Tomographic Analysis of Personalized Interbody Cages: One-Year Follow-up

Introduction: Implant-related complications and malalignment are two factors contributing to poor outcomes and revisions following adult spinal deformity surgery. Predictive analytics are used in preoperative planning to produce personalized interbody cages (PIC) to better achieve planned alignment and decrease implant-related complications. We assess tomographic findings of patients treated with PIC in the lumbar spine with one-year follow-up.

Methods: 15 patients who received lumbar spine fusion using PIC and underwent one-year follow-up CT’s. An analysis of PIC levels (24) was performed related to fusion, implant-to-endplate contact, subsidence, and achieved alignment vs. goal.

Results: Of the 15 patients, mean age was 68.2 years (SD=7.1); mean number of fused levels was 10.4 (SD=3.0); and mean number of PIC/patient was 1.6 (SD=0.6). Two patients received a hybrid construct with one PIC and one stock ALIF cage. The mix between personalized ALIF and TLIF was 22 (84.7%) and 4 (15.3%). Fusion was observed in 100% of the levels treated with PIC (Grade I of Bridwell classification). One stock implant did not present remodeling/ trabeculae bone (Grade II). There were no rod fractures. The implant-to-endplate analysis showed 93.8% average contact between the PIC and endplate. Moderate subsidence, defined as 25% - 50% of implant height, was observed in only one PIC level (4.16%). The alignment analysis of PIC levels, with mean (SD) offset between goal and achieved, showed: intervertebral lordosis=1.3° (3.8°), intervertebral coronal angle=0.7° (1.5°), posterior disc hheight=-2.1mm (2.0mm), and achieved L1/S1 lordosis within 3.1° (10°) of goal. L4-S1 angle achieved was 38.1° (5.0), with mean of -0.9° (5.8°) from goal.

Conclusion : One-year follow-up CT analysis of personalized interbody cages provides a unique opportunity to assess implant-to-endplate contact, which may contribute to improved interbody fusion rates, less subsidence, more predictable alignment, and potentially decrease the risk of implant-related complications.