Elsevier

The Spine Journal

Volume 14, Issue 1, 1 January 2014, Pages 20-30
The Spine Journal

Clinical Study
Impact of bone morphogenetic proteins on frequency of revision surgery, use of autograft bone, and total hospital charges in surgery for lumbar degenerative disease: review of the Nationwide Inpatient Sample from 2002 to 2008

https://doi.org/10.1016/j.spinee.2012.10.035Get rights and content

Abstract

Background context

Bone morphogenetic proteins (BMPs) were developed with the goal of improving clinical outcomes through the promotion of bony healing and reducing morbidity from iliac crest bone graft harvest.

Purpose

To complete a population-based assessment of the impact of BMP on use of autograft, rates of operative treatment for lumbar pseudoarthrosis, and hospital charges.

Study design

Nationwide Inpatient Sample (NIS) retrospective cohort assessment of 46,452 patients from 2002 to 2008.

Patient sample

All patients who underwent lumbar arthrodesis procedures for degenerative spinal disease.

Outcome measures

Use of BMP, revision surgery status as a percentage of total procedures, and autograft harvest in lumbar fusion procedures completed for degenerative diagnoses.

Methods

Demographic and geographic/practice data, hospital charges, and length of stay of all NIS patients with thoracolumbar and lumbosacral procedure codes for degenerative spinal diagnoses were recorded. Codes for autograft harvest, use of BMP, and revision surgery were included in multivariable regression analysis.

Results

The assessment found 46,452 patients from 2002 to 2008 undergoing thoracolumbar or lumbar arthrodesis procedures for degenerative disease. Assuming a representative sample, this cohort models more than 200,000 US patients. There was steady growth in lumbar spine fusion and in the use of BMP. The use of BMP increased from 2002 to 2008 (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.48–1.52). Revision procedures decreased over the study period (OR, 0.94; 95% CI, 0.91–0.96). The use of autograft decreased substantially after introduction of BMP but then returned to baseline levels; there was no net change in autograft use from 2002 to 2008. The use of BMP correlated with significant increases in hospital charges ($13,362.39; standard deviation±596.28, p<.00001). The use of BMP in degenerative thoracolumbar procedures potentially added more than $900 million to hospital charges from 2002 to 2008.

Conclusions

There was an overall decrease in rates of revision fusion procedures from 2002 to 2008. Introduction of BMP did not correlate with decrease in use of autograft bone harvest. Use of BMP correlated with substantial increase in hospital charges. The small decrease in revision surgeries recorded, combined with lack of significant change in autograft harvest rates, may question the financial justification for the use of BMP.

Introduction

Evidence & Methods

Between 2002 and 2008, BMP was used with increasing frequency. In this paper, the authors examined the NIS to determine the impact of BMP use on other fusion-related parameters.

With the introduction of BMP use in 2002, autograft initially decreased but then returned to baseline levels. Revision fusion rates decreased slightly while hospital charges rose rapidly during this time frame. The authors suggest each of these may be BMP-related.

These results are interesting in so far as the number of revision surgeries were not dramatically impacted by the introduction of BMP, and autograft use remarkably returned to baseline levels in a short period of time. The methodology used, however, does not allow causation to be assessed. Therefore, definite conclusions about the observations noted and BMP efficacy or use cannot be confidently drawn, as this data represents Level IV evidence. Regardless, the information provided in this study should serve as a springboard for future higher quality studies.

Lumbar disc disease and other lumbar degenerative pathologies remain an important cause of disability and a common indication for nonoperative and operative therapies [1], [2], [3], [4], [5], [6], [7]. Many patients who fail nonoperative therapy may be considered for fusion procedures [4], [8]. Advances in spinal instrumentation and bone growth biologics may influence the success of fusion procedures and may impact patient outcomes. Spine surgery continues to manifest substantial growth [9], [10].

Two bone morphogenetic proteins (BMPs) were recently introduced to the US spine market. Use of BMP in lumbar spine fusion procedures, with BMP restricted to implantation with specific cages in the anterior lumbar spine, was approved by the Food and Drug Administration (FDA) [11] in 2002. INFUSE BMP (Medtronic Sofamor-Danek, Memphis, TN, USA) and OP-1 putty (Stryker Spine, Allendale, NJ, USA) are available on the US market; OP-1 is only available as a humanitarian device exemption product for revision surgery [12]. Use of BMP requires a carrier and delivery system; the delivery system may provide support for a developing fusion mass. Some insurance policy recommendations note that when BMP is used, there should be no additional coding or billing for autograft harvest [13].

