- Email: [email protected]
Lumbar microdecompression in elderly versus general adult patients: Comparable outcomes and costs despite group differences
Journal Pre-proof Lumbar microdecompression in elderly versus general adult patients: Comparable outcomes and costs despite group differences Ziyad O. Knio, Samuel Rosas, Michael S. Schallmo, Suman Medda, Tadhg J. O'Gara PII:
S0972-978X(19)30351-4
DOI:
https://doi.org/10.1016/j.jor.2019.09.005
Reference:
JOR 817
To appear in:
Journal of Orthopaedics
Received Date: 11 July 2019 Accepted Date: 11 September 2019
Please cite this article as: Knio ZO, Rosas S, Schallmo MS, Medda S, O'Gara TJ, Lumbar microdecompression in elderly versus general adult patients: Comparable outcomes and costs despite group differences, Journal of Orthopaedics (2019), doi: https://doi.org/10.1016/j.jor.2019.09.005. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V. on behalf of Professor P K Surendran Memorial Education Foundation.
Title: Lumbar Microdecompression in Elderly Versus General Adult Patients: Comparable Outcomes and Costs Despite Group Differences
Authors: Ziyad O. Knio, BSa Samuel Rosas, MDa Michael S. Schallmo, BSa Suman Medda, MDa Tadhg J. O’Gara, MDa,b a
Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, NC
b
Department of Neurosurgery, Wake Forest School of Medicine, Winston-Salem, NC
Corresponding Author: Tadhg J. O’Gara, MD Department of Orthopaedic Surgery Wake Forest School of Medicine 1 Medical Center Boulevard Winston-Salem, NC 27157 Email: [email protected] Phone: 336-716-3950
Acknowledgements: We thank Wendy Williams and Marcy Lewis for their assistance in outcomes collection. We thank Eileen Elsner for the use of her illustrations. Keywords: Lumbar nerve decompression, microdecompression, tubular decompression, minimally invasive surgery, lumbar spinal stenosis Short Title: Elderly Versus General Adult Microdecompressions Funding Sources: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Declarations of Interest: None Institutional Review Board Approval: IRB00042783
Abstract This study investigated differences between patients < 65 and ≥ 65 years of age following lumbar microdecompression. Differences between age groups were investigated with univariate analyses. A linear mixed effects model was fit to the study outcomes. 144 patients were studied. There was no difference in two-year outcomes between the age groups. Outcome measures showed improvement compared to baseline at one- and two-years (p<0.001). Age group had a significant effect on back pain (p=0.016). Patients ≥ 65 years of age may experience greater relief in back pain following microdecompression. Nonetheless, significant improvement is observed in both age groups at two-years. Keywords: Lumbar nerve decompression, microdecompression, tubular decompression, minimally invasive surgery, lumbar spinal stenosis Declarations of Interest: None.
1 Introduction Rates of lumbar spine surgery in the United States have increased considerably in the past few decades, particularly in the Medicare population.1,2 Moreover, minimally invasive techniques have become increasingly utilized for the treatment of lumbar spinal stenosis (LSS) and are often selected over traditional approaches as they appear to reduce morbidity, increase operating room efficiency, and potentially decrease costs.3 Minimally invasive approaches have also been associated with shorter hospital stays and time to mobilization, as well as a reduced rate of opioid use, which can greatly impact patient satisfaction and outcome.4 A factor that has been found greatly associated with outcome in the treatment of LSS is patient age. Elderly patients often have a greater burden of increasing comorbidities which can ultimately decrease the rate of improvement and/or overall outcome, further confounding this relationship. Given the current trends, it is important to consider whether differences exist in microdecompression outcomes in elderly patients compared to the general adult population. This study investigated differences between patients < 65 and patients ≥ 65 years of age following microdecompression for symptomatic LSS. Patient characteristics, surgical outcomes, and patient-reported outcomes (PROMs) over a two-year follow-up period are reported. The secondary purpose of this review was to compare costs associated with these procedures between those < 65 and those ≥ 65 years of age, within Medicare and a private payer (Humana). 2 Methods A retrospective review of patients enrolled in the senior author’s surgical outcomes database was performed. Briefly, this database enrolls patients prospectively before surgery and captures a variety of validated PROMs. Patient enrollment began in January 2014 following
Institutional Review Board approval of the protocol. The resulting database of consecutive lumbar microdecompression surgeries performed by a single, fellowship-trained orthopaedic spine surgeon is maintained regularly and PROMs are collected with patient visits at regular intervals. Inclusion criteria for this study were patients ≥18 years of age with symptomatic LSS who underwent elective microdecompression of the lumbar spine. Patient selection for surgery was based on preoperative evaluation by the senior author and included persistence of neurologic deficits after at least 90 days of conservative non-operative treatment (e.g., activity modification, non-steroidal anti-inflammatory drugs, physical therapy, and/or exercises), absence of instability on radiographs, and preoperative magnetic resonance imaging to confirm the presence of pathoanatomy amenable to microdecompression (e.g., central, lateral, and/or foraminal stenosis). Exclusion criteria included deceased patients and non-index microdecompression cases. All procedures were performed by a single surgeon using previously described techniques.5-9 Microdecompression procedures included unilateral hemilaminectomy (Figure 1), unilateral laminotomy with bilateral decompression (Figure 2), and far lateral decompression of the neuroforamen (Figure 3). The METRx™ Tubular Retractor System (Medtronic Sofamor Danek, Memphis, TN) was utilized in all cases. PROMs for this study included visual analog scale (VAS) for back pain and leg pain, Oswestry Disability Index (ODI), and EuroQol-Five Dimensions Index (EQ-5D).10,11 Data were collected during office visits; in some cases, postoperative data were collected via a standardized telephone script. As ODI is a composite score based on responses to separate questions, the following correction factor was applied in cases where one or more ODI questions were left unanswered.12
Corrected ODI = ODI × (
)
EQ-5D indices were calculated using a validated valuation model for United States patient populations.11 No corrections were applied to the scores recorded for VAS. Patient characteristics, comorbidities, and operative details were retrieved from electronic medical records. The operative time reported is the operative time per level; i.e. two-level decompression operative times were reduced by a factor of two. Spondylolisthesis and scoliosis measurements were obtained from preoperative standing plain film radiographs of the lumbar spine and measured by a single reviewer. All cases of spondylolisthesis in this study were degenerative and non-lytic. 2.1 Statistical Analysis All computations and statistical tests were performed in R (R Core Team, Vienna, Austria). Two age groups were defined: patients < 65 and patients ≥ 65 years of age. Differences between age groups were investigated with a t-test for quantitative data and a chi-square test without continuity correction for discrete data. A linear mixed effects model was fitted to each of the PROMs independently. Fixed effects were visit time (preoperative, one-year, two-year) and age group. A random effects term accounted for repeated measures on individual patients. Linear mixed effects modeling was selected over a repeated measures analysis of variance in order to better accommodate for PROMs missing at some time points. Estimated marginal means were used to assess differences between age groups at each visit time. Longitudinal differences in PROMs across visit times and between age groups were investigated with a Tukey test for multiple comparisons.
