A 2-year follow-up pilot study evaluating the safety and efficacy of op-1 putty (rhbmp-7) as an adjunct to iliac crest autograft in posterolateral lumbar fusions

The ability of bone morphogenetic proteins (BMPs) to induce bone formation has led to a multitude of investigations into their use as bone graft substitutes in spinal surgery. The purpose of this multi-center clinical pilot study was to evaluate the safety and efficacy of BMP-7 (osteogenic protein 1, OP-1), in the form of a putty, combined with autograft for intertransverse process fusion of the lumbar spine in patients with symptomatic spinal stenosis and degenerative spondylolisthesis following spinal decompression. Twelve patients with spinal stenosis and degenerative lumbar spondylolisthesis underwent a laminectomy and partial or complete medial facetectomy as required for decompression of the neural elements, followed by an intertransverse process fusion by placing iliac crest autograft and OP-1 putty between the decorticated transverse processes. No instrumentation was used. Patients were followed clinically using the Oswestry scale and SF-36 outcome forms, and radiographically using static and dynamic radiographs to assess their fusion status over a 2-year period. Independent and blinded radiologists assessed the films for the presence of bridging bone between the transverse processes and measured translation and angulation on dynamic films using digital calipers. Radiographic outcome was compared to a historical control (autograft alone fusion without instrumentation for the treatment of degenerative spondylolisthesis). All adverse events were recorded prospectively. The results showed eight of the nine evaluable patients (89%) obtained at least a 20% improvement in their preoperative Oswestry score, while five of ten patients (50%) with radiographic follow-up achieved a solid fusion by the criteria used in this study. Bridging bone on the anteroposterior film was observed in seven of the ten patients (70%). No systemic toxicity, ectopic bone formation, recurrent stenosis or other adverse events related to the OP-1 putty implant were observed. A successful fusion was observed in slightly over half the patients in this study, using stringent criteria without adjunctive spinal instrumentation. This study did not demonstrate the statistical superiority of OP-1 combined with autograft over an autograft alone historical control, in which the fusion rate was 45%. There were no adverse events related to the OP-1 putty implant in this study, which supports findings in other studies suggesting the safety of bone morphogenetic proteins in spinal surgery.     

The safety and efficacy of OP-1 (rhBMP-7) as a replacement for iliac crest autograft for posterolateral lumbar arthrodesis: minimum 4-year follow-up of a pilot study.

