We report a consecutive series of 200 patients who underwent Dynesys flexible stabilisation in the management of intractable lower back pain.

Methods: Patients were only accepted for the study if exhaustive conservative management had failed. They underwent operation between September 2000 and March 2003. Patients were divided into two groups:

Group 1 - Cases where implantation was used as an adjunct to other procedures including decompression, discectomy, or posterior lumbar interbody fusion. (32 male, 36 female, Mean age 56years (range 31–85)).

Group 2 - Patients with back pain and/or sciatica in which no other procedure was used. (65 male 67 female, Mean age 58years (range 27–86))

All patients were profiled prospectively using the Oswestry Disability Index (ODI), SF36 and Visual Analogue Scale (VAS). Patients were reviewed post-operatively using the same measures at 3, 6 & 12 months, and yearly thereafter. Follow-up was 95% at 2 to 5 years.

Results: Group 1 – Mean ODI fell from 54 pre-op to 24 at four years

Group 2 – Mean ODI fell from 49 pre-op to 28 at four years

Similar trends were observed in both groups with a fall in VAS and improvement in SF36.

Discussion: Indications can only be defined following clinical outcome. Perceived indications were based on contemporary understanding of the biomechanical effects of the construct. Further investigation of these variables is clearly desirable. Screw failures (15%) have detracted from the overall success. The virtue of flexible stabilisation over fusion includes avoidance of domino effect, reversibility and possible healing of a painful segment. The key issue is whether it is as effective and this requires prospective randomised controlled investigation, both against fusion, and conservative management. We feel our results in this difficult group of patients are reasonable and continue to use it in our practice.

Objective: To present early results of a new technique of dynamic stabilisation of the lumbo-sacral spine.

Design: Prospective study

Subjects: Between September 2000 and December 2001, 43 patients underwent posterior spinal stabilisation using the Dynamic Neutralisation System (DYNESYS) (Sulzer Medica).

Outcome Measures: Oswestry Disability indices, complications, visual analogue pain scores, patient satisfaction.

Results: The perceived indications were isolated degenerative disc disease (26), spondylolisthesis (8), degenerate adult scoliosis (4), failed Graf stabilisation (1), lumbar canal stenosis (3) and traumatic compression fracture (1).

Fixation was at one level in 14, two levels in 23, and three or four levels in 6 patients. Thirty-seven had Dyne-sys fixation alone and six had additional procedures at the same operation.

Complications included facet fracture (1), broken pedicle screw (1), apparent screw loosening (1) and discitis (1). At average follow-up of eight months (range 2–14 months), the average Oswestry disability score had fallen from 52 to 32 and the visual analogue pain score from 7.5 to 1.7. 65% of patients were pleased or better with their result.

Conclusions: The Dynesys system seems to be a safe alternative to conventional operative treatment for degenerative disorders of the lumbar spine without the need for rigid fusion. The anatomic re-stabilisation may allow the spinal segment to recover. The early results are encouraging. It is hoped that longer term follow-up will clarify the groups of patients who will benefit most from this procedure.

Objective: This is a prospective study by an independent observer in which outcomes of 118 anterior lumbar interbody fusions (ALIF), done for discogram-concordant axial low back pain, were evaluated. Aims of the study were to assess overall functional and comprehensive outcomes, predictors of outcome, and whether ALIF alone can be recommended for low back pain.

Design: The functional and patient perception assessment was based on a self-evaluation back pain questionnaire, which consisted of Oswestry Disability Index, Pain Chart, Numerical Rating Scales (NRS) for back pain and leg pain and SF-36-Version II. The comprehensive outcomes were categorised as satisfactory (excellent, good or improved) and unsatisfactory (fair, poor, unimproved or worse).

Results: Overall, we had 61% satisfactory outcomes. Average percentage change in ODI, NRS and SF-36 PCS scores was statistically quite significant. However, patients who had previous posterolateral fusion at the same level had satisfactory outcome in 81%. Incidence of non-union was higher in two-level fusions than one-level fusions, and cases that developed non-unions had unsatisfactory outcome.

