Relationship of actual laminoplasty opening size and increment of the cross-sectional area based on single-door cervical laminoplasy.

Background: Amounts of clinic research have been performed to investigate the increment of cross-sectional area in single-door cervical laminoplasty (SDCL). However, no one has taken the effects of surgery drill into consideration. Methods: A mathematical model was built to investigate the relation of actual laminoplasty opening size (LOS), the transverse canal diameter (TCD), and the increment of cross-sectional area in SDCL). The model was based on geometric analysis on deformation of spinal canal; the relation was derived and characterized as: s(Delta BAB') = b/2 x 2 root a(2) - b(2)/4 = c-d/2 (n) over tilde 2 root a(2) - (c-d)(2)/4, where a is the TCD, b the actual LOS, c the size of mini-plate, and d is diameter of the surgery drill bit. In the equation, the related variables would be measured to estimate the increment of cross-sectional area before the surgery. In the current research, 25 patients authorized to use their CT scans of C3 similar to C7 as the subject samples. Results: The effects of surgery SDCL were very significant; for each patient, the cross-sectional area was enlarged dramatically after the surgery (P < .01). On the contrary, the difference between the cross-sectional area obtained by the equation and that measured by software was statistically negligible (P > .05), which confirmed the reliability of the modeling equation. Conclusions: Before the SDCL, increment of the cross-sectional area can be estimated by the above-mentioned modeling equation with a high-level reliability. This method ensures the optimum selection of mini-plate before operation for each patient.