Costs were obtained by querying the PearlDiver Server (PearlDiver technologies, Colorado Springs, CO) through International of Classification of Disease 9th revision codes and Current Procedural Terminology Codes for single level laminectomy and far lateral decompression. The costs from both Medicare and a private payer (Humana) were obtained and compared based on age. Data regarding both charges and reimbursements was available for Medicare patients from 2005 to 2014. The Humana dataset contains data from 2007 to 2017 and reimbursement only. No adjustments were made for inflation. A Kolmogrov-Smirnov test was used to evaluate normality of the data. Parametric data were compared with 2-tailed t-tests while non-parametric data were compared through Mann-Whitney tests. Alpha was set at 0.05 for all hypothesis testing purposes. 3 Results The senior author’s database of 324 consecutive microdecompression cases performed between January 2014 and June 2019 was queried. 159 consecutive cases would have had twoyear follow up at time of analysis. 11 patients were deceased. 4 additional cases were non-index microdecompressions. The analyzed sample size was comprised of 144 living primary microdecompression patients with two-year outcomes available. The < 65 age group was comprised of 67 patients (46.5%). The ≥ 65 age group was comprised of 77 patients (53.5%). Unilateral hemilaminectomy was performed in 35 patients (24.3%), unilateral laminotomy and bilateral decompression was performed in 77 patients (53.5%), and far lateral or isolated foraminal decompression was performed in 32 patients (22.2%). 3.1 Characteristic Differences Between Age Groups
Gender, obesity, tobacco use, and history of spine surgery were equally represented in the two groups. Patients < 65 years of age were more likely to require discectomy (RR=8.04 [6.889.21], p<0.001). Patients ≥ 65 years of age were more likely to have diabetes (RR=2.61 [1.883.34], p=0.006) and require multi-level decompression (RR=3.92 [2.42-5.41], p=0.050). Length of hospital stay and revision rates were comparable between the two groups (Table 1). 3.2 Patient-Reported Outcomes Measures Despite patients < 65 years of age having greater preoperative ODI (56.93 ± 14 vs. 46.37 ± 19.53, p=0.005) and one-year back pain VAS (3.66 ± 3.18 vs. 2.43 ± 2.61, p=0.017), there was no difference in any two-year PROMs between the two age groups. The linear mixed effects models confirmed significant improvement in PROMs compared to baseline at one- (p<0.001) and two- years (p<0.001), without decline between one- and two- years (p>0.05). Age group had a significant effect on back pain improvement (p=0.016), but not on leg pain (p=0.377), ODI (p=0.063), or EQ-5D (p=0.138) improvement (Table 2, Figure 4). 3.3 Costs In Medicare patients, the mean charge for patients < 65 years of age compared to patients ≥ 65 years of age is comparable for laminectomy ($7,293.29 ± $1,661.86 vs. $7,298.28 ± $1,756.98, p=0.995) and far lateral decompression ($8,441.53 ± $1,591.80 vs. $8,075.73 ± $1,464.82, p=0.599). Mean reimbursement for patients < 65 years of age compared to patients ≥ 65 years of age is comparable for laminectomy ($1,997.18 ± $607.98 vs. $1,921.52 ± $652.89, p=0.792) and far lateral decompression ($2,086.72 ± $636.33 vs. $1,880.57 ± $603.87, p=0.467). In Humana patients, the mean reimbursement for patients < 65 years of age compared to patients ≥ 65 years of age is significantly greater for laminectomy ($1,741.86 ± $292.63 vs.
