Comparative outcomes and cost-utility following surgical treatment of focal lumbar spinal stenosis compared with osteoarthritis of the hip or knee: part 2--estimated lifetime incremental cost-utility ratios.

BACKGROUND CONTEXT

Although total hip arthroplasty (THA) and total knee arthroplasty (TKA) have been widely accepted as highly cost-effective procedures, spine surgery for the treatment of degenerative conditions does not share the same perception among stakeholders. In particular, the sustainability of the outcome and cost-effectiveness following lumbar spinal stenosis (LSS) surgery compared with THA/TKA remain uncertain.

PURPOSE

The purpose of the study was to estimate the lifetime incremental cost-utility ratios for decompression and decompression with fusion for focal LSS versus THA and TKA for osteoarthritis (OA) from the perspective of the provincial health insurance system (predominantly from the hospital perspective) based on long-term health status data at a median of 5 years after surgical intervention.

STUDY DESIGN/SETTING: An incremental cost-utility analysis from a hospital perspective was based on a single-center, retrospective longitudinal matched cohort study of prospectively collected outcomes and retrospectively collected costs.

PATIENT SAMPLE

Patients who had undergone primary one- to two-level spinal decompression with or without fusion for focal LSS were compared with a matched cohort of patients who had undergone elective THA or TKA for primary OA.

OUTCOME MEASURES

Outcome measures included incremental cost-utility ratio (ICUR) ($/quality adjusted life year [QALY]) determined using perioperative costs (direct and indirect) and Short Form-6D (SF-6D) utility scores converted from the SF-36.

METHODS

Patient outcomes were collected using the SF-36 survey preoperatively and annually for a minimum of 5 years. Utility was modeled over the lifetime and QALYs were determined using the median 5-year health status data. The primary outcome measure, cost per QALY gained, was calculated by estimating the mean incremental lifetime costs and QALYs for each diagnosis group after discounting costs and QALYs at 3%. Sensitivity analyses adjusting for +25% primary and revision surgery cost, +25% revision rate, upper and lower confidence interval utility score, variable inpatient rehabilitation rate for THA/TKA, and discounting at 5% were conducted to determine factors affecting the value of each type of surgery.

RESULTS

At a median of 5 years (4-7 years), follow-up and revision surgery data was attained for 85%-FLSS, 80%-THA, and 75%-THA of the cohorts. The 5-year ICURs were $21,702/QALY for THA; $28,595/QALY for TKA; $12,271/QALY for spinal decompression; and $35,897/QALY for spinal decompression with fusion. The estimated lifetime ICURs using the median 5-year follow-up data were $5,682/QALY for THA; $6,489/QALY for TKA; $2,994/QALY for spinal decompression; and $10,806/QALY for spinal decompression with fusion. The overall spine (decompression alone and decompression and fusion) ICUR was $5,617/QALY. The estimated best- and worst-case lifetime ICURs varied from $1,126/QALY for the best-case (spinal decompression) to $39,323/QALY for the worst case (spinal decompression with fusion).

CONCLUSION

Surgical management of primary OA of the spine, hip, and knee results in durable cost-utility ratios that are well below accepted thresholds for cost-effectiveness. Despite a significantly higher revision rate, the overall surgical management of FLSS for those who have failed medical management results in similar median 5-year and lifetime cost-utility compared with those of THA and TKA for the treatment of OA from the limited perspective of a public health insurance system.