Radiographic markers in spondyloptosis: implications for spondylolisthesis progression.

STUDY DESIGN

Radiographic analysis of spinopelvic morphology and posterior element dysplasia in spondyloptosis.

SUMMARY OF BACKGROUND DATA

Spondylolisthesis treatment protocols are based on age, symptomatology, and slippage degree. Spinopelvic morphology and dysplasia can determine progression. Frequency of two denominators of high-grade spondylolisthesis-degree of dysplasia and spinopelvic morphology-is unknown.

OBJECTIVES

To determine common radiographic denominators of spondyloptosis-degree of posterior bony hook dysplasia and spinopelvic morphology-as prognostic factors for spondylolisthesis progression.

METHODS

Patients with spondyloptosis were reviewed. Bony dysplasia at lumbosacral junction was graded. Pelvic incidence and sacral kyphosis were measured.

RESULTS

A total of 53 patients had a mean sacral kyphosis of 56 degrees and pelvic incidence of 76 degrees; 62% of patients had posterior element dysplasia.

CONCLUSION

Prognostic factors for spondylolisthesis progression, such as percent of slippage, do not identify lower-grade slips at risk for progression. Progression is linked to increased shear stress across the lumbosacral junction and inability to resist it. Increased stress is related to increased verticality of the lumbosacral joint, which is individually predetermined by pelvic incidence and sacral anatomy. Pelvic incidence is fundamental in determining sagittal spine curvature required for economic spinopelvic balance. Pelvic incidence is independent of adaptive changes in higher-grade spondylolisthesis. Pelvic incidence in our spondyloptosis series (76 degrees) is higher than in normal (48.2-53.2 degrees ) and low-grade spondylolisthesis (64.5 degrees). Posterior element dysplasia decreases mechanical resistance to lumbosacral shear stress. Incidence of dysplasia in our series (62%) is higher than that reported in low-grade spondylolisthesis. Analysis of pelvic incidence and posterior element dysplasia may aid in estimation of risk for progression of spondylolisthesis.