The biomechanical effects of cervical multilevel oblique corpectomy

Study Design. A repeated-measures flexibility test was performed in vitro using human cadaveric spines. Objectives. To compare changes in cervical biomechanics associated with multilevel oblique corpectomy and standard grafted corpectomy with or without plating. Summary of Background Data. Standard multilevel plated and unplated corpectomies are susceptible to instability in vitro. The authors are unaware of any previous research on the biomechanics of multilevel oblique corpectomy. Methods. Six human cadaveric cervical spine specimens (C3 - T1) were tested: 1) normal; 2) after 2-level multilevel oblique corpectomy; 3) after expanding multilevel oblique corpectomy to represent standard grafted and plated corpectomy; and 4) after removing the anterior plate. Pure moments were applied to induce flexion, extension, lateral bending, and axial rotation while recording motion stereophotogrammetrically. Results. Compared to normal, the range of motion after multilevel oblique corpectomy increased 15% during flexion, 18% during extension, 11% during lateral bending, and 18% during axial rotation. These increases were about one-third of the increases observed after standard corpectomy without plating. Multilevel oblique corpectomy caused few alterations in locations of axes of rotation and coupling patterns, whereas standard corpectomy with or without plating significantly altered these parameters in several instances. Conclusions. Multilevel oblique corpectomy ( without graft) induced significantly less instability and altered kinematics less than standard unplated corpectomy with graft. Multilevel oblique corpectomy allowed significantly more motion than standard plated corpectomy with graft. However, the goal of standard corpectomy is fusion. Our results indicate that plating significantly limits spinal mobility after 2-level corpectomy, improving the environment for fusion.