ABSTRACT
Objective@#This cross-sectional study aimed to investigate the characteristics of malocclusions in scoliotic patients through clinical examinations. @*Methods@#Fifty-eight patients with idiopathic scoliosis (IS) and 48 patients with congenital scoliosis (CS) participated in the study. A randomly selected group of 152 orthopedically healthy children served as the control group. Standardized orthodontic and orthopedic examination protocols were used to record the occlusal patterns and type of scoliosis. Assessments were made by three experienced orthodontists and a spinal surgery team. The differences in the frequency distribution of occlusal patterns were evaluated by the chi-squared test. @*Results@#In comparison with patients showing IS, patients with CS showed a higher incidence of Cobb angle ≥ 45° (p = 0.020) and included a higher proportion of patients receiving surgical treatments (p < 0.001). The distribution of the Angle Class II subgroup was significantly higher in the IS (p < 0.001) and CS (p = 0.031) groups than in the control group. In comparison with the healthy controls, the CS and IS groups showed significantly higher (p < 0.05) frequencies of asymmetric molar and asymmetric canine relationships, upper and lower middle line deviations, anterior deep overbite, unilateral posterior crossbite, and canted occlusal plane, with the frequencies being especially higher in CS patients and to a lesser extent in IS patients. @*Conclusions@#Patients with scoliosis showed a high frequency of malocclusions, which were most obvious in patients with CS.
ABSTRACT
Objective@#To compare the biomechanical performance between the single- versus double-threaded cannulated screws in the treatment of femoral neck fractures of Pauwels type Ⅲ.@*Methods@#Models of femoral neck fracture of Pauwels type Ⅲ (70°) were made of the Sawbone synthetic composite femurs. All specimens were divided into 2 groups (n=12). Group A was fixated with single-threaded cannulated screws and group B with double-threaded cannulated screws, both in an inverted triangle configuration. The screws ranged from 90 to 95 mm in length and from 7.3 to 7.5 mm in diameter. All the specimens were subjected to axial stiffness and failure load tests with 7° valgus (simulating normal two-legged weight-bearing stance) and 25° valgus (simulating normal one-legged weight-bearing stance) and torsion test as well. The 2 groups were compared in the torques at axial stiffness angles of 1°, 2°, 3°, 5° and 7°.@*Results@#Group B had significantly greater axial stiffness at 7° valgus and 25° valgus (89±26 N/mm and 128±37 N/mm) and failure load (1,154±368 N) than group A did (36±12 N/mm and 47±16 N/mm; 688±94 N) (P< 0.05). The torques increased with the increase in rotation angle in both groups. However, the torques in group B (3.26±0.96, 4.16±1.23, 4.64±1.13, 5.59±1.26 and 6.53±1.47 N·m) were all significantly larger than in group A (1.44±0.19, 2.03±0.41, 2.33±0.62, 2.74±0.87 and 3.05±1.07 N·m) (P<0.05).@*Conclusion@#Double-threaded cannulated screws may provide better biomechanical stability than single-threaded ones, due to their substantial improvement in anti-compression and anti-rotation performance.
ABSTRACT
Objective To compare the biomechanical performance between the single-versus double-threaded cannulated screws in the treatment of femoral neck fractures of Pauwels type Ⅲ.Methods Models of femoral neck fracture of Pauwels type Ⅲ (70°) were made of the Sawbone synthetic composite femurs.All specimens were divided into 2 groups (n =12).Group A was fixated with single-threaded cannulated screws and group B with double-threaded cannulated screws,both in an inverted triangle configuration.The screws ranged from 90 to 95 mm in length and from 7.3 to 7.5 mm in diameter.All the specimens were subjected to axial stiffness and failure load tests with 7° valgus (simulating normal two-legged weight-bearing stance) and 25° valgus (simulating normal one-legged weight-bearing stance) and torsion test as well.The 2 groups were compared in the torques at axial stiffness angles of 1°,2°,3°,5° and 7°.Results Group B had significantly greater axial stiffness at 7° valgus and 25° valgus (89 ± 26 N/mm and 128 ± 37 N/mm) and failure load (1,154 ±368 N) than groupAdid (36 ±12 N/mm and 47 ±16 N/mm;688 ±94 N) (P ＜0.05).The torques increased with the increase in rotation angle in both groups.However,the torques in groupB (3.26±0.96,4.16±1.23,4.64±1.13,5.59±l.26and6.53±l.47 N·m) were all significantly larger than in group A (1.44 ±0.19,2.03 ±0.41,2.33 ±0.62,2.74 ±0.87 and 3.05 ± 1.07 N · m)(P ＜ 0.05).Conclusion Double-threaded cannulated screws may provide better biomechanical stability than single-threaded ones,due to their substantial improvement in anti-compression and anti-rotation performance.