Decreased femoral head–neck offset: a possible risk factor for ACL injuryReport as inadecuate

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Knee Surgery, Sports Traumatology, Arthroscopy

, Volume 20, Issue 12, pp 2585–2589

First Online: 28 January 2012Received: 23 May 2011Accepted: 10 January 2012


PurposeReduction in anterior cruciate ligament ACL injuries in young, active individuals continues to be a major goal in sports medicine. The purpose of this study was to determine the head–neck offset, as measured by AP pelvis alpha angles, in patients presenting to a single surgeon with isolated ACL and non-ACL knee injuries.

MethodsIn a group of 48 patients with complete, primary ACL rupture and 42 controls with non-ACL injury i.e., meniscus tear, cartilage defect, a single surgeon, blinded to the diagnosis, took radiographic measures of the AP alpha angle of both hips and the weight-bearing line at both knees. All knee pathology was confirmed with knee arthroscopy. Inclusion criteria included no previous hip or knee surgery, and long-leg standing alignment radiographic series completed at index visit.

ResultsThere was no difference in gender distribution, height, BMI or age between groups. ACL-injured patients had a significantly higher alpha angle mean = 84, SD = 14 on the injured side than the controls mean = 59, SD = 7, p < 0.0001. Ninety-four percent of the ACL-injured group had alpha angles over 60°, while only 35% of the non-ACL-injured group had alpha angles over 60° p = 0.001. Those patients with alpha angle over 60° were 27 times more likely 95% CI 6.4–131 to be in the ACL injury group than those patients with alpha angle 60° or less p = 0.001.

ConclusionOur findings establish an important preliminary correlation between ACL injury and diminished femoral head–neck offset, as characterized by abnormal, elevated alpha angles.

Level of evidencePrognostic study, Level III.

KeywordsACL injuries Femoroacetabular impingement Alpha angle Femoral head–neck offset  Download fulltext PDF

Author: Marc Philippon - Christopher Dewing - Karen Briggs - J. Richard Steadman


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