Five-Year Longitudinal Follow-up of Restorative Neurostimulation Shows Durability of Effectiveness in Patients With Refractory Chronic Low Back Pain Associated With Multifidus Muscle Dysfunction.

BACKGROUND: Adults with refractory, mechanical chronic low back pain associated with impaired neuromuscular control of the lumbar multifidus muscle have few treatment options that provide long-term clinical benefit. This study hypothesized that restorative neurostimulation, a rehabilitative treatment that activates the lumbar multifidus muscles to overcome underlying dysfunction, is safe and provides relevant and durable clinical benefit to patients with this specific etiology. MATERIALS AND METHODS: In this prospective five-year longitudinal follow-up of the ReActiv8-B pivotal trial, participants (N = 204) had activity-limiting, moderate-to-severe, refractory, mechanical chronic low back pain, a positive prone instability test result indicating impaired multifidus muscle control, and no indications for spine surgery. Low back pain intensity (10-cm visual analog scale [VAS]), disability (Oswestry Disability Index), and quality of life (EuroQol's "EQ-5D-5L" index) were compared with baseline and following the intent-to-treat principle, with a supporting mixed-effects model for repeated measures that accounted for missing data. RESULTS: At five years (n = 126), low back pain VAS had improved from 7.3 to 2.4 cm (-4.9; 95% CI, -5.3 to -4.5 cm; p < 0.0001), and 71.8% of participants had a reduction of ≥50%. The Oswestry Disability Index improved from 39.1 to 16.5 (-22.7; 95% CI, -25.4 to -20.8; p < 0.0001), and 61.1% of participants had reduction of ≥20 points. The EQ-5D-5L index improved from 0.585 to 0.807 (0.231; 95% CI, 0.195-0.267; p < 0.0001). Although the mixed-effects model attenuated completed-case results, conclusions and statistical significance were maintained. Of 52 subjects who were on opioids at baseline and had a five-year visit, 46% discontinued, and 23% decreased intake. The safety profile compared favorably with neurostimulator treatments for other types of back pain. No lead migrations were observed. CONCLUSION: Over a five-year period, restorative neurostimulation provided clinically substantial and durable benefits with a favorable safety profile in patients with refractory chronic low back pain associated with multifidus muscle dysfunction. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT02577354; registration date: October 15, 2016; principal investigator: Christopher Gilligan, MD, Brigham and Women's Hospital, Boston, MA, USA. The study was conducted in Australia (Broadmeadow, New South Wales; Noosa Heads, Queensland; Welland, South Australia; Clayton, Victoria), Belgium (Sint-Niklaas; Wilrijk), The Netherlands (Rotterdam), UK (Leeds, London, Middlesbrough), and USA (La Jolla, CA; Santa Monica, CA; Aurora, CO; Carmel, IN; Indianapolis, IN; Kansas City, KS; Boston, MA; Royal Oak, MI; Durham, NC; Winston-Salem, NC; Cleveland, OH; Providence, RI; Spartanburg, SC; Spokane, WA; Charleston, WV).

Long-Term Outcomes of Restorative Neurostimulation in Patients With Refractory Chronic Low Back Pain Secondary to Multifidus Dysfunction: Two-Year Results of the ReActiv8-B Pivotal Trial.

BACKGROUND: Impaired neuromuscular control and degeneration of the multifidus muscle have been linked to the development of refractory chronic low back pain (CLBP). An implantable restorative-neurostimulator system can override the underlying multifidus inhibition by eliciting episodic, isolated contractions. The ReActiv8-B randomized, active-sham-controlled trial provided effectiveness and safety evidence for this system, and all participants received therapeutic stimulation from four months onward. OBJECTIVE: This study aimed to evaluate the two-year effectiveness of this restorative neurostimulator in patients with disabling CLBP secondary to multifidus muscle dysfunction and no indications for spine surgery. MATERIALS AND METHODS: Open-label follow-up of 204 participants implanted with a restorative neurostimulation system (ReActiv8, Mainstay Medical, Dublin, Ireland) was performed. Pain intensity (visual analog scale [VAS]), disability (Oswestry disability index [ODI]), quality-of-life (EQ-5D-5L), and opioid intake were assessed at baseline, six months, one year, and two years after activation. RESULTS: At two years (n = 156), the proportion of participants with ≥50% CLBP relief was 71%, and 65% reported CLBP resolution (VAS ≤ 2.5 cm); 61% had a reduction in ODI of ≥20 points, 76% had improvements of ≥50% in VAS and/or ≥20 points in ODI, and 56% had these substantial improvements in both VAS and ODI. A total of 87% of participants had continued device use during the second year for a median of 43% of the maximum duration, and 60% (34 of 57) had voluntarily discontinued (39%) or reduced (21%) opioid intake. CONCLUSIONS: At two years, 76% of participants experienced substantial, clinically meaningful improvements in pain, disability, or both. These results provide evidence of long-term effectiveness and durability of restorative neurostimulation in patients with disabling CLBP, secondary to multifidus muscle dysfunction. CLINICAL TRIAL REGISTRATION: The study is registered on clinicaltrials.gov with identifier NCT02577354.

