Lowest Instrumented Vertebra Selection in Posterior Cervical Fusion: Does Cervicothoracic Junction Lowest Instrumented Vertebra Predict Mechanical Failure?

Effect of Cervicothoracic Junction LIV Selection on Posterior Cervical Fusion Mechanical Failure: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and Meta-analysis.

OBJECTIVE

Analyze and summarize literature evaluating the role of C7, T1, and T2 lowest instrumented vertebra (LIV) selection in posterior cervical fusion (PCF) and if this affects the progression of mechanical failure and revision surgery.

SUMMARY OF BACKGROUND DATA

Literature evaluating mechanical failure and adjacent segment disease in the setting of PCF at or nearby the cervicothoracic junction (CTJ) remains limited with studies reporting conflicting results.

MATERIALS AND METHODS

Two reviewers conducted a detailed systematic review using EMBASE, PubMed, Web of Science, and Google Scholar on June 28, 2021, for primary research articles comparing revision and complication rates for posterior fusions ending in the lower cervical spine (C7) and upper thoracic spine (T1-T2). The initial systematic database yielded 391 studies, of which 10 met all inclusion criteria. Random effects meta-analyses compared revision and mechanical failure rates between patients with an LIV above the CTJ and patients with an LIV below the CTJ.

RESULTS

Data from 10 studies (total sample=2001, LIV above CTJ=1046, and LIV below CTJ=955) were meta-analyzed. No differences were found between the 2 cohorts for all-cause revision [odds ratio (OR)=0.75, 95% CI=0.42-1.34, P<0.0001] and construct-specific revision (OR=0.62, 95% CI=0.25-1.53, P<0.0001). The odds of total mechanical failure in the LIV below CTJ cohort compared with the LIV above CTJ cohort were significantly lower (OR=0.38, 95% CI=0.18-0.81, P<0.0001).

CONCLUSION

The results show patients with PCFs ending below the CTJ have a lower risk of undergoing total mechanical failure compared with fusions ending above the CTJ. This is important information for both physicians and patients to consider when planning for operative treatment.

LEVEL OF EVIDENCE

Level I.

Is It Necessary to Cross the Cervicothoracic Junction in Posterior Cervical Decompression and Fusion for Multilevel Degenerative Cervical Spine Disease? A Systematic Review and Meta-Analysis

BACKGROUND

Posterior cervical decompression and fusion (PCF) is a common procedure for treating patients with multilevel degenerative cervical spine disease. The selection of lower instrumented vertebra (LIV) relative to the cervicothoracic junction (CTJ) remains controversial. This study aimed to compare the outcomes of PCF construct terminating at the lower cervical spine and crossing the CTJ.

METHODS

A comprehensive literature search was performed for relevant studies in the PubMed, EMBASE, Web of Science, and Cochrane Library database. Complications, rate of reoperation, surgical data, patient-reported outcomes (PROs), and radiographic outcomes were compared between PCF construct terminating at or above C7 (cervical group) and at or below T1 (thoracic group) in patients with multilevel degenerative cervical spine disease. A subgroup analysis based on surgical techniques and indications was performed.

RESULTS

Fifteen retrospective cohort studies comprising 2071 patients (1163 in the cervical group and 908 in the thoracic group) were included. The cervical group was associated with a lower incidence of wound-related complications (RR, 0.58; 95% CI 0.36 to 0.92, p = 0.022; 831 patients in cervical group vs. 692 patients in thoracic group), a lower reoperation rate for wound-related complications (RR, 0.55; 95% CI 0.32 to 0.96, p = 0.034; 768 vs. 624 patients), and less neck pain at the final follow-up (WMD, -0.58; 95% CI -0.93 to -0.23, p = 0.001; 327 vs. 268 patients). However the cervical group also developed a higher incidence of overall adjacent segment disease (ASD, including distal ASD and proximal ASD) (RR, 1.87; 95% CI 1.27 to 2.76, p = 0.001; 1079 vs. 860 patients), distal ASD (RR, 2.18; 95% CI 1.36 to 3.51, p = 0.001; 642 vs. 555 patients), overall hardware failure (including hardware failure of LIV and hardware failure occurring at other instrumented vertebra) (RR, 1.48; 95% CI 1.02 to 2.15, p = 0.040; 614 vs. 451 patients), and hardware failure of LIV (RR, 1.89; 95% CI 1.21 to 2.95, p = 0.005; 380 vs. 339 patients). The operating time was reasonably shorter (WMD, -43.47; 95% CI -59.42 to -27.52, p < 0.001; 611 vs. 570 patients) and the estimated blood loss was lower (WMD, -143.77; 95% CI -185.90 to -101.63, p < 0.001; 721 vs. 740 patients) when the PCF construct did not cross the CTJ.

