Early Experience With Novel Molded Allograft Anchors for the Management of Screw Loosening in Elderly Patients With Reduced Bone Density in Primary and Revision Lumbar Surgery.

BACKGROUND: Various strategies have been used to reduce pedicle screw loosening following lumbar instrumented fusion, but all strategies have limitations. In this prospective multicenter cohort study, outcomes of elderly patients with reduced bone density who underwent primary or revision fusion surgery using a novel technique of pedicle screw augmentation with demineralized bone fiber (DBF) anchors were evaluated. METHODS: This study included elderly patients (aged >65 years) with dual-energy x-ray absorptiometry-confirmed reduced bone density who required lumbar pedicle screw fixation and were treated with supplemental DBF allograft anchors during primary or revision surgery. The need for DBF anchors was determined by evaluating preoperative computed tomography (CT) scans (for revision surgery) and by the surgeons' tactile feedback intraoperatively during pedicle screw insertion and removal. After determining the pedicle screw void diameter with a sizing instrument, DBF anchors and pedicle screws of the same diameter were placed into the void. CT scans were obtained on postoperative day 2 to assess pedicle breach, pedicle fracture, or anchor material extrusion and at 6 and 12 months postoperatively to assess screw loosening. Thereafter, to minimize radiation exposure, CT scans were only performed for recurrence of pain. RESULTS: Twenty-three patients (79% women; mean age, 74 years) received 50 lumbosacral pedicle screws augmented with DBF anchors. Most surgeries (n = 18, 78%) were revisions, and most anchors were inserted into revision pedicle screw trajectories (n = 33, 66%). Day-2 CT scans revealed no pedicle breach/fracture or extrusion of anchor material. During a mean follow-up of 15 months (12-20 months), no screw loosening was detected, and no patient required pedicle screw revision surgery. There were no adverse events attributable to DBF allografts. CONCLUSIONS: DBF allograft anchors appear to be safe and effective for augmenting pedicle screws during revision surgeries in female elderly patients with reduced bone density. CLINICAL RELEVANCE: Clinically, DBF reduced the rate of pedicle screw loosening in patients with reduced bone density. A significant reduction in screw loosening can decrease the need for revision surgeries, which are costly and carry additional risks. Enhanced bone integration from the DBF may promote better healing and long-term stability.

Porous Cage Macro-Topography Improves Early Fusion Rates in Anterior Cervical Discectomy and Fusion.

Objectives: Anterior cervical discectomy and fusion (ACDF) aims to improve pain, relieve neural compression, achieve rapid solid bony arthrodesis, and restore cervical alignment. Bony fusion occurs as early as 3 months and up to 24 months after ACDF. The correlations between bony fusion and clinical outcomes after ACDF remain unclear. Macro-topographic and porous features have been introduced to interbody cage technology, aiming to improve the strength of the bone-implant interface to promote early fusion. In this study, we aimed to compare clinical outcomes and CT-evaluated fusion rates in patients undergoing ACDF using one of two different interbody cages: traditional NanoMetalene™ (NM) cages and NM cages with machined porous features (NMRT). Methods: This was a prospective, observational, nonrandomised, cohort study of consecutive patients undergoing ACDF. The NM cage cohort was enrolled first, then the NMRT cohort second. The visual analogue scale, neck disability index, and 12-item Short Form Survey scores were evaluated preoperatively and at 6 weeks, 3 months, and 6 months. The minimum clinical follow-up period was 12 months. Plain radiographs were obtained on postoperative day 2 to assess instrumentation positioning, and computed tomography (CT) was performed at 3 and 6 months postoperatively to assess interbody fusion (Bridwell grade). Results: Eighty-nine (52% male) patients with a mean age of 62 ± 10.5 years were included in this study. Forty-one patients received NM cages, and 48 received NMRT cages. All clinical outcomes improved significantly from baseline to 6 months. By 3 months, the NMRT group had significantly higher CT fusion rates than the NM group (79% vs 56%, p=0.02). By 6 months, there were no significant differences in fusion rates between the NMRT and NM groups (83% vs 78%, p=0.69). The mean Bridwell grade at 6 months was 1.4 ± 0.7 in the NMRT group and 1.8 ± 1.0 in the NM group (p=0.08). Conclusions: With both NM and NMRT cages, serial improvements in postoperative clinical outcomes were associated with fusion progression on CT. NMRT cages demonstrated significantly better fusion at 3 months and a trend toward higher quality of fusion at 6 months compared with NM cages, suggesting earlier cage integration with NMRT. An early 3-month postoperative CT is adequate for fusion assessment in almost 80% of patients undergoing ACDF with an NMRT cage, permitting an earlier return to activity.

Lateral lumbar interbody fusion - clinical outcomes, fusion rates and complications with recombinant human bone morphogenetic protein-2.

