Bennett Lesion

The Bennett lesion, first described in 1941, refers to extra-articular ossification of the posterior inferior glenoid. The ossification is thought to represent reactive bone formation from traction of the posterior band of the inferior glenohumeral ligament due to the repetitive stresses involved with overhead throwing.

The posterior ossification is associated with a posterior labral injury and posterior articular surface rotator cuff damage.

The Bennett lesion is usually asymptomatic. Throwing motion may be limited by fracture of the ossification, by a fibrous union at its base, or by capsular contracture due to the ossification.

The extra-articular ossification of the Bennett lesion is not well demonstrated on conventional frontal radiographs of the shoulder. A special view, developed by Bennett's x-ray technologist (WR Mitchell) uses a frontal projection with external rotation of the humerus and a 5-degree cephalad tilt of the x-ray tube to rotate the head of the humerus and the glenoid to a position that allows visualization of the ossification (image in Bennett's article below).

CT and MRI demonstrate the crescentic extra-articular ossification extending from the posteroinferior glenoid to the posterior labrum. Reactive sclerosis may also be seen in the posteroinferior glenoid itself. Posterior humeral subluxation can also be present. MRI can reveal labral tears, located in the posterior superior labrum.

References

• Bennett GE. Shoulder and Elbow Lesions Distinctive of Baseball Players. Ann Surg. 1947 Jul;126(1):107-10.
• Wright RW, Paletta GA Jr. Prevalence of the Bennett lesion of the shoulder in major league pitchers. Am J Sports Med. 2004 Jan-Feb;32(1):121-4.
• Ferrari JD, Ferrari DA, Coumas J, Pappas AM. Posterior ossification of the shoulder: the Bennett lesion. Etiology, diagnosis, and treatment. Am J Sports Med. 1994 Mar-Apr;22(2):171-6.