Device For Intervertebral Assisted Motion Research Articles

Comparative Analysis of Early and Long-Term Outcomes of Patients with Degenerative Lumbar Spine Disease Using the DIAM Stabilizer and Standard Rehabilitation Program: A Preliminary Prospective Randomized Controlled Trial with 1-Year Follow-Up.

Low back pain (LBP) is a leading cause of disability and work absenteeism. The cause of LBP may be degeneration of the intervertebral disc. LBP is characterized by considerable variability and tends to develop into chronic pain. Treatment of LBP includes conservative and rehabilitative treatments, surgery, and so-called minimally invasive treatment. One of the most commonly performed procedures is interspinous stabilization using a dynamic interspinous DIAM (device for intervertebral assisted motion) stabilizer. There is still no clear, strong evidence for the effectiveness and superiority of surgical treatment over conservative treatment. This study aimed to compare the early and long-term outcomes of patients with LBP using the DIAM interspinous stabilizer in relation to patients treated conservatively. A group of 86 patients was prospectively randomized into two comparison groups: A (n = 43), treated with the DIAM dynamic stabilizer for degenerative lumbar spine disease (mean age = 43.4 years ± SD = 10.8 years), and B (n = 43), treated conservatively. Pain severity was assessed using the visual analog scale (VAS), whereas disability was assessed using the Oswestry disability index (ODI). The difference in preoperative and postoperative ODI scores ≥ 15 points was used as a criterion for treatment effectiveness, and the difference in VAS scores ≥ 1 point was used as a criterion for pain reduction. In patients under general anesthesia, the procedure only included implantation of the DIAM system. Patients in the control group underwent conservative treatment, which included rehabilitation, a bed regimen, analgesic drug treatment and periarticular spinal injections of anti-inflammatory drugs. It was found that all patients (n = 43) continued to experience LBP after DIAM implantation (mean VAS score of 4.2). Of the 36 patients who experienced LBP with sciatica before the procedure, 80.5% (n = 29) experienced a reduction in pain. As for the level of fitness, the average ODI score was 19.3 ± 10.3 points. As for the difference in ODI scores in the pre-treatment results vs. after treatment, the average score was 9.1 ± 10.6. None of the patients required reoperation at 12 months after surgery. There were no statistically significant differences between the two groups in either early (p = 0.45) or long-term outcomes (p = 0.37). In conclusion, neurosurgical treatment with the DIAM interspinous stabilizer was as effective as conservative treatment and rehabilitation during the one-year follow-up period.

The effects of topping-off instrumentation on biomechanics of sacroiliac joint after lumbosacral fusion

BackgroundLumbar/lumbosacral fusion supplemented with topping-off devices has been proposed with the aim of avoiding adjacent segment degeneration proximal to the fusion construct. However, it remains unclear how the biomechanics of the sacroiliac joint (SIJ) are altered after topping-off surgery. The objective of this study was to investigate the biomechanical effects of topping-off instrumentation on SIJ after lumbosacral fusion. MethodsThe validated finite element model of an intact lumbar spine–pelvis segment was modified to simulate L5–S1 interbody fusion fixed with a pedicle screw system. An interspinous spacer, Device for Intervertebral Assisted Motion (DIAM), was used as a topping-off device and placed between interspinous processes of the L4 and L5 segments. Range of motion (ROM), von-Mises stress distribution, and ligament strain at SIJ were compared between fusion (without DIAM) and topping-off (fusion with DIAM) models under moments of four physiological motions. ResultsROM at the left and right SIJs in the topping-off model was higher by 26.9% and 27.5% in flexion, 16.8% and 16.1% in extension, 18.8% and 15.8% in lateral bending, and 3.7% and 7.4% in axial rotation, respectively, compared to those in the fusion model. The predicted stress and strain data showed that under all physiological loads, the topping-off model exhibited higher stress and ligament strain at the SIJs than the fusion model. ConclusionsMotion, stress, and ligament strain at SIJ increase when supplementing lumbosacral fusion with topping-off devices, suggesting that topping-off surgery may be associated with higher risks of SIJ degeneration and pain than fusion alone.