BACKGROUND: The authors report an Australian experience of lateral lumbar interbody fusion (LLIF) with respect to clinical outcomes, fusion rates, and complications, with recombinant human bone morphogenetic protein-2 (rhBMP-2) and other graft materials. METHODS: Retrospective cohort study of LLIF patients 2011-2021. LLIFs performed lateral decubitus by four experienced surgeons past their learning curve. Graft materials classified rhBMP-2 or non-rhBMP-2. Patient-reported outcomes assessed by VAS, ODI, and SF-12 preoperatively and postoperatively. Fusion rates assessed by CT postoperatively at 6 and 12 months. Complications classified minor or major. Clinical outcomes and complications analysed and compared between rhBMP-2 and non-rhBMP-2 groups. RESULTS: A cohort of 343 patients underwent 437 levels of LLIF. Mean age 67 ± 11 years (range 29-89) with a female preponderance (65%). Mean BMI 29kg/m2 (18-56). Most common operated levels L3/4 (36%) and L4/5 (35%). VAS, ODI and SF-12 improved significantly from baseline. Total complication rate 15% (53/343) with minor 11% (39/343) and major 4% (14/343). Ten patients returned to OR (2-wound infection, 8-further instrumentation and decompression). Most patients (264, 77%) received rhBMP-2, the remainder a non-rhBMP-2 graft material. No significant differences between groups at baseline. No increase in minor or major complications in the rhBMP-2 group compared to the non-rhBMP-2 group respectively; (10.6% vs 13.9% [p = 0.42], 2.7% vs 8.9% [p < 0.01]). Fusion rates significantly higher in the rhBMP-2 group at 6 and 12 months (63% vs 40%, [p < 0.01], 92% vs 80%, [p < 0.02]). CONCLUSION: LLIF is a safe and efficacious procedure. rhBMP-2 in LLIF produced earlier and higher fusion rates compared to available non-rhBMP-2 graft substitutes.

Lateral Lumbar Interbody Fusion Using Expandable vs Static Titanium Interbody Cages: A Prospective Cohort Study of Clinical and Radiographic Outcomes.

BACKGROUND: Expandable cages are a recent development employed to reduce subsidence and improve fusion compared with static cages as they alleviate the need for repeated trialing or overdistraction of the disc space. This study aimed to compare the radiographic and clinical outcomes in patients undergoing lateral lumbar interbody fusion (LLIF) with either an expandable or static titanium cage. METHODS: This was a prospective study of 98 consecutive patients undergoing LLIF performed over a 2-year period, with the first 50 patients receiving static cages and the following 48 receiving expandable cages. Radiographic evaluation included interbody fusion status, cage subsidence, and change in segmental lordosis and disc height. Clinical evaluation assessed patient-reported outcome measures (PROMs), including the Oswestry Disability Index, visual analog scale (VAS) for back and leg pain, and short form-12 physical and mental health survey scores collected at 3, 6, and 12 months postoperatively. RESULTS: The 98 patients had 169 cages impacted (84 expandable vs 85 static). Mean age was 69.2 years, and 53.1% were women. There was no significant difference between the 2 groups in terms of age, gender, body mass index, or smoking status. The expandable cage group had higher rates of interbody fusion (94.0% vs 82.9%, P = 0.039) at 12 months as well as significantly reduced implant subsidence rates at all follow-up timepoints (4% vs 18% at 3 months; 4% vs 20% at 6 and 12 months). Patients from the expandable cage group showed a mean 1.9 more points of reduction in VAS back pain (P = 0.006) and 2.49 points greater reduction in VAS leg pain (P = 0.023) at 12-month follow-up. CONCLUSIONS: Expandable lateral interbody spacers resulted in significantly improved fusion rates with reduced subsidence risks and statistically significant improvement in PROMs up to 12 months postoperatively compared with impacted lateral static cages. CLINICAL RELEVANCE: The data provide clinical relevance in favoring expandable cages over static cages for enhanced fusion outcomes in lumbar fusions.

Patient-specific spinal rods in adult spinal deformity surgery reduce proximal junctional failure: a review of patient outcomes and surgical technique in a prospective observational cohort.

Background: Spinal rods used for adult spinal deformity (ASD) correction are usually manufactured straight and bent manually during surgery. Pre-bent patient-specific spinal rods (PSSR) developed with software provide the surgeon with an intraoperative deformity correction consistent with the surgical plan. Our aim was to report clinical and radiological outcomes using PSSR. We investigated rates of junctional complications both proximally [kyphosis (PJK) and failure (PJF)] and distally [failure (DJF)]. Methods: Prospective case series of 20 consecutive patients who underwent ≥4 level ASD surgery with PSSR at a single institution between January 2019 and December 2022. Preoperative, 6-week, 6-month, 12-month, 24-month, and final follow-ups assessed patient satisfaction (Ottawa decision regret questionnaire) and patient reported outcome measures (PROMs) [visual analogue scale (VAS; Back/Leg), Oswestry disability index (ODI), and 12-Item Short Form Survey (SF-12)]. Sagittal spinopelvic parameters [sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence and lumbar lordosis mismatch (PI-LL)] measured by serial EOS scans were performed preoperatively then compared to planned correction and postoperative measures. Interoperative cages (narrow/wide) were placed for interbody support. PJK risk score assessed likelihood of developing kyphosis. Serial computed tomography (CT) imaging assessed complication (fusion/subsidence). Results: The mean age of the patients (75% female) was 71.9±6.9 years, and the mean follow-up was 25.2±8.6 [7-40] months. Preoperative mean PROMs showed statistically significant overall improvement (P<0.001) postoperatively to final follow-up. Four patients without wide footprint cages at L4/5 or L5/S1, suffered DJF and reported regret undergoing surgery. Statistically significant difference (P<0.001) between preoperative and surgical plan in SVA and PI-LL but not in PT (P=0.058). No statistically significant difference in surgical plan versus the postoperative SVA, PI-LL, and PT (due to difficulty achieving the surgical plan, and also to maintaining the correction). One patient suffered PJF. There was a mean proximal kyphotic angle (PKA) of 17.8±13.0 degrees and PJK risk score of 3.7±1.0 with 40% who experienced PJK. No rod breakages were observed. Conclusions: In this series, PSSR improved PROMs and treated ASD. Sagittal parameters planned preoperatively correlated with postoperative correction. PJF was reduced, compared to the literature (35%), but PJK was observed over time. DJF occurred and was related to the absence of interbody cages at the lumbosacral junction and decisional regret.

