|Comparison of interbody fusion approaches for disabling low back pain
|Hacker R J
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
Using PLIF-BAK procedure (posterior lumbar interbody fusion and an interbody fixation device (BAK; Spine-Tech, Inc., Minneapolis, MN)) in the treatment of patients with disabling low back pain.
Economic study type
Patients suffering from disabling low back pain. Those unable to perform, or who were substantially impaired in the performance of, their job or daily activities for a minimum of six months formed the patient domain.
Hospital. The economic study was carried out in the USA.
Dates to which data relate
Effectiveness and resource use data related to the 360 degree fusion technique corresponded to patients treated between 1991 and 1993. The corresponding data for patients treated by the PLIF-BAK procedure related to the period commencing 1993 and with a follow-up every 3 months for 2 years, (and, thereafter, as required). The price year was not explicitly specified.
Source of effectiveness data
Effectiveness data were derived from a single study.
Link between effectiveness and cost data
Costing was retrospectively performed on the same patient sample as that used in the effectiveness analysis.
Power calculations were not used to determine the sample size. The study sample consisted of 54 patients in the PLIF-BAK group with a mean (SD) age of 44.72 (8.16) years and 21 patients in the 360 degree fusion group with a mean (SD) age of 43.14 (9.31) years. One surgeon (the author) performed all the surgical procedures.
Retrospective cohort study, carried out in a single centre. The duration of the follow-up was every 3 months for 2 years, and as required thereafter. No loss to follow-up was reported. The patients who underwent the PLIF-BAK procedure had a choice between each of the two procedures, and all chose to be treated by the PLIF-BAK procedure.
Analysis of effectiveness
The analysis was based on intention to treat. The health outcome measures were the number of patients who were judged as fused, partially fused, or not fused using plain radiographs, blood loss, operating time, percentage of patients reporting graft pain, percentage working within 3 months, percentage working at last follow-up, percentage with good or excellent outcome (patients' satisfaction), percentage developing painful pseudarthrosis, and deep wound infection. Patients' outcomes related to employment status, activities of daily living, pain, general health, and satisfaction were collected through a self-reported evaluation questionnaire completed by patients after each follow-up assessment. Study groups were comparable in terms of age, sex, injury history, and history of previous surgery. The effects of outcome variables of potential covariates (such as age, gender, length of disability, number of fusion levels, workers' compensation insurance coverage) were assessed.
Of the 24 PLIF-BAK patients who had completed 1 or 2-year radiographic assessment, 20 (83%) had radiographic fusion, 3 had partial fusion, and 1 was not fused. The number of patients developing painful pseudarthrosis with failure of graft incorporation anteriorly was 5 in the 360 degree fusion group (reoperative fixation was performed in all 5 cases) versus 0 in the PLIF-BAK group. Four PLIF-BAK patients had an extra operation, (in 2 cases this was at an adjacent level after discography revealed discogenic pain in what had previously been a nonpainful degenerative disc). Blood loss was 900 (SD, 755) ml in the 360 degree fusion group versus 300 (248) in the PLIF-BAK group (p<0.0001). Operating time was 250 (84) minutes in the 360 degree fusion group versus 120 (34) minutes in the PLIF-BAK group (p<0.0001). Percentage of patients reporting graft pain was 45% in the 360 degree fusion group and 17% in the PLIF-BAK group, (p=0.03). Percentage working within 3 months was 0% in the 360 degree fusion group versus 47% in the PLIF-BAK group (p<0.0002). The corresponding values in terms of percentage working at last follow-up was 88% in the 360 degree fusion group versus 73% in the PLIF-BAK group (p=0.25). Percentage of patients rating their outcomes as good or excellent(patients' satisfaction) was 74% in the 360 degree fusion group and 68% in the PLIF-BAK group, (p=0.64). No deep wound infection was observed in any of the two groups.
The two PLIF-BAK reoperations for recurrent low back pain in this series confirm that adjacent-level disc abnormalities should be considered. Significantly shorter operative times, less blood loss, and quicker discharge favoured the PLIF-BAK compared with the 360 degree fusion procedure. Although PLIF operations have the potential for greater morbidity because of the necessary nerve root and thecal sack retraction, a dearth of neurologic complications in this study suggests the wide bone removal for PLIF-BAK allows safe exposure of the interspace.
Measure of benefits used in the economic analysis
No summary benefit measure was identified in the economic analysis, and only separate clinical outcomes were reported. As such, the analysis may be regarded as a cost-consequences analysis.
Costs were not discounted despite the 2-year follow-up period. Some quantities were reported separately from the costs. Cost items were reported separately in general categories. The cost analysis covered the costs of hospital treatment (operating room charges, surgeon fees, room charges, implants, etc.), other medical costs (including physical therapy, orthotics, etc), and disability (postoperative disability pay). The perspective adopted in the cost analysis was that of insurance carriers. The sources for resource use and cost data were chart entries and billing records supplied by insurance carriers. The date to which the price data referred was not explicitly specified.
Statistical analysis of costs
Median tests (for non-normally distributed variables) were used to compare the groups in terms of different cost categories.
Estimated benefits used in the economic analysis
Not applicable. The reader is referred to the effectiveness results reported earlier.
The median overall cost was about $49,800 for the PLIF-BAK group versus $73,200 for the 360 degree fusion group (the differences between the two groups were not significant in terms of hospital related costs (p=0.09) and other medical costs (p=0.09), while a significant difference was observed in terms of disability costs (p=0.0003)).
Synthesis of costs and benefits
Posterior lumbar interbody fusion-BAK achieves equal patient satisfaction but fiscally surpasses the 360 degree fusion approach. Today's environment of regulated medical practice requires the surgeon to consider cost-effectiveness when performing surgery for low back pain.
CRD COMMENTARY - Selection of comparators
The comparator (360 degree fusion procedure) was chosen because of its initial use in the study institution. You , as a database user, should consider whether this is a widely used health technology in your own setting.
Validity of estimate of measure of benefit
The internal validity of the estimates of benefit cannot reasonably be guaranteed due to the retrospective nature of the study design and its relatively small sample size (especially for the 360 degree fusion procedure). Although the study was a cost-consequence analysis this may represent the most appropriate approach for this particular type of intervention.
Validity of estimate of costs
Some quantities were reported separately from the costs. Adequate details of methods of cost estimation were given. The retrospective nature of the cost analysis plus the use of charge data rather than true costs may cast doubts on its internal validity and generalisability.
The authors' conclusion may not to be fully justified given the limitations of the study design identified above. The issue of generalisability to other settings or countries was not addressed. Appropriate comparisons were made with other studies.
Implications of the study
Longer follow-up will be needed to determine the sustainability of the favourable outcomes identified over time.
Hacker R J. Comparison of interbody fusion approaches for disabling low back pain. Spine 1997; 22(6): 660-665
Subject indexing assigned by NLM
Adult; Aged; Back Pain /physiopathology /surgery; Disabled Persons; Female; Health Care Costs; Humans; Length of Stay; Male; Middle Aged; Pain, Postoperative; Postoperative Complications; Spinal Fusion /economics /methods; Treatment Outcome
Date bibliographic record published
Date abstract record published