$1,280.2 ± $319.85, p=0.002) and far lateral decompression ($2,354.09 ± $450.82 vs. $1,428.04 ± $190.23, p<0.001; Table 3). 4 Discussion This study demonstrates comparable outcomes between elderly and general adult patients undergoing lumbar microdecompression. The PROMs that were collected in this study were selected on the basis of capturing subjective pain reporting, an objective measure of disability, and a valuation of health state.10,11,13,14 Patients demonstrated significant improvements in PROMs at one- and two- years, without decline between one- and two- years. The current literature defining minimum clinically important differences (1.2, 1.6, and 12.8 for back pain, leg pain, and ODI, respectively) suggests that the improvement observed in this study is not only statistically significant, but also clinically significant.15 Age group had a moderate effect on back pain improvement over time; the ≥ 65 age group showed greater improvement. One possible explanation is that the etiology of back pain in the two age groups may be unevenly distributed, perhaps patients < 65 years of age more likely to have arthritic back pain and patients ≥ 65 years of age more likely to have neurogenic back pain that is more amenable to decompression. Medicare charges and reimbursements are comparable between the two age groups, which supports the hypothesis that microdecompression is equally cost-effective in both elderly and general adult populations. Humana reimbursements appeared greater in patients < 65 years of age. Given that Humana is a secondary payer, this discrepancy may be explained by patients ≥ 65 years of age having costs partially covered by Medicare. Other studies have shown that surgery is superior to non-operative treatment of lumbar spinal stenosis, yielding better improvement in ODI, bodily pain, and physical function scores on the Medical Outcomes Study 36-item Short-Form General Health Survey.2,16 Surgical treatment
results in 1.64 total mean discounted quality-adjusted life-years (QALYs), while non-operative treatment is statistically significantly inferior, resulting in 1.44 total mean discounted QALYs.2 Nonetheless, the validity of these findings has not been well documented previously in regards to age. In intervertebral disc herniation, the estimated the cost per QALY gained for surgical treatment relative to non-operative care is $69,403 in the general population and $34,355 in the Medicare population, demonstrating the value-added of these procedures.2 This study has certain limitations: it is a retrospective case series with limited sample size and setting. Nonetheless, evaluating 144 patients with 2-year outcomes of new surgical techniques assessed in a variety of populations provides suggestive findings for larger multicenter studies. Another limitation to this study is the lack of age-matched non-operative controls. Yet there is still debate whether non-operative controls serve better as controls than disease-specific, older controls as performed here, given that non-operative patients may undergo surgery in the future. Other studies have demonstrated high rates of non-adherence to randomized treatment group, which would not only pose logistic challenges, but also ethical challenges.2,16 Furthermore, a third limitation is the lack of analysis of age specific cut-off points to determine an age where surgery no longer provides value. This is an ongoing research endeavor at our institution as data collection continues, outcomes of patients ≥ 80 years will be later described.3,17-19 5 Conclusion Microdecompression is an effective treatment option for symptomatic LSS in both elderly and general adult populations. Patients ≥ 65 years of age may experience greater relief in back pain following microdecompression. Nonetheless, pain, disability, and health state are comparable at two-years post-operatively, despite differences between age groups. The charge
associated with lumbar decompression is comparable in patients < 65 and patients ≥ 65 years of age, however there may exist differences in reimbursement amounts.
Figure Legends Figure 1. Illustration of unilateral hemilaminectomy using a tubular retractor. Figure 2. Illustration of unilateral laminotomy and bilateral decompression using a tubular retractor. Figure 3. Illustration of a far lateral decompression using a tubular retractor. Figure 4. Back pain and leg pain visual analog scale, Oswestry Disability Index, and EuroQolFive Dimensions Valuation vs. Time, categorized by age group. * p<0.05 ** p<0.01 ***p<0.001
References 1.
Weinstein JN, Lurie JD, Olson PR, Bronner KK, Fisher ES. United States' trends and regional variations in lumbar spine surgery: 1992-2003. Spine. 2006;31(23):2707-2714.
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Tosteson AN, Skinner JS, Tosteson TD, et al. The cost effectiveness of surgical versus nonoperative treatment for lumbar disc herniation over two years: evidence from the Spine Patient Outcomes Research Trial (SPORT). Spine. 2008;33(19):2108-2115.
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Morgalla MH, Noak N, Merkle M, Tatagiba MS. Lumbar spinal stenosis in elderly patients: is a unilateral microsurgical approach sufficient for decompression? J Neurosurg Spine. 2011;14(3):305-312.
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Mobbs RJ, Li J, Sivabalan P, Raley D, Rao PJ. Outcomes after decompressive laminectomy for lumbar spinal stenosis: comparison between minimally invasive unilateral laminectomy for bilateral decompression and open laminectomy: clinical article. J Neurosurg Spine. 2014;21(2):179-186.
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Mobbs R, Phan K. Minimally Invasive Unilateral Laminectomy for Bilateral Decompression. JBJS essential surgical techniques. 2017;7(1):e9.
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Phan K, Teng I, Schultz K, Mobbs RJ. Treatment of Lumbar Spinal Stenosis by Microscopic Unilateral Laminectomy for Bilateral Decompression: A Technical Note. Orthopaedic surgery. 2017;9(2):241-246.
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Weber C, Lonne G, Rao V, et al. Surgical management of lumbar spinal stenosis: a survey among Norwegian spine surgeons. Acta neurochirurgica. 2017;159(1):191-197.
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Alimi M, Njoku I, Jr., Cong GT, et al. Minimally invasive foraminotomy through tubular retractors via a contralateral approach in patients with unilateral radiculopathy. Neurosurgery. 2014;10 Suppl 3:436-447; discussion 446-437.
9.
Epstein NE. Case presentation and short perspective on management of foraminal/far lateral discs and stenosis. Surgical neurology international. 2018;9:87.
