrations during head-out immersion: A preliminary demonstration of underwater wearable ballistocardiography.

Ballistocardiography (BCG) measures vibrations of the body caused by ejection of blood from the heart, and the root mean square (RMS) of BCG measured with a weighing scale trends with cardiac output. However, BCG underwater has not been studied. Head-to-foot BCG signals were recorded with an accelerometer on the sternum of three human subjects. The heartbeats were clearly visible in the signals recorded underwater, and the resting change in RMS BCG was +360 µg (+36%) from air to cold water immersion (27.8 °C) while standing. This is within the 32%-62% increase in cardiac output observed in previous head-out immersion studies.

Quantitative validation of the suprasternal pressure signal to assess respiratory effort during sleep.

Objective.Intra-esophageal pressure (Pes) measurement is the recommended gold standard to quantify respiratory effort during sleep, but used to limited extent in clinical practice due to multiple practical drawbacks. Respiratory inductance plethysmography belts (RIP) in conjunction with oronasal airflow are the accepted substitute in polysomnographic systems (PSG) thanks to a better usability, although they are partial views on tidal volume and flow rather than true respiratory effort and are often used without calibration. In their place, the pressure variations measured non-invasively at the suprasternal notch (SSP) may provide a better measure of effort. However, this type of sensor has been validated only for respiratory events in the context of obstructive sleep apnea syndrome (OSA). We aim to provide an extensive verification of the suprasternal pressure signal against RIP belts and Pes, covering both normal breathing and respiratory events.Approach.We simultaneously acquired suprasternal (207) and esophageal pressure (20) signals along with RIP belts during a clinical PSG of 207 participants. In each signal, we detected breaths with a custom algorithm, and evaluated the SSP in terms of detection quality, breathing rate estimation, and similarity of breathing patterns against RIP and Pes. Additionally, we examined how the SSP signal may diverge from RIP and Pes in presence of respiratory events scored by a sleep technician.Main results.The SSP signal proved to be a reliable substitute for both esophageal pressure (Pes) and respiratory inductance plethysmography (RIP) in terms of breath detection, with sensitivity and positive predictive value exceeding 75%, and low error in breathing rate estimation. The SSP was also consistent with Pes (correlation of 0.72, similarity 80.8%) in patterns of increasing pressure amplitude that are common in OSA.Significance.This work provides a quantitative analysis of suprasternal pressure sensors for respiratory effort measurements.

Evaluation of bone strength, keel bone status, plumage condition and egg quality of two layer lines kept in small group housing systems.

1. The aim of the present study was to determine the influence of large (54 or 60) and small (36 or 40) group sizes and tiers of the small group housing system "Eurovent German" on tibia and humerus bone breaking strength, keel bone status, plumage condition and egg quality for two commercial layer lines, Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB), at the same stocking density (890 or 830 cm(2)/bird). 2. In 4 consecutive trials, 4752 hens were recorded for keel bone status. Evaluation of plumage condition was made for 1440 hens and bone breaking strength was recorded for 1200 hens. A total of 4962 eggs were analysed for internal and external egg quality traits. Analyses involved 30 small group compartments per trial. 3. The layer line had a much more pronounced influence on humerus breaking strength than on tibia breaking strength. 4. Plumage condition, particularly on the neck, was positively correlated with humerus breaking strength in both layer lines. 5. An average of 34% of LB and 23% of LSL hens showed keel bone deformities, with higher proportions of slight deformities. 6. Slight keel bone deformities, rather than moderate to severe, increased significantly during the laying period. 7. Stocking density had no influence on bone breaking strength, keel bone status and egg quality traits. 8. LB layers had a 1.4-fold higher humerus, but only a 1.06-fold higher tibia breaking strength compared to LSL layers. 9. Tibia breaking strength was significantly affected by the interaction of group size and layer line. LSL layers in small groups had lower tibia breaking strengths than those of the large groups.

Optimisation of bone marrow aspiration from the equine sternum for the safe recovery of mesenchymal stem cells.

