Doi Kazuma, Inoue Nozomu, Tani Satoshi, Mizuno Junichi
Center for Minimally Invasive Spinal Surgery, Shin Yurigaoka General Hospital, Kawasaki, Kanagawa, Japan.
Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois, United States.
Asian J Neurosurg. 2024 Nov 19;20(1):82-87. doi: 10.1055/s-0044-1793929. eCollection 2025 Mar.
Cervical open-door laminoplasty using plates and miniscrews is gaining popularity. One of the complications of this procedure is the loosening or back-out of the miniscrews inserted in the lateral mass (LM). Bone mineral density (BMD) measured by computed tomography (CT) has been used as a predictor of bone strength. However, bone density distribution in the LM remains unclear. We investigated bone density distribution in the posterior wall of the LM. A total of 120 LMs were analyzed from the patients who underwent laminoplasty. The distribution of BMD defined by Hounsfield unit (HU) in the posterior wall of the LM was measured by CT osteoabsorptiometry. The posterior wall was divided into nine zones, which consisted of three columns (lateral, center, and medial) and three rows (cranial, center, and caudal). BMD in each zone was averaged and compared by zones and cervical levels. Overall mean ± standard deviation BMD was 1,092 ± 433 HU. Averaged BMD in the entire posterior wall was highest at C4 (1,365 ± 459 HU), second highest at C3 (1,239 ± 435 HU), and lower in the lower levels. BMD in the medial-center zone (1,357 ± 443 HU) was the highest in all zones. BMD in the medial-caudal region at C7 was only 59% of the highest BMD in the medial-center region at C4. The medial-center to the cranial region was most suitable for miniscrew fixation for laminoplasty. These biomechanical findings would be useful in the preoperative planning of laminoplasty especially for the determination of the LM screw entry points and in the design of laminoplasty implants.
使用钢板和微型螺钉的颈椎开门式椎板成形术越来越受欢迎。该手术的并发症之一是插入侧块（LM）的微型螺钉松动或退出。通过计算机断层扫描（CT）测量的骨矿物质密度（BMD）已被用作骨强度的预测指标。然而，LM中的骨密度分布仍不清楚。
我们研究了LM后壁的骨密度分布。对接受椎板成形术的患者的120个LM进行了分析。通过CT骨吸收测量法测量LM后壁中由亨氏单位（HU）定义的BMD分布。后壁分为九个区域，由三列（外侧、中间和内侧）和三行（头侧、中间和尾侧）组成。对每个区域的BMD进行平均，并按区域和颈椎节段进行比较。
总体平均±标准差BMD为1092±433 HU。整个后壁的平均BMD在C4处最高（1365±459 HU），在C3处次之（1239±435 HU），在较低节段较低。内侧中间区域的BMD（1357±443 HU）在所有区域中最高。C7处内侧尾侧区域的BMD仅为C4处内侧中间区域最高BMD的59%。
内侧中间至头侧区域最适合用于椎板成形术的微型螺钉固定。这些生物力学研究结果将有助于椎板成形术的术前规划，特别是在确定LM螺钉进针点和设计椎板成形术植入物方面。
