Category: Spine

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Decompression alone versus decompression and instrumented fusion for the treatment of isthmic spondylolisthesis: a randomized controlled trial

J Neurosurg Spine 35:687–697, 2021

The most advocated surgical technique to treat symptoms of isthmic spondylolisthesis is decompression with instrumented fusion. A less-invasive classical approach has also been reported, which consists of decompression only. In this study the authors compared the clinical outcomes of decompression only with those of decompression with instrumented fusion in patients with isthmic spondylolisthesis.

METHODS Eighty-four patients with lumbar radiculopathy or neurogenic claudication secondary to low-grade isthmic spondylolisthesis were randomly assigned to decompression only (n = 43) or decompression with instrumented fusion (n = 41). Primary outcome parameters were scores on the Roland Disability Questionnaire (RDQ), separate visual analog scales (VASs) for back pain and leg pain, and patient report of perceived recovery at 12-week and 2-year follow-ups. The proportion of reoperations was scored as a secondary outcome measure. Repeated measures ANOVA according to the intention-to-treat principle was performed.

RESULTS Decompression alone did not show superiority in terms of disability scores at 12-week follow-up (p = 0.32, 95% CI −4.02 to 1.34), nor in any other outcome measure. At 2-year follow-up, RDQ disability scores improved more in the fusion group (10.3, 95% CI 3.9–8.2, vs 6.0, 95% CI 8.2–12.4; p = 0.006, 95% CI −7.3 to −1.3). Likewise, back pain decreased more in the fusion group (difference: −18.3 mm, CI −32.1 to −4.4, p = 0.01) on a 100-mm VAS scale, and a higher proportion of patients perceived recovery as showing “good results” (44% vs 74%, p = 0.01). Cumulative probabilities for reoperation were 47% in the decompression and 13% in the fusion group (p < 0.001) at the 2-year follow-up.

CONCLUSIONS In patients with isthmic spondylolisthesis, decompression with instrumented fusion resulted in comparable short-term results, significantly better long-term outcomes, and fewer reoperations than decompression alone. Decompression with instrumented fusion is a superior surgical technique that should in general be offered as a first treatment option for isthmic spondylolisthesis, but not for degenerative spondylolisthesis, which has a different etiology. Clinical trial registration number: NTR1300 (Netherlands Trial Register)

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Low-back pain after lumbar discectomy for disc herniation: what can you tell your patient?

J Neurosurg Spine 35:715–721, 2021

Lumbar discectomy (LD) is frequently performed to alleviate radicular pain resulting from disc herniation. While this goal is achieved in most patients, improvement in low-back pain (LBP) has been reported inconsistently. The goal of this study was to characterize how LBP evolves following discectomy.

METHODS The authors performed a retrospective analysis of prospectively collected patient data from the Canadian Spine Outcomes and Research Network (CSORN) registry. Patients who underwent surgery for lumbar disc herniation were eligible for inclusion. The primary outcome was a clinically significant reduction in the back pain numerical rating scale (BPNRS) assessed at 12 months. Binary logistic regression was used to model the relationship between the primary outcome and potential predictors.

RESULTS There were 557 patients included in the analysis. The chief complaint was radiculopathy in 85%; 55% of patients underwent a minimally invasive procedure. BPNRS improved at 3 months by 48% and this improvement was sustained at all follow-ups. LBP and leg pain improvement were correlated. Clinically significant improvement in BPNRS at 12 months was reported by 64% of patients. Six factors predicted a lack of LBP improvement: female sex, low education level, marriage, not working, low expectations with regard to LBP improvement, and a low BPNRS preoperatively.

CONCLUSIONS Clinically significant improvement in LBP is observed in the majority of patients after LD. These data should be used to better counsel patients and provide accurate expectations about back pain improvement.

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Negligible Systemic Uptake of Suprafascial Vancomycin Powder Following Instrumented Posterior Spinal Fusion

Neurosurgery 89:967–972, 2021

Intrawound vancomycin powder is an emerging strategy to reduce surgical site infections (SSIs) in spine surgery. However, there are concerns relating to its safety profile and toxicity. Data on systemic uptake of suprafascially administered vancomycin powder following instrumented spinal fusion is lacking.

OBJECTIVE: To study the systemic uptake and safety of suprafascially administered vancomycin powder in the early postoperative phase following open instrumented posterior spinal fusion.

METHODS: This was a substudy of an ongoing randomized clinical trial. Eligible adult patients were randomized 1:1 to either receive suprafascial vancomycin powder before wound closure or not to receive vancomycin powder. Serum vancomycin levels were assessed on postoperative days 1 and 2, serum creatinine levels were measured pre- and post-operatively. Adverse events up to 6 wk following surgery were recorded.

