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. 2018 Mar/Apr;10(2):146-151.
doi: 10.1177/1941738117725055. Epub 2017 Aug 10.

Incidence of First-Time Lateral Patellar Dislocation: A 21-Year Population-Based Study

Thomas L Sanders  1 , Ayoosh Pareek  1 , Timothy E Hewett  1 , Michael J Stuart  1 , Diane L Dahm  1 , Aaron J Krych  1
Affiliations

Incidence of First-Time Lateral Patellar Dislocation: A 21-Year Population-Based Study

Thomas L Sanders et al. Sports Health. 2018 Mar/Apr.

Abstract

Background: First-time lateral patellar dislocation is a common orthopaedic injury. The purposes of this study were to (1) evaluate the incidence of first-time lateral patellar dislocation in a geographically-determined population, (2) report trends over time in the incidence of dislocation, and (3) describe the rate of surgical treatment.

Hypothesis: The rate of patellar dislocation is highest among adolescent patients.

Study design: Cohort study.

Level of evidence: Level 3.

Methods: The study population included 609 individuals identified through a multidisciplinary geographic cohort county database who were diagnosed with first-episode lateral patellar dislocation between 1990 and 2010. The complete medical records were reviewed to confirm the diagnosis and to evaluate details of injury and treatment. Age- and sex-specific incidence rates were calculated and adjusted to the 2010 US population. Poisson regression analyses were performed to examine incidence trends by age, sex, and calendar period.

Results: The overall age- and sex-adjusted annual incidence of patellar dislocation was 23.2 (95% CI, 21.2-24.9) per 100,000 person-years. The annual incidence was similar between male and female patients and highest among adolescents aged 14 to 18 years (147.7/100,000 person-years). The mean age at dislocation was 21.4 ± 9.9 years, and 331 patients (54.4%) were female. During the study period, there was a significant decline in the incidence of patellar dislocation among men aged 19 to 25 years ( P = 0.002) and girls aged 14 to 18 years ( P = 0.025). Eighty patients received surgical treatment during the study period, including 66 patients (10.8%) for recurrent instability and 14 patients (2.3%) for acute osteochondral injury.

Conclusion: With an annual incidence of 23.2 per 100,000 person-years, lateral patellar dislocation is a frequently encountered orthopaedic injury. The incidence of dislocation among adolescent patients in this cohort is higher than previously reported. Despite a decrease in the annual incidence of dislocation in adolescent girls, the overall incidence of patellar dislocation remained relatively constant over a 21-year observation period.

Clinical relevance: This study demonstrates that the incidence of patellar dislocation in adolescents is greater than previously reported.

Keywords: incidence; instability; patellar dislocation; recurrence.

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Conflict of interest statement

The following author(s) declared potential conflicts of interest: Michael J. Stuart, MD, is a paid consultant for and receives royalties from Arthrex and receives research support from Stryker. Aaron J. Krych, MD, is a paid consultant for Arthrex and receives research support from Arthritis Foundation and Histogenics.

Figures

Figure 1.
Figure 1.
Incidence of patellar dislocation by age.
Figure 2.
Figure 2.
Incidence of patellar dislocation by year.
See this image and copyright information in PMC

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