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.

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.

Choice of Approach Does Not Affect Clinical and Radiologic Outcomes: A Comparative Cohort of Patients Having Anterior Lumbar Interbody Fusion and Patients Having Lateral Lumbar Interbody Fusion at 24 Months.

STUDY DESIGN: Retrospective analysis of prospectively collected registry data. OBJECTIVE: This study aimed to compare the clinical and radiologic outcomes between comparative cohorts of patients having anterior lumbar interbody fusion (ALIF) and patients having lateral lumbar interbody fusion (LLIF). METHODS: Ninety consecutive patients were treated by a single surgeon with either ALIF (n = 50) or LLIF (n = 40). Inclusion criteria were patients age 45 to 70 years with degenerative disk disease or grade 1 to 2 spondylolisthesis and single-level pathology from L1 to S1. Patient-reported outcome measures included pain (visual analog scale), disability (Oswestry Disability Index [ODI]), and quality of life (Short Form 36 physical component score [PCS] and mental component scores [MCS]). Assessment of fusion and measurement of lordosis and posterior disk height were performed on computed tomography scans. RESULTS: At 24 months, patients having ALIF had significant improvements in back (64%) and leg (65%) pain and ODI (60%), PCS (44%), and MCS (26%; p < 0.05) scores. Patients having LLIF had significant improvements in back (56%) and leg (57%) pain and ODI (52%), PCS (48%), and MCS (12%; p < 0.05) scores. Fourteen complications occurred in the ALIF group, and in the LLIF group, there were 17 complications (p > 0.05). The fusion rate was 100% for ALIF and 95% for LLIF (p = 0.1948). ALIF added ∼6 degrees of lordosis and 3 mm of height, primarily measured at L5-S1, and LLIF added ∼3 degrees of lordosis and 2 mm of height between L1 to L5. Mean follow-up was 34.1 months. CONCLUSIONS: In comparative cohorts of patients having ALIF and patients having LLIF at 24 months postoperatively, there were no significant differences in clinical outcomes, complication rates, or fusion rates.

Assessment and classification of subsidence after lateral interbody fusion using serial computed tomography.

OBJECT Intervertebral cage settling during bone remodeling after lumbar lateral interbody fusion (LIF) is a common occurrence during the normal healing process. Progression of this settling with endplate collapse is defined as subsidence. The purposes of this study were to 1) assess the rate of subsidence after minimally invasive (MIS) LIF by CT, 2) distinguish between early cage subsidence (ECS) and delayed cage subsidence (DCS), 3) propose a descriptive method for classifying the types of subsidence, and 4) discuss techniques for mitigating the risk of subsidence after MIS LIF. METHODS A total of 128 consecutive patients (with 178 treated levels in total) underwent MIS LIF performed by a single surgeon. The subsidence was deemed to be ECS if it was evident on postoperative Day 2 CT images and was therefore the result of an intraoperative vertebral endplate injury and deemed DCS if it was detected on subsequent CT scans (≥ 6 months postoperatively). Endplate breaches were categorized as caudal (superior endplate) and/or cranial (inferior endplate), and as ipsilateral, contralateral, or bilateral with respect to the side of cage insertion. Subsidence seen in CT images (radiographic subsidence) was measured from the vertebral endplate to the caudal or cranial margin of the cage (in millimeters). Patient-reported outcome measures included visual analog scale, Oswestry Disability Index, and 36-Item Short Form Health Survey physical and mental component summary scores. RESULTS Four patients had ECS in a total of 4 levels. The radiographic subsidence (DCS) rates were 10% (13 of 128 patients) and 8% (14 of 178 levels), with 3% of patients (4 of 128) exhibiting clinical subsidence. In the DCS levels, 3 types of subsidence were evident on coronal and sagittal CT scans: Type 1, caudal contralateral, in 14% (2 of 14), Type 2, caudal bilateral with anterior cage tilt, in 64% (9 of 14), and Type 3, both endplates bilaterally, in 21% (3 of 14). The mean subsidence in the DCS levels was 3.2 mm. There was no significant difference between the numbers of patients in the subsidence (DCS) and no-subsidence groups who received clinical benefit from the surgical procedure, based on the minimum clinically important difference (p > 0.05). There was a significant difference between the fusion rates at 6 months (p = 0.0195); however, by 12 months, the difference was not significant (p = 0.2049). CONCLUSIONS The authors distinguished between ECS and DCS. Radiographic subsidence (DCS) was categorized using descriptors for the location and severity of the subsidence. Neither interbody fusion rates nor clinical outcomes were affected by radiographic subsidence. To protect patients from subsidence after MIS LIF, the surgeon needs to take care with the caudal endplate during cage insertion. If a caudal bilateral (Type 2) endplate breach is detected, supplemental posterior fixation to arrest progression and facilitate fusion is recommended.

