Perioperative outcomes, complications, and costs associated ......Treatments for spinal stenosis and spondylolisthesis are varied, ranging from conservative therapies, such as noninvasive

Neurosurg Focus / Volume 36 / June 2014

Neurosurg Focus 36 (6):E5, 2014

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©AANS, 2014

Spinal fusion procedures have become increasingly common in the treatment of various spinal disor-ders, such as spinal stenosis and spondylolisthesis,

to facilitate spinal decompression and stabilization. Fu-sion is also used to treat degenerative disc disorder but remains controversial in the absence of other codiagno-ses, in the elderly, and at multiple levels (3 or more).16 A recent study of the Healthcare Cost and Utilization Proj-ect Nationwide Inpatient Sample database showed that from 1998 to 2008, the annual number of spinal fusion discharges in the United States increased from 174,223 to 413,171, which corresponds to 64.5 and 135.5 cases per 100,000 people, respectively.22 The therapeutic ap-proach to spinal stenosis and spondylolisthesis has also shifted toward more complicated procedures, although

the reasons for this trend are unclear. A recent review of the period from 2002 to 2007 revealed that in patients with a primary diagnosis of spinal stenosis, treatment via complex fusion procedures increased from 1.3 to 19.9 operations per 100,000 Medicare beneficiaries, whereas treatment via decompression or simple fusion decreased by approximately 10% and 20%, respectively.12

Complex procedures are generally more invasive and can involve greater risks of complication, which in turn leads to higher health care costs.6,14 Thus, as these com-plex procedures are used more frequently, it is important to identify their correct indications. There is still a lack of consensus about the surgical approaches and techniques that are most appropriate for various types of patients and disease characteristics;12 therefore, surgeon preference remains a significant factor in the type of treatment a pa-tient receives.17

Treatments for spinal stenosis and spondylolisthesis are varied, ranging from conservative therapies, such as noninvasive physical manipulation and physical therapy,

Perioperative outcomes, complications, and costs associated with lumbar spinal fusion in older patients with spinal stenosis and spondylolisthesis

Kevin L. Ong, Ph.D., P.e.,1 JOshua D. auerbach, M.D.,2 eDMunD Lau, M.s.,3 JOrDana schMier, M.a.,4 anD JOrge a. OchOa, Ph.D., P.e.3

1Exponent, Inc., Philadelphia, Pennsylvania; 2Department of Orthopaedics, Bronx-Lebanon Hospital Center, Albert Einstein College of Medicine, Bronx, New York; 3Exponent, Inc., Menlo Park, California; and 4Exponent, Inc., Alexandria, Virginia

Object. The purpose of this study was to quantify the perioperative outcomes, complications, and costs associ-ated with posterolateral spinal fusion (PSF) among Medicare enrollees with lumbar spinal stenosis (LSS) and/or spondylolisthesis by using a national Medicare claims database.

Methods. A 5% systematic sample of Medicare claims data (2005–2009) was used to identify outcomes in pa-tients who had undergone PSF for a diagnosis of LSS and/or spondylolisthesis. Patients eligible for study inclusion also required a minimum of 2 years of follow-up and a claim history of at least 12 months prior to surgery.

Results. A final cohort of 1672 patients was eligible for analysis. Approximately half (50.7%) had LSS only, 10.2% had spondylolisthesis only, and 39.1% had both LSS and spondylolisthesis. The average age was 71.4 years, and the average length of stay was 4.6 days. At 3 months and 1 and 2 years postoperatively, the incidence of spine reoperation was 10.9%, 13.3%, and 16.9%, respectively, whereas readmissions for complications occurred in 11.1%, 17.5%, and 24.9% of cases, respectively. At 2 years postoperatively, 36.2% of patients had either undergone spine reoperation and/or received an epidural injection. The average Medicare payment was $36,230 ± $17,020, $46,840 ± $31,350, and $61,610 ± $46,580 at 3 months, 1 year, and 2 years after surgery, respectively.

