The use of RhBMP-2 in single-level transforaminal lumbar interbody fusion: a clinical and radiographic analysis. Eur Spine J. 2009;18:1629-1636. [PMID: 19475434 DOI: 10.1007/s00586-009-1046-1]

Complications associated with the use of the recombinant human bone morphogenetic proteins for posterior interbody fusions of the lumbar spine

STUDY DESIGN

Systematic review.

OBJECTIVE

The objectives of this review are to examine the spectrum of complications that have been reported in the literature after posterior interbody fusions of the lumbar spine augmented with bone morphogenetic proteins (BMPs) and discuss potential methods for their prevention.

SUMMARY OF BACKGROUND DATA

The use of BMPs for spinal arthrodesis procedures has increased dramatically during the past decade. These products are commonly used in "off-label" fashion in posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) constructs. Recently, a number of adverse events have been attributed to the use of BMP for PLIF and TLIF surgical procedure, including heterotopic ossification within the epidural space or neuroforamina, postoperative radiculitis, and endplate osteolysis with interbody device subsidence.

METHODS

A computer aided literature search was performed on the electronic databases PubMed, MEDLINE, EMBASE, CINAHL, and Cochrane Database of Systematic Reviews. Key words of interest included BMPs, PLIF, TLIF, complications, heterotopic ossification, radiculitis, and osteolysis. All articles, in the English language, between 1990 and 2011 were considered relating to the use of BMPs in PLIF and TLIF constructs.

RESULTS

Seventeen articles discussing the use and potential complications of BMPs in PLIF and TLIF constructs were identified and reviewed. The studies were in the range of a level I prospective randomized trial to case reports of complications. There is a wide variation of published complications associated with BMP-augmented PLIF and TLIF constructs.

CONCLUSION

Despite high fusion rates there is a growing body of evidence that the use of BMP in PLIF and TLIF constructs does not come without potential complication. There are appreciable rates of BMP-specific complications, which include heterotopic ossification within the epidural space or neuroforamina, postoperative radiculitis, and endplate osteolysis with interbody device subsidence.

Spinal infection: state of the art and management algorithm

INTRODUCTION

Spinal infection is a rare pathology although a concerning rising incidence has been observed in recent years. This increase might reflect a progressively more susceptible population but also the availability of increased diagnostic accuracy. Yet, even with improved diagnosis tools and procedures, the delay in diagnosis remains an important issue. This review aims to highlight the importance of a methodological attitude towards accurate and prompt diagnosis using an algorithm to aid on spinal infection management.

METHODS

Appropriate literature on spinal infection was selected using databases from the US National Library of Medicine and the National Institutes of Health.

RESULTS

Literature reveals that histopathological analysis of infected tissues is a paramount for diagnosis and must be performed routinely. Antibiotic therapy is transversal to both conservative and surgical approaches and must be initiated after etiological diagnosis. Indications for surgical treatment include neurological deficits or sepsis, spine instability and/or deformity, presence of epidural abscess and upon failure of conservative treatment.

CONCLUSIONS

A methodological assessment could lead to diagnosis effectiveness of spinal infection. Towards this, we present a management algorithm based on literature findings.

Transforaminal lumbar interbody fusion with rhBMP-2 in spinal deformity, spondylolisthesis, and degenerative disease--part 2: BMP dosage-related complications and long-term outcomes in 509 patients

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

Without industry funding, the study evaluated short- and long-term complications related to off-label bone morphogenetic protein (BMP) used with transforaminal lumbar interbody fusion (TLIF) from a large consecutive series. Complications and results were analyzed by BMP dose, fusion length, and primary versus revision surgery. Based on the results, surgical technique and BMP dose recommendations were proposed.

SUMMARY OF BACKGROUND DATA

Off-label use of BMP in TLIF, although common, has only been studied in small series and case reports using various techniques, cage types, and doses of BMP. Several of these studies have reported minimal complications. Others report problems related to BMP, which has led to questions regarding current widespread use of TLIF with BMP.

