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Physician Is Hip to the Ways of Saber-Toothed Tigers

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Robert Klapper, MD, co-director of the Joint Replacement Program, examines the results of a CT scan of a bone from a saber-toothed cat found near the La Brea Tar Pits.

When the smilodon, or saber-toothed cat, roamed what is now Wilshire Boulevard more than 12,000 years ago, did the predator hunt alone or in packs?

If hips don't lie, Robert Klapper, MD, co-director of the Joint Replacement Program at Cedars-Sinai, may have the answer to a long-debated question among paleontologists.

Working with the La Brea Tar Pits and Museum, Klapper brought the best practices of medical diagnostics to bear on the saber-toothed cat in an effort to develop a clearer understanding of how the prehistoric animal lived. He used Cedars-Sinai's most advanced CT scan machines to study the pelvis and femurs of the saber-toothed mammal, so named for its foot-long curving canine teeth.

"The most modern technology allowed these bones to speak to us, and they had a lot to say," Klapper said.

One bone specimen in particular had a lot to tell Klapper. Originally, scientists speculated the animal had died from infection. But Klapper's analysis revealed the animal had been born with dysplasia, an abnormal development of the hip joint.

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Jennifer Morales, a CT technologist at Cedars-Sinai, prepares a saber-toothed cat bone for a scan.

When Klapper and a team from the Department of Imaging examined the CT scan closely, they clearly could see a mismatch between the ball and socket, which over years caused distinctive spurs to develop. The finding meant that it was highly unlikely this animal could have survived on its own, said Klapper.

"The fact that there is even one of these animals that was able to survive into adulthood told us a tremendous amount," said Klapper. "If it had been limping since birth and it couldn't run fast enough to chase its prey, it had to have survived in packs.

"If it's a fact that this is how this animal was born," added Klapper, "then it's a fact that someone else had to feed it."

The project began 20 years ago, when Klapper went to the museum as tourist and stood face-to-face with 400 prehistoric wolf skulls. He saw something the average tourist would not.

"I realized I'm in a museum filled with bones, which is what I do for a living," Klapper said. "The exhibits are gorgeous, showing you the saber-toothed cat, the wooly mammoth and the dire wolf—all these prehistoric fossilized bones from the tar pits.

"Then I became obsessed with the questions: Where is the arthritis? Where are the fractures? Where are the abnormalities?"

The curator led the orthopaedic surgeon to a collection of abnormal saber-toothed cat bones, deep in the bowels of the museum. They have since been brought out into the light thanks to Klapper, researchers from the La Brea Tar Pits and Museum, and staff from the S. Mark Taper Foundation Imaging Center at Cedars-Sinai.

"I think it's awesome," said Jennifer Morales, CT technologist at Cedars-Sinai. "This happened years ago, and yet we still have the imaging today to reveal more things that we didn't know before."

Aisling Farrell, collections manager for the La Brea Tar Pits and Museum, has been working closely with Klapper for six months to coordinate the examination of these bones.

"I've known that we've needed to do this for ages," she said.

Klapper also will use the scans to create a prosthetic hip joint, which will help him treat dysplasia in human patients of similar size. (The saber-toothed cat was about the same size of a modern-day lion.) Klapper credits Barry D. Pressman, MD, professor and chair of the Department of Imaging, for providing his staff's expertise to the study.

"What if you're 7'1"? We don't have prostheses that fit that height," Klapper said. "We also don't have prostheses that fit someone small. What we're doing is taking a CT scan to build the anatomy and then a prosthesis."

Klapper will continue his studies in partnership with the La Brea Tar Pits and Museum.

"The La Brea Tar Pits are one of the crown jewel experiences that you can have in Los Angeles," Klapper said. "They predate everything, including man running around here; you have to go visit it."

To learn more about the saber-toothed cat, visit the La Brea Tar Pits and Museum website.