Category: Spine

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Outcomes following discectomy for lumbar disc herniation in patients with substantial back pain

J Neurosurg Spine 33:623–626, 2020

Patients with lumbar disc herniation (LDH) typically present with lower-extremity radiculopathy. However, there are patients who have concomitant substantial back pain (BP) and are considered candidates for fusion. The purpose of this study was to determine if patients with LDH and substantial BP improve with discectomy alone.

METHODS The DaneSpine database was used to identify 2399 patients with LDH and baseline BP visual analog scale (VAS) scores ≥ 50 who underwent a lumbar discectomy at one of 3 facilities between June 2010 and December 2017. Standard demographic and surgical variables and patient-reported outcomes, including BP and leg pain (LP) VAS scores (0–100), Oswestry Disability Index (ODI), and European Quality of Life–5 Dimensions Questionnaire (EQ-5D) at baseline and 12 months postoperatively, were collected.

RESULTS A total of 1654 patients (69%) had 12-month data available, with a mean age of 48.7 years; 816 (49%) were male and the mean BMI was 27 kg/m2. At 12 months postoperatively, there were statistically significant improvements (p < 0.0001) in BP (72.6 to 36.9), LP (74.8 to 32.6), ODI (50.9 to 25.1), and EQ-5D (0.25 to 0.65) scores.

CONCLUSIONS Patients with LDH and LP and concomitant substantial BP can be counseled to expect improvement in their BP 12 months after surgery after a discectomy alone, as well as improvement in their LP.

 

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Low-Grade Infection and Implant Failure Following Spinal Instrumentation

Neurosurgery 87:964–970, 2020

Spinal instrumentation can be associated with complications, including implant loosening. Hitherto, implant loosening has mainly been attributed to mechanical overload.

OBJECTIVE: To examine the role of low-grade infections as the cause of implant failure in suspected aseptic implant loosening following spinal instrumentation.

METHODS: A prospective single center observational study was performed. All patients who had revision surgery following spinal instrumentation between August 2015 and February 2018 were screened. Patients with revision surgery due to screw loosening on the computed tomograhy scan constituted the study group. Patients in which the screws where not loosened but removalwas performed for other reasons formed the comparison group. Intraoperative swabswere taken and sonicationwas performedwith the explanted material. Results of microbiological cultivation were analyzed.

RESULTS: A total of 59 patients were included in the study group and 34 in the comparison group. In the study group in 42.4% of the cultures a bacterium was detected, while in the comparison group only in 17.6%. 84%, and 83.3% of these germs were detected by sonication in the study and comparison group, respectively. The rate of positive cultures was significantly higher in the study group compared to the comparison group (P= .001). The most frequent bacterium cultivated in both groups was Propionibacterium acnes, followed by Staphylococcus species.

CONCLUSION: For patients with screw loosening a high level of suspicion for a low-grade infection should be raised. Cultures should be performed from the sonication fluid of the explanted devices in all patients with symptomatic screw loosening.

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Stereotactic CT image guidance and biplanar fluoroscopy for transoral C2 vertebroplasty and direct anterolateral subaxial vertebroplasty

Acta Neurochirurgica (2020) 162:2533–2536

Metastatic cervical spine disease can cause compression fractures, cervical spine instability, and pain. Vertebroplasty can stabilize a fracture, reduce the pain associated with a compression fracture, prevent or stop the progression of a fracture, thus avoiding cervical spine fixation, and decreased mobility. Transoral C2 vertebroplasty is less invasive than open fusion surgery, but it poses its own risk of infection and cement leak in this highly sensitive area.

Methods The image guidance setup consisted of the Stryker NAV3i navigation system, Stryker CranialMask tracker, and the CranialMap 3.0 software combined with biplanar fluoroscopy.

Results The patient’s neck pain has completely resolved immediately after the surgery. There were no complications.

Conclusion Quality of life preservation is paramount in the management of metastatic spine disease. Vertebroplasty of osteolytic lesions can both relieve pain and restore stability, thus avoiding permanent stiff cervical collar, halo vest, or upfront occipitocervical fusion. With the increasing availability of surgical navigation systems, its use combined with biplanar fluoroscopy for performing transoral C2 vertebroplasty seems to be an adequate treatment in selected cases for pain relief, stabilization, and maintaining quality of life in the complex cancer population with C2 pathological fractures. The article describes as well vertebroplasty of the subaxial spine through a conventional anterior approach which again seems to be adequate in the treatment of spinal pathological fractures.