RESULTS:Among34 randomized patients (mean age 62 yr, range 31-84 yr; 18 [53%]women), 17 received vancomycin powder. No detectable serum vancomycin levels (>4.0mg/L)were found. Proportion of adverse events per patient in the vancomycin and control group, respectively,were 29.4% (5/17) vs 11.8% (2/17) (OR 3.12;95%CI, 0.52; 19.38; P=.398).No patient had nephrotoxicity or ototoxicity in either group. CONCLUSION: Suprafascial vancomycin powder in open instrumented spinal fusion surgery is safe and results in negligible systemic uptake. Final results of the VANCO Trial need to be awaited for conclusive data on the efficacy of vancomycin for SSI prevention and its impact on wound healing.

 

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Posterior fusion for fragility type 2 odontoid fractures

J Neurosurg Spine 35:644–650, 2021

The purpose of this study was to evaluate the outcomes of elderly patients with type 2 odontoid fractures treated with an instrumented posterior fusion.

METHODS Ninety-three consecutive patients older than 65 years of age in whom a type 2 odontoid fracture had been treated with a variety of C1–2 posterior screw fixation techniques were retrospectively reviewed.

RESULTS The average age was 78 years (range 65–95 years). Thirty-seven patients had an additional fracture, 30 of which involved C1. Three patients had cervical spinal cord dysfunction due to their injury. All patients had comorbidities. The average total hospitalization was 9.6 days (range 2–37 days). There were 3 deaths and 19 major complications, the most common of which was pneumonia. No patient suffered a vertebral artery injury. Imaging studies were obtained in 64 patients at least 12 months postsurgery (mean 19 months). Fusion was assessed by dynamic radiographs in all cases and with a CT scan in 80% of the cases. Four of the 64 patients did not achieve fusion (6.25% overall). All patients in whom fusion failed had undergone C1 lateral mass fixation and C2 pars (1/29, 3.4%) or laminar (3/9, 33.3%) fixation.

CONCLUSIONS Instrumented posterior cervical fusions may be performed in elderly patients with acceptable morbidity and mortality. The fusion rate is excellent except when bilateral C2 translaminar screws are used for axis fixation.

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Open-door laminoplasty with stand-alone autologous bone spacers

J Neurosurg Spine 35:633–637, 2021

The authors aimed to determine the efficacy of open-door laminoplasty with stand-alone autologous bone spacer for preserving enlarged lamina in patients with cervical myelopathy.

METHODS Patients who underwent open-door laminoplasty for cervical myelopathy with stand-alone autologous bone spacer and underwent CT 1 week and 1 year after surgery were included in this study. There were 20 men and 13 women, with an average (range) age of 65.0 (37–86) years. Seventeen patients were younger than 70 years, and 16 patients were older than 70 years. Autogenous bone spacers made from spinous processes were used in all patients. Slits were made on both sides of the spacers. The lamina was raised with a curette, and a spacer was inserted without any sutures. Before surgery and 1 week and 1 year after surgery, the anteroposterior diameter (APD) of the spinal canal was measured using midsagittal-plane CT–multiplanar reconstruction. The bone union rate of the hinge side and autogenous bone spacer of each lamina was determined using CT images obtained 1 year after surgery. Results 1 year after surgery were evaluated using Japanese Orthopaedic Association (JOA) score.

RESULTS The mean ± SD APD increase rate was 56.3% ± 21.3% 1 week after surgery and 51.7% ± 20.6% 1 year later. The average APD decrease rate was 2.9% ± 3.8%. The bone union rate on the hinge side was 100%, and that of autologous bone spacer was 93.8% 1 year after surgery. The mean APD decrease rate was 3.3% in patients younger than 70 years and 2.3% in those older than 70 years. There was no significant difference between the two groups (p > 0.05, nonpaired t-test). The JOA score averaged 10.1 before surgery and 13.3 a year after surgery (total score 17). The average improvement rate was 46.3% ± 26.4%.

CONCLUSIONS The authors devised and implemented a technique for inserting an autologous bone spacer between the opened lamina and lateral mass without sutures. The enlarged spinal canal was maintained 1 year after surgery. This simple method does not require any instrumentation or additional cost to stabilize the opened lamina.

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Spinal Arachnoid Webs

Neurosurgery 89:917–927, 2021

Spinal arachnoid webs are rarely described bands of thickened arachnoid tissue in the dorsal thoracic spine. Much is unknown regarding their origins, risk factors, natural history, and outcomes.

OBJECTIVE: To present the single largest case series, detailing presenting symptoms and outcomes amongst operative and nonoperative patients, to better understand the role of intervention.

METHODS: This retrospective chart review identified 38 patients with arachnoid webs. Patient demographics, radiologic signs, symptoms, and surgical history data were extracted from the electronic medical record. Symptoms were divided by location and character. 28 patients were successfully contacted for follow up outcome surveys.