Who bleeds during elective anterior lumbar surgery?

Background: Blood loss (BL) during elective anterior lumbar access for interbody fusion or disc replacement is a potentially major complication. This study sought to identify factors other than major vascular injury which contribute to BL and therefore this risk. Factors suggested to effect blood loss include age, increasing body mass index (BMI), sex, prothesis, intraoperative heparinization and continuation of low-dose aspirin (LD-ASA). Methods: A Cell Saver was used in all cases with BL measured and recorded by an independent autotransfusionist. Heparin was administered intravenously when one or both of 2ndtoe saturation metre signal/s lost pulsatility indicating lower limb arterial flow was interrupted. Results: The mean age of the 364 patients was 47 ± 13.2 yrs. [95% CI: 45 - 48]; and 191 (52%) were male. Age, BMI and heparinization showed a positive correlation with increased BL. There was no significant association with continuation of low-dose ASA with increased BL. Most patients underwent an ALIF - 265 (72%), 52 (14%) had a TDR, and 47 (13%) had a hybrid operation. There was a significant increase in mean BL between single- and two-level procedures in the non-heparinised group (48 vs 83 mls, p = 0.003). Intraoperative heparinization was administered in 102 patients (28%). The total mean BL for the heparin group (104 ml) which was significantly higher than for the non-heparin group (53 ml) (p = 0.001). Heparinisation did not significantly increase the mean BL in single or double level ALIF patients but did significantly increase the BL in single level TDR (57 vs 151 mls, p = 0.039). Conclusions: Younger, leaner, non-heparinized, single level ALIF patients represented the lowest bleeding risk in anterior lumbar surgery. Conversely, older, increasing BMI, two operative levels, TDR prosthesis and heparinization represent the highest bleeding risk. Continuation of LD-ASA was not associated with an increase in BL.

Negotiating for new technologies: guidelines for the procurement of assistive technologies in spinal surgery: a narrative review.

Background and Objective: This is a narrative review with the objective to discuss available assistive technologies for spinal surgery. Characteristics, costs, and compatibility of the different systems are summarized and recommendations made regarding acquiring these technologies. The availability of assistive technologies in spine surgery continues to evolve rapidly. The literature is lacking a collective summary of the available technologies and guidelines for acquisition. This is a narrative review which (I) presents an up-to-date summary of the currently available assistive technologies in spinal surgery; (II) makes comment on the utility of imaging, navigation, and robotics; (III) makes recommendations for the utility of the platform based on hospital size and (IV) discuss factors involved in negotiating for the purchase of these new technologies. Methods: We assemble the most up-to-date collection of description, characteristics and pricing of assistive technologies in spinal surgery. We compare and contrast these technologies and make recommendations regarding acquisition. Key Content and Findings: These technologies require a learning-curve for the surgeon and the operating room staff to understand how to use them efficiently. Surgeons need to be involved in the process of purchase decisions. Surgeons occupy a unique position in the health care infrastructure as their approach to care has significant ramifications on both the quality and cost of care. Surgeons should maintain conviction that their training and practice has allowed the use of these technologies to provide safer and more effective care for patients. Conclusions: Assistive technologies and prostheses for spinal fusion are evolving rapidly. This article serves as an encompassing reference to the current technologies. These technologies will play a significant role in the delivery of spinal health care in the future. All stakeholders stand to benefit from the increased value these technologies bring to patient care.

Expandable Lateral Lumbar Cages With Integrated Fixation: A Viable Option for Rostral Adjacent Segment Disease.

