Analysis of the causes of cage subsidence after oblique lateral lumbar interbody fusion / 中国骨伤

OBJECTIVE@#To observe the cage subsidence after oblique lateral interbody fusion (OLIF) for lumbar spondylosis, summarize the characteristics of the cage subsidence, analyze causes, and propose preventive measures.@*METHODS@#The data of 144 patients of lumbar spine lesions admitted to our hospital from October 2015 to December 2018 were retrospectively analyzed. There were 43 males and 101 females, and the age ranged from 20 to 81 years old, with an average of (60.90±10.06) years old. Disease types:17 patients of lumbar intervertebral disc degenerative disease, 12 patients of giant lumbar disc herniation, 5 patients of discogenic low back pain, 33 patients of lumbar spinal stenosis, 26 patients of lumbar degenerative spondylolisthesis, 28 patients of lumbar spondylolisthesis with spondylolisthesis, 11 patients of adjacent vertebral disease after lumbar internal fixation, 7 patients of primary spondylitis in the inflammatory outcome stage, and 5 patients of lumbar degenerative scoliosis. Preoperative dual-energy X-ray bone mineral density examination showed 57 patients of osteopenia or osteoporosis, and 87 patients of normal bone density. The number of fusion segments:124 patients of single-segment, 11 patients of two-segment, 8 patients of three-segment, four-segment 1 patient. There were 40 patients treated by stand-alone OLIF, and 104 patients by OLIF combined with posterior pedicle screw. Observed the occurrence of fusion cage settlement after operation, conducted monofactor analysis on possible risk factors, and observed the influence of fusion cage settlement on clinical results.@*RESULTS@#All operations were successfully completed, the median operation time was 99 min, and the median intraoperative blood loss was 106 ml. Intraoperative endplate injury occurred in 30 patients and vertebral fracture occurred in 5 patients. The mean follow-up was (14.57±7.14) months from 6 to 30 months. During the follow-up, except for the patients of primary lumbar interstitial inflammation and some patients of lumbar spondylolisthesis with spondylolisthesis, the others all had different degrees of cage subsidence. Cage subsidence classification:119 patients were normal subsidence, and 25 patients were abnormal subsidence (23 patients were gradeⅠ, and 2 patients were gradeⅡ). There was no loosening or rupture of the pedicle screw system. The height of the intervertebral space recovered from the preoperative average (9.48±1.84) mm to the postoperative average (12.65±2.03) mm, and the average (10.51±1.81) mm at the last follow-up. There were statistical differences between postoperative and preoperative, and between the last follow-up and postoperative. The interbody fusion rate was 94.4%. The low back pain VAS decreased from the preoperative average (6.55±2.2 9) to the last follow-up (1.40±0.82), and there was statistically significant different. The leg pain VAS decreased from the preoperative average (4.72±1.49) to the final follow-up (0.60±0.03), and the difference was statistically significant (t=9.13, P<0.000 1). The ODI index recovered from the preoperative average (38.50±6.98)% to the latest follow-up (11.30±3.27)%, and there was statistically significant different. The complication rate was 31.3%(45/144), and the reoperation rate was 9.72%(14/144). Among them, 8 patients were reoperated due to fusion cage subsidence or displacement, accounting for 57.14%(8/14) of reoperation. The fusion cage subsidence in this group had obvious characteristics. The monofactor analysis showed that the number of abnormal subsidence patients in the osteopenia or osteoporosis group, Stand-alone OLIF group, 2 or more segments fusion group, and endplate injury group was higher than that in the normal bone mass group, OLIF combined with pedicle screw fixation group, single segment fusion group, and no endplate injury group, and the comparison had statistical differences.@*CONCLUSION@#Cage subsidence is a common phenomenon after OLIF surgery. Preoperative osteopenia or osteoporosis, Stand-alone OLIF, 2 or more segments of fusion and intraoperative endplate injury may be important factors for postoperative fusion cage subsidence. Although there is no significant correlation between the degree of cage subsidence and clinical symptoms, there is a risk of cage migration, and prevention needs to be strengthened to reduce serious complications caused by fusion of cage subsidence, including reoperation.

3D-printed vertebral body in anterior spinal reconstruction after total spondylectomy for patients with cervical chordoma / 北京大学学报(医学版)

