Implantation Of Annular Closure Device Research Articles

Bone resorption around the annular closure device during a postoperative follow-up of 8years.

Annular closure device (ACD) implantation is considered to be an effective means of preventing reherniation after microdiscectomy; however, there is an issue: the bone may resorb around the ACD. The causes of vertebral bone resorption remain unexplored; the dynamics of changes in bone resorption around the ACD have not yet been assessed or characterized. One hundred thirty-three patients underwent ACD implantation after microdiscectomy, and 107 of them were followed up for 8years after surgery (Oswestry, VAS). Lumbar CT scans helped characterize the bone resorption area around the ACD. The median of follow-up was 85 [74; 93] months (from 73 to 105months). The prevalence of bone resorption around the ACD was up to 63.6%, and it was mainly around the polymer mesh of the ACD (70.6%). The resorbed bone volume increased with time and reached its maximum of 5.2 cm3 (12% of the vertebral body volume) once a sclerotic rim developed around the bone resorption area. No differences in VAS pain intensity or in Oswestry Disability Index were found between patients with resorption and patients without it (p > 0.05). The volume of the intervertebral disc before surgery is a predictor of bone resorption (OR = 0.79, p = 0.009): if it is less than 13.2 cm3, the risk of bone resorption increases significantly (p < 0.05). The majority of patients (up to 63.6%) with implanted ACDs have vertebral bone resorption around them. The bone resorption area around the ACD mesh increases with time to up to 12% of the vertebral body volume, with no clinical evidence, though. The formation of a sclerotic rim prevents the bone resorption area from further growth. If the volume of the intervertebral disc before surgery is less than 13.2 cm3, the risk of bone resorption increases significantly.

Lumbar discectomy with annulus fibrosus closure: A retrospective series of 53 consecutive patients

IntroductionLumbar disc herniation is most common degenerative alteration of the spine. Whenever surgical therapy proves to be necessary, recurrent disc herniation is most frequent concern. Here, primary aim was to determine the percentage of patients eligible for insertion of an annular closure device (ACD). Secondary aim to evaluate 12-month incidence of recurrent disc herniation at the operated level. Our hypothesis was that ACD might help in preventing recurrent disc herniation. MethodsPatients in a single Swiss neurosurgical center underwent limited discectomy alone (n=41, group 1) versus limited discectomy plus ACD (n=12, group 2). Mean postoperative follow-up period was 12months. ResultsTwelve out of 53 patients (22.6%) were eligible for ACD implantation. Patients of group 2 were significantly taller (mean 176cm, P=0.007) as compared with group 1 (mean 170). The only statistically significant difference of intraoperative parameters between group 1 and 2 was amount of nucleus materiel removed (P=0.01), being greater in group 2 (mean 0.9) as compared with group 1 (mean 0.3). In group 1 six patients (6/41, 14.6%) presented with symptomatic reherniation at same level of surgery, while in group 2 only one patient experienced recurrence (1/12, 8.3%). No adverse events were reported. DiscussionIn the current study one out of five patients with lumbar disc herniation was considered suitable for ACD placement. In vast majority of these patients reherniation was precluded on the short-term basis. Patients with ACD were taller and had intraoperatively a higher volume of the nucleus pulposus materiel removed.

Incidence and clinical impact of vertebral endplate changes after limited lumbar microdiscectomy and implantation of a bone-anchored annular closure device

BackgroundAn annular closure device (ACD) could potentially prevent recurrent herniation by blocking larger annular defects after limited microdiscectomy (LMD). The purpose of this study was to analyze the incidence of endplate changes (EPC) and outcome after LMD with additional implantation of an ACD to prevent reherniation.MethodsThis analysis includes data from a) RCT study-arm of patients undergoing LMD with ACD implantation and b) additional patients undergoing ACD implantation at our institution. Clinical findings (VAS, ODI), radiological outcome (reherniation, implant integrity, volume of EPC) and risk factors for EPC were assessed.ResultsSeventy-two patients (37 men, 47 ± 11.63yo) underwent LMD and ACD implantation between 2013–2016. A total of 71 (99%) patients presented with some degree of EPC during the follow-up period (14.67 ± 4.77 months). In the multivariate regression analysis, localization of the anchor was the only significant predictor of EPC (p = 0.038). The largest EPC measured 4.2 cm3. Reherniation was documented in 17 (24%) patients (symptomatic: n = 10; asymptomatic: n = 7). Six (8.3%) patients with symptomatic reherniation underwent rediscectomy. Implant failure was documented in 19 (26.4%) patients including anchor head breakage (n = 1, 1.3%), dislocation of the whole device (n = 5, 6.9%), and mesh dislocation into the spinal canal (n = 13, 18%). Mesh subsidence within the EPC was documented in 15 (20.8%) patients. Seven (9.7%) patients underwent explantation of the entire, or parts of the device.ConclusionClinical improvement after LMD and ACD implantation was proven in our study. High incidence and volume of EPC did not correlate with clinical outcome. The ACD might prevent disc reherniation despite implant failure rates. Mechanical friction of the polymer mesh with the endplate is most likely the cause of EPC after ACD.