BACKGROUND CONTEXT: Although autogenous bone is still considered to be the gold standard graft material for promoting spinal fusion, other bone graft substitutes have been developed in an attempt to improve arthrodesis rates and avoid the complications associated with the procurement of autograft. The bone morphogenetic proteins (BMPs) represent a family of osteoinductive growth factors that are known to stimulate the osteoblastic differentiation of stem cells. Osteogenic protein-1 (OP-1) Putty is a commercially available BMP preparation that is already approved for use in humans. Previous clinical studies involving patients with degenerative spondylolisthesis have reported that the efficacy and safety of OP-1 Putty is comparable to that of autograft at both 1- and 2-year follow-up. PURPOSE: The purpose of this study was to evaluate the intermediate-term efficacy and safety of OP-1 Putty as an alternative to autogenous bone by comparing the 4-year radiographic, clinical, and safety data of these same patients who underwent decompression and uninstrumented fusion with either OP-1 Putty or iliac crest autograft. STUDY DESIGN/SETTING: A prospective, randomized, controlled, multicenter clinical pilot study. PATIENT SAMPLE: Thirty-six patients undergoing decompressive laminectomy and single-level uninstrumented fusion for degenerative spondylolisthesis and symptomatic spinal stenosis were randomized in a 2:1 fashion to receive either OP-1 Putty (24 patients) or autogenous iliac crest bone graft (12 patients). OUTCOME MEASURES: Patient-reported outcome measures consisting of Oswestry Disability Index and Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) scores were used to evaluate clinical efficacy. Perioperative data including operative time, estimated blood loss, and duration of hospital stay were also recorded for each surgery. Postoperatively, a neurological examination and an assessment of donor-site pain (if applicable) were performed at every follow-up visit. Radiographic fusion success was defined as the presence of continuous bridging bone formation between the transverse processes at the level of the spondylolisthesis with minimal motion evident on dynamic lateral x-ray films. The primary efficacy endpoint was the overall success rate, a composite measure derived from both radiographic and clinical parameters. The safety of OP-1 Putty was confirmed by comparing the nature and frequency of all adverse events and complications that were prospectively observed in either of the groups. METHODS: Thirty-six patients with degenerative spondylolisthesis and symptoms of neurogenic claudication underwent decompressive laminectomy and single-level uninstrumented fusion with either OP-1 Putty or autograft. All patients were evaluated at 6 weeks and 3, 6, 9, 12, and 24 months, after which time they were instructed to return on a yearly basis. Multiple neuroradiologists blinded to the assigned treatment reviewed static and dynamic X-ray films with digital calipers to assess fusion status according to the presence of continuous bridging bone across the transverse processes as well as the amount of residual motion evident at the level of interest. Oswestry Disability Index surveys and SF-36 questionnaires were used to assess clinical outcomes. RESULTS: At the 48-month time point, complete radiographic and clinical data were available for 22 of 36 patients (16 OP-1 Putty and 6 autograft) and 25 of 36 patients (18 OP-1 Putty and 7 autograft), respectively. Radiographic evidence of a solid arthrodesis was present in 11 of 16 OP-1 Putty patients (68.8%) and 3 of 6 autograft patients (50%). Clinically successful outcomes defined as at least a 20% improvement in preoperative Oswestry scores were experienced by 14 of 19 OP-1 Putty patients (73.7%) and 4 of 7 autograft patients (57.1%); these clinical findings were corroborated by similar increases in SF-36 scores. The respective overall success rates of the OP-1 Putty and autograft group were 62.5% and 33.3%. In this study, there were no incidents of local or systemic toxicity, ectopic bone production, or other adverse events directly related to the use of OP-1 Putty. CONCLUSION: Despite the challenges associated with obtaining a solid uninstrumented fusion in patients with degenerative spondylolisthesis, the rates of radiographic fusion, clinical improvement, and overall success associated with the use of OP-1 Putty were at least comparable to that of the autograft controls for at least 48 months after surgery. These results appear to validate the short-term results previously reported for OP-1 Putty and suggest that this material may potentially represent a viable bone graft substitute for certain fusion applications.     

Demineralized bone matrix composite grafting for posterolateral spinal fusion

In a prospective series, the 24-month fusion status was evaluated radiographically among patients undergoing instrumented posterolateral lumbosacral spinal fusion. Seventy-three patients had a diagnosis of degenerative disk disease or degenerative spondylolisthesis and had supplemental bone grafting with demineralized bone matrix (DBM) putty (Grafton DBM; Osteotech, Eatontown, NJ) enriched with aspirated bone marrow (DBM bone marrow), DBM putty combined with iliac crest autograft (DBM autograft), or autograft. Overall, approximately 63% (12 of 19) of DBM bone marrow, 70% (19 of 27) of DBM autograft, and 67% (18 of 27) of autograft patients were fused at 24 months (P = .875). These findings suggest that both DBM composites offer similar performance to autograft in posterolateral spinal fusion.     

Surgical management of lumbar degenerative spinal stenosis with spondylolisthesis via posterior reduction with minimal laminectomy

Degenerative lumbar spondylolisthesis with spinal stenosis is commonly treated with laminectomy. Recent reports have consistently supported the incremental clinical benefit of associated in situ arthrodesis with or without instrumentation. Resection of the lamina may result in intraoperative dural tear or epidural scar formation. Fifty-six consecutive patients with back pain, neuroclaudication, or both, in addition to degenerative spondylolisthesis with spinal stenosis, underwent a surgical procedure that incorporated fusion after reduction of the spondylolisthesis deformity with preservation of the lamina and the balance of the posterior elements. Clinical records were reviewed and patients interviewed at a mean of 33 months after surgery. Oswestry Disability Index scores were obtained independently at baseline and at a late review. Late imaging was available a mean of 28 months after operation. Clinical and imaging analyses and Oswestry scoring confirmed results comparable to the published outcomes of in situ fusion after formal laminectomy. Resection of the lamina may not be necessary in the treatment of degenerative lumbar spinal stenosis with spondylolisthesis.     

