Innovative design of bone quality-targeted intervertebral spacer: accelerated functional fusion guiding oriented collagen and apatite microstructure without autologous bone graft

The Spine Journal 23 (2023) 609−620

Although autologous bone grafting is widely considered as an ideal source for interbody fusion, it still carries a risk of nonunion. The influence of the intervertebral device should not be overlooked. Requirements for artificial spinal devices are to join the vertebrae together and recover the original function of the spine rapidly. Ordered mineralization of apatite crystals on collagen accelerates bone functionalization during the healing process. Particularly, the stable spinal function requires the ingrowth of an ordered collagen and apatite matrix which mimics the intact intervertebral microstructure. This collagen and apatite ordering is imperative for functional bone regeneration, which has not been achieved using classical autologous grafting.

PURPOSE: We developed an intervertebral body device to achieve high stability between the host bone and synthesized bone by controlling the ordered collagen and apatite microstructure.

STUDY DESIGN: This was an in vivo animal study.

METHODS: Intervertebral spacers with a through-pore grooved surface structure, referred to as a honeycomb tree structure, were produced using metal 3D printing. These spacers were implanted into normal sheep at the L2−L3 or L4−L5 disc levels. As a control group, grafting autologous bone was embedded. The mechanical integrity of the spacer/bone interface was evaluated through push-out tests.

RESULTS: The spacer with honeycomb tree structure induced anisotropic trabecular bone growth with textured collagen and apatite orientation in the through-pore and groove directions. The pushout load of the spacer was significantly higher than that of the conventional autologous graft spacer. Moreover, the load was significantly correlated with the anisotropic texture of the newly formed bone matrix.

CONCLUSIONS: The developed intervertebral spacer guided the regenerated bone matrix orientation of collagen and apatite, resulting in greater strength at the spacer/host bone interface than that obtained using a conventional gold-standard autologous bone graft.

CLINICAL SIGNIFICANCE: Our results provide a foundation for designing future spacers for interbody fusion in human.

Radiographic alignment outcomes after the single-position prone transpsoas approach: a multi-institutional retrospective review of 363 cases

Neurosurg Focus 54(1):E3, 2023

The aim of this paper was to evaluate the changes in radiographic spinopelvic parameters in a large cohort of patients undergoing the prone transpsoas approach to the lumbar spine.

METHODS A multicenter retrospective observational cohort study was performed for all patients who underwent lateral lumber interbody fusion via the single-position prone transpsoas (PTP) approach. Spinopelvic parameters from preoperative and first upright postoperative radiographs were collected, including lumbar lordosis (LL), pelvic incidence (PI), and pelvic tilt (PT). Functional indices (visual analog scale score), and patient-reported outcomes (Oswestry Disability Index) were also recorded from pre- and postoperative appointments.

RESULTS Of the 363 patients who successfully underwent the procedure, LL after fusion was 50.0° compared with 45.6° preoperatively (p < 0.001). The pelvic incidence–lumbar lordosis mismatch (PI-LL) was 10.5° preoperatively versus 2.9° postoperatively (p < 0.001). PT did not significantly change (0.2° ± 10.7°, p > 0.05).

CONCLUSIONS The PTP approach allows significant gain in lordotic augmentation, which was associated with good functional results at follow-up.

Robot-assisted and augmented reality–assisted spinal instrumentation

J Neurosurg Spine 37:299–314, 2022

The use of technology-enhanced methods in spine surgery has increased immensely over the past decade. Here, the authors present the largest systematic review and meta-analysis to date that specifically addresses patient-centered outcomes, including the risk of inaccurate screw placement and perioperative outcomes in spinal surgeries using robotic instrumentation and/or augmented reality surgical navigation (ARSN).

METHODS A systematic review of the literature in the PubMed, EMBASE, Web of Science, and Cochrane Library databases spanning the last decade (January 2011–November 2021) was performed to present all clinical studies comparing robot-assisted instrumentation and ARSN with conventional instrumentation techniques in lumbar spine surgery. The authors compared these two technologies as they relate to screw accuracy, estimated blood loss (EBL), intraoperative time, length of stay (LOS), perioperative complications, radiation dose and time, and the rate of reoperation.