Conclusions. The data showed that 1 in 6 elderly patients treated with PSF for LSS or spondylolisthesis under-went reoperation on the spine within 2 years of surgery, and nearly 1 in 4 patients was readmitted for a surgery-related complication. These data highlight several potential areas in which improvements may be made in the effective de-livery and cost of surgical care for patients with spinal stenosis and spondylolisthesis.(http://thejns.org/doi/abs/10.3171/2014.4.FOCUS1440)

Key WOrDs • spine fusion • stenosis • spondylolisthesis • lumbar spine

Abbreviations used in this paper: CCI = Charlson Comorbid-ity Index; CPT = Current Procedural Terminology; ICD-9-CM = International Classification of Diseases, Ninth Revision, Clinical Modification; LSS = lumbar spinal stenosis; PSF = posterolateral lumbar spinal fusion.

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K. L. Ong et al.

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to invasive surgical procedures, such as spinal fusion. For patients with symptomatic degenerative lumbar spon-dylolisthesis, the use of spinal fusion with instrumenta-tion can offer better outcomes than those obtained with surgical decompression alone; however, results can vary depending on a patient’s history, age, comorbidities, and current disease-related symptoms.11,21,26 For patients with spinal stenosis without spondylolisthesis, spinal fusion is often performed after decompression to address con-comitant low-back pain from facet arthrosis or degenera-tive disc disease. Given the lack of consensus regarding the best treatment algorithm for these disorders, there is a continued need to develop surgical strategies and medical devices to improve both intraoperative and postoperative treatment and recovery. Particularly because of the wide variety of therapeutic options available, it is important to understand the burden of current surgical procedures on the health care system in terms of perioperative com-plications and health care costs. Therefore, our purpose in conducting this study was to quantify the periopera-tive outcomes, complications, and costs associated with posterolateral lumbar spinal fusion (PSF) among patients with lumbar spinal stenosis (LSS) and spondylolisthesis by using a national Medicare claims database.

MethodsA 5% systematic sample of the Medicare claims data

(2005–2009) was used to identify patients who had un-dergone PSF for LSS and/or spondylolisthesis between 2006 and 2007 and to track their outcomes. This sam-ple contained claims data for approximately 2.5 million Medicare beneficiaries in the US. From this data set, we identified patients by using the Current Procedural Ter-minology (CPT) code 22612 and LSS and spondylolisthe-sis by using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) di-agnosis codes 724.02, 738.4, and 756.12. To verify that patients did not have 360° fusion, we excluded PSFs that were coded concurrently with an interbody device (CPT code 22851) or anterior spine fusion (CPT code 22558).

To limit the amount of incomplete health and claims history, patients were excluded from the study if they were non-US residents or if they were not enrolled in Medicare Parts A (hospital providers) and B (physician providers). To further limit the confounding effects, we also excluded patients who did not have a minimum of 2 years of post-operative follow-up or a complete claims history in the full 12 months prior to PSF, as well as any patients who had undergone any spine surgery (for example, lumbar spine fusion, lumbar total disc replacement, laminectomy or laminotomy, or any operation involving interspinous devices) within 12 months prior to the PSF. Such patients were identified based on the presence of the correspond-ing ICD-9-CM or CPT codes from the claims records (Table 1). Medicare beneficiaries younger than 65 years of age were included in the study to provide an overall per-spective of the health care burden for PSF patients, even though those younger than 65 years have end-stage renal disease or physical disabilities. Patient age was taken into consideration to account for these medical conditions, as

was the Charlson Comorbidity Index (CCI). Patients who had undergone multilevel fusion were identified as those with CPT code 22614, whereas those who had undergone posterior instrumentation were identified with CPT codes 22840, 22842, 22843, or 22844.

The length of stay for the index PSF surgery was calculated from the Medicare claims data. Discharge status—that is, discharge to home, skilled nursing facil-ity, rehabilitation facility, or home health services—was also examined. Patients were followed up for 2 years to determine the incidence of postoperative complications, which included spine reoperation, infection, lumbosacral spinal cord injury, lumbosacral nerve root injury, dural tear and/or puncture, pneumonia, pulmonary embolism, myocardial infarction, mechanical complication, hemor-rhage and/or hematoma, heterotopic ossification, lumbar spine fracture, postlaminectomy syndrome, wound infec-tion, urinary tract infection, nonunion or malunion, re-moval of hardware, and readmission for associated com-plications. These complications were identified based on the presence of the corresponding ICD-9-CM diagnosis codes and ICD-9-CM or CPT procedure codes from the claims records (Table 2). The number of epidural steroid injections in the 12 months before and the 2 years after PSF, as well as the incidence of postoperative electrical stimulation use and blood transfusion, was also assessed. Treatment costs from a payer’s perspective, defined in our study as Medicare’s actual reimbursement and/or pay-ment (adjusted to May 2011 dollars7), were also evaluated for the 24 months of follow-up. Payment by the Medicare trust fund (that is, cost to payer) for care associated with these patients was compiled from the Medicare claims records.