RESULTS: 26 patients (68%) underwent surgical intervention, 12 (32%) were managed non-operatively. 15 (39%) patients had undergone a previous unsuccessful surgery at a different site for their symptoms prior to arachnoid web diagnosis. Commonly presenting symptoms included myelopathy (68%), focal thoracic back pain (68%), lower extremity weakness (45%), numbness and sensory changes (58%), and lower extremity radicular pain (42%), upper extremity weakness (24%), and radicular pain (37%). Focal thoracic pain was associated with thoracic level (P < .02). Myelopathic symptoms were less common in postoperative patients. Postoperative patients described significantly more upper extremity (P < .01) and thoracic (P < .01) numbness and paresthesias. Surveyed nonoperative patients universally described their symptoms as either stable orworsening.

CONCLUSION: Spinal arachnoid webs present with thoracic myelopathy and back pain but can also present with upper extremity symptoms. Surgical intervention stabilizes or improves symptoms and is well received. Nonoperative patients do not spontaneously improve.

 

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Effectiveness of Surgical Decompression in Patients With Degenerative Cervical Myelopathy

Neurosurgery 89:844–851, 2021

Conflicting evidence exists regarding the effectiveness of surgery for degenerative cervical myelopathy (DCM), particularly in mild DCM.

OBJECTIVE: To prospectively evaluate the impact of surgery on patient-reported outcomes in patients with mild (modified Japanese Orthopaedic Association [mJOA]≥15), moderate (mJOA 12-14), and severe (mJOA < 12) DCM.

METHODS: Prospective, multicenter cohort study of patients with DCM who underwent surgery between 2015 and 2019 and completed 1-yr follow-up. Outcome measures (mJOA, Neck Disability Index [NDI], EuroQol-5D [EQ-5D], Short Form [SF-12] Physical Component Score [PCS]/Mental Component Score [MCS], numeric rating scale [NRS] neck, and arm pain) were assessed at 3 and 12 mo postoperatively and compared to baseline, stratified by DCM severity. Changes in outcome measures that were statistically significant (P < .05) and met their respective minimum clinically important differences (MCIDs) were deemed clinically meaningful. Responder analysis was performed to compare the proportion of patients betweenDCMseverity groups whomet the MCID for each outcome measure.

RESULTS: The cohort comprised 391 patients: 110 mild, 163 moderate, and 118 severe. At 12 mo after surgery, severe DCM patients experienced significant improvements in all outcome measures; moderate DCM patients improved in mJOA, NDI, EQ-5D, and PCS; mild DCM patients improved in EQ-5D and PCS. There was no significant difference between severity groups in the proportion of patients reaching MCID at 12 mo after surgery for any outcome measure, except NDI.

CONCLUSION: At 12 mo after surgery, patients with mild, moderate, and severe DCM all demonstrated improved outcomes. Severe DCM patients experienced the greatest breadth of improvement, but the proportion of patients in each severity group achieving clinically meaningful changes did not differ significantly across most outcome measures.

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Understanding sagittal compensation in adult spinal deformity patients: relationship between pelvic tilt and lower-extremity position

J Neurosurg Spine 35:616–623, 2021

In adult spinal deformity (ASD), quantifying preoperative lower-extremity (LE) compensation is important in formulating an operative plan to achieve optimal global sagittal alignment. Whole-body radiographs are not always available. This study evaluated the possibility of estimating LE compensation without whole-body radiographs.

METHODS In total, 200 consecutive ASD patients with full-body radiographic assessment were categorized into the following three groups according to their cranio-hip balance (distance from the cranial sagittal vertical axis to the hip axis [CrSVA-H]): group 1, anterior-shift (A-shift) group (CrSVA-H > 40 mm); group 2, balanced group, −40 mm < CrSVA-H < 40 mm; and group 3, posterior-shift (P-shift) group, CrSVA-H < −40 mm. After analyzing the correlation between CrSVAH, pelvic tilt (PT), and LE parameters, the cutoff PT and PT/pelvic incidence (PI) values that correlated with the presence of LE compensation were determined. Previously published data from asymptomatic volunteers were used as a baseline threshold (sacrofemoral angle [SFA] > 217.0° and knee flexion angle [KA] > 11.0°).