RESULTS A total of 64 studies were analyzed that included 11,113 patients receiving 20,547 screws. Robot-assisted instrumentation was associated with less risk of inaccurate screw placement (p < 0.0001) regardless of control arm approach (freehand, fluoroscopy guided, or navigation guided), fewer reoperations (p < 0.0001), fewer perioperative complications (p < 0.0001), lower EBL (p = 0.0005), decreased LOS (p < 0.0001), and increased intraoperative time (p = 0.0003). ARSN was associated with decreased radiation exposure compared with robotic instrumentation (p = 0.0091) and fluoroscopy-guided (p < 0.0001) techniques.

CONCLUSIONS Altogether, the pooled data suggest that technology-enhanced thoracolumbar instrumentation is advantageous for both patients and surgeons. As the technology progresses and indications expand, it remains essential to continue investigations of both robotic instrumentation and ARSN to validate meaningful benefit over conventional instrumentation techniques in spine surgery.

Systematic review registration no.: CRD42021283631 (

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.


Using Smartphone-Based Accelerometer Data to Objectively Assess Outcomes in Spine Surgery

Neurosurgery 88:763–772, 2021

In order to deliver optimal patient care, spine surgeons must integrate technological changes to arrive at novel measures of functional outcomes. Historically, subjective patient-reported outcome (PRO) surveys have been used to determine the relative benefit of surgical treatments. Using smartphone-based accelerometers, surgeons now have the ability to arrive at objective outcome metrics.

OBJECTIVE: To use Apple Health (Apple Inc, Cupertino, California) data to approximate physical activity levels before and after spinal fusion as an objective outcome measurement.

METHODS: Personal activity data were acquired retrospectively from the cellphones of consenting patients. These data were used to measure changes in activity level (daily steps, flights climbed, and distance traveled) before and after patients underwent spine surgery at a single institution by a single surgeon. After data collection, we investigated the demographic information and daily physical activity pre- and postoperatively of participating patients.

RESULTS: Twenty-three patients were included in the study. On average, patients first exceeded their daily 1-yr average distancewalked, flights climbed, and steps taken at 10.3± 14, 7.6±21.1, and 8±9.9wk, respectively. Mean flights climbed, distance traveled, and steps taken decreased significantly from 6mo prior to surgery to 2 wk postoperatively. Distance traveled and steps taken significantly increased from 6 mo prior to surgery to 7 to 12 mo postoperatively.

CONCLUSION: We demonstrated a valuable supplement to traditional PROs by using smartphone-based activity data. This methodology yields a rich data set that has the potential to augment our understanding of patient recovery.

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.

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

Cost of Readmissions Following Anterior Cervical Discectomy and Fusion

Neurosurgery DOI:10.1093/neuros/nyz443

Postoperative readmissions are a significant driver of variation in bundled care costs associated with cervical spine surgery.

OBJECTIVE: To determine the factors predicting the cost of readmission episodes following elective anterior cervical discectomy and fusion (ACDF).

METHODS: We queried the Healthcare Cost and Utilization Project Nationwide Readmissions Database for patients undergoing elective ACDF during 2012 to 2015. Multivariable linear regression was performed to establish the factors associated with the cost of each 30-/90-d readmission episode.

RESULTS: A total of 139 877 and 113 418 patients met inclusion criteria for the evaluation of 30- and 90-d readmissions, respectively. Among these, the national rates of 30- and 90-d readmission after an elective ACDF were 3% and 6%, respectively. The median cost of a 30- and 90-d readmission episode was $6727 (IQR: $3844-$13 529) and $8507 (IQR: $4567- $17 460), respectively. Relative predictor importance analysis revealed that the number of procedures at index admission (IA), length of stay at IA, and time elapsed between index surgical admission and readmission were the top predictors of both 30- and 90-d readmission costs (all P < .001). Although cervical myelopathy accounted for only 3.6% of all 30-d readmissions, it accounted for the largest share (8%) of 30-d readmission costs.

