Does It Make a Difference to Stop Fusion at L3 Versus L4 in Terms of Disc and Facet Joint Degeneration: An MRI Study With Minimum 5 Years Follow-up.

OBJECTIVES: To compare the functional outcomes of patients with idiopathic scoliosis who had surgical correction and fusion with all pedicle screw construct down to L3 or L4 and to evaluate whether saving a mobile lumbar motion segment distally would demonstrate any difference in terms of disc degeneration (DD) and facet joint degeneration (FJD) after minimum 5 years follow-up.

SUMMARY OF BACKGROUND DATA: Selection of lowest instrumented vertebra (LIV) is often difficult when lumbar curve was included into the fusion (L3 vs L4). Saving L4 is believed to be beneficial for preserving motion and preventing degeneration of unfused lumbar spine.

METHODS: The L3 group included 21 patients (mean age of 21.4) and L4 group included 16 patients (mean age 22.9). Control group included 30 healthy individuals with no spinal deformities (mean age of 23.8). Follow-up lumbar magnetic resonance images (MRIs) were evaluated for each patient in terms of DD and FJD. Clinical evaluation was done by using the Scoliosis Research Society-22r, Oswestry Disability Index, and Numeric Rating Scale.

RESULTS: Mean follow-up period was 7.4 (5-10) years in the L3 group and 9 (5-17) years in L4 group. Average correction rates for lumbar curve magnitudes were 78% in the L3 group and 79% in the L4 group, with no significant correction loss at the final follow-up. There was no statistical difference for DD in all groups (p > .05). FJD was significantly greater in both L3 and L4 groups compared to the control group (p < .001). Clinical outcome scores were similar among all three groups (p > .05).

CONCLUSION: Spinal balance and corrections remained stable, without showing any decompensation over time. This midterm MRI study demonstrated similar disc and facet degeneration rates for L3 and L4 groups. FJD at the upper two levels adjacent to the LIV was significant for both surgically treated groups. Clinical outcome scores were similar for all groups at minimum 5 years follow-up.