Easy retrieval of polyaxial tulip-head pedicle screws by “U” rod technique

The number of fusion surgeries increase each year which also increase the need for implant removal. In some cases, it can be extremely hard to remove a pedicle screw especially when there is a mismatch of the screw and the screwdriver. Also the screwdrivers can be contaminated during the operation, and this will cause a delay till the instruments are re-sterilized. There is a need for the removal of screws without special instruments. We describe a method for removing tulip-head polyaxial pedicle screws without special instruments. The screws are removed using an Allen key, a rod bender and a “U” shaped rod. We successfully removed 76 screws in 11 recent cases without any complications. The “U” rod technique is a simple and useful technique for the removal of tulip-head polyaxial screws.     

Anatomic comparison of transarticular screws with lateral mass screws in cervical vertebrae

Objective:To compare the potential incidence of nerve root (ventral and dorsal ramus) injury caused by cervical transarticular screws and Roy-Camille lateral mass screws. Methods:Insertion techniques with Klekamp transarticular screws and Roy-Camille lateral mass screws were respectively performed in this study. Each technique involved four specimens and 40 screws, which were inserted from C3 to C7. And 20-mm-long screws were used to overpenetrate the ventral cortex. The anterolateral aspect of the cervical spine was carefully dissected to allow observation of the screw-ramus relationship. Results : The overall percentage of nerve invasion was significantly lower with Klekamp (45 %) technique than with Roy-Camille (85%) technique (P<0.05). The largest percentage of nerve invasion for Klekamp transarticular screws was found at the dorsal ramus (25%), followed by the ventral ramus (15%) and the bifurcation of the ventral dorsal ramus (5 %). The largest percentage of nerve invasion for Roy-Camille lateral mass screws was found at the ventral ramus (80 %). Conclusion : The potential risk of nerve root invasion is lower with Klekamp transarticular screws than with Roy-Camille lateral mass screws.     

Cortical screw support in femoral neck fractures: A radiographic analysis of 87 fractures with a new mensuration technique

In 87 femoral neck fractures, operated on with 2 von Bahr screws and followed for up to 2 years, the positions of the fixating screws were determined with a new mensuration technique which compensates for the variations in hip rotation in routine radiographs. The union rate of the fractures was related to the position of the screws. A posterior placement of the proximal screw and an inferior placement of the distal screw in both the femoral head and neck improved the outcome substantially.     

Anatomic comparison of transarticular screws with latera mass screws in cervical vertebrae

Objective： To compare the potential incidence of nerve root （ventral and dorsal ramus） injury caused by cervical transarticular screws and Roy-Camille lateral mass screws. Methods ： Insertion techniques with Klekamp transarticular screws and Roy-Camille lateral mass screws were respectively performed in this study. Each technique involved four specimens and 40 screws, which were inserted from C3 to C7. And 20-mm-long screws were used to overpenetrate the ventral cortex. The anterolateral aspect of the cervical spine was carefully dissected to allow observation of the screw-ramus relationship. Results ： The overall percentage of nerve invasion was significantly lower with Klekamp （45%） technique than with Roy-Camille （ 85 %） technique （ P 〈 0.05 ）. The largest percentage of nerve invasion for Klekamp transarticular screws was found at the dorsal ramus （25 % ）, followed by the ventral ramus （ 15 % ） and the bifurcation of the ventral dorsal ramus （ 5 % ）. The largest percentage of nerve invasion for Roy-Camille lateral mass screws was found at the ventral ramus （80 % ）. Conclusion ： The potential risk of nerve root invasion is lower with Klekamp transarticular screws than with Roy Camille lateral mass screws.     

Low-profile pelvic fixation with sacral alar-iliac screws

Background

In the last years, a new technique for pelvic fixation using ‘sacral alar-iliac’ screws has been proposed as an alternative to the classic ‘iliac wing’ screws and the old Galveston technique.

Methods

The authors provide a ‘step-by-step’ review of the technical details regarding this technique, as well as some important anatomical and radiological landmarks for its successful performance.

Conclusions

‘Sacral alar-iliac’ screws provide several advantages in relation to pelvic fixation with iliac bolts such as: better alignment with the rods, use of a ‘low-profile’ screw, and fixation of the sacroiliac (SI) joint, which avoids postoperative SI joint-related pain.     

