Influence of cervical spine sagittal alignment on range of motion after corpectomy: a finite element study.

BACKGROUND: Sagittal alignment of the cervical spine might influence the development of radiological adjacent segment pathology (RASP) after central corpectomy (CC). Range of motion (ROM) of the adjacent segments is closely linked to the development of RASP. METHODS: To investigate the ROM of the adjacent segments after CC, we developed a C2-T1 finite element (FE) model. The model with a lordotic sagittal alignment served as the baseline model. Models with straight and kyphotic alignment were generated using mesh morphing methods. Single-level corpectomy at C5 was done on these models. Segmental ROMs of intact and corpectomized spines were compared for physiologic flexion-extension loads. RESULTS: The flexion ROM decreased by an average of 13% with the change in sagittal alignment from lordosis to kyphosis; however, a consistent decrease was not observed in extension. After CC, the ROM increased by an average of 95% and 31% in the superior and inferior adjacent segments. With kyphotic change in the sagittal alignment, the postoperative increase in flexion ROM exhibited a decreasing trend, while this was not seen in extension. CONCLUSIONS: Kyphotic changes of the intact spine resulted in segmental stiffening, and after corpectomy, it resulted in inconsistent variations of segmental extension ROMs.

Adjacent Segment Pathology: Progressive Disease Course or a Product of Iatrogenic Fusion?

OBJECTIVE: Cervical spine clinical adjacent segment pathology (CASP) has a reported 3% annual incidence and 26% ten-year prevalence. Its pathophysiology remains controversial, whether due to mechanical stress of a fusion segment on adjacent levels or due to patient propensity to develop progressive degenerative change. We investigate this relationship by comparing prevalence of CASP in traumatic and spondylotic patient cohorts. METHOD: A retrospective review of traumatic cervical spine fusion cases performed by the local group of neurosurgeons from 2004-2008 was completed. Surgery for CASP and presence of radiological adjacent segment pathology (RASP) were identified by telephone and electronic medical record (EMR) review, and compared to those in patients having elective cervical fusion for degenerative disease. RESULTS: There was a higher proportion of males (50/100 vs. 37/46, p0.05). Mean follow-up times were different (6.4 years in the trauma group, 7.1 years in the degenerative group; p<0.01), although this was not thought to be clinically significant. The degenerative group was found to have a significantly higher reoperation rate for CASP (10/100 vs. 0/46, p=0.031, Fisher's Exact Test), and rate of RASP (20/100 vs. 1/32, p=0.025) Conclusion: This is the only cohort study to our knowledge comparing surgery for CASP in trauma patients to those with degenerative disease. A higher rate of repeat surgery in degenerative disease patients was found. This suggests that CASP is more related to patient factors predisposing to progressive degenerative disease and not increased mechanical stress.

Multilevel cervical arthroplasty: current evidence. A systematic review.

OBJECTIVE Cervical disc arthroplasty (CDA) has been demonstrated to be an effective treatment modality for single-level cervical radiculopathy or myelopathy. Its advantages over an anterior cervical discectomy and fusion (ACDF) include motion preservation and decreased reoperations at the index and adjacent segments up to 7 years postoperatively. Considering the fact that many patients have multilevel cervical disc degeneration (CDD), the authors performed a systematic review of the clinical studies evaluating patients who underwent multilevel CDA (2 or more levels). METHODS A systematic review in the MEDLINE database was performed. Clinical studies including patients who had multilevel CDA were selected and included. Case reports and literature reviews were excluded. Articles were then grouped according to their main study objective: 1) studies comparing multilevel CDA versus ACDF; 2) studies comparing single-level CDA versus multilevel CDA; and 3) multilevel CDA after a previous cervical spine surgery. RESULTS Fourteen articles met all inclusion criteria. The general conclusions were that multilevel CDA was at least as safe and effective as ACDF, with preservation of cervical motion when compared with ACDF and potentially with fewer reoperations expected in most of the studies. Multilevel CDAs are clinically effective as single-level surgeries, with good clinical and radiological outcomes. Some studies reported a higher incidence of heterotopic ossification in multilevel CDA when compared with single-level procedures, but without clinical relevance during the follow-up period. A CDA may be indicated even after a previous cervical surgery in selected cases. CONCLUSIONS The current literature supports the use of multilevel CDA. Caution is necessary regarding the more restrictive indications for CDA when compared with ACDF. Further prospective, controlled, multicenter, and randomized studies not sponsored by the device manufactures are desirable to prove the superiority of CDA surgery over ACDF as the treatment of choice for CDD in selected cases.