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Fairbank JC, Pynsent PB. The Oswestry Disability Index. Spine. 2000;25(22):2940-2952; discussion 2952.
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Shaw JW, Johnson JA, Coons SJ. US valuation of the EQ-5D health states: development and testing of the D1 valuation model. Medical care. 2005;43(3):203-220.
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Mehra A, Baker D, Disney S, Pynsent PB. Oswestry Disability Index scoring made easy. Annals of the Royal College of Surgeons of England. 2008;90(6):497-499.
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Abtahi AM, Lyman KS, Brodke DS, Lawrence BD, Zhang C, Spiker WR. Patient Satisfaction is Not Associated With Self-reported Disability in a Spine Patient Population. Clinical spine surgery. 2017;30(8):E1165-e1168.
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Carreon LY, Bratcher KR, Das N, Nienhuis JB, Glassman SD. Estimating EQ-5D values from the Oswestry Disability Index and numeric rating scales for back and leg pain. Spine. 2014;39(8):678-682.
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Copay AG, Glassman SD, Subach BR, Berven S, Schuler TC, Carreon LY. Minimum clinically important difference in lumbar spine surgery patients: a choice of methods using the Oswestry Disability Index, Medical Outcomes Study questionnaire Short Form 36, and pain scales. The spine journal : official journal of the North American Spine Society. 2008;8(6):968-974.
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Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. The New England journal of medicine. 2008;358(8):794-810.
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Lagman C, Ugiliweneza B, Boakye M, Drazin D. Spine Surgery Outcomes in Elderly Patients Versus General Adult Patients in the United States: A MarketScan Analysis. World neurosurgery. 2017;103:780-788.
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Szpalski M, Gunzburg R. Lumbar spinal stenosis in the elderly: an overview. European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. 2003;12 Suppl 2(Suppl 2):S170-175.
19.
Giannadakis C, Solheim O, Jakola AS, et al. Surgery for Lumbar Spinal Stenosis in Individuals Aged 80 and Older: A Multicenter Observational Study. Journal of the American Geriatrics Society. 2016;64(10):2011-2018.
Mean±SD or Proportion of Cases (%) Patient characteristics Age (years) Sex (male) Body Mass Index >30 kg/m² Current smoker Diabetes Prior spine surgery Preoperative radiographs Spondylolisthesis ≥ 4 mm Scoliosis ≥ 10° Operative details Disc procedure Multiple levels Operative time (minutes) Length of stay (days) Intraoperative findings Synovial cyst Durotomy Additional outcomes Subsequent open revision Subsequent minor revision
Overall
Age < 65
Age ≥ 65
n
p
63.81 ± 11.63 71/144 (49.3%) 61/135 (45.2%) 18/144 (12.5%) 32/144 (22.2%) 31/144 (21.5%)
54.49 ± 9.64 31/67 (46.3%) 29/63 (46.0%) 12/67 (17.9%) 8/67 (11.9%) 14/67 (20.9%)
71.92 ± 5.53 40/77 (51.9%) 32/72 (44.4%) 6/77 (7.8%) 24/77 (31.2%) 17/77 (22.1%)
144 144 135 144 144 144
<0.001 0.497 0.853 0.067 0.006 0.863
36/142 (25.4%) 14/142 (9.9%)
15/66 (22.7%) 4/67 (6.0%)
21/76 (27.6%) 10/75 (13.3%)
142 142
0.503 0.142
24/144 (16.7%) 11/144 (7.6%) 107.65 ± 33.81 0.82 ± 1.14
21/67 (31.3%) 2/67 (3.0%) 106.51 ± 34.46 0.71 ± 1.14
3/77 (3.9%) 9/77 (11.7%) 108.63 ± 33.44 0.90 ± 1.15
144 144 144 144
<0.001 0.050 0.710 0.319
8/144 (5.6%) 14/144 (9.7%)
6/67 (9.0%) 6/67 (9.0%)
2/77 (2.6%) 8/77 (10.4%)
144 144
0.097 0.772
15/144 (10.4%) 18/144 (12.5%)
10/67 (14.9%) 8/67 (11.9%)
5/77 (6.5%) 10/77 (13.0%)
144 144
0.099 0.850
*
*
* *
Table 1: Summary of patient characteristics, preoperative radiographic findings, operative details, intraoperative findings, and additional outcomes for patients included in this study, with subgroup comparisons of patients < 65 and patients ≥ 65 years of age. There were a small number of unreported data points, resulting in fewer patients with an entered value for body mass index, spondylolisthesis ≥4 mm, and scoliosis ≥10° compared with all other values. *Denotes significance, p<0.05, between patients < 65 and patients ≥ 65 years of age.