RESULTS Among the hip, knee, and ankle, only KA showed a significant increase in the A-shift group compared to the other two groups (p < 0.01). With a wide threshold (SFA > 208.0° and KA > 5.0°), 84.9% of the A-shift group showed LE compensation (hip or knee or both), which was a significantly greater percentage than those in the balanced and P-shift groups (48.4% and 51.9%, p < 0.01). With a narrow threshold (SFA > 217.0° and KA > 11.0°), 62.2% of the A-shift group showed any LE compensation, which was also a higher percentage than the other two groups. The CrSVA-H was moderately correlated with KA (r = 0.502), but had no correlation with PT, SFA, and ankle dorsiflexion angle (AA). PT showed a moderate/strong correlation with SFA, KA, and AA (r = 0.846, 0.624, and 0.622, respectively). With receiver operating characteristic curves, the authors determined that a 23.0° PT with PT/PI > 0.46 predicts the presence of any type of LE compensation with use of the wide threshold.

CONCLUSIONS ASD patients with increased CrSVA-H, which represents cranio-hip anterior imbalance, demonstrated a higher prevalence of LE compensation, especially knee flexion, compared to those with neutral and posterior shift of CrSVA. PT represents the extent of LE compensation in patients with spinal sagittal malalignment. Using the cutoff value of PT determined in this study, surgeons can preoperatively estimate the extent of LE compensation without obtaining a full-body radiograph.

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Independent Predictors of Revision Lumbar Fusion Outcomes and the Impact of Spine Surgeon Variability

Neurosurgery 89:836–843, 2021

There is a paucity of information regarding treatment strategies and variables affecting outcomes of revision lumbar fusions.

OBJECTIVE: To evaluate the influence of primary vs different surgeon on functional outcomes of revisions.

METHODS: All elective lumbar fusion revisions, March 2018 to August 2019, were retrospectively categorized as performed by the same or different surgeon who performed the primary surgery. Oswestry Disability Index (ODI) and clinical variables were collected. Multiple logistic regression identified multivariable-adjusted odds ratio (OR) of independent variables analyzed.

RESULTS:Of the 130 cases, 117 (90%) had complete data. There was a slight difference in age in the same (median: 59; interquartile range [IQR], 54-66) and different surgeon (median: 67; IQR, 56-72) groups (P = .02); all other demographic variables were not significantly different (P > .05). Revision surgery with a different surgeon had an ODI improvement (median: 8; IQR, 2-14) greater than revisions performed by the same surgeon (median: 1.5; IQR, −3 to 10) (P < .01). Revisions who achieved minimum clinically important difference (MCID) performed by different surgeon (59.7%) were also significantly greater than the ones performed by the same surgeon (40%) (P=.042). Multivariate analysis demonstrated that a different surgeon revising (OR, 2.37; [CI]: 1.007-5.575, P = .04) was an independent predictor of MCID achievement, each additional 2 years beyond the last surgery conferred a 2.38 ([CI]: 1.36-4.14, P < .01) times greater odds of MCID achievement, and the anterior lumbar interbody fusion approach decreased the chance of achieving MCID (OR, 0.19; [CI]: 0.04-0.861, P = .03).

CONCLUSION: All revision lumbar spinal fusion approaches may not achieve the same outcomes. This analysis suggests that revision surgeries may have better outcomes when performed by a different surgeon.

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Is there a variance in complication types associated with ALIF approaches?

Acta Neurochirurgica (2021) 163:2991–3004

Anterior lumbar interbody fusion (ALIF) is a well-established alternative to posterior-based interbody fusion techniques, with approach variations, such as retroperitoneal, transperitoneal, open, and laparoscopic well described. Variable rates of complications for each approach have been enumerated in the literature. The purpose of this study was to elucidate the comparative rates of complications across approach type.

Methods A systematic review of search databases PubMed, Google Scholar, and OVID Medline was made to identify studies related to complication-associated ALIF. PRISMA guidelines were utilised for this review. Meta-analysis was used to compare intraoperative and postoperative complications with ALIF for each approach.

Results A total of 4575 studies were identified, with 5728 patients across 31 studies included for review following application of inclusion and exclusion criteria. Meta-analysis demonstrated the transperitoneal approach resulted in higher rates of retrograde ejaculation (RE) (p < 0.001; CI = 0.05–0.21) and overall rates of complications (p = 0.05; CI = 0.00–0.23). Rates of RE were higher at the L5/S1 intervertebral level. Rates of vessel injury were not significantly higher in either approach method (p = 0.89; CI = − 0.04–0.07). Rates of visceral injury did not appear to be related to approach method. Laparoscopic approaches resulted in shorter inpatient stays (p = 0.01).

Conclusion Despite the transperitoneal approach being comparatively underpowered, its use appears to result in a significantly higher rate of intraoperative and postoperative complications, although confounders including use of bone morphogenetic protein (BMP) and spinal level should be considered. Laparoscopic approaches resulted in shorter hospital stays; however, its steep learning curve and longer operative time have deterred surgeons from its widespread adaptation.

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The trans‑laminar, facet‑joint sparing minimal invasive approach for ventral dural repair in spontaneous intracranial hypotension

Acta Neurochirurgica (2021) 163:3015–3020

We describe the minimally invasive, facet-sparing postero-lateral approach to the thoracic spine for a ventral dural repair in a patient with intracranial hypotension secondary to a spontaneous dural breach.

