Furthermore, there was no difference in the odds of surgical repair of the quadriceps tendon between the females who took testosterone and the control cohort, indicating that filling testosterone prescriptions may not be a risk factor for complete tendon rupture in females. We were unable to elucidate the indication for the testosterone prescription, the exact testosterone regimen the patients were prescribed, and the patients’ serum testosterone levels at the time of the quadriceps injury. Third, the definition of quadriceps injury in our study is based on ICD codes and can range from a muscle strain to a complete tendon rupture. Second, quadriceps injuries are uncommon; although the risk of injury with testosterone replacement therapy is higher than without, this is a rare issue. Various factors are known to predispose patients to quadriceps tendon injury such as diabetes, obesity, and osteomalacia . The number of patients in each respective cohort who experienced a quadriceps injury within 1 year of and any time after their 3 consecutive months of filled testosterone prescriptions was recorded. In contrast to anabolic steroid users who reach supraphysiologic levels of testosterone, the patients evaluated in the present study received testosterone replacement therapy prescriptions of much lower doses.
Since knee laxity changes with estrogen levels through the menstrual cycle (Shultz et al., 2005), estrogen is believed to decrease sinew stiffness. Interestingly, women suffer fewer muscle injuries, and more ligament ruptures than men (Arendt and Dick, 1995; Sewright et al., 2008; Hägglund et al., 2009; Edouard et al., 2016; Leblanc et al., 2017). The result is that a muscle attached to a stiff tendon will experience more eccentric load for a given movement.
To add complexity, it is also feasible that the ability for IGF-1 to bind to its receptor in skeletal muscle and tendon is mediated indirectly by the binding proteins. The controversy about whether anabolic tendon adaptations are due to the systemic increase or to local IGF production, or to both, is topic of current research and discussion. A plethora of experimental data emphasizes the concept that the GH/IGF-1 system is crucial in maintaining muscle-tendon homeostasis. These observations reinforce the idea of a physiological action of thyroid hormones in tendons homeostasis.
Codes used to define triceps injury are also found in Online Appendix C. Quadriceps tendon repair was captured if patients had any of the diagnosis codes for quadriceps tendon tear (Online Appendix C) on the same day as CPT "Suture of quadriceps or hamstring muscle rupture; primary" or CPT "Other Procedures on the Femur or Knee Joint." A retrospective cohort study was conducted to investigate the impact of testosterone supplementation on the risk of primary tendon tears. Providers should use these findings to aid in determining which patients are candidates for testosterone replacement therapy, considering injury history and comorbidities that may predispose patients to quadriceps injury. This population was also at increased risk of undergoing surgical repair of the quadriceps tendon. We suspect a lower incidence of quadriceps muscle and tendon injury in females overall is one of the potential factors contributing to the absence of this association. This distribution is similar to the male-female ratio of quadriceps injury in our study, which ranged from 8 to 1 in the control cohort to 9 to 1 in the testosterone group.
We must consider the possibility that the quadriceps rupture that presents in our clinic is not an isolated event but possibly the endpoint of a patient’s struggle with endocrine imbalances. Expanding the scope of our knowledge and vision as orthopaedists is to the benefit of all our patients. There are several avenues wherein we need to expand our knowledge on this topic to best serve our patients. With their large-database study, Meghani et al. provide valuable insight into the scope of the problem, and they lay the foundation for much-needed further study. Low testosterone is a topic of increasing interest in the public consciousness, which makes sense given the mounting number of prescriptions for testosterone supplementation over the last decade . The ACL rupture in an adolescent patient may be the endpoint of a failure to integrate injury prevention programs into the local youth sport. In order to promote female participation in an active lifestyle throughout their life span, more research is needed to determine how nutrition, training, and hormonal manipulation can be used to promote optimal performance at any age.