Fractures of the lesser tuberosity of the proximal humerus are uncommon but are associated with forces in an auto accident that push the ball portion of the humerus posteriorly in a dislocation. The lesser tuberosity can become fractured off or “avulsed” from the rest of the bone as the ball pushes out of joint. If a lesser tuberosity fracture is seen, then a posterior dislocation of the shoulder joint can be suspected.
Often, when the lesser tuberosity is fractured, it is actually pulled away from the bone with its attached muscle, called the subscapularis muscle. It can be mistaken for a pulled muscle and may not be treated appropriately. In other cases, the rest of the humerus is fractured along with the tuberosity. If the tuberosity is far apart from the rest of the bone it’s supposed to be attached to, the long head of the biceps muscle can become trapped between the bony fragments so that the tuberosity isn’t able to be connected to the rest of the humerus without surgery.
In one study of lesser tuberosity cases, it was found that in only six cases was the fracture identified immediately–at the time of the injury. The other four cases were only discovered later, sometimes months later, from the time of the injury. The chronic cases were often dealing with persistent shoulder and chest wall pain from a fracture that was too small to be detected.
In cases where the fracture was identified immediately, half of all of the cases were treated conservatively. In those cases, there was presumably no muscle entrapment between the fracture ends and the fracture was relatively nondisplaced. After a period of rest, these people entered into physical therapy and were able to restore normal function to the arm.
Two of the acute cases of lesser tuberosity fractures were treated with surgery with an excellent outcome. A third case treated with surgery had a satisfactory outcome. The age ranges for all these cases was wide at between 11 and 68 yrs of age.
Of the four cases not picked up at the time of the injury, physical therapy and muscle strengthening exercises were introduced, with complete recovery to satisfactory levels in two of the patients. The fracture ends healed over time. Two cases did not get better after physical therapy and required surgery to repair their lesser tuberosity fracture.
The specialists involved in the study indicated the need to diagnose these fractures as soon as possible so that open reduction and internal fixation through surgery could be attempted as this type of procedure seemed to yield the best patient results. In chronic cases, it appears that a trial of conservative physical therapy is warranted, especially if the doctor did not identify the fracture in the first place and if there is no intervening muscle trapped between the two parts of the bone.
Lesser tuberosity fractures from car accidents are not common; however, the forces that bring on these types of fractures can be seen in many head on collisions.