The rate of fusion for stand-alone anterior lumbar interbody fusion: a systematic review

Enhancing the Technical Pearls for L5-S1 Anterior Lumbar Interbody Fusion in Patients with Body Mass Index More Than 30: Clinical and Radiographic Outcomes at 1-Year Follow-Up

BACKGROUND

Performing anterior lumbar interbody fusion (ALIF) in patients with a body mass index (BMI) >30 presents surgical challenges. To overcome those challenges, a modified procedure is described.

METHODS

This study retrospectively reviewed patients with a BMI >30 who underwent the modified L5-S1 ALIF procedure from August 2017 to September 2023. Patient demographic and operative characteristics were collected. Clinical and radiographic outcomes were analyzed before surgery and at 1-year follow-up. An analysis was performed comparing patients with a BMI >30 who underwent the modified ALIF procedure versus the standard ALIF procedure.

RESULTS

A total of 26 patients with BMI >30 were evaluated. Thirteen received treatment with the modified ALIF technique, and 13 received treatment with the standard ALIF technique. Operative time was significantly shorter in the modified ALIF technique cohort (P = 0.006). Preoperative and postoperative radiographic findings indicated significant differences in anterior disc height (P < 0.001), posterior disc height (P = 0.02), and L5-S1 segmental lordosis (P < 0.001) in patients undergoing the modified ALIF technique. There were no intraoperative complications. Postoperative visual analog scale for back pain, visual analog scale for leg pain, and Oswestry Disability Index scores significantly improved after surgery (P < 0.05) in both cohorts after 1 year. Complete interbody fusion was achieved according to computed tomography evaluation 1 year after surgery in more than 80% of cases.

CONCLUSIONS

ALIF surgery is a safe technique to address lumbar pathologies. This operative technique provides complimentary abdominal exposure data for access surgeons while performing ALIFs in patients with BMI >30. This technique could reduce operative time in such patients.

Retrospective analysis of medium-term outcomes following anterior lumbar interbody fusion surgery performed in a tertiary spinal surgical centre

INTRODUCTION

Anterior lumbar interbody fusion (ALIF) can treat spondylolisthesis, degenerative disc disease and pseudoarthrosis. This approach facilitates complete discectomy, disc space distraction, indirect decompression of neural foramina and placement of large interbody devices. Several intra- and postoperative complications can be attributed to the anterior approach: vascular/visceral injury, hypogastric plexus injury and urogenital consequences. Spine-specific complications include implant migration, graft failure, pseudoarthrosis and persistent symptomology.

METHODS

This retrospective study reviewed patient demographics, medium-term outcomes and complication rates following ALIF surgery performed over a 5-year period. A total of 110 consecutive patients had undergone ALIF surgery at a single tertiary spinal centre. The database was reviewed with a primary outcome of identifying postoperative 90-day complications and whether a revision anterior operation was required after primary ALIF.

RESULTS

No patients required revision anterior operation after their primary ALIF surgery by final follow-up. Out of 110 patients, 11 (10%) recorded a complication attributed to the anterior stage of their operation within 90 days.

CONCLUSIONS

Our 90-day complication rate of 10% lies within the 2.6% acute complication and 40% overall complications rates described in previous literature. The risk of vascular/visceral injury is significant (3%) and we recommend that ALIF be performed as a dual surgeon procedure with a vascular-trained access surgeon accompanying the spinal surgeon. ALIF is a valid revision surgical option for failed posterior approaches leading to complications such as pseudoarthrosis. In our sample, 89% of patients were managed with posterior fixation to augment the anterior fusion as, biomechanically, this is a proven construct.

Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength

Background

In anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs.

Methods

Three bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force.

Results

The failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295).

Conclusion

In our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

Comparing the osteogenesis outcomes of different lumbar interbody fusions (A/O/X/T/PLIF) by evaluating their mechano-driven fusion processes

BACKGROUND

In lumbar interbody fusion (LIF), achieving proper fusion status requires osteogenesis to occur in the disc space. Current LIF techniques, including anterior, oblique, lateral, transforaminal, and posterior LIF (A/O/X/T/PLIF), may result in varying osteogenesis outcomes due to differences in biomechanical characteristics.

METHODS

A mechano-regulation algorithm was developed to predict the fusion processes of A/O/X/T/PLIF based on finite element modeling and iterative evaluations of the mechanobiological activities of mesenchymal stem cells (MSCs) and their differentiated cells (osteoblasts, chondrocytes, and fibroblasts). Fusion occurred in the grafting region, and each differentiated cell type generated the corresponding tissue proportional to its concentration. The corresponding osteogenesis volume was calculated by multiplying the osteoblast concentration by the grafting volume.

RESULTS

TLIF and ALIF achieved markedly greater osteogenesis volumes than did PLIF and O/XLIF (5.46, 5.12, 4.26, and 3.15 cm3, respectively). Grafting volume and cage size were the main factors influencing the osteogenesis outcome in patients treated with LIF. A large grafting volume allowed more osteoblasts (bone tissues) to be accommodated in the disc space. A small cage size reduced the cage/endplate ratio and therefore decreased the stiffness of the LIF. This led to a larger osteogenesis region to promote osteoblastic differentiation of MSCs and osteoblast proliferation (bone regeneration), which subsequently increased the bone fraction in the grafting space.

CONCLUSION

TLIF and ALIF produced more favorable biomechanical environments for osteogenesis than did PLIF and O/XLIF. A small cage and a large grafting volume improve osteogenesis by facilitating osteogenesis-related cell activities driven by mechanical forces.

Primary anterior lumbar interbody fusion, with and without posterior instrumentation: a 1,377-patient cohort from a multicenter spine registry

BACKGROUND CONTEXT

Lumbar interbody instrumentation techniques are common and effective surgical options for a variety of lumbar degenerative pathologies. Anterior lumbar interbody fusion (ALIF) has become a versatile and powerful means of decompression, stabilization, and reconstruction. As an anterior only technique, the integrity of the posterior muscle and ligaments remain intact. Adding posterior instrumentation to ALIF is common and may confer benefits in terms of higher fusion rate but could contribute to adjacent segment degeneration due to additional rigidity. Large clinical studies comparing stand-alone ALIF with and without posterior supplementary fixation (ALIF+PSF) are lacking.

PURPOSE

To compare rates of operative nonunion and adjacent segment disease (ASD) in ALIF with or without posterior instrumentation.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Adult patients (≥18 years old) who underwent primary ALIF for lumbar degenerative pathology between levels L4 to S1 over a 12-year period. Exclusion criteria included trauma, cancer, infection, supplemental decompression, noncontiguous fusions, prior lumbar fusions, and other interbody devices.

OUTCOME MEASURES

Reoperation for nonunion and ASD compared between ALIF only and ALIF+PSF.

METHODS

Reoperations were modeled as time-to-events where the follow-up time was defined as the difference between the primary ALIF procedure and the date of the outcome of interest. Crude cumulative reoperation probabilities were reported at 5-years follow-up. Multivariable Cox proportional hazard regression was used to evaluate risk of operative nonunion and for ASD adjusting for patient characteristics.

RESULTS

The study consisted of 1,377 cases; 307 ALIF only and 1070 ALIF+PSF. Mean follow-up time was 5.6 years. The 5-year crude nonunion incidence was 2.4% for ALIF only and 0.5% for ALIF+PSF; after adjustment for covariates, a lower operative nonunion risk was observed for ALIF+PSF (HR=0.22, 95% CI=0.06-0.76). Of the patients who are deemed potentially suitable for ALIF alone, one would need to add posterior instrumentation in 53 patients to prevent one case of operative nonunion at a 5-year follow-up (number needed to treat). Five-year operative ASD incidence was 4.3% for ALIF only and 6.2% for ALIF+PSF; with adjustments, no difference was observed between the cohorts (HR=0.96, 95% CI=0.54-1.71).

