Asymptomatic ACDF Nonunions Underestimate the True Prevalence of Radiographic Pseudarthrosis

Comparing outcomes between anterior cervical disc replacement (ACDR) and minimally invasive posterior cervical foraminotomy (MI-PCF) in the treatment of cervical radiculopathy

BACKGROUND CONTEXT

Anterior cervical disc replacement (ACDR) and minimally invasive posterior cervical foraminotomy (MI-PCF) have emerged as two increasingly popular alternatives to anterior cervical discectomy and fusion (ACDF) for the management of cervical radiculopathy. Both techniques provide advantages of segmental motion preservation and lower rates of adjacent segment degeneration (ASD) compared to ACDF.

PURPOSE

The purpose of this study was to analyze the clinical and functional outcomes of patients undergoing ACDR or MI-PCF for the treatment of unilateral cervical radiculopathy.

STUDY DESIGN/SETTING

Retrospective Cohort Review.

PATIENT SAMPLE

A total of 152 patients were included (86 ACDR and 66 MI-PCF).

OUTCOME MEASURES

(1) Patient demographics; (2) perioperative data; (3) rates of complications and revisions; (5) visual analogue scale (VAS) and Neck Disability Index (NDI) scores.

METHODS

A retrospective cohort review was performed to identify all patients at a single institution between 2012-2020 who underwent 1- or 2- level ACDR or MI-PCF from C3-C7 with a minimum follow-up of 24 months. Patient demographics, perioperative data, postoperative complications, and revisions were analyzed. Patient reported outcome measures including VAS and NDI scores were compared.

RESULTS

The ACDR group had a significantly greater mean operative time (99.8 minutes vs 79.2 minutes, p<.001), but comparable estimated blood loss and length of stay following surgical intervention (p=.899). The overall complication rate was significantly greater in the ACDR group than the MI-PCF group (24.4% vs 6.2%; p=.003) but was largely driven by approach-related dysphagia in 20.9% of ACDR patients. The MI-PCF group had significantly greater revision rates (13.6% vs 1.2%; p=.002) with an average time to revision of 20.7 months in the MI-PCF group compared to 40.3 months in the ACDR group. The ACDR cohort had significantly greater improvements in NDI scores at the final follow-up (25.0 vs 21.3, p<.001).

CONCLUSION

Our results suggest that ACDR offer clinically relevant advantages over MI-PCF in terms of long-term revision rates despite an increased approach-related risk of transient postoperative dysphagia. Additionally, patients in the ACDR cohort achieved greater mean improvements in NDI scores but these results may have limited clinical significance due to inability to reach minimally clinically important difference (MCID) thresholds.

Perioperative and safety outcomes following tissue-sparing posterior cervical fusion to revise a pseudarthrosis: A multicenter retrospective review of 150 cases

Background

Posterior cervical fusion (PCF) with lateral mass screws is a favorable treatment option to revise a symptomatic pseudarthrosis due to reliable rates of arthrodesis; however, this technique introduces elevated risk for wound infection and hospital readmission. A tissue-sparing PCF approach involving facet fixation instrumentation reduces the rates of postoperative complications while stabilizing the symptomatic level to achieve arthrodesis; however, these outcomes have been limited to small study cohorts from individual surgeons commonly with mixed indications for treatment.

Materials and Methods

One hundred and fifty cases were identified from a retrospective chart review performed by seven surgeons across six sites in the United States. All cases involved PCF revision for a pseudarthrosis at one or more levels from C3 to C7 following anterior cervical discectomy and fusion (ACDF). PCF was performed using a tissue-sparing technique with facet instrumentation. Cases involving additional supplemental fixation such as lateral mass screws, rods, wires, or other hardware were excluded. Demographics, operative notes, postoperative complications, hospital readmission, and subsequent surgical interventions were summarized as an entire cohort and according to the following risk factors: age, sex, number of levels revised, body mass index (BMI), and history of nicotine use.

Results

The average age of patients at the time of PCF revision was 55 ± 11 years and 63% were female. The average BMI was 29 ± 6 kg/m2 and 19% reported a history of nicotine use. Postoperative follow-up visits were available with a median of 68 days (interquartile range = 41-209 days) from revision PCF. There were 91 1-level, 49 2-level, 8 3-level, and 2 4±-level PCF revision cases. The mean operative duration was 52 ± 3 min with an estimated blood loss of 14 ± 1.5cc. Participants were discharged an average of 1 ± 0.05 days following surgery. Multilevel treatment resulted in longer procedure times (single = 45 min, multi = 59 min, P = 0.01) but did not impact estimated blood loss (P = 0.94). Total nights in the hospital increased by 0.2 nights with multilevel treatment (P = 0.01). Sex, age, nicotine history, and BMI had no effect on recorded perioperative outcomes. There was one instance of rehospitalization due to deep-vein thrombosis, one instance of persistent pseudarthrosis at the revised level treated with ACDF, and four instances of adjacent segment disease. In patients initially treated with multilevel ACDF, revisions occurred most commonly on the caudal level (48% of revised levels), followed by the cranial (43%), and least often in the middle level (9%).

Conclusions

This chart review of perioperative and safety outcomes provides evidence in support of tissue-sparing PCF with facet instrumentation as a treatment for symptomatic pseudarthrosis after ACDF. The most common locations requiring revision were the caudal and cranial levels. Operative duration and estimated blood loss were favorable when compared to open alternatives. There were no instances of postoperative wound infection, and the majority of patients were discharged the day following surgery.

Opioid Use Increases the Rate of Pseudarthrosis and Revision Surgery in Patients Undergoing Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective Cohort.

OBJECTIVES

To (1) quantify the risk opioids impart on pseudarthrosis development, (2) analyze the effect of pseudarthrosis on clinical outcomes, and (3) identify if the amount of opioids prescribed are predictive of pseudarthrosis revision.

METHODS

Patients who underwent ACDF at a single institution between 2017-2019 were retrospectively identified. Postoperative dynamic cervical spine radiographs were reviewed to assess fusion status. Logistic regression models measured the effect of morphine milligram equivalents (MME) prescribed on the likelihood of pseudarthrosis development. Receiver operating characteristic (ROC) curves were generated to predict the probability of surgical revision based on MME prescribed.

RESULTS

Of 298 included patients, an average of 2.01 ± 0.82 levels were included in the construct and 121 (40.9%) patients were diagnosed with a pseudarthrosis. However, only 14 (4.7%) required a pseudarthrosis revision. Patients requiring pseudarthrosis revision had worse one-year postoperative Δ PCS-12 (-1.70 vs. 7.58, P = 0.004), Δ NDI (3.33 vs. -15.26, P = 0.002), and Δ VAS Arm (2.33 vs. -2.48, P = .047). Multivariate logistic regression analyses found the three-month postoperative (OR=1.00, P = .010), one-year postoperative (OR=1.001, P = 0.025), and combined pre- and postoperative MME (OR=1.000, P = .035) increased the risk of pseudarthrosis. ROC analysis identified cutoff values to predict pseudarthrosis revision at 90.00 (area under the curve (AUC): 0.693, confidence interval (CI): 0.554-0.832), 132.86 (0.710, CI: 0.589-0.840), 224.76 (0.687, CI: 0.558-0.817) and 285.00 (0.711, CI: 0.585-0.837) MME in the preoperative, three-month postoperative, one-year postoperative, and combined pre-and postoperative period.

CONCLUSION

Increased prescription of opioid medications following ACDF procedures may increase the risk of pseudarthrosis development and revision surgery.

