Graf ligament stabilisation: mid- to long-term follow-up

Abstract

IntroductionMechanical instability in the lumbar spine is a term often used to describe an altered pattern of segmental movement causing pain. This is usually due to degenerative disease. Historically, symptoms of mechanical instability have been treated surgically with spinal fusion.In an attempt to modify the movement pattern of an abnormal motion segment, the Graf ligament system was introduced. It consists of modified titanium pedicle screws inter-connected with bands of braided polypropylene. This arrangement attempts to recreate the lumbar lordosis and allows limited movement to occur, hence the concept of 'flexible intervertebral stabilisation'. The operation is quicker, less destructive and requires less rehabilitation than a definitive spinal fusion.Previous authors [3,4,7] have reviewed early results of the system, which have been encouraging. We reviewed over 50 patients who underwent this procedure with an average follow-up time of over 5 years. Patients and methodsWe retrospectively reviewed 69 patients who underwent Graf ligament stabilisation between 1993 and 1997. Of these, 51 patients were available for follow-up. There were 23 women and 28 men. The mean age was 41 years (range, 22-67 years). All patients had chronic low back pain. Eight patients had had previous spinal surgery in the form of discectomy. Conservative management of back pain had failed in all the patients. This included physiotherapy, epidurals and facet joint injection. All patients were assessed preoperatively with an Oswestry Disability Index for low back pain. Our indication for stabilisation with the Graf ligament was intractable low back pain for which conservative measures of treatment had failed. All patients had magnetic resonance imaging (MRI) or computed tomography (CT) scans. Abnormal degenerative discs, end-plate changes or marked facet degeneration were targeted for stabilisation. Patients with equivocal scans were further investigated using discography. The surgery was performed by the two senior authors (M.A.F. and A.J.B.F.) exclusively. Fifteen patients had significant leg pain with clinical and radiological signs of nerve root entrapment and consequently underwent nerve root decompression at the same time as the spinal stabilisation. The majority of patients (n=31) had single-level stabilisation, while 17 had two-level and 3 had three-level stabilisation.Patient notes were examined. Previous history and details of surgery were recorded. Post-operative complications and length of Abstract Previous studies have looked at early follow-up of the Graf ligament stabilisation system. We present mid-to long-term results of this procedure. A retrospective review of Graf ligaments inserted since 1993 was undertaken. A total of 51 patients were reviewed. Pre-operative Oswestry Disability Index scores were compared to post-operative scores recorded via a postal questionnaire. There were 28 men and 23 women. The average age was 41 years (range, 22-67 years). The mean pre-operative score was 46 (range, 22-78), the mean follow...

Correlation between inter-vertebral disc morphology and the results in patients undergoing Graf ligament stabilisation

“…Rigby et al [ 18] also showed that 41% of their patients were not satisfied with the procedure after a mean followup of 51 months. They cautioned against the continued use of this method.…”

Does Wallis implant reduce adjacent segment degeneration above lumbosacral instrumented fusion?

“…Some of them (Graf, Dynesys) were secured to the spine by pedicle screw fixation systems [17], while other implants are secured in the interspinous space [38,48]. Although early results of pedicle-screw systems of flexible intervertebral stabilization have been encouraging [17] some longterm results have revealed possible drawbacks [18,54], including increased lumbar lordosis, stretching of the Dacron parts, and malpositioning and loosening of pedicle screws leading to increased re-operation rate.…”

“…The overall implant constitutes a ''floating'' system with no permanent fixation in the vertebral bone, which might otherwise expose in the risk of loosening. Mechanical human cadaver studies [48] have shown that Wallis permits a reduction in the mobility of intervertebral segments previously destabilized by discectomy and that it achieves an increase in the rigidity of the destabilized segment beyond normal values. There is no implant for the L5/S1 segment and thus it cannot be used below a L4/L5 fusion [63].…”

“…Non-rigid, dynamic or flexible instrumentations for lumbar spine have been developed to reduce ASD [17,18,27]. These implants are either fixed in the pedicles, or secured between the spinous processes of adjacent vertebrae [38,48]. Long-term results showed several significant drawbacks and implant-related complications in the non-rigid pedicle fixed instrumentations [18,54].…”

“…Amongst these interspinous process implants a ''second'' generation implant for non-rigid stabilization of lumbar segments, called Wallis system, has been developed [48]. A recent in vitro biomechanical and finite-element analysis of the Wallis showed that this implant reduces motion without suppressing it and lowers stress in the disc fibres and annulus matrix [32].…”