Abstract
In the absence of randomised trials comparisons are often made between historical cohorts in an effort to compare new surgical techniques. This study simply compares two historical cohorts to assess the effect of time on outcome.
Using the Oswestry disability index (ODI), low back outcome score (LBO) and visual analogue score (VAS) 305 elective spinal patients with 6 month surgical follow-up were reviewed. Cohort one was 1995–1999 and consisted of 152 cases.
Cohort two was 153 cases operated upon during 2000–2005. The pre operative scores were remarkably similar, ODI of 57 in both groups. Suggesting the threshold for surgery remained unchanged with time.
The mean improvement in outcome was greater in the later cohort. In the 1995–1999 cohort the improvements were ODI 23, LBO 16, and VAS 3.4, in the second cohort 2000–2005 the change was ODI 28, LBO 20 and VAS 3.9.
Recorded complications reduced from 40 to 27. Incidental durotomy was similar at 15 and 16 in both. Anterior approaches resulted in a single venous tear in each group. Revision cases accounted for 16 early and 12 later cases. Probably the most significant difference was the reduction in the number utilising instrumentation. The early group had 53 instrumented cases out of 152, in the later group 35 out of 153 had instrumentation. The number of anterior fusion cases decreased by almost half from 15 to 8 in the later cohort.
Conclusion: Improved outcomes occurred with time suggesting experiential learning. The decrease in complications and decreases in instrumentation usage may be linked to this. The only significant identified change in case mix was a reduction in fusion for axial back pain.
Correspondence should be addressed to: Mr N. J. Henderson, BASS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
