Testosterone may increase rat anterior cruciate ligament strength.
BACKGROUND
Women are more likely than men to injure the anterior cruciate ligament (ACL). Human and animal trials have linked circulating estradiol to injury rate and ligament strength. Fewer studies have examined the role of testosterone. The purpose of this study was to determine if male rats with normal testosterone levels would have stronger ACLs than castrated rats.


METHODS
Eight castrated (group C) and eight normal (group N) 12-week-old, male Sprague-Dawley rats were used for the study. Mean testosterone levels were 0.14ng/mL (95% CI: 0.10 to 0.17) in group C and 3.54ng/mL (95% CI: 1.32 to 5.76) in group N. After euthanasia, ACL cross-sectional area was calculated, and a servohydraulic material testing unit was used to measure ligament properties.


RESULTS
Specimens from both groups had similar cross-sectional area, but N specimens showed greater mean load-to-failure (34.5N [95% CI: 31.6 to 37.4] vs 29.2N [95% CI: 27.9 to 30.6]) and ultimate stress (38.7MPa [95% CI: 34.1 to 43.3] vs 31.8MPa [95% CI: 29.8 to 33.8]). Mean energy was 27.7mJ (95% CI: 23.1 to 32.2) in the N group and 23.4mJ (95% CI: 18.2 to 28.6) in the C group.


CONCLUSIONS
Rats with normal circulating testosterone had higher ACL load-to-failure and ultimate stress, indicating that testosterone may influence ACL strength and the injury rate of the ligament.
Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
W A
WA
Romani
Department of Orthopaedic Surgery, The Johns Hopkins University, 5210 Eastern Avenue, Baltimore, MD 21224, USA. Electronic address: editorialservices@jhmi.edu.
S M
SM
Belkoff
Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
J H
JH
Elisseeff
D000818:Animals; D016118:Anterior Cruciate Ligament / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries / Q000209:etiology*; D002369:Castration; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012307:Risk Factors; D013718:Tensile Strength; D013739:Testosterone / Q000097:blood*; D016474:Weight-Bearing
D013739:Testosterone
Cross-sectional area; Knee injuries; Ligament injuries; Sex differences; Sex hormones