Unilateral Pedicle Screw Fixation Research Articles

Comparison of the Unilateral and the Bilateral Pedicle Screw Fixation without Using an Interbody Cage: Randomized Clinical Trial

BACKGROUND: Lumbar spine instability is one of the main causes of low back pain and has become more prevalent in recent years. Bilateral pedicle screw fixation is used to perform posterior lumbar stabilization, which is complemented by the installation of an interbody cage. AIM: The aim of the study was evaluating of the results of unilateral and bilateral pedicle screw fixation without using of an interbody cage. METHODS: A prospective randomized study of 96 patients was carried out. Forty-seven patients were assigned to the group of the unilateral pedicle screw fixation versus 49 patients were moved to the group of the bilateral pedicle screw fixation of the lumbar spine. Of the 96 patients, 80 patients eventually were included in the study. However, seven patients in the first group and nine patients were lost to follow-up. Surgery timing, blood loss volume, clinical outcomes (scores on the Oswestry disability index [ODI], EQ-5D and visual analogue scale [VAS]) were evaluated in 6–12 months after surgical treatment. All the patients included in this study underwent functional and control computed tomography in 12 months after surgery. RESULTS: Both groups showed a significant improvement in VAS, EQ-5D, and ODI in 1 year after surgical treatment. The two groups significantly differed in the surgery timing (unilateral – 90.2 min; and bilateral – 129.4 min) and blood loss volume (unilateral – 152.7 ml; and bilateral – 230.1 ml), p < 0.05. CONCLUSIONS: Unilateral and bilateral pedicle screw fixation showed similar clinical results, while results in both types of fixation differed in slight manner. However, the duration of surgical treatment and intraoperative blood loss volume proved to be lower for the unilateral fixation group, which indicates that the use of the unilateral fixation can be the choice of performing posterior stabilization at a single-level instability of the spine without using an interbody cage.

Treatment of Degenerative Lumbar Scoliosis with Oblique Lumbar Interbody Fusion in Conjunction with Unilateral Pedicle Screw Fixation via the Wiltse Approach.

ObjectiveTo evaluate the clinical outcomes of oblique lumbar interbody fusion (OLIF) in conjunction with unilateral pedicle screw fixation (UPSF) via the Wiltse approach in treating degenerative lumbar scoliosis (DLS).MethodsThe article is a retrospective analysis. Twelve patients with DLS who underwent combined OLIF and UPSF between July 2017 and December 2018 were included. The study included 2 male and 10 female patients, with a mean age at the time of the operation of 67.2 ± 9.1 years. The surgical characteristics and complications were evaluated. The clinical and radiological data such as the correction of deformity, coronal and sagittal profile were analyzed.ResultsThe mean follow‐up time of the study was 26.8 ± 1.8 months. At the final follow‐up, all patients who underwent combined OLIF and UPSF achieved statistically significant improvements in coronal Cobb angle (from 19.6° ± 4.8° to 6.9° ± 3.8°, P < 0.01), distance between the C7 plumb line and central sacral vertebral line (from 2.5 ± 1.7 cm to 0.9 ± 0.6 cm, P < 0.01), sagittal vertebral axis (from 4.3 ± 4.3 cm to 1.5 ± 1.0 cm, P = 0.03), lumbar lordosis (from 29.4° ± 8.6° to 40.8° ± 5.8°, P < 0.01), pelvic tilt (from 27.6° ± 10.8° to 18.3° ± 7.0°, P < 0.01), pelvic incidence‐lumbar lordosis mismatch (from 23.3° ± 10.5° to 11.9° ± 8.4°, P < 0.01), and cross‐sectional area of the dural sac (from 87.33 ± 39.41 mm2 to 124.70 ± 39.26 mm2, P < 0.01). The visual analogue score for back and leg pain and Oswestry Disability Index of all patients significantly improved postoperatively (P < 0.01). One case of lumbar plexus injury was found after surgery. During the follow‐up period, one patient had cage subsidence. A fusion rate of 100% and good positioning of the pedicle screws were achieved in all patients at the final follow‐up.ConclusionOLIF in conjunction with UPSF is a safe and effective minimally invasive procedure for correcting both coronal and sagittal deformities, as it results in an improved quality of life in patients with DLS.

Channel-assisted fixation and interbody fusion in treating recurrent lumbar disc herniation by muscle-splitting approach