CONCLUSION: In this analysis from a national all-payer database, we determined the factors associated with the cost of readmissions following elective ACDF. These results are important in assisting policymakers and payers with a better risk adjustment in bundled care payment systems and for surgeons in implementing readmission cost-reduction efforts.

Investigating the utility of intraoperative neurophysiological monitoring for anterior cervical discectomy and fusion: analysis of over 140,000 cases from the National (Nationwide) Inpatient Sample data set

J Neurosurg Spine 31:76–86, 2019

Intraoperative neurophysiological monitoring (IONM) is a useful adjunct in spine surgery, with proven benefit in scoliosis-correction surgery. However, its utility for anterior cervical discectomy and fusion (ACDF) is unclear, as there are few head-to-head comparisons of ACDF outcomes with and without the use of IONM. The authors sought to evaluate the impact of IONM on the safety and cost of ACDF.

METHODS This was a retrospective analysis of data from the National (Nationwide) Inpatient Sample of the Healthcare Cost and Utilization Project from 2009 to 2013. Patients with a primary procedure code for ACDF were identified, and diagnosis codes were searched to identify cases with postoperative neurological complications. The authors performed univariate and multivariate logistic regression for postoperative neurological complications with use of IONM as the in- dependent variable; additional covariates included age, sex, surgical indication, multilevel fusion, Charlson Comorbidity Index (CCI) score, and admission type. They also conducted propensity score matching in a 1:1 ratio (nearest neighbor) with the use of IONM as the treatment indicator and the aforementioned variables as covariates. In the propensity score–matched cohort, they compared neurological complications, length of stay (LOS), and hospital charges (in US dollars).

RESULTS A total of 141,007 ACDF operations were identified. IONM was used in 9540 cases (6.8%). No significant association was found between neurological complications and use of IONM on univariate analysis (OR 0.80, p = 0.39) or multivariate regression (OR 0.82, p = 0.45). By contrast, age ≥ 65 years, multilevel fusion, CCI score > 0, and a non- elective admission were associated with greater incidence of neurological complication. The propensity score–matched cohort consisted of 18,760 patients who underwent ACDF with (n = 9380) or without (n = 9380) IONM. Rates of neurological complication were comparable between IONM and non-IONM (0.17% vs 0.22%, p = 0.41) groups. IONM and non-IONM groups had a comparable proportion of patients with LOS ≥ 2 days (19% vs 18%, p = 0.15). The use of IONM was associated with an additional $6843 (p < 0.01) in hospital charges.

CONCLUSIONS The use of IONM was not associated with a reduced rate of neurological complications following ACDF. Limitations of the data source precluded a specific assessment of the effectiveness of IONM in preventing neuro- logical complications in patients with more complex pathology (i.e., ossification of the posterior longitudinal ligament or cervical deformity).

Safety and accuracy of robot-assisted versus fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery

J Neurosurg Spine 30:615–622, 2019

The object of this study was to compare the safety and accuracy of pedicle screw placement using the TiRobot system versus conventional fluoroscopy in thoracolumbar spinal surgery.

METHODS Patients with degenerative or traumatic thoracolumbar spinal disorders requiring spinal instrumentation were randomly assigned to either the TiRobot-assisted group (RG) or the freehand fluoroscopy-assisted group (FG) at a 1:1 ratio. The primary outcome measure was the accuracy of screw placement according to the Gertzbein-Robbins scale; grades A and B (pedicle breach < 2 mm) were considered clinically acceptable. In the RG, discrepancies between the planned and actual screw placements were measured by merging postoperative CT images with the trajectory planning images. Secondary outcome parameters included proximal facet joint violation, duration of surgery, intraoperative blood loss, conversion to freehand approach in the RG, postoperative hospital stay, and radiation exposure.

