Analysis of the causes of trauma to the Supraspinatus muscle and tendon in Cricket athletes, and proposing recovery aids.

Abstract:

The supraspinatus muscle is one of the four muscles in the rotator cuff, and is involved in the abduction of the arm around the glenohumeral joint, for the initial 10°-15° of movement. The supraspinatus tendon is the connector between the supraspinatus muscle and the top of the humerus, thus supporting the humerus by pressing it against the scapula to stabilise the joint; this makes it such that it is mechanically positioned to bear the downward force of the arm acting on it; making it the most likely muscle in the cuff to suffer trauma due to sudden or large movements of the arm. These are the exact kind of movements that are experienced regularly in cricket, for all positions to some extent, but most often by bowlers - who are required to swing their arms around the full range of rotation during play, at least 6 times per over, for many overs in a day of play. To model this problem in a way that is easier to compute, a simple elastic model will be used to analyse the forces acting on the supraspinatus. The muscle will be modeled without external load, as well as with the expected load of a Cricket bowler. To obtain better data will require active monitoring of cricket players in play, or in training. As this data is beyond the scope of this paper to observe and analyse, suggested methods of analysis will be included for future papers who may have access to this type of live data. Additionally, while these injuries are not uncommon, the current methods of recovery require long rest periods that place players out of active play, and even most training. To aid in the recovery of the supraspinatus in the event of injury, this paper also details a possible harness to lower the load being applied at the tendon, while allowing this load to be dynamically increased as the repair occurs, thus lowering the overall recovery time for the muscle to return to the original strength.

 

Introduction:

The supraspinatus is one of the four muscles making up the support structure around the glenohumeral joint in the shoulder, the others being: the teres minor, the subscapularis, and the infraspinatus. All of these terminate to tendons around the humerus head, stabilising the head by pressing it into the scapula and preventing free rotation in the 3-axis of rotation. This stability is what allows the arm to be moved precisely around the ball-and-socket joint of the shoulder throughout its entire range of motion. However, this also means that any injuries to these muscles or their associated tendons can cause a large restriction to the movement of the arm, or cause even minor movements to result in a high amount of pain. For the most part, tears in the rotator cuff are uncommon, with the average person only straining the region till it triggers inflammation, preventing them from overstressing the muscles until the minor damage is rectified. For professional athletes, this isn’t the case as they regularly exert themselves close to their limits to train, and perform to the best of their abilities. While this method does provide results, in that it will strengthen muscles and bones over time, excess training, or overexertion while performing is always a possibility, and when the expectation is already close to the limit the body is most likely to suffer injury to some extent.

Results:

The main result of the analysis was the surprisingly low loading on the supraspinatus tendon, this may be due to the simplified approach taken for the biomechanical analysis, or perhaps due to other factors not directly relating to the forces acting on the tendon causing the injury.

The approach should have produced forces in excess of the resulting forces calculated, thus it is likely that discounting the other rotator cuff muscles as well as the arm muscles overlying the cuff was an oversimplification. This could be adjusted with more specific data in relation to each muscle individually, as well as a more precise recording of the data pertaining to the rotational arm movements of a bowler. A larger dataset would also be advantageous to determine the exact biomechanical impact of bowlers’ movements. This could be done by players wearing precise accelerometers along their arm as well as stress sensors along their shoulder muscles to find the exact action of the muscles during a pitch.

Discussion:

In the process of this analysis, the lack of precision data regarding bowlers and their biomechanics was quite surprising, however, the more likely scenario is that specific biometric data is recorded, but confidential, as records of specific professional athletes would likely not be in public domain.

The damage could also be occurring for reasons other than just the forces acting around the joint, factors such as tendon composition, age, prior damage or recovery regions, etc. One such likely factor could be the thinning of the bursa between the tendon and the acromion that protrudes anteriorly from the top of the scapula, above the supraspinatus. Thinning in this region will reduce the padding the tendon receives and allow it to rub against the acromion directly, resulting in a condition similar to arthritis, causing highly increased wear and tear on the tendon, sharply increasing the probability of injury. Another potential reason could be the weakening of another cuff muscle, thus increasing the demand on the renaming cuff muscles to compensate for the lost stability. This may be enough to overload more than just the supraspinatus, and could also result in multiple tendon injuries.

You can find the full paper linked below: