Figure 5: Stress analysis of the connecting rods in the ELIF and TLIF finite-element models under right lateral flexion. (a) ELIF + UPS. (b) TLIF + UPS. (c) ELIF + UPS + TLFS. (d) TLIF + BPS. The maximum stress concentration point on the connecting rod was the junction between the screw and its head in the ELIF and TLIF models. The stress on the proximal end was greater than that on the distal end. The stresses on the connecting rod under all operating conditions were greater in the case of unilateral pedicle screw fixation than in the case of bilateral pedicle screw fixation. Furthermore, the stress on the connecting rod was smaller in the ELIF + UPS group than in the TLIF + UPS group, especially under right lateral flexion. With additional contralateral translaminar facet screw fixation, the stress on the connecting rod was decreased as compared with simple unilateral pedicle screw fixation.