Three-Year Durability of Restorative Neurostimulation Effectiveness in Patients With Chronic Low Back Pain and Multifidus Muscle Dysfunction.

BACKGROUND: Restorative neurostimulation is a rehabilitative treatment for patients with refractory chronic low back pain (CLBP) associated with dysfunction of the lumbar multifidus muscle resulting in impaired neuromuscular control. The ReActiv8-B randomized, sham-controlled trial provided evidence of the effectiveness and safety of an implanted, restorative neurostimulator. The two-year analysis previously published in this journal demonstrated accrual of clinical benefits and long-term durability. OBJECTIVE: Evaluation of three-year effectiveness and safety in patients with refractory, disabling CLBP secondary to multifidus muscle dysfunction and no indications for spine surgery. MATERIALS AND METHODS: Prospective, observational follow-up of the 204 implanted trial participants. Low back pain visual analog scale (VAS), Oswestry Disability Index (ODI), EuroQol quality of life survey, and opioid intake were assessed at baseline, six months, and one, two, and three years after activation. The mixed-effects model repeated measures approach was used to provide implicit imputations of missing data for continuous outcomes and multiple imputation for proportion estimates. RESULTS: Data were collected from 133 participants, and 16 patients missed their three-year follow-up because of coronavirus disease restrictions but remain available for future follow-up. A total of 62% of participants had a ≥ 70% VAS reduction, and 67% reported CLBP resolution (VAS ≤ 2.5cm); 63% had a reduction in ODI of ≥ 20 points; 83% had improvements of ≥ 50% in VAS and/or ≥ 20 points in ODI, and 56% had these substantial improvements in both VAS and ODI. A total of 71% (36/51) participants on opioids at baseline had voluntarily discontinued (49%) or reduced (22%) opioid intake. The attenuation of effectiveness in the imputed (N = 204) analyses was relatively small and did not affect the statistical significance and clinical relevance of these results. The safety profile remains favorable, and no lead migrations have been observed to date. CONCLUSION: At three years, 83% of participants experienced clinically substantial improvements in pain, disability, or both. The results confirm the long-term effectiveness, durability, and safety of restorative neurostimulation in patients with disabling CLBP associated with multifidus muscle dysfunction. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT02577354.

Saphenous somatosensory-evoked potentials monitoring of femoral nerve health during prone transpsoas lateral lumbar interbody fusion.

PURPOSE: To assess whether saphenous somatosensory-evoked potentials (saphSSEP) monitoring may provide predictive information of femoral nerve health during prone lateral interbody fusion (LIF) procedures. METHODS: Intraoperative details were captured prospectively in consecutive prone LIF surgeries at a single institution. Triggered electromyography was used during the approach; saphSSEP was monitored throughout using a novel system that enables acquisition of difficult signals and real-time actionable feedback facilitating intraoperative intervention. Postoperative neural function was correlated with intraoperative findings. RESULTS: Fifty-nine patients (58% female, mean age 64, mean BMI 32) underwent LIF at 95 total levels, inclusive of L4-5 in 76%, fixated via percutaneous pedicle screws (81%) or lateral plate, with direct decompression in 39%. Total operative time averaged 149 min. Psoas retraction time averaged 16 min/level. Baseline SSEPs were unreliable in 3 due to comorbidities in 2 and anesthesia in 1; one of those resulted in transient quadriceps weakness, fully recovered at 6 weeks. In 25/56, no saphSSEP changes occurred, and none had postoperative femoral nerve deficits. In 24/31 with saphSSEP changes, responses recovered intraoperatively following intervention, with normal postoperative function in all but one with delayed quadriceps weakness, improved at 4 months and recovered at 9 months, and a second with transient isolated anterior thigh numbness. In the remaining 7/31, saphSSEP changes persisted to close, and resulted in 2 transient isolated anterior thigh numbness and 2 combined sensory and motor femoral nerve deficits, both resolved at between 4 and 8 months. CONCLUSIONS: SaphSSEP was reliably monitored in most cases and provided actionable feedback that was highly predictive of neurological events during LIF. LEVEL OF EVIDENCE: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