CONCLUSIONS

While the addition of posterior instrumentation in ALIFs is associated with lower risk of operative nonunion compared with ALIF alone, operative nonunion is rare in both techniques (<5%). Accordingly, surgeons should evaluate the added risks associated with the addition of posterior instrumentation and reserve the supplemental posterior fixation for patients that might be at higher risk for operative nonunion. Rates of operative ASD were not statistically higher with the addition of posterior instrumentation suggesting concern regarding future risk of ASD perhaps should not play a role in considering supplemental posterior instrumentation in ALIF.

Clinical and Radiographic Outcomes of Anterior Lumbar Interbody Fusion With Anterior Plate Fixation

BACKGROUND

Reports on the outcomes following instrumented anterior lumbar interbody fusion (ALIF) with anterior plate fixation are limited. The aim of this study was to assess the clinical and radiographic outcomes of patients undergoing ALIF with anterior plate fixation.  Methods: Medical records and radiographic imaging were reviewed for 100 patients who received ALIF with anterior plate fixation between 2008 to 2021 and completed at least one year of follow-up and postoperative imaging. Prospectively collected patient data included indication for surgery, BMI, age, number and location of levels treated, complications, reoperation rates, fusion rate, and measurements of global lordosis, disc space height, and segmental angulation.  Results: A total of 100 patients were included in this study. The mean length of follow-up was 81.37 months. Changes in preoperative-to-postoperative Oswestry Disability Index (ODI) and Visual Analog Score (VAS) demonstrated improvements of 30.86% and 18.56%, respectively. Major vascular injuries occurred in 3% of the cases. A hardware failure rate of 5% was observed. The reoperation rate was 10%. The radiographic fusion rate derived from computed tomography (CT) and plain film was 95.45% and 88.87%, respectively. Postoperative global lordosis demonstrated a 6.08% increase. Postoperative segmental angulation measurements increased by 57.74%. No statistically significant differences in clinical or radiographic outcomes were observed based on the spine level of fusion or the number of fusions performed.  Conclusions: ALIF with anterior plate fixation achieved an adequate fusion rate with improvements in ODI and VAS scores meeting minimal clinically important difference thresholds. Postoperative disc space heights demonstrated significant improvements compared to preoperative measurements.

Cadaveric biomechanical studies of ADDISC total lumbar disc prosthesis

BACKGROUND

Most total disc replacements provide excessive mobility and not reproduce spinal kinematics, inducing zygapophyseal joint arthritic changes and chronic back pain. In cadaveric lumbosacral spines, we studied if a new lumbar disc prosthesis kinematics mimics the intact intervertebral disc.

METHODS

In eight cold preserved cadaveric lumbosacral spines, we registered the movement ranges in flexion, extension, right and left lateral bending, and rotation in the intact status, post-discectomy, and after our prosthesis implantation, comparing them for each specimen.

FINDINGS

Comparing the intact lumbosacral spine with the L4-L5 prosthesis implanted specimens, we saw statistically significant differences in lateral bending and right rotation but not in the full range of rotation. Analyzing segments, we also noticed statistically significant differences at L4-L5 in flexion-extension and rotation. On the other hand, the L4-L5 discectomy, compared to the baseline spine condition, showed a statistically significant mobility increase in flexion, extension, lateral bending, and axial rotation, with an abnormal instantaneous center of rotation, which destabilizes the segment partly due to anterior annulus surgical removal. Disc prosthesis implantation reversed these changes in instantaneous center of rotation, but the prosthesis failed to restore the initial range of motion due to the destabilization of the ligaments in the operated disc.

INTERPRETATION

The ADDISC total disc replacement reproduces the intact disc kinematics and Instantaneous Center of Rotation, but the prosthesis fails to restore the initial range of motion due to ligament destabilization. More studies will be necessary to define a technique that restores the damaged ligaments when implanting the prosthesis.

Anterior Lumbar Interbody Fusion in Elderly Patients: Peri- and Postoperative Complications and Clinical Outcome

BACKGROUND

 Anterior lumbar interbody fusion (ALIF) is an effective surgical technique for treating various lumbar pathologies, but its use in elderly patients is controversial. Data concerning complications and effectiveness are sparse. We investigated peri- and postoperative complications, radiographic parameters, and clinical outcome in elderly patients.

METHODS

 Patients ≥65 years who underwent ALIF between January 2008 and August 2020 were included in the study. All surgeries were performed through a retroperitoneal approach. Clinical and surgical data as well as radiologic parameters were collected prospectively and analyzed retrospectively.

RESULTS

 A total of 39 patients were included; the mean age was 72.6 (±6.3) years (range: 65-90 years); and the mean American Society of Anesthesiologists (ASA) risk classification was 2.3 (±0.6). A laceration of the left common iliac vein was the only major complication recorded (2.6%). Minor complications occurred in 20.5% of patients. Fusion rate was 90.9%. Reoperation rate at the index level was 12.8 and 7.7% in adjacent segments. The multidimensional Core Outcome Measures Index (COMI) improved from 7.4 (±1.4) to 3.9 (±2.7) after 1 year and to 3.3 (±2.6) after 2 years. Oswestry disability index (ODI) improved from 41.2 (±13.7) to 20.9 (±14.9) after 1 year and to 21.5 (±18.8) after 2 years. Improvements of at least the minimal clinically important change score of 2.2 and 12.9 points in the ODI and COMI after 2 years were noted in 75 and 56.3% of the patients, respectively.

CONCLUSION

 With careful patient selection, ALIF is safe and effective in elderly patients.

Postoperative Radiculitis After L5-S1 Anterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

This study aimed to examine postoperative radiculitis after isolated L5-S1 anterior lumbar interbody fusion (ALIF), determine which factors contribute to its development, and investigate the comparative outcomes of patients with versus without postoperative radiculitis.

SUMMARY OF BACKGROUND DATA

Both standalone and traditionalALIF are common and safe lumbar spine fusion techniques. Although optimal safety and effectiveness are achieved through appropriate patient selection, postoperative radiculitis after L5-S1 ALIF is a potential complication that seems to be the least predictable in the absence of iatrogenic injury.

PATIENTS AND METHODS

All adult patients (18-80 yr) with preoperative radiculopathies who underwent L5-S1 ALIF by 9 board-certified spine surgeons at a single academic institution from January 2016 to December 2021 with a minimum of 3 months follow-up were included. Patient records were assessed for data on clinical characteristics and patient-reported outcome scores (patient-reported outcome measures). All patient records were evaluated to determine whether postoperative radiculitis developed. Radiographic measurements using x-rays were completed using all available pre and postoperative imaging. Multivariable logistic regressions were performed utilizing radiculitis as the dependent variable and various independent predictor variables.

RESULTS

One hundred forty patients were included, 48 (34%) patients developed postoperative radiculitis, with symptom onset and resolution occurring at 14.5 and 83 days, respectively. The two groups had no differences in preoperative or postoperative radiographic parameters. Multivariable regression showed 3 independent predictors of postoperative radiculitis: methylprednisolone use [OR: 6.032; (95% CI: 1.670-25.568)], increased implant height [OR: 1.509; (95% CI: 1.189-1.960)], and no posterior fixation [OR: 2.973; (95% CI: 1.353-0.806)].

