RhBMP-2 is superior to iliac crest bone graft for long fusions to the sacrum in adult spinal deformity: 4- to 14-year follow-up

Cost-Effectiveness Analyses of Bone Morphogenetic Protein 2 (rhBMP-2) in Spinal Fusion: A Systematic Review

Study DesignSystematic Review Study.ObjectivesThe objective of this study is to assess the cost-effectiveness and cost-utility of rhBMP-2 in spine surgeries.MethodsPubMed, MEDLINE, OVID and CENTRAL (Cochrane Central Register of Controlled Trials) databases were systematically searched for studies reporting the use of rhBMP-2 for spinal procedures in comparison to autograft and/or allograft and alternative graft materials under consideration of cost-effectiveness, cost-benefit, cost minimization, and/or cost-utility analysis. Relevant data points were extracted and compiled. The standardization of the selected studies was graded using the CHEERS criteria.ResultsOf the 88 eligible publications, 17 met the inclusion criteria. Overall, 8 studies showed a favorable cost-analysis profile. Three studies performed cost-consequence analyses, none of which reported positive findings. Among 7 cost-utility analyses and 7 cost-effectiveness analyses, 3 and 5, respectively, reported a likely benefit to the usage of rhBMP-2. The CHEERS scores for the included studies ranged from 15 to 23 out of 24 points, with a median score of 19.ConclusionsThere is no consensus regarding the cost-effectiveness or cost-utility of rhBMP-2 in spinal fusion. rhBMP-2 may function as a cost-effective adjunct in spinal fusion surgeries in select cases.

Developing a risk score to inform the use of rhBMP-2 in adult spinal deformity surgery

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has not shown superior benefit overall in cost-effectiveness during adult spinal deformity (ASD) surgery.

STUDY DESIGN/SETTING

Retrospective PURPOSE: Generate a risk score for pseudarthrosis to inform the utilization of rhBMP-2, balancing costs against quality of life and complications.

METHODS

ASD patients with 3-year data were included. Quality of life gained was calculated from ODI to SF-6D and translated to quality-adjusted life years (QALYs). Cost was calculated using the PearlDiver database and CMS definitions for complications and comorbidities. Established weights were generated for predictive variables via logistic regression to yield a predictive risk score for pseudarthrosis that accounted for frailty, diabetes, depression, ASA grade, thoracolumbar kyphosis and three-column osteotomy use. Risk score categories, established via conditional inference tree (CIT)-derived thresholds were tested for cost-utility of rhBMP-2 usage, controlling for age, prior fusion, and baseline deformity and disability.

RESULTS

64% of ASD patients received rhBMP-2 (308/481). There were 17 (3.5%) patients that developed pseudarthrosis. rhBMP-2 use overall did not lower pseudarthrosis rates (OR: 0.5, [0.2-1.3]). Pseudarthrosis rates for each risk category were: No Risk (NoR) 0%; Low-Risk (LowR) 1.6%; Moderate Risk (ModR) 9.3%; High-Risk (HighR) 24.3%. Patients receiving rhBMP-2 had similar QALYs overall to those that did not (0.163 vs. 0.171, p = .65). rhBMP-2 usage had worse cost-utility in the LowR cohort (p < .001). In ModR patients, rhBMP-2 usage had equivocal cost-utility ($53,398 vs. $61,581, p = .232). In the HighR cohort, the cost-utility was reduced via rhBMP-2 usage ($98,328 vs. $211,091, p < .001).

CONCLUSION

Our study shows rhBMP-2 demonstrates effective cost-utility for individuals at high risk for developing pseudarthrosis. The generated score can aid spine surgeons in the assessment of risk and enhance justification for the strategic use of rhBMP-2 in the appropriate clinical contexts.

LEVEL OF EVIDENCE

III.

Treatment of adult spine deformity: A retrospective comparison of bone morphogenic protein and bone marrow aspirate with bone allograft

BACKGROUND  : The use of bone morphogenic protein (BMP-2) in adult spine deformity (ASD) surgery remains controversial more than two decades following its approval for clinical application in spine surgery. This study was performed to assess outcomes in patients undergoing ASD surgery with BMP application compared with a combination of bone marrow aspirate, cancellous bone chips and i-Factor.

METHODS

This was a retrospective cohort study. ASD patients were stratified by use of intra-operative BMP (BMP +) or not (BMA + I) and surveyed for the development of complications and mechanical failure. Quality of life gained following the procedure was evaluated using quality-adjusted life years (QALYs). Cost was calculated using the PearlDiver database and CMS definitions. Multivariable analyses (ANCOVA) and logistic regression were used to adjust for confounding.

RESULTS

512 patients were included (60% BMP +). At baseline, BMP + patients were older (62.5 vs 60.8 years, p < 0.010). Radiographic and quality-of-life metrics did not differ at follow up timepoints (all p > 0.05). BMP use was associated with higher supplemental rod use (OR: 7.0, 1.9 - 26.2, p = 0.004), greater number of levels fused (OR: 1.1, 1.03 - 1.17, p = 0.003) and greater neurological complications (OR: 5.0, 1.3 - 18.7, p = 0.017). Controlling for rod use and levels fused, BMP use was not associated with a lower risk of mechanical complications (OR 0.3, 95% CI: 0.2 - 3.0, p = 0.353), rod breakage (OR: 3.3, 0.6 - 18.7, p = 0.182) or implant failure (OR: 0.3, 0.04 - 1.51). At 2 years, the BMP + cohort exhibited higher overall costs ($108,062 vs $95,144, p = 0.002), comparable QALYs (0.163 vs 0.171, p = 0.65) and higher cost per QALY (p = 0.001) at two years.

CONCLUSIONS

In this analysis, BMP-2 application was not associated with superior outcomes when compared to a less costly biologic alternative (bone marrow aspirate + cancellous bone chips + i-Factor) following ASD surgery. The use of BMP-2 in ASD surgery appears to have reduced cost-efficacy at two years postoperatively.

Circumferential Bone Fusion in Adult Spinal Deformity via Combination of Oblique Lateral Interbody Fusion and Grade 2 Posterior Column Osteotomy

STUDY DESIGN

Retrospective study.

OBJECTIVES

The combination of oblique lateral interbody fusion (OLIF) with grade 2 posterior column osteotomy (PCO) is an effective treatment for adult spinal deformity. However, grade 2 PCO may lead to pseudoarthrosis because it involves complete removal of the bilateral posterior facet joints. The main study objective was to determine the achievement rate of anterior and posterolateral fusion resulting in circumferential fusion in patients who underwent combined OLIF and grade 2 PCO.

METHODS

This retrospective study included consecutive patients who underwent OLIF and grade 2 PCO. The group comprised a long fusion group, with fusion from the thoracic level to the ilium, and a short fusion group, with fusion within the lumbar region. The OLIF with percutaneous pedicle screw insertion group was also used for reference. The Brantigan-Steffee-Fraser classification was used to assess interbody fusion and Lenke classification for assessment of posterolateral fusion.

RESULTS

Sixty-six patients with 109 lumbar levels were included in the study. We observed 100% anterior fusion in all 3 groups. The fusion rate for posterolateral fusion between the OLIF-grade 2 PCO group was 97%, with very low (3%) non-circumferential fusion (pseudoarthrosis only at the osteotomy site). In most cases, solid posterolateral fusions (Lenke A) occurred within 24 months.

CONCLUSIONS

The combination of OLIF and grade 2 PCO resulted in circumferential fusion for most (97%) of the cases within 24 months. OLIF and grade 2 PCO are considered a good combination treatment to achieve sufficient lumbar lordosis and solid bone fusion.

Rod fractures in thoracolumbar fusions to the sacrum/pelvis for adult symptomatic lumbar scoliosis: long-term follow-up of a prospective, multicenter cohort of 160 patients

OBJECTIVE

Previous reports of rod fracture (RF) in adult spinal deformity are limited by heterogeneous cohorts, low follow-up rates, and relatively short follow-up durations. Since the majority of RFs present > 2 years after surgery, true occurrence and revision rates remain unclear. The objectives of this study were to better understand the risk factors for RF and assess its occurrence and revision rates following primary thoracolumbar fusions to the sacrum/pelvis for adult symptomatic lumbar scoliosis (ASLS) in a prospective series with long-term follow-up.

METHODS

Patient records were obtained from the Adult Symptomatic Lumbar Scoliosis-1 (ASLS-1) database, an NIH-sponsored multicenter, prospective study. Inclusion criteria were as follows: patients aged 40-80 years undergoing primary surgeries for ASLS (Cobb angle ≥ 30° and Oswestry Disability Index ≥ 20 or Scoliosis Research Society-22r ≤ 4.0 in pain, function, and/or self-image) with instrumented fusion of ≥ 7 levels that included the sacrum/pelvis. Patients with and without RF were compared to assess risk factors for RF and revision surgery.

RESULTS

Inclusion criteria were met by 160 patients (median age 62 years, IQR 55.7-67.9 years). At a median follow-up of 5.1 years (IQR 3.8-6.6 years), there were 92 RFs in 62 patients (38.8%). The median time to RF was 3.0 years (IQR 1.9-4.54 years), and 73% occurred > 2 years following surgery. Based on Kaplan-Meier analyses, estimated RF rates at 2, 4, 5, and 8 years after surgery were 11%, 24%, 35%, and 49%, respectively. Baseline radiographic, clinical, and demographic characteristics were similar between patients with and without RF. In Cox regression models, greater postoperative pelvic tilt (HR 1.895, 95% CI 1.196-3.002, p = 0.0065) and greater estimated blood loss (HR 1.02, 95% CI 1.005-1.036, p = 0.0088) were associated with increased risk of RF. Thirty-eight patients (61% of all RFs) underwent revision surgery. Bilateral RF was predictive of revision surgery (HR 3.52, 95% CI 1.8-6.9, p = 0.0002), while patients with unilateral nondisplaced RFs were less likely to require revision (HR 0.39, 95% CI 0.18-0.84, p = 0.016).