Adjacent segment pathology: natural history or effect of anterior cervical discectomy and fusion? A 10-year follow-up radiological multicenter study using an evaluation scale of the ageing spine.

PURPOSE: Aim of this study is to compare late degenerative MRI changes in a subset of patients operated on with ACDF to a second subset of patients presenting indication to ACDF but never operated on. METHODS: Patients from both subgroups received surgical indication according to the same criteria. Both subgroups underwent a cervical spine MRI in 2004-2005 and 10 years later in 2015. These MRI scans were retrospectively evaluated with a cervical spine ageing scale. RESULTS: Comparing the two subset of patients both suffering from clinically relevant single-level disease returns no statistically significant difference in the degenerative condition of posterior ligaments, presence of degenerative spondylolisthesis, foraminal stenosis, diameter of the spinal canal, Modic alteration, and intervertebral discs degeneration at 10-year follow-up. CONCLUSIONS: The adjacent segment degeneration represents, in the present cohort, a result of the natural history of cervical spondylosis rather than a consequence of fusion.

Risk factors for adjacent segment pathology requiring additional surgery after single-level spinal fusion: impact of pre-existing spinal stenosis demonstrated by preoperative myelography.

PURPOSE: We determined the incidence of and risk factors for clinical adjacent segment pathology (C-ASP) requiring additional surgeries among patients previously treated with one-segment lumbar decompression and fusion surgery. METHODS: We retrospectively analysed 161 consecutive patients who underwent one-segment lumbar decompression and fusion surgery for L4 degenerative spondylolisthesis. Patient age, sex, body mass index (BMI), facet orientation and tropism, laminar inclination angle, spinal canal stenosis ratio [on myelography and magnetic resonance imaging (MRI)], preoperative adjacent segment instability, arthrodesis type, pseudarthrosis, segmental lordosis at L4-5, and the present L4 slip were evaluated by a log-rank test using the Kaplan-Meier method. A multivariate Cox proportional-hazards model was used to analyse all factors found significant by the log-rank test. RESULTS: Of 161 patients, 22 patients (13.7 %) had additional surgeries at cranial segments located adjacent to the index surgery's location. Pre-existing canal stenosis ≥47 % at the adjacent segment on myelography, greater facet tropism, and high BMI were significant risk factors for C-ASP. The estimated incidences at 10 years postoperatively for each of these factors were 51.3, 39.6, and 32.5 %, and the risks for C-ASP were 4.9, 3.7, and, 3.1 times higher than their counterparts, respectively. Notably, spinal canal stenosis on myelography, but not on MRI, was found to be a significant risk factor for C-ASP (log-rank test P < 0.0001 and 0.299, respectively). CONCLUSIONS: Pre-existing spinal stenosis, greater facet tropism, and higher BMI significantly increased C-ASP risk. Myelography is a more accurate method for detecting latent spinal canal stenosis as a risk factor for C-ASP.

Complications associated with the Dynesys dynamic stabilization system: a comprehensive review of the literature.

The Dynesys dynamic stabilization system is an alternative to rigid instrumentation and fusion for the treatment of lumbar degenerative disease. Although many outcomes studies have shown good results, currently lacking is a comprehensive report on complications associated with this system, especially in terms of how it compares with reported complication rates of fusion. For the present study, the authors reviewed the literature to find all studies involving the Dynesys dynamic stabilization system that reported complications or adverse events. Twenty-one studies were included for a total of 1166 patients with a mean age of 55.5 years (range 39-71 years) and a mean follow-up period of 33.7 months (range 12.0-81.6 months). Analysis of these studies demonstrated a surgical-site infection rate of 4.3%, pedicle screw loosening rate of 11.7%, pedicle screw fracture rate of 1.6%, and adjacent-segment disease (ASD) rate of 7.0%. Of studies reporting revision surgeries, 11.3% of patients underwent a reoperation. Of patients who developed ASD, 40.6% underwent a reoperation for treatment. The Dynesys dynamic stabilization system appears to have a fairly similar complication-rate profile compared with published literature on lumbar fusion, and is associated with a slightly lower incidence of ASD.