Interobserver reliability in evaluation of pedicle screw positions inserted with a modified technique

The aim of this study was to evaluate a new technique for insertion of pedicle screws. The position of the screws was assessed on postoperative plain radiographs and computed tomography (CT) scans, and the interobserver reliability in evaluation of the pedicle screw positions was studied. The technique was applied to insert 201 pedicle screws in 27 patients with various spine conditions. The positions of the screws were evaluated blindly by two independent orthopaedic surgeons and two independent radiologists. Interobserver reliability was evaluated separately for analysis of plain radiographs and CT scans, as well as for the different spinal segments and for the different spine conditions treated. The rate of malpositioned screws was between 6.5% and 32.8% in plain radiographs and between 3.5% and 6.5% in CT scans according to the different observers. In plain radiographs, the rates of malpositioned screws in the upper thoracic, lower thoracic and lumbosacral spine segments were between 3.8%-39.6%, 10.0%-36.3%, 4.4%-23.5%, respectively. In CT scans, the rates of malpositioned screws in the upper thoracic, lower thoracic and lumbosacral spine segments were between 3.8%-13.2%, 2.5%-8.8%, and 0%, respectively. Interobserver reliability was found to be poor in radiographs and fair in CT scans. The technique used for insertion of pedicle screws was found to be simple and reproducible. Assessment of the screw positions with only plain radiographs was not found reliable. A detailed and standard classification system should be developed in order to improve interobserver reliability in assessing the positions of the screws.     

Free-hand thoracic pedicle screws placed by neurosurgery residents: a CT analysis

Free-hand thoracic pedicle screw placement is becoming more prevalent within neurosurgery residency training programs. This technique implements anatomic landmarks and tactile palpation without fluoroscopy or navigation to place thoracic pedicle screws. Because this technique is performed by surgeons in training, we wished to analyze the rate at which these screws were properly placed by residents by retrospectively reviewing the accuracy of resident-placed free-hand thoracic pedicle screws using computed tomography imaging. A total of 268 resident-placed thoracic pedicle screws was analyzed using axial computed tomography by an independent attending neuroradiologist. Eighty-five percent of the screws were completely within the pedicle and that 15% of the screws violated the pedicle cortex. The majority of the breaches were lateral breaches between 2 and 4 mm (46%). There was no clinical evidence of neurovascular injury or injury to the esophagus. There were no re-operations for screw replacement. We concluded that under appropriate supervision, neurosurgery residents can safely place free-hand thoracic pedicle screws with an acceptable breach rate.     

Die perkutane transiliosakrale Zugschraubenosteosynthese des hinteren Beckenrings

BACKGROUND: In recent years, the closed reduction and percutaneous fixation of posterior pelvic ring fractures by sacroiliac screws has become a well established treatment option for stabilization of posterior pelvic ring disruptions. Stable percutaneous pelvic ring fixation also implies a very low complication rate, e.g., in operative blood loss, wound healing, and operative time. To avoid malpositioning of the screws, sufficient reduction and radiologic visualization are essential. The surgical technique has been described in several studies; however, great importance is attached to the personal experience of the surgeon. Therefore, this study was conducted to establish a standard procedure that allows different surgeons a safe positioning of sacroiliac screws. RESULTS: A total of 41 injuries of the posterior pelvic ring were stabilized with 73 sacroiliac lag screws inserted by 7 different surgeons using a standardized technique. In all cases adequate reduction of the fracture and radiologic visualization were achieved. No wound infections, no relevant bleedings, and no spiral fractures of screws were observed. In two cases malpositioning led to revision of the screws. Of interest, one case of S1 paresthesia resulting from a malpositioned screw could be revised. In contrast, two cases of screw loosening and one case of screw bending did not require further intervention. CONCLUSION: We conclude that safe positioning of the sacroiliac screws was accomplished by all surgeons given a standardized technique. For safe insertion preparation of the patients, accurate visualization of the fracture zone, and potential closed reduction is always required.     

Thoracic pedicle screw instrumentation using the "Funnel Technique": part 2. Clinical experience

This study is a retrospective review of the clinical results of patients treated with thoracic pedicle screws using the "funnel technique." The objective is to report the clinical results of patients treated with thoracic pedicle screws using the funnel technique for screw placement. A total of 115 patients treated with the use of at least one thoracic pedicle screw were retrospectively identified. All patients were treated at a single medical center, under the senior author's supervision. Twenty-five different residents were responsible for placing 50-60% of these screws, and five different fellows and the senior author placed the remainder. The accuracy of screw placement and the complications related to the use of thoracic pedicle screws were analyzed by assessing intraoperative and postoperative charts and radiographs. There were 115 patients (age range 9-82 years) with the average follow-up period of 17 months. The total number of screws used was 348; the screw diameter ranged from 4.0 to 7.75 mm. There were no vascular or pulmonary complications. There was no iatrogenic neurologic injury, except for one patient who developed a transient anterior thigh numbness from intraoperative positioning. In fracture patients, 35% (10 of 28) had documented neurologic improvement postoperatively. There were no obviously misplaced pedicle screws on detailed review of intraoperative and postoperative radiographs. No screws had to be electively removed for complications related to misplacement. There were four broken screws, one broken rod, two loose screws, and three connector disengagements. Two patients had deep infections and four patients had pseudarthrosis requiring additional surgery. The clinical results proved that thoracic pedicle screws can be safely placed with the funnel technique.     