REASONS FOR PERFORMING STUDY: Mesenchymal stem cell (MSC) therapy for orthopaedic disease is being used with increasing frequency; there is a need to define a safe, reliable and effective technique for the recovery of MSCs from the sternum of the horse. OBJECTIVES: To describe an optimised safe technique for obtaining bone marrow-derived MSCs from the sternum of the Thoroughbred horse. METHODS: The anatomical relationship of the sternum with the heart and internal anatomy was demonstrated in cadavers. Sternal anatomy was evaluated ultrasonographically and after midline sectioning. Sternebrae were examined histologically after aspiration to determine the effect of needle insertion. The quality of the aspirate was evaluated as the number of colony-forming units from sequential and separately aspirated 5 ml aliquots and assessed for their multipotency using trilineage differentiation. RESULTS: The optimal safe location for the needle was the 5th sternebra because it had a safe dorsoventral thickness and was cranial to the apex of the heart. This sternebra could be reliably identified ultrasonographically. Aspirates could also be obtained from the 4th and 6th sternebrae, although the former is between the front limbs and the latter closer to the heart. Minimal disruption of the internal bony architecture was seen after needle insertion through the thin outer cortex and the first 5 ml aliquot contained the greatest number of colony-forming units of mesenchymal stem cells with trilineage capabilities. CONCLUSIONS: Accurate placement of a Jamshidi needle into the medullary cavity of the 4th-6th individual sternebrae is facilitated by the use of ultrasonography and enables aspiration of bone marrow reliably with minimal damage to the sternum and risk to the horse. POTENTIAL CLINICAL RELEVANCE: Sternal marrow aspiration as described is a safe and reliable technique to obtain MSCs for orthopaedic cell-based therapies.

Evidence Supporting the Regulatory Relationships through a Paracrine Pathway between the Sternum and Pectoral Muscles in Ducks.

Muscles and bones are anatomically closely linked, and they can conduct communication by mechanical and chemical signals. However, the specific regulatory mechanism between the pectoral muscle and sternum in birds was largely unknown. The present study explored the potential relationship between them in ducks. The result of the sections showed that more nuclei in proliferate states were observed in the pectoral muscle fibers attached to the calcified sternum, than those attached to the un-calcified sternum. The RNA-seq identified 328 differentially expressed genes (DEGs) in the sternum between the calcified and un-calcified groups. Gene ontology (GO) showed that the DEGs were mainly enriched in pathways associated with calcification. In addition, DEGs in the muscles between the calcified and un-calcified sternum groups were mainly annotated to signal transduction receptor pathways. The expression patterns of genes encoding for secreted proteins, in bone (CXCL12, BMP7 and CTSK) and muscle (LGI1), were clustered with muscle development (MB) and bone calcification (KCNA1, OSTN, COL9A3, and DCN) related genes, respectively, indicating the regulatory relationships through a paracrine pathway existing between the sternum and pectoral muscles in ducks. Together, we demonstrated that the pectoral muscle development was affected by the sternal ossification states in ducks. The VEGFA, CXCL12, SPP1, NOG, and BMP7 were possibly the key genes to participate in the ossification of the duck sternum. We firstly listed evidence supporting the regulatory relationships through a paracrine pathway between the sternum and pectoral muscles in ducks, which provided scientific data for the study of the synergistic development of bone and skeletal muscle.

Load carrying during locomotion in the barnacle goose (Branta leucopsis): the effect of load placement and size.

Load carrying has been used to study the energetics and mechanics of locomotion in a range of taxa. Here we investigated the energetic and kinematic effects of trunk and limb loading in walking barnacle geese (Branta leucopsis). A directly proportional relationship between increasing back-load mass and metabolic rate was established, indicating that the barnacle goose can carry back loads (up to 20% of body mass) more economically than the majority of mammals. The increased cost of supporting and propelling the body during locomotion is likely to account for a major proportion of the extra metabolic cost. Sternal loads up to 15% of body mass were approximately twice as expensive to carry as back loads. Given the key role in dorso-ventral movement of the sternum during respiration we suggest that moving this extra mass may account for the elevated metabolic rate. Loading the distal limb with 5% extra mass incurred the greatest proportional rise in metabolism, and also caused increases in stride length, swing duration and stride frequency during locomotion. The increased work required to move the loaded limb may explain the high cost of walking.