OBJECTIVE@#To investigate whether 3D-printed artificial vertebral body can reduce prosthesis subsidence rate for patients with cervical chordomas, through comparing the rates of prosthesis subsidence between 3D printing artificial vertebral body and titanium mesh for anterior spinal reconstruction after total spondylectomy.@*METHODS@#This was a retrospective analysis of patients who underwent surgical treatment for cervical chordoma at our hospital from March 2005 to September 2019. There were nine patients in the group of 3D artificial vertebral body (3D group), and 15 patients in the group of titanium mesh cage (Mesh group). The patients' characteristics and treatment data were extracted from the medical records, including age, gender, CT hounsfield unit of cervical vertebra and surgical information, such as the surgical segments, time and blood loss of surgery, frequency and degree of prosthesis subsidence after surgery. Radiographic observations of prosthesis subsidence during the follow-up, including X-rays, CT, and magnetic resonance imaging were also collected. SPSS 22.0 was used to analysis the data.@*RESULTS@#There was no significant difference between the two groups in gender, age, CT hounsfield unit, surgical segments, time of surgery, blood loss of posterior surgery and total blood loss. Blood loss of anterior surgery was 700 (300, 825) mL in 3D group and 1 500 (750, 2 800) mL in Mesh group (P < 0.05). The prosthesis subsidence during the follow-up, 3 months after surgery, there was significant difference between the two groups in mild prosthesis subsidence (P < 0.05). The vertebral height of the 3D group decreased less than 1 mm in eight cases (no prosthesis subsidence) and more than 1 mm in one case (mild prosthesis subsidence). The vertebral height of the Mesh group decreased less than 1 mm in five cases (no prosthesis subsidence), and more than 1 mm in eight cases (mild prosthesis subsidence). Two patients did not have X-rays in 3 months after surgery. There was a statistically significant difference between the two groups in the prosthesis subsidence rate at the end of 12 months (P < 0.01). The vertebral height of eight cases in the 3D group decreased less than 1 mm (no prosthesis subsidence) and one case more than 3 mm (severe prosthesis subsidence). Four of the 15 cases in the Mesh group decreased less than 1 mm (no prosthesis subsidence), two cases more than 1 mm (mild prosthesis subsidence), and nine cases more than 3 mm (severe prosthesis subsidence). There was a statistically significant difference between the two groups in the prosthesis subsidence rate at the end of 24 months (P < 0.01). The vertebral height of seven cases in the 3D group decreased less than 1 mm (no prosthesis subsidence), one case more than 3 mm (severe prosthesis subsidence), and one case died with tumor. One case in the Mesh group decreased less than 1 mm (no prosthesis subsidence), one case more than 1 mm (mild prosthesis subsidence), 11 case more than 3 mm (severe prosthesis subsidence), one case died with tumor and one lost the follow-up. Moreover, at the end of 12 months and 24 months, there was significant difference between the two groups in severe prosthesis subsidence rate (P < 0.01).@*CONCLUSION@#3D-printed artificial vertebral body for anterior spinal reconstruction after total spondylectomy for patients with cervical chordoma can provide reliable spinal stability, and reduce the incidence of prosthesis subsidence after 2-year follow-up.

Effects of posterior pedicle screw internal fixation on early Cage subsidence after oblique lateral lumbar interbody fusion / 西安交通大学学报(医学版)

【Objective】 To investigate the effects of one-stage additional posterior pedicle screws （PPS） internal fixation on early Cage subsidence after oblique lateral interbody fusion （OLIF）. 【Methods】 We made a retrospective analysis of 118 patients with lumbar degenerative diseases treated with OLIF at the Department of Orthopedics， Sir Run Run Shaw Hospital， School of Medicine， Zhejiang University， from January 2016 to December 2019. We divided the patients into OLIF stand-alone group （58 ones） and OLIF with PPS fixation group （60 ones） according to the surgical procedure. All the patients had preoperative frontal and lateral radiographs of the lumbar spine， and CT and MR scans were performed. The clinical outcomes and reoperation rates of the two groups were compared at immediate postoperative follow-up and at 1， 3， 6 and 12 months. X-ray and CT examinations were performed to assess Cage subsidence in both groups at each postoperative follow-up. 【Results】 There was no statistical difference between the two groups in baseline data and surgical segmentation. Of the 118 patients with 141 discs who underwent OLIF surgery， 58 patients with 68 discs received OLIF stand-alone surgery and 60 ones with 73 discs received OLIF with PPS fixation. There were no significant differences in intraoperative bleeding， complications， or postoperative clinical outcomes between the two groups （P>0.05）， and the Cage subsidence rate was 22.4% in OLIF stand-alone group and 5% in OLIF with PPS fixation group， with significant difference between the two groups （P<0.01）. 【Conclusion】 Both OLIF stand-alone and OLIF additional PPS fixation can achieve good early clinical outcomes， and first-stage additional PPS fixation can significantly reduce the occurrence of Cage subsidence in the early postoperative period after OLIF.