Outcomes and treatment costs within the cohort were compared using logistic regression, adjusting for pa-tient sex, age, census region (Northeast, Midwest, South, West), comorbidities (CCI score), race, socioeconomic status (Medicare buy-in status), levels fused (single, mul-tiple), and primary/principal diagnosis (stenosis, spondy-lolisthesis, others). The Medicare buy-in status indicated patients whose Medicare premiums and deductibles were subsidized by the state because of their financial status and was used as a proxy for the patient’s socioeconomic status. To account for the general health status of each pa-tient, the composite CCI (Dartmouth-Manitoba version10), a metric that predicts the risk of 10-year mortality, was calculated. All disease diagnoses in a 12-month period before the index PSF were compiled from the Medicare claims. The CCI algorithm utilizes 19 categories of dis-eases based on the diagnosis and surgeries indicated in a patient. A “weight” with values of 1, 2, 3, or 6 is assigned to each category, and the final index is a composite value representing the overall degree of comorbidity. For this analysis, the CCI values were grouped into previously es-tablished categories:19 0, none; 1–2, low; 3–4, moderate; and ≥ 5, high. Statistical significance was defined at p < 0.05.

ResultsIn 2006 and 2007, approximately 90% of 106,365

patients with a diagnosis of stenosis and/or spondylolis-



Spine fusion for stenosis and spondylolisthesis

3

thesis did not receive operative care (fusion, decompres-sion, laminectomy, laminotomy, or discectomy). After applying inclusion and exclusion criteria, we obtained a final cohort of 1672 PSF patients for this study. Lumbar spinal stenosis and spondylolisthesis were the primary di-agnoses for 58.7% and 18.9% of the patients, respectively, and were secondary diagnoses for the remaining patients. Of the 1672 PSF patients, 50.7% had LSS only, 10.2% had spondylolisthesis only, and 39.1% had both LSS and spondylolisthesis. Instrumented fusion was performed in 69.8% of the patients, and multilevel fusion was per-formed in 55.8%. The patients had received an average of 2.3 ± 2.9 epidural injections in the 12 months prior to the PSF. The average number of preoperative epidural injections increased from 1.8 for those under 65 years of age to 3.2 for those 85 years and older. Two-thirds of the patients (66.7%) were female, and the majority of patients

were white (91.7% white, 6.0% black, 2.4% others). The distribution of patients by CCI scores of 0, 1–2, 3–4, and ≥ 5 was 31.2%, 49.0%, 15.4%, and 4.4%, respectively. The largest group of patients was from the South (40.2%), fol-lowed by the Midwest (31.2%), West (14.5%), and North-east (14.1%).

For the overall cohort, the average age was 71.4 ± 7.9 years (range 34–91 years), and patients younger than 65 years accounted for 11.5% of the study cohort (Fig. 1). The average length of stay (LOS) was 4.6 ± 3.2 days (Fig. 2 upper). Patients were routinely discharged to home, (42.2%) or discharged to a skilled nursing facil-ity (18.0%), home health service (19.4%), or rehabilitation facility (17.2%; Fig. 3 upper). Length of stay was sig-nificantly associated with age (p = 0.001), with patients 65 years or older tending to have longer hospital stays (Fig. 2 lower). Discharge status was also significantly as-