METHOD

TLIF with rhBMP-2 was performed at 872 discs in 509 consecutive adults who underwent open posterior instrumented fusion and had minimum 2-year follow-up; diagnoses included degenerative disease (179), spondylolisthesis (207), deformity (123). Patient age averaged 61 years: 12% were smokers and 41% had revision surgery. TLIF was performed at 1.7 levels: single level: 229, 2 levels: 201, 3 levels: 74, 4 levels: 5. Local autograft was used for backfill around and behind each rectangular cage. Varying doses of interbody BMP were used at an average 7.3 mg per disc (range: 2-12 mg per disc).

RESULTS

At 5 years average follow-up, 8 patients developed pseudoarthrosis at levels of TLIF (8 of 872 discs, 0.92%). Seroma (0.4%) and ectopic bone growth (0.6%) were too infrequent to be associated with a particular BMP dose. Deep infection was 2.6% overall (1.7% of the degenerative group). Symptomatic osteolysis or cage subsidence did not occur. Significant long-term improvement was noted in clinical and functional outcomes compared with preoperation.

CONCLUSION

Five-year follow-up after TLIF with BMP, independent of industry, confirms effective arthrodesis in short and long fusions, both primary and revision. Most complications occurred in deformity patients. BMP-related complications (seroma, ectopic bone) were rare.

LEVEL OF EVIDENCE

3.

High-concentration of BMP2 reduces cell proliferation and increases apoptosis via DKK1 and SOST in human primary periosteal cells

BMP2, a well-known osteoinductive agent approved by FDA, is currently being used for various off-label orthopedic applications. Recently, concerns about its efficacy for off-label use, concentration, and complications have emerged. Interestingly, there is an extremely large discrepancy in BMP2 concentration between clinical use (i.e. 1.5mg/ml) and in vitro studies (50-300 ng/ml). The purpose of this study was to determine the effects of a relatively high-concentration of BMP2 on cell proliferation and apoptosis using human primary periosteal cells as BMP2 is generally applied around the periosteum in orthopedic surgeries. We isolated periosteal cells from three independent patients. The cell proliferation assessed by MTT activity was significantly reduced by a high-concentration of BMP2 (~2000 ng/ml), while such a reduction was not observed by using a low-concentration of BMP2 (~200 ng/ml). The cell apoptosis assessed by caspase activity was significantly increased by high-concentration BMP2, while such an increase was not observed by low-concentration BMP2. We found that Wnt signaling activity was significantly reduced by high-concentration BMP2 along with a dramatic increase in DKK1 and SOST, key inhibitors of Wnt signaling in bone. The addition of DKK1 or SOST protein to the primary periosteal cells reduced MTT activity and significantly increased caspase activity. Silencing the DKK1 or SOST expression using the siRNA technique normalized cell proliferation and apoptosis in the periosteum-derived cells when exposed to a high-concentration BMP2. Taken together, these results suggest that a high-concentration BMP2 decreases human periosteal cell proliferation and induces apoptosis via the activation of Wnt inhibitors DKK1 and SOST. This study provides new insights to the effects of high BMP2 concentration on human periosteal cells and brings out the possibility of multiple effects of current BMP2 therapy on various skeletal tissues.

Cauda equina syndrome after a TLIF resulting from postoperative expansion of a hydrogel dural sealant

BACKGROUND

DuraSeal(™) (Coviden, Waltham, MA, USA), a hydrogel sealant, is primarily used as an adjunct to a dural repair. Its use has also been described to seal off an annulotomy after a transforaminal lumbar interbody fusion when recombinant human bone morphogenetic protein-2 (rhBMP-2) is used. This aids in the reduction of postoperative radiculitis caused by rhBMP-2. However, as a result of its hydrophilic properties, DuraSeal(™) has the potential to swell, which could lead to compression of the thecal sac.

CASE DESCRIPTION

We report a 57-year-old woman who developed cauda equina after a transforaminal lumbar 47 interbody fusion (TLIF) procedure in which the expansion of the DuraSeal(™) was believed to be the causative factor. The patient developed urinary retention, bowel incontinence, and paresthesias in the saddle region on postoperative Day 3. She underwent emergent exploration and decompression of the thecal sac. The gel-like DuraSeal™ material was causing significant compression of the thecal sac.