The effect of osteogenic protein-1 in instrumented and noninstrumented posterolateral fusion in rabbits.

BACKGROUND CONTEXT: The use of rigid instrumentation combined with bone graft makes intuitive sense given the requirements for vascular ingrowth, bone formation and a stable environment for the cellular events of healing to develop. However, with the advances of potent osteoinductive growth factors, the role of internal fixation may come into question. Whether bone morphogenic proteins (BMPs) would benefit from a more "stable" spinal segment for bone production and modeling remains unknown. In addition, it is unknown whether BMP and rigid fixation may have an additive effect on fusion healing. PURPOSE: This study is proposed to test the hypothesis that rigid fixation in the lumbar spine would be advantageous to achieve fusion for autogenous bone grafting, but fusion would occur regardless of fixation with the use of osteogenic protein (OP)-1. STUDY DESIGN/SETTING: A histologic and radiographic analysis of BMP in a rabbit lumbar fusion model. METHODS: Thirty-two rabbits were randomized into four groups: 1) control animals: in situ posterolateral L5-L6 arthrodesis using autogenous iliac crest bone graft; 2) fixation group: posterolateral arthrodesis L5-L6 with autogenous bone graft and interspinous fixation; 3) OP-1 group: in situ posterolateral L5-L6 arthrodesis using OP-1 and 4) combined OP-1 and fixation group. Radiographic fusion analysis was performed with computed tomography scans at 3 and 12 weeks after surgery. Decalcified histology was performed to assess tissue morphology and cellularity. RESULTS: Minimal evidence of fusion was noted at 3 weeks with autograft or OP-1. By 12 weeks, all OP-1-treated animals had solid fusion, whereas no fusion was noted in autograft animals. The addition of fixation slightly increased radiographic fusion at 3 weeks in autograft and OP-1 groups but did not affect OP-1 animals at 12 weeks where all were fused. Decalcified histologic results confirmed the proliferative bone formation noted with OP-1 and the variable cellular response with autograft. CONCLUSIONS: The results of the present study suggest that the osteoinductive effect of OP-1 may be only minimally enhanced early in the bone healing process but does not appear to be affected in the long term by spinal fixation in the rabbit intertransverse fusion model. Fixation appeared to enhance early fusion in the autograft group.     

Functional outcome of surgical treatment for multilevel lumbar spinal stenosis

Background?There is no consensus regarding the best treatment of patients with multilevel lumbar stenosis. We evaluated the clinical and radiological findings in 41 patients with complex degenerative spinal stenosis of the lumbar spine who were treated surgically.

Methods?Between 1997 and 2003, 41 patients suffering from degenerative lumbar spinal stenosis were included in a prospective clinical study. The spinal stenosis was multilevel in all patients and in 13 of them there was degenerative scoliosis, in 18 there was degenerative spondylolisthesis, and in 10 there was segmental instability. Plain radiographs, MRI and/or CT myelograms were obtained preoperatively. The patients were assessed clinically with the Oswestry disability index (ODI) and visual analog scale (VAS). Surgery included wide posterior decompression and fusion using a trans-pedicular instrumentation system and bone graft.

Results?After a mean follow-up of 3.7 (1–6) years, the patients' clinical improvement on the ODI and VAS was statistically significant. Recurrent stenosis was not observed, and 39 of 41 patients were satisfied with the outcome. 3 patients with improvement initially had later surgery because of instability.

Interpretation?The above-mentioned technique gives good and long lasting clinical results, when selection of patients is done carefully and when the spinal levels that are to be decompressed are selected accurately.     