Methods We performed a minimally invasive approach using a short paramedian posterior skin incision followed by a 10 × 10 mm targeted trans-laminar approach, to achieve a microsurgical repair of a symptomatic ventral dural defect causing severe disability.

Conclusion The facet-sparing postero-lateral approach is safe and effective in the surgical management of thoracic dural tears, even in the most anterior ones, and avoids the traditional costotransversectomy.

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Dural sac shrinkage signs on magnetic resonance imaging at the thoracic level in spontaneous intracranial hypotension

Acta Neurochirurgica (2021) 163:2685–2694

Spontaneous intracranial hypotension (SIH) is secondary to a cerebrospinal fluid leak at the spinal level without obvious causative events. Several signs on brain and cervical spine magnetic resonance (MR) imaging (MRI) have been associated with SIH but can be equivocal or negative. This retrospective study sought to identify characteristic SIH signs on thoracic spinal MRI.

Methods Cranial and spinal MR images of 27 consecutive patients with classic SIH symptoms, who eventually received epidural autologous blood patches (EBPs), were analyzed.

Results The most prevalent findings on T2-weighted MRI at the thoracic level were anterior shift of the spinal cord (96.3%) and dorsal dura mater (81.5%), probably caused by dural sac shrinkage. These dural sac shrinkage signs (DSSS) were frequently accompanied by cerebrospinal fluid collection in the posterior epidural space (77.8%) and a prominent epidural venous plexus (77.8%). These findings disappeared in all six patients who underwent post-EBP spinal MRI. Dural enhancement and brain sagging were minimum or absent on the cranial MR images of seven patients, although DSSS were obvious in these seven patients. For 23 patients with SIH and 28 healthy volunteers, a diagnostic test using thoracic MRI was performed by 13 experts to validate the usefulness of DSSS. The median sensitivity, specificity, positive-predictive value, negative-predictive value, and accuracy of the DSSS were high (range, 0.913–0.931).

Conclusions Detection of DSSS on thoracic MRI facilitates an SIH diagnosis without the use of invasive imaging modalities. The DSSS were positive even in patients in whom classic cranial MRI signs for SIH were equivocal or minimal.

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Surgery for Degenerative Cervical Myelopathy: A Nationwide Registry-Based Observational Study With Patient-Reported Outcomes

Neurosurgery 89:704–711, 2021

Indications and optimal timing for surgical treatment of degenerative cervical myelopathy (DCM) remain unclear, and data from daily clinical practice are warranted.

OBJECTIVE: To investigate clinical outcomes following decompressive surgery for DCM.

METHODS: Data were obtained from the Norwegian Registry for Spine Surgery. The primary outcome was change in the neck disability index (NDI) 1 yr after surgery. Secondary endpoints were the European myelopathy score (EMS), quality of life (EuroQoL 5D [EQ- 5D]), numeric rating scales (NRS) for headache, neck pain, and arm pain, complications, and perceived benefit of surgery assessed by the Global Perceived Effect (GPE) scale.

RESULTS: We included 905 patients operated between January 2012 and June 2018. There were significant improvements in all patient-reported outcome measures (PROMs) including NDI (mean −10.0, 95% CI −11.5 to −8.4, P < .001), EMS (mean 1.0, 95% CI 0.8-1.1, P < .001), EQ-5D index score (mean 0.16, 95% CI 0.13-0.19, P < .001), EQ-5D visual analogue scale (mean 13.8, 95% CI 11.7-15.9, P < .001), headache NRS (mean −1.1, 95% CI −1.4 to −0.8, P < .001), neck pain NRS (mean −1.8, 95% CI −2.0 to −1.5, P < .001), and arm pain NRS (mean −1.7, 95% CI −1.9 to −1.4, P < .001). According to GPE scale assessments, 229/513 patients (44.6%) experienced “complete recovery” or felt “much better” at 1 yr. There were signif- icant improvements in all PROMs for both mild and moderate-to-severe DCM. A total of 251 patients (27.7%) experienced adverse effects within 3 mo.

CONCLUSION: Surgery for DCM is associated with significant and clinically meaningful improvement across a wide range of PROMs.

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Does transforaminal lumbar interbody fusion induce lordosis or kyphosis?

J Neurosurg Spine 35:419–426, 2021

Conflicting reports exist about whether transforaminal lumbar interbody fusion (TLIF) induces lordosis or kyphosis, ranging from decreasing lordosis by 3.71° to increasing it by 18.8°. In this study, the authors’ aim was to identify factors that result in kyphosis or lordosis after TLIF.