CONCLUSIONS

This study provides what is to the authors' knowledge the highest-quality data to date on RF rates following ASLS surgery. At a median follow-up of 5.1 years, 38.8% of patients had at least one RF. Estimated RF rates at 2, 4, 5, and 8 years after surgery were 11%, 24%, 35%, and 49%, respectively. Greater estimated blood loss and postoperative pelvic tilt were significant risk factors for RF. These findings emphasize the importance of long-term follow-up to realize the true prevalence and cumulative incidence of RF.

Use of graft materials and biologics in spine deformity surgery: a state-of-the-art review

PURPOSE

The aim of the current review is to summarize the current evidence on graft materials used in fusion procedures for spinal deformity corrections.

METHODS

PubMed, Embase, and Cochrane Library were searched for relevant published observational studies and clinical trials using osteobiologics and biomaterials in spinal deformity surgery.

RESULTS

The use of autograft in deformity correction surgeries has been reported in a limited number of studies, with the harvest sites including iliac crest, ribs, and local bone. Various allografts and biologics have been used in the treatment of spinal deformities including idiopathic and degenerative scoliosis, either as stand alone or in combination with autograft. Limited number of studies reported no differences in fusion rates or outcomes. Use of rh-BMP2 in anterior, posterior or front/back approaches showed higher fusion rates than other graft materials in patients with spinal deformities. Due to the limited number of quality studies included in the review, as well as alternative factors, such as costs, availability, and surgeon expertise/preference, no definitive conclusion or recommendations can be made as to the ideal graft choice in spinal deformity surgery.

CONCLUSIONS

Most commonly used grafts included autograft, allograft and rh-BMP2, with new biologics and biomaterials constantly emerging in the market. Limited number of high-quality comparative studies and heterogeneity in study design prevented direct comparisons that can lead to meaningful recommendations. Further studies are needed to prove superiority of any single graft material and/or biologic that is also cost-effective and safe.

Failure in Adult Spinal Deformity Surgery: A Comprehensive Review of Current Rates, Mechanisms, and Prevention Strategies

STUDY DESIGN

Literature review.

OBJECTIVE

The aim of this review is to summarize recent literature on adult spinal deformity (ASD) treatment failure as well as prevention strategies for these failure modes.

SUMMARY OF BACKGROUND DATA

There is substantial evidence that ASD surgery can provide significant clinical benefits to patients. The volume of ASD surgery is increasing, and significantly more complex procedures are being performed, especially in the aging population with multiple comorbidities. Although there is potential for significant improvements in pain and disability with ASD surgery, these procedures continue to be associated with major complications and even outright failure.

METHODS

A systematic search of the PubMed database was performed for articles relevant to failure after ASD surgery. Institutional review board approval was not needed.

RESULTS

Failure and the potential need for revision surgery generally fall into 1 of 4 well-defined phenotypes: clinical failure, radiographic failure, the need for reoperation, and lack of cost-effectiveness. Revision surgery rates remain relatively high, challenging the overall cost-effectiveness of these procedures.

CONCLUSION

By consolidating the key evidence regarding failure, further research and innovation may be stimulated with the goal of significantly improving the safety and cost-effectiveness of ASD surgery.

Use of demineralized cortical fibers is associated with reduced risk of pseudarthrosis after pedicle subtraction osteotomy for adult spinal deformity

PURPOSE

To assess the effect of demineralized cortical fibers (DCF) on postoperative pseudarthrosis requiring revision surgery in patients undergoing pedicle subtraction osteotomy (PSO) for adult spinal deformity (ASD).

METHODS

The use of DCF was introduced across all procedures in 2017 and subsequent patients undergoing PSO surgery were prospectively and consecutively registered. Following sample-size estimation, a retrospective cohort was also registered undergoing the same procedure immediately prior to the implementation of DCF. The non-DCF group underwent surgery with ABG. Minimum follow-up was 2 years in both groups. The main outcome was postoperative pseudarthrosis, either CT-verified or verified intraoperatively during revision surgery due to rod breakage and assessed using Kaplan-Meier survival analyses.

RESULTS

A total of 48 patients were included in the DCF group and 76 in the non-DCF group. The DCF group had more frequently undergone previous spine surgery (60% vs 36%) and had shorter follow-up (32 ± 2 vs 40 ± 7 months). Pseudarthrosis occurred in 7 (15%) patients in the DCF group and 31 (41%) in the non-DCF group, corresponding to a relative risk increase of 2.6 (95%CI 1.3-2.4, P < 0.01). 1-KM survival analyses, taking time to event into account and thus the difference in follow-up, also showed increased pseudarthrosis in the non-DCF group (log-rank P = 0.022). Similarly, multivariate logistic regression adjusted for age, instrumented levels and sacral fusion was also with significantly increased odds of pseudarthrosis in the non-DCF group (OR: 4.3, 95%CI: 1.7-11.3, P < 0.01).

CONCLUSION

We found considerable and significant reductions in pseudarthrosis following PSO surgery with DCF compared to non-DCF.

LEVEL OF EVIDENCE

III.

Dose Adjustment Associated Complications of Bone Morphogenetic Protein: A Longitudinal Assessment

OBJECTIVE

Bone morphogenetic protein (BMP) is a growth factor that aids in osteoinduction and promotes bone fusion. There is a lack of literature regarding recombinant human BMP-2 (rhBMP-2) dosage in different spine surgeries. This study aims to investigate the trends in rhBMP-2 dosage and the associated complications in spinal arthrodesis.

METHODS

A retrospective study was conducted investigating spinal arthrodesis using rhBMP-2. Variables including age, procedure type, rhBMP-2 size, complications, and postoperative imaging were collected. Cases were grouped into the following surgical procedures: anterior lumbar interbody fusion/extreme lateral interbody fusion (ALIF/XLIF), posterior lumbar interbody fusion/transforaminal lumbar interbody fusion (PLIF/TLIF), posterolateral fusion (PLF), anterior cervical discectomy and fusion (ACDF), and posterior cervical fusion (PCF).

RESULTS

A total of 1209 patients who received rhBMP-2 from 2006 to 2020 were studied. Of these, 230 were categorized as ALIF/XLIF, 336 as PLIF/TLIF, 243 as PLF, 203 as ACDF, and 197 as PCF. PCF (P < 0.001), PLIF/TLIF (P < 0.001), and PLF (P < 0.001) demonstrated a significant decrease in the rhBMP-2 dose used per level, with major transitions seen in 2018, 2011, and 2013, respectively. In our sample, 129 complications following spinal arthrodesis were noted. A significant relation between rhBMP-2 size and complication rates (χ²= 73.73, P = 0.0029) was noted. rhBMP-2 dosage per level was a predictor of complication following spinal arthrodesis (odds ratio = 1.302 [1.05-1.55], P < 0.001).

CONCLUSIONS

BMP is an effective compound in fusing adjacent spine segments. However, it carries some regional complications. We demonstrate a decreasing trend in the dose/vertebral level. A decrease rhBMP-2 dose per level correlated with a decrease in complication rates.

A BMP/Activin A Chimera Induces Posterolateral Spine Fusion in Nonhuman Primates at Lower Concentrations Than BMP-2

BACKGROUND

Supraphysiologic bone morphogenetic protein (BMP)-2 concentrations are required to induce spinal fusion. In this study, a BMP-2/BMP-6/activin A chimera (BV-265), optimized for BMP receptor binding, delivered in a recombinant human collagen:CDHA [calcium-deficient hydroxyapatite] porous composite matrix (CM) or bovine collagen:CDHA granule porous composite matrix (PCM), engineered for optimal BV-265 retention and guided tissue repair, was compared with BMP-2 delivered in a bovine absorbable collagen sponge (ACS) wrapped around a MASTERGRAFT Matrix (MM) ceramic-collagen rod (ACS:MM) in a nonhuman primate noninstrumented posterolateral fusion (PLF) model.

METHODS

In vivo retention of 125I-labeled-BV-265/CM or PCM was compared with 125I-labeled-BMP-2/ACS or BMP-2/buffer in a rat muscle pouch model using scintigraphy. Noninstrumented PLF was performed by implanting CM, BV-265/CM, BV-265/PCM, or BMP-2/ACS:MM across L3-L4 and L5-L6 or L3-L4-L5 decorticated transverse processes in 26 monkeys. Computed tomography (CT) images were acquired at 0, 4, 8, 12, and 24 weeks after surgery, where applicable. Manual palpation, μCT (microcomputed tomography) or nCT (nanocomputed tomography), and histological analysis were performed following euthanasia.

RESULTS

Retention of 125I-labeled-BV-265/CM was greater than BV-265/PCM, followed by BMP-2/ACS and BMP-2/buffer. The CM, 0.43 mg/cm3 BMP-2/ACS:MM, and 0.05 mg/cm3 BV-265/CM failed to generate PLFs. The 0.15-mg/cm3 BV-265/CM or 0.075-mg/cm3 BV-265/PCM combinations were partially effective. The 0.25-mg/cm3 BV-265/CM and 0.15 and 0.3-mg/cm3 BV-265/PCM combinations generated successful 2-level PLFs at 12 and 24 weeks.

CONCLUSIONS

BV-265/CM or PCM can induce fusion in a challenging nonhuman primate noninstrumented PLF model at substantially lower concentrations than BMP-2/ACS:MM.

