56 - Long-term assessments of posterior tissue-sparing fusion with facet stabilization to revise cervical pseudarthrosis

Background Context:
Posterior cervical fusion (PCF) with lateral mass screws achieves reliably solid arthrodesis with rates exceeding 90% when performed for treatment of symptomatic pseudarthrosis following ACDF. Soft tissue dissection for PCF causes perioperative pain, wound infections, hospital re-admission, and can result in chronic myofascial pain. A tissue-sparing PCF approach involving intra-facet cages reduces the rates of post-operative complications, while adequately stabilizing the symptomatic level to achieve arthrodesis (Fig. 1). The goal of this study was to understand long term radiographic and clinical outcomes in patients revised with tissue-sparing PCF to treat pseudarthrosis.

Methods:
A surgical chart review across six sites identified 150 records of patients treated with tissue-sparing PCF to revise an ACDF pseudarthrosis. Eighty-nine patients identified in the initial chart review (59%) enrolled for prospective assessment of clinical and radiographic outcomes. The median follow-up time was 38 months (range 12-76) following their posterior fusion. A total 173 revised levels were assessed. CT and dynamic x-rays were taken to determine evidence of contiguous bridging bone at the interbody space and facet joints for each revised level. Range of motion was measured using quantitative motion analysis software. All radiographic assessments were performed by an independent core imaging laboratory.

Results:
The median number of levels revised was 2 (range 1-5). Median operative duration was 45 minutes with an estimated blood loss of 10cc. Patients were discharged a median 1 day following surgery. There was one instance of re-hospitalization due to deep vein thrombosis related to complications from the patient’s IV site. No cases required subsequent surgical intervention at the revised levels.

Segmental range of motion on dynamic x-ray was less than 2 degrees in 89% of assessed levels. Contiguous bridging bone was present across 83% of the assessed vertebral interbody space and 75% of the assessed bilateral facets. Bridging bone was present across both the interbody and facets in 73% of the assessed levels.

Satisfactory clinical outcomes were reported in 82% of respondents as determined by answering “very satisfied,” “satisfied,” or “somewhat satisfied” following revision. Subjects achieving ROM less than two degrees across all levels were more likely to report satisfactory outcomes than those with gross movement (ROM < 2=88%; ROM2=78%, p=0.021). Subjects with interbody bridging bone across all revised levels had numerically greater satisfaction however this was not statistically different (85% vs. 82%, p=0.260).

Conclusions:
These outcomes provide evidence in support of tissue-sparing PCF with facet cages as a treatment for symptomatic pseudarthrosis after ACDF (Fig. 2). Solid arthrodesis at the revised level was evident from minimal segmental ROM, with most patients achieving stabilization indirectly at the site of the interbody pseudarthrosis. Positive radiographic outcomes were complimented by positive clinical outcomes. Patients were satisfied with their surgery and none required subsequent surgical intervention.

Figure 1 Stabilization achieved through bilateral intrafacet cages with bone screw

Figure 2 Single level ACDF with pseudarthrosis revised using tissue-sparing PCF with facet
stabilization.