An implantable restorative-neurostimulator for refractory mechanical chronic low back pain: a randomized sham-controlled clinical trial.

ABSTRACT: Chronic low back pain can be caused by impaired control and degeneration of the multifidus muscles and consequent functional instability of the lumbar spine. Available treatment options have limited effectiveness and prognosis is unfavorable. We conducted an international randomized, double-blind, sham-controlled trial at 26 multidisciplinary centers to determine safety and efficacy of an implantable, restorative neurostimulator designed to restore multifidus neuromuscular control and facilitate relief of symptoms (clinicaltrials.gov identifier: NCT02577354). Two hundred four eligible participants with refractory mechanical (musculoskeletal) chronic LBP and a positive prone instability test indicating impaired multifidus control were implanted and randomized to therapeutic (N = 102) or low-level sham (N = 102) stimulation of the medial branch of the dorsal ramus nerve (multifidus nerve supply) for 30 minutes twice daily. The primary endpoint was the comparison of responder proportions (≥30% relief on the LBP visual analogue scale without analgesics increase) at 120 days. After the primary endpoint assessment, participants in the sham-control group switched to therapeutic stimulation and the combined cohort was assessed through 1 year for long-term outcomes and adverse events. The primary endpoint was inconclusive in terms of treatment superiority (57.1% vs 46.6%; difference: 10.4%; 95% confidence interval, -3.3% to 24.1%, P = 0.138). Prespecified secondary outcomes and analyses were consistent with a modest but clinically meaningful treatment benefit at 120 days. Improvements from baseline, which continued to accrue in all outcome measures after conclusion of the double-blind phase, were clinically important at 1 year. The incidence of serious procedure- or device-related adverse events (3.9%) compared favorably with other neuromodulation therapies for chronic pain.

Initial multi-centre clinical experience with prone transpsoas lateral interbody fusion: Feasibility, perioperative outcomes, and lessons learned.

BACKGROUND: Lateral interbody fusion (LIF) is traditionally performed with the patient in lateral decubitus, requiring repositioning to prone for adjunctive posterior procedures, or modifying traditional posterior techniques to be done while positioned lateral. The benefits of lateral anterior column access may be achievable with the patient prone, allowing for concomitant posterior techniques in a more familiar single-position setting. METHODS: Prone transpsoas (PTP) access was outlined and vetted by a group of LIF-experienced spine surgeons. Early clinical experience included prospectively capturing procedural details and perioperative outcomes across a multi-centre cohort of clinicians to assess feasibility and to identify efficiencies and/or challenges. RESULTS: Perioperative data was prospectively collected from 120 consecutive cases (176 levels) from 22 surgeons. Lateral exposure was achieved in an average 18 min/level, guided by triggered EMG; and retraction time averaged 25 min/level, with continued plexus monitoring via saphenous SSEP. Fixation was via percutaneous pedicle screws (65%), open pedicle screws (24%), other (11%). No re-positioning was required. Concomitant procedures facilitated by prone position included direct decompression (37%), treatment at L5-S1 (18%), posterior instrumentation revision (7%), and osteotomy/bony releases (9%). PTP procedure time, blood loss, and length of stay were consistent with established LIF experience. Challenges included patient movement with lateral instrument forces, retractor sag, stability of access relative to the patient, and surgeon ergonomics of the working channel. These challenges were overcome later in the experience through development of a specialized positioner and retractor system specific to this approach and a prescribed workflow developed by consensus of the surgeons. CONCLUSION: Initial multi-centre clinical experience suggests that PTP is not only feasible but creates efficiencies by allowing for single-position surgery maximizing both anterior and posterior column access and corrective techniques, with perioperative outcomes consistent with lateral decubitus experience. Learnings included the need for development of procedure-specific technologies and technique refinement.