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Lower Hounsfield units on CT are associated with cage subsidence after anterior cervical discectomy and fusion

J Neurosurg Spine 33:425–432, 2020

A consequence of anterior cervical discectomy and fusion (ACDF) is graft subsidence, potentially leading to kyphosis, nonunion, foraminal stenosis, and recurrent pain. Bone density, as measured in Hounsfield units (HUs) on CT, may be associated with subsidence. The authors evaluated the association between HUs and subsidence rates after ACDF.

METHODS A retrospective study of patients treated with single-level ACDF at the University of California, San Francisco, from 2008 to 2017 was performed. HU values were measured according to previously published methods. Only patients with preoperative CT, minimum 1-year follow-up, and single-level ACDF were included. Patients with posterior surgery, tumor, infection, trauma, deformity, or osteoporosis treatment were excluded. Changes in segmental height were measured at 1-year follow-up compared with immediate postoperative radiographs. Subsidence was defined as segmental height loss of more than 2 mm.

RESULTS A total of 91 patients met inclusion criteria. There was no significant difference in age or sex between the subsidence and nonsubsidence groups. Mean HU values in the subsidence group (320.8 ± 23.9, n = 8) were significantly lower than those of the nonsubsidence group (389.1 ± 53.7, n = 83, p < 0.01, t-test). There was a negative correlation between the HU values and segmental height loss (Pearson’s coefficient −0.735, p = 0.01). Using receiver operating characteristic curves, the area under the curve was 0.89, and the most appropriate threshold of HU value was 343.7 (sensitivity 77.1%, specificity 87.5%). A preoperative lower HU is a risk factor for postoperative subsidence (binary logistic regression, p < 0.05). The subsidence rate and distance between allograft and polyetheretherketone (PEEK) materials were not significantly different (PEEK 0.9 ± 0.7 mm, allograft 1.0 ± 0.7 mm; p > 0.05).

CONCLUSIONS Lower preoperative CT HU values are associated with cage subsidence in single-level ACDF. Preoperative measurement of HUs may be useful in predicting outcomes after ACDF.

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Three-dimensional assessment of robot-assisted pedicle screw placement accuracy and instrumentation reliability based on a preplanned trajectory

J Neurosurg Spine 33:519–528, 2020

Robotic spine surgery systems are increasingly used in the US market. As this technology gains traction, however, it is necessary to identify mechanisms that assess its effectiveness and allow for its continued improvement. One such mechanism is the development of a new 3D grading system that can serve as the foundation for error-based learning in robot systems. Herein the authors attempted 1) to define a system of providing accuracy data along all three pedicle screw placement axes, that is, cephalocaudal, mediolateral, and screw long axes; and 2) to use the grading system to evaluate the mean accuracy of thoracolumbar pedicle screws placed using a single commercially available robotic system.

METHODS The authors retrospectively reviewed a prospectively maintained, IRB-approved database of patients at a single tertiary care center who had undergone instrumented fusion of the thoracic or lumbosacral spine using robotic assistance. Patients with preoperatively planned screw trajectories and postoperative CT studies were included in the final analysis. Screw accuracy was measured as the net deviation of the planned trajectory from the actual screw trajectory in the mediolateral, cephalocaudal, and screw long axes.

RESULTS The authors identified 47 patients, 51% male, whose pedicles had been instrumented with a total of 254 screws (63 thoracic, 191 lumbosacral). The patients had a mean age of 61.1 years and a mean BMI of 30.0 kg/m2. The mean screw tip accuracies were 1.3 ± 1.3 mm, 1.2 ± 1.1 mm, and 2.6 ± 2.2 mm in the mediolateral, cephalocaudal, and screw long axes, respectively, for a net linear deviation of 3.6 ± 2.3 mm and net angular deviation of 3.6° ± 2.8°. According to the Gertzbein-Robbins grading system, 184 screws (72%) were classified as grade A and 70 screws (28%) as grade B. Placement of 100% of the screws was clinically acceptable.

CONCLUSIONS The accuracy of the discussed robotic spine system is similar to that described for other surgical systems. Additionally, the authors outline a new method of grading screw placement accuracy that measures deviation in all three relevant axes. This grading system could provide the error signal necessary for unsupervised machine learning by robotic systems, which would in turn support continued improvement in instrumentation placement accuracy.

 

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The Effect of Older Age on the Perioperative Outcomes of Spinal Fusion Surgery in Patients With Lumbar Degenerative Disc DiseaseWith Spondylolisthesis

Neurosurgery, Volume 87, Issue 4, 1 October 2020, Pages 672–678

Degenerative spondylolisthesis (DS) is often treated with lumbar spinal fusion (LSF). However, there is concern that the morbidity of LSF may be prohibitively high in older adults.

OBJECTIVE: To evaluate the impact of advanced age on the safety of LSF for DS.

