Depth of intraspinal wire penetration during passage of sublaminar wires

A major concern with the use of sublaminar wires for segmental spinal instrumentation is the risk of neurologic compromise associated with repeated passage of wires through the epidural space. Because of the inability to visualize the wire tip during its sublaminar passage, the surgeon is unable to appreciate the depth of wire penetration (DOWP). The purpose of this investigation was to determine, through direct measurement, the depth of intraspinal penetration during the passage of sublaminar wires. Using their model, the authors have been able to define the optimal parameters for safe wire passage. Careful attention to maintaining contact between the wire tip and the under-surface of the lamina, using a wire of optimal configuration, will result in minimal DOWP and reduce the possibility of neurologic compromise.     

Safety of sublaminar wires with Isola instrumentation for the treatment of idiopathic scoliosis

STUDY DESIGN: To investigate the incidence of acute neurologic complications of use of sublaminar wires with third-generation spine instrumentation for the treatment of idiopathic scoliosis. OBJECTIVES: To assess the safety of sublaminar wires in the surgical treatment of idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: The use of sublaminar wires in spine deformity for neuromuscular scoliosis and the Luque system has been reported. Use of sublaminar wires is an integral part of the technique in the surgical treatment of spine deformity with Isola instrumentation (AcroMed, Cleveland, OH). To date, the safety of this technique has not been documented. METHODS: The average age of the patients was 37 years (range, 11-74 years). Preoperative diagnosis was adolescent idiopathic scoliosis in 75 patients and adult idiopathic scoliosis in 66. One hundred nine were primary surgeries, and 32 were revision. Detailed evaluation of the curve type, curve magnitude, number of vertebrae instrumented, level of vertebrae wired, postoperative neurologic deficit, and the findings of intraoperative spinal cord monitoring was performed. Wires were always passed just before corrective maneuvers were performed. RESULTS: A total of 1366 wires were placed, 65% (n = 888) in the thoracic region, 22% (n = 300) in the thoracolumbar, and 13% (n = 178) in the lumbar. No permanent change in intraoperative spinal cord monitoring was detected. Stagnara wake-up test was performed in all patients. No patient with adolescent idiopathic scoliosis had neurologic complication. Two adults underwent revision surgery and had transient dysesthesia in the leg, which completely resolved with observation. CONCLUSION: Despite the increasing complexity of spinal instrumentation systems, sublaminar wire placement is a safe and useful adjunct in the surgical treatment of neurologically intact patients with idiopathic scoliosis.     

A biomechanical study of 3 different types of sublaminar wire used for constructs in the thoracic spine

A biomechanical study was carried out on 3 different types of sublaminar wire used in constructs to secure the thoracic spine: stainless steel monofilament wire (steel wire), titanium cable (cable), and ultra-high molecular weight polyethylene tape (tape). Two experiments were carried out. Experiment 1: Thirty-one fresh human thoracic vertebrae classified as osteoporotic (bone mineral density of <0.8 g/cm2) were used. The steel wire, cable, or tape was placed sublaminarly and a tensile force was applied until the steel wire, cable, or tape cut 5 mm through the lamina, and the force at this point was noted. Experiment 2: Seven fresh human thoracic spines (T7-T10) were biomechanically tested as follows: axial compression (250 N), flexion (7.5 Nm), extension (7.5 Nm), left lateral bending (7.5 Nm), right lateral bending (7.5 Nm), left axial torsion (10 Nm), and right axial torsion (10 Nm). This sequence was applied to the intact spine. The spine was then de-stabilized and then restabilized using one or other of the 3 different types of sublaminar wires. The biomechanical testing was then repeated on the restabilized spine and stiffness curves were generated. In the laminar cut-through test, the cut-through force for tape was higher than that for either steel wire or cable. In the biomechanical stiffness testing, there was no significant difference between the 3 different sublaminar wiring constructs in any of the loading modes tested. The results of both experiments suggest that tape is as good, if not better, than steel wire or cable as a sublaminar wiring construct material.     