TABLE 1: Procedure codes for identifying prior surgical procedures*

Procedure ICD-9-CM & CPT Codes

lumbar spine fusion ICD-9-CM: 81.06, 81.07, 81.08, 81.36, 81.37, 81.38, 81.61 (effective to Q3 2005), 84.51; CPT: 22533, 22534, 22558, 22585, 22612, 22614, 22630, 22632, 22840, 22851, 22849

lumbar total disc replacement ICD-9-CM: 84.64, 84.65, 84.68; CPT: 0091T, 0094T, 0097T, 0163T, 0164T, 0165T, 22857, 22862, 22865laminectomy or laminotomy ICD-9-CM: 03.02, 03.09, 80.51; CPT: 63005, 63012, 63017, 63030, 63042, 63044, 63047op involving interspinous device ICD-9-CM: 84.58 (effective Q4 2005 to Q3 2007), 84.59 (effective Q4 2005), 84.80 to 84.85 (effective Q4 2007);

CPT: 0171T, C1821, 22841

* Q3, Q4 = third quarter, fourth quarter.

TABLE 2: Diagnosis and procedure codes for identifying surgical procedures and complications

Procedure ICD-9-CM & CPT Codes

spine reop (lumbar spine fusion, laminectomy/decompression, spine fracture repair, removal of hardware, insertion of interbody device, incision & drainage, lumbar total disc replacement, op involving interspinous devices)

ICD-9-CM: 81.07, 81.08, 81.37, 81.38, 03.01, 03.02, 03.09, 80.51, 03.53, 81.65, 81.66, 81.06, 81.36, 84.51, 86.22, 86.28, 84.64, 84.65, 84.68, 84.58 (effective Q4 2005 to Q3 2007), 84.59 (effective Q4 2005), 84.80 to 84.85 (effective Q4 2007); CPT: 22533, 22534, 22612, 22614, 22630, 22632, 22840, 22849, 63005, 63012, 63017, 63030, 63042, 63044, 63047, 22305, 22310, 22315, 22325, 22521, 22524, 22850, 22852, 22855, 22558, 22585, 22851, 10180, 12020, 12021, 13160, 22015, 0091T, 0094T, 0097T, 0163T, 0164T, 0165T, 22857, 22862, 22865, 0171T, C1821, 22841

infection ICD-9-CM: 998.59, 996.67; CPT: 22015, 10180lumbosacral spinal cord injury (cauda equina) ICD-9-CM: 806.4, 806.6, 952.2, 952.3, 952.4lumbosacral nerve root injury ICD-9-CM: 953.2, 953.3, 953.5dural tear/puncture/laceration ICD-9-CM: 349.0, 349.1, 349.2, 349.3, 998.2, V45.2pneumonia ICD-9-CM: 480-486, 487.0pulmonary embolism ICD-9-CM: 415.1, 415.11, 415.19myocardial infarction ICD-9-CM: 410mechanical complication ICD-9-CM: 996.40, 996.41, 996.43, 996.44, 996.46, 996.47, 996.49hemorrhage/hematoma/seroma ICD-9-CM: 998.1heterotopic ossification ICD-9-CM: 728.13closed lumbar spine fracture ICD-9-CM: 805.4postlaminectomy syndrome ICD-9-CM: 722.83surgical wound infection or dehiscence ICD-9-CM: 998.5, 998.3urinary tract infection ICD-9-CM: 595.0, 595.2, 595.3, 595.8, 595.89, 595.9, 599.0nonunion/malunion ICD-9-CM: 733.8, 733.81, 733.82removal of hardware CPT: 22850, 22852, 22855epidural steroid injections CPT: 62282, 62284, 64483, 64484, 64475, 64622, 64623, 62311, 62319


K. L. Ong et al.


sociated with age (p < 0.001), with 59.9% of patients 65 years or older having nonroutine discharges, as compared with 41.1% of those younger than 65 years (Fig. 3 lower). Length of stay and discharge status were not significantly associated with primary diagnosis.

At the 3-month, 1-year, and 2-year follow-ups, the incidences of spine reoperation were 10.9%, 13.3%, and 16.9%, respectively, while the combined incidences of spine reoperation and/or epidural injections were 18.2%, 27.0%, and 36.2%, respectively (Table 3). The incidence of readmission for any complication was 11.1% at 3 months, 17.5% at 1 year, and 24.9% at 2 years. Spine re-operation and/or epidural injections (p = 0.004) and read-mission for complications (p = 0.011) were significantly associated with age at the 2-year follow-up, tending to be lower for those with an age ≥ 65 years (35.2% vs 43.8% for reoperation and/or epidural injections, 24.7% vs 27.1% for readmission).

