The cost-effectiveness analysis utilized data from 1,191 participants, including 775 who underwent surgery and 416 who were treated non-operatively for the entire follow-up period based on data collected through December 5, 2006. Differences in baseline characteristics by treatment received are shown in . Surgical patients were younger, less likely to be working fulltime and more likely to be receiving or have applied for disability or social security compensation and more likely to have L5-S1 herniation. At baseline, patients who went on to surgery had significantly worse bodily pain, physical function, mental health and Oswestry Disability Index and EQ-5D scores than non-operative patients.
Patient baseline demographic characteristics and health status
Mean health state values improved over time for both surgical and non-operative patients as shown in . Total mean discounted QALYs were 1.64 (95%CI: 1.62, 1.67) for surgical patients and 1.44 (95%CI: 1.41, 1.47) for non-surgical patients, a difference of 0.21 (95%CI: 0.16, 0.25).
Mean health state values and 95% confidence intervals over time by treatment received.
Most surgeries (96%, 741/771) were classified under DRG 500 (back and neck procedures without complications) and were assigned mean surgery costs of $12,754 (95%CI: $12.740, 12,760). A total of 22/771 (3%) primary surgeries were classified as having complications (DRG 499) with mean surgery costs estimated at $19,063 (95%CI: $18.960, 19,160). Spinal fusion was uncommon among primary surgeries, but occurred in 8 patients. A total of 63 repeat surgeries occurred in 53 (6.8%) surgery patients, with a mean cost of $28,019 (95%CI: $19,950, 26,730). For each surgery type, use of Medicare pricing decreased surgery costs substantially with mean costs of $6,828 for DRG 500, $7,082 for DRG 499, and $9,757 for repeat surgery.
Total mean costs were $27,273 (95%CI: $26,009, $28,644) for surgically treated patients and $13,135 (95%CI: $11,244, $14,902) for non-operative patients (). Reported use of any health care visits did not differ between the treatment groups (90% surgery vs. 88% non-operative, p=0.16). Fewer than half of participants reported physical therapy visits (50% surgery vs, 44% non-operative, p=0.064); chiropractor visits were infrequent (13% surgery vs. 15% non-operative, p=0.49); and use of acupuncture was reported by only 5% of participants. Those treated surgically reported more diagnostic test use (53% of surgery vs. 34% of non-operative patients, p<0.001) and medication use (96% of surgery vs. 89% of non-operative patients, p<0.001) than non-operative patients, with use in both groups declining over time. Treatment groups differed significantly in use of oral steroids (8% surgery vs. 4% non-operative, p=0.011) and narcotics (77% surgery vs. 32% non-operative, p<0.001). Device use was similar in both groups and occurred among 40% of participants. Among surgery patients, the most frequently reported devices were brace, cane and orthopedic pillow, which were reported by 11%, 11% and 12%, respectively. Among non-operative patients orthopedic pillow (15%) and shoe inserts (15%) were among the most commonly reported devices.
As shown in , the proportion of participants reporting any missed work days was higher for those undergoing surgery than those treated non-operatively (58% surgery vs 36% non-operative, p<0.001). There were no differences between groups in missed homemaking days or unpaid caregiver use.
Missed work, missed homemaking, and days requiring unpaid caregivers by treatment. “Surgery” means surgery within 24 months of enrollment.
As depicted in , over the two-year period, indirect costs accounted for a substantial proportion of total costs in both groups (26% of cost for surgical patients and 57% of costs for non-operative patients). The distribution of non-surgical direct medical costs was similar between groups.
Cost distributions by treatment received over 24 months for A) total costs and B) direct medical non-surgical costs.
Direct medical costs and indirect costs for each time period are shown in . Both types of cost were highest during the first six weeks among those undergoing surgery. Mean indirect costs for non-operative patients tended to be higher over time than for surgically treated patients.
Mean costs by time period and treatment received. Asterisks show time period differences between treatment groups with p-value<0.05.
When all costs were considered, the cost per QALY gained for surgical treatment relative to non-operative care in the general population was $69,403 (95%CI: $49,523, $94,999) (). For those age 65 and older for whom Medicare surgery costs are more appropriate, the cost per QALY gained decreased to $34,355 (95%CI: $20,419, $25,512). Limiting costs considered to direct medical costs alone or to direct medical costs together with lost work days had little impact on the value of surgery relative to non-operative care (). Likewise, excluding those who reported that they were receiving compensation or had it pending at baseline had little impact on the ICER, which was estimated at $33,176 (95%CI: $18,348, $54,157) under Medicare pricing.
Figure 4 Incremental cost-effectiveness analysis results. A) Results from 1,000 bootstrap estimates of the difference in total costs and difference in QALYs with the mean incremental costeffectiveness ratio shown as a dashed line and the 95% confidence interval (more ...)
Mean cost per QALY gained for surgery relative to non-operative care for the general population and for the Medicare population (95% confidence intervals) when various costs are included.