Clinical outcomes after lumbar surgery augmented with DIAM interspinous implant

[Truncated abstract] Background: The Device for Intervertebral Assisted Motion (DIAMTM; Medtronic Sofamor Danek, Memphis, USA) is an interspinous implant employed in the surgical treatment of lumbar degenerative disease. Its purported effect is a relative segmental kyphosis imposed via distraction of the posterior elements, which is believed to reduce pain-generating neural tissue compression or encroachment, while providing limitation to lumbar extension. Published evidence for the DIAM’s clinical and biomechanical efficacy is limited and generally based on year-long retrospective studies that do not reference standardised or recommended outcome instruments or thresholds defining an acceptable response. The DIAM is applied to cases with wide clinical indications that encompass various diagnostic groups. It may be implanted as an isolated procedure but is typically used to augment other lumbar surgeries, the most common being lumbar decompression. Existing evidence for the DIAM reports a promising influence on pain, function and satisfaction in the short term. However, little evidence examines the relationship between subjective postoperative improvement as determined by the patient, and objective measures in vivo of its biomechanical effect on spinal curvature. Purpose: The primary aim of this thesis investigation was to examine the effect of the DIAM on patientreported pain and function over a two year postoperative course and compared with defined recommendations for minimal clinical important differences (MID). The purported biomechanical effect of DIAM surgery was assessed in vivo by examining serial change in spinal posture from subjects’ skin surface using video rasterstereography, and radiographic vertebral alignment, over the postoperative period and compared to preoperative baseline. Interactions between subjective patient-reported pain and function, and objective measurements of spinal curvature were explored in order to better define clinical indications and prognostic determinants for successful use of the DIAM in the surgical treatment of lumbar spine disease...