P0849 - Quantitative Sensory Changes Following Posterior Spinal Fusion in Adolescent Idiopathic Scoliosis

Purpose: Hypoesthesia (numbness) typically develops after posterior spinal fusion (PSF) to treat Adolescent Idiopathic Scoliosis (AIS). Anecdotally, patients frequently experience hypoesthesia along the incision and anterior rib cage (chest wall). However, such post-surgical sensory changes are not well described quantitatively in this population. This study aims to evaluate the presence, intensity, and duration of mechanical hypoesthesia in AIS patients postoperatively.

Methods: A prospective cohort of AIS patients, 10-21 years old, was followed. Quantitative Sensory Testing (QST) included touch detection threshold (MDT) and pain detection threshold (MPT) tests, using VonFrey monofilaments and pin-prick stimulators. QST was performed on the thenar eminence, incision, left, and right chest walls. The incision site was tested at T6 lateral to the incision on the curve’s concave side. The chest wall sites were measured at the nipple line at T6. QST was collected at baseline, 3-days, 1- and 6- month postoperative. Hypoesthesia was defined as an increase in threshold relative to baseline. Statistical analysis of demographic, clinical and QST threshold was performed using descriptive methods and Mixed Effects Modeling with Dunnett post-hoc as appropriate.

Results: 34 patients (21% male, mean age 14.9 years old) with a mean curve of 58.2° completed all postoperative testing. At 3-days and 1-month, numbness at the incision was reported for both MDT (33%; 21%) and MPT (59%; 71%) but resolved at 6-months [MDT (4%); MPT (35%)]. Sensory threshold changed at the incision site over the course of follow-up (F2.2, 58.8 =0.7; p<0.0001). MDT was significantly higher at 3-days and 1-month (p<0.0001) but not at 6-months (p=0.1) compared to baseline. MPT was significantly higher at 3-days (p<0.0001), 1-month (p<0.001) and 6-months (p<0.05). At 6-months, MDT values returned to baseline levels in the majority of patients at all test locations. Persistent MPT-associated hypoesthesia was observed at the incision (56%), and chest wall (35%). Sensory thresholds over the left and right chest wall were not statistically significant at any point when compared to baseline (Dunnett, p>0.05). However, 35% of patients reported chest wall changes.

Conclusion: PSF is associated with hypoesthesia that is detectable within days, persists at 1-month, and largely resolves at 6-months postoperative. No significant changes occurred at the chest wall, although some patients reported transient changes. Although we suspect that these sensory changes are transient and will not affect long-term outcomes, this study can help with patient education. Setting expectations for postoperative sensory changes in the chest wall and incision will help us better set postoperative expectations for patients undergoing posterior spinal fusion.