General Session: Innovative Technologies
Presented by: K. Rickers - View Audio/Video Presentation (Members Only)
K. Rickers(1), S. Kitahata(2), A.A.E. Orias(2), S. Ringgaard(3), F.B. Christensen(3), G.B. Anderson(2), C. Bünger(1), J. Peterson(2), H. Li(1), E.S. Hansen(3), N. Inoue(2), B. Robie(4)
(1) Aarhus University Hospital, Department of Orthopedic Surgery, Aarhus, Denmark
(2) Rush University Medical Center, Chicago, IL, United States
(3) Aarhus University Hospital, Aarhus, Denmark
(4) ARO Medical ApS, Risskov, Denmark
Introduction: Spinal instability is a recognized cause of pain and a target for treatment (Kirkaldy-Willis, 1982). Kirkaldy-Willis described instability in each direction (F/E, LB and axial rotation (AR)). In response, devices have been created to resist flexion and lateral bending without fusion (e.g. Dynesys). AR has received less attention, though greater AR has been shown in patients with low back pain (e.g. Haughton, 2002), and increases with disc herniation (Thompson, 2000). With the premise that reducing excessive AR will improve clinical results, a novel AR stabilization implant (ARO® Spinal System, ARO Medical) was developed. Previous cadaver testing showed it reduces excessive AR, with minimal impact in LB and F/E (Schmoelz, 2010). We report AR in patients prior to, and after receiving the implant, using a recently developed technique to measure AR using MR (Kitahata, 2014).
Materials and Methods: The study was an EC approved prospective clinical trial. All subjects had a single level posterolateral lumbar herniation with symptoms lasting more than 6 weeks. 30 subjects were included. All subjects received a preoperative MR scan in three positions: supine and with the shoulders rotated 45° towards and away from the side of the herniation. 3D MRI models were reconstructed for 3D kinematic analyses. Validated 3D-3D registration techniques were used to determine AR from supine to the rotated positions (AR.T - towards the herniation, AR.A - away). AR=AR.T+AR.A. All patients then underwent an open discectomy at the symptomatic level (19@L5/S1, 11@L4/L5). In addition, 20 subjects received the implant on the side of the herniation (ARO). The subjects were followed at 6 and 12 months with repeat MR. Non-parametric statistics were used (p< 0.05).
Results: The results are shown in Table 1. There was a significant increase in both groups between pre-op and 6 months post-op. It was 62% for the controls, and only 21% for ARO, though this difference was not statistically significant. The increase in AR.T between pre-op and 6 months was significantly greater for controls than for ARO.
Discussion: The amount of motion measured is comparable to previous reports showing 2 to 3˚ of segmental motion on average (Pearcy & Tibrewal, 1984), while avoiding x-ray radiation. This study is the first to report primary axial rotation motion in discectomy patients in early post-operative period. It appears that the spine is most unstable in axial rotation prior to one year post-op. Lastly, this study shows that the ARO Spinal System resists increases in axial rotation in comparison to controls. The device may have benefit in clinical situations where excessive axial rotation is a concern. Further clinical evaluation of the device is warranted.