Frontal crash seat belt restraint effectiveness and comfort accessories used by older occupants.

Objective: Around a quarter of older occupants use some type of comfort or orthopedic aftermarket accessory on the vehicle seat while traveling in a vehicle. The aim of this study was to investigate the effect of comfort accessories on the performance of the seat belt restraint system in a frontal crash in terms of potential injury implications for older occupants.Methods: Eight frontal sled tests (43 km/h, 32 g) were carried out on a deceleration sled fitted with a three-point lap-sash seat belt and a front passenger seat from a common Australian passenger car for each test. A 5th percentile Hybrid III anthropometric test device (ATD) was positioned in the seat and measurements were recorded for head center of gravity acceleration, chest acceleration, neck forces and moments and sternal deflection. Tests were carried out in a baseline condition and with seven comfort accessories. Each comfort accessory was inserted between the ATD and vehicle seat as it is intended to be used, with the ATD otherwise positioned as close as possible to the baseline test position.Results: Initial distance between the seat belt anchor and ATD hip was associated with a statistically significant decrease in Head Injury Criterion and increase in sternal deflection. Submarining was related to the ATD torso recline angle and angle of the lap belt from the seat belt anchor.Conclusions: Accessories placed between the seat back and the lumbar region of an occupant have the potential to increase the risk of submarining due to a change in posture and should be avoided if such a change in posture when seated with an accessory is excessive. Sitting on seat cushions resulted in the greatest increase in seat belt anchor to hip distances and hence largest increase in sternal deflection. Given the fragility, frailty and particular importance of chest injuries among older vehicle occupants, further investigation is needed to determine whether these changes in ATD sternal deflection observed with seat cushion use results in injury threshold limits being exceeded and whether pretensioners and load limiters would ameliorate these effects without causing other negative changes in occupant response or kinematics.

Age estimation from ossification of sternum and true ribs using 3D post-mortem CT images in a Japanese population.

Age estimation of cadavers from post-mortem "chest plate" using conventional radiography, which involves radiographic assessment of ossification around the sternum and rib ends, has been evaluated without fruitful results. This study examined the value of images of the chest plate obtained by three-dimensional post-mortem CT for estimation of age at time of death in a Japanese population. Five chest plate ossification scores were evaluated in 320 subjects, including ossification of the first costal cartilage (OF), ossification of the second to seventh costal cartilages at the rib (OR) and sternal (OS) ends, fusion of the manubriosternal joint (FM), and fusion of the xiphisternal joint (FX). OS was found to have the highest correlation with age while FM had no significant correlation. The best composite score for age estimation was the summative score for both sides of the OS and the right side of the OF and FX, for which the coefficient of determination (R2) and the standard error of estimation (SEE) were 0.608 and 12.44 years, respectively, for men and 0.590 and 14.65 years for women. The accuracy of the model was tested in a further 26 male and 24 female subjects, and the accuracy rate within the first SEE was 57.69% and 70.83%, respectively. This rapid and non-invasive method of age estimation in the chest plate area is superior to conventional methods and could be useful for estimation of age at time of death in the Japanese population.

Effect of dietary 25-hydroxycholecalciferol on the sternal mass of meat ducks under different vitamin regimens.