To explore the clinical value and safety of unilateral pedicle screw fixation combined with contralateral translaminar facet screw fixation and interbody fusion by muscle-splitting approach treatment of recurrent lumbar disc herniation. The clinical data of 51 patients with recurrent lumbar disc herniation treated from June 2012 to December 2017 were retrospectively analyzed. There were 32 males and 19 females, aged 34 to 64 years with an average of (51.11± 7.28) years. Lesions invoved L4,5 in 38 cases and L5S1 in 13 cases. All patients had a history of lower back pain and radiation pain of lower limbs(3 bilateral and 48 unilateral)and underwent unilateral pedicle screw combined with contralateral translaminar facet screw fixation and interbody fusion, among which 24 patients were treated through median incision approach (median incision group);other 27 patients were treated through muscle-splitting approach with channel-assisted exposure(muscle-splitting approach group). Operation time, intraoperative blood loss, postoperative drainage and incision length of the two groups were recorded. Visual analogue scale (VAS) was used to score the pain of lumbar incision at 72 h after operation, and JOA low back pain scoring system was used to evaluate the lumbar function preoperatively and at final follow-up. Imaging data were analyzed, including the changes in the height of intervertebral space of diseased segment before operation, 3 to 5 days after operation, and at final follow-up;Cobb angle changes in the coronal and sagittal planes of lumbar spine preoperatively and at final follow-up;multifidus area and multifidus fatty tissue deposition grade before and 12 months after operation; postoperative pedicle screw and laminar process screw position and intervertebral fusion condition. The complications of the two groups were compared. There was no statistical difference in operation time between two groups (P>0.05). Muscle-splitting approach group was better than median incision group in light of incision length, intraoperative blood loss and postoperative drainage volume (P<0.05). VAS score of lumbar incision pain at 72 h after operation was 1.61±0.54 in median incision group and 0.76±0.28 in muscle-splitting approach group(P<0.05). All patients were followed up for 12 to 84 (43.50±15.84) months. At final follow-up, the JOA scores of the two groups were significantly improved compared with those before operation(P<0.05). The rate of pedicle screw malposition was 6.25%(3/48) in medianincision group and 9.26%(5/54) in muscle-splitting approach group, there was no statistically significant difference between two groups (P>0.05). Rate of translaminar facet screw malposition in median incision group (12.50%) was significant less than the muscle-splitting approach group (18.52%)(P< 0.05). The height of the intervertebral space of the two groups was significantly restored 3 to 5 days after operation (P<0.05), and there was also a significant loss of height at final follow-up (P<0.05). At final follow-up, the balance of lumbar coronal plane and sagittal plane in two groups were improved very well (P<0.05). The comparison of the area and grade of the multifidus muscle in two groups 12 months after operation showed that obvious damage to the multifidus muscle were present in the median incision, while the multifidus muscle was less damaged by muscle-splitting approach (P<0.05). The fusion rate was 91.7%(22/24) in the median incision group and 92.6%(25/27) in muscle-splitting approach group(P>0.05). In median incision group, there were 1 case of intraoperative pedicle entry point fracture, 1 case of intraoperative dural tear and 1 case of postoperative nerve root injury;in muscle-splitting approach group, there were 1 case of intraoperative pedicle entry point fracture, 2 cases of intraoperative dural tear, 1 case of postoperative nerve root injury, 2 cases of incision epidermal necrosis and 1 case of poor incision healing. Nerve root injuries in the two groups were caused by incorrect positions of pedicle screws, the screws were immediately adjusted upon discovery. The nerve root symptoms were completely recovered 3 and 6 months after surgery. No incision infection was occurred in two groups. During the follow-up, no pedicle screw and laminar facet screw were loosened, displaced, broken, or intervertebral fusion cage moved forward and backward. The complication rate of 25.93% in muscle-splitting approach group was higher than 12.50% in the median incision group (P<0.05). Muscle-splitting approach is feasible for thetreatment of recurrent lumbar disc herniation with pedicle screw fixation combined with contralateral translaminar facet screw fixation and interbody fusion. Compared with the median incision approach, the muscle-splitting approach has the advantages of small incision, less trauma, less bleeding, rapid recovery. Also it can protect multifidus and do not increase the incidence of serious complications. Thus, it can be used as a choice for fixation and fusion of recurrent lumbar disc herniation.

One Approach Anterior Decompression and Fixation with Posterior Unilateral Pedicle Screw Fixation for Thoracolumbar Osteoporotic Vertebral Compression Fractures.

ObjectiveThe objective of the present paper was to explore the clinical effect of one approach anterior decompression and fixation with posterior unilateral pedicle screw fixation for thoracolumbar osteoporosis vertebral compression fractures (OVCF).MethodsThis is a single‐center retrospective analysis. A total of six thoracolumbar OVCF patients (four women and two men) with an average age of 65.2 years (58–72 years) who were treated between June 2016 and May 2018 were enrolled in the present study. The lesion segments included: 1 case at T11, 1 case at T12, 3 cases at L1, and 1 case at L2. The six thoracolumbar OVCF patients were treated with one approach anterior decompression and fixation with posterior unilateral pedicle screw fixation. After general anesthesia, patients were placed in the right lateral decubitus position, an approximately 10–15‐cm oblique incision was made along corresponding ribs, and the conventional left retroperitoneal and/or the extrapleural approach was performed for anterior lateral exposure. First, anterior decompression and fixation were performed, and then through the unilateral paraspinal muscle approach, posterior pedicle screw fixation was performed under the same incision. The back pain visual analogue scale (VAS), the Oswestry disability index (ODI), and the MacNab criteria were used to evaluate the clinical outcome. The radiographic analysis included the regional kyphosis angle and the fusion rate. Neurological status, operation time, intraoperative bleeding, the time of ambulation, hospital stay, and surgical complications were also assessed.ResultsSurgery was successful in all six patients, who were followed up for 31.6 months (range, 23–46 months). The operation time was 125–163 min, with a median of 135 min. The preoperative blood loss was 580–1230 mL, with a median of 760 mL. The time of ambulation was 3–5 days, with a median of 4.2 days. The hospital stay was 8–15 days, with the median of 10.5 days. According to the Frankel classification of neurological deficits, of two patients with grade C preoperatively, one had improved to grade D and one had improved to grade E at final follow up; among four patients with grade D preoperatively, at the final follow up one remained the same and three had improved to grade E. The postoperative back pain VAS score decreased significantly, from 6.17 ± 0.75 preoperatively to 0.83 ± 0.41 postoperatively (P < 0.05). The mean ODI score was 73.7 ± 5.86 preoperatively and reduced to 21.85 ± 3.27 postoperatively (P < 0.05). According to the MacNab criteria, at the final follow up, two patients rated their satisfaction as excellent, three patients as good, and one patient as fair. The mean regional kyphosis angle was 22.17° ± 6.01°before surgery, which improved to 9.33° ± 3.88° at the final follow up (P < 0.05). At the final follow up, there were two patients who had achieved a grade 2 bony fusion (33.3%), three patients grade 3 (50.0%), and one patient grade 4 (16.7%). No incision infections, internal fixation failures or other complications were found during the perioperative and the follow‐up period.ConclusionOne approach anterior decompression and fixation with posterior unilateral pedicle screw fixation provides a novel method for thoracolumbar OVCF disease, with a satisfactory clinical outcome.