CLINICAL RELEVANCE

BV-265/CM and PCM represent potential alternatives to induce PLF in humans at substantially lower concentrations than BMP-2/ACS:MM.

Bone Morphogenetic Protein-2 Promotes Osteoclasts-mediated Osteolysis via Smad1 and p65 Signaling Pathways

STUDY DESIGN

An in vitro biological study.

OBJECTIVE

The aim of this study was to explore the role of bone morphogenetic protein-2 (BMP-2) in the regulation of osteoclast-mediated osteolysis, and the possible mechanism involving BMP-2 and nuclear factor-kappa B (NF-κB) signaling pathways.

SUMMARY OF BACKGROUND DATA

Recombinant human BMP-2 (rhBMP-2) has been approved as a therapeutic agent in spinal fusion and bone defect repair. However, its efficacy and clinical application are limited by associated complications including osteoclast-mediated bone resorption. The mechanism of BMP-2-induced osteolysis remains unknown.

METHODS

Bone marrow-derived macrophages (BMMs) were isolated from C57BL/6J mice and cultured with macrophage colony-stimulating factor (M-CSF) and receptor activator for nuclear factor-κB Ligand (RANKL) to induce osteoclast differentiation. An in vitro bone resorption assay was performed by co-culturing BMMs and bone slides. The expression of BMP canonical and NF-κB signaling factors and their interaction during signal transduction were quantitated by reverse transcription polymerase chain reaction, Western blot analysis, confocal microscopy, and co-immunoprecipitation.

RESULTS

BMP-2 enhanced osteoclast-mediated bone resorption via inducing osteoclast differentiation in a concentration-dependent manner. In addition, a high concentration of BMP-2 significant upregulated phosphorylation of BMP signaling factors p-Smad1/5/8 and NF-κB downstream factor p65, and promoted the degeneration of IκBα. In addition, BMP-2 induced osteoclast differentiation through coupling between BMP receptor II and RANK.

CONCLUSION

High concentrations of BMP-2 enhanced osteoclast-mediated bone resorption by promoting RANKL-induced pre-osteoclast differentiation, probably by mediating the cross-talk between BMP canonical and NF-κB signaling pathways.Level of Evidence: N/A.

Cost-Utility Analysis of rhBMP-2 Use in Adult Spinal Deformity Surgery

STUDY DESIGN

Economic modeling of data from a multicenter, prospective registry.

OBJECTIVE

The aim of this study was to analyze the cost utility of recombinant human bone morphogenetic protein-2 (BMP) in adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

ASD surgery is expensive and presents risk of major complications. BMP is frequently used off-label to reduce the risk of pseudarthrosis.

METHODS

Of 522 ASD patients with fusion of five or more spinal levels, 367 (70%) had at least 2-year follow-up. Total direct cost was calculated by adding direct costs of the index surgery and any subsequent reoperations or readmissions. Cumulative quality-adjusted life years (QALYs) gained were calculated from the change in preoperative to final follow-up SF-6D health utility score. A decision-analysis model comparing BMP versus no-BMP was developed with pseudarthrosis as the primary outcome. Costs and benefits were discounted at 3%. Probabilistic sensitivity analysis was performed using mixed first-order and second-order Monte Carlo simulations. One-way sensitivity analyses were performed by varying cost, probability, and QALY estimates (Alpha = 0.05).

RESULTS

BMP was used in the index surgery for 267 patients (73%). The mean (±standard deviation) direct cost of BMP for the index surgery was $14,000 ± $6400. Forty patients (11%) underwent revision surgery for symptomatic pseudarthrosis (BMP group, 8.6%; no-BMP group, 17%; P = 0.022). The mean 2-year direct cost was significantly higher for patients with pseudarthrosis ($138,000 ± $17,000) than for patients without pseudarthrosis ($61,000 ± $25,000) (P < 0.001). Simulation analysis revealed that BMP was associated with positive incremental utility in 67% of patients and considered favorable at a willingness-to-pay threshold of $150,000/QALY in >52% of patients.

CONCLUSION

BMP use was associated with reduction in revisions for symptomatic pseudarthrosis in ASD surgery. Cost-utility analysis suggests that BMP use may be favored in ASD surgery; however, this determination requires further research.

LEVEL OF EVIDENCE

2.

Advances in Spinal Fusion Strategies in Adult Deformity Surgery

BACKGROUND

As the frequency of adult deformity surgery (ADS) continues to increase, our understanding of techniques that enhance fusion must continue to evolve because pseudarthrosis can be a serious and costly event.

PURPOSES/QUESTIONS

We sought to conduct a review of the literature investigating techniques that can enhance outcomes of ADS.

METHODS

Two databases were searched for keywords such as "advances in spinal fusion," "new technology in adult spinal deformity," "interbody devices for adult spinal deformity," "adult spinal deformity rods," and "screw design in adult spinal deformity" to examine recent literature and trends in ADS.

RESULTS

We identified 45 articles for our review. Topics studied include the use of multiple rods, interbody fusion, distal fixation techniques, and bone morphogenetic protein or iliac crest bone graft.

CONCLUSIONS

Many recent innovations in treatments to enhance fusion in ADS have been studied, some more controversial than others. Further research into the efficacy of these techniques may increase fusion rates in ADS.

Pedicle Subtraction Osteotomy

Pedicle subtraction osteotomy (PSO) was originally performed in cases of ankylosing spondylitis. This procedure was invented because it was safer than trying to lengthen the anterior column via osteoclasis, which risked vascular injury and death^1-4. PSO involves the removal of the posterior elements and the use of a vertebral body wedge to shorten the spine posteriorly and achieve sagittal-plane correction^5,6. PSO has been used to correct sagittal-plane deformities not only in patients with ankylosing spondylitis but also in those with degenerative conditions or those who have previously undergone surgical procedures resulting in a loss of lumbar lordosis^7,8.

Description

The fixation points are placed with pedicle screws above and below the planned osteotomy level. The posterior elements are decompressed at the level of the osteotomy and at 1 level proximally. In addition to the use of straight and angled curets, a high-speed burr is used to decancellate the vertebral body. Pedicle osteotomes are used to remove the pedicle. Temporary rods are placed. The posterior wall of the body is then impacted into the vertebral body, and the temporary rods are loosened. To close the osteotomy, the bed is extended or the spine is pushed manually, resulting in correction of the lordosis. The temporary rods are tightened. The main rods, independent of the short rods, are used to connect multiple segments several levels above and below the osteotomy site to provide final stabilization.

Alternatives

The alternatives to PSO depend on the surgical history of the patients, as well as the flexibility and alignment of the spine. In a spine with mobile disc spaces, Smith-Petersen osteotomies can be performed posteriorly to shorten the posterior column over multiple segments to gain lordosis. A formal anterior or lateral approach can be performed to release the disc spaces and restore the disc height. A posterior release through the facet joints with segmental compression can achieve desired lumbar lordosis. A vertebral column resection can also be performed to achieve lordosis.

Rationale

PSO is ideal for patients who have undergone multiple spinal fusions and who have a very rigid, flat lumbar spine. A single posterior approach can be used to provide adequate correction of the flat lumbar spine up to 40°. Asymmetric PSO can also be performed to allow for correction in the coronal plane. Recently, PSO has been performed more frequently because of the improved osteotomy instrumentation, exposure to resection techniques, and improved positioning tables that allow correction of the osteotomy.

Autogenous Iliac Crest Bone Grafting for the Treatment of Fracture Nonunion Is Equally Effective in Elderly and Nonelderly Patients

INTRODUCTION

Autogenous iliac crest bone graft (ICBG) is considered the benchmark graft for nonunion repair. However, ICBG harvest is invasive and may provide reduced benefit to elderly patients. The purpose of this study was to compare the clinical and functional outcomes of ICBG use in fixation of fracture nonunions between elderly and nonelderly patients.

METHODS

Over a 13-year period, 242 patients who underwent operative repair of a long bone fracture nonunion and received autogenous ICBG were enrolled in a prospective research registry and followed. Data collected included patient demographics, injury information, and nonunion management. All patients had a minimum of 12 months of postoperative follow-up. Patients at least 65 years of age were classified as elderly, whereas younger patients were classified as nonelderly. Functional outcomes were evaluated at routine intervals postoperatively using the short musculoskeletal function assessment (SMFA) and visual analog scale pain scores. Bony union was determined radiographically. All postoperative complications were recorded.

RESULTS

Of the 242 patients included, 44 were elderly and 198 were nonelderly. No differences were found between groups with respect to postoperative pain scores or SMFA scores. Furthermore, time to union, rate of union, and postoperative complication rate did not differ between groups. Multivariate linear regression demonstrated that older age was not associated with time to union, postoperative pain scores, or postoperative SMFA scores after controlling for possible confounding variables.

DISCUSSION

The use of ICBG in nonunion repair among elderly patients is as effective as use in younger patients with a long bone nonunion. Concerns of increased postoperative complications and decreased rate of union in elderly patients receiving ICBG for treatment of fracture nonunion should be alleviated. ICBG remains the benchmark graft for nonunion repair among all age groups.

Estimating a price point for cost-benefit of bone morphogenetic protein in pseudarthrosis prevention for adult spinal deformity surgery

OBJECTIVE

Bone morphogenetic protein (BMP) is associated with reduced rates of pseudarthrosis and has the potential to decrease the need for revision surgery. There are limited data evaluating the cost-benefit of BMP for pseudarthrosis-related prevention surgery in adult spinal deformity.