BACKGROUND: Adjacent segment disease (ASD) above a previous posterior lumbar instrumented fusion can be managed with minimally invasive lateral lumbar interbody fusion. Earlier procedures with stand-alone lateral cages risked nonunion, and lateral cages with separate lateral plates risked lumbar plexus injury and vertebral fracture. We investigated clinical and radiographic outcomes of an expandable lateral titanium interbody cage with an integrated lateral fixation (eLLIFp) device as a stand-alone treatment for symptomatic ASD above a previous posterior lumbar fusion and performed a comparative cost analysis of eLLIFp to alternative operations for ASD. METHODS: In this prospective, observational study, patients with ASD above 1-, 2-, 3-, or 4-level instrumented posterior fusions underwent surgery with lateral expandable titanium cage(s) with an integrated lateral plate with single screws into each adjacent vertebra from August 2017 to August 2019. Multimodality intraoperative neural monitoring was performed. Patient-reported outcomes, computed tomography outcomes, and total costs were analyzed. RESULTS: A total of 33 patients received 35 eLLIFp cages. All clinical outcomes improved significantly. The eLLIFp cages added 2.2° segmental lordosis and 2.7 mm posterior disc height. Interbody fusion rate was 94% at 12 months. There were 2 neurologic complications (6%): 1 patient reported transient anterior thigh numbness and 1 had mild persistent L4 radiculopathy. No cage subsidence, cage migration, screw loosening, or vertebral fracture occurred. No revision lateral surgery, posterior decompression, or supplemental posterior fixation was required. The total eLLIFp cost (AU$19,715) was lower than the cost for all other procedures. CONCLUSIONS: eLLIFp provided a minimally invasive, low morbidity, cost-effective, and robust alternative to traditional posterior construct extension surgery for rostral lumbar ASD in selected patients with 1- to 2-level stenosis and minimal deformity. CLINICAL RELEVANCE: Traditional ASD treatment involves substantial risks and expense. eLLIFp should be considered a safe, effective, and lower cost alternative to posterior construct extension surgery.

Do evoked potentials matter? Pre-pathologic signal change and clinical outcomes with expandable cages in lateral lumbar interbody fusion surgery.

Minimally Invasive Lateral Lumbar Interbody Fusion (MIS LLIF) is a reliable technique for treatment of degenerative disk disease, foraminal stenosis and spinal deformity. The retroperitoneal transpsoas approach risks lumbar plexus injury that may result in anterior thigh pain, sensory loss and weakness. A prospective study of 64 consecutive patients undergoing MIS LLIF with expandable cages (23 standalone, 41 integrated with lateral plate) using multimodal electrophysiological monitoring was performed. We measured sequential retraction times, complications, patient reported outcome scores and electrophysiologic findings with a minimum 12-month follow-up. Incidence of evoked potential and electromyographic signal change was moderate, and rarely resulted in post-operative neurologic deficit. Evoked potential signal changes were frequently resolved by the un-breaking of the surgical table or repositioning of the retractor. Average retraction times were 24 (15-41) minutes for standalone cages and 30 (15-41) minutes for integrated cages. At follow-up, the vast majority (97%) of patients reported significant clinical improvement post-operatively with only 2 patients reporting postoperative neurologic symptoms and subsequent recovery at 12-months. The present study shows that evoked potentials combined with electromyography is a more sensitive measure of pre-pathologic lumbar plexopathy in LLIF compared to electromyography alone, especially at L3/4 and L4/5 levels. Based on our findings, there is limited clinical indication for routine neural monitoring at rostral lumbar levels. The routine inclusion of multimodal electrophysiological monitoring in lateral transpsoas surgery is recommended to minimise the risk of neural injury by enabling optimal patient and retractor positioning and continued surveillance throughout the procedure.

Recombinant human bone morphogenetic protein-2 in spine surgery: recommendations for use and alternative bone substitutes-a narrative review.

Background and Objective: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been extensively studied in preclinical, animal, and human studies and has been used widely in spine fusion surgery. Evidence demonstrates that fusion rates with rhBMP-2 are similar to or higher than those achieved with autologous bone graft. However, there have been concerns regarding the cost, optimal dosage, and potential complications of rhBMP-2 use in spine surgery. The objective of this paper is to provide a current review of the available evidence regarding rhBMP-2 and other bone graft substitutes used for spinal surgery. Methods: We searched Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, and Database of Abstracts of Review of Effectiveness for 2 studies regarding physiology of bone fusion in spine surgery, formulations and indications of rhBMP-2, cancer risk of rhBMP-2, and alternatives to rhBMP-2 published from 1965 to 2022 in English. Key Content and Findings: The debate regarding indications and cost effectiveness of rhBMP-2 is presented based on increasing data and use criteria. Here, we focus on the effectiveness and economic costs (both direct and indirect) of rhBMP-2 and alternative bone graft substitutes. Based on the cumulative literature, we provide recommendations for rhBMP-2 use in spine surgery. Conclusions: Based on our review of the literature, we recommend the following: (I) clear informed consent processes between surgeons and patients regarding current evidence of the benefits and risks of using rhBMP-2 and available alternative bone graft substitutes. (II) Consideration of rhBMP-2 for spinal fusion surgery (excluding anterior cervical procedures), especially adult spinal deformity (ASD) surgery, lumbar surgery for multilevel degenerative disease, revision surgery for pseudoarthrosis, and surgery in patients with a low-quantity or low-quality autograft. (III) Regulatory oversight of the type, volume, and dose of bone graft substitute (both per level and per procedure) to ensure appropriate indications, prevent excessive usage, and thereby enhance cost containment.

Comparison of novel machine vision spinal image guidance system with existing 3D fluoroscopy-based navigation system: a randomized prospective study.

