Posterior Column Osteotomies in Adolescent Idiopathic Scoliosis

Abstract

The posterior column osteotomy (PCO) is an adjunct technique for obtaining deformity correction during posterior spine fusion procedures. Full disarticulation of the posterior spinal column, including bony elements (namely the lamina and facet joints) and ligamentous complex is described as a PCO. This technique was originally described to allow for shortening of the posterior column during correction of excessive thoracic kyphosis; however, its indications have since been expanded to other spine deformities such as adolescent idiopathic scoliosis (AIS). Its expanded role in deformity surgery has been met with controversy: proponents tout increased flexibility and better spinal correction in three planes, while detractors cite lack of ostensible clinical benefit and potential for more complications. Differences in surgical technique are also prevalent. In this manuscript, we review the surgical technique of PCOs, including the traditional PCO as well as a modified posterior column release (PCR). Additionally, the controversy over when this technique should be utilized is further explored through summation of current literature on PCO outcomes. Key Concepts•The indications for posterior column osteotomies in pediatric spine deformity surgery are frequently debated, with the risk-benefit profile weighed differently among surgeons.•Proponents of PCO use in scoliosis assert improved flexibility and correction of spinal deformity in three dimensions, in particular the ability to better restore thoracic kyphosis.•Most studies acknowledge that there is an increased risk of a neuromonitoring alert when PCOs are performed, though a significant difference in postoperative deficits has not been described.•The traditional Posterior Column Osteotomy PCO (i.e., "Ponte" osteotomy) is performed by creating a gap in the posterior elements which can be closed down with deformity correction (namely kyphosis).•The modified Posterior Column Osteotomy (or Posterior Column Release [PCR]) can be performed by disarticulating the posterior tension band but leaving a smaller gap, perhaps limiting the ability for posterior compression but limiting spinal canal exposure.

Figure 1

Medial and Lateral columns of the posterior spine can be resected at varying timepoints.

Figure 2

Sawbones representation of common level preparation for PCO. A) Every interspace in the operative field should have inferior facetectomies performed. B) Appearance following inferior facetectomy. C) Interspaces where PCOs will be performed will need spinous process and inferior lamina resection (colored in black), resulting in D) exposure of the superior articular facets (colored black) and ligamentum flavum (tan rectangle) for eventual resection and completion of PCO.

Figure 3

Surgical representation of common level preparation for PCO. A) Posterior spine following inferior facetectomies. B) Flexibility testing and deformity assessment to determine where PCOs may be beneficial. C) Removal of spinous process and inferior lamina at levels selected for PCO. D) Exposure of ligamentum flavum and superior articular facets following preparation steps.

Figure 4

Method for Traditional Posterior Column Osteotomy (PCO). After thinning the ligamentum flavum (LF) with rongeur, A) a Woodson elevator is used to palpate and dissect LF free from the epidural contents. B) Kerrison rongeur resects ligamentum flavum and C) superior articular facet bilaterally in a “V” shape. D) Completed PCO shows full disarticulation of the posterior spinal elements with symmetric gap for closure.

Figure 5

Method for Modified Posterior Column Release. A) Superior articular facets are cut with UBS prior to instrumentation. Following screw placement, the ligamentum flavum is resected starting with B) central resection with rongeur. C) Palpation/dissection with a Woodson elevator is performed prior to D) resection of ligamentum flavum with rongeur.

Figure 6

Placement of structural graft “strips.”