METHODS

The authors performed a single-center retrospective review of 200 consecutive patients with adult spinal deformity. Demographic data and costs of BMP, primary surgery, and revision surgery for pseudarthrosis were collected. Patients with less than 12 months of follow-up or with infection, tumor, or neuromuscular disease were excluded.

RESULTS

One hundred fifty-one patients (107 [71%] women) with a mean age of 65 years met the inclusion criteria. The mean number of levels fused was 10; BMP was used in 98 cases (65%), and the mean follow-up was 23 months. Fifteen patients (10%) underwent surgical revision for pseudarthrosis; BMP use was associated with an 11% absolute risk reduction in the rate of reoperation (17% vs 6%, p = 0.033), with a number needed to treat of 9.2. There were no significant differences in age, sex, upper instrumented vertebra, or number of levels fused in patients who received BMP. In a multivariate model including age, sex, number of levels fused, and the upper instrumented vertebra, only BMP (OR 0.250, 95% CI 0.078-0.797; p = 0.019) was associated with revision surgery for pseudarthrosis. The mean direct cost of primary surgery was $87,653 ± $19,879, and the mean direct cost of BMP was $10,444 ± $4607. The mean direct cost of revision surgery was $52,153 ± $26,985. The authors independently varied the efficacy of BMP, cost of BMP, and cost of reoperation by ± 50%; only reductions in the cost of BMP resulted in a cost savings per 100 patients. Using these data, the authors estimated a price point of $5663 in order for BMP to be cost-neutral.

CONCLUSIONS

Use of BMP was associated with a significant reduction in the rates of revision surgery for pseudarthrosis. At its current price, the direct in-hospital costs for BMP exceed the costs associated with revision surgery; however, this likely underestimates the true value of BMP when considering the savings associated with reductions in rehabilitation, therapy, medication, and additional outpatient costs.

Treatment of adult thoracolumbar spinal deformity: past, present, and future

Care of the patient with adult spinal deformity (ASD) has evolved from being primarily supportive to now having the ability to directly treat and correct the spinal pathology. The focus of this narrative literature review is to briefly summarize the history of ASD treatment, discuss the current state of the art of ASD care with focus on surgical treatment and current challenges, and conclude with a discussion of potential developments related to ASD surgery.In the past, care for ASD was primarily based on supportive measures, including braces and assistive devices, with few options for surgical treatments that were often deemed high risk and reserved for rare situations. Advances in anesthetic and critical care, surgical techniques, and instrumentation now enable almost routine surgery for many patients with ASD. Despite the advances, there are many remaining challenges currently impacting the care of ASD patients, including increasing numbers of elderly patients with greater comorbidities, high complication and reoperation rates, and high procedure cost without clearly demonstrated cost-effectiveness based on standard criteria. In addition, there remains considerable variability across multiple aspects of ASD surgery. For example, there is currently very limited ability to provide preoperative individualized counseling regarding optimal treatment approaches (e.g., operative vs nonoperative), complication risks with surgery, durability of surgery, and likelihood of achieving individualized patient goals and satisfaction. Despite the challenges associated with the current state-of-the-art ASD treatment, surgery continues to be a primary option, as multiple reports have demonstrated the potential for surgery to significantly improve pain and disability. The future of ASD care will likely include techniques and technologies to markedly reduce complication rates, including greater use of navigation and robotics, and a shift toward individualized medicine that enables improved counseling, preoperative planning, procedure safety, and patient satisfaction.Advances in the care of ASD patients have been remarkable over the past few decades. The current state of the art enables almost routine surgical treatment for many types of ASD that have the potential to significantly improve pain and disability. However, significant challenges remain, including high complication rates, lack of demonstrated cost-effectiveness, and limited ability to meaningfully counsel patients preoperatively on an individual basis. The future of ASD surgery will require continued improvement of predictability, safety, and sustainability.

Repurposing Human Osteoarthritic Cartilage as a Bone Graft Substitute in an Athymic Rat Posterolateral Spinal Fusion Model

Background

Spinal fusion involves both endochondral and intramembranous bone formation. We previously demonstrated that endochondral cartilage grafts that were derived from human osteoarthritic (OA) articular cartilage can be used as a bone graft in mouse models. We hypothesized that OA cartilage could also be recycled and repurposed as a bone graft substitute in a posterolateral lumbar spinal fusion model in athymic rats.

Methods

OA articular cartilage was obtained from the femoral resection of a healthy 60-year-old man undergoing elective total knee arthroplasty. The chondrocytes recovered from this tissue were dedifferentiated in monolayer tissue culture and then transitioned to culture conditions that promote chondrocyte hypertrophy. The resultant cell pellets were then used as bone graft substitute for single-level posterolateral spinal fusion in 5 athymic rats. Decortication alone was used as the control group. Spinal fusion was assessed with manual palpation, micro-computed tomography, and histologic analysis.

Results

In the experimental group, micro-computed tomography at 4 and 8 weeks demonstrated bilateral fusion in 4 of 5 animals and unilateral fusion in 1 animal. At 8 weeks, manual palpation and histologic analysis showed direct correlation with the radiographic findings. Animals undergoing decortication alone failed to generate any spinal fusion. The difference in the fusion rate between groups was statistically significant with respect to both unilateral fusion (P = .047) and bilateral fusion (P = .007).

Conclusions

In the absence of additional surgically implanted bone graft, hypertrophic chondrocyte grafts are sufficient for generating single-level posterolateral lumbar fusion in athymic rats.

Clinical Relevance

This animal study demonstrates that cartilage harvested from OA knees can be used as a bone graft substitute. Commercially available cell-based bone grafts have previously only used mesenchymal stem cells or osteoblast precursor cells.

A Computed Tomography Analysis of the Success of Spinal Fusion Using Ultra-Low Dose (0.7 mg per Facet) of Recombinant Human Bone Morphogenetic Protein 2 in Multilevel Adult Degenerative Spinal Deformity Surgery

Study Design

Retrospective cohort study.

Purpose

To report on spinal fusion assessment using computed tomography (CT) after adult spinal deformity (ASD) surgery using ultra-low dose recombinant human bone morphogenetic protein 2 (RhBMP-2).

Overview of Literature

The reported dose of RhBMP-2 needed for successful spinal posterolateral fusion in ASD ranges from 10 to 20 mg per spinal level. This study reports the use of ultra-low dose of RhBMP-2 (0.07 mg per facet) to achieve spinal fusion in multilevel ASD surgery.

Methods

Consecutive patients who underwent ASD surgery using ultra-low dose RhBMP-2 were recruited. Routine postoperative CT analysis for spinal fusion was performed by two spine surgeons. Inter-observer agreement was calculated for facet fusion (FF) and interbody fusion (IBF) at 6 and 12 months after the procedure.

Results

Six consecutive ASD patients with a mean age of 62 years (28–72 years) were examined. Each patient received a total dose of 12 mg with an average dose of 0.69±0.2 mg (0.42–1 mg) per single FF and 1.38±0.44 mg (0.85–2 mg) for IBF. Total 131 FF and 15 IBF were examined in the study, with 88 FFs and nine IBFs being analyzed specifically at 6 months after the surgery. FF and IBF reported by surgeons A and B at 6 months were 97.7% vs. 91.9% FF, respectively (κ=0.95) and 100% vs. 100% IBF, respectively (κ=1). Two patients underwent longitudinal follow-up CT at 12 months, and the FF rates reported by surgeons A and B were 100% vs. 95.8%, respectively (κ=0.96). Five out of nine facet (56%) non-unions were identified at the cross-links. The remaining four facet pseudarthrosis were noted at 1–2 spinal levels caudal to the cross-links. At the final clinical follow-up, there was no rod breakage, deformity progression, neurological deficit, or symptom recurrence. The Oswestry Disability Index improved by an average of 32.8±6.3, while the mental component summary of the 36-item Short-Form Health Survey improved by an average of 4.7±2.1, and physical component summary improved by an average of 10.5±2.1.

Conclusions

To our knowledge, this is the first study to report a CT that defined 92%–98% FF and 100% IBF using the lowest reported dose of RhBMP-2 in multilevel ASD surgery. The use of ultra-low dose RhBMP-2 reduces the RhBMP-2 related complications and healthcare costs.

Center variation in episode-of-care costs for adult spinal deformity surgery: results from a prospective, multicenter database

BACKGROUND CONTEXT

Adult spinal deformity (ASD) surgery is associated with significant resource utilization, costing more than $958 million in charges for Medicare patients and more than $1.7 billion in charges for managed care population in the last decade. Given the recent move toward bundled payment models, it is important to understand the various care components a patient receives over the course of a defined clinical episode, its associated cost, and the proportion of cost for each component toward the bundled payment.

PURPOSE

To examine the degree and determinants of variation in inpatient episode-of-care (EOC) cost, resource utilization, and patient-reported outcomes for patients undergoing ASD surgery across four spine deformity centers in the United States.

STUDY DESIGN/SETTING

Retrospective analysis of prospective, multicenter database.

PATIENT SAMPLE

Consecutive patients enrolled in an ASD database from four spinal deformity centers.

OUTCOME MEASURES

Total in-patient EOC costs and Short Form (SF)-6D.

METHODS

The study used a multicenter database of 210 consecutively enrolled operative patients from 2008 to 2013 at four participating centers in the United States. Demographic, surgical, and direct cost data, expressed in 2013 dollars, for the entire inpatient EOC were obtained from administrative databases from the respective hospitals. Mixed models and multivariable linear regression were used to evaluate the impact of center on total costs adjusting for patient characteristics, length of stay (LOS), and surgical factors.

