A research group led by Professor Kazuo Kaneko of Juntendo University Graduate School of Medicine has performed "dislocation" where the shoulder joint comes off and "subluxation" where there is a gap, four times on the dominant hand side of the rugby player, and on the non-dominant hand side. It was clarified that dangerous bone defects are likely to occur in the joints when repeated 4 times.
In rugby competitions where there is a lot of contact between athletes, dislocation and subluxation of the shoulder joint are very common.It is said that dislocation is "prone to habit", and it is known that about half of the athletes who have once dislocated or subluxed will re-dislocate in one season.In addition, it is known that in dislocation / subluxation, "bone defect" occurs in which the anterior edge of the glenoid fossa (dent of the joint) and the posterolateral side of the head of the humerus, which constitute the shoulder joint, are missing.The more dislocations and subluxations are repeated, the larger the bone defect becomes and cannot be dealt with by standard surgery. Therefore, it is necessary to treat the bone defect before it is too late.However, until now, it has not been well understood how many times of dislocation / subluxation the bone defect reaches a dangerous size.
Therefore, the research team of Juntendo University targeted 2011 shoulders of rugby athletes who visited Juntendo Clinic for treatment of shoulder dislocation between 2016 and 144, who played at the competition level and had no history of surgery. In addition, the degree of bone defect in the shoulder joint was investigated by CT examination.Characteristics such as the number of dislocations / subluxations, age, and flaccidity (whether the joints are soft or not) are extracted from the medical record, and the bone defects evaluated by CT examination are classified according to the degree of "dangerous area = stability even after surgery". It is classified into three categories: "cannot be obtained", "quasi-dangerous area = re-dislocation and pain even after surgery", and "safety area".We analyzed the relationship with the characteristics of the players.
As a result, about 2% of the athletes reached the "dangerous area" for bone defects, and about 6% reached the "quasi-dangerous area".In addition, the result was that the "dangerous zone" was 6 times on the dominant hand side, 9 times on the non-dominant hand side, and the "quasi-dangerous zone" was 4 times on the dominant hand side and 5 times on the non-dominant hand side.The reason why the number of injuries on the dominant hand side is small and the risk zone is likely to occur is that the impact at the time of tackling is stronger than that on the non-dominant hand side.
From the results of this study, athletes suffering from repeated dislocations and subluxations will not be able to respond with standard surgery by visiting a medical institution at an early stage (up to 3 times) to evaluate and treat bone defects. It can be said that it is possible to prevent a condition in which postoperative dissatisfaction is likely to occur.In the future, it is expected that it will be recognized by on-site coaches, coaches, and athletes themselves, and will greatly contribute to the safety of athletes as an index to prevent the condition of the athlete's shoulders from becoming too late.
