Does Lordotic Angle of Cage Determine Lumbar Lordosis in Lumbar Interbody Fusion?

Abstract

Retrospective, radiological analysis. To determine that 15° lordotic angle cages create higher lumbar lordosis in open transforaminal lumbar interbody fusion (TLIF) than 4° and 8° cages. Restoration of lumbar lordosis is important to obtain good outcome after lumbar fusion surgery. Various shapes and angles of cages in interbody fusion have been used; however, it is not proved that lordotic angle of cages determine lumbar lordosis. Sixty-seven patients were evaluated after TLIF using 15° cages and screw instrumentation. For comparison, TLIF using 4° lordotic angle cages in 65 patients and 8° cages in 49 patients were analyzed. Lumbar lordosis angles, segmental lordosis angles, disc height, and bony union rate were measured on the radiographs. The lumbar lordosis was 31.1° preoperatively, improved to 42.9° postoperatively, and decreased to 36.4° at the last follow-up in the 15° group. It was 35.8° before surgery, corrected to 41.5° after surgery, and changed to 33.6° at the last follow-up in the 4° group. In the 8° group, it was 32.7° preoperatively, improved to 39.1° postoperatively, and decreased to 34.5° at the last follow-up. These changes showed statistical significances (P < 0.001). The segmental lordosis at L4-5 was 6.6° before surgery, 13.1° after surgery, and 9.8° at the last follow-up in the 15° group. It was 6.9°, 9.5°, and 6.2° in the 4° group and 6.7°, 9.8°, and 8.1° in the 8° group, respectively (P < 0.001). The disc height restoration was better in the 15° group than in the 4° and 8° groups (P < 0.001). Bony union rate was not significant among the three groups (P = 0.087). The lordotic angle of the cages determined restoration of lumbar lordosis after TLIF. Cages with sufficient lordotic angle showed better restoration of lumbar lordosis and prevention of loss of correction. 4.