METHODS A single-center, retrospective study of open TLIF without osteotomy for spondylolisthesis with a minimum 2-year follow-up was undertaken. Preoperative and postoperative clinical and radiographic parameters and cage specifics were collected. TLIFs were considered to be “lordosing” if postoperative induction of lordosis was > 0° and “kyphosing” if postoperative induction of lordosis was ≤ 0°.

RESULTS A total of 137 patients with an average follow-up of 52.5 months (range 24–130 months) were included. The overall postoperative disc angle (DA) and segmental lordosis (SL) increased by 1.96° and 1.88° (p = 0.003 and p = 0.038), respectively, whereas overall lumbar lordosis remained unchanged (p = 0.133). Seventy-nine patients had lordosing TLIFs with a mean SL increase of 5.72° ± 3.97°, and 58 patients had kyphosing TLIFs with a mean decrease of 3.02° ± 2.98°. Multivariate analysis showed that a lower preoperative DA, lower preoperative SL, and anterior cage placement were correlated with the greatest increase in postoperative SL (p = 0.040, p < 0.001, and p = 0.035, respectively). There was no difference in demographics, cage type or height, or spinopelvic parameters between the groups (p > 0.05). Linear regression showed that the preoperative DA and SL correlated with SL after TLIF (R2 = 0.198, p < 0.001; and R2 = 0.2931, p < 0.001, respectively).

CONCLUSIONS Whether a TLIF induces kyphosis or lordosis depends on the preoperative DA, preoperative SL, and cage position. Less-lordotic segments became more lordotic postoperatively, and highly lordotic segments may lose lordosis after TLIF. Cages placed more anteriorly were associated with more lordosis.

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Clinical outcomes in revision lumbar spine fusions: an observational cohort study

J Neurosurg Spine 35:437–445, 2021

The authors compared primary lumbar spine fusions with revision fusions by using patient Oswestry Disability Index (ODI) scores to evaluate the impact of the North American Spine Society (NASS) evidence-based medicine (EBM) lumbar fusion indications on patient-reported outcome measures of revision surgeries.

METHODS This study was a retrospective analysis of a prospective observational cohort of patients who underwent elective lumbar fusion between January 2018 and December 2019 at a single quaternary spine surgery service and had a minimum of 6 months of follow-up. A prospective quality improvement database was constructed that included the data from all elective lumbar spine surgeries, which were categorized prospectively as primary or revision surgeries and EBM-concordant or EBM-discordant revision surgeries based on the NASS coverage EBM policy. In total, 309 patients who met the inclusion criteria were included in the study. The ODIs of all groups (primary, revision, revision EBM concordant, and revision EBM discordant) were statistically compared. Differences in frequencies between cohorts were evaluated using chi-square and Fisher’s exact tests. The unpaired 2-tailed Student t-test and the Mann-Whitney U-test for nonparametric data were used to compare continuous variables. Logistic regression was performed to determine the associations between independent variables (surgery status and NASS criteria indications) and functional outcomes.

RESULTS Primary lumbar fusions were significantly associated with improved functional outcomes compared with revisions, as evidenced by ODI scores (OR 1.85, 95% CI 1.16–2.95 to achieve a minimal clinically important difference, p = 0.01). The percentage of patients whose functional status had declined at the 6-month postoperative evaluation was significantly higher in patients who had undergone a revision surgery than in those who underwent a primary surgery (23% vs 12.3%, respectively). An increase in ODI score, indicating worse clinical outcome after surgery, was greater in patients who underwent revision procedures (OR 2.14, 95% CI 1.17–3.91, p = 0.0014). Patients who underwent EBMconcordant revision surgery had significantly improved mean ODI scores compared with those who underwent EBMdiscordant revision surgery (7.02 ± 5.57 vs −4.6 ± 6.54, p < 0.01).

CONCLUSIONS The results of this prospective quality improvement program investigation illustrate that outcomes of primary lumbar fusions were superior to outcomes of revisions. However, revision procedures that met EBM guidelines were associated with greater improvements in ODI scores, which indicates that the use of defined EBM guideline criteria for reoperation can improve clinical outcomes of revision lumbar fusions.

 

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Impact of focal apex angle on postoperative decompression status of the spinal cord and neurological recovery after cervical laminoplasty

J Neurosurg Spine 35:410–418, 2021

Although anterior compression factors and cervical alignment affect neural decompression, cervical laminoplasty may be used to achieve indirect posterior decompression. The focal apex (FA) angle of the anterior compression factor of the spine represents the degree of anterior prominence toward the spinal cord. The authors investigated the mechanism underlying the influence of FA angle and cervical alignment on spinal cord alignment (SCA) after laminoplasty, including how high-intensity signal cord change (HISCC) on preoperative T2-weighted MRI (T2-MRI) may affect neurological improvement.

