521 - Assessment of Subsidence using Quantitative Motion Analysis on 30 Init...

Oral Posters: Cervical

Presented by: C. Carmody - View Audio/Video Presentation (Members Only)


C. Carmody(1)

(1) Texas Back InstituteSpine Consultants, Addison, NC, United States


Introduction: Anterior cervical interbody fusion is a common and generally successful procedure. However, subsidence of the supportive graft or interbody implant remains a well known, even expected occurrence in anterior neck surgery with subsidence frequently described in the literature as >2mm. This report describes the subsidence outcomes of a single site, retrospective study of subjects implanted with a 4Web Medical Cervical Spine Truss System (STS, 4WEB Medical, Frisco TX, USA) interbody fusion device.

Methods: The Cervical Spinal Truss interbody device was implanted at 58 levels in 30 subjects to promote cervical fusion. Subjects were followed for up to 12 months. Subsidence was quantified using independent assessors with a previously developed and validated computer-assisted methods (Medical Metrics, Inc, Houston TX, USA), and determined as both the change in disc height and the change in the functional spinal unit (FSU) relative to the first post-operative x-ray. FDA approved QMA software determines the relative position and motion of each vertebral body and takes into account the degree of end-plate preparation to minimize surgical variation bias (Images 1 & 2).

Results: On average, there was a significant increase in disc height that was maintained over time. There was no treated level where subsidence measured >2mm at 12 months relative to the first post-op visit. Subsidence was neither dependent on the follow-up visit nor the number of levels treated. Average decrease in disc height at all levels was 0.5mm at all visits through 12 months.

Conclusions: Average subsidence at all levels was under 0.5mm at all time points through 1 year when using the 4Web Cervical Spinal Truss System. Measured as a collapse in disc space following treatment, subsidence was less than 2mm at all levels in all patients. This contrasts subsidence in approximately 30% of treated levels previously reported in studies of other interbody devices reported in peer-reviewed literature, where subsidence was also defined as .2mm loss of disc height. Although the sample size was small, these preliminary results support the potential advantages of a modulus matched titanium implant, which covers a large portion of the endplate area.

Determining Relative Vertebral Position and Motion

Determination of Endplate Preparation