Clinical outcome after spinal fusion with a rigid versus a semi-rigid pedicle screw system

Comparing cellular bone matrices for posterolateral spinal fusion in a rat model

INTRODUCTION

Cellular bone matrices (CBM) are allograft products that provide three components essential to new bone formation: an osteoconductive scaffold, extracellular growth factors for cell proliferation and differentiation, and viable cells with osteogenic potential. This is an emerging technology being applied to augment spinal fusion procedures as an alternative to autografts.

METHODS

We aim to compare the ability of six commercially-available human CBMs (Trinity ELITE®, ViviGen®, Cellentra®, Osteocel® Pro, Bio4® and Map3®) to form a stable spinal fusion using an athymic rat model of posterolateral fusion. Iliac crest bone from syngeneic rats was used as a control to approximate the human gold standard. The allografts were implanted at L4-5 according to vendor specifications in male athymic rats, with 15 rats in each group. MicroCT scans were performed at 48 hours and 6 weeks post-implantation. The rats were euthanized 6 weeks after surgery and the lumbar spines were harvested for X-ray, manual palpation and histology analysis by blinded reviewers.

RESULTS

By manual palpation, five of 15 rats of the syngeneic bone group were fused at 6 weeks. While Trinity ELITE had eight of 15 and Cellentra 11 of 15 rats with stable fusion, only 2 of 15 of ViviGen-implanted spines were fused and zero of 15 of the Osteocel Pro, Bio4 and Map3 produced stable fusion. MicroCT analysis indicated that total bone volume increased from day 0 to week 6 for all groups except syngeneic bone group. Trinity ELITE (65%) and Cellentra (73%) had significantly greater bone volume increases over all other implants, which was consistent with the histological analysis.

CONCLUSION

Trinity ELITE and Cellentra were significantly better than other implants at forming new bone and achieving spinal fusion in this rat model at week 6. These results suggest that there may be large differences in the ability of different CBMs to elicit a successful fusion in the posterolateral spine.

Semirigid Waved Rod System for the Treatment of the Degenerative Lumbar Diseases

BACKGROUND

The semirigid pedicle screw instrumentation has gained wide popularity in recent decennium in lumbar fusion surgery. However, few data were documented to compare the clinical efficacy between semirigid and traditional rigid pedicle screw systems.

MATERIALS AND METHODS

A total of 96 patients with degenerative lumbar diseases were selected to perform operations between 2008 and 2013. The patients were prospectively randomized into 2 groups: 50 patients were managed by semirigid waved rod systems and 46 patients were intervened by traditional rigid straight stiff rod systems. X-rays and computed tomography were utilized to examine the interbody fusion status in the follow-up in detail. Surgical parameters such as operative time, blood loss, and total hospital stay were calculated and compared. Visual Analog Scale and Oswestry Disability Index were used to assess clinical efficacy postoperatively.

RESULTS

No significant differences were found about demographic data between groups. There were no significant differences regarding the surgical parameters including operative time, blood loss, and total hospital stay. Visual Analog Scale and Oswestry Disability Index postoperatively were also similar between the 2 instrumentations (P>0.05). The fusion rate was higher in the semirigid group (45/50) than in the traditional group (34/46) (P=0.039) at the final follow-up.

CONCLUSIONS

Waved rod may be better in facilitating interbody fusion compared with traditional straight rod, although waved rod and straight stiff rod can both get similar clinical efficacy. Meanwhile, waved rod is likely superior in alleviating adjacent degeneration segments.

Lumbar spinal stenosis minimally invasive treatment with bilateral transpedicular facet augmentation system

PURPOSE

The purpose of this study was to evaluate the effectiveness of a new pedicle screw-based posterior dynamic stabilization device PDS Percudyn System™ Anchor and Stabilizer (Interventional Spine Inc., Irvine, CA) as alternative minimally invasive treatment for patients with lumbar spine stenosis.

METHODS

Twenty-four consecutive patients (8 women, 16 men; mean age 61.8 yr) with lumbar spinal stenosis underwent implantation of the minimally invasive pedicle screw-based device for posterior dynamic stabilization. Inclusion criteria were lumbar stenosis without signs of instability, resistant to conservative treatment, and eligible to traditional surgical posterior decompression.

