Yang Seung Heon, Kim Chi Heon, Lee Chang Hyun, Ko Young San, Won Youngil, Chung Chun Kee
Department of Neurosurgery, Seoul National University Hospital, Seoul, Korea.
Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.
J Korean Neurosurg Soc. 2021 Jul;64(4):575-584. doi: 10.3340/jkns.2021.0024. Epub 2021 Jun 29.
Cervical expansive laminoplasty is an effective surgical method to address multilevel cervical spinal stenosis. During surgery, the spinous processes of C2 and C7 are usually preserved to keep the insertion points of the cervical musculature and nuchal ligament intact. In this regard, dome-like laminectomy (undercutting of C7 lamina) instead of laminoplasty is performed on C7 in selected cases. However, resection of the lamina can weaken the C7 lamina, and stress fractures may occur, but this complication has not been characterized in the literature. The objective of the present study was to investigate the incidence and risk factors for C7 laminar fracture after C7 dome-like laminectomy and its impact on clinical and radiological outcomes.
Patients who underwent cervical open-door laminoplasty combined with C7 dome-like laminectomy (n=123) were classified according to the presence of C7 laminar fracture. Clinical parameters (neck/arm pain score and neck disability index) and radiologic parameters (C2-7 angle, C2-7 sagittal vertical axis, and C7-T1 angle) were compared between the groups preoperatively and at postoperatively at 3, 6, 12, and 24 months. Risk factors for complications were evaluated, and a formula estimating C7 fracture risk was suggested.
C7 lamina fracture occurred in 32/123 (26%) patients and occurred at the bilateral isthmus in 29 patients and at the spinolaminar junction in three patients. All fractures appeared on X-ray within 3 months postoperatively, but patients did not present any neurological deterioration. The fracture spontaneously healed in 27/32 (84%) patients at 1 year and in 29/32 (91%) at 2 years. During follow-up, clinical outcomes were not significantly different between the groups. However, patients with C7 fractures showed a more lordotic C2-7 angle and kyphotic C7-T1 angle than patients without C7 fractures. C7 fracture was significantly associated with the extent of bone removal. By incorporating significant factors, the probability of C7 laminar fracture could be assessed with the formula 'Risk score = 1.08 × depth (%) + 1.03 × length (%, of the posterior height of C7 vertebral body)', and a cut-off value of 167.9% demonstrated a sensitivity of 90.3% and a specificity of 65.1% (area under the curve, 0.81).
C7 laminar fracture can occur after C7 dome-like laminectomy when a substantial amount of lamina is resected. Although C7 fractures may not cause deleterious clinical outcomes, they can lead to an unharmonized cervical curvature. The chance of C7 fracture should be discussed in the shared decision-making process.
颈椎扩大成形术是治疗多节段颈椎管狭窄的一种有效手术方法。手术过程中，通常保留C2和C7棘突，以保持颈部肌肉和项韧带的附着点完整。在这方面，对于部分病例，在C7处采用穹顶状椎板切除术（C7椎板下切）而非椎板成形术。然而，椎板切除会削弱C7椎板，可能发生应力性骨折，但该并发症在文献中尚未有详细描述。本研究的目的是调查C7穹顶状椎板切除术后C7椎板骨折的发生率、危险因素及其对临床和影像学结果的影响。
对接受颈椎开门式椎板成形术联合C7穹顶状椎板切除术的患者（n = 123），根据是否发生C7椎板骨折进行分类。比较两组术前以及术后3、6、12和24个月时的临床参数（颈部/手臂疼痛评分和颈部功能障碍指数）和影像学参数（C2-7角、C2-7矢状垂直轴和C7-T1角）。评估并发症的危险因素，并提出一个估计C7骨折风险的公式。
123例患者中有32例（26%）发生C7椎板骨折，其中29例发生在双侧峡部，3例发生在棘突椎板交界处。所有骨折均在术后3个月内通过X线显示，但患者均未出现神经功能恶化。27/32（84%）例患者骨折在1年时自发愈合，29/32（91%）例在2年时愈合。随访期间，两组临床结果无显著差异。然而，与未发生C7骨折的患者相比，发生C7骨折的患者C2-7角更前凸，C7-T1角后凸。C7骨折与骨质去除范围显著相关。通过纳入显著因素，可使用公式“风险评分 = 1.08 × 深度（%）+ 1.03 × 长度（C7椎体后高度的%）”评估C7椎板骨折的概率，截断值为167.9%时，敏感性为90.3%，特异性为65.1%（曲线下面积为0.81）。
当切除大量椎板时，C7穹顶状椎板切除术后可能发生C7椎板骨折。虽然C7骨折可能不会导致有害的临床结果，但可能导致颈椎曲度不协调。在共同决策过程中应讨论C7骨折的可能性。