Percutaneous Pedicle Screw Accuracy with Dynamic Electromyography: The Early Experience of a Traditionally Open Spine Surgeon.

BACKGROUND AND STUDY AIMS: The learning curve associated with the adoption of minimally invasive surgery techniques has limited its adoption by many traditionally open surgeons. The use of dynamic electromyography (EMG) to guide the placement of percutaneous pedicle screws (PS) can lessen the learning curve by providing real-time feedback on neural proximity relative to the screw. This study aimed to investigate the safety and accuracy of a single surgeon's experience transitioning from open pedicle screws (OS) to PS using intraoperative fluoroscopy and dynamic EMG. MATERIALS AND METHODS: Forty consecutive patients were treated with EMG and fluoroscopy-guided PS placement by a single surgeon and followed through a prospective registry. This was cross-referenced with a cohort of 53 consecutive patients treated with OS in 2011. Computed tomography was used to check the screw position 1 day after surgery. A misplaced pedicle screw was defined as a breach of the pedicle wall. The accuracy of PS placement in association with dynamic EMG was compared with that of OS. RESULTS: A total of 204 PS were inserted in the study cohort with 97.5% accuracy. Five (2.5%) were misplaced (three medial and two lateral). All three medial screws displayed a caution message (yellow: 8mA) on insertion. No screw caused visceral or neurologic complications postoperatively, and none required revision. In the OS cohort, 254 screws were placed with 94.9% accuracy, 13 (5.1%) were misplaced (8 medial, 3 lateral, and 2 superior), and 3 (1.2%) required revision. CONCLUSIONS: Dynamic EMG combined with intraoperative fluoroscopy and advanced instrumentation provides a safe, real-time, and accurate method for PS placement.

Clinical results and limitations of indirect decompression in spinal stenosis with laterally implanted interbody cages: results from a prospective cohort study.

PURPOSE: The lateral approach for anterior interbody fusion allows placement of a large footprint intervertebral spacer to indirectly decompress the neural elements through disc height restoration and resultant soft tissue changes. However, it is not well understood under what circumstances indirect decompression in lateral approach surgery is sufficient. This report aimed to evaluate clinical scenarios where indirect decompression was and was not sufficient in symptom resolution when using lateral interbody fusion. METHODS: A prospective study was undertaken of 122 consecutive patients treated with lateral interbody fusion without direct decompression. Pre- and postoperative symptomatology was assessed to evaluate the extent of neural decompression following implantation with a lateral polyetheretherketone spacer. Failure to improve or resolve preoperative radicular pain was considered a failure of indirect decompression and indicated these patients for additional posterior decompressive surgery. RESULTS: Unplanned second stage decompression was required in 11 patients. Of these patients, 7/11 early in this series had pathology that was underappreciated including spondylolisthesis from high grade facet arthropathy with instability (3), bony lateral recess stenosis (3) and both spondylolisthesis/stenosis (1). Three patients had iatrogenic leg pain through cage misplacement. There was one failure of indirect decompression that could not be explained through retrospective analysis of the patient's record. CONCLUSION: Indirect decompression clearly has a role in minimizing the amount of surgery that is required. However, it is important to consider the circumstances where this technique may be effective and preoperative considerations that may improve patient selection.