RESULTS

Twenty patients (83 %) progressively improved during the 1-year follow-up. Four (17 %) patients did not show any improvement and opted for surgical posterior decompression. For both responder and nonresponder patients, no device-related complications were reported.

CONCLUSIONS

Minimally invasive PDS Percudyn System™ has effectively improved the clinical setting of 83 % of highly selected patients treated, delaying the need for traditional surgical therapy.

Espondilolistesis ístmica lumbosacra del adulto: laminoartrectomía y fusión in situ

OBJETIVO: La espondilolistesis ístmica del adulto se puede tratar con reparación del defecto, descompresión (sola o con fusión), fusión circunferencial, y reducción con fijación posterior. El objetivo de este trabajo es valorar los resultados a medio plazo de la descompresión y fusión in situ en pacientes operados por un solo cirujano. MÉTODO: Criterios de Inclusión: 1) Espondilolistesis Ístmica L5-S1. 2) Operados en madurez esquelética. 3) Laminoartrectomía de L5 con Artrodesis posterolateral instrumentada sin reducción. 4) Más de 3 años de seguimiento. 5) Ausencia de pseudoartrosis al seguimiento. 6) Valoración funcional y radiológica por observador independiente. Comparación de datos con bibliografía. Análisis estadístico con t - test, Chi cuadrado y ANOVA. RESULTADOS: 16 pacientes (12 ♀/4 ♂) evaluados. Edad promedio: 40,6 años (17 - 66); seguimiento promedio: 10.3 años (3.3 - 18). Deslizamiento promedio: 42,9%. Nueve presentaban dolor radicular, 3 dolor lumbar y 4 dolor lumborradicular. Score del dolor (SRS) preoperatorio promedio: 1.38, sin diferencias entre bajo y alto grado (p=0.887). 15/16 mejoraron (score final promedio: 4.44). 13/16 retornaron a su actividad previa (81%). Hubo 2 infecciones; no hubo complicaciones neurológicas. Los parámetros espinopélvicos finales, comparados con la literatura no mostraron diferencias estadísticas. La comparación entre listesis de bajo y alto grado en la serie no mostró diferencia significativa en dichos parámetros, ni en tiempo de seguimiento, niveles artrodesados, síntomas ni retorno al trabajo. CONCLUSIÓN: La descompresión y fusión posterolateral instrumentada in situ permite un 80% de buenos resultados en la espondilolistesis ístmica lumbosacra del adulto sin importar el grado.

Factors affecting clinical outcomes in treating patients with grade 1 degenerative spondylolisthesis using interspinous soft stabilization with a tension band system: a minimum 5-year follow-up

STUDY DESIGN

Retrospective clinical study.

OBJECTIVE

To explore the factors influencing the clinical outcomes and motion-preserving stabilization after interspinous soft stabilization (ISS) with a tension band system for grade 1 degenerative spondylolisthesis (DS).

SUMMARY OF BACKGROUND DATA

Despite increasing recognition of the benefits of dynamic stabilization systems for treating lumbar degenerative disorders, the factors affecting the clinical and radiological outcomes of these systems have rarely been identified.

METHODS

Sixty-five patients (mean age, 60.3 years) who underwent ISS with a tension band system between 2002 and 2004 were analyzed. The mean follow-up period was 72.5 months. The patients were divided according to the postsurgical clinical improvements into the optimal (n = 44) and suboptimal groups (n = 21), and the radiological intergroup differences were analyzed. Multiple linear regression analysis was performed to determine the impact of the radiological factors on the clinical outcomes.

RESULTS

Significant intergroup differences were observed on the follow-up clinical examination. Radiologically, total lumbar lordosis (TLL) and segmental lumbar lordosis (SLL) were significantly improved only in the optimal group, resulting in significant intergroup differences in TLL (P = 0.023), SLL (P = 0.001), and the L1 tilt (P = 0.002). All these measures were closely associated with postoperative segmental lumbar lordosis, which also was the most influential radiological variable for the clinical parameters.

