Anatomical considerations for cervical pedicle screw insertion: the use of multiplanar computerized tomography measurements in 122 consecutive clinical cases

Background contextSuccessful placement of pedicle screws in the cervical spine requires a sufficient three-dimensional understanding of pedicle morphology to allow accurate identification of the screw axis.PurposeThe goal of the present study was to assess morphologic trends from one level to the next with respect to linear and angular parameters associated with the subaxial cervical pedicles.Study design/settingWe evaluated the pedicle morphology of cervical spine using axial and sagittal computed tomography (CT) imaging. The C3–C7 vertebrae in 122 patients (610 vertebrae) were evaluated (age range, 14–93; mean, 48 years).MethodsThin cut (2.5 mm thickness) axial CT images were measured. Sagittal reconstructions were obtained using 1.25-mm thickness slices. The following pedicle parameters were assessed: pedicle width (PW, the mediolateral diameter of the pedicle isthmus, perpendicular to the pedicle axis), pedicle height (PH, rostro-caudal dimension of the pedicle determined on the sagittal image), maximal screw length (MSL, distance from the posterior cortex of the lateral mass to the anterior wall of the vertebral body along the pedicle axis), and pedicle transverse angle (PTA, angle between the pedicle axis and the midline vertebral body).ResultsThe overall mean PW and PH ranged from 4.7 to 6.5 mm and 6.4 to 7.0 mm, respectively. For both these parameters there was a trend toward increasing size proceeding caudally in the cervical spine. The mean PW and PH was greater in males than in females, and this difference was statistically significant at all levels (p<.0001). The overall mean MSL ranged from 29.9 to 32.9 mm. All intersections of the pedicle axis and the posterior cortex of the lateral mass were located at the most lateral portion of the lateral mass for the C3–C6 vertebrae. The overall mean PTA ranged from 37.8° to 45.3°. The overall mean PTA was approximately 44° from C3 to C6 and 37.8° at C7.ConclusionThe findings of our radiological anatomical study suggest that the preoperative CT scans of patients undergoing cervical transpedicular fixation should be thoroughly analyzed and close attention paid to the pedicle size and its angulation. The placement of cervical pedicle screws should be individualized for each patient and based on detailed preoperative planning.     

The use of mini-implants in en masse retraction for the treatment of bimaxillary dentoalveolar protrusion

This case report describes the treatment of a 22-year-old girl who had incompetent lips with severe bimaxillary dentoalveolar protrusion. The treatment of choice for such patients is usually extraction of four first premolars and retraction of the anterior teeth. To maintain the extraction space, maximum anchorage is required. Mini-implants were used to provide maximum anchorage for obtaining a good facial profile.     

Hybrid Technique for Posterior Lumbar Interbody Fusion: A Combination of Open Decompression and Percutaneous Pedicle Screw Fixation

The authors describe a hybrid technique that involves a combination of open decompression and posterior lumbar interbody fusion (PLIF) and percutaneously inserted pedicle screws. This technique allows performance of PLIF and decompression via a midline incision and approach without compromising operative time and visualization. Furthermore, compared to standard open decompression, this approach reduces post‐operative wound pain because the small midline incision significantly reduces muscle trauma by obviating the need to dissect the paraspinal muscles off the facet joint complex and by avoiding posterolateral fusion, thus requiring limited lateral muscle dissection off the transverse processes. A series of patients with Grade I‐II spondylolisthesis at L_4–5 and moderate–severe canal/foraminal stenosis underwent midline PLIF at L_4–5, with closure of the midline incision. Percutaneous pedicle screws were inserted, thereby minimizing local muscle trauma, reduction of the spondylolisthesis being performed by using a pedicle screw construct. Rods were inserted percutaneously to link the L₄ and L₅ pedicle screws. Image intensification was used to confirmed satisfactory screw placement and reduction of spondylolisthesis. The results of a prospective study comparing a standard open decompression and fusion technique for spondylolisthesis versus the minimally invasive hybrid technique are discussed. The minimally invasive technique resulted in shorter hospital stay, earlier mobilization and reduced postoperative narcotic usage. The long‐term clinical outcomes were equivalent in the two groups.     