RESULTS

A total of 126 patients with complete baseline and 2-year follow-up data were included. The percentages of patients from each center were 36.5%, 7.1%, 24.6%, and 31.7%. Overall, the mean patient age was 58.4±12.6 years, 86% were women, and 94% were Caucasian. The proportion of total cost variation explained by the center at which the patient was treated was 17%. After adjusting for patient, LOS, and surgical factors the cost variation reduced to 4%. In multivariable analysis, each additional level fused increased total cost variation by $2,500, whereas recombinant human bone morphogenetic protein-2 (BMP) use and posterior-only surgical approach lowered total EOC costs by $10,500 and $9,400, respectively. No significant difference was observed in 2-year quality-adjusted life year across centers.

CONCLUSIONS

Total EOC costs for ASD surgery varied significantly by center. Levels fused, BMP use, and surgical approach were the primary drivers of cost variation across centers. Differences in resource utilization had no impact on 2-year quality-adjusted life year improvement across centers.

A UK-based pilot study of current surgical practice and implant preferences in lumbar fusion surgery

Lumbar fusion surgery is an established procedure for the treatment of low back pain. Despite the wide set of alternative fusion techniques and existing devices, uniform guidelines are not available yet and common surgical trends are scarcely investigated.The purpose of this UK-based study was to provide a descriptive portrait of current surgeons' practice and implant preferences in lumbar fusion surgery.A UK-based in-person survey was designed for this study and submitted to a group of consultant spinal surgeons (n = 32). Fifteeen queries were addressed based on different aspects of surgeons' practice: lumbar fusion techniques, implant preferences, and bone grafting procedures. Answers were analyzed by means of descriptive statistics.Thirty-two consultant spinal surgeons completed the survey. There was clear consistency on the relevance of a patient-centered management (82.3%), along with a considerable variability of practice on the preferred fusion approach. Fixation surgery was found to be largely adopted (96.0%) and favored over stand-alone cages. With regards to the materials, titanium cages were the most used (54.3%). The geometry of the implants influenced the choice of lumbar cages (81.3%). Specifically, parallel-shape cages were mostly avoided (89.2%) and hyperlordotic cages were preferred at the lower lumbar levels. However, there was no design for lumbar cages which was consistently favored. Autograft bone graft surgeries were the most common (60.0%). Amongst the synthetic options, hydroxyapatite-based bone graft substitutes (76.7%) in injectable paste form (80.8%) were preferred.Current lumbar fusion practice is variable and patient-oriented. Findings from this study highlight the need for large-scale investigative surveys and clinical studies aimed to set specific guidelines for certain pathologies or patient categories.

Is MIS-TLIF superior to open TLIF in obese patients?: A systematic review and meta-analysis

PURPOSE

Obesity is a global health problem. It increases the risk of surgical complications and re-operations. While both MIS-TLIF and O-TLIF are reported to have comparably good long-term outcomes for non-obese patients, no consensus has been reached for obese patients.

METHODS

A comprehensive search of the published literature was performed: PubMed, Scopus, Web of Science and Cochrane Central Register of Controlled Trials database in accordance to the PRISMA 2009 checklist. Data were collected with attention to baseline demographics, intra-operative blood loss, duration of surgery, surgical complications, hospitalization stay, VAS and Oswestry disability index (ODI) pre- and postoperatively.

RESULTS

A total of 863 abstracts were identified from the databases, of which 4 articles were included in the meta-analysis. A total of 430 patients were identified, of which 217(50.5%) underwent the O-TLIF, while 213(49.5%) underwent MIS-TLIF. One hundred and ninety-four (45.1%) patients were males, while 236(54.9%) were females. The average age was 54.8 ± 12.0 years. The pooled BMI was 33.4 ± 4.7 for the open-TLIF group, and 32.7 ± 3.9 for MIS-TLIF group (p = 0.22). When comparing O-TLIF to MIS-TLIF: Patients who underwent O-TLIF had 383 mls more blood loss (95% CI: 329.5-437.4, p < 0.00001), 1.2-day longer hospitalization stay (95% CI: 0.80-1.62, p < 0.00001) and 3.8 times higher risk of dural tear (95% CI: 1.61-9.87, p = 0.003) when compared to MIS-TLIF patients. A trend toward higher postoperative wound infection rates (O-TLIF: 4.5%, MIS-TLIF: 2.4%) and an inferior improvement in ODI score (O-TLIF: 39.3, MIS-TLIF: 44.1) was found in O-TLIF patients when compared to MIS-TLIF patients. However, these were not statistically significant.

CONCLUSION

MIS-TLIF is safe and may be a better option for lumbar fusion in obese patients. These slides can be retrieved under Electronic Supplementary Material.

Hmox1 promotes osteogenic differentiation at the expense of reduced adipogenic differentiation induced by BMP9 in C3H10T1/2 cells

Mesenchymal stem cells (MSCs) are multipotent progenitors that can differentiate into a variety of cell types under proper stimuli. Bone morphogenetic protein 9 (BMP9) is able to simultaneously induce both adipogenic and osteogenic differentiation of MSCs although the regulatory molecules involved remain to be fully identified and characterized. Heme oxygenase 1 (Hmox1) plays an essential role not only in fat metabolism, but also in bone development. In the present study, we investigated the functional role of Hmox1 in BMP9-induced osteogenic/adipogenic differentiation in MSCs line C3H10T1/2 and probed the possible mechanism involved. We found that BMP9 promoted the endogenous expression of Hmox1 in C3H10T1/2 cells. Overexpression of Hmox1 or cobalt protoporphyrin (CoPP), an inducer of Hmox1, increased BMP9-induced osteogenic differentiation in vitro. Subcutaneous stem cell implantation in nude mice further confirmed that Hmox1 potentiated BMP9-induced ectopic bone formation in vivo. In contrast, Hmox1 reduced BMP9-induced adipogenic differentiation in C3H10T1/2 cells. Although had no obvious effect on BMP9-induced Smad1/5/8 phosphorylation, Hmox1 enhanced phosphorylation of p38, and AKT, while decreased phosphorylation of ERK1/2. Furthermore, Hmox1 increased total β-catenin protein level, and promoted the nuclear translocation of β-catenin in C3H10T1/2 cells. Taken together, our study strongly suggests that Hmox1 is likely to potentiate osteogenic differentiation and yet decrease adipogenic differentiation induced by BMP9 possibly through regulation of multiple signaling pathways.

Clinical and radiographic outcomes of upper thoracic versus lower thoracic upper instrumented vertebrae for adult scoliosis: a meta-analysis

The aim of this study was to evaluate the clinical and radiographic outcomes of upper thoracic (UT) versus lower thoracic (LT) upper instrumented vertebrae (UIV) for adult scoliosis by meta-analysis. We conducted a literature search in three databases to retrieve related studies up to March 15, 2017. The preliminary screened studies were assessed by two reviewers according to the selection criteria. All analyses were carried out using the statistical software package R version 2.31. Odds ratios (OR) with 95% confidence intervals (CI) were used to describe the results. The I² statistic and Q statistic test were used for heterogeneity assessment. Egger's test was performed to detect publication bias. To assess the effect of each study on the overall pooled OR or standardized mean difference (SMD), sensitive analysis was conducted. Ten trials published between 2007 and 2015 were eligible and included in our study. Meta-analysis revealed that the UT group was associated with more blood loss (SMD=0.4779, 95%CI=0.3349-0.6209, Z=6.55, P<0.0001) and longer operating time (SMD=0.5780, 95%CI=0.1971-0.958, Z=2.97, P=0.0029) than the LT group. However, there was no significant difference in Oswestry Disability Index, Scoliosis Research Society (SRS) function subscores, radiographic outcomes including sagittal vertical axis, lumbar lordosis, and thoracic kyphosis, length of hospital stay, and revision rates between the two groups. No evidence of publication bias was found between the two groups. Fusion from the lower thoracic spine (below T10) has as advantages a shorter operation time and less blood loss than upper thoracic spine (above T10) in posterior long-segment fixation for degenerative lumbar scoliosis.

Incidence of Cancer in Spinal Deformity Patients Receiving High-Dose (≥40 mg) Bone Morphogenetic Protein (rhBMP-2)

STUDY DESIGN

Level III, Retrospective observational study.

OBJECTIVE

To determine if there is an increased risk of developing cancer after exposure to high-dose recombinant human bone morphogenetic protein-2 (rhBMP-2) and if risk is dose and/or exposure-dependent.

SUMMARY OF BACKGROUND DATA

Concerns have been raised regarding a relationship between rhBMP-2 and cancer.

METHODS

A total of 642 adult deformity patients from a single institution receiving a cumulative rhBMP-2 dose ≥40 mg from July, 2002 to July, 2009 were identified. Patients with a history of surveillance, epidemiology, and end result (SEER) cancer before rhBMP-2 exposure were excluded. To determine the occurrence of a cancer event, questionnaires were mailed and telephone follow up attempted for nonresponders. Only cancers tracked by the National Cancer Institute (NCI) SEER registry were included. Observed cancer counts were compared to expected cancer counts based on general population incidence rates within 5-year age strata. Cumulative incidence competing risk (CICR) modeling was used to evaluate the association between rhBMP-2 exposure and cancer controlling for potential confounding variables.

