Surgical Interbody Research Group–radiographic assessment of interbody fusion devices: fusion criteria for anterior lumbar interbody surgery

Abstract

<jats:p>The authors present their radiographic criteria for assessing fusion of the lumbar spine after anterior interbody fusion with intradiscal implants. These criteria include the assessment of plain radiographs, dynamic motion radiographs, and thin-cut computerized tomography scans. Fusion within the instrumented spinal motion segment can be determined using radiographic evaluation to assess spinal alignment on sequential examinations, angular and translational changes on dynamic motion studies, and device–host interface, and to identify new bone formation and bone remodeling. Finally, to aid the clinician in assessing fusion, the authors describe the five zones of fusion within the intervertebral disc space.</jats:p>

Is the Lateral Transpsoas Approach Feasible for the Treatment of Adult Degenerative Scoliosis?

“…Third, to minimize patients' exposure to radiation, not all patients had CT scans, only those whose fusion status was not possible to determine on radiographs. Moreover, plain films have shown strong evidence of fusion or pseudarthrosis; thus, helical CT is unlikely to provide useful new information [6,14,15]. Fourth, radiographic assessment was not performed by multiple observers so it was not possible to test interobserver agreement; rather, it was performed by experienced examiners in a unique committee as frequently performed in reports of other small case series.…”

“…Subsidence was classified as described previously [22,23] in radiographs in the AP and lateral views and CT scans, based on the amount of cage subsidence into the vertebral endplates: absent or low-grade = 0% to 49%; and high-grade = 50% to 100% collapse of the level. Fusion status was determined oriented as described previously [6,14,15] in plain neutral and flexion-extension radiographs and eventually CT scans in cases with no clear conclusion on the radiographs. Fusion was defined as bridging bone connecting the adjacent vertebral bodies either through the implants or around the implants, less than 5°of angular motion, 3 mm or less of translation, and absence of radiolucent lines around more than 50% of either of the implant surfaces.…”

Spinal fusion using adipose stem cells seeded on a radiolucent cage filler: a feasibility study of a single surgical procedure in goats

“…Lack of stability may well explain the relative high number of anterior bone bridges (sentinel signs) in our study. In fact, this sentinel sign has been described as a possible consequence of progressive instability and has therefore been termed 'radial bone spur' instead of interbody fusion [2]. Mineralized bone content as measured with micro CT, was lower for all PLCL groups compared to autologous bone as a filler material, but all show an increase from 3 to 6 months as may be expected.…”

Posterior lumbar interbody fusion with bioabsorbable spacers and local autograft in a series of 27 patients

“…7,8,13,20 The exact mechanism or mechanisms associated with this somewhat striking cavitation appear- ance seen in conjunction with the bioabsorbable device certainly warrants further analysis.…”

“…Carbon fiber or other synthetic cages are relatively radiolucent, yet the difficulties involved in the radiographic assessment of fusion with metallic intervertebral cages is an inherent limitation of many currently used devices. 7,8,13,20 These limitations led to the development of biological spacers that provide immediate spinal stability, are radiolucent, and are ultimately biodegradable. The HYDRO-SORB biodegradable device allows more accurate assessment of fusion on conventional radiographic studies but imposes a time frame on the fusion process.…”