LEVEL OF EVIDENCE

Therapeutic Level III.

Comparison of Different Osteobiologics in Terms of Imaging Modalities and Time Frames for Fusion Assessment in Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

The study's primary objective was to determine how osteobiologic choice affects fusion rates in patients undergoing anterior cervical discectomy and fusion (ACDF). The study's secondary objectives were to 1) determine the optimal timing of fusion assessment following ACDF and 2) determine if osteobiologic type affects the timing and optimal modality of fusion assessment.

METHODS

A systematic search of PubMed/MEDLINE was conducted for literature published from 2000 through October 2020 comparing anterior fusion in the cervical spine with various osteobiologics. Both comparative studies and case series of ≥10 patients were included.

RESULTS

A total of 74 studies met the inclusion criteria. Seventeen studies evaluated the efficacy of autograft on fusion outcomes, and 23 studies assessed the efficacy of allograft on fusion outcomes. 3 studies evaluated the efficacy of demineralized bone matrix, and seven assessed the efficacy of rhBMP-2 on fusion outcomes. Other limited studies evaluated the efficacy of ceramics and bioactive glasses on fusion outcomes, and 4 assessed the efficacy of stem cell products. Most studies utilized dynamic radiographs for the assessment of fusion. Overall, there was a general lack of supportive data to determine the optimal timing of fusion assessment meaningfully or if osteobiologic type influenced fusion timing.

CONCLUSIONS

Achieving fusion following ACDF appears to remain an intricate interplay between host biology and various surgical factors, including the selection of osteobiologics. While alternative osteobiologics to autograft exist and may produce acceptable fusion rates, limitations in study methodology prevent any definitive conclusions from existing literature.

Complications of the Use Allograft in 1- or 2-Level Anterior Cervical Discectomy and Fusion: A Systematic Review

Study Design: Systematic literature reviewObjective: To critically analyze the literature and describe the complications associated with the use of allograft in 1- or 2- level anterior cervical discectomy and fusion (ACDF)Methods: A systematic search of PubMed/MEDLINE, EMBASE, and ClinicalTrials.gov databases was conducted for literature published between January 2000 and August 2020 reporting complications associated with the use of allograft in 1- or 2- level ACDF.Results: From 584 potentially relevant citations, 21 met the inclusion criteria (4 randomized controlled trials (RCT), 4 prospective, and 13 retrospective studies). The patient number varied between 26 and 463 in comparative studies (RCT and non-RCT) and between 29 and 345 in non-comparative studies. Fusion rate was reported in 14 studies and ranged between 68.5-100%. The most frequently reported complication was post-operative dysphagia or dysphonia, with incidences ranging between .5% and 14.4%. Revision surgery was the second most reported complication (14 studies) and ranged between 0% and 10.3%. Wound-related complications were reported in 6 studies and ranged between 0% and 22.8%.Conclusion: The overall reporting of complications was low with very few comparative studies. Reported complications with allografts are within the range of other osteobiologics and autografts and in most cases may not attributable to the use of osteobiologics and may be complications of the procedure itself. Comparative studies with a more robust methodology analyzing complications with allograft and other osteobiologics are needed to inform current practice with strong recommendations.

Fate of pseudarthrosis detected 2 years after anterior cervical discectomy and fusion: results of a minimum 5-year follow-up

BACKGROUND CONTEXT

Prior study has shown that 70% of cervical pseudarthrosis after anterior cervical discectomy and fusion (ACDF) detected at 1 year will go on to fusion by 2 year. Pseudarthrosis detected 2 years after ACDF may have different bone healing potential compared to nonunion detected 1 year after surgery. Therefore, it might have a different clinical significance.

PURPOSE

To examine the radiographic and clinical prognosis of pseudarthrosis detected 2 years after ACDF with a minimum follow-up of 5 years.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENTS SAMPLE

A total of 249 patients who completed a 5-year follow-up after ACDF.

OUTCOMES MEASURES

Clinical outcomes such as neck pain visual analogue scale (VAS), arm pain VAS, and neck disability index (NDI) and radiographic assessment such as X-ray, computed tomography (CT) scan.

METHODS

A total of 249 patients who completed a 5-year follow-up after ACDF were retrospectively reviewed. Patients who were diagnosed with pseudarthrosis at 2 years postoperatively were included. Fusion, neck pain VAS, arm pain VAS, and NDI were assessed. The results were compared between the union group (patients who achieved union), and the nonunion group (patients with pseudarthrosis) at 5 years postoperatively.

RESULTS

Among the patients who had pseudarthrosis at 2 years postoperatively, the fusion rate at 5 years was 32.6% (14/43). While the union group showed continued improvements in neck pain VAS, arm pain VAS, and NDI until 5 years, the nonunion group showed significant worsening of arm pain VAS and NDI at 5 years, with the values of neck pain VAS, arm pain VAS, and NDI being significantly worse than those of the union group at 5 years.

CONCLUSION

The incidence of pseudarthrosis detected at 2 years postoperatively after ACDF was 67.4%, and it remained unfused at 5 years postoperatively. Nonunion identified 2 years after ACDF may be considered a poor prognostic factor because it has less potential to achieve fusion with further follow-up and a higher chance of worsening clinical symptoms. Therefore, the presence of fusion at the 2-year follow-up can be considered an indicator of the success of the surgery.

Longer Screws Decrease the Risk of Radiographic Pseudarthrosis Following Elective Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

In patients undergoing elective anterior cervical discectomy and fusion (ACDF), we sought to determine the impact of screw length on: (1) radiographic pseudarthrosis, (2) pseudarthrosis requiring reoperation, and (3) patient-reported outcome measures (PROMs).

METHODS

A single-institution, retrospective cohort study was undertaken from 2010-21. The primary independent variables were: screw length (mm), screw length divided by the anterior-posterior vertebral body diameter (VB%), and the presence of any screw with VB% < 75% vs all screws with VB% ≥ 75%. Multivariable logistic regression controlled for age, BMI, gender, smoking, American Society of Anesthesiology grade, number of levels fused, and whether a corpectomy was performed.

RESULTS

Of 406 patients undergoing ACDF, levels fused were: 1-level (39.4%), 2-level (42.9%), 3-level (16.7%), and 4-level (1.0%). Mean screw length was 14.3 ± 2.3 mm, and mean VB% was 74.4 ± 11.2. A total of 293 (72.1%) had at least one screw with VB% < 75%, 113 (27.8%) had all screws with VB% ≥ 75%, and 141 (34.7%) patients had radiographic pseudarthrosis at 1-year. Patients who had any screw with VB% < 75% had a higher rate of radiographic pseudarthrosis compared to those had all screws with VB% ≥ 75% (39.6% vs 22.1%, P < .001). Multivariable logistic regression revealed that a higher VB% (OR = .97, 95%CI = .95-.99, P = .035) and having all screws with VB% ≥ 75% (OR = .51, 95%CI = .27-.95, P = .037) significantly decreased the odds of pseudarthrosis at 1-year, with no difference in reoperation or PROMs (all P > .05).

CONCLUSION

Longer screws taking up ≥75% of the vertebral body protected against radiographic pseudarthrosis at 1-year. Maximizing screw length in ACDF is an easily modifiable factor directly under the surgeon's control that may mitigate the risk of pseudarthrosis.

