Risk factors for kyphosis progression following posterior surgery in patients with degenerative cervical kyphosis and stenosis.

OBJECTIVE: To explore the preoperative and intraoperative factors associated with the progression of cervical kyphosis following posterior decompressive surgery in patients with degenerative cervical kyphosis and stenosis. METHODS: This retrospective study reviewed patients diagnosed with multilevel cervical spinal stenosis and degenerative cervical kyphosis who underwent posterior approach surgery. Clinical outcomes were assessed using the modified Japanese Orthopedic Association (mJOA) score, Visual Analog Scale (VAS) for neck pain, Neck Disability Index (NDI), and Short Form 36 (SF36) health survey. Radiographic parameters, including C2-C7 lordosis, cervical range of motion (flexion and extension), T1 slope, and T1S-CL, were measured preoperatively and at follow-up using cervical standing X-rays. based on whether kyphosis progressed after surgery, patients were divided into 2 groups. RESULTS: A total of 102 patients (mean age 56.8 years; 75 men, 27 women) met the inclusion criteria. Forty-two patients (41.2%) experienced postoperative cervical kyphosis progression, while 60 patients (58.8%) maintained cervical alignment. There were no significant differences between the two groups in demographic characteristics, including age, sex, body mass index, smoking, drinking habits, or ASA class. Surgical characteristics, such as operative duration and fusion rates, also showed no significant differences. Both groups showed significant neurological function improvements as indicated by mJOA scores, with a comparable degree of improvement observed across the groups. Preoperative C2-C7 lordosis was similar between the groups (kyphosis progression: -4.2 ± 8.3°, alignment maintenance: -4.7 ± 6.0°). At follow-up, the kyphosis progression group had a significant decrease in C2-C7 lordosis to -10.4 ± 11.4°, while the alignment maintenance group showed a significant increase to 2.0 ± 6.2°. The kyphosis progression group also had significant increases in C2-C7 SVA (p = 0.031) and decreases in T1 slope (p = 0.048) compared to the alignment maintenance group. Preoperative extension range of motion (Ext ROM) was significantly lower in the kyphosis progression group (14.4 ± 9.3° vs. 22.2 ± 8.9°, p < 0.01). Multivariate logistic regression identified preoperative Ext ROM as a significant risk factor for postoperative kyphosis progression (odds ratio: 1.074, p = 0.010), with a cutoff value of 16° yielding a sensitivity of 85.0% and specificity of 61.9%. CONCLUSION: Patients with non-severe degenerative cervical kyphosis and stenosis experienced favorable short-term neurological improvements following posterior surgery. A preoperative cervical spine Ext ROM < 16° was identified as a potential predictor for kyphosis progression. Careful consideration is advised for patients with this risk factor, although short-term symptom deterioration was not observed.