Risk factors and clinical significance of posterior slip of the proximal vertebral body after lower lumbar fusion

BACKGROUND Adjacent segment disease(ASD)after fusion surgery is frequently manifests as a cranial segment instability,disc herniation,spinal canal stenosis,spondylolisthesis or retrolisthesis.The risk factors and mechanisms of ASD have been widely discussed but never clearly defined.AIM To investigate the risk factors and clinical significance of retrograde movement of the proximal vertebral body after lower lumbar fusion.METHODS This was a retrospective analysis of the clinical data of patients who underwent transforaminal lumbar interbody fusion surgery between September 2015 and July 2021 and who were followed up for more than 2 years.Ninety-one patients with degenerative lumbar diseases were included(22 males and 69 females),with an average age of 52.3 years(40-73 years).According to whether there was retrograde movement of the adjacent vertebral body on postoperative X-rays,the patients were divided into retrograde and nonretrograde groups.The sagittal parameters of the spine and pelvis were evaluated before surgery,after surgery,and at the final follow-up.At the same time,the Oswestry Disability Index(ODI)and Visual Analogue Scale(VAS)were used to evaluate the patients’quality of life.RESULTS Nineteen patients(20.9%)who experienced retrograde movement of proximal adjacent segments were included in this study.The pelvic incidence(PI)of the patients in the retrograde group were significantly higher than those of the patients in the nonretrograde group before surgery,after surgery and at the final follow-up(P<0.05).There was no significant difference in lumbar lordosis(LL)between the two groups before the operation,but LL in the retrograde group was significantly greater than that in the nonretrograde group postoperatively and at the final follow-up.No significant differences were detected in terms of the|PI–LL|,and there was no significant difference in the preoperative lordosis distribution index(LDI)between the two groups.The LDIs of the retrograde group were 68.1%±11.5%and 67.2%±11.9%,respectively,which were significantly lower than those of the nonretrograde group(75.7%±10.4%and 74.3%±9.4%,respectively)(P<0.05).Moreover,the patients in the retrograde group had a greater incidence of a LDI<50%than those in the nonretrograde group(P<0.05).There were no significant differences in the ODI or VAS scores between the two groups before the operation,but the ODI and VAS scores in the retrograde group were significantly worse than those in the nonretrograde group after the operation and at the last follow-up,(P<0.05).CONCLUSION The incidence of posterior slippage after lower lumbar fusion was approximately 20.9%.The risk factors are related to a higher PI and distribution of lumbar lordosis.When a patient has a high PI and insufficient reconstruction of the lower lumbar spine,adjacent segment compensation via posterior vertebral body slippage is one of the factors that significantly affects surgical outcomes.

Advances in Cervical Artificial Disc Replacement for Cervical Spondylosis

Anterior cervical decompression and fusion(ACDF)treatment for cervical spondylosis has been more than half a century,and achieved good clinical results.However,with the continuous extension of follow-up time,the fusion segment-associated postoperative complications emerged gradually.Reserved cervical stability and activity,the concept of non-fusion was born.As a non-fusion technique,cervical artificial disc replacement(CADR)developed rapidly.With the continuous development of artificial prosthesis materials and design concepts,and specification and proficiency of surgical procedures,CADR has achieved better short and mid-term clinical efficacy than ACDF.Compared with ACDF,the main advantages of CADR are that the postoperative recovery is quick,the activity and stability of cervical vertebra are maintained,the height of cervical intervertebral space is restored,and the stress of adjacent segments and the rate of surgical renovation are reduced.In clinical work,as an emerging technology,CADR requires spine surgeons to control the surgical indications,contraindications,and patients'conditions strictly.This article reviews the research progress of CADR in order to provide new ideas for clinical treatment of cervical spondylosis.