CONCLUSIONS

PCF construct crossing the CTJ was associated with a lower incidence of ASD and hardware failure but a higher incidence of wound-related complications and a small increase in qualitative neck pain, without difference in neck disability on the NDI. Based on the subgroup analysis for surgical techniques and indications, prophylactic crossing of the CTJ should be considered for patients with concurrent instability, ossification, deformity, or a combination of anterior approach surgeries as well. However, long-term follow-up outcomes and patient selection-related factors such as bone quality, frailty, and nutrition status should be addressed in further studies.

Crossing the Cervicothoracic Junction: A Review of the Current Literature

ABSTRACT

The cervicothoracic junction (CTJ) is the site of transition in biomechanical, osseous, and alignment properties of the spine. The interface between the highly mobile, lordotic cervical spine and the rigid, kyphotic thoracic spine results increased the biomechanical stress experienced at this junction. The concentration of stress at this level has led to high rates of failure when instrumenting near or across the CTJ. The changes in osseous anatomy from the cervical spine to the thoracic spine present additional challenges in construct planning. For these reasons, a thorough understanding of the complexity of the cervicothoracic junction is necessary when operating near or across the CTJ. There are multiple options for cervical fixation, including lateral mass screws, pedicle screws, and laminar screws, each with its own advantages and risks. Instrumentation at C7 is controversial, and there is data supporting both its inclusion in constructs and no risk when this level is skipped. Thoracic pedicle screws are the preferred method of fixation in this region of the spine; however, the connection between cervical and thoracic screws can be challenging due to differences in alignment. Transitional rods and rod connectors mitigate some of the difficulties with this transition and have shown to be effective options. Recently, more investigation has looked into the failure of posterior cervical constructs which end at or near the CTJ. The trend in data has favored fixation to T1 or T2 rather than ending a construct at C7 due to the decreased rates of distal junction kyphosis. Although data on patient-reported outcomes with a length of constructs and the lowest instrumented vertebra is scarce, preliminary reports show no difference at this time. As posterior cervical instrumentation continues to increase in frequency, the CTJ will continue to be an area of difficulty in navigation and instrumentation. A thorough understanding of this region is necessary and continued research is needed to improve outcomes.

LEVEL OF EVIDENCE

Level V.

Does extending a posterior cervical fusion construct into the upper thoracic spine impact patient-reported outcomes as long as 2 years after surgery in patients with degenerative cervical myelopathy?

OBJECTIVE

In multilevel posterior cervical instrumented fusion, extension of fusion across the cervicothoracic junction (CTJ) at T1 or T2 has been associated with decreased rates of reoperation and pseudarthrosis but with longer surgical time and increased blood loss. The impact on patient-reported outcomes (PROs) remains unclear. The primary objective was to determine whether extension of fusion through the CTJ influenced PROs at 3, 12, and 24 months after surgery. The secondary objective was to compare the number of patients who reached the minimal clinically important differences (MCIDs) for the PROs, modified Japanese Orthopaedic Association (mJOA) score, operative time, intraoperative blood loss, length of stay, discharge disposition, adverse events (AEs), reoperation within 24 months of surgery, and patient satisfaction.

METHODS

This was a retrospective observational cohort study of prospectively collected multicenter data of patients with degenerative cervical myelopathy. Patients who underwent posterior instrumented fusion of 4 levels or greater (between C2 and T2) between January 2015 and October 2020 and received 24 months of follow-up were included. PROs (scores on the Neck Disability Index [NDI], EQ-5D, physical component summary and mental component summary of SF-12, and numeric rating scale for arm and neck pain) and mJOA scores were compared using ANCOVA and adjusted for baseline differences. Patient demographic characteristics, comorbidities, and surgical details were abstracted. The proportions of patients who reached the MCIDs for these outcomes were compared with the chi-square test. Operative duration, intraoperative blood loss, AEs, reoperation, discharge disposition, length of stay, and satisfaction was compared by using the chi-square test for categorical variables and the independent-samples t-test for continuous variables.

RESULTS

A total of 198 patients were included in this study (101 patients with fusion not crossing the CTJ and 97 with fusion crossing the CTJ). Patients with a construct extending through the CTJ were more likely to be female and have worse baseline NDI scores (p > 0.05). When adjusted for baseline differences, there were no statistically significant differences between the two groups in terms of the PROs and mJOA scores at 3, 12, and 24 months. Surgical duration was longer (p < 0.001) and intraoperative blood loss was greater in the group with fusion extending to the upper thoracic spine (p = 0.013). There were no significant differences between groups in terms of AEs (p > 0.05). Fusion with a construct crossing the CTJ was associated with reoperation (p = 0.04). Satisfaction with surgery was not significantly different between groups. The proportions of patients who reached the MCIDs for the PROs were not statistically different at any time point.

