Evaluating fixation techniques to prevent subsidence in cervical corpectomy models using low and high-density polyurethane blocks

Abstract

Subsidence is a common complication, especially in multisegment corpectomies. In addition to the characteristics of the cage, fixation method is also an effective means of preventing subsidence. We compared three different fixation methods used after the cage placement: Anterior fixation (AF), posterior fixation (PF), and circumferential fixation (CF). Low-density (LDB) and high-density (HDB) polyurethane blocks were used to mimic osteoporotic and normal bone, respectively. Five models within the groups loaded flexion-extension testing, and maximum compressive loads (MCL), bending moment and stiffness were determined in static tests. Subsequently, the specimens were subjected to dynamic fatigue tests then the amount of subsidence was calculated. The MCL and stiffness differences between AF, PF, and CF in the LDB were statistically significant, decreasing CF, PF, AF, respectively. In the HDB group, the difference in MCL between AF, PF, and CF was significant, decreasing from CF to PF to AF, respectively. The differences between the stiffness of these models were statistically significant, from high to low CF, PF, AF. The subsidence of AF, PF and CF in the LDB were 2.3 ± 1.59 mm, 7.5 ± 1.58 mm, and 0.65 ± 0.10 mm, respectively. In this group, CF is more successful in preventing subsidence than AF and PF. Subsidence of less than 1 mm was observed in all models in the HDB. This study suggests that AF is as effective as other methods in preventing subsidence following two-level corpectomy in patients with high bone quality. In those with low bone quality, CF could provide more stable fixation and may be more reliable in preventing subsidence and potential instrumentation failure.