METHODS: Patients who underwent LSF for DS were retrospectively identified from National Surgical Quality Improvement Program datasets for 2011 to 2015 using Current Procedural Terminology codes. Data on demographic characteristics, comorbidities, surgical factors, and 30-d morbidity and mortality were collected. Propensity score matching (nearest neighbor) was performed with age (<70 vs ≥70 yr) as the dependent variable and sex, type of fusion procedure, number of levels fused, diabetes, smoking, hypertension, and chronic steroid use as covariates. Outcomes were compared between age <70 and ≥70 groups.

RESULTS: The study cohort consisted of 2238 patients (n=1119, age<70; n=1119, age≥70). The 2 age groups were balanced for key covariates including sex, race, diabetes, hypertension, CHF, smoking, chronic steroid use, type of fusion, and number of levels. Rates of all complications were similar between younger and older age groups, except urinary tract infection, which was more frequent among the ≥70 age group (OR 2.32, P = .009). Further, patients in the older age group were more likely to be discharged to a rehabilitation (OR 2.94, P < .001) or skilled care (OR 3.66, P < .001) facility, rather than directly home (OR 0.25, P < .001).

CONCLUSION: LSF may be performed safely in older adults with DS. Our results suggest older age alone should not exclude a patient from undergoing lumbar fusion for DS.

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Volumetric analysis of bilateral spinal canal decompression via hemilaminectomy versus laminoplasty in cervical spondylotic myelopathy

Acta Neurochirurgica (2020) 162:2069–2074

Cervical spondylotic myelopathy (CSM) is a degenerative process of the cervical spine requiring surgical decompression to prevent neurological deterioration. While both anterior and posterior approaches yield satisfactory results, posterior decompression is preferred in cases of the multilevel disease. In 2015, we described a muscle-sparing, novel technique of bilateral osteoligamentous decompression via hemilaminectomy (OLD) for CSM. In this study, we investigate whether this technique offers comparable volumetric results to laminoplasty in terms of spinal canal enlargement and whether this technique can yield significant clinical improvement.

Methods Patients undergoing OLD due to CSM were prospectively enrolled in this study and then matched to and compared with a historic cohort of patients with CSM treated by laminoplasty. An independent sample t test was performed to analyze whether the volumetric gain in the two separate groups was statistically significant. Patients in the OLD cohort were clinically evaluated with the mJOA score preoperatively and 3 months postoperatively. To assess clinical improvement, a paired sample t test was performed.

Results A total of 38 patients were included in the analysis: 19 underwent OLD and 19 underwent laminoplasty. Both groups were well matched in terms of sex, age, preoperative spinal canal volume, and involved levels. Both surgical methods yielded statistically significant volumetric gain in the cervical spinal canal, but a trend towards a greater volume gain was seen in the OLD group. In the OLD group, a statistically significant clinical improvement was also demonstrated.

Conclusions Our study reveals that OLD can yield a comparable extent of decompression to laminoplasty in CSM while also delivering statistically significant clinical improvement.

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PEEK versus titanium cages in lateral lumbar interbody fusion: a comparative analysis of subsidence

Neurosurg Focus 49 (3):E10, 2020

The authors have provided a review of radiographic subsidence after lateral lumbar interbody fusion (LLIF) as a comparative analysis between titanium and polyetheretherketone (PEEK) cages. Many authors describe a reluctance to use titanium cages in spinal fusion secondary to subsidence concerns due to the increased modulus of elasticity of metal cages. The authors intend for this report to provide observational data regarding the juxtaposition of these two materials in the LLIF domain.

METHODS A retrospective review of a prospectively maintained database identified 113 consecutive patients undergoing lateral fusion for degenerative indications from January to December 2017. The surgeons performing the cage implantations were two orthopedic spine surgeons and two neurosurgeons. Plain standing radiographs were obtained at 1–2 weeks, 8–12 weeks, and 12 months postoperatively. Using a validated grading system, interbody subsidence into the endplates was graded at these time points on a scale of 0 to III. The primary outcome measure was subsidence between the two groups. Secondary outcomes were analyzed as well.

RESULTS Of the 113 patients in the sample, groups receiving PEEK and titanium implants were closely matched at 57 and 56 patients, respectively. Cumulatively, 156 cages were inserted and recombinant human bone morphogenetic protein– 2 (rhBMP-2) was used in 38.1%. The average patient age was 60.4 years and average follow-up was 75.1 weeks. Subsidence in the titanium group in this study was less common than in the PEEK cage group. At early follow-up, groups had similar subsidence outcomes. Statistical significance was reached at the 8- to 12-week and 52-week follow-ups, demonstrating more subsidence in the PEEK cage group than the titanium cage group. rhBMP-2 usage was also highly correlated with higher subsidence rates at all 3 follow-up time points. Age was correlated with higher subsidence rates in univariate and multivariate analysis.