改良枢椎椎板螺钉置钉方法的临床应用

目的设计一种改良的枢椎椎板螺钉置钉方法并应用于临床,使螺钉置入更简单、更准确。方法改良枢椎椎板螺钉置钉方法的进钉点仍为棘突和椎板的交界处,但在椎板中份用磨钻磨除少许皮质开窗,用刮匙刮除松质骨,保留椎板内板,用手钻沿着枢椎椎板钻孔,在直视下通过开窗处,再继续向前钻入,探针探查钉道并攻丝后置入直径3.5~4.0 mm、长度24~30 mm螺钉。临床应用26例,其中男17例,女9例,平均年龄56.7岁。结果共置入42枚枢椎椎板螺钉,螺钉平均长度为27.1 mm(24~30 mm),术中无需透视,术中和术后无明显技术相关的并发症发生。术后即刻或随访CT示椎板螺钉位置正确,均位于椎板间。全组病例平均随访13.4个月,未发生螺钉松动、脱出或断裂。结论改良的枢椎椎板螺钉置入技术操作简单,无需透视,并保证了螺钉处于正确位置。     

Biomechanical analysis of a novel hook-screw technique for C1-2 stabilization

The Food and Drug Administration has not cleared the following medical devices for the use described in this study. The following medical devices are being discussed for an off-label use: cervical lateral mass screws. Object As an alternative for cases in which the anatomy and spatial relationship between C-2 and a vertebral artery precludes insertion of C-2 pedicle/pars or C1-2 transarticular screws, a technique that includes opposing laminar hooks (claw) at C-2 combined with C-1 lateral mass screws may be used. The biomechanical stability of this alternate technique was compared with that of a standard screw-rod technique in vitro. Methods Flexibility tests were performed in 7 specimens (occiput to C-3) in the following 6 different conditions: 1) intact; 2) after creating instability and attaching a posterior cable/graft at C1-2; 3) after removing the graft and attaching a construct comprising C-1 lateral mass screws and C-2 laminar claws; 4) after reattaching the posterior cable-graft at C1-2 (posterior hardware still in place); 5) after removing the posterior cable-graft and laminar hooks and placing C-2 pedicle screws interconnected to C-1 lateral mass screws via rod; and 6) after reattaching the posterior cable-graft at C1-2 (screw-rod construct still in place). Results All types of stabilization significantly reduced the range of motion, lax zone, and stiff zone compared with the intact condition. There was no significant biomechanical difference in terms of range of motion or lax zone between the screw-rod construct and the screw-claw-rod construct in any direction of loading. Conclusions The screw-claw-rod technique restricts motion much like the standard Harms technique, making it an acceptable alternative technique when aberrant arterial anatomy precludes the placement of C-2 pars/pedicle screws or C1-2 transarticular screws.     

青少年特发性脊柱侧凸应用Ball tip技术置入椎弓根钉的准确性

目的针对需要手术治疗的青少年特发性脊柱侧凸,通过与传统徒手置钉技术比较来评价一种新的椎弓根置钉技术—Ball tip技术置入椎弓根钉的准确性。方法自2009年5月~2011年5月,对28例青少年特发性脊柱侧凸,术中应用椎弓根球形探针(ball tip probe)置入椎弓根。结果采用Ball tip技术共置入193枚椎弓根钉,传统徒手技术置入161枚螺钉。术后CT扫描显示Ball tip组椎弓根钉钉道准确率为89.1%,共有21枚(10.9%)置钉不良螺钉,其中5枚(2.6%)穿透椎弓根内侧骨皮质,16枚(8.3%)穿透外侧骨皮质。徒手置钉组准确率为75.2%,共有40枚(24.8%)置钉不良螺钉,其中11枚(6.8%)穿透椎弓根内侧骨皮质,29枚(18.0%)穿透外侧骨皮质。两组置钉准确率的差异具有统计学意义(P<0.01),两组螺钉穿透椎弓根内侧、外侧骨皮质的差异具有统计学意义(P<0.05)。结论与传统徒手置钉技术相比,椎弓根Ball tip技术,可准确地置入椎弓根钉,减少因螺钉误置所导致的术后并发症。     

