Introduction
As shoulder arthroscopy progressed, surgeons noticed an association
between partial articular-sided rotator cuff tears and superior labral
lesions [1,2]. It has been proposed that this pathology is caused by
contact between the posterior-superior margin of the glenoid and the
humeral head when the arm is abducted and externally rotated [3,1].
This phenomenon has been labeled “Internal Impingement” as it is
believed to result in impingement of the posterior-superior labrum and
the articular side of the supraspinatus tendon [1]. Internal
impingement is classically associated with throwing and other repetitive
overhead athletic activities, particularly in the late cocking and early
acceleration phases [4]. Over time, repetitive loading at the limits
of the functional arc of motion leads to predictable osseous and
soft-tissue adaptations which have been associated with internal
impingement. Several pathological conditions may result including
articular-sided rotator cuff tears, labral tears, biceps tendonitis, and
anterior shoulder instability [5].
Over time, additional theories have emerged to explain the common
association between articular-sided rotator cuff tears and superior
labral lesions. Burkhart et al proposed that these lesions develop over
time due to the excessive shear and torsional forces placed on the
shoulder by repetitive abduction and external rotation [4]. Andrews
et al proposed that repetitive eccentric loading leads to similar
pathology [6]. Although the true etiology of these lesions remains
the subject of debate, the concept of internal impingement remains an
important framework for understanding the painful shoulder in an
overhead athlete.
The prevalence of internal impingement has not been well established due
to the constellation of findings that characterize this condition and
its strong association with other pathological lesions of the shoulder
[5]. However, several authors have identified internal impingement
as a leading cause of partial articular-sided rotator cuff tears in
throwing athletes [5,7]. The purpose of this case report is to
describe a novel etiology of internal impingement between the biceps
tendon and the undersurface of the supraspinatus tendon leading to a
symptomatic articular-sided rotator cuff tear. The patient’s symptoms
persisted despite initial treatment with arthroscopic debridement and
subacromial decompression. However, subsequent treatment with
arthroscopic debridement and open sub-pectoral biceps tenodesis was
successful and the patient has remained asymptomatic at latest
follow-up. To the authors’ knowledge, no previous study has identified
the biceps tendon as a cause of internal impingement.