Adjacent segment disease following Dynesys stabilization for lumbar disorders:A case series of mid-and long-term follow-ups

BACKGROUND Radiologic adjacent segment degeneration(ASDeg)can occur after spinal surgery.Adjacent segment disease(ASDis)is defined as the development of new clinical symptoms corresponding to radiographic changes adjacent to the level of previous spinal surgery.Greater pre-existing ASDeg is generally considered to result in more severe ASDis;nonetheless,whether the ASDeg status before index surgery influences the postoperative risk of revision surgery due to ASDis warrants investigation.AIM To identify possible risk factors for ASDis and verify the concept that greater preexisting ASDeg leads to more severe ASDis.METHODS Data from 212 patients who underwent posterior decompression with Dynesys stabilization from January 2006 to June 2016 were retrospectively analyzed.Patients who underwent surgery for ASDis were categorized as group A(n=13),whereas those who did not were classified as group B(n=199).Survival analysis and Cox proportional hazards models were used to compare the modified Pfirrmann grade,University of California-Los Angeles grade,body mass index,number of Dynesys-instrumented levels,and age.RESULTS The mean time of reoperation was 7.22(1.65–11.84)years in group A,and the mean follow-up period was 6.09(0.10–12.76)years in group B.No significant difference in reoperation risk was observed:Modified Pfirrmann grade 3 vs 4(P=0.53)or 4 vs 5(P=0.46)for the upper adjacent disc,University of California-Los Angeles grade 2 vs 3 for the upper adjacent segment(P=0.66),age of<60 vs>60 years(P=0.9),body mass index<25 vs>25 kg/m2(P=0.3),and sex(P=0.8).CONCLUSION Greater preexisting upper ASDeg was not associated with a higher rate of reoperation for ASDis after Dynesys surgery.Being overweight tended to increase reoperation risk after Dynesys surgery for ASDis.

Relationship between Facet Joint Asymmetry and Adjacent Intervertebral Disc Degeneration in Lumbar Disc Herniation

Objective: To analyze the relationship between facet joint asymmetry and adjacent intervertebral disc degeneration in lumbar disc herniation. Methods: Fifty patients with L4/5 lumbar disc herniation were enrolled in the study. All patients underwent lumbar MRI examination, to compare the facet asymmetry of lumbar disc herniation and the degeneration of cartilage endplate and intervertebral disc of adjacent segments, and analyze the relationship between them. Results: There was no significant correlation between L4/5 facet asymmetry and L5/S1 intervertebral disc degeneration score and cartilage endplate degeneration score (P > 0.05). L4/5 facet asymmetry was significantly correlated with L3/4 disc degeneration score (P < 0.01), but not with cartilage endplate degeneration score (P > 0.05). Conclusion: There was a positive correlation between the facet joint angle of lumbar disc herniation and the degeneration of upper proximal segment intervertebral disc. Early correction of lumbar facet angle asymmetry can provide beneficial guidance for further prevention and treatment.

Adjacent Segment Disease after Long Spinal Fusion Ending at L5 for Adult Spinal Deformity: A Retrospective Cohort Study

Study Design: This is a retrospective cohort study using data from the adult spinal deformity (ASD) database of a single institution. Purpose: To investigate the incidence of proximal junctional failure and distal junctional failure (DJF) after ASD surgery with a lower instrumented vertebra (LIV) at L5. Overview of Literature: Spinopelvic fixation from the lower thoracic vertebra to the pelvis is the current gold standard treatment for ASD. However, the LIV at L5 is acceptable in some cases. Methods: Fifty-six patients who underwent corrective surgery for ASD with LIV at L5 were included. The upper instrumented vertebra (UIV) was T7 in one patient, T9 in 14, T10 in three, T11 in four, T12 in eight, L1 in 10, and L2 in 16. Regarding clinical parameters, age, sex, curve types of Scoliosis Research Society-Schwab classification, number of levels fused, follow-up period, hip bone mallow density, revision surgery rate, and radiographic measurements were compared between the T (UIV: T7 - 10) and TL (UIV: T11 - L2) groups. Results: The revision surgery rate was 19.6% overall. In the T and TL groups, it was 27.8%, and 15.8%, respectively (p = 0.305). The rate of DJF in the T group (33.3%) was significantly higher than in the TL group (5.3%). The rate of proximal junctional kyphosis in the T group (55.6%) was higher than in the TL group (28.9%), with no significant difference. The mean global alignment, sagittal vertical axis, and C7 plumb line-central sacral vertical line were not different between both groups. Conclusions: ASD surgery with LIV set at L5 and UIV set at the thoracic vertebrae (T7 - T10) has a risk of adjacent segment disease.

Prone Transpsoas Approach for Adjacent Segment Disease and Flatback Deformity: Technical Note and Case Report

The prone transpsoas approach is a relatively new technique to correct segmental kyphosis and global sagittal imbalance in a minimally invasive fashion. Here, we provide a detailed case report using the prone transpsoas approach to address adjacent segment disease and flatback deformity. This technique allows considerable restoration of segmental lordosis with lateral interbody placement and posterior decompression and fusion using a single position approach. Our experience with the surgical technique and the advantages and challenges unique to this approach are discussed.

