LAUSR

PURPOSE To assess preliminary associations between fatty-infiltration (FI) of cervical spine extensor musculature, cervical sagittal balance, and clinical outcomes in cervical deformity (CD) patients. METHODS Operative CD patients (C2-C7 Cobb > 10°, CL > 10°, cSVA > 4 cm, or CBVA > 25°) with pre-operative (BL) MRIs and 1-year (1Y) post-operative MRIs or CTs were assessed for fatty-infiltration of cervical extensor musculature, using dedicated imaging software at each C2-C7 intervertebral level and the apex of deformity (apex). FI was gauged as a ratio of fat-free-muscle-cross-sectional-area (FCSA) over total-muscle-CSA (TCSA), with lower ratio values indicating greater FI. BL-1Y associations between FI, sagittal alignment, and clinical outcomes were assessed using appropriate parametric and non-parametric tests. RESULTS 22 patients were included (Age 59.22, 71.4%F, BMI 29.2, CCI:0.75, Frailty: 0.43). BL deformity presentation: TS-CL: 29.0°, C2-C7 Sagittal Cobb:-1.6°, cSVA:30.4 mm. No correlations were observed between BL fatty-infiltration, sagittal alignment, frailty, or clinical outcomes (p > 0.05). Following surgical correction, C2-C7 (BL: 0.59 vs 1Y:0.67, p = 0.005) and apex (BL: 0.59 vs. 1Y: 0.66, p = 0.33) fatty-infiltration decreased. Achievement of lordotic curvature correlated with C2-C7 fatty infiltration reduction (Rs: 0.495, p < 0.05), and patients with residual postoperative TS-CL and cSVA malalignment were associated with greater apex fatty-infiltration (Rs: -0.565, -0.561; p < 0.05). C2-C7 FI improvement was associated with NRS back pain reduction (Rs: -0.630, p < 0.05), and greater apex fatty-infiltration at BL was associated with minor perioperative complication occurrence (Rs: 0.551, p = 0.014). CONCLUSIONS Deformity correction and sagittal balance appear to influence the reestablishment of cervical muscle tone from C2-C7 and reduction of back pain for severely frail CD patients. This analysis helps to understand cervical extensor musculature's role amongst CD patients.