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Purpose: Many investigators have reported the financial conflicts of interest (COI), which could result in potential bias in the reporting of outcomes for patients undergoing total disc replacement (TDR) rather than anterior cervical discectomy and fusion (ACDF). This bias may be subconsciously introduced by the investigator in a non-blinded radiographic review. The purpose of this study was to determine if bias was present when a group of spine specialists rated adjacent segment degeneration (ASD) following cervical TDR or ACDF., Methods: Potential bias in the assessment of ASD was evaluated through the reviews of cervical radiographs (pre- and 6 years post-operative) from patients participating in the ProDisc-C FDA trial (ProDisc-C IDE #G030059). The index level was blinded on all radiographs during the first review, but unblinded in the second. Five reviewers (a radiologist, two non-TDR surgeons, and two TDR surgeons), two of whom had a COI with the ProDisc-C trial sponsor, assessed ASD on a three point scale: yes, no, or unable to assess. Intra- and inter-rater reliabilities between all raters were assessed by the Kappa statistic., Results: The intra-rater reliability between reviews was substantial, indicating little to no bias in assessing ASD development/progression. The Kappa statistics were 0.580 and 0.644 for the TDR surgeons (p < 0.0001), 0.718 and 0.572 for the non-TDR surgeons (p < 0.0001), and 0.642 for the radiologist (p < 0.0001). Inter-rater reliability for the blinded review ranged from 0.316 to 0.607 (p < 0.0001) and from 0.221 to 0.644 (p < 0.0001) for the unblinded review., Conclusions: The knowledge of the surgical procedure performed did not bias the assessment of ASD.

The relationship of the esophagus to the cervical vertebral body (CVB), disc space and longus colli (LC) muscles, to our knowledge, has not been previously studied. The purpose of this study was to quantify the relationship of the esophagus to the CVB, disc space and LC. 30 patients were selected for a retrospective review of computed tomography (CT) scans. Measurements between the esophagus and the C5, C6, and C7 vertebral bodies as well as the C5/6 and C6/7 disc spaces were performed in the midline, 3 mm right and left of midline, and at the edge of the LC on both sides. The closest distance of the esophagus to the CVB and disc space occurs at the midline (range 1.02-1.31 mm at each level). The furthest distance occurred at the edge of the right LC (range 2.67-3.30 mm at each level). The mean distance from the edge of the right LC to the midline was significantly greater (P < 0.01) than mean distance from the edge of the left LC to the midline. No statistical significant differences were observed when comparing measurements at the individual vertebral bodies and disc spaces. The results of the study demonstrate that the esophagus lies in closest proximity to the CVB and disc space in the midline. A larger potential space exists between the esophagus and the CVB and disc space at the edge of the LC. These results may provide insight into a potential cause of post-operative dysphagia. Furthermore, it may help guide the future design of cervical plates to better utilize the potential space between the esophagus and the CVB and disc space at the edge of the LC.

Study Design: Retrospective review., Objectives: To determine whether radiographic measurements derived from standard computed tomography (CT) evaluation can be used to predict failure of nonoperative treatment in patients with unilateral facet fractures., Summary of Background Data: There is no consensus regarding treatment of unilateral cervical spine facet fractures. Management of this injury is based primarily on the presence of neurologic deficits and the degree of perceived spinal instability. CT-based criteria for predicting failure of nonoperative treatment in this patient population have not been examined., Methods: Initial CT scans of all patients with unilateral cervical facet fractures were reviewed. Direct measurements included height and width of the facet fracture fragment, fracture displacement, and angulation. Calculated data included percent height and width of the fracture fragment based on the height and width of the contralateral intact facet., Results: A total of 24 patients with 26 unilateral facet fractures were identified. Five patients with 5 facet fractures failed nonoperative management and required delayed surgical stabilization. Comparing patients successfully treated nonoperatively to those failing nonoperative management, a significant difference was found in absolute height of the fracture fragment (P = 0.0002), articular fracture height (P = 0.008), and height of the fracture fragment expressed as a percentage of the contralateral intact lateral mass (P = 0.026)., Conclusion: The only significant risk factors identified for failure of nonoperative treatment were craniocaudal height of the fracture fragment and relative height of the fracture fragment expressed as a percentage of the intact lateral mass. This study suggests that patients with unilateral cervical facet fractures involving >40% of the absolute height of the intact lateral mass or an absolute height >1 cm are at increased risk for failure of nonoperative treatment. Failure of nonoperative treatment was not observed in any patient with a fracture involving less than 40% of the height of the lateral mass or an absolute height <1 cm.