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  • Author or Editor: Clinton Devin x
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Owoicho Adogwa, Scott L. Parker, David N. Shau, Stephen K. Mendenhall, Clinton J. Devin, Joseph S. Cheng and Matthew J. McGirt

Object

Over the past decade, there has been a dramatic increase in the number of spinal fusions performed in the US and a corresponding increase in the incidence of adjacent-segment disease (ASD). Surgical management of symptomatic ASD consists of decompression of neural elements and extension of fusion. It has been shown to have favorable long-term outcomes, but the cost-effectiveness remains unclear. In this study, the authors set out to assess the cost-effectiveness of revision surgery in the treatment of ASD over a 2-year period.

Methods

Fifty patients undergoing neural decompression and extension of fusion construct for ASD-associated back and leg pain were included in the study. Two-year total back-related medical resource utilization, missed work, and health state values (quality-adjusted life years [QALYs], calculated from the EQ-5D with US valuation) were assessed. Two-year resource use was multiplied by unit costs based on Medicare national allowable payment amounts (direct cost), and patient and caregiver workday losses were multiplied by the self-reported gross-of-tax wage rate (indirect cost). Mean total 2-year cost per QALY gained after revision surgery was assessed.

Results

The mean (± SD) interval between prior fusion and revision surgery for ASD was 3.07 ± 2.02 years. A mean cumulative 2-year gain of 0.76 QALYs was observed after revision surgery. The mean total 2-year cost of extension of fusion constructs was $47,846 ± $32,712 (surgery cost: $24,063 ± $300; outpatient resource utilization cost: $4175 ± $3368; indirect cost: $19,607 ± $32,187). Revision decompression and extension of fusion was associated with a mean 2-year cost per QALY gained of $62,955.

Conclusions

In the authors' practice, revision decompression and extension of fusion provided a significant gain in health state utility for patients with symptomatic ASD, with a 2-year cost per QALY gained of $62,995. When indicated, revision surgery for ASD is a valuable treatment option for patients experiencing back and leg pain secondary to ASD. The findings provide a value measure of surgery that can be compared with future cost-per-QALY-gained studies of medical management or alternative surgical approaches.

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Scott L. Parker, Stephen K. Mendenhall, David N. Shau, Owoicho Adogwa, William N. Anderson, Clinton J. Devin and Matthew J. McGirt

Object

Spine surgery outcome studies rely on patient-reported outcome (PRO) measurements to assess treatment effect, but the extent of improvement in the numerical scores of these questionnaires lacks a direct clinical meaning. Because of this, the concept of a minimum clinically important difference (MCID) has been used to measure the critical threshold needed to achieve clinically relevant treatment effectiveness. As utilization of spinal fusion has increased over the past decade, so has the incidence of same-level recurrent stenosis following index lumbar fusion, which commonly requires revision decompression and fusion. The MCID remains uninvestigated for any PROs in the setting of revision lumbar surgery for this pathology.

Methods

In 53 consecutive patients undergoing revision surgery for same-level recurrent lumbar stenosis–associated back and leg pain, PRO measures of back and leg pain were assessed preoperatively and 2 years postoperatively, using the visual analog scale for back pain (VAS-BP) and leg pain (VAS-LP), Oswestry Disability Index (ODI), Physical and Mental Component Summary categories of the 12-Item Short Form Health Survey (SF-12 PCS and MCS) for quality of life, Zung Depression Scale (ZDS), and EuroQol-5D health survey (EQ-5D). Four established anchor-based MCID calculation methods were used to calculate MCID (average change; minimum detectable change; change difference; and receiver operating characteristic curve analysis) for 2 separate anchors (health transition index of the SF-36 and the satisfaction index).

Results

All patients were available for 2-year PRO assessment. Two years after surgery, a significant improvement was observed for all PROs assessed. The 4 MCID calculation methods generated a range of MCID values for each of the PROs (VAS-BP 2.2–6.0, VAS-LP 3.9–7.5, ODI 8.2–19.9, SF-12 PCS 2.5–12.1, SF-12 MCS 7.0–15.9, ZDS 3.0–18.6, and EQ-5D 0.29–0.52). Each patient answered synchronously for the 2 anchors, suggesting both of these anchors are equally appropriate and valid for this patient population.

Conclusions

The same-level recurrent stenosis surgery-specific MCID is highly variable based on calculation technique. The “minimum detectable change” approach is the most appropriate method for calculation of MCIDs in this population because it was the only method to reliably provide a threshold above the 95% confidence interval of the unimproved cohort (greater than the measurement error). Based on this method, the MCID thresholds following neural decompression and fusion for symptomatic same-level recurrent stenosis are 2.2 points for VAS-BP, 5.0 points for VAS-LP, 8.2 points for ODI, 2.5 points for SF-12 PCS, 10.1 points for SF-12 MCS, 4.9 points for ZDS, and 0.39 QALYs for EQ-5D.