直入式注入PMMA骨水泥强化椎弓根钉内固定生物力学研究

【摘要】 目的 分析直入式骨水泥注入椎体强化方法在体外提高螺钉稳定性的效果。方法采用新鲜尸体脊柱标本共24个椎体,一侧椎弓根采用直入式注入PMMA骨水泥强化椎弓根钉固定作(试验组),另一侧椎弓根采用常规椎弓根螺钉固定(对照组),两侧进行最大轴向拔出力试验、最大旋出力矩试验、周期抗屈试验生物力学测试,比较两组测试结果。结果〓骨水泥强化组中螺钉的稳定性均显著强于单纯常规椎弓根螺钉组(P < 0.05)。结论〓应用PMMA行椎体强化椎弓根钉固定有利于增强对椎弓根钉的把持力,可有效防止椎弓根钉的松动及脱落,具有良好的临床效果。     

钉道强化提高椎弓根螺钉固定强度的生物力学研究

目的 评价椎弓根钉道局部强化技术及其结合膨胀式椎弓根螺钉提高椎弓根螺钉固定强度的效果.方法 通过自行设计及加工的钉道局部强化装置,向钉道周壁点状注入CaSO4骨水泥以强化椎弓根钉道.5具新鲜冻存人体脊柱标本,每具随机选取4个腰椎共20个腰椎标本,采用随机区组设计方法分为10个区组.设计四种固定方法:A组(普通椎弓根螺钉)、B组(普通椎弓根螺钉+钉道局部强化)、C组(膨胀式椎弓根螺钉+钉道局部强化)、D组(普通椎弓根螺钉+钉道内灌注CaSO4骨水泥),随机应用在每个区组的2个椎体共4个椎弓根钉道.分别测试每个椎弓根螺钉的最大轴向拔出力及能量吸收值.从剩余腰椎标本中任意取两个腰椎,应用钉道局部强化技术后利用Micro-CT观察钉道周壁微观结构变化.结果 C、D两组的最大轴向拔出力均值及能量吸收值均值高于A组(P＜0.01)及B组(P＜0.05),B组最大轴向拔出力均值及能量吸收值均值高于A组(P＜0.01),C、D两组之间的差异无统计学意义(P＞0.05).结论 钉道局部强化技术可显著提高椎弓根螺钉的固定强度,结合使用膨胀式椎弓根螺钉可进一步提高螺钉的固定强度.     

Ankle joint contact loads and displacement in syndesmosis injuries repaired with Tightropes compared to screw fixation in a static model

BackgroundThe effect of syndesmotic fixation on restoration of pressure mechanics in the setting of a syndesmotic injury is largely unknown. The purpose of this study is to examine the contact mechanics of the tibiotalar joint following syndesmosis fixation with screws versus a flexible fixation device for complete syndesmotic injury.MethodsSix matched pairs of cadaveric below knee specimens were dissected and motion capture trackers were fixed to the tibia, fibula, and talus and a pressure sensor was placed in the tibiotalar joint. Each specimen was first tested intact with axial compressive load followed by external rotation while maintaining axial compression. Next, syndesmotic ligaments were sectioned and randomly assigned to repair with either two TightRopes® or two 3.5 mm cortical screws and the protocol was repeated. Mean contact pressure, peak pressure, reduction in contact area, translation of the center of pressure, and relative talar and fibular motion were calculated. Specimens were then cyclically loaded in external rotation and surviving specimens were loaded in external rotation to failure.ResultsNo differences in pressure measurements were observed between the intact and instrumented states during axial load. Mean contact presure relative to intact testing was increased in the screw group at 5 Nm and 7.5 Nm torque. Likewise, peak pressure was increased in the TightRope group at 7.5 Nm torque. There was no change in center of pressure in the TightRope group at any threshold; however, at every threshold tested there was significant medial and anterior translation in the screw group relative to the intact state.ConclusionEither screws or TightRope fixation is adequate with AL alone. With lower amounts of torque, the TightRope group appears to have contact and pressure mechanics that more closely match native mechanics.     

