Lordosis Restoration After Smith-Petersen Osteotomies and Interbody Strut Placement

A Radiographic Study in Cadavers

Abstract

Study Design. 

Six human lumbar cadaveric specimens evaluated after sequential steps in restoration of lumbar lordosis.

Objective. 

To determine the effect of Smith-Petersen osteotomies (SPO) with concurrent interbody strut placement on lordosis in the lumbar spine.

Summary of Background Data. 

The importance of restoration of lumbar lordosis is well recognized. SPO have been suggested to yield roughly 10° of lordosis per level, whereas pedicle subtraction osteotomies have been shown to result in over 30° of lordosis restoration. Though the pedicle subtraction osteotomy can achieve greater degrees of lordosis, there is considerable surgical morbidity associated. We hypothesize that SPO with an interbody strut placed within the disc space will result significantly greater lordosis than SPO alone.

Methods. 

Lateral radiographs of 6 human lumbar specimens were obtained after 3 interventions as follows: (1) lumbar spine without osteotomy in maximal extension, (2) after SPO at L2, L3, and L4 and held in maximal extension with pedicle screw fixation, and (3) after SPO at L2, L3, and L4 with interbody cage placement in L2–L3, L3–L4, and L4–L5 held in maximal extension with pedicle screw fixation.

Results. 

The mean lordosis in the intact specimens was 7.03° (standard deviation [SD], 2.21°). The mean lordosis after SPO was 11.05° (SD, 1.05°). The mean lordosis after SPO and interbody strut placement was 15.72° (SD, 3.19°). The difference in lordosis in the osteotomized specimens with and without interbody strut was significantly (P < 0.01).

Conclusion. 

The addition of an interbody strut to a lumbar level after SPO may result in as much as 15° of lumbar lordosis, significantly greater than that of SPO alone.

In Brief

The importance of lordosis restoration in the lumbar spine is well recognized. Numerous spinal osteotomies have been described with varying rates of lordosis restoration and surgical morbidity. In a cadaveric model, we present the effect of Smith-Petersen osteotomies and interbody strut placement on the restoration of lordosis.