Surgery for degenerative lumbar spondylolisthesis may entail both decompression and fusion. The knee-chest position facilitates the decompression, but fixation in this position risks fusion in kyphosis. This can be avoided by intra-operative re-positioning to the prone position. The aim of this study was to quantify the restoration of lordosis achieved by intra-operative repositioning and to assess the clinical and radiological outcome.

A total of forty consecutive patients with degenerative lumbar spondylolisthesis and stenosis were treated by posterior decompression and interbody fusion with pedicle screw fixation. The screw insertion, decompression and interbody grafting were performed with the patient in the knee-chest position. The patient was then re-positioned to the fully prone position for fusion. Sagittal plane angles were measured pre-, intra- and post-operatively. Clinical assessment was performed using SF-36 scores and visual analogue scores for back and leg pain.

The sagittal plane angle increased from median 16.0 degrees pre-operatively to 23.1 degrees post-operatively (p<0.01) and this was maintained at the last follow-up (mean 21 months). The SF-36 scores improved for 7 out of 8 domains and the physical score improved from 29% to 40% (p<0.05). The mean pain scores improved significantly from 7.5 to 3.8 for back pain and from 7.6 to 3.7 for leg pain (p<0.001).

Lumbar spondylolisthesis was found to be associated with a reduction of normal lumbar lordosis and the knee-chest position exacerbates this loss of lordosis. Intra-operative repositioning restored lordosis to greater than the pre-operative angle and was associated with a good clinical outcome.

Aims: Surgery for degenerative lumbar spondylolisthesis may entail both decompression and fusion. The knee-chest position facilitates decompression, but fixation in this position risks fusion in kyphosis. This can be avoided by intra-operative re-positioning to the prone position. The aim of our study was to quantify restoration of lordosis achieved by intra-operative repositioning and to assess clinical and radiological outcome.

Patients and method: Thirty-six patients with degenerative lumbar spondylolisthesis and stenosis were treated by posterior decompression and interbody fusion with pedicle screw fixation. The decompression, interbody grafting and screw insertion were performed with the patient in the knee-chest position. The patient was repositioned to the prone position for fusion. Sagittal plane angles were measured pre, intra and post-operatively. Clinical assessment was performed using SF-36 scores and visual analogue scores for back and leg pain.

Results: The median pre-operative sagittal angle between fused spinal segments was 16.0 degrees lordosis. Intra-operatively in the knee-chest position the sagittal angle was median 13.5 degrees and after changing to the prone position increased to median 27.1 degrees. On the initial post-operative lumbar radiographs the sagittal angle was 23.1 and this was maintained at 6 months post-operatively (22.5 degrees). Overall there was a mean increase in lordosis angle after repositioning of 7.1 degrees per operative level (p< 0.01). The SF-36 scores improved for 7 out of 8 domains and the physical score improved from 29% to 40% (p< 0.05). Mean pain scores improved from 7.5 to 3.8 for back pain and from 7.6 to 3.7 for leg pain (p< 0.001).

Conclusion: Lumbar spondylolisthesis was found to be associated with a reduction of normal lumbar lordosis. The knee-chest position exacerbates this loss of lordosis. Intra-operative repositioning restores lordosis to greater than the pre-operative angle and was associated with a good clinical outcome.

Introduction and Aims: Surgery for degenerative lumbar spondylolisthesis may entail both decompression and fusion. The knee-chest position facilitates decompression, but fixation in this position risks fusion in kyphosis. This can be avoided by intra-operative re-positioning to the fully prone position. We aim to quantify restoration of lordosis achieved by this manoeuvre.

Method: Thirty-six patients with degenerative lumbar spondylolisthesis and stenosis were treated by posterior decompression and interbody fusion with pedicle screw fixation (without interbody cages). There were 16 men and 20 women with a mean age of 58.2 years (32–80). The decompression, interbody grafting and screw insertion were performed with the patient in the knee-chest position. The patient was repositioned to the fully prone position for subsequent fusion. The sagittal plane angle was measured on the pre-operative, intra-operative and post-operative x-rays. Short-Form 36 (SF-36) scores and Visual Analogue Scales (VAS) for pain (0 to 10) were determined pre- and post-operatively.

Results: Twenty-eight patients underwent single-level fusion, two patients had two levels, two patients had three levels and four patients had four levels fused. The mean pre-operative sagittal angle between the operated vertebrae was 15.7 degrees lordosis, and the intra-operative angle before re-positioning was 14.9 degrees. The mean immediate post-operative angle was 23.7, and at six-month follow-up the angle was 23.1. Overall there was a mean increase in lordosis angle after repositioning of 8.0 degrees per operative level (p< 0.01). The mean scores of the SF-36 improved in all eight domains and this was significant (p< 0.05) for social functioning (44.4 to 68.9), energy and vitality (36.0 to 49.5), pain (23.8 to 58.3) and general health perception (51.4 to 65.6). Mean VAS pain scores for back pain improved from 7.47 pre-operatively to 3.84 post-operatively (p< 0.001); and for leg pain improved from 7.56 to 3.78 (p< 0.001). No complications attributable to the manoeuvre occurred.

Conclusion: Lumbar spondylolisthesis was found to be associated with reduction of normal lumbar lordosis. The knee-chest position for surgery exacerbates this loss of lordosis. Intra-operative repositioning restores lordosis to greater than the pre-operative angle, which may improve clinical outcome.