Unilateral Pedicle Screw Fixation Research Articles

Unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation in treatment of lumbar disc herniation

Objective:To explore the application and efficiency of unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation in treatment of lumbar disc herniation.Methods:From Feb.2006 to Feb.2008,24 patients underwent unilateral vertebral plate decompression,interbody fusion and pedicle screw fixation.The patients were followed up for one year and the following data were recorded:operation time,estimated blood loss,duration of hospital-stay,short-term and medium-term clinical outcome.Results:All patients had their low back pain and/or lower extremity radicular pain improved during the one year follow-up.The last follow-up showed that the numbers of patients with Oswestry Disability Index(ODI) P0-P5 were 5,11,6,2,0,and 0,respectively.The clinical outcomes determined by modified JOA criteria showed that 18 patients had excellent outcomes,4 had good outcomes,and 2 had fair outcomes,with the excellent and good outcomes occupying 91.67%.Conclusion:The unilateral fixation can be used in patients with lumbar disc herniations who need lumbar spinal fusion.The medium-term outcomes is satisfactory.

Preliminary experiences in minimally invasive transforaminal lumbar interbody fusion

To explore clinical application of minimally invasive transforaminal lumbar interbody fusion (TLIF) for the management of lumbar disorders and discuss its indications, surgical techniques and clinical effectiveness. From Jan 2005 to Dec 2006, 31 selected patients (22 males and 9 females, aged from 41 to 63 years) with degenerative lumbar diseases were treated with minimally invasive TLIF assisted by METRx X-Tube micro-endoscopy system. The index diagnosis was lumbar disc herniation with Lumbar spinal stenosis in 7, lumbar disc herniation with segmental instability in 16, grade 1 to 2 of lumbar spondylolisthesis in 8. The surgical methods was performed with bilateral or unilateral pedicle screws insertion and a single rectangle cage posterolateral placement. The operating time, blood loss, blood transfusion, drainage, visual analogue scale (VAS), preoperative and postoperative JOA scores were observed as well as radiographic evaluation. The results were compared with standard TLIF group respectively. A total of 116 pedicle screws and 31 cages were implanted of which 4 patients were treated with unilateral pedicle screws fixation. Four pedicle screws were found misplaced in CT scans after surgery. The average operating time was 199 min, blood loss 359 ml, volume of transfusion 32 ml drainage 81 ml, and VAS was 2.37 about 72 hours after surgery, which had statistic difference compared with control group. There was no statistic difference on postoperative improvement rate and JOA scores in two groups. Minimally invasive TLIF minimizes paraspinal muscle trauma and blood loss, shortens the operating and recovery time. A good long-term outcome can be gained compared with standard procedures.

Posterior Migration of Fusion Cages in Degenerative Lumbar Disease Treated With Transforaminal Lumbar Interbody Fusion

A case report of 3 patients with posterior migration of bullet-shaped fusion cages after transforaminal lumbar interbody fusion (TLIF). One patient required emergency revision surgery; the other 2 patients are being observed during conservative treatment. To review cases of posterior migration of fusion cages and report ensuing clinical courses. TLIF is a commonly used procedure; however, there are few reports describing cage migration after the procedure. In most cases, when posterior cage migration follows posterior lumbar interbody fusion, emergency revision surgery is required. One recent study reported a case of posterior cage migration after TLIF, which was treated conservatively. Posterior migration of the bullet-shaped fusion cages occurred 1 to 2 months after TLIF in 3 patients. One of the 3 patients had isthmic spondylolisthesis treated by TLIF with bilateral pedicle screw fixation. The other 2 patients had degenerative scoliosis and were treated by TLIF with unilateral pedicle screw fixation. The patient with isthmic spondylolisthesis required revision surgery because the migrated cage caused nerve root irritation. The migrated cage was removed and a large-sized cage was employed to achieve stability. The other 2 patients had no pathologic symptoms after the posterior migration of the cage and were treated conservatively and observed. Revision surgery after TLIF appears relatively safe because the migrated cage tends to locate more laterally than in patients with cage migration after posterior lumbar interbody fusion. Cage migration subsequent to TLIF may not cause compression of neural tissues, so conservative treatment may suffice for these patients. Unilateral pedicle screw fixation may not provide sufficient stability to prevent cage migration in patients with degenerative scoliosis. Further study is needed to clarify surgical indications for unilateral pedicle screw fixation in TLIF.

