Category: Spine

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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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The Oblique Corridor at L4-L5

SPINE Volume 45, Number 10, pp E552–E559

Study Design. Cross-sectional radioanatomical study.

Objective. The aim of this study was to analyze the prevalence, size, and location of the oblique corridor (OC), and the morphology of the psoas muscle at the L4-L5 disc level.

Summary of Background Data. Lateral lumbar interbody fusion via the OC has the advantage of avoiding injury to the psoas muscle and lumbar plexus. However, the varying anatomy of major vascular structures and the iliopsoas may preclude a safe oblique access to the L4-L5 level.

Methods. Five hundred axial magnetic resonance images of the L4-L5 disc level were shortlisted. OCs were categorized into four grades: Grade 0 ¼ no corridor, Grade 1 ¼ small corridor (1 cm), Grade 2 ¼ moderate corridor (1–2 cm) and Grade 3 ¼ large corridor (>2 cm). OC location was labeled as anterooblique, oblique, or oblique-lateral. Psoas morphology was categorized based on a modified Moro’s classification, where the anterior section was further subdivided into types AI-AIV. Oblique approach was considered nonviable either when there was no corridor due to vascular obstruction (Grade 0) or when the psoas was high-rising (Types AII-AIV).

Results. 10.5% of the selected 449 patients had no measurable OC (grade 0) at the L4-L5 level. There were 35% and 37.2% patients with a grade 1and 2 OC, respectively. The location of the OC was anterior oblique, oblique, and oblique lateral in 3.7%, 89.6%, and 6.7%, respectively. According to the modified Moro’s classification, 19.4% had a high-rising psoas. Predominantly, psoas was either in line with the disc (Type I; 30.7%) or low-rising (Type AI; 47.4%).

Conclusion. Twenty-five percent of the patients did not have an accessible OC either due to obstruction by vascular structures or due to a high-rising psoas. Hence, proper evaluation of the relevant anatomy preoperatively is recommended for early adopters of this technique, as varying anatomy precludes universal suitability of oblique lateral interbody fusion for the L4-L5 level.

Level of Evidence: 3

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In Memoriam: Wolfhard Caspar (1938–2019) A Pioneer of Spinal Microsurgery

SPINE Volume 45, Number 9, pp 563–564, 2020

Dr. Wolfhard Caspar was born on December 29, 1938 in Ventspils, Latvia, and passed away on December 31, 2019 in Bamberg, Germany, just 2 days after his 81st birthday. Dr. Caspar grew up in Germany, having lived here since 1939.

Dr. Wolfhard Caspar presented his scientific and surgical work with eloquent passion. He usually attracted his listeners by his ‘‘unique” way of reporting his experiences. Additionally, he never reached out for presidential honors from different societies. He preferred to pursue achievable perfection in his fields of surgical interest. His goal: Spinal microsurgery tailored to the patient‘s need. His pioneering work in spine surgery is honored by the spine community.

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Spine surgery is kyphosing to spine surgeon

Acta Neurochirurgica (2020) 162:967–971

Spine surgery is a demanding surgical specialty which requires surgeons to operate for hours on end, often compromising good posture. Sustained poor posture in the operating room (OR) can be the source of many adverse health effects on spine surgeons. This study will analyze posture of a spine surgeon in different types of spine surgery cases.

Methods Posture of a surgeon was measured using the UPRIGHT Posture Training Device. The device was worn by the surgeon in the OR through a wide variety of spine surgery cases.

Results The percent time spent slouched while performing cervical, adult deformity, and lumbar spine surgeries is 39.9, 58.9, and 38.6, respectively. For all surgeries recorded, the percent time slouched is 41.6. The average procedure time was 145.3 min, with adult deformity cases on average being the longest (245.6 min) followed by cervical (152.9 min) and then lumbar (122.5 min).

Conclusion Poor posture while operating is very likely to occur for many spine surgeons regardless of case type. This poor posture is maintained for long periods of time given the average spine surgery procedure recorded in the study was roughly 2.5 h long. Spine surgeons should be aware of the tendency for poor posture while operating, and they should try using postureimproving techniques to maintain good spine health.

 

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Uncertainty in the Relationship Between Sagittal Alignment and Patient-Reported Outcomes

Neurosurgery 86:485–491, 2020

Previous studies have reported correlations and precise quantitative relationships between sagittal alignment and health-related quality-of-life (HRQOL) scores. These studies have not reported the extent of uncertainty in these relationships.

OBJECTIVE: To explore the uncertainty in the overall relationships between sagittal alignment and HRQOL and in the predictions of individual patient pain and disability.

METHODS: A retrospective analysis of all new adult patients with long-cassette radiographs and complete outcomes questionnaires presenting to the senior author from 2012 to 2014 was performed. Univariable maximum a posteriori linear regression analyses using Bayesian methods were performed. High-density probability intervals for mean regression relationships and for individual values were calculated using minimally informative prior distributions.

RESULTS: A total of 134 patients satisfied inclusion criteria and were included. For Oswestry Disability Index (ODI) vs pelvic incidence-lumbar lordosis (LL), the 90% high-density probability interval ranged from –0.04 to 0.23, indicating that both the magnitude and direction of the relationship were uncertain. For both ODI vs sagittal vertical axis and ODI vs LL, there was uncertainty in the magnitude of the slope.Wide regions of uncertainty were also seen for predicting individual patient scores.

CONCLUSION: We report the previously unpublished degree of uncertainty in the mean quantitative relationships between radiographic sagittal alignment and patient-reported outcomes and in individual patient outcomes scores. Based on these results, establishing treatment thresholds or predicting an individual’s outcome is unreliable. Further research efforts should be focused on developing multilevel hierarchical models incorporating parameter uncertainty and heterogeneous effects.