Unilateral pedicle screw fixation as a less invasive surgical procedure: a case series and literature review

Introduction: The principle of treatment for degenerative spinal diseases when conservative modality failed is surgery. Unilateral pedicle screw fixation is a less invasive methods with clinical outcomes that were similar to a bilateral fixation, especially for lumbar degenerative disease. Improvement of symptoms, neurological outcome and spinal stability is the utmost priority. This was a case series study with five patients with degenerative spine disease from January 2019 - January 2020. The aims are to evaluate unilateral pedicle screw surgery outcomes and elucidate the effectiveness of this method clinically.Case Description: Five patients aged 40-64 years old involved in this series. Four patients presented with lumbar radiculopathy and one patient with cervical radiculopathy. All experienced weakness (MMT score 2-4) and pain along the affected extremities. Three patients diagnosed with concomitant Herniated Nucleus Pulposus (HNP) and Foraminal Stenosis (FS) based on clinical examination and Magnetic Resonance Imaging result. The rest of two patients each diagnosed with FS and HNP. Surgery initiated with a midline incision. Muscle ipsilateral to the symptomatic side was dissected and retracted to expose the facet joint and the vertebral lamina. Screws were inserted into the vertebral body and the rod used to connect the screws was bent following the vertebral curvature. Facetectomy or Hemilaminectomy was done to expose and decompress the ipsilateral side's nerve root and intervertebral space. The incision site is then irrigated and closed. All operation was done by the same surgeon. Postoperative clinical outcomes were evaluated for six months after surgery. All patients showed a complete motor improvement and fully relieved from pain.Conclusion: Unilateral pedicle screw fixation is considered as a less invasive instrumentation system with clinical outcome comparable to bilateral screw fixation.

Biomechanical Analysis of an Interspinous Process Fixation Device with In Situ Shortening Capabilities: Does Spinous Process Compression Improve Segmental Stability?

The objective of this study was to characterize the biomechanical implications of spinous process compression, via in situ shortening of a next-generation interspinous process fixation (ISPF) device, in the context of segmental fusion. Seven lumbar cadaveric spines (L1-L4) were tested. Specimens were first tested in an intact state, followed by iterative instrumentation at L2-3 and subsequent testing. The order followed was 1) stand-alone ISPF (neutral height); 2) stand-alone ISPF (shortened in situ from neutral height; shortened); 3) lateral lumbar interbody fusion (LLIF)+ ISPF (neutral); 4) LLIF+ ISPF (shortened); 5) LLIF+ unilateral pedicle screw fixation; 6) LLIF+ bilateral pedicle screw fixation. A 7.5-Nm moment was applied in flexion/extension, lateral bending, and axial rotation via a kinematic test frame. Segmental range of motion (ROM) and lordosis were measured for all constructs. Comparative analysis was performed. Statistically significant flexion/extension ROM reductions: all constructs versus intact condition (P < 0.01); LLIF+ ISPF (neutral and shortened) versus stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF+ USPF versus ISPF (neutral) (P= 0.049); bilateral pedicle screw fixation (BPSF) versus stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF+ BPSF versus LLIF+ unilateral pedicle screw fixation (UPSF) (P < 0.01). Significant lateral bending ROM reductions: LLIF+ ISPF (neutral and shortened) versus intact condition and stand-alone ISPF (neutral) (P < 0.01); LLIF+ UPSF versus intact condition and stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF+ BPSF versus intact condition and all constructs (P < 0.01). Significant axial rotation ROM reductions: LLIF+ ISPF (shortened) and LLIF+ UPSF versus intact condition and stand-alone ISPF (neutral) (P ≤ 0.01); LLIF+ BPSF versus intact condition and all constructs (P ≤ 0.04). In situ shortening of an adjustable ISPF device may support increased segmental stabilization compared with static ISPF.