The overall average payment for all covered health care for patients who underwent PSF was $36,230 ± $17,020, $46,840 ± $31,350, and $61,610 ± $46,580, re-spectively, at 3 months, 1 year, and 2 years after surgery and corresponded to an overall cost to Medicare of $60.6 million, $78.3 million, and $103.0 million for treating these 1672 patients.

DiscussionAnalyzing the 5% Medicare data, we found that only

a small proportion of patients with LSS and spondylolis-thesis underwent fusion surgery. The relatively low rates of surgical treatment were also somewhat surprising, especially given that previous clinical trials have gener-ally shown improved outcomes when patients are treated surgically rather than nonsurgically,26 especially in those with LSS28 and spondylolisthesis.27 Furthermore, authors of another study reported that the rates of complex fusion procedures had increased more than 10-fold in patients with a primary diagnosis of spinal stenosis in the period from 2002 to 2007, although they also noted a slight de-crease in the corresponding rate of simple fusion.12

Given the more invasive nature of fusion surgery, pa-tients who undergo such procedures are more likely to re-quire added postsurgical care. Approximately half of the patients in our study were discharged in 3–4 days (49.1% total). However, after further analyzing the patients by age, we found that older patients were more likely to re-quire longer LOSs than the younger patients (p = 0.001, age < 65 vs ≥ 65 years). In addition, younger patients were also more likely to be routinely discharged, whereas older ones were more likely to be discharged to skilled nursing and/or rehabilitation facilities. Taken together, these data suggest that older patients require more extensive health care and therefore incur greater costs to help them re-cover from PSF.

In addition to the surgical recovery time, periopera-tive and postoperative complications can result from sur-gical treatment. In our analysis, we found that at the 2-year follow-up, urinary tract infection, spine reoperation and/or epidural injections, epidural injections, postlaminec-tomy syndrome, and readmission occurred in at least 1 of 4 patients. Note, however, that some of the reoperations within the first 3 months may have been planned and/or part of staged procedures and perhaps unrelated to com-plications. We did attempt to account for this factor by limiting reoperations to only those with any correspond-ing diagnoses of infection, spinal cord injury, nerve root injury, dural tear, mechanical complications, hemorrhage/

Fig. 1. Age distribution (in years) among 1672 patients who under-went PSF.

Fig. 2. Length of stay distribution among 1672 patients who under-went PSF (upper), categorized by age (lower). The x-axes represent the number of days. y.o. = years old.




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hematoma/seroma, spine fracture, postlaminectomy syn-drome, wound infection, nonunion/malunion, complica-tions due to internal orthopedic device/implant, cauda equina syndrome, acquired kyphosis postlaminectomy, or closed thoracolumbar vertebral dislocation.

Other reports on PSF have also discussed some of the complications we found. For example, revision surgery rates of 9.3% and pseudarthrosis rates of 4.65% have been documented but only after a follow-up of approximately 5 years.1 In another study, Cheng et al.4 reported a relatively higher nonunion rate of 19.7% in a patient cohort 4 years after PSF. Hardware removal rates of up to 32% have also been described.5,9,15 Regarding infection, in a multicenter randomized study comparing 2-year outcomes in patients undergoing noninstrumented and instrumented postero-lateral fusion, the latter patients had a higher infection rate of 7.4%, compared with 1.4% in the former.15 The instrumented patients also had a higher rate of nerve root pain (4.4% vs 0%). No instances of minor dural tears were found in either cohort. Moreover, relatively low dural tear rates of 1.6% were reported in a cohort of PSF patients with severe, chronic low-back pain from spondylolisthe-sis Grades 1 and 2 or from primary or secondary degen-erative segmental instability.25 In contrast, in our study we found a higher rate of dural tears of approximately 6% at 2 years post-PSF.