Risk Factors of Nonfusion after Anterior Cervical Decompression and Fusion in the Early Postoperative Period: A Retrospective Study

OBJECTIVE

Although high fusion rates have been reported for anterior cervical decompression and fusion (ACDF) in the medium and long term, the risk of nonfusion in the early period after ACDF remains substantial. This study investigates early risk factors for cage nonfusion in patients undergoing single- or multi-level ACDF.

METHODS

This was a retrospective study. From August 2020 to December 2021, 107 patients with ACDF, including 197 segments, were enrolled, with a follow-up of 3 months. Among the 197 segments, 155 were diagnosed with nonfusion (Nonfusion group), and 42 were diagnosed with fusion (Fusion group) in the early period after ACDF. We assessed the significance of the patient-specific factors, radiographic indicators, serum factors, and clinical outcomes. The Wilcoxon rank sum test, t-tests, analysis of variance, and stepwise multivariate logistic regression were used for statistical analysis.

RESULTS

Univariate analysis showed that smoking, insufficient improvement in the C2-7 Cobb angle (p = 0.024) and the functional spinal unit Cobb angle (p = 0.022) between preoperative and postoperative stages and lower serum calcium (fusion: 2.34 ± 0.12 mmol/L; nonfusion: 2.28 ± 0.17 mmol/L, p = 0.003) β-carboxyterminal telopeptide end of type 1 collagen (β-CTX) (fusion: 0.51 [0.38, 0.71]; nonfusion: 0.43 [0.31, 0.57], p = 0.008), and N-terminal fragment of osteocalcin (N-MID-BGP) (fusion: 18.30 [12.15, 22.60]; nonfusion: 14.45 [11.65, 18.60], p = 0.023) are risk factors for nonfusion in the early period after ACDF. Stepwise logistic regression analysis revealed that poor C2-7 Cobb angle improvement (odds ratio [OR], 1.107 [1.019-1.204], p = 0.017) and lower serum calcium (OR, 3.700 [1.138-12.032], p = 0.030) are risk factors.

CONCLUSIONS

Patients with successful fusion after ACDF had higher preoperative serum calcium and improved C2-7 Cobb angle than nonfusion patients at 3 months. These findings suggest that serum calcium could be used to identify patients at risk of nonfusion following ACDF and that correcting the C2-7 Cobb angle during surgery could potentially increase fusion in the early period after ACDF.

Interbody Cage Placement Without Plate Supplementation Adjacent to Plated Segments in Multilevel Anterior Cervical Decompression and Fusion

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To evaluate the clinical efficacy and safety of hybrid anterior cervical fixation, focusing on stand-alone segments.

SUMMARY OF BACKGROUND DATA

In the treatment of multilevel cervical stenosis, the number of segments fixed using a plate is limited by placing an interbody cage without plate supplementation at one end of the surgical segment to reduce long plate-related problems. However, the stand-alone segment may experience cage extrusion, subsidence, cervical alignment deterioration, and nonunion.

METHODS

Patients who underwent three-segment or four-segment fixation for cervical degenerative disease and completed one-year follow-up were included in this study. Patients were divided into two groups: a cranial group, with stand-alone segments located at the cranial end adjacent to plated segments, and a caudal group, with stand-alone segments located at the caudal end. Differences in radiographic outcomes between the groups were evaluated. Fusion was defined using dynamic radiographs or computed tomography. To identify factors associated with nonunion in stand-alone segments, multivariable logistic regression analyses were performed. To identify factors associated with cage subsidence, multiple regression analyses were performed.

RESULTS

A total of 116 patients (mean age, 59±11 y; 72% male; mean fixed segments, 3.7±0.5 segments) were included in this study. No case showed cage extrusion or plate dislodgement. In stand-alone segments, the fusion rate was significantly lower in the caudal group than in the cranial group (76% vs. 93%, P =0.019). Change in the cervical sagittal vertical axis was worse in the caudal group than in the cranial group (2.7±12.3 mm vs. -2.7±8.1 mm, P =0.006). One caudal group patient required additional surgery because of nonunion at the stand-alone segment. Multivariable logistic regression indicated factors associated with nonunion included the location of the stand-alone segment (caudal end: OR 4.67, 95% CI, 1.29-16.90), larger pre-disk space range of motion (OR 1.15, 95% CI, 1.04-1.27), and lower preoperative disk space height (OR 0.57, 95% CI, 0.37-0.87). Multiple regression analysis indicated that higher cage height and lower pre-disk space height were associated with cage subsidence.

CONCLUSION

Hybrid anterior cervical fixation with stand-alone interbody cage placement adjacent to plated segments may avoid long plate-related problems. Our results suggest that the cranial end of the construct may be more suitable for the stand-alone segment than the caudal end.

Comparison of revision surgery for pseudarthrosis with or without adjacent segment disease after anterior cervical discectomy and fusion

Background

Patients with a pseudarthrosis after anterior cervical discectomy and fusion (ACDF) may have concurrent adjacent segment disease (ASD). Although prior studies have shown posterior cervical decompression and fusion (PCDF) is effective in repairing pseudarthrosis, improvement in patient reported outcomes (PROs) has been marginal. The aim of this study is to evaluate the effectiveness of PCDF in achieving symptom relief in patients with pseudarthrosis after ACDF and whether that is altered by the additional treatment of ASD.

Methods

Thirty-two patients with pseudarthrosis were compared with 31 patients with pseudarthrosis and concurrent ASD after ACDF who underwent revision PCDF with a minimum 1-year follow-up. Primary outcomes measures included the neck disability index (NDI), and numerical rating scale (NRS) scores for neck and arm pain. Secondary measures included estimated blood loss (EBL), operating room (OR) time, and length of stay.

Results

Demographics between cohorts were similar, however there was a significantly higher mean body mass index (BMI) in the group with concurrent ASD (32.23 vs. 27.76, p=.007). Patients with concurrent ASD had more levels fused during PCDF (3.7 vs. 1.9, p<.001), greater EBL (165 cc vs. 106 cc, p=.054), and longer OR time (256 minutes vs. 202 minutes, p<.000). Preoperative PROs for NDI (56.7 vs. 56.5, p=.954), NRS arm pain (5.9 vs. 5.7, p=.758), and NRS neck pain (6.6 vs. 6.8, p=.726) were similar in both cohorts. At 12 months patients with concurrent ASD experienced a slightly greater, but not statistically significant, improvement in PROs (Δ NDI 4.40 vs. -1.44, Δ NRS neck pain 1.17 vs. 0.42, Δ NRS arm pain 1.28 vs. 0.10, p=.107).

Conclusions

PCDF is a standard procedure for treatment of pseudarthrosis following ACDF, however improvements in PROs are marginal. Slightly greater improvements were seen in patients whose indication for surgery also included concurrent ASD, rather than a diagnosis of pseudarthrosis alone.

Which Radiographic Parameter Can Aid in Deciding Optimal Allograft Height for Anterior Cervical Discectomy and Fusion?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To identify preoperative radiographic parameters that can guide optimal allograft height selection for anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Allograft height selection for ACDF depends on intraoperative assessment supported by trials; however, there is currently no radiographic reference parameter that could aid in allograft height selection for improved outcomes.

METHODS

A total of 148 patients who underwent ACDF using allografts and were followed up for more than 1 year were retrospectively reviewed. Fusion rates, subsidence, segmental lordosis, and foraminal height were assessed. Segments were divided into 2 groups according to whether the inserted allograft height was within 1 mm from the following 3 reference radiographic parameters: (1) uncinate process height, (2) adjacent disc height, and (3) preoperative disc height +2 mm.

