Anatomy of a car crash from the medical-legal angle

The Medical-Legal News asked two nurse consultants to analyze a real motor vehicle crash and assess the current and future medical injuries, forensics of the impact and the plaintiff’s credibility.

© The Medical-Legal News, 2007

LETT, on the clinical and forensic

By Sally Lett, DC, RN

This motor vehicle collision (MVC) involved a 1990 Ford Taurus where the plaintiff was rear-ended by a tractor trailer, causing the Ford to impact the vehicle in front of it.

For descriptive purposes, the target vehicle is the one that was struck, the Ford Taurus. The bullet vehicle is the one that struck the target vehicle, the tractor trailer. Thus, the female plaintiff’s car was initially a target car, then became a bullet car when it impacted the vehicle in front of it. Following the accident, both parties moved the Ford to the side of the road following the MVC.

Medically speaking

Following the accident the plaintiff did not have any difficulty walking, talking or communicating. No medical treatment was rendered immediately following the MVC. The following day the plaintiff complained of neck pain and headache, and received treatment at a medical clinic. She was diagnosed and treated for cervical, thoracic and lumbar sprain and strain.

The thoracic MRI read by the plaintiff radiologist diagnosed a T11-12 disc herniation. The defendant’s expert disputed the disc herniation but rather concluded a degenerative disc with peripheral osteophyte, desiccation and disc space narrowing, but not protruded. An independent medical exam (IME) indicated only a neck and lumbar sprain or strain of soft tissue. Most thoracic herniated discs are not surgically treated but rather conservatively treated.

This level is the transitional stage of the spine, where the thoracic meets the lumbar spine. A decreased disc at this level can reduce mobility and create muscle spasms to assist in stabilizing the spine.

Case

About one and a half years following the MVC, the plaintiff started a job that required her to work 12-hour shifts, lift 70 lbs. and stand for a large portion of her shift.

The plaintiff claimed permanent back and neck injury resulting from the MVC.

The defendant fought the case on the issue of liability. Florida is a no-fault state, an auto insurance program that allows policyholders to recover financial losses from their own insurance company, regardless of fault. Motorists may sue for severe injuries and for pain and suffering only if the case meets certain conditions. Florida’s no-fault law is scheduled to expire in Oct. 2007 unless reenacted.

Crash speed

The speed ranged from 0 mph to 15 mph at impact. For comparison, the speed one reaches in jumping from a height of 21 ft., close to the height of a second-story rooftop, equates to a 25 mph collision. The most common injury to people in rear-end crashes is whiplash, which results from the sudden differential motion of an occupant’s head and torso. Seats and head restraint combinations are intended to reduce these injuries.

Whiplash

When a vehicle is struck from the rear, the occupant’s torso is accelerated while the unrestrained head and neck are thrust backward. As the head tips back into extension, the anterior (front) cervical muscles are stretched, and when their tone is overcome, the brunt of the remaining force is taken up by the anterior longititudional ligaments and anterior fibers of the anulus fibrosus. At the end of the acceleration phase, after extension of the spine, the flexion component of the injury takes place. In other words, the occupant is quickly thrown backward, tearing the soft tissue in the front of the spine where the disc fibers attach. During that time, the occupant could also ride over the seat restraint causing further stretching before being thrown forward.

If the victim’s vehicle strikes another vehicle in front, the resulting deceleration further exacerbates the flexion injury. When wearing a shoulder harness, and during the deceleration phase, a linear tractional injury occurs near the end of forward rotation.

Delayed onset of symptoms is quite common following cervical acceleration/deceleration (CAD) trauma, which could be months or even years later. Some of these conditions represent secondary adaptations to otherwise minimally symptomatic or asymptomatic conditions. In fact, 86 percent of all neck injuries seen clinically result from automobile accidents, and 85 percent of these injuries are a result of rear-end collisions. MacNab reports that 45 percent of those suffering from neck whiplash injuries continue to be symptomatic for at least two years after settlement of their cases.

Common symptoms that occur after whiplash in order of prevalence are:

• neck pain,

• neck stiffness,

• trapeziums pain,

• headache,

• intrascapular pain,

• back pain,

• paresthesia,

• extremity pain or weakness, and

• dizziness or lightheadness.

