Segmental spinal instrumentation without sublaminar wires

We have developed a method of segmental spinal instrumentation that precludes the passage of sublaminar wires, thus reducing the likelihood of neurological complications. The technique utilizes the base of the spinous process as the purchase site for segmental fixation and a newly developed button-wire implant. The technique and early experience with this method are described.     

Tension band wiring-bone grafting for spondylolysis and spondylolisthesis. A clinical and biomechanical study

Patients with spondylolysis or spondylolisthesis with persistent symptoms often require surgical treatment. The purpose of this article is to present a new surgical technique and clinical results of 13 patients with symptomatic spondylolysis/spondylolisthesis who were treated with tension band wiring (intra- or intersegmental) and bone grafting techniques. This article also presents the results of biomechanical effects of these tension band wiring methods on canine lumbar spines with experimental spondylolytic defects. Thirteen adult patients, three with spondylolysis, and ten with spondylolytic spondylolisthesis, were treated with intrasegmental or intersegmental wiring with bone grafting technique, and the clinical results were evaluated at the mean follow-up period of 20 months. Patients with spondylolysis were treated with intrasegmental wiring (transverse processes to the spinous process of the same segment) with bone grafting at the lytic defect. Patients with spondylolytic spondylolisthesis were treated with intersegmental wiring (transverse process of the segment with defect to the spinous process of the same segment and to the spinous process of the segment below) with bone grafting to the defect and one-level fusion. All 13 patients had a solid spinal fusion and/or healing of the defect at the follow-up evaluation. Eleven had excellent clinical results; one a good, and one a fair result. The results of the biomechanical study showed that the experimental spondylolytic defect produced a significant decrease in bending stiffness (flexion-extension), and the wiring techniques (both the intra- and intersegment) increased the bending stiffness to that of the normal intact spinal segment.     

Segmental spinal instrumentation in idiopathic scoliosis. A preliminary report

Eighty-six patients with idiopathic scoliosis who underwent a posterior spinal fusion using sublaminar segmental spinal instrumentation were analyzed retrospectively. There were two operative groups: group 1, 66 patients who had Harrington rod instrumentation and segmental wiring, and group 2, 20 patients who had Luque rod instrumentation. The clinical and radiographic data of the two groups were similar except for the passage of more sublaminar wires and increased intraoperative blood loss in group 2. Twenty intraoperative or postoperative complications occurred in 19 patients (22%) including 14 neurologic complications. Three patients (3%) had major spinal cord injuries, while 11 patients (13%) had transient sensory changes. There was no significant difference in the incidence of neurologic complications between group 1 or group 2. The remaining intraoperative complications were due either to anesthesia, positioning during surgery, or technique (dural tear). Late complications occurred in two patients in group 1 only: one each with rod breakage and hook displacement. Only one patient (1%) has required additional surgery. Our results indicate that although segmental instrumentation can be beneficial in idiopathic scoliosis, the incidence of complications, primarily neurologic, will be higher than expected. The major reason appears to be surgeon inexperience with passage of sublaminar wires. As experience increases, the incidence of complications declines and becomes comparable with conventional Harrington rod instrumentation alone.     

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.     

Spinous process segmental instrumentation for scoliosis

Spinous process segmental instrumentation (SPSI) for spinal fusion was devised in 1983 by Drummond et al. in an attempt to achieve the stability of segmental fixation without the known neurologic risks of passing sublaminar wires. We used SPSI in 75 scoliosis patients. Sixty-one had idiopathic scoliosis, 12 had neurogenic scoliosis, and 2 had congenital scoliosis. There were no deep infections, pseudarthroses, or neurologic complications. Two patients experienced upper hook dislodgement with 10 degrees loss of correction. We concluded that SPSI can achieve the correction of Harrington rod instrumentation and the stability of Luque rod segmental instrumentation, without the neurologic risk of sublaminar wiring.     

Segmental spinal instrumentation without sublaminar wires

Summary We have developed a method of segmental spinal instrumentation that precludes the passage of sublaminar wires, thus reducing the likelihood of neurological complications. The technique utilizes the base of the spinous process as the purchase site for segmental fixation and a newly developed buttonwire implant. The technique and early experience with this method are described.