WITHDRAWN: Biomechanical comparison of unilateral and bilateral pedicle screws fixation for oblique lumbar inter-body fusion surgery – a finite element analysis

WITHDRAWN: Biomechanical comparison of unilateral and bilateral pedicle screws fixation for oblique lumbar inter-body fusion surgery – a finite element analysis

Unilateral versus bilateral Pedicle Screw Fixation associated with interbody fusion in degenerative Lumbar spine diseases

Abstract Background Lumbar interbody fusion is a recognized surgical technique in treatment of degenerative lumbar instability. Interbody fusion supplemented with pedicle screw fixation has several advantages over posterolateral fusion and has been advocated to improve fusion rates and clinical outcomes. Interbody fusion places the bone graft in the loadbearing position of the anterior and middle spinal columns thereby enhancing the potential for fusion. In addition, the interbody space has more vascularity than the posterolateral space, also increasing the potential for a solid fusion mass to form. Aim of the Work to assess safety and efficacy of unilateral pedicle screw fixation associated with interbody fusion in Lumbar spine degenerative diseases and to evaluate and compare outcomes of unilateral versus bilateral pedicle screw fixation associated with interbody fusion in lumbar spine degenerative diseases, as regard the operation time, bleeding, postoperative stay, cost, and the clinical and biomechanical results. Material &amp; Methods This observational prospective comparative study of the 2 groups who were operated either unilateral (Group A /25 patients) or bilateral (Group B/25 patients) pedicle screw fixation with interbody fusion was done. Patients were followed up for 1, 6, 12 months. This study occurred at Ain Shams University hospitals. Results No differences were observed between the two groups with respect to demographic data. The patients of the two groups had significant improvement in functional outcome compared to preoperatively, except in early postoperative VAS back and ODI in unilateral group which is better than bilateral group. However, no significant difference noticed in the further follow up. There was no significant difference comparing fusion rate, complication rate and duration of hospital stay between the two groups at postoperative follow-up. There was significantly less blood loss, shorter postoperative pain killer use and significantly shorter operation time in the unilateral PS fixation group as compared with the bilateral PS fixation group in our study. Conclusion Our study suggested TLIF with unilateral PS fixation was as safe and effective as that with bilateral PS fixation. Unilateral PS fixation may significantly reduce the intraoperative blood loss and shorten the operation time, somewhat improve the clinical outcome scores of ODI and VAS Back without significant difference comparing fusion rate, complication rate and duration of hospital stay between the two groups at postoperative follow-up. BPSF with TLIF likely causes more degeneration at the cranial adjacent segment compared with UPSF techniques. However, the long-term follow up is required to demonstrate the impact of these findings.

Management of recurrent unilateral lumbar disc herniation in a single level: unilateral versus bilateral pedicle screws fixation with interbody fusion

BackgroundLumbar interbody fusion procedure is a recognized surgical technique in management of a variety of lumbar pathologies including recurrent lumbar disc prolapse. Interbody fusion augmented by pedicle screw fixation has been considered to improve fusion rates and clinical outcomes. Interbody fusion is commonly associated with better fusion potentials through applying the bone graft in the load bearing, vascular position of the anterior, and middle spinal columns. However, it still remains unknown whether interbody fusion with unilateral pedicle screw fixation (UPSF) is superior to that with bilateral pedicle screw fixation (BPSF).Aim of the workThe aim of this study is to evaluate the efficacy and safety of unilateral versus bilateral pedicle screw fixation associated with interbody fusion for the management of single level unilateral recurrent lumbar disc prolapse as regard the clinical and biomechanical results, operation time, intraoperative blood loss, and postoperative stay.Material and methodsThis observational prospective comparative study of the two groups who were operated either unilateral (group A /15 patients) or bilateral (group B/15 patients) pedicle screw fixation with interbody fusion was done. Patients were followed up for 1, 6, ad 12 months.ResultsSignificant improvement in functional outcome of the two groups was noted compared to preoperatively, except in early postoperative period where the back VAS and ODI in the unilateral group was better than bilateral group. However, on further follow up, no significant difference was noticed. There was no significant difference comparing fusion rate, complication rate, and duration of hospital stay between the two groups at postoperative follow-up. There was significantly less blood loss, and significantly shorter operation time in the unilateral PS fixation group as compared with the bilateral PS fixation group in our study.ConclusionOur study suggested that TLIF with unilateral PS fixation was as safe and effective as that with bilateral PS fixation for the management of recurrent single level lumbar disc prolapse; it showed better clinical outcome scores of ODI and back VAS, and a significant reduction of the intraoperative blood loss as well as the operation time, without significant differences considering fusion rate, complication rate, and duration of hospital stay between the two groups at postoperative follow-up. However, BPSF with TLIF likely causes more degeneration at the cranial adjacent segment compared with UPSF techniques. Nevertheless, the long-term follow up is required to demonstrate the impact of these findings.

Minimally invasive injectable lumbar interbody fusion with mineralized collagen-modified PMMA bone cement: A new animal model.

