Comparison of lumbar sagittal alignment produced by different operative positions

Study Design. This study is a prospective evaluation of the effects of commonly used spinal tables on lumbar sagittal alignment. Objectives. The objective was to determine the differences, if any, in lumbar sagittal alignment produced by different positions on routinely used spinal operating tables. Summary of Background Data. Earlier studies have documented the advantages of the knee-chest position in lumbar decompressive procedures. When simultaneous fusion is performed and augmented with internal fixation, intraoperative position is the critical determinant of sagittal plane balance. Other investigators have documented an association between the knee- chest position and decreased lumbar lordosis. Methods. Ten asymptomatic volunteers underwent a series of four lateral lumbar radiographs, as follows: standing, prone on the Jackson (Orthopaedic Systems, Inc., Hayword, CA) spinal table, and prone on the Andrews (Orthopaedic Systems, Inc.) table with the hips flexed 60° and 90°, respectively. Intervertebral body angle measurements were obtained from L1 to S1. Lordosis values were compared and analyzed for each of the positions. Standing lordosis was assumed to be physiologic. Results. Physiologic lordosis values were produced only on the Jackson operative table. Both positions on the Andrews table resulted in a statistically significant decrease in lumbar lordosis. Decreasing hip flexion on the Andrews table from 90° to 60° produced a statistically significant increase in lumbar lordosis. However, this change did not reproduce physiologic values. Conclusion. When instrumentation is used to augment lumbar fusions, positions incorporating hip flexion should be avoided to ensure maintenance of sagittal plane balance.