Anatomy of lateral patellar instability: trochlear dysplasia and tibial tubercle-trochlear groove distance is more pronounced in women who dislocate the patella.
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.


OBJECTIVE
To identify differences between the sexes in the anatomy of lateral patellar instability.


METHODS
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).


CONCLUSIONS
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.
Balcarek
Peter
P
Department of Trauma Surgery, Plastic and Reconstructive Surgery, University Medicine, Robert-Koch-Str. 40, 37075 Göttingen, Germany. peter.balcarek@med.uni-goettingen.de
Jung
Klaus
K
Ammon
Jan
J
Walde
Tim Alexander
TA
Frosch
Stephan
S
Schüttrumpf
Jan Philipp
JP
Stürmer
Klaus Michael
KM
Frosch
Karl-Heinz
KH
D000328:Adult; D000704:Analysis of Variance; D001265:Athletic Injuries / Q000209:etiology / Q000473:pathology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000473:pathology*; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010329:Patella / Q000033:anatomy & histology / Q000473:pathology*; D031222:Patellar Dislocation / Q000209:etiology / Q000473:pathology*; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D013223:Statistics as Topic; D013977:Tibia / Q000293:injuries / Q000473:pathology*; D055815:Young Adult