CONCLUSIONS

Of the 34% of patients who developed postoperative radiculitis after L5-S1 ALIF, it resolved on average within 3 months of surgery. These findings may help reduce the risk of undue short-term morbidity after isolated L5-S1 ALIF by informing preoperative counseling and intraoperative decision-making.

Measuring compressive loads on a 'smart' lumbar interbody fusion cage: Proof of concept

There are several complications associated with lumbar interbody fusion surgery however, pseudarthrosis (non-union) presents a multifaceted challenge in the postoperative management of the patient. Rates of pseudarthrosis range from 3 to 20 % in patients with healthy bone and 20 to 30 % in patients with osteoporosis. The current methods in post-operative follow-up - radiographs and CT, have high false positive rates and poor agreement between them. The aim of this study was to develop and test a proof-of-concept load-sensing interbody cage that may be used to monitor fusion progression. Piezoresistive pressure sensors were calibrated and embedded within a polyether ether ketone (PEEK) interbody cage. Silicone and poly (methyl methacrylate) (PMMA) were inserted in the graft regions to simulate early and solid fusion. The load-sensing cage was subjected to distributed and eccentric compressive loads up to 900 N between synthetic lumbar vertebral bodies. Under maximum load, the anterior sensors recorded a 56-58 % reduction in pressure in the full fusion state compared to early fusion. Lateral regions measured a 36-37 % stress reduction while the central location reduced by 45 %. The two graft states were distinguishable by sensor-recorded pressure at lower loads. The sensors more effectively detected left and right eccentric loads compared to anterior and posterior. Further, the load-sensing cage was able to detect changes in endplate stiffness. The proof-of-concept 'smart' cage could detect differences in fusion state, endplate stiffness, and loading conditions in this in vitro experimental setup.

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.

Application of Oblique Lateral Interbody Fusion Combined with Bridge-Locking Cage in Adjacent Segment Disease After Lumbar Fusion

OBJECTIVE

Adjacent segment disease (ASD) is considered any abnormal process that develops in the mobile segment next to spinal fusion, accompanied by related symptoms. To evaluate the efficacy and complications of oblique lateral interbody fusion (OLIF) combined with bridge-locking fusion on ASD after lumbar fusion.

METHODS

A total of 35 ASD patients who required re-operation after lumbar fusion in our hospital from March 2014 to March 2020 were retrospectively analyzed, among which 13 cases (seven males and six females; 62.3 ± 11.3 years old) received the treatment of OLIF + bridge-locking cage internal fixation (OLIF group), and 22 cases (14 males and eight females; 52.3 ± 17.8 years old) received the treatment of transforaminal lumbar interbody fusion (TLIF) + pedicle screw fixation (TLIF group). The comparison of the operation time, intraoperative blood loss, postoperative drainage volume, and length of hospital stay between the two groups of patients was performed using the t-test. The comparison of Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) at different time points before and after the operation was performed using analysis of variance for repeated measurement data. The fusion rate and postoperative complications of the two groups of patients were also evaluated.

RESULTS

The operation time of patients in the OLIF group (55.4 ± 12.4 min) was significantly shorter than that of patients in the TLIF group (94.3 ± 22.9 min) (P < 0.05), the length of stay of patients in the OLIF group (7.4 ± 2.3 day) was significantly shorter than that of patients in the TLIF group (12.4 ± 3.2 day) (P < 0.05); the intraoperative blood loss (62.2 ± 30.1 mL) and postoperative drainage (47.3 ± 22.4 mL) of patients in the OLIF group were significantly less than those of patients in the TLIF group with intraoperative blood loss (363.4 ± 120.2 mL) and postoperative drainage (285.5 ± 57.8 mL) (all Ps < 0.05). Besides, the VAS and ODI scores of the two groups of patients were improved 3 months after the operation and at the last follow-up (all Ps < 0.05). Three patients in the OLIF group developed complications such as hip flexion weakness and fusion cage sink, with an incidence of 23.1%. Three patients in the TLIF group developed complications including wound infection and intraoperative nerve injury, with an incidence of 22.7%.

CONCLUSION

The combination of OLIF and bridge-locking cage may be a safe and effective therapy for ASD patients after lumbar fusion operation.

Outcomes Following Direct Versus Indirect Decompression Techniques for Lumbar Spondylolisthesis: A Propensity-Matched Analysis

STUDY DESIGN

Retrospective review.

OBJECTIVE

The aim was to compare outcomes at 3 and 12 months for patients with lumbar spondylolisthesis treated with direct decompression (DD) versus indirect decompression (ID) techniques.

SUMMARY OF BACKGROUND DATA

Debate persists regarding the optimal surgical strategy to treat lumbar spondylolisthesis. Novel techniques relying on ID have shown superior radiographic outcomes compared to DD, however, doubt remains regarding their effectiveness in achieving adequate decompression. Currently, there is a paucity of data comparing the clinical efficacy of DD to ID.

METHODS

The Quality Outcomes Database (QOD), a national, multicenter prospective spine registry, was queried for patients who underwent DD and ID between April 2013 and January 2019. Propensity scores for each treatment were estimated using logistic regression dependent on baseline covariates potentially associated with outcomes. The propensity scores were used to exclude nonsimilar patients. Multivariable regression analysis was performed with the treatment and covariate as independent variables and outcomes as dependent variables.

RESULTS

A total of 4163 patients were included in the DD group and 86 in the ID group. The ID group had significantly lower odds of having a longer hospital stay and for achieving 30% improvement in back and leg pain at 3 months. These trends were not statistically significant at 12 months. There were no differences in ED5D scores or Oswestry disability index 30% improvement scores at 3 or 12 months. ID patient had a significantly higher rate of undergoing a repeat operation at 3 months (4.9% vs. 1.5%, P =0.015).

CONCLUSION

Our study suggests that both DD and ID for the treatment of lumbar spondylolisthesis result in similar clinical outcomes, with the exception that those treated with ID experienced a lower reduction in back and leg pain at 3 months and a higher 3-month reoperation rate. This data can provide surgeons with additional information when counseling patients on the pros and cons of ID versus DD surgery.

Obesity: An Independent Risk Factor for Complications in Anterior Lumbar Interbody Fusion? A Systematic Review

STUDY DESIGN

Systematic Review and Meta-analysis.

OBJECTIVES

Raised patient BMI is recognised as a relative contraindication to posterior lumbar interbody fusion (PLIF) due to the anaesthetic challenges, difficult positioning and increased intraoperative and postoperative complications, with the relative risk rising in patients with a BMI >25 kg/m2. The impact of obesity defined as a BMI > 30 kg/m² on Anterior Lumbar Interbody Fusion (ALIF) outcomes is not yet established. The aim of this review was to evaluate if the presence of a raised BMI in patients undergoing ALIF procedures was an independent risk factor for intra- and postoperative complications.

METHODS

A systematic review of search databases PubMed; Google Scholar and OVID Medline was made to identify studies related to complications in patients with increased body mass index during anterior lumbar interbody fusion. PRISMA guidelines were utilised for this review. Complication rates in raised BMI patient cohort was compared to normal BMI complication rates with meta-analysis where available.

RESULTS

315 articles returned with search criteria applied. Six articles were included for review, with 2190 patients included for analysis. Vascular complications in obese vs. non-obese patients undergoing the anterior approach demonstrate no significant difference in complication rates (P = .62; CI = -.03-.02). Obesity is found to result in an increased rate of overall complications (P = .002; CI = .04-.16).