RESULTS

This study included 101 patients with 163 segments. Segments with an allograft-uncinate height difference of ≤1 mm had a significantly higher fusion rate at 1-year follow-up compared with segments with allograft-uncinate height difference of >1 mm [85/107 (79.4%) vs. 35/56 (62.5%); P =0.025]. Subsidence, segmental lordosis, and foraminal height did not significantly differ between the groups when segments were divided according to uncinate height. Multivariate logistic regression analysis demonstrated that allograft-uncinate height difference of ≤1 mm and allograft failure were factors associated with fusion.

CONCLUSIONS

The uncinate process height can guide optimal allograft height selection for ACDF. Using an allograft with an allograft-uncinate height difference of ≤1 mm resulted in a higher fusion rate. Therefore, the uncinate process height should be checked preoperatively and used in conjunction with intraoperative assessment when selecting allograft height.

High Failure Rates in Prisoners Undergoing Spine Fusion Surgery

OBJECTIVE

The medical literature on prisoner health care is limited, despite data showing that prisoners experience high rates of physical and mental health challenges. We compared clinical outcomes for prisoners undergoing spine fusion with comparable nonincarcerated patients and determined what factors were implicated in differences in outcomes.

METHODS

Prisoners who underwent spinal fusion in 2011-2021 were retrospectively compared with an age-, sex-, and procedure-matched 3:1 control group of nonincarcerated spinal fusion patients. Fusion failure was confirmed by lack of bridging bone between vertebrae on CT or radiographic images >1 year postoperatively or evidence of instrumentation failure with resultant >2 mm of translation on flexion/extension radiographs.

RESULTS

Twenty-seven identified prisoners were compared with 81 nonincarcerated controls. Ten prisoners and 6 controls experienced nonunion (37% vs. 7%, P < 0.01). Rates of risk factors for nonunion, such as smoking history, elevated body mass index, chronic steroid use, diabetes mellitus, previous spine surgery, and levels fused, were not significantly different between prisoners and controls. Among prisoners, those with nonunion were younger (45 vs. 53 years, P = 0.03), had greater body mass index (34 vs. 29, P = 0.02), and were more likely to undergo reoperation (30% vs. 0%, P = 0.02). Multivariate analysis revealed that prisoners carry a 9.62 increased odds of nonunion compared with controls.

CONCLUSIONS

This is one of few studies investigating health care outcomes in prisoners. We found they had a significantly higher rate of nonunion than matched control patients from the general population treated at the same hospital, suggesting additional measures may be necessary postoperatively to support fusion in prisoners.

Comparative Study of Anterior Transvertebral Foraminotomy and Anterior Cervical Discectomy and Fusion for Unilateral Cervical Spondylotic Radiculopathy

OBJECTIVE

To study the compared surgical and radiographic outcomes of Transvertebral foraminotomy (TVF) with anterior cervical discectomy and fusion (ACDF) in patients with unilateral cervical spondylotic radiculopathy (CSR).

METHODS

We performed a retrospective comparative study of 72 consecutive patients with 1- or 2-level CSR treated with ACDF or TVF. 27 patients who underwent TVF (group T) and 45 patients who underwent ACDF (group A) with a minimum 2-year follow-up were enrolled. We evaluated clinical outcomes and radiological assessment. Clinical outcome included Visual analog scale (VAS) scores for axial, arm pain at preoperatively and final follow-up. VAS score for painful swallowing was also evaluated 1 week after surgery. Radiological assessment included C2-7 sagittal Cobb angle (C2-7 CA), range of motion (ROM) of C2-7 CA, the height, angle and ROM of the functional spinal unit (FSU), and tip of the spinous process of the operated segment. We also evaluated the disc height, FSU angle, and ROM of the FSU at the cranial adjacent segment.

RESULTS

Both groups had good clinical outcomes. Soft tissue swelling was significantly less prominent in group T than that for group A. VAS scores for painful swallowing is lower in group T without significant difference. The ROM of C2-7 CA, FSU, and spinous processes demonstrated a significant reduction in group A compared with group T.(P < 0.05). Disc height at the cranial adjacent segment was maintained in group T.

CONCLUSIONS

TVF is as effective as ACDF for unilateral CSR and preserves whole cervical spine and segmental alignment.

The Impact of Smoking on Delayed Osseous Union After Arthrodesis Procedures in the Hand and Wrist

PURPOSE

The purpose of this study was to evaluate the relationship between smoking and delayed radiographic union after hand and wrist arthrodesis procedures. We hypothesized that smoking would be associated with a higher rate of delayed union.

METHODS

All cases of hand or wrist arthrodesis procedures in patients aged ≥18 years from 2006 to 2020 were identified. Cases were included if they had >90 days of radiographic follow-up or evidence of union before 90 days. Baseline demographics were recorded for each case including smoking status at the time of surgery. Complications were recorded and all postoperative radiographs were reviewed to assess for evidence of delayed union (defined as lack of osseous union by 90 days after surgery). We compared active smokers and nonsmokers and performed a logistic regression analysis to estimate the odds of experiencing a delayed radiographic union.

RESULTS

A total of 309 arthrodesis cases were included and 24% were active smokers. Overall, radiographic evidence of a delayed union was found in 17% of cases. Smokers were significantly more likely to have a delayed union compared with nonsmokers (27% vs 14%). Results of the adjusted logistic regression analysis demonstrated that there was a significantly increased odds of experiencing a delayed union for patients who were active smokers compared with nonsmokers (odds ratio, 2.20; 95% confidence interval, 1.09-4.43). In addition, the rate of symptomatic nonunion requiring reoperation was higher in smokers (15%) compared with nonsmokers (6%).

CONCLUSIONS

Smoking was associated with increased odds of delayed radiographic union in patients undergoing hand and wrist arthrodesis procedures. Patients should be counseled appropriately on the risks of smoking on bone healing and encouraged to abstain from nicotine use in the perioperative period.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic II.

Assessment of Fusion After Anterior Cervical Discectomy and Fusion Using Convolutional Neural Network Algorithm

BACKGROUND

A convolutional neural network (CNN) is a deep learning (DL) model specialized for image processing, analysis, and classification.

OBJECTIVE

In this study, we evaluated whether a CNN model using lateral cervical spine radiographs as input data can help assess fusion after anterior cervical discectomy and fusion (ACDF).

STUDY DESIGN

Diagnostic imaging study using DL.

PATIENT SAMPLE

We included 187 patients who underwent ACDF and fusion assessment with postoperative one-year computed tomography and neutral and dynamic lateral cervical spine radiographs.

OUTCOME MEASURES

The performance of the CNN-based DL algorithm was evaluated in terms of accuracy and area under the curve.

MATERIALS AND METHODS

Fusion or nonunion was confirmed by cervical spine computed tomography. Among the 187 patients, 69.5% (130 patients) were randomly selected as the training set, and the remaining 30.5% (57 patients) were assigned to the validation set to evaluate model performance. Radiographs of the cervical spine were used as input images to develop a CNN-based DL algorithm. The CNN algorithm used three radiographs (neutral, flexion, and extension) per patient and showed the diagnostic results as fusion (0) or nonunion (1) for each radiograph. By combining the results of the three radiographs, the final decision for a patient was determined to be fusion (fusion ≥2) or nonunion (fusion ≤1). By combining the results of the three radiographs, the final decision for a patient was determined as fusion (fusion ≥2) or nonunion (nonunion ≤1).