Back Pain Age < 65 Age ≥ 65 Preoperative Mean ± SD 6.64 ± 3.10 6.46 ± 3.06 n 55 70 p (marginal) 0.770 1-year Mean ± SD 3.66 ± 3.18 2.43 ± 2.61 n 62 70 p (marginal) 0.017* p (preoperative) <0.001* 2-year Mean ± SD 3.68 ± 3.09 2.79 ± 2.81 n 57 70 p (marginal) 0.095 p (preoperative) <0.001* p (1-year) 0.618 p (age)
0.016*
Leg Pain Age < 65 Age ≥ 65
ODI Age < 65
Age ≥ 65
EQ-5D Age < 65 Age ≥ 65
7.69 ± 2.05 6.99 ± 2.71 58 70 0.202
56.93 ± 14.00 46.37 ± 19.53 44 57 0.005*
0.31 ± 0.32 0.40 ± 0.31 53 62 0.102
2.43 ± 3.15 1.99 ± 2.86 60 70 0.379 <0.001*
25.91 ± 18.92 19.90 ± 17.4 57 61 0.065 <0.001*
0.71 ± 0.32 0.79 ± 0.24 61 71 0.141 <0.001*
2.91 ± 3.15 2.59 ± 2.93 57 69 0.582 <0.001* 0.306
27.02 ± 19.79 24.38 ± 16.95 56 68 0.365 <0.001* 0.126
0.69 ± 0.31 0.71 ± 0.28 51 67 0.558 <0.001* 0.211
0.377
0.063
0.138
Table 2: Comparison of patient-reported outcome measures preoperatively, at 1-year follow-up, and at 2-year follow-up for patients included in this study. A linear mixed effects model was fit to the data in order to accomodate for missing outcomes; the model included a random effects term to account for repeated measures on individual patients. *Denotes significance, p<0.05, of patientreported outcome measure differences between age groups at each visit time (marginal), or of longitudinal differences compared to previous visits (preoperative, 1-year), or between age groups (age).
Laminectomy Age < 65
Age ≥ 65
Far Lateral Decompression Age < 65 Age ≥ 65
Medicare Charges Mean ± SD $7,293.29 ± $1,661.86 $7,298.28 ± $1,756.98 $8,441.53 ± $1,591.80 $8,075.73 ± $1,464.82 p 0.995 0.599 Medicare Reimbursements Mean ± SD $1,997.18 ± $607.98 $1,921.52 ± $652.89 $2,086.72 ± $636.33 $1,880.57 ± $603.87 p 0.792 0.467 Humana Reimbursements Mean ± SD $1,741.86 ± $292.63 $1,280.20 ± $319.85 p 0.002*
$2,354.09 ± $450.82 $1,428.04 ± $190.23 <0.001*
Table 3: Comparisons of costs data between age groups. Medicare and Humana costs data for single level laminectomy and far lateral decompression CPTs. Data regarding both charges and reimbursements was available for Medicare patients from 2005 to 2014. The Humana dataset contains data from 2007 to 2017 and reimbursement only. *Denotes significance, p<0.05, between mean dollar amounts for age groups.
S0972-978X(19)30351-4
DOI:
https://doi.org/10.1016/j.jor.2019.09.005
Reference:
JOR 817
To appear in:
Journal of Orthopaedics
Received Date: 11 July 2019 Accepted Date: 11 September 2019
Please cite this article as: Knio ZO, Rosas S, Schallmo MS, Medda S, O'Gara TJ, Lumbar microdecompression in elderly versus general adult patients: Comparable outcomes and costs despite group differences, Journal of Orthopaedics (2019), doi: https://doi.org/10.1016/j.jor.2019.09.005. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V. on behalf of Professor P K Surendran Memorial Education Foundation.
Title: Lumbar Microdecompression in Elderly Versus General Adult Patients: Comparable Outcomes and Costs Despite Group Differences
Authors: Ziyad O. Knio, BSa Samuel Rosas, MDa Michael S. Schallmo, BSa Suman Medda, MDa Tadhg J. O’Gara, MDa,b a
Department of Orthopaedic Surgery, Wake Forest School of Medicine, Winston-Salem, NC
b
Department of Neurosurgery, Wake Forest School of Medicine, Winston-Salem, NC
Corresponding Author: Tadhg J. O’Gara, MD Department of Orthopaedic Surgery Wake Forest School of Medicine 1 Medical Center Boulevard Winston-Salem, NC 27157 Email: [email protected] Phone: 336-716-3950
Acknowledgements: We thank Wendy Williams and Marcy Lewis for their assistance in outcomes collection. We thank Eileen Elsner for the use of her illustrations. Keywords: Lumbar nerve decompression, microdecompression, tubular decompression, minimally invasive surgery, lumbar spinal stenosis Short Title: Elderly Versus General Adult Microdecompressions Funding Sources: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Declarations of Interest: None Institutional Review Board Approval: IRB00042783
Abstract This study investigated differences between patients < 65 and ≥ 65 years of age following lumbar microdecompression. Differences between age groups were investigated with univariate analyses. A linear mixed effects model was fit to the study outcomes. 144 patients were studied. There was no difference in two-year outcomes between the age groups. Outcome measures showed improvement compared to baseline at one- and two-years (p<0.001). Age group had a significant effect on back pain (p=0.016). Patients ≥ 65 years of age may experience greater relief in back pain following microdecompression. Nonetheless, significant improvement is observed in both age groups at two-years. Keywords: Lumbar nerve decompression, microdecompression, tubular decompression, minimally invasive surgery, lumbar spinal stenosis Declarations of Interest: None.