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Predicting Outcomes After Surgical Decompression for Mild Degenerative Cervical Myelopathy

Neurosurgery, Volume 86, Issue 4, April 2020 :565–573

Patients with mild degenerative cervical myelopathy (DCM) represent a heterogeneous population, and indications for surgical decompression remain controversial.

OBJECTIVE: To dissociate patient phenotypes within the broader population of mild DCM associated with degree of impairment in baseline quality of life (QOL) and surgical outcomes.

METHODS: This was a post hoc analysis of patients with mild DCM (modified Japanese Orthopedic Association [mJOA] 15-17) enrolled in the AOSpine CSM-NA/CSM-I studies. A kmeans clustering algorithm was applied to baseline QOL (Short Form-36 [SF-36]) scores to separate patients into 2 clusters. Baseline variables and surgical outcomes (change in SF- 36 scores at 1 yr) were compared between clusters. A k-nearest neighbors (kNN) algorithm was used to evaluate the ability to classify patients into the 2 clusters by significant baseline clinical variables.

RESULTS: One hundred eighty-five patients were eligible. Two groups were generated by k-means clustering. Cluster 1 had a greater proportion of females (44% vs 28%, P = .029) and symptoms of neck pain (32% vs 11%, P = .001), gait difficulty (57% vs 40%, P = .025), or weakness (75% vs 59%, P=.041). Although baseline mJOA correlated with neither baseline QOL nor outcomes, cluster 1 was associated with significantly greater improvement in disability (P = .003) and QOL (P < .001) scores following surgery. A kNN algorithm could predict cluster classification with 71% accuracy by neck pain, motor symptoms, and gender alone.

CONCLUSION: We have dissociated a distinct patient phenotype of mild DCM, characterized by neck pain, motor symptoms, and female gender associated with greater impairment in QOL and greater response to surgery.

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Percutaneous Transforaminal Endoscopic Discectomy Versus Microendoscopic Discectomy for Lumbar Disc Herniation

SPINE Volume 45, Number 8, pp 493–503

Study Design. A prospective randomized controlled study.

Objective. To clarify whether percutaneous transforaminal endoscopic discectomy (PTED) has better clinical outcomes and less surgical trauma compared with microendoscopic discectomy (MED).

Summary of Background Data. Two kinds of minimally invasive spine surgeries, PTED and MED, are now widely used for the treatment of lumbar disc herniation (LDH). It is still a controversial issue to choose the proper surgical approach.

Methods. In this single-center, open-label, randomized controlled trial, patients were included if they had persistent signs and symptoms of radiculopathy with corresponding imagingconfirmed LDH, and were randomly allocated to PTED or MED group. The primary outcome was the score of Oswestry Disability Index (ODI) and the secondary outcomes included the score of Medical Outcomes Study 36-Item Short-Form Health Survey bodily pain and physical function scales, European Quality of Life-5 Dimensions, and Visual Analogue Scales for back pain and leg pain.

Results. A total of 250 participants were randomly assigned to two treatment groups, 241 of that received the specific surgical procedure. Two hundred twenty-two patients (92.1%) have completed the 2-year follow-up. Both the primary and secondary outcomes did not differ significantly between the two treatment groups at each prespecified follow-up time (P>0.05). For PTED, the postoperative improvement of ODI score in the median herniation subgroup was less compared with paramedian subgroup. For MED, less improvement of ODI score was found in far-lateral herniation subgroup compared with paramedian subgroup. Total complication rate over the course of 2 year was 13.44% in PTED group and 15.57% in MED group (P¼0.639). Ten cases (8.40%) in PTED group and five cases (4.10%) in MED group suffered from residue/recurrence of herniation, for which reoperation was required.

Conclusion. Over the 2-year follow-up period, PTED did not show superior clinical outcomes and did not appear to be safer procedure for patients with LDH compared with MED. PTED had inferior results for median disc herniation, whereas MED did not appear to be the best option for far-lateral disc herniation.

Level of Evidence: 2

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Double-blind randomized clinical trial of vancomycin in spinal arthrodesis: no effects on surgical site infection

J Neurosurg Spine 32:473–480, 2020

Surgical site infection (SSI) results in high morbidity and mortality in patients undergoing spinal fusion. Using intravenous antibiotics in anesthesia induction reduces the rate of postoperative infection, but it is not common practice to use them topically, despite recent reports that this procedure helps reduce infection. The objective of this study was to determine whether the topical use of vancomycin reduces the rate of postoperative SSI in patients undergoing thoracolumbar fusion.

METHODS A randomized, double-blind clinical trial in a single hospital was performed comparing vancomycin and placebo in thoracolumbar fusion patients.

RESULTS A total of 96 patients were randomized to placebo or vancomycin treatment. The mean patient age was 43 ± 14.88 years, 74% were male, and the most common etiology was fall from height (46.9%). The overall rate of postoperative SSI was 8.3%, and no difference was found between the groups: postoperative infection rates in the vancomycin and placebo groups were 8.2% and 8.5% (relative risk [RR] of SSI not using vancomycin 1.04, 95% confidence interval [CI] 0.28–3.93, p = 0.951), respectively. Patients with diabetes mellitus had higher SSI rates (RR 8.98, 95% CI 1.81–44.61, p = 0.007).

CONCLUSIONS This is the first double-blind randomized clinical trial to evaluate the effects of topical vancomycin on postoperative infection rates in thoracolumbar fusion patients, and the results did not differ significantly from placebo. Clinical trial registration no.: RBR-57wppt (ReBEC; http://www.ensaiosclinicos.gov.br/)

 

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