Laminoplasty Achieves Improved Outcomes Despite Leading to a More Positive Sagittal Balance: Neither Preoperative Nor Postoperative Sagittal Balance Correlated With Spine-specific Outcome Data

Abstract

Study design: A retrospective study of prospective data.

Objective: Determine the correlation between cervical sagittal alignment, either preoperative or postoperative, and the outcomes of laminoplasty.

Summary of background data: Cervical laminoplasty is a common surgical treatment for myelopathy. However, the effect of preoperative or postoperative cervical sagittal alignment on outcomes, such as neurological improvement and patient-reported outcomes, remains unclear.

Methods: A total of 144 consecutive patients (2007-2017) with laminoplasty for myelopathy and a minimum of 1-year postoperative follow-up were reviewed. The severity of myelopathy was assessed by modified Japanese Orthopedic Association (mJOA) scores. Total pain was measured by the visual analog scale. Patient-reported outcome included neck disability index (NDI) and 12-item short-form survey (SF-12). Radiographic measures of cervical sagittal alignment on x-ray images consisted of C2-C7 angle, T1 slope, C2-C7 sagittal vertical axis (SVA), and C2-C7 forward pitch (FP). Patients were also divided into 2 groups based on the postoperative C2-C7 SVA (≥40 or <40 mm) for outcome comparison.

Results: Laminoplasty yielded improvement in functionality as evidenced by significantly increased mJOA scores, decreased total pain scores, and improved NDI scores at final follow-up. There was a change in sagittal balance postoperatively with significantly increased C2-C7 SVA and FP (7-8 mm increase). However, there was no correlation between preoperative sagittal alignment and outcomes. There was also no correlation between postoperative sagittal alignment and most outcomes, except for a significantly negative correlation between FP and short form-physical component summary (Spearman r=-0.328, P=0.011). When those with postoperative C2-C7 SVA ≥40 mm (n=60) were compared with those with <40 mm (n=84), there was no significant difference in outcomes.

Conclusions: Cervical laminoplasty yields significant neurological and functional improvement despite a more positive sagittal balance postoperatively, with increased C2-C7 SVA and FP. However, other than a lower short form-physical component summary score, neither preoperative nor postoperative sagittal alignment measures correlated with spine-specific outcomes.

Level of evidence: Level II-a retrospective cohort study.