CONCLUSIONS Titanium cages were associated with lower subsidence rates than PEEK cages in this investigation. Usage of rhBMP-2 was also robustly associated with higher endplate subsidence. Each additional year of age correlated with an increased subsidence risk. Subsidence in LLIF is likely a response to a myriad of factors that include but are certainly not limited to cage material. Hence, the avoidance of titanium interbody implants secondary solely to concerns over a modulus of elasticity likely overlooks other variables of equal or greater importance.

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Functional and radiological outcome of anterior retroperitoneal versus posterior transforaminal interbody fusion in the management of single-level lumbar degenerative disease

Neurosurg Focus 49 (3):E2, 2020

In this study the authors compared the anterior lumbar interbody fusion (ALIF) and posterior transforaminal lumbar interbody fusion (TLIF) techniques in a homogeneous group of patients affected by single-level L5–S1 degenerative disc disease (DDD) and postdiscectomy syndrome (PDS). The purpose of the study was to analyze perioperative, functional, and radiological data between the two techniques.

METHODS A retrospective analysis of patient data was performed between 2015 and 2018. Patients were clustered into two homogeneous groups (group 1 = ALIF, group 2 = TLIF) according to surgical procedure. A statistical analysis of clinical perioperative and radiological findings was performed to compare the two groups. A senior musculoskeletal radiologist retrospectively revised all radiological images.

RESULTS Seventy-two patients were comparable in terms of demographic features and surgical diagnosis and included in the study, involving 32 (44.4%) male and 40 (55.6%) female patients with an average age of 47.7 years. The mean follow-up duration was 49.7 months. Thirty-six patients (50%) were clustered in group 1, including 31 (86%) with DDD and 5 (14%) with PDS. Thirty-six patients (50%) were clustered in group 2, including 28 (78%) with DDD and 8 (22%) with PDS. A significant reduction in surgical time (107.4 vs 181.1 minutes) and blood loss (188.9 vs 387.1 ml) in group 1 (p < 0.0001) was observed. No significant differences in complications and reoperation rates between the two groups (p = 0.561) was observed. A significant improvement in functional outcome was observed in both groups (p < 0.001), but no significant difference between the two groups was found at the last follow-up. In group 1, a faster median time of return to work (2.4 vs 3.2 months) was recorded. A significant improvement in L5–S1 postoperative lordosis restoration was registered in the ALIF group (9.0 vs 5.0, p = 0.023).

CONCLUSIONS According to these results, interbody fusion is effective in the surgical management of discogenic pain. Even if clinical benefits were achieved earlier in the ALIF group (better scores and faster return to work), both procedures improved functional outcomes at last follow-up. The ALIF group showed significant reduction of blood loss, shorter surgical time, and better segmental lordosis restoration when compared to the TLIF group. No significant differences in postoperative complications were observed between the groups. Based on these results, the ALIF technique enhances radiological outcome improvement in spinopelvic parameters when compared to TLIF in the management of adult patients with L5–S1 DDD.

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C2 medial pedicle screw: a novel “in-out-in” technique as an alternative option for posterior C2 fixation in cases with a narrow C2 isthmus

J Neurosurg Spine 33:281–287, 2020

The authors describe a novel “in-out-in” technique as an alternative option for posterior C2 screw fixation in cases that involve narrow C2 isthmus. Here, they report the preliminary radiological and clinical outcomes in 12 patients who had a minimum 12-month follow-up period.

METHODS Twelve patients with basilar invagination and atlantoaxial dislocation underwent atlantoaxial reduction and fixation. All patients had unilateral hypoplasia of the C2 isthmus that prohibited insertion of pedicle screws. A new method, the C2 medial pedicle screw (C2MPS) fixation, was used as an alternative. In this technique, the inner cortex of the narrow C2 isthmus was drilled to obtain space for screw insertion, such that the lateral cortex could be well preserved and the risk of vertebral artery injury could be largely reduced. The C2MPS traveled along the drilled inner cortex into the anterior vertebral body, achieving a 3-column fixation of the axis with multicortical purchase.

RESULTS Satisfactory C2MPS placement and reduction were achieved in all 12 patients. No instance of C2MPS related vertebral artery injury or dural laceration was observed. There were no cases of implant failure, and solid fusion was demonstrated in all patients.

CONCLUSIONS This novel in-out-in technique can provide 3-column rigid fixation of the axis with multicortical purchase. Excellent clinical outcomes with low complication rates were achieved with this technique. When placement of a C2 pedicle screw is not possible due to anatomical constraints, the C2MPS can be considered as an efficient alternative.