Posterior lumbar interbody fusion versus intertransverse fusion in the treatment of lumbar spondylolisthesis

PURPOSE: To compare 2 methods of fusion in the treatment of lumbar spondylolisthesis: posterior lumbar interbody fusion (PLIF) and intertransverse fusion (ITF). METHODS: 20 patients with lumbar spondylolisthesis were randomly allocated to one of 2 groups: decompression, posterior instrumentation, and PLIF (n=10) or decompression, posterior instrumentation, and ITF (n=10). The Oswestry low back pain disability questionnaire was used for clinical assessment. Radiography was performed preoperatively and postoperatively to assess the reduction of spondylolisthesis or slip. RESULTS: In the PLIF and ITF groups, 87.5% and 100% had a satisfactory clinical result, and 48% and 39% had reduced spondylolisthesis, respectively. Both had a fusion rate of 100%. PLIF showed better reduction of spondylolisthesis, although ITF achieved a better subjective and clinical outcome. CONCLUSION: Morbidity and complications are much higher following PLIF than ITF. ITF is recommended because of the simplicity of the procedure, lower complication rate, and good clinical and radiological results.     

个体化手术治疗退变性腰椎管狭窄症

目的回顾性分析选择性减压和减压融合治疗退变性腰椎管狭窄症的临床疗效。方法对我科2008年10月-2010年10月81例行手术治疗的退变性腰椎管狭窄症的临床资料进行总结：其中男37例,女44例,年龄39~72岁,平均（59.4±6.3）岁;单节段狭窄48例,双节段狭窄25例,三个及其以上节段狭窄8例;7例伴L4椎体I°滑脱,5例伴腰椎退变性侧弯,26例存在节段性不稳。根据无或有不稳行减压（A组）或减压融合（B组）。A组43例,行经后路常规椎板开窗减压或后路椎间盘椎管探查减压;B组38例,行后路减压椎体间或横突间植骨融合及椎弓根钉棒内固定术。采用JOA评分、ODI量表评价临床疗效,比较两组的疗效。结果平均随访1.8年,总体临床优良率82.1%,A组82.1%,B组82.2%。结论在仔细分析病情的基础上,选择个体化手术方案治疗退变性腰椎管狭窄症可取得满意的临床疗效,提高生活质量。     

The surgical management of complicated spinal stenosis: spondylolisthesis

The principles of surgery in spinal stenosis follow a clear understanding of the pathology in the various types ofstenosis. This article describes how the basic technique of one-level decompression in spinal stenosis is modified to deal with the pathology in degenerative spondylolisthesis. We have provided an explanation of the pathology in spinal stenosis with degenerative spondylolisthesis, and how modifications of the basic decompressive technique are necessary to deal with these variations in pathology. The indications and technique for a concomitant lateral spinal fusion are described. Techniques of instrumentation are not covered in this article.     

腰椎滑脱的减压、内固定与融合术

目的观察采用腰椎管减压、横突间植骨、Cage椎间融合器和SOCON内固定治疗腰椎滑脱合并腰椎管狭窄的早期疗效。方法从1997年12月～1999年12月,对38例腰椎滑脱患者采用腰椎管减压,横突间植骨和SOCON内固定手术进行治疗。术前X线检查按Meyerding分度,Ⅰ度滑脱32例,Ⅱ度滑脱6例;L4,5滑脱29例,L5S1滑脱9例。结果术后平均随访18.2个月(14～26个月),比较手术前后临床症状和X线片滑脱复位程度,38例患者中,31例症状完全消失,优良率为81.6%。32例Ⅰ度滑脱完全复位,4例Ⅱ度滑脱完全复位,2例Ⅱ度滑脱复位达90%,解剖复位率达94.7%。结论应用SOCON内固定治疗腰椎滑脱,效果良好,复位满意。     

2000 Young Investigator Research Award winner. Evaluation of OP-1 as a graft substitute for intertransverse process lumbar fusion