Biomechanical change of lumbar unilateral graded facetectomy and strategies of its microsurgical reconstruction: report of 23 cases

Objective To evaluate the lumbar stability and the primary clinical results of unilateral facetectomy, transforaminal lumbar interbody fusion (TLIF) and unilateral pedicle screw fixation by X-Tube system. Methods Five human lumbar cadaveric functional spine units(FSU) were obtained and graded facetectomy by 0, 1/4, 1/2, 3/4 and 4/4 were performed respectively on the left articular process of them. The stability of these 5 models was evaluated at flexion, extension, lateral bending and axial rotation. After a serial of biomechanical researches, 23 patients from June 2004 to March 2006 in our department underwent unilateral facetectomy, transforaminal lumbar interbody fusion (posterior lumbar interbody fusion) and unilateral pedicle screw instrumentation by X-Tube system. After general anaesthesia, with the guide of fluoroscopy and using X-Tube system, procedures of unilateral endoscopic facetectomy, spinal nerve root decompression, autologus spongy bone transplantation, one cage oblique insertion and unilateral pedicle screw instrumentation were performed. Results There was no significant difference in flexion, extension, lateral bending and axial rotation of lumbar motion range after unilateral graded facetectomy. The stability of left/right axial direction was greatly affected when the range of graded facetectomy exceed 1/2. According to the Nakai criteria, for the 23 patients, the clinical result was excellent in 15 (65.2%), good in 6 (26.1%) and fair in 2 (8.7%). The fusion rate was 95.6% in excellent and good cases. Although partial absorption of bone grafts was observed in 1 case which might indicate a unsuccessful fusion, there was no loosing and replacement of instrument and no clinical symptoms occurred. Conclusion The lumbar stability will be affected significantly when the range of graded facetectomy exceeds 1/2. Procedures of unilateral facetectomy, transforaminal lumbar interbody fusion and unilateral pedicle screw fixation is an optional strategy for microsurgical reconstruction, though the indications of the procedure should be carefully restricted.

Unilateral pedicle screw fixation with X-tube in lumbar spinal fusion

Unilateral pedicle screw fixation with X-tube in lumbar spinal fusion

Minimally invasive transforaminal lumbar interbody fusion with unilateral pedicle screw fixation

Posterior lumbar interbody fusion (PLIF) has been shown to be effective in the treatment of axial low-back pain. Minimally invasive spine surgery for arthrodesis has several advantages, including quicker patient recovery, less postoperative pain, and less destruction of adjacent tissue. The purpose of this paper is to evaluate the clinical outcomes after PLIF procedures in which unilateral pedicle screw fixation was used. Prospective data were collected in 34 patients undergoing a one-level minimally invasive transforaminal lumbar interbody fusion (TLIF) in 2003. Conservative therapy, including physical therapy and aggressive multimodality pain management, had failed in all patients. Selection was based on magnetic resonance imaging studies demonstrating degenerative disc disease. All patients underwent a unilateral TLIF procedure in conjunction with posterior unilateral pedicle screw fixation. Twenty patients in whom the follow-up duration was longer than 6 months were included in this study. The follow-up duration in all patients ranged from 6 to 12 months. Seventeen (85%) of 20 patients had a good result, which was defined as a greater than 20-point reduction in the Oswestry Disability Index (ODI) score. The other three patients had no improvement. The mean preoperative ODI score of 57 improved to 25 after surgery (p < 0.005). In the 17 patients who demonstrated improvement, the mean ODI score improved from 57 to 18. The patients' visual analog scale pain scores improved from 8.3 to 1.4 (p < 0.005) after surgery. In patients who received Workers' Compensation, three (75%) of four improved. Follow-up computerized tomography scans were obtained in all 20 patients at 6 months. At that time, 13 of the patients demonstrated some degree of fusion, and no symptomatic pseudarthrosis was noted. Minimally invasive TLIF in conjunction with unilateral pedicle screw instrumentation is an effective treatment for axial low-back pain in appropriately selected patients.