CONCLUSION

In the patients with grade 1 DS, the back pain relief and functional improvement following ISS were affected by the improvements in the sagittal spinal alignment through the achievement of segmental lumbar lordosis. ISS can be an alternative treatment to fusion surgery for grade 1 DS in patients who do not require fixation or reduction.

The influence of subdiagnosis on radiographic and clinical outcomes after lumbar fusion for degenerative disc disorders: an analysis of the literature from two decades

STUDY DESIGN

A critical review of published literature from 2 decades.

OBJECTIVE

To critically analyze the literature from 1979 to 2000 in order to examine the influence of subdiagnosis on outcome after fusion for lumbar degenerative disc disorders.

SUMMARY OF BACKGROUND DATA

Numerous diagnostic subgroups of degenerative disc disorders exist. Although it is commonly believed that surgical outcomes after lumbar fusion are influenced by these subdiagnoses, there is a paucity of literature demonstrating differences in clinical outcomes or fusion rates among them. As the indications for fusion have been under greater scrutiny recently, this information would be useful in prognosticating outcomes and optimizing patient selection.

METHODS

A computer search of the English literature using the keywords "degenerative," "lumbar," and "fusion" was performed. Disorders were organized according to the following subdiagnostic groups: degenerative spondylolisthesis (DDDsp), herniated disc (DH), degenerative scoliosis (DDDsc), stable DDD (DDDs), dynamically unstable DDD (DDDu), and DDD that was not specified as either DDDu or DDDs (DDDn). For each group, the type of instrumentation, fusion location, fusion rate, clinical outcome, and complication rate were recorded in a computer database. Data were pooled by simple summation and statistically analyzed using a chi test or Fisher exact test.

RESULTS

Of 244 articles identified, 78 satisfied inclusion criteria with data from 4454 patients recorded. The most common diagnosis was DDDn (50%), followed by DDDsp (25%), DH (14%), DDDu (6%), DDDs (3%), and DDDsc (2%). The DDDn group had a higher fusion rate than DDDsp (P = 0.025), but a lower clinical outcome (P = 0.051). Complication rates were highest in DDDsc, whereas this subdiagnosis also had the best reported clinical outcomes. In comparing individual subgroups, a trend towards higher fusion rate and better clinical outcome was noted in DDDsp cases with instrumentation compared to noninstrumented cases. This trend was reversed for patients in the DDDn group, in whom better clinical outcomes were noted after noninstrumented fusions regardless of a lower fusion rate.

CONCLUSIONS

The present data indicate that clinical outcomes and fusion rates statistically differ among the various subgroups of degenerative disc disease. Concerning the use of instrumentation, it appears that it may have greater clinical benefit in patients with DDDsp than DDDn. These findings underscore the importance of delineating specific clinical diagnoses when documenting results of lumbar fusion. This information might also be useful for both selecting surgical candidates and discussing anticipated operative outcomes.

Biomechanical Study of Lumbar Pedicle Screws in a Corpectomy Model Assessing Significance of Screw Height

BACKGROUND

We tested the hypothesis that a pedicle screw construct's height is an important factor in strengthening a screw-rod system.

METHODS

Six corpectomy constructs were made, each using two ultra-high-molecular-weight polyethylene blocks, 6.5-mm pedicle screws, and two 6.35-mm rods. Pedicle screws were placed at +10-, +5-, 0-, and -5-mm depths in relation to the dorsal surface of the corpectomy model. Nondestructive testing was performed in flexion/extension and in torsion.

RESULTS

For all modes tested, the screw-rod constructs continued to increase in stiffness as the height of the construct was lowered, and this was statistically significant at all heights tested (P < 0.001). The stiffness increased 232% when comparing flexion at +10 and -5 mm and increased 231% in extension from +10 to -5 mm. The torsional stiffness increased 171% when comparing +10 and -5 mm.

CONCLUSIONS

Thus, lower-profile instrumentation systems should be used to take advantage of this by decreasing the size and bulkiness of the implants while increasing the strength of the construct.