Intraspinal pathways taken by sublaminar wires during removal. An experimental study

The neurological complications of segmental sublaminar stabilization that have been reported by other authors led us to perform a cineradiographic study of the pathways in the spinal canal that were taken by wires as they were being removed. The single wires were removed by pulling on the wire while keeping the wire perpendicular to the lamina; by winding the wire on the wire-extractor, with the wire being kept as nearly parallel with the lamina as possible (the roll-up technique); or by pulling on the wire while keeping the wire parallel with the lamina. During removal, thirty-four single wires conformed to the lamina and forty-one single wires compressed the dura. The roll-up technique caused the most erratic pathways. Double wires, although they were removed together, assumed independent pathways unless a wire-extractor guide was used. These findings suggest that the removal of sublaminar wires may cause dural compression in the clinical situation.     

Biomechanical evaluation of a new fixation device for the thoracic spine

The technology used in surgery for spinal deformity has progressed rapidly in recent years. Commonly used fixation techniques may include monofilament wires, sublaminar wires and cables, and pedicle screws. Unfortunately, neurological complications can occur with all of these, compromising the patients’ health and quality of life. Recently, an alternative fixation technique using a metal clamp and polyester belt was developed to replace hooks and sublaminar wiring in scoliosis surgery. The goal of this study was to compare the pull-out strength of this new construct with sublaminar wiring, laminar hooks and pedicle screws. Forty thoracic vertebrae from five fresh frozen human thoracic spines (T5–12) were divided into five groups (8 per group), such that BMD values, pedicle diameter, and vertebral levels were equally distributed. They were then potted in polymethylmethacrylate and anchored with metal screws and polyethylene bands. One of five fixation methods was applied to the right side of the vertebra in each group: Pedicle screw, sublaminar belt with clamp, figure-8 belt with clamp, sublaminar wire, or laminar hook. Pull-out strength was then assessed using a custom jig in a servohydraulic tester. The mean failure load of the pedicle screw group was significantly larger than that of the figure-8 clamp (P = 0.001), sublaminar belt (0.0172), and sublaminar wire groups (P = 0.04) with no significant difference in pull-out strength between the latter three constructs. The most common mode of failure was the fracture of the pedicle. BMD was significantly correlated with failure load only in the figure-8 clamp and pedicle screw constructs. Only the pedicle screw had a statistically significant higher failure load than the sublaminar clamp. The sublaminar method of applying the belt and clamp device was superior to the figure-8 method. The sublaminar belt and clamp construct compared favorably to the traditional methods of sublaminar wires and laminar hooks, and should be considered as an alternative fixation device in the thoracic spine.     

Comparison of novel ultra-high molecular weight polyethylene tape versus conventional metal wire for sublaminar segmental fixation in the treatment of adolescent idiopathic scoliosis

STUDY DESIGN: Retrospective study. OBJECTIVES: To compare the surgical outcomes of posterior translational correction and fusion using hybrid instrumentation systems with either sublaminar Nesplon tape or sublaminar metal wire to treat adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Nesplon tape, which consists of a thread of ultra-high molecular weight polyethylene fibers, has advantages over metal wire: (1) its soft and flexible properties avoid neural damage and (2) its flat configuration avoids focal distribution of the stresses to lamina; however, the efficacy of Nesplon tape in the correction of spinal deformity is as yet, still unclear. METHODS: Thirty AIS patients at a single institution underwent posterior correction and fusion using hybrid instrumentation containing hook, pedicle screw, and either sublaminar polyethylene taping (15) or sublaminar metal wiring (15). Patients were evaluated preoperatively, immediately after surgery, and at a 2-year follow-up according to the radiographic changes in curve correction, operating time, intraoperative blood loss, complications, and the Scoliosis Research Society patient questionnaire (SRS-24) score. RESULTS: The average correction rate was 63.0% in the Nesplon tape group and 59.9% in the metal wire group immediately after surgery (P = 0.62). Fusion was obtained in all the patients without significant correction loss in both groups. There was no significant difference in operative time, intraoperative blood loss, and postoperative SRS-24 scores between the 2 groups. Complications were superficial skin infection in a single patient in the Nesplon tape group, and transient sensory disturbance in 1 patient and temporal superior mesenteric artery syndrome in another patient in the metal wire group. CONCLUSIONS: The efficacy of Nesplon tape in correction of deformity is equivalent to that of metal wire, and fusion was completed without significant correction loss. The soft and flexible properties and flat configuration of Nesplon tape make this a safe application for the treatment of AIS with bone fragility or with the fusion areas containing the spinal cord.     