Facet joint changes after application of lumbar nonfusion dynamic stabilization.

OBJECTIVE The long-term effects on adjacent-segment pathology after nonfusion dynamic stabilization is unclear, and, in particular, changes at the adjacent facet joints have not been reported in a clinical study. This study aims to compare changes in the adjacent facet joints after lumbar spinal surgery. METHODS Patients who underwent monosegmental surgery at L4-5 with nonfusion dynamic stabilization using the Dynesys system (Dynesys group) or transforaminal lumbar interbody fusion with pedicle screw fixation (fusion group) were retrospectively compared. Facet joint degeneration was evaluated at each segment using the CT grading system. RESULTS The Dynesys group included 15 patients, while the fusion group included 22 patients. The preoperative facet joint degeneration CT grades were not different between the 2 groups. Compared with the preoperative CT grades, 1 side of the facet joints at L3-4 and L4-5 had significantly more degeneration in the Dynesys group. In the fusion group, significant facet joint degeneration developed on both sides at L2-3, L3-4, and L5-S1. The subjective back and leg pain scores were not different between the 2 groups during follow-up, but functional outcome based on the Oswestry Disability Index improved less in the fusion group than in the Dynesys group. CONCLUSIONS Nonfusion dynamic stabilization using the Dynesys system had a greater preventative effect on facet joint degeneration in comparison with that obtained using fusion surgery. The Dynesys system, however, resulted in facet joint degeneration at the instrumented segments and above. An improved physiological nonfusion dynamic stabilization system for lumbar spinal surgery should be developed.

Clinical adjacent-segment pathology after central corpectomy for cervical spondylotic myelopathy: incidence and risk factors.

OBJECTIVE The goal of this study was to investigate the prevalence and risk factors of clinical adjacent-segment pathology (CASP) following central corpectomy for cervical spondylotic myelopathy (CSM) or ossification of the posterior longitudinal ligament (OPLL). METHODS The authors reviewed 353 cases involving patients operated on by a single surgeon with a minimum 12-month follow-up after central corpectomy for CSM or OPLL between 1995 and 2007. Patients with symptoms consistent with CASP at follow-up were selected for the study. The authors analyzed the prevalence and risk factors for CASP after central corpectomy for CSM/OPLL. RESULTS Fourteen patients (13 male, 1 female; mean age 46.9 ± 7.7 years) were diagnosed with symptoms of CASP (3.9% of 353 patients) at follow-up. The mean interval between the initial surgery and presentation with symptoms of CASP was 95.6 ± 54.1 months (range 40-213 months). Preoperative Nurick grades ranged from 2 to 5 (mean 3.5 ± 1.2), and the Nurick grades at follow-up ranged from 1 to 5 (mean 3.0 ± 1.3, p = 0.27). Twelve patients had myelopathic symptoms and 2 had radiculopathy at follow-up. Patients with poorer preoperative Nurick grades had a higher risk for development of CASP (HR 2.6 [95% CI 1.2-5.3], p = 0.01). CONCLUSIONS In the present study, CASP was seen in 3.9% of patients following central corpectomy for CSM/OPLL. The risk of CASP after central corpectomy for CSM/OPLL was higher in patients with poorer preoperative Nurick grades.

Effect of Body Mass Index on Fusion Outcome After Short-Segment Posterior Lumbar Fusion.