RESULTS A total of 1116 pedicle screws were implanted in 234 patients (119 in the FG, and 115 in the RG). In the RG, 95.3% of the screws were perfectly positioned (grade A); the remaining screws were graded B (3.4%), C (0.9%), and D (0.4%). In the FG, 86.1% screws were perfectly positioned (grade A); the remaining screws were graded B (7.4%), C (4.6%), D (1.4%), and E (0.5%). The proportion of clinically acceptable screws was significantly greater in the RG than in the FG (p < 0.01). In the RG, the mean deviation was 1.5 ± 0.8 mm for each screw. The most common direction of screw deviation was lateral in the RG and medial in the FG. Two misplaced screws in the FG required revision surgery, whereas no revision was required in the RG. None of the screws in the RG violated the proximal facet joint, whereas 12 screws (2.1%) in the FG violated the proximal facet joint (p < 0.01). The RG had significantly less blood loss (186.0 ± 255.3 ml) than the FG (217.0 ± 174.3 ml; p < 0.05). There were no significant differences between the two groups in terms of surgical time and postoperative hospital stay. The mean cumulative radiation time was 81.5 ± 38.6 seconds in the RG and 71.5 ± 44.2 seconds in the FG (p = 0.07). Surgeon radiation exposure was significantly less in the RG (21.7 ± 11.5 μSv) than in the FG (70.5 ± 42.0 μSv; p < 0.01).

CONCLUSIONS TiRobot-guided pedicle screw placement is safe and useful in thoracolumbar spinal surgery. Clinical trial registration no.: NCT02890043 (


A Staged Protocol for Circumferential Minimally Invasive Surgical Correction of Adult Spinal Deformity

Neurosurgery 81:733–739, 2017

Minimally invasive surgery (MIS) techniques used for management of adult spinal deformity (ASD) aim to decrease the physiological demand on patients and minimize postoperative complications. A circumferential MIS (cMIS) protocol offers the potential to maximize this advantage over standard open approaches, through the concurrent use of multiple MIS techniques.

OBJECTIVE: To demonstrate through a case example the execution of a cMIS protocol for management of an ASD patient with severe deformity.

METHODS: Thorough preoperative assessment, surgical planning, and medical optimization were completed. Deformity correction was performed over 2 stages. During the first stage, interbody fusion was performed via an oblique lateral approach at all levels of the lumbar spine intended to be included in the final construct. The patient was kept as an inpatient and mobilized postoperatively. They were then re-imaged with standing films. The second stage occurred after 3 d and involved percutaneous instrumentation of all levels. Posterior fusion of the thoracic levels was achieved through decortication of pars and facets. These areas were accessed through the intermuscular plane established by the percutaneous screws. The patient was mobilizing on their first postoperative day.

RESULTS: In a 66-yr-old female with severe sagittal imbalance and debilitating back pain, effective use of this cMIS protocol allowed for correction of the Cobb angle from 52◦ to 4◦ correction of spinopelvic parameters and 13 cm of sagittal vertical axis improvement. No complications were identified by 2 yr postoperative.

CONCLUSION: As a systematization of multiple MIS techniques combined, in a specific and staged manner, this cMIS protocol could provide a safe and effective approach to the management of ASD.


Transforaminal Lumbar Interbody Fusion Versus Mini-open Anterior Lumbar Interbody Fusion With Oblique Self-anchored Stand-alone Cages for the Treatment of Lumbar Disc Herniation

Spine 2017;42:E1259–E1265

The aim of this study was to evaluate the clinical and radiological outcomes of mini-open ALIF (MO-ALIF) with self-anchored stand-alone cages for the treatment of lumbar disc herniation in comparison with transforaminal lumbar interbody fusion (TLIF). Summary of Background Data. Currently, whether ALIF is superior to TLIF for the treatment of lumbar disc herniation remains controversial.

Summary of Background Data. Currently, whether ALIF is superior to TLIF for the treatment of lumbar disc herniation remains controversial.