Paramedian approach for transforaminal lumbar interbody fusion with unilateral pedicle screw fixation

Lumbar fusion is a commonly performed procedure for a variety of pathological conditions, and it is frequently used in the treatment of degenerative lumbar instability that is refractory to medical management. Pedicle screws and interbody devices have been used for internal fixation to promote arthrodesis, prevent nonunion, and facilitate early mobilization. Recently, attempts have been made to reduce the morbidity associated with lumbar fusion by using a variety of minimally invasive techniques. Many minimally invasive lumbar fusion procedures require specialized retractors, implants, image guidance systems, or insertion instruments. Other minimally invasive techniques are primarily applied to an ideal patient population (thin, healthy, and with no previous surgery). The authors describe their experience with a paramedian approach for minimally invasive transforaminal lumbar interbody fusion (TLIF) with unilateral pedicle screw (PS) fixation. This procedure requires only standard implants, instruments, and retractors, with direct visualization for all aspects of the procedure. The authors describe encouraging early results in a challenging patient population in which there was a high incidence of obesity, medical comorbidities, and previous surgery at the same level. The paramedian approach for TLIF performed using unilateral lumbar PSs has yielded successful outcomes in this series of 47 patients, and further study of this technique may help define its role as a minimally invasive procedure for spinal fusion.

SPIRE spinous process stabilization plate: biomechanical evaluation of a novel technology

The authors studied the biomechanical properties of a novel spinous process stabilization plate (CD HORIZON SPIRE Spinal System) and present the results in comparison with those of other posterior fixation methods. Ten functional cadaveric lumbar segments were subjected to nondestructive quasistatic loading forces in 10 different conditions: intact, destabilized (discectomy), fitted with spinous process plate (SPP) alone, with anterior-column support (ACS) alone, ACS with SPP, ACS with posterior translaminar facet screw (PTFS) fixation, ACS with unilateral pedicle screw and rod (UPSR) fixation, ACS with bilateral pedicle screw and rod (BPSR) fixation, UPSR alone, or BPSR alone. Stiffness and range of motion (ROM) data were compared using a repeated-measures, one-way analysis of variance. The construct with greatest mean limitation of flexion-extension ROM was ACS/SPP at 4.14 degrees whereas it was 5.75 degrees for ACS/UPSR fixation, 5.03 degrees for ACS/BPSR fixation, and 10.13 degrees for the intact spine. The SPIRE plate alone also provided greater flexion and extension stiffness, with less ROM than other posterior stabilization options. Fixation with BPSR with or without ACS resulted in the stiffest construct in lateral bending and axial rotation. The SPP and UPSR fixation groups were equivalent in resisting lateral bending and axial rotation forces with or without ACS. The SPIRE plate effectively stabilized the spine, and the test results compare favorably with other fixation techniques that are more time consuming to perform and have greater inherent risks.

Less invasive posterior fixation method following transforaminal lumbar interbody fusion: a biomechanical analysis