RESULTS

The CNN-based DL model demonstrated an accuracy of 89.5% and an area under the curve of 0.889 (95% confidence interval, 0.793-0.984).

CONCLUSION

The CNN algorithm for fusion assessment after ACDF trained using lateral cervical radiographs showed a relatively high diagnostic accuracy of 89.5% and is expected to be a useful aid in detecting pseudarthrosis.

Endplate-specific fusion rate 1 year after surgery for two-level anterior cervical discectomy and fusion(ACDF)

STUDY DESIGN

This is a retrospective study.

OBJECTIVE

Implant nonfusion is an important prognostic factor for patients after anterior cervical discectomy and fusion (ACDF). This study aimed to investigate endplate-specific pseudarthrosis after ACDF, to determine if the rate of fusion is inferior in the lower endplate, and to identify any differences in clinical and radiological results. Research comparing each endplate on which the endplate affects nonfusion is limited.

METHODS

We analyzed 71 patients with 142 total spinal levels who underwent double-level ACDF (C4-5-6 and C5-6-7) with an allograft and plate at our hospital between January 2012 and December 2018. Fusion grades were assessed using computed tomography and the Bridwell fusion grade system at 1 year postoperatively. Radiological parameters were obtained from lateral cervical radiographs collected preoperatively and at 1 month and 1 year after surgery.

RESULTS

There was no difference in fusion between the C4-5-6 and C5-6-7 ACDF procedures, but the fusion rate and Bridwell fusion grade at the caudal surgery level were lower than those at the cranial surgery level (93 vs. 79%, p < 0.001). The lower endplate of the caudal fusion level showed the most common pseudarthrosis (18 of 71 [25%]). There was no difference in radiological parameters and clinical outcomes between the fusion and pseudarthrosis groups.

CONCLUSION

In double-level ACDF procedures, the nonfusion rate was higher at the caudal fusion levels, especially at the lower endplates of the caudal fusion levels.

Soft Cervical Orthosis Use Does Not Improve Fusion Rates After One-Level and Two-Level Anterior Cervical Discectomy and Fusion

OBJECTIVE

To determine if postoperative soft cervical orthosis use affects arthrodesis rates on a per-level or construct basis after 1-level and 2-level anterior cervical discectomy and fusion (ACDF).

METHODS

Electronic medical records were queried for 1-level and 2-level primary ACDF between 2016 and 2019 at a single academic center. Surgeons prescribed either a soft cervical orthosis or no orthosis. Pseudarthrosis rates were evaluated by dynamic cervical spine radiographs with arthrodesis defined by <1 mm of interspinous motion. Continuous and categorical data were compared using analysis of variance or χ2 tests. Multivariate logistic regression analysis was used to examine independent predictors of pseudarthrosis.

RESULTS

A total of 316 unique patients (504 instrumented levels) met the inclusion criteria. Eighty-four percent of patients were prescribed a soft cervical orthosis. Overall, arthrodesis occurred at 344 (80.9%) and 62 (78%) levels in patients with and without cervical orthosis, respectively. When evaluating patients placed in a cervical orthosis versus those who were not, there were no differences in pseudarthrosis or revision rates. Further, there were no differences in pseudarthrosis on a per-level basis. Further, cervical orthosis use was not an independent predictor of pseudarthrosis (odds ratio, 0.86; 95% confidence interval, 0.47-1.57; P =0.623) on multivariate analysis.

CONCLUSIONS

Postoperative placement of soft cervical orthoses after 1-level or 2-level ACDF was not associated with improved arthrodesis or reduced rate of revision surgery.

Segmental range of motion after cervical total disc arthroplasty at long-term follow-up: a systematic review and meta-analysis

OBJECTIVE

As an alternative procedure to anterior cervical discectomy and fusion, total disc arthroplasty (TDA) facilitates direct neural decompression and disc height restoration while also preserving cervical spine kinematics. To date, few studies have reported long-term functional outcomes after TDA. This paper reports the results of a systematic review and meta-analysis that investigated how segmental range of motion (ROM) at the operative level is maintained with long-term follow-up.

METHODS

PubMed and MEDLINE were queried for all published studies pertaining to cervical TDA. The methodology for screening adhered strictly to the PRISMA guidelines. All English-language prospective studies that reported ROM preoperatively, 1 year postoperatively, and/or at long-term follow-up of 5 years or more were included. A meta-analysis was performed using Cochran's Q and I2 to test data for statistical heterogeneity, in which case a random-effects model was used. The mean differences (MDs) and associated 95% confidence intervals (CIs) were reported.

RESULTS

Of the 12 studies that met the inclusion criteria, 8 reported the long-term outcomes of 944 patients with an average (range) follow-up of 99.86 (60-142) months and were included in the meta-analysis. There was no difference between preoperative segmental ROM and segmental ROM at 1-year follow-up (MD 0.91°, 95% CI -1.25° to 3.07°, p = 0.410). After the exclusion of 1 study from the comparison between preoperative and 1-year ROM owing to significant statistical heterogeneity according to the sensitivity analysis, ROM significantly improved at 1 year postoperatively (MD 1.92°, 95% CI 1.04°-2.79°, p < 0.001). However, at longer-term follow-up, the authors again found no difference with preoperative segmental ROM, and no study was excluded on the basis of the results of further sensitivity analysis (MD -0.22°, 95% CI -1.69° to -1.23°, p = 0.760). In contrast, there was a significant decrease in ROM from 1 year postoperatively to final long-term follow-up (MD -0.77°, 95% CI -1.29° to -0.24°, p = 0.004).

CONCLUSIONS

Segmental ROM was found to initially improve beyond preoperative values for as long as 1 year postoperatively, but then ROM deteriorated back to values consistent with preoperative motion at long-term follow-up. Although additional studies with further longitudinal follow-up are needed, these findings further support the notion that cervical TDA may successfully maintain physiological spinal kinematics over the long term.

What is the role of dynamic cervical spine radiographs in predicting pseudarthrosis revision following anterior cervical discectomy and fusion?

BACKGROUND CONTEXT

Postoperative dynamic radiographs are used to assess fusion status after anterior cervical discectomy and fusion (ACDF) with comparable accuracy to computed tomography (CT) scans.

PURPOSE

To (1) determine if dynamic radiographs accurately predict pseudarthrosis revision in a cohort of largely asymptomatic patients who underwent ACDF, (2) determine how adjacent segment motion is affected by fusion status, and (3) analyze how clinical outcomes differ between patients with symptomatic and asymptomatic pseudarthrosis.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Patients ≥ 18 years who underwent primary one- to four-level ACDF at a single institution over a 10-year period.

OUTCOME MEASURES

Interspinous motion on preoperative and postoperative flexion-extension radiographs and preoperative and postoperative Visual Analogue Scale for Neck Pain (VAS Neck) and Arm Pain (VAS Arm), Neck Disability Index (NDI), Modified Japanese Orthopaedic Association scale (mJOA), Mental and Physical Component Scores of the Short-Form 12 (SF-12) Health Survey (MCS-12 and PCS-12) METHODS: The difference in spinous process motion between flexion and extension radiographs was used to determine motion at each level of the ACDF construct. Pseudarthrosis was defined as ≥ 1 mm spinous process motion on dynamic radiographs. A receiver operating characteristic (ROC) curve was generated to predict the probability of surgical revision for pseudarthrosis based on millimeters of interspinous motion at each instrumented level. Patient reported outcome measures (PROMs) were used to assess the effect of pseudarthrosis on clinical outcomes. Alpha was set at p<.05.

