Effect of modified lateral mass screws implantation strategy on axial symptoms in cervical expansive open-door laminoplasty

Abstract

To investigate the effect of modified lateral mass screws implantation strategy on axial symptoms in cervical expansive open-door laminoplasty. A clinical data of 166 patients, who underwent cervical expansive open-door laminoplasty between August 2011 and July 2016 and met the selection criteria, was retrospective analyzed. Among them, 81 patients were admitted before August 2014 using the traditional mini-plate placement and lateral mass screws implantation strategy (control group), and 85 patients were admitted after August 2014 using modified lateral mass screws implantation strategy (modified group). There was no significant difference in the gender composition, age, clinical diagnosis, disease duration, diseased segment, and preoperative Japanese Orthopaedic Association (JOA) score, pain visual analogue scale (VAS) score, Neck Disability Index (NDI), cervical curvature and range of motion, spinal canal diameter and cross-sectional areas, and Pavlov's value between the two groups ( P>0.05). The operation time, intraoperative blood loss, the number of facet joints penetrated by lateral mass screws, effectiveness evaluation indexes (JOA score and improvement rate, VAS score, NDI), imaging evaluation indexes (cervical curvature and range of motion, spinal canal diameter and cross-sectional areas, Pavlov's value, and lamina open angle), and complications were recorded and compared between the two groups. The modified group had shorter operation time and lower intraoperative blood loss than the control group ( P<0.05). There were 121 (29.9%, 121/405) and 10 (2.4%, 10/417) facet joints penetrated by lateral mass screws in control and modified groups, respectively; and the difference in incidence was significant ( χ 2=115.797, P=0.000). Eighteen patients in control group had 3 or more facet joints penetrated while no patients in modified group suffered 3 or more facet joint penetrated. The difference between the two groups was significant ( P=0.000). All patients were followed up, the follow-up time was (28.7±4.9) months in modified group and (42.4±10.7) months in control group, showing significant difference ( t=10.718, P=0.000). The JOA score, VAS score, and NDI at last follow-up of the two groups were significantly improved compared with preoperative ( P<0.05); there was no significant difference in JOA score and improvement rate and VAS score between the two groups ( P>0.05), but the NDI was significantly lower in modified group than in control group ( P<0.05). There were significant differences in cervical curvature and range of motion, spinal canal diameter, Pavlov's value, and cross-sectional areas at last follow-up when compared with those before operation in both groups ( P<0.05). There was no significant difference in the above indicators and lamina open angle between the two groups ( P>0.05). The modified group has a relative lower axial symptom rate (23/85, 27.1%) than the control group (27/81, 33.3%), but the difference was not significant ( Z=-1.446, P=0.148). There was no significant differences between the two groups in the incidences of C 5 nerve root palsy, cerebrospinal fluid leakage, wound infection, and lung or urinary tract infection ( P>0.05). In the cervical expansive open-door laminoplasty, the modified lateral mass screws implantation strategy can effectively reduce the risk of lateral mass screw penetrated to the cervical facet joints, and thus has a positive significance in avoiding the axial symptoms caused by facet joint destruction.