Biomechanical advantage of C1 pedicle screws over C1 lateral mass screws: a cadaveric study

Purpose

The established technique for posterior C1 screw placement is via the lateral mass. Use of C1 monocortical pedicle screws is an emerging technique which utilizes the bone of the posterior arch while avoiding the paravertebral venous plexus and the C2 nerve root. This study compared the relative biomechanical fixation strengths of C1 pedicle screws with C1 lateral mass screws.

Methods

Nine human C1 vertebrae were instrumented with one lateral mass screw and one pedicle screw. The specimens were subjected to sinusoidal, cyclic (0.5 Hz) fatigue loading. Peak compressive and tensile forces started from ±25 N and constantly increased by 0.05 N every cycle. Testing was stopped at 5 mm displacement. Cycles to failure, displacement, and initial and end stiffness were measured. Finally, CT scans were taken and the removal torque measured.

Results

The pedicle screw technique consistently and significantly outperformed the lateral mass technique in cycles to failure (1,083 ± 166 vs. 689 ± 240 cycles), initial stiffness (24.6 ± 3.9 vs. 19.9 ± 3.2 N/mm), end stiffness (16.6 ± 2.7 vs. 11.6 ± 3.6 N/mm) and removal torque (0.70 ± 0.78 vs. 0.13 ± 0.09 N m). Only 33 % of pedicle screws were loose after testing compared to 100 % of lateral mass screws.

Conclusions

C1 pedicle screws were able to withstand higher toggle forces than lateral mass screws while maintaining a higher stiffness throughout and after testing. From a biomechanical point of view, the clinical use of pedicle screws in C1 is a promising alternative to lateral mass screws.     

Two-level pedicle subtraction osteotomy for severe thoracolumbar kyphotic deformity in ankylosing spondylitis

Study design

A retrospective clinical study.

Objective

To evaluate the outcomes of two-level (T12 and L3) pedicle subtraction osteotomy (PSO) for severe thoracolumbar kyphosis in ankylosing spondylitis (AS), and to discuss the surgical strategies of this surgery.

Background

Cases were limited on the results of two-level PSO for correction of severe kyphosis caused by AS, nor on surgical strategies of this type of surgery.

Methods

From March 2006 to December 2010, nine consecutive AS patients with severe kyphotic deformity, underwent T12 and L3 PSOs. Chin-brow vertical angle (CBVA) and radiographic assessments which contain thoracic kyphosis (TK), lumbar lordosis (LL), global kyphosis (GK), and sagittal vertical axis were carefully recorded pre and postoperatively to evaluate the sagittal balance. Intra and postoperative complications were also registered. All patients were asked to fill out Oswestry Disability Index before surgery and at the last follow-up visit.

Results

All nine patients (8M/1F), averaged 41.4 years old (range 35–51 years), were received two-level (T12 and L3) PSO, and were followed up after surgery for a mean of 39.9 months (range 24–68 months). Good cosmetic results were achieved in all patients. Mean correction at two-level PSO was 67.9 ± 5.5°. All CBVA, TK, LL, and GK were changed significantly after surgery (P < 0.05), the mean amount of correction of which were 59.5 ± 13.8, 34.7 ± 3.8, 33.2 ± 2.4, and 54.0 ± 14.8 degrees, respectively, and with a small loss of correction at the last follow-up visit. Sagittal imbalance was significantly improved from 27.3 ± 4.4 to 3.4 ± 0.7 cm postoperatively. Neither mortalities nor any major neurological complications were found. The mean ODI score was significantly improved from 53.4 ± 15.5 before surgery to 8.2 ± 4.7 at the last visit.

Conclusion

The outcomes of follow-up showed that two-level (T12 and L3) PSO can effectively and safely correct severe thoracolumbar kyphosis in AS.     

TLIF入路椎体间单枚融合器植骨结合椎弓根钉系统内固定治疗多节段腰椎管狭窄症并腰椎不稳

目的 评价经椎间孔腰椎体间融合术（TLIF）入路椎体间单枚融合器植骨结合椎弓根钉系统内固定治疗多节段腰椎管狭窄症并腰椎不稳的疗效。方法 自2007-01-2012-12采用TLIF入路椎管减压、GSS或SINO内固定装置复位内固定、椎体间混合植骨、单枚cage应用治疗31例多节段腰椎管狭窄症并腰椎不稳,分析术后症状、体征改善情况。结果31例获得0.5-5年,平均1.5年的随访。按侯树勋等制定的疗效评定标准评定疗效：优26例,良5例。按JOA下腰痛疾患疗效评定标准,改善率达90%-98%。结论 应用TLIF入路椎体间单枚融合器植骨结合椎弓根钉系统内固定治疗多节段腰椎管狭窄症并腰椎不稳具有减压彻底、微创植骨易融合、神经副损伤少等优点,是治疗多节段腰椎管狭窄症及腰椎不稳的理想方法。     

