2017 ISAKOS Biennial Congress Paper #60

 

Risk Factors And Time To Recurrent Ipsilateral And Contralateral Patellar Dislocation: A Population-Based Study

Tyson C Christensen, MD, Rochester, MN UNITED STATES
Thomas Lee Sanders, MD, Rochester, MN UNITED STATES
Ayoosh Pareek, BS, Rochester, MN UNITED STATES
Nick R. Johnson, BS, Rochester, MN UNITED STATES
Rohith Mohan, BA, Rochester, MN UNITED STATES
Diane L. Dahm, MD, Rochester, MN UNITED STATES
Aaron J. Krych, MD, Rochester, MN UNITED STATES

Mayo Clinic, Rochester, MN, UNITED STATES

FDA Status Cleared

Summary

At 20 years, cumulative incidence of ipsilateral recurrent patellar dislocation was 36.4% compared to 5.9% for contralateral dislocation and in addition, trochlear dysplasia, patella alta, age =18 years at time of first dislocation, and female gender were associated with recurrence

Abstract

Background

Previous studies have reported variable rates of recurrent lateral patellar instability, mainly due to limited cohort size. In addition, there is currently a lack of information on contralateral patellar instability.
Hypothesis/Purpose: The purpose of this study was to evaluate the rate of ipsilateral recurrent patellar dislocation and contralateral patellar dislocation following first-time lateral patellar dislocation. Additionally, risk factors associated with recurrent dislocation (ipsilateral or contralateral) and time to recurrence were investigated.
Study Design: Retrospective cohort study; Level of evidence III

Methods

This population-based study included 584 patients with first-time lateral patellar dislocation occurring between 1990 and 2010. A retrospective review was conducted to gather information about the injury, subsequent dislocation (ipsilateral or contralateral), and structural characteristics including; trochlear dysplasia, patella alta, and TT-TG. Risk factors were assessed to delineate associations with subsequent dislocation and time to recurrence.

Results

At mean follow up of 12.4 years, 173 patients had ipsilateral recurrence and 25 patients had a first-time contralateral dislocation. At 20 years, the cumulative incidence of ipsilateral recurrence was 36.0%, while the cumulative incidence of contralateral dislocation was 5.4%. Trochlear dysplasia [OR 18.1], patella alta [OR 10.4], age <18 years at time of first dislocation [OR 2.4], elevated TT-TG [OR 2.1], and female gender [OR 1.5] were associated with recurrent ipsilateral dislocation. Time to recurrence was significantly decreased in the presence of trochlear dysplasia (23.0 months earlier time to recurrence, p<0.001), elevated TT-TG (18.5 months, p<0.001), patella alta (16.4 months, p<0.001), and age <18 years at time of first dislocation (15.4 months, p<0.001). Risk factors for subsequent contralateral dislocation included patella alta and trochlear dysplasia.

Conclusion

At 20 years following first-time lateral patellar dislocation, cumulative incidence of ipsilateral recurrent patellar dislocation was 36.0% compared to 5.4% for contralateral dislocation. Trochlear dysplasia, elevated TT-TG, patella alta, age <18 years at time of first dislocation, and female gender were associated with recurrence. Trochlear dysplasia, elevated TT-TG, patella alta, and age <18 years at time of first dislocation were predictive of a statistically significant decrease in time to recurrence.