Abstract
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 the 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. Hyperlordotic interbody grafts and a subsequent SPO can theoretically provide a similar sagittal correction as provided by a PSO or multiple SPOs while minimizing the associated morbidities.
Materials and Methods
This is a retrospective review examining the preoperative and postoperative segmental lordosis after placement of a hyperlordotic cage and subsequent SPO. A total of 22 patient charts were reviewed. The mean patient age was 58.6. There were 8 males and 14 females. A 20-degree hyperlordotic cage was utilized at four intervertebral levels. The 30-degree cage was used at 19 levels. 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. In each instance, the hyperlordotic graft and subsequent SPO were part of a large, multilevel deformity correction and were not simply performed as a standalone procedure.
Results
Hyperlordotic cages were placed from T12–L1 to L4–L5 in this series. A total of 10 cages were placed at the L3–L4 interspace. The mean preoperative lordosis was 0.4 and 4.2 degrees in the 20 and 30-degree cohorts, respectively. The mean postoperative, segmental lordosis was 23.0 and 28.2 degrees in the two groups, yielding a mean correction of 22.6 degrees with the 20-degree cage and 24.0 degrees with the 30-degree cage. The 30-degree cage yielded a sagittal correction of 8.5 to 54.0 degrees. A correction of greater than 30 degrees was achieved in five 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 preoperative segmental kyphosis.
Conclusion
Segmental lordosis increase of approximately 20 to 25 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.