Comparison of adjacent segment degeneration five years after single level cervical fusion and cervical arthroplasty： a retrospective controlled study

Background Cervical arthroplasty is indicated to preserve cervical motion and prevent accelerated adjacent segment degeneration. Whether accelerated adjacent segment degeneration is prevented in the long term is unclear. This trial compared adjacent segment degeneration in Bryan disc arthroplasty with that in anterior cervical decompression and fusion five years after the surgery. Methods We studied patients with single level degenerative cervical disc disease. The extent of adjacent segment degeneration was estimated from lateral X-rays. Results Twenty-six patients underwent single level Bryan disc arthroplasty and twenty-four patients underwent single level anterior cervical decompression and fusion. All patients were followed up for an average of sixty months. In the Bryan arthroplasty group, nine （17.6%） segments developed adjacent segment degeneration, which was significantly lower than that （60.4%） in the anterior cervical decompression and fusion group. Eleven segments in the Bryan arthroplasty group developed heterotopic ossification according to McAfee＇s classification and two segments had range of motion less than 2%. In the heterotopic ossification group, four （19.5%） segments developed adjacent segment degeneration, similar to the number in the non-heterotopic ossification group （16.7%）. Adjacent segment degeneration rate was 50% in grade IV group but 11.8% in grade II to III. Conclusions Adjacent segment degeneration was accelerated after anterior cervical decompression and fusion. However, Bryan disc arthroplasty avoided accelerated adjacent segment degeneration by preserving motion. Patients with grade IV heterotopic ossification lost motion, and the rate of adjacent segment degeneration was higher than that in patients without heterotopic ossification.

Load Rate of Facet Joints at the Adjacent Segment Increased After Fusion

Background： The cause of the adjacent segment degeneration （ASD） after fusion remains unknown. It is reported that adjacent facet joint stresses increase alter anterior cervical discectomy and fusion. This increase of stress rate may lead to tissue injury. Thus far, the load rate of the adjacent segment facet joint after fusion remains unclear. Methods： Six C2-C7 cadaveric spine specimens were loaded under tour motion modes： Flexion, extension, rotation, and lateral bending, with a pure moment using a 6° robot arm combined with an optical motion analysis system. The Tecscan pressure test system was used for testing facet joint pressure. Results： The contact mode of the facet joints and distributions of the force center during different motions were recorded. The adjacent segment facet joint forces increased faster after fusion, compared with intact conditions. While the magnitude of pressures increased, there was no difference in distribution modes before and after fusion. No pressures were detected during flexion. The average growth velocity during extension was the fastest and was significantly faster than lateral bending. Conclusions： One of the reasons for cartilage injury was the increasing stress rate of loading. This implies that ASD after fusion may be related to habitual movement before and after fusion. More and faster extension is disadvantageous for the facet joints and should be reduced as much as possible.

Adjacent segment disease after anterior cervical decompression and fusion： analysis of risk factors on X-ray and magnetic resonance imaging

Background Adjacent segment disease （ASD） is common after cervical fusion.The aim of this study was to evaluate the risk factors for ASD on X-ray and magnetic resonance imaging （MRI）.Methods Patients included in this study had received revision surgeries after developing symptomatic ASD following anterior decompression and fusion.A control group that had not developed ASD was matched 1：1 by follow-up time and fusion segments.Plate-to-disc distances （PDDs）,developmental cervical canal stenosis on X-ray,cervical disc degeneration grading,and cervical disc bulge impingements on preoperative MRI were measured and compared between the ASD group and the control group.Results Thirty-four patients with complete radiographic data were included in the ASD group.The causative segments of ASD included nine cases of C3-4,18 cases of C4-5,three cases of C5-6,and four cases of C6-7.The ASD occurred at the upper adjacent segments in 26 patients and at the lower adjacent segments in eight patients.PDD distributions were similar between the ASD group and the control group.Developmental cervical canal stenosis was a risk factor for ASD,with an odd ratio value of 2.88.Preoperative cervical disc degenerations on MRI were similar between the ASD group and the control group.In the upper-level ASD group,the disc bulge impingement was （19.7±9.7）％,which was significantly higher than that of the control group of （11.8±4.8）％.Conclusions ASD was more likely to develop above the index level of fusion.Developmental cervical canal stenosis and greater disc bulge impingement may be risk factors for the development of ASD.

