Sacral and pelvic osteotomies for correction of spinal deformities

Introduction

Restoring a physiological sagittal spine balance is one of the main goals in spine surgery. Several technics have been described previously, as pedicle subtraction osteotomy. In more complicated cases involving spino-pelvic disorders, three authors proposed sacral osteotomy to restore sagittal balance of the spine. The authors describe the use of pelvic osteotomies for the correction of lumbo-sacral kyphosis, for decreasing pelvic incidence and for achieving sagittal balance correction in cases of lumbo-sacral sagittal deformity as an alternative of pedicle subtraction osteotomies (PSO).

Materials and methods

We simulate four types of pelvic osteotomies previously described for hip pathology (Salter, modified Salter, Chiari and posterior sacral osteotomy) on drawing software, and calculate during these osteotomies the variation of pelvic incidence (PI). Then, we compare the behaviour in this simulation to a cadaveric model where we perform the same four pelvic osteotomies. Via X-rays made the study, we calculate also the PI. Then, we analyse 11 patients who underwent pelvic osteotomies for sagittal unbalance, analysing operative and clinical data.

Results

We find a mathematical law governing the PI during anterior opening and posterior closing osteotomies (respectively Salter and sacral osteotomy):

$$ {text{PI end}} = {text{PI initial}} {-} a times {text{osteotomy angle}}.$$

These laws are confirmed in the cadaveric model which retrieves the same behaviour. In the clinical series, Salter osteotomy is easy and efficient on sagittal rebalancing; sacral osteotomy is more powerful.

Discussion

The Salter osteotomy is efficient for restoring sagittal balance of the spine. The posterior sacral osteotomy is more powerful but technically demanding. The indications of such special osteotomies are fixed lumbo-sacral kyphosis, especially high-grade spondylolisthesis, previously operated or not.

Conclusion

A study of a more substantial series would be considered.