1 Introduction Rates of lumbar spine surgery in the United States have increased considerably in the past few decades, particularly in the Medicare population.1,2 Moreover, minimally invasive techniques have become increasingly utilized for the treatment of lumbar spinal stenosis (LSS) and are often selected over traditional approaches as they appear to reduce morbidity, increase operating room efficiency, and potentially decrease costs.3 Minimally invasive approaches have also been associated with shorter hospital stays and time to mobilization, as well as a reduced rate of opioid use, which can greatly impact patient satisfaction and outcome.4 A factor that has been found greatly associated with outcome in the treatment of LSS is patient age. Elderly patients often have a greater burden of increasing comorbidities which can ultimately decrease the rate of improvement and/or overall outcome, further confounding this relationship. Given the current trends, it is important to consider whether differences exist in microdecompression outcomes in elderly patients compared to the general adult population. This study investigated differences between patients < 65 and patients ≥ 65 years of age following microdecompression for symptomatic LSS. Patient characteristics, surgical outcomes, and patient-reported outcomes (PROMs) over a two-year follow-up period are reported. The secondary purpose of this review was to compare costs associated with these procedures between those < 65 and those ≥ 65 years of age, within Medicare and a private payer (Humana). 2 Methods A retrospective review of patients enrolled in the senior author’s surgical outcomes database was performed. Briefly, this database enrolls patients prospectively before surgery and captures a variety of validated PROMs. Patient enrollment began in January 2014 following
Institutional Review Board approval of the protocol. The resulting database of consecutive lumbar microdecompression surgeries performed by a single, fellowship-trained orthopaedic spine surgeon is maintained regularly and PROMs are collected with patient visits at regular intervals. Inclusion criteria for this study were patients ≥18 years of age with symptomatic LSS who underwent elective microdecompression of the lumbar spine. Patient selection for surgery was based on preoperative evaluation by the senior author and included persistence of neurologic deficits after at least 90 days of conservative non-operative treatment (e.g., activity modification, non-steroidal anti-inflammatory drugs, physical therapy, and/or exercises), absence of instability on radiographs, and preoperative magnetic resonance imaging to confirm the presence of pathoanatomy amenable to microdecompression (e.g., central, lateral, and/or foraminal stenosis). Exclusion criteria included deceased patients and non-index microdecompression cases. All procedures were performed by a single surgeon using previously described techniques.5-9 Microdecompression procedures included unilateral hemilaminectomy (Figure 1), unilateral laminotomy with bilateral decompression (Figure 2), and far lateral decompression of the neuroforamen (Figure 3). The METRx™ Tubular Retractor System (Medtronic Sofamor Danek, Memphis, TN) was utilized in all cases. PROMs for this study included visual analog scale (VAS) for back pain and leg pain, Oswestry Disability Index (ODI), and EuroQol-Five Dimensions Index (EQ-5D).10,11 Data were collected during office visits; in some cases, postoperative data were collected via a standardized telephone script. As ODI is a composite score based on responses to separate questions, the following correction factor was applied in cases where one or more ODI questions were left unanswered.12
Corrected ODI = ODI × (
)
EQ-5D indices were calculated using a validated valuation model for United States patient populations.11 No corrections were applied to the scores recorded for VAS. Patient characteristics, comorbidities, and operative details were retrieved from electronic medical records. The operative time reported is the operative time per level; i.e. two-level decompression operative times were reduced by a factor of two. Spondylolisthesis and scoliosis measurements were obtained from preoperative standing plain film radiographs of the lumbar spine and measured by a single reviewer. All cases of spondylolisthesis in this study were degenerative and non-lytic. 2.1 Statistical Analysis All computations and statistical tests were performed in R (R Core Team, Vienna, Austria). Two age groups were defined: patients < 65 and patients ≥ 65 years of age. Differences between age groups were investigated with a t-test for quantitative data and a chi-square test without continuity correction for discrete data. A linear mixed effects model was fitted to each of the PROMs independently. Fixed effects were visit time (preoperative, one-year, two-year) and age group. A random effects term accounted for repeated measures on individual patients. Linear mixed effects modeling was selected over a repeated measures analysis of variance in order to better accommodate for PROMs missing at some time points. Estimated marginal means were used to assess differences between age groups at each visit time. Longitudinal differences in PROMs across visit times and between age groups were investigated with a Tukey test for multiple comparisons.
Costs were obtained by querying the PearlDiver Server (PearlDiver technologies, Colorado Springs, CO) through International of Classification of Disease 9th revision codes and Current Procedural Terminology Codes for single level laminectomy and far lateral decompression. The costs from both Medicare and a private payer (Humana) were obtained and compared based on age. Data regarding both charges and reimbursements was available for Medicare patients from 2005 to 2014. The Humana dataset contains data from 2007 to 2017 and reimbursement only. No adjustments were made for inflation. A Kolmogrov-Smirnov test was used to evaluate normality of the data. Parametric data were compared with 2-tailed t-tests while non-parametric data were compared through Mann-Whitney tests. Alpha was set at 0.05 for all hypothesis testing purposes. 3 Results The senior author’s database of 324 consecutive microdecompression cases performed between January 2014 and June 2019 was queried. 159 consecutive cases would have had twoyear follow up at time of analysis. 11 patients were deceased. 4 additional cases were non-index microdecompressions. The analyzed sample size was comprised of 144 living primary microdecompression patients with two-year outcomes available. The < 65 age group was comprised of 67 patients (46.5%). The ≥ 65 age group was comprised of 77 patients (53.5%). Unilateral hemilaminectomy was performed in 35 patients (24.3%), unilateral laminotomy and bilateral decompression was performed in 77 patients (53.5%), and far lateral or isolated foraminal decompression was performed in 32 patients (22.2%). 3.1 Characteristic Differences Between Age Groups
Gender, obesity, tobacco use, and history of spine surgery were equally represented in the two groups. Patients < 65 years of age were more likely to require discectomy (RR=8.04 [6.889.21], p<0.001). Patients ≥ 65 years of age were more likely to have diabetes (RR=2.61 [1.883.34], p=0.006) and require multi-level decompression (RR=3.92 [2.42-5.41], p=0.050). Length of hospital stay and revision rates were comparable between the two groups (Table 1). 3.2 Patient-Reported Outcomes Measures Despite patients < 65 years of age having greater preoperative ODI (56.93 ± 14 vs. 46.37 ± 19.53, p=0.005) and one-year back pain VAS (3.66 ± 3.18 vs. 2.43 ± 2.61, p=0.017), there was no difference in any two-year PROMs between the two age groups. The linear mixed effects models confirmed significant improvement in PROMs compared to baseline at one- (p<0.001) and two- years (p<0.001), without decline between one- and two- years (p>0.05). Age group had a significant effect on back pain improvement (p=0.016), but not on leg pain (p=0.377), ODI (p=0.063), or EQ-5D (p=0.138) improvement (Table 2, Figure 4). 3.3 Costs In Medicare patients, the mean charge for patients < 65 years of age compared to patients ≥ 65 years of age is comparable for laminectomy ($7,293.29 ± $1,661.86 vs. $7,298.28 ± $1,756.98, p=0.995) and far lateral decompression ($8,441.53 ± $1,591.80 vs. $8,075.73 ± $1,464.82, p=0.599). Mean reimbursement for patients < 65 years of age compared to patients ≥ 65 years of age is comparable for laminectomy ($1,997.18 ± $607.98 vs. $1,921.52 ± $652.89, p=0.792) and far lateral decompression ($2,086.72 ± $636.33 vs. $1,880.57 ± $603.87, p=0.467). In Humana patients, the mean reimbursement for patients < 65 years of age compared to patients ≥ 65 years of age is significantly greater for laminectomy ($1,741.86 ± $292.63 vs.
