RESOLVING WHIPLASH INJURIES PART 1 - BIOMECHANICS
Updated: Oct 14
Whiplash injuries or a Whiplash Associated Disorder (WAD) is a common group of conditions that often results from a Motor Vehicle Crash (MVC). Although many whiplash cases do resolve quickly, certain WAD cases can lead to chronic pain and disability (27) that require careful evaluation and treatment.
WADs’ often involve litigation, or potential litigation. Therefore, it is critical to have a practitioner that understands these injuries, one who conducts a thorough physical examination, and who provides the right treatment and exercise program to achieve optimal results.
What will we cover?
Here is what we will cover in this 5-part series:
In the first two parts of this five part series I will illustrate the biomechanics of a whiplash injury in three stages, and review each stage of a MVC, and the anatomical structures that are often injured.
In Part-3 I will discuss symptoms of whiplash injuries, physical examination, and review some of the fundamentals of WAD categorization.
In Part-4 I will discuss conservative treatment options, including treatment demonstrations for both soft tissue and joint injuries.
Finally in Part-5 I will discuss the importance of carefully structured exercise programs, including video demonstrations of some of the exercises we typically prescribe to patients.
Whiplash injuries are more accurately described as a hyper-extension/hyper-flexion injury as this describes the biomechanics of the actual injury. It is important to realize that these injuries often occur within one-quarter of a second (1), and that the vehicular occupants of a rear-ended collision simply do not have time to react or protect themselves from the accident.
Whiplash injuries can be breakdown into three specific sections:
Stage 1 : Vehicle Impact
Stage 2 : Neck Hyper-Extension
Stage 3 : Neck Flexion
Stage 1 : Vehicle Impact
Let’s look at the effects on the body of a person who has been rear-ended in a vehicular accident. On initial impact (where the vehicle in the rear hits the car in front)
The force of impact begins to move the front vehicle forward.
Since the seat of the impacted car is attached to the car’s frame, the driver’s seat also moves forward with the car. But because the driver is not attached to the frame of the car, he/she continues to remain in a fixed position (due to inertia).
(Physics defines inertia as “the tendency of a body to resist acceleration”, in a MVC, it’s a literal definition!)
Then, within a fraction of a second, the car seat pushes into the driver’s lower and mid-back. This rapid forward acceleration pushes the lower part of the driver’s neck (lower cervical spine) forward. This has the effect of straightening out both the normal curves in the driver’s neck (the lordotic curve) and the curve in the driver’s mid-back (the kyphotic curve). This creates a new abnormal S-shaped curve in the drivers neck (cervical spine). (9, 24)
A considerable amount of damage can be done during this Impact Phase. When the neck is pushed into this abnormal S-shaped position, the facet joints of the neck are forced to move past their normal physiological range-of-motion limit. This excessive motion causes damage to the area around the facet joints. Including: facet capsule ligament tearing, bony impingement, and intra-articular (within the joint) hemorrhages. (1,8) The degree of joint damage depends on the severity of the collision.
Stage 2 : Neck Hyper-Extension
In Stage Two the high-speed, forward motion (of the vehicle) jerks the driver’s head back. In many cases the head can move, at high velocity right back over the headrest. This often occurs when the headrest is set too low to be effective, or due to poor headrest design. (9)
If the impact of the accident is severe, a substantial amount of soft-tissue and joint damage can occur along the front of the neck as the head is thrown back.
Areas of Damage in Stage 1 and Stage 2
Muscles, nerves, facet joints, joint capsules and ligaments can become damaged during stage 1 & 2 of a MVC.
Facet Joint & Capsule Damage
Facet joints are the most commonly injured joints of the neck. These synovial facet joints support weight and control movement between each individual vertebra. (2) The facet joints are also the most common source of chronic neck pain after a whiplash injury. (3)
Due to the severity of muscle contractions and vertebral motions during whiplash accidents (4,8), the facet capsules in the neck are often injured as well.
The Anterior Longitudinal Ligament (ALL) runs down the front of the vertebral bodies and prevents excessive extension (head moving back). Damage to this ligament causes instability in the neck (cervical spine) and can be a cause of subsequent chronic neck pain long after the actual whiplash injury. (5,6)
Muscles & Nerves
Several muscles and nerves in the neck and shoulders are impacted during stage 1 & 2 of a MVC. Here are some of the most common structures injured during the hyper extension phase of a whiplash injury.
The Longus Colli muscle is a deep muscle that runs along the front of the neck between the top vertebra in your neck (C1) and the mid-upper chest (T3) and is commonly injured in whiplash injuries. (7) This muscle contains a high density of neurological receptors known as muscle spindles. Muscle spindles are stretch receptors that act to detect changes in the length of the muscle. Muscles with higher levels of spindle fibers are typically used to manage fine motor control, muscle tone, and positional sense. Injuries to these muscles will affect a broad range of motor functions. (7)
The Platysma muscle is a superficial muscle that overlaps the SCM (sternocleidomastoid muscle). (10)The Platysma arises from the connective tissue (fascia) on the upper parts of the neck and chest (pectoralis major), and extends out over the shoulder (deltoid) and down over the collar bone (clavicle). When injured, due to its fascial connections this muscle can affect multiple areas of the body. The Platysma muscle is innervated by the Facial Nerve (CN-VII). Injury to the Platysma during a MVC can affect the function of the facial nerve. Prickling feelings across the face and upper chest, are common with facial nerve involvement. (33,37,38,53)
The Scalenes are a group of three muscles on the lateral side of the neck (anterior, medial, and posterior scalenes). A network of nerves (brachial plexus) and a major artery (subclavian artery) pass through the anterior and medial scalene muscles. This is an area that is commonly injured during whiplash accidents and can cause either neurological or vascular problems in the neck, shoulder and arm, right down to the wrist and fingers. This is type damage is referred to as Thoracic Outlet Syndrome (TOS). The majority of cased of TOS are due to neurological damage (90%) and not vascular. (50,53)
The SCM (Sternocleidomastoid) muscle is a superficial muscle located on the lateral, anterior side of the neck. The SCM is involved in flexion and rotation of the neck. Two major nerves (Lesser Occipital Nerve and Greater Auricular Nerve) pass by the SCM. Compression of these nerves, as in a MVC, can results in occipital neuralgia, a medical condition characterized by chronic pain in the upper neck, back of the head, and behind the eyes. This is sometimes known as C2 Neuralgia or Arnold’s Neuralgia. (11,53)
The Spinal Accessory Nerve provides input (motor innervations) to the SCM and Trapezius muscles. Compression of the Spinal Accessory Nerve during a MVC can result in limited range-of-motion and decreased strength of the SCM and Trapezius muscles. This can greatly affect both shoulder and neck strength.
Note: Headaches characterized by chronic pain in the upper neck, back of the head, and behind the eyes are a common scenario that we often see in our clinical practice. These headaches can often be resolved with a treatment that combines manual therapy and exercise.
Part Two: In part two of “Resolving Whiplash Injuries” I will discuss the biomechanics of Stage 3 (hyper flexion) and review the anatomical structures that are commonly injured. Please note references for all five sections of this article are at the end of Part 5.
DR. BRIAN ABELSON DC.
Dr. Abelson believes in running an Evidence Based Practice (EBP). EBP's strive to adhere to the best research evidence available, while combining their clinical expertise with the specific values of each patient.
Dr. Abelson is the developer of Motion Specific Release (MSR) Treatment Systems. His clinical practice in is located in Calgary, Alberta (Kinetic Health). He has recently authored his 10th publication which will be available later this year.