Intraoperative findings, complications, and short-term results after lumbar microdiscectomy with or without implantation of annular closure device.

Standard microscopic lumbar discectomy (MLD) is a short operation with minimal blood loss, and a low rate of peri- and intraoperative complications. The objective of this study was to evaluate intraoperative findings, complications, and early postoperative neurological outcome (< 105days) in patients undergoing MLD with or without implantation of an annular closure device (ACD). This study is based on data analysis of a post-marketing, prospective, multicenter RCT in Europe including patients undergoing standard MLD with or without implantation of an ACD (Barricaid®, Intrinsic Therapeutics, Inc., Woburn, MA). Enrollment of 554 patients in 21 centers in Europe (Germany, Switzerland, Austria, Belgium, The Netherlands, and France) started in 2010 and was completed in October 2014, with 276 patients randomized to the ACD group and 278 to the control group. Mean operation time was 70min in the ACD group and 52min in the control group (p < 0.0001). Intraoperative fluoroscopy time was 24s in the ACD group and 7s in the control group (p < 0.0001). Average blood loss was 94.2ml in the ACD group and 64.7ml in the control group (p = 0.0001). Serious device- or procedure-related adverse events occurred in 3.7% (10/272) of the ACD group and 7.9% (22/278) of the control group. Dural injuries occurred in 13 (4.8%) patients in the ACD group and 7 (2.5%) in the control group. There was one device-related nerve root injury resulting in a nerve root amputation. Surgical complications included 3 hematomas in the ACD group and 4 in the control group; 3 infections occurred in both groups. Device migrations were documented in 3 patients in the ACD group. Patients in the ACD group (n = 7, 2.6%) underwent fewer reoperations compared with that in the control group (n = 16, 5.8%, OR = 2.3 (0.9-5.7)). Mean VAS leg pain at 3months was 11.9 in the ACD and 15.1 in the control group, respectively. Short-term outcome after MLD with or without implantation of ACD was similar in both groups. Patients included in the ACD group underwent fewer reoperations in the first 3months after surgery. Nevertheless, longer operation time, higher amount of blood loss, and risk of nerve root lesion during device implantation should be considered additional risks in patients undergoing ACD implantation after MLD.

Does Patient Blinding Influence Clinical Outcomes After Annular Closure Device Implantation? A Propensity Score-Matched Analysis.

BackgroundAwareness of treatment group assignment in a clinical trial may influence patient behavior and bias outcome reporting. The objective of this study was to compare 2-year clinical outcomes in blinded vs unblinded patients who were treated with lumbar discectomy and a bone-anchored annular closure device (ACD) for prevention of lumbar disc reherniation.MethodsThis was a secondary analysis of a randomized trial comparing lumbar discectomy with (n=272) vs without (n=278) implantation of a bone-anchored ACD. Among patients who received ACD implantation, 35 (13%) were blinded and 237 (87%) were unblinded to treatment allocation. In patients treated with ACD, propensity score-matching (1:1) was performed to account for imbalances in patient characteristics between blinded and unblinded groups. Key clinical outcomes were back pain severity (0–100 scale), leg pain severity (0–100 scale), Oswestry Disability Index (ODI, 0–100 scale), symptomatic reherniation, reoperation at the treated lumbar level, and device- or procedure-related serious adverse events (AEs). Outcomes were reported through 2 years of follow-up, which coincided with the time at which blinded patients were unblinded.ResultsThere were no statistically significant differences in 2-year outcomes between propensity score-matched blinded (n=35) and unblinded (n=35) patients treated with the ACD. In blinded vs unblinded ACD patients compared to baseline, back pain severity decreased by 40 vs 37 points (P=0.61), leg pain severity decreased by 75 points in each group (P>0.99), and ODI decreased by 47 vs 43 points (P=0.19). The risks of symptomatic reherniation (5.7% vs 9.1%; P=0.59), reoperation (8.6% vs 12.2%, P=0.62), and device- or procedure-related serious AEs (5.7% vs 8.9%, P=0.63) were comparably low in blinded and unblinded patients.ConclusionIn patients treated with lumbar discectomy and a bone-anchored ACD, there were no clinically important or statistically significant differences in back pain, leg pain, ODI, symptomatic reherniation, reoperation, or serious AEs over 2 years of follow-up when comparing patients who were blinded vs unblinded to their treatment assignment. The main limitations of this study were the post hoc nature of the analysis and the potential for bias due to surgeon awareness of treatment assignment.