RESULTS

A total of 597 patients met inclusion criteria including 1,203 ACDF levels. Of those, 215 patients (36.0%) were diagnosed with a pseudarthrosis on dynamic radiographs with 29 patients (4.9%) requiring pseudarthrosis revision. ROC analysis identified a "cutoff" value of 1.00 mm of interspinous process motion for generating an optimal area under the curve (AUC). The negative predictive value (NPV) was 99.6%, whereas the positive predictive value (PPV) was 13.7%. When analyzing adjacent segment motion, the Δ supra-adjacent interspinous process motion (ISM) was significantly lower for patients with a superior construct pseudarthrosis (-1.06 mm vs. 1.80 mm, p<.001), whereas the Δ infra-adjacent level ISM was significantly lower for patients with an inferior construct pseudarthrosis (-1.21 mm vs. 2.15 mm, p<.001). Patients with a pseudarthrosis not requiring revision had worse postoperative NDI (29.3 vs. 23.4, p=.027), VAS Neck (3.40 vs. 2.63, p=.012), and VAS Arm (3.09 vs. 1.85, p=.001) scores at 3 months, but not 1-year, compared with patients who were fused. Patients requiring pseudarthrosis revision had higher 1-year postoperative NDI (38.0 vs. 23.7, p=.047) and lower 1-year postoperative Δ VAS Arm (-0.22 vs. -2.97, p=.016) scores.

CONCLUSIONS

One-year postoperative dynamic radiographs have a greater than 99% negative predictive value for identifying patients requiring pseudarthrosis revision, but they have a low positive predictive value. Most patients with a pseudarthrosis remain asymptomatic with similar 1-year postoperative patient-reported outcomes compared with patients without a pseudarthrosis.

Longitudinal assessment of segmental motion of the cervical spine following total disc arthroplasty: a comparative analysis of devices

OBJECTIVE

Total disc arthroplasty (TDA) has been shown to be an effective and safe treatment for cervical degenerative disc disease at short- and midterm follow-up. However, there remains a paucity of literature reporting the differences between individual prosthesis designs with regard to device performance. In this study, the authors evaluated the long-term maintenance of segmental range of motion (ROM) at the operative cervical level across a diverse range of TDA devices.

METHODS

In this study, the authors retrospectively evaluated all consecutive patients who underwent 1- or 2-level cervical TDA between 2005 and 2020 at a single institution. Patients with a minimum of 6 months of follow-up and lateral flexion/extension radiographs preoperatively, 2 months postoperatively, and at final follow-up were included. Radiographic measurements included static segmental lordosis, segmental range of motion (ROM) on flexion/extension, global cervical (C2-7) ROM on flexion/extension, and disc space height. The paired t-test was used to evaluate improvement in radiographic parameters. Subanalysis between devices was performed using one-way ANCOVA. Significance was determined at p < 0.05.

RESULTS

A total of 85 patients (100 discs) were included, with a mean patient age of 46.01 ± 8.82 years and follow-up of 43.56 ± 39.36 months. Implantations included 22 (22.00%) M6-C, 51 (51.00%) Mobi-C, 14 (14.00%) PCM, and 13 (13.00%) ProDisc-C devices. There were no differences in baseline radiographic parameters between groups. At 2 months postoperatively, PCM provided significantly less segmental lordosis (p = 0.037) and segmental ROM (p = 0.039). At final follow-up, segmental ROM with both the PCM and ProDisc-C devices was significantly less than that with the M6-C and Mobi-C devices (p = 0.015). From preoperatively to 2 months postoperatively, PCM implantation led to a significant loss of lordosis (p < 0.001) and segmental ROM (p = 0.005) relative to the other devices. Moreover, a significantly greater decline in segmental ROM from 2 months postoperatively to final follow-up was seen with ProDisc-C, while segmental ROM increased significantly over time with Mobi-C (p = 0.049).

CONCLUSIONS

Analysis by TDA device brand demonstrated that motion preservation differs depending on disc design. Certain devices, including M6-C and Mobi-C, improve ROM on flexion/extension from preoperatively to postoperatively and continue to increase slightly at final follow-up. On the other hand, devices such as PCM and ProDisc-C contributed to greater segmental stiffness, with a gradual decline in ROM seen with ProDisc-C. Further studies are needed to understand how much segmental ROM is ideal after TDA for preservation of physiological cervical kinematics.

Assessing Postoperative Pseudarthrosis in Anterior Cervical Discectomy and Fusion (ACDF) on Dynamic Radiographs Using Novel Angular Measurements

STUDY DESIGN

A retrospective review of operative patients at a single institution.

OBJECTIVE

The aim was to validate a novel method of detecting pseudarthrosis on dynamic radiographs.

SUMMARY OF BACKGROUND DATA

A common complication after anterior cervical discectomy and fusion is pseudarthrosis. A previously published method for detecting pseudarthrosis identifies a 1 mm difference in interspinous motion (ISM), which requires calibration of images and relies on anatomic landmarks difficult to visualize. An alternative is to use angles between spinous processes, which does not require calibration and relies on more visible landmarks.

MATERIALS AND METHODS

ISM was measured on dynamic radiographs using the previously published linear method and new angular method. Angles were defined by lines from screw heads to dorsal points of spinous processes. Angular cutoff for fusion was calculated using a regression equation correlating linear and angular measures, based on the 1 mm linear cutoff. Pseudarthrosis was assessed with both cutoffs. Sensitivity, specificity, inter-reliability and intrareliability of angular and linear measures used postoperative computed tomography (CT) as the reference.

RESULTS

A total of 242 fused levels (81 allograft, 84 polyetheretherketone, 40 titanium, 37 standalone cages) were measured in 143 patients (mean age 52.0±11.5, 42%F). 36 patients (66 levels) had 1-year postoperative CTs; 13 patients (13 levels) had confirmed pseudarthrosis. Linear and angular measurements closely correlated ( R =0.872), with 2.3° corresponding to 1 mm linear ISM. Potential pseudarthroses was found in 28.0% and 18.5% levels using linear and angular cutoffs, respectively. Linear cutoff had 85% sensitivity, 87% specificity; angular cutoff had 85% sensitivity, 96% specificity for detecting CT-validated pseudarthrosis. Interclass correlation coefficients were 0.974 and 0.986 (both P <0.001); intrarater reliability averaged 0.953 and 0.974 ( P <0.001 for all) for linear and angular methods, respectively.

CONCLUSIONS

The angular measure for assessing potential pseudarthrosis is as sensitive as and more specific than published linear methods, has high interobserver reliability, and can be used without image calibration.

LEVEL OF EVIDENCE

3.

Morphologic Change of CorticoCancellous Allograft Used for Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to evaluate the incidence and clinical implications of graft morphologic changes in corticocancellous allografts used for anterior cervical discectomy and fusion (ACDF), such as graft resorption or fracture.

SUMMARY OF BACKGROUND DATA

Although cortico-cancellous allograft is one of the most commonly used interbody spacer for ACDF, clinical implications of allograft resorption or fracture is unclear.

METHODS

One-hundred and thirty-eight consecutive patients who underwent ACDF for degenerative cervical myelopathy or radiculopathy were retrospectively reviewed. Patients with allograft morphologic changes, including graft resorption and fracture (morphologic change group), were compared with patients without morphologic changes (unchanged group). Furthermore, operated segments with morphologic changes were compared with unchanged segments. Patient characteristics, cervical lordosis, segmental lordosis, fusion, subsidence, neck pain visual analogue scale (VAS), arm pain VAS, and neck disability index (NDi) scores were evaluated.