陈旧性寰枢椎脱位与枕颈不稳的手术治疗

目的　观察两种内固定方法治疗陈旧性寰枢椎脱位与不稳的疗效。方法　自 1992—2 0 0 0年收治 36例陈旧性寰枢椎脱位与枕颈不稳的患者 ,年龄 12～ 6 1岁 ,平均 38岁 ;病程 1个月～ 8年 ,平均 16个月。 2 2例颅骨牵引复位或基本复位的 ,用 Gallie法寰枢椎固定 ,C1～ 2 髂骨植骨。 9例牵引未复位和 5例枕颈区畸形的 ,用 Ransford环固定 ,枕颈区减压 (C0 ～ C2 )和枕颈植骨融合。结果　 1例术后 4天死亡 ,35例随访 3个月～ 4年。寰枢椎固定 2 2例中 2 1例获骨性融合 ,2例复位不满意 ,其中 1例植骨不愈合。Ransford法 13例有 12例骨性融合 ,1例植骨块断裂未愈合 ,但内固定无松动。术后神经功能明显改善。结论　颅骨牵引复位的陈旧性寰枢椎脱位 ,Gallie法寰枢椎固定疗满意。 Ransford环固定对枕颈区减压和枕颈融合能提供可靠的固定作用。     

The chronic local effects of sublaminar wires. An animal model

An animal model was established to determine the chronic effects of sublaminar wires. Nine dogs were instrumented with sublaminar wires, sacrificed at intervals up to 155 days, then subjected to wire removal under cineradiographic myelography and histologic analysis. Common dural sac indentation by the wires during extraction averaged 47% of the total myelographic column width, with no correlation to time implanted. Epidural, subdural, and intramedullary hemorrhage, epidural adhesions, dural lacerations, cord indentations, and neural damage were all present with no correlation to time implanted. Dural thinning was more pronounced in later specimens. These data suggest that sublaminar wires are not innocuous to the dural sac and its contents in this canine experimental model.     

Segmental spinal instrumentation using short closed wire loops

The Luque technique of segmental sublaminar instrumentation is now an established method of internal fixation in spinal surgery. The major difficulty encountered with the current technique is the danger of neurologic injury during the passage and handling of conventional wires, especially in extensive procedures. Great care is required to prevent inadvertent percussion of the wires already passed. The authors believe that by using short closed wire loops, these dangers have been minimized. Simple additional instrumentation has been devised to facilitate application of these loops. Apart from ease of application and handling, the short wire loops may offer a safer method of segmental sublaminar fixation.     

Experimental study of removal of sublaminar wires after spinal fixation

The result of experimental study of removal of sublaminar wires was reported. The experimental shows that sublaminar wires when with drawn at 45-degrees is safer than that at 90-degrees. Because of bony fusion, clinically could be drawn out only vertically either by rolling it up ward or down ward confirmed that there is no difference between this two methods. The cut end of wire should be short and straight. All the fixing wires became useless because of their loosening. Impressions were found on the inner face of lamina, fibrous sheaths. There is no different reactions between twisted and parallel double wires, but we recommend double parallel wires.     

Spinal cord monitoring during operative correction of neuromuscular scoliosis.

We report our experience of the monitoring of spinal somatosensory evoked potentials in 60 patients with neuromuscular scoliosis. In 15 cases a significant change occurred in the trace when a sublaminar wire was tightened. There were no postoperative neurological deficits attributable to the surgery.     

Posterior cervical fusion with triple-wire strut graft technique: one hundred consecutive patients.

