Richard V. Baratta Ph.D., P.E. Vice President. The Use of Biomechanics in Worker Compensation Claims

Transcription

1 Richard V. Baratta Ph.D., P.E. Vice President The Use of Biomechanics in Worker Compensation Claims

2 Bio what? Biomedical Engineering Application of principles of engineering to problems in medicine and biology Education involves traditional engineering disciplines along with biology, physiology and anatomy Biomechanics The study of the mechanics of a living body, especially of the forces exerted by muscles and gravity on the musculo-skeletal structure.

3 Mechanical testing Tensile testing to failure of a metal to determine mechanical properties and strength

4 Biomechanical Testing Facial bone fixation plates to determine best combination of titanium/resorbable plates

5 How Can Biomechanics Help? Understanding of event physics Knowledge of the mechanical properties of the human body/tissues Knowledge of kinematics (motions) & kinetics (forces) in routine activities and accidental events Determination of how the incident/injuries occurred Injury mitigation-elimination Are the physics of the event consistent with the? Injuries Versions of the event

6 Considerations Mechanism of injury Direct Contact Indirect forces Exceeding range of motion Acceleration/deceleration (brain injuries) Loads sustained by tissue Tissue tolerance to loads Pre existing conditions (tissue attenuation) F Fractured femur F >2500 lbs F Richard V. Baratta, Ph.D. 6

7 Biomechanics Approach Assessment of Situation Mechanics Witness statements Site inspection (regulations, standards, laws) Other information (police reports) Modeling Review of Medical Records Determination of claimed injuries Pre-existing conditions Analysis Correlation between claimed injuries and event mechanics Differentiate acute and chronic conditions Assess effect of pre-existing conditions 7

8 Case Study 1: Shoulder/Chest Injuries On August 7, 2006, a City employee reported a work-related injury. Mr. B was having pains on the left side of the chest and went to the ER. Diagnosed with rotator cuff injury, possible herniated discs and rib cartilage strains on his left rib cage. Cause: Mr. B felt that due to pushing and pulling posts and signs to level them at work, was the cause for his injury.

9 Case Study 1: Shoulder/Chest Injuries The motions that Mr. B was performing were directly fore and aft and did not require overhead activities. Strains to the musculature of outer chest wall would be consistent with these motions. An acute injury to the rotator cuff is not consistent with the mechanics described by Mr. B. Employer accepted strain; prevailed regarding RCT.

10 Case Study 2: Automobile Accident A 1996 Toyota Camry contacts the rear of a Chevrolet soft drink service truck Driver of Chevrolet claims debilitating injuries Passenger of Chevrolet It was just a bump, I was not sure we d been hit

11 Toyota

12 Chevrolet

13 Case Study 2: Automobile Accident The Chevrolet experienced an increase in forward speed of at most 3 miles per hour (mph). Injuries to occupants of the Chevrolet would not be consistent with the mechanics of this accident. Mr. P would have been subjected to accelerations that would not be expected to cause injuries, or aggravate existing pathology. These accelerations are similar or less to accelerations experienced during routine ADL.

14 Disposition Employer prevailed at CCH EE showed up with a walker Employee Appealed Tried in State Court (about 2 years later) EE showed up in a wheelchair Employer prevailed

15 Case Study 3: Arm Injury On April 11, 2005, Ms. P, driver of a New Flyer bus, was driving on F Street between CR and B Streets, when reportedly the bus right-front tire rolled into a pothole. This jerked the steering wheel to the left. She began to experience right shoulder pain, and later upper arm and elbow pain.

16 Repaired Pothole

17 Case Study 3: Arm Injury The driver assisting in the inspection was instructed to drive the bus on the section of road where the incident reportedly took place while holding the steering wheel with minimal input Only keep one finger on the steering wheel in order for the bus to maintain its appropriate lane and heading Pronounced amount of noise and vibration transmitted through the bus chassis as it went over the surface irregularities, there was no visible or recorded feedback onto the steering wheel

18 Case Study 3: Arm Injury

19 Other aspects of Investigation The City of Houston 311 Service Center was contacted to inquire about the dates of street repairs. A cave-in near the reported site on March 5, 2005, Repairs had been completed on March 12, No major pothole on the section of road reported by Ms. P on April 11, 2005.

20 Conclusions and Disposition Reported pothole did not exist. Injuries to the shoulder rotator cuff muscles are not consistent with the mechanics described by Ms. P Did not occur in the event she described. Lateral epicondylitis (tennis elbow) is a repetitive trauma or overuse disorder, not associated with a single event. Employer Prevailed at CCH

21 Case Study 4: Disc Injury Retail worker, walking backwards while conversing with fellow employee Back of head contacts a pole Cervical disc injuries claimed

22 Biomechanical Analysis Medical Records Developmental anomaly of C1 Degenerative changes; osteophytes, space narrowing No acute changes Spine primarily exposed to shear loads in event

23 Case Study 4: Disc Injury Pars interarticularis intact structure that resists shear loads Disc was protected from shear loads. Mechanism associated with acute disc injury not invoked in this accident Acute injuries or aggravation not consistent. Employer Prevailed at CCH

24 Case Study 5: Disc Injury 2 A multi-train collision resulted in derailment of several wagons in the rear of Train 1 After the incident the engineer was walking around w/ no signs of injuries and never complained of pain He later on reported he was ejected from his seat which caused him to have spinal disk injuries Question: Were the spinal disk injuries consistent with the accident mechanics?