Bone Morphogenetic Proteins in Spinal Surgery: What Is the Fusion Rate and Do They Cause Cancer?

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to determine the fusion rate using recombinant human bone morphogenetic protein (rhBMP) in spinal surgery and to estimate the risk of cancer subsequent to their use. SUMMARY OF BACKGROUND DATA: rhBMP may obviate the need for iliac crest bone graft harvest and provides similar or higher fusion rates than autologous bone graft. Recently, there are concerns that rhBMPs may either cause cancer or accelerate progression. METHODS: Patients were treated by 2 spine surgeons between 2002 and 2012. Inclusion criteria were patients who resided in the state of Victoria, Australia, undergoing lumbar fusion (anterior, lateral, posterior, and posterolateral) with rhBMP [either rhBMP-2 (Infuse) or rhBMP-7 (OP-1)]. Exclusion criteria were patients who reported having an invasive cancer diagnosis before the spinal fusion procedure. The occurrence of incident cancers was obtained from record linkage to the Victorian Cancer Registry. RESULTS: A total of 527 patients were included in the cohort, with a mean follow-up of 4.4 years (1.8-11.5). Patients received Infuse in 77% of cases and OP-1 in 23%. The mean Infuse does was 10.2  mg (2.5-48.0) and 3.3  mg (1.7-6.6) for OP-1. There was no significant difference in fusion rates between Infuse (90.1%) and OP-1 (91.9%) (P = 0.42). The overall success of interbody fusion with rhBMP was 93.5% at 12 months. Twenty-seven patients were diagnosed with an invasive cancer since treatment (20 Infuse and 7 OP-1 patients). Comparing the observed numbers in our study cohort with those expected on the basis of the Victorian population's age and sex-specific rates, we observed that the study cohort was not at a significantly increased risk of cancer. The standardized incidence ratio for cancer overall (of any type) was 0.84 [95% confidence interval (95% CI) 0.56-1.21]. CONCLUSION: Off-label use of rhBMP provided high fusion rates with no evidence of a significantly increased risk of cancer. LEVEL OF EVIDENCE: 4.

Anterior lumbar interbody fusion using recombinant human bone morphogenetic protein-2: a prospective study of complications.

OBJECT: The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in anterior lumbar interbody fusion (ALIF) is controversial regarding the reported complication rates and cost. The authors aimed to assess the complication rates of performing ALIF using rhBMP-2. METHODS: This is a prospective study of consecutive patients who underwent ALIF performed by a single spine surgeon and a single vascular surgeon between 2009 and 2012. All patients underwent placement of a polyetheretherketone (PEEK) cage filled with rhBMP-2 and a separate anterior titanium plate. Preoperative clinical data, operative details, postoperative complications, and clinical and radiographic outcomes were recorded for all patients. Clinical outcome measures included back and leg pain visual analog scale scores, Oswestry Disability Index (ODI), and SF-36 Physical and Mental Component Summary (PCS and MCS) scores. Radiographic assessment of fusion was performed using high-definition CT scanning. Male patients were screened pre- and postoperatively regarding sexual dysfunction, specifically retrograde ejaculation (RE). RESULTS: The study comprised 131 patients with a mean age of 45.3 years. There were 67 men (51.1%) and 64 women (48.9%). Of the 131 patients, 117 (89.3%) underwent ALIF at L5-S1, 9 (6.9%) at L4-5, and 5 (3.8%) at both L4-5 and L5-S1. The overall complication rate was 19.1% (25 of 131), with 17 patients (13.0%) experiencing minor complications and 8 (6.1%) experiencing major complications. The mean estimated blood loss per ALIF level was 115 ml. There was 1 incidence (1.5%) of RE. No significant vascular injuries occurred. No prosthesis failure occurred with the PEEK cage and separate anterior screw-plate. Back and leg pain improved 57.2% and 61.8%, respectively. The ODI improved 54.3%, with PCS and MCS scores improving 41.7% and 21.3%, respectively. Solid interbody fusion was observed in 96.9% of patients at 12 months. CONCLUSIONS: Anterior lumbar interbody fusion with a vascular access surgeon and spine surgeon, using a separate cage and anterior screw-plate, provides a very robust and reliable construct with low complication rates, high fusion rates, and positive clinical outcomes, and it is cost-effective. The authors did not experience the high rates of RE reported by other authors using rhBMP-2.