RESULTS

Ninety patients (149 segments) were included in the study. Allograft resorption or fracture was detected in 46 (51.1%) patients and 81 (54.3%) segments, respectively. The fusion rate of morphologic change segments was significantly lower than that of the unchanged segments (P < 0.001). Furthermore, segments with morphologic changes had significantly higher rates of subsidence compared to unchanged segments ( P < 0.001). Segmental lordosis at the final follow-up was significantly smaller in the morphologic change segments ( P < 0.001). Neck pain VAS, arm pain VAS, and NDI scores did not demonstrate significant intergroup differences.

CONCLUSION

Corticocancellous allograft demonstrated a high rate of graft morphologic change (54.3%). Graft resorption or fracture was associated with increased pseudarthrosis, subsidence, and decreased postoperative segmental lordosis; however, the clinical results were not significantly affected. Caution is needed when choosing to use corticocancellous allografts for ACDF due to the high rate of graft resorption or fracture and the negative implications of these risks.

Does Preoperative Bone Mineral Density Impact Fusion Success in Anterior Cervical Spine Surgery? A Prospective Cohort Study

OBJECTIVE

The purpose of this study was to identify risk factors for pseudarthrosis in patients undergoing anterior cervical discectomy and fusion (ACDF) with a focus on the role of bone mineral density (BMD) on arthrodesis.

METHODS

We retrospectively reviewed a prospectively collected database of patients undergoing 1- to 4-level ACDF for degenerative indications between 2012 and 2018 at a single institution. All patients were required to have undergone a preoperative dual-energy x-ray absorptiometry (DEXA) scan. Fusion status was assessed on computed tomography (CT) scans obtained 1 year postoperatively. Patients were divided into subgroups based on fusion status and compared on the basis of demographic, BMD, and surgical variables to determine risk factors for pseudarthrosis.

RESULTS

We identified 79 patients for inclusion in this study. Fusion was achieved in 65 patients (82%), while 14 patients (18%) developed pseudarthrosis. The pseudarthrosis subgroup demonstrated significantly lower BMD than their counterparts who achieved successful fusion in both mean hip (-1.4 ± 1.2 vs. -0.2 ± 1.2, respectively; P = 0.002) and spine T-scores (-0.8 ± 1.8 vs. 0.6 ± 1.9, respectively; P = 0.02). The pseudarthrosis group had a substantially higher proportion of patients with osteopenia (57.1% vs. 20.0%) and osteoporosis (21.5% vs. 6.2%; P < 0.001) than the fusion group. Multivariate analysis demonstrated osteopenia (odds ratio [OR] 8.76, P = 0.04), osteoporosis (OR 9.97, P = 0.03), and low BMD (OR 11.01, P = 0.002) to be associated with an increased likelihood of developing pseudarthrosis.

CONCLUSIONS

The results of this study suggest that both osteopenia and osteoporosis are associated with increased rates of pseudarthrosis in patients undergoing elective ACDF.

Pseudarthrosis of the Cervical Spine

Pseudarthrosis of the cervical spine represents a common and challenging problem for spine surgeons. Rates vary greatly from as low as 0%-20% to >60% and depend heavily on patient factors, approach, and number of levels. While some patients remain asymptomatic from pseudarthrosis, many require revision surgery due to instability, continued neck pain, or radiculopathy/myelopathy. We aimed to provide a practical, narrative review of cervical pseudarthrosis to address the following areas: (1) definitions, (2) incidence, (3) risk factors, (4) presentation and workup, (5) treatment decision-making, and (6) postoperative care. It is our hope the current review provides a concise summary for how to diagnose and treat challenging cervical nonunions.

PLF+PS or ALIF+PS: which has a lower operative nonunion rate? Analysis of a cohort of 2,061 patients from a National Spine Registry

BACKGROUND CONTEXT

Although fusion rates in posterolateral lumbar fusions with pedicle screws (PLF+PS) and anterior lumbar interbody fusions with pedicle screws (ALIF+PS) have been reported, there has been no consensus on superiority with respect to clinical outcome and nonunion rates. Most studies determine nonunion rates based on radiographic studies; however, many of these nonunions are asymptomatic and may not require reoperations. Hence, a potentially more clinically useful measure is the reoperation rate for symptomatic nonunions, which we term the operative nonunion rate.

PURPOSE

To determine if there is a difference in operative nonunion rates between PLF+PS versus ALIF+PS.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Adult patients (≥18 years old) with the diagnosis of lumbar spondylolisthesis or lumbar spinal stenosis who underwent primary elective PLF+PS and ALIF+PS for 1-level and 2-level fusions (L4-S1) between 2009 and 2018.

OUTCOME MEASURES

Reoperation rates for symptomatic nonunions (ie, operative nonunion rates).

METHODS

Patients were followed until validated operative nonunions, membership termination, death, or 03/31/2019. Descriptive statistics and 2-year incidence rates for operative nonunions were calculated by fusion-level, fusion type, and levels fused. Time-dependent multivariable Cox-Proportional Hazards regression was used to evaluate operative nonunion rates with adjustment for covariates or risk change estimates more than 10%.

RESULTS

We identified 2,061 patients (PLF+PS:1,491, ALIF+PS:570) with average follow-up time of 4.8 (±3.1) years and average time to operative nonunion of 1.3 (±1.2) yrs. Comparatively, unadjusted 1-level and 2-level incidence rates for operative nonunions were higher in PLF+PS versus ALIF+PS. For 1-level procedures these were 0.9% (95% CI=0.4-1.6) versus 0.6% (95% CI=0.1-2.1); 2-level, 2.0% (95% CI=0.8-4.0) versus 0.9% (95% CI=0.1-3.3). However, there were no observed significant differences in risks for operative nonunions in multivariable models comparing PLF+PS versus ALIF+PS (HR=0.3, 95% CI=0.1-1.1), 1-level versus 2-level fusions (HR=1.8, 95% CI=0.8-4.3), or by fusion level (L4-L5: HR=1.0, 95% CI=0.4-2.7; L5-S1: HR=2.0, 95% CI=0.7-5.4).

CONCLUSIONS

A large cohort of patients with lumbar fusions between L4 to S1 and an average follow-up of >4 years found that although there was a trend for higher operative nonunions in PLF+PS compared with ALIF+PS, this was not statistically significant. The role of spinal alignment was not investigated.

Autologous Stem Cells in Cervical Spine Fusion

STUDY DESIGN

Systematic review.

OBJECTIVES

To systematically review, critically appraise and synthesize evidence on use of stem cells from autologous stem cells from bone marrow aspirate, adipose, or any other autologous sources for fusion in the cervical spine compared with other graft materials.

METHODS

A systematic search of PubMed/MEDLINE was conducted for literature published through October 31, 2018 and through February 20, 2020 for EMBASE and ClinicalTrials.gov comparing autologous cell sources for cervical spine fusion to other graft options.

RESULTS

From 36 potentially relevant citations identified, 10 studies on cervical fusion met the inclusion criteria set a priori. Two retrospective cohort studies, one comparing cancellous bone marrow (CBM) versus hydroxyapatite (HA) and the other bone marrow aspirate (BMA) combined with autograft and HA versus autograft and HA alone, were identified. No statistical differences were seen between groups in either study for improvement in function, symptoms, or fusion; however, in the study evaluating BMA, the authors reported a statistically greater fusion rate and probability of fusion over time in the BMA versus the non-BMA group. Across case series evaluating BMA, authors reported improved function and pain and fusion ranged from 84% to 100% across the studies. In general, complications were poorly reported.

