From The Ergoweb® Learning Center

Trocar Assembly


Longmate, Arthur R., 1996, Johnson & Johnson, Ergonomic Control Measures in the Health Care Industry, Occupational Ergonomics.

Task Prior to Abatement (Description)

During the assembly process, workers first had to get the bottom half of the trocar casing and put it into the assembly nest. Then they had to get the compression spring and knife assembly and slide the compression spring over the knife stem. Then they had to get anti-backup springs and insert the tip of the knife shaft through the hole in it. During this procedure, they had to push their hands toward each other in order to overcome the pressure of the compression spring. Then they had to install the knife/spring assembly into the trocar casing half while maintaining the compression of the spring. Finally, they had to install a buckling spring and two latches into the trocar assembly, then install the trocar casing top half onto the assembly and remove the final assembly from the next and put it in a tray.

Task Prior to Abatement (Method Which Verified Hazard)

The task involved development and production of endoscopic trocar devices. Workers had to assemble different parts manually, except several ultrasonic welding operations which were performed automatically.

Task Prior to Abatement (Method Which Identified Hazard)

14 medical cases of upper extremity symptoms with left-hand specific pattern over 3 months of operation.

Ergonomic Risk Factor (Force)

During compression of the main spring, high pinch force was required to hold the anti-backup spring between the thumb and index finger.

Ergonomic Risk Factor (Posture)

Workers had to pinch and hold the anti-backup spring in the left hand during the manual assembly process. Local discomfort to the fingers was developed from the sharp edges of the anti-backup spring during the spring compression process.

Ergonomic Risk Factor (Repetition)

Workers had to complete about 550 assemblies per day.

Ergonomic Solution (Administrative Controls)

  1. Training was provided for workers in order to recognize ergonomics disorders.

Ergonomic Solution (Engineering Controls)

  1. Mechanical assist fixtures were developed to compress and hold the main spring through the assembly process.
  2. Adjustable angle in the fixture was provided to accommodate individual differences in methods performed by assemblers.
  3. Adaptable fixtures were designed to be convenient for both left and right-handed workers.

Ergonomic Solution (Benefits)

  • All workers that perform this task now have reduced exposure to upper extremity injuries.
  • New design to perform the task had been received positively by the majority of the workers, since they had important roles in the designing of the new fixtures.
  • The stressful static holding of the anti-backup spring was eliminated.

Ergonomic Solution (Cost)

Design of the new fixtures cost about $800 per fixture for the company.

Ergonomic Solution (Method Which Verified Effectiveness)

  • Within 3 months, all CTD symptoms had disappeared.
  • Medical restriction to perform the task was eliminated.


Since the degree of difficulty in the assembly process had been decreased, productivity remained constant although 3 extra job elements were added.