OBJECTIVE: Obesity is a growing epidemic in the United States. While many adverse effects of obesity on surgical outcome are well studied, a direct correlation among obesity, pseudarthrosis, and adjacent segment pathology is not well defined. In this study we aimed to identify the effect of body mass index (BMI) on pseudarthrosis, adjacent segment pathology (ASP), and reoperation after short-segment (1-3 levels) open posterior lumbar fusion (PLF). METHODS: This is a retrospective study of patients with degenerative spine pathologies who underwent 1-, 2-, or 3-level PLF surgery between 2010 and 2020. The relevant medical and imaging records were reviewed, and the following variables were recorded: age, gender, BMI, smoking status, surgical details, follow-up length, need for reoperation, indication for reoperation (pseudarthrosis or occurrence of ASP). RESULTS: We included363 patients in our study. Twenty-five patients (6.9%) developed pseudarthrosis, 109 (30%) developed ASP, and 104 patients (28.7%) underwent reoperation for either of these reasons. BMI was significantly less in those who developed pseudarthrosis compared with those who did not (28.6 ± 5.5 vs. 31.2 ± 6.2, respectively; P = 0.04). BMI was not significantly different in those who developed ASP or underwent reoperation compared with those who did not (P = 0.06 and 0.08, respectively). Multivariate regression analysis showed none of the variables in the model (age, gender, tobacco use, BMI, and its classes) significantly predicted pseudarthrosis, ASP, or reoperation (P > 0.1 for all variables). CONCLUSIONS: Obese patients undergoing short-segment open PLF have comparable results in terms of pseudarthrosis, ASP, and reoperation.

Cervical Disc Arthroplasty vs Anterior Cervical Discectomy and Fusion at 10 Years: Results From a Prospective, Randomized Clinical Trial at 3 Sites.

BACKGROUND: Over the past 20 years, multiple randomized controlled trials have shown cervical disc arthroplasty (CDA) to be safe and effective for treating 1- and 2-level degenerative disc disease (DDD). The purpose of this postmarket study is to compare 10-year outcomes between CDA and anterior cervical discectomy and fusion (ACDF) from a randomized study at 3 centers. METHODS: This study was a continuation of a randomized, prospective, multicenter clinical trial comparing CDA with the Mobi-C cervical disc (Zimmer Biomet) vs ACDF. Following completion of the 7-year US Food and Drug Administration study, 10-year follow-up was obtained from consenting patients at 3 high-enrolling centers. The clinical and radiographic endpoints collected at 10 years included composite success, Neck Disability Index, neck and arm pain, short form-12, patient satisfaction, adjacent-segment pathology, major complications, and subsequent surgery. RESULTS: A total of 155 patients were enrolled (105 CDA; 50 ACDF). Follow-up was obtained from 78.1% of patients eligible after 7 years. At 10 years, CDA demonstrated superiority to ACDF. Composite success was 62.4% in CDA and 22.2% in ACDF (P < 0.0001). The cumulative risk of subsequent surgery at 10 years was 7.2% vs 25.5% (P = .001), and the risk of adjacent-level surgery was 3.1% vs 20.5% (P = .0005) in CDA vs ACDF, respectively. The progression to radiographically significant adjacent-segment pathology at 10 years was lower in CDA vs ACDF (12.9% vs 39.3%; P = 0.006). At 10 years, patient-reported outcomes and change from baseline were generally better in CDA patients. A higher percentage of CDA patients reported they were "very satisfied" at 10 years (98.7% vs 88.9%; P = 0.05). CONCLUSIONS: In this postmarket study, CDA was superior to ACDF for treating symptomatic cervical DDD. CDA was statistically superior to ACDF for clinical success, subsequent surgery, and neurologic success. Results through 10 years demonstrate that CDA continues to be a safe and effective surgical alternative to fusion. CLINICAL RELEVANCE: The results of this study support the long-term safety and effectiveness of cervical disc arthroplasty with the Mobi-C.

Does the Number of Interbody Devices Affect the Fusion Outcome in Short-Segment Posterior Lumbar Fusion?

