This study revealed a tendency for elite wheelchair basketball players to have multiple characteristically abnormal findings in their bilateral upper extremity joints. First, it was found that bone cysts of various sizes were more likely to occur in the lateral posterior region of the elbow joint. This is consistent with what was reported as an LP lesion in a previous study (7, 10), and is therefore included in the results as LP lesions in the text (Fig. 1). In addition, the TFCC was easily injured. No significant findings were observed in the shoulder joints.
Previous reports have already shown that the frequency of LP lesions and TFCC injuries is high in general wheelchair users, consistent with the results reported here (7). The average age of the subjects in the study was approximately 50 years (7). The mean age of the subject group of general wheelchair users in this study was 30.1 years, and there were no significant abnormal findings. Therefore, it is suggested that the frequency of abnormal findings in the upper extremities of general wheelchair users increases with age.
On the other hand, the elite wheelchair basketball players, as young as 29.6 years old, showed remarkable abnormal findings. These findings suggest that LP lesions and severe TFCC injuries are characteristic upper limb joint findings in elite wheelchair basketball players.
Although these LP lesions and severe TFCC injuries have been observed in normal wheelchair users, previous literature suggests that the cause is not excessive wheelchair operation, but frequent push-up movements performed over several years to prevent pressure ulcers (7, 11, 12). The push-up motion must be performed many times a day by wheelchair users, and it is assumed that this causes TFCC injuries and LP lesions because the load is applied to the wrist joint by the forearm axis with locking of the elbow joint (7, 13, 14).
On the other hand, because elite wheelchair basketball players are still young, severe TFCC injuries and LP lesions are likely not only caused by push-ups but are also caused by the competitive characteristics of wheelchair basketball.
Although they handle the ball all the time, passing, shooting, and dribbling are not unnatural and overloaded movements for wheelchair basketball players in this study. Therefore, it is unlikely that basketball play itself produces characteristic findings for elite wheelchair basketball players.
On the other hand, compared to other wheelchair sports, wheelchair basketball is characterized by a high incidence of “tipping the wheelchair forward” (15). For example, as shown in Fig. 2, when a player makes a layup shot, the upper body is often thrown out of the wheelchair, and the wheelchair tends to fall forward (15). There are also many other cases in which the wheelchair falls forward during the game (15). This is because the player's body is fixed to the wheelchair to some extent. As shown in Fig. 2, when a wheelchair falls forward, it is most common to fall on the hands and elbows to avoid hitting the face or twisting the neck. If a person falls with his or her hands, the TFCC is overloaded (16). If the elbows are locked, the load on the TFCC is even greater (16). In addition, when the elbow is locked, it is hyperextended at the time of the fall, which increases the likelihood of the load being applied to the lateral side of the elbow. Severe TFCC injuries and LP lesions are assumed to occur under these circumstances. In addition, it is thought that keeping hands on the wheelchair from 6 o'clock direction to 9 o'clock direction when driving the wheelchair at full force is also a risk for severe TFCC injury. There is a possibility that motion analysis using motion capture will further clarify the cause of the problem, which will be the subject of future research.
The forward fall of a wheelchair is an attractive element for watching wheelchair basketball games and is difficult to avoid from a competitive standpoint. For this reason, it is essential to try to fall in a way that places as little load on the hand and elbow joints as possible. Specifically, it is desirable to brace the fall from the elbow or forearm, rather than the hand. In addition, protectors with the hand, elbow, or forearm may reduce the incidence of severe TFCC injuries and LP lesions by using a wrist joint supporter to cushion the load from the forearm to the wrist joint.
In summary, the characteristic MRI findings of the upper extremities in elite wheelchair basketball players are severe TFCC injuries and LP lesions. These lesions are observed more frequently in normal wheelchair users as they age and are thought to be caused by longstanding push-up movements. On the other hand, elite wheelchair basketball players may be at risk because they may fall with their hands in front of the wheelchair, lock their elbow joints during the fall, and keep their hands on the wheel from 6 to 9 o'clock while driving the wheelchair at full speed.
An interesting finding of this study is that there was not a large agreement between the abnormal findings on imaging and the chief complaint in both elite wheelchair basketball players and general wheelchair users. The reason for this is not clear, but we speculate that it may be due to the stabilization of joints by stronger muscle strength of the upper body in wheelchair users rather than that in a healthy person. In addition, the adaptation to disability caused by chronic injuries, such as overuse, may also be the reason.
This study had two limitations. First, only ten elite wheelchair basketball players were scanned; however, the number of elite wheelchair basketball players is small, and opportunities to gather as a group outside of training camps are limited. In the future, we will consider the use of a mobile MRI system to clarify this problem (17). In addition, while all elite wheelchair basketball players were female, most of the wheelchair users in the study were male.
The incidence of spinal cord injury has been reported to be higher in males worldwide (18). The latest epidemiology in our country also shows that spinal cord injuries are more common in males (19). In addition, head and neck trauma has been reported to be more common in males at younger ages (20). Since there are more males with spinal cord injuries and head trauma than females, it can be inferred that there are more male wheelchair users than female wheelchair users in the younger age group. This may be the biggest reason why it was difficult to gather female wheelchair users in this study. Furthermore, as already mentioned, MRI of the upper extremity joints of general wheelchair users has the influence of push-up as a basic life factor in the background (7). There is no difference between men and women in this regard (7). Therefore, we assume that the influence of gender differences on the results of this study is small.