Motor vehicle accident injuries are as a direct result of the force of the impact and the biomechanics of injury. Most motor vehicle accidents are the typical hyperextension flexion injuries, or more commonly known as “whiplash” injuries.
Motor vehicle accident injuries are a challenge to most physicians as each mechanism of injury is slightly different. Knowledge of musculoskeletal anatomy makes for a more precise diagnosis.
Most injuries are termed soft tissue injuries or musculoskeletal joint injuries. These injuries occur from a front-end impact of flexion/extension, mechanism, a rear-ended impact of hyperextension/flexion mechanism, or a side impact of lateral flexion mechanism. However, if a person is not sitting straight and looking straight ahead, then the mechanism of injury becomes more complex.
Car manufacturers have made significant modifications in motor vehicles to improve safety. Prior to seatbelts, most injuries occurred where the body was thrown forward into the dashboard and windshield as an unrestrained passenger. With the introduction of a lap seatbelt, the driver was more restrained; however, at the time of impact, his/her body sustains a jackknife movement over his pelvis which was stabilized.
The spine, however, would absorb significant force that have resulted in spinal fractures and disc herniations. Further safety included modification a headrest be positioned at the level of the occiput, and a shoulder harness being added.
These modifications helped prevent some of the higher cervical spinal cord injuries as well as allowed the torso to absorb most of the impact, by limiting the forward motion of the occupant. Recent, modifications included mandatory airbag systems safety, side impact airbags and reinforced side beams have promoted a safer compartment within the motor vehicle accident.
With the introduction of the airbag, there have been new types of injuries, but non life threatening. With the deployment of the airbag, the release of the powdery substance has caused eye injuries as well as skin abrasions. The airbag deployment can also cause upper extremity, chest and shoulder trauma from the force of the body’s forward acceleration against the deployment of the airbag.
Rear-ended impacts usually result in a more severe and disabling injury than front end or side collisions of the same force. Anatomically, humans have a built in restraint system in the neck, as the chin is limited in its forward flexion by the sternum. However, this anatomic restraint is lacking in the hyperextension movement.
Video analysis shows that in moderately high speed impacts, without a headrest, the forward motion of our head is limited as the chin strikes the sternum, whereas in hyperextension, it exceeds its functional range to the point that the top of the head may actually approach touching the upper mid back between the shoulder blades.
Side impact injuries have built in anatomical restraints being our shoulders. As the side impact throws our neck sideways, our ear will strike the shoulder as the maximal allowable range of motion.
Flexion/extension injury is often referred to as cervical strain, whiplash injury or cervicalgia. This mechanism of injury results in syndromes of pain due to straining of cervical muscles, spraining of ligaments, trauma to the discs and traction of the exiting nerve roots. The degree of damage to these structures varies depending on the degree of the force of impact.
Individuals in a motor vehicle accident should be assessed for cerebral, cervical, thoracic chest, shoulder upper extremity, lumbosacral, hip lower extremity and TMJ musculoskeletal joint structures for limitations and injury.
The cervical evaluation should be thorough as cervical pain is the most common early symptom. Assessment of range of motion should be done as well as correlating lack of range of motion to specific strained musculoskeletal structures.
Another frequent complaint is swallowing difficulty that lasts a few days following the motor vehicle accident. With significant force, a flexion/extension the anterior longitudinal ligament can be sprained resulting in edema anteriorly and creating mechanically induced swallowing pain.
Patients who are examined minutes or hours immediately after a motor vehicle accident usually show few clinical findings as they may lack the soreness or muscle tightness and may have a relatively functional range of motion.
Within a couple days, tightness and spasm with secondary edema develop, limiting range of motion and continue to get progressively worse over the next few days.
Patients with mild sprains usually improve within seven to ten days, but symptoms may last for several weeks or months in more moderate or severe injuries.
Prolonged muscle tightness and spasm leads to secondary deconditioning that further prolongs the duration of symptoms.
Headaches are usually a source of referred pain from the cervical structures. Occipital headaches with radiation bitemporally and then into the eyes are not uncommon and are usually due to referred muscle pain from the upper trapezial muscles.
Pain radiating from the neck into the shoulders and arms, is more commonly a myofascial referred pain from the muscles themselves, but in more severely injured individuals can be a manifestation of the irritation of the nerve roots or brachial plexus.
Following a motor vehicle accident neck injury, the patient tends to hold the neck in a slightly forward position. This position is probable helpful in reducing the pain, as it does not depend on any muscle contraction. Unfortunately, it produces a cumulative overstrain of the supporting posterior, musculoligamentous structures.
