Optimal area of lateral mass mini-screws implanted in plated cervical laminoplasty: a radiography anatomy study.
Lateral mass mini-screws used in plated cervical laminoplasty might penetrate into facet joints. The objective is to observe this complication incidence and to identify the optimal areas for 5- and 7-mm-long mini-screws to implant on lateral mass.



47 patients who underwent plated cervical laminoplasty were included. The optimal area for mini-screws implanting was set according to pre-operative 3D CT reconstruction data. Then, each posterior-lateral mass surface was divided into three regions: 7-mm region, 5-mm region, and dangerous area. The mini-screw implanted region was recorded. Post-operative CT images were used to identify whether the mini-screws penetrated into facet joints.



235 mini-plates and 470 lateral mass mini-screws were used in the study. 117 (24.9%) mini-screws penetrated 88 (37.4%) facet joints. The 5-mm-long mini-screw optimal area occupied the upper 72, 65, 65, 64, and 65 % area of the posterior-lateral mass surface for C3-7, while the 7-mm-long mini-screw optimal area encompassed the upper 54, 39, 40, 33, and 32 %. Only 7-mm-long mini-screws were used to fix the plate to the lateral mass. 4 of 240 mini-screws in 7-mm region, 67 of the 179 mini-screws in 5-mm region, and 46 of the 51 mini-screws in dangerous region penetrated into the facet joint. The differences in the rate of facet joint penetration related to region were statistically significant (P < 0.001).



The facet joint destruction by mini-screws was not a rare complication in plated cervical laminoplasty. The optimal areas we proposed may help guide the mini-screw implantation positions.
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Hua
H
Chen
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Huibo
H
Li
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Yuxiao
Y
Deng
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Xin
X
Rong
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Quan
Q
Gong
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Tao
T
Li
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China.
Yueming
Y
Song
Department of Orthopedics, West China Hospital, Sichuan University, 37# Guoxue Lane, Chengdu Sichuan, 610041, China. liuhao6304@163.com.
Hao
H
Liu
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D005260:Female; D006801:Humans; D065406:Laminoplasty / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed
3D CT; Facet joint destruction; Lateral mass mini-screws; Optimal area; Plated cervical laminoplasty
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