Short-segment minimally disruptive anterior column release for focal sagittal deformity correction of the thoracolumbar spine.

BACKGROUND: Sagittal malalignment is associated with poor quality of life. Correction of lumbar lordosis through anterior column release (ACR) has been shown to improve overall sagittal alignment, however typically in combination with long posterior constructs and associated morbidity. The technical feasibility and radiographic outcomes of short-segment anterior or lateral minimally invasive surgery (MIS) ACR techniques in moderate to severe lumbar sagittal deformity were evaluated. METHODS: Consecutive patients treated with short-segment MIS ACR techniques for moderate to severe lumbar sagittal deformity correction were retrospectively analyzed from a prospectively collected database. Clinical outcomes included perioperative measures of invasiveness, including operative time, blood loss, complications, and average length of stay. Radiographic outcomes included measurement of preoperative, immediate postoperative, and long-term follow-up radiographic parameters including coronal Cobb angle, lumbar lordosis (LL), pelvic incidence (PI), PI-LL mismatch, pelvic tilt (PT), T1 pelvic angle (TPA), T1 spino-pelvic inclination (T1SPI), proximal junctional angle (PJA), and sagittal vertical axis (SVA). RESULTS: The cohort included 34 patients (mean age 63) who were treated at an average 2.5 interbody levels (range 1-4) through a lateral or anterior approach (LLIF or ALIF). Of 89 total interbody levels treated, 63 (71%) were ACR levels. Posterior fixation was across an average of 3.2 levels (range 1-5). Mean total operative time and blood loss were 362 minutes and 621 mL. Surgical complications occurred in 2 (5.9%). Average hospital stay was 5.5 days (including staging). At last follow-up (average 25.4 months; range 0.5-7 years), all patients (100%) demonstrated successful achievement of one or more alignment goal, with significant improvements in coronal Cobb, LL, PI-LL mismatch, PT, and TPA. No patient was revised for PJK. CONCLUSIONS: These data show that short-segment MIS ACR correction of moderate to severe lumbar sagittal deformity is feasible and effective at achieving overall alignment goals with low procedural morbidity and risk of proximal junctional issues.

The prone transpsoas technique: preliminary radiographic results of a multicenter experience.

INTRODUCTION: The lateral lumbar interbody fusion (LLIF) is a safe and effective technique to treat a vast range of lumbar disorders. However, the technique is also burdened by some problems. A new approach to the lateral lumbar interbody fusion was devised to solve or reduce some of the problems regarding the lateral approach. Its principal difference from the standard LLIF relies on positioning the patient in a prone decubitus, which might lead to an increase in the intradiscal lordosis. METHODS: A retrospective, multicentric, non-randomized study to evaluate segmental and regional lordosis following prone transpsoas (PTP) approach to LLIF. All patients undergoing prone transpsoas surgery at the involved institutions were included. Patients with low-quality images not allowing the measurements of the required spinopelvic parameters were excluded. Measurements included pre- and postoperative index-level segmental lordosis, lumbar lordosis, pelvic incidence, and pelvic tilt. RESULTS: Thirty-two (32) patients were included in the study, in which 23 underwent single-level, six (6) underwent two-level, Two (2) underwent three-level, and one underwent four-level PTP. Mean index level segmental lordosis increased from 8.7° to 14.8°(p < 0.001); lumbar lordosis (L1-S1) increased from 42.1° to 45.8° (p = 0.11), although after excluding an outlier value L1-S1 lordosis results were 41.9° pre-op to 46.7° post-op (p = 0.003). Twenty-two (22) patients had a pre-op PI-LL mismatch of 10° or more, while at the postoperative visit, only 12 patients had a mismatch outside of 10° (p = 0.01). CONCLUSION: The prone transpsoas technique is feasible and is associated with a significant gain of segmental lordosis and correction of spinopelvic alignment parameters.

Correction to: The prone transpsoas technique: preliminary radiographic results of a multicenter experience.

Unfortunately, the third and fourth author names have been incorrectly published in the original publication. The complete correct names are given below.

Rational decision making in a wide scenario of different minimally invasive lumbar interbody fusion approaches and devices.