CONCLUSIONS

Obesity was demonstrated to have an impact on overall complication rates in Anterior Lumbar Interbody Fusion procedures, with postoperative complications including wound infections and lower fusion rates more common in patients in increased BMIs. Increased focus on patient positioning and reporting of outcomes in this patient cohort is warranted to further evaluate perioperative complications.

Indirect Lumbar Decompression Combined With or Without Additional Direct Posterior Decompression: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

Indirect decompression via lateral lumbar interbody fusion (LLIF) can ameliorate central and foraminal lumbar stenosis. In severe central stenosis, additional posterior direct decompression is utilized. The aim of this review is to synthesize existing literature on these 2 techniques and identify significant differences in outcomes between isolated indirect decompression via LLIF and combined indirect decompression supplemented with direct posterior decompression.

METHODS

A database search algorithm was utilized to query MEDLINE, COCHRANE, and EMBASE to identify literature reporting adult decompression study groups that involved an oblique or lateral fusion approach through September 2020. Improvement in outcomes measures and complication rates were pooled and tested for significance.

RESULTS

A total of 110 publications were assessed with 15 studies meeting inclusion criteria, including 557 patients and 1008 levels. Mean age was 63.1 years with BMI of 27.5 kg/m². For the combined indirect and direct decompression cohort, lumbar lordosis (LL) increased 133.9%, from 22.8^o to 48.7^o, while the indirect decompression cohort LL increased 8.9%, from 41.9^o to 45.5^o. Difference in LL improvement between cohorts was insignificant (P > .05). Oswestry Disability Index (ODI) decreased from 36.5 to 19.4 in the combined indirect and direct decompression cohort, and from 44.4 to 23.1 in the indirect decompression cohort. ODI reduction was insignificant (P = .053).

CONCLUSIONS

Prior studies of both indirect decompression as well as combined indirect and direct decompression of lumbar spine stenosis are limited by small samples, heterogeneous populations, and lack of direct comparisons. Both procedures result in improved function and pain postoperatively with direct decompression restoring more lordosis in patients with worse preoperative alignment.

Cervical Disc Replacement for Radiculopathy Versus Myeloradiculopathy: An MCID Analysis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The aim was to compare the minimally clinically important difference (MCID) across multiple patient-reported outcomes (PROs) in patients undergoing cervical disc replacement (CDR) for cervical spondylotic radiculopathy versus myeloradiculopathy.

SUMMARY OF BACKGROUND DATA

To date, a limited number of studies have demonstrated mostly similar results in patients with cervical spondylotic radiculopathy or myeloradiculopathy undergoing CDR. However, each of these previous studies have focused on statistically significant differences, which may not correlate with patient perceived improvements in outcomes or success.

METHODS

Patients who underwent 1 or 2-level CDR with radiculopathy versus myeloradiculopathy were identified, and prospectively collected data was retrospectively reviewed. Demographic variables, preoperative diagnosis, and operative variables were collected for each patient. The following PROs were prospectively collected: Neck Disability Index (NDI), visual analog scale (VAS)-Neck, VAS-Arm, Short Form-12 Health Survey (SF-12) Physical Component Score (PCS), SF-12 Mental Component Score (MCS), PROMIS Physical Function (PF). An MCID analysis of PROs for each diagnosis group was performed and the percentage of patients achieving the MCID was compared between the two diagnosis groups.

RESULTS

Eight-five patients, of which 56% had radiculopathy and 44% had myeloradiculopathy. MCID analysis demonstrated that at 6-week, 12-week, and final postoperative follow-up there was no significant difference in the percentage of patients with radiculopathy or myeloradiculopathy achieving the MCID for each PRO assessed. In both diagnosis groups the percentage of patients achieving the MCID for each PRO continued to increase from the 6-week to final postoperative follow-up except for the SF-12 MCS in patients with myeloradiculopathy.

CONCLUSIONS

The percentage of patients achieving the MCID was not significantly different at each postoperative period assessed in the radiculopathy and myeloradiculopathy groups treated with CDR. In addition, the percentage of patients achieving the MCID continued to increase from 6 weeks to final follow-up in both groups for almost all PROs assessed.

The Risk of Nonunion in Smokers Revisited: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systemic review and meta-analysis.

OBJECTIVE

To review and establish the effect of tobacco smoking on risk of nonunion following spinal fusion.

METHODS

A systematic search of Medline, Embase, Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews from inception to December 31, 2020, was conducted. Cohort studies directly comparing smokers with nonsmokers that provided the number of nonunions and fused segments were included. Following data extraction, the risk of bias was assessed using the Quality in Prognosis Studies Tool, and the strength of evidence for nonunion was evaluated using the GRADE working group criteria. All data analysis was performed in Review Manager 5, and a random effects model was used.

RESULTS

Twenty studies assessing 3009 participants, which included 1117 (37%) smokers, met inclusion criteria. Pooled analysis found that smoking was associated with increased risk of nonunion compared to not smoking ≥1 year following spine surgery (RR 1.91, 95% CI 1.56 to 2.35). Smoking was significantly associated with increased nonunion in those receiving either allograft (RR 1.39, 95% CI 1.12 to 1.73) or autograft (RR 2.04, 95% CI 1.54 to 2.72). Both multilevel and single level fusions carried increased risk of nonunion in smokers (RR 2.30, 95% CI 1.64 to 3.23; RR 1.79, 95% CI 1.12 to 2.86, respectively).

CONCLUSION

Smoking status carried a global risk of nonunion for spinal fusion procedures regardless of follow-up time, location, number of segments fused, or grafting material. Further comparative studies with robust methodology are necessary to establish treatment guidelines tailored to smokers.

Anterior lumbar interbody fusion: single institutional review of complications and associated variables

BACKGROUND CONTEXT

As more patients undergo anterior lumbar interbody fusion (ALIF) procedures and more devices are created for that purpose, it is important to understand the complications that can arise and the variables that mitigate risk for major and minor complications.

PURPOSE

To assess complication rates after ALIF with or without posterior instrumentation and variables associated with increased likelihood of postoperative complications. We aim to provide this data as benchmarking to improve patient safety and surgical care.

STUDY DESIGN

A single-center retrospective cohort study.

PATIENT SAMPLE

All adult patients who underwent ALIF between 2017 and 2019 was performed OUTCOME MEASURES: Post-operative major and minor complications were evaluated.

METHODS

Complications were recorded and presented as percentages. Patient demographics, perioperative, and postoperative data were also collected and analyzed between patients who had no complications and those that had any complication. Subgroup analysis of surgical complications were performed by nonparametric Chi-square tests. Continuous variables were compared using Mann-Whitney U tests.

RESULTS

Ninty-five of three hundred sixty-two (26.2%) of patients experienced a minor or major complication. Among the most common complications found were surgical site infections (5.8%), neurological complications (4.1%), vascular complications (3.6%), and urinary tract infections (3.3%). Patients undergoing ALIF alone with post-operative complications had higher mean age, higher BMI, higher ASA status, and experienced higher estimated blood loss. Patients undergoing ALIF and posterior instrumentation with post-operative complications were more likely to have diabetes and had a higher ASA status. Patients with any complications from both groups had longer length of stay, discharge to a non-home setting and were more likely to be readmitted or return to the operating room.

CONCLUSION

Our study reveals variables associated with complications at our institution, including age of the patient, BMI, and ASA status leading to higher complications and greater LOS, higher readmission rates, and disposition to skilled facilities.

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.

