Sagittal Deformity Correction During The Minimally Invasive Lateral Transpsoas Approach With Hyperlordotic Interbody Grafting And Adjunctive All Release

Presented at SMISS Annual Forum 2014
By Blake Staub MD
With Meng Huang MD, Darrell Hanson MD, Paul Holman MD,

Disclosures: Blake Staub MD None Meng Huang MD None, Darrell Hanson MD B; Dupuy Synthes, Nuvasive. F; Depuy Synthes, Paul Holman MD B; Biomet Spine, Medtronic Spine Navigation. F; Biomet Spine, Medtronic Spine,

Introduction:
Traditionally, surgical intervention for patients with thoracolumbar sagittal imbalance relied on posterior column shortening techniques such as the Smith Peterson Osteotomy (SPO) and pedicle subtraction osteotomy (PSO). The lateral retroperitoneal, transpsoas approach has been proven to afford significant coronal deformity correction; however, the evidence for its use in sagittal deformity correction is less robust. Recently, the use of hyperlordotic grafts has provided all the benefits of the transpsoas approach while also allowing for sagittal deformity correction.

Aims/Objectives:
To determine if a hybrid approach, combining anterior column reconstruction via hyperlordotic cage placement and a subsequent SPO can provide similar sagittal correction to a PSO. The null hypothesis is that despite being less invasive, this hybrid approach does not provide the same segmental sagittal correction afforded by a PSO alone.

Methods:
This is a retrospective review examining the preoperative and postoperative segmental lordosis after placement of a hyperlordotic cage and subsequent SPO. Twenty patient charts were reviewed. The mean patient age was 61.4. There were seven males and 13 females. A 20 degree hyperlordotic cage was utilized in four patients. The 30 degree cage was used in sixteen cases. The surgical procedure involved the release of the anterior longitudinal ligament and placement of a hyperlordotic graft (NuVasive CoRoent XL-Hyperlordotic) via the lateral, retroperitoneal, transpsoas approach followed by posterior instrumentation and SPO at that level.

Results:
Hyperlordotic cages were placed from T12-L1 to L4-L5 in this series. Ten cages were placed at the L3-L4 interspace. The mean preoperative lordosis was 6.17 and 6.0 degrees in the 20 and 30 degree cohorts, respectively. The mean postoperative, segmental lordosis was 22.9 and 27.4 degrees in the two groups, yielding a mean correction of 18.3 degrees with the 20 degree cage and 21.4 degrees with the 30 degree cage. The 30 degree cage yielded a sagittal correction of 8.5-41.1 degrees. A correction of greater than 30 degrees was achieved in 4 cases. The single case with less than 10 degrees of lordosis restoration resulted from graft subsidence. The greatest increase in lordosis occurred in patients with the most significant pre-operative segmental kyphosis.

Conclusions:
Segmental lordosis increases of approximately twenty degrees can be expected with the placement of either a 20 or 30 degree hyperlordotic cage via the transpsoas approach with subsequent SPO at that level. This hybrid approach provides a degree of correction similar to a PSO without the associated morbidity.