Indirect foraminal decompression is independent of metabolically active facet arthropathy in extreme lateral interbody fusion.

STUDY DESIGN: Retrospective analysis of prospectively collected, nonrandomized radiographical data. OBJECTIVE: To examine the relationship between the presence of preoperative metabolically active facet arthropathy (FA) and the amount of indirect foraminal decompression gained after extreme lateral interbody fusion (XLIF). SUMMARY OF BACKGROUND DATA: Although evidence of significant radiographical indirect decompression after XLIF has been shown, the relationship between the extent of indirect decompression and the presence of potentially attenuating, FA is yet to be studied. METHODS: A prospective database of consecutive patients undergoing XLIF was retrospectively analyzed. Posterior disc height, foraminal height, and cross-sectional foraminal area were measured on computed tomographic scans obtained preoperatively and 2 days postoperatively. The selected radiographical parameters were examined with respect to the presence of FA based on preoperative computed tomographic and bone scans. RESULTS: Fifty-two consecutive patients underwent 79 levels of XLIF without direct decompression. Average age was 66.4 years and 34 (65.4%) were females. Surgery resulted in significant increases in posterior disc height 3.0 to 5.7 mm (89.0% increase), P<0.0001; foraminal height 1.4 to 1.7 cm (38.0% increase), P<0.0001; and foraminal area 1.1 to 1.4 cm (45.1% increase), P<0.0001. These increases were independent of the presence of metabolically active arthropathy. CONCLUSION: Significant indirect neural decompression is possible in XLIF, regardless of the presence of metabolically active FA. LEVEL OF EVIDENCE: 3.

Cervical interbody fusion is enhanced by allogeneic mesenchymal precursor cells in an ovine model.

STUDY DESIGN: An experimental study using a sheep cervical spine interbody fusion model. OBJECTIVE: To compare allogeneic mesenchymal precursor cells combined with hydroxyapatite and tricalcium phosphate (HA/TCP) with HA/TCP alone or iliac crest autograft (AG) for cervical interbody fusion. SUMMARY OF BACKGROUND DATA: We investigated the effect of mesenchymal precursor cells on cervical fusion because of the shortcomings of using iliac crest (donor site morbidity), bone substitute (poor osteoinductive properties), and bone morphogenic proteins (serious complications). METHODS: Thirty ewes were divided randomly into four groups of six having C3-C4 anterior cervical discectomy and fusion using a Fidji cage packed with, AG, HA/TCP, HA/TCP containing 5 million MPCs, and HA/TCP containing 10 million MPCs. MPCs were derived from a single batch of immuno-selected and culture-expanded MPCs isolated from bone marrow of out-bred sheep. The fifth group were nonoperated controls. Safety, fusion parameters, and biomechanics were assessed. RESULTS: No cell-related adverse events were observed. No significant differences were found between the five or 10 million MPC groups. Evaluation of fusion by CT scan at 3 months showed that 9 of 12 (75%) MPC-treated animals had continuous bony bridging compared with only 1 of 6 AG and 2 of 6 HA/TCP (P = 0.019 and P = 0.044, respectively). By quantitative CT, density of new bone in MPC-treated animals was 121% higher than in HA/TCP (P = 0.017) and 128% higher than in AG (P < 0.0001). Functional radiology at 3 months revealed that MPC-treated animals had significantly reduced macromotion at C3/4 compared with AG and HA/TCP groups combined (P = 0.007). CONCLUSION: Implantation of allogeneic MPCs when combined with HA/TCP and an interbody spacer facilitates new bone formation after discectomy without any cell-related complications. The earlier and dense new bone formation observed with MPCs relative to autograft and HA/TCP alone suggest that this approach may offer therapeutic benefit.