337 - Osteogenesis in the Lamina of the Axis after Dome-like Cervical Lamino...

#337 Osteogenesis in the Lamina of the Axis after Dome-like Cervical Laminoplasty

Cervical Therapies and Outcomes

Poster Presented by: J. Yang

Author(s):

J.J. Yang (1)
D.-H. Lee (2)
H.S. Lee (2)
H. Noh (2)
G. Barza (2)
C. Hwang (2)

(1) Dongguk University Ilsan Hospital, Orthopedic Surgery, Ilsan, Korea, Republic of
(2) Asan Medical Center, University of Ulsan, Orthopedic Surgery, Seoul, Korea, Republic of

Abstract

Introduction: Postoperative osteogenesis in C2 lamina after dome-like cervical laminoplasty is often observed during follow-up. However, there have been no reports that evaluated the characteristics of the osteogenesis. The purpose of this study was to investigate the radiographic features and clinical significance of the osteogenesis after dome-like cervical laminoplasty.

Methods: Twenty two patients with follow-up of 1 to 6 years were retrospectively assessed. For radiographic evaluation on the degree and location of the osteogenesis, canal distance (Fig1-1), anterior (Fig1-2) or inferior base length of the dome (Fig1-3), and anterior base length of the lamina (Fig1-4) were measured. Laminectomy length and spinal cord expansion were also measured using computed tomography (CT) and magnetic resonance imaging (MRI), respectively. Osteogenesis was defined as postoperative bone growth more than 2mm at various areas of the dome measured on lateral radiographs. For investigation on the clinical correlation, neurologic recovery rates calculated from Japanese Orthopedic Association scores at last follow-up compared to preoperative values and neck disability index (NDI) scores were evaluated.

Results: The laminectomy length was 6mm (43.5% of lamina length) on average. Spinal canal expansion at C2 level in immediate postoperative period and last follow-up were 2.2mm and 1.1mm on average, respectively. The spinal cord expansion measured at C2 level in postoperative 1 year using MRI was 1.5mm on average. Postoperative osteogenesis of the axis was shown in 16 patients (72.7%, group 1). Average age at surgery in group 1 and the remaining 6 patients (group 2) was 65 years and 64.5 years, respectively. According to the location of osteogenesis at the dome, group 1 was classified into subgroups including canal extension (9.1%, 2/22 patients) (Fig2-1), anterior lamina extension (13.6%, 3/22 patients) (Fig2-2), posterior lamina extension (22.7%, 5/22 patients) (Fig2-3), and dome apex (59.1%, 13/22 patients) (Fig2-4). The dome apex subgroup was the most common and the bone growth from the apex was limited inside the dome without canal extension in all cases. The canal extension subgroup may be the most clinically significant. However, this subgroup was relatively rare and all cases demonstrated postoperative spinal canal expansion in C2 level at last follow-up compared with the preoperative canal distance. Interlaminar bony fuion at C2-3 was observed in 5 patients in group 1 (22.7%). The occurrence of osteogenesis had no significant correlation with sex, age, diagnosis, operative procedure, degree of laminectomy, and cervical sagittal ROM (p>0.2 in all variables). The average percentage of recovery in group 1 and 2 were 59.8% and 51.4%, respectively. There were no significant differences in the average percentage of recovery and NDI scores at preoperative and final follow-up between the 2 groups (p=0.741, 0.951, 0.853, respectively).

Conclusions: Postoperative osteogenesis in the axis after dome-like laminoplasty occurred in 72.7% of patients. However, the osteogenesis might not influence the effectiveness of the procedure because of the common location of osteogenesis and well maintained postoperative spinal canal expansion. In addition, neurologic recovery and functional status of the patients was not significantly affected by the osteogenesis.

Figure 1

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