This study was to develop a feasible and safe animal model for minimally invasive injectable lumbar interbody fusion using a novel biomaterial, mineralized collagen-polymethylmethacrylate bone cement (MC-PMMA), with unilateral pedicle screw fixation in an in vivo goat model. Eight goats (Capra aegagrus hircus) were divided into three groups: MC-PMMA, unmodified commercial-polymethylmethacrylate bone cement (UC-PMMA), and a control group (titanium cage filled with autogenous bone, TC-AB). Each group of goats was treated with minimally invasive lumbar interbody fusion at the L3/L4 and L5/L6 disc spaces (injected for MC-PMMA and UC-PMMA, implanted for TC-AB). The pedicle screws were inserted at the L3, L4, L5, and L6 vertebrae, respectively, and fixed on the left side. The characteristics of osteogenesis and bone growth were assessed at the third and the sixth month, respectively. The methods of evaluation included the survival of each animal, X-ray imaging, and 256-layer spiral computed tomography (256-CT) scanning, imaged with three-dimensional microfocus computed tomography (micro-CT), and histological analysis. The results showed that PMMA bone cement can be extruded smoothly after doping MC, the MC-PMMA integrates better with bone than the UC-PMMA, and all goats recovered after surgery without nerve damage. After 3 and 6 months, the implants were stable. New trabecular bone was observed in the TC-AB group. In the UC-PMMA group a thick fibrous capsule had formed around the implants. The MC-PMMA was observed to have perfect osteogenesis and bone ingrowth to adjacent bone surface. Minimally invasive injectable lumbar interbody fusion using MC-PMMA bone cement was shown to have profound clinical value, and the MC-PMMA showed potential application prospects.

Multilevel Unilateral Pedicular Screw Fixation with Interbody Fusion in Surgery of Double- and Triple-Segment Lumbar Disc Pathology

Background Data: In double- and triple-segment lumbar disc herniation, a facet hypertrophy is more encountered specially in the same side of disc herniation with subsequent ipsilateral concave curve scoliosis. Lumbar fixation with interbody fusion surgery is a scientific and feasible option. Some authors believe that unilateral pedicle screw fixation can provide similar biomechanical support to the traditional bilateral pedicle screw fixation. Purpose: To assess the strategy of use of unilateral pedicle screw fixation with lumbar interbody fusion in surgical treatment of multilevel (2-3) symptomatic lumbar disc herniation syndromes. Study Design: Retrospective observational analytic study. Patients and Methods: Retrospective evaluation of 216 patients' files who underwent unilateral pedicular screws fixation for management of degenerative lumbar disc pathology, from July 2007 to June 2017. Only 24 patient’s files were selected with multilevel symptomatic lumbar disc prolapse who were managed by unilateral pedicular screw fixation with interbody fusion. All patients were presented with symptoms of nerve root compression. Patients' data included age, gender, levels of disc prolapse, preoperative and postoperative Visual Analogue Scale (VAS) for back and leg and Oswestry Disability Index (ODI) for functional outcome, presence of complications, and finally patients’ satisfaction according to Odom’s criteria. VAS and ODI were retrieved preoperatively, immediately postoperatively, and 6 months postoperatively. Results: They were 18 males (75%) and 6 females (25%) with a male-to-female ratio of 3:1 and age ranging 35–63 years with a mean age of 49±9.8 years. Double-level disc prolapse was recorded in 20 (83.3%) patients, while it was triple in 4 cases (16.7%). At the last follow-up, back pain VAS improved from 7.5±1.47 to 1.12±1.03, leg pain VAS from 8.7±1.04 to 0.33±0.63, and ODI from 78±8.3 to 11.08±4.6. Excellent and good Odom’s outcomes were reported in 95% of our patients. Conclusion: Our study suggests that unilateral pedicular screw fixation with interbody fusion for the management of multiple level ipsilateral lumbar disc disease could be considered as an effective and less invasive method with satisfying clinical outcomes. (2019ESJ191)

Analysis of the clinical effects of different pedicle screw fixation methods for the treatment of thoracolumbar fractures

To discuss the clinical effects of the different pedicle screw fixation methods for the treatment of thoracolumbar fractures. The clinical data of 55 patients with single thoracolumbar fractures treated between January 2013 and December 2016 were retrospectively analyzed. There were 32 males and 23 females, aged from 20 to 55 years with an average of 35.6 years old. All the fractures were located on a single segment, 8 cases of T₁₁, 18 cases of T₁₂, 19 cases of L₁, 10 cases of L₂. According to the classification of AO, 10 cases were type A1, 17 cases were type A2, 18 cases were type A3, 7 cases were type B2, 2 cases were type B3, 1 case was type C1. The patients were divided into three groups according to the different fixation methods, among them, 20 cases treated by traditional short-segment 4 pedicle screws fixation were control group, 22 cases treated by intermediate bilateral pedicle screws fixation (6 pedicle screws fixation) were bilateral group, 13 cases treated by intermediate unilateral pedicle screw fixation (5 pedicle screws fixation) were unilateral group. The three groups were compared by operation time, intraoperative blood loss, hospitalization cost, VAS and ODI scores, the correction of the fractured vertebrae height and kyphosis angle postoperatively and the losing rate of the fractured vertebrae height and kyphosis angle at the final follow-up and so on. All the patients were followed up from 12 to 20 months with an average of 15.2 months. No complications such as loosening of internal fixation and breakage were found after operation. There was no significant difference in operation time and intraoperative blood loss among three groups(P>0.05). In terms of hospitalization cost, the control group[(20 932.4±298.3)yuan] was significantly lower than the unilateral group[(22 428.2±321.5)yuan] and the bilateral group [(23 630.5±310.5)yuan] (P<0.05), and the unilateral group was lower than the bilateral group (P<0.05). There was no significant difference in VAS and ODI scores at preoperative, postoperative 1 week and final follow-up among the groups(P>0.05). And there was no significant difference in the correction of the injuried vertebrae height and kyphosis angle immediately after operation among three groups(P>0.05). However, for the losing rate of the injuried vertebrae height at the final follow-up, the unilateral group[(6.3±2.1)%] and bilateral group [(5.6±2.8)%] were significantly better than the control group[(9.2±1.8)%] (P<0.05), there was no significant difference between unilateral group and bilateral group; for the losing rate of kyphosis angle at the final follow-up, the unilateral group[(15.2±6.5)%] and bilateral group[(13.9±7.2)%] were significantly better than the control group[(23.6±7.5)%] (P<0.05), but there was no statistical difference between the unilateral and bilateral group(P>0.05). All the three different pedicle screw fixation methods are suitable for the treatment of thoracolumbar fractures and the short-term clinical effects are consistent. Compared with traditional short-segment 4 pedicle screws fixation, intermediate bilateral or unilateral pedicle screw fixation were more effective in maintaining the height of the injuried vertebrae and preventing the occurrence of kyphosis. The intermediate unilateral pedicle screw fixation was comparable to that of bilateral fixation at clinical outcomes, but the unilateral fixed hospitalization cost was lower, which was worthy of clinical promotion.

