The Measurement And Clinical Significance Of Slotting Angle In Double Door Laminoplasty Involving Axis

Objective:To study the changing tendency and the difference of slotting angle for variouscervical-spine segment and investigate clinical significance by measuring LSA (laminarslope angle) of each segment of C2-7and deducing the slotting angle in double doorlaminoplasty.Method:Totally100cases of cervical-spine CT scanning (50cases of male and50cases offemale) aged from27to79with an average age of47.35were randomly selectedfrom of XX hospital outpatient. The thickest laminar of each segment of C2-7wasselected from CT axial image. A point from both lateral and medial cortex was selectedrespectively that located at the junction of superior border of laminar and spinous process,and the two points were connected for selecting the midpoint of the connecting line. Also, amidpoint was selected from the junction of inferior border of laminar and zygopophysis. Theconnecting line by threading the two midpoints was the parallel line of laminar which formsan angle with median sagittal line, that is LSA (laminar slope angle). A line threading theslotting point is formed which is perpendicular to parallel line of laminar and forms an anglewith median sagittal line, that is slotting angle in double door laminoplasty which issupplementary angle with LSA (laminar slope angle).LSA (laminar slope angle) of eachsegment on C2-7is measured at three dimensional CT work station to deduce the slottingangle. The angle is accurate to0.01°and a further statistical analysis was made upon themeasured data.Result:The average slotting angle for each segment on C2-7were42.27°、37.44°、37.20°、38.53°、38.40°and40.16°(C2>C7>C5>C6>C3>C4) respectively. The difference between C2and C3-7shows the statistical significance which also goes with the difference between C7and C3-6.（P <0.05）, while the comparison between any two groups in C3-6wasmeaningless from the perspective of statistical significance.（P>0.05）It shows that theaverage slotting angle for male is larger than female by grouping in gender, which has thestatistical significance as well.Conclusion: 1. The slotting angle should be larger than that of C3-7when need to reduce thepressure of C2segment in double door laminoplasty.2. The slotting angle for C7segmentshould be larger than that for C3-6segment in double door laminoplasty.3. The slottingangle for male should be larger than female for the same segment of C2-7.4. For the case ofdouble door laminoplasty involving C2, the slotting angle for reducing pressure segmentshould be measured through CT scanning and a personalized operation plan should be madebefore operation to reduce the risk of operation.