INTRODUCTION: Interbody devices (IBDs) have been shown to improve outcomes when used in posterior lumbar fusion (PLF) surgery; however,the exact extent of their clinical benefit remains a current topic of interest. Our primary objective in this study was to identify whether the use of an IBD at every level of fusion construct would affect fusion outcomes such as adjacent segment pathology (ASP) and pseudarthrosis after one- to three-level PLF surgery. METHODS: This was a single-institution retrospective study. We studied the association of factors such as smoking status, BMI, gender, age, and number of IBDs on the development of ASP and pseudarthrosis. To study the effect of independent variables on ASP and pseudoarthrosis, univariate and multivariate regression analyses were used. RESULTS: The study included 2,061 patients with a history of posterior lumbar fusion who were identified and reviewed. Among these, 363 patients met our inclusion criteria; 247 patients had a minimum follow-up of six months and were finally included in the study. The median follow-up was 30 months. Among the 247 patients, 105 (42.5%) and 24 (9.7%) experienced ASP and pseudarthrosis, respectively. Gender and use of IBD significantly affected the presence of pseudarthrosis (with a higher rate in males and those without any IBDs). Gender, age, BMI, and use of IBDs did not affect ASP. Moreover, using an IBD at each fused level reduced the pseudarthrosis rate significantly compared to when IBDs were not used at all levels (7.3% vs. 27.6%, p <0.001), while there was no significant difference in the rate of ASP (43.6% vs. 34.5%, p = 0.35). CONCLUSIONS: In patients undergoing one- to three-level PLF surgery, the use of an IBD at all levels of the fusion construct significantly reduces the rate of pseudarthrosis. There was no significant correlation between the rates of ASP. Studies with a larger sample size and a longer follow-up time are suggested to validate our results for pseudoarthrosis and ASP. Our results suggest the use of an IBD per fusion level in short-segment PLF surgeries.

Adjacent segment pathology of the cervical spine: A case report.

Adjacent segment pathology (ASP) refers to degenerative changes at segments immediately contiguous to previous spinal fusion. Its pathophysiology is hypothesized as being possibly due to altered biomechanical stresses on adjacent levels following spinal fusion or due to patient propensity to develop progressive degenerative change. This case report describes a 61-year-old female who presented with neck pain and cervical radiculopathy attributed to an anterior cervical discectomy and spinal fusion performed for degenerative disc disease 30 years earlier. ASP was seen on magnetic resonance imaging (MRI) and radiograph. Treatment consisted of cervical manipulation, soft-tissue mobilization, flexion-distraction decompression, and therapeutic ultrasound to release restriction and restore muscle strength. Following 34 sessions of chiropractic intervention, her symptoms were resolved. Patients with ASP will have ongoing shared care between general practitioners and secondary or tertiary care pain units. This report aims to build a shared understanding from the wider vision of ASP and help primary practitioners to manage ASP effectively.

Crossing the Cervico-Thoracic Junction in Long Posterior Cervical Fusions Reduces Caudal Adjacent Segment Pathology.

STUDY DESIGN: Retrospective case control. OBJECTIVES: The purpose of this study is to compare clinical outcomes and rates of symptomatic caudal adjacent segment pathology (ASP) in posterior cervical fusions (PCF) constructs with end-instrumented vertebrae in the cervical spine (EIV-C) to PCF constructs that end in the proximal thoracic spine (EIV-T). METHODS: Retrospective review of 1714 consecutive cervical spinal fusion cases was done. Two groups were identified: 36 cervical end-instrumented vertebra patients (age56 ± 10 yrs) and 53 thoracic EIV patients (age 57 ± 9 yrs). Symptomatic ASP was defined as revision surgery or nerve root injection (or recommended surgery or injection) at the adjacent levels. RESULTS: EIV-C patients had a significantly higher rate of caudal-level symptomatic ASP requiring intervention compared with EIV-T patients (39% vs 15%, p = 0.01). The development of caudal-level ASP was highest at C7 (41%), followed by C6 (40%). The overall complication rate and surgical revision rates, however, were similar between the groups. Neck Disability Index outcomes at 2 years postop were significantly better in the EIV-T group (24.5 vs. 34.0, p = 0.05). CONCLUSIONS: Long PCF that cross the C-T junction have superior clinical outcomes and reduced rates of caudal breakdown, at the expense of longer fusions and higher EBL, with no increase in the rate of complications. Crossing the C-T junction affords protection of the caudal adjacent levels without adding significant operative time or morbidity.

Clinical adjacent segment pathology after anterior cervical discectomy, with and without fusion, for cervical degenerative disc disease: A single center retrospective cohort study with long-term follow-up.

