Do position and size matter? An analysis of cage and placement variables for optimum lordosis in PLIF reconstruction

Abstract

Purpose To examine monosegmental lordosis after posterior lumbar interbody fusion (PLIF) surgery and relate lordosis to cage size, shape, and placement. Methods Eighty-three consecutive patients underwent single-level PLIF with paired identical lordotic cages involving a wide decompression and bilateral facetectomies. Cage parameters relating to size (height, lordosis, and length) and placement (expressed as a ratio relative to the length of the inferior vertebral endplate) were recorded. Centre point ratio (CPR) was the distance to the centre of both cages and indicated mean position of both cages. Posterior gap ratio (PGR) was the distance to the most posterior cage and indicated position and cage length indirectly. Relationships between lordosis and cage parameters were explored. Results Mean lordosis increased by 5.98°(SD 6.86°). The cages used varied in length from 20 to 27 mm, in lordosis from 10°to 18°, and in anterior cage height from 10 to 17 mm. The mean cage placement as determined by CPR was 0.54 and by PGR was 0.16. The significant correlations were: both CPR and PGR with lordosis gain at surgery (r = 0.597 and 0.537, respectively, p \ 0.001 both), cage lordosis with the final lordosis (r = 0.234, p \ 0.05), and anterior cage height was negatively correlated with a change in lordosis (r = -0.297, p \ 0.01).Conclusion Cage size, shape, and position, in addition to surgical technique, determine lordosis during PLIF surgery. Anterior placement with sufficient ''clear space'' behind the cages is recommended. In addition, cages should be of moderate height and length, so that they act as an effective pivot for lordosis.

Does interbody cage lordosis impact actual segmental lordosis achieved in minimally invasive lumbar spine fusion?

“…Our analysis also found that an anteriorly positioned cage was associated with a larger gain in SL, findings corroborated by previous investigations. 12,34 Landham et al quantified bilateral PLIF cage position using a "centre point ratio" (CPR), which represented the ratio of the distance between the posterior vertebral wall and the center of the cage to the length of the inferior endplate. 12 The investigators reported a strong correlation between the CPR and lordosis gain (r = 0.537, p < 0.001), but no association with the cage lordotic angle (p > 0.05).…”

“…7,11 The combined impact of the surgical approach, cage position, and built-in cage lordotic angle on the amount of postoperative SL achieved remains unclear. 12,13 The purpose of this study was to determine if the built-in lordotic angle of an interbody cage impacted the actual change in SL achieved with MIS lumbar interbody fusion (LIF) techniques. To our knowledge, our investigation is the largest series of MIS procedures examining the impact of cage lordotic angle on postoperative SL.…”

Impact of lordotic cages in the restoration of spinopelvic parameters after dorsal lumbar interbody fusion: a retrospective case control study

“…In addition, the positioning of the cage seems to play an important role in the restoration of segmental lordosis. Anterior positioning of the cages in PLIF and TLIF techniques with short cages results in greater post-operative segmental lordosis [ 22 , 23 ].…”

Die ventrale Abstützung bei dorsalen lumbalen Fusionsoperationen

“…nachweisen, dass eine Cage-Implantation die Steifigkeit des Konstrukts signifikant erhöht [ 7 ]. Weiter entlastet der Cage die eingebrachten Schrauben, was einer Schraubenlockerung entgegenwirkt und die LL verbessern kann [ 2 , 5 , 6 ].…”