Biomechanical study of intensity of pressure of intervertebral disc after short segment unilateral pedicle screw fixation in Chinese mini-pigs

Objective To explore the mechanical changes and distributions of pressure in each characteristic intervertebral disc after short segment unilateral pedicle screw fixation in Chinese mini-pigs. Methods Six characteristic spine segments of 6-week-old Chinese mini-pigs (T3-4、T11-12、T15-L1、L3-4、L4-5 segments with adjacent upper and lower vertebrae) were chosen as experimental models. A biomechanical machine and pressure sensitive film were used to measure the pressure on the vertebral columns when they were subjected to pressures of 200 N as unfixed group. Compression was carried out under vertical, 5 °flexion, 5 °extension and 5 °lateral bending, respectively. Then the PCF (posterior cervical fixation) system were fixed on all segments (left side) as fixed group, and biomechanical tests were repeated to obtain data. A Fujitsu densitometer (Japan) was used to measure the pressure on each direction of the pressure sensitive film. Results In vertical pressures, 5° flexion and 5°extension conditions, the posterior pressure of T3-4、T11-12、T15-L1、L3-4 and L4-5 intervertebral discs were decreased after fixation, the differences were statistically significant; The fixed side pressures of T3-4、T11-12、T15-L1、L3-4 and L4-5 in the fixed group were significantly lower than those in the unfixed group in the corresponding segments and load conditions, and the differences were statistically significant. The concave disc pressures of T3-4、T11-12、T15-L1、L3-4 and L4-5 in the fixed group were 0.83±0.12, 0.93±0.12, 0.50±0.05, 0.60±0.10 and 0.55±0.08 MPa respectively, which were lower than those of the unfixed group 1.70±0.18, 1.79±0.14, 1.84±0.22, 1.74±0.28, 1.60±0.23 MPa, and the differences were statistically significant. The total disc pressure of the fixed group was significantly lower than that of the non-fixed group in vertical compression, 5 degree flexion and 5 degree extension, and the differences were statistically significant. Conclusion Unilateral pedicle screw fixation can decrease the pressure on fixed side of fixed group in all conditions and change the distribution of pressure. The posterior pressure decreased particularly. Short- segment unilateral pedicle screw fixation can decrease the average pressure of intervertebral disc, which is an excellent surgery in curing scoliosis in young children. Key words: Biomechanics; Internal fixators; Scoliosis; Intervertebral disc

In vivo dynamic motion characteristics of the lower lumbar spine: L4\u20135 lumbar degenerative disc diseases undergoing unilateral or bilateral pedicle screw fixation combined with TLIF

ObjectiveTo evaluate the short-term in vivo dynamic motion characteristics of the lower lumbar spine (L3–S1) after unilateral pedicle screw fixation (UPSF) or bilateral pedicle screw fixation (BPSF) combined with TLIF for treatment of L4–5 lumbar degenerative disc diseases (DDD).MethodsTwenty-eight patients were recruited (13 UPSF, 15 BPSF). Each patient was CT-scanned to construct 3D models of the L3–S1 vertebrae. The dual fluoroscopic imaging system (DFIS) was then used to image the lumbar spine while the patient performed seven functional activities (upright standing, maximum extension, flexion, left–right twist, and left–right bend). The in vivo vertebral positions were reproduced using the 3D vertebral models and DFIS images. The ranges of motion (ROMs) of L3–4, L4–5, and L5–S1 segments were analyzed.ResultsAt the index L4–5 segment, the primary ROM of left–right twist of the UPSF group (2.11 ± 0.52°) was significantly larger (p = 0.000) than the BPSF group (0.73 ± 0.32°). At the proximal adjacent L3–4 segment, the primary ROMs of left–right twist, and left–right bend of the UPSF group (2.16 ± 0.73°, 2.28 ± 1.03°) were significantly less (p = 0.003, 0.023) than the BPSF group (3.17 ± 0.88, 3.12 ± 1.04°), respectively. However, at distal adjacent L5–S1 segment, no significant difference was found between the two groups during all activities.ConclusionsThe ROM in left–right twisting of UPSF group was significantly larger compared with BPSF group at the index level in the short term. The UPSF has less impact on the cranial adjacent level (L3–4) in left–right twisting and bending activities compared to the BPSF. The data implied that the UPSE and BPSF combined with TLIF would result in different biomechanics in the index and cranial adjacent segment biomechanics. Long-term follow-up studies are necessary to compare the clinical outcomes of the two surgeries.