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Minimally invasive posterior percutaneous transarticular C1–C2 screws: how I do it

Acta Neurochirurgica (2020) 162:2047–2050

Transarticular C1–C2 screw fixation, first described by Magerl, is a widely accepted used technique for C1–C2 instability with a good biomechanical stability and fusion rate.

Method We present a 69-year-old woman, who was diagnosed with a C2 Odontoid fracture type III and primarily treated with conservative treatment and collar. During first 2 weeks of follow-up, the patient developed cervical pain associated with C1–C2 instability. A minimally invasive posterior C1–C2 transarticular screw instrumentation with a percutaneus approach was performed.

Results and conclusion Minimally invasive approach with tubular transmuscular approach for C1–C2 transarticular screws instrumentation is safe and effective for C1–C2 instability.

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Longitudinal smartphone-based self-assessment of objective functional impairment in patients undergoing surgery for lumbar degenerative disc disease

Acta Neurochirurgica (2020) 162:2061–2068

The worldwide spread of smartphone usage enables new possibilities for longitudinal monitoring of objective functional impairment (OFI) in patients undergoing surgery for lumbar degenerative disc disease (DDD).

Methods Three patients, undergoing elective surgery for lumbar DDD, self-assessed OFI using a recently validated 6-min walking test (6WT) smartphone application. Results are presented as raw 6-min walking distance (6WD) as well as in reference to age- and sex-specific healthy population reference values using standardized z-scores (number of standard deviations). In parallel, patient-reported outcome measures (PROMs), including numeric rating scale (NRS) leg-pain and Core Outcome Measures Index (COMI) were obtained before (pre) and 6 weeks (6 W) as well as 3 months (3 M) after surgery. Descriptive analyses were used to compare PROMs with repeated 6WT measurements over time. The feasibility and benefits of the longitudinal OFI measurements using the 6WT app are discussed.

Results One patient presented a favorable outcome, reflected by a clinically meaningful improvement in PROMs. Correspondingly, the 6WT distance gradually improved above the normal population values ((pre 399 m (z-score − 1.96) vs. 6 W 494 m (− 0.85) vs. 3 M 557 m (− 0.1)). One patient experienced initial improvement at 6 W, followed by a decline in 6WD at 3 M which promoted further interventions with subsequent recovery ((358 m (z-score − 3.29) vs 440 m (− 2.2) vs 431 m (− 2.32) vs 471 m (− 1.78)). The last patient showed a lack of improvement in PROMs as well as in OFI (360 m (z-score 0.0) vs 401 m (0.30) vs 345 m (− 0.11)) resulting in secondary surgery.

Conclusion The longitudinal assessment of OFI using the 6WT app was feasible and provided the physician with a detailed history of patients’ postoperative walking capacity complementing commonly used PROMs.

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The safety and efficacy of anterior versus posterior decompression surgery in degenerative cervical myelopathy: a prospective randomized trial

J Neurosurg Spine 33:288–296, 2020

The safety and efficacy of anterior and posterior decompression surgery in degenerative cervical myelopathy (DCM) have not been validated in any prospective randomized trial.

METHODS In this first prospective randomized trial, the patients who had symptoms or signs of DCM were randomly assigned to undergo either anterior cervical discectomy and fusion or posterior laminectomy with or without fusion. The primary outcome measures were the change in the visual analog scale (VAS) score, Neck Disability Index (NDI), and Nurick myelopathy grade 1 year after surgery. The secondary outcome measures were intraoperative and postoperative complications, hospital stay, and Odom’s criteria. The follow-up period was at least 1 year.

RESULTS A total of 68 patients (mean age 53 ± 8.3 years, 72.3% men) underwent prospective randomization. There was a significantly better outcome in the NDI and VAS scores in the anterior group at 1 year (p < 0.05). Nurick myelopathy grading showed nonsignificant improvement using the posterior approach group (p = 0.79). The mean operative duration was significantly longer in the anterior group (p < 0.001). No significant difference in postoperative complications was found, except postoperative dysphagia was significantly higher in the anterior group (p < 0.05). There was no significant difference in postoperative patient satisfaction (Odom’s criteria) (p = 0.52). The mean hospital stay was significantly longer in the posterior group (p < 0.001).

CONCLUSIONS Among patients with multilevel DCM, the anterior approach was significantly better regarding postoperative pain, NDI, and hospital stay, while the posterior approach was significantly better in terms of postoperative dysphagia and operative duration.