$1,280.2 ± $319.85, p=0.002) and far lateral decompression ($2,354.09 ± $450.82 vs. $1,428.04 ± $190.23, p<0.001; Table 3). 4 Discussion This study demonstrates comparable outcomes between elderly and general adult patients undergoing lumbar microdecompression. The PROMs that were collected in this study were selected on the basis of capturing subjective pain reporting, an objective measure of disability, and a valuation of health state.10,11,13,14 Patients demonstrated significant improvements in PROMs at one- and two- years, without decline between one- and two- years. The current literature defining minimum clinically important differences (1.2, 1.6, and 12.8 for back pain, leg pain, and ODI, respectively) suggests that the improvement observed in this study is not only statistically significant, but also clinically significant.15 Age group had a moderate effect on back pain improvement over time; the ≥ 65 age group showed greater improvement. One possible explanation is that the etiology of back pain in the two age groups may be unevenly distributed, perhaps patients < 65 years of age more likely to have arthritic back pain and patients ≥ 65 years of age more likely to have neurogenic back pain that is more amenable to decompression. Medicare charges and reimbursements are comparable between the two age groups, which supports the hypothesis that microdecompression is equally cost-effective in both elderly and general adult populations. Humana reimbursements appeared greater in patients < 65 years of age. Given that Humana is a secondary payer, this discrepancy may be explained by patients ≥ 65 years of age having costs partially covered by Medicare. Other studies have shown that surgery is superior to non-operative treatment of lumbar spinal stenosis, yielding better improvement in ODI, bodily pain, and physical function scores on the Medical Outcomes Study 36-item Short-Form General Health Survey.2,16 Surgical treatment
results in 1.64 total mean discounted quality-adjusted life-years (QALYs), while non-operative treatment is statistically significantly inferior, resulting in 1.44 total mean discounted QALYs.2 Nonetheless, the validity of these findings has not been well documented previously in regards to age. In intervertebral disc herniation, the estimated the cost per QALY gained for surgical treatment relative to non-operative care is $69,403 in the general population and $34,355 in the Medicare population, demonstrating the value-added of these procedures.2 This study has certain limitations: it is a retrospective case series with limited sample size and setting. Nonetheless, evaluating 144 patients with 2-year outcomes of new surgical techniques assessed in a variety of populations provides suggestive findings for larger multicenter studies. Another limitation to this study is the lack of age-matched non-operative controls. Yet there is still debate whether non-operative controls serve better as controls than disease-specific, older controls as performed here, given that non-operative patients may undergo surgery in the future. Other studies have demonstrated high rates of non-adherence to randomized treatment group, which would not only pose logistic challenges, but also ethical challenges.2,16 Furthermore, a third limitation is the lack of analysis of age specific cut-off points to determine an age where surgery no longer provides value. This is an ongoing research endeavor at our institution as data collection continues, outcomes of patients ≥ 80 years will be later described.3,17-19 5 Conclusion Microdecompression is an effective treatment option for symptomatic LSS in both elderly and general adult populations. Patients ≥ 65 years of age may experience greater relief in back pain following microdecompression. Nonetheless, pain, disability, and health state are comparable at two-years post-operatively, despite differences between age groups. The charge
associated with lumbar decompression is comparable in patients < 65 and patients ≥ 65 years of age, however there may exist differences in reimbursement amounts.