Femoral Stem Subsidence and its Associated Factors after Cementless Bipolar Hemiarthroplasty in Geriatric Patients

@#Introduction: Early femoral stem subsidence has been a concern as a predictor of the beginning of implant loosening, especially on cementless hip arthroplasty implants. This study aimed to determine the factors that affect femoral stem subsidence and outcome following hemiarthroplasty in the geriatric population. Materials and Methods: This is a retrospective study of 179 patients who underwent cementless bipolar hemiarthroplasty during the 2011-2019 period at an orthopaedic and traumatology hospital. Data on the patient's demography, pre-operative American Society Anaesthesiologist (ASA) score, body mass index (BMI), canal flare index (CFI), Dorr classification, and stem alignment were obtained. The primary outcomes were post-operative femoral stem subsidence, post-operative pain, and functional outcome using Harris Hip Score (HHS). Statistical analysis was conducted to identify risk factors associated with the primary outcome. Results: The mean femoral stem subsidence was 2.16 ±3.4 mm. The mean post-operative Visual Analog Score (VAS) on follow-up was 1.38 ± 1. Mean HHS on follow-up was 85.28±10.3. American Society Anaesthesiologist score 3 (p = 0.011, OR = 2.77) and varus alignment (p=0.039, OR = 6.963) were related to worse stem subsidence. Otherwise, neutral alignment (p = 0.045 and OR = 0.405) gave protection against femoral stem subsidence. The female gender (p = 0.014, OR 2.53) was associated with postoperative pain onset. Neutral alignment had significant relationship with functional outcomes (p = 0.01; OR 0.33). Conclusion: A higher ASA score and varus stem alignment were related to a higher risk of femoral stem subsidence. Meanwhile, neutral stem alignment had a protective effect on the femoral stem subsidence and outcome.

Effects of a new anatomical adaptive titanium mesh cage on supportive load at the cervical endplate: a morphological and biomechanical study / 南方医科大学学报

OBJECTIVE@#To assess the geometrical matching of a new anatomical adaptive titanium mesh cage (AA-TMC) with the endplate and its effect on cervical segmental alignment reconstruction in single- and two-level anterior cervical corpectomy and fusion (ACCF) and compare the compressive load at the endplate between the AA-TMC and the conventional titanium mesh cage (TMC).@*METHODS@#Twelve cervical cadaveric specimens were used to perform single- and two-level ACCF. The interbody angle (IBA), interbody height (IBH) and the interval between the AA-TMC and the endplate were evaluated by comparison of the pre- and postoperative X-ray images. The maximum load at the endplate was compared between the AA-TMC and TMC based on American Society for Testing and Materials (ASTM) F2267 standard.@*RESULTS@#No significant differences were found between the preoperative and postoperative IBA and IBH in either single-level ACCF (11.62°±2.67° 12.13°±0.69° and 23.90±2.18 mm 24.23±1.13 mm, respectively; > 0.05) or two-level ACCF (15.63°±5.06° 16.16°±1.05°and 42.93±3.51 mm 43.04±1.70 mm, respectively; > 0.05). The mean interval between the AA-TMC and the endplate was 0.37 ± 0.3 mm. Compared to the conventional TMC, the use of AA-TMC significantly increased the maximum load at the endplate in both single-level ACCF (719.7±5.5 N 875.8±5.2 N, < 0.05) and two-level ACCF (634.3±5.9 N 873±6.1 N, < 0.05).@*CONCLUSIONS@#The use of AA-TMC in single-level and two-level ACCF can significantly increase the maximum load at the endplate to lower the possibility of implant subsidence and allows effective reconstruction of the cervical alignment.

Preventing Construct Subsidence Following Cervical Corpectomy: The Bump-stop Technique

Cervical corpectomy is a viable technique for the treatment of multilevel cervical spine pathology. Despite multiple advances in both surgical technique and implant technology, the rate of construct subsidence can range from 6% for single-level procedures to 71% for multilevel procedures. In this technical note, we describe a novel technique, the bump-stop technique, for cervical corpectomy. The technique positions the superior and inferior screw holes such that the vertebral bodies bisect them. This allows for fixation in the dense cortical bone of the endplate while providing a buttress to corpectomy cage subsidence. We then discuss a retrospective case review of 24 consecutive patients, who were treated using this approach, demonstrating a lower than previously reported cage subsidence rate.

Loss of correction after vertebrectomy for treatment of spinal deformities / Perda de correção após vertebrectomia no tratamento de deformidades da coluna vertebral / Pérdida de corrección después de vertebrectomía en el tratamiento de deformidades de la columna vertebral

ABSTRACT Objective: To evaluate the loss of correction after treatment of spine deformities with the technique of isolated posterior vertebrectomy. Methods: Twenty-one patients were followed-up for three years after surgery with panoramic X-rays, CT scans, SF-36 and Oswestry questionnaires. We evaluated the loss of correction, CAGE subsidence and the evolution of the pelvis-T1 angle during follow-up. The correlation among the radiographic changes and functional and quality of life scores was also assessed. Results: All patients had some degree of loss of correction and subsidence of CAGE, especially in the first year of follow-up. Such losses exerted negative impact on the function, pain and self-image of the patients. Factors such as the stiffness of the fusion mass and size of implant used appear to have contributed to the occurrence of subsidence, regardless of age and bone mineral density. Conclusions: The use of spacers with larger cross-sectional diameter and more rigid rods can reduce the overloading on the anterior column of Denis, reducing the subsidence and loss of correction. Additional stabilization strategies such as the use of orthoses postoperatively can also be useful, and should be evaluated in subsequent studies.

