Department of Orthopedic Surgery, Yonsei University College of Medicine, National Health Insurance Medical Center, 1232, Baeksok St., Ilsan District, Goyang City, Gyeonggi Province, 410-719, Republic of Korea.
Spine J. 2011 Oct;11(10):919-24. doi: 10.1016/j.spinee.2011.07.029. Epub 2011 Sep 8.
In obese patients, placing pedicle screws percutaneously is a particular challenge. As the bulky and thick configuration of obese patients may produce fuzzier fluoroscopic view and longer passage of surgical instruments, the chances of misplacement might increase.
This study was designed to evaluate the effect of patient's body habitus on the incidence of percutaneous pedicle screw misplacements.
STUDY DESIGN/SETTING: A retrospective study with prospectively collecting data.
Three hundred seventy percutaneous pedicle screws for minimally invasive lumbar spinal fusion surgery were noted in 89 consecutive patients.
The position and direction of screws to pedicle were evaluated using the findings in computed tomography (CT) scan with the following grading method: Grade A, completely in the range without pedicle cortex violation; Grade B, pedicle wall violation <2 mm; Grade C, pedicle wall violation 2 to 4 mm; and Grade D, pedicle wall violation >4 mm. The direction of violation was grouped as medial, lateral, cranial, and caudal.
Two independent observers retrospectively examined all of the postoperative CT images. All screws were assigned into one of the following three groups along with patient's body mass index (BMI): 157 screws (38 patients) in normal weight (BMI<25) group; 124 (29) in overweight (25≤BMI<30) group; and 89 (22) in obese (BMI≥30) group. A pedicle screw was considered misplaced if the grade was defined as B, C, and D. Multivariate logistic regression analyses were performed to evaluate the association between screw misplacements and BMI.
Sixty-two screws (16.8%) were misplaced with the majority of Grade B (72.6%, 45/62) and lateral direction (72.6%, 45/62). Twenty-eight screws (22.6%, 28/124) were misplaced in overweight group, 12 (13.5%, 12/89) in obese group, and 22 (14.0%, 22/157) in normal weight group. Two symptomatic pedicle violations were noted with Grade D: a caudal violation was found in overweight group, which happened in the third case of surgeon's series; a medial misplacement, which was occurred in the 29th case, was noticed in obese group. There was no statistically significant association of pedicle violations along with patient's BMI (odds ratio [OR]=1.00, 95% confidence interval [CI]=0.94-1.07, p=.99). Moreover, no other factors, such as patient's age, gender, preoperative diagnosis, number of the fused segments, and year of the surgery, had a statistically significant relationship with pedicle violations. On the contrary, pedicle violations observed approximately five times more frequently at the level of L3 (47.1%, 8/17) and L4 (28.8%, 36/125) rather than L5 (10.1%, 16/158) and S1 (2.9%, 2/70) (OR=4.95, 95% CI=2.62-9.33, p<.0001).
Although symptomatic pedicle violations were noted in the earlier period of surgeon's learning curve and in overweight and obese patients, no statistical evidence could be found between patient's body habitus and percutaneous pedicle screw misplacement. Our data also suggest that greater caution should be exercised to avoid pedicle violations especially at L3 and L4.
在肥胖患者中，经皮放置椎弓根螺钉是一项特殊的挑战。由于肥胖患者的身体结构较为庞大且厚实，可能会导致透视视野模糊，手术器械通过更为困难，因此螺钉放置错误的风险可能会增加。
本研究旨在评估患者体型对经皮椎弓根螺钉放置错误发生率的影响。
研究设计/设置：回顾性研究，前瞻性收集数据。
89 例连续患者的 370 枚经皮椎弓根螺钉用于微创腰椎融合手术。
使用 CT 扫描的结果评估螺钉与椎弓根的位置和方向，采用以下分级方法：A 级，完全在范围内且无椎弓根皮质侵犯；B 级，椎弓根壁侵犯<2mm；C 级，椎弓根壁侵犯 2-4mm；D 级，椎弓根壁侵犯>4mm。侵犯的方向分为内侧、外侧、颅侧和尾侧。
两名独立观察者回顾性检查所有术后 CT 图像。根据患者的 BMI（体重指数）将所有螺钉分为以下三组之一：157 枚螺钉（38 例）在正常体重（BMI<25）组；124 枚（29 例）在超重（25≤BMI<30）组；89 枚（22 例）在肥胖（BMI≥30）组。如果分级为 B、C 和 D，则认为螺钉放置错误。进行多变量逻辑回归分析，以评估螺钉放置错误与 BMI 之间的关联。
62 枚螺钉（16.8%）放置错误，其中大多数为 B 级（72.6%，45/62）和外侧方向（72.6%，45/62）。超重组中有 28 枚螺钉（22.6%，28/124）、肥胖组中有 12 枚螺钉（13.5%，12/89）、正常体重组中有 22 枚螺钉（14.0%，22/157）放置错误。有 2 例症状性椎弓根侵犯，均为 D 级：1 例为超重组的尾侧侵犯，发生在第 3 例手术中；1 例为肥胖组的内侧移位，发生在第 29 例手术中。患者 BMI 与椎弓根侵犯之间没有统计学显著的关联（比值比[OR]=1.00，95%置信区间[CI]=0.94-1.07，p=.99）。此外，患者的年龄、性别、术前诊断、融合节段数量和手术年份等其他因素与椎弓根侵犯均无统计学显著关系。相反，在 L3（47.1%，8/17）和 L4（28.8%，36/125）水平，椎弓根侵犯的发生率约为 L5（10.1%，16/158）和 S1（2.9%，2/70）的 4.95 倍（OR=4.95，95% CI=2.62-9.33，p<.0001）。
尽管在手术医生学习曲线的早期和超重及肥胖患者中出现了症状性椎弓根侵犯，但没有统计学证据表明患者体型与经皮椎弓根螺钉放置错误有关。我们的数据还表明，应更加小心地避免椎弓根侵犯，尤其是在 L3 和 L4 水平。