One hundred consecutive patients were treated by the triple-wire stabilization and fusion technique for acute cervical trauma (36 patients), rheumatoid arthritis (27 patients), degenerative osteoarthritis (20 patients), congenital deformities (13 patients), or neoplasms (11 patients). The triple wire technique developed by Bohlman is versatile enough to be used at any level of the cervical spine, with 60 patients undergoing subaxial fusions, 20 with atlantoaxial fusions, and 20 with stabilization to the occiput. The immediate stability is evidenced by the fact that only two of 60 subaxial triple-wire stabilizations required the use of a Halovest, 58 being managed postoperatively in two-poster orthosis. The fusion rate was 100% for subaxial fusions. The only pseudarthrosis occurred in an occiput to C2 triple wire fixation procedure, which was managed nonoperatively. There were no iatrogenic neurologic complications, unlike the use of techniques utilizing sublaminar wires, and there were no cervical infections.     

Sublaminar wiring

A technique for sublaminar wiring is described. This technique emphasizes prevention of deep penetration of the wires into the spinal canal by a method of crimping the wire around the lamina. The authors have experienced a low neurologic injury rate with this technique.     

The treatment of spinal fractures with Harrington compression rods and segmental sublaminar wiring. A dangerous combination

The increasing use of more rigid internal fixation constructs for spinal fractures, especially in association with spinal cord injury, has led surgeons to combine sublaminar segmental wiring with Harrington instrumentation systems. Two clinical cases whose neurologic condition deteriorated postoperatively were shown to have sustained direct cord injury by the combination of Harrington compression rods with segmental sublaminar wiring. Myelographic and surgical evidence of hook protrusion into the spinal canal with direct cord injury is presented. Laboratory spine simulations duplicating the clinical situation did demonstrate that sublaminar wiring of the Harrington compression rod system caused the standard hooks to protrude dangerously into the spinal canal. Caution should be exercised not to combine Harrington compression rods with segmental sublaminar wiring.     

Complications of sublaminar wiring

Complications of sublaminar wiring are reported, including four cases that involved the cervical spine and one case that included the thoracolumbar spine. The complication rate at our institution involving the cervical spine was about 7% and less than 1% for the thoracic spine. A direct correlation exists between the degree of anterior bowing, number of consecutive laminae the wire passes beneath, and the complication rate. The clinical presentations, radiologic findings, and indications for surgical removal of the wires are discussed. To our knowledge, nothing has been reported in the literature regarding the complications caused by sublaminar wiring of consecutive vertebrae.     

The effect of sublaminar wires on the rib hump deformity during scoliosis correction manoeuvres

Introduction

During thoracic curve correction, the tightening of the sublaminar wires through concavity creates a medial and a dorsal translation of the spine. However, little is known about the effect of the sublaminar wires on the axial plane.

Methods

This is prospective case series analysis of 30 consecutive surgical patients with main thoracic adolescent idiopathic scoliosis. All of the patients were fused with hybrid instrumentation (apical concavity–sublaminar wires) and differential rod contouring (over-kyphosis concavity/under-kyphosis convexity). The degrees of the rib hump were measured with a scoliometer placed at the apex of the deformity at five different times: (1) preoperatively through the Adam’s test, and during surgery (sterilised scoliometer), (2) with the patient lying prone, (3) after the Ponte osteotomies, (4) after the apical sublaminar tightening, and (5) after convexity apical derotation and compression manoeuvres.

Results

(1) Preoperatively, the Adam’s test was 16.3° ± 4.6. (2) Lying prone and under general anaesthesia, it decreased to 11.4° ± 3.9. (3) After exposure and Ponte osteotomies, it was 7.1° ± 4. (4) After the wire tightening, it was 10.8° ± 4.7. (5) After the convexity manoeuvres, it was 4.8° ± 3.7. The degrees of the rib hump final correction were 11.6° ± 4 (70 % correction). The tightening of the sublaminar wires increased the rib hump by 3.5°.

Conclusions

The sublaminar wire tightening towards the concave rod seemed to create an effect opposite of the desired effect, increasing the apical rotation and the thoracic rib hump deformity. Convexity manoeuvres (apical screw derotation and compression) are necessary and must be coupled with an under-bending of the convex rod to neutralise this effect.