RESUMO Objetivo: Avaliar a perda de correção após o tratamento de deformidades da coluna vertebral pela técnica de vertebrectomia posterior isolada. Métodos: Vinte e um pacientes foram acompanhados durante três anos após o tratamento cirúrgico com radiografias panorâmicas, tomografias computadorizadas e através dos questionários SF-36 e Oswestry. Foram avaliadas perda de correção, subsidência do CAGE e evolução do ângulo pelve-T1 durante o acompanhamento. Também foi avaliada a correlação entre as alterações radiológicas e os índices funcionais e de qualidade de vida. Resultados: Todos os pacientes apresentaram algum grau de perda de correção e subsidência do espaçador intersomático, especialmente no primeiro ano de acompanhamento. Tais perdas exerceram impacto negativo sobre função, dor e autoimagem dos pacientes. Fatores como a rigidez da massa de artrodese e as dimensões do implante utilizado parecem ter contribuído com a ocorrência de subsidência, a despeito de faixa etária e densidade mineral óssea. Conclusões: O uso de espaçadores com maior diâmetro seccional e hastes mais rígidas podem reduzir a sobrecarga da coluna anterior de Denis, diminuindo a ocorrência de subsidência e perda de correção. Estratégias de estabilização adicionais, como o uso de órteses no pós-operatório também podem ser úteis, e devem ser avaliadas em estudos subsequentes.

RESUMEN Objetivo: Evaluar la pérdida de corrección después del tratamiento de las deformidades de la columna vertebral mediante la técnica de vertebrectomía posterior aislada. Métodos: Veintiún pacientes fueron seguidos durante tres años después de la cirugía mediante radiografías panorámicas, tomografías computarizadas y con el uso de los cuestionarios SF-36 y Oswestry. Se evaluó la pérdida de la corrección, la subsidencia del CAGE y la evolución del ángulo pelvis-T1 durante el seguimiento. También se evaluó la corrección entre las alteraciones radiográficas y los índices funcionales y de calidad de vida. Resultados: Todos los pacientes presentaron algún grado de pérdida de corrección y subsidencia del espaciador intersomático, especialmente en el primer año de seguimiento. Estas pérdidas ejercen impacto negativo sobre la función, el dolor y la autoimagen de los pacientes. Factores como la rigidez de la masa de artrodesis y el tamaño del implante usado parecen haber contribuido a la aparición de subsidencia, independientemente de la edad y la densidad mineral ósea. Conclusiones: El uso de espaciadores con diámetro de la sección transversal mayor y barras más rígidas pueden reducir la sobrecarga de la columna anterior de Denis, reduciendo la ocurrencia de subsidencia y pérdida de la corrección. Las estrategias de estabilización adicionales, tales como el uso de ortesis en el postoperatorio también pueden ser útiles, y deben ser evaluadas en estudios posteriores.

Risk Factors of Cage Subsidence after Posterior Lumbar Interbody Fusion

STUDY DESIGN: Retrospective study. OBJECTIVES: The purpose of this study was to evaluate risk factors for subsidence after posterior lumbar interbody fusion (PLIF). SUMMARY OF LITERATURE REVIEW: Body mass index (BMI), bone mineral density (BMD), cage characteristics (titanium or poly-ether-ether-ketone (PEEK)) and degree of disc distraction are risk factors for cage subsidence after PLIF. MATERIALS AND METHODS: From January 2010 to January 2015, a total of 69 patients (93 segments) who were diagnosed with degenerative lumbar spine disease at the current authors' institution and underwent follow-up for at least 1 year were included in this retrospective study. Data on all factors related to cage subsidence were taken into consideration. The degree of association for each of the factors was determined through the calculation of odds ratios (ORs) with a 95% confidence interval. Logistic regression analyses were performed. The P-value that represented statistical significance was set below 0.05. RESULTS: There were no significant associations between fused segment level and cage subsidence (p=0.588), nor were there any significant associations between the kind of cage (titanium or PEEK) and cage subsidence (p=0.371). Using logistic regression, the factors with a P-value below the 0.20 level in univariate analyses were included in the multivariate analyses. In multivariate analyses, diabetes mellitus (DM) (p=0.029, OR, 4.524), osteoporosis (p=0.026, OR, 6.046), and degree of disc distraction (p=0.010, OR, 1.446) had significant associations with cage subsidence. In addition, there were significant associations between cage subsidence and instrument failure (p=0.008, OR, 8.235). CONCLUSIONS: DM and osteoporosis, which may affect bony structures, have significant associations with cage subsidence after PLIF. Cage insertion with excessive disc distraction during surgery may also affect cage subsidence after PLIF.

