Dynamic semirigid stabilization of the lumbar spine was introduced in 1994 in an attempt to overcome the drawbacks of fusion. It is supposed to preserve motion at the treated levels, while avoiding hyper- mobility and thus spondylosis at the adjacent levels. Although the early reports showed promising results, the long term effects are still debated. We retro- spectively compared outcomes of Dynesys dynamic stabilization with those of the traditional fusion technique. Thirty-two patients who had undergone Dynesys between 2004 and 2006 (group 1) were com- pared to 32 patients who had been treated with fusion between 2005 and 2006 (group 2). VAS for back and leg pain, and ODI improved significantly in both groups (p < 0.001). These scores were all better in the fusion group, and even significantly so as far as VAS for back pain was concerned (p = 0.014). Similarly, more patients were satisfied or very satisfied after fusion than after Dynesys : 87.5% versus 68.8% (p = 0.04). Interestingly, in the Dynesys group scatter plot graphs showed a positive correlation between older age and improvement in the two VAS scores and in ODI. Dynamic stabilization with Dynesys remains controversial. Older patients are relatively more satisfied about it, probably because of their low level of demands. Keywords : lumbar spondylosis ; Dynesys ; dynamic semirigid stabilization ; lumbar fusion ; retrospective ; mid-term follow-up. INTRODUCTION Abnormal load transmission across the spine is a common cause of back pain and may result in disc degeneration and facet joint osteoarthritis (16). Both rigid and dynamic spinal stabilization procedures have been adopted to treat pain arising from spinal instability. Dynamic stabilization was introduced in 1994 as a motion preserving device in an attempt to overcome the disadvantages of fusion, provide sufficient stability, and above all preserve motion at No benefits or funds were received in support of this study. The authors report no conflict of interests. Acta Orthopædica Belgica, Vol. 79 - 1 - 2013 Acta Orthop. Belg., 2012, 78, 97-103 Dynesys dynamic stabilization : less good outcome than lumbar fusion at 4-year follow-up Behrooz HADDAD, Daoud MAKKi, Sujith KONAN, Derek P ARK, Wasim KHAN, Ben OKAFOR From Whipps Cross University Hospital, London, and Royal National Orthopaedic Hospital, Stanmore, UK ORIGINAL STUDY ■ Behrooz Haddad, MD, MRCS, Registrar. ■ Daoud Makki, MBBS, MRCS, Registrar. ■ Sujith Konan, MBBS, MD, MRCS, Registrar. ■ Derek PARK, MBBS, MRCS, FRCS (orth), Registrar. ■ Ben Okafor, MBBS, FRCS (orth), Consultant Spinal Surgeon. Department of Trauma and Orthopaedics, Whipps Cross University Hospital, London, UK. ■ Behrooz Haddad, MD, MRCS, Registrar. ■ Wasim Khan, MBBS, MRCS, Registrar. Institute of Orthopaedics, Royal National Orthopaedic Hospital, Stanmore, UK. Correspondence : Behrooz Haddad, Dept Trauma and Orthopaedics, Whipps Cross University Hospital, Whipps Cross Road, Leytonstone, London, E11 1NR, UK. E-mail : behrooz.haddad@gmail.com © 2012, Acta Orthopædica Belgica.