BACKGROUND CONTEXT: The use of spinal image guidance systems (IGS) has increased patient safety, accuracy, operative efficiency, and reduced revision rates in pedicle screw placement procedures. Traditional intraoperative 3D fluoroscopy or CT imaging produces potentially harmful ionizing radiation and increases operative time to register the patient. An IGS, FLASH Navigation, uses machine vision through high resolution stereoscopic cameras and structured visible light to build a 3D topographical map of the patient's bony surface anatomy enabling navigation use without ionizing radiation. PURPOSE: We aimed to compare FLASH navigation system to a widely used 3D fluoroscopic navigation (3D) platform by comparing radiation exposure and pedicle screw accuracy. DESIGN: A randomized prospective comparative cohort study of consecutive patients undergoing open posterior lumbar instrumented fusion. PATIENT SAMPLE: Adults diagnosed with spinal pathology requiring surgical treatment and planning for open posterior lumbar fusion with pedicle screws implanted into 1-4 vertebral levels. OUTCOME MEASURES: Outcome measures included mean intraoperative fluoroscopy time and dose, mean CT dose length product (DLP) for preoperative and day 2 CT, pedicle screw accuracy by CT, estimated blood loss and revision surgery rate. METHODS: Consecutive patients were randomized 1:1 to FLASH or 3D and underwent posterior lumbar instrumented fusion. Radiation doses were recorded from pre- and postoperative CT and intraoperative 3D fluoroscopy. 2 independent blinded radiologists reviewed pedicle screw accuracy on CT. RESULTS: A total of 429 (n=210 FLASH, n=219 3D) pedicle screws were placed in 90 patients (n=45 FLASH, n=45 3D) over the 18-month study period. Mean age and indication for surgery were similar between both groups, with a non-significantly higher ratio of males in the 3D group. Mean intraoperative fluoroscopy time and doses were significantly reduced in FLASH compared to 3D (4.51±3.71s vs 79.6±23.0s, p<.001 and 80.9±68.1cGycm2 vs 3704.1±3442.4 cGycm2, p<.001, respectively). This represented a relative reduction of 94.3% in the total intraoperative radiation time and a 97.8% reduction in the total intraoperative radiation dose. Mean preoperative CT DLP and mean day 2 postoperative CT DLP were significantly reduced in FLASH compared to 3D (662.0±440.4mGy-cm vs 1008.9±616.3 mGy-cm, p<.001 and 577.9±294.3 mGy-cm vs 980.7±441.6 mGy-cm, p<.001, respectively). This represented relative reductions of 34.4% and 41.0% in the preoperative CT dose and postoperative total DLP, respectively. The FLASH group required an average of 1.2 registrations in each case with an average of 2447 (±961.3) data points registered with a mean registration time of 106s (±52.1). A rapid re-registration mechanism was utilized in 22% (n=10/45) of cases and took 22.7s (±11.3). Re-registration was used in 7% (n=3/45) in the 3D group. Pedicle screw accuracy was high in FLASH (98.1%) and 3D (97.3%) groups with no pedicle breach >2mm in either group (p<.001). EBL was not statistically different between the groups (p=.38). No neurovascular injuries occurred, and no patients required return to theatre for screw repositioning. CONCLUSIONS: FLASH and 3D IGS demonstrate high accuracy for pedicle screw placement. FLASH showed significant reduction in intraoperative radiation time and dose with lower but non-significant blood loss. FLASH showed significant reduction in preoperative and postoperative radiation, but this may be associated to the lower number of males/females preponderance in this group. FLASH provides similar accuracy to contemporary IGS without requiring 3D-fluoroscopy or radiolucent operating tables. Reducing registration time and specialized equipment may reduce costs.

Surface landmarks for anterior lumbar access: is fluoroscopy necessary?

BACKGROUND CONTEXT: Anterior lumbar fusion surgery is increasing by an estimated 24% annually in the United States. There is a paucity of precise anatomic guidelines to help surgeons determine the appropriate anterior access incision site. PURPOSE: The purpose of this study is to compare the available anterior surface landmarks for the L4/L5 and L5/S1 disk levels to the disk levels determined by fluoroscopy, with the goal of creating a guide for surgical incision sites in anterior lumbar access surgery. STUDY DESIGN: A prospective, observational cohort study of consecutive patients undergoing anterior lumbar spinal exposure for anterior lumbar interbody fusion (ALIF), total disk replacement (TDR), or a combination of the two procedures at levels L4/L5 and/or L5/S1. PATIENT SAMPLE: All patients (n=183) undergoing primary ALIF and/or TDR surgery from June 2018 to April 2021 at the study sites were assessed for inclusion, and 18 patients were excluded. The remaining 165 patients were included in the study, and a total of 208 surgical levels were exposed. OUTCOME MEASURES: Mean, standard deviation, and 95% confidence interval (CI) were calculated. At each level, the distance from the symphysis pubis to the target disk level (SD distance) and the distance from the symphysis pubis to the umbilicus (SU distance) were measured, and the SD/SU ratio was calculated. Paired 2-tailed t tests were used to assess significant differences (p<.05). An R2 (coefficient of determination) test was used to assess variability of the SD distance, SU distance, and SD/SU ratio at each level. METHODS: All physiologic and anatomic measures were collected prospectively by the investigators, including intraoperative measurements of SD and SU. Demographic and previous health history data were collected at the time of study enrollment. RESULTS: The mean age of the 165 study participants was 48±14 years (range 18-80 years), and 97 (61%) were male. A total of 208 disk levels were exposed: 140 at L5/S1 and 68 at L4/L5. For the L5/S1, the SD ranged from 0 to 12.5 cm, with a mean of 5.2±1.9 cm (95% CI 4.88-5.52). For the L4/L5 level, the SD ranged from 6 to 15.5 cm, with a mean of 10.7±2.3 cm (95% CI 10.2-11.2). SD/SU ratios at both levels were lower in overweight (body mass index [BMI] 25-29.9) and obese (BMI 30-34.9) groups than in normal body mass index groups. There was no significant difference in SD/SU ratios between females and males at either L5/S1 (p=.39) or L4/L5 (p=.66). CONCLUSION: Clinically important variability in SD distances (≥9.5 cm) was observed for both the L5/S1 and L4/L5 disk levels. SD/SU ratios provided more consistent estimates of disk location than SD distance alone, but they still displayed substantial variability. Thus, intraoperative fluoroscopy remains mandatory to accurately plan the surgical incision for anterior lumbar access surgery.

