Do New Seat Designs Decrease Facet Joint Injury in Car Crash Patients?
Vehicle crashes may cause injury to multiple structures within the cervical spine, including the facet joint and intervertebral disc. In an attempt to reduce neck injuries during rear-impact collisions, some automakers now incorporate active injury prevention systems into vehicle designs.
Previous studies have shown that active injury prevention systems could reduce injury claims and complaints of neck pain after rear crashes. A recent study sought to add to the knowledge of potential benefits of active injury prevention systems by examining whether such systems reduce the risk of injury to the facet joints or intervertebral discs.
Recently, a team of researchers simulated crashes with three types of seats: the Whiplash Protection System (WHIPS), active head restraint (AHR), and no head restraint (NHR). The researchers conducted simulated rear crashes using human cervical spine specimens mounted to the torso of a rear impact dummy.
Facet compression at C6/C7 reached 2.9mm with WHIPS, 1.9mm with AHR, and 3.2mm with NHR. When compared with no head restraint, both WHIPS and AHR generally reduced peak disc separation and ligament strain. While they limited strain below the failure threshold, they did not protect against potential facet joint compression injuries, which could lead to neck pain in some whiplash patients. Future neck injury prevention systems could be designed to reduce facet joint compression, leading to reduced neck pain following rear impact crashes.
WHIPS and AHR seat designs appear to produce mixed results when preventing whiplash. In addition to reducing the strain of a crash below the failure threshold, studies show the new seat designs are associated with a 43-75% reduction in whiplash injury claims. Despite these gains, another study suggested they still fail protect against compression of the spinal ganglia nerve roots and facet joints. Clearly more work is needed to create truly "anti-whiplash" seat designs.
Ivancic PC, Facet joint and disc kinematics during simulated rear crashes with active injury prevention systems. Spine 2011; 36(18):E1215-24.