Introduction: Clinical adjacent segment pathology (CASP) continues to be a cause of concern after anterior surgical treatment for single- or multilevel cervical degenerative disc disease (CDDD). The current literature reports inconsistent incidence rates and contended risk factors in the development of CASP. Research question: The aim is to determine the incidence of additional CASP-related surgeries after anterior cervical discectomy with fusion (ACDF) or without fusion (ACD) for CDDD. Secondary outcomes include risk factors for the development of CASP and long-term clinical outcomes. Materials & methods: This is a single-center, retrospective cohort study with a long-term follow up. Patients undergoing ACD(F) for CDDD between January 2012 and December 2019 were included. Results: A total of 601 patients were included, with an average follow-up period of 5.0 years. Most patients underwent ACDF with stand-alone cages (87.7%). CASP developed in 58 (9.7%) patients, 41 (70.7%) of which required additional adjacent level surgery. ACD significantly accelerated the development of CASP. The C2-C7 Cobb angle appeared less lordotic upon early post-operative imaging in ACDF patients that later-on developed CASP. Baseline degeneration at the index level and adjacent levels was not significantly different between patients with and without CASP. Discussion & conclusion: In this retrospective cohort, we observe a relatively low rate of additional surgery for CASP in ACDF with stand-alone cages. We suggest that surgical technique, fusion, segmental kyphosis and natural degeneration play a multifactorial role in the development of CASP. Complication rates were low and clinical outcomes were similar for all techniques used.

Artificial disc replacement and adjacent-segment pathology: 10-year outcomes of a randomized trial.

OBJECTIVE: Artificial disc replacement (ADR) is designed to preserve motion and thus protect against adjacent-segment pathology (ASP) and act as an alternative treatment to fusion surgery. The question remains, how well do ADR devices perform after 10 years of follow-up compared with fusion surgery in terms of patient satisfaction, sustainability, and protection against ASP? METHODS: This was the 10-year follow-up study of 153 participants who underwent ADR or fusion surgery after anterior decompression due to cervical degenerative radiculopathy (ISRCTN registration no. 44347115). Scores on the Neck Disability Index (NDI), EQ-5D, and visual analog scale for neck and arm pain were obtained from the Swedish Spine Registry and analyzed using ANCOVA. Information about secondary surgical procedures was collected from medical records and presented as Kaplan-Meier curves. MRI and flexion-extension radiography were performed, and ASP was graded according to the Miyazaki classification system. RESULTS: Ten participants were lost to follow-up, which left 143 participants (80 underwent ADR and 65 underwent anterior cervical discectomy and fusion). There were no differences between groups in terms of patient-reported outcome measures (10-year difference in NDI scores 1.7 points, 95% CI -5.1 to 8.5, p = 0.61). Nineteen (24%) participants in the ADR group compared with 9 (14%) in the fusion group underwent secondary surgical procedures. The higher reoperation rate of the ADR group was mainly due to 11 female participants with device loosening. The rates of reoperation due to ASP were similar between groups, which was confirmed with MRI assessment of ASP that also showed no differences between the groups (p = 0.21). CONCLUSIONS: This was the first 10-year follow-up study to compare ADR with fusion surgery and to provide MRI information for the assessment of ASP. The authors found no benefit of ADR over fusion surgery after anterior decompression for cervical degenerative radiculopathy.

Effect of cervical alignment change after anterior cervical fusion on radiological adjacent segment pathology.