Anterior Cervical Fusion Using a Zero-Profile Stand-Alone Cage: Radiological and Clinical Outcomes after More than 2 Years of Follow-Up

STUDY DESIGN: Retrospective analysis. OBJECTIVES: To analyze the usefulness of Zero-P® by analyzing the radiological and clinical outcomes with a minimum of 2 years of follow-up. SUMMARY OF LITERATURE REVIEW: Anterior discectomy and fusion (ACDF) using Zero-P® showed excellent results. However, there is a lack of studies focusing on long-term outcomes. MATERIALS AND METHODS: Ninety-eight patients who underwent single-level ACDF using Zero-P® with more than 2 years of follow-up were included for analysis. In the radiological analysis, we evaluated disc height, segmental lordosis, and subsidence in the preoperative, postoperative, and last follow-up periods. The Neck Disability Index (NDI), Neck Visual Analogue Scale (VAS), and Arm VAS were also evaluated for clinical assessment. Radiological bony fusion was assessed, and radiological and clinical differences according to bony fusion were evaluated. RESULTS: Intervertebral disc height had increased 2.92 mm after surgery and subsided to 2.36 mm at the final follow-up. Subsidence of the screw was 0.58 mm at final follow-up. Segmental lordosis was 3.97° at the preoperative assessment, 8.39° in the postoperative follow-up, and 5.83° in the last follow-up. The Neck VAS score was 4.47, 2.28, and 1.27, respectively. The Arm VAS score was 5.73, 3.13, and 2.18; and NDI score was 17.8, 11.7, and 7.89, respectively. There was no association between the radiological and clinical results. Radiological nonunion was found in 18 subjects. There were no significant differences in radiological and clinical parameters according to bony union. CONCLUSIONS: ACDF with Zero-P® for treatment of degenerative cervical disease showed subsidence in 55.1% and nonunion in 18% of cases. However, the radiological results were not related to the clinical results.

Long-Term Follow-Up Results of Anterior Cervical Inter-Body Fusion with Stand-Alone Cages

OBJECTIVE: The purpose of this study was to evaluate long-term follow-up radiologic/clinical outcomes of patients who underwent anterior cervical discectomy and inter-body fusion (ACDF) with stand-alone cages (SAC) in a single academic institution. METHODS: Total 99 patients who underwent ACDF with SAC between February 2004 and December 2012 were evaluated retrospectively. A total of 131 segments were enrolled in this study. Basic demographic information, radiographic [segmental subsidence rate, fusion rate, C2-7 global angle, and segmental angle changes)/clinical outcomes (by Odom's criteria and visual analog score (VAS)] and complications were evaluated to determine the long-term outcomes. RESULTS: The majority were males (55 vs. 44) with average age of 53.2. Mean follow-up period was 62.9 months. The segmental subsidence rate was 53.4% and fusion rate was 73.3%. In the subsidence group, anterior intervertebral height (AIH) had more tendency of subsiding than middle or posterior intervertebral height (p=0.01). The segmental angle led kyphotic change related to the subsidence of the AIH. Adjacent segmental disease was occurred in 18 (18.2%) patients. Total 6 (6%) reoperations were performed at the index level. There was no statistical significance between clinical and radiological outcomes. But, overall long-term clinical outcome by Odom's criteria was unsatisfactory (64.64%). The neck and arm VAS score were increased by over time. CONCLUSION: Long-term outcomes of ACDF with SAC group were acceptable but not satisfactory. For optimal decision making, more additional comparative long-term outcome data is needed between ACDF with SAC and ACDF with plating.

Stand-Alone Cages for Anterior Cervical Fusion: Are There No Problems?

OBJECTIVE: There are complications in stand-alone cage assisted anterior cervical discectomy and fusion (ACDF), such as cage subsidence and kyphosis. Here we report our clinical result on ACDF, comparing with stand-alone cages and with cervical plate system for degenerative cervical spine diseases. METHODS: Patients with degenerative cervical disease who were diagnosed and treated in Konyang University Hospital between January 2004 and December 2014 were included in this study. Patients who had operation in single level ACDF were selected. Patients scored the degree of pain using visual analog scale before and after the surgery. Subsidence was defined as ≥3-mm decrease of the segmental height, and cervical kyphosis was defined as progression of ≥5° at 12 months after postoperative follow-up compared to that measured at the immediate postoperative period. RESULTS: A total of 81 patients were enrolled for this study. Forty-five patients were included in a cervical plate group and the others were in stand-alone cage group. There was no statistical difference in pain score between the 2 groups. Segmental subsidence was observed in 7 patients (15.6%) in plate-assisted cervical fusion group, and 13 patients (36.1%) in stand-alone cage group. Segmental kyphosis was observed in 4 patients (8.9%) in plate-assisted cervical fusion group, and 10 patients (27.8%) in stand-alone cage group. There was statistical difference between the 2 groups. CONCLUSION: There was no difference in pain between 2 groups. But stand-alone case group showed higher incidence rate than plate-assisted cervical fusion group in segmental subsidence and cervical kyphosis. When designing cervical fusion, more attention should be given selecting the surgical technique.