METHODS We performed a retrospective study of patients who underwent laminoplasty for CSM or OPLL at two hospitals (Kanto Rosai Hospital, Kawasaki City, and Yokohama Minami Kyousai Hospital, Yokohama City, Japan) between April 2004 and March 2015. In total, 109 patients (mean age 67.3 years) with cervical compression myelopathy were included. FA angle was defined as the preoperative angle between the lines from the top of the prominence to the upper and lower adjacent vertebrae. Preoperative cervical alignment was measured between the C2 and C7 vertebrae (C2–7 angle). MRI was used to classify SCA as lordosis (type-L SCA), straight (type-S), local kyphosis (type-LK), or kyphosis (type-K). Preoperative HISCC was investigated by using T2-MRI. Neurological status was evaluated by using the Japanese Orthopaedic Association score.

RESULTS The mean preoperative FA and C2–7 angles were 32.1° and 12.4°, respectively. Preoperative SCA was type- L or type-S in 53 patients. The neurological recovery rate (NRR) was significantly higher for patients with preoperative type-L and type-S SCA (51.4% for those with type-L and 45.0% for those with type-S) than for patients with other types (35.3% for those with type-LK and 31.7% for those with type-K). Among patients with preoperative type-L or type-S SCA, 87.3% maintained SCA; however, 5/12 (41.7%) patients with a preoperative average C2–7 angle < 12.4° and an average FA angle > 32.1° had postoperative type-LK or type-K SCA. SCA changed to type-L or type-S in 13.0% of patients with preoperative type-LK or type-K SCA. Moreover, in these patients, FA angle was significantly smaller and NRR was significantly higher than in other patients in whom postoperative SCA remained type-LK or type-K. Preoperative T2- MRI showed 73 patients with HISCC (43 with type-L and type-S, and 30 with type-LK and type-K SCA) and 36 without HISCC (20 with type-L and type-S, and 16 with type-LK and type-K SCA); the NRRs of these patients were 42.6% and 41.2%, respectively. No significant differences in SCA or NRR were observed between patients with and without HISCC.

CONCLUSIONS NRR depends on preoperative SCA type; however, it is possible to change the type of SCA after laminoplasty. Preoperative FA and C2–7 angles influence change in SCA; therefore, they are important parameters for successful decompression with cervical laminoplasty.

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Poor Fusion Rates Following Cervical Corpectomy Reconstructed With an Expandable Cage

Neurosurgery 89:617–625, 2021

Expandable cages are often used to reconstruct cervical corpectomies but there are few long-term follow-up studies with large numbers.

OBJECTIVE: To analyze the clinical and radiographic results of cervical corpectomy reconstructed with expandable cages for degenerative stenosis.

METHODS: We performed a retrospective analysis of 78 patients with degenerative cervical stenosis treated with a corpectomy reconstructed with an expandable cage. We evaluated the clinical and radiographic outcomes, as well as complications of the procedure at a minimum 2-yr follow-up.

RESULTS: There was a decrease in the visual analog scale pain average from 75 mm to 8.5mm(P=.02); a decrease in the Neck Disability Index average from55% to 12% (P=.009); and improvement in the Japanese Orthopaedic Association average from 12 to 14 points (P = .01). There was a change in cervical lordosis (Cobb method) average from −9.3◦ to −15.1◦ (P = .002), without significant loss of lordosis (P = .63). The fusion rate, by criteria of theCervical Spine Research Society (CSRS), was low: using dynamic X-rays –50%(n=39/78) and using computed tomography (CT) – 47.4% (n = 37/78). A total of 11 patients (14.1%) suffered complications.

CONCLUSION: To our knowledge, this is the largest series (78)with a minimum 2-yr followup in the literature and the first using the dynamic radiographic and CT criteria endorsed by the CSRS. Using these criteria, our fusion rates were much lower than all previous reports in the literature. Despite this, patient-reported outcomes were reasonable. There was a relatively low incidence of perioperative complications, most of which were likely not implant-specific and there was only 1 case of implant failure.

 

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Risk factors for polyetheretherketone cage subsidence following minimally invasive transforaminal lumbar interbody fusion

Acta Neurochirurgica (2021) 163:2557–2565

Interbody cage subsidence is a postoperative complication leading to poor outcomes after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). This study aimed to identify risk factors of cage subsidence in lumbar spinal diseases after MIS-TLIF using polyetheretherketone (PEEK) cage.

Methods In this retrospective cohort study, plain radiographs and three-dimensional computed tomography (3D-CT) performed 12 months after MIS-TLIF were evaluated, and the risk of cage subsidence was calculated with odds ratio (OR), confidence interval (CI), and logistic regression analysis.