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Owoicho Adogwa, Scott L. Parker, David N. Shau, Stephen K. Mendenhall, Oran Aaronson, Joseph S. Cheng, Clinton J. Devin and Matthew J. McGirt

Object

Despite advances in technology and understanding in spinal physiology, reoperation for symptomatic same-level recurrent stenosis continues to occur. Although revision lumbar surgery is effective, attention has turned to the question of the utility and value of revision decompression and fusion procedures. To date, an analysis of cost and heath state gain associated with revision lumbar surgery for recurrent same-level lumbar stenosis has yet to be described. The authors set out to assess the 2-year comprehensive cost of revision surgery and determine its value in the treatment of same-level recurrent stenosis.

Methods

Forty-two patients undergoing revision decompression and instrumented fusion for same-level recurrent stenosis–associated leg and back pain were included in this study. Two-year total back-related medical resource utilization, missed work, and health state values (quality-adjusted life years [QALYs], calculated from the EQ-5D with US valuation) were assessed. Two-year resource use was multiplied by unit costs based on Medicare national allowable payment amounts (direct cost), and patient and caregiver workday losses were multiplied by the self-reported gross-of-tax wage rate (indirect cost). Mean total 2-year cost per QALY gained after revision surgery was assessed.

Results

The mean (± SD) interval between prior and revision surgery was 4.16 ± 4.64 years. Bone morphogenetic protein was used in 7 cases of revision arthrodesis (16.7%). A mean cumulative 2-year gain of 0.84 QALY was observed after revision surgery. The mean total 2-year cost of revision fusion was $49,431 ± $7583 (surgery cost $21,060 ± $4459; outpatient resource utilization cost $9748 ± $5292; indirect cost $18,623 ± $9098). Revision decompression and extension of fusion was associated with a mean 2-year cost per QALY gained of $58,846.

Conclusions

In the authors' practice, revision decompression and fusion provided a significant gain in health state utility for patients with symptomatic same-level recurrent stenosis, with a 2-year cost per QALY gained of $58,846. When indicated, revision surgery for same-level recurrent stenosis is a valuable treatment option for patients experiencing back and leg pain secondary to this disease. The authors' findings provide a value measure of surgery that can be compared with the results of future cost-per-QALY-gained studies of medical management or alternative surgical approaches.

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Scott L. Parker, Stephen K. Mendenhall, David Shau, Owoicho Adogwa, Joseph S. Cheng, William N. Anderson, Clinton J. Devin and Matthew J. McGirt

Object

Spinal surgical outcome studies rely on patient-reported outcome (PRO) measurements to assess treatment effect. A shortcoming of these questionnaires is that the extent of improvement in their numerical scores lack a direct clinical meaning. As a result, the concept of minimum clinical important difference (MCID) has been used to measure the critical threshold needed to achieve clinically relevant treatment effectiveness. As utilization of spinal fusion has increased over the past decade, so has the incidence of adjacent-segment degeneration following index lumbar fusion, which commonly requires revision laminectomy and extension of fusion. The MCID remains uninvestigated for any PROs in the setting of revision lumbar surgery for adjacent-segment disease (ASD).

Methods

In 50 consecutive patients undergoing revision surgery for ASD-associated back and leg pain, PRO measures of back and leg pain on a visual analog scale (BP-VAS and LP-VAS, respectively), Oswestry Disability Index (ODI), 12-Item Short Form Health Survey Physical and Mental Component Summaries (SF-12 PCS and MCS, respectively), and EuroQol-5D health survey (EQ-5D) were assessed preoperatively and 2 years postoperatively. The following 4 well-established anchor-based MCID calculation methods were used to calculate MCID: average change; minimum detectable change (MDC); change difference; and receiver operating characteristic curve (ROC) analysis for the following 2 separate anchors: health transition item (HTI) of the SF-36 and satisfaction index.

Results

All patients were available for 2-year PRO assessment. Two years after surgery, a statistically significant improvement was observed for all PROs (mean changes: BP-VAS score [4.80 ± 3.25], LP-VAS score [3.28 ± 3.25], ODI [10.24 ± 13.49], SF-12 PCS [8.69 ± 12.55] and MCS [8.49 ± 11.45] scores, and EQ-5D [0.38 ± 0.45]; all p < 0.001). The 4 MCID calculation methods generated a range of MCID values for each of the PROs (BP-VAS score, 2.3–6.5; LP-VAS score, 1.7–4.3; ODI, 6.8–16.9; SF-12 PCS, 6.1–12.6; SF-12 MCS, 2.4–10.8; and EQ-5D, 0.27–0.54). The area under the ROC curve was consistently greater for the HTI anchor than the satisfaction anchor, suggesting this as a more accurate anchor for MCID.

Conclusions

Adjacent-segment disease revision surgery–specific MCID is highly variable based on calculation technique. The MDC approach with HTI anchor appears to be most appropriate for calculation of MCID after revision lumbar fusion for ASD because it provided a threshold above the 95% CI of the unimproved cohort (greater than the measurement error), was closest to the mean change score reported by improved and satisfied patients, and was not significantly affected by choice of anchor. Based on this method, MCID following ASD revision lumbar surgery is 3.8 points for BP-VAS score, 2.4 points for LP-VAS score, 6.8 points for ODI, 8.8 points for SF-12 PCS, 9.3 points for SF-12 MCS, and 0.35 quality-adjusted life-years for EQ-5D.