STUDY DESIGN: An established rabbit intertransverse process lumbar fusion model was used to evaluate osteogenic protein (OP)-1 as a potential graft substitute. OBJECTIVES: To determine whether OP-1 is effective in producing intertransverse process lumbar fusion in a rabbit model. SUMMARY OF BACKGROUND DATA: Autogenous iliac crest bone is the gold standard in grafting material for inducing intertransverse process fusion. However, bone graft substitutes are being considered as supplementary or alternative means to achieve such fusion with less morbidity. Relatively little research has been undertaken to investigate the efficacy of OP-1 in this role. METHODS: Single-level intertransverse process lumbar fusions were performed at L5-L6 of 31 New Zealand White rabbits. These were divided into three study groups: autograft, carrier alone, and carrier with OP-1. The animals were killed 5 weeks after surgery. Resultant fusion masses were evaluated by manual palpation, radiography, biomechanical multidirectional flexibility testing, and histology. RESULTS: Seven rabbits (23%) were excluded because of complications. Of the remaining 24 rabbits, 5 (63%) of the 8 in the autograft group had fusion detected by manual palpation, none (0%) of the 8 in the carrier-alone group had fusion, and all 8 (100%) in the OP-1 group had fusion. Radiographs were 55% sensitive and 92% specific for determining fusion. Biomechanical testing results correlated well with those of manual palpation. Histologically, autograft specimens were predominantly fibrocartilage, OP-1 specimens were predominantly maturing bone, and carrier-alone specimens did not show significant bone formation. CONCLUSIONS: OP-1 was found to reliably induce solid intertransverse process fusion in a rabbit model at 5 weeks.     

Volumetric change of the graft bone after intertransverse fusion

STUDY DESIGN: Patients in whom good intertransverse fusion had been achieved were selected for the volumetric study of the fusion mass using sequential computed tomography scans. OBJECTIVES: To assess the natural volumetric change of intertransverse fusion mass and the effect of the disease entity and spinal instrumentation on the fusion mass volume. SUMMARY OF BACKGROUND DATA: The magnitude of volumetric change of the graft bone after intertransverse fusion is still inconclusive. METHODS: Fifteen adult patients who underwent decompression surgery with single-level lumbar and lumbosacral intertransverse fusion were selected for this study. Preoperative diagnoses were degenerative spondylolisthesis in nine patients and isthmic spondylolisthesis in six. Seven of the 15 patients received pedicle screw fixation. They were categorized into two major groups: 1) instrumented and noninstrumented groups and 2) isthmic and degenerative groups. To assess the volumetric change of the graft bone, sequential computed tomography scans were obtained 2 weeks after surgery and again 18 months after surgery. RESULTS: The overall initial mean graft volume was 6251 mm3, which decreased to 2842 mm3 by 18 months after surgery (P < 0.001). The overall mean volume loss between the two periods was 54.8% of the initial graft volume. Although there was no significant difference in the mean graft volume between the groups at either 2 weeks or 18 months after surgery (P > 0.05 in all comparisons), the mean graft volume in each group decreased significantly during the observation period (P < 0.01 in all comparisons). There was no significant difference in the mean volume loss or in the ratio of residual volume to the initial graft volume between the groups during the study period (P > 0.05 in all comparisons). The initial graft volume correlated positively with the graft volume at 18 months after surgery (r = 0.612, P < 0.01) and volume loss (r = 0.949, P < 0.01), but negatively with the residual volume ratio (r = -0.507, P < 0.01). CONCLUSIONS: These results showed that more than one half of the initial graft bone volume was being absorbed during the consolidation processes of the graft bone, and that the volume loss during the period was not significantly affected by the spinal instrumentation or by the disease entity. It was also found that the greater the amount of the initial graft bone, the larger the fusion mass at 18 months after surgery. The volume loss, however, increased proportionally to an increase in the initial graft bone volume. The efficiency (ratio of residual volume to the initial graft volume) of the intertransverse fusion also tended to decline as the initial graft volume increased.     