15-year survivorship analysis of an interspinous device in surgery for single-level lumbar disc herniation

BackgroundInterspinous devices have been introduced as alternatives to decompression or fusion in surgery for degenerative lumbar diseases. This study aimed to investigate 15-year survivorship and risk factors for reoperation of a Device for Intervertebral Assisted Motion (DIAM) in surgery for 1-level lumbar disc herniation (LDH).MethodsA total of 94 patients (54 men and 40 women) underwent discectomy and DIAM implantation for 1-level LDH, with a mean follow-up of 12.9 years (range, 6.3–15.3 years). The mean age was 46.2 years (range, 21–65 years). Sixty-two patients underwent DIAM implantation for L4–5, 27 for L5–6, and 5 for L3–4. Reoperations due to any reason associated with DIAM implantation level or adjacent levels were defined as failure and used as the end point of determining survivorship.ResultsDuring the 15-year follow-up, 8 patients (4 men and 4 women) underwent reoperation due to recurrence of LDH at the DIAM implantation level, a reoperation rate of 8.5%. The mean time to reoperation was 6.5 years (range, 0.8–13.9 years). Kaplan-Meier analysis showed a cumulative survival rate of the DIAM implantation of 97% at 5 years, 93% at 10 years, and 92% at 15 years after surgery; the cumulative reoperation rate of the DIAM implantation was 3% at 5 years, 7% at 10 years, and 8% at 15 years after surgery. Mean survival time was predicted to be 14.5 years (95% CI, 13.97–15.07). The log-rank test and Cox proportional hazard model showed that age, sex, and location did not significantly affect the reoperation rate of DIAM implantation.ConclusionsOur results showed that DIAM implantation significantly decreased reoperation rate for LDH in the 15-year survivorship analysis. We suggest that DIAM implantation could be considered a useful intermediate step procedure for LDH surgery. To the best of our knowledge, this is the longest follow-up study in which surgical outcomes of interspinous device surgery were reported.

Biomechanical study of different approach for lumbar interbody fusion surgeries under vibration load

The human spine injury and various lumbar spine diseases caused by vibration have attracted extensive attention at home and abroad. To explore the biomechanical characteristics of different approaches for lumbar interbody fusion surgery combined with an interspinous internal fixator, device for intervertebral assisted motion (DIAM), finite element models of anterior lumbar interbody fusion (ALIF), transforaminal lumbar interbody fusion (TLIF) and lateral lumbar interbody fusion (LLIF) are created by simulating clinical operation based on a three-dimensional finite element model of normal human whole lumbar spine. The fusion level is at L4-L5, and the DIAM is implanted between spinous process of L4 and L5. Transient dynamic analysis is conducted on the ALIF, TLIF and LLIF models, respectively, to compute and compare their stress responses to an axial cyclic load. The results show that compared with those in ALIF and TILF models, contact forces between endplate and cage are higher in LLIF model, where the von-Mises stress in endplate and DIAM is lower. This implies that the LLIF have a better biomechanical performance under vibration. After bony fusion between vertebrae, the endplate and DIAM stresses for all the three surgical models are decreased. It is expected that this study can provide references for selection of surgical approaches in the fusion surgery and vibration protection for the postsurgical lumbar spine.

Biomechanical analysis of a new lumbar interspinous device with optimized topology.