     

Square-lashing technique in segmental spinal instrumentation: a biomechanical study

Sublaminar wires have been used for many years for segmental spinal instrumentation in scoliosis surgery. More recently, stainless steel wires have been replaced by titanium cables. However, in rigid scoliotic curves, sublaminar wires or simple cables can either brake or pull out. The square-lashing technique was devised to avoid complications such as cable breakage or lamina cutout. The purpose of the study was therefore to test biomechanically the pull out and failure mode of simple sublaminar constructs versus the square-lashing technique. Individual vertebrae were subjected to pullout testing having one of two different constructs (single loop and square lashing) using either monofilament wire or multifilament cables. Four different methods of fixation were therefore tested: single wire construct, square-lashing wiring construct, single cable construct, and square-lashing cable construct. Ultimate failure load and failure mechanism were recorded. For the single wire the construct failed 12/16 times by wire breakage with an average ultimate failure load of 793 N. For the square-lashing wire the construct failed with pedicle fracture in 14/16, one bilateral lamina fracture, and one wire breakage. Ultimate failure load average was 1,239 N For the single cable the construct failed 12/16 times due to cable breakage (average force 1,162 N). 10/12 of these breakages were where the cable looped over the rod. For the square-lashing cable all of these constructs (16/16) failed by fracture of the pedicle with an average ultimate failure load of 1,388 N. The square-lashing construct had a higher pullout strength than the single loop and almost no cutting out from the lamina. The square-lashing technique with cables may therefore represent a new advance in segmental spinal instrumentation.     

Isola内固定系统治疗特发性脊柱侧凸椎板下钢丝的安全性

目的评价椎板下钢丝技术在特发性脊柱侧凸手术中的安全性。方法本组14例患者,平均年龄为14．5岁(9-21)岁。患者术前诊断均为青少年特发性脊柱侧凸,且均为首次手术。本文对所有患者的侧凸类型、严重程度、固定椎体的数量、钢丝固定的椎体水平、术后神经学并发症以及术中脊髓监测的变化进行了详细评估。所有患者的椎板下钢丝均在矫正操作之前进行。结果总计放置了76根钢丝,75％(n=57)位于胸椎,20％(n=15)位于胸腰段,5％(n=4)位于腰椎。术中脊髓监测未发现明显的改变。所有患者均成功进行了唤醒试验。在青少年特发性脊柱侧凸患者中未发现有神经学并发症。结论尽管脊柱内固定系统越来越复杂,椎板下穿钢丝的技术在无神经症状的特发性脊柱侧凸患者的手术治疗中还是安全有效的辅助技术。     

Stability of different wiring techniques in segmental spinal instrumentation

The pullout force of sublaminar and transspinous wires for segmental instrumentation which had been inserted into different segments of human cadaver spines were campared. Four different types of wiring were tested: single and double sublaminar wires, button-wires according to Drummond's technique and button-wires with the additional use of two crimps for each spinous process. A total of 50 tests were performed. In all attempts the bone proved to be the limiting factor. None of the 300 fixed wires failed. Typical types of fractures appeared with different wiring techniques. There was no statistically significant difference between the sublaminar wiring techniques tested. However, there were significant differences between sublaminar and transspinous wiring. The transspinous techniques achieved between 30% and 45% of the pull-out strength of sublaminar techniques. The forces decreased with increasing cranialisation. In all techniques the values in the upper segment (D5–D3) were almost half those of the lower segment (L5–L3). The differences of the transspinous techniques increased cranially, in favour of the technique with additional crimps. Thus, the crimps have the strongest effect on weak spinous processes. This study demonstrates that in non-dynamic testing, the stability of the bone and not the type of wiring is the limiting parameter in segmental spinal stabilisation. As the wires are inserted in different areas, the transspinous technique shows significantly lower tension forces in comparison with sublaminar wiring.     

Studies of an L-rod sublaminar wire spinal fusion

The spine of a 25-year-old man with Duchenne muscular dystrophy was studied postmortem, 8 years after spine fusion with L-rods and sublaminar wires. The fusion was solid. Instrumentation appeared to have had no adverse effects on the spinal cord or meninges or in the epidural space. When wire removal from the spinal canal and fusion mass was studied, increased penetration of the wires into the spinal canal was noted.