Spinal stenosis in grade I degenerative lumbar spondylolisthesis: a comparative study of outcomes following laminoplasty and laminectomy with instrumented spinal fusion

The management of grade I lumbar degenerative spondylolisthesis remains controversial. There have been few reports comparing any form of surgery with conservative treatment. As for surgical management, the need for arthrodesis with instrumentation has not been established. A series of 53 patients with single-level spinal stenosis at L4/5 due to grade I degenerative spondylolisthesis entered into a study to compare outcomes of two surgical methods of treatment with those of a control group treated conservatively: group 1, 19 patients treated by decompression laminectomy combined with posterolateral fusion and pedicle screw instrumentation; group 2, 18 patients treated by decompression of the spinal canal using a laminoplasty technique to preserve the integrity of the midline structure; group 3, 16 patients treated conservatively after being recommended that they have surgery. We compared the 2-year results among the three groups. Alleviation of symptoms was noted in groups 1 and 2, whereas the controls (group 3) showed no improvement. There was no significant difference in the degree of clinical improvement between groups 1 and 2. Spondylolisthesis was controlled in group 1, but it did not lead to better clinical results than those achieved in group 2. Our findings indicate that the technique for decompressing the spinal canal with preservation of the posterior elements of its roof can be useful for treating patients with grade I degenerative spondylolisthesis with symptoms of spinal stenosis.     

Outcome of transpedicular screw fixation and posterior spinal fusion for degenerative spondylolisthesis.

Aims (1) To assess the results of decompression instrumentation and posterior spinal fusion for degenerative spondylolisthesis in a district general hospital. (2) To establish whether this procedure can be performed safely outside a specialised unit. Methods Thirty-one consecutive patients were included for this study. All underwent decompression instrumentation, pedicle screw fixation and posterior spinal fusion for degenerative spondylolisthesis in our unit. The average age was 56 (range 34–72) years with a mean follow-up of 3.7 years. Patients were assessed by their operative and post-operative complications, radiographic analysis and postal questionnaires; 25 (81%) patients replied to the questionnaire. Results Two cases each of dural tears, instrumentation failure and superficial wound infection, and one case of deep wound infection were found. There were no cases of neurological deficit, radiculopathy, recurrent stenosis or progression of deformity at the fused level. Radiological fusion rate was 87% and 88% were satisfied with the overall results; two (8%) patients said they would not have the same procedure again. An improvement in score outcome in terms of pain, mobility, sleep, analgesia and quality of life ( P <0.0001) was also noted. Conclusions Overall complications were 17%. An improved outcome was noted in terms of radiological fusion and patients' functional and satisfaction outcome in all those who underwent decompression pedicle screw fixation in our unit. We conclude that posterior spinal fusion can be performed safely outside a specialised unit.     

Functional outcome of surgical treatment for multilevel lumbar spinal stenosis

BACKGROUND: There is no consensus regarding the best treatment of patients with multilevel lumbar stenosis. We evaluated the clinical and radiological findings in 41 patients with complex degenerative spinal stenosis of the lumbar spine who were treated surgically. METHODS: Between 1997 and 2003, 41 patients suffering from degenerative lumbar spinal stenosis were included in a prospective clinical study. The spinal stenosis was multilevel in all patients and in 13 of them there was degenerative scoliosis, in 18 there was degenerative spondylolisthesis, and in 10 there was segmental instability. Plain radiographs, MRI and/or CT myelograms were obtained preoperatively. The patients were assessed clinically with the Oswestry disability index (ODI) and visual analog scale (VAS). Surgery included wide posterior decompression and fusion using a trans-pedicular instrumentation system and bone graft. RESULTS: After a mean follow-up of 3.7 (1-6) years, the patients' clinical improvement on the ODI and VAS was statistically significant. Recurrent stenosis was not observed, and 39 of 41 patients were satisfied with the outcome. 3 patients with improvement initially had later surgery because of instability. INTERPRETATION: The above-mentioned technique gives good and long lasting clinical results, when selection of patients is done carefully and when the spinal levels that are to be decompressed are selected accurately.     

Decompression and luque rectangle fusion for degenerative spondylolisthesis

Detailed follow-up at an average of 21.3 months is reported for 24 patients undergoing decompression and fusion with the Luque rectangle as a tension band device for spinal stenosis secondary to degenerative spondylolisthesis. Leg pain and back pain were improved at rates of 91% and 90%, respectively. The average distance walked increased from 1.1 blocks preoperatively to 6.8 blocks postoperatively. The fusion rate was 96%, and minimal slip progression was observed. The instrumentation is simple to perform and appears to have few complications.     

