Abstract
Objectives:
With an increased incidence of anterior cruciate ligament (ACL) injuries and high rates of re-injury among skeletally immature individuals, investigators have attempted to identify factors that may help risk stratify patients and provide families with prognostic data concerning the risk of re-injury. Osseous morphology of the tibia as described by posterior tibial slope has received attention as a possible risk factor for ACL injury. The purpose of this study is to describe distal femoral morphology in skeletally immature, ACL-injured patients and compare that to age-matched, uninjured individuals. The authors hypothesize that the distal femoral morphology in ACL injured knees differs significantly from that of age-matched normal knees.
Methods:
A retrospective radiographic review of 58 skeletally immature patients treated at a single institution was conducted. Patients were grouped by age with Group A =>12 years and Group B =13+ years. The Blumensaat Epiphyseal Containment of the Knee (BECK) Angle, which assesses the flexion of Blumensaat’s line relative to the distal femoral physis, was measured on the involved knee for each patient on standard lateral knee radiographs. Posterior tibial slope was also measured on lateral radiographs. (Figure 1) Roof angle and posterior tibial slope of the lateral plateau were measured on sagittal T1 magnetic resonance imaging sequences of the involved knee. Paired T-tests compared distal femoral morphology in ACL injured knees to the morphology of uninjured knees.
Results:
Patients in Group A had a significantly decreased mean BECK Angle compared to Group B patients (48° ± 1.87° vs 53.4° ± 6.69°; p=0.045). When comparing Group B to age-matched patients without ACL injuries, there was a significant increase in BECK Angle values found in those with ACL injuries. (53.4° ± 6.69° compared to 48.8° ± 5.9°; p=0.009). Group A patients also tended to have higher BECK Angles compared to their uninjured counterparts, though this did not reach statistical significance (48° ± 1.87° compared to 45.8° ± 5.3°; p=0.38). Conversely, Notch Roof Angle showed significantly increased values in Group A compared to Group B (44 ± 1.581° vs. 41.85° ± 6.347°; p=0.01). Females with ACL injuries showed significantly higher BECK Angle measurements compared to males across both groups (54.56° ± 6.599° vs. 50.84° ± 6.074°; p=0.002). Posterior tibial slope of the lateral plateau on MRI showed a significantly decreased mean value in females compared to males (5.57° ± 3.532° vs 6° ± 3.536°; p=0.051).
Conclusion:
Distal femoral morphology appears to change with age and differ between females and males. Skeletally immature individuals, who have sustained an ACL injury, have significantly different morphology of the distal femur when compared to age-matched patients without ACL injuries. When risk stratifying patients for first time or repeat ACL injury, assessment of the distal femoral BECK Angle can add valuable information.