Background: Adjacent segment pathology (ASP) is one of the primary complications affecting the long-term efficacy of anterior cervical fusion (ACF). At present, the cause and mechanism of adjacent segmental lesions are still controversial. Methods: We performed a retrospective analysis on 88 patients with cervical spondylotic myelopathy (CSM) who had been followed up for at least 1 year after ACF. The patients were divided into radiological adjacent segment pathology (RASP) and non-RASP groups according to the presence of postoperative RASP. On the lateral radiographs of the cervical spine of all patients taken before and after surgery at the short-term and final follow-ups, the following parameters were measured: C2-7 Cobb angle of the cervical vertebrae; Cobb angle of the operated segments; and the anterior and posterior height of the fused segments [i.e., the anterior fusion segment height (AFH) and the posterior fusion segment height (PFH)]. The intra- and inter-group differences of the patients before and after surgery were calculated, as well as correlation of ACF with the occurrence of RASP. Results: There were 42 cases in the RASP group and 46 cases in the non-RASP group. In the RASP group, the C2-7 Cobb angle was significantly reduced in the short term after surgery (20.42±9.92° vs. 13.81±8.52°, P<0.01), while in non-RASP group the C2-7 Cobb angle was significantly increased in the short term after surgery (12.65±11.91° vs. 15.35±10.05°, P<0.05). The heights of both the anterior and posterior fused segments in the 2 groups were significantly higher after surgery, and they were significantly lower at the final follow-up than at the short-term follow-up. Post-operative AFH change was significantly correlated with C2-7 Cobb angle (r=0.274, P=0.010) and fused segment Cobb angle change (r=0.333, P=0.002). However, Cox regression analysis showed that only the postoperative C2-7 Cobb angle change was associated with RASP, with a hazard ratio of 0.336. Conclusions: Decreased cervical lordosis after ACF may be related to postoperative RASP. Maintaining good cervical curvature after surgery may reduce the incidence of RASP after ACF.

Association of Craniocervical Sagittal Alignment With the Outcomes of Cervical Disc Replacement.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To explore the association between craniocervical sagittal balance and clinical and radiological outcomes of cervical disc replacement (CDR). METHODS: Patients who underwent 1-level and 2-level CDR were retrospectively analyzed. Clinical outcomes were evaluated using scores on the Japanese Orthopaedic Association (JOA), Visual Analogue Scale (VAS), and Neck Disability Index (NDI). The craniocervical sagittal alignment parameters, including the C0-C2 Cobb angle, C2-C7 Cobb angle, C2 slope, T1 slope, C2-C7 sagittal vertical axis (SVA), C1-C7 SVA, the center of gravity of the head (CGH)-C7 SVA, and range of motion (ROM) at the surgical segments were measured. RESULTS: A total of 169 patients were involved. Significantly lower pre- and postoperative C2 slope and CGH-C7 SVA were found in arthroplasty levels with better ROMs. Patients with a higher preoperative C2 slope and CGH-C7 SVA had lower cervical lordosis and ROM after surgery. There were no significant differences in the clinical outcomes between patients with different sagittal balance statuses. C2-C7 SVA and CGH-C7 SVA were significantly associated with radiographic adjacent segment pathology (rASP). CONCLUSION: Craniocervical sagittal balance is associated with cervical lordosis and ROM at the index level after CDR. A higher preoperative SVA is related to the presence and progression of rASP. A relationship between sagittal alignment and clinical outcomes was not observed.

The Effect of Plating on Adjacent Segments in Anterior Cervical Discectomy and Fusions in Patients with Degenerative Spine Disease: A Retrospective Cohort Study.

Introduction: Plate distance is correlated with an increased incidence of adjacent segment pathologies (ASP). However, a correct plate-to-disk distance >5 mm is often not achieved. Therefore, this study aimed to quantify the effect of short plate-to-disk distance on the development of ASP using epidemiological measures in patients with cervical degenerative spine disease undergoing single-level anterior cervical discectomy and fusion (ACDFs). Methods: Medical records of all patients with cervical degeneration undergoing single-level ACDF with plating (between January 2015 and December 2017), and a follow-up of at least 1 year, were reviewed retrospectively. Radiologic and clinical outcomes were assessed preoperatively, postoperatively, and at last follow-up. The plate-to-adjacent disk distance was measured, and epidemiological measures were calculated to quantify the risk on adjacent-level ossification development (ALOD) and adjacent segment degeneration (ASD). Results: Thirty-eight (47.5%) of the 80 patients developed ALOD, and 12 (15.0%) developed ASD after a 2-year follow-up. The incidence of ALOD was significantly lower if the plate was >5 mm away from the adjacent disk space compared to <5 mm (cranial adjacent segment, 22.5% vs. 51.3% [P=0.010] and caudal, 21.4% vs. 47.8% [P=0.029]). A correct plate-to-disk distance resulted in a relative risk reduction of 57.2% for the cranial segment and 56.0% for the caudal segment, with a number needed to treat of 4. The ASD was only observed in the cranial adjacent segments, and a correct plate-to-disk distance resulted in a relative risk reduction of 32.1% and a number needed to treat of 18. Conclusions: Only four patients need to be treated with a correct plate-to-disk distance to avoid one case of ALOD. Therefore, it is advisable to keep the plate at a distance >5 mm away from the adjacent disk.