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Anterior lumbar interbody fusions combined with posterior column osteotomy in patients who had sagittal imbalance associated with degenerative lumbar flat-back deformity

Neurosurgical Review (2020) 43:1117–1125

Anterior lumbar interbody fusion (ALIF) combined with posterior column osteotomy (PCO) may be effective to achieve ideal lumbar curve correction in lumbar flat-back deformity (LFD).

We aimed to investigate the radiographic and clinical outcomes of patients with primary degenerative LFD treated with multi-level ALIFs combined with PCOs. Seventy patients with primary degenerative LFD who underwent corrective surgery were divided into three groups according to the 1-month postoperative pelvic incidence/lumbar lordosis (PI-LL) angles ( ≤ − 10°, from − 9°to 9°, and ≥ 10°). The spinopelvic parameters, including thoracic kyphosis, LL, pelvic tilt, T1 pelvic angle, and sagittal vertical axis, were analyzed at the preoperative, postoperative follow-up periods. The clinical outcomes, including the Oswestry disability index (ODI), visual analog scale (VAS), and Scoliosis Research Society (SRS)-22r, were also evaluated. Further, the paraspinal muscles were qualitatively and quantitatively examined, preoperatively.

All spinopelvic parameters were corrected as close to the normal values at the 1-month postoperative period. The spinopelvic parameters in the PI-LL ≤ − 10°group were better corrected and maintained than those in the other groups. The ODI, VAS, and SRS-22r scores improved at the final follow-up in all groups. The PI-LL ≤ − 10°group showed better clinical outcomes than the other groups. In the paraspinal muscle examination, the mean lumbar muscularity value and fatty degeneration ratio were 236.7% and 20.7%, respectively.

Multi-level ALIFs with PCOs in patients with LFD are effective in restoring sagittal balance and improving clinical symptoms. In addition, the postoperative LL angles should be larger than PI + 10°to achieve good overall outcomes in patients with severe degenerative back muscle.

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Anterior Column Realignment: Analysis of Neurological Risk and Radiographic Outcomes

Neurosurgery DOI:10.1093/neuros/nyaa064

Anterior column realignment (ACR) is a less invasive alternative to 3-column osteotomy for the correction of sagittal imbalance. We hypothesized that ACR would correct sagittal imbalance with an acceptable neurological risk. OBJECTIVE: To assess long-term neurological and radiographic outcomes after ACR.

METHODS: Patients ≥18 yr who underwent ACR from 2005 to 2013 were eligible. Standing scoliosis radiographs were studied at preoperation, postoperation (≤6 wk), and at minimum 2 yr of follow-up. Clinical/radiographic data were collected through a retrospective chart review, with thoracic 1 spino-pelvic inclination (T1SPi) used as the angular surrogate for sagittal vertical axis.

RESULTS: A total of 26 patients had complete data, with a mean follow-up of 2.8 yr (1.8- 7.4). Preoperative, sagittal parameters were lumbar lordosis (LL) of −16.1◦, pelvic incidence (PI)-LL of 41.7◦, T1SPi of 3.6◦, and pelvis tilt (PT) of 32.4◦. LL improved by 30.6◦ (P < .001) postoperation.Mean changes in PT (−8.3), sacral slope (8.9), T1SPi (−4.9), and PI-LL (−33.5) were all significant. The motion segment angle improved by 26.6◦, from 5.2◦ to −21.4◦ (P < .001). Neurological complications occurred in 32% patients postoperation (n = 8; 1 patient with both sensory and motor). New thigh numbness/paresthesia developed in 3 (13%) patients postoperation; only 1 (4%) persisted at latest follow-up. A total of 6 (24%) patients developed a new lower extremity motor deficit postoperation,with 4 (8%) having persistent new weakness at last follow-up. Out of 8 patients with preoperative motor deficit, half saw improvement postoperation and 75% improved by last follow-up.

CONCLUSION: There was net motor improvement, with 24% of patients improving and 16% having persistent new weakness at latest follow-up; 60% were unchanged. Radiographic results demonstrate that ACR is a useful tool to treat severe sagittal plane deformity.

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A Comparison of Minimally Invasive and Open Transforaminal Lumbar Interbody Fusion for Grade 1 Degenerative Lumbar Spondylolisthesis

Neurosurgery DOI:10.1093/neuros/nyaa097

It remains unclear if minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is comparable to traditional, open TLIF because of the limitations of the prior small-sample-size, single-center studies reporting comparative effectiveness.

OBJECTIVE: To compare MI-TLIF to traditional, open TLIF for grade 1 degenerative lumbar spondylolisthesis in the largest study to date by sample size.

METHODS: We utilized the prospective Quality Outcomes Database registry and queried patients with grade 1 degenerative lumbar spondylolisthesis who underwent singlesegment surgery with MI- or open TLIF methods. Outcomes were compared 24 mo postoperatively.

