Study design: Analysis of sagittal vertical axis (SVA) on lateral spine radiographs in healthy normal volunteers.
Objectives: To determine the optimal arm position with the smallest negative shift in SVA.
Summary of background data: Radiographic visualization of spinal and pelvic sagittal morphology is difficult with the participant in a relaxed standing position because of interference from the arms. Standing with shoulder flexion (SF) results in a negative shift in SVA. The fists-on-clavicles (FC) position reduces the negative shift in SVA seen in SF, but only by 25%. The best arm position to produce the smallest negative shift in SVA has yet to be determined.
Methods: The SVA was measured using standing lateral radiographs of 21 healthy participants. Five different arm positions were used: relaxed with arms at sides (RLX), arms flexed to 45 degrees (SF), FC, arms folded across the chest (FA), and arms relaxed in front with hands loosely clasped (FHC). Negative shifts in SVA resulting from the SF, FC, FA, and FHC arm positions were compared.
Results: The mean SVA with RLX was 2.3±2.0 cm. The other arm positions resulted in a significant negative SVA shift compared with RLX (P<0.001). Mean negative shifts were -5.1±1.6 cm for SF, -3.9±1.5 cm for FC, -3.1±1.1 cm for FA, and -1.8±1.7 cm for FHC. The FC position reduced negative SVA shift seen in the SF arm position by 24%, FA by 39%, and FHC by 65%. The FHC position resulted in a significantly reduced SVA negative shift (P<0.001) compared with the FC, FA, and SF positions.
Conclusion: FHC that produced the least negative shift in SVA, is the best arm position for SVA measurement.