Can Central Sensitization After Injury Persist as an Autonomous Pain Generator? A Comprehensive Search for Evidence.

OBJECTIVE: To conduct a comprehensive search for evidence with regard to whether central sensitization after an injury can act as a persistent autonomous pain generator after the inducing injury has healed. METHODS: We searched Medline on PubMed and the Cochrane Library, screening 3,572 abstracts, from which 937 full-text articles were obtained, with 186 of these discarded as irrelevant to the question being posed. The remaining 751 articles were studied for evidence. RESULTS: Fourteen publications were judged to provide weak evidence for the hypothesis of central sensitization as a persisting autonomous pain generator, but none addressed the question directly. No strong evidence for the affirmative answer was found. Sixty-one publications were judged to provide weak evidence for a negative answer, and ten were judged to provide strong evidence. Unexpectedly, serious weaknesses were discovered in the literature underpinning the validity of the clinical diagnosis of central sensitization in humans: 1) inappropriate extrapolation, in many publications, of laboratory animal data to humans; 2) failure to demonstrate the absence of peripheral pain generators that might be perpetuating central sensitization; and 3) many factors now shown to confound what is being measured by quantitative sensory testing, conditioned pain modulation, and the Central Sensitization Inventory. CONCLUSIONS: We found no evidence proving that central sensitization can persist as an autonomous pain generator after the initiating injury has healed. Our review has also shown that the evidential basis for the diagnosis of central sensitization in individual patients is seriously in question.

Modic Changes on Magnetic Resonance Imaging and Smoking History Predict Vascular Adherence During Anterior Lumbar Exposure.

BACKGROUND: Anterior approaches to surgically access the lumbar intervertebral discs are associated with a risk of developing major vascular injury and bleeding. The likelihood of injury increases in the presence of dense adherence between the disc annulus, vertebral periosteum, and vessels, which result from reactive inflammatory changes that cause fibrous scarring. OBJECTIVE: To identify factors that predict vascular adherence, which may facilitate preoperative planning and technique modifications for anterior spine surgery. STUDY DESIGN: Prospective study examining patients undergoing anterior retroperitoneal exposure for lumbar disc surgery. METHODS: A total of 246 consecutive patients were enrolled in this study, all of whom had anterior retroperitoneal exposure for lumbar disc surgery. Patient demographics, smoking status, magnetic resonance imaging (MRI) findings, operative parameters, and dissection difficulty associated with vascular adherence were recorded. Current smokers were defined as those who smoked at the time of surgery or had ceased smoking <6 months before the operation. Patients were excluded if they were morbidly obese or had previously undergone anterior spine surgery or radiotherapy. RESULTS: A multivariate regression analysis identified 2 significant risk factors for difficult dissections that are complicated by vascular adhesion: Modic Type 2 changes on MRI (P = 0.009) and any history of smoking (P = 0.007). Patients with Modic Type 2 changes or a smoking history were 2.1 and 2.2 times more likely to present with vascular adherence, respectively. CONCLUSIONS: Modic Type 2 changes on MRI and any smoking history can predict the adherence of large blood vessels to the anterior disc annulus, which enhances the difficulty of the dissection. These predictors could indicate to spinal surgeons that the patient has a 2-fold increased risk of vascular adherence. CLINICAL RELEVANCE: Modic Type 2 changes on MRI and any smoking history can predict the adherence of large blood vessels to the anterior disc annulus, which enhances the difficulty of the dissection. These predictors could indicate to spinal surgeons that the patient has a 2-fold increased risk of vascular adherence during anterior lumbar exposure. LEVEL OF EVIDENCE: 3.

What should my hospital buy next?-Guidelines for the acquisition and application of imaging, navigation, and robotics for spine surgery.

The range of assistive technology options available for spinal fusion surgery has significantly increased. However, surgeons and hospital administrators may lack sufficient information to compare options and make purchasing decisions. We summarize currently available navigation, robotics, and imaging technologies for spinal surgery, highlighting key characteristics, utility, differences, price, and compatibility with other technologies and spinal implants. Guidelines for optimal use and combinations are provided based on surgical approach, operative site, patient anatomy, optimal image quality, and workflow efficiency. Key recommendations include the following. (I) Open-platform navigation and robotics systems that provide surgeons with access to all software and hardware features regardless of implant choice are preferred. (II) Imaging systems that have maximum compatibility with navigation and robotics platforms are optimal. (III) Navigation systems that offer a universal registration mechanism should be standard. (IV) 3D fluoroscopy provides the greatest benefit when speed, operative efficiency, and mobility are required. (V) Intraoperative CT is more useful for imaging long constructs, high BMI, or cervicothoracic anatomy. (VI) Radiation safety awareness that new 3D-fluoroscopy units can deliver radiation comparable to that of CT is needed. (VII) New robotic arm platforms require more clinical and health economic data to justify increased costs.