经皮椎弓根钉内固定治疗高龄患者腰椎退变性滑脱所致腰痛的临床研究

目的观察经皮椎弓根钉治疗高龄老人腰椎退变性滑脱所致腰痛的临床疗效。方法201O年4月～2013年8月28例腰椎退变性滑脱所致腰痛的高龄老人,采用经皮椎弓根钉内固定实施治疗,对比术前、术后1周、术后6个月视觉模拟评分（VAS）和功能障碍指数（ODI）,记录手术时间及术中出血量,评价临床疗效。结果本组28例患者,术前视觉模拟评分（VAS）为（7．61±1．22）分,功能障碍指数（OO!）为（53．12±3．32）分：采用经皮椎弓根钉内固定治疗,术后1周内均带护腰支具下地活动,下地后术前腰痛症状消失或明显缓解,术后2周伤口甲级愈合并拆线。术后1周VAS为（2．30±0．98）分,0DI为（7．64±1．23）分;平均手术时间130分钟,平均出血量110ml。所有患者均获得随访,随访时间6个月,随访时VAS为（2．12±1．33）分,ODI为（8．46±2．20）分。结论经皮椎弓根钉内固定治疗高龄老人腰椎退变性滑脱所致腰痛疗效确切。     

Biomechanical study of the funnel technique applied in thoracic pedicle screw replacement

Background

Funnel technique is a method used for the insertion of screw into thoracic pedicle.

Aim

To evaluate the biomechanical characteristics of thoracic pedicle screw placement using the Funnel technique, trying to provide biomechanical basis for clinical application of this technology.

Methods

14 functional spinal units (T6 to T10) were selected from thoracic spine specimens of 14 fresh adult cadavers, and randomly divided into two groups, including Funnel technique group (n=7) and Magerl technique group (n=7). The displacement-stiffness and pull-out strength in all kinds of position were tested and compared.

Results

Two fixed groups were significantly higher than that of the intact state (P<0.05) in the spinal central axial direction, compression, anterior flexion, posterior bending, lateral bending, axial torsion, but there were no significant differences between two fixed groups (P>0.05). The mean pull-out strength in Funnel technique group (789.09±27.33) was lower than that in Magerl technique group (P<0.05).

Conclusions

The Funnel technique for the insertion point of posterior bone is a safe and accurate technique for pedicle screw placement. It exhibited no effects on the stiffness of spinal column, but decreased the pull-out strength of pedicle screw. Therefore, the funnel technique in the thoracic spine affords an alternative for the standard screw placement.     

椎弓根螺钉内固定联合后路椎间融合治疗复发性腰椎间盘突出症疗效观察

目的回顾性分析38例椎弓根螺钉内固定联合后路椎间融合治疗复发性腰椎间盘突出症病人的临床资料,评价椎弓根螺钉内固定联合后路椎间融合中的临床价值。方法38例病人,26～72岁,平均51.3岁。行腰椎后路病变节段脊柱附件切除椎管减压椎弓根螺钉内固定及椎间植骨融合术。平均随访4.7年。随访观察指标有JOA评分、植骨融合、临床症状缓解情况、并发症发生情况及病人满意度调查。结果所有患者临床症状都有不同程度的缓解。临床恢复率术后半年、术后1年及最终随访时分别为78.9%、92.1%和68.4%。最后1次随访的融合率达97.4%。2例未观察到可靠的融合,并在术后2年出现内固定的断裂而再次手术。围手术期并发症发生率为26.3%,远期并发症发生率为6.2%。病人满意率达94.7%。结论应用椎弓根螺钉内固定联合后路椎间融合治疗复发性腰椎间盘突出症病人可以取得良好疗效。     