CONCLUSIONS

There were no statistically significant differences in PROs between patients with a posterior construct extending to the upper thoracic spine and those without such extension for as long as 24 months after surgery. The AE profiles were not significantly different, but longer surgical time and increased blood loss were associated with constructs extending across the CTJ.

Instrumentation Across the Cervicothoracic Junction Does Not Improve Patient-reported Outcomes in Multilevel Posterior Cervical Decompression and Fusion

STUDY DESIGN

This was a retrospective cohort.

OBJECTIVE

The objective of this study was to determine if instrumentation across the cervicothoracic junction (CTJ) in elective multilevel posterior cervical decompression and fusion (PCF) is associated with improved patient-reported outcome measures (PROMs).

SUMMARY OF BACKGROUND DATA

Fusion across the CTJ may result in lower revision rates at the expense of prolonged operative duration. However, it is unclear whether constructs crossing the CTJ affect PROMs.

MATERIALS AND METHODS

Standard Query Language (SQL) identified patients with PROMs who underwent elective multilevel PCF (≥3 levels) at our institution. Patients were grouped based on anatomic construct: crossing the CTJ (crossed) versus not crossing the CTJ (noncrossed). Subgroup analysis compared constructs stopping at C7 or T1. Independent t tests and χ 2 tests were utilized for continuous and categorical data, respectively. Regression analysis controlled for baseline demographics. The α was set at 0.05.

RESULTS

Of the 160 patients included, the crossed group (92, 57.5%) had significantly more levels fused (5.27 vs. 3.71, P <0.001), longer operative duration (196 vs. 161 min, P =0.003), greater estimated blood loss (242 vs. 160 mL, P =0.021), and a decreased revision rate (1.09% vs. 10.3%, P =0.011). Neither crossing the CTJ (vs. noncrossed) nor constructs spanning C3-T1 (vs. C3-C7) were independent predictors of ∆PROMs (change in preoperative minus postoperative patient-reported outcomes) on regression analysis. However, C3-C7 constructs had a greater revision rate than C3-T1 constructs (15.6% vs. 1.96%, P =0.030).

CONCLUSION

Crossing the CTJ in patients undergoing elective multilevel PCF was not an independent predictor of improvement in PROMs at 1 year, but they experienced lower revision rates.

LEVEL OF EVIDENCE

Level III.

Should we bridge the cervicothoracic junction in long cervical fusions? A meta-analysis and systematic review of the literature

OBJECTIVE

Long posterior cervical decompression and fusion (PCF) is commonly performed to surgically treat patients with multilevel cervical pathology. In cases in which constructs may necessitate crossing the cervicothoracic junction (CTJ), recommendations for appropriate caudal fusion level vary in the literature. The aim of this study was to report the clinical and radiological outcomes of multilevel PCFs ending at C7 versus those crossing the CTJ.

METHODS

A systematic search of PubMed, CINAHL Plus, and Scopus was conducted to identify articles that evaluated clinical and radiological outcomes of long PCFs that ended at C7 (cervical group) or crossed the CTJ (thoracic group). Based on heterogeneity, random-effects models of a meta-analysis were used to estimate the pooled estimates and the 95% confidence intervals.

RESULTS

PCF outcome data of 1120 patients from 10 published studies were included. Compared with the cervical group, the thoracic group experienced greater mean blood loss (453.0 ml [95% CI 333.6-572.5 ml] vs 303.5 ml [95% CI 203.4-403.6 ml]), longer operative times (235.5 minutes [95% CI 187.7-283.3 minutes] vs 198.5 minutes [95% CI 157.9-239.0 minutes]), and a longer length of stay (6.7 days [95% CI 3.3-10.2 days] vs 6.2 days [95% CI 3.8-8.7 days]); however, these differences were not statistically significant. None of the included studies specifically investigated factors that led to the decision of whether to cross the CTJ. The cervical group had a mean fusion rate of 86% (95% CI 71%-94%) compared with the thoracic group with a rate of 90% (95% CI 81%-95%). Of patients in the cervical group, 17% (95% CI 10%-28%) required revision surgery compared with 7% (95% CI 4%-13%) of those in the thoracic group, but this difference was not statistically significant. The proportion of patients who experienced complications in the cervical group was found to be 28% (95% CI 12%-52%) versus 14% (95% CI 7%-26%) in the thoracic group; however, this difference was not statistically significant. There was no significant difference (no overlap of 95% CIs) in the incidence of adjacent-segment disease, pseudarthrosis, or wound-related complications between groups.