---

Zusammenfassung Wir haben eine Methode der instrumentellen segmentalen Wirbelsäulenstabilisie-rung entwickelt, die die Verwendung wirbelbogenumgreifender Drähte vermeidet and dadurch die Wahrscheinlichkeit neurologischer Komplikationen herabsetzt. Diese Technik vermendet einen neuentwickelten Knopfdraht and wählt als Ort der Fixation die Basis des Dornfortsatzes. Die Technik dieser Methode and erste Erfahrungen werden mitgeteilt.

     

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.     

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.     

Evaluation of spinous process wire fixation with Harrington instrumentation for idiopathic scoliosis

A modification of the technique of Harrington instrumentation for idiopathic scoliosis utilizes segmental spinous process wiring. The purpose of this study is to contrast and compare two populations of surgically treated patients with idiopathic scoliosis: one group with a single Harrington distraction rod and the other group with the addition of spinous process wiring. Of 252 consecutive patients between 1971 and 1987, 215 were retrievable, with an average clinical follow-up of 2.2 years. Curves were analyzed by location and patient age. Patients treated with spinous process wires were braced, those without were casted. No significant difference in terms of percent correction with time was evident between the two treatment groups. The complication rate (11.0%) and pseudarthrosis rate (4.0%) were the same in both wired and standard groups. The more rigid adult curves resulted in less correction and greater complications than adolescent curves. Spinous process wiring seemed to protect against upper hook cut-out. There were no deaths or paraplegias. Patients surgically treated with the wire modification enjoyed greater comfort with the removable brace, and curve correction was equal to that obtained in patients treated with the standard technique and post-op casting.     

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.     

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.     

Harrington instrumentation with spinous process wiring for idiopathic scoliosis

To provide the stability of segmental spinal instrumentation without the risk associated with the passing of sublaminar wires, a technique of SSI was developed that uses the base of the spinous process as a site for purchase. To provide a broad attachment to the spinous process, a button-wire implant was developed. The rods used are a Harrington distraction rod for the concave side of the curve and a Luque rod for the convexity. Both are attached to the spine at each level by the button-wire implant. Biomechanical testing confirms that the implant provides load sharing, an advantage over wire alone, and that the instrumented spine is stable when compared with other systems. Clinical review showed approximately 60 per cent correction of the average curve, a small correction loss, and a better sagittal alignment than achieved previously with Harrington distraction alone. Complications were few.     

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.     

Sublaminar wiring stabilization to prevent adjacent segment degeneration after lumbar spinal fusion

Introduction  Adjacent segment degeneration (ASD) is a complication of lumbar spinal fusion. There are some reports on the cause of this degeneration but none concerning its prevention. We performed sublaminar wiring stabilization to prevent ASD after posterolateral lumbar spinal fusion with instrumentation. The purpose of this study was to prospectively evaluate the efficacy of this procedure. Patients and methods  Between 2003 and 2004, 54 consecutive patients with lumbar spinal canal stenosis and multilevel instability of the lumbar spine underwent posterior decompression and posterolateral fusion with instrumentation. The mean age at the time of surgery was 66.7 ± 1.3 years, and the mean follow-up period was 40.0 ± 1.1 months, with a minimum of 29 months. Twenty-seven of the patients underwent conventional sublaminar wiring stabilization at the cephalad segment adjacent to the site of fusion to prevent ASD (group A), and the other 27 patients did not (group B). Some items were assessed, including clinical outcome using Japanese Orthopaedic Association (JOA) score, sagittal global lumbar alignment, and segmental motion in flexion–extension radiographs of the cephalad vertebral body adjacent to the site of fusion. Results  There were no significant differences in JOA scores between two groups, but 2 patients in group B underwent subsequent surgery due to ASD. Sagittal lumbar alignment did not change in group A but was significantly decreased in group B. With respect to segmental motion in flexion–extension radiographs, group A showed a significant decrease from 6.9° before surgery to 3.4° after surgery, on the other hand group B showed a significant increase from 5.6° before surgery to 8.4° after surgery. Conclusions  In this study, it was suggested that sublaminar wiring stabilization significantly reduces the range of motion of the adjacent segment and preserves sagittal lumbar alignment, which lead to prevention of ASD. The clinical outcome of the subsequent surgeries is relatively poor, so it is important to prevent ASD by any prevention such as sublaminar wiring stabilization.     