Methods. This study retrospectively reviewed 82 patients who underwent MO-ALIF with self-anchored standalone cages (n=42) or TLIF (n=40) for the treatment of lumbar disc herniation between April 2013 and October 2014. Patient demographics, intraoperative parameters, and perioperative complications were collated. Clinical outcomes were evaluated using the visual analog scale (VAS) scoring, the Oswestry Disability Index (ODI) for pain in the leg and back, and radiological outcomes, including fusion, lumbar lordosis (LL), disc height (DH), and cage subsidence were evaluated at each follow-up for up to 2 years.

Results. Patients who underwent TLIF had a significantly higher volume of blood loss (295.2±81.4 vs. 57.0±15.2mL) and longer surgery time (130.7±45.1 vs. 60.4±20.8 min) than those who had MO-ALIF. Compared with baseline, both groups had significant improvements in the VAS and ODI scores and DH and LL postoperatively, though no significant difference was found between the two groups regarding these indexes. All patients reached solid fusion at the final follow-up in both groups. Three patients (3/42) with three levels (3/50) suffered from cage subsidence in the MO-ALIF group; meanwhile, no cage subsidence occurred in the TLIF group. Conclusion. MO-ALIF with self-anchored stand-alone cages is a safe and effective treatment of lumbar disc herniation with less surgical trauma and similar clinical and radiological outcomes compared with TLIF.

Conclusion. MO-ALIF with self-anchored stand-alone cages is a safe and effective treatment of lumbar disc herniation with less surgical trauma and similar clinical and radiological outcomes compared with TLIF.

Level of Evidence: 3

Stabilization of Tumor-Associated Craniovertebral Junction Instability

Neurosurgery 81:251–258, 2017

Whether primary or metastatic, tumors of the craniovertebral junction (CVJ) are rare and challenging.

OBJECTIVE: To examine the surgical indications, operative variables, and outcomes in patients with tumors of the CVJ undergoing occipitocervical (OC) stabilization.

METHODS: A single-institution, retrospective case series was performed from a prospectively maintained spine database. Patients with primary or metastatic tumors of the CVJ who underwent OC stabilization were identified. Out of 46 patients who underwent OC fusion, 39 were for tumor. Paired t-tests and Wilcoxon rank-sum tests were performed to assess for postoperative changes.

RESULTS: Ten patients (26%) harbored primary tumors, and the remaining 29 (74%) had metastatic disease. Of the metastatic patients, 14 had a neurological deficit, 10 had severe neck pain, and 5 were deemed mechanically unstable. Postoperative visual analog pain scoreswere significantly reduced at all 3 follow-up times (P<.001, 95% confidence interval [CI; 3.2, 6.0]; P = .001, 95% CI [2.6, 7.7]; P = .020, 95% CI [0.6, 5.5]). The percentage of patients who were ambulatory and neurologically improved or intact remained stable postoperatively with no significant declines. There were 2 perioperative mortalities (5%), and 13 patients (33%) experienced a major complication.

CONCLUSIONS: In patients with primary or metastatic tumor of the CVJ, OC stabilization using a cervical screw-rod system affixed to a midline-keel buttress plate, with or without posterior decompression, is a reliable method for CVJ stabilization in the oncologic setting. Improvement in pain and preservation of neurological function was seen.


Unskilled unawareness and the learning curve in robotic spine surgery

SpineAssist™ robot system

Acta Neurochir (2015) 157:1819–1823

Robotic assistance for the placement of pedicle screws has been established as a safe technique. Nonetheless rare instances of screw misplacement have been reported.The aim of the present retrospective study is to assess whether experience and time affect the accuracy of screws placed with the help of the SpineAssist™ robot system.

Methods Postoperative computed tomography (CT) scans of 258 patients requiring thoracolumbar pedicle screw instrumentation from 2008 to 2013 were reviewed. Overall, 13 surgeons performed the surgeries. A pedicle breach of >3 mm was graded as a misplacement. Surgeons were dichotomised into an early and experienced period in increments of five surgeries.