RESULTS: A total of 297 patients were included: 72 (24.2%) MI-TLIF and 225 (75.8%) open TLIF. MI-TLIF surgeries had lower mean body mass indexes (29.5±5.1 vs 31.3±7.0, P=.0497) and more worker’s compensation cases (11.1% vs 1.3%, P< .001) but were otherwise similar. MI-TLIF had less blood loss (108.8 ± 85.6 vs 299.6 ± 242.2 mL, P < .001), longer operations (228.2 ± 111.5 vs 189.6 ± 66.5 min, P < .001), and a higher return-to-work (RTW) rate (100% vs 80%, P = .02). Both cohorts improved significantly from baseline for 24-mo Oswestry Disability Index (ODI), Numeric Rating Scale back pain (NRS-BP), NRS leg pain (NRS-LP), and Euro-Qol-5 dimension (EQ-5D) (P > .001). In multivariable adjusted analyses, MI-TLIF was associated with lower ODI (β =−4.7; 95% CI=−9.3 to −0.04; P= .048), higher EQ-5D (β =0.06; 95% CI=0.01-0.11; P=.02), and higher satisfaction (odds ratio for North American Spine Society [NASS] 1/2 = 3.9; 95% CI = 1.4-14.3; P = .02). Though trends favoring MI-TLIF were evident for NRS-BP (P = .06), NRS-LP (P = .07), and reoperation rate (P = .13), these results did not reach statistical significance.

CONCLUSION: For single-level grade 1 degenerative lumbar spondylolisthesis, MI-TLIF was associated with less disability, higher quality of life, and higher patient satisfaction compared with traditional, open TLIF. MI-TLIF was associated with higher rates of RTW, less blood loss, but longer operative times. Though we utilized multivariable adjusted analyses, these findings may be susceptible to selection bias.

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Microanatomy of the dura mater at the craniovertebral junction and spinal region for safe and effective surgical treatment

J Neurosurg Spine 33:165–171, 2020

Few reports have been published regarding the detailed microsurgical anatomy of the dura mater at the craniovertebral junction (CVJ), although many neurosurgeons have had the opportunity to conduct surgeries in this region, such as in cases of Chiari malformation. The authors aimed to evaluate the detailed and precise microsurgical anatomy of the dura mater at the CVJ for safe and effective surgical treatment at this area.

METHODS This study consisted of dissection of 4 formalin-fixed, continuous, human cadaveric dura maters, extending from the posterior fossa to the C2 level. After removing the occipital bone and C1 laminae, a dural incision was made to harvest the specimen. The following structural and topographical aspects of the dura mater in each region were studied: 1) thickness, 2) morphological characteristics, and 3) vascular structures.

RESULTS The average thicknesses of the dura mater were 313.4 ± 137.0 μm, 3051.5 ± 798.8 μm, and 866.5 ± 359.0 μm in the posterior cranial fossa, CVJ, and spinal region, respectively. The outer layer of the posterior cranial dura mater and the tendon of the rectus capitis posterior minor muscle were connected, forming the “myodural bridge.” The dura mater at the CVJ had a well-developed vascular network. These vascular structures were determined to be veins or the venous sinus, and were mainly located around the interface between the inner layer of the cranial dura mater and the rectus capitis posterior minor muscle layer. Regarding the morphological features, the bulging located in the inner layer of the dura mater at the CVJ was determined to be the marginal sinus, and contained a pacchionian granulation that allowed for CSF circulation. In the spinal region, the dura mater was characterized by a single, thick layer enclosing the collagen fibers with almost the same orientation.

CONCLUSIONS The dura mater at the CVJ displayed dynamic morphological changes within an extremely short segment. Its characteristic anatomical features were not similar to those in the cranial regions. The dural bulging at the CVJ was determined to be the venous sinus. During surgery in the posterior fossa, CVJ, and spinal cord, different procedures should be used because of the specific microsurgical anatomy of each region.

 

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Intermediate-term clinical and radiographic outcomes with less invasive adult spinal deformity surgery

Acta Neurochirurgica (2020) 162:1393–1400

Little information exists regarding longer-term outcomes with minimally invasive spine surgery (MISS), particularly regarding long-segment and deformity procedures. We aimed to evaluate intermediate-term outcomes of MISS for adult spinal deformity (ASD).

Methods This retrospective review of a prospectively collected multicenter database examined outcomes at 4 or more years following circumferential MIS (cMIS) or hybrid (HYB) surgery for ASD. A total of 53 patients at 8 academic centers satisfied the following inclusion criteria: age > 18 years and coronal Cobb > 20°, pelvic incidence-lumbar lordosis (PI-LL) > 10°, or sagittal vertical axis (SVA) > 5 cm.

