Long‑Term Results of PEEK and Titanium Rods in Adult Isthmic Spondylolisthesis

Aim: The research evaluated long-term clinical and radiological results between polyetheretherketone (PEEK) and titanium rod fixation in adult isthmic spondylolisthesis to establish the best implant material choice. Methods: The study included 91 patients (48 PEEK and 43 titanium) who received posterior instrumented fusion surgery for L5-S1 isthmic spondylolisthesis between January 2019-2024. The clinical evaluation included Oswestry Disability Index (ODI), Japanese Orthopaedic Association (JOA) scores, Visual Analog Scale (VAS) pain assessments, and SF-36 quality of life measurements at preoperative, 1, 6, and 12-month follow-up points. The radiological assessment included measurements of lumbar lordosis together with CT-based fusion rate evaluation and MRI-based assessment of adjacent segment degeneration. Patient satisfaction was assessed using a 5-point Likert scale. Results: The PEEK group achieved more substantial clinical improvements during the 12-month assessment through better ODI scores (30.1±7.8 vs 33.2±8.4, p=0.022), JOA scores (16.9±1.8 vs 16.5±2.0, p=0.039) and VAS scores (4.0±1.0 vs 4.4±1.1, p=0.026). The fusion success rates between PEEK and titanium groups showed no significant difference (PEEK: 91.7%, titanium: 90.7%, p=0.867) and the PEEK group demonstrated lower adjacent-segment degeneration (4.2% vs 9.3%) although this difference was not statistically significant (p=0.315). The PEEK group achieved better SF-36 quality of life scores than the titanium group with results at 80±10 compared to 75±12 (p=0.018). The patient satisfaction levels between groups showed no significant difference (89.6% vs 86.0%, p=0.588). The PEEK group demonstrated superior percentage improvements from baseline through ODI (37.6% vs 30.7%, p=0.027), VAS reduction (43.7% vs 37.1%, p=0.022), and JOA enhancement (23.4% vs 18.7%, p=0.035). Conclusions: PEEK rod fixation delivers better clinical results and improved quality of life scores than titanium rods when treating adult isthmic spondylolisthesis patients. The two implant materials showed no significant differences in fusion rates or patient satisfaction or adjacent-segment degeneration. The biomechanical advantages of PEEK lead to better load distribution which results in superior functional recovery.