使用先前的导孔和轨迹重新插入椎弓根螺钉不会降低固定强度。

Pedicle screw reinsertion using previous pilot hole and trajectory does not reduce fixation strength.

作者信息

Kang Daniel G, Lehman Ronald A, Wagner Scott C, Bevevino Adam J, Bernstock Joshua D, Gaume Rachel E, Dmitriev Anton E

机构信息

*Department of Orthopaedic Surgery, Walter Reed National Military Medical Center, Bethesda, MD; and †Division of Orthopaedics, Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD.

出版信息

Spine (Phila Pa 1976). 2014 Sep 15;39(20):1640-7. doi: 10.1097/BRS.0000000000000477.

STUDY DESIGN

Fresh-frozen human cadaveric biomechanical study.

OBJECTIVE

To evaluate the biomechanical consequence of pedicle screw reinsertion in the thoracic spine.

SUMMARY OF BACKGROUND DATA

During pedicle screw instrumentation, abnormal appearance on fluoroscopic imaging or low current reading with intraoperatively evoked electromyographic stimulation of a pedicle screw warrants complete removal to reassess for pedicle wall violation or screw malposition. However, screw fixation strength has never been evaluated biomechanically after reinsertion using a previous pilot hole and trajectory.

METHODS

Thirty-one thoracic individual fresh-frozen human cadaveric vertebral levels were instrumented bilaterally with 5.5-mm titanium polyaxial pedicle screws, and insertional torque (IT) was measured with each revolution. A paired comparison was performed for each level. Screw reinsertion was performed by completely removing the pedicle screw, palpating the tract, and then reinserting along the same trajectory. Screws were tensile loaded to failure "in-line" with the screw axis.

RESULTS

There was no significant difference for pedicle screw pullout strength (POS) between reinserted and control screws (732 ± 307 N vs. 742 ± 320 N, respectively; P = 0.78). There was no significant difference in IT between initial insertion for the test group (INI) (0.82 ± 0.40 N·m) and control (0.87 ± 0.50 N·m) (P = 0.33). IT for reinserted screws (0.58 ± 0.47 N·m) had significantly decreased compared with INI and control screws (29% decrease, P = 0.00; 33% decrease, P = 0.00, respectively). The test group screws in the thoracic spine had significant correlations between initial IT and POS (r = 0.79, P = 0.00), and moderate correlations between reinsertion IT and POS in the thoracic spine (r = 0.56, P = 0.00).

CONCLUSION

Despite a significant reduction in pedicle screw IT, there was no significant difference in pedicle screw POS with reinsertion. Therefore, when surgeons must completely remove a pedicle screw for tract inspection, reinsertion along the same trajectory may be performed without significantly compromising fixation strength.

LEVEL OF EVIDENCE

N/A.

研究设计

新鲜冷冻人体尸体生物力学研究。

目的

评估胸椎椎弓根螺钉重新置入的生物力学后果。

背景资料总结

在椎弓根螺钉置入过程中，透视影像出现异常表现或术中对椎弓根螺钉进行诱发肌电图刺激时电流读数较低，需要将螺钉完全取出，以重新评估是否存在椎弓根壁侵犯或螺钉位置不当。然而，使用先前的导孔和轨迹重新置入螺钉后，其固定强度从未进行过生物力学评估。

方法

对31个胸椎节段的新鲜冷冻人体尸体双侧置入5.5毫米钛制多轴椎弓根螺钉，每旋转一圈测量一次置入扭矩（IT）。对每个节段进行配对比较。通过完全取出椎弓根螺钉、触摸通道，然后沿相同轨迹重新置入来进行螺钉重新置入。螺钉沿螺钉轴线“直线”拉伸至破坏。

结果

重新置入的螺钉与对照螺钉的椎弓根螺钉拔出强度（POS）无显著差异（分别为732±307牛顿和742±320牛顿；P = 0.78）。试验组初始置入（INI）时的IT（0.82±0.40牛顿·米）与对照组（0.87±0.50牛顿·米）之间无显著差异（P = 0.33）。重新置入螺钉的IT（0.58±0.47牛顿·米）与INI及对照螺钉相比显著降低（分别降低29%，P = 0.00；降低33%，P = 0.00）。试验组胸椎螺钉的初始IT与POS之间存在显著相关性（r = 0.79，P = 0.00），胸椎重新置入IT与POS之间存在中度相关性（r = 0.56，P = 0.0照螺钉的椎弓根螺钉拔出强度（POS）无显著差异（分别为732±307牛顿和742±320牛顿；P = 0.78）。试验组初始置入（INI）时的IT（0.82±0.40牛顿·米）与对照组（0.87±0.5开重新置入来进行螺钉重新置入。螺钉沿螺钉轴线“直线”拉伸至破坏。

结果

结论

尽管椎弓根螺钉的IT显著降低，但重新置入时椎弓根螺钉的POS无显著差异。因此，当外科医生必须完全取出椎弓根螺钉以检查通道时，可以沿相同轨迹重新置入，而不会显著损害固定强度。

证据级别

无。