We carried out a prospective study looking at the functional outcome and post-procedure segmental instability after lumbar decompression using a flip osteotomy technique that involved unilateral subperiosteal muscle dissection with hinging of the spinous processes thereby preserving the integrity of the posterior elements for unilateral or bilateral lumbar spine decompression.

Between February 2007 and February 2008, 51 patients (29 male and 22 female) diagnosed with degenerative and congenital lumbar stenosis with an average age of 60, underwent central and lateral canal decompression using the flip osteotomy technique. An average of two segments (range 1-3 segments) was decompressed. Patients with a history of previous spinal surgery, spinal fusion, existing degenerative spondylolisthesis or cauda equina syndrome were excluded.

All patients were followed up for a mean of 1.5 years. Five outcome measures were used – visual analogue scale for pain, Likert scale for functional status, symptom specific well-being score, general well-being score, number of days incapacitated in last 4 weeks. The outcomes measures were recorded pre-operatively, 6 weeks and one year post-operatively. Successful surgical outcome was defined as an improvement in at least four out of five outcome measures.

90% (46 patients) of patients had a successful surgical outcome. There was a statistically significant improvement in all outcome criteria (p<0.005) at the 6-week post-operative mark as compared to pre-operatively, with marginal improvement at one year post-surgery. There was no evidence of progressive lumbar segmental instability at one year post-operatively using our flip osteotomy technique

Decompression of the lumbar spine for lumbar stenosis using the flip osteotomy technique is a safe approach for one or multi-level stenosis with good outcomes and no evidence of significant iatrogenic segmental spinal instability.

We declare no conflict of interest and ethical approval was obtained

Study Design: Prospective Cohort Study.

Summary of Background Data: It has previously been suggested that fulcrum bending radiographs (Cheung et al Luk 1997) and traction radiography under anaesthetic (Davis et al 2003) predict the flexibility and correction obtained following surgery better than conventional supine bending radiographs.

Objective: To compare fulcrum bending radiographs and traction radiographs for the prediction of surgical correction of idiopathic scoliosis.

Subjects: The study was based on 16 patients with a diagnosis of idiopathic scoliosis who underwent corrective surgery.

Outcome measures: The Cobb angle of the major curve was compared on the standing AP and fulcrum bending radiograph taken in the pre-op assessment clinic, the traction film undertaken under anaesthetic immediately prior to surgery and the first post operative standing radiograph taken. The post operative correction of the major curve was analysed using regression techniques and adjusted for the base line curve angle of the major curve.

Results: The results were presented as an estimate of the parameter coefficient in the model associated with 95% confidence intervals. The median pre-operative Cobb angle of the major curve was 69 degrees, on the fulcrum bending film was 47 degrees, on the traction film was 30 degrees, and on the first post operative film was 30 degrees. There was no evidence to suggest that the fulcrum Cobb had an effect on the post operative correction of the major curve. There was however evidence to suggest that the traction Cobb angle had an effect on the post operative correction of the major curve (parameter estimate 0.87) 95% CI (0.174, 1.399), T value = 2.83, P = 0.016.

Conclusion: Traction radiographs under anaesthetic better predict the surgical correction obtained in adolescent idiopathic scoliosis compared to fulcrum bending radiographs. These two techniques have not been directly compared before.