Figure Legends Figure 1. Illustration of unilateral hemilaminectomy using a tubular retractor. Figure 2. Illustration of unilateral laminotomy and bilateral decompression using a tubular retractor. Figure 3. Illustration of a far lateral decompression using a tubular retractor. Figure 4. Back pain and leg pain visual analog scale, Oswestry Disability Index, and EuroQolFive Dimensions Valuation vs. Time, categorized by age group. * p<0.05 ** p<0.01 ***p<0.001
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Mean±SD or Proportion of Cases (%) Patient characteristics Age (years) Sex (male) Body Mass Index >30 kg/m² Current smoker Diabetes Prior spine surgery Preoperative radiographs Spondylolisthesis ≥ 4 mm Scoliosis ≥ 10° Operative details Disc procedure Multiple levels Operative time (minutes) Length of stay (days) Intraoperative findings Synovial cyst Durotomy Additional outcomes Subsequent open revision Subsequent minor revision
Overall
Age < 65
Age ≥ 65
n
p
63.81 ± 11.63 71/144 (49.3%) 61/135 (45.2%) 18/144 (12.5%) 32/144 (22.2%) 31/144 (21.5%)
54.49 ± 9.64 31/67 (46.3%) 29/63 (46.0%) 12/67 (17.9%) 8/67 (11.9%) 14/67 (20.9%)
71.92 ± 5.53 40/77 (51.9%) 32/72 (44.4%) 6/77 (7.8%) 24/77 (31.2%) 17/77 (22.1%)
144 144 135 144 144 144
<0.001 0.497 0.853 0.067 0.006 0.863
36/142 (25.4%) 14/142 (9.9%)
15/66 (22.7%) 4/67 (6.0%)
21/76 (27.6%) 10/75 (13.3%)
142 142
0.503 0.142
24/144 (16.7%) 11/144 (7.6%) 107.65 ± 33.81 0.82 ± 1.14
21/67 (31.3%) 2/67 (3.0%) 106.51 ± 34.46 0.71 ± 1.14
3/77 (3.9%) 9/77 (11.7%) 108.63 ± 33.44 0.90 ± 1.15
144 144 144 144
<0.001 0.050 0.710 0.319
8/144 (5.6%) 14/144 (9.7%)
6/67 (9.0%) 6/67 (9.0%)
2/77 (2.6%) 8/77 (10.4%)
144 144
0.097 0.772
15/144 (10.4%) 18/144 (12.5%)
10/67 (14.9%) 8/67 (11.9%)
5/77 (6.5%) 10/77 (13.0%)
144 144
0.099 0.850
*
*
* *
Table 1: Summary of patient characteristics, preoperative radiographic findings, operative details, intraoperative findings, and additional outcomes for patients included in this study, with subgroup comparisons of patients < 65 and patients ≥ 65 years of age. There were a small number of unreported data points, resulting in fewer patients with an entered value for body mass index, spondylolisthesis ≥4 mm, and scoliosis ≥10° compared with all other values. *Denotes significance, p<0.05, between patients < 65 and patients ≥ 65 years of age.
Back Pain Age < 65 Age ≥ 65 Preoperative Mean ± SD 6.64 ± 3.10 6.46 ± 3.06 n 55 70 p (marginal) 0.770 1-year Mean ± SD 3.66 ± 3.18 2.43 ± 2.61 n 62 70 p (marginal) 0.017* p (preoperative) <0.001* 2-year Mean ± SD 3.68 ± 3.09 2.79 ± 2.81 n 57 70 p (marginal) 0.095 p (preoperative) <0.001* p (1-year) 0.618 p (age)
0.016*
Leg Pain Age < 65 Age ≥ 65
ODI Age < 65
Age ≥ 65
EQ-5D Age < 65 Age ≥ 65
7.69 ± 2.05 6.99 ± 2.71 58 70 0.202
56.93 ± 14.00 46.37 ± 19.53 44 57 0.005*
0.31 ± 0.32 0.40 ± 0.31 53 62 0.102
2.43 ± 3.15 1.99 ± 2.86 60 70 0.379 <0.001*
25.91 ± 18.92 19.90 ± 17.4 57 61 0.065 <0.001*
0.71 ± 0.32 0.79 ± 0.24 61 71 0.141 <0.001*
2.91 ± 3.15 2.59 ± 2.93 57 69 0.582 <0.001* 0.306
27.02 ± 19.79 24.38 ± 16.95 56 68 0.365 <0.001* 0.126
0.69 ± 0.31 0.71 ± 0.28 51 67 0.558 <0.001* 0.211
0.377
0.063
0.138
Table 2: Comparison of patient-reported outcome measures preoperatively, at 1-year follow-up, and at 2-year follow-up for patients included in this study. A linear mixed effects model was fit to the data in order to accomodate for missing outcomes; the model included a random effects term to account for repeated measures on individual patients. *Denotes significance, p<0.05, of patientreported outcome measure differences between age groups at each visit time (marginal), or of longitudinal differences compared to previous visits (preoperative, 1-year), or between age groups (age).
Laminectomy Age < 65
Age ≥ 65
Far Lateral Decompression Age < 65 Age ≥ 65
Medicare Charges Mean ± SD $7,293.29 ± $1,661.86 $7,298.28 ± $1,756.98 $8,441.53 ± $1,591.80 $8,075.73 ± $1,464.82 p 0.995 0.599 Medicare Reimbursements Mean ± SD $1,997.18 ± $607.98 $1,921.52 ± $652.89 $2,086.72 ± $636.33 $1,880.57 ± $603.87 p 0.792 0.467 Humana Reimbursements Mean ± SD $1,741.86 ± $292.63 $1,280.20 ± $319.85 p 0.002*
$2,354.09 ± $450.82 $1,428.04 ± $190.23 <0.001*
Table 3: Comparisons of costs data between age groups. Medicare and Humana costs data for single level laminectomy and far lateral decompression CPTs. Data regarding both charges and reimbursements was available for Medicare patients from 2005 to 2014. The Humana dataset contains data from 2007 to 2017 and reimbursement only. *Denotes significance, p<0.05, between mean dollar amounts for age groups.