CONCLUSIONS

This meta-analysis suggests similar clinical and radiographic outcomes in multilevel PCF, regardless of inclusion of the CTJ. The lowest instrumented level did not significantly affect revision rates or complications. The ideal stopping point must be tailored to each patient on an individualized basis.

To cross or not to cross the cervicothoracic junction in multilevel posterior cervical fusion: a systematic review and meta-analysis

BACKGROUND

Inclusion of the cervicothoracic junction (CTJ) during decision-making regarding the surgical level of multilevel posterior cervical fusion (PCF) surgery remains the subject of debate, largely due to a lack of studies on the topic. Thus, we considered that meta-analysis based on recent high-quality clinical studies might enable better-informed decision-making regarding the selection of the distal level of multilevel PCF, particularly concerning the advisability of crossing the CTJ.

PURPOSE

To compare the outcomes of patients who underwent multilevel PCF with or without crossing the CTJ (the thoracic and cervical groups, respectively) by the distal construct.

STUDY DESIGN

A systematic review and meta-analysis.

METHODS

We searched the Cochrane, Embase, and Medline databases for articles that compared the intra- and post-operative outcomes of patients who underwent multilevel PCF surgery with or without extension of surgery to include the CTJ, using January 7, 2021, as the publication cutoff date. Group differences in primary and secondary outcome measures were analyzed for significance (p<.05). All reported means were pooled.

RESULTS

A total of 1,904 publications were assessed, and eight studies met the study criteria. The cervical group had a significantly greater fusion rate than the thoracic group (p=.03), but higher adjacent segment disease (ASD) and reoperation rates (ASD: OR=3.15, p=.007; reoperation: OR=1.93, p=.008). As regards surgical outcomes, mean blood loss was less and operation time was shorter in the cervical group (p=.008 and .009, respectively). However, mean hospital stays were not significantly different (p=.12), and neither were the rates of complications, such as metal failure and hematoma.

CONCLUSIONS

In the current study, fusion rate, blood loss, and operation time were better in the cervical group than in the thoracic group, but ASD incidence and ASD-related complication rates at the CTJ were greater in the cervical group. For patients with higher risk factors for adjacent-segment degeneration, crossing the CTJ may be warranted.

Is it Better to Stop at C2 or C3/4 in Elective Posterior Cervical Decompression and Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

(a) Compare operative variables, complications, and patient-reported outcomes (PROs) in patients with an upper instrumented vertebrae (UIV) of C2 versus C3/4, and (b) assess outcomes based on C2 screw type.

SUMMARY OF BACKGROUND DATA

When performing elective posterior cervical laminectomy and fusion (PCLF), spine surgeons must choose the upper instrumented vertebrae (UIV) at the subaxial cervical spine (C3/4) versus C2. Differences in long-term complications and PROs remain unknown.

METHODS

A single-institution, retrospective cohort study from a prospective registry was conducted. All patients undergoing elective, degenerative PCLF from December 2010 to June 2018 were included. Patients were divided into a UIV of C2 versus C3/4. Groups were 2:1 propensity matched for fusion extending to the thoracic spine. Demographics, operative, perioperative, complications, and 1-year PRO data were collected.

RESULTS

One hundred seventeen patients underwent elective PCLF and were successfully propensity matched (39 C2 vs. 78 C3/4). Groups were similar in fusion extending to the thoracic spine (P = 0.588). Expectedly, the C2 group had more levels fused (5.63 ± 1.89) compared with the C3/4 group (4.50 ± 0.91) (P = 0.001). The C2 group had significantly longer operative time (P < 0.001), yet no differences were seen in estimated blood loss (EBL) (P = 0.494) or length of stay (LOS) (P = 0.424). Both groups significantly improved all PROs at 1-year (EQ-5D; NRS-NP/AP; NDI). Both groups had the same percentage of surgical adverse events at 6.8% (P = 1.00). Between C2 screw type, no differences were seen in operative time, EBL, LOS, complications, or PROs.

CONCLUSION

In patients undergoing elective PCLF, those instrumented to C2 had only longer operative times compared with those stopping at C3/4. No differences were seen in EBL, LOS, 1-year PROs, and complications. Type of C2 screw had no impact on outcomes. Besides increased operative time, instrumenting to C2 had no detectable difference on surgical outcomes or adverse event rates.Level of Evidence: 3.