Unilateral pedicle screw fixation and lumbar interbody fusion under the Quadrant tunnel for the treatment of prolapsed lumbar disc herniation in young patients

To explore the clinical effect of unilateral screw fixation and lumbar interbody fusion under the Quadrant tunnel to treat prolapsed lumbar disc herniation in young patients. Between January 2015 and January 2017, 18 young patients with prolapsed lumbar disc herniation were treated with unilateral pedicle screw fixation and lumbar interbody fusion under Quadrant tunnel. Among them, there were 10 males and 8 females, aged from 20 to 28 years old with an average of 22.5 years. The VAS, lumbar JOA scores were compared before sutgery, 1 and 3 months after surgery and at the final follow-up. The improvement of clinical symptoms and bone fusion rate were evaluated according to the improved rate of JOA score and X-rays data at the final follow-up. All 18 patients were followed up from 14 to 34 months with an average of 24.3 months. All incisions got primary healing, and no nerve root injury, screw loose or rupture, threaded fusion cage sink or other complications were found. The postoperative VAS, lumbar JOA scores were improved significantly(P<0.05). Neurologic function improved significantly in the final follow-up. The postoperative JOA improvement rate was excellent in 10 cases, good in 6 cases, and fair in 2 cases. Postoperative bone graft fusion rate was 100% at 3 to 6 months. Unilateral screw fixation and lumbar interbody fusion under the Quadrant tunnel is an effective and safe method in treating prolapsed lumbar disc herniation for young patients, it has advantage of short operation time, small trauma and short hospitalization time. However, the indications should be well considered.

Does the Cage Position in Transforaminal Lumbar Interbody Fusion Determine Unilateral versus Bilateral Screw Placement?: A Review of the Literature.

This literature review examines the relative placement of the interbody cage with respect to the unilateral screw construct to address the need for bilateral screw placement versus unilateral screw placement. Transforaminal lumbar interbody fusion (TLIF) has become a widely used technique for correcting lumbar intervertebral pathologies. This review addresses the necessity for further study on the effects of the relative position of intervertebral cage placement on the outcome of lumbar spine surgery after TLIF with unilateral pedicle screw fixation. Previous studies have addressed various factors, including posterior screw fixation, cage size, cage shape, and number of levels fused, that impact the biomechanics of the lumbar spine following TLIF. A simple survey of the literature was conducted. A search of the English literature was conducted using the keywords ‘TLIF,’ ‘transforaminal lumbar interbody fusion,’ ‘graft placement,’ ‘graft position,’ ‘cage position,’ ‘cage placement,’ ‘unilateral pedicle screw,’ ‘unilateral TLIF cage placement,’ ‘lumbar biomechanics,’ ‘lumbar stability,’ ‘lumbar fusion,’ and ‘lumbar intervertebral cage’ with various combinations of the operators ‘AND’ and ‘OR’ and no date restrictions. Seventeen articles in the English literature that were most relevant to this research question were identified. To the best of our knowledge, there are no published data addressing the effects of cage placement relative to the unilateral screw on lumbar stability in TLIF with unilateral pedicle screw fixation. Investigation of the effects of cage placement is, thus, warranted to achieve optimal clinical outcomes in patients undergoing TLIF with unilateral pedicle screw fixation.

Biomechanical Stability Before and After Graft Fusion with Unilateral and Bilateral Pedicle Screw Fixation: Finite Element Study

Minimally invasive transformational lumbar interbody fusion (MI-TLIF) with unilateral pedicle screw (UPS) fixation was controversial. The aim of this study was to compare the stability between UPS and bilateral pedicle screw (BPS) fixation before and after graft fusion. An L3-L5 finite element model was modified to simulate L4/5 MI-TLIF. Five different statuses of posterior instrumentation were simulated: UPS fixation or BPS fixation before and after graft fusion and removal of posterior instrumentation after graft fusion. Range of motion and Von Mises stress were evaluated for intact and instrumentation models in all loading planes. Range of motion of the L4/5 segment with UPS fixation was 2.1, 1.3, and 1.7 times greater than those with BPS fixation before fusion in flexion-extension, lateral bending, and axial rotation, respectively, while it was 1.3, 1.1, and 1.4 times greater after fusion. The peak Von Mises stresses on posterior instrumentations with UPS fixation ranged from 1.0 to 1.7 times greater than those in BPS fixation before fusion, while it ranged from 1.0 to 1.4 times greater after fusion. The peak Von Mises stresses on intervertebral graft with UPS fixation ranged from 1.9 to 3.5 times greater than those with BPS fixation before fusion, while it ranged from 0.9 to 1.2 times greater after fusion. Fusion of graft improved the fixation effect of posterior instrumentation system. Unilateral pedicle screw fixation could provide similar biomechanical stability to bilateral pedicle screw fixation in 1-level MI-TLIF after fusion.