LITERATURE REVIEW

Multiple reports have documented that DuraSeal(™), used as an adjunct to dural repair, can swell leading to compression of the spinal cord and/or neural elements. Our case demonstrates the use of DuraSeal(™) both over a site of a dural repair and over an annulotomy site, through which a TLIF was performed, is associated with the risk of developing postoperative cauda equina syndrome as a result of swelling of the DuraSeal(™).

CLINICAL RELEVANCE

Those using DuraSeal™ to seal off the annulotomy after a TLIF procedure performed with rhBMP-2 should use the product with an understanding of the potential postoperative swelling of the product and resulting neurologic sequela, particularly if DuraSeal(™) is used concomitantly at the site of dural repair.

Segmental lumbar sagittal correction after bilateral transforaminal lumbar interbody fusion

OBJECT

In this paper the authors sought to determine the segmental lumbar sagittal contour change after bilateral transforaminal lumbar interbody fusion (TLIF).

METHODS

Between March 2007 and October 2010, 42 consecutive patients (57 levels) underwent bilateral TLIF. Standard preoperative and 6-week postoperative standing lumbar spine radiographs were examined. Preoperative and postoperative segmental lordosis was determined by manual measurements using the Cobb method. The difference between the preoperative and postoperative values were calculated and analyzed for statistical significance.

RESULTS

The mean preoperative segmental alignment was 8.1°. The mean postoperative alignment was 15.3°, with a mean correction of 7.2° per segment. The largest gain in lordosis was obtained at the L5-S1 level (10.1°). There was a significant difference between the preoperative and postoperative values (p = 5 × 10(-9)). There was no significant difference in mean segmental correction between levels. Improvement in lordosis was higher in multilevel fusions (9.8°) than in single-level fusions (5.2°) (p = 0.047). There was an inverse correlation between preoperative sagittal lordosis measurement and change in lordosis (r = -0.599).

CONCLUSIONS

A significant improvement in lumbar lordosis can be gained by preforming bilateral facetectomies in TLIF with posterior compression. This procedure provides an additional option to a spine surgeon's armamentarium in dealing with significant lumbar sagittal plane deformities.

Strategies of spinal fusion on osteoporotic spine

The prevalence of osteoporosis has been increasing globally. Recently surgical indications for elderly patients with osteoporosis have been increasing. However, only few strategies are available for osteoporotic patients who need spinal fusion. Osteoporosis is a result of negative bone remodeling from enhanced function of the osteoclasts. Because bone formation is the result of coupling between osteoblasts and osteoclasts, anti-resorptive agents that induce osteoclast apoptosis may not be effective in spinal fusion surgery, necessitating new bone formation. Therefore, anabolic agents may be more suitable for osteoporotic patients who undergo spinal fusion surgery. The instrumentations and techniques with increased pullout strength may increase fusion rate through rigid fixation. Studies on new osteoinductive materials, methods to increase osteogenic cells, strengthened and biocompatible osteoconductive scaffolds are necessary to enable osteoporotic patients to undergo spinal fusion. When osteoporotic patients undergo spinal fusion, surgeons should consider appropriate osteoporosis medication, instrumentation and technique.

Bone morphogenetic protein-2 and spinal arthrodesis: the basic science perspective on protein interaction with the nervous system

The use and "off-label" indications for recombinant human bone morphogenetic protein-2 (rhBMP-2) in spinal arthrodesis have been significantly expanded over the last decade. New surgical approaches and pathologies treated often place the exogenous protein near the spinal cord or peripheral nerves, yet little data exist to the potential interaction between rhBMP-2 and the nervous system. The current review was undertaken to provide a basic science perspective on the wide-ranging effects that rhBMP-2, a potent growth factor, has on the injured spinal cord and the local dorsal root ganglia (DRG). Results from the early animal studies on neural safety of rhBMP-2 were compared with the more recent in vivo work characterizing protein impact on the injured spinal cord. Potential mechanism of the rhBMP-2-induced radiculitis after lumbar arthrodesis is also discussed. The original pre-FDA approval animal study did not uncover any interaction between rhBMP-2 and the spinal cord or the nerve rootlets comprising the cauda equina. Recent in vivo work indicated, however, that in a penetrating injury model, rhBMP-2 triggers direct signaling in all spinal cord cells. In the rat, this interaction was deleterious to spontaneous recovery by exacerbating the inflammatory response to injury, increasing the glial scar, and making it more inhibitory to axonal regeneration. With respect to posterolateral lumbar arthrodesis in a noninjury model, rhBMP-2 use contributed to a transient postoperative mechanical hyperalgesia. Potential mechanism of this allodynia is through an observed inflammatory response within and around the local DRG. In summary, contrary to the original beliefs in the clinical community, rhBMP-2 does elicit a profound signaling response within the spinal cord and the peripheral ganglia. Recent preclinical studies indicate that rhBMP-2, if provided direct access to the spinal cord parenchyma or the DRG, can trigger significant inflammation and morphologic changes within these tissues that could be deleterious to neurologic recovery.