Interspinous spacers used stand-alone preserve joint movement but provide little protection for diseased segments of the spine. Used as adjuncts with fusion, interspinous spacers offer rigid stability but may accelerate degeneration on adjacent levels. Our new device is intended to balance the stability and preserves motion provided by the implant. A new interspinous spacer was devised according to the results of topology optimization studies. Four finite element (FE) spine models were created that consisted of an intact spine without an implant, implantation of the novel, the device for intervertebral assisted motion (DIAM system), and the Dynesys system. All models were loaded with moments, and their range of motions (ROMs), peak disc stresses, and facet contact forces were analyzed. The limited motion segment ROMs, shielded disc stresses, and unloaded facet contact forces of the new devices were greater than those of the DIAM and Dynesys system at L3-L4 in almost all directions of movements. The ROMs, disc stresses, and facet contact forces of the new devices at L2-L3 were slightly greater than those in the DIAM system, but much lower than those in the Dynesys system in most directions. This study demonstrated that the new device provided more stability at the instrumented level than the DIAM system did, especially in lateral rotation and the bending direction. The device caused fewer adjacent ROMs, lower disc stresses, and lower facet contact forces than the Dynesys system did. Additionally, this study conducted topology optimization to design the new device and created a smaller implant for minimal invasive surgery.

Clinical outcome following DIAM implantation for symptomatic lumbar internal disk disruption: a 3-year retrospective analysis.

Background/objectiveInternal disk disruption (IDD), an early event of lumbar disk degeneration, is the most common cause of low back pain. Since increased intradiskal pressure (IDP) is associated with symptoms and progression of disk degeneration, unloading a painful disk with an interspinous process device (IPD) is a rational treatment option. The goal of this study was to evaluate the effectiveness of dynamic stabilization with an IPD in the treatment of symptomatic IDD of the lumbar spine.Patients and methodsPatients with symptomatic IDD were treated with implantation of an IPD, the device for intervertebral assisted motion (DIAM). Diagnosis of IDD was based on typical MRI finding of posterior annular high-intensity zone and positive provocative test on discography. IDP was analyzed intraoperatively. Axial back and leg pain was evaluated with visual analog scale, functional status with Oswestry Disability Index, and final clinical outcomes with Odom criteria. Data from 34 patients followed up for at least 3 years were collected.ResultsDIAM implantation significantly reduced IDP (n=11, P<0.0001). All 34 patients reported symptom relief. Thirty-one patients (91%) remained symptom free until the last followups. Three patients (9%) experienced recurrence of pain, of which the causes were unrelated to the IDD or surgery. Disk status at the DIAM-implanted segments remained stable. Segmental flexion/extension mobility was preserved in 27 of 30 patients with preoperative mobility. No proximal or distal adjacent segment degeneration was observed. The final clinical outcomes were excellent/good in 31 and fair/poor in three patients.ConclusionFor patients with symptomatic IDD, dynamic stabilization with DIAM provides pain relief and functional improvement. The implantation maintains disk status and prevents progression of disk degeneration, without compromising segmental flexion/extension mobility or causing adjacent segment degeneration.

Aseptic intrafascial and extrafascial abscesses 10 years after a 2-level DIAM insertion procedure.

With the aim to prevent the so-called adjacent-segment disease in spinal fusion surgery and to serve as the primary surgical procedure for the management of low-back pain syndrome or neurogenic claudication in spinal stenosis, the so-called dynamic spine stabilization is applied using specifically designed implants: interspinous spacers, such as DIAM (Device for Intervertebral Assisted Motion), Coflex, and X-stop. It is commonly accepted that interspinous spacers are made from material that is well tolerated by the body, that their placement is simple, that complications are rare, and that they can greatly benefit the patients. So far, there have not been published studies reporting infective or other complications 10 or more years after the placement of DIAM spacers. The aim of this paper was to present a case of an extremely late complication (after 10 years) in the form of intra- and extrafascial dumbbell abscesses, concomitantly appearing at both levels treated with the DIAM spacer. The paper presents the existence of a significant correlation between CT and MRI findings as well as the deterioration in Oswestry Disability Index and visual analog scale scores. Over time, dynamic spine stabilization might possibly impact reactive accumulation of sterile fluid in the vicinity of an implant and could therefore be related to delayed complications even 10 years after surgery. The finding of a growing layer composed of thick aseptic fluid around the DIAM implant, with a simultaneous occurrence of spinous process osteolysis and formation of a mineralized pseudocyst, bears a considerable risk of delayed inflammatory complications, including abscess, and therefore requires the explantation of the DIAM implant.