Neck pain

Neck pain is easily explained by the tearing of any soft tissue, disc injury or herniation, or end plate fractures. Immediate pain indicates more severe injury. Stiffness is the result of muscle spasm. Shoulder pain may be the result of direct shoulder injury or referred injury or referred pain from cervical disc injury.

Spondylosis

Patients with cervical spine whiplash injuries develop spondylosis [osteophyte or bony formation] approximately six times more frequently than age- and gender-matched controls. Conversely, patients with pre-existing spondylosis generally fare worse in whiplash. The degenerative process includes an initial destabilization of the disc through direct injury from a high energy combination of shear, compression, axial stretch and torsion forces. Loss of normal ligamentous integrity will allow a direct biomechanical destabilization of the spine, and probably contributes significantly to the overall degeneration scenario.

Submarining

Submarining occurs when the occupant slips below the lap belt and is responsible for abdominal, pelvic and lumbar lesions. This occurs chiefly as a result of poor positioning of restraint anchors, poorly designed seat cushions, slumped seating posture and improper placement of the lap belt about the anterior superior iliac spine.

Seat belts

All vehicles from the early 90s include specific directions in the manual that indicate that the seat belt locking device is designed for one impact only. After an accident has occurred, the seat belt locking device will not function properly again. In fact, the seat belt locking device could fail in the next accident — and allow more significant injuries.

Observe the belt for any tears or stretch marks, observe any direct damage to the casing for the locking device and jerk on the belt to ensure that it locks — all done while the vehicle is moving and has achieved at least 10 mph.

In this MVC case the attorney needs to establish if a lap belt was available in the ’90 Ford, if the auto had a prior MVC that could render the seat belt defective and if the seatbelt had been replaced.

Ramping

After rear-end impact collision, the vehicle accelerates forward, forcing the occupant backward into the seat back.

Simultaneously, some vertical motion may occur, known as ramping. Ramping reduces the effectiveness of the head restraint by allowing the head to rotate backward and over the top of the restraint. A shoulder harness can cause shoulder injury and rib fractures. With no shoulder harness there is more ramping of the neck on the seatbelt and possibly hitting on the inside of the vehicle as well. This could contribute to the thoracic disc thinning seen on the MRI in this case. Identify if a shoulder harness was used in this accident, any prior accident that impacted the seat belt’s effectiveness and if that, too, had been replaced.

Loss of curve

Loss of or reversed cervical lordotic curve is commonly seen following a rear end collision commonly at the C5-C6 level. The phenomenon of cervical acceleration/deceleration syndrome (CAD) trauma is more complex than most physicians realize. This can lead to arthritic changes at an earlier age. With the loss of a curve, the normal cervical curve is not present, thus the bones alter their configuration by producing osteophyte or bone to allow for the new center of gravity from the malposition.

Research

Check out the vehicle for a safety rating of the ’90 Ford Taurus. The web sites www.nhtsa.gov and www.iihs.org are informative about the crashworthiness and crash test performance of specific vehicles. At the IIHS site, the Ford Taurus rear crash test ratings go from 1995 to 2004, the car rates poor and marginal with marginal overall ratings for the 2004-06 Taurus. The seat and head restraint in rear end crash protection is an assessment of occupant protection against neck injury in rear impacts at low to moderate speeds.

Check out the defendant tractor trailer damages — what type and model of tractor trailer was the bullet vehicle? This goes back to the forces generated from the kinetic energy resulting from the size and weight of the vehicle.

Excess force 

The head and neck are exposed to acceleration forces up to two and one-half times those of the vehicle itself. At higher speed collisions, the head and neck may be exposed to four to ten times the car’s acceleration. This is why CAD trauma, specifically rear-impact trauma, results in greater injury than other, yet similar, types of automobile accident-related neck injuries.

Case preparation

In preparing for this case, the attorney must evaluate the target vehicle for repair costs. If rear bumpers have moved more than one inch, check for undercarriage damage and if a taller vehicle overlapped a shorter vehicle. The Ford Taurus is probably smaller in height than the tractor trailer — determine by how much. Check the target vehicle for the amount of frame time repair required and if the damage travels beyond the rear wheel well. These are just a fe