Purpose <p>To evaluate the impact of frailty, as measured by the 5-item modified frailty index (mFI-5), on short- and long-term postoperative outcomes in patients undergoing cervical posterior laminoplasty for ossification of the posterior longitudinal ligament (OPLL).</p> Study design <p>A retrospective cohort study.</p> Methods <p>198 patients who underwent cervical posterior laminoplasty were divided into three groups based on mFI-5 scores: Group A (0 point), Group B (1 point), and Group C (2 or more points). Preoperative and postoperative mJOA, NDI, and VAS scores were assessed at short-term follow-ups (1 and 6 months) and long-term follow-ups (12 and 24 months). The incidence of complications, including superficial surgical site infections (SSI) and deep vein thrombosis (DVT), was recorded. Statistical analyses included ANOVA and Spearman correlation to evaluate the association between mFI-5 scores and clinical outcomes.</p> Results <p>In the short-term (1 and 6 months), there were no significant differences in mJOA, NDI, and VAS scores among the three groups. However, in the long-term (12 and 24 months), Group C (mFI-5 ≥ 2) exhibited significantly worse mJOA and NDI scores compared to Groups A and B. Additionally, Group C had a higher incidence of complications, such as superficial SSI and DVT.</p> Conclusions <p>Frailty, as measured by mFI-5, is a significant predictor of long-term postoperative outcomes in patients undergoing cervical posterior laminoplasty for OPLL. Patients with higher mFI-5 scores experienced poorer long-term functional recovery and a higher incidence of complications. These findings emphasize the importance of assessing frailty in preoperative risk stratification and surgical planning.</p>