Reduction in adjacent-segment degeneration after multilevel posterior lumbar interbody fusion with proximal DIAM implantation.

OBJECT Multilevel long-segment lumbar fusion poses a high risk for future development of adjacent-segment degeneration (ASD). Creating a dynamic transition zone with an interspinous process device (IPD) proximal to the fusion has recently been applied as a method to reduce the occurrence of ASD. The authors report their experience with the Device for Intervertebral Assisted Motion (DIAM) implanted proximal to multilevel posterior lumbar interbody fusion (PLIF) in reducing the development of proximal ASD. METHODS This retrospective study reviewed 91 cases involving patients who underwent 2-level (L4-S1), 3-level (L3-S1), or 4-level (L2-S1) PLIF. In Group A (42 cases), the patients received PLIF only, while in Group B (49 cases), an interspinous process device, a DIAM implant, was put at the adjacent level proximal to the PLIF construct. Bone resection at the uppermost segment of the PLIF was equally limited in the 2 groups, with preservation of the upper portion of the spinous process/lamina and the attached supraspinous ligament. Outcome measures included a visual analog scale (VAS) for low-back pain and leg pain and the Oswestry Disability Index (ODI) for functional impairment. Anteroposterior and lateral flexion/extension radiographs were used to evaluate the fusion status, presence and patterns of ASD, and mobility of the DIAM-implanted segment. RESULTS Solid interbody fusion without implant failure was observed in all cases. Radiographic ASD occurred in 20 (48%) of Group A cases and 3 (6%) of Group B cases (p < 0.001). Among the patients in whom ASD was identified, 9 in Group A and 3 in Group B were symptomatic; of these patients, 3 in Group A and 1 in Group B underwent a second surgery for severe symptomatic ASD. At 24 months after surgery, Group A patients fared worse than Group B, showing higher mean VAS and ODI scores due to symptoms related to ASD. At the final follow-up evaluations, as reoperations had been performed to treat symptomatic ASD in some patients, significant differences no longer existed between the 2 groups. In Group B, flexion/extension mobility at the DIAM-implanted segment was maintained in 35 patients and restricted or lost in 14 patients, 5 of whom had already lost segmental flexion/extension mobility before surgery. No patient in Group B developed ASD at the segment proximal to the DIAM implant. CONCLUSIONS Providing a dynamic transition zone with a DIAM implant placed immediately proximal to a multilevel PLIF construct was associated with a significant reduction in the occurrence of radiographic ASD, compared with PLIF alone. Given the relatively old age and more advanced degeneration in patients undergoing multilevel PLIF, this strategy appears to be effective in lowering the risk of clinical ASD and a second surgery subsequent to PLIF.

Posterior dynamic stabilization in the treatment of degenerative lumbar stenosis: validity of its rationale

The authors undertook this study to investigate the validity of the rationale for posterior dynamic stabilization using the Device for Intervertebral Assisted Motion (DIAM) in the treatment of degenerative lumbar stenosis. A cohort of 31 patients who underwent single-level decompression and DIAM placement for degenerative lumbar stenosis were followed up for at least 2 years and data pertaining to their cases were analyzed prospectively. Of these patients, 7 had retrolisthesis. Preoperative and postoperative plain lumbar radiographs obtained in all patients and CT images obtained in 14 patients were analyzed. Posterior disc heights; range of motion (ROM) of proximal, distal, and implant segments; lordotic angles of implant segments; percentage of retrolisthesis; and cross-sectional area and heights of intervertebral foramina on CT sagittal images were analyzed. Clinical outcomes were evaluated using visual analog scale scores and Oswestry Disability Index scores. The mean values for posterior disc height before surgery, at 1 week after surgery, and at the final follow-up visits were 6.4 ± 2.0 mm, 9.7 ± 2.8 mm, and 6.8 ± 2.5 mm, respectively. The mean lordotic angles at the implant levels before surgery, at 1 week after surgery, and at the final follow-up visits were 7.1° ± 3.3°, 4.1° ± 2.7°, and 7.0° ± 3.7°, respectively. No statistically significant difference was found between the preoperative values and values from final follow-up visits for posterior disc height and lordotic angles at implant levels (p = 0.17 and p = 0.10, respectively). There was no statistically significant difference between the preoperative and final follow-up visit values for intervertebral foramen cross-sectional area and heights on CT images. The ROMs of proximal and distal segments also showed no significant decrease (p = 0.98 and p = 0.92, respectively). However, the ROMs of implant segments decreased significantly (p = 0.02). The average 31.4-month improvement for all clinical outcome measures was significant (p < 0.001). Based on radiological findings, the DIAM failed to show validity in terms of the rationale of indirect decompression, but it did restrict motion at the instrumented level without significant change in adjacent-segment ROM. The clinical condition of the patients, however, was improved, and improvement was maintained despite progressive loss of posterior disc height after surgery.