Patient-Specific Variations in Local Strain Patterns on the Surface of a Trussed Titanium Interbody Cage

Introduction: 3D printed trussed titanium interbody cages may deliver bone stimulating mechanobiological strains to cells attached at their surface. The exact size and distribution of these strains may depend on patient-specific factors, but the influence of these factors remains unknown. Therefore, this study aimed to determine patient-specific variations in local strain patterns on the surface of a trussed titanium interbody fusion cage.

Materials and Methods: Four patients eligible for spinal fusion surgery with the same cage size were selected from a larger database. For these cases, patient-specific finite element models of the lumbar spine including the same trussed titanium cage were made. Functional dynamics of the non-operated lumbar spinal segments, as well as local cage strains and caudal endplate stresses at the operated segment, were evaluated under physiological extension/flexion movement of the lumbar spine.

Results: All patient-specific models revealed physiologically realistic functional dynamics of the operated spine. In all patients, approximately 30% of the total cage surface experienced strain values relevant for preserving bone homeostasis and stimulating bone formation. Mean caudal endplate contact pressures varied up to 10 MPa. Both surface strains and endplate contact pressures varied more between loading conditions than between patients.

Conclusions: This study demonstrates the applicability of patient-specific finite element models to quantify the impact of patient-specific factors such as bone density, degenerative state of the spine, and spinal curvature on interbody cage loading. In the future, the same framework might be further developed in order to establish a pipeline for interbody cage design optimizations.

Safety and efficacy of stand-alone anterior lumbar interbody fusion in low-grade L5-S1 isthmic spondylolisthesis

Introduction

Surgical management of isthmic spondylolisthesis is controversial and reports on anterior approaches in the literature are scarce.

Research question

To evaluate the safety and efficacy of stand-alone anterior lumbar interbody fusion (ALIF) in patients with symptomatic low-grade L5-S1 isthmic spondylolisthesis.

Material and methods

All adult patients with isthmic spondylolisthesis of the lumbosacral junction treated in a single institution between 2008 and 2019 with stand-alone ALIF were screened. A titan cage was inserted at L5-S1 with vertebral anchoring screws. Prospectively collected surgical, clinical and radiographic data were analyzed retrospectively.

Results

34 patients (19 men, 15 women, mean age 52.5 ​± ​11.5 years) with a mean follow-up of 3.2 (±2.5) years were analyzed. 91.2% (n ​= ​31) of patients had a low-grade spondylolisthesis and 8.8% (n ​= ​3) grade III according to Meyerding classification. Mean COMI and ODI scores improved significantly from 6.9 (±1.5) and 35.5 (±13.0) to 2.0 (±2.5) and 10.2 (±13.0), respectively after one year, and to 1.7 (±2.5) and 8.2 (±9.6), respectively, after two years. The COMI and ODI scores improved in 86.4% and 80%, respectively, after one year and 92.9% of patients after two years by at least the minimal clinically important difference. No intraoperative complications were recorded. 8.8% (n ​= ​3) of patients needed a reoperation.

Discussion and conclusion

After stand-alone ALIF for symptomatic isthmic spondylolisthesis, the patients improved clinically important after one and two years. Stand-alone ALIF is a safe and effective surgical treatment option for low-grade isthmic spondylolisthesis.

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Report of a series of patients with symptomatic low-grade L5-S1 isthmic spondylolisthesis treated by stand-alone ALIF.

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Patient reported outcomes showed clinically important improvements after one and two years.

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Stand-alone ALIF proved to be a safe and effective technique to treat symptomatic low-grade L5-S1 isthmic spondylolisthesis.

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There were no vascular or other major complications.

Simulated tissue growth in tetragonal lattices with mechanical stiffness tuned for bone tissue engineering

Bone tissue engineering approaches have recently begun considering 3D printed lattices as viable scaffold solutions due to their highly tunable geometries and mechanical efficiency. However, scaffold design remains challenging due to the numerous biological and mechanical trade-offs related to lattice geometry. Here, we investigate novel tetragonal unit cell designs by independently adjusting unit cell height and width to find scaffolds with improved tissue growth while maintaining suitable scaffold mechanical properties for bone tissue engineering. Lattice tissue growth behavior is evaluated using a curvature-based growth model while elastic modulus is evaluated with finite element analysis. Computationally efficient modeling approaches are implemented to facilitate bulk analysis of lattice design trade-offs using design maps for biological and mechanical functionalities in relation to unit cell height and width for two contrasting unit cell topologies. Newly designed tetragonal lattices demonstrate higher tissue growth per unit volume and advantageous stiffness in preferred directions compared to cubically symmetric unit cells. When lattice beam diameter is fixed to 200 μm, Tetra and BC-Tetra lattices with elastic moduli of 200 MPa-400 MPa are compared for squashed, cubic, and stretched topologies. Squashed Tetra lattices demonstrated higher growth rates and growth densities compared to symmetrically cubic lattices. BC-Tetra lattices with the same range of elastic moduli show squashed lattices tend to achieve higher growth rates, whereas stretched lattices promote higher growth density. The results suggest tetragonal unit cells provide favorable properties for biological and mechanical tailoring, therefore enabling new strategies for diverse patient needs and applications in regenerative medicine.

Vulnerability of the L5 nerve root during anterior lumbar interbody fusion at L5-S1: case series and review of the literature

OBJECTIVE

Nerve root injuries associated with anterior lumbar interbody fusion (ALIF) are uncommonly reported in the literature. This case series and review aims to describe the etiology of L5 nerve root injury following ALIF at L5-S1.

METHODS

The authors performed a single-center retrospective review of prospectively collected data of patients who underwent surgery between 2017 and 2019 who had postoperative L5 nerve root injuries after stand-alone L5-S1 ALIF. They also reviewed the literature with regard to nerve root injuries after ALIF procedures.

RESULTS

The authors report on 3 patients with postoperative L5 radiculopathy. All 3 patients had pain that improved. Two of the 3 patients had a neurological deficit, one of which improved.

CONCLUSIONS

Stretch neuropraxia from overdistraction is an important cause of postoperative L5 radiculopathy after L5-S1 ALIF. Judicious use of implants and careful preoperative planning to determine optimal implant sizes are paramount.

Predictors of Extended Hospitalization and Early Reoperation After Elective Lumbar Disc Arthroplasty

BACKGROUND

Lumbar disc arthroplasty (LDA) has emerged as a motion-sparing alternative to lumbar fusion. Although LDA may be amenable to the ambulatory surgical setting, to date no study has identified the factors predisposing patients to extended hospital stay.

METHODS

A national surgical quality improvement database was queried from 2011 to 2019 for patients undergoing elective, single-level, primary LDA. Univariate and multivariate logistic regression analyses were performed to elucidate predictors of length of stay (LOS) at or above the 90th percentile of the study population (3 days). Secondary study endpoints included rates of complications, as well as predictors and reasons for unplanned reoperation within 30 days.

RESULTS

A total of 630 patients met eligibility criteria for the study, of whom 517 (82.1%) had LOS <3 days and 113 (17.9%) had LOS ≥3 days. Multivariate logistic regression revealed associations between prolonged hospitalization and postoperative diagnosis of degenerative disk disease, obesity, Hispanic identity, and operation length >120 minutes. Before discharge, patients with LOS ≥3 days were more likely to have venous thromboembolisms, pneumonia, surgical site infections, and reoperations. Independent predictors of reoperation were wound infections, diabetes, and smoking.