Results In 258 surgeries, 1,265 pedicle screws were placed with the aid of the robot system. Overall, 1,217 screws (96.2 %) were graded as acceptable. When displayed by surgeon, the development of percent misplacement rates peaked between 5 and 25 surgeries in 12 of 13 surgeons. The overall misplacement rate in the first five surgeries was 2.4%(6/245). The misplacement rate rose to 6.3 % between 11 and 15 surgeries (10/158; p=0.20), and reached a significant peak between 16 and 20 surgeries with a rate of 7.1 % (8/112; p= 0.03). Afterwards, misplacement rates declined.

Conclusions A major peak in screw inaccuracies occurred between cases 10 and 20, and a second, smaller one at about 40 surgeries. One potential explanation could be a transition from decreased supervision (unskilled but aware) to increased confidence of a surgeon (unskilled but unaware) who adopts this new technique prior to mastering it (skilled). We therefore advocate ensuring competent supervision for new surgeons at least during the first 25 procedures of robotic spine surgery to optimise the accuracy of robot-assisted pedicle screws.

Outcomes of Anterior Lumbar Interbody Fusion Surgery Based on Indication: A Prospective Study

Outcomes of Anterior Lumbar Interbody Fusion Surgery Based on Indication- A Prospective Study

Neurosurgery 76:7–24, 2015

There is limited information on clinical outcomes after anterior lumbar interbody fusion (ALIF) based on the indications for surgery.

OBJECTIVE: To compare the clinical and radiological outcomes of ALIF for each surgical indication.

METHODS: This prospective clinical study included 125 patients who underwent ALIF over a 2-year period. The patients were evaluated preoperatively and postoperatively. Outcome measures included the Short Form-12, Oswestry Disability Index, Visual Analog Scale, and Patient Satisfaction Index.

RESULTS: After a mean follow-up of 20 months, the clinical condition of the patients was significantly better than their preoperative status across all indications. A total of 108 patients had a Patient Satisfaction Index score of 1 or 2, indicating a successful clinical outcome in 86%. Patients with degenerative disk disease (with and without radiculopathy), spondylolisthesis, and scoliosis had the best clinical response to ALIF, with statistically significant improvement in the Short Form-12, Oswestry Disability Index, and Visual Analog Scale. Failed posterior fusion and adjacent segment disease showed statistically significant improvement in all of these clinical outcome scores, although the mean changes in the Short Form-12 Mental Component Summary, Oswestry Disability Index, and Visual Analog Scale (back pain) were lower. The overall radiological fusion rate was 94.4%. Superior radiological outcomes (fusion .90%) were observed in patients with degenerative disk disease (with and without radiculopathy), spondylolisthesis, and failed posterior fusion, whereas in adjacent segment disease, it was 80%.

CONCLUSION: ALIF is an effective treatment for degenerative disk disease (with and without radiculopathy) and spondylolisthesis. Although results were promising for scoliosis, failed posterior fusion, and adjacent segment disease, further studies are necessary to establish the effectiveness of ALIF in these conditions.

Safety and accuracy of robot-assisted versus fluoroscopy-guided pedicle screw insertion for degenerative diseases of the lumbar spine

Robot-assisted spine surgery

J Neurosurg Spine 20:636–643, 2014

Recent years have been marked by efforts to improve the quality and safety of pedicle screw placement in spinal instrumentation. The aim of the present study is to compare the accuracy of the SpineAssist robot system with conventional fluoroscopy-guided pedicle screw placement.

Methods. Ninety-five patients suffering from degenerative disease and requiring elective lumbar instrumentation were included in the study. The robot cohort (Group I; 55 patients, 244 screws) consisted of an initial open robot-assisted subgroup (Subgroup IA; 17 patients, 83 screws) and a percutaneous cohort (Subgroup IB, 38 patients, 161 screws). In these groups, pedicle screws were placed under robotic guidance and lateral fluoroscopic control. In the fluoroscopy-guided cohort (Group II; 40 patients, 163 screws) screws were inserted using anatomical landmarks and lateral fluoroscopic guidance. The primary outcome measure was accuracy of screw placement on the Gertzbein-Robbins scale (Grade A to E and R [revised]). Secondary parameters were duration of surgery, blood loss, cumulative morphine, and length of stay.

