Sex-Based Differences in Common Sports Injuries

Cordelia W. Carter, MD; Mary Lloyd Ireland, MD; Anthony E. Johnson, MD; William N. Levine, MD; Scott Martin, MD; Asheesh Bedi, MD; Elizabeth G. Matzkin, MD


J Am Acad Orthop Surg. 2018;26(13):447-454. 

In This Article

Shoulder Instability

Atraumatic Shoulder Instability

As the most mobile of the major joints, the glenohumeral joint depends on a combination of soft-tissue restraints, dynamic muscular forces, and bony morphology for stability. Owens et al[26] investigated the role of osseous anatomy in providing shoulder stability and found that a patient whose glenoid is tall and thin has a higher risk of instability than one whose glenoid is short and wide. Subsequent investigators have observed that glenoid morphology varies markedly by race and sex;[27,28] compared with males, females have markedly smaller glenoids, with higher inclination angles.[27] In addition, height-to-width ratios of glenoids markedly differ between males and females; the functional importance of this finding is that the glenoid is more oval in shape (tall and thin) in females and rounder in males.[28] These anatomic findings substantiate that females should have higher rates of shoulder instability than males because the glenoid morphology in females favors instability. The combination of innate osseous vulnerability, increased shoulder range of motion, and greater prevalence of generalized ligamentous laxity[30] in females likely contributes to the higher rates of atraumatic multidirectional shoulder instability seen in this population. Thus, although sex-based anatomic risk factors for shoulder instability are fairly well characterized, little information is available regarding sex-based differences in treatment and functional outcomes for patients with atraumatic shoulder instability.

Traumatic Anterior Shoulder Instability

In the general population, the incidence of traumatic glenohumeral dislocations is relatively low, with 0.08 to 0.24 dislocations occurring per 1,000 person-years.[31] The incidence of traumatic shoulder instability is more than seven times greater in the military population, increasing to 1.69 per 1,000 person-years; most of these dislocations are observed in cadets.[31] Research on the incidence of traumatic shoulder instability as a function of the patient's sex has revealed that traumatic dislocations occur twice as often in males than in females.[32] In fact, Zacchilli and Owens[32] found that males are 2.6 times more likely to present to the emergency department with a shoulder dislocation than are females. Traumatic dislocations have also been found to have an inverse relationship with age and a direct relationship to activity level.[32]

In addition to males having an increased risk of initial traumatic shoulder instability relative to females, this population has also shown an increased risk of developing recurrent shoulder instability after an initial traumatic dislocation. In their investigation into the risk factors and functional outcomes for young patients with recurrent shoulder instability after an initial traumatic dislocation, Robinson et al[33] found that the mean time to the development of recurrent instability was 13.3 months, with the peak risk of recurrence at 24 months. Univariate analysis demonstrated that age, sex, generalized ligamentous laxity, participation in and intensity of sports, and return to contact sports were all contributing factors to the development of recurrent shoulder instability. However, after multivariate analysis, only male sex and younger age were independently predictive of recurrent instability. The risk of recurrent instability was lower for females of all age groups compared with their age-matched male counterparts.[33] Thus, although a variety of injury- and patient-related factors may contribute to the risk of recurrent shoulder instability, the risk is highest in athletic young males.[33]

As yet, there has been little investigation into possible sex-based differences in the outcomes after surgical stabilization of the shoulder. In addition to this paucity of data, concern has been raised that the outcomes measures used in clinical research may not be valid for all patients: sex-based differences have been noted for the normalized scores of commonly used functional outcomes measures, such as the Constant-Murley score.[34] Methodologically sound, adequately powered studies that use validated, sex-neutral outcomes measures are needed to best understand how athletes' sex affects their risk of shoulder instability as well as its treatment and outcomes.