The effect of Luque-rod instrumentation on the sagittal contour of the lumbosacral spine in adolescent idiopathic scoliosis and the preservation of a physiologic lumbar lordosis.

The changes in the sagittal alignment of the lumbar spine were investigated in 28 patients with adolescent idiopathic scoliosis undergoing long posterior spinal fusion to L4 or L5 with contoured Luque rods and segmental sublaminar wiring. The lumbar lordosis over the instrumented levels was preserved, and there was no compensatory hyperlordosis of vertebral segments distal to the fusion. In situations where long posterior spinal fusions are indicated, instrumentation with contoured Luque rods and segmental sublaminar wiring can preserve the normal sagittal alignment of the lumbosacral spine.     

Neurological complications in segmental spinal instrumentation: analysis of 750 patients

The authors report on neurological damage caused by the use of sublaminar segmental fixation in the correction of vertebral deformities. Three groups were reviewed: 600 patients instrumented with Harrington rods and segmental wiring, 50 patients treated with the Hartshill system and 100 patients instrumented with Luque bars. All of the patients were operated on using sublaminar wiring fixation. We report two transitory neurological complications among the 600 patients with Harrington rod instrumentation and segmental wiring, two permanent neurological deficits among the 50 cases treated with the Hartshill system and none among the 100 patients instrumented using Luque bars. The purpose of this study is to analyse the causes of these neurological complications, which occurred late in all four of the cases described.Presented at the ESDS meeting, Birmingham, 1994, and selected for full publication     

A comparison between spinous process and sublaminar wiring combined with Harrington distraction instrumentation in the management of adolescent idiopathic scoliosis

A study of the efficacy of two techniques of spinal instrumentation on patients with adolescent idiopathic scoliosis was performed. Twenty consecutive patients treated with a single Harrington distraction rod and sublaminar wiring (H-SL) were compared with 20 consecutive patients treated with a single Harrington distraction and spinous process wiring (H-SP). The patients in both groups were similar in age, curve magnitude, curve flexibility, and curve type. The immediate postoperative correction (61% H-SL, 58% H-SP) and follow-up correction (50% H-SL, 49% H-SP) were equivalent. No pseudarthroses were recognized in either group. One patient with H-SL had transient postoperative paresthesias.     

Transarticular screw fixation for atlantoaxial instability - modified Magerl's technique in 38 patients

Background  

Symptomatic atlantoaxial instability needs stabilization of the atlantoaxial joint. Among the various techniques described in literature for the fixation of atlantoaxial joint, Magerl's technique of transarticular screw fixation remains the gold standard. Traditionally this technique combines placement of transarticular screws and posterior wiring construct. The aim of this study is to evaluate clinical and radiological outcomes in subjects of atlantoaxial instability who were operated using transarticular screws and iliac crest bone graft, without the use of sublaminar wiring (a modification of Magerl's technique).     

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.     

Postoperative neurological deficits in segmental spinal instrumentation. A study using spinal cord monitoring

We retrospectively analyzed the postoperative neurological complications in 137 patients who underwent a posterior spine fusion for scoliosis and had concomitant somatosensory cortical evoked-potential spinal-cord monitoring. The patients were divided into three specific operative groups: group 1, forty-nine patients who had a Harrington rod with segmental wiring (segmental spinal instrumentation); group 2, twenty patients who had Luque segmental spinal instrumentation; and group 3, sixty-eight patients who had a Harrington rod without segmental spinal instrumentation. There were neurological complications in twelve (17 per cent) of the sixty-nine patients in groups 1 and 2. Three patients (4 per cent) had a major injury to the spinal cord and nine patients (13 per cent) had only transient sensory changes. No difference was apparent between group 1 and group 2 in the degree of operative correction of curves or in the incidence of neurological complications. The one neurological complication (1.5 per cent) that occurred in the sixty-eight patients in group 3 was a Brown-Séquard syndrome. The factors related to increased risk for spinal cord injury in groups 1 and 2 included: (1) the passage of sublaminar wires in the thoracic and thoracolumbar spine, (2) intraoperative correction exceeding the preoperative bending correction, and (3) the surgeon's lack of adequate experience with the technique. With spinal cord monitoring we were able to predict the impending major neurological deficits, but the transient (sensory) changes that may be associated with segmental wiring were less reliably predicted.