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Pain, Impairment, Whiplash, and the New AMA Guides: What Clinicians Need to Know

Close to 3 million Americans suffer whiplash each year. Whiplash now accounts for 45% of chronic neck pain in adults. The author discusses how new car design prevents fatal crashes but increases whiplash injuries.
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Every year, approximately 3 million people in the United States suffer from whiplash,1 resulting in an estimated $43 billion in comprehensive costs.2 Over the past few decades, these injuries have been on the rise worldwide.3 Studies have reported rises in whiplash injuries from a low of 7.2% in 1982 to 30% by 1997.4

Seat belt and shoulder harness use, while providing life-saving protection in most crashes, can increase the risk for whiplash injury.5-7 The substantial rise in seatbelt use in the US since the introduction of primary- and secondary-use laws has contributed to the increased incidence of whiplash injury. Increased stiffness of seat backs also has been a contributing factor.8-10 A large population-based European study found that the increase in whiplash from 1989 through 1995 was associated with stable seatbelt usage.11 Krafft et al, showed that the relative risk of being injured in a crash was related to model year—that is, the risk of being injured in a 1990s era model was 2.7 times that of being injured in a 1980s model.12,13

As the incidence of whiplash has increased, so have the rates of disability: whiplash may account for as much as 45% of chronic neck pain in adults.1 A significant portion of people who suffer from whiplash injuries seek some form of compensation. For the past half century, various editions of the American Medical Association’s Guides to the Evaluation of Permanent Impairment (Guides), have served as a tool to help physicians evaluate injuries and rate the degree of permanent injury. Although most jurisdictions in the US do not currently use the Guides for matters of personal injury impairment rating and litigation, the latest version of the Guides, the 6th Edition,14 features a diagnosis-based impairment (DBI) assessment that mentions whiplash by name. This may portent a push by insurers to require whiplash injury claims to be rated using the Guides.

This review will discuss substantive changes to the new Guides and what clinicians need to know about these changes for the diagnosis of whiplash.

Why the Increased Incidence of Whiplash?

A significant factor in the increase in whiplash claims has been the automotive industry’s attempt to manage the increasing crash energy recommended by the National Highway Traffic Safety Administration’s (NHTSA) New Car Assessment Program (NCAP) and the Insurance Institute for Highway Safety’s (IIHS) 40% offset deformable barrier crash tests. The NCAP and IIHS tests are non-obligatory tests, designed to induce automakers to enhance efforts in crash worthiness using a “name-and-shame” approach. The results of both tests are then promulgated to the public.

While the current government-mandated compliance test (FMVSS 208) requires a frontal crash into a rigid barrier at 30 mph, the NCAP is conducted at a more rigorous 35 mph. The IIHS tests are 40% offset frontal tests into a deformable barrier on the driver’s side to simulate a typical head-on collision in which only 40% of the vehicle’s frontal area makes contact. These are run at 40 mph. To perform well on these crash tests, manufacturers have increased the stiffness of passenger cars by using stronger alloys of steel and aluminum, and have made other structural modifications. While this has led to a reduction in injuries occurring at higher speeds (30-40 mph), it has increased the stiffness of cars in lower velocity crashes. Since model year 1982 (three years after the inception of NCAP), vehicle stiffness has increased by approximately 34%.15

The increase in whiplash injury risk caused by the increased stiffness of cars and the increased use of seat belts led the IIHS and a number of other international insurance consortia to form the International Insurance Whiplash Protection Group (IIWPG).16 They developed a special seat/head restraint testing program using specially developed rear-impact crash test dummies and sophisticated sled systems. Test results are available at Rear-impact dummies have been validated in human subject biofidelity crash testing.17,18 The validation of the crash test dummies has meant that there now is a standardized dummy that reliably represents a human response in a rear impact collision, which is the most common type of collision. That allows the industry to develop more effective seat- and head-restraint designs, and to evaluate the effect of seatbelt load limiters and pretensioners. Airbags do not have any effect on whiplash injuries caused by rear impact collisions; they only deploy in frontal- or side-impact (or roll-over) collisions.

The AMA 6th Edition: How It Differs

In the development of the latest edition of the Guides, the editors employed a modified Delphi Panel. In most cases, the panel relied on published works, grading those works based on a standard hierarchy of evidence, with meta-analysis of randomized controlled trials (RCT) at the top, followed by RCTs, non-randomized interventional studies, observational studies, and so on. The authors noted the failings of earlier editions and asserted that this edition is a “paradigm shift” that will rectify earlier shortcomings.

All of the impairment areas included in the Guides share a generic template comprised of 5 classes of impairment (0-4). The percentage of impairment initially is based on these classes and varies with the diagnosis. In this sense, the system resembles the old 5th Edition diagnosis-related estimate (DRE) classes. However, unlike the old system, the DRE has been replaced with the DBI estimate. The DBI includes severity grades A through E, with A being the least severe and E being the most severe. The severity grade is determined by subtracting the class number from a number related to grade modifiers for functional history, physical examination, and clinical studies.

In the most current version of the Guides, there is now a DBI for whiplash. When a DBI is not available or appropriate, clinicians can use a pain-related impairment (PRI). The authors of the PRI chapter willingly accepted and discussed the controversy of this practice. Some of the controversy lies in the difficulty in objectifying and quantifying pain. It also was argued that empirical data was lacking on the role of pain in impairment. And while some pain experts believe that pain should be given a more prominent role in impairment rating, others argue that it should be disregarded completely.

Some experts discourage PRI, while others believe it is a necessary adaptation. In any event, the maximum rating for pain is capped at 3% of whole person impairment (WPI). One simply doesn’t get much credit for pain without a more objective DBI. Readers interested in finding out more about this are referred to Chapter 17 of the Guides, entitled The Spine and Pelvis.14

Last updated on: April 8, 2015
First published on: February 1, 2014