Critical analysis of trends in fusion for degenerative disc disease over the past 20 years: influence of technique on fusion rate and clinical outcome

STUDY DESIGN

Critical analysis of the results reported in published literature.

OBJECTIVES

The purpose of this study was to evaluate whether various technical advancements have affected the outcome of lumbar spinal fusion for degenerative disease by critically analyzing the available literature from the past two decades.

SUMMARY OF BACKGROUND DATA

To improve fusion rate and clinical outcome, various surgical options for lumbar spinal fusion for degenerative disc disorders have been introduced over the past 20 years. However, an important fundamental question still remains: What has been the impact of these new techniques and innovations on surgical results?

METHODS

A comprehensive computer search of the English literature from 1979 to 2000 concerning lumbar/lumbosacral spinal fusion was performed using the keywords degenerative, lumbar, and fusion.

RESULTS

Numerous deficiencies were noted in the reviewed literature. Nearly half of the studies failed to specify methodologic design, and documentation of brace use, graft source, fusion location, and fusion rate was missing in 38, 10, 2, and 4 of the 84 articles reviewed, respectively. From the data gathered, a noticeable trend toward the increasing use of internal fixation was noted, accounting for 23% of fusions in the 1980s versus 41% in the 1990s. Despite this trend, an improvement in overall fusion rate or clinical outcome could not be demonstrated.

CONCLUSIONS

Numerous technologic advancements in lumbar spine fusion have been made over the past 20 years. Future advances in care are dependent on review of reported results. The numerous deficiencies detected in the analyzed literature herald the necessity for a uniform system of outcomes reporting containing a core of critical demographic, perioperative, and postsurgical information. Although a shift toward a greater use of technology was noted in the published literature, the clinical benefit of this trend remains unclear.

Dynamic stabilization devices in the treatment of low back pain

Soft stabilization has an important role in the treatment of the degenerative lumbar spine. Fusion of one or two motion segments may not make a big difference in the total range of motion of the lumbar spine, but preserving flexibility of a motion segment may prevent adjacent segment disease and may permit disc replacement, even when facet joints need to be excised. If a favorable environment is created in the motion segment by unloading the disc and permitting near normal motion, the disc may be able to repair itself or may supplement the reparative potential of gene therapy. Although soft stabilization seems promising, one should take a cautious approach to any new implant system. An implant for fusion only has to serve a temporary stabilization until fusion has taken place; on the other hand, a soft stabilization system has to provide stability throughout its life. Implant loosening following fusion surgery is common in the presence of pseudarthrosis. After soft stabilization, the implant has to stay anchored to the bone despite allowing movement. This sounds like a daunting task. The flexibility of the implant system, however, should be able to protect it from loosening at the anchor point into the bone. Finally, the soft stabilization system is intended to load-share with the disc and the facet joint only partially and unloads the motion segment. Any mismatch between the kinematics of the implant system and the motion segment, in particular any discrepancy between their IAR, would result in the implant bearing unexpected load at certain ranges of motion. If that happens, it would guarantee an early implant failure or loosening. The need for strict bench testing in the laboratory, therefore, cannot be over-emphasized. The few soft stabilization systems that have had clinical applications so far have produced a clinical outcome comparable to that of fusion. No prospective randomized controlled trial has been reported yet, which is an essential requirement for practice of evidence-based medicine.

Evaluation of indication-based use of transpedicular instrumentations with different rigidity for lumbar spinal fusion: a prospective pilot study with 3 years of follow-up

In a prospective cohort study in 94 patients with 3 years' follow-up the efficacy of rigid and semi-rigid transpedicular instrumentation for lumbar spine fusion was evaluated via three established scores. Patient groups were similar in respect of anthropometric data. The indication for using the semi-rigid technique was a fairly stable intraoperative situation; for the more common unstable situations, the rigid technique was chosen. Selecting implant rigidity on these criteria led to results with an improvement rate well within the upper success range reported in the literature. Among people in employment, a lengthy preoperative sick leave was an important predictor for unsatisfactory outcome.