[Entrapment of the long head of the biceps: the "hourglass biceps". Another cause of pain and locking of the shoulder].

PURPOSE OF THE STUDY

We describe a mechanical condition affecting the long head of the biceps tendon (LHBT) causing potentially unrecognized entrapment within the joint and subsequent pain and locking. This is caused by a hypertrophic intra-articular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm.

MATERIALS AND METHODS

Twenty one patients were identified, during open (14 cases) or arthroscopic (7 cases) surgery, with a so called "hourglass biceps" i.e., hypertrophic intraarticular portion of the LHBT and incarceration of the tendon during elevation. All cases occurred in conjunction with a rotator cuff rupture except one who had a partial deep tear. All patients were treated by excision of the biceps, after tenodesis or bipolar tenotomy, and appropriate treatment of the concomitant lesions.

RESULTS

All patients presented with anterior shoulder pain and loss of passive elevation averaging 10-20 degrees. A dynamic intraoperative test involving forward elevation with the elbow extended demonstrated entrapment of the tendon within the joint in each case. This test creates a characteristic "buckling" of the tendon and "squeezing" of the tendon between the humeral head and the glenoid ("hourglass test"). Excision of the tendon allowed immediate restoration of complete elevation. Mean Constant score increased from 38 points to 76 points postoperatively.

DISCUSSION

The "hourglass biceps" is caused by a hypertrophic intraarticular portion of the tendon that is unable to slide into the bicipital groove during elevation of the arm. Loss of 10-20 degrees of passive elevation, bicipital groove tenderness, and radiographic findings of a hypertrophied tendon can aid in diagnosis. The "hourglass biceps" should not be misdiagnosed for a frozen shoulder. Definitive diagnosis is made at surgery with the "hourglass test": incarceration and squeezing of the tendon within the joint during forward elevation of the arm with the elbow extended. Simple tenotomy cannot resolve this mechanical block. Either tenotomy with excision of the intraarticular portion of the LHBT or tenodesis must be performed. The "Hourglass" biceps is an addition to the familiar pathologies of the long head of the biceps tendon (tenosynovitis, prerupture, rupture, instability), and should be considered in any case of chronic anterior shoulder pain associated with a loss of shoulder elevation.