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

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

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

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

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

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

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

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