Associations between C2 slope, C7 slope and sagittal alignment, clinical outcomes in patients with degenerative cervical focal kyphosis

English Keywords:Cervical degenerative disease  Cervical focal kyphosis  Cervical sagittal alignment  C2 slope  C7 slope

English Abstract:

  【Abstract】 Objectives: To analyze the associations between C2 slope, C7 slope and sagittal alignment, clinical outcomes in patients with degenerative cervical focal kyphosis patients. Methods: A retrospective study was conducted among patients underwent anterior cervical decompression and fusion for cervical degenerative disease between January 2015 and March 2020 in our hospital. The angle of cervical kyphosis was set as a positive value and the angle of lordosis as a negative value. Degenerative cervical focal kyphosis group was defined as cervical focal kyphosis angle >4°. After 1∶1 propensity score matching, cervical lordosis group was determined, based on the age, sex, distribution of the levels treated, number of segments fused and type of instrument. A total of 146 patients were involved. There were 73 patients with degenerative cervical focal kyphosis, including 42 S-type and 31 R-type patients, and 73 patients with cervical lordosis. C2 slope, C7 slope, C2-C7 curve, cervical focal angle of fused levels, and C2-C7 sagittal vertical axis(SVA) were measured, visual analogue scale(VAS), neck disability index (NDI), Japanese Orthopaedic Association(JOA) score were obtained before surgery and at 1-year visit after discharge. Pearson correlation analyses were performed between C2 slope, C7 slope and C2-C7 curve, cervical focal angle of fused levels, C2-C7 SVA, VAS, NDI, JOA score before surgery and at 1-year visit after discharge. Results: Positive correlation was found between preoperative C2 slope and preoperative NDI in patients with degenerative cervical kyphosis(r=0.433, P<0.001), so was there at postoperative 1-year visit(r=0.334, P=0.004). Positive correlation was found between preoperative C7 slope and preoperative 1-year visit C2-C7 SVA in patients with degenerative cervical focal kyphosis(r=0.595, P<0.001). Negative correlation was found between preoperative C7 slope and postoperative 1-year visit focal angle of fused levels in patients with degenerative cervical focal kyphosis(r=-0.617, P<0.001). There was no correlation between preoperative C2 slope and preoperative NDI in patients with cervical lordosis(P>0.05). There was no correlation between preoperative C7 slope and postoperative 1-year visit focal angle of fused levels in patients with cervical lordosis(P>0.05). There was no correlation between preoperative or postoperative 1-year visit C2 slope or C7 slope and VAS or JOA scores(P>0.05). Conclusions: In patients with degenerative cervical focal kyphosis, preoperative and postoperative C2 slope correlates with worse clinical outcomes postoperative C7 slope correlates with larger postoperative cervical global lordosis and focal lordosis of fused levels. Such correlations could not be found in patients with cervical lordosis.