Cervical Stand-Alone Polyetheretherketone Cage versus Zero-Profile Anchored Spacer in Single-Level Anterior Cervical Discectomy and Fusion : Minimum 2-Year Assessment of Radiographic and Clinical Outcome

OBJECTIVE: We compared the clinical and radiographic outcomes of stand-alone polyetheretherketone (PEEK) cage and Zero-Profile anchored spacer (Zero-P) for single level anterior cervical discectomy and fusion (ACDF). METHODS: We retrospectively reviewed 121 patients who underwent single level ACDF within 2 years (Jan 2011-Jan 2013) in a single institute. Total 50 patients were included for the analysis who were evaluated more than 2-year follow-up. Twenty-nine patients were allocated to the cage group (m : f=19 : 10) and 21 for Zero-P group (m : f=12 : 9). Clinical (neck disability index, visual analogue scale arm and neck) and radiographic (Cobb angle-segmental and global cervical, disc height, vertebral height) assessments were followed at pre-operative, immediate post-operative, post-3, 6, 12, and 24 month periods. RESULTS: Demographic features and the clinical outcome showed no difference between two groups. The change between final follow-up (24 months) and immediate post-op of Cobb-segmental angle (p=0.027), disc height (p=0.002), vertebral body height (p=0.033) showed statistically better outcome for the Zero-P group than the cage group, respectively. CONCLUSION: The Zero-Profile anchored spacer has some advantage after cage for maintaining segmental lordosis and lowering subsidence rate after single level anterior cervical discectomy and fusion.

Subsidence of Polyetheretherketone Cage after Anterior Cervical Fusion / 대한정형외과학회잡지

PURPOSE: The purpose of this study is to evaluate the rate and direction of subsidence that occurred after anterior cervical discectomy and fusion using the polyetheretherketone (PEEK) cage and to analyze the risk factors of subsidence. MATERIALS AND METHODS: Thirty two patients (36 segments) who underwent anterior cervical discectomy and fusion using the PEEK cage and autologous cancellous iliac bone graft from July 2003 to November 2011 were enrolled in this study. anterior segmental height (ASH), posterior segmental height (PSH) and cage corner distance (CCD) were measured on plain radiographs. Subsidence was defined as > or =2 mm decrease in the average of ASH and PSH at the final follow up compared to that measured in the immediate postoperative period. A decrease of more than 3 mm was defined as severe subsidence for further statistical analysis. RESULTS: Subsidence of more than 2 mm was observed in 14 segments (38.9%) and severe subsidence (> or =3 mm) was observed in seven segments (19.4%). The direction of subsidence was examined by comparison of means of decreased ASH and PSH and anterior subsidence outweighed posterior subsidence (p<0.001). Examination of CCD showed that inferior subsidence was more frequent than superior subsidence (p<0.001, p=0.047). Among the suspicious risk factors for subsidence, intraoperative disc space distraction (anterior distraction: p=0.031, posterior distraction: p=0.007) and height of inserted cage (p=0.032) showed statistical significance. CONCLUSION: Considerable incidence of subsidence was observed after use of the cage. Using a cage of appropriate height and prevention of intraoperative over-distraction of disc space will be helpful to prevention of subsidence of the cage after anterior cervical discectomy and fusion using the PEEK cage.

Anterior Cervical Discectomy and Fusion Using a Double Cylindrical Cage versus an Anterior Cervical Plating System with Iliac Crest Autografts for the Treatment of Cervical Degenerative Disc Disease

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) is often complicated by subsidence, pseudoarthrosis, kyphosis, and graft donor site morbidities. To decrease the occurrence of these complications, various types of cages have been developed. We designed this retrospective study to analyze and compare the efficacy and outcomes of ACDF using double cylindrical cages (DCC) (BK Medical, Seoul, Korea) versus an anterior cervical plating system with autogenous iliac crest grafts. METHODS: Forty-eight patients were treated with autograft and plating (plate group), and 48 with DCC group from October 2007 to October 2011. We analyzed construct length, cervical lordotic curvarture, the thickness of the prevertebral soft tissue, segmental instability, and clinical outcomes. RESULTS: There were no significant differences between the two groups with regard to the decrease in construct length or cervical lodortic curvature at the 3-, 6-, and 12-month follow-ups. The prevertebral soft tissue was thinner in the DCC group than the plate group immediately after surgery and at the 3-, 6-, and 12-month follow-ups. The difference in interspinous distance on flexion-extension was shorter in the plate group than the DCC group at the 3- and 6-month follow-ups. However, there was no significant difference in this distance between the two groups at the 12-month follow-up. CONCLUSION: A double cylindrical cage is a good alternative for fusion in patients with cervical degenerative diseases; the surgical method is relatively simple, allows good synostosis, has less associated prevertebral soft tissue swelling, and complications associated with autografting can be avoided.