急性肩锁关节全脱位手术治疗

目的：探讨急性肩锁关节脱位的手术治疗方法。观察、总结手术疗效。方法：对2000年6月～2006年3月38例急性肩锁关节全脱位患者,分别采用螺丝钉、克氏针张力带、锁骨钩钢板内固定治疗,并对临床资料进行总结和分析。结果：采用螺钉13例,其中1例用螺丝钉内固定,第7天拔起并再次脱位,改其他方法后治愈,优8例,良4例。采用克氏针张力带内固定13例,其中,优6例,良7例。采用锁骨钩钢板内固定12例,其中,优9例,良3例。结论：采用上述手术方法,均可有效固定肩锁骨关节脱位。     

PFNA和DHS治疗老年股骨转子间骨折的疗效比较

[目的]比较防旋型股骨近端髓内钉(PFNA)和动力髋螺钉(DHS)与治疗老年股骨转子间骨折的疗效.[方法]回顾性分析2011年4月至2013年4月收治的132例65岁以上股骨转子间骨折患者的临床资料,根据内固定方式不同分为两组:DHS组70例,采用DHS内固定治疗;PFNA组62例,采用PFNA内固定治疗.比较两组患者的手术时间、手术切口长度、术中透视次数、术中出血量、骨折复位质量、住院时间、下地时间、骨折愈合时间、髋关节功能Harris评分及并发症发生率等.[结果]PFNA组患者的手术时间和切口长度较DHS组长,术中出血量较DHS组少,住院时间较DHS组短,下地时间较DHS组早,差异均有统计学意义(P<0.05).两组患者术中透视次数、骨折解剖复位或接近解剖复位率、围手术期并发症发生率比较差异均无统计学意义(P>0.05).DHS组54例患者获得随访,平均随访时间为(2.62±0.79)年;PFNA组47例患者获得随访,平均随访时间为(2.54±0.72)年.末次随访时DHS组患者髋关节功能Harris评分(81.29±9.38)分和优良率79.63%较PFNA组(94.68±4.90)分和95.74%低,差异有统计学意义(P<0.05),而两组患者的骨折愈合时间、术后并发症发生率比较差异均无统计学意义(P>0.05).[结论]对于老年股骨转子间骨折,与DHS相比,应用PFNA治疗具有稳定性好、手术时间短、术中出血量少及患髋关节功能恢复好的优势.     

纽扣缝线系统与螺钉固定治疗下胫腓联合分离的疗效分析

目的比较下胫腓联合分离采用纽扣缝线系统治疗与螺钉固定治疗的效果。方法对2008年10月至2011年7月收治的有完整随访资料的30例下胫腓关节分离患者进行回顾性分析。其中采用纽扣缝线系统治疗12例,采用螺钉固定治疗18例,根据标准的踝足评分标准及X线测量结果评价两种手术方式的治疗效果。结果 30例患者随访时间为3～12个月,平均4.7个月,两组在术后踝关节功能方面的比较差异无统计学意义(P0.05)。结论纽扣缝线系统是治疗下胫腓联合分离的理想手术方法,具有可允许下胫腓有微动存在和早期负重,更符合生理特点,不存在植入物疲劳断裂,复位效果不会丢失,无合并症,不需常规取出等多项优点,其治疗效果与传统的螺钉固定方式相当。     

Factors affecting the interface of cervical spine facet screws placed in the technique by Roy-Camille et al.

The objective of the study was to investigate the influence of bone cement, length of burr hole and bone density on pullout force and insertional screw torque of cervical spine facet screws. Both facets of 24 human cervical vertebrae were scanned for bone mineral density (BMD) and assigned to two groups for measuring of insertional screw torque and pullout strength. Maximal insertional screw torque was measured and removal of the screws was performed in displacement control (0.25 mm/s) without bone cement (PMMA), with 0.1 ml of PMMA and with the burr hole completely filled with PMMA. Screw torque was 59.1 N cm (±25.7 N cm), pullout force was 382.8 N (±140.5 N) without PMMA. Injection of 0.1 ml PMMA did not change significantly both screw torque (p=0.73) and pullout (p=0.129). Filling of the burr holes with PMMA increased significantly both screw torque (p<0.0001) and pullout force (p=0.028) when compared with injection of 0.1 ml of PMMA. A positive, moderate correlation was seen between BMD and screw torque before (r=0.501; p=0.097) and after filling with PMMA (r=0.514; p=0.088), BMD and pullout force before (r=0.441; p=0.152) and after complete filling with PMMA (r=0.673; p=0.047). The PMMA does increase both screw torque (p<0.0001) and pullout force (p=0.028) of facet screws significantly if the burr hole is filled with PMMA completely when compared with injection of 0.1 ml PMMA. Bone mineral density of the cervical facets moderately correlates with peak insertional torque and pullout force. This is true for a facet without PMMA and for a facet filled with PMMA. The length of the burr hole seems to be less important.