Long-Term Outcome of Dynesys Dynamic Stabilization for Lumbar Spinal Stenosis

Background： Many clinical studies over the past decade have indicated positive outcomes for patients treated with Dynesys dynamic stabilization for lumbar degenerative disease. However, long-term outcomes of Dynesys for lumbar spinal stenosis are rarely reported. The aim of this study was to analyze the long-term clinical and radiologic outcomes for patients with lumbar spinal stenosis treated with Dynesys stabilization. Methods： Thirty-eight patients with lumbar spinal stenosis were treated with Dynesys stabilization from July 2008 to March 2010. The minimal duration of follow-up was 72 months. The patients were divided into stenosis and spondylolisthesis groups according to degenerative spondylolisthesis. Clinical outcomes were evaluated using the Oswestry Disability Index （ODI） and visual analog scale （VAS）. Radiographic evaluations included range of motion （ROM） and the disc heights of stabilized segments and the upper adjacent segments. We also evaluated the occurrence of radiographic and symptomatic adjacent segment degeneration （ASD）. Results： There were 23 patients in stenosis group and 15 patients in spondylolisthesis group. The ODl scores were significantly improved at the final follow-up evaluation, as compared to the baseline values （ 16.1± 5.7 vs. 57.2 ± 14.2, t = 61.4 l, P 〈 0.01 ）. The VA S scores for back and leg pain were significantly improved from 4.82 ±0.89 and 4.04 ± 0.82 preoperatively to 0.93± 0.61 and 0.54 ± 0.51 postoperatively （t = 6.59, P 〈 0.01, and t = 5.91, P 〈 0.01, respectively）. There were no differences between the two groups with respect to VAS and ODI scores. The ROM of stabilized segments decreased significantly from 7.8°± 2.4° to 4.5° ± 1.5° （t = 7.18, P 〈 0.05）, while the upper adjacent segments increased significantly from 8.3° ± 2.4° to 10.4° ± 2.4° （t = 2.87, P = 0.01）. The change in disc height of stabilized segments was not significant （11.9 ±2.1 preoperatively vs. 12.5 ± 1.5 postoperatively, t = 1.43, P = 0.15）, whereas the decrease in disc height of the upper adjacent segments was significant （12.5 ±2.0 preopcratively vs. 11.0 ± 1.7 postoperatively, t = 2.94, P = 0.01 ）. The occurrence of radiographic and symptomatic ASD was 16% （6/38） and 3% （1/38）, respectively. Conclusions： Decompression and Dynesys stabilization for lumbar stenosis with or without spondylolisthesis showed good long-term clinical and radiographic results. Lumbar stenosis with or without Grade I spondylolisthesis, particularly in patients 〈60 years of age with mild-to-moderate lumbar disc degeneration, would be one of the main indications for the Dynesys system.

Comparison of Topping-off and posterior lumbar interbody fusion surgery in lumbar degenerative disease： a retrospective study

Background Topping-off surgery is a newly-developed surgical technique which combines rigid fusion with an interspinous process device in the adjacent segment to prevent adjacent segment degeneration. There are few reports on Topping-off surgery and its rationality and indications remains highly controversial. Our study aims to investigate the short-term and mid-term clinical results of Topping-off surgery in preventing adjacent segment degeneration when mild or moderate adjacent segment degeneration existed before surgery. Methods The 25 cases that underwent L5-$1 posterior lumbar interbody fusion （PLIF） ＋ L4-L5 interspinous process surgeries between April 2008 and March 2010 formed Topping-off group. The 42 cases undergoing L5-$1 PLIF surgery formed PLIF group. Both groups matched in gender, age, body mass index and Pfirrmann grading （4 to 6）. The patients were evaluated with visual analogue scale （VAS） and Japanese orthopaedic association （JOA） scores before surgery and in the last follow-up. Modic changes of endplates were recorded. Results The follow-up averaged 24.8 and 23.7 months. No symptomatic or radiological adjacent segment degeneration was observed. There was no significant difference in intraoperative blood loss or postoperative drainage. VAS and lumbar JOA scores improved significantly in both groups （t=-12.1 and 13.5, P 〈0.05）. Neither anterior nor posterior disc height was significantly changed. Segmental lordosis of L4-L5 and total lordosis were all increased significantly （Topping-off group： t=-2.30 and -2.24, P 〈0.05; PLIF group： t=--2.76 and -1.83, P 〈0.01）. In the hyperextension and hyperflexion view, Topping-off group＇s range of motion （ROM） and olisthesis in the L4-L5 segment did not significantly change in flexion, but decreased in extension. In PLIF group, ROM （t=--7.82 and -4.90, P 〈0.01） and olisthesis （t=--15.67 and -18.58, P 〈0.01） both significantly increased in extension and flexion. Conclusions Compared with single segment PLIF surgery, Topping-off surgery can achieve similar symptomatic improvement in cases with pre-existing mild or moderate adjacent segment degeneration, restrict the adjacent segment＇s ROM in extension and prevent excessive olisthesis of adiacent seament in both extension and flexion