Background context Current surgical trends increasingly emphasize the minimization of surgical exposure and tissue morbidity. Previous research questioned the ability of unilateral pedicle screw instrumentation to adequately stabilize posterior fusion constructs. No study to date has addressed the effects of reduced posterior instrumentation mass on interbody construct techniques. Unilateral surgical exposure for transforaminal lumbar interbody fusion (TLIF) allows ipsilateral pedicle screw placement. Theoretically, percutanous contralateral facet screw placement could provide supplemental construct support without additional surgical exposure. Purpose Identify the biomechanical effects of reduced spinal fusion instrumentation mass on interbody construct stability. Study design An in vitro biomechanical study using human lumbar spines comparing stability of TLIF constructs augmented by: (1) bilateral pedicle screw fixation, (2) unilateral pedicle screw fixation, or (3) a novel unilateral pedicle screw fixation supplemented with contralateral facet screw construct. Methods Seven fresh frozen human cadaveric specimens were tested in random construct order in flexion/extension, lateral bending, and axial rotation using ±5.0 Nm torques and 50 N axial compressive loads. Analysis of torque rotation curves determined construct stability. Using paired statistical methods, comparison of construct stiffness and total range of motion within each specimen were performed using the Wilcoxon signed ranks test with a Holm-Sidák multiple comparison procedure (α = 0.05). Results In flexion/extension, lateral bending, and axial rotation, there were no measurable differences in either stiffness or range of motion between the standard bilateral pedicle screw and the novel construct after TLIF. After TLIF, the unilateral pedicle screw construct provided only half of the improvement in stiffness compared with bilateral or novel constructs and allows for significant off-axis rotational motions, which could be detrimental to stability and the promotion for fusion. Conclusions All tested TLIF constructs with posterior instrumentation decreased segmental range of motion and increased segmental stiffness. While placing unilateral posterior instrumentation decreases overall implant bulk and dissection, it allows for signficantly increased segmental range of motion, less stiffness, and produces off-axis movement. The technique of contralateral facet screw placement provides the surgical advantages of unilateral pedicle screw placement with stability comparable to TLIF with bilateral pedicle screws.

Biomechanical Analysis of Posterior Fixation Techniques in a 360° Arthrodesis Model

A biomechanical study to assess the ability of posterior fixation techniques to stabilize a functional spine unit (FSU) after insertion of an anterior load-sharing device. The objective of this study is to compare various posterior fixation techniques in combination with an anterior load-sharing implant. Pedicle screws and translaminar facet screws have been shown to improve the stiffness of an FSU in combination with an anterior load-sharing device. No published studies, to our knowledge, have compared translaminar facet screw fixation versus bilateral and unilateral pedicle screw fixation used with an anterior load-sharing device. Ten cadaveric FSUs were potted using methylmethacrylate and attached to a spine simulator mounted to an MTS Mini-Bionix testing machine. The simulator was configured to control compressive loading, axial torque, flexion, extension, and lateral bending. Each specimen was tested in the intact state and following the application of each of four stabilization techniques: custom cage alone, cage plus translaminar facet screw fixation, cage plus unilateral pedicle screw and plate fixation, and cage plus bilateral pedicle screw and rod fixation with transverse coupling. Compressive stiffness and total range of motion (ROM) between +/-8 Nm of torque were extracted from the raw data. Each fixation method decreased ROM in torsion, flexion-extension, and lateral bending compared with the intact state. Unilateral pedicle fixation offered less stability than either of the other posterior fixations in all modes of testing except axial loading, where it was equivalent. Translaminar facet screw fixation was equivalent to bilateral pedicle screws in all modes tested. Using a load-sharing interbody implant, translaminar facet screws are equivalent to bilateral pedicle screws in resisting motion in all three planes. Translaminar facet screws and bilateral pedicle screws offer greater stabilization in all three planes compared with unilateral pedicle screws and a single plate.

Unilateral Lumbar Fusion

Unilateral fusion of the lumbar spine is rarely necessary or indicated. However, in patients with a "far-out syndrome" requiring decompression or in cases where unilateral posterior element resection is necessary for any reason, it may be both necessary and indicated. This unilateral destabilization effectively removes one leg of the tripod, rendering that intervertebral joint potentially unstable. The charts and radiographs of 13 patients (seven men, six women) with an average age of 60 years (range, 25 to 76) who underwent unilateral fusion were retrospectively reviewed. Follow-up time ranged from 12 1/2 to 2 years with a median follow-up of 8 years. Eleven of the fusions were at one level, and two were at two levels. Seven patients had a far-out syndrome secondary to degenerative scoliosis; four were secondary to spondylolisthesis. Two patients had an osteoid osteoma involving a pedicle. A paraspinal approach was used in the majority of patients. Autologous bone graft was used in all patients. Unilateral pedicle screw fixation was used in the last patient in the series. The fusion rate was 85% (11/13). Three patients were smokers, two of whom developed pseudarthrosis. Disc space height did not appear to affect fusion rate. There was no progression of slip noted in any of the patients. One complication was noted in this group: a moderate postoperative infection, which cleared spontaneously.