Accuracy of pedicle screws following instrumented dorsal fusion of the lumbar spine]

We evaluated the placement of pedicle screws (N = 131) in 30 patients after lumbar dorsal spinal fusion. Postoperatively all patients were examined by CT. 39.9% of all screws penetrated the cortex of the vertebra. Of special interest were those implants which led to medial penetration of the pedicle, which is of potential hazard to the neural structure within the nerve root canal. 28.5% of all screws showed a medial deviation. In our study, a penetration of more than 6 mm coincided with a high risk for nerve root damage. In 2 patients there was proven damage to a nerve root due to screw placement. In another 3 patients coherence was likely to exist. The technique of transpedicular screw fixation for spinal fusion is highly demanding and should be performed only by experienced surgeons after a clear indication and after a trial of intense conservative therapy.     

Modified lumbopelvic fixation for sacral and L5 fractures associated with spinopelvic instability: a case report and introduction of the surgical technique

Posterior lumbopelvic fixation with iliac screws is the most commonly used method for unstable spinopelvic injuries. It has certain limitations including inability to use distraction along the spinopelvic rod as an indirect reduction maneuver, need for complex 3-dimensional rod contouring and complications such as hardware prominence and soft tissue coverage. In the present case report,we described a surgical technique of lumbopelvic fixation with sacral alar screws for traumatic spinopelvic instability resulted from a unilateral Denis-Ⅲ comminuted sacral fracture and the L5 burst fracture. On the opposite side of the sacral fracture, caudal screws were implanted into the pedicle of the S1, whereas on the side of sacral fracture, two sacral alar screws were placed parallel to the superior sacral endplate as well as the plane of sacroiliac joint. In addition,horizontal stabilization was conducted with cross-link connections to maintain the longitudinal traction. For sacral fracture associated with traumatic spinopelvic instability,this modified lumbopelvic fixation technique using sacral alar screws makes longitudinal reduction easier, requires less rod contouring, and reduces hardware prominence without compromising the stability.     

Cervical and upper thoracic screwing for spinal fusion: strategy for its safe insertion to avoid major complications

There are several screwing techniques to attain cervical fusion such as pedicle screw, lateral mass screw, facet screw, transarticular and laminar screw. Each screwing technique has advantages and disadvantages. In this study, we introduce our strategy for safe screwing and its clinical results. Our strategy is as follows: lateral mass screw for C1, 3, 4, 5, 6 and pedicle screw for C2, 7, and thoracic level. When the C2 pedicle is thinner than 3.5 mm, we use C2 laminar screws. We do not use Magerl transarticular screw or facet screw; 146 screws were inserted in 17 patients. There were no major complications such as spinal cord and nerve root injury. We did not observe vertebral arterial injury either. Of the 146 screws, 141 (97.0%) were accurately inserted. As for lateral mass screwing by Roy-Camille’s technique and C2 laminar screwing, all screws were inserted in the appropriate site (100%) without any complications. Five pedicle screws were misplaced. Of the 57 pedicle screws, 5 showed a minor tear of the wall at C7, Th1 and Th3, the success rate for all pedicle screws was 91%. All showed solid fusion. For cervical screwing the most important aspect should be safety to avoid severe morbidity. Our strategy, which consists in the combined use of pedicle, lateral mass and laminar screwing, is safe and reliable.     

The stability of bone screws in the os sacrum

A variety of points of insertion and implantation techniques are recommended for inserting screws into the os sacrum. On the basis of 16 complete human sacrum specimens the following axial pull-out tests were performed: 1. Insertion of convergent measuring screws, 6.0 mm and 7.0 mm in outside diameter respectively, into the body of vertebra S1 using a monocortical and bicortical technique respectively with perforation of the ventral cortex. 2. Insertion of divergent screws into the ala sacralis at the level of S1 with 6-mm and 7 mm screws respectively, using a monocortical technique without perforation of the ventral cortex. 3. Insertion of convergent 6-mm screws into the body of vertebra S2 using a monocortical and bicortical technique respectively with perforation of the ventral cortex. The highest axial pull-out force was reached using convergent 6-mm screws inserted into the body of vertebra S1 using the bicortical technique with perforation of the ventral cortex (2392.4 N). The use of a 7.0-mm screw in the same implantation technique did not result in higher pull-out forces (2274.7 N). The monocortical technique reached a pull-out force of 1657.53 N with a 6-mm screw and 1505.64 N with a 7-mm screw. Convergent insertion of 6-mm screws into the body of S2 resulted in pull-out forces of 537.02 N using a bicortical and only 297.71 N using a monocortical technique. Divergent insertion of screws into the ala sacralis reached a maximal pull-out force of 495.47 N using 6-mm screws and 449.79 N using 7-mm screws. These data resulted from a monocortical implantation technique without perforation of the ventral cortex of the ala sacralis. The results of the present biomechanical study show that convergent bicortical implantation in the body of S1 is the most stable technique for screw fixation in the sacrum. The use of 7-mm rather than 6-mm screws did not lead to increased primary stability. Anatomic studies have shown that a safe area exists in the region of the ventral promontory, so this implantation technique appears to be unobjectionable. Received: 3.0.5 May 1997 Revised: 4 October 1997 Accepted: 2 February 1998     