后路经椎弓根椎体内植骨治疗胸腰段骨折

目的探讨后路椎弓根螺钉复位内固定结合经椎弓根椎体内植骨治疗胸腰段骨折的临床疗效。方法回顾性分析2002年1月-2006年9月手术治疗的胸腰段骨折68例患者的临床资料。其中椎体内植骨组31例，行后路椎弓根螺钉复位内固定同时，经椎弓根椎体内植骨治疗；同期37例行单纯椎弓根螺钉复位内固定无植骨治疗者作为对照组。随诊3—58个月。评价两组术前、术后及随诊时伤椎高度比值、脊柱后凸成角矫正、神经功能恢复、内固定失效情况以及腰背疼痛并发症情况。结果两组伤椎前、后缘高度比值和脊柱后凸成角术前分别为（49．6±2．0）％、（93．4±1．0）％、（18．3±2．0）°和（50．3±1．0）%、（94．1±3．0）％、（17．9±2．0）°，两组比较差异无统计学意义（P〉0．05）；术后分别为（94．3±1．0）％、（96．7±3．0）％、（6．2±1．0）°和（90．1±4．0）％、（95．8±2．0）％、（7．3±2．0）°，椎体内植骨组椎体高度恢复和脊柱后凸成角矫正优于对照组（P〈0．05）；随诊时分别为（92．5±3．0）％、（94．4±1．0）％、（7．6±1．0）°和（85．2±2．0）％、（90．5±3．0）％、（11．7±1．0）°，两组高度恢复和脊柱后凸矫正丢失率分别为（2．4±0．1）％、（2．3±0．5）％、（1．2±0．1）°和（5．3±0．5）％、（5．1±0．1）％、（4．4±0．5）°。两组比较差异有统计学意义（P〈0．05）。神经功能恢复术后及随诊时平均提高1-2级，椎体内植骨组略优于对照组，但两组比较差异无统计学意义（P〉0．05）。椎体内植骨组无内固定失效，对照组内固定失效4例，占10．81％。随诊时椎体内植骨组腰背疼痛2例，占6．45％，对照组腰背疼痛5例，占13．51％。结论后路椎弓根螺钉复位内固定结合经椎弓根椎体内植骨治疗胸腰段骨折有良好的临床疗效。经椎弓根椎体内植骨能有效防止复位固定后的矫正丢失和内固定失效，并能减少术后腰背疼痛并发症。     

后路矫正特发性脊柱侧凸相关问题的探讨

目的探讨后路矫正特发性脊柱侧凸的相关问题。方法回顾2001年1月～2006年10月42例特发性脊柱侧凸患者，冠状面Cobb角45°～145°，平均76．75°；矢状面Cobb角22°～105°，平均47．08°；Bending相主胸弯侧凸平均矫正率20．51％～39．19％。侧凸Cobb角80°～145°8例，采用一期后路松解，颅盆环牵引二期后路选择性节段椎弓根螺钉固定及胸廓成形术；侧凸Cobb角60°～79°16例，行同期后路松解选择性节段椎弓根螺钉固定术；侧凸Cobb角小于60。18例，勿需松解，即行选择性节段椎弓根螺钉固定。结果Cobb角80°～145。、60°～79。和小于60。的术后矫正Cobb角分别为10°～40°（34．50°）、6°～25°（18．66。）、4°～18°（10．11°）；术后侧凸平均矫正率分别达66．88％、73．31％和80．34％。术后后凸Cobb角平均矫正角度为29．50°、27．74°和22．65°，平均矫正率分别为57．35％、40．77％和10．30％。随访12～78个月（平均36个月），16例失访，随访26例中23例内固定无松脱断裂，畸形丢失率为1．53％～5．10％，平均3．01％。2例术后1年半复查发现断棒，再次矫形术。结论重度AIS应采用后路广泛松解，凹侧松解是关键。颅盆环牵引安全可靠。选择性节段椎弓根螺钉固定同样达到全节段椎弓根螺钉固定的矫形效果。融合范围应密切结合AIS的分型。胸廓成形术后早期对肺功能有影响，通过术后肺功能训练可恢复至术前水平。     

影像导航引导椎弓根钉加椎间融合治疗腰椎滑脱症

目的探讨影像导航系统引导椎弓根钉加椎间融合治疗腰椎滑脱症的有效性和效果。方法对56例腰椎滑脱患者在脊柱影像导航系统引导下利用椎弓根螺钉滑脱椎体进行复位固定加椎管减压、椎间融合术。手术后对内植物和导航虚拟影像进行测量,疗效采用JOA下腰痛评分标准评定术前、术后分数,同时观察临床疗效及融合率。结果植入物实际影像图与导航虚拟手术路径图重叠,复查CT示内植物位置理想,椎弓钉位置评级:理想210枚(94%),术后随访时间6个月~1年10个月,术前JOA评分平均7分,随访时为12.5分,优良率91%。结论影像导航系统引导椎弓根钉加椎间融合治疗腰椎滑脱症,植入前可以虚拟出内固定植入的手术环境和路径;植入中可以实时追踪手术器械的位置变化,使内植物精确植入最佳位置,提高了椎弓根钉和融合器植入安全性,提高手术疗效。