The efficacy of a nanosynthetic bone graft substitute as a bone graft extender in rabbit posterolateral fusion

BACKGROUND CONTEXTSynthetic bone graft substitutes are commonly used in spinal fusion surgery. Preclinical data in a model of spinal fusion to support their efficacy is an important component in clinical adoption to understand how these materials provide a biological and mechanical role in spinal fusion.PURPOSETo evaluate the in vivo response of a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft compared to autograft alone or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft in a rabbit spinal fusion model.STUDY DESIGNEfficacy of a nanosynthetic silicated calcium phosphate putty as an extender to autograft was studied in an experimental animal model of posterolateral spinal fusion at 6, 9, 12 and 26 weeks, compared to a predicate device.METHODSSkeletally mature female New Zealand White rabbits (70) underwent single level bilateral posterolateral intertransverse process lumbar fusion, using either autograft alone (AG), a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft (1:1), or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft (1:1). Iliac crest autograft was harvested for each group, and a total of 2 cc of graft material was implanted in the posterolateral gutters per side. Fusion success was assessed at all time points by manual palpation, radiographic assessment, micro-CT and at 12 weeks only using non-destructive range of motion testing. Tissue response, bone formation and graft resorption were assessed by decalcified paraffin histology and by histomorphometry of PMMA embedded sections.RESULTSAssessment of fusion by manual palpation at the 12 week endpoint showed 7 out of 8 (87.5%) bilateral fusions in the OstP extender group, 4 out of 8 (50%) fusions in the MasP extender group, and 6 out of 8 (75%) fusions in the autograft alone group. Similar trends were observed with fusion scores of radiographic and micro-CT data. Histology showed a normal healing response in all groups, and increased bone formation in the OstP extender group at all timepoints compared to the MasP extender group. New bone formed directly on the OstP granule surface within the fusion mass while this was not a feature of the Collagen-Biphasic CaP material. After 26 weeks the OstP extender group exhibited 100% fusions (5 out of 5) by all measures, whereas the MasP extender group resulted in bilateral fusions in 3 out of 5 (60%), assessed by manual palpation, and fusion of only 20 and 0% by radiograph and micro-CT scoring, respectively. Histology at 26 weeks showed consistent bridging of bone between the transverse processes in the Ost P extender group, but this was not observed in the MasP extender group.CONCLUSIONSThe nanosynthetic bone graft substituted studied here, used as an extender to autograft, showed a progression to fusion between 6 and 12 weeks that was similar to that observed with autograft alone, and showed excellent fusion outcomes, bone formation and graft resorption at 26 weeks.CLINICAL SIGNIFICANCEThis preclinical study showed that the novel nanosynthetic silicated CaP putty, when combined with autograft, achieved equivalent fusion outcomes to autograft. The development of synthetic bone grafts that demonstrate efficacy in such models can eliminate the need for excessive autograft harvest and results from this preclinical study supports their effective use in spinal fusion surgery.     

Lumbar spinal stenosis. Treatment strategies and indications for surgery

Initially, all patients with degenerative lumbar spinal stenosis should be treated conservatively. Rapid deterioration is unlikely. The majority of patients may either improve or remain stable over a long-term follow-up with nonoperative treatment. Surgery should be an elective decision by the patients who fail to improve after conservative treatment. Medical evaluation is mandatory in those elderly patients with frequent comorbidities. For central spinal stenosis, without significant grade I spondylolisthesis or deformity, decompression is the surgical treatment of choice. Iatrogenic instability must be avoided during decompression surgery by preserving the facet joint and the pars interarticularis. Limited decompression with laminotomy may be indicated for lateral canal stenosis. A limited decompression may avoid postoperative instability but is associated with more frequent neurologic sequelae. Postlaminectomy instability is uncommon, and too little decompression is a more frequent mistake than too much. Decompression is usually associated with good or excellent outcome in 80% of patients. Deterioration of initial post-operative improvement may occur over long-term follow-up. When spinal stenosis is associated with instability, degenerative spondylolisthesis, deformity, postoperative instability, or recurrent stenosis, fusion is often recommended. Instrumentation often improves the fusion rate but does not influence the clinical outcome. Generous decompression but selective fusion of the unstable segment only are preferable for degenerative spondylolisthesis and type I degenerative scoliosis with minimal rotation of the spine.     