A PROSPECTIVE STUDY OF PATIENT-REPORTED OUTCOMES FOR TWO YEARS AFTER LUMBAR SURGERY AUGMENTED WITH DIAM®INTERSPINOUS IMPLANT

Purpose: The device for intervertebral assisted motion (DIAM™) is an interspinous (ISP) implant used to augment surgical decompression of lumbar degenerative conditions: Lumbar spinal stenosis [LSS; foraminal (FS) or central canal (CS)], herniated and degenerated disc disease, facet joint pain syndrome (FJPS) and minor degenerative spondylolisthesis (DS). Limited evidence guides its use in defined clinical indications, while few studies demonstrate effect according to clinically meaningful change (MCID). This prospective longitudinal study examined the efficacy of DIAM-augmented decompression surgery in the broad application of a single-center clinical reality. Methods: Eighty-one consecutive cases [37F, 44M; 52 years (SD 13)] were examined for two years after DIAM-augmented decompression surgery. Patient-reported pain [back and leg; visual analogue scale (VAS)], function [Oswestry disability index (ODI)], and satisfaction (Likert scale) were serially examined and referenced to contemporary MCID thresholds. Subjects were classified into anatomical and diagnostic categories and analyzed according to subgroups to better inform clinical pathways. Serial change was assessed with Scheffe post-hoc test; change scores with unpaired t-tests and descriptive statistics (p &lt; 0.05). Results: Subjects reported 20.4% (SD 29.5; p &lt; 0.0001) mean improvement in back pain, 20.3% (SD 30.6; p &lt; 0.0001) in leg pain, and 15.1% (SD 20.8; p &lt; 0.0001) in function at two years postoperatively. Greatest improvement was seen at six weeks for back pain (by 30.5%; p &lt; 0.0001) and leg pain (by 29.4%; p &lt; 0.0001) and three months for function (by 18.7%; p &lt; 0.0001). Leg pain deteriorated between six weeks and 18 months (p &lt; 0.05). There were more responders at one compared to two years after surgery. FS cases showed superior improvement compared to DS subjects (p &lt; 0.05). Cases receiving multiple adjunctive surgical decompressions in addition to their DIAM had superior improvement than those receiving a single procedure (p &lt; 0.05). Conclusions: Clinical improvement in back pain, leg pain and function were achieved to two years in a single-center cohort of 81 cases with lumbar degenerative disease who received DIAM-augmented decompression surgery. Subsets of the sample had a superior sustained response including foraminal/lateral recess stenosis patients and cases treated with &gt; 1 adjunctive decompression techniques. The need for assessing homogeneous cohorts in future studies is emphasized.