Anterior lumbar interbody fusion in a lateral decubitus position: technique and outcomes in obese patients.

BACKGROUND: Multilevel lumbar interbody fusion (LIF) surgery in obese patients is problematic, with positioning and anaesthetic risks during posterior approaches, vascular and visceral complications during anterior approaches, and lack of access to L5/S1 during lateral approaches. Modified anterior LIF (ALIF) via an anterolateral retroperitoneal approach in the lateral decubitus position permits access to L3/4, L4/5, and L5/S1 levels without patient repositioning. This study reports our initial experience with this lateral ALIF in obese patients and describes modifications of existing lateral and anterior techniques. METHODS: We retrospectively analysed a prospectively maintained registry including the first 30 consecutive patients who underwent lateral ALIF. In all patients, supine ALIF was relatively contraindicated because of obesity or previous abdominal surgery. All patients had a body mass index (BMI) ≥30 kg/m2. Fusion was assessed by high-definition computed tomography. Patient-reported outcomes included visual analogue scale pain scores, Oswestry Disability Index (ODI), and 36-Item Short-Form Survey (SF-36) physical and mental component scores (PCS and MCS). All patients underwent ≥2 years follow-up. RESULTS: At last follow-up (mean, 35.0 months) mean back pain improved 64%, leg pain improved 67%, ODI improved 54%, and PCS and MCS both improved 37% (P<0.05 versus preoperative for all). Mean BMI was unchanged postoperatively (P=0.83). Complications occurred in 7 (23%) patients: dysesthesia [2], retroperitoneal hematoma [2], radiculopathy [1], and subsidence [2]. Solid interbody fusion occurred in 19 (63%) patients at 12 months postoperatively and in 26 (87%) patients at 24 months. CONCLUSIONS: Lateral ALIF enables L5/S1 anterior fusion in obese patients and permits multilevel fusion using a single position. Satisfactory clinical outcomes and complication rates are achieved despite unchanged BMI and 87% radiological fusion rates. Lateral ALIF appears to be a reasonable alternative to posterior, lateral, and supine-position anterior approaches for L3/4, L4/5, and L5/S1 interbody fusions.

Early experience of placing image-guided minimally invasive pedicle screws without K-wires or bone-anchored trackers.

OBJECTIVE Image guidance for spine surgery has been reported to improve the accuracy of pedicle screw placement and reduce revision rates and radiation exposure. Current navigation and robot-assisted techniques for percutaneous screws rely on bone-anchored trackers and Kirchner wires (K-wires). There is a paucity of published data regarding the placement of image-guided percutaneous screws without K-wires. A new skin-adhesive stereotactic patient tracker (SpineMask) eliminates both an invasive bone-anchored tracker and K-wires for pedicle screw placement. This study reports the authors' early experience with the use of SpineMask for "K-wireless" placement of minimally invasive pedicle screws and makes recommendations for its potential applications in lumbar fusion. METHODS Forty-five consecutive patients (involving 204 screws inserted) underwent K-wireless lumbar pedicle screw fixation with SpineMask and intraoperative neuromonitoring. Screws were inserted by percutaneous stab or Wiltse incisions. If required, decompression with or without interbody fusion was performed using mini-open midline incisions. Multimodality intraoperative neuromonitoring assessing motor and sensory responses with triggered electromyography (tEMG) was performed. Computed tomography scans were obtained 2 days postoperatively to assess screw placement and any cortical breaches. A breach was defined as any violation of a pedicle screw involving the cortical bone of the pedicle. RESULTS Fourteen screws (7%) required intraoperative revision. Screws were removed and repositioned due to a tEMG response < 13 mA, tactile feedback, and 3D fluoroscopic assessment. All screws were revised using the SpineMask with the same screw placement technique. The highest proportion of revisions occurred with Wiltse incisions (4/12, 33%) as this caused the greatest degree of SpineMask deformation, followed by a mini midline incision (3/26, 12%). Percutaneous screws via a single stab incision resulted in the fewest revisions (7/166, 4%). Postoperative CT demonstrated 7 pedicle screw breaches (3%; 5 lateral, 1 medial, 1 superior), all with percutaneous stab incisions (7/166, 4%). The radiological accuracy of the SpineMask tracker was 97% (197/204 screws). No patients suffered neural injury or required postoperative screw revision. CONCLUSIONS The noninvasive cutaneous SpineMask tracker with 3D image guidance and tEMG monitoring provided high accuracy (97%) for percutaneous pedicle screw placement via stab incisions without K-wires.

Early experience with lateral lumbar total disc replacement: Utility, complications and revision strategies.