Conclusions: ALIF alone can be recommended for discogram-concordant axial low back pain. Radiographic evidence of spondylosis, lysis or listhesis, level of fusion, number of levels fused, floating/non-floating type of fusion, and previous back surgery did not affect the outcome. Cases in which the middle column was stabilised (such as those with (a) intervertebral cages extending up to the posterior longitudinal ligament and (b) previous posterolateral fusion at the same level), and hence biomechanically stable, showed better outcomes. Placement of intervertebral implants mainly in the anterior column lead to distraction of the disc anteriorly, resulting in compression of back wall of the disc and facet joints, and narrowing of intervertebral foramina and spinal canal at that level, thus compromising the outcome.

Aim of the study: To prove that tapered pegs are effective in reducing tibial tray subsidence in vitro and that this effect is related to the dimensions of these pegs.

Methods: The peg designs were drawn up mathematically to allow for a unified surface area – Three different designs were used. The pegs were made from cobalt chrome, were conical in shape with a cut off tip and had a variable base and height and an equal surface area. These pegs were fixed with screws to an IB 11 HA coated tibial tray.

Wet foam was used as bone substitute, this is an open cell foam that is fairly fragile but has the benefit of being constant and is cheap and readily available. This foam is not desired to have cancellous bone characteristics but is useful in observing the relative effect of adding these pegs. Two different settings in vivo were mimicked: that of a tibial tray and pegs resting fully on cancellous bone, in which case a central vertical force was applied, and that of the tray resting on the cortex on one side with a lateral vertical force applied over the other side in both the proud and flush setting (2& 4 pegs respectively). The investigation was undertaken using a home made system allowing a crude estimate of the forces producing initial subsidence, which was identified by initial fracture of the foam, and total subsidence which was identified as total failure of the foam. Each test was carried out three times. Controls were carried out on the tray with no pegs and on the pegs individually before attaching these to the tray and repeating the tests for each design.

Results: Using this crude approach, the mean control force for total subsidence of the pegs was as follows: Short with wide base 550.3 g (± 45.3 g), medium length and base 475.6 g (± 24.25 g), long with narrow base 364.5 g (± 24.25 g). The mean control force for initial subsidence of the tray without pegs when subjected to a vertical central force was 4.3 kg (4–4.5 ± 0.27 kg) and the total subsidence force for the tray was 7.32 Kg (5.5–8, ± 0.84 kg). The mean central vertical force for initial subsidence of the tray with the tapers mounted was 7.16 kg (7–7.5 ± 0.28), for the short wide pegs, 5.33 kg (5–5.5 ± 0.28) for the medium pegs and 5.33 kg (5–6 ± 0.57) for the long pegs. The mean central vertical force for total subsidence of the tray with the tapers mounted was 9 kg (8.5–9.5 ± 0.5) for the short wide pegs, 9.8 kg (8–11 ± 1.6) for the medium pegs and 9.6 kg (8.5–11.5 ± 1.6) for the long pegs. The mean lateral control force for total subsidence of the proud tray with pegs resting on the wooden ledge was 5 kg (4–6 ± 0.75). The mean lateral vertical force for total subsidence with all pegs mounted was 7.16 kg (7–7.5 ± 0.28) for the short pegs, 5.8 kg (5.5–6 ± 0.28) for the medium pegs and 5.5 (5.5–5.6 ± 0.05) for the long pegs. No definite initial subsidence force could be identified. The mean lateral control force for total subsidence of the flush tray resting on the wooden ledge was 13.16 kg (12.5–14 ± 0.76).

The mean lateral vertical force for total subsidence with pegs mounted on the foam side was 12.3 kg (11.5–13 ± 0–76) for the short pegs, 13.5 kg (12–15.5 ± 1.8) for the medium pegs and 13.83 kg (12–15.5 ± 1.7) for the long pegs. Again no definite initial subsidence force could be identified.

Conclusion: The addition of tapered conical pegs to the tibial tray increases the resistance to subsidence when subjected to a central vertical force with the tray sitting fully on foam. The initial subsidence resistance was more marked in the case of the short wide variety. In the case of the tray resting on the hard edge and a lateral force applied, the proud tray showed improved resistance to total subsidence with the short pegs while the flush tray did not show improvement with pegs and was marginally worse with the short pegs. This is probably due to a higher margin of observer error.