漏斗技术结合探针技术置入胸椎椎弓根螺钉在脊椎畸形矫形术中的应用

目的 探讨应用漏斗技术结合探针技术置入胸椎椎弓根螺钉在脊椎畸形矫形术中的实用性和安全性。方法 12例脊椎畸形患者接受了后路矫形固定术,在手术矫形过程中,胸椎椎弓根螺钉的置入均采用“漏斗技术结合探针技术”,记录术中和术后并发症;术后常规复查X线片和CT,记录穿出骨皮质螺钉数目及距离。结果 采用“漏斗技术结合探针技术”共置入胸椎椎弓根螺钉129枚,术后复查CT见129枚螺钉中2枚穿透椎弓根内侧壁,3枚螺钉穿破外侧壁;1枚螺钉穿透椎体前壁。Heary分级,其置钉准确性达96.12%。结论 在脊椎畸形矫形术中,应用“漏斗技术结合探针技术”置入胸椎椎弓根螺钉的方法是实用的、安全的。     

Effects of screw eccentricity on the initial stability of the acetabular cup

One of the major failure modes of cementless acetabular components is the loosening of the acetabular cup, which is mostly attributable to insufficient initial stability. A hemispherical cup with a porous coating which is inserted with press-fit fixation and secured with several screws is one of the most widely used approaches. Many studies have found that bone screws are very helpful aids for cup fixation, but the optimal surgical technique for inserting screws has not been clearly reported. In this study, hemispherical cups were fixed into blocks of foam bone with zero to three screws. The effects of three types of screw eccentricity (a 1-mm offset and angular eccentricities of 15 degrees and 25 degrees ) on the initial stability of the acetabular cup were evaluated. The experimental results indicate that increasing the number of screws enhances the cup stability in the case of ideal screwing (i.e., with no eccentricity). An angular eccentricity of 15 degrees did not affect the cup stability for fixation with one or two screws. However, the presence of 25 degrees of angular eccentricity significantly reduced the stability of the cup, while 1 mm of offset eccentricity produced an even greater impact.     

The ‘MW’ sacropelvic construct: an enhanced fixation of the lumbosacral junction in neuromuscular pelvic obliquity

Fixation to the lumbosacral spine to correct pelvic obliquity in neuromuscular scoliosis has always remained a surgical challenge. The strongest fixation of the lumbosacral junction has been achieved with either a Galveston technique with rods or screws or with iliosacral screws. We have devised a new fixation system, in which iliosacral screws are combined with iliac screws. This is made possible by using the AO Universal Spine System with side opening hooks above and below the iliosacral screws and iliac screws below it. The whole sacropelvis is thus encompassed by a maximum width (MW) fixation, which gives an ‘M’ appearance on the pelvic radiographs and a ‘W’ appearance in the axial plane. We report on our surgical technique and the early results where such a technique was used. We feel that this new means of fixation (by combining the strongest fixation systems) is extremely solid and should be included in the wide armamentarium of sacropelvic fixation. Received: 31 July 1998 Revised: 26 October 1998 Accepted: 10 November 1998     

Modification of the Traditional Open Latarjet Technique with the Use of Sutures and Cortical Buttons Instead of Screws

In this article we describe a modification of the open Latarjet technique, using sutures and cortical buttons, for the fixation of the coracoid. The transfer of the coracoid to the anterior glenoid is a popular technique used for complex shoulder instability. The technique is proven to be effective with consistently good results but complications have been reported related to the screws used for the fixation of the coracoid. Recent studies confirm that the suture-button technique for the fixation of the coracoid is biomechanically comparable to the screw fixation. The proposed technique combines the advantages of the open approach and avoids the use of metal screws, potentially minimizing hardware-related complications.