Decompression alone versus decompression with fusion in patients with lumbar spinal stenosis with degenerative spondylolisthesis: a systematic review and meta-analysis

Introduction

Surgical decompression is standard care in the treatment of degenerative spondylolisthesis in patients with symptomatic lumbar spinal stenosis, but there remains controversy over the benefits of adding fusion. The persistent lack of consensus on this matter and the availability of new data warrants a contemporary systematic review and meta-analysis of the literature.

Methods

Multiple online databases were systematically searched up to October 2022 for randomized controlled trials (RCTs) and prospective studies comparing outcomes of decompression alone versus decompression with fusion for lumbar spinal stenosis in patients with degenerative spondylolisthesis. Primary outcome was the Oswestry Disability Index. Secondary outcomes included leg and back pain, surgical outcomes, and radiological outcomes. Pooled effect estimates were calculated and presented as mean differences (MD) with their 95% confidence intervals (CI) at two-year follow-up.

Results

Of the identified 2403 studies, eventually five RCTs and two prospective studies were included. Overall, most studies had a low or unclear risk of selection bias and most studies were focused on low grade degenerative spondylolisthesis. All patient-reported outcomes showed low statistical heterogeneity. Overall, there was high-quality evidence suggesting no difference in functionality at two years of follow-up (MD − 0.31, 95% CI − 3.81 to 3.19). Furthermore, there was high-quality evidence of no difference in leg pain (MD − 1.79, 95% CI − 5.08 to 1.50) or back pain (MD − 2.54, 95% CI − 6.76 to 1.67) between patients undergoing decompression vs. decompression with fusion. Pooled surgical outcomes showed less blood loss after decompression only, shorter length of hospital stay, and a similar reoperation rate compared to decompression with fusion.

Conclusion

Based on the current literature, there is high-quality evidence of no difference in functionality after decompression alone compared to decompression with fusion in patients with degenerative lumbar spondylolisthesis at 2 years of follow-up. Further studies should focus on long-term comparative outcomes, health economic evaluations, and identifying those patients that may benefit more from decompression with fusion instead of decompression alone. This review was registered at Prospero (CRD42021291603).

     

How to stabilize a single level lesion of degenerative lumbar spondylolisthesis

The purpose of this study was to compare the success rate of bony fusion and the clinical results of rigid instrumentation, nonrigid instrumentation, and no instrumentation for a single level lesion for degenerative lumbar spondylolisthesis. Thirty-three patients with degenerative spondylolisthesis of L4 who had undergone posterior decompression and posterolateral fusion with autogenous bone graft that included the facet joints had a single level stabilization with a newly designed syndesmoplasty using Leeds-Keio artificial ligaments (Group Leeds-Keio-nonrigid). Thirty-four patients with degenerative spondylolisthesis of L4 who had the same procedure were stabilized with the Steffee system (Group Steffee-rigid). Thirty-five patients who had the same decompression and bony fusion without instrumentation (Group Noninstrumented) were compared with the former two groups. Clinical results were correlated with the stage of bony fusion. The Steffee system was reliable for stabilizing intervertebral angular instability such as a preoperative intervertebral angle difference of more than 11 degrees in flexion and extension. In the patients who preoperatively had an angle difference of less than 10 degrees, no significant difference was seen between Group Leeds-Keio and Group Steffee. The authors concluded that nonrigid instrumentation can be used to achieve successful bony fusion in patients with degenerative spondylolisthesis, who have a preoperative angle difference less than 10 degrees, with excellent clinical results.