Lumbar total disc replacement (TDR) is an alternative to interbody fusion for the treatment of symptomatic degenerative disc disease. Traditionally, lumbar TDR is performed via an anterior retroperitoneal approach with regional risks of vascular and visceral injury. The direct lateral retroperitoneal, transpsoas approach avoids mobilisation of the great vessels and preserves the anterior longitudinal ligament, thereby maintaining physiological limits on motion. This study aimed to (i) report one site's early experience with lateral lumbar TDR and (ii) provide case examples illustrating the utility, complications and revision strategies of the XL-TDR device. Data were collected prospectively on the first 12 consecutive patients treated with XL-TDR. Patient outcomes included pain (VAS), disability (ODI), and quality of life (SF-36 PCS and MCS). Mean follow-up was 27.5months (range 18-48months). Patients had significant improvements in back (74%) and leg (50%) pain, ODI (69%), PCS (50%) and MCS (39%) (P<0.05). Two patients had early prosthesis dislocation due to prosthesis undersizing. The same skin incision was used to retrieve the XL-TDR and perform salvage lateral lumber interbody fusion, with solid fusion by 12months. Lumbar TDR using the XL-TDR via a lateral transpsoas muscle-splitting approach is a minimally invasive alternative to anterior retroperitoneal exposures for motion preservation. Correct sizing of the XL-TDR and complete contralateral annulectomy with annulus box cutters mitigates the risk of lateral dislocation. Revision surgery for lateral dislocation of the XL-TDR is more straightforward compared to anterior TDR dislocation.

Maintenance of Segmental Lordosis and Disk Height in Stand-alone and Instrumented Extreme Lateral Interbody Fusion (XLIF).

STUDY DESIGN: A prospective single-surgeon nonrandomized clinical study. OBJECTIVE: To evaluate the radiographic and clinical outcomes, by fixation type, in extreme lateral interbody fusion (XLIF) patients and provide an algorithm for determining patients suitable for stand-alone XLIF. SUMMARY OF BACKGROUND DATA: XLIF may be supplemented with pedicle screw fixation, however, since stabilizing structures remain intact, it is suggested that stand-alone XLIF can be used for certain indications. This eliminates the associated morbidity, though subsidence rates may be elevated, potentially minimizing the clinical benefits. MATERIALS AND METHODS: A fixation algorithm was developed after evaluation of patient outcomes from the surgeon's first 30 cases. This algorithm was used prospectively for 40 subsequent patients to determine the requirement for supplemental fixation. Preoperative, postoperative, and 12-month follow-up computed tomography scans were measured for segmental and global lumbar lordosis and posterior disk height. Clinical outcome measures included back and leg pain (visual analogue scale), Oswestry Disability Index (ODI), and SF-36 physical and mental component scores (PCS and MCS). RESULTS: Preoperatively to 12-month follow-up there were increases in segmental lordosis (7.9-9.4 degrees, P=0.0497), lumbar lordosis (48.8-55.2 degrees, P=0.0328), and disk height (3.7-5.5 mm, P=0.0018); there were also improvements in back (58.6%) and leg pain (60.0%), ODI (44.4%), PCS (56.7%), and MCS (16.1%) for stand-alone XLIF. For instrumented XLIF, segmental lordosis (7.6-10.5 degrees, P=0.0120) and disk height (3.5-5.6 mm, P<0.001) increased, while lumbar lordosis decreased (51.1-45.8 degrees, P=0.2560). Back (49.8%) and leg pain (30.8%), ODI (32.3%), PCS (37.4%), and MCS (2.0%) were all improved. Subsidence occurred in 3 (7.5%) stand-alone patients. CONCLUSIONS: The XLIF treatment fixation algorithm provided a clinical pathway to select suitable patients for stand-alone XLIF. These patients achieved positive clinical outcomes, satisfactory fusion rates, with sustained correction of lordosis and restoration of disk height.

Anterior lumbar interbody fusion (ALIF) as an option for recurrent disc herniations: a systematic review and meta-analysis.

BACKGROUND: Recurrent intervertebral disc herniation is a relatively common occurrence after primary discectomy for lumbar intervertebral disc herniation. For recurrent herniations after repeat discectomies, a growing body of evidence suggests that fusion is effective in appropriately selected cases. Theoretically, anterior lumbar interbody fusion (ALIF) allows for comprehensive discectomy, less trauma to spinal nerves and paraspinal muscles and avoidance of the disadvantages of repeat posterior approaches. However, ALIF has also been associated with risk of vascular injury and retrograde ejaculation. This current systematic review and meta-analysis aims to assess the viability of ALIF as a surgical treatment for recurrent disc herniations. METHODS: Seven studies were identified from six electronic databases and secondary reference lists. Pre-defined endpoints were extracted from the included studies and meta-analyzed. RESULTS: For the 181 patients from included studies, ALIF resulted in significant average improvements in Oswestry Disability Index (ODI) scores (50.49%, P<0.001), Visual Analogue Scale (VAS) back pain scores (47.85%, P<0.001) and VAS leg pain scores (37.00%, P<0.001). Average blood loss was acceptable at 122 mL (P<0.001) and average operation duration was 89 minutes (P<0.001). Average hospital stay was 5.28 days (P<0.001). Only 22 perioperative complications were reported, with subsidence the most commonly reported complication. CONCLUSIONS: Pooled evidence suggests that ALIF is a feasible approach for the treatment of recurrent disc herniations, demonstrating significant improvements in back and leg pain and minimal complications. These findings warrant further investigation in large prospective registries and multi-center studies.