Introduction: Spinal fusions have been shown to be useful in correcting spinal deformities resulting from degenerative disc disease. We sought to produce a prospective analysis of functional outcomes following lumbar spinal fusion surgery for degenerative spondylolisthesis or degenerative scoliosis secondary to degenerative disc disease. We present the interim results from our case cohort of 74 patients.

Methods: Over a period of 3 years (2005–2007), all patients who presented to this private practice with symptoms of canal stenosis or radicular pain secondary to degenerative spondylolisthesis or degenerative scoliosis were offered decompressive laminectomy and posterior lumbar interbody fusion (PLIF) surgery with interbody cages, pedicle screw instrumentation, bone morphogenic protein (BMP) and bicalcium phosphate (BCP). Patients who presented only with low back pain and did not have radicular pain or neurogenic claudication were excluded from this study. All patients who were offered spinal fusion surgery were consecutively offered the opportunity to enrol in this functional cohort analysis. Those patients who consented were prospectively entered into this functional analysis and were asked to complete Oswestry and SF-36 function questionnaires preoperatively and post-operatively. Post-operative data has been collected in some cases up to 16 months postoperatively. Patients were also assessed post-operatively by the surgeon and given an Odom clinical assessment score. Complications were also collated.

Results: 102 patients were offered surgery with 18 patients not consenting to participate in this study. Of the 84 patients who consented to participate in this study, 10 patients failed to submit both pre-operative and postoperative questionnaires, leaving 74 patients who were followed for a median 7 months (range of 1.5–16 months). There were 30 males and 44 females in the study with a median age of 73 (range 46–89). Of these 74 patients, 63 had degenerative spondylolisthesis and 11 had degenerative scoliosis. 52 patients had sufficient follow-up to assess bony fusion, of which 1 patient failed to fuse. 32 of the patients who fused reported to have improved, but 16 did not and the remainder did not submit both pre-operative and post-operative questionnaires. For the SF-36 questionnaire, the median pre-operative SF-36 score was 30 (96.6% CI 26–35) and the median post-operative SF-36 score was 48 (95.3% CI 42–56). The mean difference between the preoperative and post-operative SF-36 scores was 14 (95% CI 11–18) (p< 0.0001. The median preoperative Oswestry score was 46 (96.6% CI 42–50) and the median post-operative Oswestry score was 30 (96.6% CI 24–40) and the median post-operative Oswestry score was 30 (96.6% CI 24–40). The mean difference between the preoperative and post-operative Oswestry scores was 14 (95% CI 10–19) (p= 0.0001). 45 patients (61%) reported improvements of greater than 20 between their pre-operative and post-operative scores in either their SF-36 or Oswestry questionnaires. Of these 45 patients, 40 (89%) were also given moderate or good Odom (clinical) scores. 29 patients (39%) reported that they had not experienced improvement in their symptoms based on either their SF-36 or Oswestry questionnaires, with 12 (41%) of those 29 patients scoring poorly on their Odom scores. In all, there were 18 complications ranging from wound collections (4) and breakdowns (2) to repositioning of screws (6) and nerve root injury (2), to DVT (1) and transfusion (3).

Discussion: Interim results suggest that most patients undergoing PLIF and pedicle screw surgery with decompressive laminectomy for treatment of degenerative spondylolisthesis and degenerative scoliosis report significant improvements in function which correlate fairly well with clinical assessments performed by the surgeon at pre-operative and post-operative reviews. IInterestingly, patients generally reported either significant improvements (rather than borderline improvements) or that they had not improved at all, and that those who did report significant improvements also generally scored well on their Odom assessments. These reported improvements currently seem to be independent of whether bony fusion is achieved or not, as 16 of the 29 patients who did not report improvement actually achieved fusion. This is not unexpected as the initial PLIF procedure provides initial pre-fusion in situ rigid internal fixation.