ABSTRACT
Methods@#From January 1, 2009 to December 31, 2018, 176 patients who were scheduled to undergo lateral mass screw fixation were enrolled. They were randomized into two groups; we inserted lateral mass screws using our new technique for one group and by using the classical Magerl technique for the other group. Intraoperative measurements were used to assess the bone-screw interface length. Postoperative radiography and postoperative computed tomography were performed to assess the trajectory of the screws. @*Results@#Total 88 patients were included in the study group, including 68 men. The control group included 65 men. The most common indication for surgery was cervical spondylotic myelopathy. The average bi-cortical length that was measured intraoperatively was 19.9 mm in the study group and 16.3 mm in the control group. This was significantly different from the average lengths of screws in the control group. @*Conclusions@#The trajectory that involves an entry point as close as possible to the posterior inferior medial angle of the lateral mass cuboid and traverses a distance of about 20 mm to obtain a bi-cortical purchase in the diagonally opposite angle may provide a much better and firmer bony purchase in the lateral mass than conventional points of entry and trajectories.
ABSTRACT
STUDY DESIGN: Prospective cohort study. PURPOSE: To study clinicoradiological parameters of zero-profile cage screw used for anterior cervical discectomy and fusion (ACDF). OVERVIEW OF LITERATURE: Radiological parameters of various implants used for ACDF are available, but those for zero-profile cage are sparse. METHODS: Patients with unilateral intractable brachialgia due to single-level cervical disc prolapse between April 1, 2011 and March 31, 2014 were included. Clinical assessment included arm and neck pain using visual analogue score (VAS) and neck disability index (NDI) scores. Radiological assessment included motion segment height, adjacent disc height (upper and lower), segmental and cervical lordosis, implant subsidence, and pseudoarthrosis. Follow-ups were scheduled at 1, 3, 6, 12, and 24 months. RESULTS: Thirty-four patients (26 males, 8 females) aged 30–50 years (mean, 42.2) showed excellent clinical improvement based on VAS scores (7.4–0 for arm and 2.0–0.6 for neck pains). Postoperative disc height improved by 11.33% (p<0.001), but at 2 years, the score deteriorated by 7.03% (p<0.001). Difference in the adjacent segment disc height at 2 years was 0.08% (p=0.8) in upper and 0.16% (p<0.001) in lower disc spaces. Average segmental lordosis achieved was 5.59° (p<0.001) from a preoperative kyphosis of 0.88°; at 2 years, an average loss of 7.05° (p<0.001) occurred, resulting in an average segmental kyphosis of 1.38°. Cervical lordosis improved from 11.59° to 14.88° (p=0.164), and at 2 years, it progressively improved to 22.59° (p<0.001). Three patients showed bone formation and two mild protrusion of the implant at 2 years without pseudoarthrosis/implant failure. CONCLUSIONS: The zero-profile cage screw device provides good fusion and cervical lordosis but is incapable of maintaining the segmental lordosis achieved up to a 2-year follow-up. We also recommend caution when using it in patients with small vertebrae.