RESULTS

Forty-nine patients were lost-to-follow up, leaving 593 patients (92.4%; 138 males/455 females) available for analysis. Mean age was 52.8 years at the time of first exposure. Mean cumulative rhBMP-2 dose was 113.5 mg with 85% having one exposure (range: 1-8). Mean follow-up [date of exposure to date of death (regardless of cause) or returned completed questionnaire] was 5.6 ± 1.9 years; median follow up was 5.4 years. A total of 342 patients have greater than 5-year follow up. Minimum follow up was 2.0 years or until occurrence of a SEER cancer. Our total 8-year cumulative incidence of new SEER cancer accounting for the competing risk of death was 7.4% for 30 cancers in 593 patients. Fewer cancers were observed than expected based on general population rates, though the difference was not statistically significant (expected = 34; standardized incidence ratio = 0.88, 95% confidence interval, CI = 0.60-1.26). CICR found neither cumulative rhBMP-2 dose (hazard ratio, HR = 0.995, 95% CI 0.988-1.003; P = 0.249) nor number of exposures (HR = 0.776, 95% CI 0.359-1.677; P = 0.519) increased the risk of developing a postexposure cancer after controlling for known cancer risk factors.

CONCLUSION

The incidence of a SEER cancer after rhBMP-2 exposure was similar to incidence reported by the NCI. There were no significant rhBMP-2 dose or multi-exposure related risks of developing a life-threatening cancer.

LEVEL OF EVIDENCE

3.

Analysis of instrumentation failures after three column osteotomies of the spine

Background

Correction of fixed spinal imbalance in a sagittal and/or coronal plane frequently needs a tricolumnar wedge resection when the deformity is rigid. Complications associated with deformity correction surgery are pseudoarthrosis and implant failure located along the construct. The purposes of this study were to assess comparative rates of pseudoarthrosis (implant failure) at weaker points along lumbosacral junction and level of osteotomy, estimate overall incidence of implant failure, and comparatively analyze failures at different points along the construct.

Methods

This was an IRB approved, single center study retrospective analysis. Twenty-six patients who underwent three column osteotomies were grouped according to procedure: pedicle subtraction osteotomy (PSO, (n = 18)); vertebral column resection (VCR, (n = 4)); hemivertebra excision (HE, (n = 2)); and extracavitary corpectomy (EC, (n = 2)). Follow-up data is presented on all of the study patients. Number of levels of fusion, anchors, percent saturation of fixation levels, type of bone graft and graft substitutes, and rod material and diameter were recorded. Radiographical data was reviewed preoperatively and postoperatively at 2 weeks and 3, 6, and 12 months and annually to determine sagittal and coronal balance, lumbopelvic parameters, presence or absence of interbody structural support, laterality or rod failure, and time to implant failure.

Results

Twenty-seven percent (7/26) patients demonstrated rod breakage either unilaterally (N = 2) or bilaterally (N = 5) during follow-up. Seventy-one percent had increasing back pain or worsening sagittal balance, while remaining failures found incidentally. No failures in children were seen.

Conclusion

Tricolumnar osteotomy by posterior approach is a valuable tool. Rod failures found approximately 1 year from surgery, with 86% located at level of osteotomy and 14% at lumbosacral junction. Possible reasons are increased stress in the rod at this point and relatively deficient bone stock secondary to wide laminectomy. The low rate of rod breakage at lumbosacral junction may be related to adoption of structural interbody graft and stronger iliac screws. Additional biomechanical studies needed to assess the importance of these factors. This was a level IV study.

Bone substitutes and expanders in Spine Surgery: A review of their fusion efficacies

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

This manuscript intends to provide a review of clinically relevant bone substitutes and bone expanders for spinal surgery in terms of efficacy and associated clinical outcomes, as reported in contemporary spine literature.

SUMMARY OF BACKGROUND DATA

Ever since the introduction of allograft as a substitute for autologous bone in spinal surgery, a sea of literature has surfaced, evaluating both established and newly emerging fusion alternatives. An understanding of the available fusion options and an organized evidence-based approach to their use in spine surgery is essential for achieving optimal results.

METHODS

A Medline search of English language literature published through March 2016 discussing bone graft substitutes and fusion extenders was performed. All clinical studies reporting radiological and/or patient outcomes following the use of bone substitutes were reviewed under the broad categories of Allografts, Demineralized Bone Matrices (DBM), Ceramics, Bone Morphogenic proteins (BMPs), Autologous growth factors (AGFs), Stem cell products and Synthetic Peptides. These were further grouped depending on their application in lumbar and cervical spine surgeries, deformity correction or other miscellaneous procedures viz. trauma, infection or tumors; wherever data was forthcoming. Studies in animal populations and experimental in vitro studies were excluded. Primary endpoints were radiological fusion rates and successful clinical outcomes.

RESULTS

A total of 181 clinical studies were found suitable to be included in the review. More than a third of the published articles (62 studies, 34.25%) focused on BMP. Ceramics (40 studies) and Allografts (39 studies) were the other two highly published groups of bone substitutes. Highest radiographic fusion rates were observed with BMPs, followed by allograft and DBM. There were no significant differences in the reported clinical outcomes across all classes of bone substitutes.

CONCLUSIONS

There is a clear publication bias in the literature, mostly favoring BMP. Based on the available data, BMP is however associated with the highest radiographic fusion rate. Allograft is also very well corroborated in the literature. The use of DBM as a bone expander to augment autograft is supported, especially in the lumbar spine. Ceramics are also utilized as bone graft extenders and results are generally supportive, although limited. The use of autologous growth factors is not substantiated at this time. Cell matrix or stem cell-based products and the synthetic peptides have inadequate data. More comparative studies are needed to evaluate the efficacy of bone graft substitutes overall.

Increasing Rates of Surgical Management of Multilevel Spinal Curvature in Elderly Patients

STUDY DESIGN

Retrospective analysis of Nationwide Inpatient Sample (NIS) database.

OBJECTIVE

To analyze trends in utilization and hospital charges for multilevel spinal curvature surgery in patients over 60 from 2004 to 2011.

SUMMARY OF BACKGROUND DATA

Multilevel spinal curvature has been increasingly recognized as a major source of morbidity in patients over sixty years of age. The economic burden of non-operative management for spinal curvature is elusive and likely underestimated. Though patient reported outcomes suggest that surgical treatment of spinal curvature may be superior to non-operative treatment in selected patients, surgical utilization trends remain unclear.

METHODS

Data were obtained from the NIS between 2004 and 2011. The NIS is the largest all-payer inpatient care database with approximately eight million annual patient discharges throughout the United States. Analysis included patients over age 60 with a spinal curvature diagnosis treated with a multi-level spinal fusion (≥3 levels fused) determined by ICD-9-CM diagnosis and procedure codes. Population-based utilization rates were calculated from US census data.

RESULTS

A total of 84,302 adult patients underwent multilevel spinal curvature surgery from 2004 to 2011. The annual number of ≥3 level spinal curvature fusions in patients over age 60 increased from 6,571 to 16,526, representing a 107.8% increase from 13.4 cases per 100,000 people in 2004 to 27.9 in 2011 (p < .001). Utilization rates in patients 65-69 years old experienced the greatest growth, increasing by 122% from 15.8 cases per 100,000 people to 35.1. Average hospital charges increased 108% from $90,557 in 2007 to $188,727 in 2011 (p < .001).

CONCLUSIONS

Rates of surgical management of multilevel spinal curvature increased from 2004 to 2011, exceeding growth of the 60+ age demographic during the same period. Growth was observed in all age demographics, and hospital charges consistently increased from 2004 to 2011 reflecting a per-user increase in expenditure.

LEVEL OF EVIDENCE

III.

Trends of Posterior Long Segment Fusion with and without Recombinant Human Bone Morphogenetic Protein 2 in Patients with Scoliosis

STUDY DESIGN

Retrospective study.

OBJECTIVE

Symptomatic scoliosis can be a source of severe pain and disability. When nonoperative treatments fail, spine fusion is considered as an effective procedure in scoliosis management. The purpose of this study was to evaluate the trends of patients with scoliosis undergoing posterior long segment fusion (PLSF) with and without recombinant human bone morphogenetic protein 2 (rhBMP-2).

METHODS

Patients within the orthopedic subset of Medicare database undergoing PLSF from 2005 to 2011 were identified using the PearlDiver Patient Records Database. Both diagnosis and procedural International Classification of Diseases, ninth edition and Current Procedural Terminology codes were used. The year of procedure, age, sex, region, and rhBMP-2 use were recorded.

RESULTS

In total, 1,265,591 patients with scoliosis were identified with 29,787 PLSF surgeries between 2005 and 2011. The incidence of PLSF procedures increased gradually from 2005 to 2009, decreased in 2010 (p < 0 0.01), and grew again in 2011. Patients over age 84 years had the highest incidence of PLSF. The lowest incidence of the procedures was in the Northeast, 5.96 per 100,000 patients. Sex differences were observed with a male-to-female ratio of 0.40 (p < 0.01). The use of rhBMP-2 for PLSF increased steadily from 2005 to 2009; the numbers dropped dramatically in 2010 and returned by 2011.

CONCLUSIONS

According to our study, patients with scoliosis demonstrated a 0.6575 average incidence increase of PLSF treatments annually. There were significant differences in incidence of PLSF procedure and patient demographics. Additionally, rhBMP-2 consumption significantly changed when we stratified it by sex, age, and region respectively.

Binding to COMP Reduces the BMP2 Dose for Spinal Fusion in a Rat Model

STUDY DESIGN

The aim of this study is to test the effect of cartilage oligomeric matrix protein (COMP) on enhancing rhBMP-2 induced spinal fusion in a prospective 8-week interventional trial of spinal fusion in rats.

OBJECTIVE

To determine whether the amount of bone morphogenetic protein-2 (BMP-2) required to achieve spinal fusion in a pre-clinical model can be reduced by the addition of COMP.