Posterior epidural migration of herniated lumbar disc fragment

Object

Posterior epidural migration of a free disc fragment in the lumbar region is a very rare condition that has only been reported in isolated cases to date. Patients with this condition present with radiculopathy or major neurological deficits. Difficulties in diagnosis and the choice and timing of surgical treatment are important in these cases. In this clinical case series, features of cases with posterior epidural migration of free lumbar disc fragments accompanied by cauda equina syndrome are discussed.

Methods

Eight cases (0.27%) of posterior epidural migration of disc fragments were detected among 2880 patients surgically treated for lumbar disc herniation between 1995 and 2008. Seven of these patients had cauda equina syndrome. The mean duration of symptoms in the 8 cases was 4.2 days (range 1–10 days). The group included 6 men and 2 women, with a mean age of 48 years (range 34–72 years). The sequestered disc fragments were at the L3–4 level in 6 patients (75%) and the L4–5 level in 2 (25%). Magnetic resonance imaging showed tumor-like ring contrast enhancement around sequestered fragments in 5 patients. The patients' motor, sensory, sexual, and urological functions were evaluated postoperatively, and modified Odom criteria and a visual analog scale were used in the assessment of postoperative outcomes.

Results

A microsurgical approach was used in all cases. Sequestrectomy with minimal hemilaminotomy and removal of the free segments were performed. The patients were followed up for a mean period of 28.5 months. Three patients (37.5%) had excellent results, 3 (37.5%) had good results, 1 patient (12.5%) had fair results, and only 1 patient had poor results according to the Odom criteria. The main factors affecting the long-term outcomes were the presence of cauda equina syndrome and the time period between onset of symptoms and surgery.

Conclusions

Patients with posterior migration of a disc fragment present with severe neurological deficits such as cauda equina syndrome. Because the radiological images of disc fragments may mimic those of other more common posterior epidural space–occupying lesions, definite diagnosis of posteriorly located disc fragments is difficult. All of these lesions can be completely removed with hemilaminotomy and sequestrectomy, and early surgical treatment is important as a first choice to prevent severe neurological deficits.

Bone grafting options for lumbar spine surgery: a review examining clinical efficacy and complications

Background

Iliac crest harvest has been considered the “gold standard” at producing successful arthrodesis of the lumbar spine but is also associated with many donor-site morbidities. Many alternatives have been used to avoid iliac crest harvest, including autologous bone from other donor sites, allogeneic bone, ceramics, and recombinant human bone morphogenetic proteins (rhBMPs). This review will highlight the properties and preparations of these graft types and their potential complications and reported clinical efficacy.

Methods

A Medline search was conducted via PubMed by use of the following terms in various combinations: lumbar fusion, freeze-dried allograft, fresh-frozen allograft, autograft, iliac crest, demineralized bone matrix, rhBMP-2, rhBMP-7, scoliosis, bone marrow aspirate, HEALOS, coralline hydroxyapatite, beta tricalcium phosphate, synthetic, ceramics, spinal fusion, PLF, PLIF, ALIF, and TLIF. Only articles written in English were assessed for appropriate material. Related articles were also assessed depending on the content of articles found in the original literature search.

Conclusions

Although iliac crest remains the gold standard, reported success with alternative approaches, especially in combination, has shown promise. Stronger evidence with limited sources of potential bias is necessary to provide a clear picture of their clinical efficacy.