Long-segment posterior cervical decompression and fusion: does caudal level affect revision rate?

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.

Lateral Mass Screws Versus Pedicle Screws at C7: Reoperation Rates for Operative Adjacent Segment Disease and Nonunion in Posterior Cervical Fusion

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To determine if there is a difference in reoperation rates for symptomatic adjacent segment disease (operative ASD) and symptomatic nonunions (operative nonunions) in posterior cervical fusions (PCFs) stopping at C7 using either lateral mass screws (LMS) or cervical pedicle screws (CPS) at C7.

SUMMARY OF BACKGROUND DATA

Stopping PCFs at C7 has been controversial because of the risks of adjacent segment disease or nonunions. The two commonly used fixation techniques at the C7 level are LMS and CPS.

MATERIALS AND METHODS

A retrospective analysis from the Kaiser Permanente Spine Registry identified a cohort of patients with cervical degenerative disk disease who underwent primary PCFs stopping at C7 with either LMS or CPS at C7. Demographic and operative data were extracted from the registry, and operative ASD and operative nonunions were adjudicated through chart review. Patients were followed until validated operative ASD or nonunion, membership termination, death, or end of study (March 31, 2022). Descriptive statistics and multivariable Cox proportional hazards models were calculated for operative ASDs and operative nonunions.

RESULTS

We found 481 patients with PCFs stopping at C7 with either LMS (n=347) or CPS (n=134) at C7 with an average follow-up time of 5.6 (±3.8) years, time to operative ASD of 3.0 (±2.8) years, and to operative nonunion of 1.2 (±0.7) years. There were 11 operative ASDs (LMS=8, CPS=3) and eight operative nonunions (LMS=4, CPS=4). There was no statistical difference between patients stopping at C7 with LMS versus CPS for operative ASDs (HR: 0.68, 95% CI=0.17-2.77, P =0.60) or operative nonunions (HR: 2.09, 95% CI=0.45-8.58, P =0.37).

CONCLUSION

A large cohort of patients with PCFs stopping at C7 with an average follow-up of > 5 years found no statistical difference in reoperation rates for symptomatic ASD (operative ASD) or operative nonunion using either LMS or CPS at C7.

Patient-Reported Outcomes Following Anterior and Posterior Surgical Approaches for Multilevel Cervical Myelopathy

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

To compare health-related quality of life (HRQoL) outcomes between approach techniques for the treatment of multilevel degenerative cervical myelopathy (DCM).

SUMMARY OF BACKGROUND DATA

Both anterior and posterior approaches for the surgical treatment of cervical myelopathy are successful techniques in the treatment of myelopathy. However, the optimal treatment has yet to be determined, especially for multilevel disease, as the different approaches have separate complication profiles and potentially different impacts on HRQoL metrics.

MATERIALS AND METHODS

Retrospective review of a prospectively managed single institution database of patient-reported outcome measures after 3 and 4-level anterior cervical discectomy and fusion (ACDF) and posterior cervical decompression and fusion (PCDF) for DCM. The electronic medical record was reviewed for patient baseline characteristics and surgical outcomes whereas preoperative radiographs were analyzed for baseline cervical lordosis and sagittal balance. Bivariate and multivariate statistical analyses were performed to compare the two groups.

RESULTS

We identified 153 patients treated by ACDF and 43 patients treated by PCDF. Patients in the ACDF cohort were younger (60.1 ± 9.8 vs . 65.8 ± 6.9 yr; P < 0.001), had a lower overall comorbidity burden (Charlson Comorbidity Index: 2.25 ± 1.61 vs . 3.07 ± 1.64; P = 0.002), and were more likely to have a 3-level fusion (79.7% vs . 30.2%; P < 0.001), myeloradiculopathy (42.5% vs . 23.3%; P = 0.034), and cervical kyphosis (25.7% vs . 7.69%; P = 0.027). Patients undergoing an ACDF had significantly more improvement in their neck disability index after surgery (-14.28 vs . -3.02; P = 0.001), and this relationship was maintained on multivariate analysis with PCDF being independently associated with a worse neck disability index (+8.83; P = 0.025). Patients undergoing an ACDF also experienced more improvement in visual analog score neck pain after surgery (-2.94 vs . -1.47; P = 0.025) by bivariate analysis.

CONCLUSIONS

Our data suggest that patients undergoing an ACDF or PCDF for multilevel DCM have similar outcomes after surgery.

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.

