Changes in Alignment at Untreated Vertebral Levels Following Short- Segment Fusion Using Personalized Interbody Cages: Leveraging Personalized Medicine to Reduce the Risk of Reoperation

Introduction: An abnormal postoperative lordosis distribution index (LDI), which quantifies the ratio
between lordosis at L4-S1 and lordosis at L1-S, contributes to the development of
adjacent segment disease (ASD) and increased revision rates in patients undergoing
short-segment lumbar intervertebral fusions. Incorporating preoperative spinopelvic
parameters and LDI into the surgical plan for short-segment fusion is important for
guiding alignment restoration or preserving normal preoperative alignment. The authors
aimed to study the findings in LDI, segmental lordosis, and lordosis of unfused levels in
patients treated with personalized interbody implants (PIC).

Methods: This retrospective study evaluated radiographic measurements from 111 consecutively
treated patients diagnosed with degenerative spinal conditions and treated with a short-
segment fusion of L4-L5, L5-S1, or L4-S1 using personalized interbody implant(s) within
six months of the fusion procedure. Comparisons of intervertebral lordosis for treated
and untreated levels as well as LDI pre- and postoperatively were performed.

Results: In patients with a preoperative hypolordotic distribution (LDI<50%) statistically
significant increases were found in LDI postoperatively, approaching the normal range
(LDI 50-80%). Likewise, patients with hyperlordotic distribution preoperatively
(LDI>80%) experienced a decrease in LDI postoperatively, trending toward the normal
range, although the changes were not statistically significant. Intervertebral lordosis for
the L5-S1 level increased significantly following placement of a PIC in the normal and
hypolordotic LDI groups. Changes in intervertebral lordosis for L5-S1 were not
significant for patients with preoperative hyperlordotic LDI. Reciprocal changes in
intervertebral lordosis at L1-L4 were not observed in any groups.

Conclusion : Focusing on LDI and global lumbar lordosis is important during the planning process for
short-segment lumbar fusion. Personalized interbody cages have the potential to further
improve patient outcomes by helping surgeons achieve patient-specific lordosis goals,
which may help to reduce the risk of ASD and revisions in patients undergoing short-
segment lumbar intervertebral fusions.