To give an example, the typical head of the human adult weighs approximately 10 to 12 pounds. Simplifying the model position a ten pound bowling ball on a broomstick. Proper erect position will correlate to a ten pound weight being balanced. However, moving the bowling ball three inches in either direction will create a force of 30 pounds needed to support on the broomstick, a factor of three times the actual weight. Therefore, it is the goal of the therapist and clinician to promote proper postures to help alleviate the secondary strains from the malaligned spine.
In an abrupt stop, the seatbelt on the left shoulder will force the torso and chest backwards. Frequently, one can see bruising over the area of the seatbelt with more moderate or severe impacts. The chest/thorax area is susceptible to rib fractures and mild subluxations or dislocations when being struck by an airbag or striking steering column. Clinical symptoms of shortness of breath, pain with breathing, coughing or laying down are symptomatic of a possible rib fracture or dislocation.
The position of the arms, hands and wrists at the time of impact will help assess for possible injury. If the individual held their arm in a fully extended position while firmly gripping the steering wheel, an individual may develop secondary wrist trauma through the carpal area. This wrist injury may predispose individuals to carpal tunnel symptomatology or tendonitisis in the forearms.
Abdominal injuries are quite uncommon. Should a patient be restrained at a high impact, then injuries to the internal organs may result. Hemorrhages of kidneys, liver and spleen have occurred with high impact injuries of flexion/extension with an abrupt stop.
The second most common site of injury is the low back, sacral, pelvic area. As the body is restrained with the legs extended, the impact is absorbed through the pelvic/sacral areas. Frequently, subluxation of the sacroiliac joints occur which directly affect the L4, L5 and S1 vertebral complexes. Impacts where the patient reports the actual driver’s seat breaking should direct the clinician to do a thorough examination of the sacroiliac structures.
The lower extremities in full extension either in the process of applying the clutch or trying to brake with the leg extended may cause injuries such as ankle sprains, lateral leg and thigh strains with secondary development of trochanteric bursitis. In certain vehicles with more protruding dashboards, long legged individuals sustain direct knee trauma across the patella/intrapatellar area. Direct knee trauma most likely causes retinacular capsular trauma and resulting knee pain. Actual meniscal or cruciate damage is unlikely. Swelling is usually superficial rather than intra-articular.
The TMJ/jaw area is frequently missed by clinicians. The jaw is a joint that allows movement. In flexion/extension injuries, the mandible moves forward and then back into position. Frequently, this causes disruption of the temporomanibular joint and disc leading to subluxation and secondary temporalis muscle strain causing referred headache pain.
Following the motor vehicle accident, the patient is assessed for injuries. At the scene of the accident frequently, emergency services will evaluate the patient. If there has been any loss of consciousness, significant neck and headache pain, the patient may be stabilized on a cervical board and brought to the emergency room for a more detailed evaluation. If the emergency room evaluation findings are primarily musculoskeletal soft tissue, the patient may be released with instruction to follow up with the primary physician.
The patient’s treatment choices are varied; however, they should be directed to some clinician who provides manual treatment. Chiropractors can provide adjustments and as co-treatment incorporate massage therapy and physical therapy within their practice.
Osteopathic physicians provide manual adjustments similar to chiropractors, but additionally utilize medications and physical therapy. Massage and neuromuscular massage therapy is effective on primarily soft tissue musculoskeletal injuries. Myofascial release can provide improved flexibility and reduce the secondary spasm and strains of specific muscular tissue.
Traction is occasionally utilized by clinicians, chiropractors and osteopathic physicians to reduce the intervertebral tightness along the spine.
Passive treatments, which include modalities, are hot, cold and ice. The first 24 hours should be reserved for icing to reduce the swelling and physical compression to limit the secondary edema. Ice is also utilized after manual therapy where tissue is actively worked on and can reaggravate the developing edema. Other modalities used by therapists include ultrasound, iontophoreses, electrical stimulation, laser as well as recently cold light treatments.
Should a patient have any radiculopathy including pain, numbness, tingling or weakness in the extremities, an MRI is indicated to rule out a disc lesion that could impinge a nerve root. Nerve conduction study to assess any nerve damage should only be done three weeks after the initial injury, as being done too early may not have the objective findings in this test.
Studies show that symptoms of extremity radicular numbness or pain, sharp reversal of cervical spine curve, prolonged spinal traction or prolonged wearing of a cervical collar more than three months, are poor prognostic factors following the motor vehicle accident.
Copyright © 2004 – 2012Taras V. Kochno, M.D. All Rights Reserved
Board Certified in Physical Medicine and Rehabilitation