SUMMARY OF BACKGROUND DATA

BMPs are applied clinically at supraphysiological doses to promote spinal fusion by inducing osseous growth, but dose-related limitations include ectopic bone formation and local inflammatory reactions. COMP is a matricellular BMP-binding protein expressed during endochondral ossification and fracture healing. In vitro studies demonstrate enhanced activity of BMP bound to COMP. We hypothesized that BMP bound to COMP could achieve equivalent spinal fusion rates at lower doses and with fewer complications.

METHODS

Posterolateral intertransverse process spinal fusion at L4 to L5 was performed in 36 Lewis rats. COMP (10 μg) was tested with or without "low-dose" rhBMP-2 (2 μg), and the results were compared with the "low-dose" (2 μg rhBMP-2) and "high-dose" (10 μg rhBMP-2) groups. All groups utilized insoluble collagen bone matrix carrier (ICBM). Fusion was evaluated by radiology, histology, and manual palpation. BMP release kinetics were evaluated in vitro.

RESULTS

Fusion grading of microCT images demonstrated that the fusion rate with the COMP+LoBMP was statistically equivalent to HiBMP, and significantly better than LoBMP without COMP. These results were confirmed with radiographs and manual palpation. BMP release kinetics suggest that COMP increased local concentrations of BMP due to decreased growth factor retention on the scaffold.

CONCLUSION

COMP enhances BMP-induced bone formation, enabling lower doses of BMP to achieve the same level of spinal fusion. COMP may function by affecting the availability and biological presentation of BMP-2. A decrease of BMP-2 required for fusion may reduce dose-related adverse effects, surgical costs, and improve clinical outcomes.

LEVEL OF EVIDENCE

N/A.

An Approach to Lumbar Revision Spine Surgery in Adults

Along with the increase in lifestyle expectations in the aging population, a dramatic rise in surgical rates has been observed over the past 2 decades. Consequently, the rate of revision spine surgery is expected to increase. A systematic approach to treatment is required for the adult patient presenting with late or chronic complications after spinal surgery. Patient assessment includes elucidating current symptoms and knowledge of the previous surgery, performing a detailed assessment, and obtaining appropriate studies. Subsequently, differential diagnoses are formulated based on whether the pathology arises from the same levels or adjacent levels of the spine and whether it relates to the previous decompression or fusion. Finally, familiarity with different surgical approaches is imperative in treating the common pathologies encountered in this patient population.

The use of bone morphogenetic proteins (BMP) and pseudarthrosis, a literature review

Bone morphogenetic proteins (BMP) are multi-functional growth factors to promote bone healing with the proposal of less morbidity compared to the usual methods of bone graft harvest. Pseudoarthrosis occur when the fusion attempt fails, a solid fusion is not achieved, or there is motion across the segment leading to it, and it can be clinically symptomatic as pain, deformity, neurocompression, or hardware failure. BMPs are used at spinal fusion as a tool for the treatment of degenerative, traumatic, neoplastic and infectious conditions of the spine. This review shows that the use of BMPS is effective and secure when compared with iliac crest bone graft (ICGB); however, depending of the location of usage (cervical spine, lumbar spine or sacrum) and the medical status of the patient (presence of comorbidities, tobacco usage), it is more likely to exhibit complications. Therefore, the use of these proteins must be an informed decision of patient and physician preferences.

Effectiveness and safety of recombinant human bone morphogenetic protein-2 for adults with lumbar spine pseudarthrosis following spinal fusion surgery: A systematic review

Objectives

We performed a systematic review of the literature to determine the safety and efficacy of bone morphogenetic protein (BMP) compared with bone graft when used specifically for revision spinal fusion surgery secondary to pseudarthrosis.

Methods

The MEDLINE, EMBASE and Cochrane Library databases were searched using defined search terms. The primary outcome measure was spinal fusion, assessed as success or failure in accordance with radiograph, MRI or CT scan review at 24-month follow-up. The secondary outcome measure was time to fusion.

Results

A total of six studies (three prospective and three retrospective) reporting on the use of BMP2 met the inclusion criteria (203 patients). Of these, four provided a comparison of BMP2 and bone graft whereas the other two solely investigated the use of BMP2. The primary outcome was seen in 92.3% (108/117) of patients following surgery with BMP2. Although none of the studies showed superiority of BMP2 to bone graft for fusion, its use was associated with a statistically quicker time to achieving fusion. BMP2 did not appear to increase the risk of complication.

Conclusion

The use of BMP2 is both safe and effective within the revision setting, ideally in cases where bone graft is unavailable or undesirable. Further research is required to define its optimum role.

Cite this article: Mr P. Bodalia. Effectiveness and safety of recombinant human bone morphogenetic protein-2 for adults with lumbar spine pseudarthrosis following spinal fusion surgery: A systematic review. Bone Joint Res 2016;5:145–152. DOI: 10.1302/2046-3758.54.2000418.

Anterior approach with expandable cage implantation in management of unstable thoracolumbar fractures: Results of a series of 93 patients

INTRODUCTION

Anterior approach indications in unstable thoracolumbar fractures (UTLF) are debated. The aim of this study was to evaluate the results of anterior fixation and expandable prosthetic vertebral body cage (EPVBC) implantation alone or combined with a posterior approach in the management of UTLF.

MATERIALS AND METHODS

Ninety-three patients underwent anterior fixation with implantation of an EPVBC for UTLF from T7 to L5. Long-term kyphosis and vertebral height loss reduction, functional outcomes including visual analogical scale and Oswestry disability index were evaluated.

RESULTS

Anterior fixation led to a significant increase of vertebral body height with a gain of 13% after a previous posterior approach, 38% after a single anterior approach and 65% after combined posterior and anterior approaches (P=0.0001). However, anterior fixation did not significantly enhance the vertebral regional kyphosis angle (P=0.08), except in cases of single anterior approach for thoracic fractures (P=0.03). No significant difference was found between early, 3 months and 1 year postoperative vertebral regional kyphosis angle and vertebral body height (P=0.6). Complete fusion was routinely observed at 1 year postoperatively. rhBMP2 implantation in selected cases appears to be a safe and reliable strategy. No infections or surgical revisions were observed after the anterior approach.

CONCLUSION

Anterior approach and EPVBC implantation, in UTLF, is a safe and effective procedure, providing long-term vertebral body height and kyphosis correction. Adverse effects of anterior approach remain acceptable. Single anterior fixation is a reliable surgical alternative in thoracic fractures without posterior spine segment injury or spinal cord compression. These results prompted us to extend anterior approach indications in oncology and infectious diseases.

Use of Recombinant Bone Morphogenetic Protein Is Associated With Reduced Risk of Reoperation After Spine Fusion for Adult Spinal Deformity

STUDY DESIGN

Retrospective review.

OBJECTIVE

This study follows the inpatient-stay administrative data that were collected for a cohort of thousands of patients who had spine fusion surgery in the state of New York. We sought to examine adult spinal deformity (ASD) for reoperation events with and without the use of bone morphogenetic protein-2 (BMP).

SUMMARY OF BACKGROUND DATA

Randomized controlled trials have suggested that BMP may increase the likelihood of solid arthrodesis in spinal surgery. This would imply fewer reoperations for pseudarthrosis, but small cohort sizes are inadequate to monitor these events.

METHODS

The 2008-2011 New York State Inpatient Database was queried using International Classification of Diseases, Ninth Revision, Clinical Modification codes. Patients age 21 years and older with a diagnosis of scoliosis and an index fusion of greater than 2 spinal motion segments were included. Patient identifiers and linkage variables were used to identify revisits. The relative risk of reoperation was calculated. The use of BMP at the initial inpatient stay was used to define the 2 cohorts for relative risk assessment.

RESULTS

A total of 3751 patients of ASD were identified in 2008. The use of BMP at the initial visit was performed at a rate of 37.6% for ASD. For posterior fusion cases longer than 8 levels, the rate of reoperation for a pseudarthrosis was 23.4%. For ASD fusions greater than 8 levels, the rate of reoperation for pseudarthrosis after using BMP at the index surgery was 5% and 33.9% when BMP was not used, a relative risk of 7.5 (P < 0.001).

CONCLUSION

Using relevant inhospital patient records from the New York State Inpatient Sample, we found a 7.5-fold decrease in the risk of reoperation for pseudarthrosis after long fusions when using BMP. Decreased reoperation rates are caused by the improved fusion with the use of BMP. If subsequent unnecessary hospitals stays can be avoided, the economics of BMP use should be reexamined.

Prospective multicenter assessment of risk factors for rod fracture following surgery for adult spinal deformity

OBJECT

Improved understanding of rod fracture (RF) following adult spinal deformity (ASD) surgery could prove valuable for surgical planning, patient counseling, and implant design. The objective of this study was to prospectively assess the rates of and risk factors for RF following surgery for ASD.

METHODS

This was a prospective, multicenter, consecutive series. Inclusion criteria were ASD, age > 18 years, ≥5 levels posterior instrumented fusion, baseline full-length standing spine radiographs, and either development of RF or full-length standing spine radiographs obtained at least 1 year after surgery that demonstrated lack of RF. ASD was defined as presence of at least one of the following: coronal Cobb angle ≥20°, sagittal vertical axis (SVA) ≥5 cm, pelvic tilt (PT) ≥25°, and thoracic kyphosis ≥60°.

