RESUMO
BACKGROUND: Nonsmokers may be affected by environmental tobacco smoke (secondhand smoke), but the effects of such exposure on fracture healing have not been well studied. QUESTIONS/PURPOSES: To explore the possible effects of passive inhalation of tobacco smoke on the healing of a diaphyseal fracture in femurs of rats. We hypothesized that secondhand exposure to tobacco smoke adversely affects fracture healing. METHODS: A mid-diaphyseal fracture was created in the femur of 41 female Wistar rats and fixed with an intramedullary metallic pin; 14 rats were excluded (nine for inadequate fractures and five for K wire extrusion). Tobacco exposure was provided by a smoking machine on a daily basis of four cigarettes a day. Each cigarette yielded 10 mg tar and 0.8 mg nicotine, and was puffed by alternating injections of fresh air for 30 seconds and smoke air for 15 seconds. The smoke exposure was previously adjusted to provide serum levels of cotinine similar to human secondhand tobacco exposure. Cotinine is a predominant catabolite of nicotine that is used as a biological biomarker for exposure to tobacco smoke. In one group (n = 11), the animals were intermittently exposed to tobacco smoke before sustaining the fracture but not afterward. In another group (n = 7), the exposure occurred before and after the fracture. The control group (n = 9) was sham-exposed before and after the fracture. We evaluated the specimens 28 days after bone fracture. The callus quality was measured by dual-energy x-ray absorptiometry (bone mineral density [BMD], bone mineral content [BMC], and callus area), µCT (callus volume and woven bone fraction), and mechanical bending (maximum force and stiffness). RESULTS: Tobacco exposure resulted in delayed bone callus formation, which is represented by decreased BMD (Control: 0.302 ± 0.008 g/cm2 vs Preexposed: 0.199 ± 0.008 g/cm2 and Pre- and Postexposed: 0.146 ± 0.009 g/cm2; mean difference = 0.103 g/cm2, 95% CI, 0.094-0.112 g/cm2and mean difference = 0.156 g/cm2, 95% CI, 0.147-0.167 g/cm2; p < 0.01), BMC (Control: 0.133 ± 0.005 g vs Preexposed: 0.085 ± 0.0034 g and Pre- and Postexposed: 0.048 ± 0.003 g; mean difference = 0.048 g, 95% CI, 0.045-0.052 g and mean difference = 0.085 g, 95% CI, 0.088-0.090 g; p < 0.01), callus volume (Control: 7.656 ± 1.963 mm3 vs Preexposed: 17.952 ± 1.600 mm3 and Pre- and Postexposed: 40.410 ± 3.340 mm3; mean difference = -10.30 mm3, 95% CI, -14.12 to 6.471 mm3 and mean difference, -32.75 mm3, 95% CI, -36.58 to 28.93 mm3; p < 0.01), woven bone fraction (Control: 42.076 ± 3.877% vs Preexposed: 16.655 ± 3.021% and Pre- and Postexposed: 8.015 ± 1.565%, mean difference = 0.103%, 95% CI, 0.094-0.112% and mean difference = 0.156%, 95% CI, 0.147-0.166%; p < 0.01), maximum force (Control: 427.122 ± 63.952 N.mm vs Preexposed: 149.230 ± 67.189 N.mm and Pre- and Postexposed: 123.130 ± 38.206 N.mm, mean difference = 277.9 N.mm, 95% CI, 201.1-354.7 N.mm and mean difference = 304 N.mm, 95% CI, 213.2-394.8 N.mm; p < 0.01) and stiffness (Control: 491.397 ± 96.444 N.mm/mm vs Preexposed: 73.157 ± 36.511 N.mm/mm and Pre- and Postexposed: 154.049 ± 134.939 N.mm/mm, mean difference = 418.2 N.mm/mm, 95% CI, 306.3-530.1 N.mm/mm and mean difference = 337.3 N.mm/mm, 95% CI, 188.8-485.9 N.mm/mm; p < 0. 01). CONCLUSIONS: Rats exposed to tobacco smoke showed delayed fracture healing and callus that was characterized by decreased maturity, density, and mechanical resistance, which was confirmed by all assessment methods of this study. Such effects were more evident when animals were exposed to tobacco smoke before and after the fracture. Future studies should be done in human passive smokers to confirm or refute our findings on fracture callus formation. CLINICAL RELEVANCE: The potential hazardous effects of secondhand smoke on fracture healing in rodents should stimulate future clinical studies in human passive smokers.
Assuntos
Fraturas do Fêmur/cirurgia , Fêmur/cirurgia , Consolidação da Fratura , Poluição por Fumaça de Tabaco/efeitos adversos , Absorciometria de Fóton , Animais , Fenômenos Biomecânicos , Densidade Óssea , Pinos Ortopédicos , Calo Ósseo/diagnóstico por imagem , Calo Ósseo/fisiopatologia , Modelos Animais de Doenças , Feminino , Fraturas do Fêmur/diagnóstico por imagem , Fraturas do Fêmur/fisiopatologia , Fêmur/diagnóstico por imagem , Fêmur/fisiopatologia , Fixação Intramedular de Fraturas/instrumentação , Exposição por Inalação/efeitos adversos , Ratos Wistar , Fatores de Tempo , Microtomografia por Raio-XRESUMO
BACKGROUND CONTEXT: Scoliosis is the most common postural alteration in adolescence and is characterized by deviations of the spine in three planes. Surgical treatment based on arthrodesis has been developed, but the effects of such restructuring on the systems involved in postural control need to be better understood. PURPOSE: To assess the influence of vision and the support base on balance in the quiet standing position in adolescents awaiting surgical treatment for idiopathic scoliosis. STUDY DESIGN/SETTING: Longitudinal study/Ribeirão Preto Clinics Hospital (HC-FMRP-USP) and Laboratory of Assessment and Rehabilitation of Equilibrium at the FMRP-USP. PATIENT SAMPLE: Adolescent idiopathic scoliosis patients and controls. OUTCOME MEASURES: Center of pressure (CoP) sway area of the 95% confidence ellipse. METHODS: Thirty female adolescents were divided into two groups according to their spinal alignment: control (n=15) and scoliosis groups (SGs) (n=15). The subjects with scoliosis were evaluated before and 7, 30, 60, and 90 days after surgery; the controls were evaluated once. The area of CoP oscillation was measured with the eyes open and closed and with two different support bases (feet apart or together). The force platform was purchased with funding support (US $8,375.00) provided by the Research Foundation of São Paulo (FAPESP). The study sponsors had no involvement in the study. Data were collected from the force platform and then statistically assessed through a linear model analysis of mixed effects. RESULTS: Data reveal that subjects in the SG oscillated more than controls, and postsurgery subjects had more oscillation than presurgery subjects. The results also indicated that both groups (control and scoliosis) showed more oscillation among those subjects with feet apart and eyes closed, but subjects with scoliosis were more affected by vision deprivation than by a reduced support base. CONCLUSIONS: Our results indicate that adolescents with idiopathic scoliosis are more dependent on visual information and that surgical correction does not change this relationship.