Radiographic and clinical outcomes in one- and two-level transforaminal lumbar interbody fusions: a comparison of bullet versus banana cages

Abstract

OBJECTIVE The aim of this study was to determine whether cage morphology influences clinical and radiographic outcomes following short-segment transforaminal lumbar interbody fusion (TLIF) procedures. METHODS The authors retrospectively reviewed one- and two-level TLIFs at a single tertiary care center between August 2012 and November 2019 with a minimum 1-year radiographic and clinical follow-up. Two cohorts were compared based on interbody cage morphology: steerable “banana” cage or straight “bullet” cage. Patient-reported outcome measures (PROMs), radiographs, and complications were analyzed. RESULTS A total of 135 patients with 177 interbody levels were identified; 45 patients had 52 straight cages and 90 patients had 125 steerable cages. Segmental lordosis increased with steerable cages, while it decreased with straight cages (+3.8 ± 4.6 vs −1.9 ± 4.3, p < 0.001). Conversely, the mean segmental lordosis of adjacent lumbar levels decreased in the former group, while it increased in the latter group (−0.52 ± 1.9 vs +0.52 ± 2.1, p = 0.004). This reciprocal relationship results in global sagittal parameters, including pelvic incidence minus lumbar lordosis and lumbar distribution index, which did not change after surgery with either cage morphology. Multivariate analysis confirmed that steerable cage morphology, anterior cage positioning, and less preoperative index-level segmental lordosis were associated with greater improvement in index-level segmental lordosis. PROMs were improved after surgery with both cage types, and the degree of improvement did not differ between cohorts (p > 0.05). Perioperative and radiographic complications were similar between cohorts (p > 0.05). Overall reoperation rates, as well as reoperation rates for adjacent-segment disease within 2 years of surgery, were not significantly different between cohorts. CONCLUSIONS Steerable cages are more likely to lie within the anterior disc space, thus increasing index-level segmental lordosis, which is accompanied by a reciprocal change in segmental alignment at the adjacent lumbar levels. The converse relationship occurs for straight cages, with a kyphotic change at the index levels and reciprocal lordosis occurring at adjacent levels.

Sagittal Alignment in the Degenerative Lumbar Spine

“…Multiple studies have shown that surgeons and implants vary in their ability to achieve lordosis at an individual segmental level utilizing TLIF 44,80,81 . Successful restoration (or retention) of segmental lordosis can be challenging via TLIF, but may be achieved with the aid of dedicated spinal tables, anteriorly placed TLIF cages, posterior column osteotomies, and compression posteriorly before the final tightening of the set screws 82,83 . Therefore, after the ideal segmental lordosis and the overall lumbar shape and apex have been chosen, choosing the proper surgical technique and implant may optimize achievement of alignment goals for the individual lumbar segments 84 .…”

Comparing Outcomes of Banana-Shaped and Straight Cages in Transforaminal Lumbar Interbody Fusion for Lumbar Degenerative Diseases: A Systematic Review and Meta-Analysis

“…TLIF involves the placement of interbody cages within the intervertebral space, which facilitates fusion, restores vertebral height, and decompresses neural structures [ 4 , 5 ]. The choice of cage type, whether banana-shaped or straight bullet cages, has garnered considerable interest in recent years due to its potential impact on clinical and radiological outcomes [ 6 , 7 ].…”