STAND ALONE AXIALIF FOR L5/S1 FUSIONS

Abstract

This is a preliminary retrospective report on a novel technique for achieving fusion at the lumbo-sacral disc. Current methods of complete discectomy and instrumented fusion involve either a posterior approach and the insertion of cages or an anterior approach. Both methods involve quite extensive dissections with potential stabilising muscle stripping. They also require significant post operative analgesia, inpatient stay and post operative recovery. There are attendant risks of nerve injury, blood loss and thrombosis.

A novel method of approach from the sacrum via a ‘safe zone’, described by Yuan et al., is presented. The technique along with the anatomical considerations is described. The operation basically consists of a posterior sacrococcygeal incision and an x-ray guided approach to the anterior surface of the S1/S2 junction with blunt obturators. The L5/S1 disc is then accessed by drilling through the sacrum. The disc is then removed from within with shaped tools leaving the bulk of the annulus. The void created is filled with bone graft and the L5 vertebra fixed to the sacrum via a bolt. The initial results of the first 20 patients are presented. 21 patients have been operated upon but one has been lost to follow up due to a psychological disorder. That patients details have been excluded.

The patients underwent surgery between 4/7/06 and 8/10/07. All operative procedures were completed without complication, the operative time improving from 60 minutes to a ‘standard’ 45 minutes. There were no post operative complications. Two patients underwent additional procedures. One was an L4/5 Wallis ligament the other an inter-transverse non instrumented fusion. Several patients required a further pain control procedure, 3 caudal epidurals, 2 facet blocks and 2 coccyx injections. One patient required an L4/5 PLIF 12 months after the first procedure and two patients required posterior stabilisation at the same level. One after 4 months the other at 18 months.

The indications for surgery are the same as for a standard fusion procedure. In this group there were 12 degenerative discs with mechanical LBP, 3 spondylolistheses, 2 previous failed posterior fusions and 3 post discectomy patients. Discography was used for confirmation of the pain source in 15 cases. The duration of symptoms ranged between 2–15 years with a mean of 6.25. There were 12 male and 8 female patients. The age ranged between 34–70 with a mean of 47. The female mean being 48 and the male 46.

The Oswestry disability index showed a mean of 47 pre-operation and 23 post-operation. 13 out of 20 have been discharged with symptoms resolved or easily bearable. The hospital stay varied between 1 night and 4 nights with a mean of 3.3.

This novel approach to the lumbar spine gives rapid and safe access to the lumbar disc space despite the unusual approach for spinal surgeons. Once the initial incision is made the procedure is carried out under x-ray control using techniques which are very familiar to Orthopaedic surgeons. The lack of intra-operative problems and post-operative complications testify to a safe procedure.

The question mark remains on the rate of fusion. Two patients and potentially a third required a secondary posterior instrumented fusion. One was due to demonstrable loosening of the bolt and the other two continued pain possibly due to inadequate stabilisation. In my view, despite the European teaching, posterior instrumentation is desirable. This can be achieved via a percutaneous technique.