The impact of patient-specific spine rods on spinopelvic parameters after short segment degenerative lumbar fusions

Patient-specific spine rods (PSSRs) are custom-designed pre-operatively to align with individual spinopelvic parameters, aiming to optimize post-operative alignment. While effective in correcting adult spinal deformities, their utility in degenerative lumbar fusions remains relatively understudied. This study seeks to assess the outcomes of PSSR utilization in degenerative lumbar fusions by comparing them to a previously published cohort by Leveque et al. in 2018. Through this analysis, we aim to contribute to the understanding of PSSR efficacy and its potential role in improving surgical outcomes in degenerative lumbar conditions.

Fifty patients who underwent primary lumbar fusion with PSSRs were included, excluding those with prior lumbar fusion or significant deformities. The study cohort was compared to a historical cohort using conventional rods. Radiographic outcomes were evaluated over a 2-year period, with follow-ups at 6 weeks, 6 months, 1 year, and 2 years postoperatively. Pre-operative and post-operative measurements of pelvic incidence (PI) and lumbar lordosis (LL) were used to assess changes in changes in PI-LL alignment. Statistical analyses included one-way analysis of variance (ANOVA) tests and one/two sample t-tests.

Patients undergoing fusion PSSRs demonstrated a greater degree of change in pre-operative to post-operative PI-LL alignment compared to non-PSSR patients (-4.2° vs. -0.1°, P<0.001). Among the PSSR group, post-operative analysis revealed that 37 patients (74%) were categorized as preserved, indicating maintenance of PI-LL alignment within a predefined range. Additionally, nine patients (18%) were classified as restored, representing an improvement in PI-LL alignment post-operatively. Conversely, two patients (4%) were categorized as not corrected and worsened, indicating no significant change or deterioration in PI-LL alignment post-operatively, respectively. Comparison between the PSSR and non-PSSR groups showed higher restored spinopelvic parameters after surgery in the PSSR group compared to the non-PSSR group (18% vs. 8.7%, P=0.05). Conversely, fewer patients in the PSSR group had not corrected parameters compared to the non-PSSR group (4% vs. 21.3%, P<0.01). These findings suggest that fusion with PSSRs was associated with greater improvement in PI-LL alignment post-operatively and a higher likelihood of achieving restored spinopelvic parameters compared to fusion without PSSRs.

PSSRs demonstrate significant improvement in spinopelvic parameters, particularly in reducing PI-LL mismatch, in degenerative lumbar fusion surgery. This improvement suggests a potential for enhanced patient outcomes. Follow-up assessments indicate that these improvements are sustained over a 2-year period. However, our findings underscore the need for further research to validate these results on a larger scale and over the long term. Larger-scale studies are necessary to confirm long-term benefits and should aim to explore the specific mechanisms by which PSSRs contribute to improved outcomes and investigate optimal strategies for incorporating PSSRs into clinical practice.