Interspinous spacers in the treatment of degenerative lumbar spinal disease: our experience with DIAM and Aperius devices

Insertion of an interspinous devices has became a common procedure for the treatment of different clinical picture of degenerative spinal disease. We present our experience in 1,575 patients with the use of two different interspinous spacers: Device for Intervertebral Assisted Motion (DIAM) and Aperius PercLID system. From 2000 through 2008, 1,315 consecutive patients underwent DIAM implantation and 260 had an Aperius PercLID procedure. The main surgical indications included: degenerative disc disease (478 patients), canal and/or foraminal stenosis (347 patients), disc herniation (283 patients), black disc and facet syndrome (143) and topping-off (64 patients). 1,100 patients underwent a single level implant and 475 had a multiple level implant. Mean operating time was 35 min for DIAM and 7 min for Aperius. Complications were detected in 20 patients (10 cases of infections, 10 fractures of the posterior spinous processes). 40 patients were subsequently treated with posterior arthrodesis (n = 30) or total disc replacement (n = 10). Patient's postoperative clinical status was rated according to the modified Macnab criteria: symptoms resolution or improvement was achieved in 1,505 patients; and unchanged or unsatisfactory results in 70. Both techniques are safe, simple and less technically demanding. These approaches appear to be an effective alternative in selected cases, although conventional posterior lumbar decompression and fusion still may be required.

Long-term reduction in pain and disability after surgery with the interspinous device for intervertebral assisted motion (DIAM) spinal stabilization system in patients with low back pain: 4-year follow-up from a longitudinal prospective case series

Patients with low back pain (LBP) suffer chronic disability. In 40% of LBP patients degenerative disc disease (DDD) seems to be the cause. This prospective case series assessed the efficacy of the interspinous device for intervertebral assisted motion (DIAM™) in patients with LBP resulting from DDD. All patients were initially assessed by physical examinations, magnetic resonance imaging, dynamic X-rays and provocative discography. Eligible patients (n=52) had LBP for a minimum of 4months, and received surgery with the DIAM™ system 2-4weeks after diagnosis. Patients were evaluated pre-/post-operatively for pain severity using a visual analogue scale (VAS), and for dysfunction and disability with the Roland-Morris Disability Questionnaire (RMDQ). VAS and RMDQ score changes were assessed using the appropriate contrasts and Bonferroni-corrected P values. As a result, significant (P<0.0001) pain score reductions were observed between baseline values, and 2 (3.7, 95% CI 3.1; 4.2) and 48 (3.1, 95% CI 2.5; 3.6) months follow-up (intent-to-treat population). Disability scores were significantly (P<0.0001) reduced between baseline and 2 (8.6, 95% CI 7.4; 9.9) and 48 (7.5, 95% CI 6.1; 8.9) months. Disability scores were similar from months 2 to 48. At 48months, 67.3% of patients reached the minimum clinically important difference (MCID; ≥1.5-unit improvement) in VAS score and 78.9% of patients reached the MCID (≥30% improvement) in RMDQ score. No complications were associated with surgery. In conclusion, patients with LBP treated with the interspinous DIAM™ system showed significant and clinically meaningful improvements in pain and disability for up to 4years.

Interspinous Implant with Unilateral Laminotomy for Bilateral Decompression of Degenerative Lumbar Spinal Stenosis in Elderly Patients

This study assessed the safety and efficacy of one level unilateral laminotomy bilateral decompression (ULBD) with the placement of a device for intervertebral assisted motion (DIAM) compared with one level ULBD only in elderly patients with degenerative lumbar spinal stenosis (DLSS). A non randomized prospective analysis was performed on 16 patients who underwent one level ULBD with DIAM (Group A) and 20 patients with one level ULBD only (Group B) between February 2007 and March 2008. Radiographic imaging, visual analog scale (VAS) and MacNab outcome scale were obtained before and after surgery at a mean interval of 21 months (range 17-27 months). The disc height, interpedicular distance, slip distance and segmental lordotic angle were similar between two groups. In the group A, there was no significant difference between the pre- and post-operative imaging in terms of the sagittal balance and disc height. Both groups showed significant improvement in the clinical outcomes. In addition, there was significantly less low-back pain in the group A than in the group B at the last follow up, while the clinical improvement of the leg pain and MacNab outcome scale showed no significant difference in the two groups. There were no major complications or DIAM associated complications. ULBD with DIAM is a safe and efficacious treatment for selective elderly patients with DLSS, particularly for relieving low back pain comparing to ULBD. ULBD with DIAM did not alter the disc height or sagittal alignment at the mean 21 months follow-up interval.