Two-year real-world results of lumbar discectomy with bone-anchored annular closure in patients at high risk of reherniation

To determine the safety and effectiveness of limited lumbar discectomy with additional implantation of an annular closure device (ACD) among patients at high risk of herniation recurrence treated in routine clinical practice. This was a prospective, single-center study of lumbar discectomy for sciatica caused by intervertebral disc herniation with adjunctive ACD implantation to reduce herniation recurrence risk among high-risk patients with large annular defects. Patients returned for follow-up visits at 6weeks, 12weeks, 26weeks, 1year, and 2years. Main outcomes included reoperation, herniation recurrence, back pain severity, leg pain severity, and Oswestry Disability Index (ODI). The minimum important difference was defined as ≥ 20mm decrease relative to baseline for leg pain severity, ≥ 20mm decrease for back pain severity, and ≥ 15-point decrease for ODI. Among 75 high-risk patients (mean age 45years, 59% female), the cumulative event incidence through 2years was 4.0% for reoperation and 1.4% for herniation recurrence. Mean leg pain severity decreased from 73 to 6 (p < 0.001), back pain severity decreased from 51 to 13 (p < 0.001), and ODI decreased from 49 to 7 (p < 0.001). The percentage of patients achieving the minimum important difference was 91% for leg pain, 65% for back pain, and 94% for ODI. In patients at high risk of herniation recurrence following limited lumbar discectomy in routine clinical practice, additional implantation of an ACD was safe and reherniation recurrence rates were low at 2-year follow-up, which is favorably compared to reported rates in high-risk patients.

Three-year results from a randomized trial of lumbar discectomy with annulus fibrosus occlusion in patients at high risk for reherniation

BackgroundA larger defect in the annulus fibrosus following lumbar discectomy is a well-known risk factor for reherniation. Procedures intended to prevent reherniation by sealing or occluding the annular defect warrant study in high-risk patients. This study sought to determine 3-year results of lumbar discectomy with a bone-anchored annular closure device (ACD) or lumbar discectomy only (controls) in patients at high risk for reherniation.MethodsThis multicenter randomized trial enrolled patients with sciatica due to lumbar intervertebral disc herniation who failed conservative treatment. Patients with large annular defects after lumbar limited microdiscectomy were intraoperatively randomly assigned to receive ACD or control. Clinical and imaging follow-up was performed at routine intervals over 3 years. Main outcomes included rate of reherniations, reoperations, and endplate changes; leg and back pain scores on a visual analogue scale; Oswestry Disability Index (ODI); Physical Component Summary (PCS) and Mental Component Summary (MCS) scores from the SF-36; and adverse events adjudicated by a data safety monitoring board.ResultsAmong 554 randomized patients, the modified intent-to-treat population consisted of 272 patients in which ACD implantation was attempted and 278 receiving control; device implantation was not attempted in 4 patients assigned to ACD. Outcomes at 3 years favored ACD for symptomatic reherniation (14.8% vs. 29.5%; P < 0.001), reoperation (11.0% vs. 19.3%; P = 0.007), leg pain (21 vs. 30; P < 0.01), back pain (23 vs. 30; P = 0.01), ODI (18 vs. 23; P = 0.02), PCS (47 vs. 44; P < 0.01), and MCS (52 vs. 49; P < 0.01). The frequency of all-cause serious adverse events was comparable between groups (42.3% vs. 44.5%; P = 0.61).ConclusionsThe addition of a bone-anchored ACD in patients with large annular defects following lumbar discectomy reduces the risk of reherniation and reoperation, and has a similar safety profile over 3-year follow-up compared with lumbar limited discectomy only.Trial registrationClinicalTrials.gov NCT01283438

Morphology and Clinical Relevance of Vertebral Endplate Changes Following Limited Lumbar Discectomy With or Without Bone-anchored Annular Closure.