Simulating the Impact of Drought on California’s Central Valley Hydrology Groundwater and Cropping.

This paper describes an efficient methodology to link a comprehensive, distributed hydrologic model for California’s Central Valley to a crop production model. The resulting hydro-economic model allows for the dynamic calculation of crop acreages in response to water availability without simplifying groundwater or stream flow dynamics by the assumption of linearity or by resorting to a lumped-parameter approach. The linked hydro-economic model is used to simulate the effects of several drought scenarios on Central Valley’s agriculture and the groundwater resources. The drought scenarios are constructed as surface flow reductions that range from 30% to 70% for periods spanning from 10 to 60 years, with a 10-year spin-up and a 30-year recovery. The main finding is that Central Valley agriculture as a whole is resilient to severe

Loss of Lordosis and Clinical Outcomes after Anterior Cervical Fusion with Dynamic Rotational Plates

PURPOSE: The cervical dynamic rotational plating system may induce bone graft subsidence, so it may cause loss of cervical lordosis. However there were few studies for alignments of cervical spines influencing the clinical results after using dynamic rotational plates. The purpose is to evaluate the effect of graft subsidence on cervical alignments due to the dynamic rotational cervical plates and correlating it with the clinical outcomes of patients undergoing anterior cervical fusion. MATERIALS AND METHODS: Thirty-three patients with disease or fracture underwent anterior cervical decompression and fusion using a dynamic rotational plate. The presence and extent of implant complications, graft subsidence, loss of lordosis were identified and Visual Analog Scale score (VAS score), Japanese Orthopaedic Association score (JOA score), clinical outcomes based on Odom's criteria were recorded. RESULTS: Fusion was achieved without implant complications in all cases. The mean graft subsidence at 6 months after the surgery was 1.46 mm. The lordotic changes in local cervical angles were 5.85degrees which was obtained postoperatively. VAS score for radicular pain was improved by 5.19 and the JOA score was improved by 3. Clinical outcomes based on Odom's criteria showed sixteen excellent, ten good and two satisfactory results. There was no significant relationship between clinical outcomes and changes in the cervical angles. CONCLUSION: Dynamic rotational anterior cervical plating provides comparable clinical outcomes to that of the reports of former static cervical platings. The loss of lordosis is related to the amount of graft settling but it is not related to the clinical outcomes.

Radiologic Changes of Anterior Cervical Discectomy and Fusion Using Allograft and Plate Augmentation: Comparison of Using Fixed and Variable Type Screw

OBJECTIVE: To evaluate radiologic result of anterior cervical discectomy and fusion with allobone graft and plate augmentation, and the change of radiologic outcome between screw type and insertion angle. METHODS: Retrospective review of clinical and radiological data of 29 patients. Segmental angle, height and screw angles were measured and followed. The fusion rate was assessed by plain radiography and CT scans. We divided the patients into two groups according to screw type and angles. Group A: fixed screw, Group B: variable screw. Interscrew angle was measured between most upper and lower screws with Cobb's methods. RESULTS: Overall fusion rate was 86.2% on plain radiography. Fusion was also assessed by CT scan and Bridwell's grading system. There was no difference in fusion and subsidence rates between two groups. Subsidence was found in 5 patients (17.2%). Segmental lordotic angle was increased from preoperative status and maximized at the immediate postoperative period and then reduced at 1 year follow up. Segmental height showed similar increase and decrease values. CONCLUSION: ACDF with allograft and plate showed favorable fusion rates, and the screw type and angle did not affect results of surgery.

Long-Term Follow-Up Radiologic and Clinical Evaluation of Cylindrical Cage for Anterior Interbody Fusion in Degenerative Cervical Disc Disease

OBJECTIVE: Various procedures have been introduced for anterior interbody fusion in degenerative cervical disc disease including plate systems with autologous iliac bone, carbon cages, and cylindrical cages. However, except for plate systems, the long-term results of other methods have not been established. In the present study, we evaluated radiologic findings for cylindrical cervical cages over long-term follow up periods. METHODS: During 4 year period, radiologic findings of 138 patients who underwent anterior cervical fusion with cylindrical cage were evaluated at 6, 12, 24, and 36 postoperative months using plain radiographs. We investigated subsidence, osteophyte formation (anterior and posterior margin), cage direction change, kyphotic angle, and bone fusion on each radiograph. RESULTS: Among the 138 patients, a minimum of 36 month follow-up was achieved in 99 patients (mean follow-up : 38.61 months) with 115 levels. Mean disc height was 7.32 mm for preoperative evaluations, 9.00 for immediate postoperative evaluations, and 4.87 more than 36 months after surgery. Osteophytes were observed in 107 levels (93%) of the anterior portion and 48 levels (41%) of the posterior margin. The mean kyphotic angle was 9.87degrees in 35 levels showing cage directional change. There were several significant findings : 1) related subsidence [T-score (p=0.039) and anterior osteophyte (p=0.009)], 2) accompanying posterior osteophyte and outcome (p=0.05). CONCLUSION: Cage subsidence and osteophyte formation were radiologically observed in most cases. Low T-scores may have led to subsidence and kyphosis during bone fusion although severe neurologic aggravation was not found, and therefore cylindrical cages should be used in selected cases.