Results Radiographic outcomes demonstrated improvements of PI-LL from 16.8° preoperatively to 10.8° and coronal Cobb angle from38° preoperatively to 18.2° at 4 years. The incidence of complications over the follow-up periodwas 56.6%.A total of 21 (39.6%) patients underwent reoperation in the thoracolumbar spine, most commonly for adjacent level disease or proximal junctional kyphosis, which occurred in 11 (20.8%) patients. Mean Oswestry Disability Index (ODI) at baseline and years 1 through 4 were 49.9, 33.1, 30.2, 32.7, and 35.0, respectively. The percentage of patients meeting minimal clinically important difference (MCID) (defined as 12% or more from baseline) decreased over time, with leg pain reduction more durable than back pain reduction.

Conclusions Intermediate-term clinical and radiographic improvement following MISS for ASD is sustained, but extent of improvement lessens over time. Outcome variability exists within a subset of patients not meeting MCID, which increases over time after year two. Loss of improvement over time wasmore notable in back than leg pain. However, average ODI improvement meets MCID at 4 years after MIS ASD surgery.

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The Efficacy of Ultrasonic Bone Scalpel for Unilateral Cervical Open-Door Laminoplasty: A Randomized Controlled Trial

Neurosurgery 86:825–834, 2020

In cervical open-door laminoplasty for cervical myelopathy, a high-speed rotatory drill and rongeurs are used to make unicortical troughs and bicortical openings in the laminae. The lamina is reflected at the trough to enlarge the spinal canal, followed by bone healing on the hinge side to stabilize laminoplasty. The ultrasonic bone scalpel (UBS) has been used due to theoretical advantages including a better hinge union rate, less soft tissue trauma, less neurological injury, and shorter operative time.

OBJECTIVE: To assess the superiority of UBS for hinge union compared to the drill through randomized controlled trial.

METHODS: In 190 randomly allocated cervical myelopathy patients, the trough and opening at the lamina were made using either the drill (n = 95) or UBS (n = 95) during 2015 to 2018. The primary outcome was the hinge union rate on 6-mo postoperative computed tomography. Secondary outcomes included the hinge union rate at 12 mo, the operative time, intraoperative/postoperative bleeding, neurological injury, complications, and clinical outcomes over a 24-mo follow-up.

RESULTS: Hinge union in all laminae was achieved in 60.0% (drill) and 43.9% (UBS) of patients at 6mo (intention-to-treat analysis; P = .02; odds ratio, 2.1) and in 91.9% (drill) and 86.5% (UBS) at 12mo. Dural injury only occurred in the drill group (2.1%), and the UBS group showed significantly less intraoperative bleeding (P < .01). The other secondary outcomes did not differ between groups.

CONCLUSION: The hinge union rate was inferior in the UBS group at 6mo postoperatively, but UBS was efficacious in reducing dural injuries and bleeding.

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Prognostic Factors for Adjacent Segment Disease After L4-L5 Lumbar Fusion

Neurosurgery 86:835–842, 2020

Adjacent segment disease (ASD) is an important consideration during decision making for lumbar spinal fusion. OBJECTIVE: To identify risk factors for development of ASD after L4-L5 fusion and differences in incidence between rostral and caudal ASD.

METHODS: We retrospectively reviewed all consecutive patients at a single institution who underwent first-time spinal fusion at the L4-L5 level for degenerative spinal disease over a 10-yr period, using posterolateral pedicular screw fixation with or without posterior interbody fusion. ASD was defined as clinical and radiographic evidence of degenerative spinal disease requiring reoperation at the level rostral (L3-L4) or caudal (L5-S1) to the index fusion.

RESULTS: Among 131 identified patients, the incidence of ASD requiring reoperation was 25.2% (n = 33). Twenty-four cases (18.3% of the entire cohort) developed rostral ASD (segment L3-L4), 3 cases (2.3%) developed caudal (L5-S1), and 6 cases (4.6%) developed bilateral ASD (both rostral and caudal). Cumulatively, the incidence of caudal ASD was significantly lower than rostral ASD (P<.001). Following multivariate logistic regression for factors associated with ASD reoperation, decompression of segments outside the fusion construct was associated with higher ASD rates (odds ratio [OR] = 2.68, P = .039), as was female gender (OR = 3.55, P = .011), whereas older age was associated with lower ASD incidence (OR = 0.95, P = .011).

CONCLUSION: When considering posterior L4-L5 fusion, surgeons should refrain from prophylactic procedures in the L5-S1 level, without clinical indications, because ASD incidence on that segment is reassuringly low.

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