It is notable that a relatively large number of the PSF patients in our study continued to receive epidural injec-tions, but it is unclear if these injections were intended to

address the previously treated spine levels or adjacent lev-els. Epidural injections are an area for further investiga-tion into whether improvements can be made in terms of effective delivery and lowered costs of surgical care, since some researchers have noted that limited data suggest that epidural steroid injections are effective for improv-ing selected short-term outcomes in some patients with lumbar spinal stenosis,2 whereas others have questioned whether the benefits outweigh the risks.13 Our study also demonstrated a readmission rate of 11.1% at 3 months for the complications listed in Table 3, which is another po-tential area for improving delivery of care in patients who undergo PSF. As a result of surgical complications and postoperative rehabilitation and treatment, the burden of care for our patient cohort averaged $61,610 ± $46,580 at 2 years after PSF and corresponded to an overall 2-year cost to Medicare of $103.0 million for treating these pa-tients, which extrapolates to an estimated $2 billion when considering the entire Medicare population.

Lumbar spine fusion has been considered the stan-dard of care for degenerative spondylolisthesis, but fusion is also commonly performed in patients with predomi-nant low-back pain and spinal stenosis without spondylo-listhesis.8,16 More recently, clinicians have suggested that motion-preserving interlaminar stabilization could be an effective treatment for patients with degenerative spondy-lolisthesis or stenosis.8,20,23 As part of a prospective, ran-domized, multicenter clinical trial comparing outcomes

Fig. 3. Discharge status distribution of 1672 patients who underwent PSF (upper), categorized by age (lower). HHS = home health service; Oth/Unk = other or unknown; Rehab = rehabilitation facility; SNF = skilled nursing facility.

TABLE 3: Complication rate at the 3-month, 1-year, and 2-year follow-ups*

Complication 3-Mo FU 1-Yr FU 2-Yr FU

spine reop 10.9% 13.3% 16.9%epidural injection 8.61% 17.1% 26.1%spine reop &/or epidural injection

18.2% 27.0% 36.2%

infection 3.83% 4.90% 5.92%spinal cord injury 0.60% 0.66% 0.78%nerve root injury 0.06% 0.12% 0.12%dural tear/puncture 5.02% 5.50% 5.98%pneumonia 4.43% 7.78% 13.1%pulmonary embolism 1.85% 2.51% 3.59%myocardial infarction 1.97% 2.81% 4.49%mechanical complication 3.47% 5.50% 8.49%hemorrhage/hematoma 2.81% 3.89% 4.84%heterotopic ossification NA NA NAlumbar spine fracture 2.45% 3.29% 4.19%postlaminectomy syndrome 11.8% 19.1% 25.4%wound infection 4.61% 6.10% 7.00%urinary tract infection 17.9% 30.3% 40.9%nonunion/malunion 1.73% 3.05% 4.13%readmission (for any of the above complications)

11.1% 17.5% 24.9%

removal of hardware 1.56% 2.51% 4.25%

* FU = follow-up; NA = not applicable.


K. L. Ong et al.


of PSF and interlaminar stabilization, a subset of 150 patients with Grade 1 spondylolisthesis were followed up for a minimum of 2 years.8 Interlaminar stabilization was found to be safe and as efficacious as PSF with similar clinical outcomes, while requiring fewer health care re-sources because of reduced LOSs, operative times, and blood loss. The PSF patients were also noted to have sig-nificantly increased superior-and inferior-level angulation and translation, as compared with the interlaminar stabi-lization patients who experienced no significant adjacent- or index-level radiographic changes. These changes in the PSF group could lead to higher risks of adjacent-segment degeneration. In a case series of 22 patients who had un-dergone a combination of unilateral microdecompression and interspinous distraction device insertion for spinal ste-nosis, significant improvements in the visual analog scale score and Oswestry Disability Index were observed.20 No major complications were encountered in this cohort. In a 2-year study of patients with spinal stenosis and neuro-genic claudication, patients were randomized to decom-pressive surgery or implantation of the X-STOP interspi-nous spacer.24 Although similar results were achieved in both groups, the investigators reported a higher number of reoperations in the X-STOP group. In another study with a follow-up to 2 years, laminectomy was a more cost-effective treatment strategy for patients with lumbar ste-nosis than X-STOP, with conservative treatment being the least cost-effective.3 At this time, studies of interlaminar stabilization have relatively short follow-ups, and thus it is unknown whether the improvement in outcomes will be demonstrated with longer-term data.