Results. In the robot group (Group I), a perfect trajectory (A) was observed in 204 screws (83.6%). The remaining screws were graded B (n = 19 [7.8%]), C (n = 9 [3.7%]), D (n = 4 [1.6%]), E (n = 2 [0.8%]), and R ( n = 6 [2.5%]). In the fluoroscopy-guided group (Group II), a completely intrapedicular course graded A was found in 79.8% (n = 130). The remaining screws were graded B (n = 12 [7.4%]), C (n = 10 [6.1%]), D (n = 6 [3.7%]), and E (n = 5 [3.1%]). The comparison of “clinically acceptable” (that is, A and B screws) was neither different between groups (I vs II [p = 0.19]) nor subgroups (Subgroup IA vs IB [p = 0.81]; Subgroup IA vs Group II [p = 0.53]; Subgroup IB vs Group II [p = 0.20]). Blood loss was lower in the robot-assisted group than in the fluoroscopy-guided group, while duration of surgery, length of stay, and cumulative morphine dose were not statistically different.

Conclusions. Robot-guided pedicle screw placement is a safe and useful tool for assisting spine surgeons in degenerative spine cases. Nonetheless, technical difficulties remain and fluoroscopy backup is advocated.

C1–2 transarticular screws combined with C1 laminar hooks fixation

C1–2 transarticular screws combined with C1 laminar hooks fixation

Eur Spine J (2013) 22:260–267

Purpose To retrospectively evaluate the outcome of C1–2 transarticular screws combined with C1 laminar hooks fixation.

Methods All patients underwent atlantoaxial fixation during a 5-year period. The surgical technique and treatment procedures were intensively reviewed and clinical symptoms, neurological function and imaging appearance were retrospectively evaluated.

Results The clinical and radiology follow-up indicated a stable arthrodesis and clinical relief from symptoms for all patients. All patients with neurological defects improved an average of 1.33 grade at their most recent clinical assessment, P≤0.05; their average admission ASIA motor score, pin prick score and light touch score improved to an average follow-up ASIA score of 99.80 (99.83 ± 0.38), 111.83 (111.83 ± 0.45), and 111.89 (111.89 ± 0.32), respectively. No neurovascular impairment and case of implant failure were observed.

Conclusions The C1–2 transarticular screws combined with C1 laminar hooks fixation is a reliable technique for atlantoaxial instability.

Nonfusion stabilization of the degenerative lumbar spine

J Neurosurg Spine 15:151–158, 2011. DOI: 10.3171/2011.3.SPINE0969

The goal of this study was to assess whether a stable but nonrigid nonfusion implant can stabilize the spine in degenerative diseases and also prevent instability following decompression. Instrumented spondylodesis is a recognized surgical treatment in degenerative disease of the lumbar spine. However, pain can develop at the bone graft donor site and the operative trauma can be very stressful in elderly patients, and it is suspected that there may be increased degenerative changes in the adjacent segments. In 2002, a nonrigid but rotationally stable pedicle screw and rod system was introduced, which could be used without additional fusion (referred to hereafter as the Cosmic system).

Methods. A total of 139 patients with degenerative disease of the lumbar spine underwent spinal stabilization with the Cosmic system without additional spondylodesis. Seventy patients had an additional decompression. The minimum follow-up was 2 years. The perioperative course, the clinical results, and the erect anteroposterior and lateral radiographs were recorded and compared with the preoperative data. The data were obtained from 6 different spine centers in Europe and documented on an Internet platform.

Results. The Oswestry Disability Index score improved from 48.9% to 22.5%, and the visual analog scale score decreased from 7.3 to 2.5. Lumbar lordosis did not change, nor did the adjacent disc height. Eleven patients underwent revision, 4 of them for implant failure. Of the 139 patients, 110 assessed the result as excellent, very good, or good; 24 as fair; and 5 as poor. A total of 122 patients would undergo surgery again. There were no significant differences between patients with or without an additional decompression.