CONCLUSIONS

The overall quality (strength) of evidence of effectiveness and safety of autologous BMA for cervical arthrodesis in the current available literature was very low. Based on currently available data, firm conclusions regarding the effectiveness or safety of BMA in cervical fusions cannot be made.

Pseudarthrosis rate following anterior cervical discectomy with fusion using an allograft cellular bone matrix: a multi-institutional analysis

OBJECTIVE

The use of osteobiologics, engineered materials designed to promote bone healing by enhancing bone growth, is becoming increasingly common for spinal fusion procedures, but the efficacy of some of these products is unclear. The authors performed a retrospective, multi-institutional study to investigate the clinical and radiographic characteristics of patients undergoing single-level anterior cervical discectomy with fusion performed using the osteobiologic agent Osteocel, an allograft mesenchymal stem cell matrix.

METHODS

The medical records across 3 medical centers and 12 spine surgeons were retrospectively queried for patients undergoing single-level anterior cervical discectomy and fusion (ACDF) with the use of Osteocel. Pseudarthrosis was determined based on CT or radiographic imaging of the cervical spine. Patients were determined to have radiographic pseudarthrosis if they met any of the following criteria: 1) lack of bridging bone on CT obtained > 300 days postoperatively, 2) evidence of instrumentation failure, or 3) motion across the index level as seen on flexion-extension cervical spine radiographs. Univariate and multivariate analyses were then performed to identify independent preoperative or perioperative predictors of pseudarthrosis in this population.

RESULTS

A total of 326 patients met the inclusion criteria; 43 (13.2%) patients met criteria for pseudarthrosis, of whom 15 (34.9%) underwent revision surgery. There were no significant differences between patients with and those without pseudarthrosis, respectively, for patient age (54.1 vs 53.8 years), sex (34.9% vs 47.4% male), race, prior cervical spine surgery (37.2% vs 33.6%), tobacco abuse (16.3% vs 14.5%), chronic kidney disease (2.3% vs 2.8%), and diabetes (18.6% vs 14.5%) (p > 0.05). Presence of osteopenia or osteoporosis (16.3% vs 3.5%) was associated with pseudarthrosis (p < 0.001). Implant type was also significantly associated with pseudarthrosis, with a 16.4% rate of pseudarthrosis for patients with polyetherethereketone (PEEK) implants versus 8.4% for patients with allograft implants (p = 0.04). Average lengths of follow-up were 27.6 and 23.8 months for patients with and those without pseudarthrosis, respectively. Multivariate analysis demonstrated osteopenia or osteoporosis (OR 4.97, 95% CI 1.51-16.4, p < 0.01) and usage of PEEK implant (OR 2.24, 95% CI 1.04-4.83, p = 0.04) as independent predictors of pseudarthrosis.

CONCLUSIONS

In patients who underwent single-level ACDF, rates of pseudarthrosis associated with the use of the osteobiologic agent Osteocel are higher than the literature-reported rates associated with the use of alternative osteobiologics. This is especially true when Osteocel is combined with a PEEK implant.

Musculoskeletal tissue engineering: Regional gene therapy for bone repair

Bone loss associated with fracture nonunion, revision total joint arthroplasty (TJA), and pseudoarthrosis of the spine presents a challenging clinical scenario for the orthopaedic surgeon. Current treatment options including autograft, allograft, bone graft substitutes, and bone transport techniques are associated with significant morbidity, high costs, and prolonged treatment regimens. Unfortunately, these treatment strategies have proven insufficient to safely and consistently heal bone defects in the stringent biological environments often encountered in clinical cases of bone loss. The application of tissue engineering (TE) to musculoskeletal pathology has uncovered exciting potential treatment strategies for challenging bone loss scenarios in orthopaedic surgery. Regional gene therapy involves the local implantation of nucleic acids or genetically modified cells to direct specific protein expression, and has shown promise as a potential TE technique for the regeneration of bone. Preclinical studies in animal models have demonstrated the ability of regional gene therapy to safely and effectively heal critical sized bone defects which otherwise do not heal. The purpose of the present review is to provide a comprehensive overview of the current status of gene therapy applications for TE in challenging bone loss scenarios, with an emphasis on gene delivery methods and models, scaffold biomaterials, preclinical results, and future directions.

Characterizing the fusion order and level-specific rates of arthrodesis in 3-level anterior cervical discectomy and fusion: A radiographic study

Pseudarthrosis is a well-recognized complication following multi-level ACDF. We aim to characterize the fusion order and level-specific rates of arthrodesis across four time points following 3-level ACDF. Patients who underwent 3-level ACDF by three UCSF spine surgeons from August 2012 to December 2019 were identified. Fusion status at each level was determined by measuring the interspinous motion on flexion and extension radiographs and assessing for evidence of bridging bone. Measurements were performed post-operatively at 6 weeks, 6 months, 12 months, and 18-24 months. A total of 77 patients with 3-level ACDF were identified and included in this study. Specific ACDF levels include C3-C6 (17 patients), C4-C7 (57 patients), and C5-T1 (3 patients). At 6 months, the cranial, middle, and caudal level fusion rates were 17.0%, 34.0%, and 3.8%, respectively. By 24 months, fusion rates were 61.1%, 88.9%, and 27.8% at the cranial, middle, and caudal level, respectively. PEEK cages were associated with lower odds of multi-level arthrodesis. Arthrodesis occurred the quickest at the middle level with an 88.9% fusion rate by 24 months after surgery. The caudal level had the slowest rate of arthrodesis with only a 27.8% fusion rate at 24 months, likely due to increased biomechanical stress at the most caudal level. Allograft was associated with higher odds of multi-level arthrodesis compared to PEEK cages.

Operative Nonunion Rates in Posterolateral Lumbar Fusions: Analysis of a Cohort of 2591 Patients from a National Spine Registry

OBJECTIVE

Radiographic nonunion rates in the literature for posterolateral lumbar fusions with pedicle screws (PLFs) range from 8.1% to 43.3% but may not represent nonunion rates. A few small studies have reported reoperations for symptomatic nonunions (operative nonunions) to range from 3.2% to 13.9%. The objective of this study is to determine operative nonunion rates for 1-level, 2-level, 3-level, and ≥4-level PLFs and to determine the risks for these nonunions.

METHODS

A retrospective cohort study, using data from the Kaiser Permanente Spine Registry, identified adult patients (≥18 years old) who underwent PLFs for degenerative disc disease. Multivariable Cox proportional hazards regression and Kaplan-Meier survival estimates using the log-rank statistic were used to evaluate operative nonunion rates.

RESULTS

The cohort consisted of 2591 patients with single-level and multilevel PLFs with mean follow-up of 4.6 years, time to operative nonunion of 1.52 years, and 2-year operative nonunion rate of 1.08%. Compared with single-level fusions, patients with 3-level and ≥4-level fusion had 2.8 and 3.7 times higher risk of operative nonunions. Patients with PLFs involving L5-S1 had 2.5 times the risk of an operative nonunion compared with those without.

CONCLUSIONS

Our study reports results from one of the largest cohort of patients for the first time with single-level and multilevel instrumented PLFs and found a 2-year operative nonunion rate of 1.08% with increased risk of nonunion for constructs that included L5-S1 and ≥3-level fusions. Operative nonunion combines clinical and radiographic data and provides an alternative measure of fusion rates.