Minimum 5-year follow-up study on the effects of the Wallis dynamic stabilization system in the treatment of lumbar degenerative disease

Background Short-term outcomes of the Wallis system in the treatment of lumbar degenerative disease （LDD） have been shown to be effective, whereas there is a paucity of studies on the mid-long-term effects of the treatment of the Wailis system. This study was to evaluate the mid-long-term effects of the Wallis dynamic stabilization system in the treatment of LDD. Methods A total of 26 patients who received the treatment of the Wallis system between February 2008 and January 2009 were included in the study, with 14 patients （Group 1） with L4/5 disc herniation and 12 patients （Group 2） with L5/S1 disc herniation and L4/5 intervertebral disc degeneration （IDD）. Visual analog scale （VAS） and Oswestry Disability Index （ODI） were used to evaluate the clinical outcomes and lumbar X-rays and MRI were obtained to observe imaging changes before and after operation. Results The mean follow-up period was （63.50＋2.12） months. The mean ODI and VAS scores decreased obviously three months and five years after operation （P 〈0.05）. In Groups 1 and 2, L4/5 Cobb angle and range of motion （ROM） decreased and L4/5 posterior disc height increased at the last follow-up （P 〈0.05）. There were no statistically significant changes in L4/5 anterior disc height and L3/4 University of California at Los Angeles grading before and after operation. There was no statistically significant change in Pfirrmann grading system of L4/5 IDD in Group 2 before and after operation. Adjacent segment degeneration at the last follow-up was found in two patients （2/26, 7.69%） and Modic changes in L4/5 endplates were detected in one patient （1/26, 3.85%）. Conclusions The mid-long-term effects of the Wallis system in the treatment of LDD were satisfied. The Wallis system, as a dynamic stabilization system, which can preserve some ROM of the fixed segment, sustain the lumbar stabilization, and prevent adjacent segment disease and fixed segment degeneration, is an effective instrument to treat LDD.

Cervical disc arthroplasty with ProDisc-C artificial disc： 5-year radiographic follow-up results

Background Cervical disc arthroplasty is an alternative surgery to standard cervical decompression and fusion for disc degeneration. Different types of cervical disc prosthesis are used in China. The aim of this study was to evaluate the radiographic outcomes of cervical arthroplasty using the ProDisc-C prosthesis.

A critical review on the biomechanical study of cervical interbody fusion cage

Anterior Cervical Discectomy and Fusion(ACDF)is the preferred surgical method for the treatment of severe cervical degenerative disc disease with radiculopathy or myelopathy,of which the objectives are to restore the normal height of intervertebral space and cervical lordosis through the implantation of cervical interbody fusion cage.The biomechanical performance of a cervical interbody fusion cage,which plays a significant role in achieving the goals of ACDF,is influenced by multiple factors.In this paper,various studies focusing on the biomechanical performance of cervical interbody fusion cage are reviewed.Furthermore,the research methods,biomechanical evaluation parameters and data analysis methods of these research are analyzed in order to obtain a comprehensive understanding of the progress and limitations of research in this field.Although great progress has been made to clarify the biomechanical behaviors of cervical interbody fusion cage,there is still controversy regarding the issues such as the relative contribution of multiple factors to the performance of cage,the interactions among these factors,as well as whether the effects of factors change with the process of intervertebral osseointegration and so on.Thus,investigations are still needed to improve the comprehension of cervical interbody fusion cage biomechanically.