Conclusions. The Cosmic system is a stable but nonrigid posterior nonfusion system. Implant complications are low and the clinical outcome is good. Longer follow-up is necessary to confirm the 2-year results.

A retrospective analysis of pedicle screws in contact with the great vessels

J Neurosurg Spine 13:403–406, 2010.DOI: 10.3171/2010.3.SPINE09657

Pedicle screws placed in the thoracic, lumbar, and sacral spine occasionally come in contact with the aorta, vena cava, or iliac vessels. When such screws are seen on postoperative imaging in an asymptomatic patient, the surgeon must decide whether it is riskier to revise the screw or to observe it. The authors hypothesized that the incidence of screw placement causing perioperative vessel injury is low and, further, that screws placed in contact with major vessels do not always result in vessel injury.

Methods. A retrospective review of the operative records of 182 consecutive patients undergoing thoracic, lumbar, and lumbosacral pedicle screw fusion was performed to determine the frequency of intraoperative vessel injury. Postoperative imaging for 107 patients was available to determine the incidence of screws in contact with major vessels. Charts were examined to determine if any adverse sequelae had resulted from malpositioned screws. Patient outcomes were documented.

Results. There were no intraoperative vessel injuries or deaths in 182 consecutive operations. One hundred seven patients with available postoperative films had 680 pedicle screws placed between T-3 and the sacrum during 115 operations. No patient had arterial screw penetration or deformation on postoperative imaging. Thirty-three of the 680 inserted screws were in contact with a major vessel on routine postoperative imaging. The contacted vessels included the aorta (4 cases), the iliac artery (7 cases), and the iliac veins (22 cases). Patients were followed up until death or November 2009, for a mean follow-up of 44 months (median 44 months, range 5–109 months). None of the patients with vessel contact was noted to suffer symptoms or sequelae as a result of vessel contact. Radiographic follow-up as long as 50 months after surgery revealed no detectable vessel abnormality at the contacted site.

Conclusions. Placing pedicle screws in contact with major vessels is a known risk of spinal surgery. The risk of repositioning a screw in contact with a major vessel but causing no symptoms must be weighed against the relative risk of leaving it in place.

Outpatient Anterior Cervical Discectomy and Fusion: Indications and Clinical Experience in a Consecutive Series of 390 Patients

Neurosurg Q 2010;20:107–110

Objective: To assess the safety and efficacy of outpatient anterior cervical discectomy and fusion (ACDF) carried out on outpatients.

Methods: We retrospectively reviewed the records of 390 consecutive patients who underwent outpatient ACDF between September 2002 and September 2007 to assess the safety and efficacy of outpatient anterior cervical surgery. The mean age of the patient sample was 46; 56% were female and 44% were male. Indications for surgery consisted of cervical radiculopathy or myelopathy. Charts were reviewed to define patient demographics and medical comorbidities. Operative data, including levels treated, surgery time, time to discharge, and intraoperative complications were collected. Clinical outcomes were collected using the PhDx Clinical Outcomes Database. Need for hospital transfer from the ambulatory surgical center, emergency room visits, and subsequent hospital admission in the perioperative period were determined from patient records. Complications, patient satisfaction, and outcome were ascertained through review of notes from the first postoperative visit.

Results: There was no mortality and there were no major complications. Out of 390 patients, operation was carried out at 1 level in 223 patients, at 2 levels in 143, and at 3 levels in 24. Pain was present in 99%, motor deficit in 31%, and myelopathy in 14%. Twenty-five percent were hypertensive, 5% were diabetic, and 2% had coronary artery disease. The incidence of hospital transfer for ACDF related complications was <1%, emergency room visits <1% and subsequent hospitalization <1%. At the time of the first postoperative visit 92% of patients believed that they were improved and only 1% of patients had transiently increased radicular weakness.

Conclusion: Outpatient ACDF is safe and efficacious in selected patients.

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