Preliminary results of the interspinous implants for treatment of lumbar degenerative diseases

Objective To describe our initial experience and evaluate the preliminary results as well as the possible complications of interspinous implant (device for intervertebral assisted motion, DIAMTM) in managing symptomatic lumbar degenerative disorders. Methods A group of 22 patients were analyzed ret-rospectively. Fourteen female and eight male patients were treated. Mean age was 38.5 (range, 24 -59) years. They had clinical evidence for lumbar facet joint pain and a facet joint injection therapy had good result. Pre-operatively MRI and CT scan was done to evaluate the lumbar spinous process, lumbar disc and facet joints. Fourteen patients were operated at single level, eight patients at double levels. Radiographic imaging, pain scores, and clinical assessments were obtained at 24th week, 66th week postoperatively. Results Pa-tients were evaluated clinically through the Odom's criteria: 31.8% (7 patients) excellent, 45.4% (10 patients) good, 4.5% (1 patient) fair and 18.1% (4 patients) poor results. A significant difference was observed in im-provement of visual analogue scale that decreased from preoperative mean 7.09±0.92 to postoperative mean 3.23±1.82. Statistically significant differences were noted in neural foraminal height and posterior disc height when comparing patients pre-and postoperatively. For the follow-up period, no migration and loosening of implant was found, and no revision surgery was needed in all cases. Conclusion In this preliminary result, it could be observed that the DIAMTM prosthesis can offer a pain relief in well selected patients suffering lum-bar facet joint pain. The indication should be very strict. The implant acts as: 1) A shock absorber, give dis-traction of the neuroforamina, realign facet interface; 2) Restore posterior column height and share in load transmission. Key words: Lumbar vertebrae; Low back pain; Zygapophyseal joint; Prostheses and implants; Treat-ment outcome

CLINICAL OUTCOMES FOLLOWING LUMBAR SURGERY AUGMENTED WITH DIAM INTERSPINOUS IMPLANT

Posterior interspinous dynamic stabilization is used increasingly in the treatment of lumbar degenerative spinal conditions, with preliminary evidence for its clinical and biomechanical efficacy emerging. The need remains to define patients who respond best to this form of surgery. This study examined clinical outcomes in 39 patients (21 females) with defined lumbar spinal pathologies, for two years after lumbar surgery augmented with the Device for Intervertebral Assisted Motion (DIAM). Anatomical patient categorization revealed involvement of disc (n=25/39) and facet (n=14/39) lumbar pathology, with clinical indications for surgery being: segmental instability (n=21/39); nerve root compression (n=11/39); and facet joint pain syndrome (n=7/39). Pain, function and satisfaction data were derived from MODEMS self-report questionnaires, which were collected prospectively over a two-year post-operative period. Results showed that L4-5 and L5-S1 were the most common DIAM-implanted spinal levels. Clinically significant post-operative improvement in pain (23.4%) and function (13.5%) occurred between three and twenty-four months. Eleven (of 39) required further lumbar surgery. Nineteen (of 28) were more satisfied at 24 months post-operatively compared to baseline. Disc involvement and segmental instability were the most common presenting lumbar segmental pathologies, yet the least successful in response to surgery augmented with DIAM. Patients with facet involvement reported superior improvement post-operatively compared with those with disc involvement. Patients with facet joint disease demonstrate better outcomes at 24 months following lumbar surgery augmented with DIAM posterior interspinous dynamic stabilization, compared with those presenting with disc pathology.

Foreign body reaction due to polyethylene’s wear after implantation of an interspinal segment

Different interspinous implants are used as minimal invasive intervention in the management of degenerative disorders of the lumbar spine. We present a case with foreign body reaction due to polyethylene's wear after a device for intervertebral assisted motion (DIAM) implantation. We conclude that the polyethylene interspinous devices can cause biological response, therefore; the surgeons and the companies should carefully watch their patients following application of such devices.

