Algorithm Appears to Predict Recurrent Patellar Dislocation

Published October 1, 2017 | Journal of Pediatric Orthopaedics

A new algorithm, based on data from 250 children and teens treated for a first-time patellar dislocation could help pediatric specialists predict the likelihood of a recurrent dislocation.

The study, led by orthopaedic surgeon Shital Parikh, MD, included injuries to 266 knees.

Of those, 83.5 percent were treated non-surgically and 16.5 percent surgically. Of the knees treated non-surgically, 34.7 percent had a recurrent patellar dislocation.

Investigators did chart reviews to track which patients experienced a recurrence and to identify each patient’s risk factors for recurrence at the time of the initial diagnosis.

They identified four significant demographic and radiographic risk factors: skeletal immaturity, trochlear dysplasia, a history of contralateral dislocation, and a Caton-Deschamps index (measuring patella height) of greater than 1.45.

Parikh and colleagues then developed a predictive model for any combination of the four risk factors.

“The data suggest that if someone has zero to two risk factors, conservative treatment is appropriate,” says Parikh, Co-Director of the Orthopaedic Sports Center here.

“But patients with three or four risk factors have a recurrence risk greater than 70 percent,” he says. “For them, surgery is likely to be the best course of action from the outset.”

Parikh is leading a larger prospective study (JUPITER) to see if the predictive algorithm holds true.

Twelve institutions are participating in the study, and 530 patients have been enrolled so far.