CONCLUSIONS

Complications following elective single-level LDA are relatively rare, with few extended hospitalizations being attributable to any specific complication. Risk factors for prolonged LOS appear to be related to diagnosis and surgical time rather than to modifiable preoperative comorbidities. Conversely, unplanned reoperations within 30 days are associated with optimizable perioperative factors such as smoking, diabetes, and surgical site infection.

The radiological outcome in lumbar interbody fusion among rheumatoid arthritis patients: a 20-year retrospective study

BACKGROUND

Clinical outcomes amongst Rheumatoid Arthritis (RA) patients have shown satisfactory results being reported after lumbar surgery. The increased adoption of the interbody fusion technique has been due to a high fusion rate and less invasive procedures. However, the radiographic outcome for RA patients after receiving interbody fusion has scarcely been addressed in the available literature.

METHODS

Patients receiving interbody fusion including ALIF, OLIF, and TLIF were examined for implant cage motion and fusion status at two-year follow-up. Parameters for the index correction level including ADH, PDH, WI, SL, FW, and FH were measured and compared at pre-OP, post-OP, and two-year follow-up.

RESULTS

We enrolled 64 RA patients at 104 levels (mean 64.0 years old, 85.9% female) received lumbar interbody fusion. There were substantial improvement in ADH, PDH, WI, SL, FW, and FH after surgery, with both ADH and PDH having significantly dropped at two-year follow up. The OLIF group suffered from a higher subsidence rate with no significant difference in fusion rate when compared to TLIF. The fusion rate and subsidence rate for all RA patients was 90.4 and 28.8%, respectively.

CONCLUSIONS

We revealed the radiographic outcomes of lumbar interbody fusions towards symptomatic lumbar disease in RA patients with good fusion outcome despite the relative high subsidence rate amongst the OLIF group. Those responsible for intra-operative endplate management should be more cautious to avoid post-OP cage subsidence.

Truss implant technology™ for interbody fusion in spinal degenerative disorders: profile of advanced structural design, mechanobiologic and performance characteristics

Introduction: Interbody fusion devices are customarily used in fusion of the anterior spinal column for treatment of degenerative disc disease. Their traditional role is to reestablish and maintain intervertebral disc height, contain bone graft and provide mechanical support for the spine while osseointegration takes place. Utilizing the principles of mechanobiology, a unique biokinetic interbody fusion device has been developed that employs an advanced structural design to facilitate and actively participate in the fusion consolidation process.Areas covered: This article profiles and characterizes 4WEB Medical's Truss Implant Technology™ which includes a range of 3D-printed titanium spinal interbody implants and non-spinal implants whose design is based on truss structures enabled by advances in additive manufacturing. Four main areas of the implant design and functionality are detailed: bio-architecture, mechanobiologic underpinnings, bioactive surface features, and subsidence resistance. Pre-clinical and clinical examples are provided to describe and specify the bioactive roles and contributions of each design feature.Expert opinion: The distinct and unique combination of features incorporated within the truss cage design results in a biokinetic implant that actively participates in the bone healing cascade and fusion process.

Lumbar Interbody Fusion Conducted on a Porcine Model with a Bioresorbable Ceramic/Biopolymer Hybrid Implant Enriched with Hyperstable Fibroblast Growth Factor 2

Many growth factors have been studied as additives accelerating lumbar fusion rates in different animal models. However, their low hydrolytic and thermal stability both in vitro and in vivo limits their workability and use. In the proposed work, a stabilized vasculogenic and prohealing fibroblast growth factor-2 (FGF2-STAB®) exhibiting a functional half-life in vitro at 37 °C more than 20 days was applied for lumbar fusion in combination with a bioresorbable scaffold on porcine models. An experimental animal study was designed to investigate the intervertebral fusion efficiency and safety of a bioresorbable ceramic/biopolymer hybrid implant enriched with FGF2-STAB® in comparison with a tricortical bone autograft used as a gold standard. Twenty-four experimental pigs underwent L2/3 discectomy with implantation of either the tricortical iliac crest bone autograft or the bioresorbable hybrid implant (BHI) followed by lateral intervertebral fixation. The quality of spinal fusion was assessed by micro-computed tomography (micro-CT), biomechanical testing, and histological examination at both 8 and 16 weeks after the surgery. While 8 weeks after implantation, micro-CT analysis demonstrated similar fusion quality in both groups, in contrast, spines with BHI involving inorganic hydroxyapatite and tricalcium phosphate along with organic collagen, oxidized cellulose, and FGF2- STAB® showed a significant increase in a fusion quality in comparison to the autograft group 16 weeks post-surgery (p = 0.023). Biomechanical testing revealed significantly higher stiffness of spines treated with the bioresorbable hybrid implant group compared to the autograft group (p < 0.05). Whilst histomorphological evaluation showed significant progression of new bone formation in the BHI group besides non-union and fibrocartilage tissue formed in the autograft group. Significant osteoinductive effects of BHI based on bioceramics, collagen, oxidized cellulose, and FGF2-STAB® could improve outcomes in spinal fusion surgery and bone tissue regeneration.

Association Between Social Determinants of Health and Postoperative Outcomes in Patients Undergoing Single-Level Lumbar Fusions: A Matched Analysis

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

The aim of this study was to analyze association between social determinants of health (SDH) disparity on postoperative complication rates, and 30-day and 90-day all-cause readmission in patients undergoing single-level lumbar fusions.

SUMMARY OF BACKGROUND DATA

Decreasing postoperative complication rates is of great interest to surgeons and healthcare systems. Postoperative complications are associated with poor convalescence, inferior patient reported outcomes measures, and increased health care resource utilization. Better understanding of the association between Social Determinants of Health (SDH) on postoperative outcomes maybe helpful to decrease postoperative complication rates.

METHODS

MARINER 2020, an all-payer claims database, was utilized to identify patients undergoing single-level lumbar fusions between 2010 and 2018. The primary outcomes were the rates of any postoperative complication, symptomatic pseudarthrosis, need for revision surgery, or 30-day and 90-day all-cause readmission.

RESULTS

The exact matched population analyzed in this study contained 16,560 patients (8280 [50.0%] patients undergoing single-level lumbar fusion with an SDH disparity; 8280 [50.0%] patients undergoing single-level lumbar fusion without a disparity). Both patient groups were balanced at baseline. The rate of symptomatic pseudarthrosis (1.0% vs. 0.6%, P < 0.05) or any postoperative complication (16.3% vs. 10.4%, P < 0.05) in the matched analysis was higher in the disparity group. The presence of a disparity was associated with 70% increased odds of developing any complication (OR 1.7, 95% CI 1.53-1.84) or symptomatic pseudarthrosis (OR 1.7, 95% CI 1.17-2.37). Unadjusted and adjusted sensitivity analyses yielded similar results as the primary analysis.

CONCLUSION

Social Determinants of Health affect outcomes in spine surgery patients and are associated with an increased risk of developing postoperative complications following lumbar spine fusion.Level of Evidence: 3.

Transfacet screws using spinal navigation in addition to anterior or oblique lumbar interbody fusion: technical note and preliminary results

Transfacet screws (TFS) are an alternative to the classic bilateral pedicular screws (BPS) in addition to anterior (ALIF) or oblique (OLIF) lumbar interbody fusion. Spinal navigation could help the surgeon in technically demanding procedures in order to avoid screw malposition. Although spinal navigation is commonly used in BPS, its contribution in TFS remains unclear. Our aim here was to assess the feasibility of TFS using spinal navigation in addition to anterior lumbar fusion. Five patients suffering from lumbar degenerative disc disease were included. During the same general anaesthesia, we performed successively an ALIF or OLIF and then a TFS according to Boucher technique using spinal navigation (O-arm). No peri-operative complication occurred, and all the screws were successfully positioned (n = 10). All clinical scores (ODI, VAS L and VAS R) improved at 6-month follow-up. Segmental lordosis increased from 6° [2.4°-12°] to 13.6° [8°-17°]. Fusion was achieved for the five patients. TFS using O-arm in addition to ALIF/OLIF is feasible. To confirm our early favourable outcomes on clinical and radiological data, this technique must be evaluated on larger samples of patients.