Comparison According to Fusion Level in ACDF Using PEEK Cage Alone for Degenerative Cervical Disease / 대한정형외과학회잡지

PURPOSE: This study examined the clinical efficacy of an anterior cervical discectomy and fusion (ACDF) with PEEK (polyetheretherketone) cage alone with regard to the clinical and radiological outcomes, as well as the risk factors for the cage subsidence. MATERIALS AND METHODS: A total of 128 patients who underwent group A (1-level, n=48), group B (2-levels, n=57), group C (3-levels, n=23) ACDF using a PEEK cage alone were enrolled in this study. The fusion rate, segmental kyphosis were assessed by radiographs. The clinical outcomes were assessed using the Visual Analog Scale (VAS) and Neck Disability Index (NDI). The risk factors for cage subsidence were analyzed according to the difference in incidence between the subsidence group and non-subsidence group. RESULTS: Solid fusion was achieved in 93.8% (45/48), 71.9% (41/57) and 69.6% (15/23) of subjects in group A, B and C, respectively. Segmental kyphosis was observed in 22.9% (11/48), 43.9% (25/57) and 47.8% (11/23) of subjects in group A, B and C, respectively. The VAS scores changed from 7.79+/-1.01 in group A, 7.74+/-1.09 in group B, 7.91+/-0.79 in group C preoperatively to 4.23+/-1.29 in group A, 5.25+/-1.34 in group B and 5.35+/-1.07 in group C at the last follow up. In addition, the NDI was also improved at the last follow up. The VAS score and NDI at the last follow up were similar in the subsidence and non-subsidence group. The 3-level ACDF (p=0.05), osteoporosis (p=0.01), and old age (p=0.01) were the risk factors for cage subsidence. CONCLUSION: Only 1 level ACDF with PEEK cage alone was similar in clinical and radiologic (solid fusion rate, local kyphosis) outcomes compared to ACDF with published other modalities. Old age, 3 fusion level, osteoporosis, and C6-7 fusion were risk factors for the cage subsidence with higher complication rates.

Subsidence and Nonunion after Anterior Cervical Interbody Fusion Using a Stand-Alone Polyetheretherketone (PEEK) Cage

BACKGROUND: The purposes of the present study are to evaluate the subsidence and nonunion that occurred after anterior cervical discectomy and fusion using a stand-alone intervertebral cage and to analyze the risk factors for the complications. METHODS: Thirty-eight patients (47 segments) who underwent anterior cervical fusion using a stand-alone polyetheretherketone (PEEK) cage and an autologous cancellous iliac bone graft from June 2003 to August 2008 were enrolled in this study. The anterior and posterior segmental heights and the distance from the anterior edge of the upper vertebra to the anterior margin of the cage were measured on the plain radiographs. Subsidence was defined as > or = a 2 mm (minor) or 3 mm (major) decrease of the segmental height at the final follow-up compared to that measured at the immediate postoperative period. Nonunion was evaluated according to the instability being > or = 2 mm in the interspinous distance on the flexion-extension lateral radiographs. RESULTS: The anterior and posterior segmental heights decreased from the immediate postoperative period to the final follow-up at 1.33 +/- 1.46 mm and 0.81 +/- 1.27 mm, respectively. Subsidence > or = 2 mm and 3 mm were observed in 12 segments (25.5%) and 7 segments (14.9%), respectively. Among the expected risk factors for subsidence, a smaller anteroposterior (AP) diameter (14 mm vs. 12 mm) of cages (p = 0.034; odds ratio [OR], 0.017) and larger intraoperative distraction (p = 0.041; OR, 3.988) had a significantly higher risk of subsidence. Intervertebral nonunion was observed in 7 segments (7/47, 14.9%). Compared with the union group, the nonunion group had a significantly higher ratio of two-level fusion to one-level fusions (p = 0.001). CONCLUSIONS: Anterior cervical fusion using a stand-alone cage with a large AP diameter while preventing anterior intraoperative over-distraction will be helpful to prevent the subsidence of cages. Two-level cervical fusion might require more careful attention for avoiding nonunion.