The effect of depression on bone fusion in a rabbit posterolateral bone fusion model

Objective: The objective of this study was to evaluate the effect of depression on bone fusion in the rabbit spine using Katz’s unpredictable chronic mild stress (UCMS) model. Methods: A total of 12 male New Zealand rabbits were divided randomly into 6 control and 6 experimental groups. Each rabbit underwent the same surgical procedure. An autograft was harvested from the iliac crest and put into the L5-L6 space, where the laminae and facets were decorticated. The animals of the control group were followed up for 8 weeks under standard laboratory conditions. The ones in the experimental group were put in Katz’s UCMS. After 8 weeks, all rabbits were sacrificed, and the vertebra segments were evaluated with manual palpation and X-rays. Results: On manual palpation, fusion was detected in 83.34% in the control group compared to just 33.32% in the UCMS group. The model showed that depression had a significant negative effect on fusion on manual palpation (p = 0.045). Second, if no fusion was detected on X-rays, 0 points were given; callus formation received 1 point, and sclerosis received 2 points. In the control group, just 16.66% showed non-union, 49.98% had a callus formation, 16.66% showed sclerosis. In the experimental group, the non-fusion rate was 66.68%. Conclusions: Depression has a negative effect on the fusion of rabbit vertebrae. However, vertebrae that are evaluated as “fused” on palpation do not show meaningful relation in their radiologic scores. We believe that our model can work as a basis for further experimental trials.