We report the outcomes of minimally invasive technique for posterior lumbar interbody fusion (PLIF) procedure using Hollow Modular Anchorage (HMA) screws supplemented by routine pedicle screw fixation (Dynesis). Seventy-nine patients, who had undergone PLIF procedure using HMA screws supplemented by pedicle screw fixation, were included. Patients deemed suitable for surgery following discography under sedation, with Marcaine instillation establishing reducibility of the listhesis and temporary relief of symptoms. Clinical outcome included visual analogue scale scores for leg pain and back pain, Oswestry Disability Index (ODI) and SF-36 questionnaires.Introduction
Patients and Methods
From our series of 570 Dynesys flexible stabilisation procedures, we studied two prospective series of patients with a minimum one-year follow-up comparing uncoated and hydroxyapatite-coated (HA) screws. Patients were entered prospectively and followed up at 6 weeks, 3, 6, and 12 months and annually thereafter. Plain radiographs were obtained annually. 58 patients who underwent Dynesys stabilisation with HA coated screws (312 screws) were evaluated. The data was compared with 71 patients who underwent Dynesys stabilisation with non-coated pedicle screws (366 screws). Outcome measures were screw loosening, breakage, implant removal or revision. Follow up was 96 %.Objective
Methods
To review the medium-term results of the Dynesys stabilisation system used in 113 consecutive patients with discogenic back pain. 113 consecutive patients with discogenic back pain were treated with Dynesys as the sole intervention. Inclusion criteria included mri proven disc degeneration and an improvement in symptoms following an injection into the disc with local anaesthetic and steroid (spinal disc probing). Patients were followed up for a minimum of 5 years, with outcome measures including SF-36, Oswestry disability index (ODI) and visual pain analogue scores (VPAS). Additional factors reviewed included previous spinal operations, complications, loosening and revision rates with subsequent outcomes. Mean pre-operative ODI was 49.5, SF-36 was 37.6 and VPAS back pain was 60.9. At one year post operatively, these scores were 36.9, 49.4 and 39.8, at five years follow up, the scores were 33.3, 51.8 and 40.1 respectively. We note wide variations in our results. Several significant factors appear to contribute to the outcome of surgery. These include undergoing surgery before the age of 43, no more than 2-level disc degeneration, leg pain less than VPAS 4, and no previous spinal surgery. 19 patients had screw loosening evident on plain film x-rays (4 requiring removal), and 2 patients had screw breakages. 19 patients had implant removal for failure and 2 patients went on to have a fusion procedure.Purpose of Study
Methods and Results
We have studied two matching cohorts of patients treated by Dynesys flexible stabilisation with and without hydroxyapatite (HA) coating of the pedicle screws. From our series of 570 Dynesys procedures, we studied patients with HA coated screws with a minimum one year follow-up. Patients were entered prospectively and followed up at 6 weeks, 3, 6, and 12 months and annually thereafter. Plain radiographs were obtained annually. 58 patients (26 males, 32 females, mean age 55 years at surgery) underwent Dynesys stabilisation with HA coated screws. The data was compared with 69 patients who underwent Dynesys stabilisation with non-coated pedicle screws between 2004 and 2006 (26 male, 53 female, mean age 54 years). Outcome measures were screw loosening, breakage, implant removal or revision. A total of 320 HA coated pedicle screws were inserted. 12 patients were lost to follow-up. 2 patients underwent subsequent level extension, and 2 had their implants removed. There were four screw breakages in three patients, all affecting S1 screws. There was no evidence of screw loosening in any patient. In the non-HA coated group 354 pedicle screws were inserted. 5 patients required revision or subsequent surgery. 12 patients had screw loosening and required implant removal. There was a significant improvement of anchorage of the HA coated screws. Change to HA coating was investigated because of high loosening in plain screws. The improvement has been highly significant. Flexible stabilisation is a better model than fusion because the implant remains under constant load. Disclosure: The authors did not receive any outside funding in support of preparation of this work.
The Short Form-36 (SF-36) health questionnaire has been put forward as a general measure of outcome in health care and has been evaluated in several recent studies in the UK. We report its use in three groups of patients after spinal operations and have compared it with the Oswestry and Low Back Pain disability scales. There was a significant correlation between all variables of the SF-36 and the low-back scores. The mental-health items had the weakest correlation. Our study shows that the SF-36 questionnaire is valid and has internal consistency when applied to these patients.