Device for intervertebral assisted motion: technique and initial results

The DIAM is a polyester-encased silicone interspinous dynamic stabilization device that can unload the anterior column and reestablish the functional integrity of the posterior column. The DIAM was implanted in 104 patients between May 1, 2001 and October 30, 2001. A retrospective evaluation was performed based on chart review and patient questionnaire at a median follow-up interval of 18.1 months. There were no implant migrations, infections, or neurological injuries. Of the 20 patients who suffered adverse events, 13 underwent second lumbar spinal operations 0 to 19 months after the initial surgery (in seven the event occurred in a location other than the lumbar spine). The pain level as recorded by the physician showed improvement in 88.5%, no change in 9.6%, aggravation in 0%, and was indeterminate in 1.9%. The questionnaire revealed that at 18 months postoperatively, analgesic usage was decreased in 63.1%, increased in 12.3%, and unchanged in 24.6% of patients, and activities of daily living were improved in 46.2%, decreased in 30.8%, and unchanged in 23.1%. Specific outcomes measures for sitting, standing, physical activity, and psychosocial functioning revealed similar results. The DIAM implant appears to be a useful and effective alternative in the surgical management of a wide range of lumbar disorders. Patient complications are few and satisfaction is high.

Biomechanics of posterior dynamic stabilizing device (DIAM) after facetectomy and discectomy

Lumbar fusion has been associated with inconsistent clinical outcomes and significant complications. Posterior dynamic devices have been developed to stabilize painful diseased lumbar motion segments while avoiding fusion. The Device for Intervertebral Assisted Motion (DIAM) is a silicone interspinous process "bumper" that is being clinically implanted for varied indications. We analyzed the effects of the DIAM device on the biomechanical response of the lumbar spine in flexion-extension, lateral bending, and axial rotation after partial facetectomy and discectomy; the clinical situations in which its use might be considered. A biomechanical study was performed using whole lumbar spine specimens (L1-sacrum). Surgical interventions were simulated at the L4-L5 level, and motions were measured at the operated and adjacent segments. Six fresh human lumbar spine specimens were used. The lumbar spines were subjected to moments in flexion-extension (+/-6 Nm), lateral bending (+/-5 Nm), and axial rotation (+/-4 Nm). The specimens were tested under the following conditions: 1) intact; 2) after unilateral hemifacetectomy at L4-L5; 3) #2 and discectomy; and 4) #3 with DIAM. The angular motion values at the operated and adjacent segments were analyzed using analysis of variance and multiple comparisons with Bonferroni correction. Unilateral hemifacetectomy did not increase angular motion. Subsequent discectomy increased L4-L5 angular motion (degrees) from 9.2+/-1.6 to 11.7+/-2.0 in flexion-extension (p=.01), from 6.7+/-1.1 to 8.5+/-1.5 in lateral bending (p=.01), and from 2.6+/-0.7 to 3.8+/-0.8 in axial rotation (p=.00). Insertion of the DIAM device after discectomy restored the angular motion to below the level of the intact segment in flexion-extension (6.7+/-0.7 vs. 9.2+/-1.6, p=.02). In lateral bending, DIAM reduced the increased motion induced by discectomy (7.8+/-1.0 vs. 8.5+/-1.5, p<.05), but not to the intact level (7.8+/-1.0 vs. 6.7+/-1.1, p=.05). DIAM insertion did not reduce the increased axial rotation induced by discectomy, and the axial rotation remained larger than the intact value (4.1+/-0.6 vs. 2.6+/-0.7, p=.00). The DIAM device is effective in stabilizing the unstable segment, reducing the increased segmental flexion-extension and lateral bending motions observed after discectomy. In flexion-extension the DIAM restored postdiscectomy motion to below the intact values (p<.05). Interestingly, the DIAM device did not reduce the increased axial rotation motion observed after discectomy. These biomechanical effects must be considered when evaluating the clinical applications of the DIAM.