Robotic Cervical Traction: Cadaveric Facet Dislocation Biomechanical Testing.

Study design: Basic science.

Objective: To characterize robotically controlled cervical traction applied to intact and C4-C5 facet injury cadaveric models and compare the radiographic results with those of weight-pulley traction.

Summary of background data: Manual application of weight-pulley cervical traction for dislocated facet reduction or cervical deformity correction has many limitations. Robotic cervical traction has demonstrated mechanical proof of concept but has not yet demonstrated reduction of dislocated facets in multiple cadaveric specimens.

Methods: Nine cephalus to T4 adult human cadaveric specimens were obtained. Intact specimens (n=4) were placed first into weight-pulley traction with Gardner-Wells tongs and then into robotic traction, and radiographs were obtained at each weight interval. Intervertebral disc heights were measured at all visualized levels. Posterior cervical dissection was performed in 5 cadaveric specimens for the iatrogenic creation of bilateral C4-C5 facet dislocation injury. These specimens were placed into weight-pulley traction, and force was applied in 5-lb increments until reduction was achieved. The injuries were then re-created, and the injured specimens were then placed into robotic traction, and force was applied in 5 lb increments until reduction was obtained. Radiographs were obtained at each force increment in the injured specimens in both traction systems.

Results: In the intact cadaveric specimens, there was no radiographic difference in intervertebral disc space height at 90 lbs of force between weight-pulley and robotic traction. In the 3 successful C4-C5 facet dislocation injury specimens, radiographic reduction was achieved at similar traction forces between robotic (mean force 31.7±11.9 lbs) and weight-pulley (mean force: 30.0±15.0 lbs) traction. Robotic traction slip-detection functions prevented unnecessary overdistraction in one injured cadaver.

Conclusions: Radiographic outcomes for robotic cervical traction and weight-pulley traction were similar at identical traction forces in intact cadaveric specimens. C4-C5 facet dislocation injuries were reduced at a similar traction force when compared with weight-pulley traction and may prevent overdistraction.