Results A total of 114 patients (mean age, 65 years) and 135 levels were included in this study: 80 (59.3%) with and 55 (40.7%) without cage subsidence. Multifidus atrophy showed the strongest association with PEEK cage subsidence (p < 0.001). Compared to those with normal mass, the odds of PEEK cage subsidence were 76.0 (95% CI: 3.9–1472.9) for severe atrophy. The factors significantly associated with cage subsistence were posterior cage position (OR = 4.2; p = 0.005), cage height ≥ 12 mm (OR = 7.6; p = 0.008), use of an autograft mixed with demineralized bone matrix (DBM) (OR = 5.8; p = 0.002), body mass index (BMI) > 27.5 kg/m2 (OR = 4.2; p = 0.03), and titanium-coated PEEK (Ti-PEEK) cage-type (OR = 38.4, p = 0.02).

Conclusions In MIS-TLIF with a PEEK cage, the factors associated with an increased risk of cage subsidence were higher BMI, increased severity of multifidus muscle atrophy, Ti-coated PEEK cage-type, cage height ≥ 12 mm, use of DBM mixed autograft, and posterior cage position.

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Incidence of adjacent-segment surgery following stand-alone lateral lumbar interbody fusion

J Neurosurg Spine 35:270–274, 2021

Adjacent-segment disease (ASD) requiring operative intervention is a relatively common long-term consequence of lumbar fusion surgery. Although the incidence of ASD requiring reoperation is well described for traditional posterior lumbar approaches (2.5%–3.9% per year), it remains poorly characterized for stand-alone lateral lumbar interbody fusion (LLIF). In this study, the authors report their institutional experience with ASD requiring reoperation after LLIF over an extended follow-up period of 4 years.

METHODS Medical records were reviewed for 276 consecutive patients who underwent stand-alone LLIF by a single surgeon for degenerative spinal disorders. Inclusion criteria (single-stage, stand-alone LLIF without posterior supplementation, with no prior lumbar instrumentation, and a minimum of 4 years of follow-up) were met by 182 patients, who were analyzed for operative ASD incidence (per-year rate), demographics, and Oswestry Disability Index (ODI) score. Operative ASD was strictly defined as new-onset pathology following index surgery at directly adjacent levels to the prior construct. Operative, rather than symptomatic or radiographic, ASD was analyzed to provide a consistent and impactful endpoint while avoiding retrospective diagnosis.

RESULTS The study cohort of 182 patients had an operative ASD rate of 3.3% (n = 6 procedures) over 4 years of follow-up, for an incidence on Kaplan-Meier survival analysis of 0.88% (95% CI 0.67%–1.09%) per year. In comparing patients with operative ASD with those without, there were no significant differences in mean age (53.7 vs 56.2 years), male sex (33.3% vs 44.9%), smoking status (16.7% vs 25.0%), or number of levels fused (mean 1.33 vs 1.46). The operative ASD cohort had a greater mean BMI (37.3 vs 30.2, p < 0.01). Operative ASD patients had lower baseline ODI scores (33.8 vs 48.3, p = 0.02); however, no difference was observed in ODI at 6 weeks (34.0 vs 39.0) or 3 months (16.0 vs 32.8) postoperatively.

CONCLUSIONS The incidence of ASD in LLIF for degenerative lumbar etiologies in this cohort was 0.88% (95% CI 0.67%–1.09%) per year. Meanwhile, the reported reoperation rates for ASD in posterior spinal approaches was 2.5% to 3.9% per year, which implies that LLIF may be preferable for well-selected patients.

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A novel endoscope-assisted technique for lateral lumbar interbody fusion

J Neurosurg Spine 35:292–298, 2021

The lateral approach to the spine is generally well tolerated, but reports of debilitating injury to the lumbar plexus, iliac vessels, ureter, and abdominal viscera are increasingly recognized, likely related to the lack of direct visualization of these nearby structures. To minimize this complication profile, the authors describe here a novel, minimally invasive, endoscope-assisted technique for the LLIF and evaluate its clinical feasibility.

Seven consecutive endoscope-assisted lateral lumbar interbody fusion (LLIF) procedures by the senior authors were reviewed for the incidence of approachrelated complications. One patient had a postoperative approach-related complication. This patient developed transient ipsilateral thigh hip flexion weakness that resolved spontaneously by the 3-month follow-up. No patient experienced visceral, urological, or vascular injury, and no patient sustained a permanent neurological injury related to the procedure.

The authors’ preliminary experience suggests that this endoscope-assisted LLIF technique may be clinically feasible to mitigate vascular, urological, and visceral injury, especially in patients with previous abdominal surgery, anomalous anatomy, and revision operations. It provides direct visualization of at-risk structures without significant additional operative time. A larger series is needed to determine whether it reduces the incidence of lumbar plexopathy or visceral injury compared with traditional lateral approaches.

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