Radiographic spinal profile changes induced by cage design after posterior lumbar interbody fusion preliminary report of a study with wedged implants.

STUDY

DESIGN

A prospective comparative radiographic study between two geometrically varying implants utilized in single-level posterior lumbar interbody fusion (PLIF) was performed.

OBJECTIVE

The aim of this study was to determine the influence of 4 degrees wedged cages on postoperative lateral lumbar spinal profile.

SUMMARY OF BACKGROUND DATA: The biomechanical and clinical importance of realigning the sagittal lumbar profile in surgical management of spinal instabilities is known. Wedged cages are therefore increasingly attaining popularity in PLIF. As yet the significance of wedged implants on postoperative sagittal spinal profile has not been assessed.

METHODS

Forty patients were randomly assigned to two equal-sized groups. In one group rectangular cages and in the second group cages with a wedged design and an inclination of 4 degrees were implanted. Quantitative assessment of the lumbar spinal profile on standing neutral lateral radiographs was performed before surgery as well as 6 weeks and 12 months after surgery. Results were statistically compared.

RESULTS

A significant improvement of lumbar sagittal profile after use of 4 degrees wedged compared with nonwedged cages was not found. The greatest effect on lumbar profile and segmental lordosis was observed in fusion of segment L4-L5 with 4 degrees wedged cages.

CONCLUSIONS

These results show that normal sagittal alignment after single-level lumbar fusion can be achieved with rectangular and 4 degrees wedged cages. Although results after utilization of 4 degrees wedged cages do not significantly differ, these implants offer the surgeon one more sizing variation with which physiologic lumbar lordosis may be attained. The biomechanical implications of wedged implants on the rigidity of a fused segment remain to be analyzed.