Selecting the lowest instrumented vertebra in a multilevel posterior cervical fusion across the cervicothoracic junction: a biomechanical investigation

OBJECTIVE

Posterior cervical fusion is a common surgical treatment for patients with myeloradiculopathy or regional deformity. Several studies have found increased stresses at the cervicothoracic junction (CTJ) and significantly higher revision surgery rates in multilevel cervical constructs that terminate at C7. The purpose of this study was to investigate the biomechanical effects of selecting C7 versus T1 versus T2 as the lowest instrumented vertebra (LIV) in multisegmental posterior cervicothoracic fusion procedures.

METHODS

Seven fresh-frozen cadaveric cervicothoracic spines (C2-L1) with ribs intact were tested. After analysis of the intact specimens, posterior rods and lateral mass screws were sequentially added to create the following constructs: C3-7 fixation, C3-T1 fixation, and C3-T2 fixation. In vitro flexibility tests were performed to determine the range of motion (ROM) of each group in flexion-extension (FE), lateral bending (LB), and axial rotation (AR), and to measure intradiscal pressure of the distal adjacent level (DAL).

RESULTS

In FE, selecting C7 as the LIV instead of crossing the CTJ resulted in the greatest increase in ROM (2.54°) and pressure (29.57 pound-force per square inch [psi]) at the DAL in the construct relative to the intact specimen. In LB, selecting T1 as the LIV resulted in the greatest increase in motion (0.78°) and the lowest increase in pressure (3.51 psi) at the DAL relative to intact spines. In AR, selecting T2 as the LIV resulted in the greatest increase in motion (0.20°) at the DAL, while selecting T1 as the LIV resulted in the greatest increase in pressure (8.28 psi) in constructs relative to intact specimens. Although these trends did not reach statistical significance, the observed differences were most apparent in FE, where crossing the CTJ resulted in less motion and lower intradiscal pressures at the DAL.

CONCLUSIONS

The present biomechanical cadaveric study demonstrated that a cervical posterior fixation construct with its LIV crossing the CTJ produces less stress in its distal adjacent discs compared with constructs with C7 as the LIV. Future clinical testing is necessary to determine the impact of this finding on patient outcomes.

No difference in reoperation rates for nonunions (operative nonunions) in posterior cervical fusions stopping at C7 versus T1/2: a cohort of 875 patients

OBJECTIVE

The challenges of posterior cervical fusions (PCFs) at the cervicothoracic junction (CTJ) are widely known, including the development of adjacent-segment disease by stopping fusions at C7. One solution has been to cross the CTJ (T1/T2) rather than stopping at C7. This approach may have undue consequences, including increased reoperations for symptomatic nonunion (operative nonunion). The authors sought to investigate if there is a difference in operative nonunion in PCFs that stop at C7 versus T1/T2.

METHODS

A retrospective analysis identified patients from the authors' spine registry (Kaiser Permanente) who underwent PCFs with caudal fusion levels at C7 and T1/T2. Demographics, diagnoses, operative times, lengths of stay, and reoperations were extracted from the registry. Operative nonunion was adjudicated via chart review. Patients were followed until validated operative nonunion, membership termination, death, or end of study (March 31, 2020). Descriptive statistics and 2-year crude incidence rates and 95% confidence intervals for operative nonunion for PCFs stopping at C7 or T1/T2 were reported. Time-dependent crude and adjusted multivariable Cox proportional hazards models were used to evaluate operative nonunion rates.

RESULTS

The authors identified 875 patients with PCFs (beginning at C3, C4, C5, or C6) stopping at either C7 (n = 470) or T1/T2 (n = 405) with a mean follow-up time of 4.6 ± 3.3 years and a mean time to operative nonunion of 0.9 ± 0.6 years. There were 17 operative nonunions, and, after adjustment for age at surgery and smoking status, the cumulative incidence rates were similar between constructs stopping at C7 and those that extended to T1/T2 (C7: 1.91% [95% CI 0.88%-3.60%]; T1/T2: 1.98% [95% CI 0.86%-3.85%]). In the crude model and model adjusted for age at surgery and smoking status, no difference in risk for constructs extended to T1/T2 compared to those stopping at C7 was found (adjusted HR 1.09 [95% CI 0.42-2.84], p = 0.86).

CONCLUSIONS

In one of the largest cohort of patients with PCFs stopping at C7 or T1/T2 with an average follow-up of > 4 years, the authors found no statistically significant difference in reoperation rates for symptomatic nonunion (operative nonunion). This finding shows that there is no added risk of operative nonunion by extending PCFs to T1/T2 or stopping at C7.