Genetic selection and intensive nutrition for increased growth rate in meat-type ducks has resulted in an imbalance between pectorales increment and sternal mass, which is detrimental to productivity and welfare. Reducing body weight and increasing sternal mass probably reverses these adverse effects. Therefore, 2 experiments (Expt.) were conducted to investigate the effects of 25-hydroxycholecalciferol (25-OH-D3), a vitamin D3 metabolites, on sternal mass. In Expt. 1, 512 1-day-old male ducks were randomly assigned to 4 low-nutrient density diets and received following treatments in a 2 × 2 factorial arrangement: (i) NRC or China Agricultural industry standards (NY/T) vitamin premixes and (ii) 0.069 mg/kg 25-HyD in feed or not. At 49 D of age, regardless of 25-OH-D3, NY/T vitamin regimen inhibited bone turnover and consequently increased sternal trabecular bone volume and mineral deposition compared with NRC vitamin premix. Supplementing 25-OH-D3 to NRC but not NY/T vitamin regimen significantly improved sternal microarchitecture and mineral content, which companied by decreased serum bone resorption markers concentration, as well as downregulation of the gene expressions of osteoclast differentiation and activity. In Expt. 2, 256 1-day-old male ducks were fed a standard nutrient density diet contained NRC vitamin premix with 0 or 0.069 mg/kg of 25-OH-D3. Results also showed that 25-OH-D3 treatment significantly improved sternal mineral accumulation and microarchitecture, along with decreasing osteoblast and osteoclast numbers in bone surface, declining serum bone turnover markers levels, and increasing serum Ca concentration. Collectively, these findings indicated that the dietary administration of 25-OH-D3 increased sternal mass in NRC vitamin diet by suppressing bone resorption in 49-day-old meat duck.

In vitro analysis of kinematics and elastostatics of the human rib cage during thoracic spinal movement for the validation of numerical models.

Neither kinematic nor stiffness properties of the rib cage during thoracic spinal motion were investigated in previous studies, while being essential for the accurate validation of numerical models of the whole thorax. The aim of this in vitro study therefore was to quantify the kinematics and elastostatics of the human rib cage under defined boundary conditions. Eight fresh frozen human thoracic spine specimens (C7-L1, median age 55 years, ranging from 40 to 60 years) including entire rib cages were loaded quasi-statically in flexion/extension, lateral bending, and axial rotation using pure moments of 5Nm. Relative motions of ribs, thoracic vertebrae, and sternal structures as well as strains on the ribs were measured using optical motion tracking of 150 reflective markers per specimen, while specimens were loaded displacement-controlled with a constant rate of 1°/s for 3.5 cycles. The third full cycle was used to determine relative angles and strains at full loading of the spine for all motion directions. Largest relative angles were found in the main loading directions with only small motions at the mid-thoracic levels. Highest strains of the intercostal spaces were detected in the anterior section of the lowest fourth of the rib cage, showing compressions and elongations of more than 10% in all spinal motion planes. Elastostatic rib deformation was generally less than 1%. Rib-sternum relative motions exhibited complex motion patterns, overall showing relative angles below 2°. The results indicate that rib cage structures are not macroscopically deformed during spinal motion, but exhibit characteristic reproducible kinematics patterns.

The Effect of Smoking on Sternal Scar Healing: A Prospective Cohort Study.

INTRODUCTION: Cardiothoracic surgery with a median sternotomy is an electing factor for the development of a hypertrophic scar. Hypertrophic scars, characterized by an increased vascularity, often result in aesthetic and functional problems. Smoking, due to its negative effects on vascularization, could therefore have an effect on scar healing. OBJECTIVE: A prospective cohort study was conducted to evaluate the effect of smoking on scar healing after cardiothoracic surgery with a median sternotomy incision. MATERIALS AND METHODS: One hundred patients who underwent cardiac surgery with a median sternotomy were divided into 3 groups: smokers, ex-smokers, and nonsmokers. Erythema values of the scar were measured with a colorimeter on 3 standardized parts of the scar. Scar evaluation was performed at 6 weeks, 3 months, 6 months, and 12 months after surgery. RESULTS: During 1 year, a total of 90 patients were followed after a median sternotomy; 10 patients were lost to follow-up. There were 23 smokers, 52 ex-smokers, and 15 nonsmokers with an overall mean age of 61.5 ± 8.83 years. No significant difference in redness as a parameter for hypertrophic scarring was observed between the 3 groups. Nevertheless, a trend in favor of the smokers was seen, as they developed less hyperemic scars. The caudal part of the scar showed a significantly higher incidence of hypertrophy compared with the middle and cranial part of the scar at all time points. CONCLUSIONS: It is presumed that a large sample size with younger patients is needed to confirm the results herein. Furthermore, more caudally located skin, especially the subxiphoidal part, is prone to hypertrophic scarring and should, for that reason, be avoided in the incision.