An unusual case of a persistent, infected retroperitoneal fluid collection 5 years after anterior lumbar fusion surgery: illustrative case

BACKGROUND

Anterior lumbar fusion procedures have many benefits and continue to grow in popularity. The technique has many potential approach- and procedure-related complications. Symptomatic retroperitoneal fluid collections are uncommon but potentially serious complications after anterior lumbar procedures. Collection types include hematomas, urinomas, chyloperitoneum, cerebrospinal fluid collections, and deep infections.

OBSERVATIONS

The authors present an unusual case of a patient with persistent symptoms related to a retroperitoneal collection over a 5-year period following anterior lumbar fusion surgery. To the authors’ knowledge, no similar case with such extensive symptom duration has been described. The patient had an infected encapsulated fluid collection. The collection was presumed to be a postoperative lymphocele that was secondarily infected after serial percutaneous drainage procedures.

LESSONS

When retroperitoneal collections occur after anterior retroperitoneal approaches, clinical clues, such as timing of symptoms, hypotension, acute anemia, urinary tract infection, hydronephrosis, elevated serum creatinine and blood urea nitrogen, low-pressure headaches, anorexia, or systemic signs of infection, can help narrow the differential. Retroperitoneal collections may continue to be symptomatic many years after anterior lumbar surgery. The collections may become infected after serial percutaneous drainage or prolonged continuous drainage. Encapsulated, infected fluid collections typically require surgical debridement of the capsule and its contents.

The effect of platelet-rich plasma on the fusion rate and clinical outcome of spinal fusion surgery: A systematic review and meta-analysis

BACKGROUND

Platelet-rich plasma (PRP) is widely used in many orthopedic surgeries and spinal disease treatments; however, the effect of PRP on spinal fusion remains controversial.

QUESTIONS/PURPOSES

To assess the fusion rate and clinical results of PRP compared with non-PRP administration in the treatment of spinal fusion with regard to decreasing pain and improving healing and function.

PATIENTS AND METHODS

Studies comparing PRP to non-PRP treatment with respect to the fusion rate and clinical outcome in patients who underwent spinal fusion surgery were included.

RESULT

Three randomized controlled trials (RCTs) and 7 prospective cohort studies were identified. The spinal fusion rate was not significantly different between the groups in all RCTs or cohort studies at the final follow-up. In comparison, PRP significantly reduced pain after surgery as evaluated in the RCT analysis and the complication rate did not differ significantly between the two groups.

CONCLUSION

According to the available studies, PRP does not contribute to the union rate, relieve pain or increase the complication rate in spinal fusion surgery. As clinical heterogeneity exists in these studies, further large, well-designed RCTs that focus on the standard assessment of PRP are needed.

Implications of sagittal alignment and complication profile with stand-alone anterior lumbar interbody fusion versus anterior posterior lumbar fusion

Background

Anterior lumbar interbody fusion (ALIF) is commonly utilized in lumbar degenerative pathologies. Standalone ALIF (ST-ALIF) systems were developed to avoid added morbidity, surgical time, and cost of anterior and posterior fusion (APF). Controversy exists in the literature about which of these two techniques yields superior clinical and radiographic outcomes, and few studies have directly compared them. This study seeks to compare ST-ALIF and APF in terms of sagittal correction and surgical complications.

Methods

Ninty-two consecutive ALIF cases performed from 2013-2018 were retrospectively reviewed and separated into 2 groups. Radiographic measurements were performed on pre- and post-operative radiographs, including segmental lordosis (SL), lumbar lordosis (LL), and pelvic incidence-lumbar lordosis mismatch (PI-LL). Surgical complications were determined. Statistical analysis was performed using chi-square test of homogeneity, Fisher's exact test, and independent sample t-test. Comparisons between groups were deemed statistically significant at the P<0.05 threshold.

Results

Fifty-seven ST-ALIF, 35 APF were identified. There were no differences in age, gender, BMI, Charlson Comorbidity Index (CCI), preoperative diagnosis, or surgical level between the 2 cohorts. Bone Morphogenetic Protein (BMP) was utilized in 24.6% of ST-ALIF versus none of APF (P=0.001). No differences were detected in SL, LL, and PI-LL mismatch. ST-ALIF cohort had significantly greater risk of subsidence and revision surgery versus APF (12.3% vs. 0%, RD 95% CI: 3.8-20.8%, P=0.042). Recurrent spondylolisthesis occurred in 5 ST-ALIF cases, 3 cases with implant failure, and 2 nonunions versus none in the APF group.

Conclusions

ST-ALIF was associated with significantly greater subsidence and revision surgery versus APF. Careful patient selection is paramount when considering ST-ALIF. The potential for revision surgery may offset the potential benefit in avoiding posterior fusion. Despite the greater risk of subsidence, sagittal alignment was not significantly affected.

Role of oxidative metabolism in osseointegration during spinal fusion

Spinal fusion is a commonly performed orthopedic surgery. Autologous bone graft obtained from the iliac crest is frequently employed to perform spinal fusion. Osteogenic bone marrow stromal (a.k.a. mesenchymal stem) cells (BMSCs) are believed to be responsible for new bone formation and development of the bridging bone during spinal fusion, as these cells are located in both the graft and at the site of fusion. Our previous work revealed the importance of mitochondrial oxidative metabolism in osteogenic differentiation of BMSCs. Our objective here was to determine the impact of BMSC oxidative metabolism on osseointegration of the graft during spinal fusion. The first part of the study was focused on correlating oxidative metabolism in bone graft BMSCs to radiographic outcomes of spinal fusion in human patients. The second part of the study was focused on mechanistically proving the role of BMSC oxidative metabolism in osseointegration during spinal fusion using a genetic mouse model. Patients’ iliac crest-derived graft BMSCs were identified by surface markers. Mitochondrial oxidative function was detected in BMSCs with the potentiometric probe, CMXRos. Spinal fusion radiographic outcomes, determined by the Lenke grade, were correlated to CMXRos signal in BMSCs. A genetic model of high oxidative metabolism, cyclophilin D knockout (CypD KO), was used to perform spinal fusion in mice. Graft osseointegration in mice was assessed with micro-computed tomography. Our study revealed that higher CMXRos signal in patients’ BMSCs correlated with a higher Lenke grade. Mice with higher oxidative metabolism (CypD KO) had greater mineralization of the spinal fusion bridge, as compared to the control mice. We therefore conclude that higher oxidative metabolism in BMSCs correlates with better spinal fusion outcomes in both human patients and in a mouse model. Altogether, our study suggests that promoting oxidative metabolism in osteogenic cells could improve spinal fusion outcomes for patients.

Outcomes of stand-alone anterior lumbar interbody fusion of L5-S1 using a novel implant with anterior plate fixation

BACKGROUND CONTEXT

Compared with other approaches, anterior lumbar interbody fusion (ALIF) is believed to be more effective at restoring segmental lordosis and reducing risks of adjacent-segment disease. It remains controversial, however, whether ALIF improves global lumbar lordosis or influences pelvic parameters, possibly because of the heterogeneity of implants and levels studied.

