Bony Adaptation of the Shoulder in Baseball Pitchers

It is well known that the glenohumeral joint (shoulder joint) goes through changes in throwing shoulder of baseball pitchers. A change in its range of motion (ROM), know as glenohumeral internal rotation deficit (GIRD), is very common in baseball pitchers. GIRD is when pitchers lose internal rotation (IR) motion and gain external rotation (ER) motion and a total arch of motion (IR + ER) is considerably less than that of the non-throwing shoulder. According to a study, a loss of more than 5 degrees of total ROM increases a risk of shoulder injury in baseball pitchers. This change in ROM may be due to soft tissue adaptation or/and bony adaptation that shoulder goes through after repetitive stress placed on the joint. Known bony adaptations are humeral head retroversion where humeral head (the ball part of ball and socket shoulder joint, a part of upper arm bone), after repetitive torsional force from pitching, turns backwards compared to the other shoulder and glenoid retroversion where glenoid fossa (socket part of the shoulder joint, a part of scapula) shifts backwards. In most shoulders, the glenohumeral joint is aligned about 30 degrees anteriorly instead of facing straight to the side. However, in the throwing shoulders of baseball pitchers that have gone through this adaptation, the alignment of the joint is slightly shifted backwards. Importance of these adaptations, which likely happens before bones complete its growing process (physis closure), is that it may be a protective mechanism of the shoulder against repetitive stress and possible injury such as SLAP tear according to several studies. 

       Will baseball pitchers whose shoulder has gone through this bony adaptation be at less risk of SLAP tear in the future?! Is it better to start pitching when they are younger that later to prevent SLAP tear?! There are many more questions to be answered.   

 

 

Common Injuries in Elite Junior Figure Skaters

Figure skating may not attract a lot of attention except for the winter Olympics. However, it is a quit unique sport with plenty of technical skills and artistic aspect in it. As this figure skating season is coming close to an end this year, we thought to discuss common injuries in figure skating. According to a study published in 2003, which looked at singles, pairs, and ice dancing, about 70% of injuries in singles figure skating were chronic injuries. 60% of injuries in pairs were acute injuries. Of all the acute injuries suffered by elite junior figure skaters, ankle sprain was the most common. Common chronic injuries among those figure skaters were stress fracture, jumper's knee, Osgood-Schlatter disease, etc. Common injury sites for stress fracture were located in the foot and lower leg. Over all, more than 44% of all the injuries suffered was chronic in nature. This means that it is very possible to prevent such injuries.

 

It is very important to know that figure skaters wear rigid type boots which prevent them from moving their ankle. The importance of this is that......when athletes jump and land, they will bend the ankles, knees, and hips to absorb a force placed on the joints. The muscles around each joint play an important role in absorbing the force so that stress placed on the joints will be minimized. However, figure skaters do not have ankles and muscles around to dissipate the ground reaction force due to the boots that they wear. From a recent study, it is known that knee and hip angle on landing correlates with the amount of pressure felt by knee and hip joints. When figure skaters do not have the ankle and the muscles around it to absorb the ground reaction force, it is a disadvantage to them. They may need to work on the knee and hip muscle strength to 1) cancel out this disadvantage and 2) relieve a compensatory stress placed on those joints.