Although FDA approval for use of BMP is restricted to anterior approaches to the lumbar spine combined with use of a specific lumbar intervertebral body fusion device, most use of BMP is off-label [14], [15]. The off-label use of BMP has been associated with significant complications, including obstructive airway edema in anterior cervical procedures and ectopic bone formation [15], [16].

Health policy reports have focused on regional variations in health-care spending and resource utilization. Fisher et al. [17], reporting on regional variation in Medicare expenditures, notes that physician factors must play a predominant role in variation in health-care expenditures. There is significant geographic variation in utilization of lumbar operative and nonoperative treatments [10], [18], [19], [20]. Control of health-care costs is a primary concern of present health-care policy.

Use of BMP may add significantly to total costs for spine surgery treatment. The added costs for use of BMP may be offset by higher fusion rates, decreasing the need for revision surgery, and elimination of harvest of iliac crest bone graft. Obviating the need for bone graft harvest decreases the potential morbidity associated with spine surgery by eliminating potential complications of graft harvest, including infection, hematoma, need for further surgery, and chronic pain [21], [22]. Other reports have noted that BMP may not be cost-effective in spine surgery [23].

The Nationwide Inpatient Sample (NIS) was developed as part of the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality and was the largest all-payer database of hospital admissions in the United States. As of 2008, NIS contains all discharge data from 1,056 hospitals located in 42 states. This sample offers a representative randomized assessment of approximately 20% of nonfederal US hospital admissions. The database has been used previously for the evaluation of spine surgery procedures and trends in utilization of health-care resources in spinal care [10], [12], [14], [24], [25], [26], [27].

We sought to assess, through the study of this administrative database, the clinical and systems impact of the introduction of BMPs on lumbar fusion patients. We analyzed the incidence of revision surgery when BMP was used, trends in the rate of autograft harvest, and overall impact on hospital charges.

Section snippets

Materials and methods

The present NIS database uses terminology for diagnoses, procedures, and complications from the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) source. Procedural codes in spine surgery are routinely altered with the introduction of new procedures, new technologies, and new operative approaches.

To assess fusions done within the study period, we searched for ICD-9-CM codes delineating both anterior and posterior lumbar and thoracolumbar arthrodesis

Demographics

Our assay of NIS found 46,452 patients from 2002 to 2008 undergoing thoracolumbar or lumbar arthrodesis procedures for degenerative disease. Most of these patients (45,524, 98% of the cohort) underwent lumbar procedures for lumbar diagnosis codes. To capture lumbar procedures crossing the thoracolumbar junction, we choose to include the additional 928 patients with lumbar or thoracolumbar procedure codes and thoracolumbar primary diagnoses. Many patients had more than one spinal diagnosis

Discussion

This report seeks to assess, via assay of a large administrative database, the impact of introduction of BMP on rates of revision procedures and on rates of autograft harvest in spinal surgery. To generate a homogenous patient sample and better isolate the effects of BMPs, the study chose an adult patient population undergoing primarily lumbar fusion procedures for degenerative conditions. Through these restrictions, the study sought to limit outliers and restrict the potential impact of

Conclusions

This assessment of an administrative database questions the validity of smaller series supporting the financial effectiveness of use of BMP in spine surgery. In this large population-based study, the introduction of BMPs correlated with slight decrease in revision surgeries, substantial increase in charges, and no change in autograft harvest rates.

After the introduction of BMP in lumbar fusion procedures, there was an overall decrease in rates of revision fusion procedures. Although both fusion

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    FDA device/drug status: Approved (bone morphogenetic protein—Infuse).

    Author disclosures: PRD: Nothing to disclose. RGW: Nothing to disclose. GAS: Nothing to disclose. MGM: Nothing to disclose. JKR: Royalties: Biomet Spine (E); Stock Ownership: Johnson and Johnson (0 shares, sold); Consulting: Stryker Spine (D).

    The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.

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