Our main purpose was to study the recovery of the spinal fusion patients during a one-year follow-up and compare our patients reported outcomes (PRO) to the values of a matched general population sample. The results showed that despite considerable improvement during the follow-up the patients did not reach the level of the matched general population in either disability or the physical component of the HRQoL.
To our knowledge, this is the first study where the PROs of spinal fusion patients have been compared to general population values. The general population subjects showed minimal disability in the mean ODI scores according to the original scoring, while the fusion patients’ mean ODI scores were preoperatively severe and at one year after the spinal fusion surgery remained moderate . Therefore, inspite of recovery the disability according to the ODI did not decrease to the level of general population in our follow-up in males or in females. One explanation for this might be, that the patients undergoing fusion operation have often suffered from longstanding spinal symptoms which may have caused permanent changes to their life and behavior.
Interestingly the change in the ODI between 3 months and one year was minimal. This finding suggests that already the early recovery at three months may probably have quite high prognostic value when assessing the success of the treatment, also over a longer period. This result is supported by a finding in the earlier literature . In a study of 96 patients undergoing spinal fusion, pain measurements were conducted at 6 months and then yearly over a total follow-up of 5 years. An interesting finding was that the improvement in the pain scale was biggest at 6 months and in the ODI at one year. The improvements seen in this early phase were maintained throughout the remainder of the follow-up period .
In the present study, one of the main findings concerning disability was that the mean levels of the ODI had not reached the values of the general population in either sex at one year post surgery. In comparison with the results in disability reported in the literature, in a trial implemented at 5 spine centers with 497 patients receiving one or two level spinal fusion, the mean ODI improved by 22 points at one year postoperatively. The preoperative level of the ODI varied in different subgroups from 48 to 56 . In the Swedish Lumbar Spine Study, which was a multicenter randomized controlled trial where patients were randomized into a surgical or a control group, 222 patients received spinal fusion either by non-instrumented fusion, by instrumented posterolateral fusion or by circumferential fusion. In the surgical group, the mean ODI improved from 47 to 36 (p < 0.0001), at two-year follow up . In a prospective randomized controlled study of 111 patients with adult isthmic spondylolisthesis the preoperative ODI scores were not reported but at two years in the surgical group the mean ODI score was 26 (95% CI 18.1 to 31.6) . In our study at one year the mean positive change of the ODI in female patients was 25 (95% CI 22 to 28) and in male patients 17 (95% CI 13 to 21) and the corresponding mean ODI scores were 22 (SD 17) and 23 (SD 20).
In the present study, the spinal fusion patients reached the values of their matched population sample in the mental component (MCS) of SF-36 but not in the physical component (PCS). Preoperatively, the value of Role Physical was highest in patients in both sexes in the mean ratio analysis. At 12 months, Vitality, Mental Health and Role-Emotional were the only dimensions in the female patients that reached general population values. In males, this was true only for Vitality and Mental Health. Interestingly, the Pain dimension was still significantly worse in patients at the one-year follow-up compared to the general population. This prompts the question: how should we manage the physical aspect in the long term recovery. The earlier literature includes a multicenter study with 497 patients undergoing one- or two-level spinal fusion with several techniques. The results showed an improvement in mean PCS of 9.9 points over a one-year follow up . This finding is confirmed by our study in which the mean PCS improved by 11 (95% CI 10 to 13) points in females and 10 (95% CI 7 to 12) in males in one-year follow-up. Another study with 100 primary spinal fusion patients who received decompression and single-level posterior lumbar interbody fusion reported HRQoL scores in both the PCS-12 and MCS-12 that approached the Australian population norm over a follow-up varying from 12 months to 5 years . The mean postoperative PCS-12 score was 39 (95% CI 37 to 42) and MCS-12 score 52 (95% CI 50 to 55) as compared with the corresponding population norm values of 44 (95% CI 43 to 46) and 54 (95% CI 53 to 55) . To our knowledge no other studies have used a population-based method when exploring the success of fusion operations.
After spinal fusion operations it is seldom a realistic goal to expect that all of the disability will disappear. It is also obvious that the level of disability, and hence quality of life, depends on various factors such as patient’s age, possible chronic neuropathic pain, and other possible diseases in addition to spinal disorders. However, in the present study, the prevalence of diabetes or most of the other co-morbidities, was similar in patients and in the general population. Interestingly only cardiovascular and rheumatoid diseases in females were more often present in patients than in the general population. Patients who have undergone spinal fusion may also get other sources of pain like osteoarthritis of hip or knee and these reasons may confuse the answers in the questionnaires. Furthermore, in spinal fusion surgery, complications and failed fusions may worsen the results. Finally, in the evaluation of disability of the patients it is essential to understand the level of disability in the general population of same age and sex. This data is important in evaluating the influence of surgery for the patients and also in surgical decision making in individual cases.
Study strengths and limitations
The present study includes register based, not selected, consecutive patient material. The main strength of this study is the comparison between patients and the general population in disability and HRQoL scores. To our knowledge, this is the only study in which the PROs of fusion patients have been compared to those of a matched general population sample. An additional strength is the accurate timing of the data collection. The preoperative data were collected one to two weeks prior to the operation and the data collection timepoints during the follow-up were strict. In addition, the population based data were collected from the same residential area compared to the patients. In the analyses, females and males have been systematically stratified. This is because the majority of the patients operated on were females and because there was a significant gender difference in the ODI in the general population between females and males. A limitation in this study is the lack of analyses stratified by surgical diagnostic indication for the fusion operation. This is due the number of patients in this material, which could have led to a too small sample size in some of the diagnostic subgroups and lack of statistical representation of the phenomenon. 3Another limitation is that as a part of the surgical procedure in our patients, also decompression through laminectomy was performed whenever appropriate. This might cause difficulty to determine how much of the total improvement of HRQoL is caused by the fusion alone and how much by the coexisting decompression procedure. Further, a limitation is also the possible bias in answering to the general population questionnaire. Would those general population individuals who have back pain, reply more eagerly, making the observed difference between general population and patients smaller than the true value? In the literature it has been shown, that the life-time prevalence of back-pain in normal population is even 84% . This leads to thinking, that even though there might be a bias in answering profile, it is not affecting the results between the patients and general population significantly. The follow-up in our study was 12 months. This period of time seemed to be sufficient to show, that results in disability and quality of life stabilized after three months. Although a one-year of follow-up indicated a trend towards recovery, further follow-ups of several years are needed to evaluate the longer term outcome.