With the proliferation of a variety of modern MIS spine surgery procedures, it is mandatory that the surgeon dominate all aspects involved in surgical indication. The information related to the decision making in patient selection for specific procedures is mandatory for surgical success. The objective of this study is to present decision-making criteria in minimally invasive surgery (MIS) selection for a variety of patients and pathologies. In this article, practicing surgeons who specialize in various MIS approaches for spinal fusion were engaged to provide expert opinion and literature review on decision making criteria for several MIS procedures. Pros, cons, relative limitations, and case examples are provided for patient selection in treatment with MIS posterolateral fusion (MIS-PLF), mini anterior lumbar interbody fusion (mini-ALIF), lateral interbody fusion (LLIF), MIS posterior lumbar interbody fusion (MIS-PLIF) and MIS transforaminal lumbar interbody fusion (MIS-TLIF). There is a variety of aspects to consider when deciding which modern MIS surgical approach is most appropriate to use based on patient and pathologic characteristics. The surgeon must adapt them to the characteristic of each type of patients, helping them to choose the most effective and efficient therapeutic option for each case.

A Multicenter Radiographic Evaluation of the Rates of Preoperative and Postoperative Malalignment in Degenerative Spinal Fusions.

STUDY DESIGN: Multicenter, retrospective, institutional-review-board -approved study at 18 institutions in the United States with 24 treating investigators. OBJECTIVE: This study was designed to retrospectively assess the prevalence of spinopelvic malalignment in patients who underwent one- or two-level lumbar fusions for degenerative (nondeformity) indications and to assess the incidence of malalignment after fusion surgery as well as the rate of alignment preservation and/or correction in this population. SUMMARY OF BACKGROUND DATA: Spinopelvic malalignment after lumbar fusion has been associated with lower postoperative health-related quality of life and elevated risk of adjacent segment failure. The prevalence of spinopelvic malalignment in short-segment degenerative lumbar fusion procedures from a large sample of patients is heretofore unreported and may lead to an under-appreciation of these factors in surgical planning and ultimate preservation or correction of alignment. METHODS: Lateral preoperative and postoperative lumbar radiographs were retrospectively acquired from 578 one- or two-level lumbar fusion patients and newly measured for lumbar lordosis (LL), pelvic incidence (PI), and pelvic tilt. Patients were categorized at preop and postop time points as aligned if PI-LL < 10° or malaligned if PI-LL≥10°. Patients were grouped into categories based on their alignment progression from pre- to postoperative, with preserved (aligned to aligned), restored (malaligned to aligned), not corrected (malaligned to malaligned), and worsened (aligned to malaligned) designations. RESULTS: Preoperatively, 173 (30%) patients exhibited malalignment. Postoperatively, 161 (28%) of patients were malaligned. Alignment was preserved in 63%, restored in 9%, not corrected in 21%, and worsened in 7% of patients. CONCLUSION: This is the first multicenter study to evaluate the preoperative prevalence and postoperative incidence of spinopelvic malalignment in a large series of short-segment degenerative lumbar fusions, finding over 25% of patients out of alignment at both time points, suggesting that alignment preservation/restoration considerations should be incorporated into the decision-making of even degenerative lumbar spinal fusions. LEVEL OF EVIDENCE: 3.

Two-Year Comparative Outcomes of MIS Lateral and MIS Transforaminal Interbody Fusion in the Treatment of Degenerative Spondylolisthesis: Part II: Radiographic Findings.

STUDY DESIGN: Prospective, multicenter, institutional review board approved study with randomized and observational study arms. OBJECTIVE: The purpose of this study was to compare radiographic outcomes between minimally invasive transforaminal (MIS TLIF) or MIS lateral interbody fusion (XLIF) in the treatment of patients with low-grade degenerative spondylolisthesis with stenosis through 2-year postoperative. SUMMARY OF BACKGROUND DATA: Few reports exist comparing different MIS approaches directly in the treatment of similar pathology, as most studies report differences between MIS and open procedures. METHODS: A total of 55 patients undergoing surgical treatment for degenerative spondylolisthesis with spinal stenosis at one or two contiguous levels between L1 and L5 were enrolled. Twenty-nine patients were treated with XLIF and 26 patients were treated with MIS TLIF. RESULTS: Disc height was significantly improved from preoperative at all postoperative time points in both groups, though the XLIF group experienced less subsidence and resultant loss of disc height than the MIS TLIF group by 24-month postoperative (P = 0.002). Postoperative change in central canal area was statistically greater in the MIS TLIF compared with the XLIF group (43.1 mmvs. 4.1 mm, P = 0.028). At several postoperative time points, foraminal height and area on the ipsilateral side and foraminal height on the contralateral side to the approach were significantly increased postoperatively in the XLIF group, and the magnitude of ipsilateral height increase was greater than in the MIS TLIF cohort (P < 0.05).Using fusion criteria of <3° range of motion and <3 mm translation on plain radiographs, 100% of patients in both groups were solidly fused at 24-month postoperative. Using computed tomography fusion criteria of presence of intervertebral bridging bone, 100% (32/32) of XLIF levels and 96% (25/26) of MIS TLIF levels were solidly bridged (P = 0.448). CONCLUSION: Different mechanisms of stenosis correction (direct vs. indirect) between the MIS TLIF and XLIF groups studied resulted in several significantly different radiographic characteristics. Despite these differences, both groups of patients experienced significant and maintained clinical improvements with high fusion rates at 2-year follow-up, suggesting that the mechanism of correction may not be critical and both MIS procedures are reasonable treatment options for degenerative spondylolisthesis with stenosis. LEVEL OF EVIDENCE: 2.

