Background:

Dwyer and Zietke anterior instruments are wide!y used in spine deformities. Derotatİon of the scolioiic spine is possible wüh the special device of the Zielke instrument However, new rigid systems don't need speciai devices in derotation maneuver. Retrolisthesİs of the Iower instrumented vertebra seem to occur as a consequence of rîgid anterior instrument rotation.

Aİm:

We retrospectiveiy evaiuated the effect of derotation, especiaüy reirolisthesis of the İower instrumented vertebra, ofth'e Anterior Aha Spinal instruments İn the sagittai piane of iumbar spine.

Materials and Methods:

There were 16 (13 femaies, 3 males) patients who un deme nt anterior İnstrumentation with Alıcı Spinal System. Average age was 14.6 years wİth a range of 10 to 29. Eleven curves were right thoracİc and lef t İumbar, two lef t iumbar, two rlght iumbar, and one lef t thoracolumbar. Upper instrumented vertebra was T12 İn two cases and L1 in 14 cases; and lower instrumented vertebra was L4 İn 8 cases, and L5 İn 8 cases. W e İdentifİed 12 cases who underwent posterior instrumentation which the lower instrumented vertebra was L4 or L5. The average age of the coniroi group was 14.1 years and there were 10 femaies and 2 males. Rod derotation maneuver was done in aü posterior instrumentation group. We have measured vertebrai corpus width on sagittai X-rays and noted any iisthesis or retrolİsthesis. Mann-Whitney Rank Sum and Wilcoxon Signed Rank Tesis were used İn statistical analysis.

Results:

We found 5 retrolisthesises of upper İnstrumented vertebra ranging from 1 to 3 mm (2.9% to S.4 (Average: 1.7%) and 16 retrolisthesises of iower instrumented vertebra ranging from 1 to 5 mm, average: 3.1; median: 3.5 mm (2.3% to 19.1% (Average: 9.8%) of the anterior instrumentation group. Where as, on the control group 5 out of 12 cases $howed retrolİsthesis of the lower İnstrumented vertebra ranging from 1 to 5 mm average: 1.1; [median: 0.5 mm (3.4% to 13.2% (Average 3.5%) (p - 0.001)].

Conciusion:

Our data, though limited, shows that the derotation of a rigid anterior system creates a retrolİsthesis of the lower instrumented vertebra. This effect seem to be İncreasedif the principles of Zielke system İs followed

Keywords: Retrolİsthesis, anterior instrumentation, spine, rod derotation.