Relationship Between T1 Slope And Cervical Sagittal Alignments For Cervical Spondylotic Myelopathy After Open Door Laminoplasty

Study Design: Prospective StudyObjectives:To investigate the relationship between T1 slope and cervical sagittal alignment for cervical spondylotic myelopathy after open door laminoplasty with plates(Group A)and without plates(Group B)and also is to compare the significant relationship between T1 S and cervical sagittal alignments in Group A & Group B.Background summary:Cervical spondylotic myelopathy(CSM)is the loss of neurologic function causing by spinal canal narrowing due to degeneration of cervical spine.Open-door laminoplasty(ODL)is the standard surgical option for patients with multilevel cervical spondylotic myelopathy.T1 slope is significant landmark factor that should be considered before ODL.T1 S has been reported the significant use of T1 S in analyzing sagittal balance and found it to play a significant role in entire sagittal alignments.Materials & Methods:The data of 56 consecutive patients who underwent open door laminoplasty with plates(as Group A)and data of 56 patients who underwent ODL without plates(as Group B)due to cervical spondylotic myelopathy have been analyzed prospectively in Orthopedic department section 2 of First affiliated hospital of Zhengzhou University from January 2017 to January 2019.The number of male and female patients in Group A is 36 & 20 and in Group B is 32 & 24 respectively.The age of the patients in Group A and Group B is ranging from 37 to 79(average age 58.5)years and 35 to 77(average age 56)years respectively.Radiographic parameters of both groups included T1 slope(T1S),C2-C7 cobb angle,C2-C7 sagittal vertical axis(SVA),Neck disability index(NDI),Cervical Lordosis(CL),T1 Slope Minus Cervical Lordosis(TIS-CL),C2 slope and C7 slope were analyzed.These preoperative and postoperative values of those radiographic parameters of both groups have been measured.Meanwhile,Japanese Orthopedic Association(JOA)score and Visual Analogue scale(VAS-Neck)score were analyzed.Thesemeasurements of both groups were analyzed by using SPSS statistical data analysis software including linear regression modelling,scatter plot analysis,bar graphs analysis,Pearson Correlation Coefficient,mean value,standard deviation etc.The relationship especially between T1 S & CL,T1S-CL & SVA,SVA & NDI Score,T1 S & C2-C7 cobb angle and T1S-CL & C2-C7 Cobb angle were analyzed.Results:In Group A,Preoperative C2-C7 Cobb angle(28.70 ± 6.77;P < 0.05),postoperative C2-C7 Cobb(23.7 ± 3.96°;P < 0.05).Preoperative cobb angle is higher than postoperative Cobb angle.Preoperative C2-C7 angle had a strong positive relationship with preoperative T1S(r= 0.624,P = 0.000)and postoperative C2-C7 angle also showed the strongest positive correlation with preoperative T1S(r = 0.904,P < 0.05).The preoperative mean T1 slope,cervical lordosis and NDI were 25.5,12.15 & 22.94 respectively.The preoperative mean C2–C7 SVA & T1S-CL were 27.4 mm & 13.34 respectively.A significant Pearson correlation was found between the preop.T1 S & T1S-CL(r=0.66),T1 S & C7 slope(0.44),C2-C7 Cobb & T1S-CL(r=0.401)and postop.NDI C2-C7 SVA(r=0.643).Preoperative & postoperative JOA Score and VAS-Neck pain score were 6.46±3.73 & 4.52± 3.22 and 3.90 ±2.6 & 3.70±2.40 respectively.In Group B,Preoperative C2-C7 Cobb angle(28.40± 6.27;P< 0.05),postoperative C2-C7 Cobb(19.53± 3.73°;P < 0.05).Preoperative cobb angle is much more higher than postoperative Cobb angle.Preoperative C2-C7 angle had a strong positive relationship with preoperative T1S(r= 0.424,P = 0.002)and postoperative C2-C7 Cobb angle also showed the strongest positive correlation with preoperative T1S(r = 0.425,P < 0.05).The preoperative mean T1 slope,cervical lordosis and NDI were 23.50,10.06 & 21.94 respectively.The preoperative mean C2–C7 SVA & T1S-CL were 26.41 mm & 13.44 respectively.A significant Pearson correlation was found between the preop.T1 S & T1S-CL(r=0.46),T1 S & C7 slope(0.34),C2-C7 Cobb & T1S-CL(r=0.201)and postop.NDI C2-C7 SVA(r=0.117).Preoperative & postoperative JOA Score and VAS-Neck pain score were 4.52±3.52 & 4.42± 3.00 and 3.96± 2.68 & 3.50 ±2.10 respectively.The results for patients underwent open door laminoplasty with plates(Group A)show more significant relationship between T1 slope and cervical sagittal alignments than the patients underwent open door laminoplasty without plates(Group B).Even Group A patients show more stability of cervical spine and long lasting results than Group B patients.Moreover Group A patients after surgery have more prominent and satisfactory outcomes than Group B patients.Conclusion:T1 slope is significantly correlated with cervical sagittal alignments in both groups;T1S of Group A showed more correlation than T1 S of Group B.T1 S was a reliable parameter which could be used to evaluate postoperative sagittal alignment of the cervical spine after ODL for CSM patients.Preoperative and postoperative cobb angle has more positive correlation with T1 S in Group A than Group B.My current study showed that increasing neck disability has more positive correlation with cervical sagittal mal-alignment following ODL with plates than ODL without plates and a greater T1S-CL mismatch was associated with a greater change of cervical mal-alignment.Comparatively,the patients in Group A has more preoperative T1 S which showed high lordotic alignments and had also demonstrated that patients with higher T1 S than Group B that may require more cervical lordosis(CL)and requires high energy expenditure to maintain cervical sagittal balance.After open door laminoplasty for CSM in each group,patients with increasing T1 slope tended to exhibit a greater change of cervical lordosis.It is demonstrated that sagittal alignments were negotiated after ODL.The results for patients underwent open door laminoplasty with plates(Group A)show more significant relationship between T1 slope and cervical sagittal alignments than the patients underwent open door laminoplasty without plates(Group B).Even Group A patients show more stability of cervical spine and long lasting results than Group B patients.Moreover Group A patients after surgery has more prominent and satisfactory outcomes than Group B patients.