• C B Tribus, T A Belanger, and T A Zdeblick.
• Department of Surgery, University of Wisconsin, Madison, USA.
• Spine. 1999 Jan 1;24(1):58-61.

Study DesignA retrospective radiographic assessment of the maintenance of sagittal alignment in patients undergoing short-segment instrumented fusions in a knee-chest position.ObjectiveTo determine whether the use of the knee-chest position adversely effects the maintenance of lumbar sagittal alignment in patients undergoing short-segment instrumented fusions of the lumbar spine.Summary Of Background DataPrevious authors have demonstrated that lumbar lordosis is reduced in the knee-chest position, but it is unknown whether the kneeling position adversely affects the maintenance of lumbar lordosis in short-segment instrumented fusions during the follow-up period.MethodsTwenty-eight patients (17 men and 11 women, 20-72 years of age) were reviewed retrospectively, having undergone short-segment fusions in the kneeling position. Seven patients underwent posterior spinal fusion from L4 to L5, 13 patients from L5 to S1, and 8 patients from L4 to S1. Transpedicular instrumentation and autogenous iliac crest bone grafting was used in all cases. Radiographs were assessed for sacral tilt, lumbar lordosis, and intervertebral angulation. Data were analyzed with repeated measures analysis of variance.ResultsThe minimum follow-up period was 33 months. For all 28 patients, lumbar lordosis measured 51 degrees before surgery, 37 degrees during surgery (P = 0.0001), and 50 degrees after surgery (P = 0.6135). In patients undergoing L4-S1 posterior spinal fusion, sacral tilt measured 49 degrees before surgery and 45 degrees after surgery (P = 0.039). Although overall lumbar lordosis was maintained, lordosis was shifted proximally in the lumbar spine, increasing at L1-L4 from 19 degrees before surgery to 24 degrees after surgery, while decreasing at L4-S1 from 32 degrees before surgery to 26 degrees after surgery.ConclusionOverall lumbar lordosis is well maintained in patients undergoing short-segment instrumented fusion in the kneeling position. With compensatory lordosis being shifted proximally and sacral tilt not returning to the preoperative status in L4 to S1 fusions, caution should be exercised in using the kneeling position for longer instrumented lumbar fusions.

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