Reliability and Validity Analysis of Pelvic Sagittal Inclination Calculated by Inverse Cosine Function Method on Pelvic Anteroposterior Radiographs.

OBJECTIVE: Evaluation of sagittal pelvic tilt is significant for hip surgeons. However, the accurate measurement of pelvic sagittal inclination (PSI) is still a challenge. The objective of this study is to propose a new method for measurement of PSI from pelvic anteroposterior radiograph based on the inverse cosine function obtained from individualized pelvic model. METHODS: Collecting the imaging data of 30 patients with both pelvic CT and full-length spine radiographs. Establishing pelvic model by customized 3D reconstruction software. The length of three groups of longitudinal and transverse line segments (A'p and B') were measured from full-length spine anteroposterior radiographs. The corresponding anatomical parameters, including A, B, b, ∠α, ∠γ, were measured and calculated on the same patient's pelvic model. The estimated PSI (ePSI) based on three groups of anatomical landmarks, including ePSI-1, ePSI-2, and ePSI-3, were calculated by equation, ePSI = arccos A ' p b * B ' - ∠ α , and compared with the actual PSI (aPSI) measured by Surgamap software. For the reliability and validation evaluation, three observers measured these parameters in two rounds. Intra-class correlation and inter-class correlation were both calculated. Bland-Altman method was used to evaluate the consistency between the estimated PSI (ePSI) and the actual PSI (aPSI). RESULTS: ePSI-1 and ePSI-2 showed excellent intra-observer reliability (0.921-0.997, p < 0.001) and inter-observer reliability (0.801-0.977, p < 0.001). ePSI-3 had a fair inter-observer reliability (0.239-0.823, p < 0.001). ePSI-1 showed the strongest correlation with aPSI (r = 0.917, p < 0.001). Mean (maximum) absolute difference of ePSI-1, ePSI-2, and ePSI-3 is 2.62° (7.42°), 4.23° (13.78°), and 7.74° (31.47°), respectively. The proportion of cases with absolute difference less than 5° in three groups were 86.7% (ePSI-1), 66.7% (ePSI-2), 56.7% (ePSI-3). CONCLUSION: This new method based on inverse cosine function has good reliability and validity when used in the evaluation of PSI on pelvic anteroposterior radiographs.

Effect of surface preparation on the failure load of a highly filled composite bonded to the polymer-monomer matrix of a fiber-reinforced composite.

PURPOSE: The purpose of the present study was to evaluate the effect of surface preparation on the maximum fracture load value of a highly filled composite bonded to the polymer-monomer matrix of a fiber-reinforced composite. MATERIALS AND METHODS: A polymer-monomer matrix was made by mixing urethane dimethacrylate and triethyleneglycol dimethacrylate at a ratio of 1:1 with camphorquinone and 2-dimethylaminoethyl methacrylate as a light initiator. The matrix was then polymerized in a disk-shaped silicone mold with a light-polymerizing unit. The flat surfaces of the polymer-monomer matrix disk were prepared in one of the following ways: (1) without preparation; (2) application of silane coupling agent; or (3) application of matrix liquid and prepolymerization. A highly filled composite material was applied and polymerized with a light-polymerizing unit. Additional test specimens made entirely of the polymer-monomer matrix were fabricated as references; the disk and cylinder were fabricated in one piece using a mold specially made for the present study (group 4). Half the specimens were thermocycled up to 10,000 times in water with a 1-minute dwell time at each temperature (5 degrees C and 55 degrees C). The maximum fracture load values were determined using a universal testing machine (n = 10). RESULTS: The maximum fracture loads for group 3 were significantly enhanced both before and after thermocycling, whereas the maximum fracture loads of group 2 were significantly enhanced before thermocycling (p < 0.05); however, the failure loads decreased for all groups after thermocycling (p < 0.05). All the specimens in groups 1 and 2 debonded during thermocycling. The failure load of group 3 was significantly lower than that of group 4 both before and after thermocycling (p < 0.05). CONCLUSION: Within the limitations of the current in vitro study, the application and prepolymerization of a mixed dimethacrylate resin liquid prior to the application of a highly filled composite was an effective surface preparation for the polymer-monomer matrix of a fiber-reinforced composite; however, the bond durability may be insufficient.

Bonding of autopolymerizing acrylic resins to magnetic stainless steel alloys using metal conditioner.

OBJECTIVES: The shear bond strengths of a barbituric acid derivative-activated autopolymerizing acrylic resin to two magnetic stainless steel alloys using a metal conditioner were investigated. METHODS: The surfaces of the two magnetic stainless steel alloys were abraded with 600-grit silicon carbide paper. The surface preparations were: Group 1 (without preparation), Group 2 (airborne particle abrasion with 50 microm alumina), and Group 3 (airborne particle abrasion followed by priming with a metal conditioner). The alloys were bonded with a barbituric acid derivative-activated autopolymerizing acrylic resin. For comparison, airborne particle abrasion and bonding with a tri-n-butylborane-initiated autopolymerizing acrylic resin (Group 4), as well as airborne particle abrasion followed by priming with a metal conditioner and bonding with the same resin (Group 5) were added. Half of the specimens were thermocycled up to 10,000 cycles. The shear bond strengths were determined. RESULTS: Group 3 had significantly improved shear bond strengths with the barbituric acid derivative-activated autopolymerizing acrylic resin to both stainless steel alloys. Although there were no significant differences in the bond strength among Groups 3-5 before thermocycling, the decrease in the bond strength of Group 3 was considerably greater than that of Groups 4 or 5 after thermocycling for both stainless steel alloys. CONCLUSIONS: Significant improvements in the bond strength of the barbituric acid derivative-activated autopolymerizing acrylic resin to two magnetic stainless steel alloys were achieved by airborne particle abrasion followed by priming with the metal conditioner. The bond durability to this resin, however, was inferior to that to a tri-n-butylborane-initiated autopolymerizing acrylic resin.