Post hoc analysis of a randomized controlled trial. To characterize the morphology and clinical relevance of vertebral endplate changes (VEPC) following limited lumbar discectomy with or without implantation of a bone-anchored annular closure device (ACD). Implantation of an ACD following limited lumbar discectomy has shown promise in reducing the risk of recurrent herniation in patients with large annular defects. However, the interaction between the ACD and the lumbar endplate over time is not well understood. Patients undergoing limited lumbar discectomy with large postsurgical annular defects were randomized intraoperatively to receive additional ACD implantation or limited lumbar discectomy only (Controls). VEPC morphology, area, and volume were assessed with low-dose computed tomography preoperatively and at 1 and 2 years follow-up. Of 554 randomized patients, the as-treated population consisted of 550 patients (267 ACD, 283 Controls). VEPC were preoperatively identified in 18% of patients in the ACD group and in 15% of Controls. At 2 years, VEPC frequency increased to 85% with ACD and 33% in Controls. Device- or procedure-related serious adverse event (8% vs. 17%, P = 0.001) and secondary surgical intervention (5% vs. 13%, P < 0.001) favored the ACD group over Controls. In the ACD group, clinical outcomes were comparable in patients with and without VEPC at 2 years follow-up. In the Control group, patients with VEPC at 2 years had higher risk of symptomatic reherniation versus patients without VEPC (35% vs. 19%, P < 0.01) CONCLUSION.: In patients with large annular defects following limited lumbar discectomy, additional implantation with a bone-anchored ACD reduces risk of postoperative complications despite a greater frequency of VEPC. VEPC were associated with higher risk of symptomatic reherniation in patients treated with limited lumbar discectomy, but not in those who received additional ACD implantation. 2.

Endplate changes after lumbar discectomy with and without implantation of an annular closure device.

The implantation of a bone-anchored annular closure device (ACD) might be associated with the developed new endplate changes (EPC) after surgery. A post hoc analysis has been done in patients from a prospective randomized multicenter study. All patients underwent limited lumbar discectomy with intraoperative randomization into the groups limited lumbar discectomy alone or additional ACD implantation. Low-dose lumbar computed tomography (CT) and clinical investigations were performed preoperatively and 12months after the operation. A total of 554 patients were randomized. After exclusion of dropouts, the per-protocol population included 493 patients (251 in the control group and 242 in the ACD group); the follow-up rate was ≥ 90%. The number of patients showing EPC at baseline was similar in both groups. The number of patients showing EPC and the total EPC lesion area significantly increased in both groups over time, but significantly increased more in the EPC group for the superior and inferior endplate (all P < 0.0001). There was no association of pre-existing number and size of EPC with sex, age, or smoking habits. Correlation of clinical variables showed no relation with number, size, and increase of EPC area after surgery. Patients with primary lumbar disc herniation show EPC in the corresponding segments. There is a significant increase of lesion number and size within 12months after discectomy. This increase is significantly more pronounced in the ACD group. Presence and growth of EPC is not correlated with low-back pain or ODI.

Effect of Annular Defects on Intradiscal Pressures in the Lumbar Spine: An in Vitro Biomechanical Study of Diskectomy and Annular Repair.

Background Integrity of intervertebral disks may influence, and be influenced by, the maintenance of hydrostatic pressures inside the nucleus pulposus. Disk degeneration causes decreased pressures, leading to overload and injury of the annulus fibrosus, increasing the risk of disk herniation. Diskectomies to treat disk herniation can cause further loss of hydrostatic pressures resulting in worsening degeneration. This study investigated the impact of opening the annulus on intradiscal pressure and whether implantation of an annular closure device (ACD) can restore physiologic pressures. Methods The pressure responses under unconstrained moments in concert with axial compressive loads of nine human cadaver lumbar disks were biomechanically tested at baseline, immediately following posterior annulotomy, and immediately following implantation of the ACD. Results The analysis of variance indicated a significant difference in the pressure response (p = 0.0001) among the three rounds of testing. Specifically, the post hoc Bonferroni test revealed that the pressure response after diskectomy was significantly different when compared with baseline (p < 0.001) and after ACD implantation (p = 0.001). However, baseline and ACD pressure responses were insignificantly different (p = 1.000). Conclusion Our findings suggest that restoration of annular integrity during diskectomy with implantation of the tested ACD may restore pressures closer to preoperative levels. Whether or not restoring pressures to preoperative levels has any clinical benefit or effect on the rate of degeneration is an area for further clinical research.