The relationship between laminoplasty opening angle and increased sagittal canal diameter and the prediction of spinal canal expansion following double-door cervical laminoplasty

Abstract

Purpose To clarify the relationship between laminoplasty opening angle (LOA) and the increase in sagittal canal diameter (SCD) in double-door cervical laminoplasty (DDCL) and to predict the increase in SCD using the resulting formula. Methods We analyzed 20 patients with multilevel cervical spondylotic myelopathy who underwent DDCL between September 2010 and January 2013. The pre-and post-operative parameters of the cervical spinal canal were measured by computed tomography. We deduced a formula describing the relationship between LOA and the increase in SCD and used it to predict the increase in SCD of these patients as LOA increased. Results When the C3-C7 LOA was 25°-45°, the magnitude of the increase in SCD was notable (increases of 3.08-5.6 mm compared with the pre-operative SCD). When the C3-C7 LOA was more than 45°, the magnitude of the increase in SCD was relatively smaller; the increase in C3-C7 SCD with a 55°LOA was merely 0.4 mm more than with a 45°LOA. When LOA was 30°at C3-C6 or 40°a t C7, the increase in SCD was more than 4 mm. When the C3-C6 LOA was 40°, SCD increased by more than 5 mm. ConclusionsThe formula accurately showed the relationship between LOA and the increase in SCD in DDCL. Based on the LOA, increases in SCD following C3-C7 laminoplasty can be accurately predicted using this formula. This enables DDCL based on accurate individual LOAs, which prevents inadequate or excessive opening.

Comparison of Spinal Canal Expansion Following Cervical Laminoplasty Based on the Preoperative Lamina Angle : A Simulation Study

“…Furthermore, they did not perform an analysis of SCA changes according to preoperative LA, which can affect SCA expansion in laminoplasty. The same group reported using a similar program in DDL and concluded that it was feasible for predicting SCA expansion 7) . They suggested that SCA expansion was proportional to the preoperative LA and OS but did not provide data regarding the differences between ODL and DDL according to preoperative LA.…”

“…However, in our clinical data, DDL resulted in more SCA expansion at every level, indicating that SCA expansion does not merely depend on the type of laminoplasty and that it instead depends on the length of the spacer, the OA, and the location of the hinge and lateral gutter ( Table 2). Few studies have been performed to predict SCA expansion using simulation modeling or computerized programs 6,7,19) . Wang et al 19) used a computer-simulated comparison to predict spinal canal expansion following cervical laminoplasty.…”

The Dural Tube Continues to Expand after Muscle-Preserving Cervical Laminectomy

“…Expansion of the dural tube after cervical laminoplasty has been previously reported [1][2][3][4] . Post-laminectomy membrane was found to deteriorate during neurological recovery after a conventional laminectomy and therefore, was a reason for the invention of laminoplasty 1,5) .…”