Differences in the Prevalence of Clinical Adjacent Segment Pathology among Continents after Anterior Cervical Fusion: Meta-Analysis of Randomized Controlled Trials.

Development of adjacent segment pathology leading to secondary operation is a matter of concern after anterior cervical discectomy and fusion (ACDF). Some studies have reported anatomic difference between races, but no epidemiological data on prevalence of clinical adjacent segment pathology (cASP) among races or continents has been published. The purpose of this study was to compare the prevalence of cASP that underwent surgery after monosegmental ACDF among continents by meta-analysis. MEDLINE, EMBASE, and Cochrane Library with manual searching in key journals, reference lists, and the National Technical Information Service were searched from inception to December 2018. Twenty studies with a total of 2009 patients were included in the meta-analysis. We extracted the publication details, sample size, and prevalence of cASP that underwent surgery. A total of 15 papers from North America, three from Europe, and two from Asia met the inclusion criteria. A total number of 2009 patients underwent monosegmental ACDF, and 113 patients (5.62%) among them had cASP that underwent surgery. The rate of cASP that underwent surgery was 4.99% in the North America, 3.65% in the Europe, 6.34% in the Asia, and there were no statistically significant differences (p = 0.63). The current study using the method of meta-analysis revealed that there were no significant differences in the rate of cASP that underwent surgery after ACDF among the continents.

The Relationship between Adjacent Segment Pathology and Facet Joint Violation by Pedicle Screw after Posterior Lumbar Instrumentation Surgery.

Transpedicular screw instrumentation systems have been increasingly utilized during the fusion of lumbar spine procedures. The superior segment facet joint violation of the pedicle screw is thought to have potential for accelerating symptomatic adjacent-segment pathology (ASP). The purpose of this study was to investigate the relationship between the superior segment facet joint violation by transpedicular screws and the development of ASP. Among all patients who underwent operations involving one- or two-level posterior lumbar arthrodesis at the Chonnam National University Hospital from 1992 to 2012, 87 patients were selected for this study. Fifty-six patients were included in the ASP group, and 31 were included in the non-ASP group. We used lumbar three-dimensional computed tomography (CT) to assess the violation of the superior facet joint by a transpedicular screw. The assessment is presented in scores ranging from zero to two, with zero indicating no violation (type I); one point indicating suspected violation (type II); and two points indicating definitely facet joint violation (type III). Facet violation was reported in 31 patients in the ASP group (n = 56), and in 13 patients in the non-ASP group (n = 31). The types of facet joint violation according to our scoring system were as follows: type I, 59 screws (52.7%); type II, 26 screws (23.2%); and type III, 27 screws (24.1%) in the ASP group; and type I, 43 screws (69.4%), type II, 14 screws (22.6 %); and type III, 5 screws (8.0%) in the non-ASP group. The score of facet joint violation in each patient according to our scoring system were as follows: 0 points, 25 patients (44.6%); 1 point, 8 patients (14.3%); 2 points, 4 patients (7.1%); 3 points, 11 patients (19.7%); 4 points, 8 patients (14.3%) in the ASP group; and 0 points, 18 patients (58.1%); 1 point, 4 patients (12.9%); 2 points, 7 patients (22.6%); 3 points, 2 patients (6.4%); 4 points, 0 patients (0%) in the non-ASP group. The mean scores were 1.4 points in the ASP group and 0.8 points in the non-ASP group (p < 0.05). We conclude that the position of the pedicle screw farther away from the facet joint surface can reduce the degeneration of the superior adjacent segment. Therefore, close attention to the screw position during surgery may reduce the rate of superior adjacent-segment pathologies.