Two-year Comparative Outcomes of MIS Lateral and MIS Transforaminal Interbody Fusion in the Treatment of Degenerative Spondylolisthesis: Part I: Clinical Findings.

STUDY DESIGN: A prospective, multicenter, institutional review board (IRB) approved study with randomized and observational study arms. OBJECTIVE: The purpose of this study was to compare clinical outcomes between minimally invasive transforaminal (MIS TLIF) and MIS lateral interbody fusion (XLIF) in the treatment of patients with low-grade degenerative spondylolisthesis with stenosis through two years postoperative. SUMMARY OF BACKGROUND DATA: Few reports exist comparing different MIS approaches directly in the treatment of similar pathology, as most studies report differences between MIS and open procedures. METHODS: A total of 55 patients undergoing surgical treatment for degenerative spondylolisthesis with spinal stenosis at one or two contiguous levels between L1 and L5 were enrolled. Twenty-nine patients were treated with XLIF and 26 patients were treated with MIS TLIF. RESULTS: Operative time and length of stay were similar between the XLIF and MIS TLIF groups (171 vs 186 minutes; two days for each group). Blood loss was significantly lower in the XLIF group, with 79% of XLIF cases and 27% of MIS TLIF cases resulting in <100 mL of blood loss, P < 0.001. Hip flexion weakness was more common in the XLIF group (31%) than in the MIS TLIF group (0%). One patient in the XLIF group had a new distal motor weakness and three patients in the XLIF group and two patients in the MIS TLIF group had new sensory changes postoperatively, all of which resolved by 12 months postoperative. Back and leg pain for both XLIF and MIS TLIF groups improved significantly from baseline to 24 months postoperative, with 73% improvement in the XLIF and 64% in the MIS TLIF group. Worst leg pain showed similar improvements through two years postoperative, with a 79% decrease seen in the XLIF group and 74% in the MIS TLIF group. Disability (ODI) improved 53% in the XLIF group and 57% in the MIS TLIF group. CONCLUSION: Despite different mechanisms of action (indirect vs direct decompression), mid-term clinical outcomes between XLIF and MIS TLIF were similar. These two-year results suggest that both XLIF and MIS TLIF are reasonable MIS approaches for the treatment of lumbar degenerative pathology. LEVEL OF EVIDENCE: 2.

Lumbar total disc replacement by less invasive lateral approach: a report of results from two centers in the US IDE clinical trial of the XL TDR® device.

