Born in Brazil, Hendrickson graduated from high school in three years and was class valedictorian. In two years, he completed his Bachelor of Science in pre-medicine studies at Indiana State University in Terre Haute. He finished his medical education at the Chicago College of Osteopathic Medicine in 1949, followed by an internship and residency in internal medicine at Doctors Hospital in Columbus, Ohio.
In 1954, he went into private practice as a cardiologist. He had met his future wife, Laura, now deceased, when she was a secretary in the medical offices. They married in 1949.
Hendrickson enlisted in the Army, but did not tell the recruiters he was a doctor.
"He wanted (the other recruits) to view him as an average Joe," his son, Steve, said.
From 1955 to 1957, he served in the Counterintelligence Corps in Maryland. After his discharge, he decided to switch medical careers and completed a residency in pathology at Detroit Osteopathic Hospital in Highland Park, Mich.
From 1960 to 1975, he was a pathologist and director of laboratories in Saginaw Osteopathic Hospital in Michigan. The family moved to Indian Head Park when he took a position as professor of pathology at Chicago Osteopathic in 1975.
In addition to teaching, he was also a pathologist at the hospital until 1987, said his daughter, Lisa Theis. "People listened to him," she said. "He was a great teacher who could explain things the way people could understand it."
In 1987, he became associate dean of the college until he took a medical retirement in 1990. He was the past president, fellow and a diplomat of the American Osteopathic College of Pathologists and founding president of the Michigan Osteopathic Pathology Society.
Survivors include his wife, Dolores; his children, Michele, Steve and wife Diane and Lisa and husband Jeff Theis; and grandchildren, Allison and Jessica Theis and Natalie and Julia D'Azzo.