Is There an Optimal Patient Stance for Obtaining a Lateral 36" X-Ray? A Critical Comparison of Three Techniques

Purpose: Different techniques for positioning patient's arms are utilized for 36 x-ray (arms extended, flexed, supported, etc.) with no data on relative accuracy. The purpose of this study is twofold: 1. To determine if one positioning technique provides superior clarity to visualize critical measurement landmarks (C-7, T-2, T-12, L5-S1). 2. To determine if there are any position dependent variations in regional measures or sagittal balance.The null hypothesis is that there is no significant difference in visualization or critical measures between the commonly used xray positions.

Method: 25 adult scoliosis patients were prospectively studied under IRB approval with 36" lateral x-rays obtained in 3 standardized stance positions varying arm location (arms straight out at "90" degrees, partially flexed at "60" degrees, and the "clavicle" position with elbows flexed and hands in supraclavicular fossae). Ten patients were also xrayed in the three AP views for analysis. Films were analyzed independently by three deformity surgeons. The critical measurement landmarks were scored based on the number of cortices clearly visible at each vertebra. Measures also included cervical and lumbar lordosis, thoracic kyphosis, and global C-7 to S-1 balance. Statistical analysis was done with a GEE model to test for significant differences between the three views.

Results: The overall score for the clavicle position (Clav) was superior to either the 60 or 90 positions and the difference was highly significant (Clav vs 60 p<0 .0001, Clav vs 90 p<0.0003). The overall score for the 60 and views were not significantly different. Critical analysis of individual vertebral landmarks showed better visualization T-2 with (p< 0.047), T-12 either 0.006) or (p<0.049) L5-S1 (p<0.02). Excellent C-7 only occurred in 73%, 77%, 68% patients Clav, 60, respectively. A "worst view" at suggests is worse than (p<0.06). Analysis all regional measures no significant differences, but sagittal balance was affected. to S-1 plumb more positive position (p<0.04) (p<0.015). (arms straight out) produced a negative balance. AP films differences landmarks, clavicle-acromion visualization, measures.

Conclusion: The Clavicle arm position for obtaining lateral 36" x-rays produces significantly better overall visualization of critical vertebral landmarks. Clav is superior to the 90 position at T-2, T-12, L5-S1, and probably at C-7. Clav is superior to the 60 position in overall score and at T-12. Regional measures do not differ between the three arm positions, but global balance is significantly more positive with the 60 position. Clinically, the superior visualization from the Clav position may result in more accurate radiographic measures and better interpretation of bony pathology. Also, this may minimize radiation from repeated x-ray exposures due to sub-optimal imaging encountered with the other arm positions."