25 Case Study 5: Disc Injury 2

26 Case Study 5: Results Analysis of the video from locomotive showed that it moved forward only 7 inches! The delta-v resulting from this impact was less than 2 mph The average acceleration to the locomotive was 0.42 g Mechanism associated with acute disc injury was not consistent with the accident mechanics Result: Defense verdict in Federal Court

27 Case Study 6: Meniscal Tear Accident about to occur Bus driver slams on brake Foot slides off the brake. Meniscal tear diagnosed CONSISTENT: Classic mechanism for meniscus tear is torsion/bending under compression braking foot places knee in compression; slipping off brake typically includes twisting motion Employer accepted liability

28 Case Study 7: Vibration Exposure Worker using electric impact wrench nearly continuously Reports tingling in hands Diagnosed with Carpal Tunnel Syndrome Question: Was CTS diagnosis related to impact wrench vibration?

29 Vibration Measurements at Wrist 15 Vibration (g) Series2 Series3 Series4 Series

30 Biomechanical Analysis Vibration levels measured at the impact wrench body exceeded recommended levels of handarm vibration, even for short periods. An employee spending significant trigger time with the impact wrench would be subject to high exposure levels of hand-arm vibration.

31 Case Study 8: Vibration Exposure 2 Truck driver indicates that a defective seat in a tractor-truck necessitated cervical fusion surgery Reason: Transmitted excessive vibration

32 Biomechanical Investigation Other drivers interviewed seat was normal Seat was inspected everything was nominal

33 Seat Operation

34 Vibration Measurements Series1

35 Biomechanical Opinions There were no defects in the driver s seat of the Mack. Vibration levels measured in the cab of the Mack during driving over oilfield roads was far below the caution zone as delineated by the applicable American National Standard. Injuries or aggravation of injuries would not be expected to result from exposure to vibration at or near the levels measured during the inspection.

36 Case Study 9: Ladder Fall Injuries On March 12, 2008, Mr. H was working on a ladder at an industrial facility. Mr. H reported that he was removing the last bolt from a valve on the snubbing unit, slipped on the ladder, and fell into the metal basket under the snubbing unit. Mr. H is claiming injuries from this fall. There were no witnesses to this fall.

37 Area of the Accident

38 Conclusion Mr. H s claim of falling backwards off the ladder is not consistent with landing in the metal basket underneath the ladder Employer Prevailed at CCH

39 Case Study 10: Rotator Cuff Tear On July 7, 2005, Ms. J, a bus operator reported a shoulder injury. According to Ms. J, she had been experiencing shoulder pain previously, and had continued driving despite the pain. Ms. J was diagnosed with a rotator cuff tear.

40 Case Study 10: Rotator Cuff Tear

41 Biomechanical Analysis The force required to turn the steering wheel was measured. The average turning force to the right under these conditions was 8.3 pounds. The average force turning force to the left was 8.0 pounds. A driver, Mr. O, was tasked with assisting in driving the bus for the inspection. Mr. O was asked to drive the bus along the route Ms. J had been driving prior to the injury report. The steering wheel was videotaped while Mr. O drove over surface irregularities to assess the effect of irregularities on steering wheel feedback. The steering wheel vibrated, but did not jerk to the left or right when the bus traveled over surface irregularities.

42 Conclusion: Injuries to the shoulder rotator cuff muscles are not consistent with the mechanics of driving the bus. Employer Prevailed in CCH

43 Case Study 11: Accident vs. Suicide Man found in a warehouse with his head entrapped between rungs of an extension ladder Essentially suffocated Question: Accident? Suicide?

44 Biomechanical Analysis Exemplar person could not reach materials at the height he was found.

45 Biomechanical Analysis But could reach materials from ground.

46 Biomechanical Elements Mr. G was found with his head trapped between the seventh rung of the base section of the ladder and the sixth rung of the fly section of the ladder. The ladder operated as expected, with positive locking when locked, and smooth sliding when disengaged. Materials on the shelf at the level Mr. G was found would not be within his grasp while on the ladder. If Mr. G was reaching for materials at or below seven feet high, it would have been easier for Mr. G to reach them from the ground. There was no reasonable practical scenario for Mr. G to place his head between the rungs of the ladder. The mechanics of this event were not consistent with an accidental event, but were consistent with a deliberate act Ruled Suicide

47 Case Study 12: Accident vs. Suicide City employee is found deceased after reported fall from a municipal water tower Body was found 26 feet away from the vertical projection of the outer edge of the water tower Requested that we look at the dynamics of the fall determine if fall or jump

48 Test with Rescue Randy

49 Biomechanical Conclusions Based on the wind conditions on the day of the incident, the body would have been pushed by the wind between 1.8 and 2.4 feet away from the vertical projection of the water tower s outer edge. The resting location of the body was incompatible with his slipping off the top of the water tower.

50 Conclusions (con t) In order for the body to be found where it was, he needed to have an initial horizontal take off speed between 12 to 14 feet per second at the top of the water tower. More likely than not, he generated forward momentum by fast walking or jogging towards the edge of the water tower. Ruled Suicide

51 Presenting Results Arrange in understandable terms Oral report Written report Letter report Formal report Litigation support: Posters, demonstrative evidence, video animation Coordination with attorney Testimony Richard V. Baratta, Ph.D. 51

52 Important Points & Limitations In many cases dealing with accident vs. deliberate acts, there s questions about intent, motive, state of mind, and other psychological issues. WE ONLY DEAL WITH MECHANICAL/BIOMECHANICAL DATA, and CANNOT FACTOR OR OPINE ON THESE OTHER QUESTIONS INTO OUR ANALYSIS Use wisely; over-use can lead to hearing officers feeling that employers overkill

53 Thank You! Questions?