Anatomy of Lateral Patellar Instability Trochlear Dysplasia and Tibial Tubercle–Trochlear Groove Distance Is More Pronounced in Women Who Dislocate the Patella

• Published in: The American journal of sports medicine Vol. 38; no. 11; pp. 2320 - 2327
• Main Authors: Balcarek, Peter, Jung, Klaus, Ammon, Jan, Walde, Tim Alexander, Frosch, Stephan, Schüttrumpf, Jan Philipp, Stürmer, Klaus Michael, Frosch, Karl-Heinz
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01-11-2010; Sage Publications; Sage Publications Ltd
• Subjects: Adult; Analysis of Variance; Athletic Injuries - etiology; Athletic Injuries - pathology; Biological and medical sciences; Case-Control Studies; Diseases of the osteoarticular system; Female; Humans; Joint Instability - etiology; Joint Instability - pathology; Knee; Knee Joint - pathology; Magnetic Resonance Imaging; Male; Medical sciences; NMR; Nuclear magnetic resonance; Patella - anatomy & histology; Patella - pathology; Patellar Dislocation - etiology; Patellar Dislocation - pathology; Reproducibility of Results; Risk Assessment; Risk Factors; Sex Factors; Sports injuries; Sports medicine; Statistics as Topic; Tibia - injuries; Tibia - pathology; Women; Young Adult; tibial tubercle—trochlear groove distance (TT-TG); gender; patellar height; patellar instability; trochlear dysplasia; Human; Dysplasia; tibial tubercle-trochlear groove distance (TT-TG); Lateral; Corporal biometry; Anatomy; Ergonomics; Patella; Tibia; Body size; Instability; Woman
• ISSN: 0363-5465; 1552-3365
• DOI: 10.1177/0363546510373887

Background
A trend toward young women being at greatest risk for primary and recurrent dislocation of the patella is evident in the current literature. However, a causative factor is missing, and differences in the anatomical risk factors between men and women are less defined.
Purpose
To identify differences between the sexes in the anatomy of lateral patellar instability.
Study Design
Case control study; Level of evidence, 3.
Methods
Knee magnetic resonance images were collected from 100 patients treated for lateral patellar instability. Images were obtained from 157 patients without patellar instability who served as controls. Using 2-way analyses of variance, the influence of patellar dislocation, gender, and their interaction were analyzed with regard to sulcus angle, trochlear depth, trochlear asymmetry, patellar height, and the tibial tubercle—trochlear groove (TT-TG) distance. Mechanisms of injury of first-time dislocations were divided into high-risk, low-risk, and no-risk pivoting activities and direct hits.
Results
For all response variables, a significant effect was observed for the incidence of patellar dislocation (all P < .01). In addition, sulcus angle, trochlear asymmetry, and trochlear depth depended significantly on gender (all P < .01) but patellar height did not (P = .13). A significant interaction between patellar dislocation and gender was observed for the TT-TG distance (P = .02). The mean difference in TT-TG distance between study and control groups was 4.1 mm for women (P < .01) and 1.6 mm for men (P = .05). Low-risk and no-risk pivoting injuries were most common in women, whereas first-time dislocations in men occurred mostly during high-risk pivoting activities (P < .01).
Conclusion
The data from this study indicate that trochlear dysplasia and the TT-TG distance is more prominent in women who dislocate the patella. Both factors might contribute to an increased risk of lateral patellar instability in the female patient as illustrated by the fact that dislocations occurred most often during low-risk or no-risk pivoting activities in women.