Rotator Cuff Function and Injury in the Female Athlete

Introduction

Shoulder problems in the female athlete occur most commonly in sports that require repetitive or forceful use of the upper extremity. While there is extensive research in male overhead athletes, most notably baseball players and in particular pitchers, there is much less research involving female athletes. There is some research in sports where both male and female athletes compete in the same events or under the same set of rules, but research often includes only males. Injury to the rotator cuff or chronic overuse of rotator cuff musculature is often not clearly defined in observational injury prevalence studies, making it difficult to ascertain the true extent of rotator cuff problems. ^, Overuse problems may not be reported by the athlete who may fear loss of a position on the team or by the athletic training staff if the injury does not involve time lost from participation. Club sports often do not have access to athletic training staff to track or report injuries. For these reasons, it is difficult to know the actual incidence or prevalence of rotator cuff problems in the female athlete for most sports, outside of “captured” athlete populations, such as the National Collegiate Athletic Association (NCAA).

There are clear similarities between the movement patterns of various men's and women's overhead sports, but differences in muscle firing patterns may only be observed with electromyographic (EMG) studies correlated with kinetic and kinematic information for the specific sport. ^, This chapter will discuss rotator cuff injury patterns for various women's sports and the activity of the rotator cuff musculature in female athletes participating in overhead sports and will incorporate information related to injury prevention programs.

Softball

The typical softball is 12 inches in circumference with a weight between 6¼ and 7 oz. A baseball has a circumference of 9¼ inch and a weight of 5¼ oz. Softball pitchers frequently throw far more innings and pitches over the course of a week in season than baseball pitchers. Werner et al. reviewed the number of pitches for a typical softball tournament weekend. The authors found that a pitcher may pitch as many as 10 games, with 7 innings per game, and a total of 1500–2000 pitches thrown over a 3-day period. There are no mandated pitch counts for fast pitch junior or senior division softball as there are for Little League Baseball. Little League Baseball mandates no more than 95 pitches per day for its oldest age group (13–16 years), with required rest periods depending on the number of pitches thrown. College and professional baseball and softball do not require pitch counts.

There is extensive literature detailing the overhead baseball pitch. EMG studies have described the muscle activation patterns ( Fig. 16.1 ). The rotator cuff acts to decelerate the arm and compress the glenohumeral joint in overhead throwing sports. The windmill pitch technique used in fast pitch softball is less studied, but the throwing cycle is well-described. The phases of the windmill pitch ( Fig. 16.2 ) include (1) windup, first ball movement to 6 o'clock; (2) 6 o'clock to 3 o'clock (ends with shoulder flexed 90 degrees); (3) 3 o'clock to 12 o'clock (shoulder flexed/abducted near 180 degrees); (4) 12 o'clock to 9 o'clock (shoulder abducted to 90 degrees); (5) 9 o'clock to ball release; and (6) ball release to completion of throw (follow-through). The total arc of movement during the windmill pitch is 450–500 degrees. ^,

Werner et al. have described the kinematics and kinetics of the elite windmill (rising) softball pitch by evaluating 24 elite female Olympic pitchers by using high-speed cameras during the 1996 Olympic Games. The authors found that shoulder distraction forces averaged 80% body weight, and they postulated that these distraction forces, which are similar to those in overhead throwers, place windmill pitchers at risk for overuse injuries. Injury data was not reported in this study.

Barrentine et al. also examined the kinematics and kinetics of the windmill fastball pitch in eight healthy female collegiate or previous collegiate pitchers. The authors found that peak forces resisting shoulder distraction occurred during the acceleration phase, as opposed to overhead pitching where the peak resistance to distraction is during deceleration. The supraspinatus and infraspinatus muscles had their highest EMG activity during phase 2. The distractive force at the shoulder was approximately 20%–40% body weight during the upward swing of the arm, resisted by the supraspinatus and infraspinatus. During phase 3, teres minor and infraspinatus reached peak activity, facilitating external rotation and resisting the approximately 50% body weight distractive force. Rapid downward acceleration and internal rotation (2000–3000 degrees/second) occur in phase 4, with the subscapularis muscle showing increased activity and peaking during phase 5. Subscapularis activity resists the distractive force, which peaks to full body weight distractive force, meaning a distractive force equal to the athlete's body weight that the subscapularis must resist. Shoulder internal rotation also peaks at 4600 degrees/second.

Maffet et al. studied collegiate softball pitchers whose release included contact of the arm with the lateral thigh at ball release, decreasing the need for shoulder muscles to decelerate the arm ( Table 16.1 ). The study included EMG and high-speed cinematography motion analysis. The authors found that the supraspinatus was most active between 6 o'clock and 3 o'clock during arm elevation. The posterior cuff and infraspinatus were most active from 3 o'clock to 12 o'clock, and the pectoralis accelerated the arm from 12 o'clock to ball release. Activity in all muscles decreased during follow-through, due to arm contact with the body, which slowed the forward momentum of the arm, decreasing the need for muscles to decelerate the arm. Escamilla and Andrews reviewed EMG studies of several overhead sports and made a distinction between the overhead throw, which involves high forces and torques during the follow-through after ball release when muscles are decelerating the arm, and the windmill pitch, which has the highest forces and torques during the acceleration phase. This is an important difference to note between the overhead pitch and the windmill pitch, in which the rotator cuff muscles are not firing to decelerate the arm during the windmill pitch compared to the overhead throw, where the rotator cuff is active in decelerating the arm.

Table 16.1

Differences and Similarities Between the Baseball and Softball Pitch.

From Maffet, MW, Jobe, FW, Pink, MM, Brault, J, Mathiyakom, W. Shoulder muscle firing patterns during the windmill softball pitch. Am J Sports Med , 1997;25(3):373.

Lear and Patel reviewed the literature on softball injury risk in youth and collegiate softball players, noting overuse injuries to be generally more common than acute injuries and shoulder injuries to be more common than injuries to other joints, especially in pitchers. Many of the studies they reviewed focused on injuries sustained by pitchers. There was no consensus as to whether there are more reinjuries versus acute injuries or whether serious injuries (i.e., those that involve time loss from participation) are more common than nonserious injuries.

In 1992, Loosli et al. surveyed athletic trainers regarding injuries to pitchers from 8 of the top 15 NCAA collegiate softball teams that season, noting a significant number of minor to severe rotator cuff injuries among pitchers. All were reported as a strain or tendinitis/overuse injuries. No full-thickness or partial thickness rotator cuff tears were reported, likely, at least in part, because this study predated the widespread use of magnetic resonance imaging (MRI).

An interesting study by Chu et al. made a comparison of female versus male overhead baseball pitchers. Although females predominantly play softball, there is growing interest in baseball for females. The authors studied 11 female overhead baseball pitchers, noting a few significant differences compared with male pitchers including a shorter more open stride, lower ball velocity, and lower maximal proximal forces at the shoulder and elbow. Females also took longer to progress through the pitching cycle.