Our analysis of the Medicare PSF patient population had several limitations. Although we were able to control for comorbid conditions and exclude patients who had un-dergone a previous surgery, we were unable to analyze either the specific types of instrumentation used in PSF or the number of levels treated. In addition, we were un-able to ascertain the accuracy or reliability of the cod-ing of various procedures and diagnoses since we used an administrative claims database, although the Medicare 5% data set still represents an important and widely used resource for research. We were also unable to evaluate functional outcomes, such as the Oswestry Disability Index and pain index, because we used the administra-tive claims data. Although lumbar spine fusion, which is considered the standard of care for degenerative spondy-lolisthesis, was the focus of our study, patients can also undergo other surgeries, such as decompression and/or laminectomy. It is unclear to what extent the costs and outcomes may differ between our PSF cohort and a case-controlled decompression/laminectomy cohort, although previous research18 has suggested that patients with lum-bar spondylolisthesis who undergo decompressive lami-nectomy and spinal arthrodesis have lower reoperation rates but higher overall costs than patients treated with laminectomy alone. Further research may provide ad-ditional insights into the costs and outcomes for various treatment modalities. Our cost analysis was limited to direct costs and did not consider indirect costs given the lack of such data in the administrative claims database. Despite these limitations, the national scope of the Medi-

care database presents a “big picture” view of complica-tions associated with PSF and is an unmatched resource, despite the inability to explore patient-reported or func-tional outcomes.

ConclusionsOur analysis of a subset of Medicare patients treated

for LSS and/or spondylolisthesis via PSF suggested that older patients may require more extensive postoperative care and may be more predisposed to certain types of surgical complications. As the rate of surgery increases and as surgical procedures and medical technologies become more complicated, medical costs will continue to increase and place a significant burden on Medicare. Therefore, it is important to continue studying outcomes to better understand which subsets of patients respond most favorably to specific types of surgery to facilitate recovery and minimize costs to both the patient and the health care system. Our data also highlighted several po-tential areas in which improvements can be made in the effective delivery and lowered cost of surgical care for patients with spinal stenosis and spondylolisthesis.

Acknowledgment

We thank Jeffrey Zigler, J.D., for contributing to the study design and data review.

Disclosure

Dr. Auerbach is a consultant for Paradigm Spine, Medacta International, Zyga Technology Inc., and Medical Metrics Inc. and holds a patent with Medacta International. Exponent, Inc. received research funding from Paradigm Spine for this study. The funding source was not involved in the design and conduct of the study; collection, management, analysis, and interpretation of the data; or preparation and approval of the manuscript. The funding source reviewed the manuscript. The authors report no conflict of interest concerning the materials or methods used in this study or the find-ings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: Ong, Auerbach, Schmier, Ochoa. Acquisition of data: Lau. Analysis and interpreta-tion of data: all authors. Drafting the article: Ong. Critically revising the article: Auerbach, Schmier, Ochoa. Reviewed submitted version of manuscript: Ong, Auerbach, Lau. Approved the final version of the manuscript on behalf of all authors: Ong. Statistical analysis: Lau. Administrative/technical/material support: Ong, Lau, Schmier, Ochoa. Study supervision: Ong, Ochoa.

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Manuscript submitted February 15, 2014.Accepted April 3, 2014.Portions of this analysis have been previously presented at the

International Society of Pharmacoeconomics and Outcomes Re-search 17th Annual International Meeting held in Washington, DC, on June 2–6, 2012; the North American Spine Society 27th An nual Meeting held in Dallas, Texas, on October 24–27, 2012; SpineWeek 2012 held in Amsterdam, Netherlands, on May 28–June 1, 2012; and the International Society for the Advancement of Spine Surgery 12th Annual Conference held in Barcelona, Spain, on March 20–23, 2012.

Please include this information when citing this paper: DOI: 10.3171/2014.4.FOCUS1440.

Address correspondence to: Kevin Ong, Ph.D., P.E., Exponent Inc., 3440 Market St., Ste. 600, Philadelphia, PA 19104. email: [email protected].


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Perioperative outcomes, complications, and costs associated ......Treatments for spinal stenosis and spondylolisthesis are varied, ranging from conservative therapies, such as noninvasive