PURPOSE: To evaluate the clinical and radiographic outcomes following total disc arthroplasty using the XL TDR(®) Lumbar Disc in the treatment of patients with symptomatic degenerative disc disease at one level between L1-2 and L4-5. METHODS: Data were compiled from two centers participating in a prospective, multi-center Food and Drug Administration-approved investigational device exemption clinical trial enrolling patients with single-level lumbar degenerative disc disease unresponsive to non-operative treatment. Longitudinal outcomes were evaluated through 3-year follow-up and included patient-reported pain, function, and general health, as well as radiographic measures such as maintenance of disc height and range of motion. RESULTS: The two-center cohort included 64 treated patients, 42 % female, averaging 45.3 years of age (range 26-67). The majority of procedures were performed at the L4-5 level (75 %), uncomplicated, with minimal blood loss (88 % 0-50 cc), and in an outpatient setting (93.8 %). Postoperative events included 10 patients (15.6 %) with new hip flexion weakness, 7 (10.9 %) with new lower extremity weakness, and 10 (15.6 %) with new lower extremity sensory deficits, all resolved by 3 months in all but two patients whose deficits were prolonged but eventually resolved. Average disc height increased postoperatively from 7.2 to 12.1 mm (69 %), and was 10.7 mm (49 % increase from preoperative) at 3 years. Flexion/extension range of motion averaged 5.9° (SD 4.8°) at 3 years, and was not statistically different from preoperative (p = 0.471). Heterotopic ossification interfering with segmental motion was noted in 3 patients (10.3 %) at 3 years, none ankylosed (Grade IV). Postoperative improvement in patient-reported outcomes was significant (p < 0.01 for all measures) and maintained through 3-year follow-up. Satisfaction with results was reported by 85 % (51/60) of patients at 2 years and 93 % (28/30) at 3 years. There were no revisions through 3 years postoperative. CONCLUSIONS: The results following XL TDR show good clinical and radiographic outcomes out to 3 years postoperative, with clinically significant improvements in pain, function, and general health, few complications, and high patient satisfaction.

Radiographical and clinical evaluation of extreme lateral interbody fusion: effects of cage size and instrumentation type with a minimum of 1-year follow-up.

STUDY DESIGN: Prospective single-cohort observational study. OBJECTIVES: To compare cage settling rates after extreme lateral interbody fusion (XLIF) across various implant sizes and fixation types. Secondary objectives were to detect factors associated with cage settling and correlation with clinical and radiographical improvement. SUMMARY OF BACKGROUND DATA: Intervertebral cage settling can occur postoperatively after interbody fusion, limiting the long-term correction achieved with surgery. METHODS: Clinical and radiographical data were collected on 140 consecutive patients treated with extreme lateral interbody fusion at 223 levels (range, 1-5). All patients received supplemental pedicle screw fixation or lateral plating. RESULTS: Average follow-up was 15.5 months (range, 12-36 mo). At 12 months, disability improved by 44%, low back pain improved by 49%, leg pain improved by 48%, and quality of life improved by 50% (P < 0.001). Foraminal height improved from 15.7 mm to 21.2 mm, disc height improved from 4.6 mm to 9.4 mm, discal lordosis improved from 4.0 to 8.1, and segmental lordosis improved from 10.7 to 13.7 (P < 0.001). Cage settling 1 mm or more occurred in 20% of cages immediately postoperatively and in 62% at 12 months. Settling more than 4 mm occurred in 5% of cages immediately postoperatively and in 24% at 12 months postoperatively. Pedicle screw fixation was associated with a higher rate of cage settling 1 mm or more compared with lateral plating, though magnitude of settling at the anterior inferior endplate was higher for lateral plating (4.9 mm vs. 3.5 mm). Taller cage height, narrower cage width, and shorter cage length were significantly associated with increased risk of cage settling more than 4 mm at 12 months postoperatively. In patients with no cage settling immediately postoperatively, risk of settling more than 4 mm at 12 months was 6.8 times greater with narrower cages. CONCLUSION: Risk of cage settling after extreme lateral interbody fusion may be reduced with the use of wider cages to engage more central endplate bone, longer cages to span the ring apophysis and osteophytes, and avoid overdistraction of the intervertebral disc space with shorter cages. LEVEL OF EVIDENCE: 3.

Adult degenerative scoliosis treated with XLIF: clinical and radiographical results of a prospective multicenter study with 24-month follow-up.