RESULTS

Of 287 patients who otherwise met inclusion criteria, 200 (70%) either demonstrated RF or had radiographic imaging obtained at a minimum of 1 year after surgery showing lack of RF. The patients' mean age was 54.8 ± 15.8 years; 81% were women; 10% were smokers; the mean body mass index (BMI) was 27.1 ± 6.5; the mean number of levels fused was 12.0 ± 3.8; and 50 patients (25%) had a pedicle subtraction osteotomy (PSO). The rod material was cobalt chromium (CC) in 53%, stainless steel (SS), in 26%, or titanium alloy (TA) in 21% of cases; the rod diameters were 5.5 mm (in 68% of cases), 6.0 mm (in 13%), or 6.35 mm (in 19%). RF occurred in 18 cases (9.0%) at a mean of 14.7 months (range 3-27 months); patients without RF had a mean follow-up of 19 months (range 12-24 months). Patients with RF were older (62.3 vs 54.1 years, p = 0.036), had greater BMI (30.6 vs 26.7, p = 0.019), had greater baseline sagittal malalignment (SVA 11.8 vs 5.0 cm, p = 0.001; PT 29.1° vs 21.9°, p = 0.016; and pelvic incidence [PI]-lumbar lordosis [LL] mismatch 29.6° vs 12.0°, p = 0.002), and had greater sagittal alignment correction following surgery (SVA reduction by 9.6 vs 2.8 cm, p < 0.001; and PI-LL mismatch reduction by 26.3° vs 10.9°, p = 0.003). RF occurred in 22.0% of patients with PSO (10 of the 11 fractures occurred adjacent to the PSO level), with rates ranging from 10.0% to 31.6% across centers. CC rods were used in 68% of PSO cases, including all with RF. Smoking, levels fused, and rod diameter did not differ significantly between patients with and without RF (p > 0.05). In cases including a PSO, the rate of RF was significantly higher with CC rods than with TA or SS rods (33% vs 0%, p = 0.010). On multivariate analysis, only PSO was associated with RF (p = 0.001, OR 5.76, 95% CI 2.01-15.8).

CONCLUSIONS

Rod fracture occurred in 9.0% of ASD patients and in 22.0% of PSO patients with a minimum of 1-year follow-up. With further follow-up these rates would likely be even higher. There was a substantial range in the rate of RF with PSO across centers, suggesting potential variations in technique that warrant future investigation. Due to higher rates of RF with PSO, alternative instrumentation strategies should be considered for these cases.

Does bone morphogenetic protein change the operative nonunion rates in spine fusions?

STUDY DESIGN

A retrospective cohort study with medical record review.

OBJECTIVE

To determine if there is difference in the operative nonunion rates with and without the use of bone morphogenetic protein (BMP) after spinal fusions by analyzing data from an integrated health care system's spine registry.

SUMMARY OF BACKGROUND DATA

BMP was first approved in 2002 for use in single-level anterior lumbar fusions. Follow-up studies have advocated its use in reducing the need for reoperations for nonunions. Recent studies, however, have questioned these conclusions and the usefulness of BMP in spinal fusions has been highly debated.

METHODS

We identified 9425 spinal fusion cases between 2009 and 2011 from a spine registry in a large integrated health care organization. Patient characteristics, diagnosis, operative times, length of stay, and reoperations were extracted from the registry. Reoperations for nonunions were adjudicated via medical record review. Cox regression models were used to evaluate the risk of reoperation while adjusting for confounders.

RESULTS

In our cohort, there were 5456 BMP cases and 3969 non-BMP cases. The mean age was 60.4 years (standard deviation: 12.9 yr), with the majority being females (53%). The median follow-up time was 1.2 years (interquartile range: 0.6-2.0 yr). Reoperation rates for BMP versus non-BMP nonunions for all fusion cases with follow-up of 1 year or more (1.9% vs. 2.2%) and follow-up of 2 years or more (2.3% vs. 2.6%) were not statistically significantly different. Operative nonunion rates did not reach statistical significance for different spine regions and for different fused columns (anterior only, posterior only, or combined). After controlling for differences in patient characteristics, operative times, levels fused, and spinal regions, the risk of reoperation in the BMP versus non-BMP groups was 0.67 (95% CI: 0.42-1.06).

CONCLUSION

In this large cohort of spinal fusions at all spine regions involving all fused columns with and without BMP, we found no statistically significant difference in operative nonunion rates.

LEVEL OF EVIDENCE

3.

A consensus statement regarding the utilization of BMP in spine surgery

Recombinant human bone morphogenetic protein - 2 (rh-BMP-2) was first approved by the United States Food and Drug Administration (FDA) in 2002 for use in anterior lumbar interbody fusions. Since that time, it has been estimated that "off label" use accounts for 85 % of applications. Original, industry sponsored studies demonstrated superior fusion rates with decreased incidence of complications when compared with traditional iliac crest bone graft. These studies have been criticized for potential bias and newer research has detailed potential complications as well as alternative applications. Potential off label uses of rhBMP-2 include: anterior lumbar fusions, single level posterior lumbar fusions, multiple level posterior lumbar fusions, posterior cervical fusions, long deformity fusions, in the presence of vertebral osteomyelitis, and in patients with history of malignancy. A review of the literature related to rhBMP-2 was conducted to evaluate its use for the above-mentioned applications with a special focus on fusion rates, observed complications, and clinical or radiographic outcomes.

Upper thoracic versus lower thoracic upper instrumented vertebrae endpoints have similar outcomes and complications in adult scoliosis

STUDY DESIGN

Retrospective review-multicenter database.

OBJECTIVE

The purpose of this study was to compare the upper thoracic (UT) and lower thoracic (LT) upper instrumented vertebrae (UIV) in long fusions to the sacrum for adult scoliosis.

SUMMARY OF BACKGROUND DATA

The optimal UIV for stopping long fusions to the sacrum/pelvis are controversial. Although a UT endpoint may lead to greater operative times, blood loss, and higher rates of pseudarthrosis, the risk for the development of proximal junctional kyphosis and need for revision surgery is likely lower.

METHODS

Retrospective analysis of a prospective database of patients with adult spinal deformity, Patients were selected on the basis of fusions to the sacrum/pelvis with UIV of T1-T6 (UT group) and those with a UIV of T9-L1 (LT group). Demographic data, operative details, and radiographical outcomes with Scoliosis Research Society scores, and Oswestry Disability Index outcomes were collected, as well as complication data were compared. The Fisher exact T tests were used for statistical analysis.

RESULTS

A total of 198 patients (UT = 91, LT = 107) with a mean age of 61.6 were followed for an average of 2.5 years. Demographic variables were similar between the groups except for larger numbers of females in the UT group and a slightly higher body mass index in the LT group. Preoperatively, the UT group demonstrated significantly more lumbar scoliosis, thoracic scoliosis, and thoracolumbar kyphosis. The UT group demonstrated a larger number of fused segments length of stay and longer operative times. There was slightly larger volume of blood loss in the UT group.The total number of complications and number of revision surgical procedures were similar between the groups. The UT group had a higher percentage of patients with 2 or more complications. Both groups had similar proximal junctional kyphosis angles and number of cases requiring revision for proximal junctional kyphosis. Scoliosis Research Society and Oswestry Disability Index outcomes were similar between the groups.

CONCLUSION

The UT and LT groups had similar outcomes. The UT group may have a higher rate of total complications, but major complications requiring return to the operative room were similar. The length of stay and operative times were higher in the UT group but may have been necessarily evidenced by the significantly higher coronal deformity and greater thoracolumbar kyphosis in the UT group.

LEVEL OF EVIDENCE

4.

Comparison of TLIF with rhBMP-2 versus no TLIF and higher posterolateral rhBMP-2 dose at L5-S1 for long fusions to the sacrum with sacropelvic fixation in patients with primary adult deformity

STUDY DESIGN

Comparvative case series. Data was prospectively entered and retrospectively analyzed.

OBJECTIVE

To evaluate the need for distal lumbar interbody fusion when sufficient recombinant human bone morphogenetic protein-2 (rhBMP-2) is used posterolaterally at L5-S1 in long spinal constructs for adult deformity via costs and radiographical and patient-reported outcome comparisons.

SUMMARY OF BACKGROUND DATA

Many authors and investigators have suggested that an interbody fusion is mandatory at L5-S1 with long fusion to the sacrum with sacropelvic fixation. Past studies have shown competitive fusion rates using rhBMP-2 versus iliac crest bone graft for long fusions. There are various advocates for anterior lumbar interbody fusion versus posterior lumbar interbody fusion versus transforaminal lumbar interbody fusion (TLIF). The optimal strategy remains elusive.

METHODS

Fifty-seven patients were studied at one institution. Thirty-one patients had no interbody fusion (NI group) with 20 mg of rhBMP-2 posterolaterally on 10 mL of carrier and 26 patients had TLIF at L5-S1 (TLIF group) with 6 mg of rhBMP-2 in the interbody space along with local bone graft and 6 mg of rhBMP-2 on carrier posterolaterally at L5-S1. Patients were followed for 24 to 87 months (mean follow-up, 3.92 yr). Demographics of the 2 groups were similar.

RESULTS

There were no detected nonunions at L5-S1 in either group. By our limited cost analysis, the expense of performing a TLIF at L5-S1 is higher than that of using extra rhBMP-2 posterolaterally at that segment. Improvement in outcomes scores, namely Scoliosis Research Society-22 and Oswestry Disability Index, were the same statistically in both groups. Blood loss was greater in the TLIF group than the NI group. There were no identified rhBMP-2 adverse events in either group.

CONCLUSION

Utilization of 20 mg of rhBMP-2 at L5-S1 has the potential to be less expensive than an interbody fusion in most patients having a primary long fusion for adult spinal deformity. The apparent fusion rates at L5-S1 were identical in both groups. Both strategies were successful in regard to improving patient outcomes and achieving apparent solid arthrodesis at the lumbosacral junction, which was the focus of this study.

LEVEL OF EVIDENCE

2.