Improvement in the results of the simple-foot-tapping test and cross-sectional area of the dural sac in patients with C5 palsy after posterior cervical spine surgery

Introduction The smaller cross-sectional areas of the dural sacs in patients without C5 palsy after posterior cervical spine surgery may lead to less neurological improvement. Objectives The aim of this retrospective study was to clarify the differences in the cross-sectional area of the dural sac in the cervical spine and neurological improvement in patients with and without C5 palsy after posterior cervical spinal surgery. Methods We retrospectively evaluated the postoperative cross-sectional areas of the dural sacs and neurological outcomes in patients with and without C5 palsy after posterior cervical spine surgery. We compared the postoperative cross-sectional areas of the dural sac at C4/5 and C5/6 on magnetic resonance images between the C5 palsy group ( n = 19) and the no-C5 palsy group ( n = 84) after posterior cervical spinal surgery 1 year postoperatively. Performance tests, namely, the 10-s grip-and-release test and the 10-s single-foot-tapping (FT) test, were compared between the two groups. Results Postoperative cross-sectional areas of the dural sac at C4/5 and C5/6 (233.3 mm 2 and 226.6 mm 2 , respectively) in the C5 palsy group were significantly larger ( P = 0.0036 and P = 0.0039, respectively) than those (195.0 mm 2 and 193.8 mm 2 , respectively) in the no-C5 palsy group. Postoperative gain in the grip-and-release test was similar between the two groups. Postoperative gain in the FT test (4.9 times) in the C5 palsy group was significantly larger ( P = 0.0060) than that (1.8 times) in the no-C5 palsy group . Conclusions In the C5 palsy group 1 year after posterior cervical spine surgery, the cross-sectional areas of the dural sac were larger, and the 10-s single FT test improved noticeably.