STUDY DESIGN: Prospective, multicenter, single-arm study. OBJECTIVE: The objective of this study was to evaluate the clinical and radiographical results of patients undergoing extreme lateral interbody fusion (XLIF), a minimally disruptive lateral transpsoas retroperitoneal surgical approach for the treatment of degenerative scoliosis (DS). SUMMARY OF BACKGROUND DATA: Surgery for the treatment of DS has been reported to have acceptable results but is traditionally associated with high morbidity and complication rates. A minimally disruptive lateral transpsoas retroperitoneal surgical approach (XLIF) has become popular for the treatment of DS. This is the first prospective, multicenter study to quantify outcomes after XLIF in this patient population. METHODS: A total of 107 patients with DS who underwent the XLIF procedure with or without supplemental posterior fixation at one or more intervertebral levels were enrolled in this study. Clinical and radiographical results were evaluated up to 24 months after surgery. RESULTS: Mean patient age was 68 years; 73% of patients were female. A mean of 3.0 (range, 1-6) levels were treated with XLIF per patient. Overall complication rate was low compared with traditional surgical treatment of DS. Significant improvement was seen in all clinical outcome measures at 24 months: Oswestry Disability Index, visual analogue scale for back pain and leg pain, and 36-Item Short Form Health Survey mental and physical component summaries (P < 0.001). Eighty-five percent of patients were satisfied with their outcome and would undergo the procedure again. In patients with hypolordosis, lumbar lordosis was corrected from a mean of 27.7° to 33.6° at 24 months (P < 0.001). Overall Cobb angle was corrected from 20.9° to 15.2°, with the greatest correction observed in patients supplemented with bilateral pedicle screws. CONCLUSION: This study demonstrates the use of the XLIF procedure in the treatment of DS. XLIF is associated with good clinical and radiographical outcomes, with a substantially lower complication rate than has been reported with traditional surgical procedures. LEVEL OF EVIDENCE: 3.

Allograft cellular bone matrix in extreme lateral interbody fusion: preliminary radiographic and clinical outcomes.

INTRODUCTION: Extreme lateral interbody fusion (XLIF) is a minimally disruptive alternative for anterior lumbar interbody fusion. Recently, synthetic and allograft materials have been increasingly used to eliminate donor-site pain and complications secondary to autogenous bone graft harvesting. The clinical use of allograft cellular bone graft has potential advantages over autograft by eliminating the need to harvest autograft while mimicking autograft's biologic function. The objective of this study was to examine 12-month radiographic and clinical outcomes in patients who underwent XLIF with Osteocel Plus, one such allograft cellular bone matrix. METHODS: Forty (40) patients were treated at 61 levels with XLIF and Osteocel Plus and included in the analysis. RESULTS: No complications were observed. From preoperative to 12-month postoperative followup, ODI improved 41%, LBP improved 55%, leg pain improved 43.3%, and QOL (SF-36) improved 56%. At 12 months, 92% reported being "very" or "somewhat" satisfied with their outcome and 86% being either "very" or "somewhat likely" to choose to undergo the procedure again. Complete fusion was observed in 90.2% (55/61) of XLIF levels. CONCLUSIONS: Complete interbody fusion with Osteocel Plus was shown in 90.2% of XLIF levels, with the remaining 9.8% being partially consolidated and progressing towards fusion at 12 months.

Dynamically evoked, discrete-threshold electromyography in the extreme lateral interbody fusion approach.

OBJECT: because the psoas muscle, which contains nerves of the lumbar plexus, is traversed during the extreme lateral interbody fusion (XLIF) approach, appropriate nerve monitoring is needed to avoid nerve injury during surgery and prevent approach-related neural deficit. This study was performed to assess the effectiveness of dynamically evoked electromyography (EMG) to detect and prevent neural injury during the XLIF approach. METHODS: one hundred two patients undergoing XLIF at L3-4 and/or L4-5 were enrolled in a prospective, multicenter, nonrandomized clinical study. The EMG threshold values for each of the 3 successive dilators were recorded at the surface of the psoas muscle, mid-psoas, and on the spine. At each location, the dilators were rotated 360°, taking recordings immediately posterior, superior, anterior, and inferior. For each dilator, the authors noted the rotational position (the angle in degrees) at which the lowest threshold was found. Findings of pre- and postoperative neurological examinations were also recorded. RESULTS: nerves were identified within proximity of the dilators (alert-level EMG feedback) in 55.7% of all cases during the XLIF approach. Although nerves were more commonly identified in the posterior margin (63%), there was significant variability in the location of nerves identified. Despite the fact that the posterior half of the disc space was targeted in 90% of cases, no significant long-lasting neural deficits were identified in any case; 27.5% experienced new iliopsoas/hip flexion weakness and 17.6% experienced new postoperative upper medial thigh sensory loss. Transient motor deficits were identified in 3 patients (2.9%), and all had resolved by the 6-month follow-up visit. CONCLUSIONS: the ability to identify and report a discrete, real-time EMG threshold during the transpsoas approach helps to avoid nerve injury and is required for the safe performance of the XLIF procedure. Additionally, nerve location is variable, thus reinforcing the need for real-time directional and proximity information.