PURPOSE

To report clinical outcomes of stand-alone ALIF with anterior plate fixation for L5-S1 and to determine the effect on global lumbar lordosis and pelvic parameters.

STUDY DESIGN

This is a retrospective case series.

PATIENT SAMPLE

Patients that underwent isolated mini-ALIF with anterior plate fixation for L5-S1.

OUTCOME MEASURES

Oswestry Disability Index (ODI), Short Form 12, lower back and legs pain on Visual Analog Scale, as well as spino-pelvic parameters.

METHODS

The authors reviewed the records of all patients that underwent retroperitoneal mini-ALIF for single-level L5-S1 fusion between August 2012 and December 2016. A total of 129 patients were included, but 9 patients had incomplete preoperative radiographic data, and one patient had schizophrenia and was unable to respond to outcome questionnaires, leaving 119 patients eligible for outcome assessment. At a minimum follow-up of 1 year, seven patients refused to participate in the study or could not be reached, which left a final cohort of 112 patients.

RESULTS

Nine patients were reoperated without implant removal (four pseudarthrosis, two hematomas, one sepsis, one L4-L5 disc hernia, and one L4-L5 disc degeneration). At a mean of 20±9 months, all scores improved significantly from baseline values, with net improvement in ODI of 23.3±19.9. Multivariable analyses confirmed better postoperative ODI in patients that received 18° cages (β=-9.0, p=.017), but revealed no significant trends for net improvement in ODI. Comparison of preoperative and last follow-up radiographs revealed that global lumbar lordosis increased by 4.2±7.1° (p<.001), L5-S1 segmental lordosis increased by 11.8±6.7° (p<.001), and L4-L5 segmental lordosis decreased by 1.9±3.3° (p<.001). All pelvic parameters changed: pelvic incidence increased by 0.6±2.7° (p=.003), pelvic tilt decreased by 2.5±4.1° (p<.001) and sacral slope increased by 3.3±4.7° (p<.001).

CONCLUSIONS

Stand-alone mini-ALIF with anterior plate fixation for L5-S1 can change pelvic parameters while improving global and segmental lumbar lordosis. The procedure resulted in a fusion rate of 96% and comparable improvements in ODI to other studies.

90-day Readmission Rates for Single Level Anterior Lumbosacral Interbody Fusion: A Nationwide Readmissions Database Analysis

STUDY DESIGN

Nationwide Readmissions Database Study.

OBJECTIVE

To investigate the patterns of readmissions and complications following hospitalization for elective single level anterior lumbobsacral interbody fusion.

SUMMARY OF BACKGROUND DATA

Lumbar interbody spine fusions for degenerative disease have increased annually in the United States, including associated hospital costs. Anterior lumbar interbody fusions (ALIFs) have become popularized secondary to higher rates of fusion compared with posterior procedures, and preservation of posterior elements. Prior national databases have sought to study readmission rates with some limitations due to older diagnosis and procedure codes. The newer 2016 International Classification of Diseases Tenth Revision, Clinical Modification (ICD-10 CM) includes more specification of the surgical site.

METHODS

We utilized the 2016 United States Nationwide Readmissions Database (NRD), this nationally representative, all-payer database that includes weighted probability sample of inpatient hospitalizations for all ages. We identified all adults (≥ 18 yrs) using the 2016 ICD-10 coding system who underwent elective primary L5-S1 ALIF and examined rates of readmissions within 90 days of discharge.

RESULTS

Between January and September 2016, a total of 7029 patients underwent elective stand-alone L5-S1 ALIF who were identified from NRD of whom 497 (7.07%) were readmitted within 90 days of their procedure. No differences in sex were appreciated. Medicare patients had statistically significant higher readmission rates (47.69%) among all payer types. With respect to intraoperative complications, vascular complications had statistically significant increased odds of readmission (OR, 3.225, 95% CI, 0.59 -1.75; P = 0.0001). Readmitted patients had higher total healthcare costs.

CONCLUSION

The 90-day readmission rate following stand-alone single level lumbosacral (L5-S1) ALIF was 7.07%. ALIF procedures have increased in frequency, and an understanding of the comorbidities, age-related demographics, and costs associated with 90-day readmissions are critical. Surgeons should consider these risk factors in preoperative planning and optimization.

LEVEL OF EVIDENCE

3.

Biomechanical evaluation of anterior and posterior lumbar surgical approaches on the adjacent segment: a finite element analysis

The purpose of this study was to use models of spine to compare range of motion and intradiscal pressure of adjacent segments performing anterior and/or posterior lumbar surgical approaches and predict potential risk of adjacent segment degeneration. A previously validated finite element model of the intact L1-S1 segments was used. Three different anterior and one posterior surgical fixation approaches for tuberculosis were performed in L3-L5. Three different anterior surgical models were constructed according to the anterior approaches involving debridement, bone graft with or without titanium mesh, and internal fixation with different number of screws and rods. The posterior surgical approach involved transforaminal lumbar interbody debridement, bone graft, and internal fixation. Range of motion and intradiscal pressure of segments adjacent to the fusion were assessed, and biomechanical influences were compared. Intradiscal pressure and range of motion of the adjacent L2/3 and L5/S1 increased during different physiological movements after anterior and/or posterior surgical approaches as compared to baseline values. Comparison between the biomechanical values assessed after different anterior surgical approaches yielded no significant difference. After anterior and posterior surgical approaches were performed on the same model, there were no significant differences in intradiscal pressure and range of motion of the adjacent L2/3 and L5/S1. Anterior and/or posterior lumbar surgical approaches increased range of motion and intradiscal pressure in L2/3 and L5/S1, suggesting each lumbar surgical approach assessed has the potential risk of adjacent segment degeneration. However, there were no significant differences between the biomechanical measurements across the different surgical approaches evaluated.

Impact of lumbar interbody fusion surgery on postoperative outcomes in patients with recurrent lumbar disc herniation: Analysis of the US national inpatient sample

Little information is available on associations between different lumbar interbody fusion (LIF) surgeries and postoperative outcomes. The present study aims to comprehensively investigate whether different LIF techniques are associated with postoperative outcomes such as complications and length of hospital stay. The United States Nationwide Inpatient Sample (NIS) was searched for patients diagnosed with recurrent lumbar disc herniation who underwent lumbar interbody fusion (LIF) surgeries between 2005 and 2014. Patients were categorized based on LIF approaches: anterior lumbar interbody fusion (ALIF); lateral lumbar interbody fusion (LLIF); or posterior lumbar interbody fusion/transforaminal lumbar interbody fusion (PLIF/TLIF). A total of 2625 patients were included in this study. After adjusting for age, severity of illness, and comorbidities, patients who received LLIF and PLIF/TLIF approaches had significantly shorter hospital stays than those receiving ALIF (LLIF vs. ALIF, β = -0.64; PLIF/TLIF vs. ALIF, β = -0.40). In addition, patients who received LLIF and PLIF/TLIF approaches had significantly lower risk of digestive system complications compared to those receiving ALIF (LLIF vs. ALIF, aOR = 0.25; PLIF/TLIF vs. ALIF, aOR = 0.18). In conclusion, in patients with recurrent lumbar disc herniation, LLIF and PLIF/TLIF approaches are associated with shorter hospital stays and lower risk of digestive system complications than ALIF. However, LIF approaches do not correlate significantly with the risk of postoperative bleeding or nervous system complications.