Anatomical Risk Factors for Anterior Cruciate Ligament Injury Are Not Important As Patellar Instability Risk Factors in Patients with Acute Knee Injury

To compare in magnetic resonance imaging the anatomical risk factors for anterior cruciate ligament (ACL) injury and patellar dislocation among patients who suffered acute knee injury, 105 patients with acute knee injury resulting in 38 patellar dislocations (patella group), 35 ACL injuries (ACL group), and 32 meniscus or medial collateral ligament injuries (control group) were included. These groups were compared for risk factors for patellar dislocation (patellar height, trochlear dysplasia, and quadriceps angle of action) and for ACL injury (intercondylar width, posterior inclination of tibial plateaus, and depth of the medial plateau). Univariate analysis found statistically significant differences ( p <0.05) between the patella and ACL groups in patellar height (Caton-Deschamps [CD] 1.23 vs. 1.07), trochlear facet asymmetry (55 vs. 68%), PTTG (13.08 vs. 8.01mm), and the patellar tip and trochlear groove (PTTG) angle (29.5 vs. 13.71 degrees). The patella group also differed from control in medial plateau inclination (4.8 vs. 1.87 degrees), patellar height (CD 1.23 vs 1.08), trochlear facet asymmetry (55 vs. 69%), lateral trochlear inclination (17.11 vs. 20.65 degrees), trochlear depth (4.1 vs. 6.05mm), PTTG (13.08 vs. 9.85mm), and the PTTG angle (29.5 vs. 17.88 degrees). The ACL and control groups were similar in all measures. Multivariate analysis found the following significant determinants between the Patella and Control groups: patellar height (CD index, odds ratio [OR]: 80.13, p =0.015), trochlear anatomy (asymmetry of facets M/L, OR: 1.06, p =0.031) and quadriceps action angle (PTTG angle, OR: 1.09, p =0.016); between the ACL and control groups: PTTG angle (OR: 0.936, p =0.04) and female gender (OR: 3.876, p =0.032); and between the patella and ACL groups, the CD index (OR: 67.62, p =0.026), asymmetry of the M/L facets (OR: 1.07, p =0.011) and PTTG angle (OR: 1.16, p <0.001). In conclusion, in patients with acute knee injury, the anatomical factors patellar height, trochlear dysplasia, and quadriceps angle of action were related to the occurrence of patellar dislocation. None of the anatomical factors studied was related to the occurrence of anterior cruciate ligament injury.