Short-term effects of combined pedicle/facet screw fixation plus interbody fusion through the channel-assisted muscle-splitting approach for the treatment of degenerative lumbar spine diseases in the elderly

Objective To examine the feasibility and early effects of unilateral pedicle screw fixation in combination with contralateral translaminar facet screw fixation plus interbody fusion through the channel-assisted muscle-splitting approach for the treatment of degenerative lumbar spine diseases in elderly patients. Methods A total of 82 elderly patients with degenerative lumbar spine diseases received treatment between January 2015 and June 2016.Of these patients, 25 had lumbar spinal stenosis, 42 had degenerative lumbar instability, 13 had giant lumbar disc herniation, and two had recurrent lumbar disc herniation; There were 69 cases of single segment and 13 cases of double segment lesions.Perioperative evaluation, imaging evaluation, and clinical evaluation were performed, and surgical complications were analyzed. Results The average length of incision was (2.6±0.4) cm in cases of single segment lesions and (4.4±0.5) cm in cases of two segment lesions.The mean operation time was (98.3±19.6) minutes and peri-operation blood loss was (232.2±25.8) ml.The post-operation height of the intervertebral disc space significantly increased at the last follow-up(P<0.05); the height of the intervertebral disc space was restored and well maintained with internal fixation showing no loosening, breakage or Cage shift.The post-operation lumbar coronal Cobb angle decreased(P<0.05)while the sagittal Cobb angle increased(P<0.05)at the last follow-up.There was no significant difference in the area and grade of the multifidus muscle on MRI 12 months after operation.Seventy-two patients were followed up for 12-18 months(mean=16.8 months), and there were 67 cases of intervertebral fusion(93.1%). The last follow-up showed a Japanese Orthopaedic Association(JOA)score of (25.8±1.7), which was significantly higher than the pre-operation score(10.6±1.3), with an excellence rate of 88.9%.The Oswestry Disability Index score was significantly reduced, from (50.9±21.6) at pre-operation to (9.6±4.8) at the last follow-up.There were 78 patients with primary wound healing, three cases of superficial wound necrosis, one case of dural tear, and one case of nerve root injury.No cardiovascular or cerebrovascular incident was observed during or after operation. Conclusions Combined pedicle/facet screw fixation plus interbody fusion through the channel-assisted muscle-splitting approach shows satisfactory short-term effects when used for the treatment of degenerative lumbar spine diseases in the elderly and possesses advantages such as minimal invasiveness, limited bleeding, quick recovery, high fusion rates and significantly improved clinical outcomes.However, further clinical studies are required to assess its medium-and long-term efficacy. Key words: Spinal fusion; Surgical procedures minimally invasive; Arthritis, degenerative

Pressure distributions inside intervertebral discs under unilateral pedicle screw fixation in a porcine spine model

BackgroundLittle data are available regarding the effects of pedicle screws on the intervertebral disc stress for different spinal segments. The aim of this study was to analyze the intervertebral disc stress in response to the placement of pedicle screws.MethodsT3–4, T11–12, T15–L1, L3–4, and L4–5 intervertebral disc segments from six porcine spine specimens were harvested. A compressive load of 200 N was applied both before and after the pedicle screw was implanted on the left side of each target segment; the resulting pressure was measured during vertical, 5° anterior flexion, 5° posterior extension, and 5° lateral bending.ResultsThe posterior intradiscal pressures of the intervertebral disc were significantly lower in the fixed group than in the unfixed group for all segments during vertical, 5° anterior flexion, and 5° posterior extension. The left pressures of the intervertebral disc were significantly lower in the fixation group for all segments. During 5° lateral bending, the left intervertebral disc pressures were significantly lower in the fixation group. Lower mean pressures were observed in the fixed group.ConclusionsUnilateral pedicle screws can effectively reduce the pressure of the fixed lateral intervertebral disc. Moreover, it can change the pressure distribution of the intervertebral disc and reduce the pressure of the entire intervertebral disc, especially the posterior side of the intervertebral disc.

Unilateral versus Bilateral Pedicle Screw Fixation Combined with Transforaminal Lumbar Interbody Fusion for the Treatment of Low Lumbar Degenerative Disc Diseases: Analysis of Clinical and Radiographic Results

To compare the clinical and radiographic results of unilateral pedicle screw fixation (UPSF) and bilateral pedicle screw fixation (BPSF) after unilateral transforaminal lumbar interbody fusion (TLIF) for the treatment of lumbar degenerative disc diseases (DDDs). A total of 63 patients who underwent UPSF or BPSF combined with unilateral TLIF at L4-L5 or L5-S1 in our hospital between 2014 and 2016 were included in this analysis. The perioperative outcomes and radiographic results were recorded at preoperative and postoperative follow-up. Fusion rates were determined according to the Bridwell-Lenke grading system. Clinical outcomes were evaluated using the visual analog scale, Oswestry Disability Index, and lumbar Japanese Orthopedic Association score. According to the perioperative assessment, the duration of operation, intraoperative and postoperative blood loss, duration of pain medication use, and hospital costs were significantly (P < 0.0001) lower in the UPSF group compared with the BPSF group. After a mean follow-up of 24 months, both the UPSF and BPSF groups showed significantly (P < 0.05) maintained disc height and segmental lordosis of the surgical segment and achieved similar clinical outcomes at the final postoperative follow-up. The impact on the cranial adjacent vertebral level was significantly (P < 0.05) less in the UPSF group than the BPSF group in the short term. UPSF techniques with TLIF can attain similar clinical efficiency as BPSF techniques in treating single-level low lumbar DDD, but with fewer surgical injuries and at lower cost. BPSF with TLIF likely causes more degeneration at the cranial adjacent segment compared with UPSF techniques. The long-term results require more study.